RNA-guided transcriptional regulation

DOEpatents

Church, George M.; Mali, Prashant G.; Esvelt, Kevin M.

2016-02-23

Methods of modulating expression of a target nucleic acid in a cell are provided including introducing into the cell a first foreign nucleic acid encoding one or more RNAs complementary to DNA, wherein the DNA includes the target nucleic acid, introducing into the cell a second foreign nucleic acid encoding a nuclease-null Cas9 protein that binds to the DNA and is guided by the one or more RNAs, introducing into the cell a third foreign nucleic acid encoding a transcriptional regulator protein or domain, wherein the one or more RNAs, the nuclease-null Cas9 protein, and the transcriptional regulator protein or domain are expressed, wherein the one or more RNAs, the nuclease-null Cas9 protein and the transcriptional regulator protein or domain co-localize to the DNA and wherein the transcriptional regulator protein or domain regulates expression of the target nucleic acid.

The Tissue-Specific RNA Binding Protein T-STAR Controls Regional Splicing Patterns of Neurexin Pre-mRNAs in the Brain

PubMed Central

Ehrmann, Ingrid; Dalgliesh, Caroline; Liu, Yilei; Danilenko, Marina; Crosier, Moira; Overman, Lynn; Arthur, Helen M.; Lindsay, Susan; Clowry, Gavin J.; Venables, Julian P.; Fort, Philippe; Elliott, David J.

2013-01-01

The RNA binding protein T-STAR was created following a gene triplication 520–610 million years ago, which also produced its two parologs Sam68 and SLM-1. Here we have created a T-STAR null mouse to identify the endogenous functions of this RNA binding protein. Mice null for T-STAR developed normally and were fertile, surprisingly, given the high expression of T-STAR in the testis and the brain, and the known infertility and pleiotropic defects of Sam68 null mice. Using a transcriptome-wide search for splicing targets in the adult brain, we identified T-STAR protein as a potent splicing repressor of the alternatively spliced segment 4 (AS4) exons from each of the Neurexin1-3 genes, and exon 23 of the Stxbp5l gene. T-STAR protein was most highly concentrated in forebrain-derived structures like the hippocampus, which also showed maximal Neurexin1-3 AS4 splicing repression. In the absence of endogenous T-STAR protein, Nrxn1-3 AS4 splicing repression dramatically decreased, despite physiological co-expression of Sam68. In transfected cells Neurexin3 AS4 alternative splicing was regulated by either T-STAR or Sam68 proteins. In contrast, Neurexin2 AS4 splicing was only regulated by T-STAR, through a UWAA-rich response element immediately downstream of the regulated exon conserved since the radiation of bony vertebrates. The AS4 exons in the Nrxn1 and Nrxn3 genes were also associated with distinct patterns of conserved UWAA repeats. Consistent with an ancient mechanism of splicing control, human T-STAR protein was able to repress splicing inclusion of the zebrafish Nrxn3 AS4 exon. Although Neurexin1-3 and Stxbp5l encode critical synaptic proteins, T-STAR null mice had no detectable spatial memory deficits, despite an almost complete absence of AS4 splicing repression in the hippocampus. Our work identifies T-STAR as an ancient and potent tissue-specific splicing regulator that uses a concentration-dependent mechanism to co-ordinately regulate regional splicing patterns of the Neurexin1-3 AS4 exons in the mouse brain. PMID:23637638

Structural Basis and Function of XRN2-Binding by XTB Domains

PubMed Central

Richter, Hannes; Katic, Iskra; Gut, Heinz; Großhans, Helge

2016-01-01

The ribonuclease XRN2 is an essential player in RNA metabolism. In Caenorhabditis elegans, XRN2 functions with PAXT-1, which shares a putative XRN2-binding domain (XTBD) with otherwise unrelated mammalian proteins. Here, we characterize structure and function of an XTBD – XRN2 complex. Although XTBD stably interconnects two XRN2 domains through numerous interacting residues, mutation of a single critical residue suffices to disrupt XTBD – XRN2 complexes in vitro, and recapitulates paxt-1 null mutant phenotypes in vivo. Demonstrating conservation of function, vertebrate XTBD-containing proteins bind XRN2 in vitro, and human CDKN2AIPNL (C2AIL) can substitute for PAXT-1 in vivo. In vertebrates, where three distinct XTBD-containing proteins exist, XRN2 may partition to distinct stable heterodimeric complexes, likely differing in subcellular localization or function. In C. elegans, complex formation with the unique PAXT-1 serves to preserve the stability of XRN2 in the absence of substrate. PMID:26779609

Hepatic effects of a methionine-choline-deficient diet in hepatocyte RXRalpha-null mice.

PubMed

Gyamfi, Maxwell Afari; Tanaka, Yuji; He, Lin; Klaassen, Curtis D; Wan, Yu-Jui Yvonne

2009-01-15

Retinoid X receptor-alpha (RXRalpha) is an obligate partner for several nuclear hormone receptors that regulate important physiological processes in the liver. In this study the impact of hepatocyte RXRalpha deficiency on methionine and choline deficient (MCD) diet-induced steatosis, oxidative stress, inflammation, and hepatic transporters gene expression were examined. The mRNA of sterol regulatory element-binding protein (SREBP)-regulated genes, important for lipid synthesis, were not altered in wild type (WT) mice, but were increased 2.0- to 5.4-fold in hepatocyte RXRalpha-null (H-RXRalpha-null) mice fed a MCD diet for 14 days. Furthermore, hepatic mRNAs and proteins essential for fatty acid beta-oxidation were not altered in WT mice, but were decreased in the MCD diet-fed H-RXRalpha-null mice, resulting in increased hepatic free fatty acid levels. Cyp2e1 enzyme activity and lipid peroxide levels were induced only in MCD-fed WT mice. In contrast, hepatic mRNA levels of pro-inflammatory factors were increased only in H-RXRalpha-null mice fed the MCD diet. Hepatic uptake transporters Oatp1a1 and Oatp1b2 mRNA levels were decreased in WT mice fed the MCD diet, whereas the efflux transporter Mrp4 was increased. However, in the H-RXRalpha-null mice, the MCD diet only moderately decreased Oatp1a1 and induced both Oatp1a4 and Mrp4 gene expression. Whereas the MCD diet increased serum bile acid levels and alkaline phosphatase activity in both WT and H-RXRalpha-null mice, serum ALT levels were induced (2.9-fold) only in the H-RXRalpha-null mice. In conclusion, these data suggest a critical role for RXRalpha in hepatic fatty acid homeostasis and protection against MCD-induced hepatocyte injury.

Metabotropic glutamate receptor-mediated use-dependent down-regulation of synaptic excitability involves the fragile X mental retardation protein.

PubMed

Repicky, Sarah; Broadie, Kendal

2009-02-01

Loss of the mRNA-binding protein FMRP results in the most common inherited form of both mental retardation and autism spectrum disorders: fragile X syndrome (FXS). The leading FXS hypothesis proposes that metabotropic glutamate receptor (mGluR) signaling at the synapse controls FMRP function in the regulation of local protein translation to modulate synaptic transmission strength. In this study, we use the Drosophila FXS disease model to test the relationship between Drosophila FMRP (dFMRP) and the sole Drosophila mGluR (dmGluRA) in regulation of synaptic function, using two-electrode voltage-clamp recording at the glutamatergic neuromuscular junction (NMJ). Null dmGluRA mutants show minimal changes in basal synapse properties but pronounced defects during sustained high-frequency stimulation (HFS). The double null dfmr1;dmGluRA mutant shows repression of enhanced augmentation and delayed onset of premature long-term facilitation (LTF) and strongly reduces grossly elevated post-tetanic potentiation (PTP) phenotypes present in dmGluRA-null animals. Null dfmr1 mutants show features of synaptic hyperexcitability, including multiple transmission events in response to a single stimulus and cyclic modulation of transmission amplitude during prolonged HFS. The double null dfmr1;dmGluRA mutant shows amelioration of these defects but does not fully restore wildtype properties in dfmr1-null animals. These data suggest that dmGluRA functions in a negative feedback loop in which excess glutamate released during high-frequency transmission binds the glutamate receptor to dampen synaptic excitability, and dFMRP functions to suppress the translation of proteins regulating this synaptic excitability. Removal of the translational regulator partially compensates for loss of the receptor and, similarly, loss of the receptor weakly compensates for loss of the translational regulator.

Differential regulation of ATP binding cassette protein A1 expression and ApoA-I lipidation by Niemann-Pick type C1 in murine hepatocytes and macrophages.

PubMed

Wang, Ming-Dong; Franklin, Vivian; Sundaram, Meenakshi; Kiss, Robert S; Ho, Kenneth; Gallant, Michel; Marcel, Yves L

2007-08-03

Niemann-Pick type C1 (Npc1) protein inactivation results in lipid accumulation in late endosomes and lysosomes, leading to a defect of ATP binding cassette protein A1 (Abca1)-mediated lipid efflux to apolipoprotein A-I (apoA-I) in macrophages and fibroblasts. However, the role of Npc1 in Abca1-mediated lipid efflux to apoA-I in hepatocytes, the major cells contributing to HDL formation, is still unknown. Here we show that, whereas lipid efflux to apoA-I in Npc1-null macrophages is impaired, the lipidation of endogenously synthesized apoA-I by low density lipoprotein-derived cholesterol or de novo synthesized cholesterol or phospholipids in Npc1-null hepatocytes is significantly increased by about 1-, 3-, and 8-fold, respectively. The increased cholesterol efflux reflects a major increase of Abca1 protein in Npc1-null hepatocytes, which contrasts with the decrease observed in Npc1-null macrophages. The increased Abca1 expression is largely post-transcriptional, because Abca1 mRNA is only slightly increased and Lxr alpha mRNA is not changed, and Lxr alpha target genes are reduced. This differs from the regulation of Abcg1 expression, which is up-regulated at both mRNA and protein levels in Npc1-null cells. Abca1 protein translation rate is higher in Npc1-null hepatocytes, compared with wild type hepatocytes as measured by [(35)S]methionine incorporation, whereas there is no difference for the degradation of newly synthesized Abca1 in these two types of hepatocytes. Cathepsin D, which we recently identified as a positive modulator of Abca1, is markedly increased at both mRNA and protein levels by Npc1 inactivation in hepatocytes but not in macrophages. Consistent with this, inhibition of cathepsin D with pepstatin A reduced the Abca1 protein level in both Npc1-inactivated and WT hepatocytes. Therefore, Abca1 expression is specifically regulated in hepatocytes, where Npc1 activity modulates cathepsin D expression and Abca1 protein translation rate.

Increasing brain serotonin corrects CO2 chemosensitivity in methyl-CpG-binding protein 2 (Mecp2)-deficient mice

PubMed Central

Toward, Marie A.; Abdala, Ana P.; Knopp, Sharon J.; Paton, Julian F. R.; Bissonnette, John M.

2013-01-01

Mice deficient in the transcription factor methyl-CpG-binding protein 2 (Mecp2), a mouse model of Rett syndrome, display reduced CO2 chemosensitivity, which may contribute to their breathing abnormalities. In addition, patients with Rett syndrome and male mice that are null for Mecp2 show reduced levels of brain serotonin (5-HT). Serotonin is known to play a role in central chemosensitivity, and we hypothesized that increasing the availability of 5-HT in this mouse model would improve their respiratory response to CO2. Here we determined the apnoeic threshold in heterozygous Mecp2-deficient female mice and examined the effects of blocking 5-HT reuptake on the CO2 response in Mecp2-null male mice. Studies were performed in B6.129P2(C)-Mecp2τm1.1Bird null males and heterozygous females. In an in situ preparation, seven of eight Mecp2-deficient heterozygous females showed arrest of phrenic nerve activity when arterial CO2 was lowered to 3%, whereas the wild-types maintained phrenic nerve amplitude at 53 ± 3% of maximal. In vivo plethysmography studies were used to determine CO2 chemosensitivity in null males. These mice were exposed sequentially to 1, 3 and 5% CO2. The percentage increase in minute ventilation in response to increased inspired CO2 was less in Mecp2−/y than in Mecp2+/y mice. Pretreatment with citalopram, a selective 5-HT reuptake inhibitor (2.5 mg kg−1 I.P.), 40 min prior to CO2 exposure, in Mecp2−/y mice resulted in an improvement in CO2 chemosensitivity to wild-type levels. These results suggest that decreased 5-HT in Mecp2-deficient mice reduces CO2 chemosensitivity, and restoring 5-HT levels can reverse this effect. PMID:23180809

Identification of biochemical adaptations in hyper- or hypocontractile hearts from phospholamban mutant mice by expression proteomics.

PubMed

Pan, Yan; Kislinger, Thomas; Gramolini, Anthony O; Zvaritch, Elena; Kranias, Evangelia G; MacLennan, David H; Emili, Andrew

2004-02-24

Phospholamban (PLN) is a critical regulator of cardiac contractility through its binding to and regulation of the activity of the sarco(endo)plasmic reticulum Ca2+ ATPase. To uncover biochemical adaptations associated with extremes of cardiac muscle contractility, we used high-throughput gel-free tandem MS to monitor differences in the relative abundance of membrane proteins in standard microsomal fractions isolated from the hearts of PLN-null mice (PLN-KO) with high contractility and from transgenic mice overexpressing a superinhibitory PLN mutant in a PLN-null background (I40A-KO) with diminished contractility. Significant differential expression was detected for a subset of the 782 proteins identified, including known membrane-associated biomarkers, components of signaling pathways, and previously uninvestigated proteins. Proteins involved in fat and carbohydrate metabolism and proteins linked to G protein-signaling pathways activating protein kinase C were enriched in I40A-KO cardiac muscle, whereas proteins linked to enhanced contractile function were enriched in PLN-KO mutant hearts. These data demonstrate that Ca2+ dysregulation, leading to elevated or depressed cardiac contractility, induces compensatory biochemical responses.

Enterocyte fatty acid-binding proteins (FABPs): different functions of liver and intestinal FABPs in the intestine.

PubMed

Gajda, Angela M; Storch, Judith

2015-02-01

Fatty acid-binding proteins (FABP) are highly abundant cytosolic proteins that are expressed in most mammalian tissues. In the intestinal enterocyte, both liver- (LFABP; FABP1) and intestinal FABPs (IFABP; FABP2) are expressed. These proteins display high-affinity binding for long-chain fatty acids (FA) and other hydrophobic ligands; thus, they are believed to be involved with uptake and trafficking of lipids in the intestine. In vitro studies have identified differences in ligand-binding stoichiometry and specificity, and in mechanisms of FA transfer to membranes, and it has been hypothesized that LFABP and IFABP have different functions in the enterocyte. Studies directly comparing LFABP- and IFABP-null mice have revealed markedly different phenotypes, indicating that these proteins indeed have different functions in intestinal lipid metabolism and whole body energy homeostasis. In this review, we discuss the evolving knowledge of the functions of LFABP and IFABP in the intestinal enterocyte. Copyright © 2014 Elsevier Ltd. All rights reserved.

ESCRT-Dependent Cell Death in a Caenorhabditis elegans Model of the Lysosomal Storage Disorder Mucolipidosis Type IV

PubMed Central

Huynh, Julie M.; Dang, Hope; Munoz-Tucker, Isabel A.; O’Ketch, Marvin; Liu, Ian T.; Perno, Savannah; Bhuyan, Natasha; Crain, Allison; Borbon, Ivan; Fares, Hanna

2016-01-01

Mutations in MCOLN1, which encodes the cation channel protein TRPML1, result in the neurodegenerative lysosomal storage disorder Mucolipidosis type IV. Mucolipidosis type IV patients show lysosomal dysfunction in many tissues and neuronal cell death. The ortholog of TRPML1 in Caenorhabditis elegans is CUP-5; loss of CUP-5 results in lysosomal dysfunction in many tissues and death of developing intestinal cells that results in embryonic lethality. We previously showed that a null mutation in the ATP-Binding Cassette transporter MRP-4 rescues the lysosomal defect and embryonic lethality of cup-5(null) worms. Here we show that reducing levels of the Endosomal Sorting Complex Required for Transport (ESCRT)-associated proteins DID-2, USP-50, and ALX-1/EGO-2, which mediate the final de-ubiquitination step of integral membrane proteins being sequestered into late endosomes, also almost fully suppresses cup-5(null) mutant lysosomal defects and embryonic lethality. Indeed, we show that MRP-4 protein is hypo-ubiquitinated in the absence of CUP-5 and that reducing levels of ESCRT-associated proteins suppresses this hypo-ubiquitination. Thus, increased ESCRT-associated de-ubiquitinating activity mediates the lysosomal defects and corresponding cell death phenotypes in the absence of CUP-5. PMID:26596346

FlnA binding to PACSIN2 F-BAR domain regulates membrane tubulation in megakaryocytes and platelets.

PubMed

Begonja, Antonija Jurak; Pluthero, Fred G; Suphamungmee, Worawit; Giannini, Silvia; Christensen, Hilary; Leung, Richard; Lo, Richard W; Nakamura, Fumihiko; Lehman, William; Plomann, Markus; Hoffmeister, Karin M; Kahr, Walter H A; Hartwig, John H; Falet, Hervé

2015-07-02

Bin-Amphiphysin-Rvs (BAR) and Fes-CIP4 homology BAR (F-BAR) proteins generate tubular membrane invaginations reminiscent of the megakaryocyte (MK) demarcation membrane system (DMS), which provides membranes necessary for future platelets. The F-BAR protein PACSIN2 is one of the most abundant BAR/F-BAR proteins in platelets and the only one reported to interact with the cytoskeletal and scaffold protein filamin A (FlnA), an essential regulator of platelet formation and function. The FlnA-PACSIN2 interaction was therefore investigated in MKs and platelets. PACSIN2 associated with FlnA in human platelets. The interaction required FlnA immunoglobulin-like repeat 20 and the tip of PACSIN2 F-BAR domain and enhanced PACSIN2 F-BAR domain membrane tubulation in vitro. Most human and wild-type mouse platelets had 1 to 2 distinct PACSIN2 foci associated with cell membrane GPIbα, whereas Flna-null platelets had 0 to 4 or more foci. Endogenous PACSIN2 and transfected enhanced green fluorescent protein-PACSIN2 were concentrated in midstage wild-type mouse MKs in a well-defined invagination of the plasma membrane reminiscent of the initiating DMS and dispersed in the absence of FlnA binding. The DMS appeared less well defined, and platelet territories were not readily visualized in Flna-null MKs. We conclude that the FlnA-PACSIN2 interaction regulates membrane tubulation in MKs and platelets and likely contributes to DMS formation. © 2015 by The American Society of Hematology.

GIGYF1/2 proteins use auxiliary sequences to selectively bind to 4EHP and repress target mRNA expression

PubMed Central

Peter, Daniel; Weber, Ramona; Sandmeir, Felix; Wohlbold, Lara; Helms, Sigrun; Bawankar, Praveen; Valkov, Eugene; Igreja, Cátia; Izaurralde, Elisa

2017-01-01

The eIF4E homologous protein (4EHP) is thought to repress translation by competing with eIF4E for binding to the 5′ cap structure of specific mRNAs to which it is recruited through interactions with various proteins, including the GRB10-interacting GYF (glycine–tyrosine–phenylalanine domain) proteins 1 and 2 (GIGYF1/2). Despite its similarity to eIF4E, 4EHP does not interact with eIF4G and therefore fails to initiate translation. In contrast to eIF4G, GIGYF1/2 bind selectively to 4EHP but not eIF4E. Here, we present crystal structures of the 4EHP-binding regions of GIGYF1 and GIGYF2 in complex with 4EHP, which reveal the molecular basis for the selectivity of the GIGYF1/2 proteins for 4EHP. Complementation assays in a GIGYF1/2-null cell line using structure-based mutants indicate that 4EHP requires interactions with GIGYF1/2 to down-regulate target mRNA expression. Our studies provide structural insights into the assembly of 4EHP–GIGYF1/2 repressor complexes and reveal that rather than merely facilitating 4EHP recruitment to transcripts, GIGYF1/2 proteins are required for repressive activity. PMID:28698298

Uncoupling phototoxicity-elicited neural dysmorphology and death by insidious function and selective impairment of Ran-binding protein 2 (Ranbp2).

PubMed

Cho, Kyoung-in; Haney, Victoria; Yoon, Dosuk; Hao, Yin; Ferreira, Paulo A

2015-12-21

Morphological disintegration of neurons is coupled invariably to neural death. In particular, disruption of outer segments of photoreceptor neurons triggers photoreceptor death regardless of the pathological stressors. We show that Ranbp2(-/-)::Tg-Ranbp2(CLDm-HA) mice with mutations in SUMO-binding motif (SBM) of cyclophilin-like domain (CLD) of Ran-binding protein 2 (Ranbp2) expressed in a null Ranbp2 background lack untoward effects in photoreceptors in the absence of light-stress. However, compared to wild type photoreceptors, light-stress elicits profound disintegration of outer segments of Ranbp2(-/-)::Tg-Ranbp2(CLDm-HA) with paradoxical age-dependent resistance of photoreceptors to death and genotype-independent activation of caspases. Ranbp2(-/-)::Tg-Ranbp2(CLDm-HA) exhibit photoreceptor death-independent changes in ubiquitin-proteasome system (UPS), but death-dependent increase of ubiquitin carrier protein 9(ubc9) levels. Hence, insidious functional impairment of SBM of Ranbp2's CLD promotes neuroprotection and uncoupling of photoreceptor degeneration and death against phototoxicity. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Interaction between cardiac myosin-binding protein C and formin Fhod3.

PubMed

Matsuyama, Sho; Kage, Yohko; Fujimoto, Noriko; Ushijima, Tomoki; Tsuruda, Toshihiro; Kitamura, Kazuo; Shiose, Akira; Asada, Yujiro; Sumimoto, Hideki; Takeya, Ryu

2018-05-08

Mutations in cardiac myosin-binding protein C (cMyBP-C) are a major cause of familial hypertrophic cardiomyopathy. Although cMyBP-C has been considered to regulate the cardiac function via cross-bridge arrangement at the C-zone of the myosin-containing A-band, the mechanism by which cMyBP-C functions remains unclear. We identified formin Fhod3, an actin organizer essential for the formation and maintenance of cardiac sarcomeres, as a cMyBP-C-binding protein. The cardiac-specific N-terminal Ig-like domain of cMyBP-C directly interacts with the cardiac-specific N-terminal region of Fhod3. The interaction seems to direct the localization of Fhod3 to the C-zone, since a noncardiac Fhod3 variant lacking the cMyBP-C-binding region failed to localize to the C-zone. Conversely, the cardiac variant of Fhod3 failed to localize to the C-zone in the cMyBP-C-null mice, which display a phenotype of hypertrophic cardiomyopathy. The cardiomyopathic phenotype of cMyBP-C-null mice was further exacerbated by Fhod3 overexpression with a defect of sarcomere integrity, whereas that was partially ameliorated by a reduction in the Fhod3 protein levels, suggesting that Fhod3 has a deleterious effect on cardiac function under cMyBP-C-null conditions where Fhod3 is aberrantly mislocalized. Together, these findings suggest the possibility that Fhod3 contributes to the pathogenesis of cMyBP-C-related cardiomyopathy and that Fhod3 is critically involved in cMyBP-C-mediated regulation of cardiac function via direct interaction.

Nrf2 deficiency improves glucose tolerance in mice fed a high-fat diet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yu-Kun Jennifer; Wu, Kai Connie; Liu, Jie

Nrf2, a master regulator of intracellular redox homeostasis, is indicated to participate in fatty acid metabolism in liver. However, its role in diet-induced obesity remains controversial. In the current study, genetically engineered Nrf2-null, wild-type (WT), and Nrf2-activated, Keap1-knockdown (K1-KD) mice were fed either a control or a high-fat Western diet (HFD) for 12 weeks. The results indicate that the absence or enhancement of Nrf2 activity did not prevent diet-induced obesity, had limited effects on lipid metabolism, but affected blood glucose homeostasis. Whereas the Nrf2-null mice were resistant to HFD-induced glucose intolerance, the Nrf2-activated K1-KD mice exhibited prolonged elevation of circulatingmore » glucose during a glucose tolerance test even on the control diet. Feeding a HFD did not activate the Nrf2 signaling pathway in mouse livers. Fibroblast growth factor 21 (Fgf21) is a liver-derived anti-diabetic hormone that exerts glucose- and lipid-lowering effects. Fgf21 mRNA and protein were both elevated in livers of Nrf2-null mice, and Fgf21 protein was lower in K1-KD mice than WT mice. The inverse correlation between Nrf2 activity and hepatic expression of Fgf21 might explain the improved glucose tolerance in Nrf2-null mice. Furthermore, a more oxidative cellular environment in Nrf2-null mice could affect insulin signaling in liver. For example, mRNA of insulin-like growth factor binding protein 1, a gene repressed by insulin in hepatocytes, was markedly elevated in livers of Nrf2-null mice. In conclusion, genetic alteration of Nrf2 does not prevent diet-induced obesity in mice, but deficiency of Nrf2 improves glucose homeostasis, possibly through its effects on Fgf21 and/or insulin signaling. -- Highlights: ► Nrf2 deficiency improves glucose tolerance in mice fed a high-fat diet. ► The anti-diabetic hormone, Fgf21, is highly expressed in livers of Nrf2-null mice. ► The absence of Nrf2 increases the insulin-regulated Igfbp-1 mRNA in liver. ► Nrf2 deficiency improves glucose tolerance by influencing Fgf21 and insulin signaling.« less

Hepatic effects of a methionine-choline-deficient diet in hepatocyte RXR{alpha}-null mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyamfi, Maxwell Afari; Tanaka, Yuji; He Lin

Retinoid X receptor-{alpha} (RXR{alpha}) is an obligate partner for several nuclear hormone receptors that regulate important physiological processes in the liver. In this study the impact of hepatocyte RXR{alpha} deficiency on methionine and choline deficient (MCD) diet-induced steatosis, oxidative stress, inflammation, and hepatic transporters gene expression were examined. The mRNA of sterol regulatory element-binding protein (SREBP)-regulated genes, important for lipid synthesis, were not altered in wild type (WT) mice, but were increased 2.0- to 5.4-fold in hepatocyte RXR{alpha}-null (H-RXR{alpha}-null) mice fed a MCD diet for 14 days. Furthermore, hepatic mRNAs and proteins essential for fatty acid {beta}-oxidation were not alteredmore » in WT mice, but were decreased in the MCD diet-fed H-RXR{alpha}-null mice, resulting in increased hepatic free fatty acid levels. Cyp2e1 enzyme activity and lipid peroxide levels were induced only in MCD-fed WT mice. In contrast, hepatic mRNA levels of pro-inflammatory factors were increased only in H-RXR{alpha}-null mice fed the MCD diet. Hepatic uptake transporters Oatp1a1 and Oatp1b2 mRNA levels were decreased in WT mice fed the MCD diet, whereas the efflux transporter Mrp4 was increased. However, in the H-RXR{alpha}-null mice, the MCD diet only moderately decreased Oatp1a1 and induced both Oatp1a4 and Mrp4 gene expression. Whereas the MCD diet increased serum bile acid levels and alkaline phosphatase activity in both WT and H-RXR{alpha}-null mice, serum ALT levels were induced (2.9-fold) only in the H-RXR{alpha}-null mice. In conclusion, these data suggest a critical role for RXR{alpha} in hepatic fatty acid homeostasis and protection against MCD-induced hepatocyte injury.« less

FABP-1 gene ablation impacts brain endocannabinoid system in male mice.

PubMed

Martin, Gregory G; Chung, Sarah; Landrock, Danilo; Landrock, Kerstin K; Huang, Huan; Dangott, Lawrence J; Peng, Xiaoxue; Kaczocha, Martin; Seeger, Drew R; Murphy, Eric J; Golovko, Mikhail Y; Kier, Ann B; Schroeder, Friedhelm

2016-08-01

Liver fatty acid-binding protein (FABP1, L-FABP) has high affinity for and enhances uptake of arachidonic acid (ARA, C20:4, n-6) which, when esterified to phospholipids, is the requisite precursor for synthesis of endocannabinoids (EC) such as arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). The brain derives most of its ARA from plasma, taking up ARA and transporting it intracellularly via cytosolic fatty acid-binding proteins (FABPs 3,5, and 7) localized within the brain. In contrast, the much more prevalent cytosolic FABP1 is not detectable in the brain but is instead highly expressed in the liver. Therefore, the possibility that FABP1 outside the central nervous system may regulate brain AEA and 2-AG was examined in wild-type (WT) and FABP1 null (LKO) male mice. LKO increased brain levels of AA-containing EC (AEA, 2-AG), correlating with increased free and total ARA in brain and serum. LKO also increased brain levels of non-ARA that contain potentiating endocannabinoids (EC*) such as oleoyl ethanolamide (OEA), PEA, 2-OG, and 2-PG. Concomitantly, LKO decreased serum total ARA-containing EC, but not non-ARA endocannabinoids. LKO did not elicit these changes in the brain EC and EC* as a result of compensatory up-regulation of brain protein levels of enzymes in EC synthesis (NAPEPLD, DAGLα) or cytosolic EC chaperone proteins (FABPs 3, 5, 7, SCP-2, HSP70), or cannabinoid receptors (CB1, TRVP1). These data show for the first time that the non-CNS fatty acid-binding protein FABP1 markedly affected brain levels of both ARA-containing endocannabinoids (AEA, 2-AG) as well as their non-ARA potentiating endocannabinoids. Fatty acid-binding protein-1 (FABP-1) is not detectable in brain but instead is highly expressed in liver. The possibility that FABP1 outside the central nervous system may regulate brain endocannabinoids arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) was examined in wild-type (WT) and FABP-1 null (LKO) male mice. LKO increased brain levels of arachidonic acid-containing endocannabinoids (AEA, 2-AG), correlating with increased free and total arachidonic acid in brain and serum. Read the Editorial Highlight for this article on page 371. © 2016 International Society for Neurochemistry.

Reduced expression of Na(v)1.6 sodium channels and compensation by Na(v)1.2 channels in mice heterozygous for a null mutation in Scn8a.

PubMed

Vega, Ana V; Henry, Diane L; Matthews, Gary

2008-09-05

The voltage-gated sodium channel alpha subunit Na(v)1.6, encoded by the Scn8a gene, accumulates at high density at mature nodes of Ranvier of myelinated axons, replacing the Na(v)1.2 channels found at nodes earlier in development. To investigate this preferential expression of Na(v)1.6 at adult nodes, we examined isoform-specific expression of sodium channels in mice heterozygous for a null mutation in Scn8a. Immunoblots from these +/- mice had 50% of the wild-type level of Na(v)1.6 protein, and their optic-nerve nodes of Ranvier had correspondingly less anti-Na(v)1.6 immunofluorescence. Protein level and nodal immunofluorescence of the Na(v)1.2 alpha subunit increased in Scn8a(+/-) mice, keeping total sodium channel expression approximately constant despite partial loss of Na(v)1.6 channels. The results are consistent with a model in which Na(v)1.6 and Na(v)1.2 compete for binding partners at sites of high channel density, such as nodes of Ranvier. We suggest that Na(v)1.6 channels normally occupy most of the molecular machinery responsible for channel clustering because they have higher binding affinity, and not because they are exclusively recognized by mechanisms for transport and insertion of sodium channels in myelinated axons. The reduced amount of Na(v)1.6 protein in Scn8a(+/-) mice is apparently insufficient to saturate the nodal binding sites, allowing Na(v)1.2 channels to compete more successfully.

Increased resistance to acetaminophen hepatotoxicity in mice lacking glutathione S-transferase Pi

PubMed Central

Henderson, Colin J.; Wolf, C. Roland; Kitteringham, Neil; Powell, Helen; Otto, Diana; Park, B. Kevin

2000-01-01

Overdose of acetaminophen, a widely used analgesic drug, can result in severe hepatotoxicity and is often fatal. This toxic reaction is associated with metabolic activation by the P450 system to form a quinoneimine metabolite, N-acetyl-p-benzoquinoneimine (NAPQI), which covalently binds to proteins and other macromolecules to cause cellular damage. At low doses, NAPQI is efficiently detoxified, principally by conjugation with glutathione, a reaction catalyzed in part by the glutathione S-transferases (GST), such as GST Pi. To assess the role of GST in acetaminophen hepatotoxicity, we examined acetaminophen metabolism and liver damage in mice nulled for GstP (GstP1/P2(−/−)). Contrary to our expectations, instead of being more sensitive, GstP null mice were highly resistant to the hepatotoxic effects of this compound. No significant differences between wild-type (GstP1/P2(+/+)) mice and GstP1/P2(−/−) nulls in either the rate or route of metabolism, particularly to glutathione conjugates, or in the levels of covalent binding of acetaminophen-reactive metabolites to cellular protein were observed. However, although a similar rapid depletion of hepatic reduced glutathione (GSH) was found in both GstP1/P2(+/+) and GstP1/P2(−/−) mice, GSH levels only recovered in the GstP1/P2(−/−) mice. These data demonstrate that GstP does not contribute in vivo to the formation of glutathione conjugates of acetaminophen but plays a novel and unexpected role in the toxicity of this compound. This study identifies new ways in which GST can modulate cellular sensitivity to toxic effects and suggests that the level of GST Pi may be an important and contributing factor in the sensitivity of patients with acetaminophen-induced hepatotoxicity. PMID:11058152

Metallothionein blocks oxidative DNA damage induced by acute inorganic arsenic exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Wei, E-mail: qu@niehs.nih.gov; Waalkes, Michael P.

We studied how protein metallothionein (MT) impacts arsenic-induced oxidative DNA damage (ODD) using cells that poorly express MT (MT-I/II double knockout embryonic cells; called MT-null cells) and wild-type (WT) MT competent cells. Arsenic (as NaAsO{sub 2}) was less cytolethal over 24 h in WT cells (LC{sub 50} = 11.0 ± 1.3 μM; mean ± SEM) than in MT-null cells (LC{sub 50} = 5.6 ± 1.2 μM). ODD was measured by the immuno-spin trapping method. Arsenic (1 or 5 μM; 24 h) induced much less ODD in WT cells (121% and 141% of control, respectively) than in MT-null cells (202% andmore » 260%). In WT cells arsenic caused concentration-dependent increases in MT expression (transcript and protein), and in the metal-responsive transcription factor-1 (MTF-1), which is required to induce the MT gene. In contrast, basal MT levels were not detectable in MT-null cells and unaltered by arsenic exposure. Transfection of MT-I gene into the MT-null cells markedly reduced arsenic-induced ODD levels. The transport genes, Abcc1 and Abcc2 were increased by arsenic in WT cells but either showed no or very limited increases in MT-null cells. Arsenic caused increases in oxidant stress defense genes HO-1 and GSTα2 in both WT and MT-null cells, but to much higher levels in WT cells. WT cells appear more adept at activating metal transport systems and oxidant response genes, although the role of MT in these responses is unclear. Overall, MT protects against arsenic-induced ODD in MT competent cells by potential sequestration of scavenging oxidant radicals and/or arsenic. - Highlights: • Metallothionein blocks arsenic toxicity. • Metallothionein reduces arsenic-induced DNA damage. • Metallothionein may bind arsenic or radicals produced by arsenic.« less

Hfq variant with altered RNA binding functions

PubMed Central

Ziolkowska, Katarzyna; Derreumaux, Philippe; Folichon, Marc; Pellegrini, Olivier; Régnier, Philippe; Boni, Irina V.; Hajnsdorf, Eliane

2006-01-01

The interaction between Hfq and RNA is central to multiple regulatory processes. Using site-directed mutagenesis, we have found a missense mutation in Hfq (V43R) which strongly affects2 the RNA binding capacity of the Hfq protein and its ability to stimulate poly(A) tail elongation by poly(A)-polymerase in vitro. In vivo, overexpression of this Hfq variant fails to stimulate rpoS–lacZ expression and does not restore a normal growth rate in hfq null mutant. Cells in which the wild-type gene has been replaced by the hfqV43R allele exhibit a phenotype intermediate between those of the wild-type and of the hfq minus or null strains. This missense mutation derepresses Hfq synthesis. However, not all Hfq functions are affected by this mutation. For example, HfqV43R represses OppA synthesis as strongly as the wild-type protein. The dominant negative effect of the V43R mutation over the wild-type allele suggests that hexamers containing variant and genuine subunits are presumably not functional. Finally, molecular dynamics studies indicate that the V43R substitution mainly changes the position of the K56 and Y55 side chains involved in the Hfq–RNA interaction but has probably no effect on the folding and the oligomerization of the protein. PMID:16449205

Impact of L-FABP and glucose on polyunsaturated fatty acid induction of PPARα-regulated β-oxidative enzymes

PubMed Central

Petrescu, Anca D.; Huang, Huan; Martin, Gregory G.; McIntosh, Avery L.; Storey, Stephen M.; Landrock, Danilo; Kier, Ann B.

2013-01-01

Liver fatty acid binding protein (L-FABP) is the major soluble protein that binds very-long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs) in hepatocytes. However, nothing is known about L-FABP's role in n-3 PUFA-mediated peroxisome proliferator activated receptor-α (PPARα) transcription of proteins involved in long-chain fatty acid (LCFA) β-oxidation. This issue was addressed in cultured primary hepatocytes from wild-type, L-FABP-null, and PPARα-null mice with these major findings: 1) PUFA-mediated increase in the expression of PPARα-regulated LCFA β-oxidative enzymes, LCFA/LCFA-CoA binding proteins (L-FABP, ACBP), and PPARα itself was L-FABP dependent; 2) PPARα transcription, robustly potentiated by high glucose but not maltose, a sugar not taken up, correlated with higher protein levels of these LCFA β-oxidative enzymes and with increased LCFA β-oxidation; and 3) high glucose altered the potency of n-3 relative to n-6 PUFA. This was not due to a direct effect of glucose on PPARα transcriptional activity nor indirectly through de novo fatty acid synthesis from glucose. Synergism was also not due to glucose impacting other signaling pathways, since it was observed only in hepatocytes expressing both L-FABP and PPARα. Ablation of L-FABP or PPARα as well as treatment with MK886 (PPARα inhibitor) abolished/reduced PUFA-mediated PPARα transcription of these genes, especially at high glucose. Finally, the PUFA-enhanced L-FABP distribution into nuclei with high glucose augmentation of the L-FABP/PPARα interaction reveals not only the importance of L-FABP for PUFA induction of PPARα target genes in fatty acid β-oxidation but also the significance of a high glucose enhancement effect in diabetes. PMID:23238934

Surfactant-Associated Protein A Provides Critical Immunoprotection in Neonatal Mice▿

PubMed Central

George, Caroline L. S.; Goss, Kelli L.; Meyerholz, David K.; Lamb, Fred S.; Snyder, Jeanne M.

2008-01-01

The collectins surfactant-associated protein A (SP-A) and SP-D are components of innate immunity that are present before birth. Both proteins bind pathogens and assist in clearing infection. The significance of SP-A and SP-D as components of the neonatal immune system has not been investigated. To determine the role of SP-A and SP-D in neonatal immunity, wild-type, SP-A null, and SP-D null mice were bred in a bacterium-laden environment (corn dust bedding) or in a semisterile environment (cellulose fiber bedding). When reared in the corn dust bedding, SP-A null pups had significant mortality (P < 0.001) compared to both wild-type and SP-D null pups exposed to the same environment. The mortality of the SP-A null pups was associated with significant gastrointestinal tract pathology but little lung pathology. Moribund SP-A null newborn mice exhibited Bacillus sp. and Enterococcus sp. peritonitis. When the mother or newborn produced SP-A, newborn survival was significantly improved (P < 0.05) compared to the results when there was a complete absence of SP-A in both the mother and the pup. Significant sources of SP-A likely to protect a newborn include the neonatal lung and gastrointestinal tract but not the lactating mammary tissue of the mother. Furthermore, exogenous SP-A delivered by mouth to newborn SP-A null pups with SP-A null mothers improved newborn survival in the corn dust environment. Therefore, a lack of SP-D did not affect newborn survival, while SP-A produced by either the mother or the pup or oral exogenous SP-A significantly reduced newborn mortality associated with environmentally induced infection in SP-A null newborns. PMID:17967856

Requirement for Pectin Methyl Esterase and Preference for Fragmented over Native Pectins for Wall-associated Kinase-activated, EDS1/PAD4-dependent Stress Response in Arabidopsis*

PubMed Central

Kohorn, Bruce D.; Kohorn, Susan L.; Saba, Nicholas J.; Martinez, Victoriano Meco

2014-01-01

The wall-associated kinases (WAKs) have a cytoplasmic protein kinase domain that spans the plasma membrane and binds pectin in the extracellular matrix of plants. WAKs are required for cell expansion during Arabidopsis seedling development but are also an integral part of the response to pathogens and stress that present oligogalacturonides (OGs), which subsequently bind to WAKs and activate a MPK6 (mitogen-activated protein kinase)-dependent pathway. It was unclear how WAKs distinguish native pectin polymers and OGs to activate one or the other of these two pathways. A dominant allele of WAK2 constitutively activates the stress response, and we show here that the effect is dependent upon EDS1 and PAD4, transcriptional activators involved in the pathogen response. Moreover, the WAK2 dominant allele is suppressed by a null allele of a pectin methyl esterase (PME3) whose activity normally leads to cross-linking of pectins in the cell wall. Although OGs activate a transcriptional response in wild type, the response is enhanced in a pme3/pme3 null, consistent with a competition by OG and native polymers for activation of WAKs. This provides a plausible mechanism for WAKs to distinguish an expansion from a stress pathway. PMID:24855660

Vsx2 Controls Eye Organogenesis and Retinal Progenitor Identity Via Homeodomain and Non-Homeodomain Residues Required for High Affinity DNA Binding

PubMed Central

Zou, Changjiang; Levine, Edward M.

2012-01-01

The homeodomain and adjacent CVC domain in the visual system homeobox (VSX) proteins are conserved from nematodes to humans. Humans with missense mutations in these regions of VSX2 have microphthalmia, suggesting both regions are critical for function. To assess this, we generated the corresponding mutations in mouse Vsx2. The homeodomain mutant protein lacked DNA binding activity and the knock-in mutant phenocopied the null mutant, ocular retardation J. The CVC mutant protein exhibited weakened DNA binding; and, although the corresponding knock-in allele was recessive, it unexpectedly caused the strongest phenotype, as indicated by severe microphthalmia and hyperpigmentation of the neural retina. This occurred through a cryptic transcriptional feedback loop involving the transcription factors Mitf and Otx1 and the Cdk inhibitor p27Kip1. Our data suggest that the phenotypic severity of the CVC mutant depends on the weakened DNA binding activity elicited by the CVC mutation and a previously unknown protein interaction between Vsx2 and its regulatory target Mitf. Our data also suggest that an essential function of the CVC domain is to assist the homeodomain in high-affinity DNA binding, which is required for eye organogenesis and unhindered execution of the retinal progenitor program in mammals. Finally, the genetic and phenotypic behaviors of the CVC mutation suggest it has the characteristics of a recessive neomorph, a rare type of genetic allele. PMID:23028343

Normal myoblast fusion requires myoferlin

PubMed Central

Doherty, Katherine R.; Cave, Andrew; Davis, Dawn Belt; Delmonte, Anthony J.; Posey, Avery; Earley, Judy U.; Hadhazy, Michele; McNally, Elizabeth M.

2014-01-01

Summary Muscle growth occurs during embryonic development and continues in adult life as regeneration. During embryonic muscle growth and regeneration in mature muscle, singly nucleated myoblasts fuse to each other to form myotubes. In muscle growth, singly nucleated myoblasts can also fuse to existing large, syncytial myofibers as a mechanism of increasing muscle mass without increasing myofiber number. Myoblast fusion requires the alignment and fusion of two apposed lipid bilayers. The repair of muscle plasma membrane disruptions also relies on the fusion of two apposed lipid bilayers. The protein dysferlin, the product of the Limb Girdle Muscular Dystrophy type 2 locus, has been shown to be necessary for efficient, calcium-sensitive, membrane resealing. We now show that the related protein myoferlin is highly expressed in myoblasts undergoing fusion, and is expressed at the site of myoblasts fusing to myotubes. Like dysferlin, we found that myoferlin binds phospholipids in a calcium-sensitive manner that requires the first C2A domain. We generated mice with a null allele of myoferlin. Myoferlin null myoblasts undergo initial fusion events, but they form large myotubes less efficiently in vitro, consistent with a defect in a later stage of myogenesis. In vivo, myoferlin null mice have smaller muscles than controls do, and myoferlin null muscle lacks large diameter myofibers. Additionally, myoferlin null muscle does not regenerate as well as wild-type muscle does, and instead displays a dystrophic phenotype. These data support a role for myoferlin in the maturation of myotubes and the formation of large myotubes that arise from the fusion of myoblasts to multinucleate myotubes. PMID:16280346

Fe65 is required for Tip60-directed histone H4 acetylation at DNA strand breaks

PubMed Central

Stante, Maria; Minopoli, Giuseppina; Passaro, Fabiana; Raia, Maddalena; Vecchio, Luigi Del; Russo, Tommaso

2009-01-01

Fe65 is a binding partner of the Alzheimer's β-amyloid precursor protein APP. The possible involvement of this protein in the cellular response to DNA damage was suggested by the observation that Fe65 null mice are more sensitive to genotoxic stress than WT counterpart. Fe65 associated with chromatin under basal conditions and its involvement in DNA damage repair requires this association. A known partner of Fe65 is the histone acetyltransferase Tip60. Considering the crucial role of Tip60 in DNA repair, we explored the hypothesis that the phenotype of Fe65 null cells depended on its interaction with Tip60. We demonstrated that Fe65 knockdown impaired recruitment of Tip60-TRRAP complex to DNA double strand breaks and decreased histone H4 acetylation. Accordingly, the efficiency of DNA repair was decreased upon Fe65 suppression. To explore whether APP has a role in this mechanism, we analyzed a Fe65 mutant unable to bind to APP. This mutant failed to rescue the phenotypes of Fe65 null cells; furthermore, APP/APLP2 suppression results in the impairment of recruitment of Tip60-TRRAP complex to DNA double strand breaks, decreased histone H4 acetylation and repair efficiency. On these bases, we propose that Fe65 and its interaction with APP play an important role in the response to DNA damage by assisting the recruitment of Tip60-TRRAP to DNA damage sites. PMID:19282473

GNL3L Inhibits Estrogen Receptor-Related Protein Activities by Competing for Coactivator Binding

PubMed Central

Yasumoto, Hiroaki; Meng, Lingjun; Lin, Tao; Zhu, Qubo; Tsai, Robert Y.L.

2010-01-01

Summary Guanine-nucleotide binding protein 3-like (GNL3L) is the closest homologue of a stem cell-enriched factor nucleostemin in vertebrates. They share the same yeast orthologue, Grn1p, but only GNL3L can rescue the growth-deficient phenotype in Grn1p-null yeasts. To determine the unique function of GNL3L, we identified estrogen receptor-related protein-γ (ERRγ) as a GNL3L-specific binding protein. GNL3L and ERRγ are coexpressed in the eye, kidney and muscle, and co-reside in the nucleoplasm. The interaction between GNL3L and ERRγ requires the intermediate domain of GNL3L and the AF2-domain of ERRγ. Gain- and loss-of-function experiments show that GNL3L can inhibit the transcriptional activities of ERR genes in a cell-based reporter system, which does not require the nucleolar localization of GNL3L. We further demonstrate that GNL3L is able to reduce the steroid receptor coactivator (SRC) binding and the SRC-mediated transcriptional coactivation of ERRγ. This work reveals a novel mechanism that negatively regulates the transcriptional function of ERRγ by GNL3L through coactivator competition. PMID:17623774

The vitamin D receptor functions as a transcription regulator in the absence of 1,25-dihydroxyvitamin D3.

PubMed

Lee, Seong Min; Pike, J Wesley

2016-11-01

The vitamin D receptor (VDR) is a critical mediator of the biological actions of 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ). As a nuclear receptor, ligand activation of the VDR leads to the protein's binding to specific sites on the genome that results in the modulation of target gene expression. The VDR is also known to play a role in the hair cycle, an action that appears to be 1,25(OH) 2 D 3 -independent. Indeed, in the absence of the VDR as in hereditary 1,25-dihydroxyvitamin D resistant rickets (HVDRR) both skin defects and alopecia emerge. Recently, we generated a mouse model of HVDRR without alopecia wherein a mutant human VDR lacking 1,25(OH) 2 D 3 -binding activity was expressed in the absence of endogenous mouse VDR. While 1,25(OH) 2 D 3 failed to induce gene expression in these mice, resulting in an extensive skeletal phenotype, the receptor was capable of restoring normal hair cycling. We also noted a level of secondary hyperparathyroidism that was much higher than that seen in the VDR null mouse and was associated with an exaggerated bone phenotype as well. This suggested that the VDR might play a role in parathyroid hormone (PTH) regulation independent of 1,25(OH) 2 D 3 . To evaluate this hypothesis further, we contrasted PTH levels in the HVDRR mouse model with those seen in Cyp27b1 null mice where the VDR was present but the hormone was absent. The data revealed that PTH was indeed higher in Cyp27b1 null mice compared to VDR null mice. To evaluate the mechanism of action underlying such a hypothesis, we measured the expression levels of a number of VDR target genes in the duodena of wildtype mice and in transgenic mice expressing either normal or hormone-binding deficient mutant VDRs. We also compared expression levels of these genes between VDR null mice and Cyp27b1 null mice. In a subset of cases, the expression of VDR target genes was lower in mice containing the VDR as opposed to mice that did not. We suggest that the VDR may function as a selective suppressor/de-repressor of gene expression in the absence of 1,25(OH) 2 D 3 . Copyright © 2015 Elsevier Ltd. All rights reserved.

In Vivo, Villin Is Required for Ca2+-Dependent F-Actin Disruption in Intestinal Brush Borders

PubMed Central

Ferrary, Evelyne; Cohen-Tannoudji, Michel; Pehau-Arnaudet, Gérard; Lapillonne, Alexandre; Athman, Rafika; Ruiz, Tereza; Boulouha, Lilia; El Marjou, Fatima; Doye, Anne; Fontaine, Jean-Jacques; Antony, Claude; Babinet, Charles; Louvard, Daniel; Jaisser, Frédéric; Robine, Sylvie

1999-01-01

Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca2+-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca2+ differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca2+, whereas Ca2+ had no effect in villin-null isolates. Moreover, increase in intracellular Ca2+ by serosal carbachol or mucosal Ca2+ ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 ± 9.6%, compared with wild-type mice, 70 ± 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury. PMID:10459016

Fasting Induces Nuclear Factor E2-Related Factor 2 and ATP-Binding Cassette Transporters via Protein Kinase A and Sirtuin-1 in Mouse and Human

PubMed Central

Kulkarni, Supriya R.; Donepudi, Ajay C.; Xu, Jialin; Wei, Wei; Cheng, Qiuqiong C.; Driscoll, Maureen V.; Johnson, Delinda A.; Johnson, Jeffrey A.; Li, Xiaoling

2014-01-01

Abstract Aims: The purpose of this study was to determine whether 3′-5′-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) and Sirtuin-1 (SIRT1) dependent mechanisms modulate ATP-binding Cassette (ABC) transport protein expression. ABC transport proteins (ABCC2–4) are essential for chemical elimination from hepatocytes and biliary excretion. Nuclear factor-E2 related-factor 2 (NRF2) is a transcription factor that mediates ABCC induction in response to chemical inducers and liver injury. However, a role for NRF2 in the regulation of transporter expression in nonchemical models of liver perturbation is largely undescribed. Results: Here we show that fasting increased NRF2 target gene expression through NRF2- and SIRT1–dependent mechanisms. In intact mouse liver, fasting induces NRF2 target gene expression by at least 1.5 to 5-fold. In mouse and human hepatocytes, treatment with 8-Bromoadenosine-cAMP, a cAMP analogue, increased NRF2 target gene expression and antioxidant response element activity, which was decreased by the PKA inhibitor, H-89. Moreover, fasting induced NRF2 target gene expression was decreased in liver and hepatocytes of SIRT1 liver-specific null mice and NRF2-null mice. Lastly, NRF2 and SIRT1 were recruited to MAREs and Antioxidant Response Elements (AREs) in the human ABCC2 promoter. Innovation: Oxidative stress mediated NRF2 activation is well described, yet the influence of basic metabolic processes on NRF2 activation is just emerging. Conclusion: The current data point toward a novel role of nutrient status in regulation of NRF2 activity and the antioxidant response, and indicates that cAMP/PKA and SIRT1 are upstream regulators for fasting-induced activation of the NRF2-ARE pathway. Antioxid. Redox Signal. 20, 15–30. PMID:23725046

Zn2+ Uptake in Streptococcus pyogenes: Characterization of adcA and lmb Null Mutants.

PubMed

Tedde, Vittorio; Rosini, Roberto; Galeotti, Cesira L

2016-01-01

An effective regulation of metal ion homeostasis is essential for the growth of microorganisms in any environment and in pathogenic bacteria is strongly associated with their ability to invade and colonise their hosts. To gain a better insight into zinc acquisition in Group A Streptococcus (GAS) we characterized null deletion mutants of the adcA and lmb genes of Streptococcus pyogenes strain MGAS5005 encoding the orthologues of AdcA and AdcAII, the two surface lipoproteins with partly redundant roles in zinc homeostasis in Streptococcus pneumoniae. Null adcA and lmb mutants were analysed for their capability to grow in zinc-depleted conditions and were found to be more susceptible to zinc starvation, a phenotype that could be rescued by the addition of Zn2+ ions to the growth medium. Expression of AdcA, Lmb and HtpA, the polyhistidine triad protein encoded by the gene adjacent to lmb, during growth under conditions of limited zinc availability was examined by Western blot analysis in wild type and null mutant strains. In the wild type strain, AdcA was always present with little variation in expression levels between conditions of excess or limited zinc availability. In contrast, Lmb and HtpA were expressed at detectable levels only during growth in the presence of low zinc concentrations or in the null adcA mutant, when expression of lmb is required to compensate for the lack of adcA expression. In the latter case, Lmb and HtpA were overexpressed by several fold, thus indicating that also in GAS AdcA is a zinc-specific importer and, although it shares this function with Lmb, the two substrate-binding proteins do not show fully overlapping roles in zinc homeostasis.

Absence of suppressor of cytokine signalling 3 reduces self-renewal and promotes differentiation in murine embryonic stem cells.

PubMed

Forrai, Ariel; Boyle, Kristy; Hart, Adam H; Hartley, Lynne; Rakar, Steven; Willson, Tracy A; Simpson, Ken M; Roberts, Andrew W; Alexander, Warren S; Voss, Anne K; Robb, Lorraine

2006-03-01

Leukemia inhibitory factor (LIF) is required to maintain pluripotency and permit self-renewal of murine embryonic stem (ES) cells. LIF binds to a receptor complex of LIFR-beta and gp130 and signals via the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, with signalling attenuated by suppressor of cytokine signalling (SOCS) proteins. Recent in vivo studies have highlighted the role of SOCS-3 in the negative regulation of signalling via gp130. To determine the role of SOCS-3 in ES cell biology, SOCS-3-null ES cell lines were generated. When cultured in LIF levels that sustain self-renewal of wild-type cells, SOCS-3-null ES cell lines exhibited less self-renewal and greater differentiation into primitive endoderm. The absence of SOCS-3 enhanced JAK-STAT and extracellular signal-related kinase 1/2 (ERK-1/2)-mitogen-activated protein kinase (MAPK) signal transduction via gp130, with higher levels of phosphorylated STAT-1, STAT-3, SH-2 domain-containing cytoplasmic protein tyrosine phosphatase 2 (SHP-2), and ERK-1/2 in steady state and in response to LIF stimulation. Attenuation of ERK signalling by the addition of MAPK/ERK kinase (MEK) inhibitors to SOCS-3-null ES cell cultures rescued the differentiation phenotype, but did not restore proliferation to wild-type levels. In summary, SOCS-3 plays a crucial role in the regulation of the LIF signalling pathway in murine ES cells. Its absence perturbs the balance between activation of the JAK-STAT and SHP-2-ERK-1/2-MAPK pathways, resulting in less self-renewal and a greater potential for differentiation into the primitive endoderm lineage.

Uncoupling Lipid Metabolism from Inflammation through Fatty Acid Binding Protein-Dependent Expression of UCP2

PubMed Central

Xu, Hongliang; Hertzel, Ann V.; Steen, Kaylee A.; Wang, Qigui; Suttles, Jill

2015-01-01

Chronic inflammation in obese adipose tissue is linked to endoplasmic reticulum (ER) stress and systemic insulin resistance. Targeted deletion of the murine fatty acid binding protein (FABP4/aP2) uncouples obesity from inflammation although the mechanism underlying this finding has remained enigmatic. Here, we show that inhibition or deletion of FABP4/aP2 in macrophages results in increased intracellular free fatty acids (FFAs) and elevated expression of uncoupling protein 2 (UCP2) without concomitant increases in UCP1 or UCP3. Silencing of UCP2 mRNA in FABP4/aP2-deficient macrophages negated the protective effect of FABP loss and increased ER stress in response to palmitate or lipopolysaccharide (LPS). Pharmacologic inhibition of FABP4/aP2 with the FABP inhibitor HTS01037 also upregulated UCP2 and reduced expression of BiP, CHOP, and XBP-1s. Expression of native FABP4/aP2 (but not the non-fatty acid binding mutant R126Q) into FABP4/aP2 null cells reduced UCP2 expression, suggesting that the FABP-FFA equilibrium controls UCP2 expression. FABP4/aP2-deficient macrophages are resistant to LPS-induced mitochondrial dysfunction and exhibit decreased mitochondrial protein carbonylation and UCP2-dependent reduction in intracellular reactive oxygen species. These data demonstrate that FABP4/aP2 directly regulates intracellular FFA levels and indirectly controls macrophage inflammation and ER stress by regulating the expression of UCP2. PMID:25582199

Caveolin-1-deficient mice show accelerated mammary gland development during pregnancy, premature lactation, and hyperactivation of the Jak-2/STAT5a signaling cascade.

PubMed

Park, David S; Lee, Hyangkyu; Frank, Philippe G; Razani, Babak; Nguyen, Andrew V; Parlow, Albert F; Russell, Robert G; Hulit, James; Pestell, Richard G; Lisanti, Michael P

2002-10-01

It is well established that mammary gland development and lactation are tightly controlled by prolactin signaling. Binding of prolactin to its cognate receptor (Prl-R) leads to activation of the Jak-2 tyrosine kinase and the recruitment/tyrosine phosphorylation of STAT5a. However, the mechanisms for attenuating the Prl-R/Jak-2/STAT5a signaling cascade are just now being elucidated. Here, we present evidence that caveolin-1 functions as a novel suppressor of cytokine signaling in the mammary gland, akin to the SOCS family of proteins. Specifically, we show that caveolin-1 expression blocks prolactin-induced activation of a STAT5a-responsive luciferase reporter in mammary epithelial cells. Furthermore, caveolin-1 expression inhibited prolactin-induced STAT5a tyrosine phosphorylation and DNA binding activity, suggesting that caveolin-1 may negatively regulate the Jak-2 tyrosine kinase. Because the caveolin-scaffolding domain bears a striking resemblance to the SOCS pseudosubstrate domain, we examined whether Jak-2 associates with caveolin-1. In accordance with this homology, we demonstrate that Jak-2 cofractionates and coimmunoprecipitates with caveolin-1. We next tested the in vivo relevance of these findings using female Cav-1 (-/-) null mice. If caveolin-1 normally functions as a suppressor of cytokine signaling in the mammary gland, then Cav-1 null mice should show premature development of the lobuloalveolar compartment because of hyperactivation of the prolactin signaling cascade via disinhibition of Jak-2. In accordance with this prediction, Cav-1 null mice show accelerated development of the lobuloalveolar compartment, premature milk production, and hyperphosphorylation of STAT5a (pY694) at its Jak-2 phosphorylation site. In addition, the Ras-p42/44 MAPK cascade is hyper-activated. Because a similar premature lactation phenotype is observed in SOCS1 (-/-) null mice, we conclude that caveolin-1 is a novel suppressor of cytokine signaling.

eIF4A RNA Helicase Associates with Cyclin-Dependent Protein Kinase A in Proliferating Cells and Is Modulated by Phosphorylation1[OPEN

PubMed Central

Bush, Maxwell S.; Pierrat, Olivier; Nibau, Candida; Mikitova, Veronika; Zheng, Tao; Corke, Fiona M. K.; Mayberry, Laura K.; Browning, Karen S.

2016-01-01

Eukaryotic initiation factor 4A (eIF4A) is a highly conserved RNA-stimulated ATPase and helicase involved in the initiation of messenger RNA translation. Previously, we found that eIF4A interacts with cyclin-dependent kinase A (CDKA), the plant ortholog of mammalian CDK1. Here, we show that this interaction occurs only in proliferating cells where the two proteins coassociate with 5′-cap-binding protein complexes, eIF4F or the plant-specific eIFiso4F. CDKA phosphorylates eIF4A on a conserved threonine residue (threonine-164) within the RNA-binding motif 1b TPGR. In vivo, a phospho-null (APGR) variant of the Arabidopsis (Arabidopsis thaliana) eIF4A1 protein retains the ability to functionally complement a mutant (eif4a1) plant line lacking eIF4A1, whereas a phosphomimetic (EPGR) variant fails to complement. The phospho-null variant (APGR) rescues the slow growth rate of roots and rosettes, together with the ovule-abortion and late-flowering phenotypes. In vitro, wild-type recombinant eIF4A1 and its phospho-null variant both support translation in cell-free wheat germ extracts dependent upon eIF4A, but the phosphomimetic variant does not support translation and also was deficient in ATP hydrolysis and helicase activity. These observations suggest a mechanism whereby CDK phosphorylation has the potential to down-regulate eIF4A activity and thereby affect translation. PMID:27388680

Requirement for pectin methyl esterase and preference for fragmented over native pectins for wall-associated kinase-activated, EDS1/PAD4-dependent stress response in Arabidopsis.

PubMed

Kohorn, Bruce D; Kohorn, Susan L; Saba, Nicholas J; Martinez, Victoriano Meco

2014-07-04

The wall-associated kinases (WAKs) have a cytoplasmic protein kinase domain that spans the plasma membrane and binds pectin in the extracellular matrix of plants. WAKs are required for cell expansion during Arabidopsis seedling development but are also an integral part of the response to pathogens and stress that present oligogalacturonides (OGs), which subsequently bind to WAKs and activate a MPK6 (mitogen-activated protein kinase)-dependent pathway. It was unclear how WAKs distinguish native pectin polymers and OGs to activate one or the other of these two pathways. A dominant allele of WAK2 constitutively activates the stress response, and we show here that the effect is dependent upon EDS1 and PAD4, transcriptional activators involved in the pathogen response. Moreover, the WAK2 dominant allele is suppressed by a null allele of a pectin methyl esterase (PME3) whose activity normally leads to cross-linking of pectins in the cell wall. Although OGs activate a transcriptional response in wild type, the response is enhanced in a pme3/pme3 null, consistent with a competition by OG and native polymers for activation of WAKs. This provides a plausible mechanism for WAKs to distinguish an expansion from a stress pathway. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

The unique GGA clathrin adaptor of Drosophila melanogaster is not essential.

PubMed

Luan, Shan; Ilvarsonn, Anne M; Eissenberg, Joel C

2012-01-01

The Golgi-localized, γ-ear-containing, ARF binding proteins (GGAs) are a highly conserved family of monomeric clathrin adaptor proteins implicated in clathrin-mediated protein sorting between the trans-Golgi network and endosomes. GGA RNAi knockdowns in Drosophila have resulted in conflicting data concerning whether the Drosophila GGA (dGGA) is essential. The goal of this study was to define the null phenotype for the unique Drosophila GGA. We describe two independently derived dGGA mutations. Neither allele expresses detectable dGGA protein. Homozygous and hemizygous flies with each allele are viable and fertile. In contrast to a previous report using RNAi knockdown, GGA mutant flies show no evidence of age-dependent retinal degeneration or cathepsin missorting. Our results demonstrate that several of the previous RNAi knockdown phenotypes were the result of off-target effects. However, GGA null flies are hypersensitive to dietary chloroquine and to starvation, implicating GGA in lysosomal function and autophagy.

Reep1 null mice reveal a converging role for hereditary spastic paraplegia proteins in lipid droplet regulation.

PubMed

Renvoisé, Benoît; Malone, Brianna; Falgairolle, Melanie; Munasinghe, Jeeva; Stadler, Julia; Sibilla, Caroline; Park, Seong H; Blackstone, Craig

2016-12-01

Hereditary spastic paraplegias (HSPs; SPG1-76 plus others) are length-dependent disorders affecting long corticospinal axons, and the most common autosomal dominant forms are caused by mutations in genes that encode the spastin (SPG4), atlastin-1 (SPG3A) and REEP1 (SPG31) proteins. These proteins bind one another and shape the tubular endoplasmic reticulum (ER) network throughout cells. They also are involved in lipid droplet formation, enlargement, or both in cells, though mechanisms remain unclear. Here we have identified evidence of partial lipoatrophy in Reep1 null mice in addition to prominent spastic paraparesis. Furthermore, Reep1-/- embryonic fibroblasts and neurons in the cerebral cortex both show lipid droplet abnormalities. The apparent partial lipodystrophy in Reep1 null mice, although less severe, is reminiscent of the lipoatrophy phenotype observed in the most common form of autosomal recessive lipodystrophy, Berardinelli-Seip congenital lipodystrophy. Berardinelli-Seip lipodystrophy is caused by autosomal recessive mutations in the BSCL2 gene that encodes an ER protein, seipin, that is also mutated in the autosomal dominant HSP SPG17 (Silver syndrome). Furthermore, REEP1 co-immunoprecipitates with seipin in cells. This strengthens the link between alterations in ER morphogenesis and lipid abnormalities, with important pathogenic implications for the most common forms of HSP. Published by Oxford University Press 2016. This work is written by US Government employees and is in the public domain in the US.

In vivo neuronal function of the fragile X mental retardation protein is regulated by phosphorylation

PubMed Central

Coffee, R. Lane; Williamson, Ashley J.; Adkins, Christopher M.; Gray, Marisa C.; Page, Terry L.; Broadie, Kendal

2012-01-01

Fragile X syndrome (FXS), caused by loss of the Fragile X Mental Retardation 1 (FMR1) gene product (FMRP), is the most common heritable cause of intellectual disability and autism spectrum disorders. It has been long hypothesized that the phosphorylation of serine 500 (S500) in human FMRP controls its function as an RNA-binding translational repressor. To test this hypothesis in vivo, we employed neuronally targeted expression of three human FMR1 transgenes, including wild-type (hFMR1), dephosphomimetic (S500A-hFMR1) and phosphomimetic (S500D-hFMR1), in the Drosophila FXS disease model to investigate phosphorylation requirements. At the molecular level, dfmr1 null mutants exhibit elevated brain protein levels due to loss of translational repressor activity. This defect is rescued for an individual target protein and across the population of brain proteins by the phosphomimetic, whereas the dephosphomimetic phenocopies the null condition. At the cellular level, dfmr1 null synapse architecture exhibits increased area, branching and bouton number. The phosphomimetic fully rescues these synaptogenesis defects, whereas the dephosphomimetic provides no rescue. The presence of Futsch-positive (microtubule-associated protein 1B) supernumerary microtubule loops is elevated in dfmr1 null synapses. The human phosphomimetic restores normal Futsch loops, whereas the dephosphomimetic provides no activity. At the behavioral level, dfmr1 null mutants exhibit strongly impaired olfactory associative learning. The human phosphomimetic targeted only to the brain-learning center restores normal learning ability, whereas the dephosphomimetic provides absolutely no rescue. We conclude that human FMRP S500 phosphorylation is necessary for its in vivo function as a neuronal translational repressor and regulator of synaptic architecture, and for the manifestation of FMRP-dependent learning behavior. PMID:22080836

Characterisation of a DNA sequence element that directs Dictyostelium stalk cell-specific gene expression.

PubMed

Ceccarelli, A; Zhukovskaya, N; Kawata, T; Bozzaro, S; Williams, J

2000-12-01

The ecmB gene of Dictyostelium is expressed at culmination both in the prestalk cells that enter the stalk tube and in ancillary stalk cell structures such as the basal disc. Stalk tube-specific expression is regulated by sequence elements within the cap-site proximal part of the promoter, the stalk tube (ST) promoter region. Dd-STATa, a member of the STAT transcription factor family, binds to elements present in the ST promoter-region and represses transcription prior to entry into the stalk tube. We have characterised an activatory DNA sequence element, that lies distal to the repressor elements and that is both necessary and sufficient for expression within the stalk tube. We have mapped this activator to a 28 nucleotide region (the 28-mer) within which we have identified a GA-containing sequence element that is required for efficient gene transcription. The Dd-STATa protein binds to the 28-mer in an in vitro binding assay, and binding is dependent upon the GA-containing sequence. However, the ecmB gene is expressed in a Dd-STATa null mutant, therefore Dd-STATa cannot be responsible for activating the 28-mer in vivo. Instead, we identified a distinct 28-mer binding activity in nuclear extracts from the Dd-STATa null mutant, the activity of this GA binding activity being largely masked in wild type extracts by the high affinity binding of the Dd-STATa protein. We suggest, that in addition to the long range repression exerted by binding to the two known repressor sites, Dd-STATa inhibits transcription by direct competition with this putative activator for binding to the GA sequence.

Comparative Proteomic Analysis of Normal and Collagen IX Null Mouse Cartilage Reveals Altered Extracellular Matrix Composition and Novel Components of the Collagen IX Interactome*

PubMed Central

Brachvogel, Bent; Zaucke, Frank; Dave, Keyur; Norris, Emma L.; Stermann, Jacek; Dayakli, Münire; Koch, Manuel; Gorman, Jeffrey J.; Bateman, John F.; Wilson, Richard

2013-01-01

The cartilage extracellular matrix is essential for endochondral bone development and joint function. In addition to the major aggrecan/collagen II framework, the interacting complex of collagen IX, matrilin-3, and cartilage oligomeric matrix protein (COMP) is essential for cartilage matrix stability, as mutations in Col9a1, Col9a2, Col9a3, Comp, and Matn3 genes cause multiple epiphyseal dysplasia, in which patients develop early onset osteoarthritis. In mice, collagen IX ablation results in severely disturbed growth plate organization, hypocellular regions, and abnormal chondrocyte shape. This abnormal differentiation is likely to involve altered cell-matrix interactions but the mechanism is not known. To investigate the molecular basis of the collagen IX null phenotype we analyzed global differences in protein abundance between wild-type and knock-out femoral head cartilage by capillary HPLC tandem mass spectrometry. We identified 297 proteins in 3-day cartilage and 397 proteins in 21-day cartilage. Components that were differentially abundant between wild-type and collagen IX-deficient cartilage included 15 extracellular matrix proteins. Collagen IX ablation was associated with dramatically reduced COMP and matrilin-3, consistent with known interactions. Matrilin-1, matrilin-4, epiphycan, and thrombospondin-4 levels were reduced in collagen IX null cartilage, providing the first in vivo evidence for these proteins belonging to the collagen IX interactome. Thrombospondin-4 expression was reduced at the mRNA level, whereas matrilin-4 was verified as a novel collagen IX-binding protein. Furthermore, changes in TGFβ-induced protein βig-h3 and fibronectin abundance were found in the collagen IX knock-out but not associated with COMP ablation, indicating specific involvement in the abnormal collagen IX null cartilage. In addition, the more widespread expression of collagen XII in the collagen IX-deficient cartilage suggests an attempted compensatory response to the absence of collagen IX. Our differential proteomic analysis of cartilage is a novel approach to identify candidate matrix protein interactions in vivo, underpinning further analysis of mutant cartilage lacking other matrix components or harboring disease-causing mutations. PMID:23530037

The E1 beta-subunit of pyruvate dehydrogenase is surface-expressed in Lactobacillus plantarum and binds fibronectin.

PubMed

Vastano, Valeria; Salzillo, Marzia; Siciliano, Rosa A; Muscariello, Lidia; Sacco, Margherita; Marasco, Rosangela

2014-01-01

Lactobacillus plantarum is among the species with a probiotic activity. Adhesion of probiotic bacteria to host tissues is an important principle for strain selection, because it represents a crucial step in the colonization process of either pathogens or commensals. Most bacterial adhesins are proteins, and a major target for them is fibronectin, an extracellular matrix glycoprotein. In this study we demonstrate that PDHB, a component of the pyruvate dehydrogenase complex, is a factor contributing to fibronectin-binding in L. plantarum LM3. By means of fibronectin overlay immunoblotting assay, we identified a L. plantarum LM3 surface protein with apparent molecular mass of 35 kDa. Mass spectrometric analysis shows that this protein is the pyruvate dehydrogenase E1 beta-subunit (PDHB). The corresponding pdhB gene is located in a 4-gene cluster encoding pyruvate dehydrogenase. In LM3-B1, carrying a null mutation in pdhB, the 35 kDa adhesin was not anymore detectable by immunoblotting assay. Nevertheless, the pdhB null mutation did not abolish pdhA, pdhC, and pdhD transcription in LM3-B1. By adhesion assays, we show that LM3-B1 cells bind to immobilized fibronectin less efficiently than wild type cells. Moreover, we show that pdhB expression is negatively regulated by the CcpA protein and is induced by bile. Copyright © 2013. Published by Elsevier GmbH.

Collagenase-3 binds to a specific receptor and requires the low density lipoprotein receptor-related protein for internalization

NASA Technical Reports Server (NTRS)

Barmina, O. Y.; Walling, H. W.; Fiacco, G. J.; Freije, J. M.; Lopez-Otin, C.; Jeffrey, J. J.; Partridge, N. C.

1999-01-01

We have previously identified a specific receptor for collagenase-3 that mediates the binding, internalization, and degradation of this ligand in UMR 106-01 rat osteoblastic osteosarcoma cells. In the present study, we show that collagenase-3 binding is calcium-dependent and occurs in a variety of cell types, including osteoblastic and fibroblastic cells. We also present evidence supporting a two-step mechanism of collagenase-3 binding and internalization involving both a specific collagenase-3 receptor and the low density lipoprotein receptor-related protein. Ligand blot analysis shows that (125)I-collagenase-3 binds specifically to two proteins ( approximately 170 kDa and approximately 600 kDa) present in UMR 106-01 cells. Western blotting identified the 600-kDa protein as the low density lipoprotein receptor-related protein. Our data suggest that the 170-kDa protein is a specific collagenase-3 receptor. Low density lipoprotein receptor-related protein-null mouse embryo fibroblasts bind but fail to internalize collagenase-3, whereas UMR 106-01 and wild-type mouse embryo fibroblasts bind and internalize collagenase-3. Internalization, but not binding, is inhibited by the 39-kDa receptor-associated protein. We conclude that the internalization of collagenase-3 requires the participation of the low density lipoprotein receptor-related protein and propose a model in which the cell surface interaction of this ligand requires a sequential contribution from two receptors, with the collagenase-3 receptor acting as a high affinity primary binding site and the low density lipoprotein receptor-related protein mediating internalization.

Steroid resistance in COPD is associated with impaired molecular chaperone Hsp90 expression by pro-inflammatory lymphocytes.

PubMed

Hodge, Greg; Roscioli, Eugene; Jersmann, Hubertus; Tran, Hai B; Holmes, Mark; Reynolds, Paul N; Hodge, Sandra

2016-10-21

Corticosteroid resistance is a major barrier to effective treatment of COPD. We have shown that the resistance is associated with decreased expression of glucocorticoid receptor (GCR) by senescent CD28nullCD8+ pro-inflammatory lymphocytes in peripheral blood of COPD patients. GCR must be bound to molecular chaperones heat shock proteins (Hsp) 70 and Hsp90 to acquire a high-affinity steroid binding conformation, and traffic to the nucleus. We hypothesized a loss of Hsp70/90 from these lymphocytes may further contribute to steroid resistance in COPD. Blood was collected from COPD (n = 10) and aged-matched controls (n = 10). To assess response to steroids, cytotoxic mediators, intracellular pro-inflammatory cytokines, CD28, GCR, Hsp70 and Hsp90 were determined in T and NKT-like cells in the presence of ± 10 μM prednisolone and 2.5 ng/mL cyclosporine A (binds to GCR-Hsp70/90 complex) using flow cytometry, western blot and fluorescence microscopy. A loss of expression of Hsp90 and GCR from CD28null CD8+ T and NKT-like cells in COPD was noted (Hsp70 unchanged). Loss of Hsp90 expression correlated with the percentage of CD28null CD8+ T and NKT-like cells producing IFNγ or TNFα in all subjects (eg, COPD: R = -0.763, p = 0.007 for T-cell IFNγ). Up-regulation of Hsp90 and associated decrease in pro-inflammatory cytokine production was found in CD28nullCD8+ T and NKT-like cells in the presence of 10 μM prednisolone and 2.5 ng/mL cyclosporine A. Loss of Hsp90 from cytotoxic/pro-inflammatory CD28nullCD8+ T and NKT-like cells could contribute to steroid resistance in COPD. Combination prednisolone and low-dose cyclosporine A therapy inhibits these pro-inflammatory cells and may reduce systemic inflammation in COPD.

Disturbance of cardiac gene expression and cardiomyocyte structure predisposes Mecp2-null mice to arrhythmias

PubMed Central

Hara, Munetsugu; Takahashi, Tomoyuki; Mitsumasu, Chiaki; Igata, Sachiyo; Takano, Makoto; Minami, Tomoko; Yasukawa, Hideo; Okayama, Satoko; Nakamura, Keiichiro; Okabe, Yasunori; Tanaka, Eiichiro; Takemura, Genzou; Kosai, Ken-ichiro; Yamashita, Yushiro; Matsuishi, Toyojiro

2015-01-01

Methyl-CpG-binding protein 2 (MeCP2) is an epigenetic regulator of gene expression that is essential for normal brain development. Mutations in MeCP2 lead to disrupted neuronal function and can cause Rett syndrome (RTT), a neurodevelopmental disorder. Previous studies reported cardiac dysfunction, including arrhythmias in both RTT patients and animal models of RTT. In addition, recent studies indicate that MeCP2 may be involved in cardiac development and dysfunction, but its role in the developing and adult heart remains unknown. In this study, we found that Mecp2-null ESCs could differentiate into cardiomyocytes, but the development and further differentiation of cardiovascular progenitors were significantly affected in MeCP2 deficiency. In addition, we revealed that loss of MeCP2 led to dysregulation of endogenous cardiac genes and myocardial structural alterations, although Mecp2-null mice did not exhibit obvious cardiac functional abnormalities. Furthermore, we detected methylation of the CpG islands in the Tbx5 locus, and showed that MeCP2 could target these sequences. Taken together, these results suggest that MeCP2 is an important regulator of the gene-expression program responsible for maintaining normal cardiac development and cardiomyocyte structure. PMID:26073556

Sf29 Gene of Spodoptera frugiperda Multiple Nucleopolyhedrovirus Is a Viral Factor That Determines the Number of Virions in Occlusion Bodies▿

PubMed Central

Simón, Oihane; Williams, Trevor; Asensio, Aaron C.; Ros, Sarhay; Gaya, Andrea; Caballero, Primitivo; Possee, Robert D.

2008-01-01

The genome of Spodoptera frugiperda multiple nucleopolyhedrovirus (NPV) was inserted into a bacmid (Sfbac) and used to produce a mutant lacking open reading frame 29 (Sf29null). Sf29null bacmid DNA was able to generate an infection in S. frugiperda. Approximately six times less DNA was present in occlusion bodies (OBs) produced by the Sf29null bacmid in comparison to viruses containing this gene. This reduction in DNA content was consistent with fewer virus particles being packaged within Sf29null bacmid OBs, as determined by fractionation of dissolved polyhedra and comparison of occlusion-derived virus (ODV) infectivity in cell culture. DNA from Sfbac, Sf29null, or Sf29null-repair, in which the gene deletion had been repaired, were equally infectious when used to transfect S. frugiperda. All three viruses produced similar numbers of OBs, although those from Sf29null were 10-fold less infectious than viruses with the gene. Insects infected with Sf29null bacmid died ∼24 h later than positive controls, consistent with the reduced virus particle content of Sf29null OBs. Transcripts from Sf29 were detected in infected insects 12 h prior to those from the polyhedrin gene. Homologs to Sf29 were present in other group II NPVs, and similar sequences were present in entomopoxviruses. Analysis of the Sf29 predicted protein sequence revealed signal peptide and transmembrane domains, but the presence of 12 potential N-glycosylation sites suggest that it is not an ODV envelope protein. Other motifs, including zinc-binding and threonine-rich regions, suggest degradation and adhesion functions. We conclude that Sf29 is a viral factor that determines the number of ODVs occluded in each OB. PMID:18550678

The missing link in plant histidine biosynthesis: Arabidopsis myoinositol monophosphatase-like2 encodes a functional histidinol-phosphate phosphatase.

PubMed

Petersen, Lindsay N; Marineo, Sandra; Mandalà, Salvatore; Davids, Faezah; Sewell, Bryan T; Ingle, Robert A

2010-03-01

Histidine (His) plays a critical role in plant growth and development, both as one of the standard amino acids in proteins, and as a metal-binding ligand. While genes encoding seven of the eight enzymes in the pathway of His biosynthesis have been characterized from a number of plant species, the identity of the enzyme catalyzing the dephosphorylation of histidinol-phosphate to histidinol has remained elusive. Recently, members of a novel family of histidinol-phosphate phosphatase proteins, displaying significant sequence similarity to known myoinositol monophosphatases (IMPs) have been identified from several Actinobacteria. Here we demonstrate that a member of the IMP family from Arabidopsis (Arabidopsis thaliana), myoinositol monophosphatase-like2 (IMPL2; encoded by At4g39120), has histidinol-phosphate phosphatase activity. Heterologous expression of IMPL2, but not the related IMPL1 protein, was sufficient to rescue the His auxotrophy of a Streptomyces coelicolor hisN mutant. Homozygous null impl2 Arabidopsis mutants displayed embryonic lethality, which could be rescued by supplying plants heterozygous for null impl2 alleles with His. In common with the previously characterized HISN genes from Arabidopsis, IMPL2 was expressed in all plant tissues and throughout development, and an IMPL2:green fluorescent protein fusion protein was targeted to the plastid, where His biosynthesis occurs in plants. Our data demonstrate that IMPL2 is the HISN7 gene product, and suggest a lack of genetic redundancy at this metabolic step in Arabidopsis, which is characteristic of the His biosynthetic pathway.

Lack of Plasma Protein Hemopexin Results in Increased Duodenal Iron Uptake.

PubMed

Fiorito, Veronica; Geninatti Crich, Simonetta; Silengo, Lorenzo; Aime, Silvio; Altruda, Fiorella; Tolosano, Emanuela

2013-01-01

The body concentration of iron is regulated by a fine equilibrium between absorption and losses of iron. Iron can be absorbed from diet as inorganic iron or as heme. Hemopexin is an acute phase protein that limits iron access to microorganisms. Moreover, it is the plasma protein with the highest binding affinity for heme and thus it mediates heme-iron recycling. Considering its involvement in iron homeostasis, it was postulated that hemopexin may play a role in the physiological absorption of inorganic iron. Hemopexin-null mice showed elevated iron deposits in enterocytes, associated with higher duodenal H-Ferritin levels and a significant increase in duodenal expression and activity of heme oxygenase. The expression of heme-iron and inorganic iron transporters was normal. The rate of iron absorption was assessed by measuring the amount of (57)Fe retained in tissues from hemopexin-null and wild-type animals after administration of an oral dose of (57)FeSO4 or of (57)Fe-labelled heme. Higher iron retention in the duodenum of hemopexin-null mice was observed as compared with normal mice. Conversely, iron transfer from enterocytes to liver and bone marrow was unaffected in hemopexin-null mice. The increased iron level in hemopexin-null duodenum can be accounted for by an increased iron uptake by enterocytes and storage in ferritins. These data indicate that the lack of hemopexin under physiological conditions leads to an enhanced duodenal iron uptake thus providing new insights to our understanding of body iron homeostasis.

Nucleostemin Delays Cellular Senescence and Negatively Regulates TRF1 Protein Stability▿ †

PubMed Central

Zhu, Qubo; Yasumoto, Hiroaki; Tsai, Robert Y. L.

2006-01-01

Nucleostemin (NS) encodes a nucleolar GTP-binding protein highly enriched in the stem cells and cancer cells. To determine its biological activity in vivo, we generated NS loss- and gain-of-function mouse models. The embryogenesis of homozygous NS-null (NS−/−) mice was aborted before the blastula stage. Although the growth and fertility of heterozygous NS-null (NS+/−) mice appeared normal, NS+/− mouse embryonic fibroblasts (MEFs) had fewer NS proteins, a lower population growth rate, and higher percentages of senescent cells from passage 5 (P5) to P7 than their wild-type littermates. Conversely, transgenic overexpression of NS could rescue the NS−/− embryo in a dose-dependent manner, increase the population growth rate, and reduce the senescent percentage of MEFs. Cell cycle analyses revealed increased pre-G1 percentages in the late-passage NS+/− MEF cultures compared to the wild-type cultures. We demonstrated that NS could interact with telomeric repeat-binding factor 1 (TRF1) and enhance the degradation but not the ubiquitination of the TRF1 protein, which negatively regulates telomere length and is essential for early embryogenesis. This work demonstrates the roles of NS in establishing early embryogenesis and delaying cellular senescence of MEFs and reveals a mechanism of a NS-regulated degradation of TRF1. PMID:17000763

Sarcospan Regulates Cardiac Isoproterenol Response and Prevents Duchenne Muscular Dystrophy-Associated Cardiomyopathy.

PubMed

Parvatiyar, Michelle S; Marshall, Jamie L; Nguyen, Reginald T; Jordan, Maria C; Richardson, Vanitra A; Roos, Kenneth P; Crosbie-Watson, Rachelle H

2015-12-23

Duchenne muscular dystrophy is a fatal cardiac and skeletal muscle disease resulting from mutations in the dystrophin gene. We have previously demonstrated that a dystrophin-associated protein, sarcospan (SSPN), ameliorated Duchenne muscular dystrophy skeletal muscle degeneration by activating compensatory pathways that regulate muscle cell adhesion (laminin-binding) to the extracellular matrix. Conversely, loss of SSPN destabilized skeletal muscle adhesion, hampered muscle regeneration, and reduced force properties. Given the importance of SSPN to skeletal muscle, we investigated the consequences of SSPN ablation in cardiac muscle and determined whether overexpression of SSPN into mdx mice ameliorates cardiac disease symptoms associated with Duchenne muscular dystrophy cardiomyopathy. SSPN-null mice exhibited cardiac enlargement, exacerbated cardiomyocyte hypertrophy, and increased fibrosis in response to β-adrenergic challenge (isoproterenol; 0.8 mg/day per 2 weeks). Biochemical analysis of SSPN-null cardiac muscle revealed reduced sarcolemma localization of many proteins with a known role in cardiomyopathy pathogenesis: dystrophin, the sarcoglycans (α-, δ-, and γ-subunits), and β1D integrin. Transgenic overexpression of SSPN in Duchenne muscular dystrophy mice (mdx(TG)) improved cardiomyofiber cell adhesion, sarcolemma integrity, cardiac functional parameters, as well as increased expression of compensatory transmembrane proteins that mediate attachment to the extracellular matrix. SSPN regulates sarcolemmal expression of laminin-binding complexes that are critical to cardiac muscle function and protects against transient and chronic injury, including inherited cardiomyopathy. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Pathogenesis of Lethal Cardiac Arrhythmias in Mecp2 Mutant Mice: Implication for Therapy in Rett Syndrome

PubMed Central

McCauley, Mark D.; Wang, Tiannan; Mike, Elise; Herrera, Jose; Beavers, David L.; Huang, Teng-Wei; Ward, Christopher S.; Skinner, Steven; Percy, Alan K.; Glaze, Daniel G.; Wehrens, Xander H. T.; Neul, Jeffrey L.

2013-01-01

Rett Syndrome is a neurodevelopmental disorder typically caused by mutations in Methyl-CpG-Binding Protein 2 (MECP2) in which 26% of deaths are sudden and of unknown cause. To explore the hypothesis that these deaths may be due to cardiac dysfunction, we characterized the electrocardiograms (ECGs) in 379 people with Rett syndrome and found that 18.5% show prolongation of the corrected QT interval (QTc), indicating a repolarization abnormality that can predispose to the development of an unstable fatal cardiac rhythm. Male mice lacking MeCP2 function, Mecp2Null/Y, also have prolonged QTc and show increased susceptibility to induced ventricular tachycardia. Female heterozygous null mice, Mecp2Null/+, show an age-dependent prolongation of QTc associated with ventricular tachycardia and cardiac-related death. Genetic deletion of MeCP2 function in only the nervous system was sufficient to cause long QTc and ventricular tachycardia, implicating neuronally-mediated changes to cardiac electrical conduction as a potential cause of ventricular tachycardia in Rett syndrome. The standard therapy for prolonged QTc in Rett syndrome, β-adrenergic receptor blockers, did not prevent ventricular tachycardia in Mecp2Null/Y mice. To determine whether an alternative therapy would be more appropriate, we characterized cardiomyocytes from Mecp2Null/Y mice and found increased persistent sodium current, which was normalized when cells were treated with the sodium channel-blocking anti-seizure drug phenytoin. Treatment with phenytoin reduced both QTc and sustained ventricular tachycardia in Mecp2Null/Y mice. These results demonstrate that cardiac abnormalities in Rett syndrome are secondary to abnormal nervous system control, which leads to increased persistent sodium current. Our findings suggest that treatment in people with Rett syndrome would be more effective if it targeted the increased persistent sodium current in order to prevent lethal cardiac arrhythmias. PMID:22174313

Rett Syndrome Mutation MeCP2 T158A Disrupts DNA Binding, Protein Stability and ERP Responses

PubMed Central

Goffin, Darren; Allen, Megan; Zhang, Le; Amorim, Maria; Wang, I-Ting Judy; Reyes, Arith-Ruth S.; Mercado-Berton, Amy; Ong, Caroline; Cohen, Sonia; Hu, Linda; Blendy, Julie A.; Carlson, Gregory C.; Siegel, Steve J.; Greenberg, Michael E.; Zhou, Zhaolan (Joe)

2011-01-01

Mutations in the MECP2 gene cause the autism spectrum disorder Rett Syndrome (RTT). One of the most common mutations associated with RTT occurs at MeCP2 Threonine 158 converting it to Methionine (T158M) or Alanine (T158A). To understand the role of T158 mutation in the pathogenesis of RTT, we generated knockin mice recapitulating MeCP2 T158A mutation. Here we show a causal role for T158A mutation in the development of RTT-like phenotypes including developmental regression, motor dysfunction, and learning and memory deficits. These phenotypes resemble those in Mecp2-null mice and manifest through a reduction in MeCP2 binding to methylated DNA and a decrease in MeCP2 protein stability. Importantly, the age-dependent development of event-related neuronal responses are disrupted by MeCP2 mutation, suggesting that impaired neuronal circuitry underlies the pathogenesis of RTT and that assessment of event-related potentials may serve as a biomarker for RTT and treatment evaluation. PMID:22119903

Tomosyn-2 is required for normal motor performance in mice and sustains neurotransmission at motor endplates.

PubMed

Geerts, Cornelia J; Plomp, Jaap J; Koopmans, Bastijn; Loos, Maarten; van der Pijl, Elizabeth M; van der Valk, Martin A; Verhage, Matthijs; Groffen, Alexander J A

2015-07-01

Tomosyn-1 (STXBP5) is a soluble NSF attachment protein receptor complex-binding protein that inhibits vesicle fusion, but the role of tomosyn-2 (STXBP5L) in the mammalian nervous system is still unclear. Here we generated tomosyn-2 null (Tom2(KO/KO)) mice, which showed impaired motor performance. This was accompanied by synaptic changes at the neuromuscular junction, including enhanced spontaneous acetylcholine release frequency and faster depression of muscle motor endplate potentials during repetitive stimulation. The postsynaptic geometric arrangement and function of acetylcholine receptors were normal. We conclude that tomosyn-2 supports motor performance by regulation of transmitter release willingness to sustain synaptic strength during high-frequency transmission, which makes this gene a candidate for involvement in neuromuscular disorders.

Small heterodimer partner blocks cardiac hypertrophy by interfering with GATA6 signaling.

PubMed

Nam, Yoon Seok; Kim, Yoojung; Joung, Hosouk; Kwon, Duk-Hwa; Choe, Nakwon; Min, Hyun-Ki; Kim, Yong Sook; Kim, Hyung-Seok; Kim, Don-Kyu; Cho, Young Kuk; Kim, Yong-Hoon; Nam, Kwang-Il; Choi, Hyoung Chul; Park, Dong Ho; Suk, Kyoungho; Lee, In-Kyu; Ahn, Youngkeun; Lee, Chul-Ho; Choi, Hueng-Sik; Eom, Gwang Hyeon; Kook, Hyun

2014-08-15

Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA-binding domain. Through interactions with other transcription factors, SHP regulates diverse biological events, including glucose metabolism in liver. However, the role of SHP in adult heart diseases has not yet been demonstrated. We aimed to investigate the role of SHP in adult heart in association with cardiac hypertrophy. The roles of SHP in cardiac hypertrophy were tested in primary cultured cardiomyocytes and in animal models. SHP-null mice showed a hypertrophic phenotype. Hypertrophic stresses repressed the expression of SHP, whereas forced expression of SHP blocked the development of hypertrophy in cardiomyocytes. SHP reduced the protein amount of Gata6 and, by direct physical interaction with Gata6, interfered with the binding of Gata6 to GATA-binding elements in the promoter regions of natriuretic peptide precursor type A. Metformin, an antidiabetic agent, induced SHP and suppressed cardiac hypertrophy. The metformin-induced antihypertrophic effect was attenuated either by SHP small interfering RNA in cardiomyocytes or in SHP-null mice. These results establish SHP as a novel antihypertrophic regulator that acts by interfering with GATA6 signaling. SHP may participate in the metformin-induced antihypertrophic response. © 2014 American Heart Association, Inc.

Anatomical location of LPA1 activation and LPA phospholipid precursors in rodent and human brain.

PubMed

González de San Román, Estibaliz; Manuel, Iván; Giralt, María Teresa; Chun, Jerold; Estivill-Torrús, Guillermo; Rodríguez de Fonseca, Fernando; Santín, Luis Javier; Ferrer, Isidro; Rodríguez-Puertas, Rafael

2015-08-01

Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors: LPA1 -LPA6 . LPA evokes several responses in the CNS, including cortical development and folding, growth of the axonal cone and its retraction process. Those cell processes involve survival, migration, adhesion proliferation, differentiation, and myelination. The anatomical localization of LPA1 is incompletely understood, particularly with regard to LPA binding. Therefore, we have used functional [(35) S]GTPγS autoradiography to verify the anatomical distribution of LPA1 binding sites in adult rodent and human brain. The greatest activity was observed in myelinated areas of the white matter such as corpus callosum, internal capsule and cerebellum. MaLPA1 -null mice (a variant of LPA1 -null) lack [(35) S]GTPγS basal binding in white matter areas, where the LPA1 receptor is expressed at high levels, suggesting a relevant role of the activity of this receptor in the most myelinated brain areas. In addition, phospholipid precursors of LPA were localized by MALDI-IMS in both rodent and human brain slices identifying numerous species of phosphatides and phosphatidylcholines. Both phosphatides and phosphatidylcholines species represent potential LPA precursors. The anatomical distribution of these precursors in rodent and human brain may indicate a metabolic relationship between LPA and LPA1 receptors. Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors (GPCR), LPA1 to LPA6 . LPA evokes several responses in the central nervous system (CNS), including cortical development and folding, growth of the axonal cone and its retraction process. We used functional [(35) S]GTPγS autoradiography to verify the anatomical distribution of LPA1 -binding sites in adult rodent and human brain. The distribution of LPA1 receptors in rat, mouse and human brains show the highest activity in white matter myelinated areas. The basal and LPA-evoked activities are abolished in MaLPA1 -null mice. The phospholipid precursors of LPA are localized by MALDI-IMS. The anatomical distribution of LPA precursors in rodent and human brain suggests a relationship with functional LPA1 receptors. © 2015 International Society for Neurochemistry.

Comparative proteomic analysis of normal and collagen IX null mouse cartilage reveals altered extracellular matrix composition and novel components of the collagen IX interactome.

PubMed

Brachvogel, Bent; Zaucke, Frank; Dave, Keyur; Norris, Emma L; Stermann, Jacek; Dayakli, Münire; Koch, Manuel; Gorman, Jeffrey J; Bateman, John F; Wilson, Richard

2013-05-10

Collagen IX is an integral cartilage extracellular matrix component important in skeletal development and joint function. Proteomic analysis and validation studies revealed novel alterations in collagen IX null cartilage. Matrilin-4, collagen XII, thrombospondin-4, fibronectin, βig-h3, and epiphycan are components of the in vivo collagen IX interactome. We applied a proteomics approach to advance our understanding of collagen IX ablation in cartilage. The cartilage extracellular matrix is essential for endochondral bone development and joint function. In addition to the major aggrecan/collagen II framework, the interacting complex of collagen IX, matrilin-3, and cartilage oligomeric matrix protein (COMP) is essential for cartilage matrix stability, as mutations in Col9a1, Col9a2, Col9a3, Comp, and Matn3 genes cause multiple epiphyseal dysplasia, in which patients develop early onset osteoarthritis. In mice, collagen IX ablation results in severely disturbed growth plate organization, hypocellular regions, and abnormal chondrocyte shape. This abnormal differentiation is likely to involve altered cell-matrix interactions but the mechanism is not known. To investigate the molecular basis of the collagen IX null phenotype we analyzed global differences in protein abundance between wild-type and knock-out femoral head cartilage by capillary HPLC tandem mass spectrometry. We identified 297 proteins in 3-day cartilage and 397 proteins in 21-day cartilage. Components that were differentially abundant between wild-type and collagen IX-deficient cartilage included 15 extracellular matrix proteins. Collagen IX ablation was associated with dramatically reduced COMP and matrilin-3, consistent with known interactions. Matrilin-1, matrilin-4, epiphycan, and thrombospondin-4 levels were reduced in collagen IX null cartilage, providing the first in vivo evidence for these proteins belonging to the collagen IX interactome. Thrombospondin-4 expression was reduced at the mRNA level, whereas matrilin-4 was verified as a novel collagen IX-binding protein. Furthermore, changes in TGFβ-induced protein βig-h3 and fibronectin abundance were found in the collagen IX knock-out but not associated with COMP ablation, indicating specific involvement in the abnormal collagen IX null cartilage. In addition, the more widespread expression of collagen XII in the collagen IX-deficient cartilage suggests an attempted compensatory response to the absence of collagen IX. Our differential proteomic analysis of cartilage is a novel approach to identify candidate matrix protein interactions in vivo, underpinning further analysis of mutant cartilage lacking other matrix components or harboring disease-causing mutations.

IQGAP1 regulates ERK1/2 and AKT signalling in the heart and sustains functional remodelling upon pressure overload

PubMed Central

Sbroggiò, Mauro; Carnevale, Daniela; Bertero, Alessandro; Cifelli, Giuseppe; De Blasio, Emanuele; Mascio, Giada; Hirsch, Emilio; Bahou, Wadie F.; Turco, Emilia; Silengo, Lorenzo; Brancaccio, Mara; Lembo, Giuseppe; Tarone, Guido

2011-01-01

Aims The Raf-MEK1/2-ERK1/2 (ERK1/2—extracellular signal-regulated kinases 1/2) signalling cascade is crucial in triggering cardiac responses to different stress stimuli. Scaffold proteins are key elements in coordinating signalling molecules for their appropriate spatiotemporal activation. Here, we investigated the role of IQ motif-containing GTPase-activating protein 1 (IQGAP1), a scaffold for the ERK1/2 cascade, in heart function and remodelling in response to pressure overload. Methods and results IQGAP1-null mice have unaltered basal heart function. When subjected to pressure overload, IQGAP1-null mice initially develop a compensatory hypertrophy indistinguishable from that of wild-type (WT) mice. However, upon a prolonged stimulus, the hypertrophic response develops towards a thinning of left ventricular walls, chamber dilation, and a decrease in contractility, in an accelerated fashion compared with WT mice. This unfavourable cardiac remodelling is characterized by blunted reactivation of the foetal gene programme, impaired cardiomyocyte hypertrophy, and increased cardiomyocyte apoptosis. Analysis of signalling pathways revealed two temporally distinct waves of both ERK1/2 and AKT phosphorylation peaking, respectively, at 10 min and 4 days after aortic banding in WT hearts. IQGAP1-null mice show strongly impaired phosphorylation of MEK1/2-ERK1/2 and AKT following 4 days of pressure overload, but normal activation of these kinases after 10 min. Pull-down experiments indicated that IQGAP1 is able to bind the three components of the ERK cascade, namely c-Raf, MEK1/2, and ERK1/2, as well as AKT in the heart. Conclusion These data demonstrate, for the first time, a key role for the scaffold protein IQGAP1 in integrating hypertrophy and survival signals in the heart and regulating long-term left ventricle remodelling upon pressure overload. PMID:21493702

Fut2-null mice display an altered glycosylation profile and impaired BabA-mediated Helicobacter pylori adhesion to gastric mucosa

PubMed Central

Magalhães, Ana; Gomes, Joana; Ismail, Mohd Nazri; Haslam, Stuart M; Mendes, Nuno; Osório, Hugo; David, Leonor; Le Pendu, Jacques; Haas, Rainer; Dell, Anne; Borén, Thomas; Reis, Celso A

2009-01-01

Glycoconjugates expressed on gastric mucosa play a crucial role in host–pathogen interactions. The FUT2 enzyme catalyzes the addition of terminal α(1,2)fucose residues, producing the H type 1 structure expressed on the surface of epithelial cells and in mucosal secretions of secretor individuals. Inactivating mutations in the human FUT2 gene are associated with reduced susceptibility to Helicobacter pylori infection. H. pylori infects over half the world's population and causes diverse gastric lesions, from gastritis to gastric cancer. H. pylori adhesion constitutes a crucial step in the establishment of a successful infection. The BabA adhesin binds the Leb and H type 1 structures expressed on gastric mucins, while SabA binds to sialylated carbohydrates mediating the adherence to inflamed gastric mucosa. In this study, we have used an animal model of nonsecretors, Fut2-null mice, to characterize the glycosylation profile and evaluate the effect of the observed glycan expression modifications in the process of H. pylori adhesion. We have demonstrated expression of terminal difucosylated glycan structures in C57Bl/6 mice gastric mucosa and that Fut2-null mice showed marked alteration in gastric mucosa glycosylation, characterized by diminished expression of α(1,2)fucosylated structures as indicated by lectin and antibody staining and further confirmed by mass spectrometry analysis. This altered glycosylation profile was further confirmed by the absence of Fucα(1,2)-dependent binding of calicivirus virus-like particles. Finally, using a panel of H. pylori strains, with different adhesin expression profiles, we have demonstated an impairment of BabA-dependent adhesion of H. pylori to Fut2-null mice gastric mucosa, whereas SabA-mediated binding was not affected. PMID:19706747

Yeast hnRNP-related proteins contribute to the maintenance of telomeres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee-Soety, Julia Y., E-mail: jlee04@sju.edu; Jones, Jennifer; MacGibeny, Margaret A.

Highlights: Black-Right-Pointing-Pointer Yeast hnRNP-related proteins are able to prevent faster senescence in telomerase-null cells. Black-Right-Pointing-Pointer The conserved RRMs in Npl3 are important for telomere maintenance. Black-Right-Pointing-Pointer Human hnRNP A1 is unable to complement the lack of NPL3 in yeast. Black-Right-Pointing-Pointer Npl3 and Cbc2 may work as telomere capping proteins. -- Abstract: Telomeres protect the ends of linear chromosomes, which if eroded to a critical length can become uncapped and lead to replicative senescence. Telomerase maintains telomere length in some cells, but inappropriate expression facilitates the immortality of cancer cells. Recently, proteins involved in RNA processing and ribosome assembly, such asmore » hnRNP (heterogeneous nuclear ribonucleoprotein) A1, have been found to participate in telomere maintenance in mammals. The Saccharomyces cerevisiae protein Npl3 shares significant amino acid sequence similarities with hnRNP A1. We found that deleting NPL3 accelerated the senescence of telomerase null cells. The highly conserved RNA recognition motifs (RRM) in Npl3 appear to be important for preventing faster senescence. Npl3 preferentially binds telomere sequences in vitro, suggesting that Npl3 may affect telomeres directly. Despite similarities between the two proteins, human hnRNP A1 is unable to complement the lack of Npl3 to rescue accelerated senescence in tlc1 npl3 cells. Deletion of CBC2, which encodes another hnRNP-related protein that associates with Npl3, also accelerates senescence. Potential mechanisms by which hnRNP-related proteins maintain telomeres are discussed.« less

Structural and functional characterizations of SsgB, a conserved activator of developmental cell division in morphologically complex actinomycetes.

PubMed

Xu, Qingping; Traag, Bjørn A; Willemse, Joost; McMullan, Daniel; Miller, Mitchell D; Elsliger, Marc-André; Abdubek, Polat; Astakhova, Tamara; Axelrod, Herbert L; Bakolitsa, Constantina; Carlton, Dennis; Chen, Connie; Chiu, Hsiu-Ju; Chruszcz, Maksymilian; Clayton, Thomas; Das, Debanu; Deller, Marc C; Duan, Lian; Ellrott, Kyle; Ernst, Dustin; Farr, Carol L; Feuerhelm, Julie; Grant, Joanna C; Grzechnik, Anna; Grzechnik, Slawomir K; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K; Klock, Heath E; Knuth, Mark W; Kozbial, Piotr; Krishna, S Sri; Kumar, Abhinav; Marciano, David; Minor, Wladek; Mommaas, A Mieke; Morse, Andrew T; Nigoghossian, Edward; Nopakun, Amanda; Okach, Linda; Oommachen, Silvya; Paulsen, Jessica; Puckett, Christina; Reyes, Ron; Rife, Christopher L; Sefcovic, Natasha; Tien, Henry J; Trame, Christine B; van den Bedem, Henry; Wang, Shuren; Weekes, Dana; Hodgson, Keith O; Wooley, John; Deacon, Ashley M; Godzik, Adam; Lesley, Scott A; Wilson, Ian A; van Wezel, Gilles P

2009-09-11

SsgA-like proteins (SALPs) are a family of homologous cell division-related proteins that occur exclusively in morphologically complex actinomycetes. We show that SsgB, a subfamily of SALPs, is the archetypal SALP that is functionally conserved in all sporulating actinomycetes. Sporulation-specific cell division of Streptomyces coelicolor ssgB mutants is restored by introduction of distant ssgB orthologues from other actinomycetes. Interestingly, the number of septa (and spores) of the complemented null mutants is dictated by the specific ssgB orthologue that is expressed. The crystal structure of the SsgB from Thermobifida fusca was determined at 2.6 A resolution and represents the first structure for this family. The structure revealed similarities to a class of eukaryotic "whirly" single-stranded DNA/RNA-binding proteins. However, the electro-negative surface of the SALPs suggests that neither SsgB nor any of the other SALPs are likely to interact with nucleotide substrates. Instead, we show that a conserved hydrophobic surface is likely to be important for SALP function and suggest that proteins are the likely binding partners.

Suppression of Chemotaxis by SSeCKS via Scaffolding of Phosphoinositol Phosphates and the Recruitment of the Cdc42 GEF, Frabin, to the Leading Edge

PubMed Central

Ko, Hyun-Kyung; Guo, Li-wu; Su, Bing; Gao, Lingqiu; Gelman, Irwin H.

2014-01-01

Chemotaxis is controlled by interactions between receptors, Rho-family GTPases, phosphatidylinositol 3-kinases, and cytoskeleton remodeling proteins. We investigated how the metastasis suppressor, SSeCKS, attenuates chemotaxis. Chemotaxis activity inversely correlated with SSeCKS levels in mouse embryo fibroblasts (MEF), DU145 and MDA-MB-231 cancer cells. SSeCKS loss induced chemotactic velocity and linear directionality, correlating with replacement of leading edge lamellipodia with fascin-enriched filopodia-like extensions, the formation of thickened longitudinal F-actin stress fibers reaching to filopodial tips, relative enrichments at the leading edge of phosphatidylinositol (3,4,5)P3 (PIP3), Akt, PKC-ζ, Cdc42-GTP and active Src (SrcpoY416), and a loss of Rac1. Leading edge lamellipodia and chemotaxis inhibition in SSeCKS-null MEF could be restored by full-length SSeCKS or SSeCKS deleted of its Src-binding domain (ΔSrc), but not by SSeCKS deleted of its three MARCKS (myristylated alanine-rich C kinase substrate) polybasic domains (ΔPBD), which bind PIP2 and PIP3. The enrichment of activated Cdc42 in SSeCKS-null leading edge filopodia correlated with recruitment of the Cdc42-specific guanine nucleotide exchange factor, Frabin, likely recruited via multiple PIP2/3-binding domains. Frabin knockdown in SSeCKS-null MEF restores leading edge lamellipodia and chemotaxis inhibition. However, SSeCKS failed to co-immunoprecipitate with Rac1, Cdc42 or Frabin. Consistent with the notion that chemotaxis is controlled by SSeCKS-PIP (vs. -Src) scaffolding activity, constitutively-active phosphatidylinositol 3-kinase could override the ability of the Src inhibitor, SKI-606, to suppress chemotaxis and filopodial enrichment of Frabin in SSeCKS-null MEF. Our data suggest a role for SSeCKS in controlling Rac1 vs. Cdc42-induced cellular dynamics at the leading chemotactic edge through the scaffolding of phospholipids and signal mediators, and through the reorganization of the actin cytoskeleton controlling directional movement. PMID:25356636

Amyloid precursor protein modulates ERK-1 and -2 signaling.

PubMed

Venezia, Valentina; Nizzari, Mario; Repetto, Emanuela; Violani, Elisabetta; Corsaro, Alessandro; Thellung, Stefano; Villa, Valentina; Carlo, Pia; Schettini, Gennaro; Florio, Tullio; Russo, Claudio

2006-12-01

The amyloid precursor protein (APP) is a transmembrane protein with a short cytoplasmic tail whose physiological function is unclear, although it is well documented that the proteolytic processing of APP could influence the development of Alzheimer's disease (AD) through the formation of membrane-bound C-terminal fragments (CTFs) and of beta-amyloid peptides (Abeta). We have recently shown that tyrosine-phosphorylated APP and CTFs may interact with Grb2 and ShcA adaptor proteins and that this coupling occurs at a higher extent in AD subjects only. To study the interaction between APP or CTFs and ShcA/Grb2 and to investigate their molecular target we have used as experimental model two different cell lines: H4 human neuroglioma cells and APP/APLP null mouse embryonic fibroblast cells (MEFs). Here we show that in H4 cells APP interacts with Grb2; conversely in APP/APLP-null MEF cells this interaction is possible only after the reintroduction of human APP by transfection. We have also shown that in MEF cells the transfection of a plasmid encoding for human APP wild-type enhances the phosphorylation of ERK-1 and -2 as revealed by Western blotting and immunofluorescence experiments. Finally, also in H4 cells the overexpression of APP upregulates the levels of phospho-ERK-1 and -2. In summary our data suggest that APP may influence phospho-ERK-1 and -2 signaling through its binding with Grb2 and ShcA adaptors. The meaning of this event is not clear, but APP interaction with these adaptors could be relevant to regulate mitogenic pathway.

Niche-Specific Requirement for Hyphal Wall protein 1 in Virulence of Candida albicans

PubMed Central

Staab, Janet F.; Datta, Kausik; Rhee, Peter

2013-01-01

Specialized Candida albicans cell surface proteins called adhesins mediate binding of the fungus to host cells. The mammalian transglutaminase (TG) substrate and adhesin, Hyphal wall protein 1 (Hwp1), is expressed on the hyphal form of C. albicans where it mediates fungal adhesion to epithelial cells. Hwp1 is also required for biofilm formation and mating thus the protein functions in both fungal-host and self-interactions. Hwp1 is required for full virulence of C. albicans in murine models of disseminated candidiasis and of esophageal candidiasis. Previous studies correlated TG activity on the surface of oral epithelial cells, produced by epithelial TG (TG1), with tight binding of C. albicans via Hwp1 to the host cell surfaces. However, the contribution of other Tgs, specifically tissue TG (TG2), to disseminated candidiasis mediated by Hwp1 was not known. A newly created hwp1 null strain in the wild type SC5314 background was as virulent as the parental strain in C57BL/6 mice, and virulence was retained in C57BL/6 mice deleted for Tgm2 (TG2). Further, the hwp1 null strains displayed modestly reduced virulence in BALB/c mice as did strain DD27-U1, an independently created hwp1Δ/Δ in CAI4 corrected for its ura3Δ defect at the URA3 locus. Hwp1 was still needed to produce wild type biofilms, and persist on murine tongues in an oral model of oropharyngeal candidiasis consistent with previous studies by us and others. Finally, lack of Hwp1 affected the translocation of C. albicans from the mouse intestine into the bloodstream of mice. Together, Hwp1 appears to have a minor role in disseminated candidiasis, independent of tissue TG, but a key function in host- and self-association to the surface of oral mucosa. PMID:24260489

FABP-1 GENE ABLATION IMPACTS BRAIN ENDOCANNABINOID SYSTEM IN MALE MICE

PubMed Central

Martin, Gregory G.; Chung, Sarah; Landrock, Danilo; Landrock, Kerstin K.; Huang, Huan; Dangott, Lawrence J.; Peng, Xiaoxue; Kaczocha, Martin; Seeger, Drew R.; Murphy, Eric J.; Golovko, Mikhail Y.; Kier, Ann B.; Schroeder, Friedhelm

2016-01-01

Liver fatty acid binding protein (FABP1, L-FABP) has high affinity for and enhances uptake of arachidonic acid (ARA, C20:4, n-6) which, when esterified to phospholipids, is the requisite precursor for synthesis of endocannabinoids (EC) such as arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). The brain derives most of its ARA from plasma, taking up ARA and transporting it intracellularly via cytosolic fatty acid binding proteins (FABPs 3,5, and 7) localized within the brain. In contrast, the much more prevalent cytosolic FABP1 is not detectable in the brain but is instead highly expressed in the liver. Therefore, the possibility that FABP1 outside the central nervous system may regulate brain AEA and 2-AG was examined in wild-type (WT) and FABP1 null (LKO) male mice. LKO increased brain levels of AA-containing EC (AEA, 2-AG), correlating with increased free and total ARA in brain and serum. LKO also increased brain levels of non-ARA that contain potentiating endocannabinoids (EC*) such as OEA, PEA, 2-OG, and 2-PG. Concomitantly, LKO decreased serum total ARA-containing EC, but not non-ARA endocannabinoids. LKO did not elicit these changes in the brain EC and EC* due to compensatory upregulation of brain protein levels of enzymes in EC synthesis (NAPEPLD, DAGLα) or cytosolic EC chaperone proteins (FABPs 3, 5, 7, SCP-2, HSP70), or cannabinoid receptors (CB1, TRVP1). These data show for the first time that the non-CNS fatty acid binding protein FABP1 markedly affected brain levels of both ARA-containing endocannabinoids (AEA, 2-AG) as well as their non-ARA potentiating endocannabinoids. PMID:27167970

Evidence that the Dictyostelium Dd-STATa protein is a repressor that regulates commitment to stalk cell differentiation and is also required for efficient chemotaxis.

PubMed

Mohanty, S; Jermyn, K A; Early, A; Kawata, T; Aubry, L; Ceccarelli, A; Schaap, P; Williams, J G; Firtel, R A

1999-08-01

Dd-STATa is a structural and functional homologue of the metazoan STAT (Signal Transducer and Activator of Transcription) proteins. We show that Dd-STATa null cells exhibit several distinct developmental phenotypes. The aggregation of Dd-STATa null cells is delayed and they chemotax slowly to a cyclic AMP source, suggesting a role for Dd-STATa in these early processes. In Dd-STATa null strains, slug-like structures are formed but they have an aberrant pattern of gene expression. In such slugs, ecmB/lacZ, a marker that is normally specific for cells on the stalk cell differentiation pathway, is expressed throughout the prestalk region. Stalk cell differentiation in Dictyostelium has been proposed to be under negative control, mediated by repressor elements present in the promoters of stalk cell-specific genes. Dd-STATa binds these repressor elements in vitro and the ectopic expression of ecmB/lacZ in the null strain provides in vivo evidence that Dd-STATa is the repressor protein that regulates commitment to stalk cell differentiation. Dd-STATa null cells display aberrant behavior in a monolayer assay wherein stalk cell differentiation is induced using the stalk cell morphogen DIF. The ecmB gene, a general marker for stalk cell differentiation, is greatly overinduced by DIF in Dd-STATa null cells. Also, Dd-STATa null cells are hypersensitive to DIF for expression of ST/lacZ, a marker for the earliest stages in the differentiation of one of the stalk cell sub-types. We suggest that both these manifestations of DIF hypersensitivity in the null strain result from the balance between activation and repression of the promoter elements being tipped in favor of activation when the repressor is absent. Paradoxically, although Dd-STATa null cells are hypersensitive to the inducing effects of DIF and readily form stalk cells in monolayer assay, the Dd-STATa null cells show little or no terminal stalk cell differentiation within the slug. Dd-STATa null slugs remain developmentally arrested for several days before forming very small spore masses supported by a column of apparently undifferentiated cells. Thus, complete stalk cell differentiation appears to require at least two events: a commitment step, whereby the repression exerted by Dd-STATa is lifted, and a second step that is blocked in a Dd-STATa null organism. This latter step may involve extracellular cAMP, a known repressor of stalk cell differentiation, because Dd-STATa null cells are abnormally sensitive to the inhibitory effects of extracellular cyclic AMP.

Peroxisome proliferator-activated receptor (PPAR)-binding protein (PBP) but not PPAR-interacting protein (PRIP) is required for nuclear translocation of constitutive androstane receptor in mouse liver.

PubMed

Guo, Dongsheng; Sarkar, Joy; Ahmed, Mohamed R; Viswakarma, Navin; Jia, Yuzhi; Yu, Songtao; Sambasiva Rao, M; Reddy, Janardan K

2006-08-25

The constitutive androstane receptor (CAR) regulates transcription of phenobarbital-inducible genes that encode xenobiotic-metabolizing enzymes in liver. CAR is localized to the hepatocyte cytoplasm but to be functional, it translocates into the nucleus in the presence of phenobarbital-like CAR ligands. We now demonstrate that adenovirally driven EGFP-CAR, as expected, translocates into the nucleus of normal wild-type hepatocytes following phenobarbital treatment under both in vivo and in vitro conditions. Using this approach we investigated the role of transcription coactivators PBP and PRIP in the translocation of EGFP-CAR into the nucleus of PBP and PRIP liver conditional null mouse hepatocytes. We show that coactivator PBP is essential for nuclear translocation of CAR but not PRIP. Adenoviral expression of both PBP and EGFP-CAR restored phenobarbital-mediated nuclear translocation of exogenously expressed CAR in PBP null livers in vivo and in PBP null primary hepatocytes in vitro. CAR translocation into the nucleus of PRIP null livers resulted in the induction of CAR target genes such as CYP2B10, necessary for the conversion of acetaminophen to its hepatotoxic intermediate metabolite, N-acetyl-p-benzoquinone imine. As a consequence, PRIP-deficiency in liver did not protect from acetaminophen-induced hepatic necrosis, unlike that exerted by PBP deficiency. These results establish that transcription coactivator PBP plays a pivotal role in nuclear localization of CAR, that it is likely that PBP either enhances nuclear import or nuclear retention of CAR in hepatocytes, and that PRIP is redundant for CAR function.

Protein expression profiling of the drosophila fragile X mutant brain reveals up-regulation of monoamine synthesis.

PubMed

Zhang, Yong Q; Friedman, David B; Wang, Zhe; Woodruff, Elvin; Pan, Luyuan; O'donnell, Janis; Broadie, Kendal

2005-03-01

Fragile X syndrome is the most common form of inherited mental retardation, associated with both cognitive and behavioral anomalies. The disease is caused by silencing of the fragile X mental retardation 1 (fmr1) gene, which encodes the mRNA-binding, translational regulator FMRP. Previously we established a disease model through mutation of Drosophila fmr1 (dfmr1) and showed that loss of dFMRP causes defects in neuronal structure, function, and behavioral output similar to the human disease state. To uncover molecular targets of dFMRP in the brain, we use here a proteomic approach involving two-dimensional difference gel electrophoresis analyses followed by mass spectrometry identification of proteins with significantly altered expression in dfmr1 null mutants. We then focus on two misregulated enzymes, phenylalanine hydroxylase (Henna) and GTP cyclohydrolase (Punch), both of which mediate in concert the synthetic pathways of two key monoamine neuromodulators, dopamine and serotonin. Brain enzymatic assays show a nearly 2-fold elevation of Punch activity in dfmr1 null mutants. Consistently brain neurochemical assays show that both dopamine and serotonin are significantly increased in dfmr1 null mutants. At a cellular level, dfmr1 null mutant neurons display a highly significant elevation of the dense core vesicles that package these monoamine neuromodulators for secretion. Taken together, these data indicate that dFMRP normally down-regulates the monoamine pathway, which is consequently up-regulated in the mutant condition. Elevated brain levels of dopamine and serotonin provide a plausible mechanistic explanation for aspects of cognitive and behavioral deficits in human patients.

Metformin ameliorates IL-6-induced hepatic insulin resistance via induction of orphan nuclear receptor small heterodimer partner (SHP) in mouse models.

PubMed

Kim, Y D; Kim, Y H; Cho, Y M; Kim, D K; Ahn, S W; Lee, J M; Chanda, D; Shong, M; Lee, C H; Choi, H S

2012-05-01

IL-6 is a proinflammatory cytokine associated with the pathogenesis of hepatic diseases. Metformin is an anti-diabetic drug used for the treatment of type 2 diabetes, and orphan nuclear receptor small heterodimer partner (SHP, also known as NR0B2), a transcriptional co-repressor, plays an important role in maintaining metabolic homeostasis. Here, we demonstrate that metformin-mediated activation of AMP-activated protein kinase (AMPK) increases SHP protein production and regulates IL-6-induced hepatic insulin resistance. We investigated metformin-mediated SHP production improved insulin resistance through the regulation of an IL-6-dependent pathway (involving signal transducer and activator of transcription 3 [STAT3] and suppressor of cytokine signalling 3 [SOCS3]) in both Shp knockdown and Shp null mice. IL-6-induced STAT3 transactivation and SOCS3 production were significantly repressed by metformin, adenoviral constitutively active AMPK (Ad-CA-AMPK), and adenoviral SHP (Ad-SHP), but not in Shp knockdown, or with the adenoviral dominant negative form of AMPK (Ad-DN-AMPK). Chromatin immunoprecipitation (ChIP), co-immunoprecipitation (Co-IP) and protein localisation studies showed that SHP inhibits DNA binding of STAT3 on the Socs3 gene promoter via interaction and colocalisation within the nucleus. Upregulation of inflammatory genes and downregulation of hepatic insulin signalling by acute IL-6 treatment were observed in wild-type mice but not in Shp null mice. Finally, chronic IL-6 exposure caused hepatic insulin resistance, leading to impaired insulin tolerance and elevated gluconeogenesis, and these phenomena were aggravated in Shp null mice. Our results demonstrate that SHP upregulation by metformin may prevent hepatic disorders by regulating the IL-6-dependent pathway, and that this pathway can help to ameliorate the pathogenesis of cytokine-mediated metabolic dysfunction.

Null missense ABCR (ABCA4) mutations in a family with stargardt disease and retinitis pigmentosa.

PubMed

Shroyer, N F; Lewis, R A; Yatsenko, A N; Lupski, J R

2001-11-01

To determine the type of ABCR mutations that segregate in a family that manifests both Stargardt disease (STGD) and retinitis pigmentosa (RP), and the functional consequences of the underlying mutations. Direct sequencing of all 50 exons and flanking intronic regions of ABCR was performed for the STGD- and RP-affected relatives. RNA hybridization, Western blot analysis, and azido-adenosine triphosphate (ATP) labeling was used to determine the effect of disease-associated ABCR mutations in an in vitro assay system. Compound heterozygous missense mutations were identified in patients with STGD and RP. STGD-affected individual AR682-03 was compound heterozygous for the mutation 2588G-->C and a complex allele, [W1408R; R1640W]. RP-affected individuals AR682-04 and-05 were compound heterozygous for the complex allele [W1408R; R1640W] and the missense mutation V767D. Functional analysis of the mutation V767D by Western blot and ATP binding revealed a severe reduction in protein expression. In vitro analysis of ABCR protein with the mutations W1408R and R1640W showed a moderate effect of these individual mutations on expression and ATP-binding; the complex allele [W1408R; R1640W] caused a severe reduction in protein expression. These data reveal that missense ABCR mutations may be associated with RP. Functional analysis reveals that the RP-associated missense ABCR mutations are likely to be functionally null. These studies of the complex allele W1408R; R1640W suggest a synergistic effect of the individual mutations. These data are congruent with a model in which RP is associated with homozygous null mutations and with the notion that severity of retinal disease is inversely related to residual ABCR activity.

An allelic series reveals essential roles for FY in plant development in addition to flowering-time control.

PubMed

Henderson, Ian R; Liu, Fuquan; Drea, Sinead; Simpson, Gordon G; Dean, Caroline

2005-08-01

The autonomous pathway functions to promote flowering in Arabidopsis by limiting the accumulation of the floral repressor FLOWERING LOCUS C (FLC). Within this pathway FCA is a plant-specific, nuclear RNA-binding protein, which interacts with FY, a highly conserved eukaryotic polyadenylation factor. FCA and FY function to control polyadenylation site choice during processing of the FCA transcript. Null mutations in the yeast FY homologue Pfs2p are lethal. This raises the question as to whether these essential RNA processing functions are conserved in plants. Characterisation of an allelic series of fy mutations reveals that null alleles are embryo lethal. Furthermore, silencing of FY, but not FCA, is deleterious to growth in Nicotiana. The late-flowering fy alleles are hypomorphic and indicate a requirement for both intact FY WD repeats and the C-terminal domain in repression of FLC. The FY C-terminal domain binds FCA and in vitro assays demonstrate a requirement for both C-terminal FY-PPLPP repeats during this interaction. The expression domain of FY supports its roles in essential and flowering-time functions. Hence, FY may mediate both regulated and constitutive RNA 3'-end processing.

Fear extinction and acute stress reactivity reveal a role of LPA(1) receptor in regulating emotional-like behaviors.

PubMed

Pedraza, C; Sánchez-López, J; Castilla-Ortega, E; Rosell-Valle, C; Zambrana-Infantes, E; García-Fernández, M; Rodriguez de Fonseca, F; Chun, J; Santín, L J; Estivill-Torrús, G

2014-09-01

LPA1 receptor is one of the six characterized G protein-coupled receptors (LPA1-6) through which lysophosphatidic acid acts as an intercellular signaling molecule. It has been proposed that this receptor has a role in controlling anxiety-like behaviors and in the detrimental consequences of stress. Here, we sought to establish the involvement of the LPA1 receptor in emotional regulation. To this end, we examined fear extinction in LPA1-null mice, wild-type and LPA1 antagonist-treated animals. In LPA1-null mice we also characterized the morphology and GABAergic properties of the amygdala and the medial prefrontal cortex. Furthermore, the expression of c-Fos protein in the amygdala and the medial prefrontal cortex, and the corticosterone response following acute stress were examined in both genotypes. Our data indicated that the absence of the LPA1 receptor significantly inhibited fear extinction. Treatment of wild-type mice with the LPA1 antagonist Ki16425 mimicked the behavioral phenotype of LPA1-null mice, revealing that the LPA1 receptor was involved in extinction. Immunohistochemistry studies revealed a reduction in the number of neurons, GABA+ cells, calcium-binding proteins and the volume of the amygdala in LPA1-null mice. Following acute stress, LPA1-null mice showed increased corticosterone and c-Fos expression in the amygdala. In conclusion, LPA1 receptor is involved in emotional behaviors and in the anatomical integrity of the corticolimbic circuit, the deregulation of which may be a susceptibility factor for anxiety disorders and a potential therapeutic target for the treatment of these diseases.

Altered Ca2+ Kinetics Associated with α-Actinin-3 Deficiency May Explain Positive Selection for ACTN3 Null Allele in Human Evolution

PubMed Central

Houweling, Peter J.; Quinlan, Kate G. R.; Murphy, Robyn; Wagner, Sören; Friedrich, Oliver; North, Kathryn N.

2015-01-01

Over 1.5 billion people lack the skeletal muscle fast-twitch fibre protein α-actinin-3 due to homozygosity for a common null polymorphism (R577X) in the ACTN3 gene. α-Actinin-3 deficiency is detrimental to sprint performance in elite athletes and beneficial to endurance activities. In the human genome, it is very difficult to find single-gene loss-of-function variants that bear signatures of positive selection, yet intriguingly, the ACTN3 null variant has undergone strong positive selection during recent evolution, appearing to provide a survival advantage where food resources are scarce and climate is cold. We have previously demonstrated that α-actinin-3 deficiency in the Actn3 KO mouse results in a shift in fast-twitch fibres towards oxidative metabolism, which would be more “energy efficient” in famine, and beneficial to endurance performance. Prolonged exposure to cold can also induce changes in skeletal muscle similar to those observed with endurance training, and changes in Ca2+ handling by the sarcoplasmic reticulum (SR) are a key factor underlying these adaptations. On this basis, we explored the effects of α-actinin-3 deficiency on Ca2+ kinetics in single flexor digitorum brevis muscle fibres from Actn3 KO mice, using the Ca2+-sensitive dye fura-2. Compared to wild-type, fibres of Actn3 KO mice showed: (i) an increased rate of decay of the twitch transient; (ii) a fourfold increase in the rate of SR Ca2+ leak; (iii) a threefold increase in the rate of SR Ca2+ pumping; and (iv) enhanced maintenance of tetanic Ca2+ during fatigue. The SR Ca2+ pump, SERCA1, and the Ca2+-binding proteins, calsequestrin and sarcalumenin, showed markedly increased expression in muscles of KO mice. Together, these changes in Ca2+ handling in the absence of α-actinin-3 are consistent with cold acclimatisation and thermogenesis, and offer an additional explanation for the positive selection of the ACTN3 577X null allele in populations living in cold environments during recent evolution. PMID:25590636

Influence of apolipoprotein A-V on the metabolic fate of triacylglycerol.

PubMed

Sharma, Vineeta; Forte, Trudy M; Ryan, Robert O

2013-04-01

Apolipoprotein (apo) A-V functions to modulate intracellular and extracellular triacylglycerol metabolism. The present review addresses molecular mechanisms underlying these effects. The relevance of apoA-V to human disease conditions is illustrated by the strong correlation between single nucleotide polymorphisms in APOA5, elevated plasma triacylglycerol and dyslipidemic disease. Despite undergoing processing for secretion from hepatocytes, a portion of apoA-V escapes this destiny and accumulates as a component of cytosolic lipid droplets. Expression of recombinant apoA-V in hepatocarcinoma cells results in increased lipid droplet size and number at the expense of triacylglycerol secretion.ApoA-V modulates atherosclerosis in hypercholesterolemic apoE null mice. ApoE null/human apoA-V transgenic mice had reduced levels of triacylglycerol and cholesterol in plasma along with decreased aortic lesion size. ApoA-V modulates triacylglycerol metabolic fate. Following its synthesis, apoA-V enters the endoplasmic reticulum and associates with membrane defects created by triacylglycerol accumulation. Association of apoA-V with endoplasmic reticulum membrane defects promotes nascent lipid droplets budding toward the cytosol. Despite its low concentration in plasma (∼150 ng/ml), apoA-V modulates lipoprotein metabolism by binding to glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1. This interaction effectively localizes triacylglycerol-rich lipoproteins in the vicinity of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein1's other ligand, lipoprotein lipase.

Influence of apolipoprotein A-V on the metabolic fate of triacylglycerol

PubMed Central

Sharma, Vineeta; Forte, Trudy M.; Ryan, Robert O.

2013-01-01

Purpose of review Apolipoprotein (apo) A-V functions to modulate intracellular and extracellular triacylglycerol metabolism. The present review addresses molecular mechanisms underlying these effects. The relevance of apoA-V to human disease conditions is illustrated by the strong correlation between single nucleotide polymorphisms in APOA5, elevated plasma triacylglycerol and dyslipidemic disease. Recent findings Despite undergoing processing for secretion from hepatocytes, a portion of apoA-V escapes this destiny and accumulates as a component of cytosolic lipid droplets. Expression of recombinant apoA-V in hepatocarcinoma cells results in increased lipid droplet size and number at the expense of triacylglycerol secretion. ApoA-V modulates atherosclerosis in hypercholesterolemic apoE null mice. ApoE null/human apoA-V transgenic mice had reduced levels of triacylglycerol and cholesterol in plasma along with decreased aortic lesion size. Summary ApoA-V modulates triacylglycerol metabolic fate. Following its synthesis, apoA-V enters the endoplasmic reticulum and associates with membrane defects created by triacylglycerol accumulation. Association of apoA-V with endoplasmic reticulum membrane defects promotes nascent lipid droplets budding toward the cytosol. Despite its low concentration in plasma (~150 ng/ml), apoA-V modulates lipoprotein metabolism by binding to glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1. This interaction effectively localizes triacylglycerol-rich lipoproteins in the vicinity of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1’s other ligand, lipoprotein lipase. PMID:23241513

The high mobility group protein Abf2p influences the level of yeast mitochondrial DNA recombination intermediates in vivo.

PubMed

MacAlpine, D M; Perlman, P S; Butow, R A

1998-06-09

Abf2p is a high mobility group (HMG) protein found in yeast mitochondria that is required for the maintenance of wild-type (rho+) mtDNA in cells grown on fermentable carbon sources, and for efficient recombination of mtDNA markers in crosses. Here, we show by two-dimensional gel electrophoresis that Abf2p promotes or stabilizes Holliday recombination junction intermediates in rho+ mtDNA in vivo but does not influence the high levels of recombination intermediates readily detected in the mtDNA of petite mutants (rho-). mtDNA recombination junctions are not observed in rho+ mtDNA of wild-type cells but are elevated to detectable levels in cells with a null allele of the MGT1 gene (Deltamgt1), which codes for a mitochondrial cruciform-cutting endonuclease. The level of recombination intermediates in rho+ mtDNA of Deltamgt1 cells is decreased about 10-fold if those cells contain a null allele of the ABF2 gene. Overproduction of Abf2p by >/= 10-fold in wild-type rho+ cells, which leads to mtDNA instability, results in a dramatic increase in mtDNA recombination intermediates. Specific mutations in the two Abf2p HMG boxes required for DNA binding diminishes these responses. We conclude that Abf2p functions in the recombination of rho+ mtDNA.

A Novel Bifunctional Alkylphenol Anesthetic Allows Characterization of γ-Aminobutyric Acid, Type A (GABAA), Receptor Subunit Binding Selectivity in Synaptosomes.

PubMed

Woll, Kellie A; Murlidaran, Sruthi; Pinch, Benika J; Hénin, Jérôme; Wang, Xiaoshi; Salari, Reza; Covarrubias, Manuel; Dailey, William P; Brannigan, Grace; Garcia, Benjamin A; Eckenhoff, Roderic G

2016-09-23

Propofol, an intravenous anesthetic, is a positive modulator of the GABAA receptor, but the mechanistic details, including the relevant binding sites and alternative targets, remain disputed. Here we undertook an in-depth study of alkylphenol-based anesthetic binding to synaptic membranes. We designed, synthesized, and characterized a chemically active alkylphenol anesthetic (2-((prop-2-yn-1-yloxy)methyl)-5-(3-(trifluoromethyl)-3H-diazirin-3-yl)phenol, AziPm-click (1)), for affinity-based protein profiling (ABPP) of propofol-binding proteins in their native state within mouse synaptosomes. The ABPP strategy captured ∼4% of the synaptosomal proteome, including the unbiased capture of five α or β GABAA receptor subunits. Lack of γ2 subunit capture was not due to low abundance. Consistent with this, independent molecular dynamics simulations with alchemical free energy perturbation calculations predicted selective propofol binding to interfacial sites, with higher affinities for α/β than γ-containing interfaces. The simulations indicated hydrogen bonding is a key component leading to propofol-selective binding within GABAA receptor subunit interfaces, with stable hydrogen bonds observed between propofol and α/β cavity residues but not γ cavity residues. We confirmed this by introducing a hydrogen bond-null propofol analogue as a protecting ligand for targeted-ABPP and observed a lack of GABAA receptor subunit protection. This investigation demonstrates striking interfacial GABAA receptor subunit selectivity in the native milieu, suggesting that asymmetric occupancy of heteropentameric ion channels by alkylphenol-based anesthetics is sufficient to induce modulation of activity. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

A Novel Bifunctional Alkylphenol Anesthetic Allows Characterization of γ-Aminobutyric Acid, Type A (GABAA), Receptor Subunit Binding Selectivity in Synaptosomes*

PubMed Central

Woll, Kellie A.; Murlidaran, Sruthi; Pinch, Benika J.; Hénin, Jérôme; Wang, Xiaoshi; Salari, Reza; Covarrubias, Manuel; Dailey, William P.; Brannigan, Grace; Garcia, Benjamin A.; Eckenhoff, Roderic G.

2016-01-01

Propofol, an intravenous anesthetic, is a positive modulator of the GABAA receptor, but the mechanistic details, including the relevant binding sites and alternative targets, remain disputed. Here we undertook an in-depth study of alkylphenol-based anesthetic binding to synaptic membranes. We designed, synthesized, and characterized a chemically active alkylphenol anesthetic (2-((prop-2-yn-1-yloxy)methyl)-5-(3-(trifluoromethyl)-3H-diazirin-3-yl)phenol, AziPm-click (1)), for affinity-based protein profiling (ABPP) of propofol-binding proteins in their native state within mouse synaptosomes. The ABPP strategy captured ∼4% of the synaptosomal proteome, including the unbiased capture of five α or β GABAA receptor subunits. Lack of γ2 subunit capture was not due to low abundance. Consistent with this, independent molecular dynamics simulations with alchemical free energy perturbation calculations predicted selective propofol binding to interfacial sites, with higher affinities for α/β than γ-containing interfaces. The simulations indicated hydrogen bonding is a key component leading to propofol-selective binding within GABAA receptor subunit interfaces, with stable hydrogen bonds observed between propofol and α/β cavity residues but not γ cavity residues. We confirmed this by introducing a hydrogen bond-null propofol analogue as a protecting ligand for targeted-ABPP and observed a lack of GABAA receptor subunit protection. This investigation demonstrates striking interfacial GABAA receptor subunit selectivity in the native milieu, suggesting that asymmetric occupancy of heteropentameric ion channels by alkylphenol-based anesthetics is sufficient to induce modulation of activity. PMID:27462076

The nucleoid protein Dps binds genomic DNA of Escherichia coli in a non-random manner

PubMed Central

Kondrashov, F. A.; Toshchakov, S. V.; Dominova, I.; Shvyreva, U. S.; Vrublevskaya, V. V.; Morenkov, O. S.; Panyukov, V. V.

2017-01-01

Dps is a multifunctional homododecameric protein that oxidizes Fe2+ ions accumulating them in the form of Fe2O3 within its protein cavity, interacts with DNA tightly condensing bacterial nucleoid upon starvation and performs some other functions. During the last two decades from discovery of this protein, its ferroxidase activity became rather well studied, but the mechanism of Dps interaction with DNA still remains enigmatic. The crucial role of lysine residues in the unstructured N-terminal tails led to the conventional point of view that Dps binds DNA without sequence or structural specificity. However, deletion of dps changed the profile of proteins in starved cells, SELEX screen revealed genomic regions preferentially bound in vitro and certain affinity of Dps for artificial branched molecules was detected by atomic force microscopy. Here we report a non-random distribution of Dps binding sites across the bacterial chromosome in exponentially growing cells and show their enrichment with inverted repeats prone to form secondary structures. We found that the Dps-bound regions overlap with sites occupied by other nucleoid proteins, and contain overrepresented motifs typical for their consensus sequences. Of the two types of genomic domains with extensive protein occupancy, which can be highly expressed or transcriptionally silent only those that are enriched with RNA polymerase molecules were preferentially occupied by Dps. In the dps-null mutant we, therefore, observed a differentially altered expression of several targeted genes and found suppressed transcription from the dps promoter. In most cases this can be explained by the relieved interference with Dps for nucleoid proteins exploiting sequence-specific modes of DNA binding. Thus, protecting bacterial cells from different stresses during exponential growth, Dps can modulate transcriptional integrity of the bacterial chromosome hampering RNA biosynthesis from some genes via competition with RNA polymerase or, vice versa, competing with inhibitors to activate transcription. PMID:28800583

RNA-binding protein DUS16 plays an essential role in primary miRNA processing in the unicellular alga Chlamydomonas reinhardtii.

PubMed

Yamasaki, Tomohito; Onishi, Masayuki; Kim, Eun-Jeong; Cerutti, Heriberto; Ohama, Takeshi

2016-09-20

Canonical microRNAs (miRNAs) are embedded in duplexed stem-loops in long precursor transcripts and are excised by sequential cleavage by DICER nuclease(s). In this miRNA biogenesis pathway, dsRNA-binding proteins play important roles in animals and plants by assisting DICER. However, these RNA-binding proteins are poorly characterized in unicellular organisms. Here we report that a unique RNA-binding protein, Dull slicer-16 (DUS16), plays an essential role in processing of primary-miRNA (pri-miRNA) transcripts in the unicellular green alga Chlamydomonas reinhardtii In animals and plants, dsRNA-binding proteins involved in miRNA biogenesis harbor two or three dsRNA-binding domains (dsRBDs), whereas DUS16 contains one dsRBD and also an ssRNA-binding domain (RRM). The null mutant of DUS16 showed a drastic reduction in most miRNA species. Production of these miRNAs was complemented by expression of full-length DUS16, but the expression of RRM- or dsRBD-truncated DUS16 did not restore miRNA production. Furthermore, DUS16 is predominantly localized to the nucleus and associated with nascent (unspliced form) pri-miRNAs and the DICER-LIKE 3 protein. These results suggest that DUS16 recognizes pri-miRNA transcripts cotranscriptionally and promotes their processing into mature miRNAs as a component of a microprocessor complex. We propose that DUS16 is an essential factor for miRNA production in Chlamydomonas and, because DUS16 is functionally similar to the dsRNA-binding proteins involved in miRNA biogenesis in animals and land plants, our report provides insight into this mechanism in unicellular eukaryotes.

Glycosylation of Cblns attenuates their receptor binding.

PubMed

Rong, Yongqi; Bansal, Parmil K; Wei, Peng; Guo, Hong; Correia, Kristen; Parris, Jennifer; Morgan, James I

2018-05-18

Cbln1 is the prototype of a family (Cbln1-Cbln4) of secreted glycoproteins and is essential for normal synapse structure and function in cerebellum by bridging presynaptic Nrxn to postsynaptic Grid2. Here we report the effects of glycosylation on the in vitro receptor binding properties of Cblns. Cbln1, 2 and 4 harbor two N-linked glycosylation sites, one at the N-terminus is in a region implicated in Nrxn binding and the second is in the C1q domain, a region involved in Grid2 binding. Mutation (asparagine to glutamine) of the N-terminal site, increased neurexin binding whereas mutation of the C1q site markedly increased Grid2 binding. These mutations did not influence subunit composition of Cbln trimeric complexes (mediated through the C1q domain) nor their assembly into hexamers (mediated by the N-terminal region). Therefore, glycosylation likely masks the receptor binding interfaces of Cblns. As Cbln4 has undetectable Grid2 binding in vitro we assessed whether transgenic expression of wild type Cbln4 or its glycosylation mutants rescued the Cbln1-null phenotype in vivo. Cbln4 partially rescued and both glycosylation mutants completely rescued ataxia in cbln1-null mice. Thus Cbln4 has intrinsic Grid2 binding that is attenuated by glycosylation, and glycosylation mutants exhibit gain of function in vivo. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Loss of Oca2 disrupts the unfolded protein response and increases resistance to endoplasmic reticulum stress in melanocytes

PubMed Central

Cheng, Tsing; Orlow, Seth J.; Manga, Prashiela

2013-01-01

Summary Accumulation of proteins in the endoplasmic reticulum (ER) typically induces stress and initiates the unfolded protein response (UPR) to facilitate recovery. If homeostasis is not restored, apoptosis is induced. However, adaptation to chronic UPR activation can increase resistance to subsequent acute ER stress. We therefore investigated adaptive mechanisms in Oculocutaneous albinism type 2 (Oca2)-null melanocytes where UPR signaling is arrested despite continued tyrosinase accumulation leading to resistance to the chemical ER stressor thapsigargin. Although thapsigargin triggers UPR activation, instead of Perk-mediated phosphorylation of eIF2α, in Oca2-null melanocytes, eIF2α was rapidly dephosphorylated upon treatment. Dephosphorylation was mediated by the Gadd34-PP1α phosphatase complex. Gadd34-complex inhibition blocked eIF2α dephosphorylation and significantly increased Oca2-null melanocyte sensitivity to thapsigargin. Thus, Oca2-null melanocytes adapt to acute ER stress by disruption of proapoptotic Perk signaling, which promotes cell survival. This is the first study to demonstrate rapid eIF2α dephosphorylation as an adaptive mechanism to ER stress. PMID:23962237

Structural and Functional Characterizations of SsgB, a Conserved Activator of Developmental Cell Division in Morphologically Complex Actinomycetes*

PubMed Central

Xu, Qingping; Traag, Bjørn A.; Willemse, Joost; McMullan, Daniel; Miller, Mitchell D.; Elsliger, Marc-André; Abdubek, Polat; Astakhova, Tamara; Axelrod, Herbert L.; Bakolitsa, Constantina; Carlton, Dennis; Chen, Connie; Chiu, Hsiu-Ju; Chruszcz, Maksymilian; Clayton, Thomas; Das, Debanu; Deller, Marc C.; Duan, Lian; Ellrott, Kyle; Ernst, Dustin; Farr, Carol L.; Feuerhelm, Julie; Grant, Joanna C.; Grzechnik, Anna; Grzechnik, Slawomir K.; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Kozbial, Piotr; Krishna, S. Sri; Kumar, Abhinav; Marciano, David; Minor, Wladek; Mommaas, A. Mieke; Morse, Andrew T.; Nigoghossian, Edward; Nopakun, Amanda; Okach, Linda; Oommachen, Silvya; Paulsen, Jessica; Puckett, Christina; Reyes, Ron; Rife, Christopher L.; Sefcovic, Natasha; Tien, Henry J.; Trame, Christine B.; van den Bedem, Henry; Wang, Shuren; Weekes, Dana; Hodgson, Keith O.; Wooley, John; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.; van Wezel, Gilles P.

2009-01-01

SsgA-like proteins (SALPs) are a family of homologous cell division-related proteins that occur exclusively in morphologically complex actinomycetes. We show that SsgB, a subfamily of SALPs, is the archetypal SALP that is functionally conserved in all sporulating actinomycetes. Sporulation-specific cell division of Streptomyces coelicolor ssgB mutants is restored by introduction of distant ssgB orthologues from other actinomycetes. Interestingly, the number of septa (and spores) of the complemented null mutants is dictated by the specific ssgB orthologue that is expressed. The crystal structure of the SsgB from Thermobifida fusca was determined at 2.6 Å resolution and represents the first structure for this family. The structure revealed similarities to a class of eukaryotic “whirly” single-stranded DNA/RNA-binding proteins. However, the electro-negative surface of the SALPs suggests that neither SsgB nor any of the other SALPs are likely to interact with nucleotide substrates. Instead, we show that a conserved hydrophobic surface is likely to be important for SALP function and suggest that proteins are the likely binding partners. PMID:19567872

Alterations in the cholinergic system of brain stem neurons in a mouse model of Rett syndrome.

PubMed

Oginsky, Max F; Cui, Ningren; Zhong, Weiwei; Johnson, Christopher M; Jiang, Chun

2014-09-15

Rett syndrome is an autism-spectrum disorder resulting from mutations to the X-linked gene, methyl-CpG binding protein 2 (MeCP2), which causes abnormalities in many systems. It is possible that the body may develop certain compensatory mechanisms to alleviate the abnormalities. The norepinephrine system originating mainly in the locus coeruleus (LC) is defective in Rett syndrome and Mecp2-null mice. LC neurons are subject to modulation by GABA, glutamate, and acetylcholine (ACh), providing an ideal system to test the compensatory hypothesis. Here we show evidence for potential compensatory modulation of LC neurons by post- and presynaptic ACh inputs. We found that the postsynaptic currents of nicotinic ACh receptors (nAChR) were smaller in amplitude and longer in decay time in the Mecp2-null mice than in the wild type. Single-cell PCR analysis showed a decrease in the expression of α3-, α4-, α7-, and β3-subunits and an increase in the α5- and α6-subunits in the mutant mice. The α5-subunit was present in many of the LC neurons with slow-decay nAChR currents. The nicotinic modulation of spontaneous GABAA-ergic inhibitory postsynaptic currents in LC neurons was enhanced in Mecp2-null mice. In contrast, the nAChR manipulation of glutamatergic input to LC neurons was unaffected in both groups of mice. Our current-clamp studies showed that the modulation of LC neurons by ACh input was reduced moderately in Mecp2-null mice, despite the major decrease in nAChR currents, suggesting possible compensatory processes may take place, thus reducing the defects to a lesser extent in LC neurons. Copyright © 2014 the American Physiological Society.

Pharmacological and immunochemical characterization of α2* nicotinic acetylcholine receptors (nAChRs) in mouse brain

PubMed Central

Whiteaker, Paul; Wilking, Jennifer A; Brown, Robert WB; Brennan, Robert J; Collins, Allan C; Lindstrom, Jon M; Boulter, Jim

2009-01-01

Aim: α2 nAChR subunit mRNA expression in mice is most intense in the olfactory bulbs and interpeduncular nucleus. We aimed to investigate the properties of α2* nAChRs in these mouse brain regions. Methods: α2 nAChR subunit-null mutant mice were engineered. Pharmacological and immunoprecipitation studies were used to determine the composition of α2 subunit-containing (α2*) nAChRs in these two regions. Results: [125I]Epibatidine (200 pmol/L) autoradiography and saturation binding demonstrated that α2 deletion reduces nAChR expression in both olfactory bulbs and interpeduncular nucleus (by 4.8±1.7 and 92±26 fmol̇mg-1 protein, respectively). Pharmacological characterization using the β2-selective drug A85380 to inhibit [125I]epibatidine binding proved inconclusive, so immunoprecipitation methods were used to further characterize α2* nAChRs. Protocols were established to immunoprecipitate β2 and β4 nAChRs. Immunoprecipitation specificity was ascertained using tissue from β2- and β4-null mutant mice, and efficacy was good (>90% of β2* and >80% of β4* nAChRs were routinely recovered). Conclusion: Immunoprecipitation experiments indicated that interpeduncular nucleus α2* nAChRs predominantly contain β2 subunits, while those in olfactory bulbs contain mainly β4 subunits. In addition, the immunoprecipitation evidence indicated that both nuclei, but especially the interpeduncular nucleus, express nAChR complexes containing both β2 and β4 subunits. PMID:19498420

Yeast Genes Controlling Responses to Topogenic Signals in a Model Transmembrane Protein

PubMed Central

Tipper, Donald J.; Harley, Carol A

2002-01-01

Yeast protein insertion orientation (PIO) mutants were isolated by selecting for growth on sucrose in cells in which the only source of invertase is a C-terminal fusion to a transmembrane protein. Only the fraction with an exocellular C terminus can be processed to secreted invertase and this fraction is constrained to 2–3% by a strong charge difference signal. Identified pio mutants increased this to 9–12%. PIO1 is SPF1, encoding a P-type ATPase located in the endoplasmic reticulum (ER) or Golgi. spf1-null mutants are modestly sensitive to EGTA. Sensitivity is considerably greater in an spf1 pmr1 double mutant, although PIO is not further disturbed. Pmr1p is the Golgi Ca2+ ATPase and Spf1p may be the equivalent ER pump. PIO2 is STE24, a metalloprotease anchored in the ER membrane. Like Spf1p, Ste24p is expressed in all yeast cell types and belongs to a highly conserved protein family. The effects of ste24- and spf1-null mutations on invertase secretion are additive, cell generation time is increased 60%, and cells become sensitive to cold and to heat shock. Ste24p and Rce1p cleave the C-AAX bond of farnesylated CAAX box proteins. The closest paralog of SPF1 is YOR291w. Neither rce1-null nor yor291w-null mutations affected PIO or the phenotype of spf1- or ste24-null mutants. Mutations in PIO3 (unidentified) cause a weaker Pio phenotype, enhanced by a null mutation in BMH1, one of two yeast 14-3-3 proteins. PMID:11950929

Abrogation of both short and long forms of latent transforming growth factor-β binding protein-1 causes defective cardiovascular development and is perinatally lethal.

PubMed

Horiguchi, Masahito; Todorovic, Vesna; Hadjiolova, Krassimira; Weiskirchen, Ralf; Rifkin, Daniel B

2015-04-01

Latent transforming growth factor-β binding protein-1 (LTBP-1) is an extracellular protein that is structurally similar to fibrillin and has an important role in controlling transforming growth factor-β (TGF-β) signaling by storing the cytokine in the extracellular matrix and by being involved in the conversion of the latent growth factor to its active form. LTBP-1 is found as both short (LTBP-1S) and long (LTBP-1L) forms, which are derived through the use of separate promoters. There is controversy regarding the importance of LTBP-1L, as Ltbp1L knockout mice showed multiple cardiovascular defects but the complete null mice did not. Here, we describe a third line of Ltbp1 knockout mice generated utilizing a conditional knockout strategy that ablated expression of both L and S forms of LTBP-1. These mice show severe developmental cardiovascular abnormalities and die perinatally; thus these animals display a phenotype similar to previously reported Ltbp1L knockout mice. We reinvestigated the other "complete" knockout line and found that these mice express a splice variant of LTBP-1L and, therefore, are not complete Ltbp1 knockouts. Our results clarify the phenotypes of Ltbp1 null mice and re-emphasize the importance of LTBP-1 in vivo. Copyright © 2015. Published by Elsevier B.V.

Disruption of insulin-like growth factor-II imprinting during embryonic development rescues the dwarf phenotype of mice null for pregnancy-associated plasma protein-A.

PubMed

Bale, Laurie K; Conover, Cheryl A

2005-08-01

Pregnancy-associated plasma protein-A (PAPP-A), an insulin-like growth factor-binding protein (IGFBP) protease, increases insulin-like growth factor (IGF) activity through cleavage of inhibitory IGFBP-4 and the consequent release of IGF peptide for receptor activation. Mice homozygous for targeted disruption of the PAPP-A gene are born as proportional dwarfs and exhibit retarded bone ossification during fetal development. Phenotype and in vitro data support a model in which decreased IGF-II bioavailability during embryogenesis results in growth retardation and reduction in overall body size. To test the hypothesis that an increase in IGF-II during embryogenesis would overcome the growth deficiencies, PAPP-A-null mice were crossed with DeltaH19 mutant mice, which have increased IGF-II expression and fetal overgrowth due to disruption of IgfII imprinting. DeltaH19 mutant mice were 126% and PAPP-A-null mice were 74% the size of controls at birth. These size differences were evident at embryonic day 16.5. Importantly, double mutants were indistinguishable from controls both in terms of size and skeletal development. Body size programmed during embryo development persisted post-natally. Thus, disruption of IgfII imprinting and consequent elevation in IGF-II during fetal development was associated with rescue of the dwarf phenotype and ossification defects of PAPP-A-null mice. These data provide strong genetic evidence that PAPP-A plays an essential role in determining IGF-II bioavailability for optimal fetal growth and development.

Analysis of TFAP2A mutations in Branchio-Oculo-Facial Syndrome indicates functional complexity within the AP-2α DNA-binding domain

PubMed Central

Li, Hong; Sheridan, Ryan; Williams, Trevor

2013-01-01

Multiple lines of evidence indicate that the AP-2 transcription factor family has an important regulatory function in human craniofacial development. Notably, mutations in TFAP2A, the gene encoding AP-2α, have been identified in patients with Branchio-Oculo-Facial Syndrome (BOFS). BOFS is an autosomal-dominant trait that commonly presents with facial clefting, eye defects and branchial skin anomalies. Examination of multiple cases has suggested either simple haploinsufficiency or more complex genetic causes for BOFS, especially as the clinical manifestations are variable, with no clear genotype–phenotype correlation. Mutations occur throughout TFAP2A, but mostly within conserved sequences within the DNA contact domain of AP-2α. However, the consequences of the various mutations for AP-2α protein function have not been evaluated. Therefore, it remains unclear if all BOFS mutations result in similar changes to the AP-2α protein or if they each produce specific alterations that underlie the spectrum of phenotypes. Here, we have investigated the molecular consequences of the mutations that localize to the DNA-binding region. We show that although individual mutations have different effects on DNA binding, they all demonstrate significantly reduced transcriptional activities. Moreover, all mutant derivatives have an altered nuclear:cytoplasmic distribution compared with the predominantly nuclear localization of wild-type AP-2α and several can exert a dominant-negative activity on the wild-type AP-2α protein. Overall, our data suggest that the individual TFAP2A BOFS mutations can generate null, hypomorphic or antimorphic alleles and that these differences in activity, combined with a role for AP-2α in epigenetic events, may influence the resultant pathology and the phenotypic variability. PMID:23578821

Structure-function analysis and genetic interactions of the SmG, SmE, and SmF subunits of the yeast Sm protein ring.

PubMed

Schwer, Beate; Kruchten, Joshua; Shuman, Stewart

2016-09-01

A seven-subunit Sm protein ring forms a core scaffold of the U1, U2, U4, and U5 snRNPs that direct pre-mRNA splicing. Using human snRNP structures to guide mutagenesis in Saccharomyces cerevisiae, we gained new insights into structure-function relationships of the SmG, SmE, and SmF subunits. An alanine scan of 19 conserved amino acids of these three proteins, comprising the Sm RNA binding sites or inter-subunit interfaces, revealed that, with the exception of Arg74 in SmF, none are essential for yeast growth. Yet, for SmG, SmE, and SmF, as for many components of the yeast spliceosome, the effects of perturbing protein-RNA and protein-protein interactions are masked by built-in functional redundancies of the splicing machine. For example, tests for genetic interactions with non-Sm splicing factors showed that many benign mutations of SmG, SmE, and SmF (and of SmB and SmD3) were synthetically lethal with null alleles of U2 snRNP subunits Lea1 and Msl1. Tests of pairwise combinations of SmG, SmE, SmF, SmB, and SmD3 alleles highlighted the inherent redundancies within the Sm ring, whereby simultaneous mutations of the RNA binding sites of any two of the Sm subunits are lethal. Our results suggest that six intact RNA binding sites in the Sm ring suffice for function but five sites may not. © 2016 Schwer et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Compensatory changes in CYP expression in three different toxicology mouse models: CAR-null, Cyp3a-null, and Cyp2b9/10/13-null mice

PubMed Central

Kumar, Ramiya; Mota, Linda C.; Litoff, Elizabeth J.; Rooney, John P.; Boswell, W. Tyler; Courter, Elliott; Henderson, Charles M.; Hernandez, Juan P.; Corton, J. Christopher; Moore, David D.

2017-01-01

Targeted mutant models are common in mechanistic toxicology experiments investigating the absorption, metabolism, distribution, or elimination (ADME) of chemicals from individuals. Key models include those for xenosensing transcription factors and cytochrome P450s (CYP). Here we investigated changes in transcript levels, protein expression, and steroid hydroxylation of several xenobiotic detoxifying CYPs in constitutive androstane receptor (CAR)-null and two CYP-null mouse models that have subfamily members regulated by CAR; the Cyp3a-null and a newly described Cyp2b9/10/13-null mouse model. Compensatory changes in CYP expression that occur in these models may also occur in polymorphic humans, or may complicate interpretation of ADME studies performed using these models. The loss of CAR causes significant changes in several CYPs probably due to loss of CAR-mediated constitutive regulation of these CYPs. Expression and activity changes include significant repression of Cyp2a and Cyp2b members with corresponding drops in 6α- and 16β-testosterone hydroxylase activity. Further, the ratio of 6α-/15α-hydroxylase activity, a biomarker of sexual dimorphism in the liver, indicates masculinization of female CAR-null mice, suggesting a role for CAR in the regulation of sexually dimorphic liver CYP profiles. The loss of Cyp3a causes fewer changes than CAR. Nevertheless, there are compensatory changes including gender-specific increases in Cyp2a and Cyp2b. Cyp2a and Cyp2b were down-regulated in CAR-null mice, suggesting activation of CAR and potentially PXR following loss of the Cyp3a members. However, the loss of Cyp2b causes few changes in hepatic CYP transcript levels and almost no significant compensatory changes in protein expression or activity with the possible exception of 6α-hydroxylase activity. This lack of a compensatory response in the Cyp2b9/10/13-null mice is probably due to low CYP2B hepatic expression, especially in male mice. Overall, compensatory and regulatory CYP changes followed the order CAR-null > Cyp3a-null > Cyp2b-null mice. PMID:28350814

Compensatory changes in CYP expression in three different toxicology mouse models: CAR-null, Cyp3a-null, and Cyp2b9/10/13-null mice.

PubMed

Kumar, Ramiya; Mota, Linda C; Litoff, Elizabeth J; Rooney, John P; Boswell, W Tyler; Courter, Elliott; Henderson, Charles M; Hernandez, Juan P; Corton, J Christopher; Moore, David D; Baldwin, William S

2017-01-01

Targeted mutant models are common in mechanistic toxicology experiments investigating the absorption, metabolism, distribution, or elimination (ADME) of chemicals from individuals. Key models include those for xenosensing transcription factors and cytochrome P450s (CYP). Here we investigated changes in transcript levels, protein expression, and steroid hydroxylation of several xenobiotic detoxifying CYPs in constitutive androstane receptor (CAR)-null and two CYP-null mouse models that have subfamily members regulated by CAR; the Cyp3a-null and a newly described Cyp2b9/10/13-null mouse model. Compensatory changes in CYP expression that occur in these models may also occur in polymorphic humans, or may complicate interpretation of ADME studies performed using these models. The loss of CAR causes significant changes in several CYPs probably due to loss of CAR-mediated constitutive regulation of these CYPs. Expression and activity changes include significant repression of Cyp2a and Cyp2b members with corresponding drops in 6α- and 16β-testosterone hydroxylase activity. Further, the ratio of 6α-/15α-hydroxylase activity, a biomarker of sexual dimorphism in the liver, indicates masculinization of female CAR-null mice, suggesting a role for CAR in the regulation of sexually dimorphic liver CYP profiles. The loss of Cyp3a causes fewer changes than CAR. Nevertheless, there are compensatory changes including gender-specific increases in Cyp2a and Cyp2b. Cyp2a and Cyp2b were down-regulated in CAR-null mice, suggesting activation of CAR and potentially PXR following loss of the Cyp3a members. However, the loss of Cyp2b causes few changes in hepatic CYP transcript levels and almost no significant compensatory changes in protein expression or activity with the possible exception of 6α-hydroxylase activity. This lack of a compensatory response in the Cyp2b9/10/13-null mice is probably due to low CYP2B hepatic expression, especially in male mice. Overall, compensatory and regulatory CYP changes followed the order CAR-null > Cyp3a-null > Cyp2b-null mice.

Elucidation of the Block to Herpes Simplex Virus Egress in the Absence of Tegument Protein UL16 Reveals a Novel Interaction with VP22

PubMed Central

Starkey, Jason L.; Han, Jun; Chadha, Pooja; Marsh, Jacob A.

2014-01-01

UL16 is a tegument protein of herpes simplex virus (HSV) that is conserved among all members of the Herpesviridae, but its function is poorly understood. Previous studies revealed that UL16 is associated with capsids in the cytoplasm and interacts with the membrane protein UL11, which suggested a “bridging” function during cytoplasmic envelopment, but this conjecture has not been tested. To gain further insight, cells infected with UL16-null mutants were examined by electron microscopy. No defects in the transport of capsids to cytoplasmic membranes were observed, but the wrapping of capsids with membranes was delayed. Moreover, clusters of cytoplasmic capsids were often observed, but only near membranes, where they were wrapped to produce multiple capsids within a single envelope. Normal virion production was restored when UL16 was expressed either by complementing cells or from a novel position in the HSV genome. When the composition of the UL16-null viruses was analyzed, a reduction in the packaging of glycoprotein E (gE) was observed, which was not surprising, since it has been reported that UL16 interacts with this glycoprotein. However, levels of the tegument protein VP22 were also dramatically reduced in virions, even though this gE-binding protein has been shown not to depend on its membrane partner for packaging. Cotransfection experiments revealed that UL16 and VP22 can interact in the absence of other viral proteins. These results extend the UL16 interaction network beyond its previously identified binding partners to include VP22 and provide evidence that UL16 plays an important function at the membrane during virion production. PMID:24131716

Six post-implantation lethal knockouts of genes for lipophilic MAPK pathway proteins are expressed in preimplantation mouse embryos and trophoblast stem cells.

PubMed

Xie, Yufen; Wang, Yingchun; Sun, Tong; Wang, Fangfei; Trostinskaia, Anna; Puscheck, Elizabeth; Rappolee, Daniel A

2005-05-01

Mitogen-activated protein kinase (MAPK) signaling pathways play an important role in controlling embryonic proliferation and differentiation. It has been demonstrated that sequential lipophilic signal transduction mediators that participate in the MAPK pathway are null post-implantation lethal. It is not clear why the lethality of these null mutants arises after implantation and not before. One hypothesis is that the gene product of these post-implantation lethal null mutants are not present before implantation in normal embryos and do not have function until after implantation. To test this hypothesis, we selected a set of lipophilic genes mediating MAPK signal transduction pathways whose null mutants result in early peri-implantation or placental lethality. These included FRS2alpha, GAB1, GRB2, SOS1, Raf-B, and Raf1. Products of these selected genes were detected and their locations and functions indicated by indirect immunocytochemistry and Western blotting for proteins and RT-polymerase chain reaction (PCR) for mRNA transcription. We report here that all six signal mediators are detected at the protein level in preimplantation mouse embryo, placental trophoblasts, and in cultured trophoblast stem cells (TSC). Proteins are all detected in E3.5 embryos at a time when the first known mitogenic intercellular communication has been documented. mRNA transcripts of two post-implantation null mutant genes are expressed in mouse preimplantation embryos and unfertilized eggs. These mRNA transcripts were detected as maternal mRNA in unfertilized eggs that could delay the lethality of null mutants. All of the proteins were detected in the cytoplasm or in the cell membrane. This study of spatial and temporal expression revealed that all of these six null mutants post-implantation genes in MAPK pathway are expressed and, where tested, phosphorylated/activated proteins are detected in the blastocyst. Studies on RNA expression using RT-PCR suggest that maternal RNA could play an important role in delaying the presence of the lethal phenotype of null mutations. Copyright (c) 2005 Wiley-Liss, Inc.

AKAP13 Rho-GEF and PKD-Binding Domain Deficient Mice Develop Normally but Have an Abnormal Response to β-Adrenergic-Induced Cardiac Hypertrophy

PubMed Central

Spindler, Matthew J.; Burmeister, Brian T.; Huang, Yu; Hsiao, Edward C.; Salomonis, Nathan; Scott, Mark J.; Srivastava, Deepak; Carnegie, Graeme K.; Conklin, Bruce R.

2013-01-01

Background A-kinase anchoring proteins (AKAPs) are scaffolding molecules that coordinate and integrate G-protein signaling events to regulate development, physiology, and disease. One family member, AKAP13, encodes for multiple protein isoforms that contain binding sites for protein kinase A (PKA) and D (PKD) and an active Rho-guanine nucleotide exchange factor (Rho-GEF) domain. In mice, AKAP13 is required for development as null embryos die by embryonic day 10.5 with cardiovascular phenotypes. Additionally, the AKAP13 Rho-GEF and PKD-binding domains mediate cardiomyocyte hypertrophy in cell culture. However, the requirements for the Rho-GEF and PKD-binding domains during development and cardiac hypertrophy are unknown. Methodology/Principal Findings To determine if these AKAP13 protein domains are required for development, we used gene-trap events to create mutant mice that lacked the Rho-GEF and/or the protein kinase D-binding domains. Surprisingly, heterozygous matings produced mutant mice at Mendelian ratios that had normal viability and fertility. The adult mutant mice also had normal cardiac structure and electrocardiograms. To determine the role of these domains during β-adrenergic-induced cardiac hypertrophy, we stressed the mice with isoproterenol. We found that heart size was increased similarly in mice lacking the Rho-GEF and PKD-binding domains and wild-type controls. However, the mutant hearts had abnormal cardiac contractility as measured by fractional shortening and ejection fraction. Conclusions These results indicate that the Rho-GEF and PKD-binding domains of AKAP13 are not required for mouse development, normal cardiac architecture, or β-adrenergic-induced cardiac hypertrophic remodeling. However, these domains regulate aspects of β-adrenergic-induced cardiac hypertrophy. PMID:23658642

Loss of Oca2 disrupts the unfolded protein response and increases resistance to endoplasmic reticulum stress in melanocytes.

PubMed

Cheng, Tsing; Orlow, Seth J; Manga, Prashiela

2013-11-01

Accumulation of proteins in the endoplasmic reticulum (ER) typically induces stress and initiates the unfolded protein response (UPR) to facilitate recovery. If homeostasis is not restored, apoptosis is induced. However, adaptation to chronic UPR activation can increase resistance to subsequent acute ER stress. We therefore investigated adaptive mechanisms in Oculocutaneous albinism type 2 (Oca2)-null melanocytes where UPR signaling is arrested despite continued tyrosinase accumulation leading to resistance to the chemical ER stressor thapsigargin. Although thapsigargin triggers UPR activation, instead of Perk-mediated phosphorylation of eIF2α, in Oca2-null melanocytes, eIF2α was rapidly dephosphorylated upon treatment. Dephosphorylation was mediated by the Gadd34-PP1α phosphatase complex. Gadd34-complex inhibition blocked eIF2α dephosphorylation and significantly increased Oca2-null melanocyte sensitivity to thapsigargin. Thus, Oca2-null melanocytes adapt to acute ER stress by disruption of pro-apoptotic Perk signaling, which promotes cell survival. This is the first study to demonstrate rapid eIF2α dephosphorylation as an adaptive mechanism to ER stress. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Structure–function analysis and genetic interactions of the SmG, SmE, and SmF subunits of the yeast Sm protein ring

PubMed Central

Schwer, Beate; Kruchten, Joshua; Shuman, Stewart

2016-01-01

A seven-subunit Sm protein ring forms a core scaffold of the U1, U2, U4, and U5 snRNPs that direct pre-mRNA splicing. Using human snRNP structures to guide mutagenesis in Saccharomyces cerevisiae, we gained new insights into structure–function relationships of the SmG, SmE, and SmF subunits. An alanine scan of 19 conserved amino acids of these three proteins, comprising the Sm RNA binding sites or inter-subunit interfaces, revealed that, with the exception of Arg74 in SmF, none are essential for yeast growth. Yet, for SmG, SmE, and SmF, as for many components of the yeast spliceosome, the effects of perturbing protein–RNA and protein–protein interactions are masked by built-in functional redundancies of the splicing machine. For example, tests for genetic interactions with non-Sm splicing factors showed that many benign mutations of SmG, SmE, and SmF (and of SmB and SmD3) were synthetically lethal with null alleles of U2 snRNP subunits Lea1 and Msl1. Tests of pairwise combinations of SmG, SmE, SmF, SmB, and SmD3 alleles highlighted the inherent redundancies within the Sm ring, whereby simultaneous mutations of the RNA binding sites of any two of the Sm subunits are lethal. Our results suggest that six intact RNA binding sites in the Sm ring suffice for function but five sites may not. PMID:27417296

Cortactin as a Target for FAK in the Regulation of Focal Adhesion Dynamics

PubMed Central

Ghassemian, Majid; Schlaepfer, David D.

2012-01-01

Background Efficient cell movement requires the dynamic regulation of focal adhesion (FA) formation and turnover. FAs are integrin-associated sites of cell attachment and establish linkages to the cellular actin cytoskeleton. Cells without focal adhesion kinase (FAK), an integrin-activated tyrosine kinase, exhibit defects in FA turnover and cell motility. Cortactin is an actin binding adaptor protein that can influence FA dynamics. FAK and cortactin interact, but the cellular role of this complex remains unclear. Principal Findings Using FAK-null fibroblasts stably reconstituted with green fluorescent protein (GFP) tagged FAK constructs, we find that FAK activity and FAK C-terminal proline-rich region 2 (PRR2) and PRR3 are required for FA turnover and cell motility. Cortactin binds directly to FAK PRR2 and PRR3 sites via its SH3 domain and cortactin expression is important in promoting FA turnover and GFP-FAK release from FAs. FAK-cortactin binding is negatively-regulated by FAK activity and associated with cortactin tyrosine phosphorylation. FAK directly phosphorylates cortactin at Y421 and Y466 and over-expression of cortactin Y421, Y466, and Y482 mutated to phenylalanine (3YF) prevented FAK-enhanced FA turnover and cell motility. However, phospho-mimetic cortactin mutated to glutamic acid (3YE) did not affect FA dynamics and did not rescue FA turnover defects in cells with inhibited FAK activity or with PRR2-mutated FAK that does not bind cortactin. Conclusions Our results support a model whereby FAK-mediated FA remodeling may occur through the formation of a FAK-cortactin signaling complex. This involves a cycle of cortactin binding to FAK, cortactin tyrosine phosphorylation, and subsequent cortactin-FAK dissociation accompanied by FA turnover and cell movement. PMID:22952866

Lipopolysaccharide-binding protein is a negative regulator of adipose tissue browning in mice and humans.

PubMed

Gavaldà-Navarro, Aleix; Moreno-Navarrete, José M; Quesada-López, Tania; Cairó, Montserrat; Giralt, Marta; Fernández-Real, José M; Villarroya, Francesc

2016-10-01

Adipocyte lipopolysaccharide-binding protein (LBP) biosynthesis is associated with obesity-induced adipose tissue dysfunction. Our purpose was to study the role of LBP in regulating the browning of adipose tissue. Adult mice were maintained at 4°C for 3 weeks or treated with the β3-adrenergic agonist, CL316,243, for 1 week to induce the browning of white fat. Precursor cells from brown and white adipose tissues were cultured under differentiation-inducing conditions to yield brown and beige/brite adipocytes, respectively. In vitro, Lbp was knocked down in 3T3-L1 adipocytes, and cells were treated with recombinant LBP or co-cultured in transwells with control 3T3-L1 adipocytes. Wild-type and Lbp-null mice, fed a standard or high fat diet (HFD) for 15 weeks, were also used in investigations. In humans, subcutaneous and visceral adipose tissue samples were obtained from a cohort of morbidly obese participants. The induction of white fat browning by exposure of mice to cold or CL316,243 treatment was strongly associated with decreased Lbp mRNA expression in white adipose tissue. The acquisition of the beige/brite phenotype in cultured cells was associated with downregulation of Lbp. Moreover, silencing of Lbp induced the expression of brown fat-related genes in adipocytes, whereas LBP treatment reversed this effect. Lbp-null mice exhibited the spontaneous induction of subcutaneous adipose tissue browning, as evidenced by a remarkable increase in Ucp1 and Dio2 gene expression and the appearance of multivacuolar adipocyte clusters. The amount of brown adipose tissue, and brown adipose tissue activity were also increased in Lbp-null mice. These changes were associated with decreased weight gain in Lbp-null mice and protection against HFD-induced inflammatory responses, as shown by reduced IL-6 levels. However, rather than improving glucose homeostasis, these effects led to glucose intolerance and insulin resistance. LBP is identified as a negative regulator of the browning process, which is likely to contribute to the obesity-promoting action of LBP. The deleterious metabolic effects of LBP deletion are compatible with the concept that the appropriate regulation of inflammatory pathways is necessary for a healthy systemic metabolic profile, regardless of body weight regulation.

Antiviral RNA silencing initiated in the absence of RDE-4, a double-stranded RNA binding protein, in Caenorhabditis elegans.

PubMed

Guo, Xunyang; Zhang, Rui; Wang, Jeffrey; Lu, Rui

2013-10-01

Small interfering RNAs (siRNAs) processed from double-stranded RNA (dsRNA) of virus origins mediate potent antiviral defense through a process referred to as RNA interference (RNAi) or RNA silencing in diverse organisms. In the simple invertebrate Caenorhabditis elegans, the RNAi process is initiated by a single Dicer, which partners with the dsRNA binding protein RDE-4 to process dsRNA into viral siRNAs (viRNAs). Notably, in C. elegans this RNA-directed viral immunity (RDVI) also requires a number of worm-specific genes for its full antiviral potential. One such gene is rsd-2 (RNAi spreading defective 2), which was implicated in RDVI in our previous studies. In the current study, we first established an antiviral role by showing that rsd-2 null mutants permitted higher levels of viral RNA accumulation, and that this enhanced viral susceptibility was reversed by ectopic expression of RSD-2. We then examined the relationship of rsd-2 with other known components of RNAi pathways and established that rsd-2 functions in a novel pathway that is independent of rde-4 but likely requires the RNA-dependent RNA polymerase RRF-1, suggesting a critical role for RSD-2 in secondary viRNA biogenesis, likely through coordinated action with RRF-1. Together, these results suggest that RDVI in the single-Dicer organism C. elegans depends on the collective actions of both RDE-4-dependent and RDE-4-independent mechanisms to produce RNAi-inducing viRNAs. Our study reveals, for the first time, a novel siRNA-producing mechanism in C. elegans that bypasses the need for a dsRNA-binding protein.

Antiviral RNA Silencing Initiated in the Absence of RDE-4, a Double-Stranded RNA Binding Protein, in Caenorhabditis elegans

PubMed Central

Guo, Xunyang; Zhang, Rui; Wang, Jeffrey

2013-01-01

Small interfering RNAs (siRNAs) processed from double-stranded RNA (dsRNA) of virus origins mediate potent antiviral defense through a process referred to as RNA interference (RNAi) or RNA silencing in diverse organisms. In the simple invertebrate Caenorhabditis elegans, the RNAi process is initiated by a single Dicer, which partners with the dsRNA binding protein RDE-4 to process dsRNA into viral siRNAs (viRNAs). Notably, in C. elegans this RNA-directed viral immunity (RDVI) also requires a number of worm-specific genes for its full antiviral potential. One such gene is rsd-2 (RNAi spreading defective 2), which was implicated in RDVI in our previous studies. In the current study, we first established an antiviral role by showing that rsd-2 null mutants permitted higher levels of viral RNA accumulation, and that this enhanced viral susceptibility was reversed by ectopic expression of RSD-2. We then examined the relationship of rsd-2 with other known components of RNAi pathways and established that rsd-2 functions in a novel pathway that is independent of rde-4 but likely requires the RNA-dependent RNA polymerase RRF-1, suggesting a critical role for RSD-2 in secondary viRNA biogenesis, likely through coordinated action with RRF-1. Together, these results suggest that RDVI in the single-Dicer organism C. elegans depends on the collective actions of both RDE-4-dependent and RDE-4-independent mechanisms to produce RNAi-inducing viRNAs. Our study reveals, for the first time, a novel siRNA-producing mechanism in C. elegans that bypasses the need for a dsRNA-binding protein. PMID:23885080

MAPK signaling pathways and HDAC3 activity are disrupted during differentiation of emerin-null myogenic progenitor cells

PubMed Central

Collins, Carol M.; Ellis, Joseph A.

2017-01-01

ABSTRACT Mutations in the gene encoding emerin cause Emery–Dreifuss muscular dystrophy (EDMD). Emerin is an integral inner nuclear membrane protein and a component of the nuclear lamina. EDMD is characterized by skeletal muscle wasting, cardiac conduction defects and tendon contractures. The failure to regenerate skeletal muscle is predicted to contribute to the skeletal muscle pathology of EDMD. We hypothesize that muscle regeneration defects are caused by impaired muscle stem cell differentiation. Myogenic progenitors derived from emerin-null mice were used to confirm their impaired differentiation and analyze selected myogenic molecular pathways. Emerin-null progenitors were delayed in their cell cycle exit, had decreased myosin heavy chain (MyHC) expression and formed fewer myotubes. Emerin binds to and activates histone deacetylase 3 (HDAC3). Here, we show that theophylline, an HDAC3-specific activator, improved myotube formation in emerin-null cells. Addition of the HDAC3-specific inhibitor RGFP966 blocked myotube formation and MyHC expression in wild-type and emerin-null myogenic progenitors, but did not affect cell cycle exit. Downregulation of emerin was previously shown to affect the p38 MAPK and ERK/MAPK pathways in C2C12 myoblast differentiation. Using a pure population of myogenic progenitors completely lacking emerin expression, we show that these pathways are also disrupted. ERK inhibition improved MyHC expression in emerin-null cells, but failed to rescue myotube formation or cell cycle exit. Inhibition of p38 MAPK prevented differentiation in both wild-type and emerin-null progenitors. These results show that each of these molecular pathways specifically regulates a particular stage of myogenic differentiation in an emerin-dependent manner. Thus, pharmacological targeting of multiple pathways acting at specific differentiation stages may be a better therapeutic approach in the future to rescue muscle regeneration in vivo. PMID:28188262

Analysis of a homologue of the adducin head gene which is a potential target for the Dictyostelium STAT protein Dd-STATa.

PubMed

Aoshima, Ryota; Hiraoka, Rieko; Shimada, Nao; Kawata, Takefumi

2006-01-01

A Dd-STATa-null mutant, which is defective in expression of a Dictyostelium homologue of the metazoan STAT (signal transducers and activators of transcription) proteins, fails to culminate and this phenotype correlates with the loss of expression of various prestalk (pst) genes. An EST clone, SSK395, encodes a close homologue of the adducin amino-terminal head domain and harbors a putative actin-binding domain. We fused promoter fragments of the cognate gene, ahhA (adducin head homologue A), to a lacZ reporter and determined their expression pattern. The proximal promoter region is necessary for the expression of ahhA at an early (pre-aggregative) stage of development and this expression is Dd-STATa independent. The distal promoter region is necessary for expression at later stages of development in pstA cells, of the slug and in upper cup and pstAB cells during culmination. The distal region is partly Dd-STATa-dependent. The ahhA-null mutant develops almost normally until culmination, but it forms slanting culminants that tend to collapse on to the substratum. The mutant also occasionally forms fruiting bodies with swollen papillae and with constrictions in the prestalk region. The AhhA protein localizes to the stalk tube entrance and also to the upper cup cells and in cells at or near to the constricted region where an F-actin ring is localized. These findings suggest that Dd-STATa regulates culmination and may be necessary for straight downward elongation of the stalk, via the putative actin-binding protein AhhA.

Appl1 Is Dispensable for Mouse Development, and Loss of Appl1 Has Growth Factor-selective Effects on Akt Signaling in Murine Embryonic Fibroblasts*

PubMed Central

Tan, Yinfei; You, Huihong; Wu, Chao; Altomare, Deborah A.; Testa, Joseph R.

2010-01-01

The adaptor protein APPL1 (adaptor protein containing pleckstrin homology (PH), phosphotyrosine binding (PTB), and leucine zipper motifs) was first identified as a binding protein of AKT2 by yeast two-hybrid screening. APPL1 was subsequently found to bind to several membrane-bound receptors and was implicated in their signal transduction through AKT and/or MAPK pathways. To determine the unambiguous role of Appl1 in vivo, we generated Appl1 knock-out mice. Here we report that Appl1 knock-out mice are viable and fertile. Appl1-null mice were born at expected Mendelian ratios, without obvious phenotypic abnormalities. Moreover, Akt activity in various fetal tissues was unchanged compared with that observed in wild-type littermates. Studies of isolated Appl1−/− murine embryonic fibroblasts (MEFs) showed that Akt activation by epidermal growth factor, insulin, or fetal bovine serum was similar to that observed in wild-type MEFs, although Akt activation by HGF was diminished in Appl1−/− MEFs. To rule out a possible redundant role played by the related Appl2, we used small interfering RNA to knock down Appl2 expression in Appl1−/− MEFs. Unexpectedly, cell survival was unaffected under normal culture conditions, and activation of Akt was unaltered following epidermal growth factor stimulation, although Akt activity did decrease further after HGF stimulation. Furthermore, we found that Appl proteins are required for HGF-induced cell survival and migration via activation of Akt. Our studies suggest that Appl1 is dispensable for development and only participate in Akt signaling under certain conditions. PMID:20040596

Genetic Evidence for Function of the bHLH-PAS Protein Gce/Met As a Juvenile Hormone Receptor

PubMed Central

Jindra, Marek; Uhlirova, Mirka; Charles, Jean-Philippe; Smykal, Vlastimil; Hill, Ronald J.

2015-01-01

Juvenile hormones (JHs) play a major role in controlling development and reproduction in insects and other arthropods. Synthetic JH-mimicking compounds such as methoprene are employed as potent insecticides against significant agricultural, household and disease vector pests. However, a receptor mediating effects of JH and its insecticidal mimics has long been the subject of controversy. The bHLH-PAS protein Methoprene-tolerant (Met), along with its Drosophila melanogaster paralog germ cell-expressed (Gce), has emerged as a prime JH receptor candidate, but critical evidence that this protein must bind JH to fulfill its role in normal insect development has been missing. Here, we show that Gce binds a native D. melanogaster JH, its precursor methyl farnesoate, and some synthetic JH mimics. Conditional on this ligand binding, Gce mediates JH-dependent gene expression and the hormone's vital role during development of the fly. Any one of three different single amino acid mutations in the ligand-binding pocket that prevent binding of JH to the protein block these functions. Only transgenic Gce capable of binding JH can restore sensitivity to JH mimics in D. melanogaster Met-null mutants and rescue viability in flies lacking both Gce and Met that would otherwise die at pupation. Similarly, the absence of Gce and Met can be compensated by expression of wild-type but not mutated transgenic D. melanogaster Met protein. This genetic evidence definitively establishes Gce/Met in a JH receptor role, thus resolving a long-standing question in arthropod biology. PMID:26161662

Extracellular matrix family proteins that are potential targets of Dd-STATa in Dictyostelium discoideum.

PubMed

Shimada, Nao; Nishio, Keiko; Maeda, Mineko; Urushihara, Hideko; Kawata, Takefumi

2004-10-01

Dd-STATa is a functional Dictyostelium homologue of metazoan STAT (signal transducers and activators of transcription) proteins, which is activated by cAMP and is thereby translocated into the nuclei of anterior tip cells of the prestalk region of the slug. By using in situ hybridization analyses, we found that the SLF308 cDNA clone, which contains the ecmF gene that encodes a putative extracellular matrix protein and is expressed in the anterior tip cells, was greatly down-regulated in the Dd-STATa-null mutant. Disruption of the ecmF gene, however, resulted in almost no phenotypic change. The absence of any obvious mutant phenotype in the ecmF-null mutant could be due to a redundancy of similar genes. In fact, a search of the Dictyostelium whole genome database demonstrates the existence of an additional 16 homologues, all of which contain a cellulose-binding module. Among these homologues, four genes show Dd-STATa-dependent expression, while the others are Dd-STATa-independent. We discuss the potential role of Dd-STATa in morphogenesis via its effect on the interaction between cellulose and these extracellular matrix family proteins.

Neuron class-specific requirements for Fragile X Mental Retardation Protein in critical period development of calcium signaling in learning and memory circuitry.

PubMed

Doll, Caleb A; Broadie, Kendal

2016-05-01

Neural circuit optimization occurs through sensory activity-dependent mechanisms that refine synaptic connectivity and information processing during early-use developmental critical periods. Fragile X Mental Retardation Protein (FMRP), the gene product lost in Fragile X syndrome (FXS), acts as an activity sensor during critical period development, both as an RNA-binding translation regulator and channel-binding excitability regulator. Here, we employ a Drosophila FXS disease model to assay calcium signaling dynamics with a targeted transgenic GCaMP reporter during critical period development of the mushroom body (MB) learning/memory circuit. We find FMRP regulates depolarization-induced calcium signaling in a neuron-specific manner within this circuit, suppressing activity-dependent calcium transients in excitatory cholinergic MB input projection neurons and enhancing calcium signals in inhibitory GABAergic MB output neurons. Both changes are restricted to the developmental critical period and rectified at maturity. Importantly, conditional genetic (dfmr1) rescue of null mutants during the critical period corrects calcium signaling defects in both neuron classes, indicating a temporally restricted FMRP requirement. Likewise, conditional dfmr1 knockdown (RNAi) during the critical period replicates constitutive null mutant defects in both neuron classes, confirming cell-autonomous requirements for FMRP in developmental regulation of calcium signaling dynamics. Optogenetic stimulation during the critical period enhances depolarization-induced calcium signaling in both neuron classes, but this developmental change is eliminated in dfmr1 null mutants, indicating the activity-dependent regulation requires FMRP. These results show FMRP shapes neuron class-specific calcium signaling in excitatory vs. inhibitory neurons in developing learning/memory circuitry, and that FMRP mediates activity-dependent regulation of calcium signaling specifically during the early-use critical period. Copyright © 2016 Elsevier Inc. All rights reserved.

Ectopic expression of phloem motor protein pea forisome PsSEO-F1 enhances salinity stress tolerance in tobacco.

PubMed

Srivastava, Vineet Kumar; Raikwar, Shailendra; Tuteja, Renu; Tuteja, Narendra

2016-05-01

PsSEOF-1 binds to calcium and its expression is upregulated by salinity treatment. PsSEOF - 1 -overexpressing transgenic tobacco showed enhanced salinity stress tolerance by maintaining cellular ion homeostasis and modulating ROS-scavenging pathway. Calcium (Ca(2+)) plays important role in growth, development and stress tolerance in plants. Cellular Ca(2+) homeostasis is achieved by the collective action of channels, pumps, antiporters and by Ca(2+) chelators present in the cell like calcium-binding proteins. Forisomes are ATP-independent mechanically active motor proteins known to function in wound sealing of injured sieve elements of phloem tissue. The Ca(2+)-binding activity of forisome and its role in abiotic stress signaling were largely unknown. Here we report the Ca(2+)-binding activity of pea forisome (PsSEO-F1) and its novel function in promoting salinity tolerance in transgenic tobacco. Native PsSEO-F1 promoter positively responded in salinity stress as confirmed using GUS reporter. Overexpression of PsSEO-F1 tobacco plants confers salinity tolerance by alleviating ionic toxicity and increased ROS scavenging activity which probably results in reduced membrane damage and improved yield under salinity stress. Evaluation of several physiological indices shows an increase in relative water content, electrolyte leakage, proline accumulation and chlorophyll content in transgenic lines as compared with null-segregant control. Expression of several genes involved in cellular homeostasis is perturbed by PsSEO-F1 overexpression. These findings suggest that PsSEO-F1 provides salinity tolerance through cellular Ca(2+) homeostasis which in turn modulates ROS machinery providing indirect link between Ca(2+) and ROS signaling under salinity-induced perturbation. PsSEO-F1 most likely functions in salinity stress tolerance by improving antioxidant machinery and mitigating ion toxicity in transgenic lines. This finding should make an important contribution in our better understanding of the significance of calcium signaling in phloem tissue leading to salinity stress tolerance.

Receptors for aggregated IgG on mouse lymphocytes: their presence on thymocytes, thymus-derived, and bone marrow-derived lymphocytes.

PubMed

Anderson, C L; Grey, H M

1974-05-01

An autoradiographic binding assay employing (125)I-labeled heat-aggregated mouse IgG2b myeloma protein (MOPC 141) was used to demonstrate receptors for IgG on 20-45% of Balb/c thymocytes and on 70-80% of splenocytes. Binding could also be shown with heat or BDB aggregates of another IgG2b (MOPC 195), with IgG1 and with human gamma-globulin, but not with aggregated chicken gamma-globulin, IgA, BSA, nor with aggregated Fab fragments of IgG2b. Optimum binding was obtained at 37 degrees C. Detection of binding was dependent upon aggregate size with complexes of more than 100 IgG molecules being optimal, aggregates of 6-25 detecting splenocytes but not thymocytes, and aggregates of less than 6 binding to a negligible extent. Comparison of grain counts on various cell types showed mastocytoma cells (P815) and macrophages averaging 40-50 grains/cell/day, allogeneically activated thymocytes 20-30, splenocytes 2-3, L5178 lymphoma cells 1, and positive thymocytes 0.6 grains/cell/day. Double labeling experiments for surface Ig, theta-antigen, and agg IgG receptor on mouse spleen cells indicated that a relatively high density of receptor was present on about 80% of B cells, 30% of T cells, and 60% of SIg(-), theta(-), null cells.

Analysis of Pax6 contiguous gene deletions in the mouse, Mus musculus, identifies regions distinct from Pax6 responsible for extreme small-eye and belly-spotting phenotypes.

PubMed

Favor, Jack; Bradley, Alan; Conte, Nathalie; Janik, Dirk; Pretsch, Walter; Reitmeir, Peter; Rosemann, Michael; Schmahl, Wolfgang; Wienberg, Johannes; Zaus, Irmgard

2009-08-01

In the mouse Pax6 function is critical in a dose-dependent manner for proper eye development. Pax6 contiguous gene deletions were shown to be homozygous lethal at an early embryonic stage. Heterozygotes express belly spotting and extreme microphthalmia. The eye phenotype is more severe than in heterozygous Pax6 intragenic null mutants, raising the possibility that deletions are functionally different from intragenic null mutations or that a region distinct from Pax6 included in the deletions affects eye phenotype. We recovered and identified the exact regions deleted in three new Pax6 deletions. All are homozygous lethal at an early embryonic stage. None express belly spotting. One expresses extreme microphthalmia and two express the milder eye phenotype similar to Pax6 intragenic null mutants. Analysis of Pax6 expression levels and the major isoforms excluded the hypothesis that the deletions expressing extreme microphthalmia are directly due to the action of Pax6 and functionally different from intragenic null mutations. A region distinct from Pax6 containing eight genes was identified for belly spotting. A second region containing one gene (Rcn1) was identified for the extreme microphthalmia phenotype. Rcn1 is a Ca(+2)-binding protein, resident in the endoplasmic reticulum, participates in the secretory pathway and expressed in the eye. Our results suggest that deletion of Rcn1 directly or indirectly contributes to the eye phenotype in Pax6 contiguous gene deletions.

Anatomical Location of LPA1 Activation and LPA Phospholipid Precursors in Rodent and Human Brain

PubMed Central

González de San Román, E; Manuel, I; Giralt, MT; Chun, J; Estivill-Torrús, G; Rodriguez de Fonseca, F; Santín, LJ; Ferrer, I; Rodriguez-Puertas, R

2016-01-01

Lysophosphatidic acid (LPA) is a signaling molecule that binds to six known G protein-coupled receptors (GPCRs): LPA1–LPA6. LPA evokes several responses in the CNS including cortical development and folding, growth of the axonal cone and its retraction process. Those cell processes involve survival, migration, adhesion proliferation, differentiation and myelination. The anatomical localization of LPA1 is incompletely understood, particularly with regard to LPA binding. Therefore, we have used functional [35S]GTPγS autoradiography to verify the anatomical distribution of LPA1 binding sites in adult rodent and human brain. The greatest activity was observed in myelinated areas of the white matter such as corpus callosum, internal capsule and cerebellum. MaLPA1-null mice (a variant of LPA1-null) lack [35S]GTPγS basal binding in white matter areas, where the LPA1 receptor is expressed at high levels, suggesting a relevant role of the activity of this receptor in the most myelinated brain areas. In addition, phospholipid precursors of LPA were localized by MALDI-IMS in both rodent and human brain slices identifying numerous species of phosphatides (PA) and phosphatidylcholines (PC). Both PA and PC species represent potential LPA precursors. The anatomical distribution of these precursors in rodent and human brain may indicate a metabolic relationship between LPA and LPA1 receptors. PMID:25857358

β-Adrenergic Receptor Stimulated Ncx1 Upregulation is Mediated via a CaMKII/AP-1 Signaling Pathway in Adult Cardiomyocytes

PubMed Central

Mani, Santhosh K.; Egan, Erin A.; Addy, Benjamin K.; Grimm, Michael; Kasiganesan, Harinath; Thiyagarajan, Thirumagal; Renaud, Ludivine; Brown, Joan Heller; Kern, Christine B.; Menick, Donald R.

2013-01-01

The Na+-Ca2+ exchanger gene (Ncx1) is upregulated in hypertrophy and is often found elevated in end-stage heart failure. Studies have shown that the change in its expression contributes to contractile dysfunction. β-adrenergic receptor (β-AR) signaling plays an important role in the regulation of calcium homeostasis in the cardiomyocyte but chronic activation in periods of cardiac stress contribute to heart failure by mechanisms which include Ncx1 upregulation. Here, using a Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKIIδc) null mouse, we demonstrate that β-AR-stimulated Ncx1 upregulation is dependent on CaMKII. β-AR-stimulated Ncx1 expression is mediated by activator protein 1 (AP-1) factors and is independent of cAMP-response element-binding protein (CREB) activation. The MAP kinases (ERK1/2, JNK and p38) are not required for AP-1 factor activation. Chromatin immunoprecipitation demonstrates that β-AR stimulation activates the ordered recruitment of JunB homodimers which then are replaced by c-Jun homodimers binding to the proximal AP-1 elements of the endogenous Ncx1 promoter. In conclusion, this work has provided insight into the intracellular signaling pathways and transcription factors regulating Ncx1 gene expression in a chronically β-AR-stimulated heart. PMID:19945464

The RNA Binding Protein Tudor-SN Is Essential for Stress Tolerance and Stabilizes Levels of Stress-Responsive mRNAs Encoding Secreted Proteins in Arabidopsis[C][W][OA

PubMed Central

dit Frey, Nicolas Frei; Muller, Philippe; Jammes, Fabien; Kizis, Dimosthenis; Leung, Jeffrey; Perrot-Rechenmann, Catherine; Bianchi, Michele Wolfe

2010-01-01

Tudor-SN (TSN) copurifies with the RNA-induced silencing complex in animal cells where, among other functions, it is thought to act on mRNA stability via the degradation of specific dsRNA templates. In plants, TSN has been identified biochemically as a cytoskeleton-associated RNA binding activity. In eukaryotes, it has recently been identified as a conserved primary target of programmed cell death–associated proteolysis. We have investigated the physiological role of TSN by isolating null mutations for two homologous genes in Arabidopsis thaliana. The double mutant tsn1 tsn2 displays only mild growth phenotypes under nonstress conditions, but germination, growth, and survival are severely affected under high salinity stress. Either TSN1 or TSN2 alone can complement the double mutant, indicating their functional redundancy. TSN accumulates heterogeneously in the cytosol and relocates transiently to a diffuse pattern in response to salt stress. Unexpectedly, stress-regulated mRNAs encoding secreted proteins are significantly enriched among the transcripts that are underrepresented in tsn1 tsn2. Our data also reveal that TSN is important for RNA stability of its targets. These findings show that TSN is essential for stress tolerance in plants and implicate TSN in new, potentially conserved mechanisms acting on mRNAs entering the secretory pathway. PMID:20484005

Activation of peroxisome proliferator-activated receptor beta/delta inhibits lipopolysaccharide-induced cytokine production in adipocytes by lowering nuclear factor-kappaB activity via extracellular signal-related kinase 1/2.

PubMed

Rodríguez-Calvo, Ricardo; Serrano, Lucía; Coll, Teresa; Moullan, Norman; Sánchez, Rosa M; Merlos, Manuel; Palomer, Xavier; Laguna, Juan C; Michalik, Liliane; Wahli, Walter; Vázquez-Carrera, Manuel

2008-08-01

Chronic activation of the nuclear factor-kappaB (NF-kappaB) in white adipose tissue leads to increased production of pro-inflammatory cytokines, which are involved in the development of insulin resistance. It is presently unknown whether peroxisome proliferator-activated receptor (PPAR) beta/delta activation prevents inflammation in adipocytes. First, we examined whether the PPARbeta/delta agonist GW501516 prevents lipopolysaccharide (LPS)-induced cytokine production in differentiated 3T3-L1 adipocytes. Treatment with GW501516 blocked LPS-induced IL-6 expression and secretion by adipocytes and the subsequent activation of the signal transducer and activator of transcription 3 (STAT3)-Suppressor of cytokine signaling 3 (SOCS3) pathway. This effect was associated with the capacity of GW501516 to impede LPS-induced NF-kappaB activation. Second, in in vivo studies, white adipose tissue from Zucker diabetic fatty (ZDF) rats, compared with that of lean rats, showed reduced PPARbeta/delta expression and PPAR DNA-binding activity, which was accompanied by enhanced IL-6 expression and NF-kappaB DNA-binding activity. Furthermore, IL-6 expression and NF-kappaB DNA-binding activity was higher in white adipose tissue from PPARbeta/delta-null mice than in wild-type mice. Because mitogen-activated protein kinase-extracellular signal-related kinase (ERK)1/2 (MEK1/2) is involved in LPS-induced NF-kappaB activation in adipocytes, we explored whether PPARbeta/delta prevented NF-kappaB activation by inhibiting this pathway. Interestingly, GW501516 prevented ERK1/2 phosphorylation by LPS. Furthermore, white adipose tissue from animal showing constitutively increased NF-kappaB activity, such as ZDF rats and PPARbeta/delta-null mice, also showed enhanced phospho-ERK1/2 levels. These findings indicate that activation of PPARbeta/delta inhibits enhanced cytokine production in adipocytes by preventing NF-kappaB activation via ERK1/2, an effect that may help prevent insulin resistance.

Two cell-counting factors regulate the aggregate size of the cellular slime mold Dictyostelium discoideum.

PubMed

Okuwa, T; Katayama, T; Takano, A; Kodaira, K; Yasukawa, H

2001-12-01

Countin, a cell-counting factor in Dictyostelium discoideum, is considered to limit the maximum size of the multicellular structure, because a countin null strain forms a huge fruiting body compared to that of the wild-type. A novel gene, countin2, that is highly homologous to countin (40% identity in amino acid sequence) was identified in the D. discoideum genome. The countin2 null strain formed a 1.7-fold higher number of the aggregates, resulting in smaller fruiting bodies compared with those of wild-type cells. Thus, the Countin2 protein is thought to limit the minimum size of the multicellular structure. The size and number of aggregates formed by a mixture of countin null and countin2 null strains were the same as those of the wild-type. These findings demonstrate that a combination of Countin and Countin2 proteins determines the appropriate size of the multicellular structure of D. discoideum.

Stable Accumulation of Photosystem II Requires ONE-HELIX PROTEIN1 (OHP1) of the Light Harvesting-Like Family1[OPEN

PubMed Central

Takahashi, Kaori; Funk, Christiane; Nomura, Yuko

2018-01-01

The cellular functions of two Arabidopsis (Arabidopsis thaliana) one-helix proteins, OHP1 and OHP2 (also named LIGHT-HARVESTING-LIKE2 [LIL2] and LIL6, respectively, because they have sequence similarity to light-harvesting chlorophyll a/b-binding proteins), remain unclear. Tagged null mutants of OHP1 and OHP2 (ohp1 and ohp2) showed stunted growth with pale-green leaves on agar plates, and these mutants were unable to grow on soil. Leaf chlorophyll fluorescence and the composition of thylakoid membrane proteins revealed that ohp1 deletion substantially affected photosystem II (PSII) core protein function and led to reduced levels of photosystem I core proteins; however, it did not affect LHC accumulation. Transgenic ohp1 plants rescued with OHP1-HA or OHP1-Myc proteins developed a normal phenotype. Using these tagged OHP1 proteins in transgenic plants, we localized OHP1 to thylakoid membranes, where it formed protein complexes with both OHP2 and High Chlorophyll Fluorescence244 (HCF244). We also found PSII core proteins D1/D2, HCF136, and HCF173 and a few other plant-specific proteins associated with the OHP1/OHP2-HCF244 complex, suggesting that these complexes are early intermediates in PSII assembly. OHP1 interacted directly with HCF244 in the complex. Therefore, OHP1 and HCF244 play important roles in the stable accumulation of PSII. PMID:29438089

The prion protein has DNA strand transfer properties similar to retroviral nucleocapsid protein.

PubMed

Gabus, C; Auxilien, S; Péchoux, C; Dormont, D; Swietnicki, W; Morillas, M; Surewicz, W; Nandi, P; Darlix, J L

2001-04-06

The transmissible spongiform encephalopathies are fatal neurodegenerative diseases that are associated with the accumulation of a protease-resistant form of the cellular prion protein (PrP). Although PrP is highly conserved and widely expressed in vertebrates, its function remains a matter of speculation. Indeed PrP null mice develop normally and are healthy. Recent results show that PrP binds to nucleic acids in vitro and is found associated with retroviral particles. Furthermore, in mice the scrapie infectious process appears to be accelerated by MuLV replication. These observations prompted us to further investigate the interaction between PrP and nucleic acids, and compare it with that of the retroviral nucleocapsid protein (NC). As the major nucleic acid-binding protein of the retroviral particle, NC protein is tightly associated with the genomic RNA in the virion nucleocapsid, where it chaperones proviral DNA synthesis by reverse transcriptase. Our results show that the human prion protein (huPrP) functionally resembles NCp7 of HIV-1. Both proteins form large nucleoprotein complexes upon binding to DNA. They accelerate the hybridization of complementary DNA strands and chaperone viral DNA synthesis during the minus and plus DNA strand transfers necessary to generate the long terminal repeats. The DNA-binding and strand transfer properties of huPrP appear to map to the N-terminal fragment comprising residues 23 to 144, whereas the C-terminal domain is inactive. These findings suggest that PrP could be involved in nucleic acid metabolism in vivo. Copyright 2001 Academic Press.

The retinol esterifying enzyme LRAT supports cell signaling by retinol-binding protein and its receptor STRA6.

PubMed

Marwarha, Gurdeep; Berry, Daniel C; Croniger, Colleen M; Noy, Noa

2014-01-01

Vitamin A, retinol, circulates in blood bound to retinol-binding protein (RBP). At some tissues, holo-RBP is recognized by a plasma membrane receptor termed STRA6, which serves a dual role: it mediates transport of retinol from RBP into cells, and it functions as a cytokine receptor that, on binding holo-RBP, activates JAK2/STAT5 signaling. As STAT target genes include SOCS3, an inhibitor of insulin receptor, holo-RBP suppresses insulin responses in STRA6-expressing cells. We have shown previously that the two functions of STRA6 are interdependent. These observations suggest factors that regulate STRA6-mediated retinol transport may also control STRA6-mediated cell signaling. One such factor is retinol metabolism, which enables cellular uptake of retinol by maintaining an inward-directed concentration gradient. We show here that lecithin:retinol acyl transferase (LRAT), which catalyzes esterification of retinol to its storage species retinyl esters, is necessary for activation of the STRA6/JAK2/STAT5 cascade by holo-RBP. In accordance, LRAT-null mice are protected from holo-RBP-induced suppression of insulin responses. Hence, STRA6 signaling, which requires STRA6-mediated retinol transport, is supported by LRAT-catalyzed retinol metabolism. The observations demonstrate that STRA6 regulates key cellular processes by coupling circulating holo-RBP levels and intracellular retinol metabolism to cell signaling.

Bioassaying Putative RNA-Binding Motifs in a Protein Encoded by a Gene That Influences Courtship and Visually Mediated Behavior in Drosophila: In Vitro Mutagenesis of Nona

PubMed Central

Stanewsky, R.; Fry, T. A.; Reim, I.; Saumweber, H.; Hall, J. C.

1996-01-01

The no-on-transient-A (nonA) gene of Drosophila melanogaster influences vision, courtship song, and viability. The nonA-encoded polypeptide is inferred to bind single-stranded nucleic acids. Although sequence-analysis of NONA implies that it belongs to a special interspecific family of this protein type, it does contain two classical RNA recognition motifs (RRM). Their behavioral significance was assayed by generating transgenic strains that were singly or multiply mutated within the relatively N-terminal motif (RRM1) or within RRM2. Neither class of mutation affected NONA binding to polytene chromosomes. The former mutations led to extremely low viability, accompanied by diminished adult longevities that were much worse than for a nonA-null mutant, implying that faulty interpolypeptide interactions might accompany the effects of the amino-acid substitutions within RRM1. All in vitro-mutated types caused optomotor blindness and an absence of transient spikes in the electroretinogram. Courtship analysis discriminated between the effects of the mutations: the RRM2-mutated type generated song pulses and trains that tended to be mildly mutant. These phenotypic abnormalities reinforce the notion that nonA's ubiquitous expression has its most important consequences in the optic lobes, the thoracic ganglia, or both, depending in part on the nonA allele. PMID:8722780

Recognition deficits in mice carrying mutations of genes encoding BLOC-1 subunits pallidin or dysbindin.

PubMed

Spiegel, S; Chiu, A; James, A S; Jentsch, J D; Karlsgodt, K H

2015-11-01

Numerous studies have implicated DTNBP1, the gene encoding dystrobrevin-binding protein or dysbindin, as a candidate risk gene for schizophrenia, though this relationship remains somewhat controversial. Variation in dysbindin, and its location on chromosome 6p, has been associated with cognitive processes, including those relying on a complex system of glutamatergic and dopaminergic interactions. Dysbindin is one of the seven protein subunits that comprise the biogenesis of lysosome-related organelles complex 1 (BLOC-1). Dysbindin protein levels are lower in mice with null mutations in pallidin, another gene in the BLOC-1, and pallidin levels are lower in mice with null mutations in the dysbindin gene, suggesting that multiple subunit proteins must be present to form a functional oligomeric complex. Furthermore, pallidin and dysbindin have similar distribution patterns in a mouse and human brain. Here, we investigated whether the apparent correspondence of pallid and dysbindin at the level of gene expression is also found at the level of behavior. Hypothesizing a mutation leading to underexpression of either of these proteins should show similar phenotypic effects, we studied recognition memory in both strains using the novel object recognition task (NORT) and social novelty recognition task (SNRT). We found that mice with a null mutation in either gene are impaired on SNRT and NORT when compared with wild-type controls. These results support the conclusion that deficits consistent with recognition memory impairment, a cognitive function that is impaired in schizophrenia, result from either pallidin or dysbindin mutations, possibly through degradation of BLOC-1 expression and/or function. © 2015 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

Severe changes in colon epithelium in the Mecp2-null mouse model of Rett syndrome.

PubMed

Millar-Büchner, Pamela; Philp, Amber R; Gutierrez, Noemí; Villanueva, Sandra; Kerr, Bredford; Flores, Carlos A

2016-12-01

Rett syndrome is best known due to its severe and devastating symptoms in the central nervous system. It is produced by mutations affecting the Mecp2 gene that codes for a transcription factor. Nevertheless, evidence for MECP2 activity has been reported for tissues other than those of the central nervous system. Patients affected by Rett presented with intestinal affections whose origin is still not known. We have observed that the Mecp2-null mice presented with episodes of diarrhea, and decided to study the intestinal phenotype in these mice. Mecp2-null mice or bearing the conditional intestinal deletion of MECP2 were used. Morphometirc and histologic analysis of intestine, and RT-PCR, western blot and immunodetection were perfomed on intestinal samples of the animals. Electrical parameters of the intestine were determined by Ussing chamber experiments in freshly isolated colon samples. First we determined that MECP2 protein is mainly expressed in cells of the lower part of the colonic crypts and not in the small intestine. The colon of the Mecp2-null mice was shorter than that of the wild-type. Histological analysis showed that epithelial cells of the surface have abnormal localization of key membrane proteins like ClC-2 and NHE-3 that participate in the electroneutral NaCl absorption; nevertheless, electrogenic secretion and absorption remain unaltered. We also detected an increase in a proliferation marker in the crypts of the colon samples of the Mecp2-null mice, but the specific silencing of Mecp2 from intestinal epithelium was not able to recapitulate the intestinal phenotype of the Mecp2-null mice. In summary, we showed that the colon is severely affected by Mecp2 silencing in mice. Changes in colon length and epithelial histology are similar to those observed in colitis. Changes in the localization of proteins that participate in fluid absorption can explain watery stools, but the exclusive deletion of Mecp2 from the intestine did not reproduce colon changes observed in the Mecp2-null mice, indicating the participation of other cells in this phenotype and the complex interaction between different cell types in this disease.

The IKAROS interaction with a complex including chromatin remodeling and transcription elongation activities is required for hematopoiesis.

PubMed

Bottardi, Stefania; Mavoungou, Lionel; Pak, Helen; Daou, Salima; Bourgoin, Vincent; Lakehal, Yahia A; Affar, El Bachir; Milot, Eric

2014-12-01

IKAROS is a critical regulator of hematopoietic cell fate and its dynamic expression pattern is required for proper hematopoiesis. In collaboration with the Nucleosome Remodeling and Deacetylase (NuRD) complex, it promotes gene repression and activation. It remains to be clarified how IKAROS can support transcription activation while being associated with the HDAC-containing complex NuRD. IKAROS also binds to the Positive-Transcription Elongation Factor b (P-TEFb) at gene promoters. Here, we demonstrate that NuRD and P-TEFb are assembled in a complex that can be recruited to specific genes by IKAROS. The expression level of IKAROS influences the recruitment of the NuRD-P-TEFb complex to gene regulatory regions and facilitates transcription elongation by transferring the Protein Phosphatase 1α (PP1α), an IKAROS-binding protein and P-TEFb activator, to CDK9. We show that an IKAROS mutant that is unable to bind PP1α cannot sustain gene expression and impedes normal differentiation of Ik(NULL) hematopoietic progenitors. Finally, the knock-down of the NuRD subunit Mi2 reveals that the occupancy of the NuRD complex at transcribed regions of genes favors the relief of POL II promoter-proximal pausing and thereby, promotes transcription elongation.

The IKAROS Interaction with a Complex Including Chromatin Remodeling and Transcription Elongation Activities Is Required for Hematopoiesis

PubMed Central

Bottardi, Stefania; Mavoungou, Lionel; Pak, Helen; Daou, Salima; Bourgoin, Vincent; Lakehal, Yahia A.; Affar, El Bachir; Milot, Eric

2014-01-01

IKAROS is a critical regulator of hematopoietic cell fate and its dynamic expression pattern is required for proper hematopoiesis. In collaboration with the Nucleosome Remodeling and Deacetylase (NuRD) complex, it promotes gene repression and activation. It remains to be clarified how IKAROS can support transcription activation while being associated with the HDAC-containing complex NuRD. IKAROS also binds to the Positive-Transcription Elongation Factor b (P-TEFb) at gene promoters. Here, we demonstrate that NuRD and P-TEFb are assembled in a complex that can be recruited to specific genes by IKAROS. The expression level of IKAROS influences the recruitment of the NuRD-P-TEFb complex to gene regulatory regions and facilitates transcription elongation by transferring the Protein Phosphatase 1α (PP1α), an IKAROS-binding protein and P-TEFb activator, to CDK9. We show that an IKAROS mutant that is unable to bind PP1α cannot sustain gene expression and impedes normal differentiation of IkNULL hematopoietic progenitors. Finally, the knock-down of the NuRD subunit Mi2 reveals that the occupancy of the NuRD complex at transcribed regions of genes favors the relief of POL II promoter-proximal pausing and thereby, promotes transcription elongation. PMID:25474253

Arabidopsis synaptotagmin 1 is required for the maintenance of plasma membrane integrity and cell viability.

PubMed

Schapire, Arnaldo L; Voigt, Boris; Jasik, Jan; Rosado, Abel; Lopez-Cobollo, Rosa; Menzel, Diedrik; Salinas, Julio; Mancuso, Stefano; Valpuesta, Victoriano; Baluska, Frantisek; Botella, Miguel A

2008-12-01

Plasma membrane repair in animal cells uses synaptotagmin 7, a Ca(2+)-activated membrane fusion protein that mediates delivery of intracellular membranes to wound sites by a mechanism resembling neuronal Ca(2+)-regulated exocytosis. Here, we show that loss of function of the homologous Arabidopsis thaliana Synaptotagmin 1 protein (SYT1) reduces the viability of cells as a consequence of a decrease in the integrity of the plasma membrane. This reduced integrity is enhanced in the syt1-2 null mutant in conditions of osmotic stress likely caused by a defective plasma membrane repair. Consistent with a role in plasma membrane repair, SYT1 is ubiquitously expressed, is located at the plasma membrane, and shares all domains characteristic of animal synaptotagmins (i.e., an N terminus-transmembrane domain and a cytoplasmic region containing two C2 domains with phospholipid binding activities). Our analyses support that membrane trafficking mediated by SYT1 is important for plasma membrane integrity and plant fitness.

HIGH GLUCOSE POTENTIATES L-FABP MEDIATED FIBRATE INDUCTION OF PPARα IN MOUSE HEPATOCYTES

PubMed Central

Petrescu, Anca D.; McIntosh, Avery L.; Storey, Stephen M.; Huang, Huan; Martin, Gregory G.; Landrock, Danilo; Kier, Ann B.; Schroeder, Friedhelm

2013-01-01

Although liver fatty acid binding protein (L-FABP) binds fibrates and PPARα in vitro and enhances fibrate induction of PPARα in transformed cells, the functional significance of these findings is unclear, especially in normal hepatocytes. Studies with cultured primary mouse hepatocytes show that: 1) At physiological (6 mM) glucose, fibrates (bezafibrate, fenofibrate) only weakly activated PPARα transcription of genes in LCFA β-oxidation; 2) High (11–20 mM) glucose, but not maltose (osmotic control), significantly potentiated fibrate-induction of mRNA of these and other PPARα target genes to increase LCFA β-oxidation. These effects were associated with fibrate-mediated redistribution of L-FABP into nuclei—an effect prolonged by high glucose—but not with increased de novo fatty acid synthesis from glucose; 3) Potentiation of bezafibrate action by high glucose required an intact L-FABP/PPARα signaling pathway as shown with L-FABP null, PPARα null, PPARα inhibitor-treated WT, or PPARα-specific fenofibrate-treated WT hepatocytes. High glucose alone in the absence of fibrate was ineffective. Thus, high glucose potentiation of PPARα occurred through FABP/PPARα rather than indirectly through other PPARs or glucose induced signaling pathways. These data indicated L-FABP’s importance in fibrate-induction of hepatic PPARα LCFA β-oxidative genes, especially in the context of high glucose levels. PMID:23747828

PspG, a New Member of the Yersinia enterocolitica Phage Shock Protein Regulon

PubMed Central

Green, Rebecca C.; Darwin, Andrew J.

2004-01-01

The Yersinia enterocolitica phage shock protein (Psp) system is induced when the Ysc type III secretion system is produced or when only the YscC secretin component is synthesized. Some psp null mutants have a growth defect when YscC is produced and a severe virulence defect in animals. The Y. enterocolitica psp locus is made up of two divergently transcribed cistrons, pspF and pspABCDycjXF. pspA operon expression is dependent on RpoN (σ54) and the enhancer-binding protein PspF. Previous data indicated that PspF also controls at least one gene that is not part of the psp locus. In this study we describe the identification of pspG, a new member of the PspF regulon. Predicted RpoN-binding sites upstream of the pspA genes from different bacteria have a common divergence from the consensus sequence, which may be a signature of PspF-dependent promoters. The Y. enterocolitica pspG gene was identified because its promoter also has this signature. Like the pspA operon, pspG is positively regulated by PspF, negatively regulated by PspA, and induced in response to the production of secretins. Purified His6-PspF protein specifically interacts with the pspA and pspG control regions. A pspA operon deletion mutant has a growth defect when the YscC secretin is produced and a virulence defect in a mouse model of infection. These phenotypes were exacerbated by a pspG null mutation. Therefore, PspG is the missing component of the Y. enterocolitica Psp regulon that was previously predicted to exist. PMID:15262928

A novel bifunctional histone protein in Streptomyces: a candidate for structural coupling between DNA conformation and transcription during development and stress?

PubMed Central

Aldridge, Matthew; Facey, Paul; Francis, Lewis; Bayliss, Sion; Del Sol, Ricardo; Dyson, Paul

2013-01-01

Antibiotic-producing Streptomyces are complex bacteria that remodel global transcription patterns and their nucleoids during development. Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp. Owing to its N-terminal domain, the protein can efficiently bind and condense DNA in vitro. Loss of function of this DNA-binding protein results in changes in both DNA condensation during development and the ability to adjust DNA supercoiling in response to osmotic stress. Initial analysis of the DksA-like activity of DdbA indicates that overexpression of the protein suppresses a conditional deficiency in antibiotic production of relA mutants that are unable to synthesise ppGpp, just as DksA overexpression in Escherichia coli can suppress ppGpp0 phenotypes. The null mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor. Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress. PMID:23525459

GuiTope: an application for mapping random-sequence peptides to protein sequences.

PubMed

Halperin, Rebecca F; Stafford, Phillip; Emery, Jack S; Navalkar, Krupa Arun; Johnston, Stephen Albert

2012-01-03

Random-sequence peptide libraries are a commonly used tool to identify novel ligands for binding antibodies, other proteins, and small molecules. It is often of interest to compare the selected peptide sequences to the natural protein binding partners to infer the exact binding site or the importance of particular residues. The ability to search a set of sequences for similarity to a set of peptides may sometimes enable the prediction of an antibody epitope or a novel binding partner. We have developed a software application designed specifically for this task. GuiTope provides a graphical user interface for aligning peptide sequences to protein sequences. All alignment parameters are accessible to the user including the ability to specify the amino acid frequency in the peptide library; these frequencies often differ significantly from those assumed by popular alignment programs. It also includes a novel feature to align di-peptide inversions, which we have found improves the accuracy of antibody epitope prediction from peptide microarray data and shows utility in analyzing phage display datasets. Finally, GuiTope can randomly select peptides from a given library to estimate a null distribution of scores and calculate statistical significance. GuiTope provides a convenient method for comparing selected peptide sequences to protein sequences, including flexible alignment parameters, novel alignment features, ability to search a database, and statistical significance of results. The software is available as an executable (for PC) at http://www.immunosignature.com/software and ongoing updates and source code will be available at sourceforge.net.

ACF7 regulates cytoskeletal-focal adhesion dynamics and migration and has ATPase activity.

PubMed

Wu, Xiaoyang; Kodama, Atsuko; Fuchs, Elaine

2008-10-03

Coordinated interactions between microtubule (MT) and actin cytoskeletons are involved in many polarized cellular processes. Spectraplakins are enormous (>500 kDa) proteins able to bind both MTs and actin filaments (F-actin) directly. To elucidate the physiological significance and functions of mammalian spectraplakin ACF7, we've conditionally targeted it in skin epidermis. Intriguingly, ACF7 deficiency compromises the targeting of microtubules along F-actin to focal adhesions (FAs), stabilizes FA-actin networks, and impairs epidermal migration. Exploring underlying mechanisms, we show that ACF7's binding domains for F-actin, MTs, and MT plus-end proteins are not sufficient to rescue the defects in FA-cytoskeletal dynamics and migration functions of ACF7 null keratinocytes. We've uncovered an intrinsic actin-regulated ATPase domain in ACF7 and demonstrate that it is both functional and essential for these roles. Our findings provide insight into the functions of this important cytoskeletal crosslinking protein in regulating dynamic interactions between MTs and F-actin to sustain directional cell movement.

Contribution of cellular retinol-binding protein type 1 to retinol metabolism during mouse development.

PubMed

Matt, Nicolas; Schmidt, Carsten K; Dupé, Valérie; Dennefeld, Christine; Nau, Heinz; Chambon, Pierre; Mark, Manuel; Ghyselinck, Norbert B

2005-05-01

Within cells, retinol (ROL) is bound to cytoplasmic proteins (cellular retinol-binding proteins [CRBPs]), whose proposed function is to protect it from unspecific enzymes through channeling to retinoid-metabolizing pathways. We show that, during development, ROL and retinyl ester levels are decreased in CRBP type 1 (CRBP1) -deficient embryos and fetuses by 50% and 80%, respectively. The steady state level of retinoic acid (RA) is also decreased but to a lesser extent. However, CRBP1-null fetuses do not exhibit the abnormalities characteristic of a vitamin A-deficiency syndrome. Neither CRBP1 deficiency alters the expression patterns of RA-responding genes during development, nor does CRBP1 availability modify the expression of an RA-dependent gene in primary embryonic fibroblasts treated with ROL. Therefore, CRBP1 is required in prenatal life to maintain normal amounts of ROL and to ensure its efficient storage but seems of secondary importance for RA synthesis, at least under conditions of maternal vitamin A sufficiency. Copyright 2005 Wiley-Liss, Inc.

Fgfr1 regulates development through the combinatorial use of signaling proteins.

PubMed

Brewer, J Richard; Molotkov, Andrei; Mazot, Pierre; Hoch, Renée V; Soriano, Philippe

2015-09-01

Fibroblast growth factor (Fgf) signaling governs multiple processes important in development and disease. Many lines of evidence have implicated Erk1/2 signaling induced through Frs2 as the predominant effector pathway downstream from Fgf receptors (Fgfrs), but these receptors can also signal through other mechanisms. To explore the functional significance of the full range of signaling downstream from Fgfrs in mice, we engineered an allelic series of knock-in point mutations designed to disrupt Fgfr1 signaling functions individually and in combination. Analysis of each mutant indicates that Frs2 binding to Fgfr1 has the most pleiotropic functions in development but also that the receptor uses multiple proteins additively in vivo. In addition to Frs2, Crk proteins and Plcγ also contribute to Erk1/2 activation, affecting axis elongation and craniofacial and limb development and providing a biochemical mechanism for additive signaling requirements. Disruption of all known signaling functions diminished Erk1/2 and Plcγ activation but did not recapitulate the peri-implantation Fgfr1-null phenotype. This suggests that Erk1/2-independent signaling pathways are functionally important for Fgf signaling in vivo. © 2015 Brewer et al.; Published by Cold Spring Harbor Laboratory Press.

Ecsit is required for Bmp signaling and mesoderm formation during mouse embryogenesis

PubMed Central

Xiao, Changchun; Shim, Jae-hyuck; Klüppel, Michael; Zhang, Samuel Shao-Min; Dong, Chen; Flavell, Richard A.; Fu, Xin-Yuan; Wrana, Jeffrey L.; Hogan, Brigid L.M.; Ghosh, Sankar

2003-01-01

Bone morphogenetic proteins (Bmps) are members of the transforming growth factor β (TGFβ) superfamily that play critical roles during mouse embryogenesis. Signaling by Bmp receptors is mediated mainly by Smad proteins. In this study, we show that a targeted null mutation of Ecsit, encoding a signaling intermediate of the Toll pathway, leads to reduced cell proliferation, altered epiblast patterning, impairment of mesoderm formation, and embryonic lethality at embryonic day 7.5 (E7.5), phenotypes that mimic the Bmp receptor type1a (Bmpr1a) null mutant. In addition, specific Bmp target gene expression is abolished in the absence of Ecsit. Biochemical analysis demonstrates that Ecsit associates constitutively with Smad4 and associates with Smad1 in a Bmp-inducible manner. Together with Smad1 and Smad4, Ecsit binds to the promoter of specific Bmp target genes. Finally, knock-down of Ecsit with Ecsit-specific short hairpin RNA inhibits both Bmp and Toll signaling. Therefore, these results show that Ecsit functions as an essential component in two important signal transduction pathways and establishes a novel role for Ecsit as a cofactor for Smad proteins in the Bmp signaling pathway. PMID:14633973

Myosin Va binding to neurofilaments is essential for correct myosin Va distribution and transport and neurofilament density

PubMed Central

Rao, Mala V.; Engle, Linda J.; Mohan, Panaiyur S.; Yuan, Aidong; Qiu, Dike; Cataldo, Anne; Hassinger, Linda; Jacobsen, Stephen; Lee, Virginia M-Y.; Andreadis, Athena; Julien, Jean-Pierre; Bridgman, Paul C.; Nixon, Ralph A.

2002-01-01

The identification of molecular motors that modulate the neuronal cytoskeleton has been elusive. Here, we show that a molecular motor protein, myosin Va, is present in high proportions in the cytoskeleton of mouse CNS and peripheral nerves. Immunoelectron microscopy, coimmunoprecipitation, and blot overlay analyses demonstrate that myosin Va in axons associates with neurofilaments, and that the NF-L subunit is its major ligand. A physiological association is indicated by observations that the level of myosin Va is reduced in axons of NF-L–null mice lacking neurofilaments and increased in mice overexpressing NF-L, but unchanged in NF-H–null mice. In vivo pulse-labeled myosin Va advances along axons at slow transport rates overlapping with those of neurofilament proteins and actin, both of which coimmunoprecipitate with myosin Va. Eliminating neurofilaments from mice selectively accelerates myosin Va translocation and redistributes myosin Va to the actin-rich subaxolemma and membranous organelles. Finally, peripheral axons of dilute-lethal mice, lacking functional myosin Va, display selectively increased neurofilament number and levels of neurofilament proteins without altering axon caliber. These results identify myosin Va as a neurofilament-associated protein, and show that this association is essential to establish the normal distribution, axonal transport, and content of myosin Va, and the proper numbers of neurofilaments in axons. PMID:12403814

V-1 regulates capping protein activity in vivo

PubMed Central

Jung, Goeh; Wu, Xufeng S.; Piszczek, Grzegorz; Chen, Bi-Chang; Betzig, Eric; Hammer, John A.

2016-01-01

Capping Protein (CP) plays a central role in the creation of the Arp2/3-generated branched actin networks comprising lamellipodia and pseudopodia by virtue of its ability to cap the actin filament barbed end, which promotes Arp2/3-dependent filament nucleation and optimal branching. The highly conserved protein V-1/Myotrophin binds CP tightly in vitro to render it incapable of binding the barbed end. Here we addressed the physiological significance of this CP antagonist in Dictyostelium, which expresses a V-1 homolog that we show is very similar biochemically to mouse V-1. Consistent with previous studies of CP knockdown, overexpression of V-1 in Dictyostelium reduced the size of pseudopodia and the cortical content of Arp2/3 and induced the formation of filopodia. Importantly, these effects scaled positively with the degree of V-1 overexpression and were not seen with a V-1 mutant that cannot bind CP. V-1 is present in molar excess over CP, suggesting that it suppresses CP activity in the cytoplasm at steady state. Consistently, cells devoid of V-1, like cells overexpressing CP described previously, exhibited a significant decrease in cellular F-actin content. Moreover, V-1–null cells exhibited pronounced defects in macropinocytosis and chemotactic aggregation that were rescued by V-1, but not by the V-1 mutant. Together, these observations demonstrate that V-1 exerts significant influence in vivo on major actin-based processes via its ability to sequester CP. Finally, we present evidence that V-1’s ability to sequester CP is regulated by phosphorylation, suggesting that cells may manipulate the level of active CP to tune their “actin phenotype.” PMID:27791032

V-1 regulates capping protein activity in vivo.

PubMed

Jung, Goeh; Alexander, Christopher J; Wu, Xufeng S; Piszczek, Grzegorz; Chen, Bi-Chang; Betzig, Eric; Hammer, John A

2016-10-25

Capping Protein (CP) plays a central role in the creation of the Arp2/3-generated branched actin networks comprising lamellipodia and pseudopodia by virtue of its ability to cap the actin filament barbed end, which promotes Arp2/3-dependent filament nucleation and optimal branching. The highly conserved protein V-1/Myotrophin binds CP tightly in vitro to render it incapable of binding the barbed end. Here we addressed the physiological significance of this CP antagonist in Dictyostelium, which expresses a V-1 homolog that we show is very similar biochemically to mouse V-1. Consistent with previous studies of CP knockdown, overexpression of V-1 in Dictyostelium reduced the size of pseudopodia and the cortical content of Arp2/3 and induced the formation of filopodia. Importantly, these effects scaled positively with the degree of V-1 overexpression and were not seen with a V-1 mutant that cannot bind CP. V-1 is present in molar excess over CP, suggesting that it suppresses CP activity in the cytoplasm at steady state. Consistently, cells devoid of V-1, like cells overexpressing CP described previously, exhibited a significant decrease in cellular F-actin content. Moreover, V-1-null cells exhibited pronounced defects in macropinocytosis and chemotactic aggregation that were rescued by V-1, but not by the V-1 mutant. Together, these observations demonstrate that V-1 exerts significant influence in vivo on major actin-based processes via its ability to sequester CP. Finally, we present evidence that V-1's ability to sequester CP is regulated by phosphorylation, suggesting that cells may manipulate the level of active CP to tune their "actin phenotype."

Regulation of glycolysis in Kluyveromyces lactis: role of KlGCR1 and KlGCR2 in glucose uptake and catabolism.

PubMed

Neil, H; Lemaire, M; Wésolowski-Louvel, M

2004-03-01

In Kluyveromyces lactis, the casein kinase I (Rag8p) regulates the transcription of glycolytic genes and the expression of the low-affinity glucose transporter gene RAG1. This control involves the transcription factor Sck1p, a homologue of Sgc1p of Saccharomyces cerevisiae. SGC1 is known to interact genetically with ScGCR1 and ScGCR2, which code for regulators of glycolytic gene expression. Therefore, we studied the role of KlGCR1 and KlGCR2 genes in K. lactis. The Klgcr1 null mutant could not grow on glucose when respiration was blocked by antimycin A (Rag(- )phenotype). In contrast, the Klgcr2 null mutant could grow under the same conditions, although at a reduced rate. In both mutants, the transcription of glycolytic genes was affected, while that of ribosomal protein genes was not modified. Furthermore, the transcription of the glucose permease genes was also found to be affected in the two mutants, although dissimilarly. While RAG1 transcription decreased at high glucose concentrations, the expression of the high-affinity glucose permease gene HGT1 was unexpectedly impaired under gluconeogenic conditions, in the absence of glucose. Gel mobility shift assays performed with purified maltose-binding protein-KlGcr1p showed that KlGcr1p could interact directly with the promoters of the glycolytic genes, but not with the promoters of the glucose permease genes. Thus, the control exerted by KlGcr1p and KlGcr2p upon glucose transporter genes is probably indirect.

The LIM Protein Zyxin Binds CARP-1 and Promotes Apoptosis

PubMed Central

Hervy, Martial; Hoffman, Laura M.; Jensen, Christopher C.; Smith, Mark; Beckerle, Mary C.

2010-01-01

Zyxin is a dual-function LIM domain protein that regulates actin dynamics in response to mechanical stress and shuttles between focal adhesions and the cell nucleus. Here we show that zyxin contributes to UV-induced apoptosis. Exposure of wild-type fibroblasts to UV-C irradiation results in apoptotic cell death, whereas cells harboring a homozygous disruption of the zyxin gene display a statistically significant survival advantage. To gain insight into the molecular mechanism by which zyxin promotes apoptotic signaling, we expressed an affinity-tagged zyxin variant in zyxin-null cells and isolated zyxin-associated proteins from cell lysates under physiological conditions. A 130-kDa protein that was co-isolated with zyxin was identified by microsequence analysis as the Cell Cycle and Apoptosis Regulator Protein-1 (CARP-1). CARP-1 associates with the LIM region of zyxin. Zyxin lacking the CARP-1 binding region shows reduced proapoptotic activity in response to UV-C irradiation. We demonstrate that CARP-1 is a nuclear protein. Zyxin is modified by phosphorylation in cells exposed to UV-C irradiation, and nuclear accumulation of zyxin is induced by UV-C exposure. These findings highlight a novel mechanism for modulating the apoptotic response to UV irradiation. PMID:20852740

The common missense mutation D489N in TRIM32 causing limb girdle muscular dystrophy 2H leads to loss of the mutated protein in knock-in mice resulting in a Trim32-null phenotype.

PubMed

Kudryashova, Elena; Struyk, Arie; Mokhonova, Ekaterina; Cannon, Stephen C; Spencer, Melissa J

2011-10-15

Mutations in tripartite motif protein 32 (TRIM32) are responsible for several hereditary disorders that include limb girdle muscular dystrophy type 2H (LGMD2H), sarcotubular myopathy (STM) and Bardet Biedl syndrome. Most LGMD2H mutations in TRIM32 are clustered in the NHL β-propeller domain at the C-terminus and are predicted to interfere with homodimerization. To get insight into TRIM32's role in the pathogenesis of LGMD2H and to create an accurate model of disease, we have generated a knock-in mouse (T32KI) carrying the c.1465G > A (p.D489N) mutation in murine Trim32 corresponding to the human LGMD2H/STM pathogenic mutation c.1459G > A (p.D487N). Our data indicate that T32KI mice have both a myopathic and a neurogenic phenotype, very similar to the one described in the Trim32-null mice that we created previously. Analysis of Trim32 gene expression in T32KI mice revealed normal mRNA levels, but a severe reduction in mutant TRIM32 (D489N) at the protein level. Our results suggest that the D489N pathogenic mutation destabilizes the protein, leading to its degradation, and results in the same mild myopathic and neurogenic phenotype as that found in Trim32-null mice. Thus, one potential mechanism of LGMD2H might be destabilization of mutated TRIM32 protein leading to a null phenotype.

Identification of Mutations in SLC24A4, Encoding a Potassium-Dependent Sodium/Calcium Exchanger, as a Cause of Amelogenesis Imperfecta

PubMed Central

Parry, David A.; Poulter, James A.; Logan, Clare V.; Brookes, Steven J.; Jafri, Hussain; Ferguson, Christopher H.; Anwari, Babra M.; Rashid, Yasmin; Zhao, Haiqing; Johnson, Colin A.; Inglehearn, Chris F.; Mighell, Alan J.

2013-01-01

A combination of autozygosity mapping and exome sequencing identified a null mutation in SLC24A4 in a family with hypomineralized amelogenesis imperfect a (AI), a condition in which tooth enamel formation fails. SLC24A4 encodes a calcium transporter upregulated in ameloblasts during the maturation stage of amelogenesis. Screening of further AI families identified a missense mutation in the ion-binding site of SLC24A4 expected to severely diminish or abolish the ion transport function of the protein. Furthermore, examination of previously generated Slc24a4 null mice identified a severe defect in tooth enamel that reflects impaired amelogenesis. These findings support a key role for SLC24A4 in calcium transport during enamel formation. PMID:23375655

Planar cell polarity proteins differentially regulate extracellular matrix organization and assembly during zebrafish gastrulation.

PubMed

Dohn, Michael R; Mundell, Nathan A; Sawyer, Leah M; Dunlap, Julie A; Jessen, Jason R

2013-11-01

Zebrafish gastrulation cell movements occur in the context of dynamic changes in extracellular matrix (ECM) organization and require the concerted action of planar cell polarity (PCP) proteins that regulate cell elongation and mediolateral alignment. Data obtained using Xenopus laevis gastrulae have shown that integrin-fibronectin interactions underlie the formation of polarized cell protrusions necessary for PCP and have implicated PCP proteins themselves as regulators of ECM. By contrast, the relationship between establishment of PCP and ECM assembly/remodeling during zebrafish gastrulation is unclear. We previously showed that zebrafish embryos carrying a null mutation in the four-pass transmembrane PCP protein vang-like 2 (vangl2) exhibit increased matrix metalloproteinase activity and decreased immunolabeling of fibronectin. These data implicated for the first time a core PCP protein in the regulation of pericellular proteolysis of ECM substrates and raised the question of whether other zebrafish PCP proteins also impact ECM organization. In Drosophila melanogaster, the cytoplasmic PCP protein Prickle binds Van Gogh and regulates its function. Here we report that similar to vangl2, loss of zebrafish prickle1a decreases fibronectin protein levels in gastrula embryos. We further show that Prickle1a physically binds Vangl2 and regulates both the subcellular distribution and total protein level of Vangl2. These data suggest that the ability of Prickle1a to impact fibronectin organization is at least partly due to effects on Vangl2. In contrast to loss of either Vangl2 or Prickle1a function, we find that glypican4 (a Wnt co-receptor) and frizzled7 mutant gastrula embryos with disrupted non-canonical Wnt signaling exhibit the opposite phenotype, namely increased fibronectin assembly. Our data show that glypican4 mutants do not have decreased proteolysis of ECM substrates, but instead have increased cell surface cadherin protein expression and increased intercellular adhesion. These data indicate that Wnt/Glypican4/Frizzled signaling regulates ECM assembly through effects on cadherin-mediated cell cohesion. Together, our results demonstrate that zebrafish Vangl2/Prickle1a and non-canonical Wnt/Frizzled signaling have opposing effects on ECM organization underlying PCP and gastrulation cell movements. © 2013 Elsevier Inc. All rights reserved.

Protection of a Ceramide Synthase 2 Null Mouse from Drug-induced Liver Injury

PubMed Central

Park, Woo-Jae; Park, Joo-Won; Erez-Roman, Racheli; Kogot-Levin, Aviram; Bame, Jessica R.; Tirosh, Boaz; Saada, Ann; Merrill, Alfred H.; Pewzner-Jung, Yael; Futerman, Anthony H.

2013-01-01

Very long chain (C22-C24) ceramides are synthesized by ceramide synthase 2 (CerS2). A CerS2 null mouse displays hepatopathy because of depletion of C22-C24 ceramides, elevation of C16-ceramide, and/or elevation of sphinganine. Unexpectedly, CerS2 null mice were resistant to acetaminophen-induced hepatotoxicity. Although there were a number of biochemical changes in the liver, such as increased levels of glutathione and multiple drug-resistant protein 4, these effects are unlikely to account for the lack of acetaminophen toxicity. A number of other hepatotoxic agents, such as d-galactosamine, CCl4, and thioacetamide, were also ineffective in inducing liver damage. All of these drugs and chemicals require connexin (Cx) 32, a key gap junction protein, to induce hepatotoxicity. Cx32 was mislocalized to an intracellular location in hepatocytes from CerS2 null mice, which resulted in accelerated rates of its lysosomal degradation. This mislocalization resulted from the altered membrane properties of the CerS2 null mice, which was exemplified by the disruption of detergent-resistant membranes. The lack of acetaminophen toxicity and Cx32 mislocalization were reversed upon infection with recombinant adeno-associated virus expressing CerS2. We establish that Gap junction function is compromised upon altering the sphingolipid acyl chain length composition, which is of relevance for understanding the regulation of drug-induced liver injury. PMID:24019516

Investigating the Role of Helicobacter pylori PriA Protein.

PubMed

Singh, Aparna; Blaskovic, Dusan; Joo, Jungsoo; Yang, Zhen; Jackson, Sharon H; Coleman, William G; Yan, Ming

2016-08-01

In bacteria, PriA protein, a conserved DEXH-type DNA helicase, plays a central role in replication restart at stalled replication forks. Its unique DNA binding property allows it to recognize and stabilize stalled forks and the structures derived from them. PriA plays a very critical role in replication fork stabilization and DNA repair in E. coli and N. gonorrhoeae. In our in vivo expression technology screen, priA gene was induced in vivo when Helicobacter pylori infects mouse stomach. We decided to elucidate the role of H. pylori PriA protein in survival in mouse stomach, survival in gastric epithelial cells and macrophage cells, DNA repair, acid stress, and oxidative stress. The priA null mutant strain was unable to colonize mice stomach mucosa after long-term infections. Mouse colonization was observed after 1 week of infection, but the levels were much lower than the wild-type HpSS1 strain. PriA protein was found to be important for intracellular survival of epithelial cell-/macrophage cell-ingested H. pylori. Also, a priA null mutant was more sensitive to DNA-damaging agents and was much more sensitive to acid and oxidative stress as compared to the wild-type strain. These data suggest that the PriA protein is needed for survival and persistence of H. pylori in mice stomach mucosa. © 2016 John Wiley & Sons Ltd.

Ameloblast Modulation and Transport of Cl⁻, Na⁺, and K⁺ during Amelogenesis.

PubMed

Bronckers, A L J J; Lyaruu, D; Jalali, R; Medina, J F; Zandieh-Doulabi, B; DenBesten, P K

2015-12-01

Ameloblasts express transmembrane proteins for transport of mineral ions and regulation of pH in the enamel space. Two major transporters recently identified in ameloblasts are the Na(+)K(+)-dependent calcium transporter NCKX4 and the Na(+)-dependent HPO4 (2-) (Pi) cotransporter NaPi-2b. To regulate pH, ameloblasts express anion exchanger 2 (Ae2a,b), chloride channel Cftr, and amelogenins that can bind protons. Exposure to fluoride or null mutation of Cftr, Ae2a,b, or Amelx each results in formation of hypomineralized enamel. We hypothesized that enamel hypomineralization associated with disturbed pH regulation results from reduced ion transport by NCKX4 and NaPi-2b. This was tested by correlation analyses among the levels of Ca, Pi, Cl, Na, and K in forming enamel of mice with null mutation of Cftr, Ae2a,b, and Amelx, according to quantitative x-ray electron probe microanalysis. Immunohistochemistry, polymerase chain reaction analysis, and Western blotting confirmed the presence of apical NaPi-2b and Nckx4 in maturation-stage ameloblasts. In wild-type mice, K levels in enamel were negatively correlated with Ca and Cl but less negatively or even positively in fluorotic enamel. Na did not correlate with P or Ca in enamel of wild-type mice but showed strong positive correlation in fluorotic and nonfluorotic Ae2a,b- and Cftr-null enamel. In hypomineralizing enamel of all models tested, 1) Cl(-) was strongly reduced; 2) K(+) and Na(+) accumulated (Na(+) not in Amelx-null enamel); and 3) modulation was delayed or blocked. These results suggest that a Na(+)K(+)-dependent calcium transporter (likely NCKX4) and a Na(+)-dependent Pi transporter (potentially NaPi-2b) located in ruffle-ended ameloblasts operate in a coordinated way with the pH-regulating machinery to transport Ca(2+), Pi, and bicarbonate into maturation-stage enamel. Acidification and/or associated physicochemical/electrochemical changes in ion levels in enamel fluid near the apical ameloblast membrane may reduce the transport activity of mineral transporters, which results in hypomineralization. © International & American Associations for Dental Research 2015.

Metalloproteinase pregnancy-associated plasma protein A is a critical growth regulatory factor during fetal development.

PubMed

Conover, Cheryl A; Bale, Laurie K; Overgaard, Michael T; Johnstone, Edward W; Laursen, Ulla H; Füchtbauer, Ernst-Martin; Oxvig, Claus; van Deursen, Jan

2004-03-01

Pregnancy-associated plasma protein A (PAPPA) is a metzincin superfamily metalloproteinase in the insulin-like growth factor (IGF) system. PAPPA increases IGF bioavailability and mitogenic effectiveness in vitro through regulated cleavage of IGF-binding protein 4 (IGFBP4). To determine its function in vivo, we generated PAPPA-null mice by gene targeting. Mice homozygous for targeted disruption of the PAPPA gene were viable but 60% the size of wild-type littermates at birth. The impact of the mutation was exerted during the early embryonic period prior to organogenesis, resulting in proportional dwarfism. PAPPA, IGF2 and IGFBP4 transcripts co-localized in wild-type embryos, and expression of IGF2 and IGFBP4 mRNA was not altered in PAPPA-deficient embryos. However, IGFBP4 proteolytic activity was completely lacking in fibroblasts derived from PAPPA-deficient embryos, and IGFBP4 effectively inhibited IGF-stimulated mitogenesis in these cells. These results provide the first direct evidence that PAPPA is an essential growth regulatory factor in vivo, and suggest a novel mechanism for regulated IGF bioavailability during early fetal development.

Incorporation of Tenascin-C into the Extracellular Matrix by Periostin Underlies an Extracellular Meshwork Architecture*

PubMed Central

Kii, Isao; Nishiyama, Takashi; Li, Minqi; Matsumoto, Ken-ichi; Saito, Mitsuru; Amizuka, Norio; Kudo, Akira

2010-01-01

Extracellular matrix (ECM) underlies a complicated multicellular architecture that is subjected to significant forces from mechanical environment. Although various components of the ECM have been enumerated, mechanisms that evolve the sophisticated ECM architecture remain to be addressed. Here we show that periostin, a matricellular protein, promotes incorporation of tenascin-C into the ECM and organizes a meshwork architecture of the ECM. We found that both periostin null mice and tenascin-C null mice exhibited a similar phenotype, confined tibial periostitis, which possibly corresponds to medial tibial stress syndrome in human sports injuries. Periostin possessed adjacent domains that bind to tenascin-C and the other ECM protein: fibronectin and type I collagen, respectively. These adjacent domains functioned as a bridge between tenascin-C and the ECM, which increased deposition of tenascin-C on the ECM. The deposition of hexabrachions of tenascin-C may stabilize bifurcations of the ECM fibrils, which is integrated into the extracellular meshwork architecture. This study suggests a role for periostin in adaptation of the ECM architecture in the mechanical environment. PMID:19887451

Incorporation of tenascin-C into the extracellular matrix by periostin underlies an extracellular meshwork architecture.

PubMed

Kii, Isao; Nishiyama, Takashi; Li, Minqi; Matsumoto, Ken-Ichi; Saito, Mitsuru; Amizuka, Norio; Kudo, Akira

2010-01-15

Extracellular matrix (ECM) underlies a complicated multicellular architecture that is subjected to significant forces from mechanical environment. Although various components of the ECM have been enumerated, mechanisms that evolve the sophisticated ECM architecture remain to be addressed. Here we show that periostin, a matricellular protein, promotes incorporation of tenascin-C into the ECM and organizes a meshwork architecture of the ECM. We found that both periostin null mice and tenascin-C null mice exhibited a similar phenotype, confined tibial periostitis, which possibly corresponds to medial tibial stress syndrome in human sports injuries. Periostin possessed adjacent domains that bind to tenascin-C and the other ECM protein: fibronectin and type I collagen, respectively. These adjacent domains functioned as a bridge between tenascin-C and the ECM, which increased deposition of tenascin-C on the ECM. The deposition of hexabrachions of tenascin-C may stabilize bifurcations of the ECM fibrils, which is integrated into the extracellular meshwork architecture. This study suggests a role for periostin in adaptation of the ECM architecture in the mechanical environment.

Absence of erythroblast macrophage protein (Emp) leads to failure of erythroblast nuclear extrusion.

PubMed

Soni, Shivani; Bala, Shashi; Gwynn, Babette; Sahr, Kenneth E; Peters, Luanne L; Hanspal, Manjit

2006-07-21

In mammals, the functional unit for definitive erythropoiesis is the erythroblastic island, a multicellular structure composed of a central macrophage surrounded by developing erythroblasts. Erythroblast-macrophage interactions play a central role in the terminal maturation of erythroblasts, including enucleation. One possible mediator of this cell-cell interaction is the protein Emp (erythroblast macrophage protein). We used targeted gene inactivation to define the function of Emp during hematopoiesis. Emp null embryos die perinatally and show profound alterations in the hematopoietic system. A dramatic increase in the number of nucleated, immature erythrocytes is seen in the peripheral blood of Emp null fetuses. In the fetal liver virtually no erythroblastic islands are observed, and the number of F4/80-positive macrophages is substantially reduced. Those present lack cytoplasmic projections and are unable to interact with erythroblasts. Interestingly, wild type macrophages can bind Emp-deficient erythroblasts, but these erythroblasts do not extrude their nuclei, suggesting that Emp impacts enucleation in a cell autonomous fashion. Previous studies have implicated the actin cytoskeleton and its reorganization in both erythroblast enucleation as well as in macrophage development. We demonstrate that Emp associates with F-actin and that this interaction is important in the normal distribution of F-actin in both erythroblasts and macrophages. Thus, Emp appears to be required for erythroblast enucleation and in the development of the mature macrophages. The availability of an Emp null model provides a unique experimental system to study the enucleation process and to evaluate the function of macrophages in definitive erythropoiesis.

Novel role of ADAMTS-5 protein in proteoglycan turnover and lipoprotein retention in atherosclerosis.

PubMed

Didangelos, Athanasios; Mayr, Ursula; Monaco, Claudia; Mayr, Manuel

2012-06-01

Atherosclerosis is initiated by the retention of lipoproteins on proteoglycans in the arterial intima. However, the mechanisms leading to proteoglycan accumulation and lipoprotein retention are poorly understood. In this study, we set out to investigate the role of ADAMTS-5 (a disintegrin and metalloprotease with thrombospondin motifs-5) in the vasculature. ADAMTS-5 was markedly reduced in atherosclerotic aortas of apolipoprotein E-null (apoE(-/-)) mice. The reduction of ADAMTS-5 was accompanied by accumulation of biglycan and versican, the major lipoprotein-binding proteoglycans, in atherosclerosis. ADAMTS-5 activity induced the release of ADAMTS-specific versican (DPEAAE(441)) and aggrecan ((374)ALGS) fragments as well as biglycan and link protein from the aortic wall. Fibroblast growth factor 2 (FGF-2) inhibited ADAMTS-5 expression in isolated aortic smooth muscle cells and blocked the spontaneous release of ADAMTS-generated versican and aggrecan fragments from aortic explants. In aortas of ADAMTS-5-deficient mice, DPEAAE(441) versican neoepitopes were not detectable. Instead, biglycan levels were increased, highlighting the role of ADAMTS-5 in the catabolism of vascular proteoglycans. Importantly, ADAMTS-5 proteolytic activity reduced the LDL binding ability of biglycan and released LDL from human aortic lesions. This study provides the first evidence implicating ADAMTS-5 in the regulation of proteoglycan turnover and lipoprotein retention in atherosclerosis.

Ameloblast Modulation and Transport of Cl−, Na+, and K+ during Amelogenesis

PubMed Central

Bronckers, A.L.J.J.; Lyaruu, D.; Jalali, R.; Medina, J.F.; Zandieh-Doulabi, B.; DenBesten, P.K.

2015-01-01

Ameloblasts express transmembrane proteins for transport of mineral ions and regulation of pH in the enamel space. Two major transporters recently identified in ameloblasts are the Na+K+-dependent calcium transporter NCKX4 and the Na+-dependent HPO42– (Pi) cotransporter NaPi-2b. To regulate pH, ameloblasts express anion exchanger 2 (Ae2a,b), chloride channel Cftr, and amelogenins that can bind protons. Exposure to fluoride or null mutation of Cftr, Ae2a,b, or Amelx each results in formation of hypomineralized enamel. We hypothesized that enamel hypomineralization associated with disturbed pH regulation results from reduced ion transport by NCKX4 and NaPi-2b. This was tested by correlation analyses among the levels of Ca, Pi, Cl, Na, and K in forming enamel of mice with null mutation of Cftr, Ae2a,b, and Amelx, according to quantitative x-ray electron probe microanalysis. Immunohistochemistry, polymerase chain reaction analysis, and Western blotting confirmed the presence of apical NaPi-2b and Nckx4 in maturation-stage ameloblasts. In wild-type mice, K levels in enamel were negatively correlated with Ca and Cl but less negatively or even positively in fluorotic enamel. Na did not correlate with P or Ca in enamel of wild-type mice but showed strong positive correlation in fluorotic and nonfluorotic Ae2a,b- and Cftr-null enamel. In hypomineralizing enamel of all models tested, 1) Cl− was strongly reduced; 2) K+ and Na+ accumulated (Na+ not in Amelx-null enamel); and 3) modulation was delayed or blocked. These results suggest that a Na+K+-dependent calcium transporter (likely NCKX4) and a Na+-dependent Pi transporter (potentially NaPi-2b) located in ruffle-ended ameloblasts operate in a coordinated way with the pH-regulating machinery to transport Ca2+, Pi, and bicarbonate into maturation-stage enamel. Acidification and/or associated physicochemical/electrochemical changes in ion levels in enamel fluid near the apical ameloblast membrane may reduce the transport activity of mineral transporters, which results in hypomineralization. PMID:26403673

Neil2-null Mice Accumulate Oxidized DNA Bases in the Transcriptionally Active Sequences of the Genome and Are Susceptible to Innate Inflammation* ♦

PubMed Central

Chakraborty, Anirban; Wakamiya, Maki; Venkova-Canova, Tatiana; Pandita, Raj K.; Aguilera-Aguirre, Leopoldo; Sarker, Altaf H.; Singh, Dharmendra Kumar; Hosoki, Koa; Wood, Thomas G.; Sharma, Gulshan; Cardenas, Victor; Sarkar, Partha S.; Sur, Sanjiv; Pandita, Tej K.; Boldogh, Istvan; Hazra, Tapas K.

2015-01-01

Why mammalian cells possess multiple DNA glycosylases (DGs) with overlapping substrate ranges for repairing oxidatively damaged bases via the base excision repair (BER) pathway is a long-standing question. To determine the biological role of these DGs, null animal models have been generated. Here, we report the generation and characterization of mice lacking Neil2 (Nei-like 2). As in mice deficient in each of the other four oxidized base-specific DGs (OGG1, NTH1, NEIL1, and NEIL3), Neil2-null mice show no overt phenotype. However, middle-aged to old Neil2-null mice show the accumulation of oxidative genomic damage, mostly in the transcribed regions. Immuno-pulldown analysis from wild-type (WT) mouse tissue showed the association of NEIL2 with RNA polymerase II, along with Cockayne syndrome group B protein, TFIIH, and other BER proteins. Chromatin immunoprecipitation analysis from mouse tissue showed co-occupancy of NEIL2 and RNA polymerase II only on the transcribed genes, consistent with our earlier in vitro findings on NEIL2's role in transcription-coupled BER. This study provides the first in vivo evidence of genomic region-specific repair in mammals. Furthermore, telomere loss and genomic instability were observed at a higher frequency in embryonic fibroblasts from Neil2-null mice than from the WT. Moreover, Neil2-null mice are much more responsive to inflammatory agents than WT mice. Taken together, our results underscore the importance of NEIL2 in protecting mammals from the development of various pathologies that are linked to genomic instability and/or inflammation. NEIL2 is thus likely to play an important role in long term genomic maintenance, particularly in long-lived mammals such as humans. PMID:26245904

Loss of fibulin-4 disrupts collagen synthesis and maturation: implications for pathology resulting from EFEMP2 mutations

PubMed Central

Papke, Christina L.; Tsunezumi, Jun; Ringuette, Léa-Jeanne; Nagaoka, Hideaki; Terajima, Masahiko; Yamashiro, Yoshito; Urquhart, Greg; Yamauchi, Mitsuo; Davis, Elaine C.; Yanagisawa, Hiromi

2015-01-01

Homozygous recessive mutations in either EFEMP2 (encoding fibulin-4) or FBLN5 (encoding fibulin-5), critical genes for elastogenesis, lead to autosomal recessive cutis laxa types 1B and 1A, respectively. Previously, fibulin-4 was shown to bind lysyl oxidase (LOX), an elastin/collagen cross-linking enzyme, in vitro. Consistently, reported defects in humans with EFEMP2 mutations are more severe and broad in range than those due to FBLN5 mutations and encompass both elastin-rich and collagen-rich tissues. However, the underlying disease mechanism in EFEMP2 mutations has not been fully addressed. Here, we show that fibulin-4 is important for the integrity of aortic collagen in addition to elastin. Smooth muscle-specific Efemp2 loss in mouse (termed SMKO) resulted in altered fibrillar collagen localization with larger, poorly organized fibrils. LOX activity was decreased in Efemp2-null cells, and collagen cross-linking was diminished in SMKO aortas; however, elastin cross-linking was unaffected and the level of mature LOX was maintained to that of wild-type aortas. Proteomic screening identified multiple proteins involved in procollagen processing and maturation as potential fibulin-4-binding partners. We showed that fibulin-4 binds procollagen C-endopeptidase enhancer 1 (Pcolce), which enhances proteolytic cleavage of the procollagen C-terminal propeptide during procollagen processing. Interestingly, however, procollagen cleavage was not affected by the presence or absence of fibulin-4 in vitro. Thus, our data indicate that fibulin-4 serves as a potential scaffolding protein during collagen maturation in the extracellular space. Analysis of collagen in other tissues affected by fibulin-4 loss should further increase our understanding of underlying pathologic mechanisms in patients with EFEMP2 mutations. PMID:26220971

Drosophila fragile X mental retardation protein and metabotropic glutamate receptor A convergently regulate the synaptic ratio of ionotropic glutamate receptor subclasses.

PubMed

Pan, Luyuan; Broadie, Kendal S

2007-11-07

A current hypothesis proposes that fragile X mental retardation protein (FMRP), an RNA-binding translational regulator, acts downstream of glutamatergic transmission, via metabotropic glutamate receptor (mGluR) G(q)-dependent signaling, to modulate protein synthesis critical for trafficking ionotropic glutamate receptors (iGluRs) at synapses. However, direct evidence linking FMRP and mGluR function with iGluR synaptic expression is limited. In this study, we use the Drosophila fragile X model to test this hypothesis at the well characterized glutamatergic neuromuscular junction (NMJ). Two iGluR classes reside at this synapse, each containing common GluRIIC (III), IID and IIE subunits, and variable GluRIIA (A-class) or GluRIIB (B-class) subunits. In Drosophila fragile X mental retardation 1 (dfmr1) null mutants, A-class GluRs accumulate and B-class GluRs are lost, whereas total GluR levels do not change, resulting in a striking change in GluR subclass ratio at individual synapses. The sole Drosophila mGluR, DmGluRA, is also expressed at the NMJ. In dmGluRA null mutants, both iGluR classes increase, resulting in an increase in total synaptic GluR content at individual synapses. Targeted postsynaptic dmGluRA overexpression causes the exact opposite GluR phenotype to the dfmr1 null, confirming postsynaptic GluR subtype-specific regulation. In dfmr1; dmGluRA double null mutants, there is an additive increase in A-class GluRs, and a similar additive impact on B-class GluRs, toward normal levels in the double mutants. These results show that both dFMRP and DmGluRA differentially regulate the abundance of different GluR subclasses in a convergent mechanism within individual postsynaptic domains.

NudEL targets dynein to microtubule ends through LIS1

PubMed Central

Li, Jun; Lee, Wei-Lih; Cooper, John A.

2006-01-01

Dynein is a minus-end-directed microtubule motor with critical roles in mitosis, membrane transport and intracellular transport. Several proteins regulate dynein activity, including dynactin1, LIS1 (refs 2, 3) and NudEL (NudE-like)2,4–8. Here, we identify a NUDEL homologue in budding yeast and name it Ndl1. The ndl1Δ null mutant shows decreased targeting of dynein to microtubule plus ends, an essential element of the model for dynein function. We find that Ndl1 regulates dynein targeting through LIS1, with which it interacts biochemically, but not through CLIP170, another plus-end protein involved in dynein targeting9. Ndl1 is found at far fewer microtubule ends than are LIS1 and dynein. However, when Ndl1 is present at a plus end, the molar amount of Ndl1 approaches that of LIS1 and dynein. We propose a model in which Ndl1 binds transiently to the plus end to promote targeting of LIS1, which cooperatively recruits dynein. PMID:15965467

The M-phase specific hyperphosphorylation of Staufen2 involved the cyclin-dependent kinase CDK1.

PubMed

Beaujois, Rémy; Ottoni, Elizabeth; Zhang, Xin; Gagnon, Christina; HSine, Sami; Mollet, Stéphanie; Viranaicken, Wildriss; DesGroseillers, Luc

2017-07-14

Staufen2 (STAU2) is an RNA-binding protein involved in the post-transcriptional regulation of gene expression. This protein was shown to be required for organ formation and cell differentiation. Although STAU2 functions have been reported in neuronal cells, its role in dividing cells remains deeply uncharacterized. Especially, its regulation during the cell cycle is completely unknown. In this study, we showed that STAU2 isoforms display a mitosis-specific slow migration pattern on SDS-gels in all tested transformed and untransformed cell lines. Deeper analyses in hTert-RPE1 and HeLa cells further indicated that the slow migration pattern of STAU2 isoforms is due to phosphorylation. Time course studies showed that STAU2 phosphorylation occurs before prometaphase and terminates as cells exit mitosis. Interestingly, STAU2 isoforms were phosphorylated on several amino acid residues in the C-terminal half via the cyclin-dependent kinase 1 (Cdk1), an enzyme known to play crucial roles during mitosis. Introduction of phospho-mimetic or phospho-null mutations in STAU2 did not impair its RNA-binding capacity, its stability, its interaction with protein co-factors or its sub-cellular localization, suggesting that STAU2 phosphorylation in mitosis does not regulate these functions. Similarly, STAU2 phosphorylation is not likely to be crucial for cell cycle progression since expression of phosphorylation mutants in hTert-RPE1 cells did not impair cell proliferation. Altogether, these results indicate that STAU2 isoforms are phosphorylated during mitosis and that the phosphorylation process involves Cdk1. The meaning of this post-translational modification is still elusive.

The transcription factor MTF-1 is essential for basal and heavy metal-induced metallothionein gene expression.

PubMed

Heuchel, R; Radtke, F; Georgiev, O; Stark, G; Aguet, M; Schaffner, W

1994-06-15

We have described and cloned previously a factor (MTF-1) that binds specifically to heavy metal-responsive DNA sequence elements in the enhancer/promoter region of metallothionein genes. MTF-1 is a protein of 72.5 kDa that contains six zinc fingers and multiple domains for transcriptional activation. Here we report the disruption of both alleles of the MTF-1 gene in mouse embryonic stem cells by homologous recombination. The resulting null mutant cell line fails to produce detectable amounts of MTF-1. Moreover, due to the loss of MTF-1, the endogenous metallothionein I and II genes are silent, indicating that MTF-1 is required for both their basal and zinc-induced transcription. In addition to zinc, other heavy metals, including cadmium, copper, nickel and lead, also fail to activate metal-responsive promoters in null mutant cells. However, cotransfection of an MTF-1 expression vector and metal-responsive reporter genes yields strong basal transcription that can be further boosted by zinc treatment of cells. These results demonstrate that MTF-1 is essential for metallothionein gene regulation. Finally, we present evidence that MTF-1 itself is a zinc sensor, which exhibits increased DNA binding activity upon zinc treatment.

Identifying Neurofibromin-Specific Regulatory Nodes for Therapeutic Targeting in NF1

DTIC Science & Technology

2016-10-01

adapter protein SPRED1, to function, and we are utilizing the latest technical innovations including CRISPR technology to find genes that regulate...neurofibromin depends on the adapter protein SPRED1, to function, and we are utilizing the latest technical innovations including CRISPR technology...signaling NF1-Null HEK 293T cells have been generated using CRISPR /Cas9 and single clones have been expanded for biochemical assays (Figure 2). NF1-Null

Activation of peroxisome proliferator-activated receptor-β/-δ (PPAR-β/-δ) ameliorates insulin signaling and reduces SOCS3 levels by inhibiting STAT3 in interleukin-6-stimulated adipocytes.

PubMed

Serrano-Marco, Lucía; Rodríguez-Calvo, Ricardo; El Kochairi, Ilhem; Palomer, Xavier; Michalik, Liliane; Wahli, Walter; Vázquez-Carrera, Manuel

2011-07-01

It has been suggested that interleukin (IL)-6 is one of the mediators linking obesity-derived chronic inflammation with insulin resistance through activation of STAT3, with subsequent upregulation of suppressor of cytokine signaling 3 (SOCS3). We evaluated whether peroxisome proliferator-activated receptor (PPAR)-β/-δ prevented activation of the IL-6-STAT3-SOCS3 pathway and insulin resistance in adipocytes. Adipocytes and white adipose tissue from wild-type and PPAR-β/-δ-null mice were used to evaluate the effect of PPAR-β/-δ on the IL-6-STAT3-SOCS3 pathway. First, we observed that the PPAR-β/-δ agonist GW501516 prevented both IL-6-dependent reduction in insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. In addition, this drug treatment abolished IL-6-induced SOCS3 expression in differentiated 3T3-L1 adipocytes. This effect was associated with the capacity of the drug to prevent IL-6-induced STAT3 phosphorylation on Tyr(705) and Ser(727) residues in vitro and in vivo. Moreover, GW501516 prevented IL-6-dependent induction of extracellular signal-related kinase (ERK)1/2, a serine-threonine-protein kinase involved in serine STAT3 phosphorylation. Furthermore, in white adipose tissue from PPAR-β/-δ-null mice, STAT3 phosphorylation (Tyr(705) and Ser(727)), STAT3 DNA-binding activity, and SOCS3 protein levels were higher than in wild-type mice. Several steps in STAT3 activation require its association with heat shock protein 90 (Hsp90), which was prevented by GW501516 as revealed in immunoprecipitation studies. Consistent with this finding, the STAT3-Hsp90 association was enhanced in white adipose tissue from PPAR-β/-δ-null mice compared with wild-type mice. Collectively, our findings indicate that PPAR-β/-δ activation prevents IL-6-induced STAT3 activation by inhibiting ERK1/2 and preventing the STAT3-Hsp90 association, an effect that may contribute to the prevention of cytokine-induced insulin resistance in adipocytes. © 2011 by the American Diabetes Association.

Characterization of a Nucleus-Encoded Chitinase from the Yeast Kluyveromyces lactis

PubMed Central

Colussi, Paul A.; Specht, Charles A.; Taron, Christopher H.

2005-01-01

Endogenous proteins secreted from Kluyveromyces lactis were screened for their ability to bind to or to hydrolyze chitin. This analysis resulted in identification of a nucleus-encoded extracellular chitinase (KlCts1p) with a chitinolytic activity distinct from that of the plasmid-encoded killer toxin α-subunit. Sequence analysis of cloned KlCTS1 indicated that it encodes a 551-amino-acid chitinase having a secretion signal peptide, an amino-terminal family 18 chitinase catalytic domain, a serine-threonine-rich domain, and a carboxy-terminal type 2 chitin-binding domain. The association of purified KlCts1p with chitin is stable in the presence of high salt concentrations and pH 3 to 10 buffers; however, complete dissociation and release of fully active KlCts1p occur in 20 mM NaOH. Similarly, secreted human serum albumin harboring a carboxy-terminal fusion with the chitin-binding domain derived from KlCts1p also dissociates from chitin in 20 mM NaOH, demonstrating the domain's potential utility as an affinity tag for reversible chitin immobilization or purification of alkaliphilic or alkali-tolerant recombinant fusion proteins. Finally, haploid K. lactis cells harboring a cts1 null mutation are viable but exhibit a cell separation defect, suggesting that KlCts1p is required for normal cytokinesis, probably by facilitating the degradation of septum-localized chitin. PMID:15932978

Characterization of a nucleus-encoded chitinase from the yeast Kluyveromyces lactis.

PubMed

Colussi, Paul A; Specht, Charles A; Taron, Christopher H

2005-06-01

Endogenous proteins secreted from Kluyveromyces lactis were screened for their ability to bind to or to hydrolyze chitin. This analysis resulted in identification of a nucleus-encoded extracellular chitinase (KlCts1p) with a chitinolytic activity distinct from that of the plasmid-encoded killer toxin alpha-subunit. Sequence analysis of cloned KlCTS1 indicated that it encodes a 551-amino-acid chitinase having a secretion signal peptide, an amino-terminal family 18 chitinase catalytic domain, a serine-threonine-rich domain, and a carboxy-terminal type 2 chitin-binding domain. The association of purified KlCts1p with chitin is stable in the presence of high salt concentrations and pH 3 to 10 buffers; however, complete dissociation and release of fully active KlCts1p occur in 20 mM NaOH. Similarly, secreted human serum albumin harboring a carboxy-terminal fusion with the chitin-binding domain derived from KlCts1p also dissociates from chitin in 20 mM NaOH, demonstrating the domain's potential utility as an affinity tag for reversible chitin immobilization or purification of alkaliphilic or alkali-tolerant recombinant fusion proteins. Finally, haploid K. lactis cells harboring a cts1 null mutation are viable but exhibit a cell separation defect, suggesting that KlCts1p is required for normal cytokinesis, probably by facilitating the degradation of septum-localized chitin.

FKBP65-dependent peptidyl-prolyl isomerase activity potentiates the lysyl hydroxylase 2-driven collagen cross-link switch.

PubMed

Chen, Yulong; Terajima, Masahiko; Banerjee, Priyam; Guo, Houfu; Liu, Xin; Yu, Jiang; Yamauchi, Mitsuo; Kurie, Jonathan M

2017-04-05

Bruck Syndrome is a connective tissue disease associated with inactivating mutations in lysyl hydroxylase 2 (LH2/PLOD2) or FK506 binding protein 65 (FKBP65/FKBP10). However, the functional relationship between LH2 and FKBP65 remains unclear. Here, we postulated that peptidyl prolyl isomerase (PPIase) activity of FKBP65 positively modulates LH2 enzymatic activity and is critical for the formation of hydroxylysine-aldehyde derived intermolecular collagen cross-links (HLCCs). To test this hypothesis, we analyzed collagen cross-links in Fkbp10-null and -wild-type murine embryonic fibroblasts. Although LH2 protein levels did not change, FKBP65 deficiency significantly diminished HLCCs and increased the non-hydroxylated lysine-aldehyde-derived collagen cross-links (LCCs), a pattern consistent with loss of LH2 enzymatic activity. The HLCC-to-LCC ratio was rescued in FKBP65-deficient murine embryonic fibroblasts by reconstitution with wild-type but not mutant FKBP65 that lacks intact PPIase domains. Findings from co-immunoprecipitation, protein-fragment complementation, and co-immunofluorescence assays showed that LH2 and FKBP65 are part of a common protein complex. We conclude that FKBP65 regulates LH2-mediated collagen cross-linking. Because LH2 promotes fibrosis and cancer metastasis, our findings suggest that pharmacologic strategies to target FKBP65 and LH2 may have complementary therapeutic activities.

FKBP65-dependent peptidyl-prolyl isomerase activity potentiates the lysyl hydroxylase 2-driven collagen cross-link switch

PubMed Central

Chen, Yulong; Terajima, Masahiko; Banerjee, Priyam; Guo, Houfu; Liu, Xin; Yu, Jiang; Yamauchi, Mitsuo; Kurie, Jonathan M.

2017-01-01

Bruck Syndrome is a connective tissue disease associated with inactivating mutations in lysyl hydroxylase 2 (LH2/PLOD2) or FK506 binding protein 65 (FKBP65/FKBP10). However, the functional relationship between LH2 and FKBP65 remains unclear. Here, we postulated that peptidyl prolyl isomerase (PPIase) activity of FKBP65 positively modulates LH2 enzymatic activity and is critical for the formation of hydroxylysine-aldehyde derived intermolecular collagen cross-links (HLCCs). To test this hypothesis, we analyzed collagen cross-links in Fkbp10-null and –wild-type murine embryonic fibroblasts. Although LH2 protein levels did not change, FKBP65 deficiency significantly diminished HLCCs and increased the non-hydroxylated lysine-aldehyde–derived collagen cross-links (LCCs), a pattern consistent with loss of LH2 enzymatic activity. The HLCC-to-LCC ratio was rescued in FKBP65-deficient murine embryonic fibroblasts by reconstitution with wild-type but not mutant FKBP65 that lacks intact PPIase domains. Findings from co-immunoprecipitation, protein-fragment complementation, and co-immunofluorescence assays showed that LH2 and FKBP65 are part of a common protein complex. We conclude that FKBP65 regulates LH2-mediated collagen cross-linking. Because LH2 promotes fibrosis and cancer metastasis, our findings suggest that pharmacologic strategies to target FKBP65 and LH2 may have complementary therapeutic activities. PMID:28378777

New Class of Precision Antimicrobials Redefines Role of Clostridium difficile S-layer in Virulence and Viability

PubMed Central

Kirk, Joseph A.; Gebhart, Dana; Buckley, Anthony M.; Lok, Stephen; Scholl, Dean; Douce, Gillian R.; Govoni, Gregory R.; Fagan, Robert P.

2017-01-01

Avidocin-CDs are a new class of precision bactericidal agents that do not damage resident gut microbiota and are unlikely to promote the spread of antibiotic resistance. The precision killing properties result from the fusion of bacteriophage receptor binding proteins (RBPs) to a lethal contractile scaffold from an R-type bacteriocin. We recently described the prototypic Avidocin-CD, Av-CD291.2, that specifically kills C. difficile ribotype 027 strains and prevents colonization of mice. We have since selected two rare Av-CD291.2 resistant mutants of strain R20291 (RT027; S-layer cassette type-4, SCLT-4). These mutants have distinct point mutations in the slpA gene that result in an S-layer null phenotype. Reversion of the mutations to wild-type restored normal SLCT-4 S-layer formation and Av-CD291.2 sensitivity; however, complementation with other SCLT alleles did not restore Av-CD291.2 sensitivity despite restoring S-layer formation. Using newly identified phage RBPs, we constructed a panel of new Avidocin-CDs that kill C. difficile isolates in an SLCT-dependent manner, confirming the S-layer as the receptor in every case. In addition to bacteriophage adsorption, characterization of the S-layer null mutant also uncovered important roles for SlpA in sporulation, resistance to lysozyme and LL-37, and toxin production. Surprisingly, the S-layer-null mutant was found to persist in the hamster gut despite its completely attenuated virulence. Avidocin-CDs have significant therapeutic potential for the treatment and prevention of C. difficile Infection (CDI) given their exquisite specificity for the pathogen. Furthermore, the emergence of resistance forces mutants to trade virulence for continued viability and, therefore, greatly reduce their potential clinical impact. PMID:28878013

The Arabidopsis COP9 signalosome subunit 7 is a model PCI domain protein with subdomains involved in COP9 signalosome assembly.

PubMed

Dessau, Moshe; Halimi, Yair; Erez, Tamir; Chomsky-Hecht, Orna; Chamovitz, Daniel A; Hirsch, Joel A

2008-10-01

The COP9 Signalosome (CSN) is a multiprotein complex that was originally identified in Arabidopsis thaliana as a negative regulator of photomorphogenesis and subsequently shown to be a general eukaryotic regulator of developmental signaling. The CSN plays various roles, but it has been most often implicated in regulating protein degradation pathways. Six of eight CSN subunits bear a sequence motif called PCI. Here, we report studies of subunit 7 (CSN7) from Arabidopsis, which contains such a motif. Our in vitro and structural results, based on 1.5 A crystallographic data, enable a definition of a PCI domain, built from helical bundle and winged helix subdomains. Using functional binding assays, we demonstrate that the PCI domain (residues 1 to 169) interacts with two other PCI proteins, CSN8 and CSN1. CSN7 interactions with CSN8 use both PCI subdomains. Furthermore, we show that a C-terminal tail outside of this PCI domain is responsible for association with the non-PCI subunit, CSN6. In vivo studies of transgenic plants revealed that the overexpressed CSN7 PCI domain does not assemble into the CSN, nor can it complement a null mutation of CSN7. However, a CSN7 clone that contains the PCI domain plus part of the CSN6 binding domain can complement the null mutation in terms of seedling viability and photomorphogenesis. These transgenic plants, though, are defective in adult growth, suggesting that the CSN7 C-terminal tail plays additional functional roles. Together, the findings have implications for CSN assembly and function, highlighting necessary interactions between subunits.

Murine Hyperglycemic Vasculopathy and Cardiomyopathy: Whole-Genome Gene Expression Analysis Predicts Cellular Targets and Regulatory Networks Influenced by Mannose Binding Lectin

PubMed Central

Zou, Chenhui; La Bonte, Laura R.; Pavlov, Vasile I.; Stahl, Gregory L.

2012-01-01

Hyperglycemia, in the absence of type 1 or 2 diabetes, is an independent risk factor for cardiovascular disease. We have previously demonstrated a central role for mannose binding lectin (MBL)-mediated cardiac dysfunction in acute hyperglycemic mice. In this study, we applied whole-genome microarray data analysis to investigate MBL’s role in systematic gene expression changes. The data predict possible intracellular events taking place in multiple cellular compartments such as enhanced insulin signaling pathway sensitivity, promoted mitochondrial respiratory function, improved cellular energy expenditure and protein quality control, improved cytoskeleton structure, and facilitated intracellular trafficking, all of which may contribute to the organismal health of MBL null mice against acute hyperglycemia. Our data show a tight association between gene expression profile and tissue function which might be a very useful tool in predicting cellular targets and regulatory networks connected with in vivo observations, providing clues for further mechanistic studies. PMID:22375142

Activation of Peroxisome Proliferator–Activated Receptor β/δ Inhibits Lipopolysaccharide-Induced Cytokine Production in Adipocytes by Lowering Nuclear Factor-κB Activity via Extracellular Signal–Related Kinase 1/2

PubMed Central

Rodríguez-Calvo, Ricardo; Serrano, Lucía; Coll, Teresa; Moullan, Norman; Sánchez, Rosa M.; Merlos, Manuel; Palomer, Xavier; Laguna, Juan C.; Michalik, Liliane; Wahli, Walter; Vázquez-Carrera, Manuel

2008-01-01

OBJECTIVE—Chronic activation of the nuclear factor-κB (NF-κB) in white adipose tissue leads to increased production of pro-inflammatory cytokines, which are involved in the development of insulin resistance. It is presently unknown whether peroxisome proliferator–activated receptor (PPAR) β/δ activation prevents inflammation in adipocytes. RESEARCH DESIGN AND METHODS AND RESULTS—First, we examined whether the PPARβ/δ agonist GW501516 prevents lipopolysaccharide (LPS)-induced cytokine production in differentiated 3T3-L1 adipocytes. Treatment with GW501516 blocked LPS-induced IL-6 expression and secretion by adipocytes and the subsequent activation of the signal transducer and activator of transcription 3 (STAT3)–Suppressor of cytokine signaling 3 (SOCS3) pathway. This effect was associated with the capacity of GW501516 to impede LPS-induced NF-κB activation. Second, in in vivo studies, white adipose tissue from Zucker diabetic fatty (ZDF) rats, compared with that of lean rats, showed reduced PPARβ/δ expression and PPAR DNA-binding activity, which was accompanied by enhanced IL-6 expression and NF-κB DNA-binding activity. Furthermore, IL-6 expression and NF-κB DNA-binding activity was higher in white adipose tissue from PPARβ/δ-null mice than in wild-type mice. Because mitogen-activated protein kinase–extracellular signal–related kinase (ERK)1/2 (MEK1/2) is involved in LPS-induced NF-κB activation in adipocytes, we explored whether PPARβ/δ prevented NF-κB activation by inhibiting this pathway. Interestingly, GW501516 prevented ERK1/2 phosphorylation by LPS. Furthermore, white adipose tissue from animal showing constitutively increased NF-κB activity, such as ZDF rats and PPARβ/δ-null mice, also showed enhanced phospho-ERK1/2 levels. CONCLUSIONS—These findings indicate that activation of PPARβ/δ inhibits enhanced cytokine production in adipocytes by preventing NF-κB activation via ERK1/2, an effect that may help prevent insulin resistance. PMID:18443198

Null alleles and sequence variations at primer binding sites of STR loci within multiplex typing systems.

PubMed

Yao, Yining; Yang, Qinrui; Shao, Chengchen; Liu, Baonian; Zhou, Yuxiang; Xu, Hongmei; Zhou, Yueqin; Tang, Qiqun; Xie, Jianhui

2018-01-01

Rare variants are widely observed in human genome and sequence variations at primer binding sites might impair the process of PCR amplification resulting in dropouts of alleles, named as null alleles. In this study, 5 cases from routine paternity testing using PowerPlex ® 21 System for STR genotyping were considered to harbor null alleles at TH01, FGA, D5S818, D8S1179, and D16S539, respectively. The dropout of alleles was confirmed by using alternative commercial kits AGCU Expressmarker 22 PCR amplification kit and AmpFℓSTR ® . Identifiler ® Plus Kit, and sequencing results revealed a single base variation at the primer binding site of each STR locus. Results from the collection of previous reports show that null alleles at D5S818 were frequently observed in population detected by two PowerPlex ® typing systems and null alleles at D19S433 were mostly observed in Japanese population detected by two AmpFℓSTR™ typing systems. Furthermore, the most popular mutation type appeared the transition from C to T with G to A, which might have a potential relationship with DNA methylation. Altogether, these results can provide helpful information in forensic practice to the elimination of genotyping discrepancy and the development of primer sets. Copyright © 2017 Elsevier B.V. All rights reserved.

Brief Report: Functional Interaction of Endoplasmic Reticulum Aminopeptidase 2 and HLA-B27 Activates the Unfolded Protein Response.

PubMed

Zhang, Zhenbo; Ciccia, Francesco; Zeng, Fanxing; Guggino, Giuliana; Yee, Kirby; Abdullah, Hasan; Silverberg, Mark S; Alessandro, Riccardo; Triolo, Giovanni; Haroon, Nigil

2017-05-01

The basic mechanisms underlying the pathogenesis of ankylosing spondylitis (AS) remain unresolved. We previously reported an association of the single-nucleotide polymorphism (SNP) rs2549782 in the endoplasmic reticulum aminopeptidase 2 gene (ERAP2) with AS. It is known that patients homozygous for the G allele (GG) of another ERAP2 SNP, rs2248374, lack expression of ERAP2 (ERAP2 null). The present study utilized this information to study the impact of ERAP2 deficiency on HLA-B27 expression in patients with AS, specifically focusing on the functional interaction of ERAP2 and HLA-B27 in peripheral blood mononuclear cells (PBMCs) from patients with AS and assessing the effects in vitro in specific cell lines. Expression of intact peptide HLA-B27 (pB27) or the major histocompatibility complex class I free heavy chains (FHCs) was assessed in PBMCs isolated from HLA-B27-positive patients with AS. ERAP2-suppressed, stable B27-expressing C1R cells (C1R-B27) were tested for the expression levels of pB27 and FHCs, as well as for markers of the unfolded protein response (UPR). Distribution of the ERAP2 SNPs rs2549782 and rs2248374 in patients with AS and in patients with Crohn's disease was assessed. PBMCs from AS patients lacking ERAP2 expressed higher levels of FHCs than did PBMCs from patients positive for ERAP2. This finding was replicated in C1R-B27 cells after suppression of ERAP2. In addition, ERAP2 suppression led to increased levels of the UPR markers BiP, CCAAT/enhancer binding protein homologous protein 10, and X-box binding protein 1 [spliced] as compared to that in short hairpin RNA-treated control cells. There was strong linkage disequilibrium in the ERAP2 locus. All patients with the rs2549782 T allele (which reportedly increases the function of the ERAP-2 protein) were homozygous for the G allele of rs2248374, leading to absence of ERAP2. ERAP2 deficiency causes increased FHC expression and up-regulation of the UPR pathway. © 2016, American College of Rheumatology.

A Conserved START Domain Coenzyme Q-binding Polypeptide is Required for Efficient Q Biosynthesis, Respiratory Electron Transport, and Antioxidant Function in Saccharomyces cerevisiae

PubMed Central

Morvaridi, Susan; Saiki, Ryoichi; Johnson, Jarrett S.; Liau, Wei-Siang; Hirano, Kathleen; Kawashima, Tadashi; Ji, Ziming; Loo, Joseph A.; Shepherd, Jennifer N.; Clarke, Catherine F.

2014-01-01

Coenzyme Qn (ubiquinone or Qn) is a redox active lipid composed of a fully substituted benzoquinone ring and a polyisoprenoid tail of n isoprene units. Saccharomyces cerevisiae coq1-coq9 mutants have defects in Q biosynthesis, lack Q6, are respiratory defective, and sensitive to stress imposed by polyunsaturated fatty acids. The hallmark phenotype of the Q-less yeast coq mutants is that respiration in isolated mitochondria can be rescued by the addition of Q2, a soluble Q analog. Yeast coq10 mutants share each of these phenotypes, with the surprising exception that they continue to produce Q6. Structure determination of the Caulobacter crescentus Coq10 homolog (CC1736) revealed a steroidogenic acute regulatory protein-related lipid transfer (START) domain, a hydrophobic tunnel known to bind specific lipids in other START domain family members. Here we show that purified CC1736 binds Q2, Q3, Q10, or demethoxy-Q3 in an equimolar ratio, but fails to bind 3-farnesyl-4-hydroxybenzoic acid, a farnesylated analog of an early Q-intermediate. Over-expression of C. crescentus CC1736 or COQ8 restores respiratory electron transport and antioxidant function of Q6 in the yeast coq10 null mutant. Studies with stable isotope ring precursors of Q reveal that early Q-biosynthetic intermediates accumulate in the coq10 mutant and de novo Q-biosynthesis is less efficient than in the wild-type yeast or rescued coq10 mutant. The results suggest that the Coq10 polypeptide:Q (protein:ligand) complex may serve essential functions in facilitating de novo Q biosynthesis and in delivering newly synthesized Q to one or more complexes of the respiratory electron transport chain. PMID:23270816

Serum antibodies to huntingtin interacting protein-1: a new blood test for prostate cancer.

PubMed

Bradley, Sarah V; Oravecz-Wilson, Katherine I; Bougeard, Gaelle; Mizukami, Ikuko; Li, Lina; Munaco, Anthony J; Sreekumar, Arun; Corradetti, Michael N; Chinnaiyan, Arul M; Sanda, Martin G; Ross, Theodora S

2005-05-15

Huntingtin-interacting protein 1 (HIP1) is frequently overexpressed in prostate cancer. HIP1 is a clathrin-binding protein involved in growth factor receptor trafficking that transforms fibroblasts by prolonging the half-life of growth factor receptors. In addition to human cancers, HIP1 is also overexpressed in prostate tumors from the transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse model. Here we provide evidence that HIP1 plays an important role in mouse tumor development, as tumor formation in the TRAMP mice was impaired in the Hip1null/null background. In addition, we report that autoantibodies to HIP1 developed in the sera of TRAMP mice with prostate cancer as well as in the sera from human prostate cancer patients. This led to the development of an anti-HIP1 serum test in humans that had a similar sensitivity and specificity to the anti-alpha-methylacyl CoA racemase (AMACR) and prostate-specific antigen tests for prostate cancer and when combined with the anti-AMACR test yielded a specificity of 97%. These data suggest that HIP1 plays a functional role in tumorigenesis and that a positive HIP1 autoantibody test may be an important serum marker of prostate cancer.

Tbx1 Regulates Progenitor Cell Proliferation in the Dental Epithelium by Modulating PITX2 Activation of p21

PubMed Central

Cao, Huojun; Florez, Sergio; Amen, Melanie; Huynh, Tuong; Skobe, Ziedonis; Baldini, Antonio; Amendt, Brad A.

2012-01-01

Tbx1−/− mice present with phenotypic effects observed in DiGeorge syndrome patients however, the molecular mechanisms of Tbx1 regulating craniofacial and tooth development are unclear. Analyses of the Tbx1 null mice reveal incisor microdontia, small cervical loops and BrdU labeling reveals a defect in epithelial cell proliferation. Furthermore, Tbx1 null mice molars are lacking normal cusp morphology. Interestingly, p21 (associated with cell cycle arrest) is up regulated in the dental epithelium of Tbx1−/− embryos. These data suggest that Tbx1 inhibits p21 expression to allow for cell proliferation in the dental epithelial cervical loop, however Tbx1 does not directly regulate p21 expression. A new molecular mechanism has been identified where Tbx1 inhibits Pitx2 transcriptional activity and decreases the expression of Pitx2 target genes, p21, Lef-1 and Pitx2c. p21 protein is increased in PITX2C transgenic mouse embryo fibroblasts (MEF) and chromatin immunoprecipitation assays demonstrate endogenous Pitx2 binding to the p21 promoter. Tbx1 attenuates PITX2 activation of endogenous p21 expression and Tbx1 null MEFs reveal increased Pitx2a and activation of Pitx2c isoform expression. Tbx1 physically interacts with the PITX2 C-terminus and represses PITX2 transcriptional activation of the p21, LEF-1, and Pitx2c promoters. Tbx1−/+/Pitx2−/+ double heterozygous mice present with an extra premolar-like tooth revealing a genetic interaction between these factors. The ability of Tbx1 to repress PITX2 activation of p21 may promote cell proliferation. In addition, PITX2 regulation of p21 reveals a new role for PITX2 in repressing cell proliferation. These data demonstrate new functional mechanisms for Tbx1 in tooth morphogenesis and provide a molecular basis for craniofacial defects in DiGeorge syndrome patients. PMID:20816801

Tbx1 regulates progenitor cell proliferation in the dental epithelium by modulating Pitx2 activation of p21.

PubMed

Cao, Huojun; Florez, Sergio; Amen, Melanie; Huynh, Tuong; Skobe, Ziedonis; Baldini, Antonio; Amendt, Brad A

2010-11-15

Tbx1(-/-) mice present with phenotypic effects observed in DiGeorge syndrome patients however, the molecular mechanisms of Tbx1 regulating craniofacial and tooth development are unclear. Analyses of the Tbx1 null mice reveal incisor microdontia, small cervical loops and BrdU labeling reveals a defect in epithelial cell proliferation. Furthermore, Tbx1 null mice molars are lacking normal cusp morphology. Interestingly, p21 (associated with cell cycle arrest) is up regulated in the dental epithelium of Tbx1(-/-) embryos. These data suggest that Tbx1 inhibits p21 expression to allow for cell proliferation in the dental epithelial cervical loop, however Tbx1 does not directly regulate p21 expression. A new molecular mechanism has been identified where Tbx1 inhibits Pitx2 transcriptional activity and decreases the expression of Pitx2 target genes, p21, Lef-1 and Pitx2c. p21 protein is increased in PITX2C transgenic mouse embryo fibroblasts (MEF) and chromatin immunoprecipitation assays demonstrate endogenous Pitx2 binding to the p21 promoter. Tbx1 attenuates PITX2 activation of endogenous p21 expression and Tbx1 null MEFs reveal increased Pitx2a and activation of Pitx2c isoform expression. Tbx1 physically interacts with the PITX2 C-terminus and represses PITX2 transcriptional activation of the p21, LEF-1, and Pitx2c promoters. Tbx1(-/+)/Pitx2(-/+) double heterozygous mice present with an extra premolar-like tooth revealing a genetic interaction between these factors. The ability of Tbx1 to repress PITX2 activation of p21 may promote cell proliferation. In addition, PITX2 regulation of p21 reveals a new role for PITX2 in repressing cell proliferation. These data demonstrate new functional mechanisms for Tbx1 in tooth morphogenesis and provide a molecular basis for craniofacial defects in DiGeorge syndrome patients. Copyright © 2010 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Xingguo, E-mail: chengx@stjohns.edu; Vispute, Saurabh G.; Liu, Jie

The toxic effects of dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), mainly through activation of the aryl hydrocarbon receptor (AhR) are well documented. Fibroblast growth factor (Fgf) 21 plays critical roles in metabolic adaptation to fasting by increasing lipid oxidation and ketogenesis in the liver. The present study was performed to determine whether activation of the AhR induces Fgf21 expression. In mouse liver, TCDD increased Fgf21 mRNA in both dose- and time-dependent manners. In addition, TCDD markedly increased Fgf21 mRNA expression in cultured mouse and human hepatocytes. Moreover, TCDD increased mRNA (in liver) and protein levels (in both liver and serum) ofmore » Fgf21 in wild-type mice, but not in AhR-null mice. Chromatin immunoprecipitation assays showed that TCDD increased AhR protein binding to the Fgf21 promoter (− 105/+ 1 base pair). Fgf21-null mice administered 200 μg/kg of TCDD died within 20 days, whereas wild-type mice receiving the same treatment were still alive at one month after administration. This indicates that TCDD-induced Fgf21 expression protects against TCDD toxicity. Diethylhexylphthalate (DEHP) pretreatment attenuated TCDD-induced Fgf21 expression in mouse liver and white adipose tissue, which may explain a previous report that DEHP pretreatment decreases TCDD-induced wasting. In conclusion, Fgf21 appears to be a target gene of AhR-signaling pathway in mouse and human liver. - Highlights: • TCDD induced Fgf21 expression at both mRNA and protein levels. • Fgf21 induction by TCDD is AhR-dependent. • DEHP attenuated TCDD-induced Fgf21 expression.« less

VE-Cadherin–Mediated Epigenetic Regulation of Endothelial Gene Expression

PubMed Central

Morini, Marco F.; Giampietro, Costanza; Corada, Monica; Pisati, Federica; Lavarone, Elisa; Cunha, Sara I.; Conze, Lei L.; O’Reilly, Nicola; Joshi, Dhira; Kjaer, Svend; George, Roger; Nye, Emma; Ma, Anqi; Jin, Jian; Mitter, Richard; Lupia, Michela; Cavallaro, Ugo; Pasini, Diego; Calado, Dinis P.

2018-01-01

Rationale: The mechanistic foundation of vascular maturation is still largely unknown. Several human pathologies are characterized by deregulated angiogenesis and unstable blood vessels. Solid tumors, for instance, get their nourishment from newly formed structurally abnormal vessels which present wide and irregular interendothelial junctions. Expression and clustering of the main endothelial-specific adherens junction protein, VEC (vascular endothelial cadherin), upregulate genes with key roles in endothelial differentiation and stability. Objective: We aim at understanding the molecular mechanisms through which VEC triggers the expression of a set of genes involved in endothelial differentiation and vascular stabilization. Methods and Results: We compared a VEC-null cell line with the same line reconstituted with VEC wild-type cDNA. VEC expression and clustering upregulated endothelial-specific genes with key roles in vascular stabilization including claudin-5, vascular endothelial-protein tyrosine phosphatase (VE-PTP), and von Willebrand factor (vWf). Mechanistically, VEC exerts this effect by inhibiting polycomb protein activity on the specific gene promoters. This is achieved by preventing nuclear translocation of FoxO1 (Forkhead box protein O1) and β-catenin, which contribute to PRC2 (polycomb repressive complex-2) binding to promoter regions of claudin-5, VE-PTP, and vWf. VEC/β-catenin complex also sequesters a core subunit of PRC2 (Ezh2 [enhancer of zeste homolog 2]) at the cell membrane, preventing its nuclear translocation. Inhibition of Ezh2/VEC association increases Ezh2 recruitment to claudin-5, VE-PTP, and vWf promoters, causing gene downregulation. RNA sequencing comparison of VEC-null and VEC-positive cells suggested a more general role of VEC in activating endothelial genes and triggering a vascular stability-related gene expression program. In pathological angiogenesis of human ovarian carcinomas, reduced VEC expression paralleled decreased levels of claudin-5 and VE-PTP. Conclusions: These data extend the knowledge of polycomb-mediated regulation of gene expression to endothelial cell differentiation and vessel maturation. The identified mechanism opens novel therapeutic opportunities to modulate endothelial gene expression and induce vascular normalization through pharmacological inhibition of the polycomb-mediated repression system. PMID:29233846

VE-Cadherin-Mediated Epigenetic Regulation of Endothelial Gene Expression.

PubMed

Morini, Marco F; Giampietro, Costanza; Corada, Monica; Pisati, Federica; Lavarone, Elisa; Cunha, Sara I; Conze, Lei L; O'Reilly, Nicola; Joshi, Dhira; Kjaer, Svend; George, Roger; Nye, Emma; Ma, Anqi; Jin, Jian; Mitter, Richard; Lupia, Michela; Cavallaro, Ugo; Pasini, Diego; Calado, Dinis P; Dejana, Elisabetta; Taddei, Andrea

2018-01-19

The mechanistic foundation of vascular maturation is still largely unknown. Several human pathologies are characterized by deregulated angiogenesis and unstable blood vessels. Solid tumors, for instance, get their nourishment from newly formed structurally abnormal vessels which present wide and irregular interendothelial junctions. Expression and clustering of the main endothelial-specific adherens junction protein, VEC (vascular endothelial cadherin), upregulate genes with key roles in endothelial differentiation and stability. We aim at understanding the molecular mechanisms through which VEC triggers the expression of a set of genes involved in endothelial differentiation and vascular stabilization. We compared a VEC-null cell line with the same line reconstituted with VEC wild-type cDNA. VEC expression and clustering upregulated endothelial-specific genes with key roles in vascular stabilization including claudin-5 , vascular endothelial-protein tyrosine phosphatase ( VE-PTP ), and von Willebrand factor ( vWf ). Mechanistically, VEC exerts this effect by inhibiting polycomb protein activity on the specific gene promoters. This is achieved by preventing nuclear translocation of FoxO1 (Forkhead box protein O1) and β-catenin, which contribute to PRC2 (polycomb repressive complex-2) binding to promoter regions of claudin-5 , VE-PTP , and vWf . VEC/β-catenin complex also sequesters a core subunit of PRC2 (Ezh2 [enhancer of zeste homolog 2]) at the cell membrane, preventing its nuclear translocation. Inhibition of Ezh2/VEC association increases Ezh2 recruitment to claudin-5 , VE-PTP , and vWf promoters, causing gene downregulation. RNA sequencing comparison of VEC-null and VEC-positive cells suggested a more general role of VEC in activating endothelial genes and triggering a vascular stability-related gene expression program. In pathological angiogenesis of human ovarian carcinomas, reduced VEC expression paralleled decreased levels of claudin-5 and VE-PTP. These data extend the knowledge of polycomb-mediated regulation of gene expression to endothelial cell differentiation and vessel maturation. The identified mechanism opens novel therapeutic opportunities to modulate endothelial gene expression and induce vascular normalization through pharmacological inhibition of the polycomb-mediated repression system. © 2017 The Authors.

E4orf1: a novel ligand that improves glucose disposal in cell culture.

PubMed

Dhurandhar, Emily J; Dubuisson, Olga; Mashtalir, Nazar; Krishnapuram, Rashmi; Hegde, Vijay; Dhurandhar, Nikhil V

2011-01-01

Reducing dietary fat intake and excess adiposity, the cornerstones of behavioral treatment of insulin resistance (IR), are marginally successful over the long term. Ad36, a human adenovirus, offers a template to improve IR, independent of dietary fat intake or adiposity. Ad36 increases cellular glucose uptake via a Ras-mediated activation of phosphatidyl inositol 3-kinase(PI3K), and improves hyperglycemia in mice, despite a high-fat diet and without reducing adiposity. Ex-vivo studies suggest that Ad36 improves hyperglycemia in mice by increasing glucose uptake by adipose tissue and skeletal muscle, and by reducing hepatic glucose output. It is impractical to use Ad36 for therapeutic action. Instead, we investigated if the E4orf1 protein of Ad36, mediates its anti-hyperglycemic action. Such a candidate protein may offer an attractive template for therapeutic development. Experiment-1 determined that Ad36 'requires' E4orf1 protein to up-regulate cellular glucose uptake. Ad36 significantly increased glucose uptake in 3T3-L1 preadipocytes, which was abrogated by knocking down E4orf1 with siRNA. Experiment-2 identified E4orf1 as 'sufficient' to up-regulate glucose uptake. 3T3-L1 cells that inducibly express E4orf1, increased glucose uptake in an induction-dependent manner, compared to null vector control cells. E4orf1 up-regulated PI3K pathway and increased abundance of Ras--the obligatory molecule in Ad36-induced glucose uptake. Experiment-3: Signaling studies of cells transiently transfected with E4orf1 or a null vector, revealed that E4orf1 may activate Ras/PI3K pathway by binding to Drosophila discs-large (Dlg1) protein. E4orf1 activated total Ras and, particularly the H-Ras isoform. By mutating the PDZ domain binding motif (PBM) of E4orf1, Experiment-4 showed that E4orf1 requires its PBM to increase Ras activation or glucose uptake. Experiment-5: In-vitro, a transient transfection by E4orf1 significantly increased glucose uptake in preadipocytes, adipocytes, or myoblasts, and reduced glucose output by hepatocytes. Thus, the highly attractive anti-hyperglycemic effect of Ad36 is mirrored by E4orf1 protein, which may offer a novel ligand to develop anti-hyperglycemic drugs.

E4orf1: A Novel Ligand That Improves Glucose Disposal in Cell Culture

PubMed Central

Dhurandhar, Emily J.; Dubuisson, Olga; Mashtalir, Nazar; Krishnapuram, Rashmi; Hegde, Vijay; Dhurandhar, Nikhil V.

2011-01-01

Reducing dietary fat intake and excess adiposity, the cornerstones of behavioral treatment of insulin resistance(IR), are marginally successful over the long term. Ad36, a human adenovirus, offers a template to improve IR, independent of dietary fat intake or adiposity. Ad36 increases cellular glucose uptake via a Ras-mediated activation of phosphatidyl inositol 3-kinase(PI3K), and improves hyperglycemia in mice, despite a high-fat diet and without reducing adiposity. Ex-vivo studies suggest that Ad36 improves hyperglycemia in mice by increasing glucose uptake by adipose tissue and skeletal muscle, and by reducing hepatic glucose output. It is impractical to use Ad36 for therapeutic action. Instead, we investigated if the E4orf1 protein of Ad36, mediates its anti-hyperglycemic action. Such a candidate protein may offer an attractive template for therapeutic development. Experiment-1 determined that Ad36 ‘requires’ E4orf1 protein to up-regulate cellular glucose uptake. Ad36 significantly increased glucose uptake in 3T3-L1 preadipocytes, which was abrogated by knocking down E4orf1 with siRNA. Experiment-2 identified E4orf1 as ‘sufficient’ to up-regulate glucose uptake. 3T3-L1 cells that inducibly express E4orf1, increased glucose uptake in an induction-dependent manner, compared to null vector control cells. E4orf1 up-regulated PI3K pathway and increased abundance of Ras–the obligatory molecule in Ad36-induced glucose uptake. Experiment-3: Signaling studies of cells transiently transfected with E4orf1 or a null vector, revealed that E4orf1 may activate Ras/PI3K pathway by binding to Drosophila discs-large(Dlg1) protein. E4orf1 activated total Ras and, particularly the H-Ras isoform. By mutating the PDZ domain binding motif(PBM) of E4orf1, Experiment-4 showed that E4orf1 requires its PBM to increase Ras activation or glucose uptake. Experiment-5: In-vitro, a transient transfection by E4orf1 significantly increased glucose uptake in preadipocytes, adipocytes, or myoblasts, and reduced glucose output by hepatocytes. Thus, the highly attractive anti-hyperglycemic effect of Ad36 is mirrored by E4orf1 protein, which may offer a novel ligand to develop anti-hyperglycemic drugs. PMID:21886789

ACF7: an essential integrator of microtubule dynamics.

PubMed

Kodama, Atsuko; Karakesisoglou, Iakowos; Wong, Ellen; Vaezi, Alec; Fuchs, Elaine

2003-10-31

ACF7 is a member of the spectraplakin family of cytoskeletal crosslinking proteins possessing actin and microtubule binding domains. Here, we show that ACF7 is an essential integrator of MT-actin dynamics. In endodermal cells, ACF7 binds along microtubules but concentrates at their distal ends and at cell borders when polarized. In ACF7's absence, microtubules still bind EB1 and CLIP170, but they no longer grow along polarized actin bundles, nor do they pause and tether to actin-rich cortical sites. The consequences are less stable, long microtubules with skewed cytoplasmic trajectories and altered dynamic instability. In response to wounding, ACF7 null cultures activate polarizing signals, but fail to maintain them and coordinate migration. Rescue of these defects requires ACF7's actin and microtubule binding domains. Thus, spectraplakins are important for controlling microtubule dynamics and reinforcing links between microtubules and polarized F-actin, so that cellular polarization and coordinated cell movements can be sustained.

p62-enriched inclusion bodies in macrophages protect against atherosclerosis

PubMed Central

Sergin, Ismail; Bhattacharya, Somashubhra; Emanuel, Roy; Esen, Emel; Stokes, Carl J.; Evans, Trent D.; Arif, Batool; Curci, John A.; Razani, Babak

2016-01-01

Autophagy is a catabolic cellular mechanism that degrades dysfunctional proteins and organelles. Atherosclerotic plaque formation is enhanced in mice with macrophages that cannot undergo autophagy because of a deficiency of an autophagy component such as ATG5. We showed that exposure of macrophages to atherogenic lipids led to an increase in the abundance of the autophagy chaperone p62, which colocalized with polyubiquitinated proteins in cytoplasmic inclusions. p62 accumulation was increased in ATG5-null macrophages, which had large cytoplasmic ubiquitin-positive p62 inclusions. Aortas from atherosclerotic mice and plaques from human endarterectomy samples showed increased abundance of p62 and polyubiquitinated proteins that co-localized with plaque macrophages, suggesting that p62-enriched protein aggregates were characteristic of atherosclerosis. The formation of the cytoplasmic inclusions depended on p62 because lipid-loaded p62-null macrophages accumulated polyubiquitinated proteins in a diffuse cytoplasmic pattern. The failure of these aggregates to form was associated with increased secretion of IL-1β and enhanced macrophage apoptosis, which depended on the p62 ubiquitin-binding domain and at least partly involved p62-mediated clearance of NLRP3 inflammasomes. Consistent with our in vitro observations, p62-deficient mice formed greater numbers of more complex atherosclerotic plaques, and p62 deficiency further increased atherosclerotic plaque burden in mice with a macrophage-specific ablation of ATG5. Together, these data suggested that sequestration of cytotoxic ubiquitinated proteins by p62 protects against atherogenesis, a condition in which the clearance of protein aggregates is disrupted. PMID:26732762

Expression of Ca2+-permeable two-pore channels rescues NAADP signalling in TPC-deficient cells

PubMed Central

Ruas, Margarida; Davis, Lianne C; Chen, Cheng-Chang; Morgan, Anthony J; Chuang, Kai-Ting; Walseth, Timothy F; Grimm, Christian; Garnham, Clive; Powell, Trevor; Platt, Nick; Platt, Frances M; Biel, Martin; Wahl-Schott, Christian; Parrington, John; Galione, Antony

2015-01-01

The second messenger NAADP triggers Ca2+ release from endo-lysosomes. Although two-pore channels (TPCs) have been proposed to be regulated by NAADP, recent studies have challenged this. By generating the first mouse line with demonstrable absence of both Tpcn1 and Tpcn2 expression (Tpcn1/2−/−), we show that the loss of endogenous TPCs abolished NAADP-dependent Ca2+ responses as assessed by single-cell Ca2+ imaging or patch-clamp of single endo-lysosomes. In contrast, currents stimulated by PI(3,5)P2 were only partially dependent on TPCs. In Tpcn1/2−/− cells, NAADP sensitivity was restored by re-expressing wild-type TPCs, but not by mutant versions with impaired Ca2+-permeability, nor by TRPML1. Another mouse line formerly reported as TPC-null likely expresses truncated TPCs, but we now show that these truncated proteins still support NAADP-induced Ca2+ release. High-affinity [32P]NAADP binding still occurs in Tpcn1/2−/− tissue, suggesting that NAADP regulation is conferred by an accessory protein. Altogether, our data establish TPCs as Ca2+-permeable channels indispensable for NAADP signalling. PMID:25872774

Novel Structure and Unexpected RNA-Binding Ability of the C-Terminal Domain of Herpes Simplex Virus 1 Tegument Protein UL21

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metrick, Claire M.; Heldwein, Ekaterina E.; Sandri-Goldin, R. M.

Proteins forming the tegument layers of herpesviral virions mediate many essential processes in the viral replication cycle, yet few have been characterized in detail. UL21 is one such multifunctional tegument protein and is conserved among alphaherpesviruses. While UL21 has been implicated in many processes in viral replication, ranging from nuclear egress to virion morphogenesis to cell-cell spread, its precise roles remain unclear. Here we report the 2.7-Å crystal structure of the C-terminal domain of herpes simplex virus 1 (HSV-1) UL21 (UL21C), which has a unique α-helical fold resembling a dragonfly. Analysis of evolutionary conservation patterns and surface electrostatics pinpointed fourmore » regions of potential functional importance on the surface of UL21C to be pursued by mutagenesis. In combination with the previously determined structure of the N-terminal domain of UL21, the structure of UL21C provides a 3-dimensional framework for targeted exploration of the multiple roles of UL21 in the replication and pathogenesis of alphaherpesviruses. Additionally, we describe an unanticipated ability of UL21 to bind RNA, which may hint at a yet unexplored function. IMPORTANCEDue to the limited genomic coding capacity of viruses, viral proteins are often multifunctional, which makes them attractive antiviral targets. Such multifunctionality, however, complicates their study, which often involves constructing and characterizing null mutant viruses. Systematic exploration of these multifunctional proteins requires detailed road maps in the form of 3-dimensional structures. In this work, we determined the crystal structure of the C-terminal domain of UL21, a multifunctional tegument protein that is conserved among alphaherpesviruses. Structural analysis pinpointed surface areas of potential functional importance that provide a starting point for mutagenesis. In addition, the unexpected RNA-binding ability of UL21 may expand its functional repertoire. The structure of UL21C and the observation of its RNA-binding ability are the latest additions to the navigational chart that can guide the exploration of the multiple functions of UL21.« less

Deficient Gene Expression in Protein Kinase Inhibitor α Null Mutant Mice

PubMed Central

Gangolli, Esha A.; Belyamani, Mouna; Muchinsky, Sara; Narula, Anita; Burton, Kimberly A.; McKnight, G. Stanley; Uhler, Michael D.; Idzerda, Rejean L.

2000-01-01

Protein kinase inhibitor (PKI) is a potent endogenous inhibitor of the cyclic AMP (cAMP)-dependent protein kinase (PKA). It functions by binding the free catalytic (C) subunit with a high affinity and is also known to export nuclear C subunit to the cytoplasm. The significance of these actions with respect to PKI's physiological role is not well understood. To address this, we have generated by homologous recombination mutant mice that are deficient in PKIα, one of the three isoforms of PKI. The mice completely lack PKI activity in skeletal muscle and, surprisingly, show decreased basal and isoproterenol-induced gene expression in muscle. Further examination revealed reduced levels of the phosphorylated (active) form of the transcription factor CREB (cAMP response element binding protein) in the knockouts. This phenomenon stems, at least in part, from lower basal PKA activity levels in the mutants, arising from a compensatory increase in the level of the RIα subunit of PKA. The deficit in gene induction, however, is not easily explained by current models of PKI function and suggests that PKI may play an as yet undescribed role in PKA signaling. PMID:10779334

Drosophila RISC component VIG and its homolog Vig2 impact heterochromatin formation.

PubMed

Gracheva, Elena; Dus, Monica; Elgin, Sarah C R

2009-07-08

Heterochromatin formation plays an important role in gene regulation and the maintenance of genome integrity. Here we present results from a study of the D. melanogaster gene vig, encoding an RNAi complex component and its homolog vig2 (CG11844) that support their involvement in heterochromatin formation and/or maintenance. Protein null mutations vig(EP812) and vig2(PL470) act as modifiers of Position Effect Variegation (PEV). VIG and Vig2 are present in polytene chromosomes and partially overlap with HP1. Quantitative immunoblots show depletion of HP1 and HP2 (large isoform) in isolated nuclei from the vig(EP812) mutant. The vig2(PL470) mutant strain demonstrates a decreased level of H3K9me2. Pull-down experiments using antibodies specific to HP1 recovered both VIG and Vig2. The association between HP1 and both VIG and Vig2 proteins depends on an RNA component. The above data and the developmental profiles of the two genes suggest that Vig2 may be involved in heterochromatin targeting and establishment early in development, while VIG may have a role in stabilizing HP1/HP2 chromatin binding during later stages.

Different CHD chromatin remodelers are required for expression of distinct gene sets and specific stages during development of Dictyostelium discoideum

PubMed Central

Platt, James L.; Rogers, Benjamin J.; Rogers, Kelley C.; Harwood, Adrian J.; Kimmel, Alan R.

2013-01-01

Control of chromatin structure is crucial for multicellular development and regulation of cell differentiation. The CHD (chromodomain-helicase-DNA binding) protein family is one of the major ATP-dependent, chromatin remodeling factors that regulate nucleosome positioning and access of transcription factors and RNA polymerase to the eukaryotic genome. There are three mammalian CHD subfamilies and their impaired functions are associated with several human diseases. Here, we identify three CHD orthologs (ChdA, ChdB and ChdC) in Dictyostelium discoideum. These CHDs are expressed throughout development, but with unique patterns. Null mutants lacking each CHD have distinct phenotypes that reflect their expression patterns and suggest functional specificity. Accordingly, using genome-wide (RNA-seq) transcriptome profiling for each null strain, we show that the different CHDs regulate distinct gene sets during both growth and development. ChdC is an apparent ortholog of the mammalian Class III CHD group that is associated with the human CHARGE syndrome, and GO analyses of aberrant gene expression in chdC nulls suggest defects in both cell-autonomous and non-autonomous signaling, which have been confirmed through analyses of chdC nulls developed in pure populations or with low levels of wild-type cells. This study provides novel insight into the broad function of CHDs in the regulation development and disease, through chromatin-mediated changes in directed gene expression. PMID:24301467

Cardiac Myosin Binding Protein C Phosphorylation Affects Cross-Bridge Cycle's Elementary Steps in a Site-Specific Manner

PubMed Central

Wang, Li; Sadayappan, Sakthivel; Kawai, Masakata

2014-01-01

Based on our recent finding that cardiac myosin binding protein C (cMyBP-C) phosphorylation affects muscle contractility in a site-specific manner, we further studied the force per cross-bridge and the kinetic constants of the elementary steps in the six-state cross-bridge model in cMyBP-C mutated transgenic mice for better understanding of the influence of cMyBP-C phosphorylation on contractile functions. Papillary muscle fibres were dissected from cMyBP-C mutated mice of ADA (Ala273-Asp282-Ala302), DAD (Asp273-Ala282-Asp302), SAS (Ser273-Ala282-Ser302), and t/t (cMyBP-C null) genotypes, and the results were compared to transgenic mice expressing wide-type (WT) cMyBP-C. Sinusoidal analyses were performed with serial concentrations of ATP, phosphate (Pi), and ADP. Both t/t and DAD mutants significantly reduced active tension, force per cross-bridge, apparent rate constant (2πc), and the rate constant of cross-bridge detachment. In contrast to the weakened ATP binding and enhanced Pi and ADP release steps in t/t mice, DAD mice showed a decreased ADP release without affecting the ATP binding and the Pi release. ADA showed decreased ADP release, and slightly increased ATP binding and cross-bridge detachment steps, whereas SAS diminished the ATP binding step and accelerated the ADP release step. t/t has the broadest effects with changes in most elementary steps of the cross-bridge cycle, DAD mimics t/t to a large extent, and ADA and SAS predominantly affect the nucleotide binding steps. We conclude that the reduced tension production in DAD and t/t is the result of reduced force per cross-bridge, instead of the less number of strongly attached cross-bridges. We further conclude that cMyBP-C is an allosteric activator of myosin to increase cross-bridge force, and its phosphorylation status modulates the force, which is regulated by variety of protein kinases. PMID:25420047

Cardiac myosin binding protein C phosphorylation affects cross-bridge cycle's elementary steps in a site-specific manner.

PubMed

Wang, Li; Sadayappan, Sakthivel; Kawai, Masakata

2014-01-01

Based on our recent finding that cardiac myosin binding protein C (cMyBP-C) phosphorylation affects muscle contractility in a site-specific manner, we further studied the force per cross-bridge and the kinetic constants of the elementary steps in the six-state cross-bridge model in cMyBP-C mutated transgenic mice for better understanding of the influence of cMyBP-C phosphorylation on contractile functions. Papillary muscle fibres were dissected from cMyBP-C mutated mice of ADA (Ala273-Asp282-Ala302), DAD (Asp273-Ala282-Asp302), SAS (Ser273-Ala282-Ser302), and t/t (cMyBP-C null) genotypes, and the results were compared to transgenic mice expressing wide-type (WT) cMyBP-C. Sinusoidal analyses were performed with serial concentrations of ATP, phosphate (Pi), and ADP. Both t/t and DAD mutants significantly reduced active tension, force per cross-bridge, apparent rate constant (2πc), and the rate constant of cross-bridge detachment. In contrast to the weakened ATP binding and enhanced Pi and ADP release steps in t/t mice, DAD mice showed a decreased ADP release without affecting the ATP binding and the Pi release. ADA showed decreased ADP release, and slightly increased ATP binding and cross-bridge detachment steps, whereas SAS diminished the ATP binding step and accelerated the ADP release step. t/t has the broadest effects with changes in most elementary steps of the cross-bridge cycle, DAD mimics t/t to a large extent, and ADA and SAS predominantly affect the nucleotide binding steps. We conclude that the reduced tension production in DAD and t/t is the result of reduced force per cross-bridge, instead of the less number of strongly attached cross-bridges. We further conclude that cMyBP-C is an allosteric activator of myosin to increase cross-bridge force, and its phosphorylation status modulates the force, which is regulated by variety of protein kinases.

Altered microtubule dynamics and vesicular transport in mouse and human MeCP2-deficient astrocytes

PubMed Central

Delépine, Chloé; Meziane, Hamid; Nectoux, Juliette; Opitz, Matthieu; Smith, Amos B.; Ballatore, Carlo; Saillour, Yoann; Bennaceur-Griscelli, Annelise; Chang, Qiang; Williams, Emily Cunningham; Dahan, Maxime; Duboin, Aurélien; Billuart, Pierre; Herault, Yann; Bienvenu, Thierry

2016-01-01

Rett syndrome (RTT) is a rare X-linked neurodevelopmental disorder, characterized by normal post-natal development followed by a sudden deceleration in brain growth with progressive loss of acquired motor and language skills, stereotypic hand movements and severe cognitive impairment. Mutations in the methyl-CpG-binding protein 2 (MECP2) cause more than 95% of classic cases. Recently, it has been shown that the loss of Mecp2 from glia negatively influences neurons in a non-cell-autonomous fashion, and that in Mecp2-null mice, re-expression of Mecp2 preferentially in astrocytes significantly improved locomotion and anxiety levels, restored respiratory abnormalities to a normal pattern and greatly prolonged lifespan compared with globally null mice. We now report that microtubule (MT)-dependent vesicle transport is altered in Mecp2-deficient astrocytes from newborn Mecp2-deficient mice compared with control wild-type littermates. Similar observation has been made in human MECP2 p.Arg294* iPSC-derived astrocytes. Importantly, administration of Epothilone D, a brain-penetrant MT-stabilizing natural product, was found to restore MT dynamics in Mecp2-deficient astrocytes and in MECP2 p.Arg294* iPSC-derived astrocytes in vitro. Finally, we report that relatively low weekly doses of Epothilone D also partially reversed the impaired exploratory behavior in Mecp2308/y male mice. These findings represent a first step toward the validation of an innovative treatment for RTT. PMID:26604147

Altered Anterior Segment Biometric Parameters in Mice Deficient in SPARC.

PubMed

Ho, Henrietta; Htoon, Hla M; Yam, Gary Hin-Fai; Toh, Li Zhen; Lwin, Nyein Chan; Chu, Stephanie; Lee, Ying Shi; Wong, Tina T; Seet, Li-Fong

2017-01-01

Secreted protein acidic and rich in cysteine (SPARC) and Hevin are structurally related matricellular proteins involved in extracellular matrix assembly. In this study, we compared the anterior chamber biometric parameters and iris collagen properties in SPARC-, Hevin- and SPARC-/Hevin-null with wild-type (WT) mice. The right eyes of 53 WT, 35 SPARC-, 56 Hevin-, and 63 SPARC-/Hevin-null mice were imaged using the RTVue-100 Fourier-domain optical coherence tomography system. The parameters measured were anterior chamber depth (ACD), trabecular-iris space area (TISA), angle opening distance (AOD), and pupil diameter. Biometric data were analyzed using analysis of covariance and adjusted for age, sex, and pupil diameter. Expression of Col1a1, Col8a1, and Col8a2 transcripts in the irises was measured by quantitative polymerase chain reaction. Collagen fibril thickness was evaluated by transmission electron microscopy. Mice that were SPARC- and SPARC-/Hevin-null had 1.28- and 1.25-fold deeper ACD, 1.45- and 1.53-fold larger TISA, as well as 1.42- and 1.51-fold wider AOD than WT, respectively. These measurements were not significantly different between SPARC- and SPARC-/Hevin-null mice. The SPARC-null iris expressed lower Col1a1, but higher Col8a1 and Col8a2 transcripts compared with WT. Collagen fibrils in the SPARC- and SPARC-/Hevin-null irises were 1.5- and 1.7-fold thinner than WT, respectively. The Hevin-null iris did not differ from WT in these collagen properties. SPARC-null mice have deeper anterior chamber as well as wider drainage angles compared with WT. Therefore, SPARC plays a key role in influencing the spatial organization of the anterior segment, potentially via modulation of collagen properties, while Hevin is not likely to be involved.

FABP4 attenuates PPARγ and adipogenesis and is inversely correlated with PPARγ in adipose tissues.

PubMed

Garin-Shkolnik, Tali; Rudich, Assaf; Hotamisligil, Gökhan S; Rubinstein, Menachem

2014-03-01

Fatty acid binding protein 4 (FABP4, also known as aP2) is a cytoplasmic fatty acid chaperone expressed primarily in adipocytes and myeloid cells and implicated in the development of insulin resistance and atherosclerosis. Here we demonstrate that FABP4 triggers the ubiquitination and subsequent proteasomal degradation of peroxisome proliferator-activated receptor γ (PPARγ), a master regulator of adipogenesis and insulin responsiveness. Importantly, FABP4-null mouse preadipocytes as well as macrophages exhibited increased expression of PPARγ, and complementation of FABP4 in the macrophages reversed the increase in FABP4 expression. The FABP4-null preadipocytes exhibited a remarkably enhanced adipogenesis compared with wild-type cells, indicating that FABP4 regulates adipogenesis by downregulating PPARγ. We found that the FABP4 level was higher and PPARγ level was lower in human visceral fat and mouse epididymal fat compared with their subcutaneous fat. Furthermore, FABP4 was higher in the adipose tissues of obese diabetic individuals compared with healthy ones. Suppression of PPARγ by FABP4 in visceral fat may explain the reported role of FABP4 in the development of obesity-related morbidities, including insulin resistance, diabetes, and atherosclerosis.

Integrin α1β1 participates in Chondrocyte Transduction of Osmotic Stress.

PubMed Central

Jablonski, Christina L.; Ferguson, Samuel; Pozzi, Ambra; Clark, Andrea L.

2014-01-01

Background/purpose: The goal of this study was to determine the role of the collagen binding receptor integrin α1β1 in regulating osmotically induced [Ca2+]i transients in chondrocytes. Methods: The [Ca2+]i transient response of chondrocytes to osmotic stress was measured using real-time confocal microscopy. Chondrocytes from wildtype and integrin α1-null mice were imaged ex vivo (in the cartilage of intact murine femora) and in vitro (isolated from the matrix, attached to glass coverslips). Immunocytochemistry was performed to detect the presence of the osmosensor, transient receptor potential vanilloid-4 (TRPV4), and the agonist GSK1016790A (GSK101) was used to test for its functionality on chondrocytes from wildtype and integrin α1-null mice. Results/interpretation: Deletion of the integrin α1 subunit inhibited the ability of chondrocytes to respond to a hypo-osmotic stress with [Ca2+]i transients ex vivo and in vitro. The percentage of chondrocytes responding ex vivo was smaller than in vitro and of the cells that responded, more single [Ca2+]i transients were observed ex vivo compared to in vitro. Immunocytochemistry confirmed the presence of TRPV4 on wildtype and integrin α1-null chondrocytes, however application of GSK101 revealed that TRPV4 could be activated on wildtype but not integrin α1-null chondrocytes. Integrin α1β1 is a key participant in chondrocyte transduction of a hypo-osmotic stress. Furthermore, the mechanism by which integrin α1β1 influences osmotransduction is independent of matrix binding, but likely dependent on the chondrocyte osmosensor TRPV4. PMID:24495803

Integrin α1β1 participates in chondrocyte transduction of osmotic stress.

PubMed

Jablonski, Christina L; Ferguson, Samuel; Pozzi, Ambra; Clark, Andrea L

2014-02-28

The goal of this study was to determine the role of the collagen binding receptor integrin α1β1 in regulating osmotically induced [Ca(2+)]i transients in chondrocytes. The [Ca(2+)]i transient response of chondrocytes to osmotic stress was measured using real-time confocal microscopy. Chondrocytes from wildtype and integrin α1-null mice were imaged ex vivo (in the cartilage of intact murine femora) and in vitro (isolated from the matrix, attached to glass coverslips). Immunocytochemistry was performed to detect the presence of the osmosensor, transient receptor potential vanilloid-4 (TRPV4), and the agonist GSK1016790A (GSK101) was used to test for its functionality on chondrocytes from wildtype and integrin α1-null mice. Deletion of the integrin α1 subunit inhibited the ability of chondrocytes to respond to a hypo-osmotic stress with [Ca(2+)]i transients ex vivo and in vitro. The percentage of chondrocytes responding ex vivo was smaller than in vitro and of the cells that responded, more single [Ca(2+)]i transients were observed ex vivo compared to in vitro. Immunocytochemistry confirmed the presence of TRPV4 on wildtype and integrin α1-null chondrocytes, however application of GSK101 revealed that TRPV4 could be activated on wildtype but not integrin α1-null chondrocytes. Integrin α1β1 is a key participant in chondrocyte transduction of a hypo-osmotic stress. Furthermore, the mechanism by which integrin α1β1 influences osmotransduction is independent of matrix binding, but likely dependent on the chondrocyte osmosensor TRPV4. Copyright © 2014 Elsevier Inc. All rights reserved.

A critical role for the transcription factor Scl in platelet production during stress thrombopoiesis.

PubMed

McCormack, Matthew P; Hall, Mark A; Schoenwaelder, Simone M; Zhao, Quan; Ellis, Sarah; Prentice, Julia A; Clarke, Ashleigh J; Slater, Nicholas J; Salmon, Jessica M; Jackson, Shaun P; Jane, Stephen M; Curtis, David J

2006-10-01

The generation of platelets from megakaryocytes in the steady state is regulated by a variety of cytokines and transcription factors, including thrombopoietin (TPO), GATA-1, and NF-E2. Less is known about platelet production in the setting of stress thrombopoiesis, a pivotal event in the context of cytotoxic chemotherapy. Here we show in mice that the transcription factor Scl is critical for platelet production after chemotherapy and in thrombopoiesis induced by administration of TPO. Megakaryocytes from these mice showed appropriate increases in number and ploidy but failed to shed platelets. Ultrastructural examination of Scl-null megakaryocytes revealed a disorganized demarcation membrane and reduction in platelet granules. Quantitative real-time polymerase chain reaction showed that Scl-null platelets lacked NF-E2, and chromatin immunoprecipitation analysis demonstrated Scl binding to the NF-E2 promoter in the human megakaryoblastic-cell line Meg-01, along with its binding partners E47, Lmo2, and the cofactors Ldb1 and GATA-2. These findings suggest that Scl acts up-stream of NF-E2 expression to control megakaryocyte development and platelet release in settings of thrombopoietic stress.

Neil2-null Mice Accumulate Oxidized DNA Bases in the Transcriptionally Active Sequences of the Genome and Are Susceptible to Innate Inflammation.

PubMed

Chakraborty, Anirban; Wakamiya, Maki; Venkova-Canova, Tatiana; Pandita, Raj K; Aguilera-Aguirre, Leopoldo; Sarker, Altaf H; Singh, Dharmendra Kumar; Hosoki, Koa; Wood, Thomas G; Sharma, Gulshan; Cardenas, Victor; Sarkar, Partha S; Sur, Sanjiv; Pandita, Tej K; Boldogh, Istvan; Hazra, Tapas K

2015-10-09

Why mammalian cells possess multiple DNA glycosylases (DGs) with overlapping substrate ranges for repairing oxidatively damaged bases via the base excision repair (BER) pathway is a long-standing question. To determine the biological role of these DGs, null animal models have been generated. Here, we report the generation and characterization of mice lacking Neil2 (Nei-like 2). As in mice deficient in each of the other four oxidized base-specific DGs (OGG1, NTH1, NEIL1, and NEIL3), Neil2-null mice show no overt phenotype. However, middle-aged to old Neil2-null mice show the accumulation of oxidative genomic damage, mostly in the transcribed regions. Immuno-pulldown analysis from wild-type (WT) mouse tissue showed the association of NEIL2 with RNA polymerase II, along with Cockayne syndrome group B protein, TFIIH, and other BER proteins. Chromatin immunoprecipitation analysis from mouse tissue showed co-occupancy of NEIL2 and RNA polymerase II only on the transcribed genes, consistent with our earlier in vitro findings on NEIL2's role in transcription-coupled BER. This study provides the first in vivo evidence of genomic region-specific repair in mammals. Furthermore, telomere loss and genomic instability were observed at a higher frequency in embryonic fibroblasts from Neil2-null mice than from the WT. Moreover, Neil2-null mice are much more responsive to inflammatory agents than WT mice. Taken together, our results underscore the importance of NEIL2 in protecting mammals from the development of various pathologies that are linked to genomic instability and/or inflammation. NEIL2 is thus likely to play an important role in long term genomic maintenance, particularly in long-lived mammals such as humans. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

FABP4/aP2 Regulates Macrophage Redox Signaling and Inflammasome Activation via Control of UCP2.

PubMed

Steen, Kaylee A; Xu, Hongliang; Bernlohr, David A

2017-01-15

Obesity-linked metabolic disease is mechanistically associated with the accumulation of proinflammatory macrophages in adipose tissue, leading to increased reactive oxygen species (ROS) production and chronic low-grade inflammation. Previous work has demonstrated that deletion of the adipocyte fatty acid-binding protein (FABP4/aP2) uncouples obesity from inflammation via upregulation of the uncoupling protein 2 (UCP2). Here, we demonstrate that ablation of FABP4/aP2 regulates systemic redox capacity and reduces cellular protein sulfhydryl oxidation and, in particular, oxidation of mitochondrial protein cysteine residues. Coincident with the loss of FABP4/aP2 is the upregulation of the antioxidants superoxide dismutase (SOD2), catalase, methionine sulfoxide reductase A, and the 20S proteasome subunits PSMB5 and αβ. Reduced mitochondrial protein oxidation in FABP4/aP2 -/- macrophages attenuates the mitochondrial unfolded-protein response (mtUPR) as measured by expression of heat shock protein 60, Clp protease, and Lon peptidase 1. Consistent with a diminished mtUPR, FABP4/aP2 -/- macrophages exhibit reduced expression of cleaved caspase-1 and NLRP3. Secretion of interleukin 1β (IL-1β), in response to inflammasome activation, is ablated in FABP4/aP2 -/- macrophages, as well as in FABP4/aP2 inhibitor-treated cells, but partially rescued in FABP4/aP2-null macrophages when UCP2 is silenced. Collectively, these data offer a novel pathway whereby FABP4/aP2 regulates macrophage redox signaling and inflammasome activation via control of UCP2 expression. Copyright © 2017 American Society for Microbiology.

Neto Auxiliary Protein Interactions Regulate Kainate and NMDA Receptor Subunit Localization at Mossy Fiber–CA3 Pyramidal Cell Synapses

PubMed Central

Wyeth, Megan S.; Pelkey, Kenneth A.; Petralia, Ronald S.; Salter, Michael W.; McInnes, Roderick R.

2014-01-01

Neto1 and Neto2 auxiliary subunits coassemble with NMDA receptors (NMDARs) and kainate receptors (KARs) to modulate their function. In the hippocampus, Neto1 enhances the amplitude and prolongs the kinetics of KAR-mediated currents at mossy fiber (MF)–CA3 pyramidal cell synapses. However, whether Neto1 trafficks KARs to synapses or simply alters channel properties is unresolved. Therefore, postembedding electron microscopy was performed to investigate the localization of GluK2/3 subunits at MF–CA3 synapses in Neto-null mice. Postsynaptic GluK2/3 Immunogold labeling was substantially reduced in Neto-null mice compared with wild types. Moreover, spontaneous KAR-mediated synaptic currents and metabotropic KAR signaling were absent in CA3 pyramidal cells of Neto-null mice. A similar loss of ionotropic and metabotropic KAR function was observed in Neto1, but not Neto2, single knock-out mice, specifically implicating Neto1 in regulating CA3 pyramidal cell KAR localization and function. Additional controversy pertains to the role of Neto proteins in modulating synaptic NMDARs. While Immunogold labeling for GluN2A at MF–CA3 synapses was comparable between wild-type and Neto-null mice, labeling for postsynaptic GluN2B was robustly increased in Neto-null mice. Accordingly, NMDAR-mediated currents at MF–CA3 synapses exhibited increased sensitivity to a GluN2B-selective antagonist in Neto1 knockouts relative to wild types. Thus, despite preservation of the overall MF–CA3 synaptic NMDAR-mediated current, loss of Neto1 alters NMDAR subunit composition. These results confirm that Neto protein interactions regulate synaptic localization of KAR and NMDAR subunits at MF–CA3 synapses, with implications for both ionotropic and metabotropic glutamatergic recruitment of the CA3 network. PMID:24403160

Cooperative activity of GABP with PU.1 or C/EBPε regulates lamin B receptor gene expression, implicating their roles in granulocyte nuclear maturation1

PubMed Central

Malu, Krishnakumar; Garhwal, Rahul; Pelletier, Margery G. H.; Gotur, Deepali; Halene, Stephanie; Zwerger, Monika; Yang, Zhong-Fa; Rosmarin, Alan G.; Gaines, Peter

2016-01-01

Nuclear segmentation is a hallmark feature of mammalian neutrophil differentiation, but the mechanisms that control this process are poorly understood. Gene expression in maturing neutrophils requires combinatorial actions of lineage-restricted and more widely expressed transcriptional regulators. Examples include interactions of the widely expressed ETS transcription factor, GA-binding protein (GABP), with the relatively lineage-restricted ETS factor, PU.1, and with CCAAT enhancer binding proteins, C/EBPα and C/EBPε. Whether such cooperative interactions between these transcription factors also regulate the expression of genes encoding proteins that control nuclear segmentation is unclear. We investigated the roles of ETS and C/EBP family transcription factors in regulating the gene encoding the lamin B receptor (LBR), an inner nuclear membrane protein whose expression is required for neutrophil nuclear segmentation. Although C/EBPε was previously shown to bind the Lbr promoter, surprisingly, we found that neutrophils derived from Cebpe null mice exhibited normal Lbr gene and protein expression. Instead, GABP provided transcriptional activation through the Lbr promoter in the absence of C/EBPε, and activities supported by GABP were greatly enhanced by either C/EBPε or PU.1. Both GABP and PU.1 bound Ets sites in the Lbr promoter in vitro, and in vivo within both early myeloid progenitors and differentiating neutrophils. These findings demonstrate that GABP, PU.1, and C/EBPε cooperate to control transcription of the gene encoding LBR, a nuclear envelope protein that is required for the characteristic lobulated morphology of mature neutrophils. PMID:27342846

Missense mutation in APOC3 within the C-terminal lipid binding domain of human ApoC-III results in impaired assembly and secretion of triacylglycerol-rich very low density lipoproteins: evidence that ApoC-III plays a major role in the formation of lipid precursors within the microsomal lumen.

PubMed

Qin, Wen; Sundaram, Meenakshi; Wang, Yuwei; Zhou, Hu; Zhong, Shumei; Chang, Chia-Ching; Manhas, Sanjay; Yao, Erik F; Parks, Robin J; McFie, Pamela J; Stone, Scot J; Jiang, Zhenghui G; Wang, Congrong; Figeys, Daniel; Jia, Weiping; Yao, Zemin

2011-08-05

Hepatic assembly of triacylglycerol (TAG)-rich very low density lipoproteins (VLDL) is achieved through recruitment of bulk TAG (presumably in the form of lipid droplets within the microsomal lumen) into VLDL precursor containing apolipoprotein (apo) B-100. We determined protein/lipid components of lumenal lipid droplets (LLD) in cells expressing recombinant human apoC-III (C3wt) or a mutant form (K58E, C3KE) initially identified in humans that displayed hypotriglyceridemia. Although expression of C3wt markedly stimulated secretion of TAG and apoB-100 as VLDL(1), the K58E mutation (located at the C-terminal lipid binding domain) abolished the effect in transfected McA-RH7777 cells and in apoc3-null mice. Metabolic labeling studies revealed that accumulation of TAG in LLD was decreased (by 50%) in cells expressing C3KE. A Fat Western lipid protein overlay assay showed drastically reduced lipid binding of the mutant protein. Substituting Lys(58) with Arg demonstrated that the positive charge at position 58 is crucial for apoC-III binding to lipid and for promoting TAG secretion. On the other hand, substituting both Lys(58) and Lys(60) with Glu resulted in almost entire elimination of lipid binding and loss of function in promoting TAG secretion. Thus, the lipid binding domain of apoC-III plays a key role in the formation of LLD for hepatic VLDL assembly and secretion.

Drosophila Spag is the homolog of RNA polymerase II-associated protein 3 (RPAP3) and recruits the heat shock proteins 70 and 90 (Hsp70 and Hsp90) during the assembly of cellular machineries.

PubMed

Benbahouche, Nour El Houda; Iliopoulos, Ioannis; Török, István; Marhold, Joachim; Henri, Julien; Kajava, Andrey V; Farkaš, Robert; Kempf, Tore; Schnölzer, Martina; Meyer, Philippe; Kiss, István; Bertrand, Edouard; Mechler, Bernard M; Pradet-Balade, Bérengère

2014-02-28

The R2TP is a recently identified Hsp90 co-chaperone, composed of four proteins as follows: Pih1D1, RPAP3, and the AAA(+)-ATPases RUVBL1 and RUVBL2. In mammals, the R2TP is involved in the biogenesis of cellular machineries such as RNA polymerases, small nucleolar ribonucleoparticles and phosphatidylinositol 3-kinase-related kinases. Here, we characterize the spaghetti (spag) gene of Drosophila, the homolog of human RPAP3. This gene plays an essential function during Drosophila development. We show that Spag protein binds Drosophila orthologs of R2TP components and Hsp90, like its yeast counterpart. Unexpectedly, Spag also interacts and stimulates the chaperone activity of Hsp70. Using null mutants and flies with inducible RNAi, we show that spaghetti is necessary for the stabilization of snoRNP core proteins and target of rapamycin activity and likely the assembly of RNA polymerase II. This work highlights the strong conservation of both the HSP90/R2TP system and its clients and further shows that Spag, unlike Saccharomyces cerevisiae Tah1, performs essential functions in metazoans. Interaction of Spag with both Hsp70 and Hsp90 suggests a model whereby R2TP would accompany clients from Hsp70 to Hsp90 to facilitate their assembly into macromolecular complexes.

ELAV, a Drosophila neuron-specific protein, mediates the generation of an alternatively spliced neural protein isoform.

PubMed

Koushika, S P; Lisbin, M J; White, K

1996-12-01

Tissue-specific alternative pre-mRNA splicing is a widely used mechanism for gene regulation and the generation of different protein isoforms, but relatively little is known about the factors and mechanisms that mediate this process. Tissue-specific RNA-binding proteins could mediate alternative pre-mRNA splicing. In Drosophila melanogaster, the RNA-binding protein encoded by the elav (embryonic lethal abnormal visual system) gene is a candidate for such a role. The ELAV protein is expressed exclusively in neurons, and is important for the formation and maintenance of the nervous system. In this study, photoreceptor neurons genetically depleted of ELAV, and elav-null central nervous system neurons, were analyzed immunocytochemically for the expression of neural proteins. In both situations, the lack of ELAV corresponded with a decrease in the immunohistochemical signal of the neural-specific isoform of Neuroglian, which is generated by alternative splicing. Furthermore, when ELAV was expressed ectopically in cells that normally express only the non-neural isoform of Neuroglian, we observed the generation of the neural isoform of Neuroglian. Drosophila ELAV promotes the generation of the neuron-specific isoform of Neuroglian by the regulation of pre-mRNA splicing. The findings reported in this paper demonstrate that ELAV is necessary, and the ectopic expression of ELAV in imaginal disc cells is sufficient, to mediate neuron-specific alternative splicing.

Thioredoxin binding protein (TBP)-2/Txnip and α-arrestin proteins in cancer and diabetes mellitus.

PubMed

Masutani, Hiroshi; Yoshihara, Eiji; Masaki, So; Chen, Zhe; Yodoi, Junji

2012-01-01

Thioredoxin binding protein -2/ thioredoxin interacting protein is an α-arrestin protein that has attracted much attention as a multifunctional regulator. Thioredoxin binding protein -2 expression is downregulated in tumor cells and the level of thioredoxin binding protein is correlated with clinical stage of cancer. Mice with mutations or knockout of the thioredoxin binding protein -2 gene are much more susceptible to carcinogenesis than wild-type mice, indicating a role for thioredoxin binding protein -2 in cancer suppression. Studies have also revealed roles for thioredoxin binding protein -2 in metabolic control. Enhancement of thioredoxin binding protein -2 expression causes impairment of insulin sensitivity and glucose-induced insulin secretion, and β-cell apoptosis. These changes are important characteristics of type 2 diabetes mellitus. Thioredoxin binding protein -2 regulates transcription of metabolic regulating genes. Thioredoxin binding protein -2-like inducible membrane protein/ arrestin domain containing 3 regulates endocytosis of receptors such as the β(2)-adrenergic receptor. The α-arrestin family possesses PPXY motifs and may function as an adaptor/scaffold for NEDD family ubiquitin ligases. Elucidation of the molecular mechanisms of α-arrestin proteins would provide a new pharmacological basis for developing approaches against cancer and type 2 diabetes mellitus.

A BDNF loop-domain mimetic acutely reverses spontaneous apneas and respiratory abnormalities during behavioral arousal in a mouse model of Rett syndrome

PubMed Central

Kron, Miriam; Lang, Min; Adams, Ian T.; Sceniak, Michael; Longo, Frank; Katz, David M.

2014-01-01

Reduced levels of brain-derived neurotrophic factor (BDNF) are thought to contribute to the pathophysiology of Rett syndrome (RTT), a severe neurodevelopmental disorder caused by loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2). In Mecp2 mutant mice, BDNF deficits have been associated with breathing abnormalities, a core feature of RTT, as well as with synaptic hyperexcitability within the brainstem respiratory network. Application of BDNF can reverse hyperexcitability in acute brainstem slices from Mecp2-null mice, suggesting that therapies targeting BDNF or its receptor, TrkB, could be effective at acute reversal of respiratory abnormalities in RTT. Therefore, we examined the ability of LM22A-4, a small-molecule BDNF loop-domain mimetic and TrkB partial agonist, to modulate synaptic excitability within respiratory cell groups in the brainstem nucleus tractus solitarius (nTS) and to acutely reverse abnormalities in breathing at rest and during behavioral arousal in Mecp2 mutants. Patch-clamp recordings in Mecp2-null brainstem slices demonstrated that LM22A-4 decreases excitability at primary afferent synapses in the nTS by reducing the amplitude of evoked excitatory postsynaptic currents and the frequency of spontaneous and miniature excitatory postsynaptic currents. In vivo, acute treatment of Mecp2-null and -heterozygous mutants with LM22A-4 completely eliminated spontaneous apneas in resting animals, without sedation. Moreover, we demonstrate that respiratory dysregulation during behavioral arousal, a feature of human RTT, is also reversed in Mecp2 mutants by acute treatment with LM22A-4. Together, these data support the hypothesis that reduced BDNF signaling and respiratory dysfunction in RTT are linked, and establish the proof-of-concept that treatment with a small-molecule structural mimetic of a BDNF loop domain and a TrkB partial agonist can acutely reverse abnormal breathing at rest and in response to behavioral arousal in symptomatic RTT mice. PMID:25147297

Fission yeast Alp14 is a dose-dependent plus end–tracking microtubule polymerase

PubMed Central

Al-Bassam, Jawdat; Kim, Hwajin; Flor-Parra, Ignacio; Lal, Neeraj; Velji, Hamida; Chang, Fred

2012-01-01

XMAP215/Dis1 proteins are conserved tubulin-binding TOG-domain proteins that regulate microtubule (MT) plus-end dynamics. Here we show that Alp14, a XMAP215 orthologue in fission yeast, Schizosaccharomyces pombe, has properties of a MT polymerase. In vivo, Alp14 localizes to growing MT plus ends in a manner independent of Mal3 (EB1). alp14-null mutants display short interphase MTs with twofold slower assembly rate and frequent pauses. Alp14 is a homodimer that binds a single tubulin dimer. In vitro, purified Alp14 molecules track growing MT plus ends and accelerate MT assembly threefold. TOG-domain mutants demonstrate that tubulin binding is critical for function and plus end localization. Overexpression of Alp14 or only its TOG domains causes complete MT loss in vivo, and high Alp14 concentration inhibits MT assembly in vitro. These inhibitory effects may arise from Alp14 sequestration of tubulin and effects on the MT. Our studies suggest that Alp14 regulates the polymerization state of tubulin by cycling between a tubulin dimer–bound cytoplasmic state and a MT polymerase state that promotes rapid MT assembly. PMID:22696680

Capsule null locus meningococci: typing of antigens used in an investigational multicomponent meningococcus serogroup B vaccine.

PubMed

Claus, Heike; Jördens, Markus S; Kriz, Pavla; Musilek, Martin; Jarva, Hanna; Pawlik, Marie-Christin; Meri, Seppo; Vogel, Ulrich

2012-01-05

The investigational multicomponent meningococcus serogroup B vaccine (4CMenB) targets the antigenetically variable population of serogroup B meningococci. Forty-one strains of capsule null locus (cnl) meningococci, which are frequent among healthy carriers, were selected from nine sequence types (ST), which belong to four clonal complexes (cc), and three countries. They were antigen sequence typed and analyzed for antigen expression to predict whether these strains harbor the genes and express the four vaccine antigens of 4CMenB as measured by the meningococcal antigen typing system (MATS). The PorA variant used in the vaccine was not found. The nadA gene was absent in all but one strain, which did not express the antigen in vitro. Only strains of clonal complex ST-198 harbored a factor H binding protein (FHBP) allele of the cross-reactive variant 1 family which is included in the vaccine. All these strains expressed the antigen. Five variants of the Neisserial heparin binding antigen (NHBA) gene were identified. Expression of NHBA was observed in all strains with highest levels in ST-198 cc and ST-845. The data suggest a potential impact of 4CMenB immunization at least on cnl meningococci of the ST-198 cc and ST-845. Copyright © 2011 Elsevier Ltd. All rights reserved.

Ablating L-FABP in SCP-2/SCP-x null mice impairs bile acid metabolism and biliary HDL-cholesterol secretion

PubMed Central

Martin, Gregory G.; Atshaves, Barbara P.; Landrock, Kerstin K.; Landrock, Danilo; Storey, Stephen M.; Howles, Philip N.; Kier, Ann B.

2014-01-01

On the basis of their abilities to bind bile acids and/or cholesterol, the physiological role(s) of liver fatty acid-binding protein (L-FABP) and sterol carrier protein (SCP) 2/SCP-x (SCP-2/SCP-x) gene products in biliary bile acid and cholesterol formation was examined in gene-ablated male mice. L-FABP (LKO) or L-FABP/SCP-2/SCP-x [triple-knockout (TKO)] ablation markedly decreased hepatic bile acid concentration, while SCP-2/SCP-x [double-knockout (DKO)] ablation alone had no effect. In contrast, LKO increased biliary bile acid, while DKO and TKO had no effect on biliary bile acid levels. LKO and DKO also altered biliary bile acid composition to increase bile acid hydrophobicity. Furthermore, LKO and TKO decreased hepatic uptake and biliary secretion of high-density lipoprotein (HDL)-derived 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), while DKO alone had no effect. Finally, LKO and, to a lesser extent, DKO decreased most indexes contributing to cholesterol solubility in biliary bile. These results suggest different, but complementary, roles for L-FABP and SCP-2/SCP-x in biliary bile acid and cholesterol formation. L-FABP appears to function more in hepatic retention of bile acids as well as hepatic uptake and biliary secretion of HDL-cholesterol. Conversely, SCP-2/SCP-x may function more in formation and biliary secretion of bile acid, with less impact on hepatic uptake or biliary secretion of HDL-cholesterol. PMID:25277800

Role of RhAG and AQP1 in NH3 and CO2 gas transport in red cell ghosts: a stopped-flow analysis.

PubMed

Ripoche, P; Goossens, D; Devuyst, O; Gane, P; Colin, Y; Verkman, A S; Cartron, J-P

2006-01-01

To clarify the potential role Rh/RhAG and AQP1 proteins in erythrocyte gas transport, NH3 and CO2 transport was measured in erythrocyte ghost membrane vesicles from rare human variants (Rh(null), CO(null),) and knockout mice (homozygous AQP1-/-, Rh-/- and Rhag-/-) exhibiting well-characterized protein defects. Transport was measured from intracellular pH (pHi) changes in a stopped-flow fluorimeter. NH3 transport was measured in chloride-free conditions with ghosts exposed to 20 mM inwardly directed gradients of gluconate salts of ammonium, hydrazine and methylammonium at 15 degrees C. Alkalinization rates of control samples were 6.5+/-0.3, 4.03+/-0.17, 0.95+/-0.08 s(-1) for each solute, respectively, but were significantly reduced for Rh(null) and CO(null) samples that are deficient in RhAG and AQP1 proteins, respectively. Alkalinization rates of Rh(null) ghosts were about 60%, 83% and 94% lower than that in control ghosts, respectively, for each solute. In CO(null) ghosts, the lack of AQP1 resulted in about 30% reduction of the alkalinization rates as compared to controls, but the transport selectivity of RhAG for the three solutes was preserved. Similar observations were made with ghosts from KO mice Rhag-/- and AQP1-/-. These results confirm the major contribution of RhAG/Rhag in the NH3 conductance of erythrocytes and suggest that the reduction of transport rates in the absence of AQP1 would be better explained by a direct or indirect effect on RhAG/Rhag-mediated transport. When ghosts were preloaded with carbonic anhydrase and exposed to a 25 mM CO2/HCO3- gradient at 6 degrees C, an extremely rapid kinetics of acidification corresponding to CO2 influx was observed. The rate constants were not significantly different between controls and human variants (125+/-6 s(-1)), or between wild-type and KO mice, suggesting no major role of RhAG or AQP1 in CO2 transport, at least in our experimental conditions.

CASK interacts with PMCA4b and JAM-A on the Mouse Sperm Flagellum to Regulate Ca2+ Homeostasis and Motility1

PubMed Central

Aravindan, Rolands G.; Fomin, Victor P.; Naik, Ulhas P.; Modelski, Mark J.; Naik, Meghna U.; Galileo, Deni S.; Duncan, Randall L.; Martin-DeLeon, Patricia A.

2012-01-01

Deletion of the highly conserved gene for the major Ca2+ efflux pump, Plasma membrane calcium/calmodulin-dependent ATPase 4b (Pmca4b), in the mouse leads to loss of progressive and hyperactivated sperm motility and infertility. Here we first demonstrate that compared to wild-type (WT), Junctional adhesion molecule-A (Jam-A) null sperm, previously shown to have motility defects and an abnormal mitochondrial phenotype reminiscent of that seen in Pmca4b nulls, exhibit reduced (P<0.001) ATP levels, significantly (P<0.001) greater cytosolic Ca2+ concentration ([Ca2+]c) and ~10-fold higher mitochondrial sequestration, indicating Ca2+ overload. Investigating the mechanism involved, we used coimmunoprecipitation studies to show that CASK (Ca2+/calmodulin-dependent serine kinase), identified for the first time on the sperm flagellum where it co-localizes with both PMCA4b and JAM-A on the proximal principal piece, acts as a common interacting partner of both. Importantly, CASK binds alternatively and non-synergistically with each of these molecules via its single PDZ (PDS-95/Dlg/ZO-1) domain to either inhibit or promote efflux. In the absence of CASK-JAM-A interaction in Jam-A null sperm, CASK-PMCA4b interaction is increased, resulting in inhibition of PMCA4b’s enzymatic activity, consequent Ca2+ accumulation, and a ~6-fold over-expression of constitutively ATP-utilizing CASK, compared to WT. Thus, CASK negatively regulates PMCA4b by directly binding to it and JAM-A positively regulates it indirectly through CASK. The decreased motility is likely due to the collateral net deficit in ATP observed in nulls. Our data indicate that Ca2+ homeostasis in sperm is maintained by the relative ratios of CASK-PMCA4b and CASK-JAM-A interactions. PMID:22020416

3D Plasma Nanotextured® Polymeric Surfaces for Protein or Antibody Arrays, and Biomolecule and Cell Patterning.

PubMed

Tsougeni, Katerina; Ellinas, Kosmas; Koukouvinos, George; Petrou, Panagiota S; Tserepi, Angeliki; Kakabakos, Sotirios E; Gogolides, Evangelos

2018-01-01

Plasma micro-nanotexturing is a generic technology for topographical and chemical modification of surfaces and their implementation in microfluidics and microarrays. Nanotextured surfaces with desirable chemical functionality (and wetting behavior) have shown excellent biomolecule immobilization and cell adhesion. Specifically, nanotextured hydrophilic areas show (a) strong binding of biomolecules and (b) strong adhesion of cells, while nanotextured superhydrophobic areas show null adsorption of (a) proteins and (b) cells. Here we describe the protocols for (a) biomolecule adsorption control on nanotextured surfaces for microarray fabrication and (b) cell adhesion on such surfaces. 3D plasma nanotextured® substrates are commercialized through Nanoplasmas private company, a spin-off of the National Centre for Scientific Research Demokritos.

Mechanisms of action of escapin, a bactericidal agent in the ink secretion of the sea hare Aplysia californica: rapid and long-lasting DNA condensation and involvement of the OxyR-regulated oxidative stress pathway.

PubMed

Ko, Ko-Chun; Tai, Phang C; Derby, Charles D

2012-04-01

The marine snail Aplysia californica produces escapin, an L-amino acid oxidase, in its defensive ink. Escapin uses L-lysine to produce diverse products called escapin intermediate products of L-lysine (EIP-K), including α-amino-ε-caproic acid, Δ¹-piperidine-2-carboxylic acid, and Δ²-piperidine-2-carboxylic acid. EIP-K and H₂O₂ together, but neither alone, is a powerful bactericide. Here, we report bactericidal mechanisms of escapin products on Escherichia coli. We show that EIP-K and H₂O₂ together cause rapid and long-lasting DNA condensation: 2-min treatment causes significant DNA condensation and killing, and 10-min treatment causes maximal effect, lasting at least 70 h. We isolated two mutants resistant to EIP-K plus H₂O₂, both having a single missense mutation in the oxidation regulatory gene, oxyR. A complementation assay showed that the mutated gene, oxyR(A233V), renders resistance to EIP-K plus H₂O₂, and a gene dosage effect leads to reduction of resistance for strains carrying wild-type oxyR. Temperature stress with EIP-K does not produce the bactericidal effect, suggesting the effect is due to a specific response to oxidative stress. The null mutant for any single DNA-binding protein--Dps, H-NS, Hup, Him, or MukB--was not resistant to EIP-K plus H₂O₂, suggesting that no single DNA-binding protein is necessary to mediate this bactericidal effect, but allowing for the possibility that EIP-K plus H₂O₂ could function through a combination of DNA-binding proteins. The bactericidal effect of EIP-K plus H₂O₂ was eliminated by the ferrous ion chelator 1,10-phenanthroline, and it was reduced by the hydroxyl radical scavenger thiourea, suggesting hydroxyl radicals mediate the effects of EIP-K plus H₂O₂.

Long-term improvements in sensory inhibition with gestational choline supplementation linked to α7 nicotinic receptors through studies in Chrna7 null mutation mice.

PubMed

Stevens, Karen E; Choo, Kevin S; Stitzel, Jerry A; Marks, Michael J; Adams, Catherine E

2014-03-13

Perinatal choline supplementation has produced several benefits in rodent models, from improved learning and memory to protection from the behavioral effects of fetal alcohol exposure. We have shown that supplemented choline through gestation and lactation produces long-term improvement in deficient sensory inhibition in DBA/2 mice which models a similar deficit in schizophrenia patients. The present study extends that research by feeding normal or supplemented choline diets to DBA/2 mice carrying the null mutation for the α7 nicotinic receptor gene (Chrna7). DBA/2 mice heterozygotic for Chrna7 were bred together. Dams were placed on supplemented (5 gm/kg diet) or normal (1.1 gm/kg diet) choline at mating and remained on the specific diet until offspring weaning. Thereafter, offspring were fed standard rodent chow. Adult offspring were assessed for sensory inhibition. Brains were obtained to ascertain hippocampal α7 nicotinic receptor levels. Choline-supplemented mice heterozygotic or null-mutant for Chrna7 failed to show improvement in sensory inhibition. Only wildtype choline-supplemented mice showed improvement with the effect solely through a decrease in test amplitude. This supports the hypothesis that gestational-choline supplementation is acting through the α7 nicotinic receptor to improve sensory inhibition. Although there was a significant gene-dose-related change in hippocampal α7 receptor numbers, binding studies did not reveal any choline-dose-related change in binding in any hippocampal region, the interaction being driven by a significant genotype main effect (wildtype>heterozygote>null mutant). These data parallel a human study wherein the offspring of pregnant women receiving choline supplementation during gestation, showed better sensory inhibition than offspring of women on placebo. Published by Elsevier B.V.

Long-term improvements in sensory inhibition with gestational choline supplementation linked to α7 nicotinic receptors through studies in Chrna7 null mutation mice

PubMed Central

Stevens, Karen E.; Choo, Kevin S.; Stitzel, Jerry A.; Marks, Michael J.; Adams, Catherine E.

2014-01-01

Perinatal choline supplementation has produced several benefits in rodent models, from improved learning and memory to protection from the behavioral effects of fetal alcohol exposure. We have shown that supplemented choline through gestation and lactation produces long-term improvement in deficient sensory inhibition in DBA/2 mice which models a similar deficit in schizophrenia patients. The present study extends that research by feeding normal or supplemented choline diets to DBA/2 mice carrying the null mutation for the α7 nicotinic receptor gene (Chrna7). DBA/2 mice heterozygotic for Chrna7 were bred together. Dams were placed on supplemented (5 gm/kg diet) or normal (1.1 gm/kg diet) choline at mating and remained on the specific diet until offspring weaning. Thereafter, offspring were fed standard rodent chow. Adult offspring were assessed for sensory inhibition. Brains were obtained to ascertain hippocampal α7 nicotinic receptor levels. Choline-supplemented mice heterozygotic or null-mutant for Chrna7 failed to show improvement in sensory inhibition. Only wildtype choline-supplemented mice showed improvement with the effect solely through a decrease in test amplitude. This supports the hypothesis that gestational-choline supplementation is acting through the α7 nicotinic receptor to improve sensory inhibition. Although there was a significant gene-dose-related change in hippocampal α7 receptor numbers, binding studies did not reveal any choline-dose-related change in binding in any hippocampal region, the interaction being driven by a significant genotype main effect (wildtype>heterozygote>null mutant). These data parallel a human study wherein the offspring of pregnant women receiving choline supplementation during gestation, showed better sensory inhibition than offspring of women on placebo. PMID:24462939

BCL2-BH4 antagonist BDA-366 suppresses human myeloma growth.

PubMed

Deng, Jiusheng; Park, Dongkyoo; Wang, Mengchang; Nooka, Ajay; Deng, Qiaoya; Matulis, Shannon; Kaufman, Jonathan; Lonial, Sagar; Boise, Lawrence H; Galipeau, Jacques; Deng, Xingming

2016-05-10

Multiple myeloma (MM) is a heterogeneous plasma cell malignancy and remains incurable. B-cell lymphoma-2 (BCL2) protein correlates with the survival and the drug resistance of myeloma cells. BH3 mimetics have been developed to disrupt the binding between BCL2 and its pro-apoptotic BCL2 family partners for the treatment of MM, but with limited therapeutic efficacy. We recently identified a small molecule BDA-366 as a BCL2 BH4 domain antagonist, converting it from an anti-apoptotic into a pro-apoptotic molecule. In this study, we demonstrated that BDA-366 induces robust apoptosis in MM cell lines and primary MM cells by inducing BCL2 conformational change. Delivery of BDA-366 substantially suppressed the growth of human MM xenografts in NOD-scid/IL2Rγnull mice, without significant cytotoxic effects on normal hematopoietic cells or body weight. Thus, BDA-366 functions as a novel BH4-based BCL2 inhibitor and offers an entirely new tool for MM therapy.

BCL2-BH4 antagonist BDA-366 suppresses human myeloma growth

PubMed Central

Deng, Jiusheng; Park, Dongkyoo; Wang, Mengchang; Nooka, Ajay; Deng, Qiaoya; Matulis, Shannon; Kaufman, Jonathan; Lonial, Sagar; Boise, Lawrence H.; Galipeau, Jacques; Deng, Xingming

2016-01-01

Multiple myeloma (MM) is a heterogeneous plasma cell malignancy and remains incurable. B-cell lymphoma-2 (BCL2) protein correlates with the survival and the drug resistance of myeloma cells. BH3 mimetics have been developed to disrupt the binding between BCL2 and its pro-apoptotic BCL2 family partners for the treatment of MM, but with limited therapeutic efficacy. We recently identified a small molecule BDA-366 as a BCL2 BH4 domain antagonist, converting it from an anti-apoptotic into a pro-apoptotic molecule. In this study, we demonstrated that BDA-366 induces robust apoptosis in MM cell lines and primary MM cells by inducing BCL2 conformational change. Delivery of BDA-366 substantially suppressed the growth of human MM xenografts in NOD-scid/IL2Rγnull mice, without significant cytotoxic effects on normal hematopoietic cells or body weight. Thus, BDA-366 functions as a novel BH4-based BCL2 inhibitor and offers an entirely new tool for MM therapy. PMID:27049723

Characterization of the Bacteroides fragilis bfr Gene Product Identifies a Bacterial DPS-Like Protein and Suggests Evolutionary Links in the Ferritin Superfamily

PubMed Central

Gauss, George H.; Reott, Michael A.; Rocha, Edson R.; Young, Mark J.; Douglas, Trevor

2012-01-01

A factor contributing to the pathogenicity of Bacteroides fragilis, the most common anaerobic species isolated from clinical infections, is the bacterium's extreme aerotolerance, which allows survival in oxygenated tissues prior to anaerobic abscess formation. We investigated the role of the bacterioferritin-related (bfr) gene in the B. fragilis oxidative stress response. The bfr mRNA levels are increased in stationary phase or in response to O2 or iron. In addition, bfr null mutants exhibit reduced aerotolerance, and the bfr gene product protects DNA from hydroxyl radical cleavage in vitro. Crystallographic studies revealed a protein with a dodecameric structure and greater similarity to an archaeal DNA protection in starved cells (DPS)-like protein than to the 24-subunit bacterioferritins. Similarity to the DPS-like (DPSL) protein extends to the subunit and includes a pair of conserved cysteine residues juxtaposed to a buried dimetal binding site within the four-helix bundle. Compared to archaeal DPSLs, however, this bacterial DPSL protein contains several unique features, including a significantly different conformation in the C-terminal tail that alters the number and location of pores leading to the central cavity and a conserved metal binding site on the interior surface of the dodecamer. Combined, these characteristics confirm this new class of miniferritin in the bacterial domain, delineate the similarities and differences between bacterial DPSL proteins and their archaeal homologs, allow corrected annotations for B. fragilis bfr and other dpsl genes within the bacterial domain, and suggest an evolutionary link within the ferritin superfamily that connects dodecameric DPS to the (bacterio)ferritin 24-mer. PMID:22020642

Mutations in the Arabidopsis Peroxisomal ABC Transporter COMATOSE Allow Differentiation between Multiple Functions In Planta: Insights from an Allelic Series

PubMed Central

Dietrich, Daniela; Schmuths, Heike; Lousa, Carine De Marcos; Baldwin, Jocelyn M.; Baldwin, Stephen A.; Baker, Alison; Holdsworth, Michael J.

2009-01-01

COMATOSE (CTS), the Arabidopsis homologue of human Adrenoleukodystrophy protein (ALDP), is required for import of substrates for peroxisomal β-oxidation. A new allelic series and a homology model based on the bacterial ABC transporter, Sav1866, provide novel insights into structure-function relations of ABC subfamily D proteins. In contrast to ALDP, where the majority of mutations result in protein absence from the peroxisomal membrane, all CTS mutants produced stable protein. Mutation of conserved residues in the Walker A and B motifs in CTS nucleotide-binding domain (NBD) 1 resulted in a null phenotype but had little effect in NBD2, indicating that the NBDs are functionally distinct in vivo. Two alleles containing mutations in NBD1 outside the Walker motifs (E617K and C631Y) exhibited resistance to auxin precursors 2,4-dichlorophenoxybutyric acid (2,4-DB) and indole butyric acid (IBA) but were wild type in all other tests. The homology model predicted that the transmission interfaces are domain-swapped in CTS, and the differential effects of mutations in the conserved “EAA motif” of coupling helix 2 supported this prediction, consistent with distinct roles for each NBD. Our findings demonstrate that CTS functions can be separated by mutagenesis and the structural model provides a framework for interpretation of phenotypic data. PMID:19019987

NudEL targets dynein to microtubule ends through LIS1.

PubMed

Li, Jun; Lee, Wei-Lih; Cooper, John A

2005-07-01

Dynein is a minus-end-directed microtubule motor with critical roles in mitosis, membrane transport and intracellular transport. Several proteins regulate dynein activity, including dynactin, LIS1 (refs 2, 3) and NudEL (NudE-like). Here, we identify a NUDEL homologue in budding yeast and name it Ndl1. The ndl1delta null mutant shows decreased targeting of dynein to microtubule plus ends, an essential element of the model for dynein function. We find that Ndl1 regulates dynein targeting through LIS1, with which it interacts biochemically, but not through CLIP170, another plus-end protein involved in dynein targeting. Ndl1 is found at far fewer microtubule ends than are LIS1 and dynein. However, when Ndl1 is present at a plus end, the molar amount of Ndl1 approaches that of LIS1 and dynein. We propose a model in which Ndl1 binds transiently to the plus end to promote targeting of LIS1, which cooperatively recruits dynein.

Badh2, Encoding Betaine Aldehyde Dehydrogenase, Inhibits the Biosynthesis of 2-Acetyl-1-Pyrroline, a Major Component in Rice Fragrance[W

PubMed Central

Chen, Saihua; Yang, Yi; Shi, Weiwei; Ji, Qing; He, Fei; Zhang, Ziding; Cheng, Zhukuan; Liu, Xiangnong; Xu, Mingliang

2008-01-01

In rice (Oryza sativa), the presence of a dominant Badh2 allele encoding betaine aldehyde dehydrogenase (BADH2) inhibits the synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor component in rice fragrance. By contrast, its two recessive alleles, badh2-E2 and badh2-E7, induce 2AP formation. Badh2 was found to be transcribed in all tissues tested except for roots, and the transcript was detected at higher abundance in young, healthy leaves than in other tissues. Multiple Badh2 transcript lengths were detected, and the complete, full-length Badh2 transcript was much less abundant than partial Badh2 transcripts. 2AP levels were significantly reduced in cauliflower mosaic virus 35S-driven transgenic lines expressing the complete, but not the partial, Badh2 coding sequences. In accordance, the intact, full-length BADH2 protein (503 residues) appeared exclusively in nonfragrant transgenic lines and rice varieties. These results indicate that the full-length BADH2 protein encoded by Badh2 renders rice nonfragrant by inhibiting 2AP biosynthesis. The BADH2 enzyme was predicted to contain three domains: NAD binding, substrate binding, and oligomerization domains. BADH2 was distributed throughout the cytoplasm, where it is predicted to catalyze the oxidization of betaine aldehyde, 4-aminobutyraldehyde (AB-ald), and 3-aminopropionaldehyde. The presence of null badh2 alleles resulted in AB-ald accumulation and enhanced 2AP biosynthesis. In summary, these data support the hypothesis that BADH2 inhibits 2AP biosynthesis by exhausting AB-ald, a presumed 2AP precursor. PMID:18599581

Thioredoxin binding protein (TBP)-2/Txnip and α-arrestin proteins in cancer and diabetes mellitus

PubMed Central

Masutani, Hiroshi; Yoshihara, Eiji; Masaki, So; Chen, Zhe; Yodoi, Junji

2012-01-01

Thioredoxin binding protein −2/ thioredoxin interacting protein is an α-arrestin protein that has attracted much attention as a multifunctional regulator. Thioredoxin binding protein −2 expression is downregulated in tumor cells and the level of thioredoxin binding protein is correlated with clinical stage of cancer. Mice with mutations or knockout of the thioredoxin binding protein −2 gene are much more susceptible to carcinogenesis than wild-type mice, indicating a role for thioredoxin binding protein −2 in cancer suppression. Studies have also revealed roles for thioredoxin binding protein −2 in metabolic control. Enhancement of thioredoxin binding protein −2 expression causes impairment of insulin sensitivity and glucose-induced insulin secretion, and β-cell apoptosis. These changes are important characteristics of type 2 diabetes mellitus. Thioredoxin binding protein −2 regulates transcription of metabolic regulating genes. Thioredoxin binding protein −2-like inducible membrane protein/ arrestin domain containing 3 regulates endocytosis of receptors such as the β2-adrenergic receptor. The α-arrestin family possesses PPXY motifs and may function as an adaptor/scaffold for NEDD family ubiquitin ligases. Elucidation of the molecular mechanisms of α-arrestin proteins would provide a new pharmacological basis for developing approaches against cancer and type 2 diabetes mellitus. PMID:22247597

Spam1-associated transmission ratio distortion in mice: Elucidating the mechanism

PubMed Central

Martin-DeLeon, Patricia A; Zhang, Hong; Morales, Carlos R; Zhao, Yutong; Rulon, Michelle; Barnoski, Barry L; Chen, Hong; Galileo, Deni S

2005-01-01

Background While transmission ratio distortion, TRD, (a deviation from Mendelian ratio) is extensive in humans and well-documented in mice, the underlying mechanisms are unknown. Our earlier studies on carriers of spontaneous mutations of mouse Sperm Adhesion Molecule 1 (Spam1) suggested that TRD results from biochemically different sperm, due to a lack of transcript sharing through the intercellular cytoplasmic bridges of spermatids. These bridges usually allow transcript sharing among genetically different spermatids which develop into biochemically and functionally equivalent sperm. Objectives The goals of the study were to provide support for the lack of sharing (LOS) hypothesis, using transgene and null carriers of Spam1, and to determine the mechanism of Spam1-associated TRD. Methods Carriers of Spam1-Hyal5 BAC transgenes were mated with wild-type female mice and the progeny analyzed for TRD by PCR genotyping. Sperm from transgene and Spam1 null carriers were analyzed using flow cytometry and immunocytochemistry to detect quantities of Spam1 and/or Hyal5. Transgene-bearing sperm with Spam1 overexpression were detected by fluorescence in situ hybridization. In wild-type animals, EM studies of in situ transcript hybridization of testis sections and Northern analysis of biochemically fractionated testicular RNA were performed to localize Spam1 transcript. Finally, AU-rich motifs identified in the 3' UTR of Spam1 RNA were assayed by UV cross-linking to determine their ability to interact with testicular RNA binding proteins. Results The Tg8 line of transgene carriers had a significant (P < 0.001) TRD, due to reduced fertilizing ability of transgene-bearing sperm. These sperm retained large cytoplasmic droplets engorged with overexpressed Spam1 or Hyal5 protein. Caudal sperm from transgene carriers and caput sperm of null carriers showed a bimodal distribution of Spam1, indicating that the sperm in a male were biochemically different with respect to Spam1 quantities. Spam1 RNA was absent from the bridges, associated exclusively with the ER, and was shown to be anchored to the cytoskeleton. This compartmentalization of the transcript, mediated by cytoskeletal binding, occurs via protein interactions with 3' UTR AU-rich sequences that are likely involved in its stabilization. Conclusion We provide strong support for the LOS hypothesis, and have elucidated the mechanism of Spam1-associated TRD. PMID:16092963

A member of the polymerase beta nucleotidyltransferase superfamily is required for RNA interference in C. elegans.

PubMed

Chen, Chun-Chieh G; Simard, Martin J; Tabara, Hiroaki; Brownell, Daniel R; McCollough, Jennifer A; Mello, Craig C

2005-02-22

RNA interference (RNAi) is an ancient, highly conserved mechanism in which small RNA molecules (siRNAs) guide the sequence-specific silencing of gene expression . Several silencing machinery protein components have been identified, including helicases, RNase-related proteins, double- and single-stranded RNA binding proteins, and RNA-dependent RNA polymerase-related proteins . Work on these factors has led to the revelation that RNAi mechanisms intersect with cellular pathways required for development and fertility . Despite rapid progress in understanding key steps in the RNAi pathway, it is clear that many factors required for both RNAi and related developmental mechanisms have not yet been identified. Here, we report the characterization of the C. elegans gene rde-3. Genetic analysis of presumptive null alleles indicates that rde-3 is required for siRNA accumulation and for efficient RNAi in all tissues, and it is essential for fertility and viability at high temperatures. RDE-3 contains conserved domains found in the polymerase beta nucleotidyltransferase superfamily, which includes conventional poly(A) polymerases, 2'-5' oligoadenylate synthetase (OAS), and yeast Trf4p . These findings implicate a new enzymatic modality in RNAi and suggest possible models for the role of RDE-3 in the RNAi mechanism.

Identification of a common single nucleotide polymorphism at the primer binding site of D2S1360 that causes heterozygote peak imbalance when using the Investigator HDplex Kit.

PubMed

Inokuchi, Shota; Yamashita, Yasuhiro; Nishimura, Kazuma; Nakanishi, Hiroaki; Saito, Kazuyuki

2017-11-01

Phenomena known as null alleles and peak imbalance can occur because of mutations in the primer binding sites used for DNA typing. In these cases, an accurate statistical evaluation of DNA typing is difficult. The estimated likelihood ratio is incorrectly calculated because of the null allele and allele dropout caused by mutation-induced peak imbalance. Although a number of studies have attempted to uncover examples of these phenomena, few reports are available on the human identification kit manufactured by Qiagen. In this study, 196 Japanese individuals who were heterozygous at D2S1360 were genotyped using an Investigator HDplex Kit with optimal amounts of DNA. A peak imbalance was frequently observed at the D2S1360 locus. We performed a sequencing analysis of the area surrounding the D2S1360 repeat motif to identify the cause for peak imbalance. A point mutation (G>A transition) 136 nucleotides upstream from the D2S1360 repeat motif was discovered in a number of samples. The allele frequency of the mutation was 0.0566 in the Japanese population. Therefore, human identification or kinship testing using the Investigator HDplex Kit requires caution because of the higher frequency of single nucleotide polymorphisms at the primer binding site of D2S1360 locus in the Japanese population.

Up-regulation of Ciliary Neurotrophic Factor in Astrocytes by Aspirin

PubMed Central

Modi, Khushbu K.; Sendtner, Michael; Pahan, Kalipada

2013-01-01

Ciliary neurotrophic factor (CNTF) is a promyelinating trophic factor, and the mechanisms by which CNTF expression could be increased in the brain are poorly understood. Acetylsalicylic acid (aspirin) is one of the most widely used analgesics. Interestingly, aspirin increased mRNA and protein expression of CNTF in primary mouse and human astrocytes in a dose- and time-dependent manner. Aspirin induced the activation of protein kinase A (PKA) but not protein kinase C (PKC). H-89, an inhibitor of PKA, abrogated aspirin-induced expression of CNTF. The activation of cAMP-response element-binding protein (CREB), but not NF-κB, by aspirin, the abrogation of aspirin-induced expression of CNTF by siRNA knockdown of CREB, the presence of a consensus cAMP-response element in the promoter of CNTF, and the recruitment of CREB and CREB-binding protein to the CNTF promoter by aspirin suggest that aspirin increases the expression of the Cntf gene via the activation of CREB. Furthermore, we demonstrate that aspirin-induced astroglial CNTF was also functionally active and that supernatants of aspirin-treated astrocytes of wild type, but not Cntf null, mice increased myelin-associated proteins in oligodendrocytes and protected oligodendrocytes from TNF-α insult. These results highlight a new and novel myelinogenic property of aspirin, which may be of benefit for multiple sclerosis and other demyelinating disorders. PMID:23653362

MeCP2 SUMOylation rescues Mecp2-mutant-induced behavioural deficits in a mouse model of Rett syndrome

PubMed Central

Tai, Derek J. C.; Liu, Yen C.; Hsu, Wei L.; Ma, Yun L.; Cheng, Sin J.; Liu, Shau Y.; Lee, Eminy H. Y.

2016-01-01

The methyl-CpG-binding protein 2 (MeCP2) gene, MECP2, is an X-linked gene encoding the MeCP2 protein, and mutations of MECP2 cause Rett syndrome (RTT). However, the molecular mechanism of MECP2-mutation-caused RTT is less known. Here we find that MeCP2 could be SUMO-modified by the E3 ligase PIAS1 at Lys-412. MeCP2 phosphorylation (at Ser-421 and Thr-308) facilitates MeCP2 SUMOylation, and MeCP2 SUMOylation is induced by NMDA, IGF-1 and CRF in the rat brain. MeCP2 SUMOylation releases CREB from the repressor complex and enhances Bdnf mRNA expression. Several MECP2 mutations identified in RTT patients show decreased MeCP2 SUMOylation. Re-expression of wild-type MeCP2 or SUMO-modified MeCP2 in Mecp2-null neurons rescues the deficits of social interaction, fear memory and LTP observed in Mecp2 conditional knockout (cKO) mice. These results together reveal an important role of MeCP2 SUMOylation in social interaction, memory and synaptic plasticity, and that abnormal MeCP2 SUMOylation is implicated in RTT. PMID:26842955

The impact of plant biotechnology on food allergy.

PubMed

Herman, Eliot M; Burks, A Wesley

2011-04-01

Concerns about food allergy and its societal growth are intertwined with the growing advances in plant biotechnology. The knowledge of plant genes and protein structures provides the key foundation to understanding biochemical processes that produce food allergy. Biotechnology offers the prospect of producing low-allergen or allergen null plants that could mitigate the allergic response. Modified low-IgE binding variants of allergens could be used as a vaccine to build immunotolerance in sensitive individuals. The potential to introduce new allergens into the food supply by biotechnology products is a regulatory concern. Copyright © 2010 Elsevier Ltd. All rights reserved.

Identification and Analysis of Mot3, a Zinc Finger Protein That Binds to the Retrotransposon Ty Long Terminal Repeat (δ) in Saccharomyces cerevisiae

PubMed Central

Madison, Jon M.; Dudley, Aimée M.; Winston, Fred

1998-01-01

Spt3 and Mot1 are two transcription factors of Saccharomyces cerevisiae that are thought to act in a related fashion to control the function of TATA-binding protein (TBP). Current models suggest that while Spt3 and Mot1 do not directly interact, they do function in a related fashion to stabilize the TBP-TATA interaction at particular promoters. Consistent with this model, certain combinations of spt3 and mot1 mutations are inviable. To identify additional proteins related to Spt3 and Mot1 functions, we screened for high-copy-number suppressors of the mot1 spt3 inviability. This screen identified a previously unstudied gene, MOT3, that encodes a zinc finger protein. We show that Mot3 binds in vitro to three sites within the retrotransposon Ty long terminal repeat (δ) sequence. One of these sites is immediately 5′ of the δ TATA region. Although a mot3 null mutation causes no strong phenotypes, it does cause some mild phenotypes, including a very modest increase in Ty mRNA levels, partial suppression of transcriptional defects caused by a mot1 mutation, and partial suppression of an spt3 mutation. These results, in conjunction with those of an independent study of Mot3 (A. Grishin, M. Rothenberg, M. A. Downs, and K. J. Blumer, Genetics, in press), suggest that this protein plays a varied role in gene expression that may be largely redundant with other factors. PMID:9528759

NullSeq: A Tool for Generating Random Coding Sequences with Desired Amino Acid and GC Contents.

PubMed

Liu, Sophia S; Hockenberry, Adam J; Lancichinetti, Andrea; Jewett, Michael C; Amaral, Luís A N

2016-11-01

The existence of over- and under-represented sequence motifs in genomes provides evidence of selective evolutionary pressures on biological mechanisms such as transcription, translation, ligand-substrate binding, and host immunity. In order to accurately identify motifs and other genome-scale patterns of interest, it is essential to be able to generate accurate null models that are appropriate for the sequences under study. While many tools have been developed to create random nucleotide sequences, protein coding sequences are subject to a unique set of constraints that complicates the process of generating appropriate null models. There are currently no tools available that allow users to create random coding sequences with specified amino acid composition and GC content for the purpose of hypothesis testing. Using the principle of maximum entropy, we developed a method that generates unbiased random sequences with pre-specified amino acid and GC content, which we have developed into a python package. Our method is the simplest way to obtain maximally unbiased random sequences that are subject to GC usage and primary amino acid sequence constraints. Furthermore, this approach can easily be expanded to create unbiased random sequences that incorporate more complicated constraints such as individual nucleotide usage or even di-nucleotide frequencies. The ability to generate correctly specified null models will allow researchers to accurately identify sequence motifs which will lead to a better understanding of biological processes as well as more effective engineering of biological systems.

Alanine scan of core positions in ubiquitin reveals links between dynamics, stability, and function

PubMed Central

Lee, Shirley Y.; Pullen, Lester; Virgil, Daniel J.; Castañeda, Carlos A.; Abeykoon, Dulith; Bolon, Daniel N. A.; Fushman, David

2014-01-01

Mutations at solvent inaccessible core positions in proteins can impact function through many biophysical mechanisms including alterations to thermodynamic stability and protein dynamics. As these properties of proteins are difficult to investigate, the impacts of core mutations on protein function are poorly understood for most systems. Here, we determined the effects of alanine mutations at all 15 core positions in ubiquitin on function in yeast. The majority (13 of 15) of alanine substitutions supported yeast growth as the sole ubiquitin. The two null mutants (I30A and L43A) were both less stable to temperature-induced unfolding in vitro than wild-type, but were well folded at physiological temperatures. Heteronuclear NMR studies indicated that the L43A mutation reduces temperature stability while retaining a ground-state structure similar to wild-type. This structure enables L43A to bind to common ubiquitin receptors in vitro. Many of the core alanine ubiquitin mutants, including one of the null variants (I30A), exhibited an increased accumulation of high molecular weight species, suggesting that these mutants caused a defect in the processing of ubiquitin-substrate conjugates. In contrast, L43A exhibited a unique accumulation pattern with reduced levels of high molecular weight species and undetectable levels of free ubiquitin. When conjugation to other proteins was blocked, L43A ubiquitin accumulated as free ubiquitin in yeast. Based on these findings we speculate that ubiquitin's stability to unfolding may be required for efficient recycling during proteasome-mediated substrate degradation. PMID:24361330

Abscisic Acid Regulates Inflammation via Ligand-binding Domain-independent Activation of Peroxisome Proliferator-activated Receptor γ*

PubMed Central

Bassaganya-Riera, Josep; Guri, Amir J.; Lu, Pinyi; Climent, Montse; Carbo, Adria; Sobral, Bruno W.; Horne, William T.; Lewis, Stephanie N.; Bevan, David R.; Hontecillas, Raquel

2011-01-01

Abscisic acid (ABA) has shown efficacy in the treatment of diabetes and inflammation; however, its molecular targets and the mechanisms of action underlying its immunomodulatory effects remain unclear. This study investigates the role of peroxisome proliferator-activated receptor γ (PPAR γ) and lanthionine synthetase C-like 2 (LANCL2) as molecular targets for ABA. We demonstrate that ABA increases PPAR γ reporter activity in RAW 264.7 macrophages and increases ppar γ expression in vivo, although it does not bind to the ligand-binding domain of PPAR γ. LANCL2 knockdown studies provide evidence that ABA-mediated activation of macrophage PPAR γ is dependent on lancl2 expression. Consistent with the association of LANCL2 with G proteins, we provide evidence that ABA increases cAMP accumulation in immune cells. ABA suppresses LPS-induced prostaglandin E2 and MCP-1 production via a PPAR γ-dependent mechanism possibly involving activation of PPAR γ and suppression of NF-κB and nuclear factor of activated T cells. LPS challenge studies in PPAR γ-expressing and immune cell-specific PPAR γ null mice demonstrate that ABA down-regulates toll-like receptor 4 expression in macrophages and T cells in vivo through a PPAR γ-dependent mechanism. Global transcriptomic profiling and confirmatory quantitative RT-PCR suggest novel candidate targets and demonstrate that ABA treatment mitigates the effect of LPS on the expression of genes involved in inflammation, metabolism, and cell signaling, in part, through PPAR γ. In conclusion, ABA decreases LPS-mediated inflammation and regulates innate immune responses through a bifurcating pathway involving LANCL2 and an alternative, ligand-binding domain-independent mechanism of PPAR γ activation. PMID:21088297

Abscisic acid regulates inflammation via ligand-binding domain-independent activation of peroxisome proliferator-activated receptor gamma.

PubMed

Bassaganya-Riera, Josep; Guri, Amir J; Lu, Pinyi; Climent, Montse; Carbo, Adria; Sobral, Bruno W; Horne, William T; Lewis, Stephanie N; Bevan, David R; Hontecillas, Raquel

2011-01-28

Abscisic acid (ABA) has shown efficacy in the treatment of diabetes and inflammation; however, its molecular targets and the mechanisms of action underlying its immunomodulatory effects remain unclear. This study investigates the role of peroxisome proliferator-activated receptor γ (PPAR γ) and lanthionine synthetase C-like 2 (LANCL2) as molecular targets for ABA. We demonstrate that ABA increases PPAR γ reporter activity in RAW 264.7 macrophages and increases ppar γ expression in vivo, although it does not bind to the ligand-binding domain of PPAR γ. LANCL2 knockdown studies provide evidence that ABA-mediated activation of macrophage PPAR γ is dependent on lancl2 expression. Consistent with the association of LANCL2 with G proteins, we provide evidence that ABA increases cAMP accumulation in immune cells. ABA suppresses LPS-induced prostaglandin E(2) and MCP-1 production via a PPAR γ-dependent mechanism possibly involving activation of PPAR γ and suppression of NF-κB and nuclear factor of activated T cells. LPS challenge studies in PPAR γ-expressing and immune cell-specific PPAR γ null mice demonstrate that ABA down-regulates toll-like receptor 4 expression in macrophages and T cells in vivo through a PPAR γ-dependent mechanism. Global transcriptomic profiling and confirmatory quantitative RT-PCR suggest novel candidate targets and demonstrate that ABA treatment mitigates the effect of LPS on the expression of genes involved in inflammation, metabolism, and cell signaling, in part, through PPAR γ. In conclusion, ABA decreases LPS-mediated inflammation and regulates innate immune responses through a bifurcating pathway involving LANCL2 and an alternative, ligand-binding domain-independent mechanism of PPAR γ activation.

Activation of Peroxisome Proliferator–Activated Receptor-β/-δ (PPAR-β/-δ) Ameliorates Insulin Signaling and Reduces SOCS3 Levels by Inhibiting STAT3 in Interleukin-6–Stimulated Adipocytes

PubMed Central

Serrano-Marco, Lucía; Rodríguez-Calvo, Ricardo; El Kochairi, Ilhem; Palomer, Xavier; Michalik, Liliane; Wahli, Walter; Vázquez-Carrera, Manuel

2011-01-01

OBJECTIVE It has been suggested that interleukin (IL)-6 is one of the mediators linking obesity-derived chronic inflammation with insulin resistance through activation of STAT3, with subsequent upregulation of suppressor of cytokine signaling 3 (SOCS3). We evaluated whether peroxisome proliferator–activated receptor (PPAR)-β/-δ prevented activation of the IL-6-STAT3-SOCS3 pathway and insulin resistance in adipocytes. RESEARCH DESIGN AND METHODS Adipocytes and white adipose tissue from wild-type and PPAR-β/-δ-null mice were used to evaluate the effect of PPAR-β/-δ on the IL-6-STAT3-SOCS3 pathway. RESULTS First, we observed that the PPAR-β/-δ agonist GW501516 prevented both IL-6–dependent reduction in insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. In addition, this drug treatment abolished IL-6–induced SOCS3 expression in differentiated 3T3-L1 adipocytes. This effect was associated with the capacity of the drug to prevent IL-6–induced STAT3 phosphorylation on Tyr705 and Ser727 residues in vitro and in vivo. Moreover, GW501516 prevented IL-6–dependent induction of extracellular signal–related kinase (ERK)1/2, a serine-threonine-protein kinase involved in serine STAT3 phosphorylation. Furthermore, in white adipose tissue from PPAR-β/-δ–null mice, STAT3 phosphorylation (Tyr705 and Ser727), STAT3 DNA-binding activity, and SOCS3 protein levels were higher than in wild-type mice. Several steps in STAT3 activation require its association with heat shock protein 90 (Hsp90), which was prevented by GW501516 as revealed in immunoprecipitation studies. Consistent with this finding, the STAT3-Hsp90 association was enhanced in white adipose tissue from PPAR-β/-δ–null mice compared with wild-type mice. CONCLUSIONS Collectively, our findings indicate that PPAR-β/-δ activation prevents IL-6–induced STAT3 activation by inhibiting ERK1/2 and preventing the STAT3-Hsp90 association, an effect that may contribute to the prevention of cytokine-induced insulin resistance in adipocytes. PMID:21617181

Induction and persistence of abnormal testicular germ cells following gestational exposure to di-(n-butyl) phthalate in p53-null mice.

PubMed

Saffarini, Camelia M; Heger, Nicholas E; Yamasaki, Hideki; Liu, Tao; Hall, Susan J; Boekelheide, Kim

2012-01-01

Phthalate esters are commonly used plasticizers found in many household items, personal care products, and medical devices. Animal studies have shown that in utero exposure to di-(n-butyl) phthalate (DBP) within a critical window during gestation causes male reproductive tract abnormalities resembling testicular dysgenesis syndrome. Our studies utilized p53-deficient mice for their ability to display greater resistance to apoptosis during development. This model was chosen to determine whether multinucleated germ cells (MNG) induced by gestational DBP exposure could survive postnatally and evolve into testicular germ cell cancer. Pregnant dams were exposed to DBP (500 mg/kg/day) by oral gavage from gestational day 12 until birth. Perinatal effects were assessed on gestational day 19 and postnatal days 1, 4, 7, and 10 for the number of MNGs present in control and DBP-treated p53-heterozygous and null animals. As expected, DBP exposure induced MNGs, with greater numbers found in p53-null mice. Additionally, there was a time-dependent decrease in the incidence of MNGs during the early postnatal period. Histologic examination of adult mice exposed in utero to DBP revealed persistence of abnormal germ cells only in DBP-treated p53-null mice, not in p53-heterozygous or wild-type mice. Immunohistochemical staining of perinatal MNGs and adult abnormal germ cells was negative for both octamer-binding protein 3/4 and placental alkaline phosphatase. This unique model identified a role for p53 in the perinatal apoptosis of DBP-induced MNGs and provided insight into the long-term effects of gestational DBP exposure within a p53-null environment.

Regulation of ecmF gene expression and genetic hierarchy among STATa, CudA, and MybC on several prestalk A-specific gene expressions in Dictyostelium.

PubMed

Saga, Yukika; Inamura, Tomoka; Shimada, Nao; Kawata, Takefumi

2016-05-01

STATa, a Dictyostelium homologue of metazoan signal transducer and activator of transcription, is important for the organizer function in the tip region of the migrating Dictyostelium slug. We previously showed that ecmF gene expression depends on STATa in prestalk A (pstA) cells, where STATa is activated. Deletion and site-directed mutagenesis analysis of the ecmF/lacZ fusion gene in wild-type and STATa null strains identified an imperfect inverted repeat sequence, ACAAATANTATTTGT, as a STATa-responsive element. An upstream sequence element was required for efficient expression in the rear region of pstA zone; an element downstream of the inverted repeat was necessary for sufficient prestalk expression during culmination. Band shift analyses using purified STATa protein detected no sequence-specific binding to those ecmF elements. The only verified upregulated target gene of STATa is cudA gene; CudA directly activates expL7 gene expression in prestalk cells. However, ecmF gene expression was almost unaffected in a cudA null mutant. Several previously reported putative STATa target genes were also expressed in cudA null mutant but were downregulated in STATa null mutant. Moreover, mybC, which encodes another transcription factor, belonged to this category, and ecmF expression was downregulated in a mybC null mutant. These findings demonstrate the existence of a genetic hierarchy for pstA-specific genes, which can be classified into two distinct STATa downstream pathways, CudA dependent and independent. The ecmF expression is indirectly upregulated by STATa in a CudA-independent activation manner but dependent on MybC, whose expression is positively regulated by STATa. © 2016 Japanese Society of Developmental Biologists.

Hydrogenase activity in the foodborne pathogen Campylobacter jejuni depends upon a novel ABC-type nickel transporter (NikZYXWV) and is SlyD-independent.

PubMed

Howlett, Robert M; Hughes, Bethan M; Hitchcock, Andrew; Kelly, David J

2012-06-01

Campylobacter jejuni is a human pathogen of worldwide significance. It is commensal in the gut of many birds and mammals, where hydrogen is a readily available electron donor. The bacterium possesses a single membrane-bound, periplasmic-facing NiFe uptake hydrogenase that depends on the acquisition of environmental nickel for activity. The periplasmic binding protein Cj1584 (NikZ) of the ATP binding cassette (ABC) transporter encoded by the cj1584c-cj1580c (nikZYXWV) operon in C. jejuni strain NCTC 11168 was found to be nickel-repressed and to bind free nickel ions with a submicromolar K(d) value, as measured by fluorescence spectroscopy. Unlike the Escherichia coli NikA protein, NikZ did not bind EDTA-chelated nickel and lacks key conserved residues implicated in metallophore interaction. A C. jejuni cj1584c null mutant strain showed an approximately 22-fold decrease in intracellular nickel content compared with the wild-type strain and a decreased rate of uptake of (63)NiCl(2). The inhibition of residual nickel uptake at higher nickel concentrations in this mutant by hexa-ammine cobalt (III) chloride or magnesium ions suggests that low-affinity uptake occurs partly through the CorA magnesium transporter. Hydrogenase activity was completely abolished in the cj1584c mutant after growth in unsupplemented media, but was fully restored after growth with 0.5 mM nickel chloride. Mutation of the putative metallochaperone gene slyD (cj0115) had no effect on either intracellular nickel accumulation or hydrogenase activity. Our data reveal a strict dependence of hydrogenase activity in C. jejuni on high-affinity nickel uptake through an ABC transporter that has distinct properties compared with the E. coli Nik system.

C-terminus of HSC70-Interacting Protein (CHIP) Inhibits Adipocyte Differentiation via Ubiquitin- and Proteasome-Mediated Degradation of PPARγ

PubMed Central

Kim, Jung-Hoon; Shin, Soyeon; Seo, Jinho; Lee, Eun-Woo; Jeong, Manhyung; Lee, Min-sik; Han, Hyun-Ji; Song, Jaewhan

2017-01-01

PPARγ (Peroxisome proliferator-activated receptor γ) is a nuclear receptor involved in lipid homeostasis and related metabolic diseases. Acting as a transcription factor, PPARγ is a master regulator for adipocyte differentiation. Here, we reveal that CHIP (C-terminus of HSC70-interacting protein) suppresses adipocyte differentiation by functioning as an E3 ligase of PPARγ. CHIP directly binds to and induces ubiquitylation of the PPARγ protein, leading to proteasome-dependent degradation. Stable overexpression or knockdown of CHIP inhibited or promoted adipogenesis, respectively, in 3T3-L1 cells. On the other hand, a CHIP mutant defective in E3 ligase could neither regulate PPARγ protein levels nor suppress adipogenesis, indicating the importance of CHIP-mediated ubiquitylation of PPARγ in adipocyte differentiation. Lastly, a CHIP null embryo fibroblast exhibited augmented adipocyte differentiation with increases in PPARγ and its target protein levels. In conclusion, CHIP acts as an E3 ligase of PPARγ, suppressing PPARγ-mediated adipogenesis. PMID:28059128

Characterization of CpSte11, a MAPKKK gene of Cryphonectria parasitica, and initial evidence of its involvement in the pheromone response pathway.

PubMed

Park, Jin-Ah; Kim, Jung-Mi; Park, Seung-Moon; Kim, Dae-Hyuk

2012-04-01

The gene CpSte11 of Cryphonectria parasitica, which encodes a yeast Ste11 homologue, was cloned and characterized. Gene replacement analysis revealed a high frequency of CpSte11 null mutants. When compared with the wild-type parent strain, CpSte11 null mutants showed no difference in terms of growth rate or pigmentation. However, CpSte11 null mutants showed a marked decrease in both the number and size of stromal pustules on chestnut twigs. The virulence test showed that, in comparison with those of the wild-type and virus-infected hypovirulent strains, CpSte11 null mutants produced necrotic areas of intermediate size. Disruption of the CpSte11 gene also resulted in defects in female fertility. Down-regulation of transcripts for the mating pheromone precursor gene, Mf2/2, and mating response transcription factors, such as cpst12 and pro1, was observed in CpSte11 null mutants. The down-regulation of Mf2/2, cpst12 and pro1 was also observed in the mutant phenotype of Cpmk2, a mating response Fus3-like mitogen-activated protein kinase (MAPK) gene, but not in the mutant of Cpmk1, a high-osmolarity glycerol Hog1-like MAPK gene. These results indicate that the cloned CpSte11 gene is functionally involved in the mating response pathway and acts through downstream targets, including Cpmk2, cpst12, pro1 and Mf2/2. However, the characteristics of the CpSte11 null mutant were fully phenocopied only in the cpst12 null mutant, but not in other studied null mutants of components of the putative mating response pathway. © 2011 THE AUTHORS. MOLECULAR PLANT PATHOLOGY © 2011 BSPP AND BLACKWELL PUBLISHING LTD.

Multimer Formation Explains Allelic Suppression of PRDM9 Recombination Hotspots.

PubMed

Baker, Christopher L; Petkova, Pavlina; Walker, Michael; Flachs, Petr; Mihola, Ondrej; Trachtulec, Zdenek; Petkov, Petko M; Paigen, Kenneth

2015-09-01

Genetic recombination during meiosis functions to increase genetic diversity, promotes elimination of deleterious alleles, and helps assure proper segregation of chromatids. Mammalian recombination events are concentrated at specialized sites, termed hotspots, whose locations are determined by PRDM9, a zinc finger DNA-binding histone methyltransferase. Prdm9 is highly polymorphic with most alleles activating their own set of hotspots. In populations exhibiting high frequencies of heterozygosity, questions remain about the influences different alleles have in heterozygous individuals where the two variant forms of PRDM9 typically do not activate equivalent populations of hotspots. We now find that, in addition to activating its own hotspots, the presence of one Prdm9 allele can modify the activity of hotspots activated by the other allele. PRDM9 function is also dosage sensitive; Prdm9+/- heterozygous null mice have reduced numbers and less active hotspots and increased numbers of aberrant germ cells. In mice carrying two Prdm9 alleles, there is allelic competition; the stronger Prdm9 allele can partially or entirely suppress chromatin modification and recombination at hotspots of the weaker allele. In cell cultures, PRDM9 protein variants form functional heteromeric complexes which can bind hotspots sequences. When a heteromeric complex binds at a hotspot of one PRDM9 variant, the other PRDM9 variant, which would otherwise not bind, can still methylate hotspot nucleosomes. We propose that in heterozygous individuals the underlying molecular mechanism of allelic suppression results from formation of PRDM9 heteromers, where the DNA binding activity of one protein variant dominantly directs recombination initiation towards its own hotspots, effectively titrating down recombination by the other protein variant. In natural populations with many heterozygous individuals, allelic competition will influence the recombination landscape.

Multimer Formation Explains Allelic Suppression of PRDM9 Recombination Hotspots

PubMed Central

Baker, Christopher L.; Petkova, Pavlina; Walker, Michael; Flachs, Petr; Mihola, Ondrej; Trachtulec, Zdenek; Petkov, Petko M.; Paigen, Kenneth

2015-01-01

Genetic recombination during meiosis functions to increase genetic diversity, promotes elimination of deleterious alleles, and helps assure proper segregation of chromatids. Mammalian recombination events are concentrated at specialized sites, termed hotspots, whose locations are determined by PRDM9, a zinc finger DNA-binding histone methyltransferase. Prdm9 is highly polymorphic with most alleles activating their own set of hotspots. In populations exhibiting high frequencies of heterozygosity, questions remain about the influences different alleles have in heterozygous individuals where the two variant forms of PRDM9 typically do not activate equivalent populations of hotspots. We now find that, in addition to activating its own hotspots, the presence of one Prdm9 allele can modify the activity of hotspots activated by the other allele. PRDM9 function is also dosage sensitive; Prdm9 +/- heterozygous null mice have reduced numbers and less active hotspots and increased numbers of aberrant germ cells. In mice carrying two Prdm9 alleles, there is allelic competition; the stronger Prdm9 allele can partially or entirely suppress chromatin modification and recombination at hotspots of the weaker allele. In cell cultures, PRDM9 protein variants form functional heteromeric complexes which can bind hotspots sequences. When a heteromeric complex binds at a hotspot of one PRDM9 variant, the other PRDM9 variant, which would otherwise not bind, can still methylate hotspot nucleosomes. We propose that in heterozygous individuals the underlying molecular mechanism of allelic suppression results from formation of PRDM9 heteromers, where the DNA binding activity of one protein variant dominantly directs recombination initiation towards its own hotspots, effectively titrating down recombination by the other protein variant. In natural populations with many heterozygous individuals, allelic competition will influence the recombination landscape. PMID:26368021

Correction of respiratory disorders in a mouse model of Rett syndrome

PubMed Central

Abdala, Ana P. L.; Dutschmann, Mathias; Bissonnette, John M.; Paton, Julian F. R.

2010-01-01

Rett syndrome (RTT) is an autism spectrum disorder caused by mutations in the X-linked gene that encodes the transcription factor methyl-CpG-binding protein 2 (MeCP2). A major debilitating phenotype in affected females is frequent apneas, and heterozygous Mecp2-deficient female mice mimic the human respiratory disorder. GABA defects have been demonstrated in the brainstem of Mecp2-deficient mice. Here, using an intact respiratory network, we show that apnea in RTT mice is characterized by excessive excitatory activity in expiratory cranial and spinal nerves. Augmenting GABA markedly improves the respiratory phenotype. In addition, a serotonin 1a receptor agonist that depresses expiratory neuron activity also reduces apnea, corrects the irregular breathing pattern, and prolongs survival in MeCP2 null males. Combining a GABA reuptake blocker with a serotonin 1a agonist in heterozygous females completely corrects their respiratory defects. The results indicate that GABA and serotonin 1a receptor activity are candidates for treatment of the respiratory disorders in Rett syndrome. PMID:20921395

The WAVE2/Abi1 complex differentially regulates megakaryocyte development and spreading: implications for platelet biogenesis and spreading machinery.

PubMed

Eto, Koji; Nishikii, Hidekazu; Ogaeri, Takunori; Suetsugu, Shiro; Kamiya, Akihide; Kobayashi, Toshihiro; Yamazaki, Daisuke; Oda, Atsushi; Takenawa, Tadaomi; Nakauchi, Hiromitsu

2007-11-15

Actin polymerization is crucial in throm-bopoiesis, platelet adhesion, and mega-karyocyte (MK) and platelet spreading. The Wiskott-Aldrich syndrome protein (WASp) homolog WAVE functions downstream of Rac and plays a pivotal role in lamellipodia formation. While MKs and platelets principally express WAVE1 and WAVE2, which are associated with Abi1, the physiologic significance of WAVE isoforms remains undefined. We generated WAVE2(-/-) embryonic stem (ES) cells because WAVE2-null mice die by embryonic day (E) 12.5. We found that while WAVE2(-/-) ES cells differentiated into immature MKs on OP9 stroma, they were severely impaired in terminal differentiation and in platelet production. WAVE2(-/-) MKs exhibited a defect in peripheral lamellipodia on fibrinogen even with phorbol 12-myristate 13-acetate (PMA) costimulation, indicating a requirement of WAVE2 for integrin alpha(IIb)beta(3)-mediated full spreading. MKs in which expression of Abi1 was reduced by small interfering RNA (siRNA) exhibited striking similarity to WAVE2(-/-) MKs in maturation and spreading. Interestingly, the knockdown of IRSp53, a Rac effector that preferentially binds to WAVE2, impaired the development of lamellipodia without affecting proplatelet production. In contrast, thrombopoiesis in vivo and platelet spreading on fibrinogen in vitro were intact in WAVE1-null mice. These observations clarify indispensable roles for the WAVE2/Abi1 complex in alpha(IIb)beta(3)-mediated lamellipodia by MKs and platelets through Rac and IRSp53, and additionally in thrombopoiesis independent of Rac and IRSp53.

The Dictyostelium discoideum RACK1 orthologue has roles in growth and development

PubMed Central

2014-01-01

Background The receptor for activated C-kinase 1 (RACK1) is a conserved protein belonging to the WD40 repeat family of proteins. It folds into a beta propeller with seven blades which allow interactions with many proteins. Thus it can serve as a scaffolding protein and have roles in several cellular processes. Results We identified the product of the Dictyostelium discoideum gpbB gene as the Dictyostelium RACK1 homolog. The protein is mainly cytosolic but can also associate with cellular membranes. DdRACK1 binds to phosphoinositides (PIPs) in protein-lipid overlay and liposome-binding assays. The basis of this activity resides in a basic region located in the extended loop between blades 6 and 7 as revealed by mutational analysis. Similar to RACK1 proteins from other organisms DdRACK1 interacts with G protein subunits alpha, beta and gamma as shown by yeast two-hybrid, pulldown, and immunoprecipitation assays. Unlike the Saccharomyces cerevisiae and Cryptococcus neoformans RACK1 proteins it does not appear to take over Gβ function in D. discoideum as developmental and other defects were not rescued in Gβ null mutants overexpressing GFP-DdRACK1. Overexpression of GFP-tagged DdRACK1 and a mutant version (DdRACK1mut) which carried a charge-reversal mutation in the basic region in wild type cells led to changes during growth and development. Conclusion DdRACK1 interacts with heterotrimeric G proteins and can through these interactions impact on processes specifically regulated by these proteins. PMID:24930026

The de-ubiquitinating enzyme ataxin-3 does not modulate disease progression in a knock-in mouse model of Huntington disease.

PubMed

Zeng, Li; Tallaksen-Greene, Sara J; Wang, Bo; Albin, Roger L; Paulson, Henry L

2013-01-01

Ataxin-3 is a deubiquitinating enzyme (DUB) that participates in ubiquitin-dependent protein quality control pathways and, based on studies in model systems, may be neuroprotective against toxic polyglutamine proteins such as the Huntington's disease (HD) protein, huntingtin (htt). HD is one of at least nine polyglutamine neurodegenerative diseases in which disease-causing proteins accumulate in ubiquitin-positive inclusions within neurons. In studies crossing mice null for ataxin-3 to an established HD knock-in mouse model (HdhQ200), we tested whether loss of ataxin-3 alters disease progression, perhaps by impairing the clearance of mutant htt or the ubiquitination of inclusions. While loss of ataxin-3 mildly exacerbated age-dependent motor deficits, it did not alter inclusion formation, ubiquitination of inclusions or levels of mutant or normal htt. Ataxin-3, itself a polyglutamine-containing protein with multiple ubiquitin binding domains, was not observed to localize to htt inclusions. Changes in neurotransmitter receptor binding known to occur in HD knock-in mice also were not altered by the loss of ataxin-3, although we unexpectedly observed increased GABAA receptor binding in the striatum of HdhQ200 mice, which has not previously been noted. Finally, we confirmed that CNS levels of hsp70 are decreased in HD mice as has been reported in other HD mouse models, regardless of the presence or absence of ataxin-3. We conclude that while ataxin-3 may participate in protein quality control pathways, it does not critically regulate the handling of mutant htt or contribute to major features of disease pathogenesis in HD.

The impact of p53 protein core domain structural alteration on ovarian cancer survival.

PubMed

Rose, Stephen L; Robertson, Andrew D; Goodheart, Michael J; Smith, Brian J; DeYoung, Barry R; Buller, Richard E

2003-09-15

Although survival with a p53 missense mutation is highly variable, p53-null mutation is an independent adverse prognostic factor for advanced stage ovarian cancer. By evaluating ovarian cancer survival based upon a structure function analysis of the p53 protein, we tested the hypothesis that not all missense mutations are equivalent. The p53 gene was sequenced from 267 consecutive ovarian cancers. The effect of individual missense mutations on p53 structure was analyzed using the International Agency for Research on Cancer p53 Mutational Database, which specifies the effects of p53 mutations on p53 core domain structure. Mutations in the p53 core domain were classified as either explained or not explained in structural or functional terms by their predicted effects on protein folding, protein-DNA contacts, or mutation in highly conserved residues. Null mutations were classified by their mechanism of origin. Mutations were sequenced from 125 tumors. Effects of 62 of the 82 missense mutations (76%) could be explained by alterations in the p53 protein. Twenty-three (28%) of the explained mutations occurred in highly conserved regions of the p53 core protein. Twenty-two nonsense point mutations and 21 frameshift null mutations were sequenced. Survival was independent of missense mutation type and mechanism of null mutation. The hypothesis that not all missense mutations are equivalent is, therefore, rejected. Furthermore, p53 core domain structural alteration secondary to missense point mutation is not functionally equivalent to a p53-null mutation. The poor prognosis associated with p53-null mutation is independent of the mutation mechanism.

Targeted Elimination of G Proteins and Arrestins Defines Their Specific Contributions to Both Intensity and Duration of G Protein-coupled Receptor Signaling.

PubMed

Alvarez-Curto, Elisa; Inoue, Asuka; Jenkins, Laura; Raihan, Sheikh Zahir; Prihandoko, Rudi; Tobin, Andrew B; Milligan, Graeme

2016-12-30

G protein-coupled receptors (GPCRs) can initiate intracellular signaling cascades by coupling to an array of heterotrimeric G proteins and arrestin adaptor proteins. Understanding the contribution of each of these coupling options to GPCR signaling has been hampered by a paucity of tools to selectively perturb receptor function. Here we employ CRISPR/Cas9 genome editing to eliminate selected G proteins (Gα q and Gα 11 ) or arrestin2 and arrestin3 from HEK293 cells together with the elimination of receptor phosphorylation sites to define the relative contribution of G proteins, arrestins, and receptor phosphorylation to the signaling outcomes of the free fatty acid receptor 4 (FFA4). A lack of FFA4-mediated elevation of intracellular Ca 2+ in Gα q /Gα 11 -null cells and agonist-mediated receptor internalization in arrestin2/3-null cells confirmed previously reported canonical signaling features of this receptor, thereby validating the genome-edited HEK293 cells. FFA4-mediated ERK1/2 activation was totally dependent on G q / 11 but intriguingly was substantially enhanced for FFA4 receptors lacking sites of regulated phosphorylation. This was not due to a simple lack of desensitization of G q / 11 signaling because the G q / 11 -dependent calcium response was desensitized by both receptor phosphorylation and arrestin-dependent mechanisms, whereas a substantially enhanced ERK1/2 response was only observed for receptors lacking phosphorylation sites and not in arrestin2/3-null cells. In conclusion, we validate CRISPR/Cas9 engineered HEK293 cells lacking G q / 11 or arrestin2/3 as systems for GPCR signaling research and employ these cells to reveal a previously unappreciated interplay of signaling pathways where receptor phosphorylation can impact on ERK1/2 signaling through a mechanism that is likely independent of arrestins. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

In vitro cytotoxicity induced by Clostridium perfringens isolate carrying a chromosomal cpe gene is exclusively dependent on sporulation and enterotoxin production.

PubMed

Yasugi, Mayo; Sugahara, Yuki; Hoshi, Hidenobu; Kondo, Kaori; Talukdar, Prabhat K; Sarker, Mahfuzur R; Yamamoto, Shigeki; Kamata, Yoichi; Miyake, Masami

2015-08-01

Clostridium perfringens type A is a common source of food poisoning (FP) and non-food-borne (NFB) gastrointestinal diseases in humans. In the intestinal tract, the vegetative cells sporulate and produce a major pathogenic factor, C. perfringens enterotoxin (CPE). Most type A FP isolates carry a chromosomal cpe gene, whereas NFB type A isolates typically carry a plasmid-encoded cpe. In vitro, the purified CPE protein binds to a receptor and forms pores, exerting a cytotoxic activity in epithelial cells. However, it remains unclear if CPE is indispensable for C. perfringens cytotoxicity. In this study, we examined the cytotoxicity of cpe-harboring C. perfringens isolates co-cultured with human intestinal epithelial Caco-2 cells. The FP strains showed severe cytotoxicity during sporulation and CPE production, but not during vegetative cell growth. While Caco-2 cells were intact during co-culturing with cpe-null mutant derivative of strain SM101 (a FP strain carrying a chromosomal cpe gene), the wild-type level cytotoxicity was observed with cpe-complemented strain. In contrast, both wild-type and cpe-null mutant derivative of the NFB strain F4969 induced Caco-2 cell death during both vegetative and sporulation growth. Collectively, the Caco-2 cell cytotoxicity caused by C. perfringens strain SM101 is considered to be exclusively dependent on CPE production, whereas some additional toxins should be involved in F4969-mediated in vitro cytotoxicity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cell-type specific role of the RNA-binding protein, NONO, in the DNA double-strand break response in the mouse testes.

PubMed

Li, Shuyi; Shu, Feng-Jue; Li, Zhentian; Jaafar, Lahcen; Zhao, Shourong; Dynan, William S

2017-03-01

The tandem RNA recognition motif protein, NONO, was previously identified as a candidate DNA double-strand break (DSB) repair factor in a biochemical screen for proteins with end-joining stimulatory activity. Subsequent work showed that NONO and its binding partner, SFPQ, have many of the properties expected for bona fide repair factors in cell-based assays. Their contribution to the DNA damage response in intact tissue in vivo has not, however, been demonstrated. Here we compare DNA damage sensitivity in the testes of wild-type mice versus mice bearing a null allele of the NONO homologue (Nono gt ). In wild-type mice, NONO protein was present in Sertoli, peritubular myoid, and interstitial cells, with an increase in expression following induction of DNA damage. As expected for the product of an X-linked gene, NONO was not detected in germ cells. The Nono gt/0 mice had at most a mild testis developmental phenotype in the absence of genotoxic stress. However, following irradiation at sublethal, 2-4 Gy doses, Nono gt/0 mice displayed a number of indicators of radiosensitivity as compared to their wild-type counterparts. These included higher levels of persistent DSB repair foci, increased numbers of apoptotic cells in the seminiferous tubules, and partial degeneration of the blood-testis barrier. There was also an almost complete loss of germ cells at later times following irradiation, evidently arising as an indirect effect reflecting loss of stromal support. Results demonstrate a role for NONO protein in protection against direct and indirect biological effects of ionizing radiation in the whole animal. Copyright © 2017 Elsevier B.V. All rights reserved.

A Simple PB/LIE Free Energy Function Accurately Predicts the Peptide Binding Specificity of the Tiam1 PDZ Domain.

PubMed

Panel, Nicolas; Sun, Young Joo; Fuentes, Ernesto J; Simonson, Thomas

2017-01-01

PDZ domains generally bind short amino acid sequences at the C-terminus of target proteins, and short peptides can be used as inhibitors or model ligands. Here, we used experimental binding assays and molecular dynamics simulations to characterize 51 complexes involving the Tiam1 PDZ domain and to test the performance of a semi-empirical free energy function. The free energy function combined a Poisson-Boltzmann (PB) continuum electrostatic term, a van der Waals interaction energy, and a surface area term. Each term was empirically weighted, giving a Linear Interaction Energy or "PB/LIE" free energy. The model yielded a mean unsigned deviation of 0.43 kcal/mol and a Pearson correlation of 0.64 between experimental and computed free energies, which was superior to a Null model that assumes all complexes have the same affinity. Analyses of the models support several experimental observations that indicate the orientation of the α 2 helix is a critical determinant for peptide specificity. The models were also used to predict binding free energies for nine new variants, corresponding to point mutants of the Syndecan1 and Caspr4 peptides. The predictions did not reveal improved binding; however, they suggest that an unnatural amino acid could be used to increase protease resistance and peptide lifetimes in vivo . The overall performance of the model should allow its use in the design of new PDZ ligands in the future.

A Simple PB/LIE Free Energy Function Accurately Predicts the Peptide Binding Specificity of the Tiam1 PDZ Domain

PubMed Central

Panel, Nicolas; Sun, Young Joo; Fuentes, Ernesto J.; Simonson, Thomas

2017-01-01

PDZ domains generally bind short amino acid sequences at the C-terminus of target proteins, and short peptides can be used as inhibitors or model ligands. Here, we used experimental binding assays and molecular dynamics simulations to characterize 51 complexes involving the Tiam1 PDZ domain and to test the performance of a semi-empirical free energy function. The free energy function combined a Poisson-Boltzmann (PB) continuum electrostatic term, a van der Waals interaction energy, and a surface area term. Each term was empirically weighted, giving a Linear Interaction Energy or “PB/LIE” free energy. The model yielded a mean unsigned deviation of 0.43 kcal/mol and a Pearson correlation of 0.64 between experimental and computed free energies, which was superior to a Null model that assumes all complexes have the same affinity. Analyses of the models support several experimental observations that indicate the orientation of the α2 helix is a critical determinant for peptide specificity. The models were also used to predict binding free energies for nine new variants, corresponding to point mutants of the Syndecan1 and Caspr4 peptides. The predictions did not reveal improved binding; however, they suggest that an unnatural amino acid could be used to increase protease resistance and peptide lifetimes in vivo. The overall performance of the model should allow its use in the design of new PDZ ligands in the future. PMID:29018806

The lethal form of Cushing's in 7B2 null mice is caused by multiple metabolic and hormonal abnormalities.

PubMed

Sarac, Miroslav S; Zieske, Arthur W; Lindberg, Iris

2002-06-01

The neuroendocrine-specific protein 7B2, which serves as a molecular escort for proPC2 in the secretory pathway, promotes the production of enzymatically active PC2 and may have non-PC2 related endocrine roles. Mice null for 7B2 exhibit a lethal phenotype with a complex Cushing's-like pathology, which develops from intermediate lobe ACTH hypersecretion as a consequences of interruption of PC2-mediated peptide processing as well as undefined consequences of the loss of 7B2. In this study we investigated the endocrine and metabolic alterations of 7B2 null mice from pathological and biochemical points of view. Our results show that 7B2 nulls exhibit a multisystem disorder that includes severe pathoanatomical and histopathologic alterations of vital organs, including the heart and spleen but most notably the liver, in which massive steatosis and necrosis are observed. Metabolic derangements in glucose metabolism result in glycogen and fat deposition in liver under conditions of chronic hypoglycemia. Liver failure is also likely to contribute to abnormalities in blood coagulation and blood chemistry, such as lactic acidosis. A hypoglycemic crisis coupled with respiratory distress and intensive internal thrombosis most likely results in rapid deterioration and death of the 7B2 null.

Interleukin-6 inhibits hepatic growth hormone signaling via upregulation of Cis and Socs-3.

PubMed

Denson, Lee A; Held, Matthew A; Menon, Ram K; Frank, Stuart J; Parlow, Albert F; Arnold, Dodie L

2003-04-01

Cytokines may cause an acquired growth hormone (GH) resistance in patients with inflammatory diseases. Anabolic effects of GH are mediated through activation of STAT5 transcription factors. We have reported that TNF-alpha suppresses hepatic GH receptor (GHR) gene expression, whereas the cytokine-inducible SH2-containing protein 1 (Cis)/suppressors of cytokine signaling (Socs) genes are upregulated by TNF-alpha and IL-6 and inhibit GH activation of STAT5. However, the relative importance of these mechanisms in inflammatory GH resistance was not known. We hypothesized that IL-6 would prevent GH activation of STAT5 and that this would involve Cis/Socs protein upregulation. GH +/- LPS was administered to TNF receptor 1 (TNFR1) or IL-6 null mice and wild-type (WT) controls. STAT5, STAT3, GHR, Socs 1-3, and Cis phosphorylation and abundance were assessed by using immunoblots, EMSA, and/or real time RT-PCR. TNF-alpha and IL-6 abundance were assessed by using ELISA. GH activated STAT5 in WT and TNFR1 or IL-6 null mice. LPS pretreatment prevented STAT5 activation in WT and TNFR1 null mice; however, STAT5 activation was preserved in IL-6 null mice. GHR abundance did not change with LPS administration. Inhibition of STAT5 activation by LPS was temporally associated with phosphorylation of STAT3 and upregulation of Cis and Socs-3 protein in WT and TNFR1 null mice; STAT3, Cis, and Socs-3 were not induced in IL-6 null mice. IL-6 inhibits hepatic GH signaling by upregulating Cis and Socs-3, which may involve activation of STAT3. Therapies that block IL-6 may enhance GH signaling in inflammatory diseases.

Roles of Heparan Sulfate Sulfation in Dentinogenesis*

PubMed Central

Hayano, Satoru; Kurosaka, Hiroshi; Yanagita, Takeshi; Kalus, Ina; Milz, Fabian; Ishihara, Yoshihito; Islam, Md. Nurul; Kawanabe, Noriaki; Saito, Masahiro; Kamioka, Hiroshi; Adachi, Taiji; Dierks, Thomas; Yamashiro, Takashi

2012-01-01

Cell surface heparan sulfate (HS) is an essential regulator of cell signaling and development. HS traps signaling molecules, like Wnt in the glycosaminoglycan side chains of HS proteoglycans (HSPGs), and regulates their functions. Endosulfatases Sulf1 and Sulf2 are secreted at the cell surface to selectively remove 6-O-sulfate groups from HSPGs, thereby modifying the affinity of cell surface HSPGs for its ligands. This study provides molecular evidence for the functional roles of HSPG sulfation and desulfation in dentinogenesis. We show that odontogenic cells are highly sulfated on the cell surface and become desulfated during their differentiation to odontoblasts, which produce tooth dentin. Sulf1/Sulf2 double null mutant mice exhibit a thin dentin matrix and short roots combined with reduced expression of dentin sialophosphoprotein (Dspp) mRNA, encoding a dentin-specific extracellular matrix precursor protein, whereas single Sulf mutants do not show such defective phenotypes. In odontoblast cell lines, Dspp mRNA expression is potentiated by the activation of the Wnt canonical signaling pathway. In addition, pharmacological interference with HS sulfation promotes Dspp mRNA expression through activation of Wnt signaling. On the contrary, the silencing of Sulf suppresses the Wnt signaling pathway and subsequently Dspp mRNA expression. We also show that Wnt10a protein binds to cell surface HSPGs in odontoblasts, and interference with HS sulfation decreases the binding affinity of Wnt10a for HSPGs, which facilitates the binding of Wnt10a to its receptor and potentiates the Wnt signaling pathway, thereby up-regulating Dspp mRNA expression. These results demonstrate that Sulf-mediated desulfation of cellular HSPGs is an important modification that is critical for the activation of the Wnt signaling in odontoblasts and for production of the dentin matrix. PMID:22351753

Factor H-binding protein is important for meningococcal survival in human whole blood and serum and in the presence of the antimicrobial peptide LL-37.

PubMed

Seib, K L; Serruto, D; Oriente, F; Delany, I; Adu-Bobie, J; Veggi, D; Aricò, B; Rappuoli, R; Pizza, M

2009-01-01

Factor H-binding protein (fHBP; GNA1870) is one of the antigens of the recombinant vaccine against serogroup B Neisseria meningitidis, which has been developed using reverse vaccinology and is the basis of a meningococcal B vaccine entering phase III clinical trials. Binding of factor H (fH), an inhibitor of the complement alternative pathway, to fHBP enables N. meningitidis to evade killing by the innate immune system. All fHBP null mutant strains analyzed were sensitive to killing in ex vivo human whole blood and serum models of meningococcal bacteremia with respect to the isogenic wild-type strains. The fHBP mutant strains of MC58 and BZ83 (high fHBP expressors) survived in human blood and serum for less than 60 min (decrease of >2 log(10) CFU), while NZ98/254 (intermediate fHBP expressor) and 67/00 (low fHBP expressor) showed decreases of >1 log(10) CFU after 60 to 120 min of incubation. In addition, fHBP is important for survival in the presence of the antimicrobial peptide LL-37 (decrease of >3 log(10) CFU after 2 h of incubation), most likely due to electrostatic interactions between fHBP and the cationic LL-37 molecule. Hence, the expression of fHBP by N. meningitidis strains is important for survival in human blood and human serum and in the presence of LL-37, even at low levels. The functional significance of fHBP in mediating resistance to the human immune response, in addition to its widespread distribution and its ability to induce bactericidal antibodies, indicates that it is an important component of the serogroup B meningococcal vaccine.

Autochthonous tumors driven by Rb1 loss have an ongoing requirement for the RBP2 histone demethylase.

PubMed

McBrayer, Samuel K; Olenchock, Benjamin A; DiNatale, Gabriel J; Shi, Diana D; Khanal, Januka; Jennings, Rebecca B; Novak, Jesse S; Oser, Matthew G; Robbins, Alissa K; Modiste, Rebecca; Bonal, Dennis; Moslehi, Javid; Bronson, Roderick T; Neuberg, Donna; Nguyen, Quang-De; Signoretti, Sabina; Losman, Julie-Aurore; Kaelin, William G

2018-04-17

Inactivation of the retinoblastoma gene ( RB1 ) product, pRB, is common in many human cancers. Targeting downstream effectors of pRB that are central to tumorigenesis is a promising strategy to block the growth of tumors harboring loss-of-function RB1 mutations. One such effector is retinoblastoma-binding protein 2 (RBP2, also called JARID1A or KDM5A), which encodes an H3K4 demethylase. Binding of pRB to RBP2 has been linked to the ability of pRB to promote senescence and differentiation. Importantly, genetic ablation of RBP2 is sufficient to phenocopy pRB's ability to induce these cellular changes in cell culture experiments. Moreover, germline Rbp2 deletion significantly impedes tumorigenesis in Rb1 +/- mice. The value of RBP2 as a therapeutic target in cancer, however, hinges on whether loss of RBP2 could block the growth of established tumors as opposed to simply delaying their onset. Here we show that conditional, systemic ablation of RBP2 in tumor-bearing Rb1 +/- mice is sufficient to slow tumor growth and significantly extend survival without causing obvious toxicity to the host. These findings show that established Rb1 -null tumors require RBP2 for growth and further credential RBP2 as a therapeutic target in human cancers driven by RB1 inactivation.

Placental glucose and amino acid transport in calorie-restricted wild-type and Glut3 null heterozygous mice.

PubMed

Ganguly, Amit; Collis, Laura; Devaskar, Sherin U

2012-08-01

Calorie restriction (CR) decreased placenta and fetal weights in wild-type (wt) and glucose transporter (Glut) 3 heterozygous null (glut3(+/-)) mice. Because placental nutrient transport is a primary energy determinant of placentofetal growth, we examined key transport systems. Maternal CR reduced intra- and transplacental glucose and leucine transport but enhanced system A amino acid transport in wt mice. These transport perturbations were accompanied by reduced placental Glut3 and leucine amino acid transporter (LAT) family member 2, no change in Glut1 and LAT family member 1, but increased sodium coupled neutral amino acid transporter (SNAT) and SNAT2 expression. We also noted decreased total and active phosphorylated forms of mammalian target of rapamycin, which is the intracellular nutrient sensor, the downstream total P70S6 kinase, and pS6 ribosomal protein with no change in total and phosphorylated 4E-binding protein 1. To determine the role of placental Glut3 in mediating CR-induced placental transport changes, we next investigated the effect of gestational CR in glut3(+/-) mice. In glut3(+/-) mice, a key role of placental Glut3 in mediating transplacental and intraplacental glucose transport was established. In addition, reduced Glut3 results in a compensatory increase of leucine and system A transplacental transport. On the other hand, diminished Glut3-mediated intraplacental glucose transport reduced leucine transport and mammalian target of rapamycin and preserved LAT and enhancing SNAT. CR in glut3(+/-) mice further reduced transplacental glucose transport and enhanced system A amino acid transport, although the increased leucine transport was lost. In addition, increased Glut3 was seen and preserved Glut1, LAT, and SNAT. These placental changes collectively protect survival of wt and glut3(+/-) fetuses against maternal CR-imposed reduction of macromolecular nutrients.

The EWS–Oct-4 fusion gene encodes a transforming gene

PubMed Central

Lee, Jungwoon; Kim, Ja Young; Kang, In Young; Kim, Hye Kyoung; Han, Yong-Mahn; Kim, Jungho

2007-01-01

The t(6;22)(p21;q12) translocation associated with human bone and soft-tissue tumours results in a chimaeric molecule fusing the NTD (N-terminal domain) of the EWS (Ewing's sarcoma) gene to the CTD (C-terminal domain) of the Oct-4 (octamer-4) embryonic gene. Since the N-terminal domains of EWS and Oct-4 are structurally different, in the present study we have assessed the functional consequences of the EWS–Oct-4 fusion. We find that this chimaeric gene encodes a nuclear protein which binds DNA with the same sequence specificity as the parental Oct-4 protein. Comparison of the transactivation properties of EWS–Oct-4 and Oct-4 indicates that the former has higher transactivation activity for a known target reporter gene containing Oct-4 binding. Deletion analysis of the functional domains of EWS–Oct-4 indicates that the EWS (NTD), the POU domain and the CTD of EWS–Oct-4 are necessary for full transactivation potential. EWS–Oct-4 induced the expression of fgf-4 (fibroblast growth factor 4) and nanog, which are potent mitogens as well as Oct-4 downstream target genes whose promoters contain potential Oct-4-binding sites. Finally, ectopic expression of EWS–Oct-4 in Oct-4-null ZHBTc4 ES (embryonic stem) cells resulted in increased tumorigenic growth potential in nude mice. These results suggest that the oncogenic effect of the t(6;22) translocation is due to the EWS–Oct-4 chimaeric protein and that fusion of the EWS NTD to the Oct-4 DNA-binding domain produces a transforming chimaeric product. PMID:17564582

Identifying Neurofibromin Specific Regulatory Nodes for Therapeutic Targeting in NF1

DTIC Science & Technology

2017-10-01

neurofibromin depends on the adapter protein SPRED1, to function, and we are utilizing the latest technical innovations including CRISPR technology... CRISPR technology to find genes that regulate neurofibromin SPRED function. Keywords Neurofibromin, Spred1, Spred2, EGFR, mutant EGFR(L858R), Ras...Establish good NF1 and Spred1/2 knockdown protocols for indicated cell lines NF1-Null and Spred1-Null HEK 293T cells have been generated using CRISPR /Cas9

Toll-like receptor 4 and myeloid differentiation factor 88 provide mechanistic insights into the cause and effects of interleukin-6 activation in mouse liver regeneration.

PubMed

Vaquero, Javier; Campbell, Jean S; Haque, Jamil; McMahan, Ryan S; Riehle, Kimberly J; Bauer, Renay L; Fausto, Nelson

2011-08-01

Partial hepatectomy (PH) consistently results in an early increase of circulating interleukin-6 (IL-6), which is thought to play a major role in liver regeneration. Activation of this cytokine after PH requires the adaptor protein, MyD88, but the specific MyD88-related receptors involved remain unidentified. It is also unknown whether the magnitude of IL-6 elevation determines the extent of subsequent hepatocyte proliferation. Here, we uncovered artifacts in the assessment of circulating IL-6 levels when using cardiac puncture in mice after PH. By using retro-orbital bleed sampling, we show that the circulating levels of IL-6 after PH were not directly correlated with the extent of hepatocyte DNA synthesis in individual mice. The IL-6 increase after PH was attenuated in all lipopolysaccharide-hyporesponsive mouse strains studied (e.g., C3H/HeJ, Tlr4 null, Cd14 null, Tlr2,4,9 null, and Tlr2,4-Caspase1 null) and was severely abrogated in Myd88 null mice. Despite attenuated IL-6 levels, Tlr4 null mice showed normal signaling downstream of IL-6 and normal hepatocyte proliferation. In contrast, Myd88 null mice showed severe impairments in signal transducer and activator of transcription 3 phosphorylation and Socs3 induction, but had enhanced and prolonged extracellular signal-related kinase 1 and 2 phosphorylation in the first 6 hours after PH. Unexpectedly, these changes were associated with accelerated initiation of hepatocyte proliferation, as assessed by hepatocyte bromodeoxyuridine incorporation, phospho-histone H3 immunostaining, and cyclin E and A protein expression. TLR-4 signaling contributes to IL-6 activation after PH, but the Tlr4-independent component appears sufficient for ensuring intact signaling downstream of IL-6. The lack of correlation between IL-6 levels and hepatocyte proliferation after PH, and the accelerated start of hepatocyte proliferation in Myd88 null mice despite abrogated cytokine activation, may highlight relevant antiproliferative effects of IL-6 signaling, possibly via Socs3, in the regulation of liver regeneration. Copyright © 2011 American Association for the Study of Liver Diseases.

Toll-Like Receptor 4 and Myeloid Differentiation Factor 88 Provide Mechanistic Insights Into the Cause and Effects of Interleukin-6 Activation in Mouse Liver Regeneration

PubMed Central

Vaquero, Javier; Campbell, Jean S.; Haque, Jamil; McMahan, Ryan S.; Riehle, Kimberly J.; Bauer, Renay L.; Fausto, Nelson

2014-01-01

Partial hepatectomy (PH) consistently results in an early increase of circulating interleukin- 6 (IL-6), which is thought to play a major role in liver regeneration. Activation of this cytokine after PH requires the adaptor protein, MyD88, but the specific MyD88-related receptors involved remain unidentified. It is also unknown whether the magnitude of IL-6 elevation determines the extent of subsequent hepatocyte proliferation. Here, we uncovered artifacts in the assessment of circulating IL-6 levels when using cardiac puncture in mice after PH. By using retro-orbital bleed sampling, we show that the circulating levels of IL-6 after PH were not directly correlated with the extent of hepatocyte DNA synthesis in individual mice. The IL-6 increase after PH was attenuated in all lipopolysaccharide-hyporesponsive mouse strains studied (e.g., C3H/HeJ, Tlr4 null, Cd14 null, Tlr2,4,9 null, and Tlr2,4-Caspase1 null) and was severely abrogated in Myd88 null mice. Despite attenuated IL-6 levels, Tlr4 null mice showed normal signaling downstream of IL-6 and normal hepatocyte proliferation. In contrast, Myd88 null mice showed severe impairments in signal transducer and activator of transcription 3 phosphorylation and Socs3 induction, but had enhanced and prolonged extracellular signal-related kinase 1 and 2 phosphorylation in the first 6 hours after PH. Unexpectedly, these changes were associated with accelerated initiation of hepatocyte proliferation, as assessed by hepatocyte bromodeoxyuridine incorporation, phospho-histone H3 immunostaining, and cyclin E and A protein expression. Conclusion TLR-4 signaling contributes to IL-6 activation after PH, but the Tlr4-independent component appears sufficient for ensuring intact signaling downstream of IL-6. The lack of correlation between IL-6 levels and hepatocyte proliferation after PH, and the accelerated start of hepatocyte proliferation in Myd88 null mice despite abrogated cytokine activation, may highlight relevant antiproliferative effects of IL-6 signaling, possibly via Socs3, in the regulation of liver regeneration. PMID:21574169

Prolonged Stationary-Phase Incubation Selects for lrp Mutations in Escherichia coli K-12

PubMed Central

Zinser, Erik R.; Kolter, Roberto

2000-01-01

Evolution by natural selection occurs in cultures of Escherichia coli maintained under carbon starvation stress. Mutants of increased fitness express a growth advantage in stationary phase (GASP) phenotype, enabling them to grow and displace the parent as the majority population. The first GASP mutation was identified as a loss-of-function allele of rpoS, encoding the stationary-phase global regulator, ςS (M. M. Zambrano, D. A. Siegele, M. A. Almirón, A. Tormo, and R. Kolter, Science 259:1757–1760, 1993). We now report that a second global regulator, Lrp, can also play a role in stationary-phase competition. We found that a mutant that took over an aged culture of an rpoS strain had acquired a GASP mutation in lrp. This GASP allele, lrp-1141, encodes a mutant protein lacking the critical glycine in the turn of the helix-turn-helix DNA-binding domain. The lrp-1141 allele behaves as a null mutation when in single copy and is dominant negative when overexpressed. Hence, the mutant protein appears to retain stability and the ability to dimerize but lacks DNA-binding activity. We also demonstrated that a lrp null allele generated by a transposon insertion has a fitness gain identical to that of the lrp-1141 allele, verifying that cells lacking Lrp activity have a competitive advantage during prolonged starvation. Finally, we tested by genetic analysis the hypothesis that the lrp-1141 GASP mutation confers a fitness gain by enhancing amino acid catabolism during carbon starvation. We found that while amino acid catabolism may play a role, it is not necessary for the lrp GASP phenotype, and hence the lrp GASP phenotype is due to more global physiological changes. PMID:10894750

Functional mapping of yeast genomes by saturated transposition

PubMed Central

Michel, Agnès H; Hatakeyama, Riko; Kimmig, Philipp; Arter, Meret; Peter, Matthias; Matos, Joao; De Virgilio, Claudio; Kornmann, Benoît

2017-01-01

Yeast is a powerful model for systems genetics. We present a versatile, time- and labor-efficient method to functionally explore the Saccharomyces cerevisiae genome using saturated transposon mutagenesis coupled to high-throughput sequencing. SAturated Transposon Analysis in Yeast (SATAY) allows one-step mapping of all genetic loci in which transposons can insert without disrupting essential functions. SATAY is particularly suited to discover loci important for growth under various conditions. SATAY (1) reveals positive and negative genetic interactions in single and multiple mutant strains, (2) can identify drug targets, (3) detects not only essential genes, but also essential protein domains, (4) generates both null and other informative alleles. In a SATAY screen for rapamycin-resistant mutants, we identify Pib2 (PhosphoInositide-Binding 2) as a master regulator of TORC1. We describe two antagonistic TORC1-activating and -inhibiting activities located on opposite ends of Pib2. Thus, SATAY allows to easily explore the yeast genome at unprecedented resolution and throughput. DOI: http://dx.doi.org/10.7554/eLife.23570.001 PMID:28481201

How to talk about protein-level false discovery rates in shotgun proteomics.

PubMed

The, Matthew; Tasnim, Ayesha; Käll, Lukas

2016-09-01

A frequently sought output from a shotgun proteomics experiment is a list of proteins that we believe to have been present in the analyzed sample before proteolytic digestion. The standard technique to control for errors in such lists is to enforce a preset threshold for the false discovery rate (FDR). Many consider protein-level FDRs a difficult and vague concept, as the measurement entities, spectra, are manifestations of peptides and not proteins. Here, we argue that this confusion is unnecessary and provide a framework on how to think about protein-level FDRs, starting from its basic principle: the null hypothesis. Specifically, we point out that two competing null hypotheses are used concurrently in today's protein inference methods, which has gone unnoticed by many. Using simulations of a shotgun proteomics experiment, we show how confusing one null hypothesis for the other can lead to serious discrepancies in the FDR. Furthermore, we demonstrate how the same simulations can be used to verify FDR estimates of protein inference methods. In particular, we show that, for a simple protein inference method, decoy models can be used to accurately estimate protein-level FDRs for both competing null hypotheses. © 2016 The Authors. Proteomics Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Suppression of the ATP-binding cassette transporter ABCC4 impairs neuroblastoma tumour growth and sensitises to irinotecan in vivo.

PubMed

Murray, Jayne; Valli, Emanuele; Yu, Denise M T; Truong, Alan M; Gifford, Andrew J; Eden, Georgina L; Gamble, Laura D; Hanssen, Kimberley M; Flemming, Claudia L; Tan, Alvin; Tivnan, Amanda; Allan, Sophie; Saletta, Federica; Cheung, Leanna; Ruhle, Michelle; Schuetz, John D; Henderson, Michelle J; Byrne, Jennifer A; Norris, Murray D; Haber, Michelle; Fletcher, Jamie I

2017-09-01

The ATP-binding cassette transporter ABCC4 (multidrug resistance protein 4, MRP4) mRNA level is a strong predictor of poor clinical outcome in neuroblastoma which may relate to its export of endogenous signalling molecules and chemotherapeutic agents. We sought to determine whether ABCC4 contributes to development, growth and drug response in neuroblastoma in vivo. In neuroblastoma patients, high ABCC4 protein levels were associated with reduced overall survival. Inducible knockdown of ABCC4 strongly inhibited the growth of human neuroblastoma cells in vitro and impaired the growth of neuroblastoma xenografts. Loss of Abcc4 in the Th-MYCN transgenic neuroblastoma mouse model did not impact tumour formation; however, Abcc4-null neuroblastomas were strongly sensitised to the ABCC4 substrate drug irinotecan. Our findings demonstrate a role for ABCC4 in neuroblastoma cell proliferation and chemoresistance and provide rationale for a strategy where inhibition of ABCC4 should both attenuate the growth of neuroblastoma and sensitise tumours to ABCC4 chemotherapeutic substrates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Immunohistochemical null-phenotype for mismatch repair proteins in colonic carcinoma associated with concurrent MLH1 hypermethylation and MSH2 somatic mutations.

PubMed

Wang, Tao; Stadler, Zsofia K; Zhang, Liying; Weiser, Martin R; Basturk, Olca; Hechtman, Jaclyn F; Vakiani, Efsevia; Saltz, Lenard B; Klimstra, David S; Shia, Jinru

2018-04-01

Microsatellite instability, a well-established driver pathway in colorectal carcinogenesis, can develop in both sporadic and hereditary conditions via different molecular alterations in the DNA mismatch repair (MMR) genes. MMR protein immunohistochemistry (IHC) is currently widely used for the detection of MMR deficiency in solid tumors. The IHC test, however, can show varied staining patterns, posing challenges in the interpretation of the staining results in some cases. Here we report a case of an 80-year-old female with a colonic adenocarcinoma that exhibited an unusual "null" IHC staining pattern with complete loss of all four MMR proteins (MLH1, MSH2, MSH6, and PMS2). This led to subsequent MLH1 methylation testing and next generation sequencing which demonstrated that the loss of all MMR proteins was associated with concurrent promoter hypermethylation of MLH1 and double somatic truncating mutations in MSH2. These molecular findings, in conjunction with the patient's age being 80 years and the fact that the patient had no personal or family cancer history, indicated that the MMR deficiency was highly likely sporadic in nature. Thus, the stringent Lynch syndrome type surveillance programs were not recommended to the patient and her family members. This case illustrates a rare but important scenario where a null IHC phenotype signifies complex underlying molecular alternations that bear clinical management implications, highlighting the need for recognition and awareness of such unusual IHC staining patterns.

Bacteriophage P2 ogr and P4 delta genes act independently and are essential for P4 multiplication.

PubMed Central

Halling, C; Calendar, R

1990-01-01

Satellite bacteriophage P4 requires the products of the late genes of a helper phage such as P2 for lytic growth. Expression of the P2 late genes is positively regulated by the P2 ogr gene in a process requiring P2 DNA replication. Transactivation of P2 late gene expression by P4 requires the P4 delta gene product and works even in the absence of P2 DNA replication. We have made null mutants of the P2 ogr and P4 delta genes. In the absence of the P4 delta gene product, P4 multiplication required both the P2 ogr protein and P2 DNA replication. In the absence of the P2 ogr gene product, P4 multiplication required the P4 delta protein. In complementation experiments, we found that the P2 ogr protein was made in the absence of P2 DNA replication but could not function unless P2 DNA replicated. We produced P4 delta protein from a plasmid and found that it complemented the null P4 delta and P2 ogr mutants. Images PMID:2193911

Ablating L-FABP in SCP-2/SCP-x null mice impairs bile acid metabolism and biliary HDL-cholesterol secretion.

PubMed

Martin, Gregory G; Atshaves, Barbara P; Landrock, Kerstin K; Landrock, Danilo; Storey, Stephen M; Howles, Philip N; Kier, Ann B; Schroeder, Friedhelm

2014-12-01

On the basis of their abilities to bind bile acids and/or cholesterol, the physiological role(s) of liver fatty acid-binding protein (L-FABP) and sterol carrier protein (SCP) 2/SCP-x (SCP-2/SCP-x) gene products in biliary bile acid and cholesterol formation was examined in gene-ablated male mice. L-FABP (LKO) or L-FABP/SCP-2/SCP-x [triple-knockout (TKO)] ablation markedly decreased hepatic bile acid concentration, while SCP-2/SCP-x [double-knockout (DKO)] ablation alone had no effect. In contrast, LKO increased biliary bile acid, while DKO and TKO had no effect on biliary bile acid levels. LKO and DKO also altered biliary bile acid composition to increase bile acid hydrophobicity. Furthermore, LKO and TKO decreased hepatic uptake and biliary secretion of high-density lipoprotein (HDL)-derived 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), while DKO alone had no effect. Finally, LKO and, to a lesser extent, DKO decreased most indexes contributing to cholesterol solubility in biliary bile. These results suggest different, but complementary, roles for L-FABP and SCP-2/SCP-x in biliary bile acid and cholesterol formation. L-FABP appears to function more in hepatic retention of bile acids as well as hepatic uptake and biliary secretion of HDL-cholesterol. Conversely, SCP-2/SCP-x may function more in formation and biliary secretion of bile acid, with less impact on hepatic uptake or biliary secretion of HDL-cholesterol. Copyright © 2014 the American Physiological Society.

Regulatory Interactions of Csr Components: the RNA Binding Protein CsrA Activates csrB Transcription in Escherichia coli

PubMed Central

Gudapaty, Seshagirirao; Suzuki, Kazushi; Wang, Xin; Babitzke, Paul; Romeo, Tony

2001-01-01

The global regulator CsrA (carbon storage regulator) of Escherichia coli is a small RNA binding protein that represses various metabolic pathways and processes that are induced in the stationary phase of growth, while it activates certain exponential phase functions. Both repression and activation by CsrA involve posttranscriptional mechanisms, in which CsrA binding to mRNA leads to decreased or increased transcript stability, respectively. CsrA also binds to a small untranslated RNA, CsrB, forming a ribonucleoprotein complex, which antagonizes CsrA activity. We have further examined the regulatory interactions of CsrA and CsrB RNA. The 5′ end of the CsrB transcript was mapped, and a csrB::cam null mutant was constructed. CsrA protein and CsrB RNA levels were estimated throughout the growth curves of wild-type and isogenic csrA, csrB, rpoS, or csrA rpoS mutant strains. CsrA levels exhibited modest or negligible effects of these mutations. The intracellular concentration of CsrA exceeded the total CsrA-binding capacity of intracellular CsrB RNA. In contrast, CsrB levels were drastically decreased (∼10-fold) in the csrA mutants. CsrB transcript stability was unaffected by csrA. The expression of a csrB-lacZ transcriptional fusion containing the region from −242 to +4 bp of the csrB gene was decreased ∼20-fold by a csrA::kanR mutation in vivo but was unaffected by CsrA protein in vitro. These results reveal a significant, though most likely indirect, role for CsrA in regulating csrB transcription. Furthermore, our findings suggest that CsrA mediates an intriguing form of autoregulation, whereby its activity, but not its levels, is modulated through effects on an RNA antagonist, CsrB. PMID:11567002

A conserved START domain coenzyme Q-binding polypeptide is required for efficient Q biosynthesis, respiratory electron transport, and antioxidant function in Saccharomyces cerevisiae.

PubMed

Allan, Christopher M; Hill, Shauna; Morvaridi, Susan; Saiki, Ryoichi; Johnson, Jarrett S; Liau, Wei-Siang; Hirano, Kathleen; Kawashima, Tadashi; Ji, Ziming; Loo, Joseph A; Shepherd, Jennifer N; Clarke, Catherine F

2013-04-01

Coenzyme Qn (ubiquinone or Qn) is a redox active lipid composed of a fully substituted benzoquinone ring and a polyisoprenoid tail of n isoprene units. Saccharomyces cerevisiae coq1-coq9 mutants have defects in Q biosynthesis, lack Q6, are respiratory defective, and sensitive to stress imposed by polyunsaturated fatty acids. The hallmark phenotype of the Q-less yeast coq mutants is that respiration in isolated mitochondria can be rescued by the addition of Q2, a soluble Q analog. Yeast coq10 mutants share each of these phenotypes, with the surprising exception that they continue to produce Q6. Structure determination of the Caulobacter crescentus Coq10 homolog (CC1736) revealed a steroidogenic acute regulatory protein-related lipid transfer (START) domain, a hydrophobic tunnel known to bind specific lipids in other START domain family members. Here we show that purified CC1736 binds Q2, Q3, Q10, or demethoxy-Q3 in an equimolar ratio, but fails to bind 3-farnesyl-4-hydroxybenzoic acid, a farnesylated analog of an early Q-intermediate. Over-expression of C. crescentus CC1736 or COQ8 restores respiratory electron transport and antioxidant function of Q6 in the yeast coq10 null mutant. Studies with stable isotope ring precursors of Q reveal that early Q-biosynthetic intermediates accumulate in the coq10 mutant and de novo Q-biosynthesis is less efficient than in the wild-type yeast or rescued coq10 mutant. The results suggest that the Coq10 polypeptide:Q (protein:ligand) complex may serve essential functions in facilitating de novo Q biosynthesis and in delivering newly synthesized Q to one or more complexes of the respiratory electron transport chain. Copyright © 2012 Elsevier B.V. All rights reserved.

The real factor for polypeptide elongation in Dictyostelium cells is EF-2B, not EF-2A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshino, Tomoko; Maeda, Yasuo; Amagai, Aiko

2007-08-03

Polypeptide elongation factor 2 (EF-2) plays an essential role in protein synthesis and is believed to be indispensable for cell proliferation. Recently, it has been demonstrated that there are two kinds of EF-2 (EF-2A and EF-2B with 76.6% of sequence identity at the amino acid level) in Dictyostelium discoideum. Although the knockout of EF-2A slightly impaired cytokinesis, EF-2A null cells exhibited almost normal protein synthesis and cell growth, suggesting that there is another molecule capable of compensating for EF-2 function. Since EF-2B is the most likely candidate, we examined its function using ef-2b knockdown cells prepared by the RNAi method.more » Our results strongly suggest that EF-2B is required for protein synthesis and cell proliferation, functioning as the real EF-2. Interestingly, the expressions of ef-2a and ef-2b mRNAs during development are reversely regulated, and the ef-2b expression is greatly augmented in ef-2a null cells.« less

Bit-1 is an essential regulator of myogenic differentiation

PubMed Central

Griffiths, Genevieve S.; Doe, Jinger; Jijiwa, Mayumi; Van Ry, Pam; Cruz, Vivian; de la Vega, Michelle; Ramos, Joe W.; Burkin, Dean J.; Matter, Michelle L.

2015-01-01

Muscle differentiation requires a complex signaling cascade that leads to the production of multinucleated myofibers. Genes regulating the intrinsic mitochondrial apoptotic pathway also function in controlling cell differentiation. How such signaling pathways are regulated during differentiation is not fully understood. Bit-1 (also known as PTRH2) mutations in humans cause infantile-onset multisystem disease with muscle weakness. We demonstrate here that Bit-1 controls skeletal myogenesis through a caspase-mediated signaling pathway. Bit-1-null mice exhibit a myopathy with hypotrophic myofibers. Bit-1-null myoblasts prematurely express muscle-specific proteins. Similarly, knockdown of Bit-1 expression in C2C12 myoblasts promotes early differentiation, whereas overexpression delays differentiation. In wild-type mice, Bit-1 levels increase during differentiation. Bit-1-null myoblasts exhibited increased levels of caspase 9 and caspase 3 without increased apoptosis. Bit-1 re-expression partially rescued differentiation. In Bit-1-null muscle, Bcl-2 levels are reduced, suggesting that Bcl-2-mediated inhibition of caspase 9 and caspase 3 is decreased. Bcl-2 re-expression rescued Bit-1-mediated early differentiation in Bit-1-null myoblasts and C2C12 cells with knockdown of Bit-1 expression. These results support an unanticipated yet essential role for Bit-1 in controlling myogenesis through regulation of Bcl-2. PMID:25770104

Impaired Angiogenesis and Mobilization of Circulating Angiogenic Cells in HIF-1α Heterozygous-Null Mice after Burn Wounding

PubMed Central

Zhang, Xianjie; Liu, Lixin; Wei, Xiaofei; Tan, Yee Sun; Tong, Lana; Chang, Ryan; Ghanamah, Mohammed S.; Reinblatt, Maura; Marti, Guy P.; Harmon, John W.; Semenza, Gregg L.

2014-01-01

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that controls vascular responses to hypoxia and ischemia. In this study, mice that were heterozygous for a null allele at the locus encoding the HIF-1α subunit (HET mice) and their wild type (WT) littermates were subjected to thermal injury involving 10% of body surface area. HIF-1α protein levels were increased in burn wounds of WT but not of HET mice on day 2. Serum levels of stromal-derived factor 1α, which binds to CXCR4, were increased on day 2 in WT but not in HET mice. Circulating angiogenic cells were also increased on day 2 in WT but not in HET mice and included CXCR4+Sca1+ cells. Laser Doppler perfusion imaging demonstrated increased blood flow in burn wounds of WT but not HET mice on day 7. Immunohistochemistry on day 7 revealed a reduced number of CD31+ vessels at the healing margin of burn wounds in HET as compared to WT mice. Vessel maturation was also impaired in wounds of HET mice as determined by the number of α-smooth muscle actin-positive vessels on day 21. The remaining wound area on day 14 was significantly increased in HET mice compared to WT littermates. The percentage of healed wounds on day 14 was significantly decreased in HET mice. These data delineate a signaling pathway by which HIF-1 promotes angiogenesis during burn wound healing. PMID:20163569

Ion-binding properties of Calnuc, Ca2+ versus Mg2+--Calnuc adopts additional and unusual Ca2+-binding sites upon interaction with G-protein.

PubMed

Kanuru, Madhavi; Samuel, Jebakumar J; Balivada, Lavanya M; Aradhyam, Gopala K

2009-05-01

Calnuc is a novel, highly modular, EF-hand containing, Ca(2+)-binding, Golgi resident protein whose functions are not clear. Using amino acid sequences, we demonstrate that Calnuc is a highly conserved protein among various organisms, from Ciona intestinalis to humans. Maximum homology among all sequences is found in the region that binds to G-proteins. In humans, it is known to be expressed in a variety of tissues, and it interacts with several important protein partners. Among other proteins, Calnuc is known to interact with heterotrimeric G-proteins, specifically with the alpha-subunit. Herein, we report the structural implications of Ca(2+) and Mg(2+) binding, and illustrate that Calnuc functions as a downstream effector for G-protein alpha-subunit. Our results show that Ca(2+) binds with an affinity of 7 mum and causes structural changes. Although Mg(2+) binds to Calnuc with very weak affinity, the structural changes that it causes are further enhanced by Ca(2+) binding. Furthermore, isothermal titration calorimetry results show that Calnuc and the G-protein bind with an affinity of 13 nm. We also predict a probable function for Calnuc, that of maintaining Ca(2+) homeostasis in the cell. Using Stains-all and terbium as Ca(2+) mimic probes, we demonstrate that the Ca(2+)-binding ability of Calnuc is governed by the activity-based conformational state of the G-protein. We propose that Calnuc adopts structural sites similar to the ones seen in proteins such as annexins, c2 domains or chromogrannin A, and therefore binds more calcium ions upon binding to Gialpha. With the number of organelle-targeted G-protein-coupled receptors increasing, intracellular communication mediated by G-proteins could become a new paradigm. In this regard, we propose that Calnuc could be involved in the downstream signaling of G-proteins.

Leucine supplementation via drinking water reduces atherosclerotic lesions in apoE null mice

PubMed Central

Zhao, Yang; Dai, Xiao-yan; Zhou, Zhou; Zhao, Ge-xin; Wang, Xian; Xu, Ming-jiang

2016-01-01

Aim: Recent evidence suggests that the essential amino acid leucine may be involved in systemic cholesterol metabolism. In this study, we investigated the effects of leucine supplementation on the development of atherosclerosis in apoE null mice. Methods: ApoE null mice were fed with chow supplemented with leucine (1.5% w/v) in drinking water for 8 week. Aortic atherosclerotic lesions were examined using Oil Red O staining. Plasma lipoprotein-cholesterol levels were measured with fast protein liquid chromatography. Hepatic gene expression was detected using real-time PCR and Western blot analyses. Results: Leucine supplementation resulted in 57.6% reduction of aortic atherosclerotic lesion area in apoE null mice, accompanied by 41.2% decrease of serum LDL-C levels and 40.2% increase of serum HDL-C levels. The body weight, food intake and blood glucose level were not affected by leucine supplementation. Furthermore, leucine supplementation increased the expression of Abcg5 and Abcg8 (that were involved in hepatic cholesterol efflux) by 1.28- and 0.86-fold, respectively, and significantly increased their protein levels. Leucine supplementation also increased the expression of Srebf1, Scd1 and Pgc1b (that were involved in hepatic triglyceride metabolism) by 3.73-, 1.35- and 1.71-fold, respectively. Consequently, leucine supplementation resulted in 51.77% reduction of liver cholesterol content and 2.2-fold increase of liver triglyceride content. Additionally, leucine supplementation did not affect the serum levels of IL-6, IFN-γ, TNF-α, IL-10 and IL-12, but markedly decreased the serum level of MCP-1. Conclusion: Leucine supplementation effectively attenuates atherosclerosis in apoE null mice by improving the plasma lipid profile and reducing systemic inflammation. PMID:26687933

Mechanisms of Action of Escapin, a Bactericidal Agent in the Ink Secretion of the Sea Hare Aplysia californica: Rapid and Long-Lasting DNA Condensation and Involvement of the OxyR-Regulated Oxidative Stress Pathway

PubMed Central

Ko, Ko-Chun; Tai, Phang C.

2012-01-01

The marine snail Aplysia californica produces escapin, an l-amino acid oxidase, in its defensive ink. Escapin uses l-lysine to produce diverse products called escapin intermediate products of l-lysine (EIP-K), including α-amino-ε-caproic acid, Δ1-piperidine-2-carboxylic acid, and Δ2-piperidine-2-carboxylic acid. EIP-K and H2O2 together, but neither alone, is a powerful bactericide. Here, we report bactericidal mechanisms of escapin products on Escherichia coli. We show that EIP-K and H2O2 together cause rapid and long-lasting DNA condensation: 2-min treatment causes significant DNA condensation and killing, and 10-min treatment causes maximal effect, lasting at least 70 h. We isolated two mutants resistant to EIP-K plus H2O2, both having a single missense mutation in the oxidation regulatory gene, oxyR. A complementation assay showed that the mutated gene, oxyR(A233V), renders resistance to EIP-K plus H2O2, and a gene dosage effect leads to reduction of resistance for strains carrying wild-type oxyR. Temperature stress with EIP-K does not produce the bactericidal effect, suggesting the effect is due to a specific response to oxidative stress. The null mutant for any single DNA-binding protein—Dps, H-NS, Hup, Him, or MukB—was not resistant to EIP-K plus H2O2, suggesting that no single DNA-binding protein is necessary to mediate this bactericidal effect, but allowing for the possibility that EIP-K plus H2O2 could function through a combination of DNA-binding proteins. The bactericidal effect of EIP-K plus H2O2 was eliminated by the ferrous ion chelator 1,10-phenanthroline, and it was reduced by the hydroxyl radical scavenger thiourea, suggesting hydroxyl radicals mediate the effects of EIP-K plus H2O2. PMID:22232273

Exposure to benzo[a]pyrene of Hepatic Cytochrome P450 Reductase Null (HRN) and P450 Reductase Conditional Null (RCN) mice: Detection of benzo[a]pyrene diol epoxide-DNA adducts by immunohistochemistry and 32P-postlabelling.

PubMed

Arlt, Volker M; Poirier, Miriam C; Sykes, Sarah E; John, Kaarthik; Moserova, Michaela; Stiborova, Marie; Wolf, C Roland; Henderson, Colin J; Phillips, David H

2012-09-03

Benzo[a]pyrene (BaP) is a widespread environmental carcinogen activated by cytochrome P450 (P450) enzymes. In Hepatic P450 Reductase Null (HRN) and Reductase Conditional Null (RCN) mice, P450 oxidoreductase (Por) is deleted specifically in hepatocytes, resulting in the loss of essentially all hepatic P450 function. Treatment of HRN mice with a single i.p. or oral dose of BaP (12.5 or 125mg/kg body weight) resulted in higher DNA adduct levels in liver (up to 10-fold) than in wild-type (WT) mice, indicating that hepatic P450s appear to be more important for BaP detoxification in vivo. Similar results were obtained in RCN mice. We tested whether differences between hepatocytes and non-hepatocytes in P450 activity may underlie the increased liver BaP-DNA binding in HRN mice. Cellular localisation by immunohistochemistry of BaP-DNA adducts showed that HRN mice have ample capacity for formation of BaP-DNA adducts in liver, indicating that the metabolic process does not result in the generation of a reactive species different from that formed in WT mice. However, increased protein expression of cytochrome b(5) in hepatic microsomes of HRN relative to WT mice suggests that cytochrome b(5) may modulate the P450-mediated bioactivation of BaP in HRN mice, partially substituting the function of Por. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Drosophila GPCR Han is a receptor for the circadian clock neuropeptide PDF.

PubMed

Hyun, Seogang; Lee, Youngseok; Hong, Sung-Tae; Bang, Sunhoe; Paik, Donggi; Kang, Jongkyun; Shin, Jinwhan; Lee, Jaejung; Jeon, Keunhye; Hwang, Seungyoon; Bae, Eunkyung; Kim, Jaeseob

2005-10-20

The pigment-dispersing factor (PDF) is a neuropeptide controlling circadian behavioral rhythms in Drosophila, but its receptor is not yet known. From a large-scale temperature preference behavior screen in Drosophila, we isolated a P insertion mutant that preferred different temperatures during the day and night. This mutation, which we named han, reduced the transcript level of CG13758. We found that Han was expressed specifically in 13 pairs of circadian clock neurons in the adult brain. han null flies showed arrhythmic circadian behavior in constant darkness. The behavioral characteristics of han null mutants were similar to those of pdf null mutants. We also found that PDF binds specifically to S2 cells expressing Han, which results in the elevation of cAMP synthesis. Therefore, we herein propose that Han is a PDF receptor regulating circadian behavioral rhythm through coordination of activities of clock neurons.

Ablation of the Sam68 RNA Binding Protein Protects Mice from Age-Related Bone Loss

PubMed Central

Richard, Stéphane; Torabi, Nazi; Franco, Gladys Valverde; Tremblay, Guy A; Chen, Taiping; Vogel, Gillian; Morel, Mélanie; Cléroux, Patrick; Forget-Richard, Alexandre; Komarova, Svetlana; Tremblay, Michel L; Li, Wei; Li, Ailian; Gao, Yun Jing; Henderson, Janet E

2005-01-01

The Src substrate associated in mitosis of 68 kDa (Sam68) is a KH-type RNA binding protein that has been shown to regulate several aspects of RNA metabolism; however, its physiologic role has remained elusive. Herein we report the generation of Sam68-null mice by homologous recombination. Aged Sam68−/− mice preserved their bone mass, in sharp contrast with 12-month-old wild-type littermates in which bone mass was decreased up to approximately 75%. In fact, the bone volume of the 12-month-old Sam68−/− mice was virtually indistinguishable from that of 4-month-old wild-type or Sam68−/− mice. Sam68−/− bone marrow stromal cells had a differentiation advantage for the osteogenic pathway. Moreover, the knockdown of Sam68 using short hairpin RNA in the embryonic mesenchymal multipotential progenitor C3H10T1/2 cells resulted in more pronounced expression of the mature osteoblast marker osteocalcin when differentiation was induced with bone morphogenetic protein-2. Cultures of mouse embryo fibroblasts generated from Sam68+/+ and Sam68−/− littermates were induced to differentiate into adipocytes with culture medium containing pioglitazone and the Sam68−/− mouse embryo fibroblasts shown to have impaired adipocyte differentiation. Furthermore, in vivo it was shown that sections of bone from 12-month-old Sam68−/− mice had few marrow adipocytes compared with their age-matched wild-type littermate controls, which exhibited fatty bone marrow. Our findings identify endogenous Sam68 as a positive regulator of adipocyte differentiation and a negative regulator of osteoblast differentiation, which is consistent with Sam68 being a modulator of bone marrow mesenchymal cell differentiation, and hence bone metabolism, in aged mice. PMID:16362077

Redundant role of tissue-selective TAF(II)105 in B lymphocytes.

PubMed

Freiman, Richard N; Albright, Shane R; Chu, Leslie E; Zheng, Shuang; Liang, Hong-Erh; Sha, William C; Tjian, Robert

2002-09-01

Regulated gene expression is a complex process achieved through the function of multiple protein factors acting in concert at a given promoter. The transcription factor TFIID is a central component of the machinery regulating mRNA synthesis by RNA polymerase II. This large multiprotein complex is composed of the TATA box binding protein (TBP) and several TBP-associated factors (TAF(II)s). The recent discovery of multiple TBP-related factors and tissue-specific TAF(II)s suggests the existence of specialized TFIID complexes that likely play a critical role in regulating transcription in a gene- and tissue-specific manner. The tissue-selective factor TAF(II)105 was originally identified as a component of TFIID derived from a human B-cell line. In this report we demonstrate the specific induction of TAF(II)105 in cultured B cells in response to bacterial lipopolysaccharide (LPS). To examine the in vivo role of TAF(II)105, we have generated TAF(II)105-null mice by homologous recombination. Here we show that B-lymphocyte development is largely unaffected by the absence of TAF(II)105. TAF(II)105-null B cells can proliferate in response to LPS, produce relatively normal levels of resting antibodies, and can mount an immune response by producing antigen-specific antibodies in response to immunization. Taken together, we conclude that the function of TAF(II)105 in B cells is likely redundant with the function of other TAF(II)105-related cellular proteins.

Trigger Factor can antagonize both SecB and DnaK/DnaJ chaperone functions in Escherichia coli

PubMed Central

Ullers, Ronald S.; Ang, Debbie; Schwager, Françoise; Georgopoulos, Costa; Genevaux, Pierre

2007-01-01

Polypeptides emerging from the ribosome are assisted by a pool of molecular chaperones and targeting factors, which enable them to efficiently partition as cytoplasmic, integral membrane, or exported proteins. In Escherichia coli, the chaperones SecB, Trigger Factor (TF), and DnaK are key players in this process. Here, we report that, as with dnaK or dnaJ mutants, a secB null strain exhibits a strong cold-sensitive (Cs) phenotype. Through suppressor analyses, we found that inactivating mutations in the tig gene encoding TF fully relieve both the Cs phenotype and protein aggregation observed in the absence of SecB. This antagonistic effect of TF depends on its ribosome-binding and chaperone activities but unrelated to its peptidyl-prolyl cis/trans isomerase (PPIase) activity. Furthermore, in contrast to the previously known synergistic action of TF and DnaK/DnaJ above 30°C, a tig null mutation partially suppresses the Cs phenotype exhibited by a compromised DnaK/DnaJ chaperone machine. The antagonistic role of TF is further exemplified by the fact that the secB dnaJ double mutant is viable only in the absence of TF. Finally, we show that, in the absence of TF, more SecA and ribosomes are associated with the inner membrane, suggesting that the presence of TF directly or indirectly interferes with the process of cotranslational protein targeting to the Sec translocon. PMID:17360615

sirt1-null mice develop an autoimmune-like condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sequeira, Jedon; Boily, Gino; Bazinet, Stephanie

2008-10-01

The sirt1 gene encodes a protein deacetylase with a broad spectrum of reported substrates. Mice carrying null alleles for sirt1 are viable on outbred genetic backgrounds so we have examined them in detail to identify the biological processes that are dependent on SIRT1. Sera from adult sirt1-null mice contain antibodies that react with nuclear antigens and immune complexes become deposited in the livers and kidneys of these animals. Some of the sirt1-null animals develop a disease resembling diabetes insipidus when they approach 2 years of age although the relationship to the autoimmunity remains unclear. We interpret these observations as consistentmore » with a role for SIRT1 in sustaining normal immune function and in this way delaying the onset of autoimmune disease.« less

Akt regulates the subcellular localization of the Rab27a-binding protein JFC1 by phosphorylation.

PubMed

Johnson, Jennifer L; Pacquelet, Sandrine; Lane, William S; Eam, Boreth; Catz, Sergio D

2005-08-01

Here, we show that the Rab27a-binding protein JFC1/Slp1 (synaptotagmin-like protein) is regulated by Akt-mediated phosphorylation. Using the phosphatase and tensin homolog-null LNCaP cells and the phosphatidylinositol 3-kinase inhibitor LY294002, we show that the phosphorylation of endogenous JFC1 is dependent on the phosphatidylinositol 3-kinase/Akt pathway. JFC1 was phosphorylated in cells expressing a constitutively active Akt, confirming that it is an Akt substrate in vivo. Direct phosphorylation of JFC1 by Akt was confirmed in vitro. Using microcapillary high-performance liquid chromatography tandem mass spectrometry, we identified five Akt-phosphorylation sites in JFC1. By mutagenesis analysis and subsequent immunoprecipitation (IP), we established that Akt phosphorylates JFC1 at serine 241. JFC1 and Rab27a colocalize in the proximity of the plasma membrane in LNCaP cells. The interaction was confirmed by IP analysis and was abolished by the point mutation W83S in JFC1. Phosphorylation did not alter the ability of JFC1 to bind to Rab27a. Instead, phosphorylation by Akt dramatically decreased when JFC1 was bound to Rab27a. Finally, we show that as a consequence of in vivo phosphorylation, JFC1 dissociates from the membrane, promoting JFC1 redistribution to the cytosol. Our results suggest that Akt regulates JFC1/Slp1 function by phosphorylation and may have implications on Rab27a-containing vesicle secretion.

Impaired Thermogenesis and a Molecular Signature for Brown Adipose Tissue in Id2 Null Mice

PubMed Central

Zhou, Peng; Robles-Murguia, Maricela; Mathew, Deepa; Duffield, Giles E.

2016-01-01

Inhibitor of DNA binding 2 (ID2) is a helix-loop-helix transcriptional repressor rhythmically expressed in many adult tissues. Our previous studies have demonstrated that Id2 null mice have sex-specific elevated glucose uptake in brown adipose tissue (BAT). Here we further explored the role of Id2 in the regulation of core body temperature over the circadian cycle and the impact of Id2 deficiency on genes involved in insulin signaling and adipogenesis in BAT. We discovered a reduced core body temperature in Id2−/− mice. Moreover, in Id2−/− BAT, 30 genes including Irs1, PPARs, and PGC-1s were identified as differentially expressed in a sex-specific pattern. These data provide valuable insights into the impact of Id2 deficiency on energy homeostasis of mice in a sex-specific manner. PMID:27144179

Twin Attributes of Tyrosyl-tRNA Synthetase of Leishmania donovani: A HOUSEKEEPING PROTEIN TRANSLATION ENZYME AND A MIMIC OF HOST CHEMOKINE.

PubMed

Anand, Sneha; Madhubala, Rentala

2016-08-19

Aminoacyl-tRNA synthetases (aaRSs) are housekeeping enzymes essential for protein synthesis. Apart from their parent aminoacylation activity, several aaRSs perform non-canonical functions in diverse biological processes. The present study explores the twin attributes of Leishmania tyrosyl-tRNA synthetase (LdTyrRS) namely, aminoacylation, and as a mimic of host CXC chemokine. Leishmania donovani is a protozoan parasite. Its genome encodes a single copy of tyrosyl-tRNA synthetase. We first tested the canonical aminoacylation role of LdTyrRS. The recombinant protein was expressed, and its kinetic parameters were determined by aminoacylation assay. To study the physiological role of LdTyrRS in Leishmania, gene deletion mutations were attempted via targeted gene replacement. The heterozygous mutants showed slower growth kinetics and exhibited attenuated virulence. LdTyrRS appears to be an essential gene as the chromosomal null mutants did not survive. Our data also highlights the non-canonical function of L. donovani tyrosyl-tRNA synthetase. We show that LdTyrRS protein is present in the cytoplasm and exits from the parasite cytoplasm into the extracellular medium. The released LdTyrRS functions as a neutrophil chemoattractant. We further show that LdTyrRS specifically binds to host macrophages with its ELR (Glu-Leu-Arg) peptide motif. The ELR-CXCR2 receptor interaction mediates this binding. This interaction triggers enhanced secretion of the proinflammatory cytokines TNF-α and IL-6 by host macrophages. Our data indicates a possible immunomodulating role of LdTyrRS in Leishmania infection. This study provides a platform to explore LdTyrRS as a potential target for drug development. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Phosphorylation of serine96 of histidine-rich calcium-binding protein by the Fam20C kinase functions to prevent cardiac arrhythmia

PubMed Central

Pollak, Adam J.; Haghighi, Kobra; Kunduri, Swati; Arvanitis, Demetrios A.; Liu, Guan-Sheng; Singh, Vivek P.; Gonzalez, David J.; Sanoudou, Despina; Wiley, Sandra E.; Dixon, Jack E.; Kranias, Evangelia G.

2017-01-01

Precise Ca cycling through the sarcoplasmic reticulum (SR), a Ca storage organelle, is critical for proper cardiac muscle function. This cycling initially involves SR release of Ca via the ryanodine receptor, which is regulated by its interacting proteins junctin and triadin. The sarco/endoplasmic reticulum Ca ATPase (SERCA) pump then refills SR Ca stores. Histidine-rich Ca-binding protein (HRC) resides in the lumen of the SR, where it contributes to the regulation of Ca cycling by protecting stressed or failing hearts. The common Ser96Ala human genetic variant of HRC strongly correlates with life-threatening ventricular arrhythmias in patients with idiopathic dilated cardiomyopathy. However, the underlying molecular pathways of this disease remain undefined. Here, we demonstrate that family with sequence similarity 20C (Fam20C), a recently characterized protein kinase in the secretory pathway, phosphorylates HRC on Ser96. HRC Ser96 phosphorylation was confirmed in cells and human hearts. Furthermore, a Ser96Asp HRC variant, which mimics constitutive phosphorylation of Ser96, diminished delayed aftercontractions in HRC null cardiac myocytes. This HRC phosphomimetic variant was also able to rescue the aftercontractions elicited by the Ser96Ala variant, demonstrating that phosphorylation of Ser96 is critical for the cardioprotective function of HRC. Phosphorylation of HRC on Ser96 regulated the interactions of HRC with both triadin and SERCA2a, suggesting a unique mechanism for regulation of SR Ca homeostasis. This demonstration of the role of Fam20C-dependent phosphorylation in heart disease will open new avenues for potential therapeutic approaches against arrhythmias. PMID:28784772

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yang; National Institute of Biological Sciences, Beijing 102206; Xiong, Wei

Although a deficiency in CRY1 or CRY2 correlates with a shorter or longer circadian period, the regulation of CRY proteins in the circadian period has not been well studied. In this study, we found that both CRY1 and CRY2 were able to rescue oscillation in CRY null cells and that they displayed different periods. Furthermore, we demonstrated that protein nuclear import rates, not protein stability, regulate the period-length at the cellular level. Co-transfection of CRY1 and CRY2 in various ratios in the same cells gives rise to the predicted period length in a dose-dependent manner. Given the distinct characteristics ofmore » the C-terminal tails of the CRY1 and CRY2 proteins, our study addresses a long-standing hypothesis that the ratio of these two CRY molecules affects the clock period. - Highlights: • Rhythmic CRY2, like CRY1, in the correct CRY1 phase is sufficient to rescue clock oscillation in CRY null cells. • The short-period mammalian CRY2 protein is more stable than the CRY1 protein. • The N-terminal polypeptide of CRY2 contributes to its stability and Per2 repression, but it does not affect the period. • The C-terminal tails of CRYs regulate their protein stability and nuclear import, but the import rate governs the period. • The ratio, rather than the absolute amounts of CRY1 and CRY2 proteins, determines the period in mammalian cells.« less

Loss of REDD1 augments the rate of the overload-induced increase in muscle mass

PubMed Central

Liu, Chang; Steiner, Jennifer L.; Nader, Gustavo A.; Jefferson, Leonard S.; Kimball, Scot R.

2016-01-01

The overload-induced increase in muscle mass is accompanied by protein accretion; however, the initiating events are poorly understood. Regulated in Development and DNA Damage 1 (REDD1), a repressor of the mechanistic target of rapamycin in complex 1 (mTORC1), blunts the elevation in protein synthesis induced by acute muscle contractions. Therefore, this study was designed to determine whether REDD1 alters the rate of the overload-induced increase in muscle mass. Wild-type (WT) and REDD1-null mice underwent unilateral functional overload (OV) of the plantaris, while the contralateral sham leg served as a control. After 3 and 5 days of OV, puromycin incorporation was used as a measurement of protein synthesis. The percent increase in plantaris wet weight and protein content was greater in REDD1-null mice after 3, 5, and 10 days OV. The overload-stimulated rate of protein synthesis in the plantaris was similar between genotypes after 3 days OV, but translational capacity was lower in REDD1-null mice, indicating elevated translational efficiency. This was likely due to elevated absolute mTORC1 signaling [phosphorylation of p70S6K1 (Thr-389) and 4E-BP1 (Ser-65)]. By 5 days of OV, the rate of protein synthesis in REDD1-null mice was lower than WT mice with no difference in absolute mTORC1 signaling. Additionally, markers of autophagy (LC3II/I ratio and p62 protein) were decreased to a greater absolute extent after 3 days OV in REDD1-null mice. These data suggest that loss of REDD1 augments the rate of the OV-induced increase in muscle mass by altering multiple protein balance pathways. PMID:27465734

The Essential Role of Mbd5 in the Regulation of Somatic Growth and Glucose Homeostasis in Mice

PubMed Central

Du, Yarui; Liu, Bo; Guo, Fan; Xu, Guifang; Ding, Yuqiang; Liu, Yong; Sun, Xin; Xu, Guoliang

2012-01-01

Methyl-CpG binding domain protein 5 (MBD5) belongs to the MBD family proteins, which play central roles in transcriptional regulation and development. The significance of MBD5 function is highlighted by recent studies implicating it as a candidate gene involved in human 2q23.1 microdeletion syndrome. To investigate the physiological role of Mbd5, we generated knockout mice. The Mbd5-deficient mice showed growth retardation, wasting and pre-weaning lethality. The observed growth retardation was associated with the impairment of GH/IGF-1 axis in Mbd5-null pups. Conditional knockout of Mbd5 in the brain resulted in the similar phenotypes as whole body deletion, indicating that Mbd5 functions in the nervous system to regulate postnatal growth. Moreover, the mutant mice also displayed enhanced glucose tolerance and elevated insulin sensitivity as a result of increased insulin signaling, ultimately resulting in disturbed glucose homeostasis and hypoglycemia. These results indicate Mbd5 as an essential factor for mouse postnatal growth and maintenance of glucose homeostasis. PMID:23077600

The essential role of Mbd5 in the regulation of somatic growth and glucose homeostasis in mice.

PubMed

Du, Yarui; Liu, Bo; Guo, Fan; Xu, Guifang; Ding, Yuqiang; Liu, Yong; Sun, Xin; Xu, Guoliang

2012-01-01

Methyl-CpG binding domain protein 5 (MBD5) belongs to the MBD family proteins, which play central roles in transcriptional regulation and development. The significance of MBD5 function is highlighted by recent studies implicating it as a candidate gene involved in human 2q23.1 microdeletion syndrome. To investigate the physiological role of Mbd5, we generated knockout mice. The Mbd5-deficient mice showed growth retardation, wasting and pre-weaning lethality. The observed growth retardation was associated with the impairment of GH/IGF-1 axis in Mbd5-null pups. Conditional knockout of Mbd5 in the brain resulted in the similar phenotypes as whole body deletion, indicating that Mbd5 functions in the nervous system to regulate postnatal growth. Moreover, the mutant mice also displayed enhanced glucose tolerance and elevated insulin sensitivity as a result of increased insulin signaling, ultimately resulting in disturbed glucose homeostasis and hypoglycemia. These results indicate Mbd5 as an essential factor for mouse postnatal growth and maintenance of glucose homeostasis.

Cytosolic T3-binding protein modulates dynamic alteration of T3-mediated gene expression in cells.

PubMed

Takeshige, Keiko; Sekido, Takashi; Kitahara, Jun-ichirou; Ohkubo, Yousuke; Hiwatashi, Dai; Ishii, Hiroaki; Nishio, Shin-ichi; Takeda, Teiji; Komatsu, Mitsuhisa; Suzuki, Satoru

2014-01-01

μ-Crystallin (CRYM) is also known as NADPH-dependent cytosolic T3-binding protein. A study using CRYM-null mice suggested that CRYM stores triiodothyronine (T3) in tissues. We previously established CRYM-expressing cells derived from parental GH3 cells. To examine the precise regulation of T3-responsive genes in the presence of CRYM, we evaluated serial alterations of T3-responsive gene expression by changing pericellular T3 concentrations in the media. We estimated the constitutive expression of three T3-responsive genes, growth hormone (GH), deiodinase 1 (Dio1), and deiodinase 2 (Dio2), in two cell lines. Subsequently, we measured the responsiveness of these three genes at 4, 8, 16, and 24 h after adding various concentrations of T3. We also estimated the levels of these mRNAs 24 and 48 h after removing T3. The levels of constitutive expression of GH and Dio1 were low and high in C8 cells, respectively, while Dio2 expression was not significantly different between GH3 and C8 cells. When treated with T3, Dio2 expression was significantly enhanced in C8 cells, while there were no differences in GH or Dio1 expression between GH3 and C8 cell lines. In contrast, removal of T3 retained the mRNA expression of GH and Dio2 in C8 cells. These results suggest that CRYM expression increases and sustains the T3 responsiveness of genes in cells, especially with alteration of the pericellular T3 concentration. The heterogeneity of T3-related gene expression is dependent on cellular CRYM expression in cases of dynamic changes in pericellular T3 concentration.

Potential role of alpha-synuclein and metallothionein in lead-induced inclusion body formation.

PubMed

Zuo, Peijun; Qu, Wei; Cooper, Ryan N; Goyer, Robert A; Diwan, Bhalchandra A; Waalkes, Michael P

2009-09-01

Lead (Pb) produces aggresome-like inclusion bodies (IBs) in target cells as a toxic response. Our prior work shows metallothionein (MT) is required for this process. We used MT-I/II double knockout (MT-null) and parental wild-type (WT) cell lines to further explore the formation process of Pb-induced IBs. Unlike WT cells, MT-null cells did not form IBs after Pb exposure. Western blot of cytosol showed soluble MT protein in WT cells was lost during Pb exposure as IBs formed. Transfection of MT-I into MT-null cells allowed IBs formation after Pb exposure. Considering Pb-induced IBs may be like disease-related aggresomes, which often contain alpha-synuclein (Scna), we investigated Scna expression in cells capable (WT) and incapable (MT-null) of producing IBs after Pb exposure. Scna protein showed poor basal expression in MT-null cells. Pb exposure increased Scna expression only in WT cells. MT transfection increased Scna transcript to WT levels. In WT or MT-transfected MT-null cells, Pb-induced Scna expression rapidly increased and then decreased over 48 h as Pb-induced IBs were formed. A direct interaction between Scna and MT was confirmed ex vivo by antibody pulldown assay where the proteins coprecipitated with an antibody to MT. Pb exposure caused increased colocalization of MT and Scna proteins with time only in WT cells. In WT mice after chronic Pb exposure Scna was localized in renal cells containing forming IBs, whereas MT-null mice did not form IBs. Thus, Scna could be component of Pb-induced IBs and, with MT, may play a role in IBs formation.

The aryl hydrocarbon receptor (AHR) transcription factor regulates megakaryocytic polyploidization

PubMed Central

Lindsey, Stephan; T. Papoutsakis, Eleftherios

2012-01-01

Summary We propose that the aryl hydrocarbon receptor (AHR) is a novel transcriptional regulator of megakaryopoietic polyploidization. Functional evidence was obtained that AHR impacts in vivo megakaryocytic differentiation and maturation; compared to wild-type mice, AHR-null mice had lower platelet counts, fewer numbers of newly synthesized platelets, increased bleeding times and lower-ploidy megakaryocytes (Mks). AHR mRNA increased 3·6-fold during ex vivo megakaryocytic differentiation, but reduced or remained constant during parallel isogenic granulocytic or erythroid differentiation. We interrogated the role of AHR in megakaryopoiesis using a validated Mk model of megakaryopoiesis, the human megakaryoblastic leukaemia CHRF cell line. Upon CHRF Mk differentiation, AHR mRNA and protein levels increased, AHR protein shifted from the cytoplasm to the nucleus and AHR binding to its consensus DNA binding sequence increased. Protein and mRNA levels of the AHR transcriptional target HES1 also increased. Mk differentiation of CHRF cells where AHR or HES1 was knocked-down using RNAi resulted in lower ploidy distributions and cells that were incapable of reaching ploidy classes ≥16n. AHR knockdown also resulted in increased DNA synthesis of lower ploidy cells, without impacting apoptosis. Together, these data support a role for AHR in Mk polyploidization and in vivo platelet function, and warrant further detailed investigations. PMID:21226706

The aryl hydrocarbon receptor (AHR) transcription factor regulates megakaryocytic polyploidization.

PubMed

Lindsey, Stephan; Papoutsakis, Eleftherios T

2011-02-01

We propose that the aryl hydrocarbon receptor (AHR) is a novel transcriptional regulator of megakaryopoietic polyploidization. Functional evidence was obtained that AHR impacts in vivo megakaryocytic differentiation and maturation; compared to wild-type mice, AHR-null mice had lower platelet counts, fewer numbers of newly synthesized platelets, increased bleeding times and lower-ploidy megakaryocytes (Mks). AHR mRNA increased 3·6-fold during ex vivo megakaryocytic differentiation, but reduced or remained constant during parallel isogenic granulocytic or erythroid differentiation. We interrogated the role of AHR in megakaryopoiesis using a validated Mk model of megakaryopoiesis, the human megakaryoblastic leukaemia CHRF cell line. Upon CHRF Mk differentiation, AHR mRNA and protein levels increased, AHR protein shifted from the cytoplasm to the nucleus and AHR binding to its consensus DNA binding sequence increased. Protein and mRNA levels of the AHR transcriptional target HES1 also increased. Mk differentiation of CHRF cells where AHR or HES1 was knocked-down using RNAi resulted in lower ploidy distributions and cells that were incapable of reaching ploidy classes ≥16n. AHR knockdown also resulted in increased DNA synthesis of lower ploidy cells, without impacting apoptosis. Together, these data support a role for AHR in Mk polyploidization and in vivo platelet function, and warrant further detailed investigations. © 2011 Blackwell Publishing Ltd.

IgG red blood cell autoantibodies in autoimmune hemolytic anemia bind to epitopes on red blood cell membrane band 3 glycoprotein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Victoria, E.J.; Pierce, S.W.; Branks, M.J.

1990-01-01

Red blood cell (RBC) autoantibodies from patients with IgG warm-type autoimmune hemolytic anemia were labeled with iodine 125 and their RBC binding behavior characterized. Epitope-bearing RBC membrane polypeptides were identified after autoantibody immunoprecipitation of labeled membranes and immunoblotting. Immunoaffinity isolation of labeled membrane proteins with 12 different IgG hemolytic autoantibodies with protein A-agarose revealed a major polypeptide at Mr 95 to 110 kd, which coelectrophoresed on sodium dodecylsulfate-polyacrylamide gel electrophoresis with a membrane component isolated with sheep IgG anti-band 3. Immunoprecipitation studies with chymotrypsinized RBCs resulted in the recovery of two labeled membrane polypeptides with molecular weights characteristically resulting frommore » the chymotryptic fragmentation of band 3. Immunoblotting with sheep IgG anti-band 3 of the immunoprecipitated polypeptides confirmed that hemolytic autoantibody binding led to recovery of band 3 or its fragments. Two 125I-labeled IgG hemolytic autoantibodies showed binding behavior consistent with epitope localization on band 3. The labeled RBC autoantibodies bound immunospecifically to all types of human RBC tested, including those of rare Rh type (Rh-null, D--) at a site density of approximately 10(6) per RBC. The 125I-IgG in two labeled autoantibodies was 84% and 92% adsorbable by human and higher nonhuman primate RBCs. Antigen-negative animal RBC bound less than 10%, consistent with immunospecific RBC binding. IgG-1 was the major subclass in five autoantibodies tested; one of six fixed complement; and autoantibody IgG appeared polyclonal by isoelectric focusing. We conclude that IgG eluted from RBCs of patients with autoimmune hemolytic anemia consists predominantly of a single totally RBC-adsorbable antibody population that binds to antigenic determinants on band 3.« less

The transcriptional co-factor RIP140 regulates mammary gland development by promoting the generation of key mitogenic signals.

PubMed

Nautiyal, Jaya; Steel, Jennifer H; Mane, Meritxell Rosell; Oduwole, Olayiwola; Poliandri, Ariel; Alexi, Xanthippi; Wood, Nicholas; Poutanen, Matti; Zwart, Wilbert; Stingl, John; Parker, Malcolm G

2013-03-01

Nuclear receptor interacting protein (Nrip1), also known as RIP140, is a co-regulator for nuclear receptors that plays an essential role in ovulation by regulating the expression of the epidermal growth factor-like family of growth factors. Although several studies indicate a role for RIP140 in breast cancer, its role in the development of the mammary gland is unclear. By using RIP140-null and RIP140 transgenic mice, we demonstrate that RIP140 is an essential factor for normal mammary gland development and that it functions by mediating oestrogen signalling. RIP140-null mice exhibit minimal ductal elongation with no side-branching, whereas RIP140-overexpressing mice show increased cell proliferation and ductal branching with age. Tissue recombination experiments demonstrate that RIP140 expression is required in both the mammary epithelial and stromal compartments for ductal elongation during puberty and that loss of RIP140 leads to a catastrophic loss of the mammary epithelium, whereas RIP140 overexpression augments the mammary basal cell population and shifts the progenitor/differentiated cell balance within the luminal cell compartment towards the progenitors. For the first time, we present a genome-wide global view of oestrogen receptor-α (ERα) binding events in the developing mammary gland, which unravels 881 ERα binding sites. Unbiased evaluation of several ERα binding sites for RIP140 co-occupancy reveals selectivity and demonstrates that RIP140 acts as a co-regulator with ERα to regulate directly the expression of amphiregulin (Areg), the progesterone receptor (Pgr) and signal transducer and activator of transcription 5a (Stat5a), factors that influence key mitogenic pathways that regulate normal mammary gland development.

The SAMPL4 host-guest blind prediction challenge: an overview.

PubMed

Muddana, Hari S; Fenley, Andrew T; Mobley, David L; Gilson, Michael K

2014-04-01

Prospective validation of methods for computing binding affinities can help assess their predictive power and thus set reasonable expectations for their performance in drug design applications. Supramolecular host-guest systems are excellent model systems for testing such affinity prediction methods, because their small size and limited conformational flexibility, relative to proteins, allows higher throughput and better numerical convergence. The SAMPL4 prediction challenge therefore included a series of host-guest systems, based on two hosts, cucurbit[7]uril and octa-acid. Binding affinities in aqueous solution were measured experimentally for a total of 23 guest molecules. Participants submitted 35 sets of computational predictions for these host-guest systems, based on methods ranging from simple docking, to extensive free energy simulations, to quantum mechanical calculations. Over half of the predictions provided better correlations with experiment than two simple null models, but most methods underperformed the null models in terms of root mean squared error and linear regression slope. Interestingly, the overall performance across all SAMPL4 submissions was similar to that for the prior SAMPL3 host-guest challenge, although the experimentalists took steps to simplify the current challenge. While some methods performed fairly consistently across both hosts, no single approach emerged as consistent top performer, and the nonsystematic nature of the various submissions made it impossible to draw definitive conclusions regarding the best choices of energy models or sampling algorithms. Salt effects emerged as an issue in the calculation of absolute binding affinities of cucurbit[7]uril-guest systems, but were not expected to affect the relative affinities significantly. Useful directions for future rounds of the challenge might involve encouraging participants to carry out some calculations that replicate each others' studies, and to systematically explore parameter options.

The mitochondrial SIR2 related protein 2 (SIR2RP2) impacts Leishmania donovani growth and infectivity

PubMed Central

Mittal, Nimisha; Muthuswami, Rohini

2017-01-01

Background Leishmania donovani, a protozoan parasite is the major causative agent of visceral leishmaniasis. Increased toxicity and resistance to the existing repertoire of drugs has been reported. Hence, an urgent need exists for identifying newer drugs and drug targets. Previous reports have shown sirtuins (Silent Information Regulator) from kinetoplastids as promising drug targets. Leishmania species code for three SIR2 (Silent Information Regulator) related proteins. Here, we for the first time report the functional characterization of SIR2 related protein 2 (SIR2RP2) of L. donovani. Methodology Recombinant L. donovani SIR2RP2 was expressed in E. coli and purified. The enzymatic functions of SIR2RP2 were determined. The subcellular localization of LdSIR2RP2 was done by constructing C-terminal GFP-tagged full-length LdSIR2RP2. Deletion mutants of LdSIR2RP2 were generated in Leishmania by double targeted gene replacement methodology. These null mutants were tested for their proliferation, virulence, cell cycle defects, mitochondrial functioning and sensitivity to known SIR2 inhibitors. Conclusion Our data suggests that LdSIR2RP2 possesses NAD+-dependent ADP-ribosyltransferase activity. However, NAD+-dependent deacetylase and desuccinylase activities were not detected. The protein localises to the mitochondrion of the promastigotes. Gene deletion studies showed that ΔLdSIR2RP2 null mutants had restrictive growth phenotype associated with accumulation of cells in the G2/M phase and compromised mitochondrial functioning. The null mutants had attenuated infectivity. Deletion of LdSIR2RP2 resulted in increased sensitivity of the parasites to the known SIR2 inhibitors. The sirtuin inhibitors inhibited the ADP-ribosyltransferase activity of recombinant LdSIR2RP2. In conclusion, sirtuins could be used as potential new drug targets for visceral leishmaniasis. PMID:28493888

In vivo replication of an ICP34.5 second-site suppressor mutant following corneal infection correlates with in vitro regulation of eIF2 alpha phosphorylation.

PubMed

Ward, Stephen L; Scheuner, Donalyn; Poppers, Jeremy; Kaufman, Randal J; Mohr, Ian; Leib, David A

2003-04-01

In animal models of herpes simplex virus type 1 (HSV-1) infection, ICP34.5-null viruses are avirulent and also fail to grow in a variety of cultured cells due to their inability to prevent RNA-dependent protein kinase (PKR)-mediated inhibition of protein synthesis. We show here that the inability of ICP34.5 mutants to grow in vitro is due specifically to the accumulation of phosphorylated eIF2 alpha. Mutations suppressing the in vitro phenotype of ICP34.5-null mutants have been described which map to the unique short region of the HSV-1 genome, resulting in dysregulated expression of the US11 gene. Despite the inability of the suppressor mutation to suppress the avirulent phenotype of the ICP34.5-null parental virus following intracranial inoculation, the suppressor mutation enhanced virus growth in the cornea, trigeminal ganglia, and periocular skin following corneal infection compared to that with the ICP34.5-null virus. The phosphorylation state of eIF2 alpha following in vitro infection with the suppressor virus was examined to determine if in vivo differences could be attributed to differential regulation of eIF2 alpha phosphorylation. The suppressor virus prevented accumulation of phosphorylated eIF2 alpha, while the wild-type virus substantially reduced eIF2 alpha phosphorylation levels. These data suggest that US11 functions as a PKR antagonist in vivo, although its activity may be modulated by tissue-specific differences in translation regulation.

In Vivo Replication of an ICP34.5 Second-Site Suppressor Mutant following Corneal Infection Correlates with In Vitro Regulation of eIF2α Phosphorylation

PubMed Central

Ward, Stephen L.; Scheuner, Donalyn; Poppers, Jeremy; Kaufman, Randal J.; Mohr, Ian; Leib, David A.

2003-01-01

In animal models of herpes simplex virus type 1 (HSV-1) infection, ICP34.5-null viruses are avirulent and also fail to grow in a variety of cultured cells due to their inability to prevent RNA-dependent protein kinase (PKR)-mediated inhibition of protein synthesis. We show here that the inability of ICP34.5 mutants to grow in vitro is due specifically to the accumulation of phosphorylated eIF2α. Mutations suppressing the in vitro phenotype of ICP34.5-null mutants have been described which map to the unique short region of the HSV-1 genome, resulting in dysregulated expression of the US11 gene. Despite the inability of the suppressor mutation to suppress the avirulent phenotype of the ICP34.5-null parental virus following intracranial inoculation, the suppressor mutation enhanced virus growth in the cornea, trigeminal ganglia, and periocular skin following corneal infection compared to that with the ICP34.5-null virus. The phosphorylation state of eIF2α following in vitro infection with the suppressor virus was examined to determine if in vivo differences could be attributed to differential regulation of eIF2α phosphorylation. The suppressor virus prevented accumulation of phosphorylated eIF2α, while the wild-type virus substantially reduced eIF2α phosphorylation levels. These data suggest that US11 functions as a PKR antagonist in vivo, although its activity may be modulated by tissue-specific differences in translation regulation. PMID:12663769

Selective enrichment of metal-binding proteins based on magnetic core/shell microspheres functionalized with metal cations.

PubMed

Fang, Caiyun; Zhang, Lei; Zhang, Xiaoqin; Lu, Haojie

2015-06-21

Metal binding proteins play many important roles in a broad range of biological processes. Characterization of metal binding proteins is important for understanding their structure and biological functions, thus leading to a clear understanding of metal associated diseases. The present study is the first to investigate the effectiveness of magnetic microspheres functionalized with metal cations (Ca(2+), Cu(2+), Zn(2+) and Fe(3+)) as the absorbent matrix in IMAC technology to enrich metal containing/binding proteins. The putative metal binding proteins in rat liver were then globally characterized by using this strategy which is very easy to handle and can capture a number of metal binding proteins effectively. In total, 185 putative metal binding proteins were identified from rat liver including some known less abundant and membrane-bound metal binding proteins such as Plcg1, Acsl5, etc. The identified proteins are involved in many important processes including binding, catalytic activity, translation elongation factor activity, electron carrier activity, and so on.

[Determination of plasma protein binding rate of arctiin and arctigenin with ultrafiltration].

PubMed

Han, Xue-Ying; Wang, Wei; Tan, Ri-Qiu; Dou, De-Qiang

2013-02-01

To determine the plasma protein binding rate of arctiin and arctigenin. The ultrafiltration combined with HPLC was employed to determine the plasma protein binding rate of arctiin and arctigenin as well as rat plasma and healthy human plasma proteins. The plasma protein binding rate of arctiin with rat plasma at the concentrations of 64. 29, 32.14, 16.07 mg x L(-1) were (71.2 +/- 2.0)%, (73.4 +/- 0.61)%, (78.2 +/- 1.9)%, respectively; while the plasma protein binding rate of arctiin with healthy human plasma at the above concentrations were (64.8 +/- 3.1)%, (64.5 +/- 2.5)%, (77.5 +/- 1.7)%, respectively. The plasma protein binding rate of arctigenin with rat plasma at the concentrations of 77.42, 38.71, 19.36 mg x L(-1) were (96.7 +/- 0.41)%, (96.8 +/- 1.6)%, (97.3 +/- 0.46)%, respectively; while the plasma protein binding rate of arctigenin with normal human plasma at the above concentrations were (94.7 +/- 3.1)%, (96.8 +/- 1.6)%, (97.9 +/- 1.3)%, respectively. The binding rate of arctiin with rat plasma protein was moderate, which is slightly higher than the binding rate of arctiin with healthy human plasma protein. The plasma protein binding rates of arctigenin with both rat plasma and healthy human plasma are very high.

A mutant of the Arabidopsis thaliana Toc159 gene accumulates reduced levels of linolenic acid and monogalactosyldiacylglycerol

USDA-ARS?s Scientific Manuscript database

Previous studies have shown that a null mutant of Arabidopsis that lacks Toc159 receptor is impaired in chloroplast biogenesis and incapable of importing photosynthetic proteins. The mutant is referred to as plastid protein import 2 or ppi2, and has an albino phenotype. In this study, we measured ...

How to talk about protein‐level false discovery rates in shotgun proteomics

PubMed Central

The, Matthew; Tasnim, Ayesha

2016-01-01

A frequently sought output from a shotgun proteomics experiment is a list of proteins that we believe to have been present in the analyzed sample before proteolytic digestion. The standard technique to control for errors in such lists is to enforce a preset threshold for the false discovery rate (FDR). Many consider protein‐level FDRs a difficult and vague concept, as the measurement entities, spectra, are manifestations of peptides and not proteins. Here, we argue that this confusion is unnecessary and provide a framework on how to think about protein‐level FDRs, starting from its basic principle: the null hypothesis. Specifically, we point out that two competing null hypotheses are used concurrently in today's protein inference methods, which has gone unnoticed by many. Using simulations of a shotgun proteomics experiment, we show how confusing one null hypothesis for the other can lead to serious discrepancies in the FDR. Furthermore, we demonstrate how the same simulations can be used to verify FDR estimates of protein inference methods. In particular, we show that, for a simple protein inference method, decoy models can be used to accurately estimate protein‐level FDRs for both competing null hypotheses. PMID:27503675

INVOLVED IN DE NOVO 2-containing complex involved in RNA-directed DNA methylation in Arabidopsis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ausin, Israel; Greenberg, Maxim V.C.; Simanshu, Dhirendra K.

2012-10-23

At least three pathways control maintenance of DNA cytosine methylation in Arabidopsis thaliana. However, the RNA-directed DNA methylation (RdDM) pathway is solely responsible for establishment of this silencing mark. We previously described INVOLVED IN DE NOVO 2 (IDN2) as being an RNA-binding RdDM component that is required for DNA methylation establishment. In this study, we describe the discovery of two partially redundant proteins that are paralogous to IDN2 and that form a stable complex with IDN2 in vivo. Null mutations in both genes, termed IDN2-LIKE 1 and IDN2-LIKE 2 (IDNL1 and IDNL2), result in a phenotype that mirrors, but doesmore » not further enhance, the idn2 mutant phenotype. Genetic analysis suggests that this complex acts in a step in the downstream portion of the RdDM pathway. We also have performed structural analysis showing that the IDN2 XS domain adopts an RNA recognition motif (RRM) fold. Finally, genome-wide DNA methylation and expression analysis confirms the placement of the IDN proteins in an RdDM pathway that affects DNA methylation and transcriptional control at many sites in the genome. Results from this study identify and describe two unique components of the RdDM machinery, adding to our understanding of DNA methylation control in the Arabidopsis genome.« less

Myelin Proteolipid Protein Complexes with αv Integrin and AMPA Receptors In Vivo and Regulates AMPA-Dependent Oligodendrocyte Progenitor Cell Migration through the Modulation of Cell-Surface GluR2 Expression

PubMed Central

Harlow, Danielle E.; Saul, Katherine E.; Komuro, Hitoshi

2015-01-01

In previous studies, stimulation of ionotropic AMPA/kainate glutamate receptors on cultured oligodendrocyte cells induced the formation of a signaling complex that includes the AMPA receptor, integrins, calcium-binding proteins, and, surprisingly, the myelin proteolipid protein (PLP). AMPA stimulation of cultured oligodendrocyte progenitor cells (OPCs) also caused an increase in OPC migration. The current studies focused primarily on the formation of the PLP–αv integrin–AMPA receptor complex in vivo and whether complex formation impacts OPC migration in the brain. We found that in wild-type cerebellum, PLP associates with αv integrin and the calcium-impermeable GluR2 subunit of the AMPA receptor, but in mice lacking PLP, αv integrin did not associate with GluR2. Live imaging studies of OPC migration in ex vivo cerebellar slices demonstrated altered OPC migratory responses to neurotransmitter stimulation in the absence of PLP and GluR2 or when αv integrin levels were reduced. Chemotaxis assays of purified OPCs revealed that AMPA stimulation was neither attractive nor repulsive but clearly increased the migration rate of wild-type but not PLP null OPCs. AMPA receptor stimulation of wild-type OPCs caused decreased cell-surface expression of the GluR2 AMPA receptor subunit and increased intracellular Ca2+ signaling, whereas PLP null OPCs did not reduce GluR2 at the cell surface or increase Ca2+ signaling in response to AMPA treatment. Together, these studies demonstrate that PLP is critical for OPC responses to glutamate signaling and has important implications for OPC responses when levels of glutamate are high in the extracellular space, such as following demyelination. SIGNIFICANCE STATEMENT After demyelination, such as occurs in multiple sclerosis, remyelination of axons is often incomplete, leading to loss of neuronal function and clinical disability. Remyelination may fail because oligodendrocyte precursor cells (OPCs) do not completely migrate into demyelinated areas or OPCs in lesions may not mature into myelinating oligodendrocytes. We have found that the myelin proteolipid protein is critical to regulating OPC migratory responses to the neurotransmitter glutamate through modulation of cell-surface expression of the calcium-impermeable GluR2 subunit of the AMPA glutamate receptor and increased intercellular Ca2+ signaling. Altered glutamate homeostasis has been reported in demyelinated lesions. Therefore, understanding how OPCs respond to glutamate has important implications for treatment after white matter injury and disease. PMID:26311781

Complexity of CNC transcription factors as revealed by gene targeting of the Nrf3 locus.

PubMed

Derjuga, Anna; Gourley, Tania S; Holm, Teresa M; Heng, Henry H Q; Shivdasani, Ramesh A; Ahmed, Rafi; Andrews, Nancy C; Blank, Volker

2004-04-01

Cap'n'collar (CNC) family basic leucine zipper transcription factors play crucial roles in the regulation of mammalian gene expression and development. To determine the in vivo function of the CNC protein Nrf3 (NF-E2-related factor 3), we generated mice deficient in this transcription factor. We performed targeted disruption of two Nrf3 exons coding for CNC homology, basic DNA-binding, and leucine zipper dimerization domains. Nrf3 null mice developed normally and revealed no obvious phenotypic differences compared to wild-type animals. Nrf3(-/-) mice were fertile, and gross anatomy as well as behavior appeared normal. The mice showed normal age progression and did not show any apparent additional phenotype during their life span. We observed no differences in various blood parameters and chemistry values. We infected wild-type and Nrf3(-/-) mice with acute lymphocytic choriomeningitis virus and found no differences in these animals with respect to their number of virus-specific CD8 and CD4 T cells as well as their B-lymphocyte response. To determine whether the mild phenotype of Nrf3 null animals is due to functional redundancy, we generated mice deficient in multiple CNC factors. Contrary to our expectations, an absence of Nrf3 does not seem to cause additional lethality in compound Nrf3(-/-)/Nrf2(-/-) and Nrf3(-/-)/p45(-/-) mice. We hypothesize that the role of Nrf3 in vivo may become apparent only after appropriate challenge to the mice.

Hyperactivation of Nrf2 in early tubular development induces nephrogenic diabetes insipidus

PubMed Central

Suzuki, Takafumi; Seki, Shiori; Hiramoto, Keiichiro; Naganuma, Eriko; Kobayashi, Eri H.; Yamaoka, Ayaka; Baird, Liam; Takahashi, Nobuyuki; Sato, Hiroshi; Yamamoto, Masayuki

2017-01-01

NF-E2-related factor-2 (Nrf2) regulates cellular responses to oxidative and electrophilic stress. Loss of Keap1 increases Nrf2 protein levels, and Keap1-null mice die of oesophageal hyperkeratosis because of Nrf2 hyperactivation. Here we show that deletion of oesophageal Nrf2 in Keap1-null mice allows survival until adulthood, but the animals develop polyuria with low osmolality and bilateral hydronephrosis. This phenotype is caused by defects in water reabsorption that are the result of reduced aquaporin 2 levels in the kidney. Renal tubular deletion of Keap1 promotes nephrogenic diabetes insipidus features, confirming that Nrf2 activation in developing tubular cells causes a water reabsorption defect. These findings suggest that Nrf2 activity should be tightly controlled during development in order to maintain renal homeostasis. In addition, tissue-specific ablation of Nrf2 in Keap1-null mice might create useful animal models to uncover novel physiological functions of Nrf2. PMID:28233855

PLEKHM1/DEF8/RAB7 complex regulates lysosome positioning and bone homeostasis

PubMed Central

Fujiwara, Toshifumi; Ye, Shiqiao; Winchell, Caylin G.; Andrews, Norma W.; Voth, Daniel E.; Varughese, Kottayil I.; Mackintosh, Samuel G.; Feng, Yunfeng; Nakamura, Takashi; Manolagas, Stavros C.

2016-01-01

Mutations of the Plekhm1 gene in humans and rats cause osteopetrosis, an inherited bone disease characterized by diminished bone resorption by osteoclasts. PLEKHM1 binds to RAB7 and is critical for lysosome trafficking. However, the molecular mechanisms by which PLEKHM1 regulates lysosomal pathways remain unknown. Here, we generated germline and conditional Plekhm1-deficient mice. These mice displayed no overt abnormalities in major organs, except for an increase in trabecular bone mass. Furthermore, loss of PLEKHM1 abrogated the peripheral distribution of lysosomes and bone resorption in osteoclasts. Mechanistically, we indicated that DEF8 interacts with PLEKHM1 and promotes its binding to RAB7, whereas the binding of FAM98A and NDEL1 with PLEKHM1 connects lysosomes to microtubules. Importantly, suppression of these proteins results in lysosome positioning and bone resorption defects similar to those of Plekhm1-null osteoclasts. Thus, PLHKEM1, DEF8, FAM98A, and NDEL1 constitute a molecular complex that regulates lysosome positioning and secretion through RAB7. PMID:27777970

Cellular prion protein protects from inflammatory and neuropathic pain

PubMed Central

2011-01-01

Cellular prion protein (PrPC) inhibits N-Methyl-D-Aspartate (NMDA) receptors. Since NMDA receptors play an important role in the transmission of pain signals in the dorsal horn of spinal cord, we thus wanted to determine if PrPC null mice show a reduced threshold for various pain behaviours. We compared nociceptive thresholds between wild type and PrPC null mice in models of inflammatory and neuropathic pain, in the presence and the absence of a NMDA receptor antagonist. 2-3 months old male PrPC null mice exhibited an MK-801 sensitive decrease in the paw withdrawal threshold in response both mechanical and thermal stimuli. PrPC null mice also exhibited significantly longer licking/biting time during both the first and second phases of formalin-induced inflammation of the paw, which was again prevented by treatment of the mice with MK-801, and responded more strongly to glutamate injection into the paw. Compared to wild type animals, PrPC null mice also exhibited a significantly greater nociceptive response (licking/biting) after intrathecal injection of NMDA. Sciatic nerve ligation resulted in MK-801 sensitive neuropathic pain in wild-type mice, but did not further augment the basal increase in pain behaviour observed in the null mice, suggesting that mice lacking PrPC may already be in a state of tonic central sensitization. Altogether, our data indicate that PrPC exerts a critical role in modulating nociceptive transmission at the spinal cord level, and fit with the concept of NMDA receptor hyperfunction in the absence of PrPC. PMID:21843375

Mechanism of the G-protein mimetic nanobody binding to a muscarinic G-protein-coupled receptor.

PubMed

Miao, Yinglong; McCammon, J Andrew

2018-03-20

Protein-protein binding is key in cellular signaling processes. Molecular dynamics (MD) simulations of protein-protein binding, however, are challenging due to limited timescales. In particular, binding of the medically important G-protein-coupled receptors (GPCRs) with intracellular signaling proteins has not been simulated with MD to date. Here, we report a successful simulation of the binding of a G-protein mimetic nanobody to the M 2 muscarinic GPCR using the robust Gaussian accelerated MD (GaMD) method. Through long-timescale GaMD simulations over 4,500 ns, the nanobody was observed to bind the receptor intracellular G-protein-coupling site, with a minimum rmsd of 2.48 Å in the nanobody core domain compared with the X-ray structure. Binding of the nanobody allosterically closed the orthosteric ligand-binding pocket, being consistent with the recent experimental finding. In the absence of nanobody binding, the receptor orthosteric pocket sampled open and fully open conformations. The GaMD simulations revealed two low-energy intermediate states during nanobody binding to the M 2 receptor. The flexible receptor intracellular loops contribute remarkable electrostatic, polar, and hydrophobic residue interactions in recognition and binding of the nanobody. These simulations provided important insights into the mechanism of GPCR-nanobody binding and demonstrated the applicability of GaMD in modeling dynamic protein-protein interactions.

2-Oxoglutarate levels control adenosine nucleotide binding by Herbaspirillum seropedicae PII proteins.

PubMed

Oliveira, Marco A S; Gerhardt, Edileusa C M; Huergo, Luciano F; Souza, Emanuel M; Pedrosa, Fábio O; Chubatsu, Leda S

2015-12-01

Nitrogen metabolism in Proteobacteria is controlled by the Ntr system, in which PII proteins play a pivotal role, controlling the activity of target proteins in response to the metabolic state of the cell. Characterization of the binding of molecular effectors to these proteins can provide information about their regulation. Here, the binding of ATP, ADP and 2-oxoglutarate (2-OG) to the Herbaspirillum seropedicae PII proteins, GlnB and GlnK, was characterized using isothermal titration calorimetry. Results show that these proteins can bind three molecules of ATP, ADP and 2-OG with homotropic negative cooperativity, and 2-OG binding stabilizes the binding of ATP. Results also show that the affinity of uridylylated forms of GlnB and GlnK for nucleotides is significantly lower than that of the nonuridylylated proteins. Furthermore, fluctuations in the intracellular concentration of 2-OG in response to nitrogen availability are shown. Results suggest that under nitrogen-limiting conditions, PII proteins tend to bind ATP and 2-OG. By contrast, after an ammonium shock, a decrease in the 2-OG concentration is observed causing a decrease in the affinity of PII proteins for ATP. This phenomenon may facilitate the exchange of ATP for ADP on the ligand-binding pocket of PII proteins, thus it is likely that under low ammonium, low 2-OG levels would favor the ADP-bound state. © 2015 FEBS.

LmaPA2G4, a Homolog of Human Ebp1, Is an Essential Gene and Inhibits Cell Proliferation in L. major

PubMed Central

Joyce, Michelle V.; Morales, Miguel A.

2014-01-01

We have identified LmaPA2G4, a homolog of the human proliferation-associated 2G4 protein (also termed Ebp1), in a phosphoproteomic screening. Multiple sequence alignment and cluster analysis revealed that LmaPA2G4 is a non-peptidase member of the M24 family of metallopeptidases. This pseudoenzyme is structurally related to methionine aminopeptidases. A null mutant system based on negative selection allowed us to demonstrate that LmaPA2G4 is an essential gene in Leishmania major. Over-expression of LmaPA2G4 did not alter cell morphology or the ability to differentiate into metacyclic and amastigote stages. Interestingly, the over-expression affected cell proliferation and virulence in mouse footpad analysis. LmaPA2G4 binds a synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid [poly(I∶C)] as shown in an electrophoretic mobility shift assay (EMSA). Quantitative proteomics revealed that the over-expression of LmaPA2G4 led to accumulation of factors involved in translation initiation and elongation. Significantly, we found a strong reduction of de novo protein biosynthesis in transgenic parasites using a non-radioactive metabolic labeling assay. In conclusion, LmaPA2G4 is an essential gene and is potentially implicated in fundamental biological mechanisms, such as translation, making it an attractive target for therapeutic intervention. PMID:24421916

A novel class of plant-specific zinc-dependent DNA-binding protein that binds to A/T-rich DNA sequences

PubMed Central

Nagano, Yukio; Furuhashi, Hirofumi; Inaba, Takehito; Sasaki, Yukiko

2001-01-01

Complementary DNA encoding a DNA-binding protein, designated PLATZ1 (plant AT-rich sequence- and zinc-binding protein 1), was isolated from peas. The amino acid sequence of the protein is similar to those of other uncharacterized proteins predicted from the genome sequences of higher plants. However, no paralogous sequences have been found outside the plant kingdom. Multiple alignments among these paralogous proteins show that several cysteine and histidine residues are invariant, suggesting that these proteins are a novel class of zinc-dependent DNA-binding proteins with two distantly located regions, C-x2-H-x11-C-x2-C-x(4–5)-C-x2-C-x(3–7)-H-x2-H and C-x2-C-x(10–11)-C-x3-C. In an electrophoretic mobility shift assay, the zinc chelator 1,10-o-phenanthroline inhibited DNA binding, and two distant zinc-binding regions were required for DNA binding. A protein blot with 65ZnCl2 showed that both regions are required for zinc-binding activity. The PLATZ1 protein non-specifically binds to A/T-rich sequences, including the upstream region of the pea GTPase pra2 and plastocyanin petE genes. Expression of the PLATZ1 repressed those of the reporter constructs containing the coding sequence of luciferase gene driven by the cauliflower mosaic virus (CaMV) 35S90 promoter fused to the tandem repeat of the A/T-rich sequences. These results indicate that PLATZ1 is a novel class of plant-specific zinc-dependent DNA-binding protein responsible for A/T-rich sequence-mediated transcriptional repression. PMID:11600698

Proteomic Analysis of ABCA1-Null Macrophages Reveals a Role for Stomatin-Like Protein-2 in Raft Composition and Toll-Like Receptor Signaling.

PubMed

Chowdhury, Saiful M; Zhu, Xuewei; Aloor, Jim J; Azzam, Kathleen M; Gabor, Kristin A; Ge, William; Addo, Kezia A; Tomer, Kenneth B; Parks, John S; Fessler, Michael B

2015-07-01

Lipid raft membrane microdomains organize signaling by many prototypical receptors, including the Toll-like receptors (TLRs) of the innate immune system. Raft-localization of proteins is widely thought to be regulated by raft cholesterol levels, but this is largely on the basis of studies that have manipulated cell cholesterol using crude and poorly specific chemical tools, such as β-cyclodextrins. To date, there has been no proteome-scale investigation of whether endogenous regulators of intracellular cholesterol trafficking, such as the ATP binding cassette (ABC)A1 lipid efflux transporter, regulate targeting of proteins to rafts. Abca1(-/-) macrophages have cholesterol-laden rafts that have been reported to contain increased levels of select proteins, including TLR4, the lipopolysaccharide receptor. Here, using quantitative proteomic profiling, we identified 383 proteins in raft isolates from Abca1(+/+) and Abca1(-/-) macrophages. ABCA1 deletion induced wide-ranging changes to the raft proteome. Remarkably, many of these changes were similar to those seen in Abca1(+/+) macrophages after lipopolysaccharide exposure. Stomatin-like protein (SLP)-2, a member of the stomatin-prohibitin-flotillin-HflK/C family of membrane scaffolding proteins, was robustly and specifically increased in Abca1(-/-) rafts. Pursuing SLP-2 function, we found that rafts of SLP-2-silenced macrophages had markedly abnormal composition. SLP-2 silencing did not compromise ABCA1-dependent cholesterol efflux but reduced macrophage responsiveness to multiple TLR ligands. This was associated with reduced raft levels of the TLR co-receptor, CD14, and defective lipopolysaccharide-induced recruitment of the common TLR adaptor, MyD88, to rafts. Taken together, we show that the lipid transporter ABCA1 regulates the protein repertoire of rafts and identify SLP-2 as an ABCA1-dependent regulator of raft composition and of the innate immune response. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Proteomic Analysis of ABCA1-Null Macrophages Reveals a Role for Stomatin-Like Protein-2 in Raft Composition and Toll-Like Receptor Signaling*

PubMed Central

Chowdhury, Saiful M.; Zhu, Xuewei; Aloor, Jim J.; Azzam, Kathleen M.; Gabor, Kristin A.; Ge, William; Addo, Kezia A.; Tomer, Kenneth B.; Parks, John S.; Fessler, Michael B.

2015-01-01

Lipid raft membrane microdomains organize signaling by many prototypical receptors, including the Toll-like receptors (TLRs) of the innate immune system. Raft-localization of proteins is widely thought to be regulated by raft cholesterol levels, but this is largely on the basis of studies that have manipulated cell cholesterol using crude and poorly specific chemical tools, such as β-cyclodextrins. To date, there has been no proteome-scale investigation of whether endogenous regulators of intracellular cholesterol trafficking, such as the ATP binding cassette (ABC)A1 lipid efflux transporter, regulate targeting of proteins to rafts. Abca1−/− macrophages have cholesterol-laden rafts that have been reported to contain increased levels of select proteins, including TLR4, the lipopolysaccharide receptor. Here, using quantitative proteomic profiling, we identified 383 proteins in raft isolates from Abca1+/+ and Abca1−/− macrophages. ABCA1 deletion induced wide-ranging changes to the raft proteome. Remarkably, many of these changes were similar to those seen in Abca1+/+ macrophages after lipopolysaccharide exposure. Stomatin-like protein (SLP)-2, a member of the stomatin-prohibitin-flotillin-HflK/C family of membrane scaffolding proteins, was robustly and specifically increased in Abca1−/− rafts. Pursuing SLP-2 function, we found that rafts of SLP-2-silenced macrophages had markedly abnormal composition. SLP-2 silencing did not compromise ABCA1-dependent cholesterol efflux but reduced macrophage responsiveness to multiple TLR ligands. This was associated with reduced raft levels of the TLR co-receptor, CD14, and defective lipopolysaccharide-induced recruitment of the common TLR adaptor, MyD88, to rafts. Taken together, we show that the lipid transporter ABCA1 regulates the protein repertoire of rafts and identify SLP-2 as an ABCA1-dependent regulator of raft composition and of the innate immune response. PMID:25910759

Loss of the Greatwall Kinase Weakens the Spindle Assembly Checkpoint.

PubMed

Diril, M Kasim; Bisteau, Xavier; Kitagawa, Mayumi; Caldez, Matias J; Wee, Sheena; Gunaratne, Jayantha; Lee, Sang Hyun; Kaldis, Philipp

2016-09-01

The Greatwall kinase/Mastl is an essential gene that indirectly inhibits the phosphatase activity toward mitotic Cdk1 substrates. Here we show that although Mastl knockout (MastlNULL) MEFs enter mitosis, they progress through mitosis without completing cytokinesis despite the presence of misaligned chromosomes, which causes chromosome segregation defects. Furthermore, we uncover the requirement of Mastl for robust spindle assembly checkpoint (SAC) maintenance since the duration of mitotic arrest caused by microtubule poisons in MastlNULL MEFs is shortened, which correlates with premature disappearance of the essential SAC protein Mad1 at the kinetochores. Notably, MastlNULL MEFs display reduced phosphorylation of a number of proteins in mitosis, which include the essential SAC kinase MPS1. We further demonstrate that Mastl is required for multi-site phosphorylation of MPS1 as well as robust MPS1 kinase activity in mitosis. In contrast, treatment of MastlNULL cells with the phosphatase inhibitor okadaic acid (OKA) rescues the defects in MPS1 kinase activity, mislocalization of phospho-MPS1 as well as Mad1 at the kinetochore, and premature SAC silencing. Moreover, using in vitro dephosphorylation assays, we demonstrate that Mastl promotes persistent MPS1 phosphorylation by inhibiting PP2A/B55-mediated MPS1 dephosphorylation rather than affecting Cdk1 kinase activity. Our findings establish a key regulatory function of the Greatwall kinase/Mastl->PP2A/B55 pathway in preventing premature SAC silencing.

Loss of the Greatwall Kinase Weakens the Spindle Assembly Checkpoint

PubMed Central

Kitagawa, Mayumi; Caldez, Matias J.; Gunaratne, Jayantha; Lee, Sang Hyun

2016-01-01

The Greatwall kinase/Mastl is an essential gene that indirectly inhibits the phosphatase activity toward mitotic Cdk1 substrates. Here we show that although Mastl knockout (MastlNULL) MEFs enter mitosis, they progress through mitosis without completing cytokinesis despite the presence of misaligned chromosomes, which causes chromosome segregation defects. Furthermore, we uncover the requirement of Mastl for robust spindle assembly checkpoint (SAC) maintenance since the duration of mitotic arrest caused by microtubule poisons in MastlNULL MEFs is shortened, which correlates with premature disappearance of the essential SAC protein Mad1 at the kinetochores. Notably, MastlNULL MEFs display reduced phosphorylation of a number of proteins in mitosis, which include the essential SAC kinase MPS1. We further demonstrate that Mastl is required for multi-site phosphorylation of MPS1 as well as robust MPS1 kinase activity in mitosis. In contrast, treatment of MastlNULL cells with the phosphatase inhibitor okadaic acid (OKA) rescues the defects in MPS1 kinase activity, mislocalization of phospho-MPS1 as well as Mad1 at the kinetochore, and premature SAC silencing. Moreover, using in vitro dephosphorylation assays, we demonstrate that Mastl promotes persistent MPS1 phosphorylation by inhibiting PP2A/B55-mediated MPS1 dephosphorylation rather than affecting Cdk1 kinase activity. Our findings establish a key regulatory function of the Greatwall kinase/Mastl->PP2A/B55 pathway in preventing premature SAC silencing. PMID:27631493

Requirement of the yeast MSH3 and MSH6 genes for MSH2-dependent genomic stability.

PubMed

Johnson, R E; Kovvali, G K; Prakash, L; Prakash, S

1996-03-29

Defects in DNA mismatch repair result in instability of simple repetitive DNA sequences and elevated levels of spontaneous mutability. The human G/T mismatch binding protein, GTBP/p160, has been suggested to have a role in the repair of base-base and single nucleotide insertion-deletion mismatches. Here we examine the role of the yeast GTBP homolog, MSH6, in mismatch repair. We show that both MSH6 and MSH3 genes are essential for normal genomic stability. Interestingly, although mutations in either MSH3 or MSH6 do not cause the extreme microsatellite instability and spontaneous mutability observed in the msh2 mutant, yeast cells harboring null mutations in both the MSH3 and MSH6 genes exhibit microsatellite instability and mutability similar to that in the msh2 mutant. Results from epistasis analyses indicate that MSH2 functions in mismatch repair in conjunction with MSH3 or MSH6 and that MSH3 and MSH6 constitute alternate pathways of MSH2-dependent mismatch repair.

Impaired wound healing in mice deficient in a matricellular protein SPARC (osteonectin, BM-40)

PubMed Central

Basu, Amitabha; Kligman, Lorraine H; Samulewicz, Stefan J; Howe, Chin C

2001-01-01

Background SPARC is a matricellular protein involved in cell-matrix interactions. From expression patterns at the wound site and in vitro studies, SPARC has been implicated in the control of wound healing. Here we examined the function of SPARC in cutaneous wound healing using SPARC-null mice and dermal fibroblasts derived from them. Results In large (25 mm) wounds, SPARC-null mice showed a significant delay in healing as compared to wild-type mice (31 days versus 24 days). Granulation tissue formation and extracellular matrix protein production were delayed in small 6 mm SPARC-null wounds initially but were resolved by day 6. In in vitro wound-healing assays, while wild-type primary dermal fibroblasts showed essentially complete wound closure at 11 hours, wound closure of SPARC-null cells was incomplete even at 31 hours. Addition of purified SPARC restored the normal time course of wound closure. Treatment of SPARC-null cells with mitomycin C to analyze cell migration without cell proliferation showed that wound repair remained incomplete after 31 hours. Cell proliferation as measured by 3H-thymidine incorporation and collagen gel contraction by SPARC-null cells were not compromised. Conclusions A significant delay in healing large excisional wounds and setback in granulation tissue formation and extracellular matrix protein production in small wounds establish that SPARC is required for granulation tissue formation during normal repair of skin wounds in mice. A defect in wound closure in vitro indicates that SPARC regulates cell migration. We conclude that SPARC plays a role in wound repair by promoting fibroblast migration and thus granulation tissue formation. PMID:11532190

Rational design of a conformation-switchable Ca2+- and Tb3+-binding protein without the use of multiple coupled metal-binding sites.

PubMed

Li, Shunyi; Yang, Wei; Maniccia, Anna W; Barrow, Doyle; Tjong, Harianto; Zhou, Huan-Xiang; Yang, Jenny J

2008-10-01

Ca2+, as a messenger of signal transduction, regulates numerous target molecules via Ca2+-induced conformational changes. Investigation into the determinants for Ca2+-induced conformational change is often impeded by cooperativity between multiple metal-binding sites or protein oligomerization in naturally occurring proteins. To dissect the relative contributions of key determinants for Ca2+-dependent conformational changes, we report the design of a single-site Ca2+-binding protein (CD2.trigger) created by altering charged residues at an electrostatically sensitive location on the surface of the host protein rat Cluster of Differentiation 2 (CD2).CD2.trigger binds to Tb3+ and Ca2+ with dissociation constants of 0.3 +/- 0.1 and 90 +/- 25 microM, respectively. This protein is largely unfolded in the absence of metal ions at physiological pH, but Tb3+ or Ca2+ binding results in folding of the native-like conformation. Neutralization of the charged coordination residues, either by mutation or protonation, similarly induces folding of the protein. The control of a major conformational change by a single Ca2+ ion, achieved on a protein designed without reliance on sequence similarity to known Ca2+-dependent proteins and coupled metal-binding sites, represents an important step in the design of trigger proteins.

Keep your fingers off my DNA: protein-protein interactions mediated by C2H2 zinc finger domains.

PubMed

Brayer, Kathryn J; Segal, David J

2008-01-01

Cys2-His2 (C2H2) zinc finger domains (ZFs) were originally identified as DNA-binding domains, and uncharacterized domains are typically assumed to function in DNA binding. However, a growing body of evidence suggests an important and widespread role for these domains in protein binding. There are even examples of zinc fingers that support both DNA and protein interactions, which can be found in well-known DNA-binding proteins such as Sp1, Zif268, and Ying Yang 1 (YY1). C2H2 protein-protein interactions (PPIs) are proving to be more abundant than previously appreciated, more plastic than their DNA-binding counterparts, and more variable and complex in their interactions surfaces. Here we review the current knowledge of over 100 C2H2 zinc finger-mediated PPIs, focusing on what is known about the binding surface, contributions of individual fingers to the interaction, and function. An accurate understanding of zinc finger biology will likely require greater insights into the potential protein interaction capabilities of C2H2 ZFs.

Normalization, bias correction, and peak calling for ChIP-seq

PubMed Central

Diaz, Aaron; Park, Kiyoub; Lim, Daniel A.; Song, Jun S.

2012-01-01

Next-generation sequencing is rapidly transforming our ability to profile the transcriptional, genetic, and epigenetic states of a cell. In particular, sequencing DNA from the immunoprecipitation of protein-DNA complexes (ChIP-seq) and methylated DNA (MeDIP-seq) can reveal the locations of protein binding sites and epigenetic modifications. These approaches contain numerous biases which may significantly influence the interpretation of the resulting data. Rigorous computational methods for detecting and removing such biases are still lacking. Also, multi-sample normalization still remains an important open problem. This theoretical paper systematically characterizes the biases and properties of ChIP-seq data by comparing 62 separate publicly available datasets, using rigorous statistical models and signal processing techniques. Statistical methods for separating ChIP-seq signal from background noise, as well as correcting enrichment test statistics for sequence-dependent and sonication biases, are presented. Our method effectively separates reads into signal and background components prior to normalization, improving the signal-to-noise ratio. Moreover, most peak callers currently use a generic null model which suffers from low specificity at the sensitivity level requisite for detecting subtle, but true, ChIP enrichment. The proposed method of determining a cell type-specific null model, which accounts for cell type-specific biases, is shown to be capable of achieving a lower false discovery rate at a given significance threshold than current methods. PMID:22499706

Heterozygous Null Bone Morphogenetic Protein Receptor Type 2 Mutations Promote SRC Kinase-dependent Caveolar Trafficking Defects and Endothelial Dysfunction in Pulmonary Arterial Hypertension*

PubMed Central

Prewitt, Allison R.; Ghose, Sampa; Frump, Andrea L.; Datta, Arumima; Austin, Eric D.; Kenworthy, Anne K.; de Caestecker, Mark P.

2015-01-01

Hereditary pulmonary arterial hypertension (HPAH) is a rare, fatal disease of the pulmonary vasculature. The majority of HPAH patients inherit mutations in the bone morphogenetic protein type 2 receptor gene (BMPR2), but how these promote pulmonary vascular disease is unclear. HPAH patients have features of pulmonary endothelial cell (PEC) dysfunction including increased vascular permeability and perivascular inflammation associated with decreased PEC barrier function. Recently, frameshift mutations in the caveolar structural protein gene Caveolin-1 (CAV-1) were identified in two patients with non-BMPR2-associated HPAH. Because caveolae regulate endothelial function and vascular permeability, we hypothesized that defects in caveolar function might be a common mechanism by which BMPR2 mutations promote pulmonary vascular disease. To explore this, we isolated PECs from mice carrying heterozygous null Bmpr2 mutations (Bmpr2+/−) similar to those found in the majority of HPAH patients. We show that Bmpr2+/− PECs have increased numbers and intracellular localization of caveolae and caveolar structural proteins CAV-1 and Cavin-1 and that these defects are reversed after blocking endocytosis with dynasore. SRC kinase is also constitutively activated in Bmpr2+/− PECs, and localization of CAV-1 to the plasma membrane is restored after treating Bmpr2+/− PECs with the SRC kinase inhibitor 3-(4-chlorophenyl)-1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine (PP2). Late outgrowth endothelial progenitor cells isolated from HPAH patients show similar increased activation of SRC kinase. Moreover, Bmpr2+/− PECs have impaired endothelial barrier function, and barrier function is restored after treatment with PP2. These data suggest that heterozygous null BMPR2 mutations promote SRC-dependent caveolar trafficking defects in PECs and that this may contribute to pulmonary endothelial barrier dysfunction in HPAH patients. PMID:25411245

EMK protein kinase-null mice: dwarfism and hypofertility associated with alterations in the somatotrope and prolactin pathways.

PubMed

Bessone, S; Vidal, F; Le Bouc, Y; Epelbaum, J; Bluet-Pajot, M T; Darmon, M

1999-10-01

Gene trapping was used in embryonic stem (ES) cells in an attempt to inactivate genes involved in development. The Emk (ELKL motif kinase) gene has been disrupted and a mutant mouse line derived. Previous work had shown that EMK kinases, called MARK in the rat, exert a major control on microtubule stability by phosphorylating microtubule-associated proteins and that genes homologous to Emk in yeast or Caenorhabditis elegans are essential for cell and embryonic polarity. Although we found the Emk gene to be active in the preimplantation mouse embryo and then to show a widespread expression, Emk-null mice had no embryonic defect and were viable. They show an overall proportionate dwarfism and a peculiar hypofertility: homozygotes are not fertile when intercrossed, but are fertile in other types of crosses. Insulin-like growth factor I (IGF I) and IGF-binding protein 3 (IGFBP3) were reduced in the plasma of homozygotes of both sexes. A direct implication of the EMK kinase in IGF I plasmatic production is unlikely because the Emk gene does not seem to be expressed in hepatocytes. Nevertheless, GH assayed at arbitrary times in plasma did not show differences between genotypes and GH concentrations in pituitary extracts were not found to be altered in homozygotes. Our results, though, do not exclude the possibility that in the mutants the overall quantity of GH secreted daily is reduced. Our observation of a smaller size of the pituitaries of the mutants is in favor of this hypothesis. The prolactin concentration in the pituitaries was much lowered in homozygous females, but it was normal in males. The possible involvement of EMK protein kinase in hormone secretion in the pituitary and/or the hypothalamus, via the microtubule network, is discussed. Copyright 1999 Academic Press.

A pollen-specific novel calmodulin-binding protein with tetratricopeptide repeats

NASA Technical Reports Server (NTRS)

Safadi, F.; Reddy, V. S.; Reddy, A. S.

2000-01-01

Calcium is essential for pollen germination and pollen tube growth. A large body of information has established a link between elevation of cytosolic Ca(2+) at the pollen tube tip and its growth. Since the action of Ca(2+) is primarily mediated by Ca(2+)-binding proteins such as calmodulin (CaM), identification of CaM-binding proteins in pollen should provide insights into the mechanisms by which Ca(2+) regulates pollen germination and tube growth. In this study, a CaM-binding protein from maize pollen (maize pollen calmodulin-binding protein, MPCBP) was isolated in a protein-protein interaction-based screening using (35)S-labeled CaM as a probe. MPCBP has a molecular mass of about 72 kDa and contains three tetratricopeptide repeats (TPR) suggesting that it is a member of the TPR family of proteins. MPCBP protein shares a high sequence identity with two hypothetical TPR-containing proteins from Arabidopsis. Using gel overlay assays and CaM-Sepharose binding, we show that the bacterially expressed MPCBP binds to bovine CaM and three CaM isoforms from Arabidopsis in a Ca(2+)-dependent manner. To map the CaM-binding domain several truncated versions of the MPCBP were expressed in bacteria and tested for their ability to bind CaM. Based on these studies, the CaM-binding domain was mapped to an 18-amino acid stretch between the first and second TPR regions. Gel and fluorescence shift assays performed with CaM and a CaM-binding synthetic peptide further confirmed MPCBP binding to CaM. Western, Northern, and reverse transcriptase-polymerase chain reaction analysis have shown that MPCBP expression is specific to pollen. MPCBP was detected in both soluble and microsomal proteins. Immunoblots showed the presence of MPCBP in mature and germinating pollen. Pollen-specific expression of MPCBP, its CaM-binding properties, and the presence of TPR motifs suggest a role for this protein in Ca(2+)-regulated events during pollen germination and growth.

Mild myelin disruption elicits early alteration in behavior and proliferation in the subventricular zone.

PubMed

Gould, Elizabeth A; Busquet, Nicolas; Shepherd, Douglas; Dietz, Robert M; Herson, Paco S; Simoes de Souza, Fabio M; Li, Anan; George, Nicholas M; Restrepo, Diego; Macklin, Wendy B

2018-02-13

Myelin, the insulating sheath around axons, supports axon function. An important question is the impact of mild myelin disruption. In the absence of the myelin protein proteolipid protein (PLP1), myelin is generated but with age, axonal function/maintenance is disrupted. Axon disruption occurs in Plp1 -null mice as early as 2 months in cortical projection neurons. High-volume cellular quantification techniques revealed a region-specific increase in oligodendrocyte density in the olfactory bulb and rostral corpus callosum that increased during adulthood. A distinct proliferative response of progenitor cells was observed in the subventricular zone (SVZ), while the number and proliferation of parenchymal oligodendrocyte progenitor cells was unchanged. This SVZ proliferative response occurred prior to evidence of axonal disruption. Thus, a novel SVZ response contributes to the region-specific increase in oligodendrocytes in Plp1 -null mice. Young adult Plp1- null mice exhibited subtle but substantial behavioral alterations, indicative of an early impact of mild myelin disruption. © 2018, Gould et al.

Mild myelin disruption elicits early alteration in behavior and proliferation in the subventricular zone

PubMed Central

Gould, Elizabeth A; Busquet, Nicolas; Shepherd, Douglas; Dietz, Robert M; Herson, Paco S; Simoes de Souza, Fabio M; Li, Anan; George, Nicholas M

2018-01-01

Myelin, the insulating sheath around axons, supports axon function. An important question is the impact of mild myelin disruption. In the absence of the myelin protein proteolipid protein (PLP1), myelin is generated but with age, axonal function/maintenance is disrupted. Axon disruption occurs in Plp1-null mice as early as 2 months in cortical projection neurons. High-volume cellular quantification techniques revealed a region-specific increase in oligodendrocyte density in the olfactory bulb and rostral corpus callosum that increased during adulthood. A distinct proliferative response of progenitor cells was observed in the subventricular zone (SVZ), while the number and proliferation of parenchymal oligodendrocyte progenitor cells was unchanged. This SVZ proliferative response occurred prior to evidence of axonal disruption. Thus, a novel SVZ response contributes to the region-specific increase in oligodendrocytes in Plp1-null mice. Young adult Plp1-null mice exhibited subtle but substantial behavioral alterations, indicative of an early impact of mild myelin disruption. PMID:29436368

Pyruvate dehydrogenase subunit β of Lactobacillus plantarum is a collagen adhesin involved in biofilm formation.

PubMed

Salzillo, Marzia; Vastano, Valeria; Capri, Ugo; Muscariello, Lidia; Marasco, Rosangela

2017-04-01

Multi-functional surface proteins have been observed in a variety of pathogenic bacteria, where they mediate host cell adhesion and invasion, as well as in commensal bacterial species, were they mediate positive interaction with the host. Among these proteins, some glycolytic enzymes, expressed on the bacterial cell surface, can bind human extracellular matrix components (ECM). A major target for them is collagen, an abundant glycoprotein of connective tissues. We have previously shown that the enolase EnoA1 of Lactobacillus plantarum, one of the most predominant species in the gut microbiota of healthy individuals, is involved in binding with collagen type I (CnI). In this study, we found that PDHB, a component of the pyruvate dehydrogenase complex, contributes to the L. plantarum LM3 adhesion to CnI. By a cellular adhesion assay to immobilized CnI, we show that LM3-B1 cells, carrying a null mutation in the pdhB gene, bind to CnI - coated surfaces less efficiently than wild-type cells. Moreover, we show that the PDHB-CnI interaction requires a native state for PDHB. We also analyzed the ability to develop biofilm in wild-type and mutant strains and we found that the lack of the PDHB on cell surface generates cells partially impaired in biofilm development. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

SH2 Domains Serve as Lipid-Binding Modules for pTyr-Signaling Proteins.

PubMed

Park, Mi-Jeong; Sheng, Ren; Silkov, Antonina; Jung, Da-Jung; Wang, Zhi-Gang; Xin, Yao; Kim, Hyunjin; Thiagarajan-Rosenkranz, Pallavi; Song, Seohyeon; Yoon, Youngdae; Nam, Wonhee; Kim, Ilshin; Kim, Eui; Lee, Dong-Gyu; Chen, Yong; Singaram, Indira; Wang, Li; Jang, Myoung Ho; Hwang, Cheol-Sang; Honig, Barry; Ryu, Sungho; Lorieau, Justin; Kim, You-Me; Cho, Wonhwa

2016-04-07

The Src-homology 2 (SH2) domain is a protein interaction domain that directs myriad phosphotyrosine (pY)-signaling pathways. Genome-wide screening of human SH2 domains reveals that ∼90% of SH2 domains bind plasma membrane lipids and many have high phosphoinositide specificity. They bind lipids using surface cationic patches separate from pY-binding pockets, thus binding lipids and the pY motif independently. The patches form grooves for specific lipid headgroup recognition or flat surfaces for non-specific membrane binding and both types of interaction are important for cellular function and regulation of SH2 domain-containing proteins. Cellular studies with ZAP70 showed that multiple lipids bind its C-terminal SH2 domain in a spatiotemporally specific manner and thereby exert exquisite spatiotemporal control over its protein binding and signaling activities in T cells. Collectively, this study reveals how lipids control SH2 domain-mediated cellular protein-protein interaction networks and suggest a new strategy for therapeutic modulation of pY-signaling pathways. Copyright © 2016 Elsevier Inc. All rights reserved.

The Yersiniabactin-Associated ATP Binding Cassette Proteins YbtP and YbtQ Enhance Escherichia coli Fitness during High-Titer Cystitis

PubMed Central

Koh, Eun-Ik; Hung, Chia S.

2016-01-01

The Yersinia high-pathogenicity island (HPI) is common to multiple virulence strategies used by Escherichia coli strains associated with urinary tract infection (UTI). Among the genes in this island are ybtP and ybtQ, encoding distinctive ATP binding cassette (ABC) proteins associated with iron(III)-yersiniabactin import in Yersinia pestis. In this study, we compared the impact of ybtPQ on a model E. coli cystitis strain during in vitro culture and experimental murine infections. A ybtPQ-null mutant exhibited no growth defect under standard culture conditions, consistent with nonessentiality in this background. A growth defect phenotype was observed and genetically complemented in vitro during iron(III)-yersiniabactin-dependent growth. Following inoculation into the bladders of C3H/HEN and C3H/HeOuJ mice, this strain exhibited a profound, 106-fold competitive infection defect in the subgroup of mice that progressed to high-titer bladder infections. These results identify a virulence role for YbtPQ in the highly inflammatory microenvironment characteristic of high-titer cystitis. The profound competitive defect may relate to the apparent selection of Yersinia HPI-positive E. coli in uncomplicated clinical UTIs. PMID:26883590

Improved Spin-Echo-Edited NMR Diffusion Measurements

NASA Astrophysics Data System (ADS)

Otto, William H.; Larive, Cynthia K.

2001-12-01

The need for simple and robust schemes for the analysis of ligand-protein binding has resulted in the development of diffusion-based NMR techniques that can be used to assay binding in protein solutions containing a mixture of several ligands. As a means of gaining spectral selectivity in NMR diffusion measurements, a simple experiment, the gradient modified spin-echo (GOSE), has been developed to reject the resonances of coupled spins and detect only the singlets in the 1H NMR spectrum. This is accomplished by first using a spin echo to null the resonances of the coupled spins. Following the spin echo, the singlet magnetization is flipped out of the transverse plane and a dephasing gradient is applied to reduce the spectral artifacts resulting from incomplete cancellation of the J-coupled resonances. The resulting modular sequence is combined here with the BPPSTE pulse sequence; however, it could be easily incorporated into any pulse sequence where additional spectral selectivity is desired. Results obtained with the GOSE-BPPSTE pulse sequence are compared with those obtained with the BPPSTE and CPMG-BPPSTE experiments for a mixture containing the ligands resorcinol and tryptophan in a solution of human serum albumin.

DACH1 inhibits transforming growth factor-beta signaling through binding Smad4.

PubMed

Wu, Kongming; Yang, Ying; Wang, Chenguang; Davoli, Maria A; D'Amico, Mark; Li, Anping; Cveklova, Kveta; Kozmik, Zbynek; Lisanti, Michael P; Russell, Robert G; Cvekl, Ales; Pestell, Richard G

2003-12-19

The vertebrate homologues of Drosophila dachsund, DACH1 and DACH2, have been implicated as important regulatory genes in development. DACH1 plays a role in retinal and pituitary precursor cell proliferation and DACH2 plays a specific role in myogenesis. DACH proteins contain a domain (DS domain) that is conserved with the proto-oncogenes Ski and Sno. Since the Ski/Sno proto-oncogenes repress AP-1 and SMAD signaling, we hypothesized that DACH1 might play a similar cellular function. Herein, DACH1 was found to be expressed in breast cancer cell lines and to inhibit transforming growth factor-beta (TGF-beta)-induced apoptosis. DACH1 repressed TGF-beta induction of AP-1 and Smad signaling in gene reporter assays and repressed endogenous TGF-beta-responsive genes by microarray analyses. DACH1 bound to endogenous NCoR and Smad4 in cultured cells and DACH1 co-localized with NCoR in nuclear dotlike structures. NCoR enhanced DACH1 repression, and the repression of TGF-beta-induced AP-1 or Smad signaling by DACH1 required the DACH1 DS domain. The DS domain of DACH was sufficient for NCoR binding at a Smad4-binding site. Smad4 was required for DACH1 repression of Smad signaling. In Smad4 null HTB-134 cells, DACH1 inhibited the activation of SBE-4 reporter activity induced by Smad2 or Smad3 only in the presence of Smad4. DACH1 participates in the negative regulation of TGF-beta signaling by interacting with NCoR and Smad4.

In vivo binding properties of SH2 domains from GTPase-activating protein and phosphatidylinositol 3-kinase.

PubMed Central

Cooper, J A; Kashishian, A

1993-01-01

We have used a transient expression system and mutant platelet-derived growth factor (PDGF) receptors to study the binding specificities of the Src homology 2 (SH2) regions of the Ras GTPase-activator protein (GAP) and the p85 alpha subunit of phosphatidylinositol 3-kinase (PI3 kinase). A number of fusion proteins, each tagged with an epitope allowing recognition by a monoclonal antibody, were expressed at levels comparable to those of endogenous GAP. Fusion proteins containing the central SH2-SH3-SH2 region of GAP or the C-terminal region of p85 alpha, which includes two SH2 domains, bound to PDGF receptors in response to PDGF stimulation. Both fusion proteins showed the same requirements for tyrosine phosphorylation sites in the PDGF receptor as the full-length proteins from which they were derived, i.e., binding of the GAP fusion protein was reduced by mutation of Tyr-771, and binding of the p85 fusion protein was reduced by mutation of Tyr-740, Tyr-751, or both residues. Fusion proteins containing single SH2 domains from either GAP or p85 alpha did not bind detectably to PDGF receptors in this system, suggesting that two SH2 domains in a single polypeptide cooperate to raise the affinity of binding. The sequence specificities of individual SH2 domains were deduced from the binding properties of fusion proteins containing one SH2 domain from GAP and another from p85. The results suggest that the C-terminal GAP SH2 domain specifies binding to Tyr-771, the C-terminal p85 alpha SH2 domain binds to either Tyr-740 or Tyr-751, and each protein's N-terminal SH2 domain binds to unidentified phosphorylation sites.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:8382774

[Glutamate-binding membrane proteins from human platelets].

PubMed

Gurevich, V S; Popov, Iu G; Gorodinskiĭ, A I; Dambinova, S A

1991-09-01

Solubilization of the total membrane fraction of human platelets in a 2% solution of sodium deoxycholate and subsequent affinity chromatography on glutamate agarose resulted in two protein fractions possessing a glutamate-binding activity. As can be evidenced from radioligand binding data, the first fraction contains two types of binding sites (Kd1 = 1 microM, Bmax 1 = 100 pmol/mg of protein; Kd2 = 9.3 microMm Bmax2 = 395 pmol/mg of protein). The second fraction has only one type of binding sites (Kd = 1 microM, Bmax = = 110 pmol/mg of protein). SDS-PAAG electrophoresis revealed the presence in the first fraction of proteins with Mr of 14, 24, 56 and 155 kDa, whereas the second fraction was found to contain 14, 46, 71 and 155 kDa proteins. Solid phase immunoenzymatic analysis using poly- and monoclonal specific antibodies against mammalian brain glutamate-binding proteins revealed a marked immunochemical similarity of the isolated protein fractions with human brain synaptic membrane glutamate-binding proteins.

The Sequence-specific Peptide-binding Activity of the Protein Sulfide Isomerase AGR2 Directs Its Stable Binding to the Oncogenic Receptor EpCAM.

PubMed

Mohtar, M Aiman; Hernychova, Lenka; O'Neill, J Robert; Lawrence, Melanie L; Murray, Euan; Vojtesek, Borek; Hupp, Ted R

2018-04-01

AGR2 is an oncogenic endoplasmic reticulum (ER)-resident protein disulfide isomerase. AGR2 protein has a relatively unique property for a chaperone in that it can bind sequence-specifically to a specific peptide motif (TTIYY). A synthetic TTIYY-containing peptide column was used to affinity-purify AGR2 from crude lysates highlighting peptide selectivity in complex mixtures. Hydrogen-deuterium exchange mass spectrometry localized the dominant region in AGR2 that interacts with the TTIYY peptide to within a structural loop from amino acids 131-135 (VDPSL). A peptide binding site consensus of Tx[IL][YF][YF] was developed for AGR2 by measuring its activity against a mutant peptide library. Screening the human proteome for proteins harboring this motif revealed an enrichment in transmembrane proteins and we focused on validating EpCAM as a potential AGR2-interacting protein. AGR2 and EpCAM proteins formed a dose-dependent protein-protein interaction in vitro Proximity ligation assays demonstrated that endogenous AGR2 and EpCAM protein associate in cells. Introducing a single alanine mutation in EpCAM at Tyr251 attenuated its binding to AGR2 in vitro and in cells. Hydrogen-deuterium exchange mass spectrometry was used to identify a stable binding site for AGR2 on EpCAM, adjacent to the TLIYY motif and surrounding EpCAM's detergent binding site. These data define a dominant site on AGR2 that mediates its specific peptide-binding function. EpCAM forms a model client protein for AGR2 to study how an ER-resident chaperone can dock specifically to a peptide motif and regulate the trafficking a protein destined for the secretory pathway. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Saccharomyces cerevisiae FKBP12 binds Arabidopsis thaliana TOR and its expression in plants leads to rapamycin susceptibility.

PubMed

Sormani, Rodnay; Yao, Lei; Menand, Benoît; Ennar, Najla; Lecampion, Cécile; Meyer, Christian; Robaglia, Christophe

2007-06-01

The eukaryotic TOR pathway controls translation, growth and the cell cycle in response to environmental signals such as nutrients or growth-stimulating factors. The TOR protein kinase can be inactivated by the antibiotic rapamycin following the formation of a ternary complex between TOR, rapamycin and FKBP12 proteins. The TOR protein is also found in higher plants despite the fact that they are rapamycin insensitive. Previous findings using the yeast two hybrid system suggest that the FKBP12 plant homolog is unable to form a complex with rapamycin and TOR, while the FRB domain of plant TOR is still able to bind to heterologous FKBP12 in the presence of rapamycin. The resistance to rapamycin is therefore limiting the molecular dissection of the TOR pathway in higher plants. Here we show that none of the FKBPs from the model plant Arabidopsis (AtFKBPs) is able to form a ternary complex with the FRB domain of AtTOR in the presence of rapamycin in a two hybrid system. An antibody has been raised against the AtTOR protein and binding of recombinant yeast ScFKBP12 to native Arabidopsis TOR in the presence of rapamycin was demonstrated in pull-down experiments. Transgenic lines expressing ScFKBP12 were produced and were found to display a rapamycin-dependent reduction of the primary root growth and a lowered accumulation of high molecular weight polysomes. These results further strengthen the idea that plant resistance to rapamycin evolved as a consequence of mutations in plant FKBP proteins. The production of rapamycin-sensitive plants through the expression of the ScFKBP12 protein illustrates the conservation of the TOR pathway in eukaryotes. Since AtTOR null mutants were found to be embryo lethal 1, transgenic ScFKBP12 plants will provide an useful tool for the post-embryonic study of plant TOR functions. This work also establish for the first time a link between TOR activity and translation in plant cells.

Regulation of COX-2–mediated signaling by α3 type IV noncollagenous domain in tumor angiogenesis

PubMed Central

Boosani, Chandra Shekhar; Mannam, Arjuna P.; Cosgrove, Dominic; Silva, Rita; Hodivala-Dilke, Kairbaan M.; Keshamouni, Venkateshwar G.

2007-01-01

Human α3 chain, a noncollagenous domain of type IV collagen [α3(IV)NC1], inhibits angiogenesis and tumor growth. These biologic functions are partly attributed to the binding of α3(IV)NC1 to αVβ3 and α3β1 integrins. α3(IV)NC1 binds αVβ3 integrin, leading to translation inhibition by inhibiting focal adhesion kinase/phosphatidylinositol 3-kinase/Akt/mTOR/4E-BP1 pathways. In the present study, we evaluated the role of α3β1 and αVβ3 integrins in tube formation and regulation of cyclooxygenase-2 (COX-2) on α3(IV)NC1 stimulation. We found that although both integrins were required for the inhibition of tube formation by α3(IV)NC1 in endothelial cells, only α3β1 integrin was sufficient to regulate COX-2 in hypoxic endothelial cells. We show that binding of α3(IV)NC1 to α3β1 integrin leads to inhibition of COX-2–mediated pro-angiogenic factors, vascular endothelial growth factor, and basic fibroblast growth factor by regulating IκBα/NFκB axis, and is independent of αVβ3 integrin. Furthermore, β3 integrin–null endothelial cells, when treated with α3(IV)NC1, inhibited hypoxia-mediated COX-2 expression, whereas COX-2 inhibition was not observed in α3 integrin–null endothelial cells, indicating that regulation of COX-2 by α3(IV)NC1 is mediated by integrin α3β1. Our in vitro and in vivo findings demonstrate that α3β1 integrin is critical for α3(IV)NC1-mediated inhibition of COX-2–dependent angiogenic signaling and inhibition of tumor progression. PMID:17426256

Unique and shared functions of nuclear lamina LEM domain proteins in Drosophila.

PubMed

Barton, Lacy J; Wilmington, Shameika R; Martin, Melinda J; Skopec, Hannah M; Lovander, Kaylee E; Pinto, Belinda S; Geyer, Pamela K

2014-06-01

The nuclear lamina is an extensive protein network that contributes to nuclear structure and function. LEM domain (LAP2, emerin, MAN1 domain, LEM-D) proteins are components of the nuclear lamina, identified by a shared ∼45-amino-acid motif that binds Barrier-to-autointegration factor (BAF), a chromatin-interacting protein. Drosophila melanogaster has three nuclear lamina LEM-D proteins, named Otefin (Ote), Bocksbeutel (Bocks), and dMAN1. Although these LEM-D proteins are globally expressed, loss of either Ote or dMAN1 causes tissue-specific defects in adult flies that differ from each other. The reason for such distinct tissue-restricted defects is unknown. Here, we generated null alleles of bocks, finding that loss of Bocks causes no overt adult phenotypes. Next, we defined phenotypes associated with lem-d double mutants. Although the absence of individual LEM-D proteins does not affect viability, loss of any two proteins causes lethality. Mutant phenotypes displayed by lem-d double mutants differ from baf mutants, suggesting that BAF function is retained in animals with a single nuclear lamina LEM-D protein. Interestingly, lem-d double mutants displayed distinct developmental and cellular mutant phenotypes, suggesting that Drosophila LEM-D proteins have developmental functions that are differentially shared with other LEM-D family members. This conclusion is supported by studies showing that ectopically produced LEM-D proteins have distinct capacities to rescue the tissue-specific phenotypes found in single lem-d mutants. Our findings predict that cell-specific mutant phenotypes caused by loss of LEM-D proteins reflect both the constellation of LEM-D proteins within the nuclear lamina and the capacity of functional compensation of the remaining LEM-D proteins. Copyright © 2014 by the Genetics Society of America.

Unique and Shared Functions of Nuclear Lamina LEM Domain Proteins in Drosophila

PubMed Central

Barton, Lacy J.; Wilmington, Shameika R.; Martin, Melinda J.; Skopec, Hannah M.; Lovander, Kaylee E.; Pinto, Belinda S.; Geyer, Pamela K.

2014-01-01

The nuclear lamina is an extensive protein network that contributes to nuclear structure and function. LEM domain (LAP2, emerin, MAN1 domain, LEM-D) proteins are components of the nuclear lamina, identified by a shared ∼45-amino-acid motif that binds Barrier-to-autointegration factor (BAF), a chromatin-interacting protein. Drosophila melanogaster has three nuclear lamina LEM-D proteins, named Otefin (Ote), Bocksbeutel (Bocks), and dMAN1. Although these LEM-D proteins are globally expressed, loss of either Ote or dMAN1 causes tissue-specific defects in adult flies that differ from each other. The reason for such distinct tissue-restricted defects is unknown. Here, we generated null alleles of bocks, finding that loss of Bocks causes no overt adult phenotypes. Next, we defined phenotypes associated with lem-d double mutants. Although the absence of individual LEM-D proteins does not affect viability, loss of any two proteins causes lethality. Mutant phenotypes displayed by lem-d double mutants differ from baf mutants, suggesting that BAF function is retained in animals with a single nuclear lamina LEM-D protein. Interestingly, lem-d double mutants displayed distinct developmental and cellular mutant phenotypes, suggesting that Drosophila LEM-D proteins have developmental functions that are differentially shared with other LEM-D family members. This conclusion is supported by studies showing that ectopically produced LEM-D proteins have distinct capacities to rescue the tissue-specific phenotypes found in single lem-d mutants. Our findings predict that cell-specific mutant phenotypes caused by loss of LEM-D proteins reflect both the constellation of LEM-D proteins within the nuclear lamina and the capacity of functional compensation of the remaining LEM-D proteins. PMID:24700158

Amplification of TLO Mediator Subunit Genes Facilitate Filamentous Growth in Candida Spp.

PubMed Central

Liu, Zhongle; Moran, Gary P.; Myers, Lawrence C.

2016-01-01

Filamentous growth is a hallmark of C. albicans pathogenicity compared to less-virulent ascomycetes. A multitude of transcription factors regulate filamentous growth in response to specific environmental cues. Our work, however, suggests the evolutionary history of C. albicans that resulted in its filamentous growth plasticity may be tied to a change in the general transcription machinery rather than transcription factors and their specific targets. A key genomic difference between C. albicans and its less-virulent relatives, including its closest relative C. dubliniensis, is the unique expansion of the TLO (TeLOmere-associated) gene family in C. albicans. Individual Tlo proteins are fungal-specific subunits of Mediator, a large multi-subunit eukaryotic transcriptional co-activator complex. This amplification results in a large pool of ‘free,’ non-Mediator associated, Tlo protein present in C. albicans, but not in C. dubliniensis or other ascomycetes with attenuated virulence. We show that engineering a large ‘free’ pool of the C. dubliniensis Tlo2 (CdTlo2) protein in C. dubliniensis, through overexpression, results in a number of filamentation phenotypes typically associated only with C. albicans. The amplitude of these phenotypes is proportional to the amount of overexpressed CdTlo2 protein. Overexpression of other C. dubliniensis and C. albicans Tlo proteins do result in these phenotypes. Tlo proteins and their orthologs contain a Mediator interaction domain, and a potent transcriptional activation domain. Nuclear localization of the CdTlo2 activation domain, facilitated naturally by the Tlo Mediator binding domain or artificially through an appended nuclear localization signal, is sufficient for the CdTlo2 overexpression phenotypes. A C. albicans med3 null mutant causes multiple defects including the inability to localize Tlo proteins to the nucleus and reduced virulence in a murine systemic infection model. Our data supports a model in which the activation domain of ‘free’ Tlo protein competes with DNA bound transcription factors for targets that regulate key aspects of C. albicans cell physiology. PMID:27741243

Amplification of TLO Mediator Subunit Genes Facilitate Filamentous Growth in Candida Spp.

PubMed

Liu, Zhongle; Moran, Gary P; Sullivan, Derek J; MacCallum, Donna M; Myers, Lawrence C

2016-10-01

Filamentous growth is a hallmark of C. albicans pathogenicity compared to less-virulent ascomycetes. A multitude of transcription factors regulate filamentous growth in response to specific environmental cues. Our work, however, suggests the evolutionary history of C. albicans that resulted in its filamentous growth plasticity may be tied to a change in the general transcription machinery rather than transcription factors and their specific targets. A key genomic difference between C. albicans and its less-virulent relatives, including its closest relative C. dubliniensis, is the unique expansion of the TLO (TeLOmere-associated) gene family in C. albicans. Individual Tlo proteins are fungal-specific subunits of Mediator, a large multi-subunit eukaryotic transcriptional co-activator complex. This amplification results in a large pool of 'free,' non-Mediator associated, Tlo protein present in C. albicans, but not in C. dubliniensis or other ascomycetes with attenuated virulence. We show that engineering a large 'free' pool of the C. dubliniensis Tlo2 (CdTlo2) protein in C. dubliniensis, through overexpression, results in a number of filamentation phenotypes typically associated only with C. albicans. The amplitude of these phenotypes is proportional to the amount of overexpressed CdTlo2 protein. Overexpression of other C. dubliniensis and C. albicans Tlo proteins do result in these phenotypes. Tlo proteins and their orthologs contain a Mediator interaction domain, and a potent transcriptional activation domain. Nuclear localization of the CdTlo2 activation domain, facilitated naturally by the Tlo Mediator binding domain or artificially through an appended nuclear localization signal, is sufficient for the CdTlo2 overexpression phenotypes. A C. albicans med3 null mutant causes multiple defects including the inability to localize Tlo proteins to the nucleus and reduced virulence in a murine systemic infection model. Our data supports a model in which the activation domain of 'free' Tlo protein competes with DNA bound transcription factors for targets that regulate key aspects of C. albicans cell physiology.

Analysis of the promoter of the cudA gene reveals novel mechanisms of Dictyostelium cell type differentiation.

PubMed

Fukuzawa, M; Williams, J G

2000-06-01

The cudA gene encodes a nuclear protein that is essential for normal multicellular development. At the slug stage cudA is expressed in the prespore cells and in a sub-region of the prestalk zone. We show that cap site distal promoter sequences direct cudA expression in prespore cells, while proximal sequences direct expression in the prestalk sub-region. The promoter domain that directs prespore-specific transcription consists of a positively acting region, that has the potential to direct expression in all cells within the slug, and a negatively acting region that prevents expression in the prestalk cells. Dd-STATa is the STAT protein that regulates commitment to stalk cell gene expression, where it is known to function as a transcriptional repressor. We show that Dd-STATa binds in vitro to the positively acting part of the prespore domain of the cudA promoter. However, Dd-STATa cannot be utilised for this purpose in vivo, because analysis of a Dd-STATa null mutant strain shows that Dd-STATa is not necessary for cudA transcription in prespore cells. In contrast, the part of the cudA promoter that directs prestalk-specific expression contains a binding site for Dd-STATa that is essential for its biological activity. Dd-STATa appears therefore to serve as a direct activator of cudA transcription in prestalk cells, while a protein with a DNA binding specificity highly related to that of Dd-STATa is utilised to activate cudA transcription in prespore cells.

Wolfram syndrome 1 gene (WFS1) product localizes to secretory granules and determines granule acidification in pancreatic beta-cells.

PubMed

Hatanaka, Masayuki; Tanabe, Katsuya; Yanai, Akie; Ohta, Yasuharu; Kondo, Manabu; Akiyama, Masaru; Shinoda, Koh; Oka, Yoshitomo; Tanizawa, Yukio

2011-04-01

Wolfram syndrome is an autosomal recessive disorder characterized by juvenile-onset insulin-dependent diabetes mellitus and optic atrophy. The gene responsible for the syndrome (WFS1) encodes an endoplasmic reticulum (ER) resident transmembrane protein. The Wfs1-null mouse exhibits progressive insulin deficiency causing diabetes. Previous work suggested that the function of the WFS1 protein is connected to unfolded protein response and to intracellular Ca(2+) homeostasis. However, its precise molecular function in pancreatic β-cells remains elusive. In our present study, immunofluorescent and electron-microscopic analyses revealed that WFS1 localizes not only to ER but also to secretory granules in pancreatic β-cells. Intragranular acidification was assessed by measuring intracellular fluorescence intensity raised by the acidotrophic agent, 3-[2,4-dinitroanilino]-3'-amino-N-methyldipropyramine. Compared with wild-type β-cells, there was a 32% reduction in the intensity in WFS1-deficient β-cells, indicating the impairment of granular acidification. This phenotype may, at least partly, account for the evidence that Wfs1-null islets have impaired proinsulin processing, resulting in an increased circulating proinsulin level. Morphometric analysis using electron microscopy evidenced that the density of secretory granules attached to the plasma membrane was significantly reduced in Wfs1-null β-cells relative to that in wild-type β-cells. This may be relevant to the recent finding that granular acidification is required for the priming of secretory granules preceding exocytosis and may partly explain the fact that glucose-induced insulin secretion is profoundly impaired in young prediabetic Wfs1-null mice. These results thus provide new insights into the molecular mechanisms of β-cell dysfunction in patients with Wolfram syndrome.

Implication of the oligomeric state of the N-terminal PTX3 domain in cumulus matrix assembly

PubMed Central

Ievoli, Elena; Lindstedt, Ragnar; Inforzato, Antonio; Camaioni, Antonella; Palone, Francesca; Day, Anthony J.; Mantovani, Alberto; Salvatori, Giovanni; Salustri, Antonietta

2011-01-01

Pentraxin 3 (PTX3) plays a key role in the formation of the hyaluronan-rich matrix of the cumulus oophorus surrounding ovulated eggs that is required for successful fertilization and female fertility. PTX3 is a multimeric protein consisting of eight identical protomers held together by a combination of non-covalent interactions and disulfide bonds. Recent findings suggest that the oligomeric status of PTX3 is important for stabilizing the cumulus matrix. Because the role of PTX3 in the cumulus resides in the unique N-terminal sequence of the protomer, we investigated further this issue by testing the ability of distinct Cys/Ser mutants of recombinant N-terminal region of PTX3 (N_PTX3) with different oligomeric arrangement to promote in vitro normal expansion in cumuli from Ptx3-null mice. Here we report that the dimer of the N_PTX3 is unable to rescue cumulus matrix organization, and that the tetrameric assembly of the protein is the minimal oligomeric state required for accomplishing this function. We have previously demonstrated that PTX3 binds to HCs of IαI and TSG-6, which are essential for cumulus matrix formation and able to interact with hyaluronan. Interestingly, here we show by solid-phase binding experiments that the dimer of the N_PTX3 retains the ability to bind to both IαI and TSG-6, suggesting that the octameric structure of PTX3 provides multiple binding sites for each of these ligands. These findings support the hypothesis that PTX3 contributes to cumulus matrix organization by cross-linking HA polymers through interactions with multiple HCs of IαI and/or TSG-6. The N-terminal PTX3 tetrameric oligomerization was recently reported to be also required for recognition and inhibition of FGF2. Given that this growth factor has been detected in the mammalian preovulatory follicle, we wondered whether FGF2 negatively influences cumulus expansion and PTX3 may also serve in vivo to antagonize its activity. We found that a molar excess of FGF2, above PTX3 binding capacity, does not affect in vitro cumulus matrix formation thus ruling out this possibility. In conclusion, the data strength the view that PTX3 acts as a nodal molecule in cross-linking HA in the matrix. PMID:21619930

Role of cytochrome P450 2E1 in protein nitration and ubiquitin-mediated degradation during acetaminophen toxicity.

PubMed

Abdelmegeed, Mohamed A; Moon, Kwan-Hoon; Chen, Chi; Gonzalez, Frank J; Song, Byoung-Joon

2010-01-01

It is well established that following a toxic dose of acetaminophen (APAP), nitrotyrosine protein adducts (3-NT), a hallmark of peroxynitrite production, were colocalized with necrotic hepatic centrilobular regions where cytochrome P450 2E1 (CYP2E1) is highly expressed, suggesting that 3-NT formation may be essential in APAP-mediated toxicity. This study was aimed at investigating the relationship between CYP2E1 and nitration (3-NT formation) followed by ubiquitin-mediated degradation of proteins in wild-type and Cyp2e1-null mice exposed to APAP (200 and 400mg/kg) for 4 and 24h. Markedly increased centrilobular liver necrosis and 3-NT formation were only observed in APAP-exposed wild-type mice in a dose- and time-dependent manner, confirming an important role for CYP2E1 in APAP biotransformation and toxicity. However, the pattern of 3-NT protein adducts, not accompanied by concurrent activation of nitric oxide synthase (NOS), was similar to that of protein ubiquitination. Immunoblot analysis further revealed that immunoprecipitated nitrated proteins were ubiquitinated in APAP-exposed wild-type mice, confirming the fact that nitrated proteins are more susceptible than the native proteins for ubiquitin-dependent degradation, resulting in shorter half-lives. For instance, cytosolic superoxide dismutase (SOD1) levels were clearly decreased and immunoprecipitated SOD1 was nitrated and ubiquitinated, likely leading to its accelerated degradation in APAP-exposed wild-type mice. These data suggest that CYP2E1 appears to play a key role in 3-NT formation, protein degradation, and liver damage, which is independent of NOS, and that decreased levels of many proteins in the wild-type mice (compared with Cyp2e1-null mice) likely contribute to APAP-related toxicity.

Chimeric Plant Calcium/Calmodulin-Dependent Protein Kinase Gene with a Neural Visinin-Like Calcium-Binding Domain

NASA Technical Reports Server (NTRS)

Patil, Shameekumar; Takezawa, D.; Poovaiah, B. W.

1995-01-01

Calcium, a universal second messenger, regulates diverse cellular processes in eukaryotes. Ca-2(+) and Ca-2(+)/calmodulin-regulated protein phosphorylation play a pivotal role in amplifying and diversifying the action of Ca-2(+)- mediated signals. A chimeric Ca-2(+)/calmodulin-dependent protein kinase (CCaMK) gene with a visinin-like Ca-2(+)- binding domain was cloned and characterized from lily. The cDNA clone contains an open reading frame coding for a protein of 520 amino acids. The predicted structure of CCaMK contains a catalytic domain followed by two regulatory domains, a calmodulin-binding domain and a visinin-like Ca-2(+)-binding domain. The amino-terminal region of CCaMK contains all 11 conserved subdomains characteristic of serine/threonine protein kinases. The calmodulin-binding region of CCaMK has high homology (79%) to alpha subunit of mammalian Ca-2(+)/calmodulin-dependent protein kinase. The calmodulin-binding region is fused to a neural visinin-like domain that contains three Ca-2(+)-binding EF-hand motifs and a biotin-binding site. The Escherichia coli-expressed protein (approx. 56 kDa) binds calmodulin in a Ca-2(+)-dependent manner. Furthermore, Ca-45-binding assays revealed that CCaMK directly binds Ca-2(+). The CCaMK gene is preferentially expressed in developing anthers. Southern blot analysis revealed that CCaMK is encoded by a single gene. The structural features of the gene suggest that it has multiple regulatory controls and could play a unique role in Ca-2(+) signaling in plants.

Integration and diversity of the regulatory network composed of Maf and CNC families of transcription factors.

PubMed

Motohashi, Hozumi; O'Connor, Tania; Katsuoka, Fumiki; Engel, James Douglas; Yamamoto, Masayuki

2002-07-10

Recent progress in the analysis of transcriptional regulation has revealed the presence of an exquisite functional network comprising the Maf and Cap 'n' collar (CNC) families of regulatory proteins, many of which have been isolated. Among Maf factors, large Maf proteins are important in the regulation of embryonic development and cell differentiation, whereas small Maf proteins serve as obligatory heterodimeric partner molecules for members of the CNC family. Both Maf homodimers and CNC-small Maf heterodimers bind to the Maf recognition element (MARE). Since the MARE contains a consensus TRE sequence recognized by AP-1, Jun and Fos family members may act to compete or interfere with the function of CNC-small Maf heterodimers. Overall then, the quantitative balance of transcription factors interacting with the MARE determines its transcriptional activity. Many putative MARE-dependent target genes such as those induced by antioxidants and oxidative stress are under concerted regulation by the CNC family member Nrf2, as clearly proven by mouse germline mutagenesis. Since these genes represent a vital aspect of the cellular defense mechanism against oxidative stress, Nrf2-null mutant mice are highly sensitive to xenobiotic and oxidative insults. Deciphering the molecular basis of the regulatory network composed of Maf and CNC families of transcription factors will undoubtedly lead to a new paradigm for the cooperative function of transcription factors.

Attenuated progression of diet-induced steatohepatitis in glutathione-deficient mice

PubMed Central

Haque, Jamil A; McMahan, Ryan S; Campbell, Jean S; Shimizu-Albergine, Masami; Wilson, Angela M; Botta, Dianne; Bammler, Theo K; Beyer, Richard P; Montine, Thomas J; Yeh, Matthew M; Kavanagh, Terrance J; Fausto, Nelson

2011-01-01

In nonalcoholic fatty liver disease (NAFLD), depletion of hepatic antioxidants may contribute to the progression of steatosis to nonalcoholic steatohepatitis (NASH) by increasing oxidative stress that produces lipid peroxidation, inflammation, and fibrosis. We investigated whether depletion of glutathione (GSH) increases NASH-associated hepatic pathology in mice fed a diet deficient in methionine and choline (MCD diet). Wild-type (wt) mice and genetically GSH-deficient mice lacking the modifier subunit of glutamate cysteine ligase (Gclm null mice), the rate-limiting enzyme for de novo synthesis of GSH, were fed the MCD diet, a methionine/choline-sufficient diet, or standard chow for 21 days. We assessed NASH-associated hepatic pathology, including steatosis, fibrosis, inflammation, and hepatocyte ballooning, and used the NAFLD Scoring System to evaluate the extent of changes. We measured triglyceride levels, determined the level of lipid peroxidation products, and measured by qPCR the expression of mRNAs for several proteins associated with lipid metabolism, oxidative stress, and fibrosis. MCD-fed GSH-deficient Gclm null mice were to a large extent protected from MCD diet-induced excessive fat accumulation, hepatocyte injury, inflammation, and fibrosis. Compared with wt animals, MCD-fed Gclm null mice had much lower levels of F2-isoprostanes, lower expression of acyl-CoA oxidase, carnitine palmitoyltransferase 1a, uncoupling protein-2, stearoyl-coenzyme A desaturase-1, transforming growth factor-β, and plas-minogen activator inhibitor-1 mRNAs, and higher activity of catalase, indicative of low oxidative stress, inhibition of triglyceride synthesis, and lower expression of profibrotic proteins. Global gene analysis of hepatic RNA showed that compared with wt mice, the livers of Gclm null mice have a high capacity to metabolize endogenous and exogenous compounds, have lower levels of lipogenic proteins, and increased antioxidant activity. Thus, metabolic adaptations resulting from severe GSH deficiency seem to protect against the development of steatohepatitis. PMID:20548286

Genetic ablation of zyxin causes Mena/VASP mislocalization, increased motility, and deficits in actin remodeling

PubMed Central

Hoffman, Laura M.; Jensen, Christopher C.; Kloeker, Susanne; Wang, C.-L. Albert; Yoshigi, Masaaki; Beckerle, Mary C.

2006-01-01

Focal adhesions are specialized regions of the cell surface where integrin receptors and associated proteins link the extracellular matrix to the actin cytoskeleton. To define the cellular role of the focal adhesion protein zyxin, we characterized the phenotype of fibroblasts in which the zyxin gene was deleted by homologous recombination. Zyxin-null fibroblasts display enhanced integrin-dependent adhesion and are more migratory than wild-type fibroblasts, displaying reduced dependence on extracellular matrix cues. We identified differences in the profiles of 75- and 80-kD tyrosine-phosphorylated proteins in the zyxin-null cells. Tandem array mass spectrometry identified both modified proteins as isoforms of the actomyosin regulator caldesmon, a protein known to influence contractility, stress fiber formation, and motility. Zyxin-null fibroblasts also show deficits in actin stress fiber remodeling and exhibit changes in the molecular composition of focal adhesions, most notably by severely reduced accumulation of Ena/VASP proteins. We postulate that zyxin cooperates with Ena/VASP proteins and caldesmon to influence integrin-dependent cell motility and actin stress fiber remodeling. PMID:16505170

Mdm-2 binding and TAF(II)31 recruitment is regulated by hydrogen bond disruption between the p53 residues Thr18 and Asp21.

PubMed

Jabbur, James R; Tabor, Amy D; Cheng, Xiaodong; Wang, Hua; Uesugi, Motonari; Lozano, Guillermina; Zhang, Wei

2002-10-10

Analyses of five wild-type p53 containing cell lines revealed lineage specific differences in phosphorylation of Thr18 after treatment with ionizing (IR) or ultraviolet (UV) radiation. Importantly, Thr18 phosphorylation correlated with induction of the p53 downstream targets p21(Waf1/Cip1) (p21) and Mdm-2, suggesting a transactivation enhancing role. Thr18 phosphorylation has been shown to abolish side-chain hydrogen bonding between Thr18 and Asp21, an interaction necessary for stabilizing alpha-helical conformation within the transactivation domain. Mutagenesis-derived hydrogen bond disruption attenuated the interaction of p53 with the transactivation repressor Mdm-2 but had no direct effect on the interaction of p53 with the basal transcription factor TAF(II)31. However, prior incubation of p53 mutants with Mdm-2 modulated TAF(II)31 interaction with p53, suggesting Mdm-2 blocks the accessibility of p53 to TAF(II)31. Consistently, p53-null cells transfected with hydrogen bond disrupting p53 mutants demonstrated enhanced endogenous p21 expression, whereas p53/Mdm-2-double null cells exhibited no discernible differences in p21 expression. We conclude disruption of intramolecular hydrogen bonding between Thr18 and Asp21 enhances p53 transactivation by modulating Mdm-2 binding, facilitating TAF(II)31 recruitment.

Expression profile and ligand-binding characterization of odorant-binding protein 2 in Batocera horsfieldi (Hope)

USDA-ARS?s Scientific Manuscript database

Odorant-binding proteins (OBPs) are important components in insect olfactory systems that transport semiochemicals through the aqueous sensillum lymph to surface of olfactory receptor neurons. In this study, we cloned the cDNA of odorant-binding protein 2 (BhorOBP2) in Batocera horsfieldi (Hope) and...

Tic40, a membrane-anchored co-chaperone homolog in the chloroplast protein translocon

PubMed Central

Chou, Ming-Lun; Fitzpatrick, Lynda M.; Tu, Shuh-Long; Budziszewski, Gregory; Potter-Lewis, Sharon; Akita, Mitsuru; Levin, Joshua Z.; Keegstra, Kenneth; Li, Hsou-min

2003-01-01

The function of Tic40 during chloroplast protein import was investigated. Tic40 is an inner envelope membrane protein with a large hydrophilic domain located in the stroma. Arabidopsis null mutants of the atTic40 gene were very pale green and grew slowly but were not seedling lethal. Isolated mutant chloroplasts imported precursor proteins at a lower rate than wild-type chloroplasts. Mutant chloroplasts were normal in allowing binding of precursor proteins. However, during subsequent translocation across the inner membrane, fewer precursors were translocated and more precursors were released from the mutant chloroplasts. Cross-linking experiments demonstrated that Tic40 was part of the translocon complex and functioned at the same stage of import as Tic110 and Hsp93, a member of the Hsp100 family of molecular chaperones. Tertiary structure prediction and immunological studies indicated that the C-terminal portion of Tic40 contains a TPR domain followed by a domain with sequence similarity to co-chaperones Sti1p/Hop and Hip. We propose that Tic40 functions as a co-chaperone in the stromal chaperone complex that facilitates protein translocation across the inner membrane. PMID:12805212

Crystal structure of coelenterazine-binding protein from Renilla muelleri at 1.7 A: why it is not a calcium-regulated photoprotein.

PubMed

Stepanyuk, Galina A; Liu, Zhi-Jie; Markova, Svetlana S; Frank, Ludmila A; Lee, John; Vysotski, Eugene S; Wang, Bi-Cheng

2008-04-01

Bioluminescence in the sea pansy Renilla involves two distinct proteins, a Ca2+-triggered coelenterazine-binding protein (CBP), and Renilla luciferase. CBP contains one tightly bound coelenterazine molecule, which becomes available for reaction with luciferase and O2 only subsequent to Ca2+ binding. CBP belongs to the EF-hand superfamily of Ca2+-binding proteins and contains three "EF-hand" Ca2+-binding sites. The overall spatial structure of recombinant selenomethionine-labeled CBP determined at 1.7 A, is found to approximate the protein scaffold characteristic of the class of Ca2+-regulated photoproteins. Photoproteins however, catalyze molecular oxygen addition to coelenterazine producing a 2-hydroperoxycoelenterazine intermediate, which is stabilized within the binding cavity in the absence of Ca2+. Addition of Ca2+ triggers the bioluminescence reaction. However in CBP this first step of oxygen addition is not allowed. The different amino acid environments and hydrogen bond interactions within the binding cavity, are proposed to account for the different properties of the two classes of proteins.

The unique Leishmania EIF4E4 N-terminus is a target for multiple phosphorylation events and participates in critical interactions required for translation initiation.

PubMed

de Melo Neto, Osvaldo P; da Costa Lima, Tamara D C; Xavier, Camila C; Nascimento, Larissa M; Romão, Tatiany P; Assis, Ludmila A; Pereira, Mariana M C; Reis, Christian R S; Papadopoulou, Barbara

2015-01-01

The eukaryotic initiation factor 4E (eIF4E) recognizes the mRNA cap structure and, together with eIF4G and eIF4A, form the eIF4F complex that regulates translation initiation in eukaryotes. In trypanosomatids, 2 eIF4E homologues (EIF4E3 and EIF4E4) have been shown to be part of eIF4F-like complexes with presumed roles in translation initiation. Both proteins possess unique N-terminal extensions, which can be targeted for phosphorylation. Here, we provide novel insights on the Leishmania infantum EIF4E4 function and regulation. We show that EIF4E4 is constitutively expressed throughout the parasite development but is preferentially phosphorylated in exponentially grown promastigote and amastigote life stages, hence correlating with high levels of translation. Phosphorylation targets multiple serine-proline or threonine-proline residues within the N-terminal extension of EIF4E4 but does not require binding to the EIF4E4's partner, EIF4G3, or to the cap structure. We also report that EIF4E4 interacts with PABP1 through 3 conserved boxes at the EIF4E4 N-terminus and that this interaction is a prerequisite for efficient EIF4E4 phosphorylation. EIF4E4 is essential for Leishmania growth and an EIF4E4 null mutant was only obtained in the presence of an ectopically provided wild type gene. Complementation for the loss of EIF4E4 with several EIF4E4 mutant proteins affecting either phosphorylation or binding to mRNA or to EIF4E4 protein partners revealed that, in contrast to other eukaryotes, only the EIF4E4-PABP1 interaction but neither the binding to EIF4G3 nor phosphorylation is essential for translation. These studies also demonstrated that the lack of both EIF4E4 phosphorylation and EIF4G3 binding leads to a non-functional protein. Altogether, these findings further highlight the unique features of the translation initiation process in trypanosomatid protozoa.

The unique Leishmania EIF4E4 N-terminus is a target for multiple phosphorylation events and participates in critical interactions required for translation initiation

PubMed Central

de Melo Neto, Osvaldo P; da Costa Lima, Tamara D C; Xavier, Camila C; Nascimento, Larissa M; Romão, Tatiany P; Assis, Ludmila A; Pereira, Mariana M C; Reis, Christian R S; Papadopoulou, Barbara

2015-01-01

The eukaryotic initiation factor 4E (eIF4E) recognizes the mRNA cap structure and, together with eIF4G and eIF4A, form the eIF4F complex that regulates translation initiation in eukaryotes. In trypanosomatids, 2 eIF4E homologues (EIF4E3 and EIF4E4) have been shown to be part of eIF4F-like complexes with presumed roles in translation initiation. Both proteins possess unique N-terminal extensions, which can be targeted for phosphorylation. Here, we provide novel insights on the Leishmania infantum EIF4E4 function and regulation. We show that EIF4E4 is constitutively expressed throughout the parasite development but is preferentially phosphorylated in exponentially grown promastigote and amastigote life stages, hence correlating with high levels of translation. Phosphorylation targets multiple serine-proline or threonine-proline residues within the N-terminal extension of EIF4E4 but does not require binding to the EIF4E4's partner, EIF4G3, or to the cap structure. We also report that EIF4E4 interacts with PABP1 through 3 conserved boxes at the EIF4E4 N-terminus and that this interaction is a prerequisite for efficient EIF4E4 phosphorylation. EIF4E4 is essential for Leishmania growth and an EIF4E4 null mutant was only obtained in the presence of an ectopically provided wild type gene. Complementation for the loss of EIF4E4 with several EIF4E4 mutant proteins affecting either phosphorylation or binding to mRNA or to EIF4E4 protein partners revealed that, in contrast to other eukaryotes, only the EIF4E4-PABP1 interaction but neither the binding to EIF4G3 nor phosphorylation is essential for translation. These studies also demonstrated that the lack of both EIF4E4 phosphorylation and EIF4G3 binding leads to a non-functional protein. Altogether, these findings further highlight the unique features of the translation initiation process in trypanosomatid protozoa. PMID:26338184

Prolyl 3-hydroxylase 1 and CRTAP are mutually stabilizing in the endoplasmic reticulum collagen prolyl 3-hydroxylation complex.

PubMed

Chang, Weizhong; Barnes, Aileen M; Cabral, Wayne A; Bodurtha, Joann N; Marini, Joan C

2010-01-15

Null mutations in cartilage-associated protein (CRTAP) and prolyl 3-hydroxylase 1 (P3H1/LEPRE1) cause types VII and VIII OI, respectively, two novel recessive forms of osteogenesis imperfecta (OI) with severe to lethal bone dysplasia and overmodification of the type I collagen helical region. CRTAP and P3H1 form a complex with cyclophilin B (CyPB) in the endoplasmic reticulum (ER) which 3-hydroxylates the Pro986 residue of alpha1(I) and alpha1(II) collagen chains. We investigated the interaction of complex components in fibroblasts from types VII and VIII OI patients. Both CRTAP and P3H1 are absent or reduced on western blots and by immunofluorescence microscopy in cells containing null mutations in either gene. Levels of LEPRE1 or CRTAP transcripts, however, are normal in CRTAP- or LEPRE1-null cells, respectively. Stable transfection of a CRTAP or LEPRE1 expression construct into cells with null mutations for the transfected cDNA restored both CRTAP and P3H1 protein levels. Normalization of collagen helical modification in transfected CRTAP-null cells demonstrated that the restored proteins functioned effectively as a complex. These data indicate that CRTAP and P3H1 are mutually stabilized in the collagen prolyl 3-hydroxylation complex. CyPB levels were unaffected by mutations in either CRTAP or LEPRE1. Proteasomal inhibitors partially rescue P3H1 protein in CRTAP-null cells. In LEPRE1-null cells, secretion of CRTAP is increased compared with control cells and accounts for 15-20% of the decreased CRTAP detected in cells. Thus, mutual stabilization of P3H1 and CRTAP in the ER collagen modification complex is an underlying mechanism for the overlapping phenotype of types VII and VIII OI.

Flow-induced protein kinase A–CREB pathway acts via BMP signaling to promote HSC emergence

PubMed Central

Kim, Peter Geon; Nakano, Haruko; Das, Partha P.; Chen, Michael J.; Rowe, R. Grant; Chou, Stephanie S.; Ross, Samantha J.; Sakamoto, Kathleen M.; Zon, Leonard I.; Schlaeger, Thorsten M.; Orkin, Stuart H.; Nakano, Atsushi

2015-01-01

Fluid shear stress promotes the emergence of hematopoietic stem cells (HSCs) in the aorta–gonad–mesonephros (AGM) of the developing mouse embryo. We determined that the AGM is enriched for expression of targets of protein kinase A (PKA)–cAMP response element-binding protein (CREB), a pathway activated by fluid shear stress. By analyzing CREB genomic occupancy from chromatin-immunoprecipitation sequencing (ChIP-seq) data, we identified the bone morphogenetic protein (BMP) pathway as a potential regulator of CREB. By chemical modulation of the PKA–CREB and BMP pathways in isolated AGM VE-cadherin+ cells from mid-gestation embryos, we demonstrate that PKA–CREB regulates hematopoietic engraftment and clonogenicity of hematopoietic progenitors, and is dependent on secreted BMP ligands through the type I BMP receptor. Finally, we observed blunting of this signaling axis using Ncx1-null embryos, which lack a heartbeat and intravascular flow. Collectively, we have identified a novel PKA–CREB–BMP signaling pathway downstream of shear stress that regulates HSC emergence in the AGM via the endothelial-to-hematopoietic transition. PMID:25870201

Evaluating the binding efficiency of pheromone binding protein with its natural ligand using molecular docking and fluorescence analysis

NASA Astrophysics Data System (ADS)

Ilayaraja, Renganathan; Rajkumar, Ramalingam; Rajesh, Durairaj; Muralidharan, Arumugam Ramachandran; Padmanabhan, Parasuraman; Archunan, Govindaraju

2014-06-01

Chemosignals play a crucial role in social and sexual communication among inter- and intra-species. Chemical cues are bound with protein that is present in the pheromones irrespective of sex are commonly called as pheromone binding protein (PBP). In rats, the pheromone compounds are bound with low molecular lipocalin protein α2u-globulin (α2u). We reported farnesol is a natural endogenous ligand (compound) present in rat preputial gland as a bound volatile compound. In the present study, an attempt has been made through computational method to evaluating the binding efficiency of α2u with the natural ligand (farnesol) and standard fluorescent molecule (2-naphthol). The docking analysis revealed that the binding energy of farnesol and 2-naphthol was almost equal and likely to share some binding pocket of protein. Further, to extrapolate the results generated through computational approach, the α2u protein was purified and subjected to fluorescence titration and binding assay. The results showed that the farnesol is replaced by 2-naphthol with high hydrophobicity of TYR120 in binding sites of α2u providing an acceptable dissociation constant indicating the binding efficiency of α2u. The obtained results are in corroboration with the data made through computational approach.

A novel germ cell protein, SPIF (sperm PKA interacting factor), is essential for the formation of a PKA/TCP11 complex that undergoes conformational and phosphorylation changes upon capacitation.

PubMed

Stanger, Simone J; Law, Estelle A; Jamsai, Duangporn; O'Bryan, Moira K; Nixon, Brett; McLaughlin, Eileen A; Aitken, R John; Roman, Shaun D

2016-08-01

Spermatozoa require the process of capacitation to enable them to fertilize an egg. PKA is crucial to capacitation and the development of hyperactivated motility. Sperm PKA is activated by cAMP generated by the germ cell-enriched adenylyl cyclase encoded by Adcy10 Male mice lacking Adcy10 are sterile, because their spermatozoa are immotile. The current study was designed to identify binding partners of the sperm-specific (Cα2) catalytic subunit of PKA (PRKACA) by using it as the "bait" in a yeast 2-hybrid system. This approach was used to identify a novel germ cell-enriched protein, sperm PKA interacting factor (SPIF), in 25% of the positive clones. Homozygous Spif-null mice were embryonically lethal. SPIF was coexpressed and coregulated with PRKACA and with t-complex protein (TCP)-11, a protein associated with PKA signaling. We established that these 3 proteins form part of a novel complex in mouse spermatozoa. Upon capacitation, the SPIF protein becomes tyrosine phosphorylated in >95% of sperm. An apparent molecular rearrangement in the complex occurs, bringing PRKACA and TCP11 into proximity. Taken together, these results suggest a role for the novel complex of SPIF, PRKACA, and TCP11 during sperm capacitation, fertilization, and embryogenesis.-Stanger, S. J., Law, E. A., Jamsai, D., O'Bryan, M. K., Nixon, B., McLaughlin, E. A., Aitken, R. J., Roman, S. D. A novel germ cell protein, SPIF (sperm PKA interacting factor), is essential for the formation of a PKA/TCP11 complex that undergoes conformational and phosphorylation changes upon capacitation. © FASEB.

Recruitment of DNA polymerase eta by FANCD2 in the early response to DNA damage.

PubMed

Fu, Dechen; Dudimah, Fred Duafalia; Zhang, Jun; Pickering, Anna; Paneerselvam, Jayabal; Palrasu, Manikandan; Wang, Hong; Fei, Peiwen

2013-03-01

How Fanconi anemia (FA) protein D2 (FANCD2) performs DNA damage repair remains largely elusive. We report here that translesion synthesis DNA polymerase (pol) eta is a novel mediator of FANCD2 function. We found that wild type (wt) FANCD2, not K561R (mt) FANCD2, can interact with pol eta. Upon DNA damage, the interaction of pol eta with FANCD2 occurs earlier than that with PCNA, which is in concert with our finding that FANCD2 monoubiquitination peaks at an earlier time point than that of PCNA monoubiquitination. FANCD2-null FA patient cells (PD20) carrying histone H2B-fused pol eta and wtFANCD2, respectively, show a similar tendency of low Mitomycin C (MMC) sensitivity, while cells transfected with empty vector control or pol eta alone demonstrate a similar high level of MMC sensitivity. It therefore appears that FANCD2 monoubiquitination plays a similar anchor role as histone to bind DNA in regulating pol eta. Collectively, our study indicates that, in the early phase of DNA damage response, FANCD2 plays crucial roles in recruiting pol eta to the sites of DNA damage for repair.

Recruitment of DNA polymerase eta by FANCD2 in the early response to DNA damage

PubMed Central

Fu, Dechen; Dudimah, Fred Duafalia; Zhang, Jun; Pickering, Anna; Paneerselvam, Jayabal; Palrasu, Manikandan; Wang, Hong; Fei, Peiwen

2013-01-01

How Fanconi anemia (FA) protein D2 (FANCD2) performs DNA damage repair remains largely elusive. We report here that translesion synthesis DNA polymerase (pol) eta is a novel mediator of FANCD2 function. We found that wild type (wt) FANCD2, not K561R (mt) FANCD2, can interact with pol eta. Upon DNA damage, the interaction of pol eta with FANCD2 occurs earlier than that with PCNA, which is in concert with our finding that FANCD2 monoubiquitination peaks at an earlier time point than that of PCNA monoubiquitination. FANCD2-null FA patient cells (PD20) carrying histone H2B-fused pol eta and wtFANCD2, respectively, show a similar tendency of low Mitomycin C (MMC) sensitivity, while cells transfected with empty vector control or pol eta alone demonstrate a similar high level of MMC sensitivity. It therefore appears that FANCD2 monoubiquitination plays a similar anchor role as histone to bind DNA in regulating pol eta. Collectively, our study indicates that, in the early phase of DNA damage response, FANCD2 plays crucial roles in recruiting pol eta to the sites of DNA damage for repair. PMID:23388460

CRISPR-mediated HDAC2 disruption identifies two distinct classes of target genes in human cells.

PubMed

Somanath, Priyanka; Herndon Klein, Rachel; Knoepfler, Paul S

2017-01-01

The transcriptional functions of the class I histone deacetylases (HDACs) HDAC1 and HDAC2 are mainly viewed as both repressive and redundant based on murine knockout studies, but they may have additional independent roles and their physiological functions in human cells are not as clearly defined. To address the individual epigenomic functions of HDAC2, here we utilized CRISPR-Cas9 to disrupt HDAC2 in human cells. We find that while HDAC2 null cells exhibited signs of cross-regulation between HDAC1 and HDAC2, specific epigenomic phenotypes were still apparent using RNA-seq and ChIP assays. We identified specific targets of HDAC2 repression, and defined a novel class of genes that are actively expressed in a partially HDAC2-dependent manner. While HDAC2 was required for the recruitment of HDAC1 to repressed HDAC2-gene targets, HDAC2 was dispensable for HDAC1 binding to HDAC2-activated targets, supporting the notion of distinct classes of targets. Both active and repressed classes of gene targets demonstrated enhanced histone acetylation and methylation in HDAC2-null cells. Binding of the HDAC1/2-associated SIN3A corepressor was altered at most HDAC2-targets, but without a clear pattern. Overall, our study defines two classes of HDAC2 targets in human cells, with a dependence of HDAC1 on HDAC2 at one class of targets, and distinguishes unique functions for HDAC2.

The gammaPE complex contains both SATB1 and HOXB2 and has positive and negative roles in human gamma-globin gene regulation.

PubMed

Case, S S; Huber, P; Lloyd, J A

1999-11-01

A large nuclear protein complex, termed gammaPE (for gamma-globin promoter and enhancer binding factor), binds to five sites located 5' and 3' of the human y-globin gene. Two proteins, SATB1 (special A-T-rich binding protein 1) and HOXB2, can bind to yPE binding sites. SATB1 binds to nuclear matrix-attachment sites, and HOXB2 is a homeodomain protein important in neural development that is also expressed during erythropoiesis. The present work showed that antisera directed against either SATB1 or HOXB2 reacted specifically with the entire gammaPE complex in electrophoretic mobility shift assays (EMSAs), suggesting that the two proteins can bind to the gammaPE binding site simultaneously. When SATB1 or HOXB2 was expressed in vitro, they could bind independently to gammaPE binding sites in EMSA. Interestingly, the proteins expressed in vitro competed effectively with each other for the gammaPE binding site, suggesting that this may occur under certain conditions in vivo. Transient cotransfections of a HOXB2 cDNA and a y-globin-luciferase reporter gene construct into cells expressing SATB1 suggested that SATB1 has a positive and HOXB2 a negative regulatory effect on transcription. Taking into account their potentially opposing effects and binding activities, SATB1 and HOXB2 may modulate the amount of gamma-globin mRNA expressed during development and differentiation.

In silico analysis of different generation β lactams antibiotics with penicillin binding protein-2 of Neisseria meningitidis for curing meningococcal disease.

PubMed

Tripathi, Vijay; Tripathi, Pooja; Srivastava, Navita; Gupta, Dwijendra

2014-12-01

Neisseria meningitidis is a gram negative, diplococcic pathogen responsible for the meningococcal disease and fulminant septicemia. Penicillin-binding proteins-2 (PBPs) is crucial for the cell wall biosynthesis during cell proliferation of N. meningitidis and these are the target for β-lactam antibiotics. For many years penicillin has been recognized as the antibiotic for meningococcal disease but the meningococcus has seemed to be antibiotic resistance. In the present work we have verified the molecular interaction of Penicillin binding protein-2 N. meningitidis to different generation of β-lactam antibiotics and concluded that the third generation of β-lactam antibiotics shows efficient binding with Penicillin binding protein-2 of N. meningitidis. On the basis of binding efficiency and inhibition constant, ceftazidime emerged as the most efficient antibiotic amongst the other advanced β-lactam antibiotics against Penicillin-binding protein-2 of N. meningitidis.

Arabidopsis TRIGALACTOSYLDIACYLGLYCEROL5 Interacts with TGD1, TGD2, and TGD4 to Facilitate Lipid Transfer from the Endoplasmic Reticulum to Plastids

DOE PAGES

Fan, Jilian; Zhai, Zhiyang; Yan, Chengshi; ...

2015-09-26

The biogenesis of photosynthetic membranes in the plastids of higher plants requires an extensive supply of lipid precursors from the endoplasmic reticulum (ER). Four TRIGALACTOSYLDIACYLGLYCEROL (TGD) proteins (TGD1,2,3,4) have thus far been implicated in this lipid transfer process. While TGD1, TGD2, and TGD3 constitute an ATP binding cassette transporter complex residing in the plastid inner envelope, TGD4 is a transmembrane lipid transfer protein present in the outer envelope. These observations raise questions regarding how lipids transit across the aqueous intermembrane space. Here in this paper, we describe the isolation and characterization of a novel Arabidopsis thaliana gene, TGD5. Disruption ofmore » TGD5 results in similar phenotypic effects as previously described in tgd1,2,3,4 mutants, including deficiency of ER-derived thylakoid lipids, accumulation of oligogalactolipids, and triacylglycerol. Genetic analysis indicates that TGD4 is epistatic to TGD5 in ER-to-plastid lipid trafficking, whereas double mutants of a null tgd5 allele with tgd1-1 or tgd2-1 show a synergistic embryo-lethal phenotype. TGD5 encodes a small glycine-rich protein that is localized in the envelope membranes of chloroplasts. In addition, coimmunoprecipitation assays show that TGD5 physically interacts with TGD1, TGD2, TGD3, and TGD4. Collectively, these results suggest that TGD5 facilitates lipid transfer from the outer to the inner plastid envelope by bridging TGD4 with the TGD1,2,3 transporter complex.« less

MSH1 Is a Plant Organellar DNA Binding and Thylakoid Protein under Precise Spatial Regulation to Alter Development

DOE PAGES

Virdi, Kamaldeep S.; Wamboldt, Yashitola; Kundariya, Hardik; ...

2015-11-14

As metabolic centers, plant organelles participate in maintenance, defense, and signaling. MSH1 is a plant-specific protein involved in organellar genome stability in mitochondria and plastids. Plastid depletion of MSH1 causes heritable, non-genetic changes in development and DNA methylation. We investigated the msh1 phenotype using hemi-complementation mutants and transgene-null segregants from RNAi suppression lines to sub-compartmentalize MSH1 effects. We show that MSH1 expression is spatially regulated, specifically localizing to plastids within the epidermis and vascular parenchyma. The protein binds DNA and localizes to plastid and mitochondrial nucleoids, but fractionation and protein–protein interactions data indicate that MSH1 also associates with the thylakoidmore » membrane. Plastid MSH1 depletion results in variegation, abiotic stress tolerance, variable growth rate, and delayed maturity. Depletion from mitochondria results in 7%–10% of plants altered in leaf morphology, heat tolerance, and mitochondrial genome stability. MSH1 does not localize within the nucleus directly, but plastid depletion produces non-genetic changes in flowering time, maturation, and growth rate that are heritable independent of MSH1. MSH1 depletion alters non-photoactive redox behavior in plastids and a sub-set of mitochondrially altered lines. Ectopic expression produces deleterious effects, underlining its strict expression control. Unraveling the complexity of the MSH1 effect offers insight into triggers of plant-specific, transgenerational adaptation behaviors.« less

AAV-mediated gene therapy in Dystrophin-Dp71 deficient mouse leads to blood-retinal barrier restoration and oedema reabsorption.

PubMed

Vacca, Ophélie; Charles-Messance, Hugo; El Mathari, Brahim; Sene, Abdoulaye; Barbe, Peggy; Fouquet, Stéphane; Aragón, Jorge; Darche, Marie; Giocanti-Aurégan, Audrey; Paques, Michel; Sahel, José-Alain; Tadayoni, Ramin; Montañez, Cecilia; Dalkara, Deniz; Rendon, Alvaro

2016-07-15

Dystrophin-Dp71 being a key membrane cytoskeletal protein, expressed mainly in Müller cells that provide a mechanical link at the Müller cell membrane by direct binding to actin and a transmembrane protein complex. Its absence has been related to blood-retinal barrier (BRB) permeability through delocalization and down-regulation of the AQP4 and Kir4.1 channels (1). We have previously shown that the adeno-associated virus (AAV) variant, ShH10, transduces Müller cells in the Dp71-null mouse retina efficiently and specifically (2,3). Here, we use ShH10 to restore Dp71 expression in Müller cells of Dp71 deficient mouse to study molecular and functional effects of this restoration in an adult mouse displaying retinal permeability. We show that strong and specific expression of exogenous Dp71 in Müller cells leads to correct localization of Dp71 protein restoring all protein interactions in order to re-establish a proper functional BRB and retina homeostasis thus preventing retina from oedema. This study is the basis for the development of new therapeutic strategies in dealing with diseases with BRB breakdown and macular oedema such as diabetic retinopathy (DR). © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

GBF-dependent family genes morphologically suppress the partially active Dictyostelium STATa strain.

PubMed

Shimada, Nao; Kanno-Tanabe, Naoko; Minemura, Kakeru; Kawata, Takefumi

2008-02-01

Transcription factor Dd-STATa, a functional Dictyostelium homologue of metazoan signal transducers and activators of transcription proteins, is necessary for culmination during development. We have isolated more than 18 putative multicopy suppressors of Dd-STATa using genetic screening. One was hssA gene, whose expression is known to be G-box-binding-factor-dependent and which was specific to prestalk A (pstA) cells, where Dd-STATa is activated. Also, hssA mRNA was expressed in pstA cells in the Dd-STATa-null mutant. At least 40 hssA-related genes are present in the genome and constitute a multigene family. The tagged HssA protein was translated; hssA encodes an unusually high-glycine-serine-rich small protein (8.37 kDa), which has strong homology to previously reported cyclic-adenosine-monophosphate-inducible 2C and 7E proteins. Overexpression of hssA mRNA as well as frame-shifted versions of hssA RNA suppressed the phenotype of the partially active Dd-STATa strain, suggesting that translation is not necessary for suppression. Although overexpression of prespore-specific genes among the family did not suppress the parental phenotype, prestalk-specific family members did. Although overexpression of the hssA did not revert the expression of Dd-STATa target genes, and although its suppression mechanism remains unknown, morphological reversion implies functional relationships between Dd-STATa and hssA.

Recruitment of CREB1 and Histone Deacetylase 2 (HDAC2) to the Mouse Ltbp-1 Promoter Regulates its Constitutive Expression in a Dioxin Receptor-dependent Manner

PubMed Central

Gomez-Duran, Aurea; Ballestar, Esteban; Carvajal-Gonzalez, Jose M.; Marlowe, Jennifer L.; Puga, Alvaro; Esteller, Manel; Fernandez-Salguero, Pedro M.

2010-01-01

Latent TGFβ-binding protein 1 (LTBP-1) is a key regulator of TGFβ targeting and activation in the extracellular matrix. LTBP-1 is recognized as a major docking molecule to localize, and possibly to activate, TGFβ in the extracellular matrix. Despite this relevant function, the molecular mechanisms regulating Ltbp-1 transcription remain largely unknown. Previous results from our laboratory revealed that mouse embryonic fibroblasts (MEF) lacking dioxin receptor (AhR) had increased Ltbp-1 mRNA expression and elevated TGFβ activity, suggesting that AhR repressed Ltbp-1 transcription. Here, we have cloned the mouse Ltbp-1 gene promoter and analysed its mechanism of transcriptional repression by AhR. Reporter gene assays, AhR over-expression and site-directed mutagenesis showed that basal Ltbp-1 transcription is AhR-dependent. Chromatin immunoprecipitation (ChIP) and RNA interference (RNAi) revealed that AhR regulates Ltbp-1 transcription by a mechanism involving recruitment of co-activators such as CREB1 and co-repressors such as HDAC2 to the Ltbp-1 promoter. In AhR-expressing (AhR+/+) MEF cells, the recruitment of HDAC1, 2 and 4 correlated with decreased K8H4 acetylation and impaired binding of pCREBSer133 to the Ltbp-1 promoter, likely maintaining a constitutive repressed state. AhR−/− MEF cells had the opposite pattern of HDACs and pCREB1Ser133 binding to Ltbp-1 promoter, and therefore, over-expressed Ltbp-1 mRNA. In agreement, siRNA for HDAC2 increased Ltbp-1 expression and K8H4 acetylation in AhR+/+ but not in AhR−/− MEF cells. We suggest that HDAC2 binding keeps Ltbp-1 promoter repressed in AhR+/+ MEF cells, whereas in AhR-null MEF cells the absence of HDAC2 and the binding of pCREBSer133 allow Ltbp-1 transcription. Thus, epigenetics can contribute to constitutive Ltbp-1 repression by a mechanism requiring AhR activity. PMID:18508077

Identification of AOSC-binding proteins in neurons

NASA Astrophysics Data System (ADS)

Liu, Ming; Nie, Qin; Xin, Xianliang; Geng, Meiyu

2008-11-01

Acidic oligosaccharide sugar chain (AOSC), a D-mannuronic acid oligosaccharide, derived from brown algae polysaccharide, has been completed Phase I clinical trial in China as an anti-Alzheimer’s Disease (AD) drug candidate. The identification of AOSC-binding protein(s) in neurons is very important for understanding its action mechanism. To determine the binding protein(s) of AOSC in neurons mediating its anti-AD activities, confocal microscopy, affinity chromatography, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis were used. Confocal microscopy analysis shows that AOSC binds to SH-SY5Y cells in concentration-, time-, and temperature-dependent fashions. The AOSC binding proteins were purified by affinity chromatography and identified by LC-MS/MS analysis. The results showed that there are 349 proteins binding AOSC, including clathrin, adaptor protein-2 (AP-2) and amyloid precursor protein (APP). These results suggest that the binding/entrance of AOSC to neurons is probably responsible for anti-AD activities.

Ca sup 2+ binding capacity of cytoplasmic proteins from rod photoreceptors is mainly due to arrestin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huppertz, B.; Weyand, I.; Bauer, P.J.

1990-06-05

Arrestin (also called S-antigen or 48-kDa protein) binds to photoexcited and phosphorylated rhodopsin and, thereby, blocks competitively the activation of transducin. Using Ca{sup 2+} titration in the presence of the indicator arsenazo III and {sup 45}Ca{sup 2+} autoradiography, we show that arrestin is a Ca2(+)-binding protein. The Ca{sup 2+} binding capacity of arresting-containing protein extracts from bovine rod outer segments is about twice as high as that of arrestin-depleted extracts. The difference in the Ca{sup 2+} binding of arrestin-containing and arrestin-depleted protein extracts was attributed to arrestin. Both, these difference-measurements of protein extracts and the measurements of purified arrestin yieldmore » dissociation constants for the Ca{sup 2+} binding of arrestin between 2 and 4 microM. The titration curves are consistent with a molar ratio of one Ca{sup 2+} binding site per arrestin. No Ca{sup 2+} binding in the micromolar range was found in extracts containing mainly transducin and cGMP-phosphodiesterase. Since arrestin is one of the most abundant proteins in rod photoreceptors occurring presumably up to millimolar concentrations in rod outer segments, we suggest that aside from its function to prevent the activation of transducin, arrestin acts probably as an intracellular Ca{sup 2+} buffer.« less

Reversing hypomyelination in BACE1-null mice with Akt-DD overexpression.

PubMed

Hu, Xiangyou; Schlanger, Rita; He, Wanxia; Macklin, Wendy B; Yan, Riqiang

2013-05-01

β-Site amyloid precursor protein convertase enzyme 1 (BACE1), a type I transmembrane aspartyl protease required to cleave amyloid precursor protein for releasing a toxic amyloid peptide, also cleaves type I and type III neuregulin-1 (Nrg-1). BACE1 deficiency in mice causes hypomyelination during development and impairs remyelination if injured. In BACE1-null mice, the abolished cleavage of neuregulin-1 by BACE1 is speculated to cause reduced myelin sheath thickness in both the central nervous system and peripheral nervous system because reduced cleavage of Nrg-1 correlates with reduced Akt phosphorylation, a downstream signaling molecule of the Nrg-1/ErbB pathway. Here we tested specifically whether increasing Akt activity alone in oligodendrocytes would be sufficient to reverse the hypomyelination phenotype in BACE1-null mice. BACE1-null mice were bred with transgenic mice expressing constitutively active Akt (Akt-DD; mutations with D(308)T and D(473)S) in oligodendrocytes. Relative to littermate BACE1-null controls, BACE1(-/-)/Akt-DD mice exhibited enhanced expression of myelin basic protein and promoter of proteolipid protein. The elevated expression of myelin proteins correlated with a thicker myelin sheath in optic nerves; comparison of quantified g ratios with statistic significance was used to confirm this reversion. However, it appeared that myelin sheath thickness in the sciatic nerves was not increased in BACE1(-/-)/Akt-DD mice, as the g ratio was not significantly different from the control. Hence, increased Akt activity in BACE1-null myelinating cells only compensates for the loss of BACE1 activity in the central nervous system, which is consistent with the observation that overexpression of Akt-DD in Schwann cells did not induce hypermyelination. Our results suggest that signaling activity other than Akt may also contribute to proper myelination in peripheral nerves.

New fluorescent reagents specific for Ca{sup 2+}-binding proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ben-Hail, Danya; Lemelson, Daniela; Israelson, Adrian

2012-09-14

Highlights: Black-Right-Pointing-Pointer New reagents specifically inhibit the activity of Ca{sup 2+}-dependent proteins. Black-Right-Pointing-Pointer FITC-Ru and EITC-Ru allow for mechanism-independent probing of Ca{sup 2+}-binding proteins. Black-Right-Pointing-Pointer Changes in reagents fluorescence allow characterization of protein Ca{sup 2+}-binding properties. -- Abstract: Ca{sup 2+} carries information pivotal to cell life and death via its interactions with specific binding sites in a protein. We previously developed a novel photoreactive reagent, azido ruthenium (AzRu), which strongly inhibits Ca{sup 2+}-dependent activities. Here, we synthesized new fluorescent ruthenium-based reagents containing FITC or EITC, FITC-Ru and EITC-Ru. These reagents were purified, characterized and found to specifically interact with andmore » markedly inhibit Ca{sup 2+}-dependent activities but not the activity of Ca{sup 2+}-independent reactions. In contrast to many reagents that serve as probes for Ca{sup 2+}, FITC-Ru and EITC-Ru are the first fluorescent divalent cation analogs to be synthesized and characterized that specifically bind to Ca{sup 2+}-binding proteins and inhibit their activity. Such reagents will assist in characterizing Ca{sup 2+}-binding proteins, thereby facilitating better understanding of the function of Ca{sup 2+} as a key bio-regulator.« less

Phosphatidic acid binding proteins display differential binding as a function of membrane curvature stress and chemical properties.

PubMed

Putta, Priya; Rankenberg, Johanna; Korver, Ruud A; van Wijk, Ringo; Munnik, Teun; Testerink, Christa; Kooijman, Edgar E

2016-11-01

Phosphatidic acid (PA) is a crucial membrane phospholipid involved in de novo lipid synthesis and numerous intracellular signaling cascades. The signaling function of PA is mediated by peripheral membrane proteins that specifically recognize PA. While numerous PA-binding proteins are known, much less is known about what drives specificity of PA-protein binding. Previously, we have described the ionization properties of PA, summarized in the electrostatic-hydrogen bond switch, as one aspect that drives the specific binding of PA by PA-binding proteins. Here we focus on membrane curvature stress induced by phosphatidylethanolamine and show that many PA-binding proteins display enhanced binding as a function of negative curvature stress. This result is corroborated by the observation that positive curvature stress, induced by lyso phosphatidylcholine, abolishes PA binding of target proteins. We show, for the first time, that a novel plant PA-binding protein, Arabidopsis Epsin-like Clathrin Adaptor 1 (ECA1) displays curvature-dependence in its binding to PA. Other established PA targets examined in this study include, the plant proteins TGD2, and PDK1, the yeast proteins Opi1 and Spo20, and, the mammalian protein Raf-1 kinase and the C2 domain of the mammalian phosphatidylserine binding protein Lact as control. Based on our observations, we propose that liposome binding assays are the preferred method to investigate lipid binding compared to the popular lipid overlay assays where membrane environment is lost. The use of complex lipid mixtures is important to elucidate further aspects of PA binding proteins. Copyright © 2016. Published by Elsevier B.V.

Liver Fatty Acid Binding Protein Gene-ablation Exacerbates Weight Gain in High-Fat Fed Female Mice

PubMed Central

McIntosh, Avery L.; Atshaves, Barbara P.; Landrock, Danilo; Landrock, Kerstin K.; Martin, Gregory G.; Storey, Stephen M.; Kier, Ann B.; Schroeder, Friedhelm

2013-01-01

Loss of liver fatty acid binding protein (L-FABP) decreases long chain fatty acid uptake and oxidation in primary hepatocytes and in vivo. On this basis, L-FABP gene ablation would potentiate high-fat diet-induced weight gain and weight gain/energy intake. While this was indeed the case when L-FABP null (−/−) mice on the C57BL/6NCr background were pair-fed high fat diet, whether this would also be observed under high-fat diet fed ad libitum was not known. Therefore, this possibility was examined in female L-FABP (−/−) mice on the same background. L-FABP (−/−) mice consumed equal amounts of defined high-fat or isocaloric control diets fed ad libitum. However, on the ad libitum fed high-fat diet the L-FABP (−/−) mice exhibited: 1) Decreased hepatic long chain fatty acid (LCFA) β-oxidation as indicated by lower serum β–hydroxybutyrate level; 2) Decreased hepatic protein levels of key enzymes mitochondrial (rate limiting carnitine palmitoyl acyltransferase A1, CPT1A; HMG-CoA synthase) and peroxisomal (acyl CoA oxidase 1, ACOX1) LCFA β-oxidation; 3) Increased fat tissue mass (FTM) and FTM/energy intake to the greatest extent; and 4) Exacerbated body weight gain, weight gain/energy intake, liver weight, and liver weight/body weight to the greatest extent. Taken together, these findings showed that L-FABP gene-ablation exacerbated diet-induced weight gain and fat tissue mass gain in mice fed high-fat diet ad libitum—consistent with the known biochemistry and cell biology of L-FABP. PMID:23539345

Occludin confers adhesiveness when expressed in fibroblasts.

PubMed

Van Itallie, C M; Anderson, J M

1997-05-01

Occludin is an integral membrane protein specifically associated with tight junctions. Previous studies suggest it is likely to function in forming the intercellular seal. In the present study, we expressed occludin under an inducible promotor in occludin-null fibroblasts to determine whether this protein confers intercellular adhesion. When human occludin is stably expressed in NRK and Rat-1 fibroblasts, which lack endogenous occludin and tight junctions but do have well developed ZO-1-containing adherens-like junctions, occludin colocalizes with ZO-1 to points of cell-cell contact. In contrast, L-cell fibroblasts which lack cadherin-based adherens junctions, target neither ZO-1 nor occludin to sites of cell contact. Occludin-induced adhesion was next quantified using a suspended cell assay. In NRK and Rat-1 cells, occludin expression induces adhesion in the absence of calcium, thus independent of cadherin-cadherin contacts. In contrast, L-cells are nonadhesive in this assay and show no increase in adhesion after induction of occludin expression. Binding of an antibody to the first of the putative extracellular loops of occludin confirmed that this sequence was exposed on the cell surface, and synthetic peptides containing the amino acid sequence of this loop inhibit adhesion induced by occludin expression. These results suggest that the extracellular surface of occludin is directly involved in cell-cell adhesion and the ability to confer adhesiveness correlates with the ability to colocalize with its cytoplasmic binding protein, ZO-1.

Myopathic changes in murine skeletal muscle lacking synemin

PubMed Central

García-Pelagio, Karla P.; Muriel, Joaquin; O'Neill, Andrea; Desmond, Patrick F.; Lovering, Richard M.; Lund, Linda; Bond, Meredith

2015-01-01

Diseases of striated muscle linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus and its links to costameres, which connect the sarcomeres to the cell membrane. Here we study the role in skeletal muscle of synemin, a type IV IF protein, by examining mice null for synemin (synm-null). Synm-null mice have a mild skeletal muscle phenotype. Tibialis anterior (TA) muscles show a significant decrease in mean fiber diameter, a decrease in twitch and tetanic force, and an increase in susceptibility to injury caused by lengthening contractions. Organization of proteins associated with the contractile apparatus and costameres is not significantly altered in the synm-null. Elastimetry of the sarcolemma and associated contractile apparatus in extensor digitorum longus myofibers reveals a reduction in tension consistent with an increase in sarcolemmal deformability. Although fatigue after repeated isometric contractions is more marked in TA muscles of synm-null mice, the ability of the mice to run uphill on a treadmill is similar to controls. Our results suggest that synemin contributes to linkage between costameres and the contractile apparatus and that the absence of synemin results in decreased fiber size and increased sarcolemmal deformability and susceptibility to injury. Thus synemin plays a moderate but distinct role in fast twitch skeletal muscle. PMID:25567810

Inositol Hexakisphosphate Kinase-3 Regulates the Morphology and Synapse Formation of Cerebellar Purkinje Cells via Spectrin/Adducin

PubMed Central

Fu, Chenglai; Xu, Jing; Li, Ruo-Jing; Crawford, Joshua A.; Khan, A. Basit; Ma, Ting Martin; Cha, Jiyoung Y.; Snowman, Adele M.; Pletnikov, Mikhail V.

2015-01-01

The inositol hexakisphosphate kinases (IP6Ks) are the principal enzymes that generate inositol pyrophosphates. There are three IP6Ks (IP6K1, 2, and 3). Functions of IP6K1 and IP6K2 have been substantially delineated, but little is known of IP6K3's role in normal physiology, especially in the brain. To elucidate functions of IP6K3, we generated mice with targeted deletion of IP6K3. We demonstrate that IP6K3 is highly concentrated in the brain in cerebellar Purkinje cells. IP6K3 physiologically binds to the cytoskeletal proteins adducin and spectrin, whose mutual interactions are perturbed in IP6K3-null mutants. Consequently, IP6K3 knock-out cerebella manifest abnormalities in Purkinje cell structure and synapse number, and the mutant mice display deficits in motor learning and coordination. Thus, IP6K3 is a major determinant of cytoskeletal disposition and function of cerebellar Purkinje cells. SIGNIFICANCE STATEMENT We identified and cloned a family of three inositol hexakisphosphate kinases (IP6Ks) that generate the inositol pyrophosphates, most notably 5-diphosphoinositol pentakisphosphate (IP7). Of these, IP6K3 has been least characterized. In the present study we generated IP6K3 knock-out mice and show that IP6K3 is highly expressed in cerebellar Purkinje cells. IP6K3-deleted mice display defects of motor learning and coordination. IP6K3-null mice manifest aberrations of Purkinje cells with a diminished number of synapses. IP6K3 interacts with the cytoskeletal proteins spectrin and adducin whose altered disposition in IP6K3 knock-out mice may mediate phenotypic features of the mutant mice. These findings afford molecular/cytoskeletal mechanisms by which the inositol polyphosphate system impacts brain function. PMID:26245967

Placental Glucose and Amino Acid Transport in Calorie-Restricted Wild-Type and Glut3 Null Heterozygous Mice

PubMed Central

Ganguly, Amit; Collis, Laura

2012-01-01

Calorie restriction (CR) decreased placenta and fetal weights in wild-type (wt) and glucose transporter (Glut) 3 heterozygous null (glut3+/−) mice. Because placental nutrient transport is a primary energy determinant of placentofetal growth, we examined key transport systems. Maternal CR reduced intra- and transplacental glucose and leucine transport but enhanced system A amino acid transport in wt mice. These transport perturbations were accompanied by reduced placental Glut3 and leucine amino acid transporter (LAT) family member 2, no change in Glut1 and LAT family member 1, but increased sodium coupled neutral amino acid transporter (SNAT) and SNAT2 expression. We also noted decreased total and active phosphorylated forms of mammalian target of rapamycin, which is the intracellular nutrient sensor, the downstream total P70S6 kinase, and pS6 ribosomal protein with no change in total and phosphorylated 4E-binding protein 1. To determine the role of placental Glut3 in mediating CR-induced placental transport changes, we next investigated the effect of gestational CR in glut3+/− mice. In glut3+/− mice, a key role of placental Glut3 in mediating transplacental and intraplacental glucose transport was established. In addition, reduced Glut3 results in a compensatory increase of leucine and system A transplacental transport. On the other hand, diminished Glut3-mediated intraplacental glucose transport reduced leucine transport and mammalian target of rapamycin and preserved LAT and enhancing SNAT. CR in glut3+/− mice further reduced transplacental glucose transport and enhanced system A amino acid transport, although the increased leucine transport was lost. In addition, increased Glut3 was seen and preserved Glut1, LAT, and SNAT. These placental changes collectively protect survival of wt and glut3+/− fetuses against maternal CR-imposed reduction of macromolecular nutrients. PMID:22700768

CXCL4 is a novel nickel-binding protein and augments nickel allergy.

PubMed

Kuroishi, T; Bando, K; Tanaka, Y; Shishido, K; Kinbara, M; Ogawa, T; Muramoto, K; Endo, Y; Sugawara, S

2017-08-01

Nickel (Ni) is the most frequent metal allergen and induces a TH 1 -dependent type-IV allergy. Although Ni 2+ is considered to bind to endogenous proteins, it currently remains unclear whether these Ni-binding proteins are involved in Ni allergy in vivo. We previously reported the adjuvant effects of lipopolysaccharide (LPS) in a Ni allergy mouse model. As LPS induces a number of inflammatory mediators, we hypothesized that Ni-binding protein(s) are also induced by LPS. The objective of this study was to purify and identify Ni-binding protein(s) from serum taken from LPS-injected mice (referred as LPS serum) and examined the augmenting effects of these Ni-binding protein(s) on Ni allergy in an in vivo model. BALB/cA mice were sensitized with an i.p. injection of NiCl 2 and LPS. Ten days after sensitization, mice were challenged with NiCl 2 by an i.d. injection into ear pinnae. Ni-binding protein(s) were purified by Ni-affinity column chromatography and gel filtration. Lipopolysaccharide serum, but not serum taken from saline-injected mice, augmented ear swelling induced by Ni-allergic inflammation. Ni-binding, but not non-binding fraction, purified from LPS serum augmented Ni-allergic inflammation. Mass spectrometry and Western blotting detected CXCL4 in the active fraction. A batch analysis with Ni-sepharose and a surface plasmon resonance analysis revealed direct binding between CXCL4 and Ni 2+ . Recombinant CXCL4 augmented Ni-allergic inflammation and exerted adjuvant effects at the sensitization phase. These results indicate that CXCL4 is a novel Ni-binding protein that augments Ni allergy at the elicitation and sensitization phases. This is the first study to demonstrate that the Ni-binding protein augments Ni allergy in vivo. © 2017 John Wiley & Sons Ltd.

Constitutive Smad signaling and Smad-dependent collagen gene expression in mouse embryonic fibroblasts lacking peroxisome proliferator-activated receptor-{gamma}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Asish K; Wei, Jun; Wu, Minghua

2008-09-19

Transforming growth factor-{beta} (TGF-{beta}), a potent inducer of collagen synthesis, is implicated in pathological fibrosis. Peroxisome proliferator-activated receptor-{gamma} (PPAR-{gamma}) is a nuclear hormone receptor that regulates adipogenesis and numerous other biological processes. Here, we demonstrate that collagen gene expression was markedly elevated in mouse embryonic fibroblasts (MEFs) lacking PPAR-{gamma} compared to heterozygous control MEFs. Treatment with the PPAR-{gamma} ligand 15d-PGJ{sub 2} failed to down-regulate collagen gene expression in PPAR-{gamma} null MEFs, whereas reconstitution of these cells with ectopic PPAR-{gamma} resulted in their normalization. Compared to control MEFs, PPAR-{gamma} null MEFs displayed elevated levels of the Type I TGF-{beta} receptor (T{beta}RI),more » and secreted more TGF-{beta}1 into the media. Furthermore, PPAR-{gamma} null MEFs showed constitutive phosphorylation of cellular Smad2 and Smad3, even in the absence of exogenous TGF-{beta}, which was abrogated by the ALK5 inhibitor SB431542. Constitutive Smad2/3 phosphorylation in PPAR-{gamma} null MEFs was associated with Smad3 binding to its cognate DNA recognition sequences, and interaction with coactivator p300 previously implicated in TGF-{beta} responses. Taken together, these results indicate that loss of PPAR-{gamma} in MEFs is associated with upregulation of collagen synthesis, and activation of intracellular Smad signal transduction, due, at least in part, to autocrine TGF-{beta} stimulation.« less

Discovery of a Coregulatory Interaction between Kaposi's Sarcoma-Associated Herpesvirus ORF45 and the Viral Protein Kinase ORF36.

PubMed

Avey, Denis; Tepper, Sarah; Pifer, Benjamin; Bahga, Amritpal; Williams, Hunter; Gillen, Joseph; Li, Wenwei; Ogden, Sarah; Zhu, Fanxiu

2016-07-01

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of three human malignancies. KSHV ORF36 encodes a serine/threonine viral protein kinase, which is conserved throughout all herpesviruses. Although several studies have identified the viral and cellular substrates of conserved herpesvirus protein kinases (CHPKs), the precise functions of KSHV ORF36 during lytic replication remain elusive. Here, we report that ORF36 interacts with another lytic protein, ORF45, in a manner dependent on ORF36 kinase activity. We mapped the regions of ORF36 and ORF45 involved in the binding. Their association appears to be mediated by electrostatic interactions, since deletion of either the highly basic N terminus of ORF36 or an acidic patch of ORF45 abolished the binding. In addition, the dephosphorylation of ORF45 protein dramatically reduced its association with ORF36. Importantly, ORF45 enhances both the stability and kinase activity of ORF36. Consistent with previous studies of CHPK homologs, we detected ORF36 protein in extracellular virions. To investigate the roles of ORF36 in the context of KSHV lytic replication, we used bacterial artificial chromosome mutagenesis to engineer both ORF36-null and kinase-dead mutants. We found that ORF36-null/mutant virions are moderately defective in viral particle production and are further deficient in primary infection. In summary, our results uncover a functionally important interaction between ORF36 and ORF45 and indicate a significant role of ORF36 in the production of infectious progeny virions. Kaposi's sarcoma-associated herpesvirus (KSHV) is a human tumor virus with a significant public health burden. KSHV ORF36 encodes a serine/threonine viral protein kinase, whose functions throughout the viral life cycle have not been elucidated. Here, we report that ORF36 interacts with another KSHV protein, ORF45. We mapped the regions of ORF36 and ORF45 involved in their association and further characterized the consequences of this interaction. We engineered ORF36 mutant viruses in order to investigate the functional roles of ORF36 in the context of KSHV lytic replication, and we confirmed that ORF36 is a component of KSHV virions. Moreover, we found that ORF36 mutants are defective in virion production and primary infection. In summary, we discovered and characterized a functionally important interaction between KSHV ORF36 and ORF45, and our results suggest a significant role of ORF36 in the production of infectious progeny virions, a process critical for KSHV pathogenesis. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Isolation and characterizations of oxalate-binding proteins in the kidney

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roop-ngam, Piyachat; Chaiyarit, Sakdithep; Pongsakul, Nutkridta

Highlights: Black-Right-Pointing-Pointer The first large-scale characterizations of oxalate-binding kidney proteins. Black-Right-Pointing-Pointer The recently developed oxalate-conjugated EAH Sepharose 4B beads were applied. Black-Right-Pointing-Pointer 38 forms of 26 unique oxalate-binding kidney proteins were identified. Black-Right-Pointing-Pointer 25/26 (96%) of identified proteins had 'L-x(3,5)-R-x(2)-[AGILPV]' domain. -- Abstract: Oxalate-binding proteins are thought to serve as potential modulators of kidney stone formation. However, only few oxalate-binding proteins have been identified from previous studies. Our present study, therefore, aimed for large-scale identification of oxalate-binding proteins in porcine kidney using an oxalate-affinity column containing oxalate-conjugated EAH Sepharose 4B beads for purification followed by two-dimensional gel electrophoresis (2-DE) tomore » resolve the recovered proteins. Comparing with those obtained from the controlled column containing uncoupled EAH-Sepharose 4B (to subtract the background of non-specific bindings), a total of 38 protein spots were defined as oxalate-binding proteins. These protein spots were successfully identified by quadrupole time-of-flight mass spectrometry (MS) and/or tandem MS (MS/MS) as 26 unique proteins, including several nuclear proteins, mitochondrial proteins, oxidative stress regulatory proteins, metabolic enzymes and others. Identification of oxalate-binding domain using the PRATT tool revealed 'L-x(3,5)-R-x(2)-[AGILPV]' as a functional domain responsible for oxalate-binding in 25 of 26 (96%) unique identified proteins. We report herein, for the first time, large-scale identification and characterizations of oxalate-binding proteins in the kidney. The presence of positively charged arginine residue in the middle of this functional domain suggested its significance for binding to the negatively charged oxalate. These data will enhance future stone research, particularly on stone modulators.« less

Hyperdiversity of Genes Encoding Integral Light-Harvesting Proteins in the Dinoflagellate Symbiodinium sp

PubMed Central

Boldt, Lynda; Yellowlees, David; Leggat, William

2012-01-01

The superfamily of light-harvesting complex (LHC) proteins is comprised of proteins with diverse functions in light-harvesting and photoprotection. LHC proteins bind chlorophyll (Chl) and carotenoids and include a family of LHCs that bind Chl a and c. Dinophytes (dinoflagellates) are predominantly Chl c binding algal taxa, bind peridinin or fucoxanthin as the primary carotenoid, and can possess a number of LHC subfamilies. Here we report 11 LHC sequences for the chlorophyll a-chlorophyll c 2-peridinin protein complex (acpPC) subfamily isolated from Symbiodinium sp. C3, an ecologically important peridinin binding dinoflagellate taxa. Phylogenetic analysis of these proteins suggests the acpPC subfamily forms at least three clades within the Chl a/c binding LHC family; Clade 1 clusters with rhodophyte, cryptophyte and peridinin binding dinoflagellate sequences, Clade 2 with peridinin binding dinoflagellate sequences only and Clades 3 with heterokontophytes, fucoxanthin and peridinin binding dinoflagellate sequences. PMID:23112815

Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria.

PubMed

Herrou, Julien; Willett, Jonathan W; Czyż, Daniel M; Babnigg, Gyorgy; Kim, Youngchang; Crosson, Sean

2017-03-01

Brucella abortus σ E1 is an EcfG family sigma factor that regulates the transcription of dozens of genes in response to diverse stress conditions and is required for maintenance of chronic infection in a mouse model. A putative ATP-binding cassette transporter operon, bab1_0223-bab1_0226 , is among the most highly activated gene sets in the σ E1 regulon. The proteins encoded by the operon resemble quaternary ammonium-compatible solute importers but are most similar in sequence to the broadly conserved YehZYXW system, which remains largely uncharacterized. Transcription of yehZYXW is activated by the general stress sigma factor σ S in Enterobacteriaceae , which suggests a functional role for this transport system in bacterial stress response across the classes Alphaproteobacteria and Gammaproteobacteria We present evidence that B. abortus YehZYXW does not function as an importer of known compatible solutes under physiological conditions and does not contribute to the virulence defect of a σ E1 -null strain. The sole in vitro phenotype associated with genetic disruption of this putative transport system is reduced growth in the presence of high Li + ion concentrations. A crystal structure of B. abortus YehZ revealed a class II periplasmic binding protein fold with significant structural homology to Archaeoglobus fulgidus ProX, which binds glycine betaine. However, the structure of the YehZ ligand-binding pocket is incompatible with high-affinity binding to glycine betaine. This is consistent with weak measured binding of YehZ to glycine betaine and related compatible solutes. We conclude that YehZYXW is a conserved, stress-regulated transport system that is phylogenetically and functionally distinct from quaternary ammonium-compatible solute importers. IMPORTANCE Brucella abortus σ E1 regulates transcription in response to stressors encountered in its mammalian host and is necessary for maintenance of chronic infection in a mouse model. The functions of the majority of genes regulated by σ E1 remain undefined. We present a functional/structural analysis of a conserved putative membrane transport system (YehZYXW) whose expression is strongly activated by σ E1 Though annotated as a quaternary ammonium osmolyte uptake system, experimental physiological studies and measured ligand-binding properties of the periplasmic binding protein (PBP), YehZ, are inconsistent with this function. A crystal structure of B. abortus YehZ provides molecular insight into differences between bona fide quaternary ammonium osmolyte importers and YehZ-related proteins, which form a distinct phylogenetic and functional group of PBPs. Copyright © 2017 American Society for Microbiology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrou, Julien; Willett, Jonathan W.; Czyż, Daniel M.

ABSTRACT Brucella abortusσ E1is an EcfG family sigma factor that regulates the transcription of dozens of genes in response to diverse stress conditions and is required for maintenance of chronic infection in a mouse model. A putative ATP-binding cassette transporter operon,bab1_0223-bab1_0226, is among the most highly activated gene sets in the σ E1regulon. The proteins encoded by the operon resemble quaternary ammonium-compatible solute importers but are most similar in sequence to the broadly conserved YehZYXW system, which remains largely uncharacterized. Transcription ofyehZYXWis activated by the general stress sigma factor σ SinEnterobacteriaceae, which suggests a functional role for this transport systemmore » in bacterial stress response across the classesAlphaproteobacteriaandGammaproteobacteria. We present evidence thatB. abortusYehZYXW does not function as an importer of known compatible solutes under physiological conditions and does not contribute to the virulence defect of a σ E1-null strain. The solein vitrophenotype associated with genetic disruption of this putative transport system is reduced growth in the presence of high Li +ion concentrations. A crystal structure ofB. abortusYehZ revealed a class II periplasmic binding protein fold with significant structural homology toArchaeoglobus fulgidusProX, which binds glycine betaine. However, the structure of the YehZ ligand-binding pocket is incompatible with high-affinity binding to glycine betaine. This is consistent with weak measured binding of YehZ to glycine betaine and related compatible solutes. We conclude that YehZYXW is a conserved, stress-regulated transport system that is phylogenetically and functionally distinct from quaternary ammonium-compatible solute importers. IMPORTANCEBrucella abortusσ E1regulates transcription in response to stressors encountered in its mammalian host and is necessary for maintenance of chronic infection in a mouse model. The functions of the majority of genes regulated by σ E1remain undefined. We present a functional/structural analysis of a conserved putative membrane transport system (YehZYXW) whose expression is strongly activated by σ E1. Though annotated as a quaternary ammonium osmolyte uptake system, experimental physiological studies and measured ligand-binding properties of the periplasmic binding protein (PBP), YehZ, are inconsistent with this function. A crystal structure ofB. abortusYehZ provides molecular insight into differences between bona fide quaternary ammonium osmolyte importers and YehZ-related proteins, which form a distinct phylogenetic and functional group of PBPs.« less

Conserved ABC Transport System Regulated by the General Stress Response Pathways of Alpha- and Gammaproteobacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrou, Julien; Willett, Jonathan W.; Czyż, Daniel M.

ABSTRACT Brucella abortusσ E1is an EcfG family sigma factor that regulates the transcription of dozens of genes in response to diverse stress conditions and is required for maintenance of chronic infection in a mouse model. A putative ATP-binding cassette transporter operon,bab1_0223-bab1_0226, is among the most highly activated gene sets in the σ E1regulon. The proteins encoded by the operon resemble quaternary ammonium-compatible solute importers but are most similar in sequence to the broadly conserved YehZYXW system, which remains largely uncharacterized. Transcription ofyehZYXWis activated by the general stress sigma factor σ SinEnterobacteriaceae, which suggests a functional role for this transport systemmore » in bacterial stress response across the classesAlphaproteobacteriaandGammaproteobacteria. We present evidence thatB. abortusYehZYXW does not function as an importer of known compatible solutes under physiological conditions and does not contribute to the virulence defect of a σ E1-null strain. The solein vitrophenotype associated with genetic disruption of this putative transport system is reduced growth in the presence of high Li +ion concentrations. A crystal structure ofB. abortusYehZ revealed a class II periplasmic binding protein fold with significant structural homology toArchaeoglobus fulgidusProX, which binds glycine betaine. However, the structure of the YehZ ligand-binding pocket is incompatible with high-affinity binding to glycine betaine. This is consistent with weak measured binding of YehZ to glycine betaine and related compatible solutes. We conclude that YehZYXW is a conserved, stress-regulated transport system that is phylogenetically and functionally distinct from quaternary ammonium-compatible solute importers. IMPORTANCEBrucella abortusσ E1regulates transcription in response to stressors encountered in its mammalian host and is necessary for maintenance of chronic infection in a mouse model. The functions of the majority of genes regulated by σ E1remain undefined. We present a functional/structural analysis of a conserved putative membrane transport system (YehZYXW) whose expression is strongly activated by σ E1. Though annotated as a quaternary ammonium osmolyte uptake system, experimental physiological studies and measured ligand-binding properties of the periplasmic binding protein (PBP), YehZ, are inconsistent with this function. A crystal structure ofB. abortusYehZ provides molecular insight into differences between bona fide quaternary ammonium osmolyte importers and YehZ-related proteins, which form a distinct phylogenetic and functional group of PBPs.« less

Protein and quality characterization of complete and partial near isogenic lines of waxy wheat

USDA-ARS?s Scientific Manuscript database

The objective of this study was to evaluate protein composition and its effects on flour quality and physical dough test parameters using waxy wheat near-isogenic lines. Partial waxy (single and double nulls) and waxy (null at all three waxy loci, Wx-A1, Wx-B1, and Wx-D1) lines of N11 set (bread whe...

Cyclooxygenase-2 is an obligatory factor in methamphetamine-induced neurotoxicity.

PubMed

Thomas, David M; Kuhn, Donald M

2005-05-01

Methamphetamine causes persistent damage to dopamine nerve endings of the striatum. The mechanisms underlying its neurotoxicity are not fully understood, but considerable evidence points to oxidative stress as a probable mechanism. A recent microarray analysis of gene expression changes caused by methamphetamine revealed that cyclooxygenase-2 (COX-2) was induced along with its transcription factor CCAAT/enhancer-binding protein (Thomas DM, Francescutti-Verbeem DM, Liu X, and Kuhn DM, 2004). We report presently that methamphetamine increases striatal expression of COX-2 protein. Cyclooxygenase-1 (COX-1) expression was not changed. Mice bearing a null mutation of the gene for COX-2 were resistant to methamphetamine-induced neurotoxicity. COX-1 knockouts, like wild-type mice, showed extensive dopamine nerve terminal damage. Selective inhibitors of COX-1 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethyl pyrazole (SC-560)], COX-2 [N-[2-(cyclohexyloxy)-4-nitrophenyl] methanesulfonamide (NS-398), rofecoxib], or COX-3 (antipyrine) or a nonselective inhibitor of the COX-1/2 isoforms (ketoprofen) did not protect mice from neurotoxicity. Finally, methamphetamine did not change striatal prostaglandin E(2) content. Taken together, these data suggest that COX-2 is an obligatory factor in methamphetamine-induced neurotoxicity. The functional aspect of COX-2 that contributes to drug-induced neurotoxicity does not appear to be its prostaglandin synthetic capacity. Instead, the peroxidase activity associated with COX-2, which can lead to the formation of reactive oxygen species and dopamine quinones, can account for its role.

Downregulation of hepatic betaine:homocysteine methyltransferase (BHMT) expression in taurine-deficient mice is reversed by taurine supplementation in vivo

PubMed Central

Jurkowska, Halina; Niewiadomski, Julie; Hirschberger, Lawrence L.; Roman, Heather B.; Mazor, Kevin M.; Liu, Xiaojing; Locasale, Jason W.; Park, Eunkyue

2016-01-01

The cysteine dioxygenase (Cdo1)-null and the cysteine sulfinic acid decarboxylase (Csad)-null mouse are not able to synthesize hypotaurine/taurine by the cysteine/cysteine sulfinate pathway and have very low tissue taurine levels. These mice provide excellent models for studying the effects of taurine on biological processes. Using these mouse models, we identified betaine:homocysteine methyltransferase (BHMT) as a protein whose in vivo expression is robustly regulated by taurine. BHMT levels are low in liver of both Cdo1-null and Csad-null mice, but are restored to wild-type levels by dietary taurine supplementation. A lack of BHMT activity was indicated by an increase in the hepatic betaine level. In contrast to observations in liver of Cdo1-null and Csad-null mice, BHMT was not affected by taurine supplementation of primary hepatocytes from these mice. Likewise, CSAD abundance was not affected by taurine supplementation of primary hepatocytes, although it was robustly upregulated in liver of Cdo1-null and Csad-null mice and lowered to wild-type levels by dietary taurine supplementation. The mechanism by which taurine status affects hepatic CSAD and BHMT expression appears to be complex and to require factors outside of hepatocytes. Within the liver, mRNA abundance for both CSAD and BHMT was upregulated in parallel with protein levels, indicating regulation of BHMT and CSAD mRNA synthesis or degradation. PMID:26481005

Molecular cloning and preliminary function study of iron responsive element binding protein 1 gene from cypermethrin-resistant Culex pipiens pallens

PubMed Central

2011-01-01

Background Insecticide resistance jeopardizes the control of mosquito populations and mosquito-borne disease control, which creates a major public health concern. Two-dimensional electrophoresis identified one protein segment with high sequence homology to part of Aedes aegypti iron-responsive element binding protein (IRE-BP). Method RT-PCR and RACE (rapid amplification of cDNA end) were used to clone a cDNA encoding full length IRE-BP 1. Real-time quantitative RT-PCR was used to evaluate the transcriptional level changes in the Cr-IRE strain Aedes aegypti compared to the susceptible strain of Cx. pipiens pallens. The expression profile of the gene was established in the mosquito life cycle. Methyl tritiated thymidine (3H-TdR) was used to observe the cypermethrin resistance changes in C6/36 cells containing the stably transfected IRE-BP 1 gene of Cx. pipiens pallens. Results The complete sequence of iron responsive element binding protein 1 (IRE-BP 1) has been cloned from the cypermethrin-resistant strain of Culex pipiens pallens (Cr-IRE strain). Quantitative RT-PCR analysis indicated that the IRE-BP 1 transcription level was 6.7 times higher in the Cr-IRE strain than in the susceptible strain of 4th instar larvae. The IRE-BP 1 expression was also found to be consistently higher throughout the life cycle of the Cr-IRE strain. A protein of predicted size 109.4 kDa has been detected by Western blotting in IRE-BP 1-transfected mosquito C6/36 cells. These IRE-BP 1-transfected cells also showed enhanced cypermethrin resistance compared to null-transfected or plasmid vector-transfected cells as determined by 3H-TdR incorporation. Conclusion IRE-BP 1 is expressed at higher levels in the Cr-IRE strain, and may confer some insecticide resistance in Cx. pipiens pallens. PMID:22075242

UO₂²⁺ uptake by proteins: understanding the binding features of the super uranyl binding protein and design of a protein with higher affinity.

PubMed

Odoh, Samuel O; Bondarevsky, Gary D; Karpus, Jason; Cui, Qiang; He, Chuan; Spezia, Riccardo; Gagliardi, Laura

2014-12-17

The capture of uranyl, UO2(2+), by a recently engineered protein (Zhou et al. Nat. Chem. 2014, 6, 236) with high selectivity and femtomolar sensitivity has been examined by a combination of density functional theory, molecular dynamics, and free-energy simulations. It was found that UO2(2+) is coordinated to five carboxylate oxygen atoms from four amino acid residues of the super uranyl binding protein (SUP). A network of hydrogen bonds between the amino acid residues coordinated to UO2(2+) and residues in its second coordination sphere also affects the protein's uranyl binding affinity. Free-energy simulations show how UO2(2+) capture is governed by the nature of the amino acid residues in the binding site, the integrity and strength of the second-sphere hydrogen bond network, and the number of water molecules in the first coordination sphere. Alteration of any of these three factors through mutations generally results in a reduction of the binding free energy of UO2(2+) to the aqueous protein as well as of the difference between the binding free energies of UO2(2+) and other ions (Ca(2+), Cu(2+), Mg(2+), and Zn(2+)), a proxy for the protein's selectivity over these ions. The results of our free-energy simulations confirmed the previously reported experimental results and allowed us to discover a mutant of SUP, specifically the GLU64ASP mutant, that not only binds UO2(2+) more strongly than SUP but that is also more selective for UO2(2+) over other ions. The predictions from the computations were confirmed experimentally.

Control of Cell Morphology: Signalling by the Receptor Notch.

DTIC Science & Technology

1996-10-01

missense mutations or small deletions at the extreme C-terminus of NOTCH, and lie within the minimal region that includes the C-terminal binding site for...20 Figure 4. Genetic interaction of null and hypomorphic alleles of Notch with abl mutations ...wide variety of cell types during Drosophila embryogenesis [1, 2]. Mutations in the Notch gene lead to severe defects in cell identity in the nervous

The mCpG-binding domain of human MBD3 does not bind to mCpG but interacts with NuRD/Mi2 components HDAC1 and MTA2.

PubMed

Saito, Motoki; Ishikawa, Fuyuki

2002-09-20

Although mammalian MBD3 contains the mCpG-binding domain (MBD) and is highly homologous with the authentic mCpG-binding protein MBD2, it was reported that the protein does not bind to mCpG specifically. Using recombinant human wild type and mutant MBD3 proteins, we demonstrated that atypical amino acids found in MBD3 MBD, namely, His-30 and Phe-34, are responsible for the inability of MBD3 to bind to mCpG. Interestingly, although H30K/F34Y MBD3 mutant protein binds to mCpG efficiently in vitro, it was not localized at the mCpG-rich pericentromeric regions in mouse cells. We also showed that Y34F MBD2b MBD, which possesses not the mCpG-specific DNA-binding activity but the nonspecific DNA-binding activity, was localized at the pericentromeric regions. These results suggested that the mCpG-specific DNA-binding activity is largely dispensable, and another factor(s) is required for the localization of MBD proteins in vivo. MBD3 was identified as a component of the NuRD/Mi2 complex that shows chromatin remodeling and histone deacetylase activities. We demonstrated that MBD3 MBD is necessary and sufficient for binding to HDAC1 and MTA2, two components of the NuRD/Mi2 complex. It was therefore suggested that mCpG-binding-defective MBD3 has evolutionarily conserved its MBD because of the secondary role played by the MBD in protein-protein interactions.

A non-canonical role for Rgnef in promoting integrin-stimulated focal adhesion kinase activation

PubMed Central

Miller, Nichol L. G.; Lawson, Christine; Kleinschmidt, Elizabeth G.; Tancioni, Isabelle; Uryu, Sean; Schlaepfer, David D.

2013-01-01

Summary Rgnef (also known as p190RhoGEF or ARHGEF28) is a Rho guanine-nucleotide-exchange factor (GEF) that binds focal adhesion kinase (FAK). FAK is recruited to adhesions and activated by integrin receptors binding to matrix proteins, such as fibronectin (FN). Canonical models place Rgnef downstream of integrin–FAK signaling in regulating Rho GTPase activity and cell movement. Herein, we establish a new, upstream role for Rgnef in enhancing FAK localization to early peripheral adhesions and promoting FAK activation upon FN binding. Rgnef-null mouse embryo fibroblasts (MEFs) exhibit defects in adhesion formation, levels of FAK phosphotyrosine (pY)-397 and FAK localization to peripheral adhesions upon re-plating on FN. Rgnef re-expression rescues these defects, but requires Rgnef–FAK binding. A mutation in the Rgnef pleckstrin homology (PH) domain inhibits adhesion formation, FAK localization, and FAK-Y397 and paxillin-Y118 phosphorylation without disrupting the Rgnef–FAK interaction. A GEF-inactive Rgnef mutant rescues FAK-Y397 phosphorylation and early adhesion localization, but not paxillin-Y118 phosphorylation. This suggests that, downstream of FN binding, paxillin-pY118 requires Rgnef GEF activity through a mechanism distinct from adhesion formation and FAK activation. These results support a scaffolding role for Rgnef in FAK localization and activation at early adhesions in a PH-domain-dependent but GEF-activity-independent manner. PMID:24006257

Specific binding of tubeimoside-2 with proteins in hepatocarcinoma HepG2 cells: investigation by molecular spectroscopy

NASA Astrophysics Data System (ADS)

Yang, Sun; Shi-Sheng, Sun; Ying-Yong, Zhao; Jun, Fan

2012-07-01

In this study, we compared different binding interactions of TBMS2 with proteins both in hepatocarcinoma HepG2 cells and in normal embryo hepatic L02 cells by using fluorescence, absorption, and CD spectroscopy. The fluorescence data revealed that the fluorescence intensity of proteins in the HepG2 and L02 cells decreased in the presence of TBMS2 by 30.79% and 12.01%, respectively. Binding constants and thermodynamic parameters were obtained for systems of TBMS2 with the two kinds of cell proteins. The results indicated that HepG2 cell proteins had a higher TBMS2 binding activity than those in the L02 cells. Analysis of the TBMS2 cytotoxic activities showed that TBMS2 could selectively induce apoptosis of HepG2 cells by binding to them, while its apoptotic effect on L02 cells was relatively weaker.

Treatment with N- and C-Terminal Peptides of Parathyroid Hormone-Related Protein Partly Compensate the Skeletal Abnormalities in IGF-I Deficient Mice

PubMed Central

Portal-Núñez, Sergio; Murillo-Cuesta, Silvia; Lozano, Daniel; Cediel, Rafael; Esbrit, Pedro

2014-01-01

Insulin-like growth factor-I (IGF-I) deficiency causes growth delay, and IGF-I has been shown to partially mediate bone anabolism by parathyroid hormone (PTH). PTH-related protein (PTHrP) is abundant in bone, and has osteogenic features by poorly defined mechanisms. We here examined the capacity of PTHrP (1–36) and PTHrP (107–111) (osteostatin) to reverse the skeletal alterations associated with IGF-I deficiency. Igf1-null mice and their wild type littermates were treated with each PTHrP peptide (80 µg/Kg/every other day/2 weeks; 2 males and 4 females for each genotype) or saline vehicle (3 males and 3 females for each genotype). We found that treatment with either PTHrP peptide ameliorated trabecular structure in the femur in both genotypes. However, these peptides were ineffective in normalizing the altered cortical structure at this bone site in Igf1-null mice. An aberrant gene expression of factors associated with osteoblast differentiation and function, namely runx2, osteoprotegerin/receptor activator of NF-κB ligand ratio, Wnt3a , cyclin D1, connexin 43, catalase and Gadd45, as well as in osteocyte sclerostin, was found in the long bones of Igf1-null mice. These mice also displayed a lower amount of trabecular osteoblasts and osteoclasts in the tibial metaphysis than those in wild type mice. These alterations in Igf1-null mice were only partially corrected by each PTHrP peptide treatment. The skeletal expression of Igf2, Igf1 receptor and Irs2 was increased in Igf1-null mice, and this compensatory profile was further improved by treatment with each PTHrP peptide related to ERK1/2 and FoxM1 activation. In vitro, PTHrP (1–36) and osteostatin were effective in promoting bone marrow stromal cell mineralization in normal mice but not in IGF-I-deficient mice. Collectively, these findings indicate that PTHrP (1–36) and osteostatin can exert several osteogenic actions even in the absence of IGF-I in the mouse bone. PMID:24503961

RANBP17 is localized to the XY body of spermatocytes and interacts with SPEM1 on the manchette of elongating spermatids

PubMed Central

Bao, Jianqiang; Wu, Qiuxia; Song, Rui; Jie, Zhang; Zheng, Huili; Xu, Chen; Yan, Wei

2010-01-01

We identified Ran-binding protein 17 (RANBP17) as one of the interacting partners of sperm maturation 1 (SPEM1) using yeast 2-hybrid screening and immunoprecipitation assays. Expression profiling analyses suggested that RANBP17 was preferentially expressed in the testis. Immunofluorescent confocal microscopy revealed a dynamic localization pattern of RANBP17 during spermatogenesis. In primary spermatocytes RANBP17 was mainly localized to the XY body. In the subsequent spermiogenesis, RANBP17 was first observed in the nuclei of round spermatids (steps1–7) and then confined to the manchette of elongating spermatids (steps 8–14) together with its interacting partner SPEM1. In the Spem1-null testes, levels of RANBP17 were significantly elevated. As a member of a large protein family involved in the nucleocytoplasmic transport, RANBP17 may have a role in sex chromosome inactivation during the meiotic phase of spermatogenesis, and also in the intramanchette transport during spermiogenesis. Interactions between RANBP17 and SPEM1, for the first time, point to a potential function of SPEM1 in the RANBP17-mediated nucleocytoplasmic transport. PMID:21184802

p53 Involvement in the Control of Murine Hair Follicle Regression

PubMed Central

Botchkarev, Vladimir A.; Komarova, Elena A.; Siebenhaar, Frank; Botchkareva, Natalia V.; Sharov, Andrei A.; Komarov, Pavel G.; Maurer, Marcus; Gudkov, Andrei V.; Gilchrest, Barbara A.

2001-01-01

p53 is a transcription factor mediating a variety of biological responses including apoptotic cell death. p53 was recently shown to control apoptosis in the hair follicle induced by ionizing radiation and chemotherapy, but its role in the apoptosis-driven physiological hair follicle regression (catagen) remains to be elucidated. Here, we show that p53 protein is strongly expressed and co-localized with apoptotic markers in the regressing hair follicle compartments during catagen. In contrast to wild-type mice, p53 knockout mice show significant retardation of catagen accompanied by significant decrease in the number of apoptotic cells in the hair matrix. Furthermore, p53 null hair follicles are characterized by alterations in the expression of markers that are encoded by p53 target genes and are implicated in the control of catagen (Bax, Bcl-2, insulin-like growth factor binding protein-3). These data suggest that p53 is involved in the control of apoptosis in the hair follicle during physiological regression and imply that p53 antagonists may be useful for the management of hair growth disorders characterized by premature entry into catagen, such as androgenetic alopecia, alopecia areata, and telogen effluvium. PMID:11395365

RBFOX2 protein domains and cellular activities.

PubMed

Arya, Anurada D; Wilson, David I; Baralle, Diana; Raponi, Michaela

2014-08-01

RBFOX2 (RNA-binding protein, Fox-1 homologue 2)/RBM9 (RNA-binding-motif protein 9)/RTA (repressor of tamoxifen action)/HNRBP2 (hexaribonucleotide-binding protein 2) encodes an RNA-binding protein involved in tissue specific alternative splicing regulation and steroid receptors transcriptional activity. Its ability to regulate specific splicing profiles depending on context has been related to different expression levels of the RBFOX2 protein itself and that of other splicing regulatory proteins involved in the shared modulation of specific genes splicing. However, this cannot be the sole explanation as to why RBFOX2 plays a widespread role in numerous cellular mechanisms from development to cell survival dependent on cell/tissue type. RBFOX2 isoforms with altered protein domains exist. In the present article, we describe the main RBFOX2 protein domains, their importance in the context of splicing and transcriptional regulation and we propose that RBFOX2 isoform distribution may play a fundamental role in RBFOX2-specific cellular effects.

FlnA-null megakaryocytes prematurely release large and fragile platelets that circulate poorly

PubMed Central

Jurak Begonja, Antonija; Hoffmeister, Karin M.; Hartwig, John H.

2011-01-01

Filamin A (FlnA) is a large cytoplasmic protein that crosslinks actin filaments and anchors membrane receptors and signaling intermediates. FlnAloxP PF4-Cre mice that lack FlnA in the megakaryocyte (MK) lineage have a severe macrothrombocytopenia because of accelerated platelet clearance. Macrophage ablation by injection of clodronate-encapsulated liposomes increases blood platelet counts in FlnAloxP PF4-Cre mice and reveals the desintegration of FlnA-null platelets into microvesicles, a process that occurs spontaneously during storage. FlnAloxP PF4-Cre bone marrows and spleens have a 2.5- to 5-fold increase in MK numbers, indicating increased thrombopoiesis in vivo. Analysis of platelet production in vitro reveals that FlnA-null MKs prematurely convert their cytoplasm into large CD61+ platelet-sized particles, reminiscent of the large platelets observed in vivo. FlnA stabilizes the platelet von Willebrand factor receptor, as surface expression of von Willebrand factor receptor components is normal on FlnA-null MKs but decreased on FlnA-null platelets. Further, FlnA-null platelets contain multiple GPIbα degradation products and have increased expression of the ADAM17 and MMP9 metalloproteinases. Together, the findings indicate that FlnA-null MKs prematurely release large and fragile platelets that are removed rapidly from the circulation by macrophages. PMID:21652675

Ubiquitin Regulates Caspase Recruitment Domain-mediated Signaling by Nucleotide-binding Oligomerization Domain-containing Proteins NOD1 and NOD2*

PubMed Central

Ver Heul, Aaron M.; Fowler, C. Andrew; Ramaswamy, S.; Piper, Robert C.

2013-01-01

NOD1 and NOD2 (nucleotide-binding oligomerization domain-containing proteins) are intracellular pattern recognition receptors that activate inflammation and autophagy. These pathways rely on the caspase recruitment domains (CARDs) within the receptors, which serve as protein interaction platforms that coordinately regulate immune signaling. We show that NOD1 CARD binds ubiquitin (Ub), in addition to directly binding its downstream targets receptor-interacting protein kinase 2 (RIP2) and autophagy-related protein 16-1 (ATG16L1). NMR spectroscopy and structure-guided mutagenesis identified a small hydrophobic surface of NOD1 CARD that binds Ub. In vitro, Ub competes with RIP2 for association with NOD1 CARD. In vivo, we found that the ligand-stimulated activity of NOD1 with a mutant CARD lacking Ub binding but retaining ATG16L1 and RIP2 binding is increased relative to wild-type NOD1. Likewise, point mutations in the tandem NOD2 CARDs at positions analogous to the surface residues defining the Ub interface on NOD1 resulted in loss of Ub binding and increased ligand-stimulated NOD2 signaling. These data suggest that Ub binding provides a negative feedback loop upon NOD-dependent activation of RIP2. PMID:23300079

RNA binding properties of the US11 protein from four primate simplexviruses.

PubMed

Tohme, Sarah; Cukier, Cyprian D; Severini, Alberto

2011-11-03

The protein encoded by the Us11 gene of herpes simplex viruses is a dsRNA binding protein which inhibits protein kinase R activity, thereby preventing the interferon-induced shut down of protein synthesis following viral infection. Us11 protein is not essential for infectivity in vitro and in mice in herpes simplex virus type 1 (HSV1), however this virus has a second, and apparently more important, inhibitor of PKR activity, the γ134.5 protein. Recently sequenced simian simplexviruses SA8, HVP2 and B virus do not have an ORF corresponding to the γ134.5 protein, yet they have similar, or greater, infectivity as HSV1 and HSV2. We have expressed the US11 proteins of the simplexviruses HSV1, HSV2, HVP2 and B virus and measured their abilities to bind dsRNA, in order to investigate possible differences that could complement the absence of the γ134.5 protein. We employed a filter binding technique that allows binding of the Us11 protein under condition of excess dsRNA substrate and therefore a measurement of the true Kd value of Us11-dsRNA binding. The results show a Kd of binding in the range of 0.89 nM to 1.82 nM, with no significant difference among the four Us11 proteins.

RNA binding properties of the US11 protein from four primate simplexviruses

PubMed Central

2011-01-01

Background The protein encoded by the Us11 gene of herpes simplex viruses is a dsRNA binding protein which inhibits protein kinase R activity, thereby preventing the interferon-induced shut down of protein synthesis following viral infection. Us11 protein is not essential for infectivity in vitro and in mice in herpes simplex virus type 1 (HSV1), however this virus has a second, and apparently more important, inhibitor of PKR activity, the γ134.5 protein. Recently sequenced simian simplexviruses SA8, HVP2 and B virus do not have an ORF corresponding to the γ134.5 protein, yet they have similar, or greater, infectivity as HSV1 and HSV2. Methods We have expressed the US11 proteins of the simplexviruses HSV1, HSV2, HVP2 and B virus and measured their abilities to bind dsRNA, in order to investigate possible differences that could complement the absence of the γ134.5 protein. We employed a filter binding technique that allows binding of the Us11 protein under condition of excess dsRNA substrate and therefore a measurement of the true Kd value of Us11-dsRNA binding. Results and Conclusions The results show a Kd of binding in the range of 0.89 nM to 1.82 nM, with no significant difference among the four Us11 proteins. PMID:22054255

A novel Ras-interacting protein required for chemotaxis and cyclic adenosine monophosphate signal relay in Dictyostelium.

PubMed

Lee, S; Parent, C A; Insall, R; Firtel, R A

1999-09-01

We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced approximately 60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras-regulated pathway involved in integrating chemotaxis and signal relay pathways that are essential for aggregation.

A Surface Groove Essential for Viral Bcl-2 Function During Chronic Infection In Vivo

PubMed Central

Petros, Andrew M; Nettesheim, David; van Dyk, Linda F.; Labrada, Lucia; Speck, Samuel H; Levine, Beth

2005-01-01

Antiapoptotic Bcl-2 family proteins inhibit apoptosis in cultured cells by binding BH3 domains of proapoptotic Bcl-2 family members via a hydrophobic BH3 binding groove on the protein surface. We investigated the physiological importance of the BH3 binding groove of an antiapoptotic Bcl-2 protein in mammals in vivo by analyzing a viral Bcl-2 family protein. We show that the γ-herpesvirus 68 (γHV68) Bcl-2 family protein (γHV68 v-Bcl-2), which is known to inhibit apoptosis in cultured cells, inhibits both apoptosis in primary lymphocytes and Bax toxicity in yeast. Nuclear magnetic resonance determination of the γHV68 v-Bcl-2 structure revealed a BH3 binding groove that binds BH3 domain peptides from proapoptotic Bcl-2 family members Bax and Bak via a molecular mechanism shared with host Bcl-2 family proteins, involving a conserved arginine in the BH3 peptide binding groove. Mutations of this conserved arginine and two adjacent amino acids to alanine (SGR to AAA) within the BH3 binding groove resulted in a properly folded protein that lacked the capacity of the wild-type γHV68 v-Bcl-2 to bind Bax BH3 peptide and to block Bax toxicity in yeast. We tested the physiological importance of this v-Bcl-2 domain during viral infection by engineering viral mutants encoding a v-Bcl-2 containing the SGR to AAA mutation. This mutation resulted in a virus defective for both efficient reactivation of γHV68 from latency and efficient persistent γHV68 replication. These studies demonstrate an essential functional role for amino acids in the BH3 peptide binding groove of a viral Bcl-2 family member during chronic infection. PMID:16201011

Plasma Levels of Fatty Acid-Binding Protein 4, Retinol-Binding Protein 4, High-Molecular-Weight Adiponectin, and Cardiovascular Mortality Among Men With Type 2 Diabetes: A 22-Year Prospective Study.

PubMed

Liu, Gang; Ding, Ming; Chiuve, Stephanie E; Rimm, Eric B; Franks, Paul W; Meigs, James B; Hu, Frank B; Sun, Qi

2016-11-01

To examine select adipokines, including fatty acid-binding protein 4, retinol-binding protein 4, and high-molecular-weight (HMW) adiponectin in relation to cardiovascular disease (CVD) mortality among patients with type 2 diabetes mellitus. Plasma levels of fatty acid-binding protein 4, retinol-binding protein 4, and HMW adiponectin were measured in 950 men with type 2 diabetes mellitus in the Health Professionals Follow-up Study. After an average of 22 years of follow-up (1993-2015), 580 deaths occurred, of whom 220 died of CVD. After multivariate adjustment for covariates, higher levels of fatty acid-binding protein 4 were significantly associated with a higher CVD mortality: comparing extreme tertiles, the hazard ratio and 95% confidence interval of CVD mortality was 1.78 (1.22-2.59; P trend=0.001). A positive association was also observed for HMW adiponectin: the hazard ratio (95% confidence interval) was 2.07 (1.42-3.06; P trend=0.0002), comparing extreme tertiles, whereas higher retinol-binding protein 4 levels were nonsignificantly associated with a decreased CVD mortality with an hazard ratio (95% confidence interval) of 0.73 (0.50-1.07; P trend=0.09). A Mendelian randomization analysis suggested that the causal relationships of HMW adiponectin and retinol-binding protein 4 would be directionally opposite to those observed based on the biomarkers, although none of the Mendelian randomization associations achieved statistical significance. These data suggest that higher levels of fatty acid-binding protein 4 and HMW adiponectin are associated with elevated CVD mortality among men with type 2 diabetes mellitus. Biological mechanisms underlying these observations deserve elucidation, but the associations of HMW adiponectin may partially reflect altered adipose tissue functionality among patients with type 2 diabetes mellitus. © 2016 American Heart Association, Inc.

Functions of Intracellular Retinoid Binding-Proteins.

PubMed

Napoli, Joseph L

Multiple binding and transport proteins facilitate many aspects of retinoid biology through effects on retinoid transport, cellular uptake, metabolism, and nuclear delivery. These include the serum retinol binding protein sRBP (aka Rbp4), the plasma membrane sRBP receptor Stra6, and the intracellular retinoid binding-proteins such as cellular retinol-binding proteins (CRBP) and cellular retinoic acid binding-proteins (CRABP). sRBP transports the highly lipophilic retinol through an aqueous medium. The major intracellular retinol-binding protein, CRBP1, likely enhances efficient retinoid use by providing a sink to facilitate retinol uptake from sRBP through the plasma membrane or via Stra6, delivering retinol or retinal to select enzymes that generate retinyl esters or retinoic acid, and protecting retinol/retinal from excess catabolism or opportunistic metabolism. Intracellular retinoic acid binding-proteins (CRABP1 and 2, and FABP5) seem to have more diverse functions distinctive to each, such as directing retinoic acid to catabolism, delivering retinoic acid to specific nuclear receptors, and generating non-canonical actions. Gene ablation of intracellular retinoid binding-proteins does not cause embryonic lethality or gross morphological defects. Metabolic and functional defects manifested in knockouts of CRBP1, CRBP2 and CRBP3, however, illustrate their essentiality to health, and in the case of CRBP2, to survival during limited dietary vitamin A. Future studies should continue to address the specific molecular interactions that occur between retinoid binding-proteins and their targets and their precise physiologic contributions to retinoid homeostasis and function.

R521C and R521H mutations in FUS result in weak binding with Karyopherinβ2 leading to Amyotrophic lateral sclerosis: a molecular docking and dynamics study.

PubMed

Swetha, Rayapadi G; Ramaiah, Sudha; Anbarasu, Anand

2017-08-01

Fused in sarcoma (FUS) gene encodes the RNA binding protein FUS. This gene is mapped to chromosome 16p11.2. The FUS protein binds with karyopherineβ2 (Kapβ2) through its proline/tyrosine nuclear localization signal (PY-NLS) that helps in the localization of FUS protein within the nucleus. Arginine residue in 521 position (R521) of PY-NLS plays a vital role in the binding of FUS protein with Kapβ2. Mutations in this position (R521C and R521H) are the most predominant mutations associated with amyotrophic lateral sclerosis (ALS). However, the mechanism by which these mutations lead to ALS is poorly understood. We examined the binding behaviour of the mutants FUS (R521C) and FUS (R521H) with Kapβ2 through protein-protein docking and molecular dynamics simulation. The binding patterns of mutants were compared with the binding behaviour of wild FUS-Kapβ2. Our results suggest that these mutants have relatively weak binding affinity with Kapβ2 when compared with wild FUS-Kapβ2 as indicated by the lesser number of interactions found between the mutant FUS and Kapβ2. Hence, these mutations weakens the binding and this results in the cytoplasmic mislocalization of mutant FUS; and thereby it increases the severity of ALS.

Sls1p is a membrane-bound regulator of transcription-coupled processes involved in Saccharomyces cerevisiae mitochondrial gene expression.

PubMed Central

Bryan, Anthony C; Rodeheffer, Matthew S; Wearn, Christopher M; Shadel, Gerald S

2002-01-01

Mitochondrial translation is largely membrane-associated in S. cerevisiae. Recently, we discovered that the matrix protein Nam1p binds the amino-terminal domain of yeast mtRNA polymerase to couple translation and/or RNA-processing events to transcription. To gain additional insight into these transcription-coupled processes, we performed a genetic screen for genes that suppress the petite phenotype of a point mutation in mtRNA polymerase (rpo41-R129D) when overexpressed. One suppressor identified in this screen was SLS1, which encodes a mitochondrial membrane protein required for assembly of respiratory-chain enzyme complexes III and IV. The mtRNA-processing defects associated with the rpo41-R129D mutation were corrected in the suppressed strain, linking Sls1p to a pathway that includes mtRNA polymerase and Nam1p. This was supported by the observation that SLS1 overexpression rescued the petite phenotype of a NAM1 null mutation. In contrast, overexpression of Nam1p did not rescue the petite phenotype of a SLS1 null mutation, indicating that Nam1p and Sls1p are not functionally redundant but rather exist in an ordered pathway. On the basis of these data, a model in which Nam1p coordinates the delivery of newly synthesized transcripts to the membrane, where Sls1p directs or regulates their subsequent handling by membrane-bound factors involved in translation, is proposed. PMID:11805046

Poly(ADP-Ribosyl)ation of hnRNP A1 Protein Controls Translational Repression in Drosophila

PubMed Central

Ji, Yingbiao

2016-01-01

Poly(ADP-ribosyl)ation of heterogeneous nuclear ribonucleoproteins (hnRNPs) regulates the posttranscriptional fate of RNA during development. Drosophila hnRNP A1, Hrp38, is required for germ line stem cell maintenance and oocyte localization. The mRNA targets regulated by Hrp38 are mostly unknown. We identified 428 Hrp38-associated gene transcripts in the fly ovary, including mRNA of the translational repressor Nanos. We found that Hrp38 binds to the 3′ untranslated region (UTR) of Nanos mRNA, which contains a translation control element. We have demonstrated that translation of the luciferase reporter bearing the Nanos 3′ UTR is enhanced by dsRNA-mediated Hrp38 knockdown as well as by mutating potential Hrp38-binding sites. Our data show that poly(ADP-ribosyl)ation inhibits Hrp38 binding to the Nanos 3′ UTR, increasing the translation in vivo and in vitro. hrp38 and Parg null mutants showed an increased ectopic Nanos translation early in the embryo. We conclude that Hrp38 represses Nanos translation, whereas its poly(ADP-ribosyl)ation relieves the repression effect, allowing restricted Nanos expression in the posterior germ plasm during oogenesis and early embryogenesis. PMID:27402862

Identification of poly(rC) binding protein 2 (PCBP2) as a target protein of immunosuppressive agent 15-deoxyspergualin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murahashi, Masataka; Simizu, Siro; Morioka, Masahiko

15-Deoxyspergualin (DSG) is an immunosuppressive agent being clinically used. Unlike tacrolimus and cyclosporine A, it does not inhibit the calcineurin pathway, and its mechanism of action and target molecule have not been elucidated. Therefore, we previously prepared biotinylated derivative of DSG (BDSG) to fish up the target protein. In the present research, we identified poly(rC) binding protein 2 (PCBP2) as a DSG-binding protein using this probe. DSG was confirmed to bind to PCBP2 by pull-down assay. Intracellular localization of PCBP2 was changed from the nucleus to the cytoplasm by DSG treatment. DSG inhibited the cell growth, and over-expression of PCBP2more » reduced the anti-proliferative activity of DSG. PCBP2 is known to regulate various proteins including STAT1/2. Thus, we found PCBP2 as the first target protein of DSG that can explain the immunosuppressive activity. -- Highlights: •Fifteen-deoxyspergualin (DSG) is an immunosuppressive agent clinically used. •We have identified PCBP2, an RNA-binding protein, as a molecular target of DSG. •Alteration of PCBP2 activity may explain the immunosuppressive activity of DSG.« less

Novel interactions of CAPS (Ca2+-dependent activator protein for secretion) with the three neuronal SNARE proteins required for vesicle fusion.

PubMed

Daily, Neil J; Boswell, Kristin L; James, Declan J; Martin, Thomas F J

2010-11-12

CAPS (aka CADPS) is required for optimal vesicle exocytosis in neurons and endocrine cells where it functions to prime the exocytic machinery for Ca(2+)-triggered fusion. Fusion is mediated by trans complexes of the SNARE proteins VAMP-2, syntaxin-1, and SNAP-25 that bridge vesicle and plasma membrane. CAPS promotes SNARE complex formation on liposomes, but the SNARE binding properties of CAPS are unknown. The current work revealed that CAPS exhibits high affinity binding to syntaxin-1 and SNAP-25 and moderate affinity binding to VAMP-2. CAPS binding is specific for a subset of exocytic SNARE protein isoforms and requires membrane integration of the SNARE proteins. SNARE protein binding by CAPS is novel and mediated by interactions with the SNARE motifs in the three proteins. The C-terminal site for CAPS binding on syntaxin-1 does not overlap the Munc18-1 binding site and both proteins can co-reside on membrane-integrated syntaxin-1. As expected for a C-terminal binding site on syntaxin-1, CAPS stimulates SNARE-dependent liposome fusion with N-terminal truncated syntaxin-1 but exhibits impaired activity with C-terminal syntaxin-1 mutants. Overall the results suggest that SNARE complex formation promoted by CAPS may be mediated by direct interactions of CAPS with each of the three SNARE proteins required for vesicle exocytosis.

Novel Interactions of CAPS (Ca2+-dependent Activator Protein for Secretion) with the Three Neuronal SNARE Proteins Required for Vesicle Fusion*

PubMed Central

Daily, Neil J.; Boswell, Kristin L.; James, Declan J.; Martin, Thomas F. J.

2010-01-01

CAPS (aka CADPS) is required for optimal vesicle exocytosis in neurons and endocrine cells where it functions to prime the exocytic machinery for Ca2+-triggered fusion. Fusion is mediated by trans complexes of the SNARE proteins VAMP-2, syntaxin-1, and SNAP-25 that bridge vesicle and plasma membrane. CAPS promotes SNARE complex formation on liposomes, but the SNARE binding properties of CAPS are unknown. The current work revealed that CAPS exhibits high affinity binding to syntaxin-1 and SNAP-25 and moderate affinity binding to VAMP-2. CAPS binding is specific for a subset of exocytic SNARE protein isoforms and requires membrane integration of the SNARE proteins. SNARE protein binding by CAPS is novel and mediated by interactions with the SNARE motifs in the three proteins. The C-terminal site for CAPS binding on syntaxin-1 does not overlap the Munc18-1 binding site and both proteins can co-reside on membrane-integrated syntaxin-1. As expected for a C-terminal binding site on syntaxin-1, CAPS stimulates SNARE-dependent liposome fusion with N-terminal truncated syntaxin-1 but exhibits impaired activity with C-terminal syntaxin-1 mutants. Overall the results suggest that SNARE complex formation promoted by CAPS may be mediated by direct interactions of CAPS with each of the three SNARE proteins required for vesicle exocytosis. PMID:20826818

Big Domains Are Novel Ca2+-Binding Modules: Evidences from Big Domains of Leptospira Immunoglobulin-Like (Lig) Proteins

PubMed Central

Palaniappan, Raghavan U. M.; Lin, Yi-Pin; He, Hongxuan; McDonough, Sean P.; Sharma, Yogendra; Chang, Yung-Fu

2010-01-01

Background Many bacterial surface exposed proteins mediate the host-pathogen interaction more effectively in the presence of Ca2+. Leptospiral immunoglobulin-like (Lig) proteins, LigA and LigB, are surface exposed proteins containing Bacterial immunoglobulin like (Big) domains. The function of proteins which contain Big fold is not known. Based on the possible similarities of immunoglobulin and βγ-crystallin folds, we here explore the important question whether Ca2+ binds to a Big domains, which would provide a novel functional role of the proteins containing Big fold. Principal Findings We selected six individual Big domains for this study (three from the conserved part of LigA and LigB, denoted as Lig A3, Lig A4, and LigBCon5; two from the variable region of LigA, i.e., 9th (Lig A9) and 10th repeats (Lig A10); and one from the variable region of LigB, i.e., LigBCen2. We have also studied the conserved region covering the three and six repeats (LigBCon1-3 and LigCon). All these proteins bind the calcium-mimic dye Stains-all. All the selected four domains bind Ca2+ with dissociation constants of 2–4 µM. Lig A9 and Lig A10 domains fold well with moderate thermal stability, have β-sheet conformation and form homodimers. Fluorescence spectra of Big domains show a specific doublet (at 317 and 330 nm), probably due to Trp interaction with a Phe residue. Equilibrium unfolding of selected Big domains is similar and follows a two-state model, suggesting the similarity in their fold. Conclusions We demonstrate that the Lig are Ca2+-binding proteins, with Big domains harbouring the binding motif. We conclude that despite differences in sequence, a Big motif binds Ca2+. This work thus sets up a strong possibility for classifying the proteins containing Big domains as a novel family of Ca2+-binding proteins. Since Big domain is a part of many proteins in bacterial kingdom, we suggest a possible function these proteins via Ca2+ binding. PMID:21206924

Functional importance of evolutionally conserved Tbx6 binding sites in the presomitic mesoderm-specific enhancer of Mesp2.

PubMed

Yasuhiko, Yukuto; Kitajima, Satoshi; Takahashi, Yu; Oginuma, Masayuki; Kagiwada, Harumi; Kanno, Jun; Saga, Yumiko

2008-11-01

The T-box transcription factor Tbx6 controls the expression of Mesp2, which encodes a basic helix-loop-helix transcription factor that has crucial roles in somitogenesis. In cultured cells, Tbx6 binding to the Mesp2 enhancer region is essential for the activation of Mesp2 by Notch signaling. However, it is not known whether this binding is required in vivo. Here we report that an Mesp2 enhancer knockout mouse bearing mutations in two crucial Tbx6 binding sites does not express Mesp2 in the presomitic mesoderm. This absence leads to impaired skeletal segmentation identical to that reported for Mesp2-null mice, indicating that these Tbx6 binding sites are indispensable for Mesp2 expression. T-box binding to the consensus sequences in the Mesp2 upstream region was confirmed by chromatin immunoprecipitation assays. Further enhancer analyses indicated that the number and spatial organization of the T-box binding sites are critical for initiating Mesp2 transcription via Notch signaling. We also generated a knock-in mouse in which the endogenous Mesp2 enhancer was replaced by the core enhancer of medaka mespb, an ortholog of mouse Mesp2. The homozygous enhancer knock-in mouse was viable and showed normal skeletal segmentation, indicating that the medaka mespb enhancer functionally replaced the mouse Mesp2 enhancer. These results demonstrate that there is significant evolutionary conservation of Mesp regulatory mechanisms between fish and mice.

Interaction of the amyloid precursor protein-like protein 1 (APLP1) E2 domain with heparan sulfate involves two distinct binding modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahms, Sven O., E-mail: sdahms@fli-leibniz.de; Mayer, Magnus C.; Miltenyi Biotec GmbH, Robert-Koch-Strasse 1, 17166 Teterow

2015-03-01

Two X-ray structures of APLP1 E2 with and without a heparin dodecasaccharide are presented, revealing two distinct binding modes of the protein to heparan sulfate. The data provide a mechanistic explanation of how APP-like proteins bind to heparan sulfates and how they specifically recognize nonreducing structures of heparan sulfates. Beyond the pathology of Alzheimer’s disease, the members of the amyloid precursor protein (APP) family are essential for neuronal development and cell homeostasis in mammals. APP and its paralogues APP-like protein 1 (APLP1) and APP-like protein 2 (APLP2) contain the highly conserved heparan sulfate (HS) binding domain E2, which effects variousmore » (patho)physiological functions. Here, two crystal structures of the E2 domain of APLP1 are presented in the apo form and in complex with a heparin dodecasaccharide at 2.5 Å resolution. The apo structure of APLP1 E2 revealed an unfolded and hence flexible N-terminal helix αA. The (APLP1 E2){sub 2}–(heparin){sub 2} complex structure revealed two distinct binding modes, with APLP1 E2 explicitly recognizing the heparin terminus but also interacting with a continuous heparin chain. The latter only requires a certain register of the sugar moieties that fits to a positively charged surface patch and contributes to the general heparin-binding capability of APP-family proteins. Terminal binding of APLP1 E2 to heparin specifically involves a structure of the nonreducing end that is very similar to heparanase-processed HS chains. These data reveal a conserved mechanism for the binding of APP-family proteins to HS and imply a specific regulatory role of HS modifications in the biology of APP and APP-like proteins.« less

Renal calcinosis and stone formation in mice lacking osteopontin, Tamm-Horsfall protein, or both.

PubMed

Mo, Lan; Liaw, Lucy; Evan, Andrew P; Sommer, Andre J; Lieske, John C; Wu, Xue-Ru

2007-12-01

Although often supersaturated with mineral salts such as calcium phosphate and calcium oxalate, normal urine possesses an innate ability to keep them from forming harmful crystals. This inhibitory activity has been attributed to the presence of urinary macromolecules, although controversies abound regarding their role, or lack thereof, in preventing renal mineralization. Here, we show that 10% of the mice lacking osteopontin (OPN) and 14.3% of the mice lacking Tamm-Horsfall protein (THP) spontaneously form interstitial deposits of calcium phosphate within the renal papillae, events never seen in wild-type mice. Lack of both proteins causes renal crystallization in 39.3% of the double-null mice. Urinalysis revealed elevated concentrations of urine phosphorus and brushite (calcium phosphate) supersaturation in THP-null and OPN/THP-double null mice, suggesting that impaired phosphorus handling may be linked to interstitial papillary calcinosis in THP- but not in OPN-null mice. In contrast, experimentally induced hyperoxaluria provokes widespread intratubular calcium oxalate crystallization and stone formation in OPN/THP-double null mice, while completely sparing the wild-type controls. Whole urine from OPN-, THP-, or double-null mice all possessed a dramatically reduced ability to inhibit the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells. These data establish OPN and THP as powerful and functionally synergistic inhibitors of calcium phosphate and calcium oxalate crystallization in vivo and suggest that defects in either molecule may contribute to renal calcinosis and stone formation, an exceedingly common condition that afflicts up to 12% males and 5% females.

Mechanism of Disruption of the Amt-GlnK Complex by PII-Mediated Sensing of 2-Oxoglutarate

PubMed Central

Maier, Sarah; Schleberger, Paula; Lü, Wei; Wacker, Tobias; Pflüger, Tobias; Litz, Claudia; Andrade, Susana L. A.

2011-01-01

GlnK proteins regulate the active uptake of ammonium by Amt transport proteins by inserting their regulatory T-loops into the transport channels of the Amt trimer and physically blocking substrate passage. They sense the cellular nitrogen status through 2-oxoglutarate, and the energy level of the cell by binding both ATP and ADP with different affinities. The hyperthermophilic euryarchaeon Archaeoglobus fulgidus possesses three Amt proteins, each encoded in an operon with a GlnK ortholog. One of these proteins, GlnK2 was recently found to be incapable of binding 2-OG, and in order to understand the implications of this finding we conducted a detailed structural and functional analysis of a second GlnK protein from A. fulgidus, GlnK3. Contrary to Af-GlnK2 this protein was able to bind both ATP/2-OG and ADP to yield inactive and functional states, respectively. Due to the thermostable nature of the protein we could observe the exact positioning of the notoriously flexible T-loops and explain the binding behavior of GlnK proteins to their interaction partner, the Amt proteins. A thermodynamic analysis of these binding events using microcalorimetry evaluated by microstate modeling revealed significant differences in binding cooperativity compared to other characterized PII proteins, underlining the diversity and adaptability of this class of regulatory signaling proteins. PMID:22039461

The histone deacetylase HDAC3 is essential for Purkinje cell function, potentially complicating the use of HDAC inhibitors in SCA1

PubMed Central

Venkatraman, Anand; Hu, Yuan-Shih; Didonna, Alessandro; Cvetanovic, Marija; Krbanjevic, Aleksandar; Bilesimo, Patrice; Opal, Puneet

2014-01-01

Spinocerebellar ataxia type 1 (SCA1) is an incurable neurodegenerative disease caused by a pathogenic glutamine repeat expansion in the protein ataxin-1 (ATXN1). One likely mechanism mediating pathogenesis is excessive transcriptional repression induced by the expanded ATXN-1. Because ATXN1 binds HDAC3, a Class I histone deacetylase (HDAC) that we have found to be required for ATXN1-induced transcriptional repression, we tested whether genetically depleting HDAC3 improves the phenotype of the SCA1 knock-in mouse (SCA1154Q/2Q), the most physiologically relevant model of SCA1. Given that HDAC3 null mice are embryonic lethal, we used for our analyses a combination of HDAC3 haploinsufficient and Purkinje cell (PC)-specific HDAC3 null mice. Although deleting a single allele of HDAC3 in the context of SCA1 was insufficient to improve cerebellar and cognitive deficits of the disease, a complete loss of PC HDAC3 was highly deleterious both behaviorally, with mice showing early onset ataxia, and pathologically, with progressive histologic evidence of degeneration. Inhibition of HDAC3 may yet have a role in SCA1 therapy, but our study provides cautionary evidence that this approach could produce untoward effects. Indeed, the neurotoxic consequences of HDAC3 depletion could prove relevant, wherever pharmacologic inhibition of HDAC3 is being contemplated, in disorders ranging from cancer to neurodegeneration. PMID:24594842

Genetic characterization of p27(kip1) and stathmin in controlling cell proliferation in vivo.

PubMed

Berton, Stefania; Pellizzari, Ilenia; Fabris, Linda; D'Andrea, Sara; Segatto, Ilenia; Canzonieri, Vincenzo; Marconi, Daniela; Schiappacassi, Monica; Benevol, Sara; Gattei, Valter; Colombatti, Alfonso; Belletti, Barbara; Baldassarre, Gustavo

2014-01-01

The CDK inhibitor p27(kip1) is a critical regulator of cell cycle progression, but the mechanisms by which p27(kip1) controls cell proliferation in vivo are still not fully elucidated. We recently demonstrated that the microtubule destabilizing protein stathmin is a relevant p27(kip1) binding partner. To get more insights into the in vivo significance of this interaction, we generated p27(kip1) and stathmin double knock-out (DKO) mice. Interestingly, thorough characterization of DKO mice demonstrated that most of the phenotypes of p27(kip1) null mice linked to the hyper-proliferative behavior, such as the increased body and organ weight, the outgrowth of the retina basal layer and the development of pituitary adenomas, were reverted by co-ablation of stathmin. In vivo analyses showed a reduced proliferation rate in DKO compared to p27(kip1) null mice, linked, at molecular level, to decreased kinase activity of CDK4/6, rather than of CDK1 and CDK2. Gene expression profiling of mouse thymuses confirmed the phenotypes observed in vivo, showing that DKO clustered with WT more than with p27 knock-out tissue. Taken together, our results demonstrate that stathmin cooperates with p27(kip1) to control the early phase of G1 to S phase transition and that this function may be of particular relevance in the context of tumor progression.

Genetic characterization of p27kip1 and stathmin in controlling cell proliferation in vivo

PubMed Central

Berton, Stefania; Pellizzari, Ilenia; Fabris, Linda; D'Andrea, Sara; Segatto, Ilenia; Canzonieri, Vincenzo; Marconi, Daniela; Schiappacassi, Monica; Benevol, Sara; Gattei, Valter; Colombatti, Alfonso; Belletti, Barbara; Baldassarre, Gustavo

2014-01-01

The CDK inhibitor p27kip1 is a critical regulator of cell cycle progression, but the mechanisms by which p27kip1 controls cell proliferation in vivo are still not fully elucidated. We recently demonstrated that the microtubule destabilizing protein stathmin is a relevant p27kip1 binding partner. To get more insights into the in vivo significance of this interaction, we generated p27kip1 and stathmin double knock-out (DKO) mice. Interestingly, thorough characterization of DKO mice demonstrated that most of the phenotypes of p27kip1 null mice linked to the hyper-proliferative behavior, such as the increased body and organ weight, the outgrowth of the retina basal layer and the development of pituitary adenomas, were reverted by co-ablation of stathmin. In vivo analyses showed a reduced proliferation rate in DKO compared to p27kip1 null mice, linked, at molecular level, to decreased kinase activity of CDK4/6, rather than of CDK1 and CDK2. Gene expression profiling of mouse thymuses confirmed the phenotypes observed in vivo, showing that DKO clustered with WT more than with p27 knock-out tissue. Taken together, our results demonstrate that stathmin cooperates with p27kip1 to control the early phase of G1 to S phase transition and that this function may be of particular relevance in the context of tumor progression. PMID:25486569

The Role of Intercalated Cell Nedd4-2 in BP Regulation, Ion Transport, and Transporter Expression.

PubMed

Nanami, Masayoshi; Pham, Truyen D; Kim, Young Hee; Yang, Baoli; Sutliff, Roy L; Staub, Olivier; Klein, Janet D; Lopez-Cayuqueo, Karen I; Chambrey, Regine; Park, Annie Y; Wang, Xiaonan; Pech, Vladimir; Verlander, Jill W; Wall, Susan M

2018-06-01

Background Nedd4-2 is an E3 ubiquitin-protein ligase that associates with transport proteins, causing their ubiquitylation, and then internalization and degradation. Previous research has suggested a correlation between Nedd4-2 and BP. In this study, we explored the effect of intercalated cell (IC) Nedd4-2 gene ablation on IC transporter abundance and function and on BP. Methods We generated IC Nedd4-2 knockout mice using Cre-lox technology and produced global pendrin/ Nedd4-2 null mice by breeding global Nedd4-2 null ( Nedd4-2 -/- ) mice with global pendrin null ( Slc26a4 -/- ) mice. Mice ate a diet with 1%-4% NaCl; BP was measured by tail cuff and radiotelemetry. We measured transepithelial transport of Cl - and total CO 2 and transepithelial voltage in cortical collecting ducts perfused in vitro Transporter abundance was detected with immunoblots, immunohistochemistry, and immunogold cytochemistry. Results IC Nedd4-2 gene ablation markedly increased electroneutral Cl - /HCO 3 - exchange in the cortical collecting duct, although benzamil-, thiazide-, and bafilomycin-sensitive ion flux changed very little. IC Nedd4-2 gene ablation did not increase the abundance of type B IC transporters, such as AE4 ( Slc4a9 ), H + -ATPase, barttin, or the Na + -dependent Cl - /HCO 3 - exchanger ( Slc4a8 ). However, IC Nedd4-2 gene ablation increased CIC-5 total protein abundance, apical plasma membrane pendrin abundance, and the ratio of pendrin expression on the apical membrane to the cytoplasm. IC Nedd4-2 gene ablation increased BP by approximately 10 mm Hg. Moreover, pendrin gene ablation eliminated the increase in BP observed in global Nedd4-2 knockout mice. Conclusions IC Nedd4-2 regulates Cl - /HCO 3 - exchange in ICs., Nedd4-2 gene ablation increases BP in part through its action in these cells. Copyright © 2018 by the American Society of Nephrology.

Dmc1 Functions in a Saccharomyces Cerevisiae Meiotic Pathway That Is Largely Independent of the Rad51 Pathway

PubMed Central

Dresser, M. E.; Ewing, D. J.; Conrad, M. N.; Dominguez, A. M.; Barstead, R.; Jiang, H.; Kodadek, T.

1997-01-01

Meiotic recombination in the yeast Saccharomyces cerevisiae requires two similar recA-like proteins, Dmc1p and Rad51p. A screen for dominant meiotic mutants provided DMC1-G126D, a dominant allele mutated in the conserved ATP-binding site (specifically, the A-loop motif) that confers a null phenotype. A recessive null allele, dmc1-K69E, was isolated as an intragenic suppressor of DMC1-G126D. Dmc1-K69Ep, unlike Dmc1p, does not interact homotypically in a two-hybrid assay, although it does interact with other fusion proteins identified by two-hybrid screen with Dmc1p. Dmc1p, unlike Rad51p, does not interact in the two-hybrid assay with Rad52p or Rad54p. However, Dmc1p does interact with Tid1p, a Rad54p homologue, with Tid4p, a Rad16p homologue, and with other fusion proteins that do not interact with Rad51p, suggesting that Dmc1p and Rad51p function in separate, though possibly overlapping, recombinational repair complexes. Epistasis analysis suggests that DMC1 and RAD51 function in separate pathways responsible for meiotic recombination. Taken together, our results are consistent with a requirement for DMC1 for meiosis-specific entry of DNA double-strand break ends into chromatin. Interestingly, the pattern on CHEF gels of chromosome fragments that result from meiotic DNA double-strand break formation is different in DMC1 mutant strains from that seen in rad50S strains. PMID:9335591

KIAA0556 is a novel ciliary basal body component mutated in Joubert syndrome.

PubMed

Sanders, Anna A W M; de Vrieze, Erik; Alazami, Anas M; Alzahrani, Fatema; Malarkey, Erik B; Sorusch, Nasrin; Tebbe, Lars; Kuhns, Stefanie; van Dam, Teunis J P; Alhashem, Amal; Tabarki, Brahim; Lu, Qianhao; Lambacher, Nils J; Kennedy, Julie E; Bowie, Rachel V; Hetterschijt, Lisette; van Beersum, Sylvia; van Reeuwijk, Jeroen; Boldt, Karsten; Kremer, Hannie; Kesterson, Robert A; Monies, Dorota; Abouelhoda, Mohamed; Roepman, Ronald; Huynen, Martijn H; Ueffing, Marius; Russell, Rob B; Wolfrum, Uwe; Yoder, Bradley K; van Wijk, Erwin; Alkuraya, Fowzan S; Blacque, Oliver E

2015-12-29

Joubert syndrome (JBTS) and related disorders are defined by cerebellar malformation (molar tooth sign), together with neurological symptoms of variable expressivity. The ciliary basis of Joubert syndrome related disorders frequently extends the phenotype to tissues such as the eye, kidney, skeleton and craniofacial structures. Using autozygome and exome analyses, we identified a null mutation in KIAA0556 in a multiplex consanguineous family with hallmark features of mild Joubert syndrome. Patient-derived fibroblasts displayed reduced ciliogenesis potential and abnormally elongated cilia. Investigation of disease pathophysiology revealed that Kiaa0556 (-/-) null mice possess a Joubert syndrome-associated brain-restricted phenotype. Functional studies in Caenorhabditis elegans nematodes and cultured human cells support a conserved ciliary role for KIAA0556 linked to microtubule regulation. First, nematode KIAA0556 is expressed almost exclusively in ciliated cells, and the worm and human KIAA0556 proteins are enriched at the ciliary base. Second, C. elegans KIAA0056 regulates ciliary A-tubule number and genetically interacts with an ARL13B (JBTS8) orthologue to control cilium integrity. Third, human KIAA0556 binds to microtubules in vitro and appears to stabilise microtubule networks when overexpressed. Finally, human KIAA0556 biochemically interacts with ciliary proteins and p60/p80 katanins. The latter form a microtubule-severing enzyme complex that regulates microtubule dynamics as well as ciliary functions. We have identified KIAA0556 as a novel microtubule-associated ciliary base protein mutated in Joubert syndrome. Consistent with the mild patient phenotype, our nematode, mice and human cell data support the notion that KIAA0556 has a relatively subtle and variable cilia-related function, which we propose is related to microtubule regulation.

Differential expression of pancreatic protein and chemosensing receptor mRNAs in NKCC1-null intestine.

PubMed

Bradford, Emily M; Vairamani, Kanimozhi; Shull, Gary E

2016-02-15

To investigate the intestinal functions of the NKCC1 Na(+)-K(+)-2Cl cotransporter (SLC12a2 gene), differential mRNA expression changes in NKCC1-null intestine were analyzed. Microarray analysis of mRNA from intestines of adult wild-type mice and gene-targeted NKCC1-null mice (n = 6 of each genotype) was performed to identify patterns of differential gene expression changes. Differential expression patterns were further examined by Gene Ontology analysis using the online Gorilla program, and expression changes of selected genes were verified using northern blot analysis and quantitative real time-polymerase chain reaction. Histological staining and immunofluorescence were performed to identify cell types in which upregulated pancreatic digestive enzymes were expressed. Genes typically associated with pancreatic function were upregulated. These included lipase, amylase, elastase, and serine proteases indicative of pancreatic exocrine function, as well as insulin and regenerating islet genes, representative of endocrine function. Northern blot analysis and immunohistochemistry showed that differential expression of exocrine pancreas mRNAs was specific to the duodenum and localized to a subset of goblet cells. In addition, a major pattern of changes involving differential expression of olfactory receptors that function in chemical sensing, as well as other chemosensing G-protein coupled receptors, was observed. These changes in chemosensory receptor expression may be related to the failure of intestinal function and dependency on parenteral nutrition observed in humans with SLC12a2 mutations. The results suggest that loss of NKCC1 affects not only secretion, but also goblet cell function and chemosensing of intestinal contents via G-protein coupled chemosensory receptors.

Contractile Ring-independent Localization of DdINCENP, a Protein Important for Spindle Stability and CytokinesisD⃞V⃞

PubMed Central

Chen, Qian; Li, Hui; De Lozanne, Arturo

2006-01-01

Dictyostelium DdINCENP is a chromosomal passenger protein associated with centromeres, the spindle midzone, and poles during mitosis and the cleavage furrow during cytokinesis. Disruption of the single DdINCENP gene revealed important roles for this protein in mitosis and cytokinesis. DdINCENP null cells lack a robust spindle midzone and are hypersensitive to microtubule-depolymerizing drugs, suggesting that their spindles may not be stable. Furthermore DdCP224, a protein homologous to the microtubule-stabilizing protein TOGp/XMAP215, was absent from the spindle midzone of DdINCENP null cells. Overexpression of DdCP224 rescued the weak spindle midzone defect of DdINCENP null cells. Although not required for the localization of the myosin II contractile ring and subsequent formation of a cleavage furrow, DdINCENP is important for the abscission of daughter cells at the end of cytokinesis. Finally, we show that the localization of DdINCENP at the cleavage furrow is modulated by myosin II but it occurs by a mechanism different from that controlling the formation of the contractile ring. PMID:16339076

A Drosophila SNAP-25 null mutant reveals context-dependent redundancy with SNAP-24 in neurotransmission.

PubMed Central

Vilinsky, Ilya; Stewart, Bryan A; Drummond, James; Robinson, Iain; Deitcher, David L

2002-01-01

The synaptic protein SNAP-25 is an important component of the neurotransmitter release machinery, although its precise function is still unknown. Genetic analysis of other synaptic proteins has yielded valuable information on their role in synaptic transmission. In this study, we performed a mutagenesis screen to identify new SNAP-25 alleles that fail to complement our previously isolated recessive temperature-sensitive allele of SNAP-25, SNAP-25(ts). In a screen of 100,000 flies, 26 F(1) progeny failed to complement SNAP-25(ts) and 21 of these were found to be null alleles of SNAP-25. These null alleles die at the pharate adult stage and electroretinogram recordings of these animals reveal that synaptic transmission is blocked. At the third instar larval stage, SNAP-25 nulls exhibit nearly normal neurotransmitter release at the neuromuscular junction. This is surprising since SNAP-25(ts) larvae exhibit a much stronger synaptic phenotype. Our evidence indicates that a related protein, SNAP-24, can substitute for SNAP-25 at the larval stage in SNAP-25 nulls. However, if a wild-type or mutant form of SNAP-25 is present, then SNAP-24 does not appear to take part in neurotransmitter release at the larval NMJ. These results suggest that the apparent redundancy between SNAP-25 and SNAP-24 is due to inappropriate genetic substitution. PMID:12242238

Modeling Conformational Transitions and Energetics of Ligand Binding with the Glutamate Receptor Ligand Binding Domain

NASA Astrophysics Data System (ADS)

Kurnikova, Maria

2009-03-01

Understanding of protein motion and energetics of conformational transitions is crucial to understanding protein function. The glutamate receptor ligand binding domain (GluR2 S1S2) is a two lobe protein, which binds ligand at the interface of two lobes and undergoes conformational transition. The cleft closure conformational transition of S1S2 has been implicated in gating of the ion channel formed by the transmembrane domain of the receptor. In this study we present a composite multi-faceted theoretical analysis of the detailed mechanism of this conformational transition based on rigid cluster decomposition of the protein structure [1] and identifying hydrogen bonds that are responsible for stabilizing the closed conformation [2]. Free energy of the protein reorganization upon ligand binding was calculated using combined Thermodynamic Integration (TI) and Umbrella Sampling (US) simulations [3]. Ligand -- protein interactions in the binding cleft were analyzed using Molecular Dynamics, continuum electrostatics and QM/MM models [4]. All model calculations compare well with corresponding experimental measurements. [4pt] [1] Protein Flexibility using Constraints from Molecular Dynamics Simulations T. Mamonova, B. Hespenheide, R. Straub, M. F. Thorpe, M. G. Kurnikova , Phys. Biol., 2, S137 (2005)[0pt] [2] Theoretical Study of the Glutamate Receptor Ligand Binding Domain Flexibility and Conformational Reorganization T. Mamonova, K. Speranskiy, and M. Kurnikova , Prot.: Struct., Func., Bioinf., 73,656 (2008)[0pt] [3] Energetics of the cleft closing transition and glutamate binding in the Glutamate Receptor ligand Binding Domain T. Mamonova, M. Yonkunas, and M. Kurnikova Biochemistry 47, 11077 (2008)[0pt] [4] On the Binding Determinants of the Glutamate Agonist with the Glutamate Receptor Ligand Binding Domain K. Speranskiy and M. Kurnikova Biochemistry 44, 11208 (2005)

Organic Anion Transporting Polypeptide 1a1 Null Mice Are Sensitive to Cholestatic Liver Injury

PubMed Central

Zhang, Youcai; Csanaky, Iván L.; Cheng, Xingguo; Lehman-McKeeman, Lois D.; Klaassen, Curtis D.

2012-01-01

Organic anion transporting polypeptide 1a1 (Oatp1a1) is predominantly expressed in livers of mice and is thought to transport bile acids (BAs) from blood into liver. Because Oatp1a1 expression is markedly decreased in mice after bile duct ligation (BDL). We hypothesized that Oatp1a1-null mice would be protected against liver injury during BDL-induced cholestasis due largely to reduced hepatic uptake of BAs. To evaluate this hypothesis, BDL surgeries were performed in both male wild-type (WT) and Oatp1a1-null mice. At 24 h after BDL, Oatp1a1-null mice showed higher serum alanine aminotransferase levels and more severe liver injury than WT mice, and all Oatp1a1-null mice died within 4 days after BDL, whereas all WT mice survived. At 24 h after BDL, surprisingly Oatp1a1-null mice had higher total BA concentrations in livers than WT mice, suggesting that loss of Oatp1a1 did not prevent BA accumulation in the liver. In addition, secondary BAs dramatically increased in serum of Oatp1a1-null BDL mice but not in WT BDL mice. Oatp1a1-null BDL mice had similar basolateral BA uptake (Na+-taurocholate cotransporting polypeptide and Oatp1b2) and BA-efflux (multidrug resistance–associated protein [Mrp]-3, Mrp4, and organic solute transporter α/β) transporters, as well as BA-synthetic enzyme (Cyp7a1) in livers as WT BDL mice. Hepatic expression of small heterodimer partner Cyp3a11, Cyp4a14, and Nqo1, which are target genes of farnesoid X receptor, pregnane X receptor, peroxisome proliferator-activated receptor alpha, and NF-E2-related factor 2, respectively, were increased in WT BDL mice but not in Oatp1a1-null BDL mice. These results demonstrate that loss of Oatp1a1 function exacerbates cholestatic liver injury in mice and suggest that Oatp1a1 plays a unique role in liver adaptive responses to obstructive cholestasis. PMID:22461449

Calcitonin plays a critical role in regulating skeletal mineral metabolism during lactation.

PubMed

Woodrow, Janine P; Sharpe, Christopher J; Fudge, Neva J; Hoff, Ana O; Gagel, Robert F; Kovacs, Christopher S

2006-09-01

The maternal skeleton rapidly demineralizes during lactation to provide calcium to milk, responding to the stimuli of estrogen deficiency and mammary-secreted PTH-related protein. We used calcitonin/calcitonin gene-related peptide-alpha (Ctcgrp) null mice to determine whether calcitonin also modulates lactational mineral metabolism. During 21 d of lactation, spine bone mineral content dropped 53.6% in Ctcgrp nulls vs. 23.6% in wild-type (WT) siblings (P < 0.0002). After weaning, bone mineral content returned fully to baseline in 18.1 d in Ctcgrp null vs. 13.1 d in WT (P < 0.01) mice. Daily treatment with salmon calcitonin from the onset of lactation normalized the losses in Ctcgrp null mice, whereas calcitonin gene-related peptide-alpha or vehicle was without effect. Compared with WT, Ctcgrp null mice had increased circulating levels of PTH and up-regulation of mammary gland PTH-related protein mRNA. In addition, lactation caused the Ctcgrp null skeleton to undergo more trabecular thinning and increased trabecular separation compared with WT. Our studies confirm that an important physiological role of calcitonin is to protect the maternal skeleton against excessive resorption and attendant fragility during lactation and reveal that the postweaning skeleton has the remarkable ability to rapidly recover even from losses of over 50% of skeletal mineral content.

Tet1 facilitates hypoxia tolerance by stabilizing the HIF-α proteins independent of its methylcytosine dioxygenase activity.

PubMed

Wang, Jing; Zhang, Dawei; Du, Juan; Zhou, Chi; Li, Zhi; Liu, Xing; Ouyang, Gang; Xiao, Wuhan

2017-12-15

Because of the requirement of oxygen (O2) to produce energy, aerobic organisms developed mechanisms to protect themselves against a shortage of oxygen in both acute status and chronic status. To date, how organisms tolerate acute hypoxia and the underlying mechanisms remain largely unknown. Here, we identify that Tet1, one member of the ten-eleven translocation (TET) family of methylcytosine dioxygenases, is required for hypoxia tolerance in zebrafish and mice. Tet1-null zebrafish and mice are more sensitive to hypoxic conditions compared with their wild-type siblings. We demonstrate that Tet1 stabilizes hypoxia-inducible factor α (HIF-α) and enhances HIF-α transcription activity independent of its enzymatic activity. In addition, we show that Tet1 modulates HIF-2α and HIF-1α through different mechanisms. Tet1 competes with prolyl hydroxylase protein 2 (PHD2) to bind to HIF-2α, resulting in a reduction of HIF-2α hydroxylation by PHD2. For HIF-1α, however, Tet1 has no effect on HIF-1α hydroxylation, but rather it appears to stabilize the C-terminus of HIF-1α by affecting lysine site modification. Furthermore, we found that Tet1 enhances rather than prevents poly-ubiquitination on HIF-α. Our results reveal a previously unrecognized function of Tet1 independent of its methylcytosine dioxygenase activity in hypoxia signaling. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Binding of carbonyl flavours to canola, pea and wheat proteins using GC/MS approach.

PubMed

Wang, Kun; Arntfield, Susan D

2014-08-15

Interactions of homologous aldehydes (hexanal, heptanal, and octanal) and ketones (2-hexanone, 2-heptanone, and 2-octanone) to salt and alkaline-extracted canola and pea proteins and commercial wheat gluten were studied using GC/MS. Long-chain aldehyde flavours exhibited higher binding affinity, regardless of protein type and isolation method. Salt-extracted canola protein isolates (CPIs) revealed the highest binding capacity to all aldehydes followed by wheat gluten and salt-extracted pea protein isolates (PPIs), while binding of ketone flavours decreased in the order: PPIs>wheat gluten>CPIs. Two aldolisation products, 2-butyl-2-octenal and 2-pentyl-2-nonenal, were detected from the interactions between CPIs with hexanal and heptanal, respectively. Protein thermal behaviour in the presence of these compounds was analysed by differential scanning calorimeter, where decreased ΔH inferred potential conformational changes due to partial denaturation of PPIs. Compared to ketones, aldehyde flavours possessed much higher "unfolding capacity" (lower ΔH), which accounted for their higher binding affinities. Copyright © 2014 Elsevier Ltd. All rights reserved.

Eukaryotic Initiation Factor eIFiso4G1 and eIFiso4G2 Are Isoforms Exhibiting Distinct Functional Differences in Supporting Translation in Arabidopsis*

PubMed Central

Gallie, Daniel R.

2016-01-01

The eukaryotic translation initiation factor (eIF) 4G is required during protein synthesis to promote the assembly of several factors involved in the recruitment of a 40S ribosomal subunit to an mRNA. Although many eukaryotes express two eIF4G isoforms that are highly similar, the eIF4G isoforms in plants, referred to as eIF4G and eIFiso4G, are highly divergent in size, sequence, and domain organization but both can interact with eIF4A, eIF4B, eIF4E isoforms, and the poly(A)-binding protein. Nevertheless, eIF4G and eIFiso4G from wheat exhibit preferences in the mRNAs they translate optimally. For example, mRNA containing the 5′-leader (called Ω) of tobacco mosaic virus preferentially uses eIF4G in wheat germ lysate. In this study, the eIF4G isoform specificity of Ω was used to examine functional differences of the eIF4G isoforms in Arabidopsis. As in wheat, Ω-mediated translation was reduced in an eif4g null mutant. Loss of the eIFiso4G1 isoform, which is similar in sequence to wheat eIFiso4G, did not substantially affect Ω-mediated translation. However, loss of the eIFiso4G2 isoform substantially reduced Ω-mediated translation. eIFiso4G2 is substantially divergent from eIFiso4G1 and is present only in the Brassicaceae, suggesting a recent evolution. eIFiso4G2 isoforms exhibit sequence-specific differences in regions representing partner protein and RNA binding sites. Loss of any eIF4G isoform also resulted in a substantial reduction in reporter transcript level. These results suggest that eIFiso4G2 appeared late in plant evolution and exhibits more functional similarity with eIF4G than with eIFiso4G1 during Ω-mediated translation. PMID:26578519

Lanthanide binding and IgG affinity construct: Potential applications in solution NMR, MRI, and luminescence microscopy

PubMed Central

Barb, Adam W; Ho, Tienhuei Grace; Flanagan-Steet, Heather; Prestegard, James H

2012-01-01

Paramagnetic lanthanide ions when bound to proteins offer great potential for structural investigations that utilize solution nuclear magnetic resonance spectroscopy, magnetic resonance imaging, or optical microscopy. However, many proteins do not have native metal ion binding sites and engineering a chimeric protein to bind an ion while retaining affinity for a protein of interest represents a significant challenge. Here we report the characterization of an immunoglobulin G-binding protein redesigned to include a lanthanide binding motif in place of a loop between two helices (Z-L2LBT). It was shown to bind Tb3+ with 130 nM affinity. Ions such as Dy3+, Yb3+, and Ce3+ produce paramagnetic effects on NMR spectra and the utility of these effects is illustrated by their use in determining a structural model of the metal-complexed Z-L2LBT protein and a preliminary characterization of the dynamic distribution of IgG Fc glycan positions. Furthermore, this designed protein is demonstrated to be a novel IgG-binding reagent for magnetic resonance imaging (Z-L2LBT:Gd3+ complex) and luminescence microscopy (Z-L2LBT: Tb3+ complex). PMID:22851279

AmrZ Beta-Sheet Residues Are Essential for DNA Binding and Transcriptional Control of Pseudomonas aeruginosa Virulence Genes ▿ †

PubMed Central

Waligora, Elizabeth A.; Ramsey, Deborah M.; Pryor, Edward E.; Lu, Haiping; Hollis, Thomas; Sloan, Gina P.; Deora, Rajendar; Wozniak, Daniel J.

2010-01-01

AmrZ is a putative ribbon-helix-helix (RHH) transcriptional regulator. RHH proteins utilize residues within the β-sheet for DNA binding, while the α-helices promote oligomerization. AmrZ is of interest due to its dual roles as a transcriptional activator and as a repressor, regulating genes encoding virulence factors associated with both chronic and acute Pseudomonas aeruginosa infection. In this study, cross-linking revealed that AmrZ forms oligomers in solution but that the amino terminus, containing an unordered region and a β-sheet, were not required for oligomerization. The first 12 unordered residues (extended amino terminus) contributed minimally to DNA binding. Mutagenesis of the AmrZ β-sheet demonstrated that residues 18, 20, and 22 were essential for DNA binding at both activation and repressor sites, suggesting that AmrZ utilizes a similar mechanism for binding to these sites. Mice infected with amrZ mutants exhibited reduced bacterial burden, morbidity, and mortality. Direct in vivo competition assays showed a 5-fold competitive advantage for the wild type over an isogenic amrZ mutant. Finally, the reduced infection phenotype of the amrZ-null strain was similar to that of a strain expressing a DNA-binding-deficient AmrZ variant, indicating that DNA binding and transcriptional regulation by AmrZ is responsible for the in vivo virulence defect. These recent infection data, along with previously identified AmrZ-regulated virulence factors, suggest the necessity of AmrZ transcriptional regulation for optimal virulence during acute infection. PMID:20709902

Restoration of On-Time Embryo Implantation Corrects the Timing of Parturition in Cytosolic Phospholipase A2 Group IVA Deficient Mice1

PubMed Central

Brown, Naoko; Morrow, Jason D.; Slaughter, James C.; Paria, Bibhash C.; Reese, Jeff

2009-01-01

Cytosolic phospholipase A2 (cPLA2, PLA2G4A) catalyzes the release of arachidonic acid for prostaglandin synthesis by cyclooxygenase 1 (PTGS1) and cyclooxygenase 2 (PTGS2). Mice with Pla2g4a deficiency have parturition delay and other reproductive deficits, including deferred onset of implantation, crowding of implantation sites, and small litters. In this study, we examined the contribution of PLA2G4A to parturition in mice. Pla2g4a mRNA and protein expression were discretely localized in the term and preterm uterine luminal epithelium and colocalized with Ptgs1, but not Ptgs2, expression. The levels of PGE2, PGF2alpha, 6-keto-PGF1alpha, and TxB2 were significantly decreased in Pla2g4a-null uterine tissues, similar to Ptgs1-null uteri, consistent with predominance of PLA2G4A-PTGS1-mediated prostaglandin synthesis in preparation for murine parturition. Litter size was strongly associated with the timing of parturition in Pla2g4a-null mice but could not fully account for the parturition delay. Pla2g4a-null females that received PGE2 + carbaprostacyclin at the time of implantation delivered earlier (20.5 ± 0.2 days vs. 21.6 ± 0.2 days, P < 0.01), although litter size was not improved (4.6 vs. 4.4 pups per litter, P = 0.6). After correction for small litter size, multivariate analysis indicated that Pla2g4a-null mice given prostaglandin treatment to improve implantation timing had gestational length that was similar to wild-type and Pla2g4a heterozygous mice. These results indicate that, despite specific Pla2g4a expression and function in term gestation uteri, the delayed parturition phenotype in Pla2g4a-null mice is primarily due to deferral of implantation. The role of PLA2G4A in timely parturition appears to be critically related to its actions in early pregnancy. PMID:19684335

The VirD2 pilot protein of Agrobacterium-transferred DNA interacts with the TATA box-binding protein and a nuclear protein kinase in plants

PubMed Central

Bakó, László; Umeda, Masaaki; Tiburcio, Antonio F.; Schell, Jeff; Koncz, Csaba

2003-01-01

The bacterial virulence protein VirD2 plays an important role in nuclear import and chromosomal integration of Agrobacterium-transferred DNA in fungal, plant, animal, and human cells. Here we show that in nuclei of alfalfa cells, VirD2 interacts with and is phosphorylated by CAK2Ms, a conserved plant ortholog of cyclin-dependent kinase-activating kinases. CAK2Ms binds to and phosphorylates the C-terminal regulatory domain of RNA polymerase II largest subunit, which can recruit the TATA box-binding protein. VirD2 is found in tight association with the TATA box-binding protein in vivo. These results indicate that recognition of VirD2 is mediated by widely conserved nuclear factors in eukaryotes. PMID:12900506

Fragile X-like behaviors and abnormal cortical dendritic spines in cytoplasmic FMR1-interacting protein 2-mutant mice.

PubMed

Han, Kihoon; Chen, Hogmei; Gennarino, Vincenzo A; Richman, Ronald; Lu, Hui-Chen; Zoghbi, Huda Y

2015-04-01

Silencing of fragile X mental retardation 1 (FMR1) gene and loss of fragile X mental retardation protein (FMRP) cause fragile X syndrome (FXS), a genetic disorder characterized by intellectual disability and autistic behaviors. FMRP is an mRNA-binding protein regulating neuronal translation of target mRNAs. Abnormalities in actin-rich dendritic spines are major neuronal features in FXS, but the molecular mechanism and identity of FMRP targets mediating this phenotype remain largely unknown. Cytoplasmic FMR1-interacting protein 2 (Cyfip2) was identified as an interactor of FMRP, and its mRNA is a highly ranked FMRP target in mouse brain. Importantly, Cyfip2 is a component of WAVE regulatory complex, a key regulator of actin cytoskeleton, suggesting that Cyfip2 could be implicated in the dendritic spine phenotype of FXS. Here, we generated and characterized Cyfip2-mutant (Cyfip2(+/-)) mice. We found that Cyfip2(+/-) mice exhibited behavioral phenotypes similar to Fmr1-null (Fmr1(-/y)) mice, an animal model of FXS. Synaptic plasticity and dendritic spines were normal in Cyfip2(+/-) hippocampus. However, dendritic spines were altered in Cyfip2(+/-) cortex, and the dendritic spine phenotype of Fmr1(-/y) cortex was aggravated in Fmr1(-/y); Cyfip2(+/-) double-mutant mice. In addition to the spine changes at basal state, metabotropic glutamate receptor (mGluR)-induced dendritic spine regulation was impaired in both Fmr1(-/y) and Cyfip2(+/-) cortical neurons. Mechanistically, mGluR activation induced mRNA translation-dependent increase of Cyfip2 in wild-type cortical neurons, but not in Fmr1(-/y) or Cyfip2(+/-) neurons. These results suggest that misregulation of Cyfip2 function and its mGluR-induced expression contribute to the neurobehavioral phenotypes of FXS. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen*

PubMed Central

Terajima, Masahiko; Taga, Yuki; Chen, Yulong; Cabral, Wayne A.; Hou-Fu, Guo; Srisawasdi, Sirivimol; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Kurie, Jonathan M.; Marini, Joan C.; Yamauchi, Mitsuo

2016-01-01

Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet. 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1–3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation. PMID:26934917

Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen.

PubMed

Terajima, Masahiko; Taga, Yuki; Chen, Yulong; Cabral, Wayne A; Hou-Fu, Guo; Srisawasdi, Sirivimol; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Kurie, Jonathan M; Marini, Joan C; Yamauchi, Mitsuo

2016-04-29

Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1-3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

SNF1-related protein kinases 2 are negatively regulated by a plant-specific calcium sensor.

PubMed

Bucholc, Maria; Ciesielski, Arkadiusz; Goch, Grażyna; Anielska-Mazur, Anna; Kulik, Anna; Krzywińska, Ewa; Dobrowolska, Grażyna

2011-02-04

SNF1-related protein kinases 2 (SnRK2s) are plant-specific enzymes involved in environmental stress signaling and abscisic acid-regulated plant development. Here, we report that SnRK2s interact with and are regulated by a plant-specific calcium-binding protein. We screened a Nicotiana plumbaginifolia Matchmaker cDNA library for proteins interacting with Nicotiana tabacum osmotic stress-activated protein kinase (NtOSAK), a member of the SnRK2 family. A putative EF-hand calcium-binding protein was identified as a molecular partner of NtOSAK. To determine whether the identified protein interacts only with NtOSAK or with other SnRK2s as well, we studied the interaction of an Arabidopsis thaliana orthologue of the calcium-binding protein with selected Arabidopsis SnRK2s using a two-hybrid system. All kinases studied interacted with the protein. The interactions were confirmed by bimolecular fluorescence complementation assay, indicating that the binding occurs in planta, exclusively in the cytoplasm. Calcium binding properties of the protein were analyzed by fluorescence spectroscopy using Tb(3+) as a spectroscopic probe. The calcium binding constant, determined by the protein fluorescence titration, was 2.5 ± 0.9 × 10(5) M(-1). The CD spectrum indicated that the secondary structure of the protein changes significantly in the presence of calcium, suggesting its possible function as a calcium sensor in plant cells. In vitro studies revealed that the activity of SnRK2 kinases analyzed is inhibited in a calcium-dependent manner by the identified calcium sensor, which we named SCS (SnRK2-interacting calcium sensor). Our results suggest that SCS is involved in response to abscisic acid during seed germination most probably by negative regulation of SnRK2s activity.

Usher syndrome: animal models, retinal function of Usher proteins, and prospects for gene therapy

PubMed Central

Williams, David S.

2009-01-01

Usher syndrome is a deafness-blindness disorder. The blindness occurs from a progressive retinal degeneration that begins after deafness and after the retina has developed. Three clinical subtypes of Usher syndrome have been identified, with mutations in any one of six different genes giving rise to type 1, in any one of three different genes to type 2, and in one identified gene causing Usher type 3. Mutant mice for most of the genes have been studied; while they have clear inner ear defects, retinal phenotypes are relatively mild and have been difficult to characterize. The retinal functions of the Usher proteins are still largely unknown. Protein binding studies have suggested many interactions among the proteins, and a model of interaction among all the proteins in the photoreceptor synapse has been proposed. However this model is not supported by localization data from some laboratories, or the indication of any synaptic phenotype in mutant mice. An earlier suggestion, based on patient pathologies, of Usher protein function in the photoreceptor cilium continues to gain support from immunolocalization and mutant mouse studies, which are consistent with Usher protein interaction in the photoreceptor ciliary/periciliary region. So far, the most characterized Usher protein is myosin VIIa. It is present in the apical RPE and photoreceptor ciliary/periciliary region, where it is required for organelle transport and clearance of opsin from the connecting cilium, respectively. Usher syndrome is amenable to gene replacement therapy, but also has some specific challenges. Progress in this treatment approach has been achieved by correction of mutant phenotypes in Myo7a-null mouse retinas, following lentiviral delivery of MYO7A. PMID:17936325

Proteome-wide Identification of Novel Ceramide-binding Proteins by Yeast Surface cDNA Display and Deep Sequencing.

PubMed

Bidlingmaier, Scott; Ha, Kevin; Lee, Nam-Kyung; Su, Yang; Liu, Bin

2016-04-01

Although the bioactive sphingolipid ceramide is an important cell signaling molecule, relatively few direct ceramide-interacting proteins are known. We used an approach combining yeast surface cDNA display and deep sequencing technology to identify novel proteins binding directly to ceramide. We identified 234 candidate ceramide-binding protein fragments and validated binding for 20. Most (17) bound selectively to ceramide, although a few (3) bound to other lipids as well. Several novel ceramide-binding domains were discovered, including the EF-hand calcium-binding motif, the heat shock chaperonin-binding motif STI1, the SCP2 sterol-binding domain, and the tetratricopeptide repeat region motif. Interestingly, four of the verified ceramide-binding proteins (HPCA, HPCAL1, NCS1, and VSNL1) and an additional three candidate ceramide-binding proteins (NCALD, HPCAL4, and KCNIP3) belong to the neuronal calcium sensor family of EF hand-containing proteins. We used mutagenesis to map the ceramide-binding site in HPCA and to create a mutant HPCA that does not bind to ceramide. We demonstrated selective binding to ceramide by mammalian cell-produced wild type but not mutant HPCA. Intriguingly, we also identified a fragment from prostaglandin D2synthase that binds preferentially to ceramide 1-phosphate. The wide variety of proteins and domains capable of binding to ceramide suggests that many of the signaling functions of ceramide may be regulated by direct binding to these proteins. Based on the deep sequencing data, we estimate that our yeast surface cDNA display library covers ∼60% of the human proteome and our selection/deep sequencing protocol can identify target-interacting protein fragments that are present at extremely low frequency in the starting library. Thus, the yeast surface cDNA display/deep sequencing approach is a rapid, comprehensive, and flexible method for the analysis of protein-ligand interactions, particularly for the study of non-protein ligands. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

CD36 Is a Matrix Metalloproteinase-9 Substrate That Stimulates Neutrophil Apoptosis and Removal During Cardiac Remodeling.

PubMed

DeLeon-Pennell, Kristine Y; Tian, Yuan; Zhang, Bai; Cates, Courtney A; Iyer, Rugmani Padmanabhan; Cannon, Presley; Shah, Punit; Aiyetan, Paul; Halade, Ganesh V; Ma, Yonggang; Flynn, Elizabeth; Zhang, Zhen; Jin, Yu-Fang; Zhang, Hui; Lindsey, Merry L

2016-02-01

After myocardial infarction, the left ventricle undergoes a wound healing response that includes the robust infiltration of neutrophils and macrophages to facilitate removal of dead myocytes as well as turnover of the extracellular matrix. Matrix metalloproteinase (MMP)-9 is a key enzyme that regulates post-myocardial infarction left ventricular remodeling. Infarct regions from wild-type and MMP-9 null mice (n=8 per group) analyzed by glycoproteomics showed that of 541 N-glycosylated proteins quantified, 45 proteins were at least 2-fold upregulated or downregulated with MMP-9 deletion (all P<0.05). Cartilage intermediate layer protein and platelet glycoprotein 4 (CD36) were identified as having the highest fold increase in MMP-9 null mice. By immunoblotting, CD36 but not cartilage intermediate layer protein decreased steadily during the time course post-myocardial infarction, which identified CD36 as a candidate MMP-9 substrate. MMP-9 was confirmed in vitro and in vivo to proteolytically degrade CD36. In vitro stimulation of day 7 post-myocardial infarction macrophages with MMP-9 or a CD36-blocking peptide reduced phagocytic capacity. Dual immunofluorescence revealed concomitant accumulation of apoptotic neutrophils in the MMP-9 null group compared with wild-type group. In vitro stimulation of isolated neutrophils with MMP-9 decreased neutrophil apoptosis, indicated by reduced caspase-9 expression. Our data reveal a new cell-signaling role for MMP-9 through CD36 degradation to regulate macrophage phagocytosis and neutrophil apoptosis. © 2015 American Heart Association, Inc.

Characterization of binding of N'-nitrosonornicotine to protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, M.F.

1986-01-01

The NADPH-dependent activation of the carcinogenic nitrosamine, N'-nitrosonornicotine (NNN) to a reactive intermediate which binds covalently to protein was assessed using male Sprague-Dawley rat liver and lung microsomes. The NADPH-dependent covalent binding of (/sup 14/C)NNN to liver and lung microsomes was linear with time up to 90 and 45 min, respectively and was also linear with protein concentrations up to 3.0 and 2.0 mg/ml, respectively. The apparent K/sub m/ and V/sub max/ of the NADPH-dependent binding to liver microsomes were determined from the initial velocities. Addition of the thiols glutathione, cystein, N-acetylcysteine or 2-mercapthoethanol significantly decreased the non-NADPH-dependent binding tomore » liver microsomal protein, but did not affect the NADPH-dependent binding. Glutathione was required in order to observe any NADPH-dependent binding to lung microsomal protein. In lung microsomes, SKF-525A significantly decreased the NADPH-dependent binding by 79%. Replacement of an air atmosphere with N/sub 2/ or CO:O/sub 2/ (8:2) significantly decreased the NADPH-dependent binding of (/sup 14/C)NNN to liver microsomal protein by 40% or 27% respectively. Extensive covalent binding of (/sup 14/C)NNN to liver and muscle microsomal protein occurred in the absence of an NADPH-generating system, in the presence of 50% methanol and also to bovine serum albumin, indicating a nonenzymatic reaction. These data indicate that cytochrome P-450 is at least in part responsible for the metabolic activation of the carcinogen NNN, but also suggest additional mechanisms of activation.« less

Protein Kinase A Regulatory Subunit Isoforms Regulate Growth and Differentiation in Mucor circinelloides: Essential Role of PKAR4

PubMed Central

Ocampo, J.; McCormack, B.; Navarro, E.; Moreno, S.; Garre, V.

2012-01-01

The protein kinase A (PKA) signaling pathway plays a role in regulating growth and differentiation in the dimorphic fungus Mucor circinelloides. PKA holoenzyme is comprised of two catalytic (C) and two regulatory (R) subunits. In M. circinelloides, four genes encode the PKAR1, PKAR2, PKAR3, and PKAR4 isoforms of R subunits. We have constructed null mutants and demonstrate that each isoform has a different role in growth and differentiation. The most striking finding is that pkaR4 is an essential gene, because only heterokaryons were obtained in knockout experiments. Heterokaryons with low levels of wild-type nuclei showed an impediment in the emission of the germ tube, suggesting a pivotal role of this gene in germ tube emergence. The remaining null strains showed different alterations in germ tube emergence, sporulation, and volume of the mother cell. The pkaR2 null mutant showed an accelerated germ tube emission and was the only mutant that germinated under anaerobic conditions when glycine was used as a nitrogen source, suggesting that pkaR2 participates in germ tube emergence by repressing it. From the measurement of the mRNA and protein levels of each isoform in the wild-type and knockout strains, it can be concluded that the expression of each subunit has its own mechanism of differential regulation. The PKAR1 and PKAR2 isoforms are posttranslationally modified by ubiquitylation, suggesting another regulation point in the specificity of the signal transduction. The results indicate that each R isoform has a different role in M. circinelloides physiology, controlling the dimorphism and contributing to the specificity of cyclic AMP (cAMP)-PKA pathway. PMID:22635921

The Role of Na:K:2Cl Cotransporter 1 (NKCC1/SLC12A2) in Dental Epithelium during Enamel Formation in Mice

PubMed Central

Jalali, Rozita; Lodder, Johannes C.; Zandieh-Doulabi, Behrouz; Micha, Dimitra; Melvin, James E.; Catalan, Marcelo A.; Mansvelder, Huibert D.; DenBesten, Pamela; Bronckers, Antonius

2017-01-01

Na+:K+:2Cl− cotransporters (NKCCs) belong to the SLC12A family of cation-coupled Cl− transporters. We investigated whether enamel-producing mouse ameloblasts express NKCCs. Transcripts for Nkcc1 were identified in the mouse dental epithelium by RT-qPCR and NKCC1 protein was immunolocalized in outer enamel epithelium and in the papillary layer but not the ameloblast layer. In incisors of Nkcc1-null mice late maturation ameloblasts were disorganized, shorter and the mineral density of the enamel was reduced by 10% compared to wild-type controls. Protein levels of gap junction protein connexin 43, Na+-dependent bicarbonate cotransporter e1 (NBCe1), and the Cl−-dependent bicarbonate exchangers SLC26A3 and SLC26A6 were upregulated in Nkcc1-null enamel organs while the level of NCKX4/SLC24A4, the major K+, Na+ dependent Ca2+ transporter in maturation ameloblasts, was slightly downregulated. Whole-cell voltage clamp studies on rat ameloblast-like HAT-7 cells indicated that bumetanide increased ion-channel activity conducting outward currents. Bumetanide also reduced cell volume of HAT-7 cells. We concluded that non-ameloblast dental epithelium expresses NKCC1 to regulate cell volume in enamel organ and provide ameloblasts with Na+, K+ and Cl− ions required for the transport of mineral- and bicarbonate-ions into enamel. Absence of functional Nkcc1 likely is compensated by other types of ion channels and ion transporters. The increased amount of Cx43 in enamel organ cells in Nkcc1-null mice suggests that these cells display a higher number of gap junctions to increase intercellular communication. PMID:29209227

(−)-EPICATECHIN IMPROVES MITOCHONDRIAL RELATED PROTEIN LEVELS AND AMELIORATES OXIDATIVE STRESS IN DYSTROPHIC DELTA SARCOGLYCAN NULL MOUSE STRIATED MUSCLE

PubMed Central

Ramirez-Sanchez, Israel; De los Santos, Sergio; Gonzalez-Basurto, Silvia; Canto, Patricia; Mendoza-Lorenzo, Patricia; Palma-Flores, Carlos; Ceballos-Reyes, Guillermo; Villarreal, Francisco; Zentella-Dehesa, Alejandro; Coral-Vazquez, Ramon

2014-01-01

Muscular dystrophies (MD) are a group of heterogeneous genetic disorders characterized by progressive striated muscle wasting and degeneration. Although the genetic basis for many of these disorders has been identified, the exact mechanism for disease pathogenesis remains unclear. The presence of oxidative stress (OS) is known to contribute to the pathophysiology and severity of the MD. Mitochondrial dysfunction is observed in MD and likely represents an important determinant of increased OS. Experimental antioxidant therapies have been implemented with the aim of protecting against disease progression, but results from clinical trials have been disappointing. In this study, we explored the capacity of the cacao flavonoid (−)-epicatechin (Epi) to mitigate OS by acting as a positive regulator of mitochondrial structure/function endpoints and redox balance control systems in skeletal and cardiac muscles of dystrophic, δ-sarcoglycan (δ-SG) null mice. Wild type or δ-SG null 2.5 month old male mice were treated via oral gavage with either water (control animals) or Epi (1 mg/kg, twice/day) for 2 weeks. Results evidence a significant normalization of total protein carbonylation, recovery of reduced/oxidized glutathione (GSH/GSSG ratio) and enhanced superoxide dismutase 2, catalase and citrate synthase activities with Epi treatment. These effects were accompanied by increases in protein levels for thiolredoxin, glutathione peroxidase, superoxide dismutase 2, catalase and mitochondrial endpoints. Furthermore, we evidence decreases in heart and skeletal muscle fibrosis, accompanied with an improvement in skeletal muscle function with treatment. These results warrant the further investigation of Epi as a potential therapeutic agent to mitigate MD associated muscle degeneration. PMID:25284161

Dictyostelium mutants lacking the cytoskeletal protein coronin are defective in cytokinesis and cell motility

PubMed Central

1993-01-01

Coronin is an actin-binding protein in Dictyostelium discoideum that is enriched at the leading edge of the cells and in projections of the cell surface called crowns. The polypeptide sequence of coronin is distinguished by its similarities to the beta-subunits of trimeric G proteins (E. L. de Hostos, B. Bradtke, F. Lottspeich, R. Guggenheim, and G. Gerisch, 1991. EMBO (Eur. Mol. Biol. Organ.) J. 10:4097-4104). To elucidate the in vivo function of coronin, null mutants have been generated by gene replacement. The mutant cells lacking coronin grow and migrate more slowly than wild-type cells. When these cor- cells grow in liquid medium they become multinucleate, indicating a role of coronin in cytokinesis. To explore this role, coronin has been localized in mitotic wild-type cells by immunofluorescence labeling. During separation of the daughter cells, coronin is strongly accumulated at their distal portions including the leading edges. This contrasts with the localization of myosin II in the cleavage furrow and suggests that coronin functions independently of the conventional myosin in facilitating cytokinesis. PMID:8380174

Native Hydrophobic Binding Interactions at the Transition State for Association between the TAZ1 Domain of CBP and the Disordered TAD-STAT2 Are Not a Requirement.

PubMed

Lindström, Ida; Dogan, Jakob

2017-08-15

A significant fraction of the eukaryotic proteome consists of proteins that are either partially or completely disordered under native-like conditions. Intrinsically disordered proteins (IDPs) are common in protein-protein interactions and are involved in numerous cellular processes. Although many proteins have been identified as disordered, much less is known about the binding mechanisms of the coupled binding and folding reactions involving IDPs. Here we have analyzed the rate-limiting transition state for binding between the TAZ1 domain of CREB binding protein and the intrinsically disordered transactivation domain of STAT2 (TAD-STAT2) by site-directed mutagenesis and kinetic experiments (Φ-value analysis) and found that the native protein-protein binding interface is not formed at the transition state for binding. Instead, native hydrophobic binding interactions form late, after the rate-limiting barrier has been crossed. The association rate constant in the absence of electrostatic enhancement was determined to be rather high. This is consistent with the Φ-value analysis, which showed that there are few or no obligatory native contacts. Also, linear free energy relationships clearly demonstrate that native interactions are cooperatively formed, a scenario that has usually been observed for proteins that fold according to the so-called nucleation-condensation mechanism. Thus, native hydrophobic binding interactions at the rate-limiting transition state for association between TAD-STAT2 and TAZ1 are not a requirement, which is generally in agreement with previous findings on other IDP systems and might be a common mechanism for IDPs.

E2 Proteins from High- and Low-Risk Human Papillomavirus Types Differ in Their Ability To Bind p53 and Induce Apoptotic Cell Death

PubMed Central

Parish, Joanna L.; Kowalczyk, Anna; Chen, Hsin-Tien; Roeder, Geraldine E.; Sessions, Richard; Buckle, Malcolm; Gaston, Kevin

2006-01-01

The E2 proteins from oncogenic (high-risk) human papillomaviruses (HPVs) can induce apoptotic cell death in both HPV-transformed and non-HPV-transformed cells. Here we show that the E2 proteins from HPV type 6 (HPV6) and HPV11, two nononcogenic (low-risk) HPV types, fail to induce apoptosis. Unlike the high-risk HPV16 E2 protein, these low-risk E2 proteins fail to bind p53 and fail to induce p53-dependent transcription activation. Interestingly, neither the ability of p53 to activate transcription nor the ability of p53 to bind DNA, are required for HPV16 E2-induced apoptosis in non-HPV-transformed cells. However, mutations that reduce the binding of the HPV16 E2 protein to p53 inhibit E2-induced apoptosis in non-HPV-transformed cells. In contrast, the interaction between HPV16 E2 and p53 is not required for this E2 protein to induce apoptosis in HPV-transformed cells. Thus, our data suggest that this high-risk HPV E2 protein induces apoptosis via two pathways. One pathway involves the binding of E2 to p53 and can operate in both HPV-transformed and non-HPV-transformed cells. The second pathway requires the binding of E2 to the viral genome and can only operate in HPV-transformed cells. PMID:16611918

Minimal influence of G-protein null mutations on ozone-induced changes in gene expression, foliar injury, gas exchange and peroxidase activity in Arabidopsis thaliana L

PubMed Central

Booker, Fitzgerald; Burkey, Kent; Morgan, Patrick; Fiscus, Edwin; Jones, Alan

2016-01-01

Ozone (O3) uptake by plants leads to an increase in reactive oxygen species (ROS) in the intercellular space of leaves and induces signalling processes reported to involve the membrane-bound heterotrimeric G-protein complex. Therefore, potential G-protein-mediated response mechanisms to O3 were compared between Arabidopsis thaliana L. lines with null mutations in the α- and β-subunits (gpa1-4, agb1-2 and gpa1-4/agb1-2) and Col-0 wild-type plants. Plants were treated with a range of O3 concentrations (5, 125, 175 and 300 nL L−1) for 1 and 2 d in controlled environment chambers. Transcript levels of GPA1, AGB1 and RGS1 transiently increased in Col-0 exposed to 125 nL L−1 O3 compared with the 5 nL L−1 control treatment. However, silencing of α and β G-protein genes resulted in little alteration of many processes associated with O3 injury, including the induction of ROS-signalling genes, increased leaf tissue ion leakage, decreased net photosynthesis and stomatal conductance, and increased peroxidase activity, especially in the leaf apoplast. These results indicated that many responses to O3 stress at physiological levels were not detectably influenced by α and β G-proteins. PMID:21988569

Cysteine shotgun–mass spectrometry (CS-MS) reveals dynamic sequence of protein structure changes within mutant and stressed cells

PubMed Central

Krieger, Christine C.; An, Xiuli; Tang, Hsin-Yao; Mohandas, Narla; Speicher, David W.; Discher, Dennis E.

2011-01-01

Questions of if and when protein structures change within cells pervade biology and include questions of how the cytoskeleton sustains stresses on cells—particularly in mutant versus normal cells. Cysteine shotgun labeling with fluorophores is analyzed here with mass spectrometry of the spectrin–actin membrane skeleton in sheared red blood cell ghosts from normal and diseased mice. Sheared samples are compared to static samples at 37 °C in terms of cell membrane intensity in fluorescence microscopy, separated protein fluorescence, and tryptic peptide modification in liquid chromatography–tandem mass spectrometry (LC-MS/MS). Spectrin labeling proves to be the most sensitive to shear, whereas binding partners ankyrin and actin exhibit shear thresholds in labeling and both the ankyrin-binding membrane protein band 3 and the spectrin–actin stabilizer 4.1R show minimal differential labeling. Cells from 4.1R-null mice differ significantly from normal in the shear-dependent labeling of spectrin, ankyrin, and band 3: Decreased labeling of spectrin reveals less stress on the mutant network as spectrin dissociates from actin. Mapping the stress-dependent labeling kinetics of α- and β-spectrin by LC-MS/MS identifies Cys in these antiparallel chains that are either force-enhanced or force-independent in labeling, with structural analyses indicating the force-enhanced sites are sequestered either in spectrin’s triple-helical domains or in interactions with actin or ankyrin. Shear-sensitive sites identified comprehensively here in both spectrin and ankyrin appear consistent with stress relief through forced unfolding followed by cytoskeletal disruption. PMID:21527722

Effects of starch synthase IIa gene dosage on grain, protein and starch in endosperm of wheat.

PubMed

Konik-Rose, Christine; Thistleton, Jenny; Chanvrier, Helene; Tan, Ihwa; Halley, Peter; Gidley, Michael; Kosar-Hashemi, Behjat; Wang, Hong; Larroque, Oscar; Ikea, Joseph; McMaugh, Steve; Regina, Ahmed; Rahman, Sadequr; Morell, Matthew; Li, Zhongyi

2007-11-01

Starch synthases (SS) are responsible for elongating the alpha-1,4 glucan chains of starch. A doubled haploid population was generated by crossing a line of wheat, which lacks functional ssIIa genes on each genome (abd), and an Australian wheat cultivar, Sunco, with wild type ssIIa alleles on each genome (ABD). Evidence has been presented previously indicating that the SGP-1 (starch granule protein-1) proteins present in the starch granule in wheat are products of the ssIIa genes. Analysis of 100 progeny lines demonstrated co-segregation of the ssIIa alleles from the three genomes with the SGP-1 proteins, providing further evidence that the SGP-1 proteins are the products of the ssIIa genes. From the progeny lines, 40 doubled haploid lines representing the eight possible genotypes for SSIIa (ABD, aBD, AbD, ABd, abD, aBd, Abd, abd) were characterized for their grain weight, protein content, total starch content and starch properties. For some properties (chain length distribution, pasting properties, swelling power, and gelatinization properties), a progressive change was observed across the four classes of genotypes (wild type, single nulls, double nulls and triple nulls). However, for other grain properties (seed weight and protein content) and starch properties (total starch content, granule morphology and crystallinity, granule size distribution, amylose content, amylose-lipid dissociation properties), a statistically significant change only occurred for the triple nulls, indicating that all three genes had to be missing or inactive for a change to occur. These results illustrate the importance of SSIIa in controlling grain and starch properties and the importance of amylopectin fine structure in controlling starch granule properties in wheat.

Heterologous Expression of Der Homologs in an Escherichia coli der Mutant and Their Functional Complementation

PubMed Central

Choi, Eunsil; Kang, Nalae; Jeon, Young; Pai, Hyun-Sook

2016-01-01

ABSTRACT The unique Escherichia coli GTPase Der (double Era-like GTPase), which contains tandemly repeated GTP-binding domains, has been shown to play an essential role in 50S ribosomal subunit biogenesis. The depletion of Der results in the accumulation of precursors of 50S ribosomal subunits that are structurally unstable at low Mg2+ concentrations. Der homologs are ubiquitously found in eubacteria. Conversely, very few are conserved in eukaryotes, and none is conserved in archaea. In the present study, to verify their conserved role in bacterial 50S ribosomal subunit biogenesis, we cloned Der homologs from two gammaproteobacteria, Klebsiella pneumoniae and Salmonella enterica serovar Typhimurium; two pathogenic bacteria, Staphylococcus aureus and Neisseria gonorrhoeae; and the extremophile Deinococcus radiodurans and then evaluated whether they could functionally complement the E. coli der-null phenotype. Only K. pneumoniae and S. Typhimurium Der proteins enabled the E. coli der-null strain to grow under nonpermissive conditions. Sucrose density gradient experiments revealed that the expression of K. pneumoniae and S. Typhimurium Der proteins rescued the structural instability of 50S ribosomal subunits, which was caused by E. coli Der depletion. To determine what allows their complementation, we constructed Der chimeras. We found that only Der chimeras harboring both the linker and long C-terminal regions could reverse the growth defects of the der-null strain. Our findings suggest that ubiquitously conserved essential GTPase Der is involved in 50S ribosomal subunit biosynthesis in various bacteria and that the linker and C-terminal regions may participate in species-specific recognition or interaction with the 50S ribosomal subunit. IMPORTANCE In Escherichia coli, Der (double Era-like GTPase) is an essential GTPase that is important for the production of mature 50S ribosomal subunits. However, to date, its precise role in ribosome biogenesis has not been clarified. In this study, we used five Der homologs from gammaproteobacteria, pathogenic bacteria, and an extremophile to elucidate their conserved function in 50S ribosomal subunit biogenesis. Among them, Klebsiella pneumoniae and Salmonella enterica serovar Typhimurium Der homologs implicated the participation of Der in ribosome assembly in E. coli. Our results show that the linker and C-terminal regions of Der homologs are correlated with its functional complementation in E. coli der mutants, suggesting that they are involved in species-specific recognition or interaction with 50S ribosomal subunits. PMID:27297882

Competitive tuning: Competition's role in setting the frequency-dependence of Ca2+-dependent proteins

PubMed Central

Patel, Neal M.; Kinzer-Ursem, Tamara L.

2017-01-01

A number of neurological disorders arise from perturbations in biochemical signaling and protein complex formation within neurons. Normally, proteins form networks that when activated produce persistent changes in a synapse’s molecular composition. In hippocampal neurons, calcium ion (Ca2+) flux through N-methyl-D-aspartate (NMDA) receptors activates Ca2+/calmodulin signal transduction networks that either increase or decrease the strength of the neuronal synapse, phenomena known as long-term potentiation (LTP) or long-term depression (LTD), respectively. The calcium-sensor calmodulin (CaM) acts as a common activator of the networks responsible for both LTP and LTD. This is possible, in part, because CaM binding proteins are “tuned” to different Ca2+ flux signals by their unique binding and activation dynamics. Computational modeling is used to describe the binding and activation dynamics of Ca2+/CaM signal transduction and can be used to guide focused experimental studies. Although CaM binds over 100 proteins, practical limitations cause many models to include only one or two CaM-activated proteins. In this work, we view Ca2+/CaM as a limiting resource in the signal transduction pathway owing to its low abundance relative to its binding partners. With this view, we investigate the effect of competitive binding on the dynamics of CaM binding partner activation. Using an explicit model of Ca2+, CaM, and seven highly-expressed hippocampal CaM binding proteins, we find that competition for CaM binding serves as a tuning mechanism: the presence of competitors shifts and sharpens the Ca2+ frequency-dependence of CaM binding proteins. Notably, we find that simulated competition may be sufficient to recreate the in vivo frequency dependence of the CaM-dependent phosphatase calcineurin. Additionally, competition alone (without feedback mechanisms or spatial parameters) could replicate counter-intuitive experimental observations of decreased activation of Ca2+/CaM-dependent protein kinase II in knockout models of neurogranin. We conclude that competitive tuning could be an important dynamic process underlying synaptic plasticity. PMID:29107982

A systems wide mass spectrometric based linear motif screen to identify dominant in-vivo interacting proteins for the ubiquitin ligase MDM2.

PubMed

Nicholson, Judith; Scherl, Alex; Way, Luke; Blackburn, Elizabeth A; Walkinshaw, Malcolm D; Ball, Kathryn L; Hupp, Ted R

2014-06-01

Linear motifs mediate protein-protein interactions (PPI) that allow expansion of a target protein interactome at a systems level. This study uses a proteomics approach and linear motif sub-stratifications to expand on PPIs of MDM2. MDM2 is a multi-functional protein with over one hundred known binding partners not stratified by hierarchy or function. A new linear motif based on a MDM2 interaction consensus is used to select novel MDM2 interactors based on Nutlin-3 responsiveness in a cell-based proteomics screen. MDM2 binds a subset of peptide motifs corresponding to real proteins with a range of allosteric responses to MDM2 ligands. We validate cyclophilin B as a novel protein with a consensus MDM2 binding motif that is stabilised by Nutlin-3 in vivo, thus identifying one of the few known interactors of MDM2 that is stabilised by Nutlin-3. These data invoke two modes of peptide binding at the MDM2 N-terminus that rely on a consensus core motif to control the equilibrium between MDM2 binding proteins. This approach stratifies MDM2 interacting proteins based on the linear motif feature and provides a new biomarker assay to define clinically relevant Nutlin-3 responsive MDM2 interactors. Copyright © 2014 Elsevier Inc. All rights reserved.

Conditional and constitutive expression of a Tbx1-GFP fusion protein in mice

PubMed Central

2013-01-01

Background Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is caused by a 1.5-3 Mb microdeletion of chromosome 22q11.2, frequently referred to as 22q11.2 deletion syndrome (22q11DS). This region includes TBX1, a T-box transcription factor gene that contributes to the etiology of 22q11DS. The requirement for TBX1 in mammalian development is dosage-sensitive, such that loss-of-function (LOF) and gain-of-function (GOF) of TBX1 in both mice and humans results in disease relevant congenital malformations. Results To further gain insight into the role of Tbx1 in development, we have targeted the Rosa26 locus to generate a new GOF mouse model in which a Tbx1-GFP fusion protein is expressed conditionally using the Cre/LoxP system. Tbx1-GFP expression is driven by the endogenous Rosa26 promoter resulting in ectopic and persistent expression. Tbx1 is pivotal for proper ear and heart development; ectopic activation of Tbx1-GFP in the otic vesicle by Pax2-Cre and Foxg1-Cre represses neurogenesis and produces morphological defects of the inner ear. Overexpression of a single copy of Tbx1-GFP using Tbx1Cre/+ was viable, while overexpression of both copies resulted in neonatal lethality with cardiac outflow tract defects. We have partially rescued inner ear and heart anomalies in Tbx1Cre/- null embryos by expression of Tbx1-GFP. Conclusions We have generated a new mouse model to conditionally overexpress a GFP-tagged Tbx1 protein in vivo. This provides a useful tool to investigate in vivo direct downstream targets and protein binding partners of Tbx1. PMID:23971992

Use of a cryptic splice site for the expression of huntingtin interacting protein 1 in select normal and neoplastic tissues.

PubMed

Graves, Chiron W; Philips, Steven T; Bradley, Sarah V; Oravecz-Wilson, Katherine I; Li, Lina; Gauvin, Alice; Ross, Theodora S

2008-02-15

Huntingtin interacting protein 1 (HIP1) is a 116-kDa endocytic protein, which is necessary for the maintenance of several tissues in vivo as its deficiency leads to degenerative adult phenotypes. HIP1 deficiency also inhibits prostate tumor progression in mice. To better understand how deficiency of HIP1 leads to such phenotypes, we analyzed tumorigenic potential in mice homozygous for a Hip1 mutant allele, designated Hip1(Delta 3-5), which is predicted to result in a frame-shifted, nonsense mutation in the NH(2) terminus of HIP1. In contrast to our previous studies using the Hip1 null allele, an inhibition of tumorigenesis was not observed as a result of the homozygosity of the nonsense Delta 3-5 allele. To further examine the contrasting results from the prior Hip1 mutant mice, we cultured tumor cells from homozygous Delta 3-5 allele-bearing mice and discovered the presence of a 110-kDa form of HIP1 in tumor cells. Upon sequencing of Hip1 DNA and message from these tumors, we determined that this 110-kDa form of HIP1 is the product of splicing of a cryptic U12-type AT-AC intron. This event results in the insertion of an AG dinucleotide between exons 2 and 6 and restoration of the reading frame. Remarkably, this mutant protein retains its capacity to bind lipids, clathrin, AP2, and epidermal growth factor receptor providing a possible explanation for why tumorigenesis was not altered after this knockout mutation. Our data show how knowledge of the transcript that is produced by a knockout allele can lead to discovery of novel types of molecular compensation at the level of splicing.

Use of a Cryptic Splice Site for the Expression of Huntingtin Interacting Protein 1 in Select Normal and Neoplastic Tissues

PubMed Central

Graves, Chiron W.; Philips, Steven T.; Bradley, Sarah V.; Oravecz-Wilson, Katherine I.; Li, Lina; Gauvin, Alice; Ross, Theodora S.

2011-01-01

Huntingtin interacting protein 1 (HIP1) is a 116-kDa endocytic protein, which is necessary for the maintenance of several tissues in vivo as its deficiency leads to degenerative adult phenotypes. HIP1 deficiency also inhibits prostate tumor progression in mice. To better understand how deficiency of HIP1 leads to such phenotypes, we analyzed tumorigenic potential in mice homozygous for a Hip1 mutant allele, designated Hip1Δ3-5, which is predicted to result in a frame-shifted, nonsense mutation in the NH2 terminus of HIP1. In contrast to our previous studies using the Hip1 null allele, an inhibition of tumorigenesis was not observed as a result of the homozygosity of the nonsense Δ3-5 allele. To further examine the contrasting results from the prior Hip1 mutant mice, we cultured tumor cells from homozygous Δ3-5 allele–bearing mice and discovered the presence of a 110-kDa form of HIP1 in tumor cells. Upon sequencing of Hip1 DNA and message from these tumors, we determined that this 110-kDa form of HIP1 is the product of splicing of a cryptic U12-type AT-AC intron. This event results in the insertion of an AG dinucleotide between exons 2 and 6 and restoration of the reading frame. Remarkably, this mutant protein retains its capacity to bind lipids, clathrin, AP2, and epidermal growth factor receptor providing a possible explanation for why tumorigenesis was not altered after this knockout mutation. Our data show how knowledge of the transcript that is produced by a knockout allele can lead to discovery of novel types of molecular compensation at the level of splicing. PMID:18281481

Deficiency of heat shock transcription factor 1 suppresses heat stress-associated increase in slow soleus muscle mass of mice.

PubMed

Ohno, Y; Egawa, T; Yokoyama, S; Nakai, A; Sugiura, T; Ohira, Y; Yoshioka, T; Goto, K

2015-12-01

Effects of heat shock transcription factor 1 (HSF1) deficiency on heat stress-associated increase in slow soleus muscle mass of mice were investigated. Both HSF1-null and wild-type mice were randomly assigned to control and heat-stressed groups. Mice in heat-stressed group were exposed to heat stress (41 °C for 60 min) in an incubator without anaesthesia. Significant increase in wet and dry weights, and protein content of soleus muscle in wild-type mice was observed seven days after the application of the heat stress. However, heat stress had no impact on soleus muscle mass in HSF1-null mice. Neither type of mice exhibited much effect of heat stress on HSF mRNA expression (HSF1, HSF2 and HSF4). On the other hand, heat stress upregulated heat shock proteins (HSPs) at the mRNA (HSP72) and protein (HSP72 and HSP110) levels in wild-type mice, but not in HSF1-null mice. The population of Pax7-positive nuclei relative to total myonuclei of soleus muscle in wild-type mice was significantly increased by heat stress, but not in HSF1-null mice. Furthermore, the absence of HSF1 gene suppressed heat stress-associated phosphorylation of Akt and p70 S6 kinase (p-p70S6K) in soleus muscle. Heat stress-associated increase in skeletal muscle mass may be induced by HSF1 and/or HSF1-mediated stress response that activates muscle satellite cells and Akt/p70S6K signalling pathway. © 2015 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Role of B-type natriuretic peptide in epoxyeicosatrienoic acid-mediated improved post-ischaemic recovery of heart contractile function

PubMed Central

Chaudhary, Ketul R.; Batchu, Sri Nagarjun; Das, Dipankar; Suresh, Mavanur R.; Falck, John R.; Graves, Joan P.; Zeldin, Darryl C.; Seubert, John M.

2009-01-01

Aims This study examined the functional role of B-type natriuretic peptide (BNP) in epoxyeicosatrienoic acid (EET)-mediated cardioprotection in mice with targeted disruption of the sEH or Ephx2 gene (sEH null). Methods and results Isolated mouse hearts were perfused in the Langendorff mode and subjected to global no-flow ischaemia followed by reperfusion. Hearts were analysed for recovery of left ventricular developed pressure (LVDP), mRNA levels, and protein expression. Naïve hearts from sEH null mice had similar expression of preproBNP (Nppb) mRNA compared with wild-type (WT) hearts. However, significant increases in Nppb mRNA and BNP protein expression occurred during post-ischaemic reperfusion and correlated with improved post-ischaemic recovery of LVDP. Perfusion with the putative EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid prior to ischaemia reduced the preproBNP mRNA in sEH null hearts. Inhibitor studies demonstrated that perfusion with the natriuretic peptide receptor type-A (NPR-A) antagonist, A71915, limited the improved recovery in recombinant full-length mouse BNP (rBNP)- and 11,12-EET-perfused hearts as well as in sEH null mice. Increased expression of phosphorylated protein kinase C ε and Akt were found in WT hearts perfused with either 11,12-EET or rBNP, while mitochondrial glycogen synthase kinase-3β was significantly lower in the same samples. Furthermore, treatment with the phosphoinositide 3-kinase (PI3K) inhibitor wortmannin abolished improved LVDP recovery in 11,12-EET-treated hearts but not did significantly inhibit recovery of rBNP-treated hearts. Conclusion Taken together, these data indicate that EET-mediated cardioprotection involves BNP and PI3K signalling events. PMID:19401302

p65 fragments, homologous to the C2 region of protein kinase C, bind to the intracellular receptors for protein kinase C.

PubMed

Mochly-Rosen, D; Miller, K G; Scheller, R H; Khaner, H; Lopez, J; Smith, B L

1992-09-08

Receptors for activated protein kinase C (RACKs) have been isolated from the particulate cell fraction of heart and brain. We previously demonstrated that binding of protein kinase C (PKC) to RACKs requires PKC activators and is via a site on PKC that is distinct from the substrate binding site. Here, we examine the possibility that the C2 region in the regulatory domain of PKC is involved in binding of PKC to RACKs. The synaptic vesicle-specific p65 protein contains two regions homologous to the C2 region of PKC. We found that three p65 fragments, containing either one or two of these PKC C2 homologous regions, bound to highly purified RACKs. Binding of the p65 fragments and PKC to RACKs was mutually exclusive; preincubation of RACKs with the p65 fragments inhibited PKC binding, and preincubation of RACKs with PKC inhibited binding of the p65 fragments. Preincubation of the p65 fragments with a peptide resembling the PKC binding site on RACKs also inhibited p65 binding to RACKs, suggesting that PKC and p65 bind to the same or nearby regions on RACKs. Since the only homologous region between PKC and the p65 fragments is the C2 region, these results suggest that the C2 region on PKC contains at least part of the RACK binding site.

Progressive renal papillary calcification and ureteral stone formation in mice deficient for Tamm-Horsfall protein

PubMed Central

Liu, Yan; Mo, Lan; Goldfarb, David S.; Evan, Andrew P.; Liang, Fengxia; Khan, Saeed R.; Lieske, John C.

2010-01-01

Mammalian urine contains a range of macromolecule proteins that play critical roles in renal stone formation, among which Tamm-Horsfall protein (THP) is by far the most abundant. While THP is a potent inhibitor of crystal aggregation in vitro and its ablation in vivo predisposes one of the two existing mouse models to spontaneous intrarenal calcium crystallization, key controversies remain regarding the role of THP in nephrolithiasis. By carrying out a long-range follow-up of more than 250 THP-null mice and their wild-type controls, we demonstrate here that renal calcification is a highly consistent phenotype of the THP-null mice that is age and partially gene dosage dependent, but is gender and genetic background independent. Renal calcification in THP-null mice is progressive, and by 15 mo over 85% of all the THP-null mice develop spontaneous intrarenal crystals. The crystals consist primarily of calcium phosphate in the form of hydroxyapatite, are located more frequently in the interstitial space of the renal papillae than intratubularly, particularly in older animals, and lack accompanying inflammatory cell infiltration. The interstitial deposits of hydroxyapatite observed in THP-null mice bear strong resemblances to the renal crystals found in human kidneys bearing idiopathic calcium oxalate stones. Compared with 24-h urine from the wild-type mice, that of THP-null mice is supersaturated with brushite (calcium phosphate), a stone precursor, and has reduced urinary excretion of citrate, a stone inhibitor. While less frequent than renal calcinosis, renal pelvic and ureteral stones and hydronephrosis occur in the aged THP-null mice. These results provide direct in vivo evidence indicating that normal THP plays an important role in defending the urinary system against calcification and suggest that reduced expression and/or decreased function of THP could contribute to nephrolithiasis. PMID:20591941

Herpes Simplex Virus Glycoprotein B Associates with Target Membranes via Its Fusion Loops▿

PubMed Central

Hannah, Brian P.; Cairns, Tina M.; Bender, Florent C.; Whitbeck, J. Charles; Lou, Huan; Eisenberg, Roselyn J.; Cohen, Gary H.

2009-01-01

Herpes simplex virus (HSV) glycoproteins gB, gD, and gH/gL are necessary and sufficient for virus entry into cells. Structural features of gB are similar to those of vesicular stomatitis virus G and baculovirus gp64, and together they define the new class III group of fusion proteins. Previously, we used mutagenesis to show that three hydrophobic residues (W174, Y179, and A261) within the putative gB fusion loops are integral to gB function. Here we expanded our analysis, using site-directed mutagenesis of each residue in both gB fusion loops. Mutation of most of the nonpolar or hydrophobic amino acids (W174, F175, G176, Y179, and A261) had severe effects on gB function in cell-cell fusion and null virus complementation assays. Of the six charged amino acids, mutation of H263 or R264 also negatively affected gB function. To further analyze the mutants, we cloned the ectodomains of the W174R, Y179S, H263A, and R264A mutants into a baculovirus expression system and compared them with the wild-type (WT) form, gB730t. As shown previously, gB730t blocks virus entry into cells, suggesting that gB730t competes with virion gB for a cell receptor. All four mutant proteins retained this function, implying that fusion loop activity is separate from gB-receptor binding. However, unlike WT gB730t, the mutant proteins displayed reduced binding to cells and were either impaired or unable to bind naked, cholesterol-enriched liposomes, suggesting that it may be gB-lipid binding that is disrupted by the mutations. Furthermore, monoclonal antibodies with epitopes proximal to the fusion loops abrogated gB-liposome binding. Taken together, our data suggest that gB associates with lipid membranes via a fusion domain of key hydrophobic and hydrophilic residues and that this domain associates with lipid membranes during fusion. PMID:19369321

Structural analyses of von Willebrand factor C domains of collagen 2A and CCN3 reveal an alternative mode of binding to bone morphogenetic protein-2.

PubMed

Xu, Emma-Ruoqi; Blythe, Emily E; Fischer, Gerhard; Hyvönen, Marko

2017-07-28

Bone morphogenetic proteins (BMPs) are secreted growth factors that promote differentiation processes in embryogenesis and tissue development. Regulation of BMP signaling involves binding to a variety of extracellular proteins, among which are many von Willebrand factor C (vWC) domain-containing proteins. Although the crystal structure of the complex of crossveinless-2 (CV-2) vWC1 and BMP-2 previously revealed one mode of the vWC/BMP-binding mechanism, other vWC domains may bind to BMP differently. Here, using X-ray crystallography, we present for the first time structures of the vWC domains of two proteins thought to interact with BMP-2: collagen IIA and matricellular protein CCN3. We found that these two vWC domains share a similar N-terminal fold that differs greatly from that in CV-2 vWC, which comprises its BMP-2-binding site. We analyzed the ability of these vWC domains to directly bind to BMP-2 and detected an interaction only between the collagen IIa vWC and BMP-2. Guided by the collagen IIa vWC domain crystal structure and conservation of surface residues among orthologous domains, we mapped the BMP-binding epitope on the subdomain 1 of the vWC domain. This binding site is different from that previously observed in the complex between CV-2 vWC and BMP-2, revealing an alternative mode of interaction between vWC domains and BMPs. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Active sites prediction and binding analysis E1-E2 protein human papillomavirus with biphenylsulfonacetic acid

NASA Astrophysics Data System (ADS)

Iryani, I.; Amelia, F.; Iswendi, I.

2018-04-01

Cervix cancer triggered by Human papillomavirus infection is the second cause to woman death in worldwide. The binding site of E1-E2 protein of HPV 16 is not known from a 3-D structure yet, so in this study we address this issue to study the structure of E1-E2 protein from Human papillomavirus type 16 and to find its potential binding sites using biphenylsulfonacetic acid as inhibitor. Swiss model was used for 3D structure prediction and PDB: 2V9P (E1 protein) and 2NNU (E2 protein) having 52.32% and 100% identity respectively was selected as a template. The 3D model structure developed of E1 and E2 in the core and allowed regions were 99.2% and 99.5%. The ligand binding sites were predicted using online server meta pocket 2.0 and MOE 2009.10 was used for docking. E1-and E2 protein of HPV-16 has three potential binding site that can interact with the inhibitors. The Docking biphenylsulfonacetic acid using these binding sites shows that ligand interact with the protein through hydrogen bonds on Lys 403, Arg 410, His 551 in the first pocket, on Tyr 32, Leu 99 in the second pocket, and Lys 558m Lys 517 in the third pocket.

Coelenterazine-binding protein of Renilla muelleri: cDNA cloning, overexpression, and characterization as a substrate of luciferase.

PubMed

Titushin, Maxim S; Markova, Svetlana V; Frank, Ludmila A; Malikova, Natalia P; Stepanyuk, Galina A; Lee, John; Vysotski, Eugene S

2008-02-01

The Renilla bioluminescent system in vivo is comprised of three proteins--the luciferase, green-fluorescent protein, and coelenterazine-binding protein (CBP), previously called luciferin-binding protein (LBP). This work reports the cloning of the full-size cDNA encoding CBP from soft coral Renilla muelleri, its overexpression and properties of the recombinant protein. The apo-CBP was quantitatively converted to CBP by simple incubation with coelenterazine. The physicochemical properties of this recombinant CBP are determined to be practically the same as those reported for the CBP (LBP) of R. reniformis. CBP is a member of the four-EF-hand Ca(2+)-binding superfamily of proteins with only three of the EF-hand loops having the Ca(2+)-binding consensus sequences. There is weak sequence homology with the Ca(2+)-regulated photoproteins but only as a result of the necessary Ca(2+)-binding loop structure. In combination with Renilla luciferase, addition of only one Ca(2+) is sufficient to release the coelenterazine as a substrate for the luciferase for bioluminescence. This combination of the two proteins generates bioluminescence with higher reaction efficiency than using free coelenterazine alone as the substrate for luciferase. This increased quantum yield, a difference of bioluminescence spectra, and markedly different kinetics, implicate that a CBP-luciferase complex might be involved.

RGS10 exerts a neuroprotective role through the PKA/c-AMP response-element (CREB) pathway in dopaminergic neuron-like cells

PubMed Central

Lee, Jae-Kyung; Chung, Jaegwon; Druey, Kirk M.; Tansey, Malú G.

2012-01-01

Regulator of G-protein signaling-10 (RGS10) is a GTPase activating protein (GAP) for Gαi/q/z subunits that is highly expressed in the immune system and in a broad range of brain regions including the hippocampus, striatum, dorsal raphe, and ventral midbrain. Previously, we reported that RGS10-null mice display increased vulnerability to chronic systemic inflammation-induced degeneration of nigral dopaminergic (DA) neurons. Given that RGS10 is expressed in DA neurons, we investigated the extent to which RGS10 regulates cell survival under conditions of inflammatory stress. Because of the inherent limitations associated with use of primary DA neurons for biochemical analyses, we employed a well-characterized ventral mesencephalon DA neuroblastoma cell line (MN9D) for our studies. We found that stable over-expression of RGS10 rendered them resistant to TNF-induced cytotoxicity; whereas MN9D cells expressing mutant RGS10-S168A (which is resistant to phosphorylation by protein kinase A (PKA) at a serine residue that promotes its nuclear translocation) showed similar sensitivity to TNF as the parental MN9D cells. Using biochemical and pharmacological approaches, we identified protein kinase A (PKA) and the downstream phospho-cAMP response element-binding (CREB) signaling pathway (and ruled out ERK 1/2, JNK, and NFkB) as key mediators of the neuroprotective effect of RGS10 against inflammatory stress. PMID:22564151

Simultaneous Binding of Two Peptidyl Ligands by a Src Homology 2 Domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yanyan; Zhang, Jinjin; Yuan, Chunhua

Src homology 2 (SH2) domains mediate protein-protein interactions by recognizing phosphotyrosine (pY)-containing sequences of target proteins. In all of the SH2 domain-pY peptide interactions described to date, the SH2 domain binds to a single pY peptide. Here, determination of the cocrystal structure of the N-terminal SH2 domain of phosphatase SHP-2 bound to a class IV peptide (VIpYFVP) revealed a noncanonical 1:2 (protein-peptide) complex. The first peptide binds in a canonical manner with its pY side chain inserted in the usual binding pocket, while the second pairs up with the first to form two antiparallel {beta}-strands that extend the central {beta}-sheetmore » of the SH2 domain. This unprecedented binding mode was confirmed in the solution phase by NMR experiments and shown to be adopted by pY peptides derived from cellular proteins. Site-directed mutagenesis and surface plasmon resonance studies revealed that the binding of the first peptide is pY-dependent, but phosphorylation is not required for the second peptide. Our findings suggest a potential new function for the SH2 domain as a molecular clamp to promote dimerization of signaling proteins.« less

A microscopic insight from conformational thermodynamics to functional ligand binding in proteins.

PubMed

Sikdar, Samapan; Chakrabarti, J; Ghosh, Mahua

2014-12-01

We show that the thermodynamics of metal ion-induced conformational changes aid to understand the functions of protein complexes. This is illustrated in the case of a metalloprotein, alpha-lactalbumin (aLA), a divalent metal ion binding protein. We use the histograms of dihedral angles of the protein, generated from all-atom molecular dynamics simulations, to calculate conformational thermodynamics. The thermodynamically destabilized and disordered residues in different conformational states of a protein are proposed to serve as binding sites for ligands. This is tested for β-1,4-galactosyltransferase (β4GalT) binding to the Ca(2+)-aLA complex, in which the binding residues are known. Among the binding residues, the C-terminal residues like aspartate (D) 116, glutamine (Q) 117, tryptophan (W) 118 and leucine (L) 119 are destabilized and disordered and can dock β4GalT onto Ca(2+)-aLA. No such thermodynamically favourable binding residues can be identified in the case of the Mg(2+)-aLA complex. We apply similar analysis to oleic acid binding and predict that the Ca(2+)-aLA complex can bind to oleic acid through the basic histidine (H) 32 of the A2 helix and the hydrophobic residues, namely, isoleucine (I) 59, W60 and I95, of the interfacial cleft. However, the number of destabilized and disordered residues in Mg(2+)-aLA are few, and hence, the oleic acid binding to Mg(2+)-bound aLA is less stable than that to the Ca(2+)-aLA complex. Our analysis can be generalized to understand the functionality of other ligand bound proteins.

Cardiac myosin binding protein C regulates postnatal myocyte cytokinesis

PubMed Central

Jiang, Jianming; Burgon, Patrick G.; Wakimoto, Hiroko; Onoue, Kenji; Gorham, Joshua M.; O’Meara, Caitlin C.; Fomovsky, Gregory; McConnell, Bradley K.; Lee, Richard T.; Seidman, J. G.; Seidman, Christine E.

2015-01-01

Homozygous cardiac myosin binding protein C-deficient (Mybpct/t) mice develop dramatic cardiac dilation shortly after birth; heart size increases almost twofold. We have investigated the mechanism of cardiac enlargement in these hearts. Throughout embryogenesis myocytes undergo cell division while maintaining the capacity to pump blood by rapidly disassembling and reforming myofibrillar components of the sarcomere throughout cell cycle progression. Shortly after birth, myocyte cell division ceases. Cardiac MYBPC is a thick filament protein that regulates sarcomere organization and rigidity. We demonstrate that many Mybpct/t myocytes undergo an additional round of cell division within 10 d postbirth compared with their wild-type counterparts, leading to increased numbers of mononuclear myocytes. Short-hairpin RNA knockdown of Mybpc3 mRNA in wild-type mice similarly extended the postnatal window of myocyte proliferation. However, adult Mybpct/t myocytes are unable to fully regenerate the myocardium after injury. MYBPC has unexpected inhibitory functions during postnatal myocyte cytokinesis and cell cycle progression. We suggest that human patients with homozygous MYBPC3-null mutations develop dilated cardiomyopathy, coupled with myocyte hyperplasia (increased cell number), as observed in Mybpct/t mice. Human patients, with heterozygous truncating MYBPC3 mutations, like mice with similar mutations, have hypertrophic cardiomyopathy. However, the mechanism leading to hypertrophic cardiomyopathy in heterozygous MYBPC3+/− individuals is myocyte hypertrophy (increased cell size), whereas the mechanism leading to cardiac dilation in homozygous Mybpc3−/− mice is primarily myocyte hyperplasia. PMID:26153423

Perilipin-2 null mice are protected against diet-induced obesity, adipose inflammation, and fatty liver disease

USDA-ARS?s Scientific Manuscript database

The cytoplasmic lipid droplet (CLD) protein perilipin-2 (Plin2) is expressed in multiple nonadipose tissues, where it is thought to play a role in regulating their lipid storage properties. However, the extent to which Plin2 functions in nutrient utilization and metabolism, or how it influences the ...

PI(4,5)P2-binding effector proteins for vesicle exocytosis

PubMed Central

Martin, Thomas F. J.

2014-01-01

PI(4,5)P2 participates directly in priming and possibly fusion steps of Ca2+-triggered vesicle exocytosis. High concentration nanodomains of PI(4,5)P2 reside on the plasma membrane of neuroendocrine cells. A subset of vesicles that co-localize with PI(4,5)P2 domains appear to undergo preferential exocytosis in stimulated cells. PI(4,5)P2 directly regulates vesicle exocytosis by recruiting and activating PI(4,5)P2-binding proteins that regulate SNARE protein function including CAPS, Munc13-1/2, synaptotagmin-1, and other C2 domain-containing proteins. These PI(4,5)P2 effector proteins are coincidence detectors that engage in multiple interactions at vesicle exocytic sites. The SNARE protein syntaxin-1 also binds to PI(4,5)P2, which promotes clustering, but an activating role for PI(4,5)P2 in syntaxin-1 function remains to be fully characterized. Similar principles underlie polarized constitutive vesicle fusion mediated in part by the PI(4,5)P2-binding subunits of the exocyst complex (Sec3, Exo70). Overall, focal vesicle exocytosis occurs at sites landmarked by PI(4,5)P2, which serves to recruit and/or activate multifunctional PI(4,5)P2-binding proteins. PMID:25280637

A multiprotein binding interface in an intrinsically disordered region of the tumor suppressor protein interferon regulatory factor-1.

PubMed

Narayan, Vikram; Halada, Petr; Hernychová, Lenka; Chong, Yuh Ping; Žáková, Jitka; Hupp, Ted R; Vojtesek, Borivoj; Ball, Kathryn L

2011-04-22

The interferon-regulated transcription factor and tumor suppressor protein IRF-1 is predicted to be largely disordered outside of the DNA-binding domain. One of the advantages of intrinsically disordered protein domains is thought to be their ability to take part in multiple, specific but low affinity protein interactions; however, relatively few IRF-1-interacting proteins have been described. The recent identification of a functional binding interface for the E3-ubiquitin ligase CHIP within the major disordered domain of IRF-1 led us to ask whether this region might be employed more widely by regulators of IRF-1 function. Here we describe the use of peptide aptamer-based affinity chromatography coupled with mass spectrometry to define a multiprotein binding interface on IRF-1 (Mf2 domain; amino acids 106-140) and to identify Mf2-binding proteins from A375 cells. Based on their function as known transcriptional regulators, a selection of the Mf2 domain-binding proteins (NPM1, TRIM28, and YB-1) have been validated using in vitro and cell-based assays. Interestingly, although NPM1, TRIM28, and YB-1 all bind to the Mf2 domain, they have differing amino acid specificities, demonstrating the degree of combinatorial diversity and specificity available through linear interaction motifs.

Revealing of Saccharomyces cerevisiae yeast cell wall proteins capable of binding thioflavin T, a fluorescent dye specifically interacting with amyloid fibrils.

PubMed

Gorkovskii, A A; Bezsonov, E E; Plotnikova, T A; Kalebina, T S; Kulaev, I S

2009-11-01

Proteins binding thioflavin T leading to its specific fluorescence were discovered in a fraction of noncovalently bound Saccharomyces cerevisiae yeast cell wall mannoproteins. Thioflavin-binding proteins display high resistance to trypsin digestion in solution. These data are the first experimental evidence for the presence of proteins whose properties are characteristic of amyloids in yeast cell wall, except for data on glucanotransferase Bgl2p that has amyloid properties. Our data suggest the anchoring of these proteins in the cell wall by a trypsin-sensitive part of the protein molecule. Experiments with a mutant strain devoid of the BGL2 gene suggest the compensation of absent amyloid-like protein Bgl2p by increase in contents of thioflavin-binding proteins in the cell wall.

Functional Differentiation of Uterine Stromal Cells Involves Cross-regulation between Bone Morphogenetic Protein 2 and Kruppel-like Factor (KLF) Family Members KLF9 and KLF13

USDA-ARS?s Scientific Manuscript database

The inability of the uterine epithelium to enter a state of receptivity for the embryo to implant is a significant underlying cause of early pregnancy loss. We previously showed that mice null for the Progesterone Receptor (PGR)-interacting protein Kruppel-like Factor (KLF) 9 are subfertile and exhi...

Rhnull syndrome: identification of a novel mutation in RHce.

PubMed

Rosa, K A; Reid, M E; Lomas-Francis, C; Powell, V I; Costa, F F; Stinghen, S T; Watanabe, A M; Carboni, E K; Baldon, J P; Jucksch, M M F; Castilho, L

2005-11-01

The deficiency of Rh proteins on red blood cells (RBCs) from individuals of the Rh(null) amorph type are the result of homozygosity for a silent RHCE in cis with a deleted RHD. A novel mutation in RHce was identified in two Caucasian Brazilian girls with the amorph type of Rh(null) who were born to parents who were first cousins. RBCs from the Rh(null) sisters and from family members were analyzed by serology and flow cytometry with specific antibodies. Genomic DNA and transcripts were tested by polymerase chain reaction and sequence analysis. Rh(null) RBCs were nonreactive with anti-Rh and anti-LW. Molecular analyses showed a deletion of RHD and of one nucleotide (960/963; GGGG-->GGG) in exon 7 of the RHce. This deletion introduced a frameshift after Gly321, a new C-terminal sequence, and a premature stop codon, resulting in a shorter predicted protein with 357 amino acids. The detection of a unique RHce transcript indicated that the two sisters were homozygous, whereas the other family members were heterozygous for the mutation. A novel mutation resulting in the amorph Rh(null) with loss of Rh antigen expression is described.

IGFBP2 is a candidate biomarker for Ink4a-Arf status and a therapeutic target for high-grade gliomas.

PubMed

Moore, Lynette M; Holmes, Kristen M; Smith, Sarah M; Wu, Ying; Tchougounova, Elena; Uhrbom, Lene; Sawaya, Raymond; Bruner, Janet M; Fuller, Gregory N; Zhang, Wei

2009-09-29

The levels of insulin-like growth factor-binding protein 2 (IGFBP2) are elevated during progression of many human cancers. By using a glial-specific transgenic mouse system (RCAS/Ntv-a), we reported previously that IGFBP2 is an oncogenic factor for glioma progression in combination with platelet-derived growth factor-beta (PDGFB). Because the INK4a-ARF locus is often deleted in high-grade gliomas (anaplastic oligodendroglioma and glioblastoma), we investigated the effect of the Ink4a-Arf-null background on IGFBP2-mediated progression of PDGFB-initiated oligodendroglioma. We demonstrate here that homozygous deletion of Ink4a-Arf bypasses the requirement of exogenously introduced IGFBP2 for glioma progression. Instead, absence of Ink4a-Arf resulted in elevated endogenous tumor cell IGFBP2. An inverse relationship between p16(INK4a) and IGFBP2 expression was also observed in human glioma tissue samples and in 90 different cancer cell lines by using Western blotting and reverse-phase protein lysate arrays. When endogenous IGFBP2 expression was attenuated by an RCAS vector expressing antisense IGFBP2 in our mouse model, a decreased incidence of anaplastic oligodendroglioma as well as prolonged survival was observed. Thus, p16(INK4a) is a negative regulator of the IGFBP2 oncogene. Loss of Ink4a-Arf results in increased IGFBP2, which contributes to glioma progression, thereby implicating IGFBP2 as a marker and potential therapeutic target for Ink4a-Arf-deleted gliomas.

IGFBP2 is a candidate biomarker for Ink4a-Arf status and a therapeutic target for high-grade gliomas

PubMed Central

Moore, Lynette M.; Holmes, Kristen M.; Smith, Sarah M.; Wu, Ying; Tchougounova, Elena; Uhrbom, Lene; Sawaya, Raymond; Bruner, Janet M.; Fuller, Gregory N.; Zhang, Wei

2009-01-01

The levels of insulin-like growth factor-binding protein 2 (IGFBP2) are elevated during progression of many human cancers. By using a glial-specific transgenic mouse system (RCAS/Ntv-a), we reported previously that IGFBP2 is an oncogenic factor for glioma progression in combination with platelet-derived growth factor-β (PDGFB). Because the INK4a-ARF locus is often deleted in high-grade gliomas (anaplastic oligodendroglioma and glioblastoma), we investigated the effect of the Ink4a-Arf-null background on IGFBP2-mediated progression of PDGFB-initiated oligodendroglioma. We demonstrate here that homozygous deletion of Ink4a-Arf bypasses the requirement of exogenously introduced IGFBP2 for glioma progression. Instead, absence of Ink4a-Arf resulted in elevated endogenous tumor cell IGFBP2. An inverse relationship between p16INK4a and IGFBP2 expression was also observed in human glioma tissue samples and in 90 different cancer cell lines by using Western blotting and reverse-phase protein lysate arrays. When endogenous IGFBP2 expression was attenuated by an RCAS vector expressing antisense IGFBP2 in our mouse model, a decreased incidence of anaplastic oligodendroglioma as well as prolonged survival was observed. Thus, p16INK4a is a negative regulator of the IGFBP2 oncogene. Loss of Ink4a-Arf results in increased IGFBP2, which contributes to glioma progression, thereby implicating IGFBP2 as a marker and potential therapeutic target for Ink4a-Arf-deleted gliomas. PMID:19805356

Tyrosine Phosphorylation of the Lyn Src Homology 2 (SH2) Domain Modulates Its Binding Affinity and Specificity*

PubMed Central

Jin, Lily L.; Wybenga-Groot, Leanne E.; Tong, Jiefei; Taylor, Paul; Minden, Mark D.; Trudel, Suzanne; McGlade, C. Jane; Moran, Michael F.

2015-01-01

Src homology 2 (SH2) domains are modular protein structures that bind phosphotyrosine (pY)-containing polypeptides and regulate cellular functions through protein-protein interactions. Proteomics analysis showed that the SH2 domains of Src family kinases are themselves tyrosine phosphorylated in blood system cancers, including acute myeloid leukemia, chronic lymphocytic leukemia, and multiple myeloma. Using the Src family kinase Lyn SH2 domain as a model, we found that phosphorylation at the conserved SH2 domain residue Y194 impacts the affinity and specificity of SH2 domain binding to pY-containing peptides and proteins. Analysis of the Lyn SH2 domain crystal structure supports a model wherein phosphorylation of Y194 on the EF loop modulates the binding pocket that engages amino acid side chains at the pY+2/+3 position. These data indicate another level of regulation wherein SH2-mediated protein-protein interactions are modulated by SH2 kinases and phosphatases. PMID:25587033

A Novel Ras-interacting Protein Required for Chemotaxis and Cyclic Adenosine Monophosphate Signal Relay in Dictyostelium

PubMed Central

Lee, Susan; Parent, Carole A.; Insall, Robert; Firtel, Richard A.

1999-01-01

We have identified a novel Ras-interacting protein from Dictyostelium, RIP3, whose function is required for both chemotaxis and the synthesis and relay of the cyclic AMP (cAMP) chemoattractant signal. rip3 null cells are unable to aggregate and lack receptor activation of adenylyl cyclase but are able, in response to cAMP, to induce aggregation-stage, postaggregative, and cell-type-specific gene expression in suspension culture. In addition, rip3 null cells are unable to properly polarize in a cAMP gradient and chemotaxis is highly impaired. We demonstrate that cAMP stimulation of guanylyl cyclase, which is required for chemotaxis, is reduced ∼60% in rip3 null cells. This reduced activation of guanylyl cyclase may account, in part, for the defect in chemotaxis. When cells are pulsed with cAMP for 5 h to mimic the endogenous cAMP oscillations that occur in wild-type strains, the cells will form aggregates, most of which, however, arrest at the mound stage. Unlike the response seen in wild-type strains, the rip3 null cell aggregates that form under these experimental conditions are very small, which is probably due to the rip3 null cell chemotaxis defect. Many of the phenotypes of the rip3 null cell, including the inability to activate adenylyl cyclase in response to cAMP and defects in chemotaxis, are very similar to those of strains carrying a disruption of the gene encoding the putative Ras exchange factor AleA. We demonstrate that aleA null cells also exhibit a defect in cAMP-mediated activation of guanylyl cyclase similar to that of rip3 null cells. A double-knockout mutant (rip3/aleA null cells) exhibits a further reduction in receptor activation of guanylyl cyclase, and these cells display almost no cell polarization or movement in cAMP gradients. As RIP3 preferentially interacts with an activated form of the Dictyostelium Ras protein RasG, which itself is important for cell movement, we propose that RIP3 and AleA are components of a Ras-regulated pathway involved in integrating chemotaxis and signal relay pathways that are essential for aggregation. PMID:10473630

The prolyl isomerase Pin1 modulates development of CD8+ cDC in mice.

PubMed

Barberi, Theresa J; Dunkle, Alexis; He, You-Wen; Racioppi, Luigi; Means, Anthony R

2012-01-01

Pin1 has previously been described to regulate cells that participate in both innate and adaptive immunity. Thus far, however, no role for Pin1 has been described in modulating conventional dendritic cells, innate antigen presenting cells that potently activate naïve T cells, thereby bridging innate and adaptive immune responses. When challenged with LPS, Pin1-null mice failed to accumulate spleen conventional dendritic cells (cDC). Analysis of steady-state spleen DC populations revealed that Pin1-null mice had fewer CD8+ cDC. This defect was recapitulated by culturing Pin1-null bone marrow with the DC-instructive cytokine Flt3 Ligand. Additionally, injection of Flt3 Ligand for 9 days failed to induce robust expansion of CD8+ cDC in Pin1-null mice. Upon infection with Listeria monocytogenes, Pin1-null mice were defective in stimulating proliferation of adoptively transferred WT CD8+ T cells, suggesting that decreases in Pin1 null CD8+ cDC may affect T cell responses to infection in vivo. Finally, upon analyzing expression of proteins involved in DC development, elevated expression of PU.1 was detected in Pin1-null cells, which resulted from an increase in PU.1 protein half-life. We have identified a novel role for Pin1 as a modulator of CD8+ cDC development. Consistent with reduced numbers of CD8+ cDC in Pin1-null mice, we find that the absence of Pin1 impairs CD8+ T cell proliferation in response to infection with Listeria monocytogenes. These data suggest that, via regulation of CD8+ cDC production, Pin1 may serve as an important modulator of adaptive immunity.

The MTA family proteins as novel histone H3 binding proteins.

PubMed

Wu, Meng; Wang, Lina; Li, Qian; Li, Jiwen; Qin, Jun; Wong, Jiemin

2013-01-03

The nucleosome remodeling and histone deacetylase complex (Mi2/NRD/NuRD/NURD) has a broad role in regulation of transcription, DNA repair and cell cycle. Previous studies have revealed a specific interaction between NURD and histone H3N-terminal tail in vitro that is not observed for another HDAC1/2-containing complex, Sin3A. However, the subunit(s) responsible for specific binding of H3 by NURD has not been defined. In this study, we show among several class I HDAC-containing corepressor complexes only NURD exhibits a substantial H3 tail-binding activity in vitro. We present the evidence that the MTA family proteins within the NURD complex interact directly with H3 tail. Extensive in vitro binding assays mapped the H3 tail-binding domain to the C-terminal region of MTA1 and MTA2. Significantly, although the MTA1 and MTA2 mutant proteins with deletion of the C-terminal H3 tail binding domain were assembled into the endogenous NURD complex when expressed in mammalian cells, the resulting NURD complexes were deficient in binding H3 tail in vitro, indicating that the MTA family proteins are required for the observed specific binding of H3 tail peptide by NURD in vitro. However, chromatin fractionation experiments show that the NURD complexes with impaired MTA1/2-H3 tail binding activity remained to be associated with chromatin in cells. Together our study reveals a novel histone H3-binding activity for the MTA family proteins and provides evidence that the MTA family proteins mediate the in vitro specific binding of H3 tail peptide by NURD complex. However, multiple mechanisms are likely to contribute to the chromatin association of NURD complex in cells. Our finding also raises the possibility that the MTA family proteins may exert their diverse biological functions at least in part through their direct interaction with H3 tail.