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1

Laminin receptor activation inhibits endothelial tissue factor expression  

Microsoft Academic Search

Tissue factor (TF) is an important trigger of arterial thrombosis. The green tea catechin epigallocatechin-3-gallate (EGCG) is a ligand of the 67-kDa laminin receptor (67LR) and exhibits cardioprotective effects. This study investigates whether 67LR regulates TF expression in human endothelial cells. Immunofluorescence demonstrated that human aortic endothelial cells expressed 67LR. Cells grown on laminin expressed 35% less TF in response

Erik W. Holy; Simon F. Stämpfli; Alexander Akhmedov; Niels Holm; Giovanni G. Camici; Thomas F. Lüscher; Felix C. Tanner

2010-01-01

2

Presence of Laminin Receptors in Staphylococcus aureus  

NASA Astrophysics Data System (ADS)

A characteristic feature of infection by Staphylococcus aureus is bloodstream invasion and widespread metastatic abscess formation. The ability to extravasate, which entails crossing the vascular basement membrane, appears to be critical for the organism's pathogenicity. Extravasation by normal and neoplastic mammalian cells has been correlated with the presence of specific cell surface receptors for the basement membrane glycoprotein laminin. Similar laminin receptors were found in Staphylococcus aureus but not in Staphylococcus epidermidis, a noninvasive pathogen. There were about 100 binding sites per cell, with an apparent binding affinity of 2.9 nanomolar. The molecular weight of the receptor was 50,000 and pI was 4.2. Eukaryotic laminin receptors were visualized by means of the binding of S. aureus in the presence of laminin. Prokaryotic and eukaryotic invasive cells might utilize similar, if not identical, mechanisms for invasion.

Lopes, J. D.; Dos Reis, M.; Brentani, R. R.

1985-07-01

3

Functionally distinct laminin receptors mediate cell adhesion and spreading: the requirement for surface galactosyltransferase in cell spreading.  

PubMed

The molecular mechanisms underlying cell attachment and subsequent cell spreading on laminin are shown to be distinct form one another. Cell spreading is dependent upon the binding of cell surface galactosyltransferase (GalTase) to laminin oligosaccharides, while initial cell attachment to laminin occurs independent of GalTase activity. Anti-GalTase IgG, as well as the GalTase modifier protein, alpha-lactalbumin, both block GalTase activity and inhibited B16-F10 melanoma cell spreading on laminin, but not initial attachment. On the other hand, the addition of UDP galactose, which increases the catalytic turnover of GalTase, slightly increased cell spreading. None of these reagents had any effect on cell spreading on fibronectin. When GalTase substrates within laminin were either blocked by affinity-purified GalTase or eliminated by prior galactosylation, cell attachment appeared normal, but subsequent cell spreading was totally inhibited. The laminin substrate for GalTase was identified as N-linked oligosaccharides primarily on the A chain, and to a lesser extent on B chains. That N-linked oligosaccharides are necessary for cell spreading was shown by the inability of cells to spread on laminin surfaces pretreated with N-glycanase, even though cell attachment was normal. Cell surface GalTase was distinguished from other reported laminin binding proteins, most notably the 68-kD receptor, since they were differentially eluted from laminin affinity columns. These data show that surface GalTase does not participate during initial cell adhesion to laminin, but mediates subsequent cell spreading by binding to its appropriate N-linked oligosaccharide substrate. These results also emphasize that some of laminin's biological properties can be attributed to its oligosaccharide residues. PMID:2972732

Runyan, R B; Versalovic, J; Shur, B D

1988-11-01

4

The human integrin VLA-2 is a collagen receptor on some cells and a collagen/laminin receptor on others  

SciTech Connect

The integrin heterodimer VLA-2, previously known as a collagen receptor, is now shown also to be a laminin receptor. Adhesion of the human melanoma cell line LOX to laminin was inhibited by anti-VLA {alpha}{sup 2} antibodies. Because VLA-2-mediated LOX cell attachment to laminin was not inhibited by digestion with collagenase, collagen contamination of laminin was not a factor. In addition, VLA-2 from LOX cells bound to immobilized laminin, and binding was disrupted by EDTA but not by Arg-Gly-Asp (RGD) peptides. VLA-3 also bound to laminin-Sepharose, although less avidly than VLA-2. Thus, at least four separate members of the integrin {beta}{sub 1} subfamily serve as laminin receptors - i.e., VLA-2 and VLA-3 (this study) together with VLA-1 and VLA-6 (other reports). Whereas LOX and other cell lines used VLA-2 as both a laminin and collagen receptor, fibroblast VLA-2 mediated collagen but not laminin binding. Likewise, VLA-2 from platelets did not interact with laminin. Despite this functional discordancy, VLA-2 from laminin-binding and nonbinding sources was indistinguishable by all immunochemical and biochemical criteria examined. Thus, functional differences in VLA-2 may be due to cell type-specific modulation.

Elices, M.J.; Hemler, M.E. (Harvard Medical School, Boston, MA (USA))

1989-12-01

5

Laminin E8 alveolarization site: heparin sensitivity, cell surface receptors, and role in cell spreading  

E-print Network

Laminin E8 alveolarization site: heparin sensitivity, cell surface receptors, and role in cell. Laurie, Roy C. Ogle, and Gordon W. Laurie. Laminin E8 alveolarization site: heparin sensitivity, cell were fully adherent. Adhesion was heparin, but not chondroitin sulfate or heparinase, sensitive, much

6

Multiple cell surface receptors for the short arms of laminin: alpha 1 beta 1 integrin and RGD-dependent proteins mediate cell attachment only to domains III in murine tumor laminin  

PubMed Central

Cell surface molecules that interact with the cross formed by the three short arms of murine tumor laminin were studied using thermal perturbation, antibody and peptide blocking, and affinity chromatography. Several potential receptors for the laminin short arms were revealed that differed from those mediating cell attachment to the E8 (long arm) fragment. Two cell lines, Rugli and L8 attached well to E1-X (short arm) fragments of laminin. This attachment was blocked by antibodies against alpha 1 integrin chains. Other cells were unable to attach strongly to E1-X, but attached to P1. This attachment was unaffected by anti-beta 1 integrin antibodies, but specifically blocked by the peptide GRGDS. By contrast, binding of Rugli cells was RGD independent and blocked by anti-beta 1 integrin antibodies. G7 and C2C12 myoblasts were very sensitive to GRGDS (ID50 approximately 2 micrograms.ml-1) for attachment to P1 which implied that a non-beta 1 series integrin, possibly alpha v beta 3, was involved. On heat denaturation of P1(3) attachment remained sensitive to RGDS and ID50 was unchanged. On heat denaturation of E1-X, attachment remained sensitive to RGDS but the ID50 increased to approximately 200 micrograms.ml-1. Cellular beta 1 integrins were retained on laminin affinity columns. A beta 1 integrin with an approximately 190 kD alpha- chain could be isolated from Rugli cells whose attachment could be blocked by anti-alpha 1 antibodies and not from cells blocked by RGDS peptides. Anti-alpha 1 antibodies blocked Rugli attachment to native laminin, but only when the E8 cell binding sites on laminin were also blocked. Thus, a receptor related to alpha 1 beta 1 integrin can function simultaneously with a receptor for E8. Anti-alpha 1 also blocked attachment to heated laminin, suggesting that the heat-stable attachment activity in laminin involved the E1-X binding site. Thus, at least two putative receptors mediate attachment to the short arms of laminin. One, related to alpha 1 beta 1 integrin, recognizes RGDS- independent sites in E1-X defined by P1 (within domains III, IIIa, IIIb), and one is an RGD-dependent molecule recognizing sites in P1, and is not a beta 1 integrin. PMID:1827447

1991-01-01

7

Chemical inhibition of prometastatic lysyl-tRNA synthetase–laminin receptor interaction  

PubMed Central

Lysyl-tRNA synthetase (KRS), a protein synthesis enzyme in the cytosol, relocates to the plasma membrane after a laminin signal and stabilizes a 67-kDa laminin receptor (67LR) that is implicated in cancer metastasis; however, its potential as an antimetastatic therapeutic target has not been explored. We found that the small compound BC-K-YH16899, which binds to KRS, impinged on interaction of KRS with 67LR and suppressed metastasis in 3 different mouse models. The compound inhibited KRS–67LR interaction in two ways. First, it directly blocked the association between KRS and 67LR. Second, it suppressed the dynamic movement of the N-terminal extension of KRS and reduced membrane localization of KRS. However, it did not affect the catalytic activity of KRS. Our results suggest that specific modulation of a cancer-related KRS–67LR interaction may offer a way to control metastasis while avoiding the toxicities associated with inhibition of the normal functions of KRS. PMID:24212136

Kim, Dae Gyu; Lee, Jin Young; Kwon, Nam Hoon; Fang, Pengfei; Zhang, Qian; Wang, Jing; Young, Nicolas L.; Guo, Min; Cho, Hye Young; Mushtaq, AmeeqUl; Jeon, Young Ho; Choi, Jin Woo; Han, Jung Min; Kang, Ho Woong; Joo, Jae Eun; Hur, Youn; Kang, Wonyoung; Yang, Heekyoung; Nam, Do-Hyun; Lee, Mi-Sook; Lee, Jung Weon; Kim, Eun-Sook; Moon, Aree; Kim, Kibom; Kim, Doyeun; Kang, Eun Joo; Moon, Youngji; Rhee, Kyung Hee; Han, Byung Woo; Yang, Jee Sun; Han, Gyoonhee; Yang, Won Suk; Lee, Cheolju; Wang, Ming-Wei; Kim, Sunghoon

2014-01-01

8

Drosophila PS1 integrin is a laminin receptor and differs in ligand specificity from PS2.  

PubMed Central

We have expressed Drosophila position-specific (PS) integrins on the surfaces of Schneider S2 cells and tested for adhesion and spreading on various matrix molecules. We report that PS1 integrin is a laminin receptor and that PS1 and PS2 integrins promote cell spreading on two different Drosophila extracellular matrix molecules, laminin and tiggrin, respectively. The differing ligand specificities of these two integrins, combined with data on the in vivo expression patterns of the integrins and their ligands, lead to a model for the structure of integrin-dependent attachments in the pupal wings and embryonic muscles of Drosophila. Images PMID:7972082

Gotwals, P J; Fessler, L I; Wehrli, M; Hynes, R O

1994-01-01

9

Alterations in integrin receptor expression on chemically transformed human cells: specific enhancement of laminin and collagen receptor complexes  

PubMed Central

The abilities of malignant tumor cells to bind and migrate through basement membranes are important steps in invasion and metastasis. Malignant tumor cells would therefore be expected to express receptors on their surfaces for basement membrane and stromal components, such as collagens, laminin, and fibronectin, although the pattern of expression of these receptors on the malignant cells may be different from that on their normal progenitors. We report here that chemically transformed tumorigenic human cells express an altered pattern of integrin receptors on their cell surfaces as compared with their untransformed nontumorigenic counterparts. Specifically, N-methyl-N'-nitro-N- nitrosoguanidine transformation of HOS cells into highly tumorigenic cells results in a significant specific increase in the expression of (in descending order of level of cell surface expression) the integrins alpha 6/beta 1, alpha 2/beta 1, and alpha 1/beta 1, which are receptors for laminin, collagens, and collagen type IV and laminin, respectively. The level of expression of two fibronectin receptor integrins, alpha 5/beta 1 and alpha 3/beta 1, are, however, unaltered, whereas the level of expression of vitronectin receptor integrin, alpha v/beta 3, is drastically reduced on the transformed cells. Consistent with the increased expression of laminin and collagen receptors and the decreased expression of vitronectin receptors on the transformed cells, these cells attached three- to fivefold more strongly to laminin and collagen but attached very poorly to vitronectin. The MNNG-HOS cells were also found to have a greater potential for invasion through reconstituted basement membrane, matrigel, the major components of which are laminin and type IV collagen. The invasion of both the HOS and MNNG-HOS cells was inhibited 45-50% by a polyclonal anti- fibronectin receptor antibody. However, although the invasion of HOS cells could be inhibited up to 75% by an anti-alpha 6 monoclonal antibody, a similar concentration of this antibody had no effect on the alpha 6-overproducing MNNG-HOS cells. A fivefold higher concentration of this antibody did result in partial inhibition of MNNG-HOS invasion. These data indicate a critical role for the alpha 6/beta 1 laminin receptor in the invasion of these cells through basement membranes and demonstrate that chemical transformation of nontumorigenic human cells to highly tumorigenic cells is associated with an altered pattern of integrin expression which may play a direct role in the increased capacity of these cells to bind and invade through basement membranes. PMID:1688858

1990-01-01

10

Laminin Receptor 37/67LR Regulates Adhesion and Proliferation of Normal Human Intestinal Epithelial Cells  

PubMed Central

Interactions between the cell basal membrane domain and the basement membrane are involved in several cell functions including proliferation, migration and differentiation. Intestinal epithelial cells can interact with laminin, a major intestinal basement membrane glycoprotein, via several cell-surface laminin-binding proteins including integrin and non-integrin receptors. The 37/67kDa laminin receptor (37/67LR) is one of these but its role in normal epithelial cells is still unknown. The aim of this study was to characterise the expression pattern and determine the main function of 37/67LR in the normal human small intestinal epithelium. Immunolocalization studies revealed that 37/67LR was predominantly present in the undifferentiated/proliferative region of the human intestinal crypt in both the immature and adult intestine. Using a human intestinal epithelial crypt (HIEC) cell line as experimental model, we determined that 37/67LR was expressed in proliferative cells in both the cytoplasmic and membrane compartments. Small-interfering RNA-mediated reduction of 37/67LR expression led to HIEC cell-cycle reduction and loss of the ability to adhere to laminin-related peptides under conditions not altering ribosomal function. Taken together, these findings indicate that 37/67LR regulates proliferation and adhesion in normal intestinal epithelial cells independently of its known association with ribosomal function. PMID:23991217

Khalfaoui, Taoufik; Groulx, Jean-François; Sabra, Georges; GuezGuez, Amel; Basora, Nuria; Vermette, Patrick; Beaulieu, Jean-François

2013-01-01

11

Biological activities of the homologous loop regions in the laminin ? chain LG modules.  

PubMed

Each laminin ? chain (?1-?5 chains) has chain-specific diverse biological functions. The C-terminal globular domain of the ? chain consists of five laminin-like globular (LG1-5) modules and plays a critical role in biological activities. The LG modules consist of a 14-stranded ?-sheet (A-N) sandwich structure. Previously, we described the chain-specific biological activities of the loop regions between the E and F strands in the LG4 modules using five homologous peptides (G4EF1-G4EF5). Here, we further analyze the biological activities of the E-F strands loop regions in the rest of LG modules. We designed 20 homologous peptides (approximately 20 amino acid length), and 17 soluble peptides were used for the cell attachment assay. Thirteen peptides promoted cell attachment activity with different cell morphologies. Cell attachment to peptides G1EF1, G1EF2, G2EF1, G3EF4, and G5EF4 was inhibited by heparin, and peptides G1EF1, G1EF2, and G2EF1 specifically bound to syndecan-overexpressing cells. Cell attachment to peptides G2EF3, G3EF1, G3EF3, G5EF1, G5EF3, and G5EF5 was inhibited EDTA. Further, cell attachment to peptides G3EF3, G5EF1, and G5EF5 was inhibited by both anti-integrin ?2 and ?1 antibodies, whereas cell attachment to peptide G5EF3 was inhibited by only anti-integrin ?1 antibody. Cell attachment to peptides G1EF4, G3EF4, and G5EF4 was inhibited by both heparin and EDTA and was not inhibited by anti-integrin antibodies. The active peptide sequence alignments suggest that the syndecan-binding peptides contain a "basic amino acid (BAA)-Gly-BAA" motif in the middle of the molecule and that the integrin-binding peptides contain an "acidic amino acid (AAA)"-Gly-BAA motif. Core-switched peptide analyses suggested that the "BAA-Gly-BAA" motif is critical for binding to syndecans and that the "AAA-Gly-BAA" motif has potential to recognize integrins. These findings are useful for understanding chain-specific biological activities of laminins and to evaluate receptor-specific binding mechanisms. PMID:24850085

Katagiri, Fumihiko; Hara, Toshihiro; Yamada, Yuji; Urushibata, Shunsuke; Hozumi, Kentaro; Kikkawa, Yamato; Nomizu, Motoyoshi

2014-06-10

12

A Biologically Active Sequence of the Laminin ?2 Large Globular 1 Domain Promotes Cell Adhesion through Syndecan-1 by Inducing Phosphorylation and Membrane Localization of Protein Kinase C?*  

PubMed Central

Laminin-2 promotes basement membrane assembly and peripheral myelinogenesis; however, a receptor-binding motif within laminin-2 and the downstream signaling pathways for motif-mediated cell adhesion have not been fully established. The human laminin-2 ?2 chain cDNAs cloned from human keratinocytes and fibroblasts correspond to the laminin ?2 chain variant sequence from the human brain. Individually expressed recombinant large globular (LG) 1 protein promotes cell adhesion and has heparin binding activities. Studies with synthetic peptides delineate the DLTIDDSYWYRI motif (Ln2-P3) within the LG1 as a major site for both heparin and cell binding. Cell adhesion to LG1 and Ln2-P3 is inhibited by treatment of heparitinase I and chondroitinase ABC. Syndecan-1 from PC12 cells binds to LG1 and Ln2-P3 and colocalizes with both molecules. Suppression of syndecan-1 with RNA interference inhibits cell adhesion to LG1 and Ln2-P3. The binding of syndecan-1 with LG1 and Ln2-P3 induces the recruitment of protein kinase C? (PKC?) into the membrane and stimulates its tyrosine phosphorylation. A decrease in PKC? activity significantly reduces cell adhesion to LG1 and Ln2-P3. Taken together, these results indicate that the Ln2-P3 motif and LG1 domain, containing the motif, within the human laminin-2 ?2 chain are major ligands for syndecan-1, which mediates cell adhesion through the PKC? signaling pathway. PMID:19762914

Jung, Sung Youn; Kim, Jin-Man; Kang, Hyun Ki; Jang, Da Hyun; Min, Byung-Moo

2009-01-01

13

Functionally distinct laminin receptors mediate cell adhesion and spreading: the requirement for surface galactosyltransferase in cell spreading  

Microsoft Academic Search

The molecular mechanisms underlying cell attachment and subsequent cell spreading on laminin are shown to be distinct form one another. Cell spreading is dependent upon the binding of cell sur- face galactosyltransferase (GalTase) to laminin oligosaccharides, while initial cell attachment to lami- nin occurs independent of GalTase activity. Anti- GalTase IgG, as well as the GalTase modifier protein, a-lactalbumin, both

Raymond B. Runyan; James Versalovic; Barry D. Shur

1988-01-01

14

Laminin5 Is a Marker of Invading Cancer Cells in Some Human Carcinomas and Is Coexpressed with the Receptor for Urokinase Plasminogen Activator in Budding Cancer Cells in Colon Adenocarcinomas1  

Microsoft Academic Search

Recombinant human y 2 chain of laminin-5 was expressed in Esche- ni hut coli, and used to generate specific polyclonal antibodies which were used to study the distribution of the protein in human cancers. A total of 72 biopsies of human cancers were stained, including 23 cases of colon adenocarcinomas, 16 ductal breast carcinomas, 9 malignant melanomas, 14 squamous cell

Charles Pyke; Sirpa Salo; Karl Tryggvason

1995-01-01

15

Molecular cloning of the rat integrin alpha 1-subunit: a receptor for laminin and collagen  

PubMed Central

Integrin heterodimers mediate a variety of adhesive interactions, including neuronal attachment to and process outgrowth on laminin. We report here the cloning and primary sequence of an M-200 kD integrin alpha subunit that associates with the integrin beta 1 subunit to form a receptor for both laminin and collagen. Similarities in ligand- binding specificity, relative molecular mass and NH2-terminal sequence make this a strong candidate for the rat homologue of the alpha subunit of the human integrin VLA-1. The full-length rat alpha 1 cDNAs encode a protein containing a purative signal sequence and a mature polypeptide of 1,152 amino acids, with extracellular, transmembrane and cytoplasmic domains. Several structural features are conserved with other integrin alpha chains, including (a) a sequence motif repeated seven times in the NH2-terminal half; (b) potential Ca2+/Mg2+ binding sites in repeats 5, 6, and 7, and (c) alignment of at least 14 of 23 cysteine residues. This rat alpha 1 sequence also contains a 206-amino acid I domain, inserted between repeats 2 and 3, that is homologous to I domains found in the same position in the alpha subunits of several integrins (VLA-2, Mac-1, LFA-1, p150). The rat alpha 1 and human VLA-2 apha subunits share greater than 50% sequence identity in the seven repeats and I domain, suggesting that these sequence identities may underlie some of their similar ligand-binding specificities. However, the rat integrin alpha 1 subunit has several unique features, including a 38-residue insert between two Ca2+/Mg2+ binding domains, and a divergent 15- residue cytoplasmic sequence, that may potentially account for unique functions of this integrin. PMID:2380249

1990-01-01

16

Laminin receptor mediates anti-inflammatory and anti-thrombogenic effects of pigment epithelium-derived factor in myeloma cells.  

PubMed

Pigment epithelium-derived factor (PEDF) has anti-inflammatory and anti-thrombogenic properties both in cell culture and animal models. Although adipose triglyceride lipase (ATGL) and laminin receptor (LR) are two putative receptors for PEDF, which receptor mainly mediates the beneficial effects of PEDF is largely unknown. In this study, we addressed the issue. siRNA raised against LR (siLR) and siATGL transfection dramatically decreased LR and ATGL levels in human cultured myeloma cells, respectively. Ten nM PEDF significantly reduced vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), intercellular cell adhesion molecule-1 (ICAM-1) and plasminogen activator inhibitor-1 (PAI-1) mRNA levels in siCon- or siATGL-transfected myeloma cells, whereas PEDF increased rather than decreased these gene expressions in siLR-transfected cells. Neutralizing antibody directed against LR (LR-Ab) or LR antagonist actually bound to LR and reduced mRNA levels of VEGF, MCP-1, ICAM-1 and PAI-1 in myeloma cells. Further, pre-treatment of LR-Ab or LR antagonist suppressed the binding of PEDF to LR and resultantly blocked the effects of PEDF in myeloma cells. In addition, high concentration of LR agonist mimicked the actions of PEDF on these gene expressions in myeloma cells. This study indicates that PEDF causes anti-angiogenic, anti-inflammatory and anti-thrombogenic reactions in myeloma cells through the interaction with LR. Target domain of LR agonist and antagonist might be involved in the PEDF-signaling to gene suppression in myeloma cells. PMID:24342618

Matsui, Takanori; Higashimoto, Yuichiro; Yamagishi, Sho-ichi

2014-01-17

17

Serum laminin and type III procollagen in chronic hepatitis C. Diagnostic value in the assessment of disease activity and fibrosis  

Microsoft Academic Search

Laminin P1 (pepsin-resistant fragment of laminin) and aminoterminal peptide of type III procollagen are measurable in serum and are now considered useful serum markers of fibrogenesis and inflammation in chronic liver diseases. However, very few studies thus far have focused on assessing the diagnostic value of these markers in detecting fibrosis and necro-inflammatory activity in chronically diseased liver. The aim

Giovanni Battista Gabrielli; Franco Capra; Massimo Casaril; Stefano Squarzoni; Patrizia Tognella; Roberta Dagradi; Elena De Maria; Romano Colombari; Roberto Corrocher; Giorgio De Sandre

1997-01-01

18

The 37kDa/67kDa Laminin Receptor acts as a receptor for A?42 internalization  

PubMed Central

Neuronal loss is a major neuropathological hallmark of Alzheimer's disease (AD). The associations between soluble A? oligomers and cellular components cause this neurotoxicity. The 37?kDa/67?kDa laminin receptor (LRP/LR) has recently been implicated in A? pathogenesis. In this study the mechanism underlying the pathological role of LRP/LR was elucidated. Försters Resonance Energy Transfer (FRET) revealed that LRP/LR and A? form a biologically relevant interaction. The ability of LRP/LR to form stable associations with endogenously shed A? was confirmed by pull down assays and A?-ELISAs. Antibody blockade of this association significantly lowered A?42 induced apoptosis. Furthermore, antibody blockade and shRNA mediated downregulation of LRP/LR significantly hampered A?42 internalization. These results suggest that LRP/LR is a receptor for A?42 internalization, mediating its endocytosis and contributing to the cytotoxicity of the neuropeptide by facilitating intra-cellular A?42 accumulation. These findings recommend anti-LRP/LR specific antibodies and shRNAs as potential therapeutic tools for AD treatment. PMID:24990253

Da Costa Dias, Bianca; Jovanovic, Katarina; Gonsalves, Danielle; Moodley, Kiashanee; Reusch, Uwe; Knackmuss, Stefan; Weinberg, Marc S.; Little, Melvyn; Weiss, Stefan F. T.

2014-01-01

19

Peptides derived from the human laminin alpha4 and alpha5 chains exhibit antimicrobial activity.  

PubMed

Laminins are a family of heterotrimeric extracellular matrix glycoproteins in the basement membrane of different tissues and are composed of alpha, beta, and gamma chains. In mammals, five different alpha chains, three beta chains, and three gamma chains have been identified that assemble into 15 different laminins. Each alpha-chain possesses a C-terminal globular domain which can be subdivided into the five subdomains LG1-LG5. LG1-LG3 modules are connected to LG4-LG5 by a linker domain which is known to be sensitive to proteolytic processing. Here, we show that peptides derived from the human laminin alpha4 and alpha5 chain, exhibit a dose-dependent antimicrobial activity against gram-positive and gram-negative bacteria. Furthermore, we show that these peptides permeabilize the bacterial membrane and are able to bind to bacterial DNA. Interestingly, the ability to kill the microorganisms correlated with their ability to bind to heparin. These data suggest that extracellular matrix components are able to protect the respective tissues from invading pathogens and are part of the host defense response. PMID:20433883

Senyürek, Ilknur; Klein, Gerd; Kalbacher, Hubert; Deeg, Martin; Schittek, Birgit

2010-08-01

20

Laminin receptors in the retina: sequence analysis of the chick integrin alpha 6 subunit. Evidence for transcriptional and posttranslational regulation  

PubMed Central

The integrin alpha 6 beta 1 is a prominent laminin receptor used by many cell types. In the present work, we isolate clones and determine the primary sequence of the chick integrin alpha 6 subunit. We show that alpha 6 beta 1 is a prominent integrin expressed by cells in the developing chick retina. Between embryonic days 6 and 12, both retinal ganglion cells and other retinal neurons lose selected integrin functions, including the ability to attach and extend neurites on laminin. In retinal ganglion cells, we show that this is correlated with a dramatic decrease in alpha 6 mRNA and protein, suggesting that changes in gene expression account for the developmental regulation of the interactions of these neurons with laminin. In other retinal neurons the expression of alpha 6 mRNA and protein remains high while function is lost, suggesting that the function of the alpha 6 beta 1 heterodimer in these cells is regulated by posttranslational mechanisms. PMID:1826298

1991-01-01

21

A biologically active sequence of the laminin alpha2 large globular 1 domain promotes cell adhesion through syndecan-1 by inducing phosphorylation and membrane localization of protein kinase Cdelta.  

PubMed

Laminin-2 promotes basement membrane assembly and peripheral myelinogenesis; however, a receptor-binding motif within laminin-2 and the downstream signaling pathways for motif-mediated cell adhesion have not been fully established. The human laminin-2 alpha2 chain cDNAs cloned from human keratinocytes and fibroblasts correspond to the laminin alpha2 chain variant sequence from the human brain. Individually expressed recombinant large globular (LG) 1 protein promotes cell adhesion and has heparin binding activities. Studies with synthetic peptides delineate the DLTIDDSYWYRI motif (Ln2-P3) within the LG1 as a major site for both heparin and cell binding. Cell adhesion to LG1 and Ln2-P3 is inhibited by treatment of heparitinase I and chondroitinase ABC. Syndecan-1 from PC12 cells binds to LG1 and Ln2-P3 and colocalizes with both molecules. Suppression of syndecan-1 with RNA interference inhibits cell adhesion to LG1 and Ln2-P3. The binding of syndecan-1 with LG1 and Ln2-P3 induces the recruitment of protein kinase Cdelta (PKCdelta) into the membrane and stimulates its tyrosine phosphorylation. A decrease in PKCdelta activity significantly reduces cell adhesion to LG1 and Ln2-P3. Taken together, these results indicate that the Ln2-P3 motif and LG1 domain, containing the motif, within the human laminin-2 alpha2 chain are major ligands for syndecan-1, which mediates cell adhesion through the PKCdelta signaling pathway. PMID:19762914

Jung, Sung Youn; Kim, Jin-Man; Kang, Hyun Ki; Jang, Da Hyun; Min, Byung-Moo

2009-11-13

22

Contribution of the 37-kDa laminin receptor precursor in the anti-metastatic PSP94-derived peptide PCK3145 cell surface binding  

SciTech Connect

Purpose: PCK3145 is an anti-metastatic synthetic peptide with promising therapeutic efficacy against hormone-refractory prostate cancer. The characterization of the PCK3145 peptide cell surface binding/internalization mechanisms and of the receptors involved remained to be explored. Results: [{sup 14}C]PCK3145 cell surface binding assays showed rapid and transient kinetic profile, that was inhibited by RGD peptides, laminin, hyaluronan, and type-I collagen. RGD peptides were however unable to inhibit PCK3145 intracellular uptake. Far-Western ligand binding studies enabled the identification of the 37-kDa laminin receptor precursor (37LRP) as a potential ligand for PCK3145. Overexpression of the recombinant 37LRP indeed led to an increase in PCK3145 binding but unexpectedly not to its uptake. Conclusions: Our data support the implication of laminin receptors in cell surface binding and in transducing PCK3145 anti-metastatic effects, and provide a rational for targeting cancers that express high levels of such laminin receptors.

Annabi, Borhane [Laboratoire d'Oncologie Moleculaire, Departement de Chimie, Universite du Quebec a Montreal, Que. (Canada); Currie, Jean-Christophe [Laboratoire d'Oncologie Moleculaire, Departement de Chimie, Universite du Quebec a Montreal, Que. (Canada); Bouzeghrane, Mounia [Centre de Cancerologie Charles-Bruneau, Hopital Sainte-Justine-UQAM, Que. (Canada); Dulude, Helene [Procyon BioPharma, Inc., Montreal, Que. (Canada); Daigneault, Luc [Procyon BioPharma, Inc., Montreal, Que. (Canada); Garde, Seema [Procyon BioPharma, Inc., Montreal, Que. (Canada); Rabbani, Shafaat A. [Department of Medicine, Physiology, and Oncology, McGill University Health Centre, Montreal, Que. (Canada); Panchal, Chandra [Procyon BioPharma, Inc., Montreal, Que. (Canada); Wu, Jinzi J. [Procyon BioPharma, Inc., Montreal, Que. (Canada); Beliveau, Richard [Centre de Cancerologie Charles-Bruneau, Hopital Sainte-Justine-UQAM, Que. (Canada)]. E-mail: oncomol@nobel.si.uqam.ca

2006-07-21

23

Attenuated migration by green tea extract (-)-epigallocatechin gallate (EGCG): involvement of 67 kDa laminin receptor internalization in macrophagic cells.  

PubMed

Excessive activation of the microglia in the brain is involved in the development of several neurodegenerative diseases. Previous studies have indicated that (-)-epigallocatechin gallate (EGCG), a major active constituent of green tea, exhibits potent suppressive effects on the activation of microglia. As the 67 kDa laminin receptor (67LR) is a key element in cellular activation and migration, we investigated the effect of EGCG on cell migration and 67LR in lipopolysaccharide (LPS)-activated macrophagic RAW264.7 cells. The presence of EGCG (1-25 ?M) markedly attenuated LPS-induced cell migration in a dose-dependent manner. However, the total amount of 67LR protein in the RAW264.7 cells was unaffected by EGCG, as revealed by Western blot analysis. In addition, confocal immunofluorescence microscopy indicated that EGCG caused a marked membrane translocation of 67LR from the membrane surface towards the cytoplasm. Cell-surface biotinylation analysis confirmed that EGCG induced a significant internalization of 67LR by 24-68% in a dose-dependent manner. This study helps to explain the pharmacological action of EGCG on 67LR, suggesting its potential use in the treatment of diseases associated with macrophage/microglia activation, such as neurodegenerative diseases and cancer. PMID:24953562

Ren, Xuezhi; Guo, Xingzhi; Chen, Li; Guo, Minxia; Peng, Ning; Li, Rui

2014-08-01

24

Green tea polyphenol epigallocatechin-3-gallate inhibits TLR4 signaling through the 67-kDa laminin receptor on lipopolysaccharide-stimulated dendritic cells  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Expressions of CD80, CD86, and MHC class I/II were inhibited by EGCG via 67LR. Black-Right-Pointing-Pointer EGCG-treated DCs inhibited LPS-induced pro-inflammatory cytokines via 67LR. Black-Right-Pointing-Pointer EGCG-treated DCs inhibited MAPKs activation and NF-{kappa}B p65 translocation via 67LR. Black-Right-Pointing-Pointer EGCG elevated the expression of the Tollip protein through 67LR in DCs. -- Abstract: Epigallocatechin-3-gallate (EGCG), a major active polyphenol of green tea, has been shown to down-regulate inflammatory responses in dendritic cells (DCs); however, the underlying mechanism has not been understood. Recently, we identified the 67-kDa laminin receptor (67LR) as a cell-surface EGCG receptor. In this study, we showed the molecular basis for the down-regulation of toll-like receptor 4 (TLR4) signal transduction by EGCG in DCs. The expressions of CD80, CD86, and MHC class I and II, which are molecules essential for antigen presentation by DCs, were inhibited by EGCG via 67LR. In addition, EGCG-treated DCs inhibited lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines (tumor necrosis factor [TNF]-{alpha}, interleukin [IL]-1{beta}, and IL-6) and activation of mitogen-activated protein kinases (MAPKs), e.g., extracellular signal-regulated kinase 1/2 (ERK1/2), p38, c-Jun N-terminal kinase (JNK), and nuclear factor {kappa}B (NF-{kappa}B) p65 translocation through 67LR. Interestingly, we also found that EGCG markedly elevated the expression of the Tollip protein, a negative regulator of TLR signaling, through 67LR. These novel findings provide new insight into the understanding of negative regulatory mechanisms of the TLR4 signaling pathway and consequent inflammatory responses that are implicated in the development and progression of many chronic diseases.

Byun, Eui-Baek [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of)] [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Choi, Han-Gyu [Department of Microbiology and Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon 301-747 (Korea, Republic of)] [Department of Microbiology and Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon 301-747 (Korea, Republic of); Sung, Nak-Yun [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of)] [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Byun, Eui-Hong, E-mail: ehbyun80@gmail.com [Department of Microbiology and Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon 301-747 (Korea, Republic of)] [Department of Microbiology and Research Institute for Medical Sciences, College of Medicine, Chungnam National University, Daejeon 301-747 (Korea, Republic of)

2012-10-05

25

Bovine Prion Is Endocytosed by Human Enterocytes via the 37 kDa/67 kDa Laminin Receptor  

PubMed Central

Some forms of transmissible spongiform encephalopathies result from oral infection. We have thus analyzed the early mechanisms that could account for an uptake of infectious prion particles by enterocytes, the major cell population of the intestinal epithelium. Human Caco-2/TC7 enterocytes cultured on microporous filters were incubated with different prion strains and contaminated brain homogenates in the apical compartment. Internalization of infectious particles was analyzed by Western blotting and immunofluorescence. We observed internalization by enterocytes of prion particles from bovine spongiform encephalopathy brain homogenates but not from mouse-adapted scrapie-strain brain homogenates or purified bovine spongiform encephalopathy scrapie-associated fibrils. Bovine prion particles were internalized via endocytosis within minutes of infection and were associated with subapical vesicular structures related to early endosomes. The endocytosis of the infectious bovine PrPSc was reduced by preincubating the cells with an anti-LRP/LR blocking antibody, identifying the 37 kDa/67 kDa laminin receptor (LRP/LR), which is apically expressed in Caco-2/TC7 cells, as the receptor for the infectious prion protein. Altogether, our results underscore a potential role of enterocytes in the absorption of bovine prions during oral infection through specific LRP/LR-dependent endocytosis. PMID:16192638

Morel, Etienne; Andrieu, Thibault; Casagrande, Fabrice; Gauczynski, Sabine; Weiss, Stefan; Grassi, Jacques; Rousset, Monique; Dormont, Dominique; Chambaz, Jean

2005-01-01

26

Receptor functions for the integrin VLA3: fibronectin, collagen, and laminin binding are differentially influenced by Arg-Gly-Asp peptide and by divalent cations  

Microsoft Academic Search

The capability of the integrin VLA-3 to function as a receptor for collagen (Coil), laminin (Lm), and fibronectin (Fn) was addressed using both whole cell adhesion assays and Iigand affinity columns. Analysis of VLA-3-mediated cell adhesion was facilitated by the use of a small cell lung carci- noma line (NCI-H69), which expresses VLA-3 but few other integrins. While VLA-3 interaction

M. J. Elices; Lisa A. Urry; Martin E. Hemler

1991-01-01

27

Laminin-1 induces neurite outgrowth in human mesenchymal stem cells in serum/differentiation factors-free conditions through activation of FAK-MEK/ERK signaling pathways.  

PubMed

Mesenchymal stem cells (MSCs) can be differentiated into cell types derived from all three germ layers by manipulating culture conditions in vitro. A multitude of growth and differentiation factors have been employed for driving MSCs towards a neuronal phenotype. In the present study, we investigated the potential of extracellular matrix (ECM) proteins-fibronectin, collagen-1, collagen-IV, laminin-1, and laminin-10/11, to induce a neuronal phenotype in bone marrow derived human MSCs in the absence of growth factors/differentiating agents. All of the ECM proteins tested were found to support adhesion of MSCs to different extents. However, direct interaction only with laminin-1 triggered sprouting of neurite-like processes. Cells plated on laminin-1 exhibited neurite out growth as early as 3h, and by 24h, the cells developed elaborate neurites with contracted cell bodies and neuronal-like morphology. Function-blocking antibodies directed against alpha6 and beta1 integrin subunits inhibited neurite formation on laminin-1 which confirmed the involvement of integrin alpha6beta1 in neurite outgrowth. Mechanistic studies revealed that cell adhesion to laminin-1 activated focal adhesion kinase (FAK), and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) signaling pathways. Abrogation of FAK phosphorylation by herbimycin-A inhibited neurite formation and also decreased activities of MEK and ERK. Pharmacological inhibitors of MEK (U0126) and ERK (PD98059) also blocked neurite outgrowth in cells plated on laminin-1. Our study demonstrates the involvement of integrin alpha6beta1 and FAK-MEK/ERK signaling pathways in laminin-1-induced neurite outgrowth in MSCs in the absence of serum and differentiation factors. PMID:19895795

Mruthyunjaya, S; Manchanda, Rumma; Godbole, Ravibhushan; Pujari, Radha; Shiras, Anjali; Shastry, Padma

2010-01-01

28

Laminin receptor specific therapeutic gold nanoparticles ((AuNP)-Au-198-EGCg) show efficacy in treating prostate cancer  

SciTech Connect

Systemic delivery of therapeutic agents to solid tumors is hindered by vascular and interstitial barriers. We hypothesized that prostate tumor specific epigallocatechingallate( EGCg) functionalized radioactive gold nanoparticles, when delivered intratumorally (IT), will circumvent transport barriers, resulting in targeted delivery of therapeutic payloads. The results described herein provide unequivocal validation of our hypothesis. We report the development of inherently therapeutic gold nanoparticles derived from Au-198 isotope; the range of 198Au ?-particle ( ~ 11 mm in tissue or ~1100 cell diameters) is sufficiently long to provide cross-fire effects of radiation dose delivered to cells within the prostate gland and short enough to minimize radiation dose to critical tissues near the periphery of the capsule. The formulation of biocompatible 198AuNPs utilizes the redox chemistry of prostate tumor specific phytochemical EGCg as it converts gold salt into gold nanoparticles and also selectively binds with excellent affinity to Laminin67R receptors which are over expressed in prostate tumor cells. Pharmacokinetic studies in PC-3 xenograft SCID mice showed ~72% retention of 198AuNP-EGCg in tumors 24 h after intratumoral administration. Therapeutic studies showed 80% reduction of tumor volumes after 28 days demonstrating significant inhibition of tumor growth compared to controls. This innovative “green nanotechnological“approach serves as a basis for designing target specific antineoplastic agents. This novel intratumorally injectable 198AuNP-EGCg nanotherapeutic agent may provide significant advances in oncology for use as an effective treatment for prostate and other solid tumors.

Shukla, Ravi; Chanda, Nripen; Zambre, Ajit; Katti, Kavita; Upendran, Anandhi; Kulkarni, Rajesh R.; Nune, Satish K.; Casteel, Stan W.; Smith, C. J.; Boote, Evan; Robertson, J. D.; Kan, Para; Engelbrecht, Hendrik; Watkinson, Lisa D.; Carmack, Terry L.; Lever, John R.; Cutler, Cathy; Caldwell, Charles; Kannan, Raghuraman; Katti, Kattesh V.

2012-07-31

29

Biologically-active laminin-111 fragment that modulates the epithelial-to-mesenchymal transition in embryonic stem cells.  

PubMed

The dynamic interplay between the extracellular matrix and embryonic stem cells (ESCs) constitutes one of the key steps in understanding stem cell differentiation in vitro. Here we report a biologically-active laminin-111 fragment generated by matrix metalloproteinase 2 (MMP2) processing, which is highly up-regulated during differentiation. We show that the ?1-chain-derived fragment interacts via ?3?1-integrins, thereby triggering the down-regulation of MMP2 in mouse and human ESCs. Additionally, the expression of MMP9 and E-cadherin is up-regulated in mouse ESCs--key players in the epithelial-to-mesenchymal transition. We also demonstrate that the fragment acts through the ?3?1-integrin/extracellular matrix metalloproteinase inducer complex. This study reveals a previously unidentified role of laminin-111 in early stem cell differentiation that goes far beyond basement membrane assembly and a mechanism by which an MMP2-cleaved laminin fragment regulates the expression of E-cadherin, MMP2, and MMP9. PMID:24706882

Horejs, Christine-Maria; Serio, Andrea; Purvis, Alan; Gormley, Adam J; Bertazzo, Sergio; Poliniewicz, Anna; Wang, Alex J; DiMaggio, Peter; Hohenester, Erhard; Stevens, Molly M

2014-04-22

30

Title: Laminin-5 activates extracellular matrix production and osteogenic gene focusing in human mesenchymal stem cells  

E-print Network

;Introduction Human mesenchymal stem cells (hMSC) are a population of multipotent cells found within the bone mesenchymal stem cells Authors: Robert F. Klees1 , Roman M. Salasznyk1 , Scott Vandenberg3 , Kristin P@rpi.edu George E. Plopper: ploppg@rpi.edu Key words: Laminin-5, extracellular matrix, mesenchymal stem cells

Vandenberg, Scott

31

BRIDGING STRUCTURE WITH FUNCTION: STRUCTURAL, REGULATORY, AND DEVELOPMENTAL ROLE OF LAMININS  

PubMed Central

The basement membrane is a highly intricate and organized portion of the extracellular matrix that interfaces with a variety of cell types including epithelial, endothelial, muscle, nerve, and fat cells. The laminin family of glycoproteins is a major constituent of the basement membrane. The sixteen known laminin isoforms are formed from combinations of ?, ?, and ? chains, with each chain containing specific domains capable of interacting with cellular receptors such as integrins and other extracellular ligands. In addition to its role in the assembly and architectural integrity of the basement membrane, laminins interact with cells to influence proliferation, differentiation, adhesion, and migration, processes activated in normal and pathologic states. In vitro these functions are regulated by the posttranslational modifications of the individual laminin chains. In vivo laminin knock-out mouse studies have been particularly instructive in defining the function of specific laminins in mammalian development and have also highlighted its role as a key component of the basement membrane. In this review, we will define how laminin structure complements function and explore its role in both normal and pathologic processes. PMID:17855154

Tzu, Julia; Marinkovich, M. Peter

2008-01-01

32

A simplified laminin nomenclature  

Microsoft Academic Search

A simplification of the laminin nomenclature is presented. Laminins are multidomain heterotrimers composed of ?, ? and ? chains. Previously, laminin trimers were numbered with Arabic numerals in the order discovered, that is laminins-1 to -5. We introduce a new identification system for a trimer using three Arabic numerals, based on the ?, ? and ? chain numbers. For example,

Monique Aumailley; Leena Bruckner-Tuderman; William G. Carter; Rainer Deutzmann; David Edgar; Peter Ekblom; Jürgen Engel; Eva Engvall; Erhard Hohenester; Jonathan C. R. Jones; Hynda K. Kleinman; M. Peter Marinkovich; George R. Martin; Ulrike Mayer; Guerrino Meneguzzi; Jeffrey H. Miner; Kaoru Miyazaki; Manuel Patarroyo; Mats Paulsson; Vito Quaranta; Joshua R. Sanes; Takako Sasaki; Kiyotoshi Sekiguchi; Lydia M. Sorokin; Jan F. Talts; Karl Tryggvason; Jouni Uitto; Ismo Virtanen; Klaus von der Mark; Ulla M. Wewer; Yoshihiko Yamada; Peter D. Yurchenco

2005-01-01

33

Angiotensin II type 1 receptor antagonists alleviate muscle pathology in the mouse model for laminin-?2-deficient congenital muscular dystrophy (MDC1A)  

PubMed Central

Background Laminin-?2-deficient congenital muscular dystrophy (MDC1A) is a severe muscle-wasting disease for which no curative treatment is available. Antagonists of the angiotensin II receptor type 1 (AT1), including the anti-hypertensive drug losartan, have been shown to block also the profibrotic action of transforming growth factor (TGF)-? and thereby ameliorate disease progression in mouse models of Marfan syndrome. Because fibrosis and failure of muscle regeneration are the main reasons for the severe disease course of MDC1A, we tested whether L-158809, an analog derivative of losartan, could ameliorate the dystrophy in dyW/dyW mice, the best-characterized model of MDC1A. Methods L-158809 was given in food to dyW/dyW mice at the age of 3?weeks, and the mice were analyzed at the age of 6 to 7?weeks. We examined the effect of L-158809 on muscle histology and on muscle regeneration after injury as well as the locomotor activity and muscle strength of the mice. Results We found that TGF-? signaling in the muscles of the dyW/dyW mice was strongly increased, and that L-158809 treatment suppressed this signaling. Consequently, L-158809 reduced fibrosis and inflammation in skeletal muscle of dyW/dyW mice, and largely restored muscle regeneration after toxin-induced injury. Mice showed improvement in their locomotor activity and grip strength, and their body weight was significantly increased. Conclusion These data provide evidence that AT1 antagonists ameliorate several hallmarks of MDC1A in dyW/dyW mice, the best-characterized mouse model for this disease. Because AT1 antagonists are well tolerated in humans and widely used in clinical practice, these results suggest that losartan may offer a potential future treatment of patients with MDC1A. PMID:22943509

2012-01-01

34

Screening of integrin-binding peptides in a laminin peptide library derived from the mouse laminin ? chain short arm regions.  

PubMed

Laminins, major components of basement membrane, consist of three different subunits, ?, ?, and ? chains, and so far, five ?, three ?, and three ? chains have been identified. We have constructed synthetic peptide libraries derived from the laminin sequences and identified various cell-adhesive peptides. Ten active peptides from the laminin ? chain sequences (?1-?5) were found to promote integrin-mediated cell adhesion. Previously, we found fourteen cell-adhesive peptides from the ?1 chain sequence but their receptors have not been analyzed. Here, we expanded the synthetic peptide library to add peptides from the short arm regions of the laminin ?2 and ?3 chains and screened for integrin-binding peptides. Twenty-seven peptides promoted human dermal fibroblast (HDF) attachment in a peptide-coated plate assay. The morphological appearance of HDFs on the peptide-coated plates differed depending on the peptides. B34 (REKYYYAVYDMV, mouse laminin ?1 chain, 255-266), B67 (IPYSMEYEILIRY, mouse laminin ?1 chain, 604-616), B2-105 (APNFWNFTSGRG, mouse laminin ?2 chain, 1081-1092), and B3-19 (GHLTGGKVQLNL, mouse laminin ?3 chain, 182-193) promoted HDF spreading and HDF attachment was inhibited by EDTA, suggesting that the peptides interact with integrins. Immunostaining analyses revealed that B67 induced well-organized actin stress fibers and focal contacts containing vinculin, however, B34, B2-105, and B3-19 did not exhibit stress fiber formation or focal contacts. The inhibition assay using anti-integrin antibodies indicated that B67 interacts with ?3, ?6, and ?1 integrins, and B34 and B3-19 interact with ?1 integrin. Based on adhesion analysis of peptides modified with an alanine scan and on switching analysis with the homologous inactive sequence B2-64 (LPRAMDYDLLLRW, mouse laminin ?2 chain, 618-630), the Glu(8) residue in the B67 peptide was critical for HDF adhesion. These findings are useful for identifying an integrin binding motif. The B67 peptide has potential for use as a molecular probe for integrins. PMID:24785228

Katagiri, Fumihiko; Takagi, Masaharu; Nakamura, Minako; Tanaka, Yoichiro; Hozumi, Kentaro; Kikkawa, Yamato; Nomizu, Motoyoshi

2014-05-15

35

A simplified laminin nomenclature.  

PubMed

A simplification of the laminin nomenclature is presented. Laminins are multidomain heterotrimers composed of alpha, beta and gamma chains. Previously, laminin trimers were numbered with Arabic numerals in the order discovered, that is laminins-1 to -5. We introduce a new identification system for a trimer using three Arabic numerals, based on the alpha, beta and gamma chain numbers. For example, the laminin with the chain composition alpha5beta1gamma1 is termed laminin-511, and not laminin-10. The current practice is also to mix two overlapping domain and module nomenclatures. Instead of the older Roman numeral nomenclature and mixed nomenclature, all modules are now called domains. Some domains are renamed or renumbered. Laminin epidermal growth factor-like (LE) domains are renumbered starting at the N-termini, to be consistent with general protein nomenclature. Domain IVb of alpha chains is named laminin 4a (L4a), domain IVa of alpha chains is named L4b, domain IV of gamma chains is named L4, and domain IV of beta chains is named laminin four (LF). The two coiled-coil domains I and II are now considered one laminin coiled-coil domain (LCC). The interruption in the coiled-coil of beta chains is named laminin beta-knob (Lbeta) domain. The chain origin of a domain is specified by the chain nomenclature, such as alpha1L4a. The abbreviation LM is suggested for laminin. Otherwise, the nomenclature remains unaltered. PMID:15979864

Aumailley, Monique; Bruckner-Tuderman, Leena; Carter, William G; Deutzmann, Rainer; Edgar, David; Ekblom, Peter; Engel, Jürgen; Engvall, Eva; Hohenester, Erhard; Jones, Jonathan C R; Kleinman, Hynda K; Marinkovich, M Peter; Martin, George R; Mayer, Ulrike; Meneguzzi, Guerrino; Miner, Jeffrey H; Miyazaki, Kaoru; Patarroyo, Manuel; Paulsson, Mats; Quaranta, Vito; Sanes, Joshua R; Sasaki, Takako; Sekiguchi, Kiyotoshi; Sorokin, Lydia M; Talts, Jan F; Tryggvason, Karl; Uitto, Jouni; Virtanen, Ismo; von der Mark, Klaus; Wewer, Ulla M; Yamada, Yoshihiko; Yurchenco, Peter D

2005-08-01

36

The LG1-3 tandem of laminin alpha5 harbors the binding sites of Lutheran/basal cell adhesion molecule and alpha3beta1/alpha6beta1 integrins.  

PubMed

The laminin-type globular (LG) domains of laminin alpha chains have been implicated in various cellular interactions that are mediated through receptors such as integrins, alpha-dystroglycan, syndecans, and the Lutheran blood group glycoprotein (Lu). Lu, an Ig superfamily transmembrane receptor specific for laminin alpha5, is also known as basal cell adhesion molecule (B-CAM). Although Lu/B-CAM binds to the LG domain of laminin alpha5, the binding site has not been precisely defined. To better delineate this binding site, we produced a series of recombinant laminin trimers containing modified alpha chains, such that all or part of alpha5LG was replaced with analogous segments of human laminin alpha1LG. In solid phase binding assays using a soluble Lu (Lu-Fc) composed of the Lu extracellular domain and human IgG1 Fc, we found that Lu bound to Mr5G3, a recombinant laminin containing alpha5 domains LN through LG3 fused to human laminin alpha1LG4-5. However, Lu/B-CAM did not bind other recombinant laminins containing alpha5LG3 unless alpha5LG1-2 was also present. A recombinant alpha5LG1-3 tandem lacking the laminin coiled coil (LCC) domain did not reproduce the activity of Lu/B-CAM binding. Therefore, proper structure of the alpha5LG1-3 tandem with the LCC domain was essential for the binding of Lu/B-CAM to laminin alpha5. Our results also suggest that the binding site for Lu/B-CAM on laminin alpha5 may overlap with that of integrins alpha3beta1 and alpha6beta1. PMID:17383963

Kikkawa, Yamato; Sasaki, Takako; Nguyen, Mai Tuyet; Nomizu, Motoyoshi; Mitaka, Toshihiro; Miner, Jeffrey H

2007-05-18

37

Cell surface galactosyltransferase mediates the initiation of neurite outgrowth from PC12 cells on laminin.  

PubMed

Neurite outgrowth from PC12 pheochromocytoma cells, as well as from peripheral and central nervous system neurons in vitro, is mediated by the extracellular matrix molecule, laminin. We have recently shown that mesenchymal cell spreading and migration on laminin is mediated, in part, by the cell surface enzyme, beta 1,4 galactosyltransferase (GalTase). GalTase is localized on lamellipodia of migrating cells where it functions as a laminin receptor by binding to specific N-linked oligosaccharides in laminin (Runyan et al., 1988; Eckstein and Shur, 1989). In the present study, we examined whether GalTase functions similarly during neutrite outgrowth on laminin using biochemical and immunological analyses. PC12 neurite outgrowth was inhibited by reagents that perturb cell surface GalTase activity, including anti-GalTase IgG and Fab fragments, as well as the GalTase modifier protein alpha-lactalbumin. Control reagents had no effect on neurite outgrowth. Furthermore, blocking GalTase substrates on laminin matrices by earlier galactosyltion or enzymatic removal of GalTase substrates also inhibited neurite outgrowth. Conversely, neurite outgrowth was enhanced by the addition of UDP-galactose, which completes the GalTase enzymatic reaction, while inappropriate sugar nucleotides had no effect. The effects of all these treatments were dose and/or time dependent. Surface GalTase was shown to function during both neurite initiation and elongation, although the effects of GalTase perturbation were most striking during the initiation stages of neurite formation. Consistent with this, surface GalTase was localized by indirect immunofluorescence to the growth cone and developing neurite. Collectively, these results demonstrate that GalTase mediates the initiation of neurite outgrowth on laminin, and to a lesser extent, neurite elongation. Furthermore, this study demonstrates that process extension from both mesenchymal cells and neuronal cells is partly dependent upon specific oligosaccharide residues in laminin. PMID:2105324

Begovac, P C; Shur, B D

1990-02-01

38

Extraribosomal Functions Associated with the C Terminus of the 37/67 kDa Laminin Receptor are Required for Maintaining Cell Viability  

SciTech Connect

The 37/67 kDa laminin receptor (LAMR) is a multifunctional protein, acting as an extracellular receptor, localizing to the nucleus, and playing roles in rRNA processing and ribosome assembly. LAMR is important for cell viability; however, it is unclear which of its functions are essential. We developed a silent mutant LAMR construct, resistant to siRNA, to rescue the phenotypic effects of knocking down endogenous LAMR, which include inhibition of protein synthesis, cell cycle arrest, and apoptosis. In addition, we generated a C-terminal-truncated silent mutant LAMR construct structurally homologous to the Archaeoglobus fulgidus S2 ribosomal protein and missing the C-terminal 75 residues of LAMR, which displays more sequence divergence. We found that HT1080 cells stably expressing either silent mutant LAMR construct still undergo arrest in the G{sub 1} phase of the cell cycle when treated with siRNA. However, the expression of full-length silent mutant LAMR rescues cell viability, whereas the expression of the C-terminal-truncated LAMR does not. Interestingly, we also found that both silent mutant constructs restore protein translation and localize to the nucleus. Our findings indicate that the ability of LAMR to regulate viability is associated with its C-terminal 75 residues. Furthermore, this function is distinct from its role in cell proliferation, independent of its ribosomal functions, and may be regulated by a nonnuclear localization.

J Scheiman; K Jamieson; J Ziello; J Tseng; D Meruelo

2011-12-31

39

Endorepellin laminin-like globular 1/2 domains bind Ig3-5 of vascular endothelial growth factor (VEGF) receptor 2 and block pro-angiogenic signaling by VEGFA in endothelial cells.  

PubMed

Endorepellin, a processed fragment of perlecan protein core, possesses anti-angiogenic activity by antagonizing endothelial cells. Endorepellin contains three laminin G-like (LG) domains and binds simultaneously to vascular endothelial growth factor receptor 2 (VEGFR2) and ?2?1 integrin, resulting in dual receptor antagonism. Treatment of endothelial cells with endorepellin inhibits transcription of VEGFA, the natural ligand for VEGFR2, attenuating the pro-survival and migratory activities of VEGFA/VEGFR2 signaling cascade. Here, we investigated the specific binding site of endorepellin within the ectodomain of VEGFR2. Full-length endorepellin was not capable of displacing VEGFA binding from VEGFR2 and LG3 domain alone did not bind VEGFR2. This suggested different binding mechanisms of the extracellular Ig domains of VEGFR2. Therefore, we hypothesized that endorepellin would bind through its proximal LG1/2 domains to VEGFR2 in a different region than VEGFA. Indeed, we found that LG1/2 did not bind Ig1-3, but did bind with high affinity to Ig3-5, distal to the known VEGFA binding site, i.e. Ig2-3. These results support a role for endorepellin as an allosteric inhibitor of VEGFR2. Moreover, we found that LG1/2 blocked the rapid VEGFA activation of VEGFR2 at Tyr1175 in endothelial cells. In contrast, LG1/2 did not result in actin cytoskeletal disassembly in endothelial cells whereas LG3 alone did induce cytoskeletal collapse. However, LG1/2 did inhibit VEGFA-dependent endothelial migration through fibrillar collagen I. These studies provide a mechanistic understanding of how the different LG domains of endorepellin signal in endothelial cells while serving as a template for protein design of receptor tyrosine kinase antagonists. PMID:23374253

Willis, Chris D; Poluzzi, Chiara; Mongiat, Maurizio; Iozzo, Renato V

2013-05-01

40

Decreased sickle red blood cell adhesion to laminin by hydroxyurea is associated with inhibition of Lu/BCAM protein phosphorylation  

E-print Network

1 Decreased sickle red blood cell adhesion to laminin by hydroxyurea is associated with inhibition, published in "Blood 2010;116(12):2152-9" DOI : 10.1182/blood-2009-12-257444 #12;2 Abstract Sickle-cell laminin receptor Lu/BCAM was increased but red blood cell adhesion to laminin decreased. Because Lu

Paris-Sud XI, Université de

41

Laminin alpha3 LG4 module induces keratinocyte migration: involvement of matrix metalloproteinase-9.  

PubMed

Laminin alpha3 chain, a functionally key subunit of laminin-5, contains a large globular module (G module) which consists of a tandem repeat of five homologous LG modules (LG1-5). We previously demonstrated that the LG4 module of laminin alpha3 chain (alpha3 LG4) induces a matrix metalloproteinase-1 (MMP-1) expression through the interaction with syndecans leading to MAPK activation/IL-1beta expression signaling loop (Utani et al., J. Biol. Chem. 278, 34483-34490, 2003). Here, we show that a recombinant alpha3 LG4 and synthetic peptides containing syndecan binding motif induced a cell motility and a MMP-9 expression in ketarinocytes. The synthetic peptide (A3G756)-induced cell migration and MMP-9 upregulation were inhibited by each application of a heparin and an IL-1 receptor antagonist (IL-1RA), suggesting the involvement of syndecans and IL-1beta autocrine. Furthermore, the A3G756-induced cell motility was inhibited by an MMP-9 inhibitor and a neutralizing antibody of MMP-9, indicating induced cell motility was dependent on an MMP-9 activity. Taken these together, laminin-5 alpha3 LG4 module may play an important role in re-epithelialization at tissue remodeling. PMID:15960391

Momota, Yutaka; Suzuki, Nobuharu; Kasuya, Yoshitoshi; Kobayashi, Takashi; Mizoguchi, Masako; Yokoyama, Fumiharu; Nomizu, Motoyoshi; Shinkai, Hiroshi; Iwasaki, Toshiroh; Utani, Atsushi

2005-01-01

42

Mutational analysis of the cleavage of the cancer-associated laminin receptor by stromelysin-3 reveals the contribution of flanking sequences to site recognition and cleavage efficiency  

PubMed Central

The matrix metalloproteinase stromelysin-3 (ST3) has long been implicated to play an important role in cell fate determination during normal and pathological processes. Using the thyroid hormone-dependent Xenopus laevis metamorphosis as a model, we have previously shown that ST3 is required for apoptosis during intestinal remodeling and that laminin receptor (LR) is an in vivo substrate of ST3 during this process. ST3 cleaves LR at two distinct sites that are conserved in mammalian LR. Human ST3 and LR are both associated with tumor development and cancer progression and human LR can also be cleaved by ST3, implicating a role of LR cleavage by ST3 in human cancers. Here, we carried out a series of mutational analyses on the two cleavage sites in LR. Our findings revealed that in addition to primary sequence at the cleavage site (positions P3-P3?, with the cleavage occurring between P1-P1?), flanking sequences/conformation also influenced the cleavage of LR by ST3. Furthermore, alanine substitution studies led to a surprising finding that surrounding sequence and/or conformation dictated the site of cleavage in LR by ST3. These results thus have important implications in our understanding of substrate recognition and cleavage by ST3 and argue for the importance of studying ST3 cleavage in the context of full-length substrates. Furthermore, the LR cleavage mutants generated here will also be valuable tools for future studies on the role of LR cleavage by ST3 in vertebrate development and cancer progression. PMID:19212658

Fiorentino, Maria; Fu, Liezhen; Shi, Yun-Bo

2008-01-01

43

Laminin Mediates Tissue-specific Gene Expression in Mammary Epithelia  

SciTech Connect

Tissue-specific gene expression in mammary epithelium is dependent on the extracellular matrix as well as hormones. There is good evidence that the basement membrane provides signals for regulating beta-casein expression, and that integrins are involved in this process. Here, we demonstrate that in the presence of lactogenic hormones, laminin can direct expression of the beta-casein gene. Mouse mammary epithelial cells plated on gels of native laminin or laminin-entactin undergo functional differentiation. On tissue culture plastic, mammary cells respond to soluble basement membrane or purified laminin, but not other extracellular matrix components, by synthesizing beta-casein. In mammary cells transfected with chloramphenicol acetyl transferase reporter constructs, laminin activates transcription from the beta-casein promoter through a specific enhancer element. The inductive effect of laminin on casein expression was specifically blocked by the E3 fragment of the carboxy terminal region of the alpha 1 chain of laminin, by antisera raised against the E3 fragment, and by a peptide corresponding to a sequence within this region. Our results demonstrate that laminin can direct tissue-specific gene expression in epithelial cells through its globular domain.

Streuli, Charles H; Schmidhauser, Christian; Bailey, Nina; Yurchenco, Peter; Skubitz, Amy P. N.; Roskelley, Calvin; Bissell, Mina J

1995-04-01

44

Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction  

PubMed Central

A prominent feature of synaptic maturation at the neuromuscular junction (NMJ) is the topological transformation of the acetylcholine receptor (AChR)-rich postsynaptic membrane from an ovoid plaque into a complex array of branches. We show here that laminins play an autocrine role in promoting this transformation. Laminins containing the ?4, ?5, and ?2 subunits are synthesized by muscle fibers and concentrated in the small portion of the basal lamina that passes through the synaptic cleft at the NMJ. Topological maturation of AChR clusters was delayed in targeted mutant mice lacking laminin ?5 and arrested in mutants lacking both ?4 and ?5. Analysis of chimeric laminins in vivo and of mutant myotubes cultured aneurally demonstrated that the laminins act directly on muscle cells to promote postsynaptic maturation. Immunohistochemical studies in vivo and in vitro along with analysis of targeted mutants provide evidence that laminin-dependent aggregation of dystroglycan in the postsynaptic membrane is a key step in synaptic maturation. Another synaptically concentrated laminin receptor, Bcam, is dispensable. Together with previous studies implicating laminins as organizers of presynaptic differentiation, these results show that laminins coordinate post- with presynaptic maturation. PMID:18794334

Nishimune, Hiroshi; Valdez, Gregorio; Jarad, George; Moulson, Casey L.; Müller, Ulrich; Miner, Jeffrey H.; Sanes, Joshua R.

2008-01-01

45

Single-cell force spectroscopy as a technique to quantify human red blood cell adhesion to subendothelial laminin.  

PubMed

Single-cell force spectroscopy (SCFS), an atomic force microscopy (AFM)-based assay, enables quantitative study of cell adhesion while maintaining the native state of surface receptors in physiological conditions. Human healthy and pathological red blood cells (RBCs) express a large number of surface proteins which mediate cell-cell interactions, or cell adhesion to the extracellular matrix. In particular, RBCs adhere with high affinity to subendothelial matrix laminin via the basal cell adhesion molecule and Lutheran protein (BCAM/Lu). Here, we established SCFS as an in vitro technique to study human RBC adhesion at baseline and following biochemical treatment. Using blood obtained from healthy human subjects, we recorded adhesion forces from single RBCs attached to AFM cantilevers as the cell was pulled-off of substrates coated with laminin protein. We found that an increase in the overall cell adhesion measured via SCFS is correlated with an increase in the resultant total force measured on 1 µm(2) areas of the RBC membrane. Further, we showed that SCFS can detect significant changes in the adhesive response of RBCs to modulation of the cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) pathway. Lastly, we identified variability in the RBC adhesion force to laminin amongst the human subjects, suggesting that RBCs maintain diverse levels of active BCAM/Lu adhesion receptors. By using single-cell measurements, we established a powerful new method for the quantitative measurement of single RBC adhesion with specific receptor-mediated binding. PMID:25458578

Maciaszek, Jamie L; Partola, Kostyantyn; Zhang, Jing; Andemariam, Biree; Lykotrafitis, George

2014-12-18

46

Agrin and Synaptic Laminin Are Required to Maintain Adult Neuromuscular Junctions  

PubMed Central

As synapses form and mature the synaptic partners produce organizing molecules that regulate each other’s differentiation and ensure precise apposition of pre- and post-synaptic specializations. At the skeletal neuromuscular junction (NMJ), these molecules include agrin, a nerve-derived organizer of postsynaptic differentiation, and synaptic laminins, muscle-derived organizers of presynaptic differentiation. Both become concentrated in the synaptic cleft as the NMJ develops and are retained in adulthood. Here, we used mutant mice to ask whether these organizers are also required for synaptic maintenance. Deletion of agrin from a subset of adult motor neurons resulted in the loss of acetylcholine receptors and other components of the postsynaptic apparatus and synaptic cleft. Nerve terminals also atrophied and eventually withdrew from muscle fibers. On the other hand, mice lacking the presynaptic organizer laminin-?4 retained most of the synaptic cleft components but exhibited synaptic alterations reminiscent of those observed in aged animals. Although we detected no marked decrease in laminin or agrin levels at aged NMJs, we observed alterations in the distribution and organization of these synaptic cleft components suggesting that such changes could contribute to age-related synaptic disassembly. Together, these results demonstrate that pre- and post-synaptic organizers actively function to maintain the structure and function of adult NMJs. PMID:23056392

Samuel, Melanie A.; Valdez, Gregorio; Tapia, Juan C.; Lichtman, Jeff W.; Sanes, Joshua R.

2012-01-01

47

Astrocytic laminin regulates pericyte differentiation and maintains blood brain barrier integrity  

NASA Astrophysics Data System (ADS)

Blood brain barrier (BBB) breakdown is not only a consequence of but also contributes to many neurological disorders, including stroke and Alzheimer’s disease. How the basement membrane (BM) contributes to the normal functioning of the BBB remains elusive. Here we use conditional knockout mice and an acute adenovirus-mediated knockdown model to show that lack of astrocytic laminin, a brain-specific BM component, induces BBB breakdown. Using functional blocking antibody and RNAi, we further demonstrate that astrocytic laminin, by binding to integrin ?2 receptor, prevents pericyte differentiation from the BBB-stabilizing resting stage to the BBB-disrupting contractile stage, and thus maintains the integrity of BBB. Additionally, loss of astrocytic laminin decreases aquaporin-4 (AQP4) and tight junction protein expression. Altogether, we report a critical role for astrocytic laminin in BBB regulation and pericyte differentiation. These results indicate that astrocytic laminin maintains the integrity of BBB through, at least in part, regulation of pericyte differentiation.

Yao, Yao; Chen, Zu-Lin; Norris, Erin H.; Strickland, Sidney

2014-03-01

48

Human amnion contains a novel laminin variant, laminin 7, which like laminin 6, covalently associates with laminin 5 to promote stable epithelial-stromal attachment  

PubMed Central

Stable attachment of external epithelia to the basement membrane and underlying stroma is mediated by transmembrane proteins such as the integrin alpha6beta4 and bullous pemphigoid antigen 2 within the hemidesmosomes along the basolateral surface of the epithelial cell and their ligands that include a specialized subfamily of laminins. The laminin 5 molecule (previously termed kalinin/nicein/epiligrin) is a member of this epithelial-specific subfamily. Laminin 5 chains are not only considerably truncated within domains III-VI, but are also extensively proteolytically processed in vitro and in vivo. As a result, the domains expected to be required for the association of laminins with other basement membrane components are lacking in the mature laminin 5 molecule. Therefore, the tight binding of laminin 5 to the basement membrane may occur by a unique mechanism. To examine laminin 5 in tissue, we chose human amnion as the source, because of its availability and the similarity of the amniotic epithelial basement membrane with that of skin. We isolated the laminin 5 contained within the basement membrane of human amnion. In addition to monomeric laminin 5, we find that much of the laminin 5 isolated is covalently adducted with laminin 6 (alpha3beta1gamma1) and a novel laminin isotype we have termed laminin 7 (alpha3beta2gamma1). We propose that the association between laminin 5 and laminins 6 and 7 is a mechanism used in amnion to allow stable association of laminin 5 with the basement membrane. The beta2 chain is seen at the human amniotic epithelial-stromal interface and at the dermal-epidermal junction of fetal and adult bovine skin by immunofluorescence, but is not present, or only weakly present, in neonatal human skin. PMID:8601594

1996-01-01

49

Epigallocatechin 3-O-gallate induces 67 kDa laminin receptor-mediated cell death accompanied by downregulation of ErbB proteins and altered lipid raft clustering in mammary and epidermoid carcinoma cells.  

PubMed

Since the administration of synthetic medicines is associated with drug resistance and undesired side effects, utilization of natural compounds could be an alternative and complementary modality to inhibit or prevent the development of tumors. Epigallocatechin 3-O-gallate (EGCG, 1), the major flavan component of green tea, and genistein (2), a soy isoflavonoid, are known to have chemopreventive and chemotherapeutic effects against cancer. This study demonstrated that both flavonoids inhibit cell proliferation, an effect enhanced under serum-free conditions. Compound 1, but not 2, induced downregulation of ErbB1 and ErbB2 in mammary and epidermoid carcinoma cells, and its inhibitory effect on cell viability was mediated by the 67 kDa laminin receptor (67LR). While 1 was superior in inducing cell death, 2 was more efficient in arresting the tumor cells in the G2/M phase. Furthermore, number and brightness analysis revealed that 1 decreased the homoclustering of a lipid raft marker, glycosylphosphatidylinositol-anchored GFP, and it also reduced the co-localization between lipid rafts and 67LR. The main conclusion made is that the primary target of 1 may be the lipid raft component of the plasma membrane followed by secondary changes in the expression of ErbB proteins. Compound 2, on the other hand, must have other unidentified targets. PMID:24456004

Mocanu, Maria-Magdalena; Ganea, Constan?a; Georgescu, Laura; Váradi, Tímea; Shrestha, Dilip; Baran, Irina; Katona, Eva; Nagy, Peter; Szöll?si, János

2014-02-28

50

High Resolution Imaging Study of Interactions between the 37 kDa/67 kDa Laminin Receptor and APP, Beta-Secretase and Gamma-Secretase in Alzheimer's Disease  

PubMed Central

Alzheimer's disease (AD) is the most prevalent form of dementia affecting the elderly. Neurodegeneration is caused by the amyloid beta (A?) peptide which is generated from the sequential proteolytic cleavage of the Amyloid Precursor Protein (APP) by the ?– and ?- secretases. Previous reports revealed that the 37 kDa/67 kDa laminin receptor (LRP/LR) is involved in APP processing, however, the exact mechanism by which this occurs remains largely unclear. This study sought to assess whether LRP/LR interacted with APP, ?- or ?-secretase. Detailed confocal microscopy revealed that LRP/LR showed a strong co-localisation with APP, ?- and ?-secretase, respectively, at various sub-cellular locations. Superresolution Structured Illumination Microscopy (SR-SIM) showed that interactions were unlikely between LRP/LR and APP and ?-secretase, respectively, while there was strong co-localisation between LRP/LR and ?-secretase at this 80 nm resolution. FRET was further employed to assess the possibility of protein-protein interactions and only an interaction between LRP/LR and ?-secretase was found. FLAG co-immunoprecipitation confirmed these findings as LRP/LR co-immunoprecipitated with ?-secretase, but failed to do so with APP. These findings indicate that LRP/LR exerts its influence on A? shedding via a direct interaction with the ?-secretase and possibly an indirect interaction with the ?-secretase. PMID:24972054

Jovanovic, Katarina; Loos, Ben; Da Costa Dias, Bianca; Penny, Clement; Weiss, Stefan F. T.

2014-01-01

51

Laminin peptide YIGSR induces collagen synthesis in Hs27 human dermal fibroblasts  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer We identify a function of the YIGSR peptide to enhance collagen synthesis in Hs27. Black-Right-Pointing-Pointer YIGSR peptide enhanced collagen type 1 synthesis both of gene and protein levels. Black-Right-Pointing-Pointer There were no changes in cell proliferation and MMP-1 level in YIGSR treatment. Black-Right-Pointing-Pointer The YIGSR effect on collagen synthesis mediated activation of FAK, pyk2 and ERK. Black-Right-Pointing-Pointer The YIGSR-induced FAK and ERK activation was modulated by FAK and MEK inhibitors. -- Abstract: The dermal ECM is synthesized from fibroblasts and is primarily compromised of fibrillar collagen and elastic fibers, which support the mechanical strength and resiliency of skin, respectively. Laminin, a major glycoprotein located in the basement membrane, promotes cell adhesion, cell growth, differentiation, and migration. The laminin tyrosine-isoleucine-glycine-serine-arginine (YIGSR) peptide, corresponding to the 929-933 sequence of the {beta}1 chain, is known to be a functional motif with effects on the inhibition of tumor metastasis, the regulation of sensory axonal response and the inhibition of angiogenesis through high affinity to the 67 kDa laminin receptor. In this study, we identified a novel function of the YIGSR peptide to enhance collagen synthesis in human dermal fibroblasts. To elucidate this novel function regarding collagen synthesis, we treated human dermal fibroblasts with YIGSR peptide in both a time- and dose-dependent manner. According to subsequent experiments, we found that the YIGSR peptide strongly enhanced collagen type 1 synthesis without changing cell proliferation or cellular MMP-1 level. This YIGSR peptide-mediated collagen type 1 synthesis was modulated by FAK inhibitor and MEK inhibitor. This study clearly reveals that YIGSR peptide plays a novel function on the collagen type 1 synthesis of dermal fibroblasts and also suggests that YIGSR is a strong candidate peptide for the treatment of skin aging and wrinkles.

Yoon, Jong Hyuk; Kim, Jaeyoon; Lee, Hyeongjoo [NovaCell Technology Inc., Pohang, Kyungbuk 790-784 (Korea, Republic of)] [NovaCell Technology Inc., Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, So Young [Department of Dermatology, Chung-Ang University College of Medicine, Seoul 156-756 (Korea, Republic of) [Department of Dermatology, Chung-Ang University College of Medicine, Seoul 156-756 (Korea, Republic of); Department of Convergence Medicine and Pharmaceutical Biosciences, Graduate School, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Jang, Hwan-Hee [Functional Food and Nutrition Division, Department of Agrofood Resources, Rural Development Administration, Suwon 441-853 (Korea, Republic of)] [Functional Food and Nutrition Division, Department of Agrofood Resources, Rural Development Administration, Suwon 441-853 (Korea, Republic of); Ryu, Sung Ho [Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk 790-784 (Korea, Republic of)] [Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, Beom Joon [Department of Dermatology, Chung-Ang University College of Medicine, Seoul 156-756 (Korea, Republic of) [Department of Dermatology, Chung-Ang University College of Medicine, Seoul 156-756 (Korea, Republic of); Department of Convergence Medicine and Pharmaceutical Biosciences, Graduate School, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Lee, Taehoon G., E-mail: taehoon@novacelltech.com [NovaCell Technology Inc., Pohang, Kyungbuk 790-784 (Korea, Republic of)

2012-11-23

52

Processing of laminin ? chains generates peptides involved in wound healing and host defense.  

PubMed

Laminins play a fundamental role in basement membrane architecture and function in human skin. The C-terminal laminin G domain-like (LG) modules of laminin ? chains are modified by proteolysis to generate LG1-3 and secreted LG4-5 tandem modules. In this study, we provide evidence that skin-derived cells process and secrete biologically active peptides from the LG4-5 module of the laminin ?3, ?4 and ?5 chain in vitro and in vivo. We show enhanced expression and processing of the LG4-5 module of laminin ?3 in keratinocytes after infection and in chronic wounds in which the level of expression and further processing of the LG4-5 module correlated with the speed of wound healing. Furthermore, bacterial or host-derived proteases promote processing of laminin ?3 LG4-5. On a functional level, we show that LG4-5-derived peptides play a role in wound healing. Moreover, we demonstrate that LG4-derived peptides from the ?3, ?4 and ?5 chains have broad antimicrobial activity and possess strong chemotactic activity to mononuclear cells. Thus, the data strongly suggest a novel multifunctional role for laminin LG4-5-derived peptides in human skin and its involvement in physiological processes and pathological conditions such as inflammation, chronic wounds and skin infection. PMID:24458132

Senyürek, Ilknur; Kempf, Wolfgang E; Klein, Gerd; Maurer, Andreas; Kalbacher, Hubert; Schäfer, Luisa; Wanke, Ines; Christ, Christina; Stevanovic, Stefan; Schaller, Martin; Rousselle, Patricia; Garbe, Claus; Biedermann, Tilo; Schittek, Birgit

2014-01-01

53

Laminin-based Nanomaterials for Peripheral Nerve Tissue Engineering  

NASA Astrophysics Data System (ADS)

Peripheral nerve transection occurs commonly in traumatic injury, causing motor and sensory deficits distal to the site of injury. One option for surgical repair is the nerve conduit. Conduits currently on the market are hollow tubes into which the nerve ends are sutured. Although these conduits fill the gap, they often fail due to the slow rate of regeneration over long gaps. To facilitate increased speed of regeneration and greater potential for functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in peripheral nerve regeneration. In this dissertation, I fabricated laminin-1 and laminin-polycaprolactone (PCL) blend nanofibers that mimic the geometry and functionality of the peripheral nerve basement membrane. These fibers resist hydration in aqueous media and require no harsh chemical crosslinkers. Adhesion and differentiation of both neuron-like and neuroprogenitor cells is improved on laminin nanofibrous meshes over two-dimensional laminin substrates. Blend meshes with varying laminin content were characterized for composition, tensile properties, degradation rates, and bioactivity in terms of cell attachment and axonal elongation. I have established that 10% (wt) laminin content is sufficient to retain the significant neurite-promoting effects of laminin critical in peripheral nerve repair. In addition, I utilized modified collector plate design to manipulate electric field gradients during electrospinning for the fabrication of aligned nanofibers. These aligned substrates provide enhanced directional guidance cues to the regenerating axons. Finally, I replicated the clinical problem of peripheral nerve transection using a rat tibial nerve defect model for conduit implantation. When the lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment, I observed significant recovery of sensory and motor function over six weeks. This recovery was supported by nerve conduction studies and electromyography which described impulse transmission, muscle stimulation, and foot twitch through the region of regeneration. These studies provide a firm foundation for the use of natural-synthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits. The similarity in surgical technique and obvious benefit to the patient should lead to rapid translation into clinical application.

Neal, Rebekah Anne

54

Paired inhibitory and activating receptor signals.  

PubMed

The immunological literature has become inundated with reports regarding paired inhibitory receptors. Paired inhibitory receptor systems are highly conserved families that contain receptors involved in either cellular inhibition or activation. In most cases the paired putative biochemical antagonists are co-expressed on a given cell and thought to bind similar, if not identical, ligands making their biological role difficult to understand. Examples of these systems include immunoglobulin (Ig)-like receptors (Killer Ig Receptors, Immunoglobulin-like Transcripts/Leukocyte Ig-like Receptors/Monocyte Macrophage Ig Receptors, and Paired Ig-like Receptors), and type II lectin-like receptor systems (NKG2 and Ly49). General characteristics of these inhibitory receptors include a cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM). The ITIM is phosphorylated upon engagement and recruits protein tyrosine phosphatases that dephosphorylate cellular substrates that would otherwise mediate activation. In contrast, the activating receptors of these pairs use charged residues within their transmembrane domains to associate with various signal transduction chains including the gamma chain of the receptor for the Fc portion of IgE, DAP12 or DAP10. Once phosphorylated, these chains direct the signal transduction cascade resulting in cellular activation. Here we review the signaling of several paired systems and present the current models for their signal transduction cascades. PMID:11258418

Taylor, L S; Paul, S P; McVicar, D W

2000-01-01

55

Native Chick Laminin4 Containing the 132 Chain (s-Laminin) Promotes Motor Axon Growth  

Microsoft Academic Search

After denervation of muscle, motor axons reinnervate original synaptic sites. A recombinant frag- ment of the synapse specific laminin 132 chain (s-laminin) was reported to inhibit motor axon growth. Conse- quently, a specific sequence (leucine-arginine- glutamate, LRE) of the laminin 132 chain was proposed to act as a stop signal and to mediate specific reinnerva- tion at the neuromuscular junction

Ralph Brandenberger; Richard A. Kammerer; Jiirgen Engel; Matthias Chiquet

1996-01-01

56

Laminin-511 in human pluripotent stem cells.  

E-print Network

??Extracellular matrix consists of complex proteins, like collagens, which primarily provide mechanical support and non-collagenous proteins, like fibronectin and laminins (LM). Essentially, extracellular matrix can… (more)

Vuoristo, Sanna

2013-01-01

57

Cellular Interaction of Integrin ?3?1 with Laminin 5 Promotes Gap Junctional Communication  

PubMed Central

Wounding of skin activates epidermal cell migration over exposed dermal collagen and fibronectin and over laminin 5 secreted into the provisional basement membrane. Gap junctional intercellular communication (GJIC) has been proposed to integrate the individual motile cells into a synchronized colony. We found that outgrowths of human keratinocytes in wounds or epibole cultures display parallel changes in the expression of laminin 5, integrin ?3?1, E-cadherin, and the gap junctional protein connexin 43. Adhesion of keratinocytes on laminin 5, collagen, and fibronectin was found to differentially regulate GJIC. When keratinocytes were adhered on laminin 5, both structural (assembly of connexin 43 in gap junctions) and functional (dye transfer) assays showed a two- to threefold increase compared with collagen and five- to eightfold over fibronectin. Based on studies with immobilized integrin antibody and integrin-transfected Chinese hamster ovary cells, the interaction of integrin ?3?1 with laminin 5 was sufficient to promote GJIC. Mapping of intermediate steps in the pathway linking ?3?1–laminin 5 interactions to GJIC indicated that protein trafficking and Rho signaling were both required. We suggest that adhesion of epithelial cells to laminin 5 in the basement membrane via ?3?1 promotes GJIC that integrates individual cells into synchronized epiboles. PMID:9852164

Lampe, Paul D.; Nguyen, Beth P.; Gil, Susana; Usui, Marcia; Olerud, John; Takada, Yoshikazu; Carter, William G.

1998-01-01

58

Laminin and fibronectin in adenoid cystic carcinoma.  

PubMed Central

The distribution of fibronectin and laminin was examined by immunohistochemistry in 11 adenoid cystic breast carcinomas, six adenoid cystic carcinomas of mouth and salivary gland, and six cribriform ductal breast carcinomas. Both proteins were present lining cystic lumina and around tumour islands in all the adenoid cystic breast carcinomas and in five of six salivary gland tumours. Abundant laminin and fibronectin were dispersed among adenoid cystic tumour cells arranged in sheets. One adenoid cystic carcinoma from buccal mucosa showed a transition from a cribriform tumour positive for both fibronectin and laminin to a cribriform tumour negative for fibronectin and laminin to undifferentiated carcinoma. Fibronectin and laminin seemed to disappear simultaneously from tumour cell surfaces. Another adenoid cystic carcinoma from buccal mucosa was negative for fibronectin and laminin from the time of initial biopsy. This was the only tumour that gave rise to disseminated metastases, resulting in the death of the patient within two years of surgery. In cribriform invasive ductal breast carcinomas the linings of cystic lumina were always negative for fibronectin and laminin. Varying quantities were present at the tumour boundaries. We suggest that staining for fibronectin and laminin may be a valuable aid to the diagnosis of adenoid cystic carcinomas and that the absence of these proteins may have important prognostic implications. Images PMID:3005373

d'Ardenne, A J; Kirkpatrick, P; Wells, C A; Davies, J D

1986-01-01

59

Rethinking Molecular Mimicry in Rheumatic Heart Disease and Autoimmune Myocarditis: Laminin, Collagen IV, CAR, and B1AR as Initial Targets of Disease  

PubMed Central

Rationale: Molecular mimicry theory (MMT) suggests that epitope mimicry between pathogens and human proteins can activate autoimmune disease. Group A streptococci (GAS) mimics human cardiac myosin in rheumatic heart disease (RHD) and coxsackie viruses (CX) mimic actin in autoimmune myocarditis (AM). But myosin and actin are immunologically inaccessible and unlikely initial targets. Extracellular cardiac proteins that mimic GAS and CX would be more likely. Objectives: To determine whether extracellular cardiac proteins such as coxsackie and adenovirus receptor (CAR), beta 1 adrenergic receptor (B1AR), CD55/DAF, laminin, and collagen IV mimic GAS, CX, and/or cardiac myosin or actin. Methods: BLAST 2.0 and LALIGN searches of the UniProt protein database were employed to identify potential molecular mimics. Quantitative enzyme-linked immunosorbent assay was used to measure antibody cross-reactivity. Measurements: Similarities were considered to be significant if a sequence contained at least 5 identical amino acids in 10. Antibodies were considered to be cross-reactive if the binding constant had a Kd less than 10-9 M. Main results: Group A streptococci mimics laminin, CAR, and myosin. CX mimics actin and collagen IV and B1AR. The similarity search results are mirrored by antibody cross-reactivities. Additionally, antibodies against laminin recognize antibodies against collagen IV; antibodies against actin recognize antibodies against myosin, and antibodies against GAS recognize antibodies against CX. Thus, there is both mimicry of extracellular proteins and antigenic complementarity between GAS-CX in RHD/AM. Conclusion: Rheumatic heart disease/AM may be due to combined infections of GAS with CX localized at cardiomyocytes that may produce a synergistic, hyperinflammatory response that cross-reacts with laminin, collagen IV, CAR, and/or B1AR. Epitope drift shifts the immune response to myosin and actin after cardiomyocytes become damaged. PMID:25191648

Root-Bernstein, Robert

2014-01-01

60

Mammalian and Drosophila cells adhere to the laminin alpha4 LG4 domain through syndecans, but not glypicans.  

PubMed

We have previously shown that the LG4 (laminin G-like) domain of the laminin alpha4 chain is responsible for the significantly higher affinity of the alpha4 chain to heparin than found for other alpha chains [Yamaguchi, Yamashita, Mori, Okazaki, Nomizu, Beck and Kitagawa (2000) J. Biol. Chem. 275, 29458-29465]; four basic residues were identified to be essential for this activity [Yamashita, Beck and Kitagawa (2004) J. Mol. Biol. 335, 1145-1149]. By creating GST (glutathione S-transferase)-fused LG1, LG2, LG4 and LG5 proteins, we found that only LG4 is active for the adhesion of human HT1080 cells, human umbilical vein endothelial cells and Drosophila haemocytes Kc167 with a half-saturating concentration of 20 microg/ml. Adhesion was counteracted by treatment of the cells with heparin, heparan sulphate and heparitinase I. Upon mutating the four basic residues essential for heparin binding within LG4, the adhesion activity was abolished. Pull-down experiments using glutathione beads/GST-fusion proteins indicate a direct interaction of LG4 with syndecan-4, which might be the major receptor for cell adhesion. Neither the release of glypican-1 by treating human cells with phosphatidylinositol-specific phospholipase C nor targeted knockdown of dally or dally-like protein impaired the cell-adhesion activity. As the LG4-LG5 domain of the alpha4 chain is cleaved in vivo from the main body of laminin-8 (alpha4beta1gamma1), we suggest that the heparan sulphate proteoglycan-binding activity of LG4 is significant in modulating the signalling of Wnt, Decapentaplegic and fibroblast growth factors. PMID:15182231

Yamashita, Hironobu; Goto, Akira; Kadowaki, Tatsuhiko; Kitagawa, Yasuo

2004-09-15

61

O-Mannosyl Phosphorylation of Alpha-Dystroglycan is Required for Laminin Binding  

PubMed Central

Alpha-dystroglycan is a cell-surface glycoprotein that acts as a receptor for both extracellular matrix proteins containing laminin-G domains and certain arenaviruses. Receptor binding is thought to be mediated by a post-translational modification, and defective binding with laminin underlies a subclass of congenital muscular dystrophy. Here, using mass spectrometry- and NMR-based structural analyses, we identified a phosphorylated O-mannosyl glycan on the mucin-like domain of recombinant alpha-dystroglycan, which was required for laminin binding. We demonstrated that patients with muscle-eye-brain disease and Fukuyama congenital muscular dystrophy, as well as mice with myodystrophy, commonly have defects in a post-phosphoryl modification of this phosphorylated O-linked mannose, and that this modification is mediated by the like-acetylglucosaminyltransferase (LARGE) protein. Our findings expand our understanding of the mechanisms that underlie congenital muscular dystrophy. PMID:20044576

Yoshida-Moriguchi, Takako; Yu, Liping; Stalnaker, Stephanie H.; Davis, Sarah; Kunz, Stefan; Oldstone, Michael B.A.; Schachter, Harry; Wells, Lance; Campbell, Kevin P.

2010-01-01

62

Cryptic fragment alpha4 LG4-5 derived from laminin alpha4 chain inhibits de novo adipogenesis by modulating the effect of fibroblast growth factor-2.  

PubMed

Cleavage of the extracellular matrix (ECM) by proteolysis unmasks cryptic sites and generates novel fragments with biological activities functionally distinct from those of the intact ECM molecule. The laminin G-like (LG)4-5 fragment has been shown to be excised from the laminin alpha4 chain in various tissues. However, the functional role of this fragment has remained unknown to date. To investigate this, we prepared alpha4 LG1-3 and alpha4 LG4-5 fragments by elastase digestion of recombinant alpha4 LG1-5, and examined their effects on de novo adipogenesis in mice at the site of injection of basement membrane extract (Matrigel) and fibroblast growth factor (FGF)-2. Although the addition of whole alpha4 LG1-5 suppressed adipogenesis to some extent, the alpha4 LG4-5 fragment could strongly suppress adipogenesis at a concentration of less than 20 nm. Addition of the alpha4 LG4 module, which contains a heparin-binding region, had a suppressive effect, but this was lost in mutants with reduced heparin-binding activity. In addition, antibodies against the extracellular domain of syndecan-2 and -4, which are known receptors for the alpha4 LG4 module, suppressed adipogenesis. Thus, these results suggest that the cryptic alpha4 LG4-5 fragment derived from the laminin alpha4 chain inhibits de novo adipogenesis by modulating the effect of FGF-2 through syndecans. PMID:18067585

Yamashita, Hironobu; Goto, Chie; Tajima, Rie; Koparal, Ayse Tansu; Kobori, Masato; Ohki, Yuji; Shitara, Kenya; Narita, Ryo; Toriyama, Kazuhiro; Torii, Shuhei; Niimi, Tomoaki; Kitagawa, Yasuo

2008-02-01

63

Proteinase-Activated Receptors and Arthritis  

Microsoft Academic Search

\\u000a The novel family of proteinase-activated receptors (PARs) is activated through proteolytic cleavage by serine proteinases.\\u000a This family of G protein-coupled receptors and their activating enzymes are found widely throughout the body. It has been\\u000a known for some time that during arthritic conditions, high levels of serine proteinases are released from joint tissue and\\u000a contribute to joint degradation. Expression of PARs

Fiona A. Russell; Jason J. McDougall

64

Laminin121 – Recombinant expression and interactions with integrins  

PubMed Central

Laminin-121, previously referred as to laminin-3, was expressed recombinantly in human embryonic kidney (HEK) 293 cells by triple transfection of full-length cDNAs encoding mouse laminin ?1, ?2 and ?1 chains. The recombinant laminin-121 was purified using Heparin-Sepharose followed by molecular sieve chromatography and shown to be correctly folded by electron microscopy and circular dichroism (CD). The CD spectra of recombinant laminin-121 were very similar to those of laminin-111 isolated from Engelbreth-Holm Swarm tumor (EHS-laminin) but its Tm value was smaller than EHS-laminin and recombinant lamnin-111 suggesting that the replacement of the ? chain reduced the stability of the coiled-coil structure of laminin-121. Its binding to integrins was compared with EHS-laminin, laminin-3A32 purified from murine epidermal cell line and recombinantly expressed laminins-111, -211 and -221. Laminin-121 showed the highest affinity to ?6?1 and ?7?1 integrins and furthermore, laminin-121 most effectively supported neurite outgrowth. Together, this suggests that the ?2 laminins have higher affinity for integrins than the ?1 laminins. PMID:20566382

Sasaki, Takako; Takagi, Junichi; Giudici, Camilla; Yamada, Yoshihiko; Arikawa-Hirasawa, Eri; Deutzmann, Rainer; Timpl, Rupert; Sonnenberg, Arnoud; Bächinger, Hans Peter; Tonge, David

2010-01-01

65

Notch Receptor Activation Inhibits Oligodendrocyte Differentiation  

Microsoft Academic Search

In this study, we show that oligodendrocyte differentiation is powerfully inhibited by activation of the Notch pathway. Oligodendrocytes and their precursors in the developing rat optic nerve express Notch1 receptors and, at the same time, retinal ganglion cells express Jagged1, a ligand of the Notch1 receptor, along their axons. Jagged1 expression is developmentally regulated, decreasing with a time course that

Songli Wang; Andrei D Sdrulla; Guy diSibio; Gay Bush; Donna Nofziger; Carol Hicks; Gerry Weinmaster; Ben A Barres

1998-01-01

66

Crystal structure of the LG1-3 region of the laminin alpha2 chain.  

PubMed

Laminins are large heterotrimeric glycoproteins with many essential functions in basement membrane assembly and function. Cell adhesion to laminins is mediated by a tandem of five laminin G-like (LG) domains at the C terminus of the alpha chain. Integrin binding requires an intact LG1-3 region, as well as contributions from the coiled coil formed by the alpha, beta, and gamma chains. We have determined the crystal structure at 2.8-A resolution of the LG1-3 region of the laminin alpha2 chain (alpha 2LG1-3). The three LG domains adopt typical beta-sandwich folds, with canonical calcium binding sites in LG1 and LG2. LG2 and LG3 interact through a substantial interface, but LG1 is completely dissociated from the LG2-3 pair. We suggest that the missing gamma chain tail may be required to stabilize the interaction between LG1 and LG2-3 in the biologically active conformation. A global analysis of N-linked glycosylation sites shows that the beta-sandwich faces of LG1 are free of carbohydrate modifications in all five laminin alpha chains, suggesting that these surfaces may harbor the integrin binding site. The alpha 2LG1-3 structure provides the first atomic view of the integrin binding region of laminins. PMID:19553699

Carafoli, Federico; Clout, Naomi J; Hohenester, Erhard

2009-08-21

67

Interdomain movements in metabotropic glutamate receptor activation.  

PubMed

Many cell surface receptors are multimeric proteins, composed of several structural domains, some involved in ligand recognition, whereas others are responsible for signal transduction. In most cases, the mechanism of how ligand interaction in the extracellular domains leads to the activation of effector domains remains largely unknown. Here we examined how the extracellular ligand binding to the venus flytrap (VFT) domains of the dimeric metabotropic glutamate receptors activate the seven transmembrane (7TM) domains responsible for G protein activation. These two domains are interconnected by a cysteine-rich domain (CRD). We show that any of the four disulfide bridges of the CRD are required for the allosteric coupling between the VFT and the 7TM domains. More importantly, we show that a specific association of the two CRDs corresponds to the active state of the receptor. Indeed, a specific crosslinking of the CRDs with intersubunit disulfide bridges leads to fully constitutively active receptors, no longer activated by agonists nor by allosteric modulators. These data demonstrate that intersubunit movement at the level of the CRDs represents a key step in metabotropic glutamate receptor activation. PMID:21896740

Huang, Siluo; Cao, Jianhua; Jiang, Ming; Labesse, Gilles; Liu, Jianfeng; Pin, Jean-Philippe; Rondard, Philippe

2011-09-13

68

Laminin Expression in Adult and Developing Retinae: Evidence of Two Novel CNS Laminins  

Microsoft Academic Search

Components of the extracellular matrix exert myriad effects on tissues throughout the body. In particular, the laminins, a family of heterotrimeric extracellular glycoproteins, have been shown to affect tissue development and integrity in such diverse organs as the kidney, lung, skin, and nervous system. Of these, we have focused on the roles that laminins play in the differentiation and maintenance

Richard T. Libby; Marie-France Champliaud; Thomas Claudepierre; Yin Xu; Erin P. Gibbons; Manuel Koch; Robert E. Burgeson; Dale D. Hunter; William J. Brunken

2000-01-01

69

Endosomal signaling by protease-activated receptors.  

PubMed

Protease-activated receptors (PARs) are a family of G protein-coupled receptors (GPCRs) that are uniquely activated by proteolysis. There are four members of the PAR family including: PAR1, PAR2, PAR3, and PAR4. PARs are expressed primarily in the cells of the vasculature and elicit cellular responses to coagulant and anticoagulant proteases. PAR1 exemplifies the unusual proteolytic mechanism of receptor activation. Thrombin binds to and cleaves the N-terminal exodomain of PAR1, generating a new N-terminus that functions as a tethered ligand. The N-terminal tethered ligand domain of PAR1 binds intramolecularly to the receptor to trigger transmembrane signaling and cannot diffuse away. Similar to other GPCRs, activation of PARs promotes coupling to heterotrimeric G proteins at the plasma membrane. After activation, PARs are rapidly internalized to endosomes and then sorted to lysosomes and degraded. Internalization functions to uncouple PARs from heterotrimeric G proteins at the cell surface. However, recent studies indicate that activated internalized PARs signal from endosomes through the recruitment of ?-arrestins and potentially other pathways. Here, we provide an overview of methods and strategies used to examine endosomal signaling by PARs. PMID:24377935

Grimsey, Neil; Lin, Huilan; Trejo, JoAnn

2014-01-01

70

Endosomal Signaling by Protease-activated Receptors  

PubMed Central

Protease-activated receptors (PARs) are a family of G protein-coupled receptors (GPCRs) that are uniquely activated by proteolysis. There are four members of the PAR family including: PAR1, PAR2, PAR3 and PAR4. PARs are expressed primarily in cells of the vasculature and elicit cellular responses to coagulant and anti-coagulant proteases. PAR1 exemplifies the unusual proteolytic mechanism of receptor activation. Thrombin binds to and cleaves the N-terminal exodomain of PAR1 generating a new N-terminus that functions as a tethered ligand. The N-terminal tethered ligand domain of PAR1 binds intramolecularly to the receptor to trigger transmembrane signaling and cannot diffuse away. Similar to other GPCRs, activation of PARs promotes coupling to heterotrimeric G proteins at the plasma membrane. After activation, PARs are rapidly internalized to endosomes and then sorted to lysosomes and degraded. Internalization functions to uncouple PARs from heterotrimeric G proteins at the cell surface. However, recent studies indicate that activated internalized PARs signal from endosomes through the recruitment of ?-arrestins and potentially other pathways. Here we provide an overview of methods and strategies used to examine endosomal signaling by PARs. PMID:24377935

Grimsey, Neil; Lin, Huilan; Trejo, JoAnn

2014-01-01

71

Nuclear estrogen receptors co-activation mechanisms.  

PubMed

Estrogens play very important role in opening the transcription event, which is a final step of activation of the first order mediators as receptors or channels in the cell wall by information coming from the outside of the cell. For the long time the exact step by step mechanism of cellular transfer of information to the cell nuclei was not known. Currently many new informations are available. Very important seems the step of phosphorylation and therefore desensitization of the target proteins. All peptide kinases, especially serine and threonine, like protein kinases A and C, RAS and MAP kinases, cycline kinases are potential or confirmed biological targets. Except them elements of the transcription complexes like p160.SRC-1, histon acetyltransferase and histon deacetylase, CBP/p300, TRAP/DRIP, NSD1, PPAR?/PGC-1, NCOR1, SMRT, REA were also found useful. Finally estrogens are able to activate other receptors, namely aryl hydrocarbon receptors (AhR) and estrogen receptor related proteins (ERR). It is well known that many types of cancer are related to the direct or indirect excessive activation of nuclear estrogen receptors, therefore their inhibition could be crucial in many estrogen-related cancers. Understanding the interactions in such complexes would help in developing new and better multi-target cures and finding new ligands with better pharmacological and pharmacokinetic properties. PMID:23651307

Skrzypczak, M; Kapka-Skrzypczak, L; Cyranka, M; Treeck, O; Wrobel, A; Matosiuk, D

2013-01-01

72

Laminin-binding integrin alpha 7 beta 1: functional characterization and expression in normal and malignant melanocytes.  

PubMed Central

A novel integrin, alpha 7 beta 1, that specifically binds with high affinity to laminin has been identified on melanoma cells. This complex was purified from both human and murine melanoma cells by laminin-affinity chromatography, and the alpha 7 subunit was recovered after gel electrophoresis. N-terminal amino acid sequence analysis of the alpha 7 subunit from both human and mouse cells verifies that this integrin is distinct from other alpha chains in the beta 1 family, although strikingly similar to the alpha 6 subunit. By using specific proteolytically derived fragments of laminin, it was determined that the alpha 7 beta 1 complex binds selectively to the E8 region, which represents part of the long arm of laminin. In contrast, the receptor failed to bind to the P1 fragment, which contains the intersection of the short arms of laminin. Although the alpha 7 beta 1 complex was commonly expressed in melanoma cells, this integrin was not detected in normal melanocytes, suggesting that alpha 7 expression may be associated with malignant transformation. These results establish the existence of a novel integrin that binds to the E8 domain of laminin and appears to mediate cell adhesion to this ligand. Images PMID:1839357

Kramer, R H; Vu, M P; Cheng, Y F; Ramos, D M; Timpl, R; Waleh, N

1991-01-01

73

Alignment and composition of laminin–polycaprolactone nanofiber blends enhance peripheral nerve regeneration  

PubMed Central

Peripheral nerve transection occurs commonly in traumatic injury, causing deficits distal to the injury site. Conduits for repair currently on the market are hollow tubes; however, they often fail due to slow regeneration over long gaps. To facilitate increased regeneration speed and functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in regeneration. To that end, laminin and laminin–polycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane. In vitro assays established 10% (wt) laminin content is sufficient to retain neurite-promoting effects of laminin. In addition, modified collector plate design to introduce an insulating gap enabled the fabrication of aligned nanofibers. The effects of laminin content and fiber orientation were evaluated in rat tibial nerve defect model. The lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment to assess changes in motor and sensory recovery. Retrograde nerve conduction speed at 6 weeks was significantly faster in animals receiving aligned nanofiber conduits than in those receiving random nanofiber conduits. Animals receiving nanofiber-filled conduits showed some conduction in both anterograde and retrograde directions, whereas in animals receiving hollow conduits, no impulse conduction was detected. Aligned PCL nanofibers significantly improved motor function; aligned laminin blend nanofibers yielded the best sensory function recovery. In both cases, nanofiber-filled conduits resulted in better functional recovery than hollow conduits. These studies provide a firm foundation for the use of natural–synthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits. PMID:22106069

Neal, Rebekah A.; Tholpady, Sunil S.; Foley, Patricia L.; Swami, Nathan; Ogle, Roy C.; Botchwey, Edward A.

2012-01-01

74

Secretion of collagen I and tenascin is modulated by laminin-111 in 3D culture of human adenoid cystic carcinoma cells  

PubMed Central

Adenoid cystic carcinoma is a frequent malignant salivary gland neoplasm with high levels of recurrence and metastasis. This neoplasm expresses prominent extracellular matrix (ECM). We are studying regulatory mechanisms underlying secretion of ECM molecules in adenoid cystic carcinoma. We have previously demonstrated that laminin modulates the phenotype of a human adenoid cystic carcinoma (CAC2) cell line. Thus, this molecule would be a good candidate to regulate secretion of ECM molecules in these cells. Here we analysed the role played by laminin-111 [formerly laminin-1; Aumailley et al. (2005). Matrix Biol. 24, 326] stimulating secretory activity of CAC2 cells. Three-dimensional cultures of cells in laminin-111 (treated) or agarose (controls) were studied by light and electron microscopy. Ultrastructural analysis of CAC2 cells grown within laminin-111 showed pseudocysts filled with secretory-like material. Cells exhibited prominent and dilated endoplasmic reticulum and coated and uncoated vesicles. Ultrastructural findings suggested that laminin-111 induced secretory activity in CAC2 cells. We further investigated this point by light microscopy, immunofluorescence and confocal microscopy. Histochemistry showed periodic acid-Schiff (PAS)-positive diastase-resistant material in CAC2 cells treated by laminin-111. This material could represent laminin-induced secretion of ECM molecules. We searched for collagen I and tenascin in CAC2 cells treated by laminin-111. Confocal microscopy and immunoblot showed that laminin-111 enhanced secretion of collagen I and tenascin in CAC2 cells. We suggest that laminin-111 modulates secretion of collagen I and tenascin in cells derived from human adenoid cystic carcinoma. PMID:18336527

Jaeger, Ruy G; Scarabotto-Neto, Normando; Azambuja, Nilton; Freitas, Vanessa M

2008-01-01

75

A Conformational Intermediate in Glutamate Receptor Activation  

PubMed Central

SUMMARY Ionotropic glutamate receptors (iGluRs) transduce the chemical signal of neurotransmitter release into membrane depolarization at excitatory synapses in the brain. The opening of the transmembrane ion channel of these ligand-gated receptors is driven by conformational transitions that are induced by the association of glutamate molecules to the ligand-binding domains (LBDs). Here, we describe the crystal structure of a GluA2 LBD tetramer in a configuration that involves an ~30° rotation of the LBD dimers relative to the crystal structure of the full-length receptor. The configuration is stabilized by an engineered disulfide crosslink. Biochemical and electrophysiological studies on full-length receptors incorporating either this crosslink or an engineered metal bridge show that this LBD configuration corresponds to an intermediate state of receptor activation. GluA2 activation therefore involves a combination of both intra-LBD (cleft closure) and inter-LBD dimer conformational transitions. Overall, these results provide a comprehensive structural characterization of an iGluR intermediate state. PMID:23931998

Lau, Albert Y.; Salazar, Héctor; Blachowicz, Lydia; Ghisi, Valentina; Plested, Andrew J.R.; Roux, Benoît

2013-01-01

76

Purinergic receptor activation facilitates astrocytic GABAB receptor calcium signalling.  

PubMed

Gamma-aminobutyric acid B receptors (GABABRs) are heterodimeric G-protein coupled receptors, which mediate slow synaptic inhibition in the brain. Emerging evidence suggests astrocytes also express GABABRs, although their physiological significance remains unknown. To begin addressing this issue, we have used imaging and biochemical analysis to examine the role GABABRs play in regulating astrocytic Ca(2+) signalling. Using live imaging of cultured cortical astrocytes loaded with calcium indicator Fluo-4/AM, we found that astrocytic GABABRs are able to induce astrocytic calcium transients only if they are pre-activated by P2 purinoceptors (P2YRs). The GABABR-mediated calcium transients were attenuated by the removal of extracellular calcium. Furthermore, P2YRs enhance the phosphorylation of astrocytic GABABR R2 subunits on both serine 783 (S783) and serine 892 (S892), two phosphorylation sites that are well known to regulate the activity and the cell surface stability of GABABRs. Collectively these results suggest that P2YR mediated signalling is an important determinant of GABABR activity and phosphorylation in astrocytes. This article is part of the Special Issue entitled 'GABAergic Signaling in Health and Disease'. PMID:25261019

Terunuma, Miho; Haydon, Philip G; Pangalos, Menelas N; Moss, Stephen J

2015-01-01

77

Peroxisome proliferator-activated receptors and liver X receptors in epidermal biology  

Microsoft Academic Search

The epidermis is a very active site of lipid metab- olism, and all peroxisome proliferator-activated receptor (PPAR) and liver X receptor (LXR) isoforms are expressed in the epidermis. Activation of PPARa ,- b\\/d ,o r -g or LXRs stimulates keratinocyte differentiation. Additionally, activa- tion of these receptors also improves permeability barrier homeostasis by a number of mechanisms, including stimu- lating

Matthias Schmuth; Yan J. Jiang; Sandrine Dubrac; Peter M. Elias; Kenneth R. Feingold

78

Biased Signaling of Protease-Activated Receptors  

PubMed Central

In addition to their role in protein degradation and digestion, proteases can also function as hormone-like signaling molecules that regulate vital patho-physiological processes, including inflammation, hemostasis, pain, and repair mechanisms. Certain proteases can signal to cells by cleaving protease-activated receptors (PARs), a family of four G protein-coupled receptors. PARs are expressed by almost all cell types, control important physiological and disease-relevant processes, and are an emerging therapeutic target for major diseases. Most information about PAR activation and function derives from studies of a few proteases, for example thrombin in the case of PAR1, PAR3, and PAR4, and trypsin in the case of PAR2 and PAR4. These proteases cleave PARs at established sites with the extracellular N-terminal domains, and expose tethered ligands that stabilize conformations of the cleaved receptors that activate the canonical pathways of G protein- and/or ?-arrestin-dependent signaling. However, a growing number of proteases have been identified that cleave PARs at divergent sites to activate distinct patterns of receptor signaling and trafficking. The capacity of these proteases to trigger distinct signaling pathways is referred to as biased signaling, and can lead to unique patho-physiological outcomes. Given that a different repertoire of proteases are activated in various patho-physiological conditions that may activate PARs by different mechanisms, signaling bias may account for the divergent actions of proteases and PARs. Moreover, therapies that target disease-relevant biased signaling pathways may be more effective and selective approaches for the treatment of protease- and PAR-driven diseases. Thus, rather than mediating the actions of a few proteases, PARs may integrate the biological actions of a wide spectrum of proteases in different patho-physiological conditions. PMID:24860547

Zhao, Peishen; Metcalf, Matthew; Bunnett, Nigel W.

2014-01-01

79

Proteinase-activated receptors (PARs) – focus on receptor-receptor-interactions and their physiological and pathophysiological impact  

PubMed Central

Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects. In this review, we summarize current information about PAR-initiated physical and functional receptor interactions and their physiological and pathological roles. We focus especially on PAR homo- and heterodimerization, transactivation of receptor tyrosine kinases (RTKs) and receptor serine/threonine kinases (RSTKs), communication with other GPCRs, toll-like receptors and NOD-like receptors, ion channel receptors, and on PAR association with cargo receptors. In addition, we discuss the suitability of these receptor interaction mechanisms as targets for modulating PAR signalling in disease. PMID:24215724

2013-01-01

80

Structural requirements of bitter taste receptor activation  

PubMed Central

An important question in taste research is how 25 receptors of the human TAS2R family detect thousands of structurally diverse compounds. An answer to this question may arise from the observation that TAS2Rs in general are broadly tuned to interact with numerous substances. Ultimately, interaction with chemically diverse agonists requires architectures of binding pockets tailored to combine flexibility with selectivity. The present study determines the structure of hTAS2R binding pockets. We focused on a subfamily of closely related hTAS2Rs exhibiting pronounced amino acid sequence identities but unique agonist activation spectra. The generation of chimeric and mutant receptors followed by calcium imaging analyses identified receptor regions and amino acid residues critical for activation of hTAS2R46, -R43, and -R31. We found that the carboxyl-terminal regions of the investigated receptors are crucial for agonist selectivity. Intriguingly, exchanging two residues located in transmembrane domain seven between hTAS2R46, activated by strychnine, and hTAS2R31, activated by aristolochic acid, was sufficient to invert agonist selectivity. Further mutagenesis revealed additional positions involved in agonist interaction. The transfer of functionally relevant amino acids identified in hTAS2R46 to the corresponding positions of hTAS2R43 and -R31 resulted in pharmacological properties indistinguishable from the parental hTAS2R46. In silico modeling of hTAS2R46 allowed us to visualize the putative mode of interaction between agonists and hTAS2Rs. Detailed structure-function analyses of hTAS2Rs may ultimately pave the way for the development of specific antagonists urgently needed for more sophisticated analyses of human bitter taste perception. PMID:20534469

Brockhoff, Anne; Behrens, Maik; Niv, Masha Y.; Meyerhof, Wolfgang

2010-01-01

81

Serum laminin, hydrocarbon exposure, and glomerular damage.  

PubMed

It has been postulated that occupational exposure to hydrocarbons may damage the kidney and lead to glomerulonephritis and chronic renal failure. As laminin is a ubiquitous basement membrane component that seems to play a central part in the structure and function of basement membranes and as the normal renal filtration process is highly dependent on an intact glomerular basement membrane, the serum laminin concentration was examined in a population of workers exposed to hydrocarbons. The hydrocarbon exposure was assessed by exposure surrogates (exposure duration and exposure score). An interaction between occupational exposure to hydrocarbons and hypertension increased the laminin concentration whereas the laminin concentration decreased in workers exposed for a long time probably because of a selection effect. In a subgroup of printers exposed to toluene whose hippuric acid excretion had been recorded for several years this interaction was confirmed when the hippuric acid excretion was substituted for the other exposure indices. In the exposed group, the age-related decline in creatinine clearance was accelerated. These results seem to confirm that occupational exposure to hydrocarbons is a non-specific factor that may promote a deterioration of renal function. PMID:8280641

Hotz, P; Thielemans, N; Bernard, A; Gutzwiller, F; Lauwerys, R

1993-12-01

82

Serum laminin, hydrocarbon exposure, and glomerular damage.  

PubMed Central

It has been postulated that occupational exposure to hydrocarbons may damage the kidney and lead to glomerulonephritis and chronic renal failure. As laminin is a ubiquitous basement membrane component that seems to play a central part in the structure and function of basement membranes and as the normal renal filtration process is highly dependent on an intact glomerular basement membrane, the serum laminin concentration was examined in a population of workers exposed to hydrocarbons. The hydrocarbon exposure was assessed by exposure surrogates (exposure duration and exposure score). An interaction between occupational exposure to hydrocarbons and hypertension increased the laminin concentration whereas the laminin concentration decreased in workers exposed for a long time probably because of a selection effect. In a subgroup of printers exposed to toluene whose hippuric acid excretion had been recorded for several years this interaction was confirmed when the hippuric acid excretion was substituted for the other exposure indices. In the exposed group, the age-related decline in creatinine clearance was accelerated. These results seem to confirm that occupational exposure to hydrocarbons is a non-specific factor that may promote a deterioration of renal function. PMID:8280641

Hotz, P; Thielemans, N; Bernard, A; Gutzwiller, F; Lauwerys, R

1993-01-01

83

Laminin-alpha6beta1 integrin interaction enhances survival and proliferation and modulates steroidogenesis of ovine granulosa cells  

Microsoft Academic Search

This study aimed to determine the physiological role of laminin (LN) and its receptor, 61 integrin, in controlling the functions of granulosa cells (GC) during follicular development in sheep ovary. Immunohistochemistry experiments showed the presence of increasing levels of LN (P<0·0001), and high levels of mature 61 integrin in GC layers of healthy antral follicles during the follicular and the

F Le Bellego; C Pisselet; C Huet; P Monget; D Monniaux

2002-01-01

84

Myofibrillar and cytoskeletal assembly in neonatal rat cardiac myocytes cultured on laminin and collagen  

Microsoft Academic Search

Neonatal rat cardiomyocytes were cultured on extracellular matrix components laminin and collagens I+III to examine effects of extracellular matrix on the assembly of cytoskeletal proteins during myofibrillogenesis. Myofibril assembly was visualized by immunofluorescence of marker proteins for myofibrils (f-actin for I bands and a-actinin for Z bands), focal adhesions (vinculin), and transmembrane extracellular matrix receptors (ß1 integrin) as cells spread

Lula L. Hilenski; Louis Terracio; Thomas K. Borg

1991-01-01

85

Peroxisome proliferator-activated receptors for hypertension  

PubMed Central

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily, which is composed of four members encoded by distinct genes (?, ?, ?, and ?). The genes undergo transactivation or transrepression under specific mechanisms that lead to the induction or repression of target gene expression. As is the case with other nuclear receptors, all four PPAR isoforms contain five or six structural regions in four functional domains; namely, A/B, C, D, and E/F. PPARs have many functions, particularly functions involving control of vascular tone, inflammation, and energy homeostasis, and are, therefore, important targets for hypertension, obesity, obesity-induced inflammation, and metabolic syndrome in general. Hence, PPARs also represent drug targets, and PPAR? and PPAR? agonists are used clinically in the treatment of dyslipidemia and type 2 diabetes mellitus, respectively. Because of their pleiotropic effects, they have been identified as active in a number of diseases and are targets for the development of a broad range of therapies for a variety of diseases. It is likely that the range of PPAR? agonist therapeutic actions will result in novel approaches to lifestyle and other diseases. The combination of PPARs with reagents or with other cardiovascular drugs, such as diuretics and angiotensin II receptor blockers, should be studied. This article provides a review of PPAR isoform characteristics, a discussion of progress in our understanding of the biological actions of PPARs, and a summary of PPAR agonist development for patient management. We also include a summary of the experimental and clinical evidence obtained from animal studies and clinical trials conducted to evaluate the usefulness and effectiveness of PPAR agonists in the treatment of lifestyle-related diseases. PMID:25228953

Usuda, Daisuke; Kanda, Tsugiyasu

2014-01-01

86

The role of fibronectin and laminin in development and migration of the avian Wolffian duct with reference to somitogenesis.  

PubMed

It has been suggested that matrix molecules like fibronectin and laminin influence the differentiation and migration of embryonic cells. We investigated the role of these two glycoproteins in somitogenesis as well as in the differentiation and migration of the avian Wolffian (pronephric and mesonephric) duct. At first, we described essential steps in the development of these two organ anlagen by light microscopy, SEM and TEM. To localize fibronectin and laminin more exactly in the actual stages, we used the indirect immunoperoxidase reaction at the light microscopic level and the peroxidase-antiperoxidase technique at the ultrastructural level. Fibronectin was found at the surface of the unsegmented paraxial mesoderm, increasing in the cranial direction, and in the basal laminae of somites and Wolffian duct. The mesenchymal tip of the duct contains a moderate amount of fibronectin. In the two investigated organ anlagen, laminin was found mainly in the basal laminae. The role of fibronectin and laminin was investigated further by using synthetic peptides that mimic the main cell binding domain of either fibronectin or laminin, and that competitively inhibit their cell surface receptors. Thus, the pentapeptides GRGDS, YIGSR, and for control, SHLVE were micro-injected under the ectoderm of 2-day-old embryos. After treatment with GRDS, the Wolffian duct and the segmental plate are more compact. The rounded cells exhibit only short processes and narrow intercellular spaces. At the side of injection the duct shows a delay in migration. After treatment with YIGSR the Wolffian duct migrated laterally over the somatopleure. The basal laminae seem to be incomplete. SHLVE had no effect. Our results suggest that fibronectin is a prerequisite for the migration of the Wolffian duct, and that laminin probably plays a role in guiding the duct. The epithelialization during somitogenesis and differentiation of the duct is a more complex process involving also fibronectin and laminin. PMID:1867390

Jacob, M; Christ, B; Jacob, H J; Poelmann, R E

1991-01-01

87

Activating Fc ? receptors contribute to the antitumor activities of immunoregulatory receptor-targeting antibodies  

PubMed Central

Fc ? receptor (Fc?R) coengagement can facilitate antibody-mediated receptor activation in target cells. In particular, agonistic antibodies that target tumor necrosis factor receptor (TNFR) family members have shown dependence on expression of the inhibitory Fc?R, Fc?RIIB. It remains unclear if engagement of Fc?RIIB also extends to the activities of antibodies targeting immunoregulatory TNFRs expressed by T cells. We have explored the requirement for activating and inhibitory Fc?Rs for the antitumor effects of antibodies targeting the TNFR glucocorticoid-induced TNFR-related protein (GITR; TNFRSF18; CD357) expressed on activated and regulatory T cells (T reg cells). We found that although Fc?RIIB was dispensable for the in vivo efficacy of anti-GITR antibodies, in contrast, activating Fc?Rs were essential. Surprisingly, the dependence on activating Fc?Rs extended to an antibody targeting the non-TNFR receptor CTLA-4 (CD152) that acts as a negative regulator of T cell immunity. We define a common mechanism that correlated with tumor efficacy, whereby antibodies that coengaged activating Fc?Rs expressed by tumor-associated leukocytes facilitated the selective elimination of intratumoral T cell populations, particularly T reg cells. These findings may have broad implications for antibody engineering efforts aimed at enhancing the therapeutic activity of immunomodulatory antibodies. PMID:23897982

Bulliard, Yannick; Jolicoeur, Rose; Windman, Maurice; Rue, Sarah M.; Ettenberg, Seth; Knee, Deborah A.; Wilson, Nicholas S.; Dranoff, Glenn

2013-01-01

88

The role of laminins in basement membrane function  

PubMed Central

Laminins are a family of multifunctional macromolecules, ubiquitous in basement membranes, and represent the most abundant structural noncollagenous glycoproteins of these highly specialised extracellular matrices. Their discovery started with the difficult task of isolating molecules produced by cultivated cells or extracted from tissues. The development of molecular biology techniques has facilitated and accelerated the identification and the characterisation of new laminin variants making it feasible to identify full-length polypeptides which have not been purified. Further, genetically engineered laminin fragments can be generated for studies of their structure-function relationship, permitting the demonstration that laminins are involved in multiple interactions with themselves, with other components of the basal lamina, and with cells. It endows laminins with a central role in the formation, the architecture, and the stability of basement membranes. In addition, laminins may both separate and connect different tissues, i.e. the parenchymal and the interstitial connective tissues. Laminins also provide adjacent cells with a mechanical scaffold and biological information either directly by interacting with cell surface components, or indirectly by trapping growth factors. In doing so they trigger and control cellular functions. Recently, the structural and biological diversity of the laminins has started to be elucidated by gene targeting and by the identification of laminin defects in acquired or inherited human diseases. The consequent phenotypes highlight the pivotal role of laminins in determining heterogeneity in basement membrane functions. PMID:9758133

AUMAILLEY, MONIQUE; SMYTH, NEIL

1998-01-01

89

Phorbol esters enhance attachment of NIH/3T3 cells to laminin and type IV collagen substrates  

SciTech Connect

The effect of phorbol esters on the adhesive properties of NIH/3T3 mouse fibroblasts was investigated using plastic substrates precoated with the extracellular matrix proteins fibronectin, collagen, and laminin. Treatment with phorbol 12-myristate 13-acetate (PMA) enhanced NIH/3T3 cell attachment to laminin and type IV collagen substrates but had little or no effect on attachment to fibronectin and type I collagen substrates. The effect of PMA in enhancing cell attachment to laminin and type IV collagen substrates was dose dependent between 10{sup {minus}9} and 10{sup {minus}7} M. PMA was effective as early as 30 min; the effect reached a maximum at 2 h and decreased gradually. Phorbol 12, 13-dibenzoate and phorbol 12, 13-diacetate were effective but to a lesser extent and phorbol 12-myristate and phorbol 13-acetate showed little or no effect. These results suggest that PMA may enhance NIH/3T3 cell adhesion through effects on laminin and type IV collagen receptors. Retinoic acid, which itself requires at least 6 h to show an effect on attachment, did not have any effect on cell attachment in 2 h and, if anything, slightly inhibited PMA-enhanced cell attachment to laminin and type IV collagen substrates.

Kato, Shigemi; Ben, T.L.; De Luca, L.M. (National Institutes of Health, Bethesda, MD (USA))

1988-11-01

90

Opioid receptor random mutagenesis reveals a mechanism for G protein–coupled receptor activation  

Microsoft Academic Search

The high resolution structure of rhodopsin has greatly enhanced current understanding of G protein–coupled receptor (GPCR) structure in the off-state, but the activation process remains to be clarified. We investigated molecular mechanisms of ?-opioid receptor activation without a preconceived structural hypothesis. Using random mutagenesis of the entire receptor, we identified 30 activating point mutations. Three-dimensional modeling revealed an activation path

Fabien M Décaillot; Katia Befort; Dominique Filliol; ShiYi Yue; Philippe Walker; Brigitte L Kieffer

2003-01-01

91

Targeting proteinase-activated receptors: therapeutic potential and challenges  

Microsoft Academic Search

Proteinase-activated receptors (PARs), a family of four seven-transmembrane G protein-coupled receptors, act as targets for signalling by various proteolytic enzymes. PARs are characterized by a unique activation mechanism involving the proteolytic unmasking of a tethered ligand that stimulates the receptor. Given the emerging roles of these receptors in cancer as well as in disorders of the cardiovascular, musculoskeletal, gastrointestinal, respiratory

Farshid Noorbakhsh; Kathryn DeFea; Rithwik Ramachandran; Morley D. Hollenberg

2012-01-01

92

Targeting of polymeric nanoparticles to lung metastases by surface-attachment of YIGSR peptide from laminin.  

PubMed

Effective therapy for disseminated metastatic cancer is currently impossible because of low drug accumulation in target sites. Here, we aimed to enhance nanoparticle (NP) targeting to lung melanoma metastases via interactions with the laminin receptor, whose expression is upregulated in metastatic cells. To enable NP follow-up and a framework for targeting ligand binding, Estapor(®) fluorescent NPs (299 ± 6 nm in diameter) with surface carboxylic groups were employed and the laminin receptor binding peptide (YIGSR) was attached to their surface to facilitate targeting. In vitro uptake studies performed under medium flow conditions revealed that the uptake of YIGSR-attached NPs by monolayers of B16 melanoma cells was 2-fold higher compared to the uptake of scrambled peptide-NPs. In cultures of healthy lung cells, the uptake of YIGSR-NPs was low and similar to the uptake of scrambled peptide-NPs. Competition assays using cultured B16 melanoma cells pre-incubated with soluble laminin confirmed that the entry of the YIGSR-modified NPs was mediated via interaction with the laminin receptor. Following intravenous (i.v.) administration into B16 melanoma tumor-bearing mice, targeting of the tumor by the YIGSR-NPs was up to five-fold higher than the scrambled peptide-NPs, with no heart, liver or lung tropism. In an experimental lung metastases model, following i.v. administration the YIGSR-NPs targeted the cancerous metastatic cells in lungs, with nearly no targeting to the healthy lung cells. Collectively, the data indicate that YIGSR-targeted NPs have a potential to be used for systemic delivery of chemotherapeutic drugs for the treatment of metastatic lung cancer. PMID:20889205

Sarfati, Gadi; Dvir, Tal; Elkabets, Moshe; Apte, Ron N; Cohen, Smadar

2011-01-01

93

Adhesion of membranes via actively switched receptors  

E-print Network

We consider a theoretical model for membranes with adhesive receptors, or stickers, that are actively switched between two conformational states. In their 'on'-state, the stickers bind to ligands in an apposing membrane, whereas they do not interact with the ligands in their 'off'-state. We show that the adhesiveness of the membranes depends sensitively on the rates of the conformational switching process. This dependence is reflected in a resonance at intermediate switching rates, which can lead to large membrane separations and unbinding. Our results may provide insights into novel mechanisms for the controlled adhesion of biological or biomimetic membranes.

Bartosz Rozycki; Reinhard Lipowsky; Thomas R. Weikl

2005-12-20

94

Adhesion, growth, and matrix production by fibroblasts on laminin substrates  

Microsoft Academic Search

Human embryonic skin fibroblasts have been shown to attach and spread on laminin substrates in the absence of protein synthesis and presence of fibronectin-depleted serum and anti-fibronectin antibodies. Rates of attachment and the type of spreading are virtually identical on fibronectin and laminin-coated substrates with the development of microfilament bundles and focal adhesions. Antibodies to laminin, but not fibronectin, will

JOHN R. COUCHMAN; MAGNUS HOOK; DAVID A. REES; RUPERT TIMPL

1983-01-01

95

Identification of Gene Markers for Activation of the Nuclear Receptor Pregnane X Receptor  

EPA Science Inventory

Many environmentally-relevant chemicals and drugs activate the nuclear receptor pregnane X receptor (PXR). Activation of PXR in the mouse liver can lead to increases in liver weight in part through increased hepatocyte replication similar to chemicals that activate other nuclear ...

96

Model for growth hormone receptor activation based on subunit rotation within a receptor dimer  

SciTech Connect

Growth hormone is believed to activate the growth hormone receptor (GHR) by dimerizing two identical receptor subunits, leading to activation of JAK2 kinase associated with the cytoplasmic domain. However, we have reported previously that dimerization alone is insufficient to activate full-length GHR. By comparing the crystal structure of the liganded and unliganded human GHR extracellular domain, we show here that there is no substantial change in its conformation on ligand binding. However, the receptor can be activated by rotation without ligand by inserting a defined number of alanine residues within the transmembrane domain. Fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET) and coimmunoprecipitation studies suggest that receptor subunits undergo specific transmembrane interactions independent of hormone binding. We propose an activation mechanism involving a relative rotation of subunits within a dimeric receptor as a result of asymmetric placement of the receptor-binding sites on the ligand.

Brown, Richard J.; Adams, Julian J.; Pelekanos, Rebecca A.; Wan, Yu; McKinstry, William J.; Palethorpe, Kathryn; Seeber, Ruth M.; Monks, Thea A.; Eidne, Karin A.; Parker, Michael W.; Waters, Michael J. (UWA); (St. Vincent); (Queensland)

2010-07-13

97

The molecular mechanism of transcriptional activation by the peroxisome proliferator activated-receptor alpha  

Microsoft Academic Search

The peroxisome proliferator-activated receptor (PPAR?) is a member of the nuclear receptor superfamily, a growing class of transcriptional activators. Many of these proteins, including PPAR?, function as intracellular receptors for hormones and upon the binding of agonist, activate the transcription of target genes. PPAR? is an integral regulator of fatty acid metabolism and as such is activated by fatty acids

Kenji Sean Miyata

1999-01-01

98

Endomorphins fully activate a cloned human mu opioid receptor  

Microsoft Academic Search

Endomorphins were recently identified as endogenous ligands with high selectivity for mu opioid receptors. We have characterized the ability of endomorphins to bind to and functionally activate the cloned human mu opioid receptor. Both endomorphin-1 and endomorphin-2 exhibited binding selectivity for the mu opioid receptor over the delta and kappa opioid receptors. Both agonists inhibited forskolin-stimulated increase of cAMP in

Jianhua Gong; Judith A Strong; Shengwen Zhang; Xia Yue; Robert N DeHaven; Jeffrey D Daubert; Joel A Cassel; Guangling Yu; Erik Mansson; Lei Yu

1998-01-01

99

Stimulation of peroxisome proliferator-activated receptor ? inhibits estrogen receptor ? transcriptional activity in endometrial carcinoma cells.  

PubMed

Peroxisome proliferator-activated receptor ? (PPAR?) and estrogen receptor (ER) belong to a family of nuclear hormone receptors that have been demonstrated to affect each other's transcriptional activity. At present, little is known regarding the effect of PPAR? on ER-mediated transcriptional activity in endometrial carcinoma. In the present study, we aimed to demonstrate the correlation between PPAR? and ER in endometrial carcinoma and to elucidate the biological effects of abnormal expression of PPAR? on endometrial carcinoma cell lines. Immunohistochemical and western blotting methods were used to detect the expression of PPAR?, ER? and ER? in normal and malignant endometrium. Next, we performed transient transfection to assess the interaction between PPAR? and ER in vitro. Furthermore, we examined cell migration, invasion and proliferation as a biological counterpart. PPAR? and ER? expression levels were significantly associated with pathological grade and clinical stage in endometrial carcinoma (P<0.05). Pearson correlation analysis revealed that PPAR? expression was positively correlated with ER? expression (P<0.05). Using KLE and ER?-positive cells (ECC-1), we demonstrated that the PPAR? regulation of ER expression occurred predominantly through ER?. Moreover, our findings suggest that PPAR? activation inhibited the migration, invasion and proliferation of endometrial carcinoma cells; ECC-1 cells were more sensitive to this inhibition. The present study demonstrated that PPAR? activation inhibited ER? expression in ER?-positive endometrial carcinoma cell lines. This crosstalk may facilitate the development of novel therapeutic methods targeting PPAR? in endometrial carcinoma treatment, particularly ER?-positive carcinomas. PMID:25592200

Zhang, Guiyu; Hou, Xinxin; Gao, Shuhong

2015-03-01

100

Fatty Acids and Retinoids Control Lipid Metabolism through Activation of Peroxisome Proliferator-Activated Receptor-Retinoid X Receptor Heterodimers  

Microsoft Academic Search

The nuclear hormone receptors called PPARs (peroxisome proliferator-activated receptors alpha, beta, and gamma) regulate the peroxisomal beta-oxidation of fatty acids by induction of the acyl-CoA oxidase gene that encodes the rate-limiting enzyme of the pathway. Gel retardation and cotransfection assays revealed that PPARalpha heterodimerizes with retinoid X receptor beta (RXRbeta RXR is the receptor for 9-cis-retinoic acid) and that the

Hansjorg Keller; Christine Dreyer; Jeffrey Medin; Abderrahim Mahfoudi; Keiko Ozato; Walter Wahli

1993-01-01

101

Activities of mixed NOP and ?-opioid receptor ligands  

PubMed Central

Background and purpose: Compounds that activate both NOP and ?-opioid receptors might be useful as analgesics and drug abuse medications. Studies were carried out to better understand the biological activity of such compounds. Experimental approach: Binding affinities were determined on membranes from cells transfected with NOP and opioid receptors. Functional activity was determined by [35S]GTP?S binding on cell membranes and using the mouse vas deferens preparation in vitro and the tail flick antinociception assay in vivo. Key results: Compounds ranged in affinity from SR14150, 20-fold selective for NOP receptors, to buprenorphine, 50-fold selective for ?-opioid receptors. In the [35S]GTP?S assay, SR compounds ranged from full agonist to antagonist at NOP receptors and most were partial agonists at ?-opioid receptors. Buprenorphine was a low efficacy partial agonist at ?-opioid receptors, but did not stimulate [35S]GTP?S binding through NOP. In the mouse vas deferens, each compound, except for SR16430, inhibited electrically induced contractions. In each case, except for N/OFQ itself, the inhibition was due to ?-opioid receptor activation, as determined by equivalent results in NOP receptor knockout tissues. SR14150 showed antinociceptive activity in the tail flick test, which was reversed by the opioid antagonist naloxone. Conclusions and implications: Compounds that bind to both ?-opioid and NOP receptors have antinociceptive activity but the relative contribution of each receptor is unclear. These experiments help characterize compounds that bind to both receptors, to better understand the mechanism behind their biological activities, and identify new pharmacological tools to characterize NOP and opioid receptors. PMID:18059322

Spagnolo, B; Calo, G; Polgar, W E; Jiang, F; Olsen, C M; Berzetei-Gurske, I; Khroyan, T V; Husbands, S M; Lewis, J W; Toll, L; Zaveri, N T

2007-01-01

102

Sustained activation of STAT5 is essential for chromatin remodeling and maintenance of mammary-specific function  

SciTech Connect

Epithelial cells, once dissociated and placed in two-dimensional (2D) cultures, rapidly lose tissue-specific functions. We showed previously that in addition to prolactin, signaling by laminin-111 was necessary to restore functional differentiation of mammary epithelia. Here, we elucidate two additional aspects of laminin-111 action. We show that in 2D cultures, the prolactin receptor is basolaterally localized and physically segregated from its apically placed ligand. Detachment of the cells exposes the receptor to ligation by prolactin leading to signal transducers and activators of transcription protein 5 (STAT5) activation, but only transiently and not sufficiently for induction of milk protein expression. We show that laminin-111 reorganizes mammary cells into polarized acini, allowing both the exposure of the prolactin receptor and sustained activation of STAT5. The use of constitutively active STAT5 constructs showed that the latter is necessary and sufficient for chromatin reorganization and {beta}-casein transcription. These results underscore the crucial role of continuous laminin signaling and polarized tissue architecture in maintenance of transcription factor activation, chromatin organization, and tissue-specific gene expression.

Xu, Ren; Nelson, Celeste M.; Muschler, John L.; Veiseh, Mandana; Vonderhaar, Barbara K.; Bissell, Mina J.

2009-06-03

103

Immunohistochemical analysis of laminin expression in adenoid cystic carcinoma  

PubMed Central

Background and Objectives: This study aims at the observation of the immunohistochemical expression of laminin in adenoid cystic carcinoma (ACC) of salivary gland origin and to analyze the distribution of laminin in various components of the tumor and correlate the expression of laminin with the growth and differentiation of the tumor. Materials and Methods: Thirty cases of ACC were subjected to immunohistochemical study using polyclonal antihuman laminin primary antibody, distribution of laminin in each case of ACC was observed in the following areas: Intracellularly, inner borders of the pseudocystic spaces, within the lumen of the pseudocysts, around the tumor islands and in the intervening stroma. Results: Laminin positivity was observed in the inner aspect of the pseudocystic spaces in 15 cases, within the lumen of pseudocystic spaces in 22 cases, in the intervening stroma in 20 cases, bordering the tumor islands in 16 cases and intracellularly in 4 cases. Interpretation and Conclusion: Based on these observations, it can be assumed that laminin plays a major role in proliferation of the tumor cells and in pseudocyst formation. Thus, laminin might play a significant role in the growth and differentiation of ACC and also help in assessing the prognosis of the tumor. PMID:25364175

Anupriya, S; Mahesh, Pushpalatha; Sharada, P; Swaminathan, Uma; Nagamalini, BR; Hosthor, Sreelatha S

2014-01-01

104

Laminins affect T cell trafficking and allograft fate  

PubMed Central

Lymph nodes (LNs) are integral sites for the generation of immune tolerance, migration of CD4+ T cells, and induction of Tregs. Despite the importance of LNs in regulation of inflammatory responses, the LN-specific factors that regulate T cell migration and the precise LN structural domains in which differentiation occurs remain undefined. Using intravital and fluorescent microscopy, we found that alloreactive T cells traffic distinctly into the tolerant LN and colocalize in exclusive regions with alloantigen-presenting cells, a process required for Treg induction. Extracellular matrix proteins, including those of the laminin family, formed regions within the LN that were permissive for colocalization of alloantigen-presenting cells, alloreactive T cells, and Tregs. We identified unique expression patterns of laminin proteins in high endothelial venule basement membranes and the cortical ridge that correlated with alloantigen-specific immunity or immune tolerance. The ratio of laminin ?4 to laminin ?5 was greater in domains within tolerant LNs, compared with immune LNs, and blocking laminin ?4 function or inducing laminin ?5 overexpression disrupted T cell and DC localization and transmigration through tolerant LNs. Furthermore, reducing ?4 laminin circumvented tolerance induction and induced cardiac allograft inflammation and rejection in murine models. This work identifies laminins as potential targets for immune modulation. PMID:24691446

Warren, Kristi J.; Iwami, Daiki; Harris, Donald G.; Bromberg, Jonathan S.; Burrell, Bryna E.

2014-01-01

105

Modelling of the activation of G-protein coupled receptors: drug free constitutive receptor activity  

Microsoft Academic Search

G-protein coupled receptors (GPCRs) form a crucial component of approximately 80% of hormone pathways. In this paper, the\\u000a most popular mechanism for activation of GPCRs—the shuttling mechanism—is modelled mathematically. An asymptotic analysis\\u000a of this model clarifies the dynamics of the system in the absence of drug, in particular which reactions dominate during the\\u000a different timescales. Equilibrium analysis of the model

P. J. Woodroffe; L. J. Bridge; J. R. King; C. Y. Chen; S. J. Hill

2010-01-01

106

Cell death sensitization of leukemia cells by opioid receptor activation.  

PubMed

Cyclic AMP (cAMP) regulates a number of cellular processes and modulates cell death induction. cAMP levels are altered upon stimulation of specific G-protein-coupled receptors inhibiting or activating adenylyl cyclases. Opioid receptor stimulation can activate inhibitory Gi-proteins which in turn block adenylyl cyclase activity reducing cAMP. Opioids such as D,L-methadone induce cell death in leukemia cells. However, the mechanism how opioids trigger apoptosis and activate caspases in leukemia cells is not understood. In this study, we demonstrate that downregulation of cAMP induced by opioid receptor activation using the opioid D,L-methadone kills and sensitizes leukemia cells for doxorubicin treatment. Enhancing cAMP levels by blocking opioid-receptor signaling strongly reduced D,L-methadone-induced apoptosis, caspase activation and doxorubicin-sensitivity. Induction of cell death in leukemia cells by activation of opioid receptors using the opioid D,L-methadone depends on critical levels of opioid receptor expression on the cell surface. Doxorubicin increased opioid receptor expression in leukemia cells. In addition, the opioid D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux in leukemia cells, suggesting that the opioid D,L-methadone as well as doxorubicin mutually increase their cytotoxic potential. Furthermore, we found that opioid receptor activation using D,L-methadone alone or in addition to doxorubicin inhibits tumor growth significantly in vivo. These results demonstrate that opioid receptor activation via triggering the downregulation of cAMP induces apoptosis, activates caspases and sensitizes leukemia cells for doxorubicin treatment. Hence, opioid receptor activation seems to be a promising strategy to improve anticancer therapies. PMID:23633472

Friesen, Claudia; Roscher, Mareike; Hormann, Inis; Fichtner, Iduna; Alt, Andreas; Hilger, Ralf A; Debatin, Klaus-Michael; Miltner, Erich

2013-05-01

107

The Effect of Laminin-1-Doped Nanoroughened Implant Surfaces: Gene Expression and Morphological Evaluation  

PubMed Central

Aim. This study aimed to observe the morphological and molecular effect of laminin-1 doping to nanostructured implant surfaces in a rabbit model. Materials and Methods. Nanostructured implants were coated with laminin-1 (test; dilution, 100??g/mL) and inserted into the rabbit tibiae. Noncoated implants were used as controls. After 2 weeks of healing, the implants were removed and subjected to morphological analysis using scanning electron microscopy (SEM) and gene expression analysis using the real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Results. SEM revealed bony tissue attachment for both control and test implants. Real-time RT-PCR analysis showed that the expression of osteoblast markers RUNX-2, osteocalcin, alkaline phosphatase, and collagen I was higher (1.62-fold, 1.53-fold, 1.97-fold, and 1.04-fold, resp.) for the implants modified by laminin-1 relative to the control. All osteoclast markers investigated in the study presented higher expression on the test implants than controls as follows: tartrate-resistant acid phosphatase (1.67-fold), calcitonin receptor (1.35-fold), and ATPase (1.25-fold). The test implants demonstrated higher expression of inflammatory markers interleukin-10 (1.53-fold) and tumour necrosis factor-? (1.61-fold) relative to controls. Conclusion. The protein-doped surface showed higher gene expression of typical genes involved in the osseointegration cascade than the control surface. PMID:23304151

Schwartz-Filho, Humberto Osvaldo; Bougas, Kostas; Coelho, Paulo G.; Xue, Ying; Hayashi, Mariko; Faeda, Rafael Silveira; Marcantonio, Rosemary Adriana Chiérici; Ono, Daisuke; Kobayashi, Fumio; Mustafa, Kamal; Wennerberg, Ann; Jimbo, Ryo

2012-01-01

108

An adhesome comprising laminin, dystroglycan and myosin IIA is required during notochord development in Xenopus laevis.  

PubMed

Dystroglycan (Dg) is a transmembrane receptor for laminin that must be expressed at the right time and place in order to be involved in notochord morphogenesis. The function of Dg was examined in Xenopus laevis embryos by knockdown of Dg and overexpression and replacement of the endogenous Dg with a mutated form of the protein. This analysis revealed that Dg is required for correct laminin assembly, for cell polarization during mediolateral intercalation and for proper differentiation of vacuoles. Using mutations in the cytoplasmic domain, we identified two sites that are involved in cell polarization and are required for mediolateral cell intercalation, and a site that is required for vacuolation. Furthermore, using a proteomic analysis, the cytoskeletal non-muscle myosin IIA has been identified for the first time as a molecular link between the Dg-cytoplasmic domain and cortical actin. The data allowed us to identify the adhesome laminin-Dg-myosin IIA as being required to maintain the cortical actin cytoskeleton network during vacuolation, which is crucial to maintain the shape of notochordal cells. PMID:25359726

Buisson, Nicolas; Sirour, Cathy; Moreau, Nicole; Denker, Elsa; Le Bouffant, Ronan; Goullancourt, Aline; Darribère, Thierry; Bello, Valérie

2014-12-01

109

Combinatorial Fibronectin and Laminin Signaling Promote Highly Efficient Cardiac Differentiation of Human Embryonic Stem Cells  

PubMed Central

Abstract Cardiomyocytes (CMs) differentiated from human embryonic stem cells (hESCs) are a promising and potentially unlimited cell source for myocardial repair and regeneration. Recently, multiple methodologies—primarily based on the optimization of growth factors—have been described for efficient cardiac differentiation of hESCs. However, the role of extracellular matrix (ECM) signaling in CM differentiation has not yet been explored fully. This study examined the role of ECM signaling in the efficient generation of CMs from both H7 and H9 ESCs. The hESCs were differentiated on ECM substrates composed of a range of fibronectin (FN) and laminin (LN) ratios and gelatin and evaluated by the fluorescence activated cell scanning (FACS) analysis on day 14. Of the ECM substrates examined, the 70:30 FN:LN reproducibly generated the greatest numbers of CMs from both hESC lines. Moreover, the LN receptor integrin ?4 (ITGB4) and FN receptor integrin ?5 (ITGB5) genes, jointly with increased phosphorylated focal adhension kinase and phosphorylated extracellular signal-regulated kinases (p-ERKs), were up-regulated over 13-fold in H7 and H9 cultured on 70:30 FN:LN compared with gelatin. Blocking studies confirmed the role of all these molecules in CM specification, suggesting that the 70:30 FN:LN ECM promotes highly efficient differentiation of CMs through the integrin-mediated MEK/ERK signaling pathway. Lastly, the data suggest that FN:LN-induced signaling utilizes direct cell-to-cell signaling from distinct ITGB4+ and ITGB5+ cells. PMID:25126479

Sa, Silin; Wong, Lian

2014-01-01

110

Constitutive Activity of the Androgen Receptor  

PubMed Central

Prostate cancer (PCa) is the most frequently diagnosed cancer in the United States. The androgen receptor (AR) signaling axis is central to all stages of PCa pathophysiology and serves as the main target for endocrine-based therapy. The most advanced stage of the disease, castration resistant prostate cancer (CRPC), is presently incurable and accounts for most PCa mortality. In this review, we highlight the mechanisms by which the AR signaling axis can bypass endocrine-targeted therapies and drive progression of CRPC. These mechanisms include alterations in growth factor, cytokine, and inflammatory signaling pathways, altered expression or activity of transcriptional co-regulators, AR point mutations, and AR gene amplification leading to AR protein overexpression. Additionally, we will discuss the mechanisms underlying the synthesis of constitutively active AR splice variants (AR-Vs) lacking the COOH-terminal ligand binding domain, as well as the role and regulation of AR-Vs in supporting therapeutic resistance in CRPC. Finally, we summarize the ongoing development of inhibitors targeting discrete AR functional domains as well as the status of new biomarkers for monitoring the AR signaling axis in patients. PMID:24931201

Chan, Siu Chiu; Dehm, Scott M.

2014-01-01

111

The Orphan Nuclear Receptor TR4 Is a Vitamin A-activated Nuclear Receptor  

SciTech Connect

Testicular receptors 2 and 4 (TR2/4) constitute a subgroup of orphan nuclear receptors that play important roles in spermatogenesis, lipid and lipoprotein regulation, and the development of the central nervous system. Currently, little is known about the structural features and the ligand regulation of these receptors. Here we report the crystal structure of the ligand-free TR4 ligand binding domain, which reveals an autorepressed conformation. The ligand binding pocket of TR4 is filled by the C-terminal half of helix 10, and the cofactor binding site is occupied by the AF-2 helix, thus preventing ligand-independent activation of the receptor. However, TR4 exhibits constitutive transcriptional activity on multiple promoters, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, or ligand binding substantially reduce the transcriptional activity of this receptor. Importantly, both retinol and retinoic acid are able to promote TR4 to recruit coactivators and to activate a TR4-regulated reporter. These findings demonstrate that TR4 is a ligand-regulated nuclear receptor and suggest that retinoids might have a much wider regulatory role via activation of orphan receptors such as TR4.

Zhou, X. Edward; Suino-Powell, Kelly M.; Xu, Yong; Chan, Cee-Wah; Tanabe, Osamu; Kruse, Schoen W.; Reynolds, Ross; Engel, James Douglas; Xu, H. Eric (Van Andel); (Michigan-Med)

2011-11-17

112

Laminin-5 and type I collagen promote adhesion and osteogenic differentiation of animal serum-free expanded human mesenchymal stromal cells  

PubMed Central

Mesenchymal stromal cells (MSC) are differentiation competent cells and may generate, among others, mature osteoblasts or chondrocytes in vitro and in vivo. Laminin-5 and type I collagen are important components of the extracellular matrix. They are involved in a variety of cellular and extracellular activities including cell attachment and osteogenic differentiation of MSC. MSC were isolated and expanded using media conforming good medical practice (GMP)-regulations for medical products. Cells were characterized according to the defined minimal criteria for multipotent MSC. MTT- and BrdU-assays were performed to evaluate protein-dependent (laminin-5, laminin-1, type I collagen) metabolic activity and proliferation of MSC. MSC-attachment assays were performed using protein-coated culture plates. Osteogenic differentiation of MSC was measured by protein-dependant mineralization and expression of osteogenic marker genes (osteopontin, alkaline phophatase, Runx2) after three, seven and 28 days of differentiation. Marker genes were identified using quantitative reverse-transcription polymerase chain reaction. Expansion of MSC in GMP-conforming media yielded vital cells meeting all minimal criteria for MSC. Attachment assay revealed a favorable binding of MSC to laminin-5 and type I collagen at a protein concentration of 1–5 fmol/µL. Compared to plastic, osteogenic differentiation was significantly increased by laminin-5 after 28 days of culture (P<0.04). No significant differences in gene expression patterns were observed. We conclude that laminin-5 and type I collagen promote attachment, but laminin-1 and laminin-5 promote osteogenic differentiation of MSC. This may influence future clinical applications. PMID:23589764

Mittag, Falk; Falkenberg, Eva-Maria; Janczyk, Alexandra; Götze, Marco; Felka, Tino; Aicher, Wilhelm K.; Kluba, Torsten

2012-01-01

113

Plant cysteine proteases that evoke itch activate protease-activated receptors  

PubMed Central

Background Bromelain, ficin and papain are cysteine proteases from plants that produce itch upon injection into skin. Their mechanism of action has not been considered previously. Objectives To determine the mechanism by which these proteases function. Methods The ability of these proteases to activate protease-activated receptors was determined by ratiometric calcium imaging. Results We show here that bromelain, ficin and papain activate protease-activated receptors 2 and 4. Conclusions Bromelain, ficin and papain function as signalling molecules and activate protease-activated receptors. Activation of these receptors is the likely mechanism by which these proteases evoke itch. PMID:20491769

Reddy, V.B.; Lerner, E.A.

2013-01-01

114

Characterization of peroxisome proliferator-activiated receptor alpha (PPARalpha)-independent effects of PPARalpha activators in the rodent liver: Di(2-ethylehexyl) phthalate activates the constitutive activated receptor  

EPA Science Inventory

Peroxisome proliferator chemicals (PPC) are thought to mediate their effects in rodents on hepatocyte growth and liver cancer through the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARalpha). Recent studies indicate that the plasticizer di-2-ethylhexyl ph...

115

Activities of nicotinic acetylcholine receptors modulate neurotransmission and synaptic architecture  

PubMed Central

The cholinergic system is involved in a broad spectrum of brain function, and its failure has been implicated in Alzheimer's disease. Acetylcholine transduces signals through muscarinic and nicotinic acetylcholine receptors, both of which influence synaptic plasticity and cognition. However, the mechanisms that relate the rapid gating of nicotinic acetylcholine receptors to persistent changes in brain function have remained elusive. Recent evidence indicates that nicotinic acetylcholine receptors activities affect synaptic morphology and density, which result in persistent rearrangements of neural connectivity. Further investigations of the relationships between nicotinic acetylcholine receptors and rearrangements of neural circuitry in the central nervous system may help understand the pathogenesis of Alzheimer's disease.

Oda, Akira; Tanaka, Hidekazu

2014-01-01

116

?(2)-Adrenergic receptor polymorphisms and signaling: Do variants influence the "memory" of receptor activation?  

PubMed

Nonsynonymous, coding sequence single-nucleotide polymorphisms in ?(2)-adrenergic receptors were first recognized almost 20 years ago, but a full understanding of their impact on signal transduction-especially on receptor abundance in native cells and their clinical importance-remains unclear. New evidence has revealed a feature of the Arg(16)Gly variant of ?(2)-adrenergic receptors that has not been previously noted: a difference in the rate of response upon repeated stimulation of the receptors, such that the Arg(16) variant shows slower activation and the Gly(16) variant faster activation of cyclic adenosine monophosphate (cAMP) formation-a feature that the authors term "receptor memory." This is an intriguing idea but will require confirmation and demonstration of its functional importance in vivo and its possible contribution to clinical responses, especially in terms of the administration of ?(2)-adrenergic agonists. PMID:21868355

Insel, Paul A

2011-08-01

117

{beta}2-Adrenergic Receptor Polymorphisms and Signaling: Do Variants Influence the "Memory" of Receptor Activation?  

NSDL National Science Digital Library

Nonsynonymous, coding sequence single-nucleotide polymorphisms in ?2-adrenergic receptors were first recognized almost 20 years ago, but a full understanding of their impact on signal transduction—especially on receptor abundance in native cells and their clinical importance—remains unclear. New evidence has revealed a feature of the Arg16Gly variant of ?2-adrenergic receptors that has not been previously noted: a difference in the rate of response upon repeated stimulation of the receptors, such that the Arg16 variant shows slower activation and the Gly16 variant faster activation of cyclic adenosine monophosphate (cAMP) formation—a feature that the authors term “receptor memory.” This is an intriguing idea but will require confirmation and demonstration of its functional importance in vivo and its possible contribution to clinical responses, especially in terms of the administration of ?2-adrenergic agonists.

Paul A. Insel (University of California at San Diego; Departments of Pharmacology and Medicine REV)

2011-08-09

118

Immobilization and therapeutic passive stretching generate thickening and increase the expression of laminin and dystrophin in skeletal muscle  

PubMed Central

Extracellular matrix and costamere proteins transmit the concentric, isometric, and eccentric forces produced by active muscle contraction. The expression of these proteins after application of passive tension stimuli to muscle remains unknown. This study investigated the expression of laminin and dystrophin in the soleus muscle of rats immobilized with the right ankle in plantar flexion for 10 days and subsequent remobilization, either by isolated free movement in a cage or associated with passive stretching for up to 10 days. The intensity of the macrophage response was also evaluated. One hundred and twenty-eight female Wistar rats were divided into 8 groups: free for 10 days; immobilized for 10 days; immobilized/free for 1, 3, or 10 days; or immobilized/stretched/free for 1, 3, or 10 days. After the experimental procedures, muscle tissue was processed for immunofluorescence (dystrophin/laminin/CD68) and Western blot analysis (dystrophin/laminin). Immobilization increased the expression of dystrophin and laminin but did not alter the number of macrophages in the muscle. In the stretched muscle groups, there was an increase in dystrophin and the number of macrophages after 3 days compared with the other groups; dystrophin showed a discontinuous labeling pattern, and laminin was found in the intracellular space. The amount of laminin was increased in the muscles treated by immobilization followed by free movement for 10 days. In the initial stages of postimmobilization (1 and 3 days), an exacerbated macrophage response and an increase of dystrophin suggested that the therapeutic stretching technique induced additional stress in the muscle fibers and costameres. PMID:24820070

Cação-Benedini, L.O.; Ribeiro, P.G.; Prado, C.M.; Chesca, D.L.; Mattiello-Sverzut, A.C.

2014-01-01

119

Peroxisome proliferator-activated receptors (PPARs): Nuclear receptors at the crossroads between lipid metabolism and inflammation  

Microsoft Academic Search

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor family. PPARs function as regulators of lipid and lipoprotein metabolism and glucose homeostasis and influence cellular proliferation, differentiation and apoptosis. PPAR! is highly expressed in tissues such as liver, muscle, kidney and heart, where it stimulates the #-oxidative degradation of fatty acids. PPAR% is predominantly expressed in

G. Chinetti; J.-C. Fruchart; B. Staels

2000-01-01

120

Acetylcholine Receptor-Inducing Activity Stimulates Expression of the ?-Subunit Gene of the Muscle Acetylcholine Receptor  

Microsoft Academic Search

Motor neurons regulate the transcription of acetylcholine receptor subunit genes in postsynaptic muscle fibers both through muscle electrical activity produced by motor neuron acetylcholine release and by mechanisms independent of such transmitter release. Factors secreted by the motor neuron may mediate activity-independent regulation, including the postnatal switch from alpha_2betagammadelta (embryonic type) to alpha_2beta?delta (adult type) receptors. We have investigated the

Jean-Claude Martinou; Douglas L. Falls; Gerald D. Fischbach; John P. Merlie

1991-01-01

121

Antibodies to laminin in American cutaneous leishmaniasis.  

PubMed Central

We found that serum samples from patients with different clinical forms of American cutaneous leishmaniasis (ACL) contained immunoglobulin G and immunoglobulin M antibodies which reacted with laminin but not with various other purified connective tissue components, such as collagen types I, III, IV, and V and fibronectin. Eighty-one percent of ACL patients had high antilaminin antibody levels, with a relationship existing between ACL ulcers and antibody levels. This was not, however, the case with patients having treated and healed ACL ulcers; only 34% of these patients had elevated antilaminin antibodies. Eighty-four percent of chronic Chagas' disease patients were also found to contain antilaminin antibodies that were limited to the immunoglobulin G class, but these were not detected in patients suffering from any of 11 other infectious diseases. PMID:6418660

Avila, J L; Rojas, M; Rieber, M

1984-01-01

122

Activation of the Mineralocorticoid Receptor Increases Striatin Levels  

Microsoft Academic Search

BackgroundAldosterone (ALDO), a critical regulator of sodium homeostasis, mediates its effects via activation of the mineralocorticoid receptor (MR) through mechanisms that are not entirely clear. Striatin, a membrane associated protein, interacts with estrogen receptors in endothelial cells.MethodsWe studied the effects of MR activation in vitro and in vivo on striatin levels in vascular tissue.ResultsWe observed that dietary sodium restriction was

Luminita H. Pojoga; Patricia Coutinho; Alicia Rivera; Tham M. Yao; Enrique R. Maldonado; Rodeler Youte; Gail K. Adler; Jonathan Williams; Alexander Turchin; Gordon H. Williams; Jose R. Romero

2012-01-01

123

5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation  

PubMed Central

The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and G?s-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both G?s and G?12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands. PMID:25426041

Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S.; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G.; Beazely, Michael A.

2014-01-01

124

Down-Regulation of Protease-activated Receptor1 Is Regulated by Sorting Nexin 1  

Microsoft Academic Search

ABSTRACT Degradation or “down -regulation” of protease -activated receptor-1 (PAR1), a G protein-coupled receptor for thrombin, is critical for termination of receptor signaling. Towards,understanding,the molecular,mechanisms,by which activated

Yingjie Wang; Yixing Zhou; Carol Renfrew Haft; JoAnn Trejo

2002-01-01

125

The atypical antidepressant mianserin exhibits agonist activity at ?-opioid receptors  

PubMed Central

BACKGROUND AND PURPOSE Antidepressants are known to interact with the opioid system through mechanisms not completely understood. We previously reported that tricyclic antidepressants act as agonists at distinct opioid receptors. Here, we investigated the effect of the atypical antidepressant mianserin at cloned and native opioid receptors. EXPERIMENTAL APPROACH Effects of mianserin were examined in CHO cells transfected with human opioid receptors, C6 glioma cells and rat brain membranes by the use of radioligand binding and functional assays including the stimulation of [35S]GTP?S binding and MAPK phosphorylation. KEY RESULTS Mianserin displayed 12- and 18-fold higher affinity for ?- than µ- and ?-opioid receptors respectively. In [35S]GTP?S assays, mianserin selectively activated ?-opioid receptors. The agonist activity was antagonized by the selective ?-opioid blocker nor-binaltorphimine (nor-BNI). The mianserin analogue mirtazapine also displayed ?-opioid agonist activity. Mianserin and mirtazapine increased ERK1/2 phosphorylation in CHO cells expressing ?-opioid receptors and C6 cells, and these effects were antagonized by nor-BNI. In rat striatum and nucleus accumbens, mianserin stimulated [35S]GTP?S binding in a nor-BNI-sensitive manner with maximal effects lower than those of the full ?-opioid agonists (–)-U50,488 and dynorphin A. When combined, mianserin antagonized the effects of the full ?-opioid receptor agonists in [35S]GTP?S assays and reduced the stimulation of p38 MAPK and ERK1/2 phosphorylation by dynorphin A. CONCLUSIONS AND IMPLICATIONS In different cell systems, mianserin directly activates ?-opioid receptors, displaying partial agonist activity at brain receptors. Thus, this property appears to be a common feature of different classes of antidepressants. PMID:22708686

Olianas, Maria C; Dedoni, Simona; Onali, Pierluigi

2012-01-01

126

M5 Receptor Activation Produces Opposing Physiological Outcomes in Dopamine Neurons Depending on the Receptor's Location  

PubMed Central

Of the five muscarinic receptor subtypes, the M5 receptor is the only one detectable in midbrain dopaminergic neurons, making it an attractive potential therapeutic target for treating disorders in which dopaminergic signaling is disrupted. However, developing an understanding of the role of M5 in regulating midbrain dopamine neuron function has been hampered by a lack of subtype-selective compounds. Here, we extensively characterize the novel compound VU0238429 and demonstrate that it acts as a positive allosteric modulator with unprecedented selectivity for the M5 receptor. We then used VU0238429, along with M5 knock-out mice, to elucidate the role of this receptor in regulating substantia nigra pars compacta (SNc) neuron physiology in both mice and rats. In sagittal brain slices that isolate the SNc soma from their striatal terminals, activation of muscarinic receptors induced Ca2+ mobilization and inward currents in SNc dopamine neurons, both of which were potentiated by VU0238429 and absent in M5 knock-out mice. Activation of M5 also increased the spontaneous firing rate of SNc neurons, suggesting that activation of somatodendritic M5 increases the intrinsic excitability of SNc neurons. However, in coronal slices of the striatum, potentiation of M5 with VU0238429 resulted in an inhibition in dopamine release as monitored with fast scan cyclic voltammetry. Accordingly, activation of M5 can lead to opposing physiological outcomes depending on the location of the receptor. Although activation of somatodendritic M5 receptors on SNc neurons leads to increased neuronal firing, activation of M5 receptors in the striatum induces an inhibition in dopamine release. PMID:24573284

Foster, Daniel J.; Gentry, Patrick R.; Lizardi-Ortiz, Jose E.; Bridges, Thomas M.; Wood, Michael R.; Niswender, Colleen M.; Sulzer, David; Lindsley, Craig W.; Xiang, Zixiu

2014-01-01

127

Presence and Bronchomotor Activity of Protease-Activated Receptor2 in Guinea Pig Airways  

Microsoft Academic Search

The protease activated receptor-2 (PAR-2) belongs to a family of G-protein-coupled receptors that are activated by proteolysis. Tryp- sin cleaves PAR-2, exposing an N -terminal tethered ligand (SLIGRL) that activates the receptor. Messenger RNA (mRNA) for PAR-2 was found in guinea pig airway tissue by reverse transcription-poly- merase chain reaction, and PAR-2 was found by immunohistochem- istry in airway epithelial

FABIO L. M. RICCIARDOLO; MARTIN STEINHOFF; SILVIA AMADESI; REMO GUERRINI; MICHELE TOGNETTO; MARCELLO TREVISANI; CHRISTOPHE CREMINON; CLAUDE BERTRAND; NIGEL W. BUNNETT; LEONARDO M. FABBRI; SEVERO SALVADORI; PIERANGELO GEPPETTI

2000-01-01

128

Hedgehog Signaling and Laminin Play Unique and Synergistic Roles in Muscle Development  

PubMed Central

Hedgehog (Hh) signaling and laminin-111, a basement membrane protein, are required for early muscle development. Hh signaling specifies different populations of muscle fibers and laminin-111 is critical for early muscle morphogenesis. However, additional requirements for Hh signaling and laminin during later phases of muscle development are not known. Furthermore, interactions between Hh signaling and laminin in this context are unknown. We used laminin gamma1 mutant zebrafish and cyclopamine to block Hh signal transduction separately and in combination to investigate their functions and interactions. We found that both Hh signaling and laminin are required for normal myosin chain expression. In addition, Hh signaling and laminin act synergistically during fast-twitch fiber elongation: fast muscle cells do not elongate in embryos deficient for both Hh signaling and laminin. Finally, we present evidence which suggests that Hh signaling is indirectly required via slow fiber specification for recovery of fast fiber elongation in laminin gamma1 mutant embryos. PMID:20063418

Peterson, Matthew T.; Henry, Clarissa A.

2010-01-01

129

Ligand Activation of Peroxisome ProliferatorActivated Receptor B Inhibits Colon Carcinogenesis  

E-print Network

- creased colon polyp multiplicity in colon cancer bioassays, suggesting that ligand activation or attenuates colon cancer. Overexpression of the adenoma- tous polyposis coli (APC) gene productLigand Activation of Peroxisome Proliferator­Activated Receptor B Inhibits Colon Carcinogenesis

Omiecinski, Curtis

130

Enhanced laminin adsorption on nanowires compared to flat surfaces.  

PubMed

Semiconductor nanowires are widely used to interface living cells, and numerous nanowire-based devices have been developed to manipulate or sense cell behavior. We have, however, little knowledge on the nature of the cell-nanowire interface. Laminin is an extracellular matrix protein promoting cell attachment and growth. Here, we used a method based on fluorescence microscopy and measured the relative amount of laminin adsorbed on nanowires compared to flat surfaces. The amount of adsorbed laminin per surface area is up to 4 times higher on 55nm diameter gallium phosphide nanowires compared to the flat gallium phosphide surface between the nanowires. We show that this enhanced adsorption on nanowires cannot be attributed to electrostatic effects, nor to differences in surface chemistry, but possibly to pure geometrical effects, as increasing the nanowire diameter results in a decreased amount of adsorbed protein. The increased adsorption of laminin on nanowires may explain the exceptionally beneficial properties of nanowire substrates for cellular growth reported in the literature since laminin is often used as surface coating prior to cell cultures in order to promote cell growth, and also because primary cell suspensions contain endogenous laminin. PMID:25024109

Hammarin, Greger; Persson, Henrik; Dabkowska, Aleksandra P; Prinz, Christelle N

2014-10-01

131

Activation and allosteric modulation of a muscarinic acetylcholine receptor  

PubMed Central

Despite recent advances in crystallography of G protein-coupled receptors (GPCRs), little is known about the mechanism of their activation process, as only the ?2 adrenergic receptor (?2AR) and rhodopsin have been crystallized in fully active conformations. Here, we report the structure of an agonist-bound, active state of the human M2 muscarinic acetylcholine receptor stabilized by a G-protein mimetic camelid antibody fragment isolated by conformational selection using yeast surface display. In addition to the expected changes in the intracellular surface, the structure reveals larger conformational changes in the extracellular region and orthosteric binding site than observed in the active states of the ?2AR and rhodopsin. We also report the structure of the M2 receptor simultaneously binding the orthosteric agonist iperoxo and the positive allosteric modulator LY2119620. This structure reveals that LY2119620 recognizes a largely pre-formed binding site in the extracellular vestibule of the iperoxo-bound receptor, inducing a slight contraction of this outer binding pocket. These structures offer important insights into activation mechanism and allosteric modulation of muscarinic receptors. PMID:24256733

Kruse, Andrew C.; Ring, Aaron M.; Manglik, Aashish; Hu, Jianxin; Hu, Kelly; Eitel, Katrin; Hübner, Harald; Pardon, Els; Valant, Celine; Sexton, Patrick M.; Christopoulos, Arthur; Felder, Christian C.; Gmeiner, Peter; Steyaert, Jan; Weis, William I.; Garcia, K. Christopher; Wess, Jürgen; Kobilka, Brian K.

2014-01-01

132

Understanding Cytokine and Growth Factor Receptor Activation Mechanisms  

PubMed Central

Our understanding of the detailed mechanism of action of cytokine and growth factor receptors – and particularly our quantitative understanding of the link between structure, mechanism and function – lags significantly behind our knowledge of comparable functional protein classes such as enzymes, G protein-coupled receptors, and ion channels. In particular, it remains controversial whether such receptors are activated by a mechanism of ligand-induced oligomerization, versus a mechanism in which the ligand binds to a pre-associated receptor dimer or oligomer that becomes activated through subsequent conformational rearrangement. A major limitation to progress has been the relative paucity of methods for performing quantitative mechanistic experiments on unmodified receptors expressed at endogenous levels on live cells. In this article we review the current state of knowledge on the activation mechanisms of cytokine and growth factor receptors, critically evaluate the evidence for and against the different proposed mechanisms, and highlight other key questions that remain unanswered. New approaches and techniques have led to rapid recent progress in this area, and the field is poised for major advances in the coming years, which promises to revolutionize our understanding of this large and biologically and medically important class of receptors. PMID:23046381

Atanasova, Mariya; Whitty, Adrian

2012-01-01

133

CD160: a unique activating NK cell receptor.  

PubMed

Here we discuss CD160 an essential NK cell activating receptor that remains poorly understood. CD160 receptor exhibits a number of unique structural and functional characteristics that are not common to other killer immunoglobulin-like receptors that recognize major histocompatibility complex (MHC) class I molecules: (1) In addition to humans and mice, the cd160 gene is conserved in several other mammal species; (2) cd160 is located outside the NK gene complex and the Leukocyte Receptor Complex in humans; (3) CD160 expression is associated to the CD56(dim) CD16+ cytotoxic NK cell phenotype; (4) both human and mouse CD160 recognize MHC class Ia and Ib molecules; (5) unlike the other MHC class I-dependent activating NK receptors, CD160 is a glycosylphosphatidylinositol-anchored molecule with a single immunoglobulin-like domain, and does not bear immunoreceptor tyrosine-based activation motifs. Consequently, CD160 cannot signal by itself, requiring the recruitment of adaptor proteins. CD160 recruits phosphoinositide-3 kinase to trigger cytotoxicity and cytokine secretion; (6) specific engagement of NK CD160 receptor expressed by circulating NK cells produces proinflammatory cytokines IFN-?, TNF-?, and, most notably, IL-6 and IL-8 as well as MIP1-? chemokine. The level of CD160-mediated IFN-? production is always higher than the one observed after engagement of the CD16 receptor. PMID:21324341

Le Bouteiller, Philippe; Tabiasco, Julie; Polgar, Beata; Kozma, Noemi; Giustiniani, Jérôme; Siewiera, Johan; Berrebi, Alain; Aguerre-Girr, Maryse; Bensussan, Armand; Jabrane-Ferrat, Nabila

2011-08-30

134

Histidine(7.36(305)) in the conserved peptide receptor activation domain of the gonadotropin releasing hormone receptor couples peptide binding and receptor activation.  

PubMed

Transmembrane helix seven residues of G protein-coupled receptors (GPCRs) couple agonist binding to a conserved receptor activation mechanism. Amino-terminal residues of the GnRH peptide determine agonist activity. We investigated GnRH interactions with the His(7.36(305)) residue of the GnRH receptor, using functional and computational analysis of modified GnRH receptors and peptides. Non-polar His(7.36(305)) substitutions decreased receptor affinity for GnRH four- to forty-fold, whereas GnRH signaling potency was more decreased (~150-fold). Uncharged polar His(7.36(305)) substitutions decreased GnRH potency, but not affinity. [2-Nal(3)]-GnRH retained high affinity at receptors with non-polar His(7.36(305)) substitutions, supporting a role for His(7.36(305)) in recognizing Trp(3) of GnRH. Compared with GnRH, [2-Nal(3)]-GnRH potency was lower at the wild type GnRH receptor, but unchanged or higher at mutant receptors. Results suggest that His(7.36(305)) of the GnRH receptor forms two distinct interactions that determine binding to Trp(3) and couple agonist binding to the conserved transmembrane domain network that activates GPCRs. PMID:25583361

Mayevu, Nkateko M I; Choe, Han; Abagyan, Ruben; Seong, Jae Young; Millar, Robert P; Katz, Arieh A; Flanagan, Colleen A

2015-02-15

135

Identification and characterization of cell-substratum adhesion receptors on cultured human endothelial cells.  

PubMed Central

A series of immunological approaches was utilized to identify the molecules involved in cell-substratum adhesion of human endothelial cells (EC) derived from adult large vessels, fat capillaries, and umbilical veins. A polyclonal antibody prepared against partially purified extracellular matrix receptors disrupted adhesion of EC to a wide variety of substrates and identified four groups of glycoproteins migrating with apparent Mr of 150, 125, 110, and 95 kD in immunoprecipitation experiments. Specific monoclonal antibodies identified these proteins as members of the Integrin family of extracellular matrix receptors and included the alpha and beta chains of the fibronectin receptor (alpha 5/beta 1), a collagen receptor (alpha 2 beta 1), a multifunctional receptor that binds to fibronectin, collagen, and laminin (alpha 3/beta 1), as well as a receptor related to platelet IIb/IIIa (alpha v/beta 3). To directly test the importance of these molecules in cell-substratum adhesion, these proteins were purified by a combination of ion exchange, lectin affinity, and immunoaffinity chromatography and used to block the biological activity of the adhesion-disrupting polyclonal antibody. Immunofluorescence experiments further supported the role of these glycoproteins in adhesion. The GPIIb/IIIa-like receptor localized to well-formed adhesion plaques on EC plated on fibrinogen, but not on fibronectin, laminin, or type IV collagen. Receptors containing the beta 1 subunit were visualized as discontinuous fibrils which colocalized with fibronectin fibrils and actin stress fibers. Images PMID:2786007

Albelda, S M; Daise, M; Levine, E M; Buck, C A

1989-01-01

136

Metabolic Regulation by Lipid Activated Receptors  

E-print Network

weight loss alone(9). Hepatocyte specific CB1 -/- mice are immune to dietdiet and genetic induced models of obesity. Interestingly, the weight loss,weight loss(9). Pharmacological or genetic ablation of the cannabinoid type 1 receptor (CB1) in diet-

Ruby, Maxwell A.

2010-01-01

137

AMPA receptor activation; not a square dance.  

PubMed

AMPA receptors are tetramers assembled as a dimer-of-dimers with a 2-fold rotational symmetry in their extracellular domains. Two papers in this issue of Neuron, by Horning and Mayer and Sobolevsky et al., provide complementary data that extend this view and highlight the role of dimers in channel gating. PMID:14766169

Stern-Bach, Yael

2004-02-01

138

Activation of spinal GABAB receptors normalizes N-methyl-D-aspartate receptor in diabetic neuropathy.  

PubMed

N-methyl-D-aspartate receptor (NMDAR) activity is increased, while GABAB receptor is downregulated in the spinal cord dorsal horn in diabetic neuropathy. In this study, we determined the interaction of NMDARs and GABAB receptors in streptozotocin (STZ)-induced diabetic neuropathy. The paw withdrawal threshold (PWT) was significantly lower in STZ-treated rats than in vehicle-treated rats. Intrathecal injection of baclofen, a GABAB receptor agonist, significantly increased the PWT in STZ-treated rats, an effect that was abolished by pre-administration of the GABAB receptor specific antagonist CGP55845. Spinal NR2B, an NMDA receptor subunit, protein and mRNA expression levels were significantly higher in STZ-treated rats than in vehicle-treated rats. Intrathecal baclofen significantly reduced the NR2B protein and mRNA expression levels in STZ-treated rats. Intrathecal administration of CGP55845 eliminated baclofen-induced reduction of NR2B protein and mRNA levels in STZ-treated rats. In addition, the phosphorylated cAMP response element-binding (CREB) protein level was significantly higher in the spinal cord dorsal horn in STZ-treated rats compared with vehicle-treated rats. Intrathecal injection of baclofen significantly decreased phosphorylated CREB protein level in STZ-treated rats; an effect was blocked by CGP55845. These data suggest that activation of GABAB receptors in the spinal cord dorsal horn normalizes NMDAR expression level in diabetic neuropathic pain. PMID:24787504

Bai, Hui-Ping; Liu, Peng; Wu, Yu-Ming; Guo, Wen-Ya; Guo, Yue-Xian; Wang, Xiu-Li

2014-06-15

139

Protease activated receptor 2: a new target for IBS treatment.  

PubMed

Proteinase-activated receptors (PARs) are G-protein-coupled receptors that are activated by the proteolytic cleavage of their N-terminal domain. The new N-terminal sequence that is exposed by proteolysis acts as a tethered ligand, which binds to and activates the receptor. PAR-2 is highly expressed in the gastrointestinal tract, where it is found in endothelial cells, colonic myocytes, enterocytes (both on basolateral and apical membranes), enteric neurons, terminals of mesenteric afferent nerves and immune cells. In the gastrointestinal tract, PAR-2 may be activated by tryptase from mast cells but also by luminal proteases such as trypsin and possibly bacterial proteases. In addition to effects on motility, ion and mucus secretion, activation of PAR-2 receptors from luminal affects visceral pain. In rats, the intracolonic infusion of PAR-2 agonists (SLIGRL, trypsin) initiates a delayed hypersensitivity to colonic distension. These effects are locally mediated since they are not observed for systemic administration. Interestingly, such pronociceptive effect of local activation of PAR-2 is associated with increased colonic paracellular permeability. Blockade of such increase in permeability, prevents the occurrence of hypersensitivity to rectal distension suggesting that activation of the local immune system by luminal toxins and antigens is responsible for the sensitization of primary afferent terminals to mechanical stimuli. Consequently, blockade of PAR-2 receptors at the periphery and/or inhibition of colonic luminal protease activity may be new interesting targets for the treatment of gut hypersensitivity and IBS. A recent study has evidenced that stool supernatants from diarrhea predominant IBS patients have a high level of serine-protease activity that increases permeability and colonic hypersensitivity when infused intra-colonically in mice, and these effects are linked to activation of PAR-2 receptors. These data support a possible role of luminal proteases in the pathogenesis of IBS and give a rationale to target PARs and more specifically PAR-2 as future treatment of IBS. PMID:18924448

Bueno, L

2008-08-01

140

Selective suppression of Toll-like receptor 4 activation by chemokine receptor 4  

Microsoft Academic Search

The response of Toll-like receptor 4 (TLR4) to lipopolysaccharide (LPS) is thought vital for resisting infection. Since aberrant TLR4 signaling may initiate inflammatory conditions such as the sepsis syndrome, we sought a component of normal cells that might provide local control of TLR4 activation. We found that antibodies that block chemokine receptor 4 (CXCR4) function enhanced TLR4 signaling, while increased

Sandeep P. Kishore; Marlo K. Bungum; Jeffrey L. Platt; Gregory J. Brunn

2005-01-01

141

A human vitamin D receptor mutant activated by cholecalciferol.  

PubMed

The human vitamin D receptor (hVDR) is a member of the nuclear receptor superfamily, involved in calcium and phosphate homeostasis; hence implicated in a number of diseases, such as Rickets and Osteoporosis. This receptor binds 1?,25-dihydroxyvitamin D(3) (also referred to as 1,25(OH)(2)D(3)) and other known ligands, such as lithocholic acid. Specific interactions between the receptor and ligand are crucial for the function and activation of this receptor, as implied by the single point mutation, H305Q, causing symptoms of Type II Rickets. In this work, further understanding of the significant and essential interactions between the ligand and the receptor was deciphered, through a combination of rational and random mutagenesis. A hVDR mutant, H305F, was engineered with increased sensitivity towards lithocholic acid, with an EC(50) value of 10 ?M and 40±14 fold activation in mammalian cell assays, while maintaining wild-type activity with 1,25(OH)(2)D(3). Furthermore, via random mutagenesis, a hVDR mutant, H305F/H397Y, was discovered to bind a novel small molecule, cholecalciferol, a precursor in the 1?,25-dihydroxyvitamin D(3) biosynthetic pathway, which does not activate wild-type hVDR. This variant, H305F/H397Y, binds and activates in response to cholecalciferol concentrations as low as 100 nM, with an EC(50) value of 300 nM and 70±11 fold activation in mammalian cell assays. In silico docking analysis of the variant displays a dramatic conformational shift of cholecalciferol in the ligand binding pocket in comparison to the docked analysis of cholecalciferol with wild-type hVDR. This shift is hypothesized to be due to the introduction of two bulkier residues, suggesting that the addition of these bulkier residues introduces molecular interactions between the ligand and receptor, leading to activation with cholecalciferol. PMID:21397016

Ousley, Amanda M; Castillo, Hilda S; Duraj-Thatte, Anna; Doyle, Donald F; Azizi, Bahareh

2011-07-01

142

A Human Vitamin D Receptor Mutant Activated by Cholecalciferol  

PubMed Central

The human vitamin D receptor (hVDR) is a member of the nuclear receptor superfamily, involved in calcium and phosphate homeostasis; hence implicated in a number of diseases, such as Rickets and Osteoporosis. This receptor binds 1?,25-dihydroxyvitamin D3 (also referred to as 1,25(OH)2D3) and other known ligands, such as lithocholic acid. Specific interactions between the receptor and ligand are crucial for the function and activation of this receptor, as implied by the single point mutation, H305Q, causing symptoms of Type II Rickets. In this work, further understanding of the significant and essential interactions between the ligand and the receptor were deciphered, through a combination of rational and random mutagenesis. A hVDR mutant, H305F, was engineered with increased sensitivity towards lithocholic acid, with an EC50 value of 10 µM and 40 ± 14 fold activation in mammalian cell assays, while maintaining wild-type activity with 1,25(OH)2D3. Furthermore, via random mutagenesis, a hVDR mutant, H305F/H397Y, was discovered to bind a novel small molecule, cholecalciferol, a precursor in the 1?,25-dihydroxyvitamin D3 biosynthetic pathway, which does not activate wild-type hVDR. This variant, H305F/H397Y, binds and activates in response to cholecalciferol concentrations as low as 100 nM, with an EC50 value of 300 nM and 70 ± 11 fold activation in mammalian cell assays. In silico docking analysis of the variant displays a dramatic conformational shift of cholecalciferol in the ligand binding pocket in comparison to the docked analysis of cholecalciferol with wild-type hVDR. This shift is hypothesized to be due to the introduction of two bulkier residues, suggesting that the addition of these bulkier residues introduces molecular interactions between the ligand and receptor, leading to activation with cholecalciferol. PMID:21397016

Ousley, Amanda M.; Castillo, Hilda S.; Duraj-Thatte, Anna; Doyle, Donald F.; Azizi, Bahareh

2011-01-01

143

Flavonoids as dietary regulators of nuclear receptor activity  

PubMed Central

Metabolic diseases such as obesity, type II diabetes, and dyslipidemia are a rising cause of mortality worldwide. The progression of many metabolic diseases is fundamentally regulated on the transcriptional level by a family of ligand-activated transcription factors, called nuclear receptors, which detect and respond to metabolic changes. Their role in maintaining metabolic homeostasis makes nuclear receptors an important pharmaceutical and dietary target. This review will present the growing evidence that flavonoids, natural secondary plant metabolites, are important regulators of nuclear receptor activity. Structural similarities between flavonoids and cholesterol derivatives combined with the promiscuous nature of most nuclear receptors provide a wealth of possibilities for pharmaceutical and dietary modulation of metabolism. While the challenges of bringing flavonoid-derived therapeutics to the market are significant, we consider this rapidly growing field to be an essential aspect of the functional food initiative and an important mine for pharmaceutical compounds. PMID:23598551

Avior, Yishai; Bomze, David; Ramon, Ory

2013-01-01

144

Identification of COUP-TFII Orphan Nuclear Receptor as a Retinoic Acid?Activated Receptor  

SciTech Connect

The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 {angstrom} crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix {alpha}10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site, thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation.

Kruse, Schoen W.; Suino-Powell, Kelly; Zhou, X. Edward; Kretschman, Jennifer E.; Reynolds, Ross; Vonrhein, Clemens; Xu, Yong; Wang, Liliang; Tsai, Sophia Y.; Tsai, Ming-Jer; Xu, H. Eric (Baylor); (Van Andel); (Globel Phasing); (Grand Valley)

2010-01-12

145

Serotonin Augments Gut Pacemaker Activity via 5-HT3 Receptors  

PubMed Central

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca2+ and electric activities in ICC were performed by employing fluorescent Ca2+ imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca2+ antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca2+ oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT3 receptor antagonist suppressed spontaneous Ca2+ activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT3 receptor agonist, restored it. GR113808, a selective antagonist for 5-HT4, and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT3 receptors, had little effect on ICC Ca2+ activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT3 receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT3 receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome. PMID:21949791

Liu, Hong-Nian; Ohya, Susumu; Nishizawa, Yuji; Sawamura, Kenta; Iino, Satoshi; Syed, Mohsin Md; Goto, Kazunori; Imaizumi, Yuji; Nakayama, Shinsuke

2011-01-01

146

Importance of Vitamin D Receptor Activation in Clinical Practice  

Microsoft Academic Search

Continuously emerging evidence indicates that defi ciencies in 25-hydroxyvitamin D and consequently vitamin D receptor (VDR) activation play crucial roles in adversely affecting cardiovascular (CV) health in the general population and those at high risk of CV disease, as well as in patients with chronic kidney disease (CKD). In CKD patients, a lack of VDR activation is one of the

Mario Cozzolino; Giuditta Fallabrino; Sabina Pasho; Laura Olivi; Paola Ciceri; Elisa Volpi; Maurizio Gallieni; Diego Brancaccio

2009-01-01

147

NGF enhances sensory axon growth induced by laminin but not by the L1 cell adhesion molecule.  

PubMed

Neurotrophins and cell adhesion molecules regulate axon guidance, but their potential coordinate interactions are not well defined. In particular, it has been difficult to define the role of signaling from different surface molecules in neurotrophin-induced axon growth because of the strong dependence of embryonic neurons on this class of molecules for survival. We have addressed this issue using Bax deficient neurons, which do not require neurotrophins for survival. The L1 neural cell adhesion molecule and laminin each supported NGF-independent axon growth of cultured sensory neurons from dorsal root ganglia of embryonic Bax(-/-) mice. However, nerve growth factor (NGF) stimulated additional axon growth of sensory neurons on laminin but not on L1 substrates. Inhibition of the small GTPase RhoA by the dominant-negative mutant RhoA(T19N) restored NGF responsiveness of axon growth on L1 to Bax(-/-) neurons. Constitutively activated RhoA(Q63L) did not affect axon growth on L1 but inhibited NGF-stimulated axon growth on laminin. Consistent with the concept that RhoA was downregulated by NGF in neurons on laminin but not L1, the RhoA inhibitor C2IN-C3 toxin stimulated axon growth on L1 in wild-type DRG neurons in NGF. These results demonstrate a novel substrate-dependent regulation of NGF-induced growth of embryonic sensory axons mediated by RhoA GTPase. PMID:12056835

Liu, Rong-Yu; Schmid, Ralf-Steffen; Snider, William D; Maness, Patricia F

2002-05-01

148

Folate receptor-? in activated macrophages: ligand binding and receptor recycling kinetics.  

PubMed

Activated macrophages overexpress a receptor for the vitamin folic acid termed the folate receptor ? (FR-?). Because conjugation of folate to low molecular weight drugs, genes, liposomes, nanoparticles, and imaging agents has minor effects on FR binding, the vitamin can be exploited to target both therapeutic and imaging agents to activated macrophages without promoting their uptake by other healthy cells. In this paper, we characterize the binding, internalization, and recycling kinetics of FR-? on activated macrophages in inflamed tissues of rats with adjuvant-induced arthritis. Our results demonstrate that saturation of macrophage FR is achieved at injection doses of ?150-300 nmol/kg, with more rapidly perfused tissues saturating at lower doses than inflamed appendages. After binding, FR-? internalizes and recycles back to the cell surface every ?10-20 min, providing empty receptors for additional folate conjugate uptake. Because the half-life of low molecular weight folate conjugates in the vasculature is usually <1 h, these data suggest that targeting of folate conjugates to activated macrophages in vivo can be maximized by frequent dosing at conjugate concentrations that barely saturate FR (?150 nmol/kg), thereby minimizing nonspecific binding to receptor-negative tissues and maximizing the probability that unoccupied cell surface receptors will be exposed to folate-drug conjugate. PMID:25166491

Varghese, Bindu; Vlashi, Erina; Xia, Wei; Ayala Lopez, Wilfredo; Paulos, Chrystal M; Reddy, Joseph; Xu, Le-Cun; Low, Philip S

2014-10-01

149

Regulation of Proteome Maintenance Gene Expression by Activators of Peroxisome Proliferator-Activated Receptor a (PPARa)  

EPA Science Inventory

The nuclear receptor peroxisome proliferator-activated receptor alpha (PPARa) is activated by a large number of xenobiotic and hypolipidemic compounds called peroxisome proliferator chemicals (PPC). One agonist of PPARa (WY-14,643) regulates responses in the mouse liver to chemic...

150

Down-regulation of cellular platelet-derived growth factor receptors induced by an activated neu receptor tyrosine kinase.  

PubMed Central

The functional integration of growth factor signaling occurs at several levels in target cells. One of the most proximal mechanisms is receptor transmodulation, by which one activated receptor can regulate the expression of other receptors in the same cells. Well-established transregulatory loops involve platelet-derived growth factor (PDGF) down-regulation of epidermal growth factor (EGF) receptors and beta-type transforming growth factors modulation of PDGF receptors. We have studied the relationship between neu tyrosine kinase activation and the expression of the PDGF receptors in transfected NIH/3T3 cells. Expression of the neu oncogene, but not of the neu proto-oncogene, was associated with a decrease of PDGF alpha- and beta-receptors on the cell surface, as measured by [125-I]PDGF-AA and -BB binding. These results were corroborated by metabolic labeling and immunoprecipitation of the PDGF beta-receptors. PDGF alpha- and beta-receptor mRNAs were strongly decreased in the neu oncogene-transformed cells in comparison with control cells expressing the neu proto-oncogene. Down-regulation of the PDGF receptors and their mRNAs was also observed after EGF treatment of cells expressing a chimeric EGF receptor/neu receptor, where the neu tyrosine kinase is activated by EGF binding. These results show that the neu tyrosine kinase can down-modulate PDGF receptor expression, and the effect is mediated via decreased PDGF receptor mRNA levels. Images PMID:1685673

Lehtola, L; Nistér, M; Hölttä, E; Westermark, B; Alitalo, K

1991-01-01

151

Histamine 3 Receptor Activation Reduces the Expression of Neuronal Angiotensin II Type 1 Receptors in the Heart  

PubMed Central

In severe myocardial ischemia, histamine 3 (H3) receptor activation affords cardioprotection by preventing excessive norepinephrine release and arrhythmias; pivotal to this action is the inhibition of neuronal Na+/H+ exchanger (NHE). Conversely, angiotensin II, formed locally by mast cell-derived renin, stimulates NHE via angiotensin II type 1 (AT1) receptors, facilitating norepinephrine release and arrhythmias. Thus, ischemic dysfunction may depend on a balance between the NHE-modulating effects of H3 receptors and AT1 receptors. The purpose of this investigation was therefore to elucidate the H3/AT1 receptor interaction in myocardial ischemia/reperfusion. We found that H3 receptor blockade with clobenpropit increased norepinephrine overflow and arrhythmias in Langendorff-perfused guinea pig hearts subjected to ischemia/reperfusion. This coincided with increased neuronal AT1 receptor expression. NHE inhibition with cariporide prevented both increases in norepinephrine release and AT1 receptor expression. Moreover, norepinephrine release and AT1 receptor expression were increased by the nitric oxide (NO) synthase inhibitor NG-methyl-l-arginine and the protein kinase C activator phorbol myristate acetate. H3 receptor activation in differentiated sympathetic neuron-like PC12 cells permanently transfected with H3 receptor cDNA caused a decrease in protein kinase C activity and AT1 receptor protein abundance. Collectively, our findings suggest that neuronal H3 receptor activation inhibits NHE by diminishing protein kinase C activity. Reduced NHE activity sequentially causes intracellular acidification, increased NO synthesis, and diminished AT1 receptor expression. Thus, H3 receptor-mediated NHE inhibition in ischemia/reperfusion not only opposes the angiotensin II-induced stimulation of NHE in cardiac sympathetic neurons, but also down-regulates AT1 receptor expression. Cardioprotection ultimately results from the combined attenuation of angiotensin II and norepinephrine effects and alleviation of arrhythmias. PMID:22011436

Hashikawa-Hobara, Narumi; Chan, Noel Yan-Ki

2012-01-01

152

Structural mechanism of ligand activation in human GABAB receptor  

PubMed Central

Human GABAB receptor is a G-protein coupled receptor central to inhibitory neurotransmission in the brain. It functions as an obligatory heterodimer of GBR1 and GBR2 subunits. Here we present the first crystal structures of a heterodimeric complex between the extracellular domains of GBR1 and GBR2 in the apo, agonist-bound, and antagonist-bound forms. The apo and antagonist-bound structures represent the resting state of the receptor; the agonist-bound complex corresponds to the active state. Both subunits adopt an open conformation at rest, and only GBR1 closes upon agonist-induced receptor activation. The agonists and antagonists are anchored in the interdomain crevice of GBR1 by an overlapping set of residues. An antagonist confines GBR1 to the open conformation of the inactive state, while an agonist induces its domain closure for activation. Our data reveals a unique activation mechanism for GABAB receptor that involves the formation of a novel heterodimer interface between subunits. PMID:24305054

Geng, Yong; Bush, Martin; Mosyak, Lidia; Wang, Feng; Fan, Qing R.

2013-01-01

153

Steroid signaling activation and intracellular localization of sex steroid receptors.  

PubMed

In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migration through cytoskeleton changes. These findings have raised the question of intracellular localization of sex steroid receptors mediating these responses. During the past years, increasing evidence has shown that classical sex steroid receptors localized in the extra-nuclear compartment or close to membranes of target cells induce these events. The emerging picture is that a process of bidirectional control between signaling activation and sex steroid receptor localization regulates the outcome of hormonal responses in target cells. This mechanism ensures cell cycle progression in estradiol-treated breast cancer cells, and its derangement might occur in progression of human proliferative diseases. These findings will be reviewed here together with unexpected examples of the relationship between sex steroid receptor localization, signaling activation and biological responses in target cells. We apologize to scientists whose reports are not mentioned or extensively discussed owing to space limitations. PMID:21234121

Giraldi, Tiziana; Giovannelli, Pia; Di Donato, Marzia; Castoria, Gabriella; Migliaccio, Antimo; Auricchio, Ferdinando

2010-12-01

154

Steroid signaling activation and intracellular localization of sex steroid receptors  

PubMed Central

In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migration through cytoskeleton changes. These findings have raised the question of intracellular localization of sex steroid receptors mediating these responses. During the past years, increasing evidence has shown that classical sex steroid receptors localized in the extra-nuclear compartment or close to membranes of target cells induce these events. The emerging picture is that a process of bidirectional control between signaling activation and sex steroid receptor localization regulates the outcome of hormonal responses in target cells. This mechanism ensures cell cycle progression in estradiol-treated breast cancer cells, and its derangement might occur in progression of human proliferative diseases. These findings will be reviewed here together with unexpected examples of the relationship between sex steroid receptor localization, signaling activation and biological responses in target cells. We apologize to scientists whose reports are not mentioned or extensively discussed owing to space limitations. PMID:21234121

Giraldi, Tiziana; Giovannelli, Pia; Di Donato, Marzia; Migliaccio, Antimo; Auricchio, Ferdinando

2010-01-01

155

Neurotransmitter GABA Activates Muscle but Not ?7 Nicotinic Receptors.  

PubMed

Cys-loop receptors are neurotransmitter-activated ion channels involved in synaptic and extrasynaptic transmission in the brain and are also present in non-neuronal cells. As GABAA and nicotinic receptors (nAChR) belong to this family, we explored by macroscopic and single-channel recordings whether the inhibitory neurotransmitter GABA has the ability to activate excitatory nAChRs. GABA differentially activates nAChR subtypes. It activates muscle nAChRs, with maximal peak currents of about 10% of those elicited by acetylcholine (ACh) and 15-fold higher EC50 with respect to ACh. At the single-channel level, the weak agonism is revealed by the requirement of 20-fold higher concentration of GABA for detectable channel openings, a major population of brief openings, and absence of clusters of openings when compared with ACh. Mutations at key residues of the principal binding-site face of muscle nAChRs (?Y190 and ?G153) affect GABA activation similarly as ACh activation, whereas a mutation at the complementary face (?G57) shows a selective effect for GABA. Studies with subunit-lacking receptors show that GABA can activate muscle nAChRs through the ?/? interface. Interestingly, single-channel activity elicited by GABA is similar to that elicited by ACh in gain-of-function nAChR mutants associated to congenital myasthenic syndromes, which could be important in the progression of the disorders due to steady exposure to serum GABA. In contrast, GABA cannot elicit single-channel or macroscopic currents of ?7 or the chimeric ?7-serotonin-type 3 receptor, a feature important for preserving an adequate excitatory/inhibitory balance in the brain as well as for avoiding activation of non-neuronal receptors by serum GABA. PMID:25492812

Dionisio, Leonardo; Bergé, Ignacio; Bravo, Matías; Esandi, María Del Carmen; Bouzat, Cecilia

2015-03-01

156

Probing the integrin-binding site within the globular domain of laminin-511 with the function-blocking monoclonal antibody 4C7.  

PubMed

In an attempt to elucidate the integrin-binding site within laminin-511 (alpha5beta1gamma1), we mapped the epitope for mAb 4C7, which recognizes the globular (G) domain of the laminin alpha5 chain and inhibits binding of integrin alpha6beta1 to laminin-511, using a series of recombinant laminin-511 mutants with deletions or substitutions in the G domain. Deletion of the LG2-5 modules only partially compromised the 4C7 binding activity, while deletion of all 5 LG modules completely abrogated the activity, indicating that the epitope for 4C7 resides in the LG1 module. In support of this conclusion, 4C7 reactivity was abolished when the LG1 module of laminin-511 was swapped with the corresponding module of laminin-111, but the reactivity was retained after swapping the LG2 or LG3 module. Despite the requirement of LG1 for 4C7 binding, a recombinant LG1 module failed to bind to 4C7 when expressed alone or in tandem with LG2, but exhibited significant 4C7 binding activity when expressed as an array of LG1-3. These results indicate that 4C7 recognizes an epitope in the LG1 module, whose active conformation is stabilized in the context of the LG1-3 modules. Despite their 4C7 binding activities, neither the recombinant LG1-3 fragment nor the LG2 and LG3 swap mutants were capable of binding to integrin alpha6beta1. Thus, the integrin binding activity does not necessarily parallel the 4C7 reactivity, and possibly requires a strictly defined conformation of the LG1 module which can only be attained within an array of the intact LG1-3 modules connected to the preceding coiled-coil domain. PMID:16324831

Ido, Hiroyuki; Harada, Kenji; Yagi, Yoshiko; Sekiguchi, Kiyotoshi

2006-03-01

157

Allosteric modulation of protease-activated receptor signaling.  

PubMed

The protease-activated receptors (PARs) are G protein-coupled receptors (GPCRs) that are uniquely activated by proteolysis. PARs mediate hemostasis, thrombosis, inflammation, embryonic development and progression of certain malignant cancers. The family of PARs include four members: PAR1, PAR2, PAR3 and PAR4. PARs harbor a cryptic ligand sequence within their N-terminus that is exposed following proteolytic cleavage. The newly formed PAR Nterminus functions as a tethered ligand that binds intramolecularly to the receptor to trigger transmembrane signaling. This unique mechanism of activation would indicate that regardless of the activating protease, cleavage of PARs would unmask a tethered ligand sequence that would induce a similar active receptor conformation and signaling response. However, this is not the case. Recent studies demonstrate that PARs can be differentially activated by synthetic peptide agonists, proteases or through dimerization, that ultimately result in distinct cellular responses. In some cases, allosteric modulation of PARs involves compartmentalization in caveolae, plasma membrane microdomains enriched in cholesterol. Here, we discuss some mechanisms that lead to allosteric modulation of PAR signaling. PMID:22681248

Canto, I; Soh, U J K; Trejo, J

2012-08-01

158

Protease-activated receptors as therapeutic targets in visceral pain.  

PubMed

The protease-activated receptors (PARs) play a pivotal role in inflammatory and nociceptive processes. PARs have raised considerable interest because of their capacity to regulate numerous aspects of viscera physiology and pathophysiology. The present article summarizes research on PARs and proteases as signalling molecules in visceral pain. In particular, experiments in animal models suggest that PAR2 is important for visceral hypersensitivity. Moreover, endogenous PAR2 agonists seem to be released by colonic tissue of patients suffering from irritable bowel syndrome, suggesting a role for this receptor in visceral pain perception. Thus, PARs, together with proteases that activate them, represent exciting targets for therapeutic intervention on visceral pain. PMID:24396336

Cenac, Nicolas

2013-12-01

159

Activation of Estrogen Receptor-? by the Anion Nitrite  

PubMed Central

In this study, the ability of nitrite and nitrate to mimic the effects of estradiol on growth and gene expression was measured in the human breast cancer cell line MCF-7. Similar to estradiol, treatment of MCF-7 cells with either 1 ?mol/L nitrite or 1 ?mol/L nitrate resulted in ~4-fold increase in cell growth and 2.3-fold to 3-fold increase in progesterone receptor (PgR), pS2, and cathepsin D mRNAs that were blocked by the antiestrogen ICI 182,780. The anions also recruited estrogen receptor-? (ER?) to the pS2 promoter and activated exogenously expressed ER? when tested in transient cotransfection assays. To determine whether nitrite or nitrate was the active anion, diphenyleneiodonium was used to inhibit oxidation/reduction reactions in the cell. The ability of diphenyleneiodonium to block the effects of nitrate, but not nitrite, on the induction of PgR mRNA and the activation of exogenously expressed ER? suggests that nitrite is the active anion. Concentrations of nitrite, as low as 100 nmol/L, induced a significant increase in PgR mRNA, suggesting that physiologically and environmentally relevant doses of the anion activate ER?. Nitrite activated the chimeric receptor Gal-ER containing the DNA-binding domain of GAL-4 and the ligand-binding domain of ER? and blocked the binding of estradiol to the receptor, suggesting that the anion activates ER? through the ligand-binding domain. Mutational analysis identified the amino acids Cys381, His516, Lys520, Lys529, Asn532, and His547 as important for nitrite activation of the receptor. PMID:18483281

Veselik, David J.; Divekar, Shailaja; Dakshanamurthy, Sivanesan; Storchan, Geoffrey B.; Turner, Jasmine M.A.; Graham, Kelly L.; Huang, Li; Stoica, Adriana; Martin, Mary Beth

2013-01-01

160

NMDA receptor activation induces translocation and activation of Rac in mouse hippocampal area CA1  

PubMed Central

Neuronal development requires several discrete morphological steps that are believed to involve the small GTPase Rac. For example, neural activity, through NMDA receptors and/or AMPA receptors, activates Rac leading to elaboration of dendritic arbors. In the current study, we have conducted studies which indicate that Rac might be an important molecule involved in morphological plasticity in the adult mouse. We demonstrate that Rac is expressed at synapses in the adult mouse hippocampus. We also demonstrate that treatment of hippocampal slices with NMDA induces membrane translocation and activation of Rac in area CA1. Interestingly, we also find that there is an increase in Rac that is associated with NMDA receptor complexes following NMDA receptor activation. Taken together, our data are consistent with the idea that Rac could be participating in NMDA receptor-dependent changes in morphology that occur during synaptic plasticity and memory formation in the adult mouse hippocampus. PMID:16546126

Tejada-Simon, Maria V.; Villasana, Laura E.; Serrano, Faridis; Klann, Eric

2007-01-01

161

Evidence for nicotinic acetylcholine receptor activation in rat cerebellar slices.  

PubMed

Neuronal nicotinic ACh receptor (nAChR) activation is known to enhance glutamate and GABA release in different brain areas. Moreover, nAChRs play an important role in neuronal differentiation. By using the patch-clamp technique, we have investigated the presence of nAChRs in cerebellar granule cells in slices from P5-P14 rats. Application of ACh (1 mM) could elicit a variety of effects. Some cells did not respond at all. In other cells, a somatic current was activated. In a proportion of cells, postsynaptic currents (PSCs), with or without somatic current, were elicited. Somatic nAChRs are likely to be of the alpha(4)beta(2) subtype, but the presence of other subunit combinations (alpha(7)- or beta(4)-containing receptors) cannot be ruled out. The ACh-induced PSCs were glutamatergic in nature. Thus, in a reasonable proportion of cells, nicotinic receptors are present presynaptically. They are likely to be alpha(7) receptors whose activation elicits Glu release via a TTX-sensitive mechanism. Our experiments are the first electrophysiological evidence showing, in a native cerebellar preparation, the presence of nicotinic receptors at the mossy fibre-granule cell synapse at early developmental stages. PMID:11796144

De Filippi, G; Baldwinson, T; Sher, E

2001-12-01

162

Mechanisms of Activation of Receptor Tyrosine Kinases: Monomers or Dimers  

PubMed Central

Receptor tyrosine kinases (RTKs) play essential roles in cellular processes, including metabolism, cell-cycle control, survival, proliferation, motility and differentiation. RTKs are all synthesized as single-pass transmembrane proteins and bind polypeptide ligands, mainly growth factors. It has long been thought that all RTKs, except for the insulin receptor (IR) family, are activated by ligand-induced dimerization of the receptors. An increasing number of diverse studies, however, indicate that RTKs, previously thought to exist as monomers, are present as pre-formed, yet inactive, dimers prior to ligand binding. The non-covalently associated dimeric structures are reminiscent of those of the IR family, which has a disulfide-linked dimeric structure. Furthermore, recent progress in structural studies has provided insight into the underpinnings of conformational changes during the activation of RTKs. In this review, I discuss two mutually exclusive models for the mechanisms of activation of the epidermal growth factor receptor, the neurotrophin receptor and IR families, based on these new insights. PMID:24758840

Maruyama, Ichiro N.

2014-01-01

163

Modulation of Opioid Receptor Ligand Affinity and Efficacy Using Active and Inactive State Receptor Models  

PubMed Central

Mu opioid receptor (MOR) agonists are widely used for the treatment of pain; however chronic use results in the development of tolerance and dependence. It has been demonstrated that co-administration of a MOR agonist with a delta opioid receptor (DOR) antagonist maintains the analgesia associated with MOR agonists, but with reduced negative side effects. Using our newly refined opioid receptor models for structure-based ligand design, we have synthesized several pentapeptides with tailored affinity and efficacy profiles. In particular, we have obtained pentapeptides 8, Tyr-c(S-S)[DCys-1Nal-Nle-Cys]NH2, and 12, Tyr-c(S-S)[DCys-1Nal-Nle-Cys]OH, which demonstrates high affinity and full agonist behavior at MOR, high affinity but very low efficacy for DOR, and minimal affinity for the kappa opioid receptor (KOR). Functional properties of these peptides as MOR agonists/DOR antagonists lacking undesired KOR activity make them promising candidates for future in vivo studies of MOR/DOR interactions. Subtle structural variation of 12, by substituting D-Cys5 for L-Cys5, generated analog 13 which maintains low nanomolar MOR and DOR affinity, but which displays no efficacy at either receptor. These results demonstrate the power and utility of accurate receptor models for structure-based ligand design, as well as the profound sensitivity of ligand function on its structure. PMID:22882801

Anand, Jessica P.; Purington, Lauren C.; Pogozheva, Irina D.; Traynor, John R.; Mosberg, Henry I.

2012-01-01

164

Distribution of laminin, fibronectin, and interstitial collagen type III in soft tissue tumours  

Microsoft Academic Search

The distributions of laminin, fibronectin, and interstitial collagen type III have been investigated in a series of 60 soft tissue tumours by immunochemistry. Positive laminin staining was seen in sites predicted by the distribution of ultrastructurally visible basal lamina. Pericellular laminin was present in all benign tumours of Schwann cell and smooth muscle origin examined, in the two malignant Schwannomas

A J dArdenne; P Kirkpatrick; B C Sykes

1984-01-01

165

Differential effects of quercetin glycosides on GABAC receptor channel activity.  

PubMed

Quercetin, a representative flavonoid, is a compound of low molecular weight found in various colored plants and vegetables. Quercetin shows a wide range of neuropharmacological activities. In fact, quercetin naturally exists as monomer-(quercetin-3-O-rhamnoside) (Rham1), dimer-(Rutin), or trimer-glycosides [quercetin-3-(2(G)-rhamnosylrutinoside)] (Rham2) at carbon-3 in fruits and vegetables. The carbohydrate components are removed after ingestion into gastrointestinal systems. The role of the glycosides attached to quercetin in the regulation of ?-aminobutyric acid class C (GABAC) receptor channel activity has not been determined. In the present study, we examined the effects of quercetin glycosides on GABAC receptor channel activity by expressing human GABAC alone in Xenopus oocytes using a two-electrode voltage clamp technique and also compared the effects of quercetin glycosides with quercetin. We found that GABA-induced inward current (I GABA ) was inhibited by quercetin or quercetin glycosides. The inhibitory effects of quercetin and its glycosides on I GABA were concentration-dependent and reversible in the order of Rutin ? quercetin ? Rham 1 > Rham 2. The inhibitory effects of quercetin and its glycosides on I GABA were noncompetitive and membrane voltage-insensitive. These results indicate that quercetin and its glycosides regulate GABAC receptor channel activity through interaction with a different site from that of GABA, and that the number of carbohydrate attached to quercetin might play an important role in the regulation of GABAC receptor channel activity. PMID:24895146

Kim, Hyeon-Joong; Lee, Byung-Hwan; Choi, Sun-Hye; Jung, Seok-Won; Kim, Hyun-Sook; Lee, Joon-Hee; Hwang, Sung-Hee; Pyo, Mi-Kyung; Kim, Hyoung-Chun; Nah, Seung-Yeol

2015-01-01

166

A bacterial tyrosine phosphatase inhibits plant pattern recognition receptor activation.  

PubMed

Innate immunity relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the host cell's surface. Many plant PRRs are kinases. Here, we report that the Arabidopsis receptor kinase EF-TU RECEPTOR (EFR), which perceives the elf18 peptide derived from bacterial elongation factor Tu, is activated upon ligand binding by phosphorylation on its tyrosine residues. Phosphorylation of a single tyrosine residue, Y836, is required for activation of EFR and downstream immunity to the phytopathogenic bacterium Pseudomonas syringae. A tyrosine phosphatase, HopAO1, secreted by P. syringae, reduces EFR phosphorylation and prevents subsequent immune responses. Thus, host and pathogen compete to take control of PRR tyrosine phosphorylation used to initiate antibacterial immunity. PMID:24625928

Macho, Alberto P; Schwessinger, Benjamin; Ntoukakis, Vardis; Brutus, Alexandre; Segonzac, Cécile; Roy, Sonali; Kadota, Yasuhiro; Oh, Man-Ho; Sklenar, Jan; Derbyshire, Paul; Lozano-Durán, Rosa; Malinovsky, Frederikke Gro; Monaghan, Jacqueline; Menke, Frank L; Huber, Steven C; He, Sheng Yang; Zipfel, Cyril

2014-03-28

167

Structural basis for selective activation of ABA receptors  

SciTech Connect

Changing environmental conditions and lessening fresh water supplies have sparked intense interest in understanding and manipulating abscisic acid (ABA) signaling, which controls adaptive responses to drought and other abiotic stressors. We recently discovered a selective ABA agonist, pyrabactin, and used it to discover its primary target PYR1, the founding member of the PYR/PYL family of soluble ABA receptors. To understand pyrabactin's selectivity, we have taken a combined structural, chemical and genetic approach. We show that subtle differences between receptor binding pockets control ligand orientation between productive and nonproductive modes. Nonproductive binding occurs without gate closure and prevents receptor activation. Observations in solution show that these orientations are in rapid equilibrium that can be shifted by mutations to control maximal agonist activity. Our results provide a robust framework for the design of new agonists and reveal a new mechanism for agonist selectivity.

Peterson, Francis C.; Burgie, E. Sethe; Park, Sang-Youl; Jensen, Davin R.; Weiner, Joshua J.; Bingman, Craig A.; Chang, Chia-En A.; Cutler, Sean R.; Phillips, Jr., George N.; Volkman, Brian F. (MCW); (UW); (UCR)

2010-11-01

168

Liver X Receptor and Peroxisome Proliferator-Activated Receptor Agonist from Cornus alternifolia  

PubMed Central

Background Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptors superfamily and are transcription factors activated by specific ligands. Liver X receptors (LXR) belong to the nuclear hormone receptors and have been shown to play an important role in cholesterol homeostasis. From the previous screening of several medicinal plants for potential partial PPAR? agonists, the extracts of Cornus alternifolia were found to exhibit promising bioactivity. In this paper, we report the isolation and structural elucidation of four new compounds and their potential as ligands for PPAR. Methods The new compounds were extracted from the leaves of Cornus alternifolia and fractionated by high-performance liquid chromatography. Their structures were elucidated on the basis of spectroscopic evidence and analysis of their hydrolysis products. Results Three new iridoid glycosides including an iridolactone, alternosides A-C (1–3), a new megastigmane glycoside, cornalternoside (4) and 10 known compounds, were obtained from the leaves of Cornus alternifolia. Kaempferol-3-O-?-glucopyranoside (5) exhibited potent agonistic activities for PPAR?, PPAR? and LXR with EC50 values of 0.62, 3.0 and 1.8 ? M, respectively. Conclusions We isolated four new and ten known compounds from Cornus alternifolia, and one known compound showed agonistic activities for PPAR?, PPAR? and LXR. General significance Compound 1 is the first example of a naturally occurring iridoid glycoside containing a ?-glucopyranoside moiety at C-6. PMID:22353334

He, Yang-Qing; Ma, Guo-Yi; Peng, Jiang-nan; Ma, Zhan-Ying; Hamann, Mark T.

2012-01-01

169

Cofactoring and dimerization of proteinase-activated receptors.  

PubMed

Proteinase-activated receptors (PARs) are G protein-coupled receptors that transmit cellular responses to extracellular proteases and have important functions in vascular physiology, development, inflammation, and cancer progression. The established paradigm for PAR activation involves proteolytic cleavage of the extracellular N terminus, which reveals a new N terminus that functions as a tethered ligand by binding intramolecularly to the receptor to trigger transmembrane signaling. Most cells express more than one PAR, which can influence the mode of PAR activation and signaling. Clear examples include murine PAR3 cofactoring of PAR4 and transactivation of PAR2 by PAR1. Thrombin binds to and cleaves murine PAR3, which facilitates PAR4 cleavage and activation. This process is essential for thrombin signaling and platelet activation, since murine PAR3 cannot signal alone. Although PAR1 and PAR4 are both competent to signal, PAR1 is able to act as a cofactor for PAR4, facilitating more rapid cleavage and activation by thrombin. PAR1 can also facilitate PAR2 activation through a different mechanism. Cleavage of the PAR1 N terminus by thrombin generates a tethered ligand domain that can bind intermolecularly to PAR2 to activate signaling. Thus, PARs can regulate each other's activity by localizing thrombin when in complex with PAR3 and PAR4 or by cleaved PAR1, providing its tethered ligand domain for PAR2 activation. The ability of PARs to cofactor or transactivate other PARs would necessitate that the two receptors be in close proximity, likely in the form of a heterodimer. Here, we discuss the cofactoring and dimerization of PARs and the functional consequences on signaling. PMID:24064459

Lin, Huilan; Liu, Allen P; Smith, Thomas H; Trejo, JoAnn

2013-01-01

170

Laminin promotes vascular network formation in 3D in vitro collagen scaffolds by regulating VEGF uptake  

PubMed Central

Angiogenesis is an essential neovascularisation process, which if recapitulated in 3D in vitro, will provide better understanding of endothelial cell (EC) behaviour. Various cell types and growth factors are involved, with vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 key components. We were able to control the aggregation pattern of ECs in 3D collagen hydrogels, by varying the matrix composition and/or having a source of cells signalling angiogenic proteins. These aggregation patterns reflect the different developmental pathways that ECs take to form different sized tubular structures. Cultures with added laminin and thus increased expression of ?6 integrin showed a significant increase (p<0.05) in VEGFR2 positive ECs and increased VEGF uptake. This resulted in the end-to-end network aggregation of ECs. In cultures without laminin and therefore low ?6 integrin expression, VEGFR2 levels and VEGF uptake were significantly lower (p<0.05). These ECs formed contiguous sheets, analogous to the ‘wrapping’ pathway in development. We have identified a key linkage between integrin expression on ECs and their uptake of VEGF, regulated by VEGFR2, resulting in different aggregation patterns in 3D. PMID:24907654

Stamati, Katerina; Priestley, John V.; Mudera, Vivek; Cheema, Umber

2014-01-01

171

RhoA-dependent Switch between ?2?1 and ?3?1 Integrins Is Induced by Laminin-5 during Early Stage of HT-29 Cell Differentiation  

PubMed Central

Integrin-mediated interactions between the basement membrane and epithelial cells control the differentiation of epithelia. We characterized the modulation of adhesive behaviors to basement membrane proteins and of integrin function in the human colon adenocarcinoma HT-29 cell line, which differentiates into enterocytes after the substitution of galactose for glucose in the medium. We demonstrate an increased capability of these cells to adhere to collagen type IV during the early stage of differentiation. This effect occurs without any changes in integrin cell surface expression but rather results from an ?2?1/?3?1 integrin switch, ?3?1 integrin becoming the major collagen receptor. The increase in laminin-5 secretion and deposit on the matrix is a key factor in the mechanism regulating cell adhesion, because it is responsible for the activation of ?3?1 integrin. Furthermore, down-regulation of RhoA GTPase activity occurs during HT-29 cell differentiation and correlates with the activation of the integrin ?3?1. Indeed, C3 transferase, a RhoA GTPase inhibitor, induces a similar ?2?1/?3?1 switch in undifferentiated HT-29 cells. These results indicate that the decrease in RhoA activation is the biochemical mechanism underlying this integrin switch observed during cell differentiation. The physiological relevance of such modulation of integrin activity in the functioning of the crypt-villus axis is discussed. PMID:11598208

Gout, Stéphanie P.; Jacquier-Sarlin, Muriel R.; Rouard-Talbot, Laurence; Rousselle, Patricia; Block, Marc R.

2001-01-01

172

Platelet-activating factor (PAF) receptor and genetically engineered PAF receptor mutant mice  

Microsoft Academic Search

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a biologically active phospholipid mediator. Although PAF was initially recognized for its potential to induce platelet aggregation and secretion, intense investigations have elucidated potent biological actions of PAF in a broad range of cell types and tissues, many of which also produce the molecule. PAF acts by binding to a unique G-protein-coupled seven transmembrane receptor.

Satoshi Ishii; Takao Shimizu

2000-01-01

173

Covalent agonists for studying G protein-coupled receptor activation  

PubMed Central

Structural studies on G protein-coupled receptors (GPCRs) provide important insights into the architecture and function of these important drug targets. However, the crystallization of GPCRs in active states is particularly challenging, requiring the formation of stable and conformationally homogeneous ligand-receptor complexes. Native hormones, neurotransmitters, and synthetic agonists that bind with low affinity are ineffective at stabilizing an active state for crystallogenesis. To promote structural studies on the pharmacologically highly relevant class of aminergic GPCRs, we here present the development of covalently binding molecular tools activating Gs-, Gi-, and Gq-coupled receptors. The covalent agonists are derived from the monoamine neurotransmitters noradrenaline, dopamine, serotonin, and histamine, and they were accessed using a general and versatile synthetic strategy. We demonstrate that the tool compounds presented herein display an efficient covalent binding mode and that the respective covalent ligand-receptor complexes activate G proteins comparable to the natural neurotransmitters. A crystal structure of the ?2-adrenoreceptor in complex with a covalent noradrenaline analog and a conformationally selective antibody (nanobody) verified that these agonists can be used to facilitate crystallogenesis. PMID:25006259

Weichert, Dietmar; Kruse, Andrew C.; Manglik, Aashish; Hiller, Christine; Zhang, Cheng; Hübner, Harald; Kobilka, Brian K.; Gmeiner, Peter

2014-01-01

174

Glucocorticoid receptor mediates the gluconeogenic activity of the farnesoid X receptor in the fasting condition.  

PubMed

The glucocorticoid receptor (GR) is a master gene orchestrating the activation of gluconeogenic genes in the liver in response to food withdrawal. Mechanisms of GR regulation by other nuclear receptors, however, are poorly defined. Here, we report that the farnesoid X receptor (FXR), a bile acid sensor, activates gluconeogenic pathways in the liver and regulates GR expression and activity. FXR-null mice are hypoglycemic in the unfed state and exhibit both a reduced hepatic production of glucose in response to the pyruvate challenge and a decreased expression of two rate-limiting enzymes involved in gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase), along with blunted liver expression of GR. Treating wild-type mice with a semisynthetic FXR ligand (6E-CDCA) increases the liver expression of GR, PEPCK, and G6Pase. This effect was lost in fed animals, as well as in FXR(-/-) mice. The human and mouse GR promoters contain a conserved FXR-responsive element (an ER-8 sequence) whose activation by FXR ligation leads to GR transcription. GR silencing by siRNA in vitro or its pharmacological antagonism in vivo with mifepristone reverses the effect of FXR activation on expression of gluconeogenic genes. These findings demonstrate that an FXR-GR pathway regulates the activation of hepatic gluconeogenesis in the transition from the unfed to the fed state. PMID:22447981

Renga, Barbara; Mencarelli, Andrea; D'Amore, Claudio; Cipriani, Sabrina; Baldelli, Franco; Zampella, Angela; Distrutti, Eleonora; Fiorucci, Stefano

2012-07-01

175

Nociceptin/Orphanin FQ Receptor Activation Attenuates Antinociception Induced by Mixed Nociceptin/Orphanin FQ/?-Opioid Receptor Agonists  

PubMed Central

Activation of brain nociceptin/orphanin FQ (NOP) receptors leads to attenuation of ?-opioid receptor (MOP receptor)-mediated antinociception. Buprenorphine, a high-affinity partial MOP receptor agonist also binds to NOP receptors with 80 nM affinity. The buprenorphine-induced inverted U-shaped dose-response curve for antinociception may be due to NOP receptor activation, given that, in the presence of the NOP receptor antagonist, 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J113397), or in NOP receptor knockout mice, buprenorphine has a steeper dose-response curve and acts as a full agonist. To further explore the involvement of the direct activation of NOP receptors by buprenorphine and other compounds that activate both NOP and MOP receptors, the antinociceptive effects of 1-(1-(2,3,3?,4,5,6-hexahydro-1H-phenalen-1-yl)piperidin-4-yl)-indolin-2-one. (SR16435), 3-ethyl-1-(1-(4-isopropylcyclohexyl)piperidin-4-yl)-indolin-2-one (SR16507), buprenorphine, pentazocine, and morphine, compounds with varying levels of MOP and NOP receptor affinity and efficacy, were assessed in mice using the tail-flick assay. The ability of the selective NOP receptor antagonist (?)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB-612111) to potentiate antinociception induced by the above compounds was examined to investigate whether activation of NOP receptors leads to attenuation of MOP receptor-mediated antinociception. SB-612111 potentiated antinociception induced by buprenorphine and the other mixed NOP/MOP receptor agonists SR16435 and SR16507. However, SB-612111 had no effect on pentazocine or morphine antinociception, two compounds with no NOP receptor-binding affinity. These results further support the hypothesis that activation of NOP receptors can lead to attenuation of MOP receptor-mediated antinociception elicited by mixed NOP/MOP receptor compounds such as buprenorphine, SR16435, and SR16507 and that, although buprenorphine has low efficacy in vitro, it has significant NOP receptor agonist activity in vivo. PMID:19713488

Khroyan, Taline V.; Polgar, Willma E.; Jiang, Faming; Zaveri, Nurulain T.

2009-01-01

176

Nociceptin/orphanin FQ receptor activation attenuates antinociception induced by mixed nociceptin/orphanin FQ/mu-opioid receptor agonists.  

PubMed

Activation of brain nociceptin/orphanin FQ (NOP) receptors leads to attenuation of mu-opioid receptor (MOP receptor)-mediated antinociception. Buprenorphine, a high-affinity partial MOP receptor agonist also binds to NOP receptors with 80 nM affinity. The buprenorphine-induced inverted U-shaped dose-response curve for antinociception may be due to NOP receptor activation, given that, in the presence of the NOP receptor antagonist, 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J113397), or in NOP receptor knockout mice, buprenorphine has a steeper dose-response curve and acts as a full agonist. To further explore the involvement of the direct activation of NOP receptors by buprenorphine and other compounds that activate both NOP and MOP receptors, the antinociceptive effects of 1-(1-(2,3,3alpha,4,5,6-hexahydro-1H-phenalen-1-yl)piperidin-4-yl)-indolin-2-one. (SR16435), 3-ethyl-1-(1-(4-isopropylcyclohexyl)piperidin-4-yl)-indolin-2-one (SR16507), buprenorphine, pentazocine, and morphine, compounds with varying levels of MOP and NOP receptor affinity and efficacy, were assessed in mice using the tail-flick assay. The ability of the selective NOP receptor antagonist (-)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB-612111) to potentiate antinociception induced by the above compounds was examined to investigate whether activation of NOP receptors leads to attenuation of MOP receptor-mediated antinociception. SB-612111 potentiated antinociception induced by buprenorphine and the other mixed NOP/MOP receptor agonists SR16435 and SR16507. However, SB-612111 had no effect on pentazocine or morphine antinociception, two compounds with no NOP receptor-binding affinity. These results further support the hypothesis that activation of NOP receptors can lead to attenuation of MOP receptor-mediated antinociception elicited by mixed NOP/MOP receptor compounds such as buprenorphine, SR16435, and SR16507 and that, although buprenorphine has low efficacy in vitro, it has significant NOP receptor agonist activity in vivo. PMID:19713488

Khroyan, Taline V; Polgar, Willma E; Jiang, Faming; Zaveri, Nurulain T; Toll, Lawrence

2009-12-01

177

Pregnancy loss and endometriosis: pathogenic role of anti-laminin-1 autoantibodies.  

PubMed

Laminin-1 is a major multifunctional glycoprotein that forms an integral part of the scaffolding network of basement membranes, and is the earliest synthesized component during embryogenesis. This protein (alpha1beta1gamma1) plays an important role in basement membrane assembly and epiblast differentiation during embryonic development. Anti-laminin-1 autoantibodies are known to cause infertility and recurrent spontaneous abortion in animals. Recently, we reported that the presence of IgG anti-laminin-1 antibodies (Abs) in the blood is significantly associated with recurrent first-trimester miscarriages and subsequent negative pregnancy outcomes. Interestingly, these antibodies are also strongly associated with infertility, especially infertility caused by endometriosis. Laminin-alpha1, laminin-beta1, and laminin-gamma1 mRNAs were also detected in 90% of endometriotic lesions, and all laminin-alpha1, laminin-beta1, and laminin-gamma1 chains were localized to the basement membranes of glandular epithelium in endometriotic peritoneal lesions. ELISA showed specific reactivity of the autoantibodies to a particular region of the laminin-1 molecule, that is, the alpha1 chain G domain. IgM monoclonal anti-laminin-1 Abs, which we recently established, also recognized the G domain and cross-reacted with human alpha1 chain located in the basement membrane of the glandular epithelium of human endometrium. We also established an animal model that produced high titers of anti-laminin-1 Abs after immunization with mouse laminin-1. Anti-laminin-1 Abs from the immunized mice caused a higher fetal resorption rate with lower embryonic and placental weights. Thus, anti-laminin-1 Abs may be important in the development of autoimmune-mediated reproductive failures, and the assessment of the such antibodies may provide a novel means for noninvasive diagnosis of endometriosis. PMID:16126957

Inagaki, Junko; Kondo, Akane; Lopez, Luis R; Shoenfeld, Yehuda; Matsuura, Eiji

2005-06-01

178

Guggulsterone activates multiple nuclear receptors and induces CYP3A gene expression through the pregnane X receptor.  

PubMed

Gugulipid is an extract of the guggul tree, Commiphora mukul, that is used to treat hyperlipidemia in humans. The lipid-lowering activity is found in the stereoisomers and plant sterols Z-guggulsterone and E-guggulsterone. The molecular basis for the lipid-lowering action of guggulsterone has been suggested to be antagonism of the farnesoid X receptor, a member of the nuclear receptor superfamily of ligand-activated transcription factors. To determine whether guggulsterone has the ability to function as an agonist of other nuclear receptor family members, we screened a panel of these proteins for their ability to transactivate reporter genes. Here, we show that guggulsterones activate the estrogen receptor alpha isoform, progesterone receptor, and pregnane X receptor. Concentration-response analysis using reporter gene assays indicate that guggulsterones activate these three receptors with EC(50) values in the low micromolar range. Furthermore, we show that guggulsterone-mediated activation of the pregnane X receptor induces the expression of CYP3A genes in both rodent and human hepatocytes. Protein interaction assays indicate that guggulsterones interact directly with pregnane X receptor, thereby modulating interaction with protein cofactors. We introduce a novel method to screen herbal remedies for their ability to activate pregnane X receptor. Pregnane X receptor activation is known to cause herb-drug interactions, and our data suggest that gugulipid therapy should be used cautiously in patients taking prescription medications that are metabolized by CYP3A family members. Moreover, our data suggest the need for additional studies of guggulsterones agonist activity against estrogen receptor alpha isoform and the progesterone receptor. PMID:15075359

Brobst, Dan E; Ding, Xunshan; Creech, Katrina L; Goodwin, Bryan; Kelley, Brian; Staudinger, Jeff L

2004-08-01

179

The Search for Endogenous Activators of the Aryl Hydrocarbon Receptor  

PubMed Central

In its simplest aspect, this review is an attempt to describe the major ligand classes of the aryl hydrocarbon receptor (AHR). A grander objective is to provide models that may help define the physiological activator or “endogenous ligand” of the AHR. We begin by presenting evidence that supports a developmental function for the AHR. This is followed by proposing mechanisms by which an endogenous ligand and consequent AHR activation might be important during normal physiology and development. With this background, we then present a survey of the known xenobiotic, endogenous, dietary and “un-conventional” activators of the AHR. When possible, this includes information about their induction potency, receptor binding affinity and potential for exposure. Because of the essential function of the AHR in embryonic development, we discuss the candidacy of each of these compounds as physiologically important activators. PMID:18076143

Nguyen, Linh P.; Bradfield, Christopher A.

2008-01-01

180

Weaver granule neurons are rescued by calcium channel antagonists and antibodies against a neurite outgrowth domain of the B2 chain of laminin  

PubMed Central

The weaver mutation impairs migration of the cerebellar granular neurons and induces neuronal death during the first two weeks of postnatal life. To elucidate the molecular mechanisms for the impaired neuronal migration, we investigated the rescue mechanisms of the weaver (wv/wv) granule neurons in vitro. We found that Fab2 fragments of antibodies against a neurite outgrowth domain of the B2 chain of laminin enhanced neurite outgrowth and neuronal migration of the weaver granule neurons on a laminin substratum and in the established cable culture system. The rescue of the weaver granule neurons by antibodies against the B2 chain of laminin may result from the neutralizing effect of these antibodies against the elevated B2 chain levels of the weaver brain. The L-type calcium channel blocker, verapamil (1-5 microM), also rescued the weaver granule neurons. High concentrations of MK-801 (10- 20 microM), a glutamate receptor antagonist and voltage-gated calcium channel blocker, rescued the weaver granule neurons similar to verapamil, but low concentrations of MK-801 (1 microM) had no rescue effect. Simultaneous patch-clamp studies indicated that the weaver granule neurons did not express functional N-methyl-D-aspartate receptors further indicating that the rescue of the weaver granule neurons by MK-801 resulted from its known inhibition of voltage-gated calcium channels. The present results indicate that antibodies against the B2 chain of laminin, verapamil, and high concentrations of MK-801 protect the weaver granule neurons from the otherwise destructive action of the weaver gene. Thus, both the laminin system and calcium channel function contribute to the migration deficiency of the weaver granule neurons. PMID:8707831

1996-01-01

181

Activation of D4 Dopamine Receptor Decreases Angiotensin II Type 1 Receptor Expression in Rat Renal Proximal Tubule Cells.  

PubMed

The dopaminergic and renin-angiotensin systems interact to regulate blood pressure. Disruption of the D4 dopamine receptor gene in mice produces hypertension that is associated with increased renal angiotensin type 1 (AT1) receptor expression. We hypothesize that the D4 receptor can inhibit AT1 receptor expression and function in renal proximal tubule cells from Wistar-Kyoto (WKY) rats, but the D4 receptor regulation of AT1 receptor is aberrant in renal proximal tubule cells from spontaneously hypertensive rats (SHRs). The D4 receptor agonist, PD168077, decreased AT1 receptor protein expression in a time- and concentration-dependent manner in WKY cells. By contrast, in SHR cells, PD168077 increased AT1 receptor protein expression. The inhibitory effect of D4 receptor on AT1 receptor expression in WKY cells was blocked by a calcium channel blocker, nicardipine, or calcium-free medium, indicating that calcium is involved in the D4 receptor-mediated signaling pathway. Angiotensin II increased Na(+)-K(+) ATPase activity in WKY cells. Pretreatment with PD168077 decreased the stimulatory effect of angiotensin II on Na(+)-K(+) ATPase activity in WKY cells. In SHR cells, the inhibitory effect of D4 receptor on angiotensin II-mediated stimulation of Na(+)-K(+) ATPase activity was aberrant; pretreatment with PD168077 augmented the stimulatory effect of AT1 receptor on Na(+)-K(+) ATPase activity in SHR cells. This was confirmed in vivo; pretreatment with PD128077 for 1 week augmented the antihypertensive and natriuretic effect of losartan in SHRs but not in WKY rats. We suggest that an aberrant interaction between D4 and AT1 receptors may play a role in the abnormal regulation of sodium excretion in hypertension. PMID:25368031

Chen, Ken; Deng, Kun; Wang, Xiaoyan; Wang, Zhen; Zheng, Shuo; Ren, Hongmei; He, Duofen; Han, Yu; Asico, Laureano D; Jose, Pedro A; Zeng, Chunyu

2015-01-01

182

The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A  

SciTech Connect

Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.

Sato, Shoko, E-mail: satosho@rs.tus.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Shirakawa, Hitoshi, E-mail: shirakah@m.tohoku.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Tomita, Shuhei, E-mail: tomita@med.tottori-u.ac.jp [Division of Molecular Pharmacology, Department of Pathophysiological and Therapeutic Science, Yonago 683-8503 (Japan); Tohkin, Masahiro, E-mail: tohkin@phar.nagoya-cu.ac.jp [Department of Medical Safety Science, Graduate School of Pharmaceutical Science, Nagoya City University, Nagoya 267-8603 (Japan); Gonzalez, Frank J., E-mail: gonzalef@mail.nih.gov [Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Komai, Michio, E-mail: mkomai@m.tohoku.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan)

2013-11-15

183

?-Apo-13-carotenone regulates retinoid X receptor transcriptional activity through tetramerization of the receptor.  

PubMed

Retinoid X receptor (RXR?) is activated by 9-cis-retinoic acid (9cRA) and regulates transcription as a homodimer or as a heterodimer with other nuclear receptors. We have previously demonstrated that ?-apo-13-carotenone, an eccentric cleavage product of ?-carotene, antagonizes the activation of RXR? by 9cRA in mammalian cells overexpressing this receptor. However, the molecular mechanism of ?-apo-13-carotenone's modulation on the transcriptional activity of RXR? is not understood and is the subject of this report. We performed transactivation assays using full-length RXR? and reporter gene constructs (RXRE-Luc) transfected into COS-7 cells, and luciferase activity was examined. ?-Apo-13-carotenone was compared with the RXR? antagonist UVI3003. The results showed that both ?-apo-13-carotenone and UVI3003 shifted the dose-dependent RXR? activation by 9cRA. In contrast, the results of assays using a hybrid Gal4-DBD:RXR?LBD receptor reporter cell assay that detects 9cRA-induced coactivator binding to the ligand binding domain demonstrated that UVI3003 significantly inhibited 9cRA-induced coactivator binding to RXR?LBD, but ?-apo-13-carotenone did not. However, both ?-apo-13-carotenone and UVI3003 inhibited 9-cRA induction of caspase 9 gene expression in the mammary carcinoma cell line MCF-7. To resolve this apparent contradiction, we investigated the effect of ?-apo-13-carotenone on the oligomeric state of purified recombinant RXR?LBD. ?-Apo-13-carotenone induces tetramerization of the RXR?LBD, although UVI3003 had no effect on the oligomeric state. These observations suggest that ?-apo-13-carotenone regulates RXR? transcriptional activity by inducing the formation of the "transcriptionally silent" RXR? tetramer. PMID:25324544

Sun, Jian; Narayanasamy, Sureshbabu; Curley, Robert W; Harrison, Earl H

2014-11-28

184

Orvinols with Mixed Kappa/Mu Opioid Receptor Agonist Activity  

PubMed Central

Dual-acting kappa opioid receptor (KOR) agonist and mu opioid receptor (MOR) partial agonist ligands have been put forward as potential treatment agents for cocaine and other psychostimulant abuse. Members of the orvinol series of ligands are known for their high binding affinity to both KOR and MOR, but efficacy at the individual receptors has not been thoroughly evaluated. In this study, it is shown that a predictive model for efficacy at KOR can be derived, with efficacy being controlled by the length of the group attached to C20 and by the introduction of branching into the side chain. In vivo evaluation of two ligands with the desired in vitro profile confirms both display KOR, and to a lesser extent MOR, activity in an analgesic assay suggesting that, in this series, in vitro measures of efficacy using the [35S]GTP?S assay are predictive of the in vivo profile. PMID:23438330

2013-01-01

185

Polymerized Laminin-332 Matrix Supports Rapid and Tight Adhesion of Keratinocytes, Suppressing Cell Migration  

PubMed Central

Laminin-332 (?3ß3?2) (Lm332) supports the stable anchoring of basal keratinocytes to the epidermal basement membrane, while it functions as a motility factor for wound healing and cancer invasion. To understand these contrasting activities of Lm332, we investigated Lm332 matrices deposited by normal human keratinocytes and other Lm332-expressing cell lines. All types of the cells efficiently deposited Lm332 on the culture plates in specific patterns. On the contrary, laminins containing laminin ß1 and/or ?1 chains, such as Lm511 and Lm311, were not deposited on the culture plates even if secreted into culture medium. The Lm332 deposition was not inhibited by function-blocking antibodies to the ?3 and ?6 integrins but was inhibited by sodium selenate, suggesting that sulfated glycosaminoglycans on cell surface, e.g. heparan sulfate proteoglycans, might be involved in the process. HEK293 cells overexpressing exogenous Lm332 (Lm332-HEK) almost exclusively deposited Lm332 on the plates. The deposited Lm332 matrix showed a mesh-like network structure as analyzed by electron microscopy, suggesting that Lm332 was highly polymerized. When biological activity was analyzed, the Lm332 matrix rather suppressed the migration of keratinocytes as compared with purified Lm332, which highly promoted the cell migration. The Lm332 matrix supported adhesion of keratinocytes much more strongly and stably than purified Lm332. Integrin ?3ß1 bound to the Lm332 matrix at a three times higher level than purified Lm332. Normal keratinocytes prominently showed integrin ?6ß4-containing, hemidesmosome-like structures on the Lm332 matrix but not on the purified one. These results indicate that the polymerized Lm332 matrix supports stable cell adhesion by interacting with both integrin ?6ß4 and ?3ß1, whereas unassembled soluble Lm332 supports cell migration. PMID:22563463

Kariya, Yoshinobu; Sato, Hiroki; Katou, Naoko; Kariya, Yukiko; Miyazaki, Kaoru

2012-01-01

186

Development/Plasticity/Repair GABAB Receptor Activation Triggers BDNF Release and  

E-print Network

Development/Plasticity/Repair GABAB Receptor Activation Triggers BDNF Release and Promotes(GABAB- Rs)andtime-lapsefluorescenceimagingonculturedhippocampalneuronsexpressingGFP-taggedbrain-derivedneurotrophicfactor(BDNF), we found that activation of metabotropic GABAB receptors (GABAB-Rs) triggers secretion of BDNF

Paris-Sud XI, Université de

187

Localization of a tumor cell adhesion domain of laminin by a monoclonal antibody  

SciTech Connect

Monoclonal antibodies were prepared to localize the domain(s) of laminin to which tumor cells adhere. Rat Y3-Ag 1.2.3 myeloma cells were fused with spleen cells from a rat immunized with a purified 440-kDa fragment of chymotrypsin-digested laminin. Three monoclonal antibodies (AL-1 to AL-3) that bound to intact laminin in a solid-phase radioimmunoassay were chosen for further analysis. The epitopes recognized by these antibodies were characterized by radioimmunoassays, immunoblotting, radioimmunoprecipitation, and immunoaffinity chromatography. In cell adhesion assays, monoclonal antibody AL-2 inhibited the highly metastatic melanoma cell line, K-1735-M4, to both intact laminin and the 440-kDa fragment of laminin. Electron microscopic examination of laminin-monoclonal antibody interactions showed that monoclonal antibody AL-2 reacted with the long arm of laminin directly below the cross-region. Two monoclonal antibodies that failed to inhibit tumor cell adhesion to laminin reacted with epitopes on the lateral short arms or cross-region of laminin as seen by electron microscopy. These results suggest that a new tumor cell binding domain of laminin may be located close to the cross-region on the long arm of laminin.

Skubitz, A.P.N.; Charonis, A.S.; Tsilibary, E.C.; Furcht, L.T. (Univ. of Minnesota, Minneapolis (United States))

1987-12-01

188

Peroxisome Proliferator-Activated Receptor Alpha Target Genes  

PubMed Central

The peroxisome proliferator-activated receptor alpha (PPAR?) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPAR? serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPAR? binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPAR? governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPAR? is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPAR? in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPAR? target genes. The emphasis is on gene regulation by PPAR? in liver although many of the results likely apply to other organs and tissues as well. PMID:20936127

Rakhshandehroo, Maryam; Knoch, Bianca; Müller, Michael; Kersten, Sander

2010-01-01

189

Regulation of ligands for the NKG2D activating receptor  

PubMed Central

NKG2D is an activating receptor expressed by all NK cells and subsets of T cells. It serves as a major recognition receptor for detection and elimination of transformed and infected cells and participates in the genesis of several inflammatory diseases. The ligands for NKG2D are self-proteins that are induced by pathways that are active in certain pathophysiological states. NKG2D ligands are regulated transcriptionally, at the level of mRNA and protein stability, and by cleavage from the cell surface. In some cases, ligand induction can be attributed to pathways that are activated specifically in cancer cells or infected cells. We review the numerous pathways that have been implicated in the regulation of NKG2D ligands, discuss the pathologic states in which those pathways are likely to act, and attempt to synthesize the findings into general schemes of NKG2D ligand regulation in NK cell responses to cancer and infection. PMID:23298206

Raulet, David H.; Gasser, Stephan; Gowen, Benjamin G.; Deng, Weiwen; Jung, Heiyoun

2014-01-01

190

Adiponectin and its receptors are expressed in adult ventricular cardiomyocytes and upregulated by activation of peroxisome proliferator-activated receptor ?  

PubMed Central

Adiponectin is a protein hormone involved in maintaining energy homeostasis in metabolically active tissues. It enhances glucose and lipid metabolism via activation of AMP-dependent kinase (AMPK) in skeletal muscle and liver. Energy homeostasis is vital for the heart to work as a pump. In this study, we investigated whether adiponectin and its receptors are expressed in adult ventricular cardiomyocytes. We observed adiponectin transcript and protein in cultured ventricular cardiomyocytes isolated from adult rat, by quantitative real-time PCR, ELISA assays, Western blots, and immunofluorescent staining. In addition, we detected adiponectin receptor (AdipoR1 and AdipoR2) expression in the heart. AdipoR1 was expressed in rat myocardium at a level of about 50% of that in skeletal muscle; whereas adipoR2 was expressed at a similar level to that in liver. Rosiglitazone, a Peroxisome proliferator activated receptor ? (PPAR?) activator, substantially elevated expression of adiponectin in cultured cardiomyocytes and its secretion into cultured media. Rosiglitazone also increased adipoR1 and adipoR2 expression in cardiomyocytes. Treatment of recombinant globular adiponectin in cultured cardiomyocytes increased fatty acid oxidation and glucose uptake via activation of AMPK, suggesting a role for adiponectin in cardiac energy metabolism. Together, these data establish the existence of a local cardiac-specific adiponectin system that is regulated by PPAR?. Moreover, these findings indicate a role for adiponectin on normal myocardial energy homeostasis, in part, through the activation of AMPK. PMID:17532004

Ding, Guoliang; Qin, Qianhong; He, Nu; Francis-David, Sharon C.; Hou, Jie; Ricks, Ernest; Yang., Qinglin

2007-01-01

191

Injectable Laminin-Functionalized Hydrogel for Nucleus Pulposus Regeneration  

PubMed Central

Cell delivery to the pathological intervertebral disc (IVD) has significant therapeutic potential for enhancing IVD regeneration. The development of injectable biomaterials that retain delivered cells, promote cell survival, and maintain or promote an NP cell phenotype in vivo remains a significant challenge. Previous studies have demonstrated NP cell – laminin interactions in the nucleus pulposus (NP) region of the IVD that promote cell attachment and biosynthesis. These findings suggest that incorporating laminin ligands into carriers for cell delivery may be beneficial for promoting NP cell survival and phenotype. Here, an injectable, laminin-111 functionalized poly(ethylene glycol) (PEG-LM111) hydrogel was developed as a biomaterial carrier for cell delivery to the IVD. We evaluated the mechanical properties of the PEG-LM111 hydrogel, and its ability to retain delivered cells in the IVD space. Gelation occurred in approximately 20 minutes without an initiator, with dynamic shear moduli in the range of 0.9 – 1.4 kPa. Primary NP cell retention in cultured IVD explants was significantly higher over 14 days when cells were delivered within a PEG-LM111 carrier, as compared to cells in liquid suspension. Together, these results suggest this injectable laminin-functionalized biomaterial may be an easy to use carrier for delivering cells to the IVD. PMID:23849345

Francisco, Aubrey T.; Mancino, Robert J.; Bowles, Robby D.; Brunger, Jonathan M.; Tainter, David M.; Chen, Yi-Te; Richardson, William J; Guilak, Farshid; Setton, Lori A.

2013-01-01

192

Hyaluronic Acid Induces Activation of the ?-Opioid Receptor  

PubMed Central

Introduction Nociceptive pain is one of the most common types of pain that originates from an injury involving nociceptors. Approximately 60% of the knee joint innervations are classified as nociceptive. The specific biological mechanism underlying the regulation of nociceptors is relevant for the treatment of symptoms affecting the knee joint. Intra-articular administration of exogenous hyaluronic acid (HA) in patients with osteoarthritis (OA) appears to be particularly effective in reducing pain and improving patient function. Methods We performed an in vitro study conducted in CHO cells that expressed a panel of opioid receptors and in primary rat dorsal root ganglion (DRG) neurons to determine if HA induces the activation of opioid peptide receptors (OPr) using both aequorin and the fluorescent dye Fura-2/AM. Results Selective agonists and antagonists for each OPr expressed on CHO cells were used to test the efficacy of our in vitro model followed by stimulation with HA. The results showed that HA induces stimulatory effects on the ? receptor (KOP). These effects of HA were also confirmed in rat DRG neurons, which express endogenously the OPr. Conclusions HA activates the KOP receptor in a concentration dependent manner, with a pEC50 value of 7.57. PMID:23383210

Zavan, Barbara; Ferroni, Letizia; Giorgi, Carlotta; Calò, Girolamo; Brun, Paola; Cortivo, Roberta; Abatangelo, Giovanni; Pinton, Paolo

2013-01-01

193

Activation of a member of the steroid hormone receptor superfamily by peroxisome proliferators  

Microsoft Academic Search

We have cloned a member of the steroid hormone receptor superfamily of ligand-activated transcription factors. The receptor homologue is activated by a diverse class of rodent hepatocarcinogens that causes proliferation of peroxisomes. Identification of a peroxisome proliferator-activated receptor should help elucidate the mechanism of the hypolipidaemic effect of these hepatocarcinogens and aid evaluation of their potential carcinogenic risk to man.

Isabelle Issemann; Stephen Green

1990-01-01

194

YB-1 Acts as a Ligand for Notch-3 Receptors and Modulates Receptor Activation*  

PubMed Central

Y-box (YB) protein-1 is secreted by mesangial and immune cells after cytokine challenge, but extracellular functions are unknown. Here, we demonstrate that extracellular YB-1 associates with outer cell membrane components and interacts with extracellular Notch-3 receptor domains. The interaction appears to be specific for Notch-3, as YB-1-green fluorescent protein binds to the extracellular domains and full-length forms of Notch-3 but not to Notch-1. YB-1-green fluorescent protein and Notch-3 proteins co-localize at cell membranes, and extracellular YB-1 activates Notch-3 signaling, resulting in nuclear translocation of the Notch-3 intracellular domain and up-regulation of Notch target genes. The YB-1/Notch-3 interaction may be of particular relevance for inflammatory mesangioproliferative disease, as both proteins co-localize in an experimental nephritis model and receptor activation temporally and spatially correlates with YB-1 expression. PMID:19640841

Rauen, Thomas; Raffetseder, Ute; Frye, Björn C.; Djudjaj, Sonja; Mühlenberg, Philipp J. T.; Eitner, Frank; Lendahl, Urban; Bernhagen, Jürgen; Dooley, Steven; Mertens, Peter R.

2009-01-01

195

Dopamine-2 receptor activation suppresses PACAP expression in gonadotrophs.  

PubMed

Pituitary adenylate cyclase-activating polypeptide (PACAP) is expressed at a high level in the fetal pituitary and decreases profoundly between embryonic day 19 and postnatal day 1 (PN1), with a further decrease from PN1 to PN4. In this series of experiments, we investigated the hypothesis that dopamine 2 receptor (Drd2) activation interrupts a cAMP-dependent feed-forward loop that maintains PACAP expression at a high level in the fetal pituitary. Using single-cell RT-PCR of pituitary cell cultures from newborn rats, Drd2 mRNA was identified in gonadotrophs that were also positive for PACAP mRNA. PACAP expression in pituitary cultures from embryonic day 19 rats was suppressed by the PACAP6-38 antagonist and by the Drd2 agonist bromocriptine. Increasing concentrations of bromocriptine inhibited cAMP production as well as cAMP signaling based on cAMP response element-luciferase activity, decreased PACAP promoter activity, and decreased PACAP mRNA levels in ?T3-1 gonadotroph cells. Furthermore, blockade of dopamine receptors by injecting haloperidol into newborn rat pups partially reversed the developmental decline in pituitary PACAP mRNA that occurs between PN1 and PN4. These results provide evidence that dopamine receptor signaling regulates PACAP expression under physiological conditions and lend support to the hypothesis that a rise in hypothalamic dopamine at birth abrogates cAMP signaling in fetal gonadotrophs to interrupt a feed-forward mechanism that maintains PACAP expression at a high level in the fetal pituitary. We propose that this perinatal decline in pituitary PACAP reduces pituitary follistatin which permits GnRH receptors and FSH-? to increase to facilitate activation of the neonatal gonad. PMID:24823390

Winters, Stephen J; Ghooray, Dushan T; Yang, Rong Q; Holmes, Joshua B; O'Brien, Andrew Rw; Morgan, Jay; Moore, Joseph P

2014-07-01

196

?7 Receptor-selective agonists and modes of ?7 receptor activation  

Microsoft Academic Search

The ?7-selective agonists 3-(2,4-dimethoxybenzylidene)-anabaseine (GTS-21), also known as DMXB, and 3-(4-hydroxy,2-methoxybenzylidene)anabaseine (4OH-GTS-21) produce a variety of behavioral and cytoprotective effects that may be related to the activation of either large transient currents at high concentrations or small sustained currents at lower agonist concentrations. We are using acutely dissociated hypothalamic neurons, which express a central nervous system (CNS) ?7-type receptor, to

Roger L. Papke; Edwin Meyer; Tom Nutter; Vladimir V. Uteshev

2000-01-01

197

Visualising Androgen Receptor Activity in Male and Female Mice  

PubMed Central

Androgens, required for normal development and fertility of males and females, have vital roles in the reproductive tract, brain, cardiovascular system, smooth muscle and bone. Androgens function via the androgen receptor (AR), a ligand-dependent transcription factor. To assay and localise AR activity in vivo we generated the transgenic “ARE-Luc” mouse, expressing a luciferase reporter gene under the control of activated endogenous AR. In vivo imaging of androgen-mediated luciferase activity revealed several strongly expressing tissues in the male mouse as expected and also in certain female tissues. In males the testes, prostate, seminal vesicles and bone marrow all showed high AR activity. In females, strong activity was seen in the ovaries, uterus, omentum tissue and mammary glands. In both sexes AR expression and activity was also found in salivary glands, the eye (and associated glands), adipose tissue, spleen and, notably, regions of the brain. Luciferase protein expression was found in the same cell layers as androgen receptor expression. Additionally, mouse AR expression and activity correlated well with AR expression in human tissues. The anti-androgen bicalutamide reduced luciferase signal in all tissues. Our model demonstrates that androgens can act in these tissues directly via AR, rather than exclusively via androgen aromatisation to estrogens and activation of the estrogen receptor. Additionally, it visually demonstrates the fundamental importance of AR signalling outside the normal role in the reproductive organs. This model represents an important tool for physiological and developmental analysis of androgen signalling, and for characterization of known and novel androgenic or antiandrogenic compounds. PMID:23940781

Dart, D. Alwyn; Waxman, Jonathan; Aboagye, Eric O.; Bevan, Charlotte L.

2013-01-01

198

Visualising androgen receptor activity in male and female mice.  

PubMed

Androgens, required for normal development and fertility of males and females, have vital roles in the reproductive tract, brain, cardiovascular system, smooth muscle and bone. Androgens function via the androgen receptor (AR), a ligand-dependent transcription factor. To assay and localise AR activity in vivo we generated the transgenic "ARE-Luc" mouse, expressing a luciferase reporter gene under the control of activated endogenous AR. In vivo imaging of androgen-mediated luciferase activity revealed several strongly expressing tissues in the male mouse as expected and also in certain female tissues. In males the testes, prostate, seminal vesicles and bone marrow all showed high AR activity. In females, strong activity was seen in the ovaries, uterus, omentum tissue and mammary glands. In both sexes AR expression and activity was also found in salivary glands, the eye (and associated glands), adipose tissue, spleen and, notably, regions of the brain. Luciferase protein expression was found in the same cell layers as androgen receptor expression. Additionally, mouse AR expression and activity correlated well with AR expression in human tissues. The anti-androgen bicalutamide reduced luciferase signal in all tissues. Our model demonstrates that androgens can act in these tissues directly via AR, rather than exclusively via androgen aromatisation to estrogens and activation of the estrogen receptor. Additionally, it visually demonstrates the fundamental importance of AR signalling outside the normal role in the reproductive organs. This model represents an important tool for physiological and developmental analysis of androgen signalling, and for characterization of known and novel androgenic or antiandrogenic compounds. PMID:23940781

Dart, D Alwyn; Waxman, Jonathan; Aboagye, Eric O; Bevan, Charlotte L

2013-01-01

199

Regulation of Nuclear Receptor Transcriptional Activity by a Novel DEAD Box RNA Helicase (DP97)*  

E-print Network

of several members of the nuclear receptor family, including thyroid and retinoic acid receptorsRegulation of Nuclear Receptor Transcriptional Activity by a Novel DEAD Box RNA Helicase (DP97 cancer cDNA library that in- teracts in a hormone-dependent manner with nuclear receptors and represses

Carpenter, Anne E.

200

Sphingosine-1-phosphate receptor 1 reporter mice reveal receptor activation sites in vivo  

PubMed Central

Activation of the GPCR sphingosine-1-phosphate receptor 1 (S1P1) by sphingosine-1-phosphate (S1P) regulates key physiological processes. S1P1 activation also has been implicated in pathologic processes, including autoimmunity and inflammation; however, the in vivo sites of S1P1 activation under normal and disease conditions are unclear. Here, we describe the development of a mouse model that allows in vivo evaluation of S1P1 activation. These mice, known as S1P1 GFP signaling mice, produce a S1P1 fusion protein containing a transcription factor linked by a protease cleavage site at the C terminus as well as a ?-arrestin/protease fusion protein. Activated S1P1 recruits the ?-arrestin/protease, resulting in the release of the transcription factor, which stimulates the expression of a GFP reporter gene. Under normal conditions, S1P1 was activated in endothelial cells of lymphoid tissues and in cells in the marginal zone of the spleen, while administration of an S1P1 agonist promoted S1P1 activation in endothelial cells and hepatocytes. In S1P1 GFP signaling mice, LPS-mediated systemic inflammation activated S1P1 in endothelial cells and hepatocytes via hematopoietically derived S1P. These data demonstrate that S1P1 GFP signaling mice can be used to evaluate S1P1 activation and S1P1-active compounds in vivo. Furthermore, this strategy could be potentially applied to any GPCR to identify sites of receptor activation during normal physiology and disease. PMID:24667638

Kono, Mari; Tucker, Ana E.; Tran, Jennifer; Bergner, Jennifer B.; Turner, Ewa M.; Proia, Richard L.

2014-01-01

201

HPV binding assay to Laminin-332/integrin ?6?4 on human keratinocytes.  

PubMed

Human papillomaviruses (HPVs) have been shown to bind to Laminin-332 (Ln-332) on the extracellular matrix (ECM) secreted by human keratinocytes. The assay described here is an important tool to study HPV receptor binding to the ECM. The assay can also be modified to study the receptors required for HPV infection and for binding to tissues. We previously showed that Ln-332 is essential for the binding of HPV11 to human keratinocytes and that infectious entry of HPV11 requires ?6?4 integrin for the transfer of HPV11 from ECM to host cells (Culp et al., J Virol 80:8940-8950, 2006). We also demonstrated that several of the high-risk HPV types (16, 18, 31 and 45) bind to Ln-332 and/or other components of the ECM in vitro (Broutian et al., J Gen Virol 91:531-540, 2010). The exact binding and internalization mechanism(s) for HPV are still under investigation. A better understanding of these mechanisms will aid in the design of therapeutics against HPVs and ultimately help prevent many cancers. In this chapter, we describe the HPV binding assay to Ln-332/integrin ?6?4 on human keratinocytes (ECM). We also present data and suggestions for modifying the assay for testing the specificity of HPV for receptors (by blocking receptors) and binding to human tissues (basement membrane, BM) in order to study binding mechanisms. PMID:25348297

Brendle, Sarah A; Christensen, Neil D

2015-01-01

202

Activation of RIG-I-like Receptor Signal Transduction  

PubMed Central

Mammalian cells have the ability to recognize virus infection and mount a powerful antiviral response. Pattern recognition receptor proteins detect molecular signatures of virus infection and activate antiviral signaling cascades. The RIG-I-like receptors are cytoplasmic DExD/H box proteins that can specifically recognize virus-derived RNA species as a molecular feature discriminating the pathogen from the host. The RIG-I-like receptor family is composed of three homologous proteins, RIG-I, MDA5, and LGP2. All of these proteins can bind double-stranded RNA species with varying affinities via their conserved DExD/H box RNA helicase domains and C-terminal regulatory domains. The recognition of foreign RNA by the RLRs activates enzymatic functions and initiates signal transduction pathways resulting in the production of antiviral cytokines and the establishment of a broadly effective cellular antiviral state that protects neighboring cells from infection and triggers innate and adaptive immune systems. The propagation of this signal via the interferon antiviral system has been studied extensively, while the precise roles for enzymatic activities of the RNA helicase domain in antiviral responses are only beginning to be elucidated. Here, current models for RLR ligand recognition and signaling are reviewed. PMID:22066529

Bruns, Annie; Horvath, Curt M.

2011-01-01

203

Tissue Kallikrein Elicits Cardioprotection by Direct Kinin B2 Receptor Activation Independent of Kinin Formation  

Microsoft Academic Search

Abstract—Tissue kallikrein exerts various biological functions through kinin formation with subsequent kinin B2 receptor activation. Recent studies showed,that tissue kallikrein directly activates kinin B2 receptor in cultured cells expressing human kinin B2 receptor. In the present study, we investigated the role of tissue kallikrein in protection against cardiac injury through direct kinin B2 receptor activation using kininogen-deficient Brown Norway Katholiek

Julie Chao; Hang Yin; Lin Gao; Makoto Hagiwara; Bo Shen; Zhi-Rong Yang; Lee Chao

2010-01-01

204

Protein kinase C?/? inhibitor Gö6976 promotes PC12 cell adhesion and spreading through membrane recruitment and activation of protein kinase C?.  

PubMed

Gö6976 is a nonglycosidic indolocarbazole compound widely used as a specific inhibitor of PKC?/?. In experiments probing for a role of PKC? in human laminin-2-integrin-mediated cell adhesion and spreading of PC12 cells, we observed unexpected enhancements of adhesion, spreading and stress fiber formation to 1 ?M Gö6976 with concomitant increase in membrane translocation of PKC? and autophosphorylation of focal adhesion kinase (FAK). Importantly, enhanced cellular behavior and membrane translocation of PKC? induced by Gö6976 was retained in siRNA-transfected PC12 cells to knockdown PKC? expression. Gö6976 also induced laminin-dependent cell adhesion in NIH/3T3 and CV-1 fibroblasts, suggesting of a mechanism that may be common to multiple cell-types. A specific inhibitor of PKC?, rottlerin, completely abrogated Gö6976-dependent increase in PC12 cell adhesion to laminin as well as the activation of small GTPases, Rac1 and Cdc42, that are downstream of PKC? in adhesion receptor signaling. siRNA knockdown of Rac1 and Cdc42 expression inhibited cell spreading and lamellipodia formation in PC12 cells. Overall, these results suggest that Gö6976 may stimulate membrane recruitment of PKC? through a mechanism that is independent of PKC?/? signaling. In addition, the activation of Rac1 and Cdc42 by human laminin-2-integrin-dependent activation of PKC?/FAK signaling mediates cell spreading and lamellipodia formation in PC12 cells. PMID:23063429

Jung, Sung Youn; Kim, O Bok; Kang, Hyun Ki; Jang, Da Hyun; Min, Byung-Moo; Yu, Frank H

2013-02-01

205

Expanding the Paradigm for Estrogen Receptor Binding and Transcriptional Activation  

PubMed Central

Estrogen receptor (ER) binds to a spectrum of functional estrogen response elements (ERE) within the human genome, including ERE half-sites (HERE), inverted and direct repeats. This has been confounding, because ER has been reported to bind weakly, if at all, to these sites in vitro. We show that ER binds strongly to these nonconventional EREs, and the binding is enhanced by the presence of high-mobility group protein B1 (HMGB1). Collectively, these and previous findings reinforce the notion of the plasticity of strong ER/ERE interactions, consistent with their broader range of observed binding specificity. In addition, transient transfection studies using luciferase reporter gene assays show that these EREs drive luciferase activity, and HMGB1 enhances transcriptional activity. Furthermore, HMGB1 gene expression knockdown results in a precipitous drop in luciferase activity, suggesting a prominent role for HMGB1 in activation of estrogen/ER-responsive genes. Therefore, these data advocate that the minimal target site for ER is a cHERE (consensus HERE) that occurs in many different contexts and that HMGB1 enhances both the binding affinity and transcriptional activity. This challenges the current paradigm for ER binding affinity and functional activity and suggests that the paradigm requires significant reevaluation and modification. These findings also suggest a possible mechanism for a cross talk between genes regulated by ER and class II nuclear receptors. PMID:21527498

Joshi, S. R.; Ghattamaneni, R. B.

2011-01-01

206

Endothelial mineralocorticoid receptor activation enhances endothelial protein C receptor and decreases vascular thrombosis in mice.  

PubMed

Previous studies have shown that aldosterone, which activates the mineralocorticoid receptor (MR), promotes thrombosis in animal models. Our objective was to determine whether MR activation/expression in the vascular endothelium could modify thrombotic risk in vivo and to examine thrombin generation at the surface of aortic endothelial cells (HAECs). MR was conditionally overexpressed in vivo in vascular endothelial cells in mice (MR-EC mice) or stimulated with aldosterone in HAECs. Thrombosis after ferric chloride injury was delayed in MR-EC mice compared with controls as well as in wild-type FVB/NRj mice treated with aldosterone (60 ?g/kg/d for 21 d). Thrombin generation in platelet-poor plasma did not differ between MR-EC mice and controls. In MR-EC mice, aortic endothelial cell protein C receptor (EPCR) expression was increased. Aldosterone (10(-8) M) attenuated thrombin generation at the surface of cultured HAECs, and this effect was associated with up-regulation of expression of EPCR, which promotes formation of activated protein C. Aldosterone increases EPCR expression via a transcriptional mechanism involving interaction of MR with the specificity protein 1 site. These findings demonstrate that MR activation acts on endothelial cells to protect against thrombosis in physiological conditions and that MR-mediated EPCR overexpression drives this antithrombotic property through enhancing protein C activation. PMID:24451386

Lagrange, Jérémy; Li, Zhenlin; Fassot, Céline; Bourhim, Mustapha; Louis, Huguette; Nguyen Dinh Cat, Aurélie; Parlakian, Ara; Wahl, Denis; Lacolley, Patrick; Jaisser, Fréderic; Regnault, Véronique

2014-05-01

207

Selective suppression of Toll-like receptor 4 activation by chemokine receptor 4.  

PubMed

The response of Toll-like receptor 4 (TLR4) to lipopolysaccharide (LPS) is thought vital for resisting infection. Since aberrant TLR4 signaling may initiate inflammatory conditions such as the sepsis syndrome, we sought a component of normal cells that might provide local control of TLR4 activation. We found that antibodies that block chemokine receptor 4 (CXCR4) function enhanced TLR4 signaling, while increased expression of CXCR4 or addition of the CXCR4 ligand SDF-1 suppressed TLR4 signaling induced by LPS. These findings suggest that CXCR4 could exert local control of TLR4 and suggest the possibility of new therapeutic approaches to suppression of TLR4 function. PMID:15670831

Kishore, Sandeep P; Bungum, Marlo K; Platt, Jeffrey L; Brunn, Gregory J

2005-01-31

208

A peroxisome-proliferator activated receptor-? ligand could regulate the expression of leptin receptor on human hepatic stellate cells  

Microsoft Academic Search

Leptin is a peptide known to play a profibrogenic role in hepatic stellate cells (HSCs). Peroxisome-proliferator activated\\u000a receptor (PPAR)-? ligands are suggested to have an anti-fibrogenic effect on HSCs. Since the association of these two factors\\u000a in HSC activation has not been demonstrated, we hypothesized that PPAR-? ligands would suppress leptin-induced HSC activation\\u000a and regulate leptin receptor expression. Immortalized human

Jung Il Lee; Yong-Han Paik; Kwan Sik Lee; Jin Woo Lee; Yong Soo Kim; Seok Jeong; Kye Sook Kwon; Dong Haeng Lee; Hyung Gil Kim; Yong Woon Shin; Min Ah Kim

2007-01-01

209

Regulation of Peroxisome Proliferator–Activated Receptor-? by MDM2  

PubMed Central

Peroxisome proliferator–activated receptor-alpha (PPAR?) belongs to the nuclear receptor (NR) family of transcription factors and regulates lipid and glucose metabolism. Like other NRs, the regulation of gene expression by PPAR? depends on cofactor recruitment to the transcription complex and multiple protein-protein interactions. In this study, Murine Double Minute 2 (MDM2), an E3 ubiquitin ligase, is identified as a PPAR?-interacting protein that regulates PPAR? transcriptional activity. MDM2 modulated the transcriptional activity of PPAR? and PPAR?/?, but not PPAR? in reporter assays. Knockdown of MDM2 by small interfering RNA in rat hepatoma cells inhibited ligand-induced mRNA levels of several PPAR? target genes involved in lipid metabolism. MDM2 associated with PPAR? on target gene promoters, and this association increased in response to Wy14,643 treatment. MDM2 interacted with PPAR? and this interaction occurred with the A/B domain of PPAR?. Coexpression of MDM2 increased PPAR? ubiquitination and the E3 ubiquitin ligase activity of MDM2 affected PPAR? protein expression and transcriptional activity. MDM2 expression was decreased in response to clofibrate in wild-type (WT), but not in PPAR? null mice, indicating a PPAR?-dependent regulation. These studies identify a role for MDM2 in regulating PPAR?-mediated pathways of lipid metabolism. PMID:19103650

Gopinathan, Lakshmi; Hannon, Daniel B.; Peters, Jeffrey M.; Vanden Heuvel, John P.

2009-01-01

210

Vasopeptidase-activated latent ligands of the histamine receptor-1.  

PubMed

Whether peptidases present in vascular cells can activate prodrugs active on vascular cells has been tested with 2 potential latent ligands of the histamine H1 receptor (H1R). First, a peptide consisting of the antihistamine cetirizine (CTZ) condensed at the N-terminus of ?-aminocaproyl-bradykinin (?ACA-BK) was evaluated for an antihistamine activity that could be revealed by degradation of the peptide part of the molecule. CTZ-?ACA-BK had a submicromolar affinity for the BK B2 receptor (B2R; IC50 of 590 nM, [(3)H]BK binding competition), but a non-negligible affinity for the human H1 receptor (H1R; IC50 of 11 ?M for [(3)H]pyrilamine binding). In the human isolated umbilical vein, a system where both endogenous B2R and H1R mediate strong contractions, CTZ-?ACA-BK exerted mild antagonist effects on histamine-induced contraction that were not modified by omapatrilat or by a B2R antagonist that prevents endocytosis of the BK conjugate. Cells expressing recombinant ACE or B2R incubated with CTZ-?ACA-BK did not release a competitor of [(3)H]pyrilamine binding to H1Rs. Thus, there is no evidence that CTZ-?ACA-BK can release free cetirizine in biological environments. The second prodrug was a blocked agonist, L-alanyl-histamine, potentially activated by aminopeptidase N (APN). This compound did not compete for [(3)H]pyrilamine binding to H1Rs. The human umbilical vein contractility assay responded to L-alanyl-histamine (EC50 54.7 ?M), but the APN inhibitor amastatin massively (17-fold) reduced its apparent potency. Amastatin did not influence the potency of histamine as a contractile agent. One of the 2 tested latent H1R ligands, L-alanyl-histamine, supported the feasibility of pro-drug activation by vascular ectopeptidases. PMID:24016859

Gera, Lajos; Roy, Caroline; Charest-Morin, Xavier; Marceau, François

2013-11-01

211

The Toxicology of Ligands for Peroxisome Proliferator-Activated Receptors (PPAR)  

E-print Network

REVIEW The Toxicology of Ligands for Peroxisome Proliferator-Activated Receptors (PPAR) Marjorie A of Veterinary and Biomedical Sciences and Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania; carcinogenesis; receptor-mediated toxicology. Peroxisome proliferator-activated receptor-a (PPARa) was the first

Omiecinski, Curtis

212

Selective Activation of Liver X Receptors by Acanthoic Acid-Related Diterpenes  

E-print Network

Selective Activation of Liver X Receptors by Acanthoic Acid-Related Diterpenes Paqui G. Traves substitutions at the C4 position in ring A are potent activators of liver X receptors (LXR and LXR ) in both://molpharm.aspetjournals.org. doi:10.1124/mol.106.031906. ABBREVIATIONS: LXR, liver X receptor; DTP, diterpe

Theodorakis, Emmanuel

213

An Orphan Nuclear Receptor Activated by Pregnanes Defines a Novel Steroid Signaling Pathway  

Microsoft Academic Search

Steroid hormones exert profound effects on differentiation, development, and homeostasis in higher eukaryotes through interactions with nuclear receptors. We describe a novel orphan nuclear receptor, termed the pregnane X receptor (PXR), that is activated by naturally occurring steroids such as pregnenolone and progesterone, and synthetic glucocorticoids and antiglucocorticoids. PXR exists as two isoforms, PXR.1 and PXR.2, that are differentially activated

Steven A. Kliewer; John T. Moore; Laura Wade; Jeff L. Staudinger; Michael A. Watson; Stacey A. Jones; David D. McKee; Beverly B. Oliver; Timothy M. Willson; Rolf H. Zetterstrom; Thomas Perlmann; Jürgen M Lehmann

1998-01-01

214

Combined Targeting of Endothelin A Receptor and Epidermal Growth Factor Receptor in Ovarian Cancer Shows Enhanced Antitumor Activity  

Microsoft Academic Search

Ovarian carcinomas overexpress endothelin A receptors (ETAR) and epidermal growth factor (EGF) receptor (EGFR). In these cells, endothelin-1 (ET-1) triggers mitogenic and invasive signaling pathways that are in part mediated by EGFR trans- activation. Combined targeting of ETAR, by the specific ETAR antagonist ZD4054, and of EGFR by the EGFR inhibitor gefitinib (IRESSA), may offer improvements in ovarian carcinoma treatment.

Laura Rosano; Valeriana Di Castro; Francesca Spinella; Giampaolo Tortora; Maria Rita Nicotra; Pier Giorgio Natali; Anna Bagnato

2007-01-01

215

FATTY ACIDS MODULATE TOLL-LIKE RECEPTOR 4 ACTIVATION THROUGH REGULATION OF RECEPTOR DIMERIZATION AND RECRUITMENT INTO LIPID RAFTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The saturated fatty acids acylated on Lipid A of lipopolysaccharide (LPS) or bacterial lipoproteins play critical roles in ligand recognition and receptor activation for Toll-like Receptor 4 (TLR4) and TLR2. The results from our previous studies (J Biol Chem 2003, 2004) demonstrated that saturated ...

216

Peroxisome proliferator-activated receptor ? confers resistance to peroxisome proliferator-activated receptor ?-induced apoptosis in colorectal cancer cells  

PubMed Central

Peroxisome proliferator-activated receptor ? (PPAR?) may serve as a useful target for drug development in non-diabetic diseases. However, some colorectal cancer cells are resistant to PPAR? agonists by mechanisms that are poorly understood. Here we provide the first evidence that elevated PPAR? expression and/or activation of PPAR? antagonize the ability of PPAR? to induce colorectal carcinoma cell death. More importantly, the opposing effects of PPAR? and PPAR? in regulating programmed cell death are mediated by survivin and caspase-3. We found that activation of PPAR? results in decreased survivin expression and increased caspase-3 activity, whereas activation of PPAR? counteracts these effects. Our findings suggest that PPAR? and PPAR? coordinately regulate cancer cell fate by controlling the balance between the cell death and survival and demonstrate that inhibition of PPAR? can reprogram PPAR? ligand-resistant cells to respond to PPAR? agonists. PMID:21765467

Wang, Dingzhi; Ning, Wei; Xie, Dianren; Guo, Lixia; DuBois, Raymond N.

2014-01-01

217

Dual activities of odorants on olfactory and nuclear hormone receptors.  

PubMed

We have screened an odorant compound library and discovered molecules acting as chemical signals that specifically activate both G-protein-coupled olfactory receptors (ORs) on the cell surface of olfactory sensory neurons and the human nuclear estrogen receptor alpha (ER) involved in transcriptional regulation of cellular differentiation and proliferation in a wide variety of tissues. Hence, these apparent dual active odorants induce distinct signal transduction pathways at different subcellular localizations, which affect both neuronal signaling, resulting in odor perception, and the ER-dependent transcriptional control of specific genes. We demonstrate these effects using fluorescence-based in vitro and cellular assays. Among these odorants, we have identified synthetic sandalwood compounds, an important class of molecules used in the fragrance industry. For one estrogenic odorant we have also identified the cognate OR. This prompted us to compare basic molecular recognition principles of odorants on the two structurally and apparent functionally non-related receptors using computational modeling in combination with functional assays. Faced with the increasing evidence that ORs may perform chemosensory functions in a number of tissues outside of the nasal olfactory epithelium, the unraveling of these molecular ligand-receptor interaction principles is of critical importance. In addition the evidence that certain olfactory sensory neurons naturally co-express ORs and ERs may provide a direct functional link between the olfactory and hormonal systems in humans. Our results are therefore useful for defining the structural and functional characteristics of ER-specific odorants and the role of odorant molecules in cellular processes other than olfaction. PMID:19723634

Pick, Horst; Etter, Sylvain; Baud, Olivia; Schmauder, Ralf; Bordoli, Lorenza; Schwede, Torsten; Vogel, Horst

2009-10-30

218

Role of peroxisome proliferator-activated receptors in mechanisms of rejection in heart transplantation  

E-print Network

Peroxisome proliferator-activated receptors (PPARs) belong to a nuclear receptor superfamily; two major isoforms, PPAR? and PPAR[gamma], are primarily involved in lipid and glucose homeostasis. However, evidence also ...

Binello, Emanuela

2004-01-01

219

The Novel Leptospiral Surface Adhesin Lsa20 Binds Laminin and Human Plasminogen and Is Probably Expressed during Infection?  

PubMed Central

Leptospirosis is an emerging infectious disease caused by pathogenic species of Leptospira. In this work, we report the cloning, expression, purification, and characterization of two predicted leptospiral outer membrane proteins, LIC11469 and LIC11030. The LIC11469 protein is well conserved among leptospiral strains, while LIC11030 was identified only in Leptospira interrogans. We confirmed by surface proteolysis of intact leptospires with proteinase K that these proteins are most likely new surface leptospiral proteins. The recombinant proteins were evaluated for their capacity to attach to extracellular matrix (ECM) components and to plasminogen. The leptospiral protein encoded by LIC11469, named Lsa20 (leptospiral surface adhesin of 20 kDa), binds to laminin and to plasminogen. The binding with both components was not detected when Lsa20 was previously denatured or blocked with anti-Lsa20 antibodies. Moreover, Lsa20 binding to laminin was also confirmed by surface plasmon resonance (SPR). Laminin competes with plasminogen for binding to Lsa20, suggesting the same ligand-binding site. Lsa20-bound plasminogen could be converted to enzymatically active plasmin, capable of cleaving plasmin substrate d-valyl-leucyl-lysine-p-nitroanilide dihydrochloride. Lsa20 was recognized by antibodies in confirmed-leptospirosis serum samples, suggesting that this protein is expressed during infection. Taken together, our results indicate that Lsa20 is a novel leptospiral adhesin that in concert with the host-derived plasmin may help the bacteria to adhere and to spread through the hosts. PMID:21844229

Mendes, Renata Siqueira; Von Atzingen, Marina; de Morais, Zenaide Maria; Gonçales, Amane Paldes; Serrano, Solange M. T.; Asega, Amanda F.; Romero, Eliete Caló; Vasconcellos, Silvio Arruda; Nascimento, Ana Lucia Tabet O.

2011-01-01

220

Role of Peroxisome Proliferator-Activated Receptor-? in Vascular Inflammation  

PubMed Central

Vascular inflammation plays a crucial role in atherosclerosis, and its regulation is important to prevent cerebrovascular and coronary artery disease. The inflammatory process in atherogenesis involves a variety of immune cells including monocytes/macrophages, lymphocytes, dendritic cells, and neutrophils, which all express peroxisome proliferator-activated receptor-? (PPAR-?). PPAR-? is a nuclear receptor and transcription factor in the steroid superfamily and is known to be a key regulator of adipocyte differentiation. Increasing evidence from mainly experimental studies has demonstrated that PPAR-? activation by endogenous and synthetic ligands is involved in lipid metabolism and anti-inflammatory activity. In addition, recent clinical studies have shown a beneficial effect of thiazolidinediones, synthetic PPAR-? ligands, on cardiovascular disease beyond glycemic control. These results suggest that PPAR-? activation is an important regulator in vascular inflammation and is expected to be a therapeutic target in the treatment of atherosclerotic complications. This paper reviews the recent findings of PPAR-? involvement in vascular inflammation and the therapeutic potential of regulating the immune system in atherosclerosis. PMID:22888436

Ohshima, Kousei; Mogi, Masaki; Horiuchi, Masatsugu

2012-01-01

221

Thiophene-core estrogen receptor ligands having superagonist activity.  

PubMed

To probe the importance of the heterocyclic core of estrogen receptor (ER) ligands, we prepared a series of thiophene-core ligands by Suzuki cross-coupling of aryl boronic acids with bromo-thiophenes and we assessed their receptor binding and cell biological activities. The disposition of the phenol substituents on the thiophene core, at alternate or adjacent sites, and the nature of substituents on these phenols, all contribute to binding affinity and subtype selectivity. Most of the bis(hydroxyphenyl)-thiophenes were ER? selective, whereas the tris(hydroxyphenyl)-thiophenes were ER? selective; analogous furan-core compounds generally have lower affinity and less selectivity. Some diarylthiophenes show distinct superagonist activity in reporter gene assays, giving maximal activities 2-3 times that of estradiol, and modeling suggests that these ligands have a different interaction with a hydrogen-bonding residue in helix-11. Ligand-core modification may be a new strategy for developing ER ligands whose selectivity is based on having transcriptional activity greater than that of estradiol. PMID:23586645

Min, Jian; Wang, Pengcheng; Srinivasan, Sathish; Nwachukwu, Jerome C; Guo, Pu; Huang, Minjian; Carlson, Kathryn E; Katzenellenbogen, John A; Nettles, Kendall W; Zhou, Hai-Bing

2013-04-25

222

High constitutive activity of native H3 receptors regulates histamine neurons in brain  

Microsoft Academic Search

Some G-protein-coupled receptors display `constitutive activity', that is, spontaneous activity in the absence of agonist. This means that a proportion of the receptor population spontaneously undergoes an allosteric transition, leading to a conformation that can bind G proteins. The process has been shown to occur with recombinant receptors expressed at high density, and\\/or mutated, but also non-mutated recombinant receptors expressed

Séverine Morisset; Agnès Rouleau; Xavier Ligneau; Florence Gbahou; Joël Tardivel-Lacombe; Holger Stark; Walter Schunack; C. Robin Ganellin; Jean-Michel Arrang

2000-01-01

223

Short Laminin Peptide for Improved Neural Stem Cell Growth  

PubMed Central

Human neural stem/progenitor cells (hNSCs) are very difficult to culture and require human or animal source extracellular matrix molecules, such as laminin or collagen type IV, to support attachment and to regulate their survival and proliferation. These extracellular matrix molecules are difficult to purify from human or animal tissues, have high batch-to-batch variability, and may cause an immune response if used in clinical applications. Although several laminin- and collagen IV-derived peptides are commercially available, they do not support long-term hNSC attachment and growth. To solve this problem, we developed a novel peptide sequence with only 12 amino acids based on the Ile-Lys-Val-Ala-Val, or IKVAV, sequence: Ac-Cys-Cys-Arg-Arg-Ile-Lys-Val-Ala-Val-Trp-Leu-Cys. This short peptide sequence, similar to tissue-derived full laminin molecules, supported hNSCs to attach and proliferate to confluence for continuous passage and subculture. This short peptide also directed hNSCs to differentiate into neurons. When conjugated to poly(ethylene glycol) hydrogels, this short peptide benefited hNSC attachment and proliferation on the surface of hydrogels and promoted cell migration inside the hydrogels with maximum enhancement at a peptide density of 10 ?M. This novel short peptide shows great promise in artificial niche development for supporting hNSC culture in vitro and in vivo and for promoting hNSC transplantation in future clinical therapy. PMID:24692587

Li, Xiaowei; Liu, Xiaoyan; Josey, Benjamin; Chou, C. James; Tan, Yu; Zhang, Ning

2014-01-01

224

Five Layers of Receptor Signaling in ?? T-Cell Differentiation and Activation  

PubMed Central

The contributions of ?? T-cells to immunity to infection or tumors critically depend on their activation and differentiation into effectors capable of secreting cytokines and killing infected or transformed cells. These processes are molecularly controlled by surface receptors that capture key extracellular cues and convey downstream intracellular signals that regulate ?? T-cell physiology. The understanding of how environmental signals are integrated by ?? T-cells is critical for their manipulation in clinical settings. Here, we discuss how different classes of surface receptors impact on human and murine ?? T-cell differentiation, activation, and expansion. In particular, we review the role of five receptor types: the T-cell receptor (TCR), costimulatory receptors, cytokine receptors, NK receptors, and inhibitory receptors. Some of the key players are the costimulatory receptors CD27 and CD28, which differentially impact on pro-inflammatory subsets of ?? T-cells; the cytokine receptors IL-2R, IL-7R, and IL-15R, which drive functional differentiation and expansion of ?? T-cells; the NK receptor NKG2D and its contribution to ?? T-cell cytotoxicity; and the inhibitory receptors PD-1 and BTLA that control ?? T-cell homeostasis. We discuss these and other receptors in the context of a five-step model of receptor signaling in ?? T-cell differentiation and activation, and discuss its implications for the manipulation of ?? T-cells in immunotherapy. PMID:25674089

Ribeiro, Sérgio T.; Ribot, Julie C.; Silva-Santos, Bruno

2015-01-01

225

Mode of action framework analysis for receptor-mediated toxicity: the Peroxisome Proliferator-Activated Receptor alpha (PPARa) as a case study  

EPA Science Inventory

Therapeutic hypolipidemic agents and industrial chemicals that cause peroxisome proliferation and induce liver tumors in rodents activate the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARa). Research has elucidated the cellular and molecular events by w...

226

A new mechanism for growth hormone receptor activation of JAK2, and implications for related cytokine receptors  

PubMed Central

The growth hormone receptor was the first cytokine receptor to be cloned and crystallized, and provides a valuable exemplar for activation of its cognate kinase, JAK2. We review progress in understanding its activation mechanism, in particular the molecular movements made by this constitutively dimerized receptor in response to ligand binding, and how these lead to a separation of JAK-binding Box1 motifs. Such a separation leads to removal of the pseudokinase inhibitory domain from the kinase domain of a partner JAK2 bound to the receptor, and vice versa, leading to apposition of the kinase domains and transactivation. This may be a general mechanism for class I cytokine receptor action. PMID:25101218

Waters, Michael J; Brooks, Andrew J; Chhabra, Yash

2014-01-01

227

Structure-dependent binding and activation of perfluorinated compounds on human peroxisome proliferator-activated receptor ?.  

PubMed

Perfluorinated compounds (PFCs) have been shown to disrupt lipid metabolism and even induce cancer in rodents through activation of peroxisome proliferator-activated receptors (PPARs). Lines of evidence showed that PPAR? was activated by PFCs. However, the information on the binding interactions between PPAR? and PFCs and subsequent alteration of PPAR? activity is still limited and sometimes inconsistent. In the present study, in vitro binding of 16 PFCs to human PPAR? ligand binding domain (hPPAR?-LBD) and their activity on the receptor in cells were investigated. The results showed that the binding affinity was strongly dependent on their carbon number and functional group. For the eleven perfluorinated carboxylic acids (PFCAs), the binding affinity increased with their carbon number from 4 to 11, and then decreased slightly. The binding affinity of the three perfluorinated sulfonic acids (PFSAs) was stronger than their PFCA counterparts. No binding was detected for the two fluorotelomer alcohols (FTOHs). Circular dichroim spectroscopy showed that PFC binding induced distinctive structural change of the receptor. In dual luciferase reporter assays using transiently transfected Hep G2 cells, PFCs acted as hPPAR? agonists, and their potency correlated with their binding affinity with hPPAR?-LBD. Molecular docking showed that PFCs with different chain length bind with the receptor in different geometry, which may contribute to their differences in binding affinity and transcriptional activity. PMID:24998974

Zhang, Lianying; Ren, Xiao-Min; Wan, Bin; Guo, Liang-Hong

2014-09-15

228

Molecular Details of the Activation of the ? Opioid Receptor  

PubMed Central

Molecular details of ? opioid receptor activations were obtained using molecular dynamics simulations of the receptor in the presence of 3 agonists, 3 antagonists, a partial agonist and on the constitutively active T279K mutant. Agonists have a higher probability of direct interactions of their basic nitrogen (N) with Asp147 as compared to antagonists, indicating that direct ligand-Asp147 interactions modulate activation. Medium size substituents on the basic N of antagonists lead to steric interactions that perturb N-Asp147 interactions, while additional favorable interactions occur with larger basic N substituents, such as in N-phenethylnormorphine, restoring N-Asp147 interactions, leading to agonism. With the orvinols, the increased size of the C19 substituent in buprenorphine over diprenorphine leads increased interactions with residues adjacent to Asp147, partially overcoming the presence of the cyclopropyl N substituent, such that buprenorphine is a partial agonist. Results also indicate different conformational properties of the intracellular regions of the transmembrane helices in agonists versus antagonists. PMID:23758404

Shim, Jihyun; Coop, Andrew; MacKerell, Alexander D.

2013-01-01

229

D-Serine Regulation of NMDA Receptor Activity  

NSDL National Science Digital Library

The N-Methyl-D-aspartate–type glutamate receptor (NMDAR) plays a key role in several important processes involving the nervous system, including brain development, synaptic plasticity, and learning. Unlike other neurotransmitter receptors, which are activated by individual neurotransmitters, activation of NMDARs requires the binding of a coagonist (D-serine or glycine) in addition to glutamate. Although previously considered an "unnatural" amino acid, D-serine is a key regulator of NMDAR activity and may be the main physiological ligand at the coagonist site. D-Serine is synthesized in the mammalian brain and is enriched in astrocytes, a class of glial cells that ensheath synapses in the brain. Astrocytes physiologically affect NMDAR neurotransmission by releasing D-serine, suggesting that D-serine acts as a gliotransmitter. However, recent findings indicate that D-serine signaling does not depend solely on glia, because D-serine and its biosynthetic enzyme are also present in substantial amounts in neurons. Here, we discuss these new findings, which begin to shed light on the relative roles of glia and neurons in D-serine signaling.

Herman Wolosker (Technion-Israel Institute of Technology;Department of Biochemistry REV)

2006-10-10

230

Molecular details of the activation of the ? opioid receptor.  

PubMed

Molecular details of ? opioid receptor activations were obtained using molecular dynamics simulations of the receptor in the presence of three agonists, three antagonists, and a partial agonist and on the constitutively active T279K mutant. Agonists have a higher probability of direct interactions of their basic nitrogen (N) with Asp147 as compared with antagonists, indicating that direct ligand-Asp147 interactions modulate activation. Medium-size substituents on the basic N of antagonists lead to steric interactions that perturb N-Asp147 interactions, while additional favorable interactions occur with larger basic N substituents, such as in N-phenethylnormorphine, restoring N-Asp147 interactions, leading to agonism. With the orvinols, the increased size of the C19 substituent in buprenorphine over diprenorphine leads to increased interactions with residues adjacent to Asp147, partially overcoming the presence of the cyclopropyl N substituent, such that buprenorphine is a partial agonist. Results also indicate different conformational properties of the intracellular regions of the transmembrane helices in agonists versus antagonists. PMID:23758404

Shim, Jihyun; Coop, Andrew; MacKerell, Alexander D

2013-07-01

231

Methamphetamine Increases Locomotion and Dopamine Transporter Activity in Dopamine D5 Receptor-Deficient Mice  

PubMed Central

Dopamine regulates the psychomotor stimulant activities of amphetamine-like substances in the brain. The effects of dopamine are mediated through five known dopamine receptor subtypes in mammals. The functional relevance of D5 dopamine receptors in the central nervous system is not well understood. To determine the functional relevance of D5 dopamine receptors, we created D5 dopamine receptor-deficient mice and then used these mice to assess the roles of D5 dopamine receptors in the behavioral response to methamphetamine. Interestingly, D5 dopamine receptor-deficient mice displayed increased ambulation in response to methamphetamine. Furthermore, dopamine transporter threonine phosphorylation levels, which regulate amphetamine-induced dopamine release, were elevated in D5 dopamine receptor-deficient mice. The increase in methamphetamine-induced locomotor activity was eliminated by pretreatment with the dopamine transporter blocker GBR12909. Taken together, these results suggest that dopamine transporter activity and threonine phosphorylation levels are regulated by D5 dopamine receptors. PMID:24155877

Hayashizaki, Seiji; Hirai, Shinobu; Ito, Yumi; Honda, Yoshiko; Arime, Yosefu; Sora, Ichiro; Okado, Haruo; Kodama, Tohru; Takada, Masahiko

2013-01-01

232

Engineered epidermal growth factor mutants with faster binding on-rates correlate with enhanced receptor activation  

PubMed Central

Receptor tyrosine kinases (RTKs) regulate critical cell signaling pathways, yet the properties of their cognate ligands that influence receptor activation are not fully understood. There is great interest in parsing these complex ligand-receptor relationships using engineered proteins with altered binding properties. Here we focus on the interaction between two engineered epidermal growth factor (EGF) mutants and the EGF receptor (EGFR), a model member of the RTK superfamily. We found that EGF mutants with faster kinetic on-rates stimulate increased EGFR activation compared to wild-type EGF. These findings support previous predictions that faster association rates correlate with enhanced receptor activity. PMID:21439278

Lahti, Jennifer L.; Lui, Bertrand H.; Beck, Stayce E.; Lee, Stephen S.; Ly, Daphne P.; Longaker, Michael T.; Yang, George P.; Cochran, Jennifer R.

2011-01-01

233

Shear stress activation of nuclear receptor PXR in endothelial detoxification  

PubMed Central

Endothelial cells (ECs) are constantly exposed to xenobiotics and endobiotics or their metabolites, which perturb EC function, as well as to shear stress, which plays a crucial role in vascular homeostasis. Pregnane X receptor (PXR) is a nuclear receptor and a key regulator of the detoxification of xeno- and endobiotics. Here we show that laminar shear stress (LSS), the atheroprotective flow, activates PXR in ECs, whereas oscillatory shear stress, the atheroprone flow, suppresses PXR. LSS activation of PXR in cultured ECs led to the increased expression of a PXR target gene, multidrug resistance 1 (MDR1). An in vivo study using rats showed that the expression of MDR1 was significantly higher in the endothelium from the descending thoracic aorta, where flow is mostly laminar, than from the inner curvature of aortic arch, where flow is disturbed. Functionally, LSS-activated PXR protects ECs from apoptosis triggered by doxorubicin via the induction of MDR1 and other detoxification genes. PXR also suppressed the expression of proinflammatory adhesion molecules and monocyte adhesion in response to TNF-? and lipopolysaccharide. Overexpression of a constitutively active PXR in rat carotid arteries potently attenuated proinflammatory responses. In addition, cDNA microarray revealed a large number of the PXR-activated endothelial genes whose products are responsible for major steps of detoxification, including phase I and II metabolizing enzymes and transporters. These detoxification genes in ECs are induced by LSS in ECs in a PXR-dependent manner. In conclusion, our results indicate that PXR represents a flow-activated detoxification system to protect ECs against damage by xeno- and endobiotics. PMID:23878263

Wang, Xiaohong; Fang, Xi; Zhou, Jing; Chen, Zhen; Zhao, Beilei; Xiao, Lei; Liu, Ao; Li, Yi-Shuan J.; Shyy, John Y.-J.; Guan, Youfei; Chien, Shu; Wang, Nanping

2013-01-01

234

Artificial masculinization in tilapia involves androgen receptor activation.  

PubMed

Estrogens have a pivotal role in natural female sexual differentiation of tilapia while lack of steroids results in testicular development. Despite the fact that androgens do not participate in natural sex differentiation, synthetic androgens, mainly 17-?-methyltestosterone (MT) are effective in the production of all-male fish in aquaculture. The sex inversion potency of synthetic androgens may arise from their androgenic activity or else as inhibitors of aromatase activity. The current study is an attempt to differentiate between the two alleged activities in order to evaluate their contribution to the sex inversion process and aid the search for novel sex inversion agents. In the present study, MT inhibited aromatase activity, when applied in vitro as did the non-aromatizable androgen dihydrotestosterone (DHT). In comparison, exposure to fadrozole, a specific aromatase inhibitor, was considerably more effective. Androgenic activity of MT was evaluated by exposure of Sciaenochromis fryeri fry to the substance and testing for the appearance of blue color. Flutamide, an androgen antagonist, administered concomitantly with MT, reduced the appearance of the blue color and the sex inversion potency of MT in a dose-dependent manner. In tilapia, administration of MT, fadrozole or DHT resulted in efficient sex inversion while flutamide reduced the sex inversion potency of all three compounds. In the case of MT and DHT the decrease in sex inversion efficiency caused by flutamide is most likely due to the direct blocking of the androgen binding to its cognate receptor. The negative effect of flutamide on the efficiency of the fadrozole treatment may indicate that the masculinizing activity of fadrozole may be attributed to excess, un-aromatized, androgens accumulated in the differentiating gonad. The present study shows that when androgen receptors are blocked, there is a reduction in the efficiency of sex inversion treatments. Our results suggest that in contrast to natural sex differentiation, during sex inversion treatments, androgens, either endogenous or exogenous, participate in inducing testicular differentiation. PMID:24815887

Golan, Matan; Levavi-Sivan, Berta

2014-10-01

235

A restricted population of CB1 cannabinoid receptors with neuroprotective activity  

PubMed Central

The CB1 cannabinoid receptor, the main molecular target of endocannabinoids and cannabis active components, is the most abundant G protein-coupled receptor in the mammalian brain. Of note, CB1 receptors are expressed at the synapses of two opposing (i.e., GABAergic/inhibitory and glutamatergic/excitatory) neuronal populations, so the activation of one and/or another receptor population may conceivably evoke different effects. Despite the widely reported neuroprotective activity of the CB1 receptor in animal models, the precise pathophysiological relevance of those two CB1 receptor pools in neurodegenerative processes is unknown. Here, we first induced excitotoxic damage in the mouse brain by (i) administering quinolinic acid to conditional mutant animals lacking CB1 receptors selectively in GABAergic or glutamatergic neurons, and (ii) manipulating corticostriatal glutamatergic projections remotely with a designer receptor exclusively activated by designer drug pharmacogenetic approach. We next examined the alterations that occur in the R6/2 mouse, a well-established model of Huntington disease, upon (i) fully knocking out CB1 receptors, and (ii) deleting CB1 receptors selectively in corticostriatal glutamatergic or striatal GABAergic neurons. The data unequivocally identify the restricted population of CB1 receptors located on glutamatergic terminals as an indispensable player in the neuroprotective activity of (endo)cannabinoids, therefore suggesting that this precise receptor pool constitutes a promising target for neuroprotective therapeutic strategies. PMID:24843137

Chiarlone, Anna; Bellocchio, Luigi; Blázquez, Cristina; Resel, Eva; Soria-Gómez, Edgar; Cannich, Astrid; Ferrero, José J.; Sagredo, Onintza; Benito, Cristina; Romero, Julián; Sánchez-Prieto, José; Lutz, Beat; Fernández-Ruiz, Javier; Galve-Roperh, Ismael; Guzmán, Manuel

2014-01-01

236

Spontaneous olfactory receptor neuron activity determines follower cell response properties  

PubMed Central

Noisy or spontaneous activity is common in neural systems and poses a challenge to detecting and discriminating signals. Here we use the locust to answer fundamental questions about noise in the olfactory system: Where does spontaneous activity originate? How is this activity propagated or reduced throughout multiple stages of neural processing? What mechanisms favor the detection of signals despite the presence of spontaneous activity? We found that spontaneous activity long observed in the secondary projection neurons (PNs) originates almost entirely from the primary olfactory receptor neurons (ORNs) rather than from spontaneous circuit interactions in the antennal lobe, and that spontaneous activity in ORNs tonically depolarizes the resting membrane potentials of their target PNs and local neurons (LNs), and indirectly tonically depolarizes tertiary Kenyon cells (KCs). However, because these neurons have different response thresholds, in the absence of odor stimulation, ORNs and PNs display a high spontaneous firing rate but KCs are nearly silent. Finally, we used a simulation of the olfactory network to show that discrimination of signal and noise in the KCs is best when threshold levels are set so that baseline activity in PNs persists. Our results show how the olfactory system benefits from making a signal detection decision after a point of maximal information convergence, e.g., after KCs pool inputs from many PNs. PMID:22357872

Joseph, Joby; Dunn, Felice A.; Stopfer, Mark

2012-01-01

237

Spontaneous olfactory receptor neuron activity determines follower cell response properties.  

PubMed

Noisy or spontaneous activity is common in neural systems and poses a challenge to detecting and discriminating signals. Here we use the locust to answer fundamental questions about noise in the olfactory system: Where does spontaneous activity originate? How is this activity propagated or reduced throughout multiple stages of neural processing? What mechanisms favor the detection of signals despite the presence of spontaneous activity? We found that spontaneous activity long observed in the secondary projection neurons (PNs) originates almost entirely from the primary olfactory receptor neurons (ORNs) rather than from spontaneous circuit interactions in the antennal lobe, and that spontaneous activity in ORNs tonically depolarizes the resting membrane potentials of their target PNs and local neurons (LNs) and indirectly tonically depolarizes tertiary Kenyon cells (KCs). However, because these neurons have different response thresholds, in the absence of odor stimulation, ORNs and PNs display a high spontaneous firing rate but KCs are nearly silent. Finally, we used a simulation of the olfactory network to show that discrimination of signal and noise in the KCs is best when threshold levels are set so that baseline activity in PNs persists. Our results show how the olfactory system benefits from making a signal detection decision after a point of maximal information convergence, e.g., after KCs pool inputs from many PNs. PMID:22357872

Joseph, Joby; Dunn, Felice A; Stopfer, Mark

2012-02-22

238

Muscarinic Receptor Activation Elicits Sustained, Recurring Depolarizations in Reticulospinal Neurons  

PubMed Central

In lampreys, brain stem reticulospinal (RS) neurons constitute the main descending input to the spinal cord and activate the spinal locomotor central pattern generators. Cholinergic nicotinic inputs activate RS neurons, and consequently, induce locomotion. Cholinergic muscarinic agonists also induce locomotion when applied to the brain stem of birds. This study examined whether bath applications of muscarinic agonists could activate RS neurons and initiate motor output in lampreys. Bath applications of 25 ?M muscarine elicited sustained, recurring depolarizations (mean duration of 5.0 ± 0.5 s recurring with a mean period of 55.5 ± 10.3 s) in intracellularly recorded rhombencephalic RS neurons. Calcium imaging experiments revealed that muscarine induced oscillations in calcium levels that occurred synchronously within the RS neuron population. Bath application of TTX abolished the muscarine effect, suggesting the sustained depolarizations in RS neurons are driven by other neurons. A series of lesion experiments suggested the caudal half of the rhombencephalon was necessary. Microinjections of muscarine (75 ?M) or the muscarinic receptor (mAchR) antagonist atropine (1 mM) lateral to the rostral pole of the posterior rhombencephalic reticular nucleus induced or prevented, respectively, the muscarinic RS neuron response. Cells immunoreactive for muscarinic receptors were found in this region and could mediate this response. Bath application of glutamatergic antagonists (6-cyano-7-nitroquinoxaline-2,3-dione/D-2-amino-5-phosphonovaleric acid) abolished the muscarine effect, suggesting that glutamatergic transmission is needed for the effect. Ventral root recordings showed spinal motor output coincides with RS neuron sustained depolarizations. We propose that unilateral mAchR activation on specific cells in the caudal rhombencephalon activates a circuit that generates synchronous sustained, recurring depolarizations in bilateral populations of RS neurons. PMID:17344371

Smetana, R. W.; Alford, S.; Dubuc, R.

2008-01-01

239

Canonical Wnt signalling regulates epithelial patterning by modulating levels of laminins in zebrafish appendages  

PubMed Central

The patterning and morphogenesis of body appendages – such as limbs and fins – is orchestrated by the activities of several developmental pathways. Wnt signalling is essential for the induction of limbs. However, it is unclear whether a canonical Wnt signalling gradient exists and regulates the patterning of epithelium in vertebrate appendages. Using an evolutionarily old appendage – the median fin in zebrafish – as a model, we show that the fin epithelium exhibits graded changes in cellular morphology along the proximo-distal axis. This epithelial pattern is strictly correlated with the gradient of canonical Wnt signalling activity. By combining genetic analyses with cellular imaging, we show that canonical Wnt signalling regulates epithelial cell morphology by modulating the levels of laminins, which are extracellular matrix components. We have unravelled a hitherto unknown mechanism involved in epithelial patterning, which is also conserved in the pectoral fins – evolutionarily recent appendages that are homologous to tetrapod limbs. PMID:25519245

Nagendran, Monica; Arora, Prateek; Gori, Payal; Mulay, Aditya; Ray, Shinjini; Jacob, Tressa; Sonawane, Mahendra

2015-01-01

240

Canonical Wnt signalling regulates epithelial patterning by modulating levels of laminins in zebrafish appendages.  

PubMed

The patterning and morphogenesis of body appendages - such as limbs and fins - is orchestrated by the activities of several developmental pathways. Wnt signalling is essential for the induction of limbs. However, it is unclear whether a canonical Wnt signalling gradient exists and regulates the patterning of epithelium in vertebrate appendages. Using an evolutionarily old appendage - the median fin in zebrafish - as a model, we show that the fin epithelium exhibits graded changes in cellular morphology along the proximo-distal axis. This epithelial pattern is strictly correlated with the gradient of canonical Wnt signalling activity. By combining genetic analyses with cellular imaging, we show that canonical Wnt signalling regulates epithelial cell morphology by modulating the levels of laminins, which are extracellular matrix components. We have unravelled a hitherto unknown mechanism involved in epithelial patterning, which is also conserved in the pectoral fins - evolutionarily recent appendages that are homologous to tetrapod limbs. PMID:25519245

Nagendran, Monica; Arora, Prateek; Gori, Payal; Mulay, Aditya; Ray, Shinjini; Jacob, Tressa; Sonawane, Mahendra

2015-01-15

241

Antitussive Activity of Withania somnifera and Opioid Receptors.  

PubMed

Arabinogalactan is a polysaccharide isolated from the roots of the medicinal plant Withania somnifera L. It contains 65 % arabinose and 18 % galactose. The aim of the present study was to evaluate the antitussive activity of arabinogalactan in conscious, healthy adult guinea pigs and the role of the opioid pathway in the antitussive action. A polysaccharide extract was given orally in a dose of 50 mg/kg. Cough was induced by an aerosol of citric acid in a concentration 0.3 mol/L, generated by a jet nebulizer into a plethysmographic chamber. The intensity of cough response was defined as the number of cough efforts counted during a 3-min exposure to the aerosol. The major finding was that arabinogalactan clearly suppressed the cough reflex; the suppression was comparable with that of codeine that was taken as a reference drug. The involvement of the opioid system was tested with the use of a blood-brain barrier penetrable, naloxone hydrochloride, and non-penetrable, naloxone methiodide, to distinguish between the central and peripheral mu-opioid receptor pathways. Both opioid antagonists acted to reverse the arabinogalactan-induced cough suppression; the reversion was total over time with the latter antagonist. We failed to confirm the presence of a bronchodilating effect of the polysaccharide, which could be involved in its antitussive action. We conclude that the polysaccharide arabinogalactan from Withania somnifera has a distinct antitussive activity consisting of cough suppression and that this action involves the mu-opioid receptor pathways. PMID:25252908

Nosálová, Gabriela; Sivová, Veronika; Ray, Bimalendu; Fra?ová, So?a; Ondrejka, Igor; Flešková, Dana

2015-01-01

242

Potentiation of glucocorticoid receptor transcriptional activity by sumoylation.  

PubMed

The glucocorticoid receptor (GR) is a transcription factor, subject to several types of posttranslational modifications including phosphorylation and ubiquitination. We showed that the GR is covalently modified by the small ubiquitin-related modifier-1 (SUMO-1) peptide in mammalian cells. We demonstrated that GR sumoylation is not dependent on the presence of the ligand and regulates the stability of the protein as well as its transcriptional activity. SUMO-1 overexpression induces dramatic GR degradation, abolished by proteasome inhibition. We also found that SUMO-1 stimulates the transactivation capacity of GRs to an extent largely exceeding those observed so far for other sumoylated transcription factors. Overexpression of SUMO-1 specifically enhances the ligand-induced transactivation of GR up to 8-fold. However, this hyperactivation occurs only in the context of a synergy between multiple molecules of GRs. It requires more than one receptor DNA-binding site in promoter and becomes more prominent as the number of sites increases. Interestingly, these observations may be related to the transcriptional properties of the synergy control region of GRs, which precisely contains two evolutionary conserved sumoylation sites. We propose a model in which SUMO-1 regulates the synergy control function of GR and serves as a unique signal for activation and destruction. PMID:12193561

Le Drean, Yves; Mincheneau, Nathalie; Le Goff, Pascale; Michel, Denis

2002-09-01

243

Protease-activated receptors mediate crosstalk between coagulation and fibrinolysis.  

PubMed

The coagulation and fibrinolytic systems contribute to malignancy by increasing angiogenesis, tumor growth, tumor invasion, and tumor metastasis. Oncogenic transformation increases the expression of tissue factor (TF) that results in local generation of coagulation proteases and activation of protease-activated receptor (PAR)-1 and PAR-2. We compared the PAR-dependent expression of urokinase plasminogen activator (uPA) and plasminogen activator inhibitor (PAI)-1 in 2 murine mammary adencocarcinoma cell lines: metastatic 4T1 cells and nonmetastatic 67NR cells. 4T1 cells expressed TF, PAR-1 and PAR-2 whereas 67NR cells expressed TF and PAR-1. We also silenced PAR-1 or PAR-2 expression in the 4T1 cells. We discovered 2 distinct mechanisms for PAR-dependent expression of uPA and PAI-1. First, we found that factor Xa or thrombin activation of PAR-1 led to a rapid release of stored intracellular uPA into the culture supernatant. Second, thrombin transactivation of a PAR-1/PAR-2 complex resulted in increases in PAI-1 mRNA and protein expression. Cells lacking PAR-2 failed to express PAI-1 in response to thrombin and factor Xa did not activate the PAR-1/PAR-2 complex. Our results reveal how PAR-1 and PAR-2 on tumor cells mediate crosstalk between coagulation and fibrinolysis. PMID:20736455

McEachron, Troy A; Pawlinski, Rafal; Richards, Kristy L; Church, Frank C; Mackman, Nigel

2010-12-01

244

Identification of a nuclear receptor that is activated by farnesol metabolites  

Microsoft Academic Search

Nuclear hormone receptors comprise a superfamily of ligand-modulated transcription factors that mediate the transcriptional activities of steroids, retinoids, and thyroid hormones. A growing number of related proteins have been identified that possess the structural features of hormone receptors, but that lack known ligands. Known as orphan receptors, these proteins represents targets for novel signaling molecules. We have isolated a mammalian

Barry M Forman; Elizabeth Goode; Jasmine Chen; Anthony E Oro; David J Bradley; Thomas Perlmann; Daniel J Noonan; Leo T Burka; Trevor McMorris; William W Lamph; Ronald M Evans; Cary Weinberger

1995-01-01

245

?-Lactotensin derived from bovine ?-lactoglobulin exhibits anxiolytic-like activity as an agonist for neurotensin NTS(2) receptor via activation of dopamine D(1) receptor in mice.  

PubMed

?-Lactotensin (His-Ile-Arg-Leu) is a bioactive peptide derived from bovine milk ?-lactoglobulin, acting as a natural agonist for neurotensin receptors. We found that ?-lactotensin exhibited anxiolytic-like activity in an elevated plus-maze test after its intraperitoneal (i.p.) administration in mice. ?-Lactotensin was also orally active. The anxiolytic-like activity of ?-lactotensin after i.p. administration was blocked by levocabastine, an antagonist for the neurotensin NTS(2) receptor. ?-Lactotensin had anxiolytic-like activity in wild-type but not Ntsr2-knockout mice. ?-Lactotensin increased intracellular Ca(2+) flux in glial cells derived from wild-type mice but not Ntsr2 knockout mice. These results suggest that ?-lactotensin acts as an NTS(2) receptor agonist having anxiolytic-like activity. The anxiolytic-like activity of ?-lactotensin was also blocked by SCH23390 and SKF83566, antagonists for dopamine D(1) receptor, but not by raclopride, an antagonist for D(2) receptor. Taken together, ?-lactotensin may exhibit anxiolytic-like activity via NTS(2) receptor followed by D(1) receptor. PMID:21895659

Hou, I-Ching; Suzuki, Chihiro; Kanegawa, Norimasa; Oda, Ayako; Yamada, Ayako; Yoshikawa, Masaaki; Yamada, Daisuke; Sekiguchi, Masayuki; Wada, Etsuko; Wada, Keiji; Ohinata, Kousaku

2011-11-01

246

Endogenous laminin is required for human airway smooth muscle cell maturation  

PubMed Central

Background Airway smooth muscle (ASM) contraction underlies acute bronchospasm in asthma. ASM cells can switch between a synthetic-proliferative phenotype and a contractile phenotype. While the effects of extracellular matrix (ECM) components on modulation of ASM cells to a synthetic phenotype have been reported, the role of ECM components on maturation of ASM cells to a contractile phenotype in adult lung is unclear. As both changes in ECM components and accumulation of contractile ASM are features of airway wall remodelling in asthma, we examined the role of the ECM protein, laminin, in the maturation of contractile phenotype in human ASM cells. Methods Human ASM cells were made senescence-resistant by stable expression of human telomerase reverse transcriptase. Maturation to a contractile phenotype was induced by 7-day serum deprivation, as assessed by immunoblotting for desmin and calponin. The role of laminin on ASM maturation was investigated by comparing the effects of exogenous laminin coated on culture plates, and of soluble laminin peptide competitors. Endogenous expression of laminin chains during ASM maturation was also measured. Results Myocyte binding to endogenously expressed laminin was required for ASM phenotype maturation, as laminin competing peptides (YIGSR or GRGDSP) significantly reduced desmin and calponin protein accumulation that otherwise occurs with prolonged serum deprivation. Coating of plastic cell culture dishes with different purified laminin preparations was not sufficient to further promote accumulation of desmin or calponin during 7-day serum deprivation. Expression of ?2, ?1 and ?1 laminin chains by ASM cells was specifically up-regulated during myocyte maturation, suggesting a key role for laminin-2 in the development of the contractile phenotype. Conclusion While earlier reports suggest exogenously applied laminin slows the spontaneous modulation of ASM to a synthetic phenotype, we show for the first time that endogenously expressed laminin is required for ASM maturation to the contractile phenotype. As endogenously expressed laminin chains ?2, ?1 and ?1 are uniquely increased during myocyte maturation, these laminin chains may be key in this process. Thus, human ASM maturation appears to involve regulated endogenous expression of a select set of laminin chains that are essential for accumulation of contractile phenotype myocytes. PMID:16968549

Tran, Thai; McNeill, Karol D; Gerthoffer, William T; Unruh, Helmut; Halayko, Andrew J

2006-01-01

247

?1- and ?5-containing Laminins Regulate the Development of Bile Ducts via ?1 Integrin Signals*  

PubMed Central

Signals derived from basal lamina components are important for developing three-dimensional architecture of epithelial tissues. Laminins consisting of ?, ?, and ? subunits in basal lamina play pivotal roles in the formation and maintenance of epithelial tissue structures. However, it remains unclear which laminin isoforms transmit signals and how epithelial cells receive them to regulate multiple developmental processes. In three-dimensional culture of a liver progenitor cell line, Hepatic Progenitor Cells Proliferating on Laminin (HPPL), the cells establish apicobasal polarity and form cysts with a central lumen. Neutralizing antibody against ?1 integrin blocked the formation and maintenance of the cyst structure, indicating that ?1 integrin signaling was necessary throughout the morphogenesis. Although the addition of ?1-containing laminin, a ligand of ?1 integrin, induced cyst formation, it was dispensable for the maintenance of the cyst, suggesting that HPPL produces another ligand for ?1 integrin to maintain the structure. Indeed, we found that HPPL produced ?5-containing laminin, and siRNA against laminin ?5 partially inhibited the lumen formation. In fetal liver, p75NTR+ periportal fibroblasts and bile duct epithelial cells, known as cholangiocytes, expressed ?1- and ?5-containing laminins, respectively. In laminin ?5 KO liver, cholangiocytes normally emerged, but the number of bile ducts was decreased. These results suggest that ?1-containing laminin is sufficient as a component of the basal lamina for the commitment of bipotential liver progenitors to cholangiocytes and the apicobasal polarization, whereas ?5-containing laminin is necessary for the formation of mature duct structures. Thus, ?1- and ?5-containing laminins differentially regulate the sequential events to form epithelial tissues via ?1 integrin signals. PMID:22761447

Tanimizu, Naoki; Kikkawa, Yamato; Mitaka, Toshihiro; Miyajima, Atsushi

2012-01-01

248

Interaction of lipopolysaccharides of Helicobacter pylori with basement membrane protein laminin.  

PubMed Central

The ability of hemagglutinating and poorly hemagglutinating strains of the gastroduodenal pathogen Helicobacter pylori to bind 125I-radiolabelled laminin was quantitated in a liquid phase assay. Although all strains bound laminin, some hemagglutinating strains were good binders of laminin (maximum of 31% binding), whereas poorly hemagglutinating strains bound intermediate to small amounts of laminin (minimum of 6% binding). Since a hydrophobic component of the bacterium has been reported to be involved in binding of laminin (T. J. Trust, P. Doig, L. Emödy, Z. Kienle, T. Wadström, and P. O'Toole, Infect. Immun. 59:4398-4404, 1991), we investigated the role of lipopolysaccharide (LPS) in the interaction of both types of strains with laminin. Although the extent of inhibition varied among strains, laminin binding to hemagglutinating and poorly hemagglutinating strains was inhibited with homologous and heterologous smooth-form LPS. The ability of heterologous rough-form LPS to produce inhibition comparable to that shown by smooth-form LPS indicated that the O side chain of H. pylori LPS was not involved in the interaction. Further inhibition experiments with dephosphorylated LPS, isolated core oligosaccharide, and free lipid A suggested that a phosphorylated structure in the core oligosaccharide mediates the interaction of a hemagglutinating strain of H. pylori with laminin, whereas a conserved nonphosphorylated structure in the core oligosaccharide mediates the interaction of a poorly hemagglutinating strain. Furthermore, we showed that the interaction of H. pylori LPS with 125I-radiolabelled laminin in a solid phase assay was saturable, specific, and inhibitable with unlabelled laminin. It was postulated that the initial recognition and binding of laminin by H. pylori may occur through LPS and that subsequently a more specific interaction with a lectin-like adhesin on the bacterial surface occurs. PMID:8063380

Valkonen, K H; Wadström, T; Moran, A P

1994-01-01

249

Oxidized low-density lipoprotein and peroxisome-proliferator-activated receptor alpha down-regulate platelet-activating-factor receptor expression in human macrophages.  

PubMed Central

Regulation of the expression of platelet-activating factor (PAF) receptor by atherogenic lipoproteins might contribute to atherogenesis. We show that progressive oxidation of low-density lipoprotein (LDL) gradually inhibits PAF receptor expression on the macrophage cell surface. We tested the effect of oxidized LDL (oxLDL) on PAF receptor expression in human monocytes that do not contain peroxisome-proliferator-activated receptor gamma (PPARgamma), a nuclear receptor activated by oxLDL. OxLDL decreased by 50% (P < or = 0.001) and by 29% (P < or = 0.05) the binding of PAF and the expression of PAF receptor mRNA respectively. Next we demonstrated that progressive oxidation of LDLs significantly activated PPARalpha-dependent transcription in transfected mouse aortic endothelial cells. Finally we demonstrated, in mature macrophages, that fenofibrate (20 microM), a specific PPARalpha agonist, but not the specific PPARgamma agonist BRL49653 (20 nM), significantly decreased both PAF binding and PAF receptor mRNA expression, by 65% and 40% (P < or = 0.001) respectively. Additionally, another PPARalpha agonist, Wy14,643, decreased PAF receptor promoter activity by 70% (P < or = 0.05) in transfected THP-1 cells, suggesting the involvement of the proximal promoter region (-980 to -500) containing a series of four nuclear factor (NF)-kappaB motifs. Thus PPARalpha might be involved in the down-regulation of PAF receptor gene expression by oxLDLs in human monocytes/macrophages. The oxidation of one or more lipid components of LDLs might result in the formation of natural activators of PPARalpha. It is hypothesized that such activators might modulate inflammation and apoptosis upon atherogenesis by decreasing the expression of PAF receptor. PMID:11171098

Hourton, D; Delerive, P; Stankova, J; Staels, B; Chapman, M J; Ninio, E

2001-01-01

250

Discovery of furan-2-carbohydrazides as orally active glucagon receptor antagonists.  

PubMed

Furan-2-carbohydrazides were found as orally active glucagon receptor antagonists. Starting from the hit compound 5, we successfully determined the structure activity relationships of a series of derivatives obtained by modifying the acidity of the phenol. We identified the ortho-nitrophenol as a good scaffold for glucagon receptor inhibitory activity. Our efforts have led to the discovery of compound 7l as a potent glucagon receptor antagonist with good bioavailability and satisfactory long half-life. PMID:25127101

Hasegawa, Futoshi; Niidome, Kazumi; Migihashi, Chiaki; Murata, Makoto; Negoro, Toshiyuki; Matsumoto, Takafumi; Kato, Kaori; Fujii, Akihito

2014-09-01

251

Diabetes or peroxisome proliferator-activated receptor alpha agonist increases mitochondrial thioesterase I activity in heart  

Technology Transfer Automated Retrieval System (TEKTRAN)

Peroxisome proliferator-activated receptor alpha (PPAR alpha) is a transcriptional regulator of the expression of mitochondrial thioesterase I (MTE-I) and uncoupling protein 3 (UCP3), which are induced in the heart at the mRNA level in response to diabetes. Little is known about the regulation of pr...

252

Arterioscler Thromb Vasc Biol . Author manuscript Peroxisome proliferator-activated receptor-alpha gene level differently  

E-print Network

-activated receptor-alpha gene level differently affects lipid metabolism and inflammation in apolipoprotein E2 knock-Activated Receptor (PPAR ) is a ligand-activated transcription factor which controls lipid metabolism ; pathology ; Lipid Metabolism ; drug effects ; genetics ; Lipids ; blood ; Liver ; drug effects ; metabolism

Boyer, Edmond

253

Antitussive activity of sigma-1 receptor agonists in the guinea-pig  

Microsoft Academic Search

1 Current antitussive medications have limited efficacy and often contain the opiate-like agent dextromethorphan (DEX). The mechanism whereby DEX inhibits cough is ill defined. DEX displays affinity at both NMDA and sigma receptors, suggesting that the antitussive activity may involve central or peripheral activity at either of these receptors. This study examined and compared the antitussive activity of DEX and

Claire Brown; Malika Fezoui; William M. Selig; Carl E. Schwartz; James L. Ellis

2004-01-01

254

Common structural basis for constitutive activity of the ghrelin receptor family.  

PubMed

Three members of the ghrelin receptor family were characterized in parallel: the ghrelin receptor, the neurotensin receptor 2 and the orphan receptor GPR39. In transiently transfected COS-7 and human embryonic kidney 293 cells, all three receptors displayed a high degree of ligand-independent signaling activity. The structurally homologous motilin receptor served as a constitutively silent control; upon agonist stimulation, however, it signaled with a similar efficacy to the three related receptors. The constitutive activity of the ghrelin receptor and of neurotensin receptor 2 through the G(q), phospholipase C pathway was approximately 50% of their maximal capacity as determined through inositol phosphate accumulation. These two receptors also showed very high constitutive activity in activation of cAMP response element-driven transcription. GPR39 displayed a clear but lower degree of constitutive activity through the inositol phosphate and cAMP response element pathways. In contrast, GPR39 signaled with the highest constitutive activity in respect of activation of serum response element-dependent transcription, in part, possibly, through G(12/13) and Rho kinase. Antibody feeding experiments demonstrated that the epitope-tagged ghrelin receptor was constitutively internalized but could be trapped at the cell surface by an inverse agonist, whereas GPR39 remained at the cell surface. Mutational analysis showed that the constitutive activity of both the ghrelin receptor and GPR39 could systematically be tuned up and down depending on the size and hydrophobicity of the side chain in position VI:16 in the context of an aromatic residue at VII:09 and a large hydrophobic residue at VII:06. It is concluded that the three ghrelin-like receptors display an unusually high degree of constitutive activity, the structural basis for which is determined by an aromatic cluster on the inner face of the extracellular ends of TMs VI and VII. PMID:15383539

Holst, Birgitte; Holliday, Nicholas D; Bach, Anders; Elling, Christian E; Cox, Helen M; Schwartz, Thue W

2004-12-17

255

Angiotensin II AT1 receptor constitutive activation: from molecular mechanisms to pathophysiology.  

PubMed

Mutations activating the angiotensin II AT(1) receptor are important to identify and characterize because they give access to the activation mechanisms of this G protein coupled receptor and help to characterize the signaling pathways and the potential pathophysiology of this receptor. The different constitutively activated mutations of the AT(1) receptor are mostly localized in transmembrane domains (TM) and their characterization demonstrated that release of intramolecular constraints and movements among these TM are a necessary step for receptor activation. These mutations constitutively activate Gq linked signaling pathways, receptor internalization and maybe the G protein-independent signaling pathways. Expression of such mutations in mice is linked to hypertension and cardiovascular diseases, but such natural mutations have not been identified in human pathology. PMID:19061936

Petrel, Christophe; Clauser, Eric

2009-04-29

256

Purinergic signaling negatively regulates activity of an olfactory receptor in an odorant-dependent manner.  

PubMed

Extracellular purines and pyrimidines are important signaling molecules that mediate diverse biological functions via cell surface purinergic receptors. Although purinergic modulation to olfactory activity has been reported, cell-specific expression and action of purinergic receptors deserve further exploration. We physiologically characterized expression of purinergic receptors in a set of olfactory sensory neurons that are responsive to both acetophenone and benzaldehyde (AB-OSNs). Sparsely distributed in the most ventral olfactory receptor zone, AB-OSNs were activated by P2 purinergic receptor agonists but not by P1 purinergic receptor agonist adenosine. Both P2X-selective agonist ?,?-methylene ATP and P2Y-selective agonist uridine 5'-triphosphate (UTP) were stimulatory to AB-OSNs, indicating expression of both P2X and P2Y purinergic receptors in AB-OSNs. Pharmacological characterization of receptor specificity using various P2X and P2Y agonists and antagonists illustrated that P2X1 and P2Y2 receptors played major roles in purinergic signaling in AB-OSNs. Interestingly, the results of purinergic modulation to acetophenone-evoked responses were different from those to benzaldehyde-evoked responses within the same neurons. Activation of P2X1 receptors had more profound inhibitory effects on benzaldehyde-evoked intracellular calcium elevation than on acetophenone-evoked responses within the same neurons, and the reverse was true when P2Y2 receptors were activated. Cross-adaptation data showed that acetophenone and benzaldehyde bound to the same olfactory receptor. Thus, our study has demonstrated that purinergic signaling of P2X and P2Y receptors has different effects on olfactory transduction mediated by a defined olfactory receptor and the consequences of purinergic modulation of olfactory activity might depend on stereotypic structures of the odorant-receptor complex. PMID:24928349

Yu, Y; Zhang, C

2014-09-01

257

Paired immunoglobulin-like receptor B regulates platelet activation.  

PubMed

Murine paired immunoglobulin-like receptors B (PIRB), as the ortholog of human leukocyte immunoglobulin-like receptor B2 (LILRB2), is involved in a variety of biological functions. Here, we found that PIRB and LILRB2 were expressed in mouse and human platelets, respectively. PIRB intracellular domain deletion (PIRB-TM) mice had thrombocythemia and significantly higher proportions of megakaryocytes in bone marrow. Agonist-induced aggregation and spreading on immobilized fibrinogen were facilitated in PIRB-TM platelets. The rate of clot retraction in platelet-rich plasma containing PIRB-TM platelets was also increased. Characterization of signaling confirmed that PIRB associated with phosphatases Shp1/2 in platelets. The phosphorylation of Shp1/2 was significantly downregulated in PIRB-TM platelets stimulated with collagen-related peptide (CRP) or on spreading. The results further revealed that the phosphorylation levels of the linker for activation of T cells, SH2 domain-containing leukocyte protein of 76kDa, and phospholipase C were enhanced in PIRB-TM platelets stimulated with CRP. The phosphorylation levels of FAK Y397 and integrin ?3 Y759 were also enhanced in PIRB-TM platelet spread on fibrinogen. The PIRB/LILRB2 ligand angiopoietin-like-protein 2 (ANGPTL2) was expressed and stored in platelet ?-granules. ANGPTL2 inhibited agonist-induced platelet aggregation and spreading on fibrinogen. The data presented here reveal that PIRB and its ligand ANGPTL2 possess an antithrombotic function by suppressing collagen receptor glycoprotein VI and integrin ?IIb?3-mediated signaling. PMID:25075127

Fan, Xuemei; Shi, Panlai; Dai, Jing; Lu, Yeling; Chen, Xue; Liu, Xiaoye; Zhang, Kandi; Wu, Xiaolin; Sun, Yueping; Wang, Kemin; Zhu, Li; Zhang, Cheng Cheng; Zhang, Junfeng; Chen, Guo-Qiang; Zheng, Junke; Liu, Junling

2014-10-01

258

Activation and Regulation of Purinergic P2X Receptor Channels  

PubMed Central

Mammalian ATP-gated nonselective cation channels (P2XRs) can be composed of seven possible subunits, denoted P2X1 to P2X7. Each subunit contains a large ectodomain, two transmembrane domains, and intracellular N and C termini. Functional P2XRs are organized as homomeric and heteromeric trimers. This review focuses on the binding sites involved in the activation (orthosteric) and regulation (allosteric) of P2XRs. The ectodomains contain three ATP binding sites, presumably located between neighboring subunits and formed by highly conserved residues. The detection and coordination of three ATP phosphate residues by positively charged amino acids are likely to play a dominant role in determining agonist potency, whereas an AsnPheArg motif may contribute to binding by coordinating the adenine ring. Nonconserved ectodomain histidines provide the binding sites for trace metals, divalent cations, and protons. The transmembrane domains account not only for the formation of the channel pore but also for the binding of ivermectin (a specific P2X4R allosteric regulator) and alcohols. The N- and C- domains provide the structures that determine the kinetics of receptor desensitization and/or pore dilation and are critical for the regulation of receptor functions by intracellular messengers, kinases, reactive oxygen species and mercury. The recent publication of the crystal structure of the zebrafish P2X4.1R in a closed state provides a major advance in the understanding of this family of receptor channels. We will discuss data obtained from numerous site-directed mutagenesis experiments accumulated during the last 15 years with reference to the crystal structure, allowing a structural interpretation of the molecular basis of orthosteric and allosteric ligand actions. PMID:21737531

Coddou, Claudio; Yan, Zonghe; Obsil, Tomas; Huidobro-Toro, J. Pablo

2011-01-01

259

Chain-specific heparin-binding sequences in the laminin alpha chain LG45 modules.  

PubMed

Laminin alpha chains contain five tandem globular modules (LG1-5) at the C-terminus. Here, we focused on the LG45 module, which play a critical biological role via binding to heparin/heparan sulfate, and examined their chain-specific heparin-binding affinity. The relative heparin-binding affinity of recombinant laminin alpha chain LG45 proteins was as follows: alpha5 > alpha4 > alpha1 > alpha2 and alpha3. The alpha5 chain LG45 module also promoted the strongest cell attachment. We screened heparin-binding sequences using the recombinant alpha5LG45 protein and 43 synthetic peptides. Four peptides, A5G71 (GPLPSYLQFVGI) (IC(50) = 91.8 microM), A5G77 (LVLFLNHGHFVA) (IC(50) = 7.0 microM), A5G81 (AGQWHRVSVRWG) (IC(50) = 5.9 microM), and A5G94 (KMPYVSLELEMR) (IC(50) = 0.84 microM), inhibited the heparin-binding of rec-alpha5LG45. Additionally, the same four peptides exhibited dose-dependent heparin-binding activity in a solid-phase assay. We found that the alpha5 chain LG45 module contains four heparin-binding sequences, and this number is higher than that of the other LG45 modules (alpha2 and alpha3, one sequence; alpha1 and alpha4, two sequences). The data suggest that the active sequences identified from the synthetic peptide screening contribute to the heparin-binding activity of the LG45 module. Most of the heparin-binding sequences in the LG45 modules are located in the N-terminal regions of the LG4 module within the loop regions in the proteins. The data suggest that the N-terminal loop regions of the LG4 module are mainly involved in the heparin/heparan sulfate-mediated biological functions. PMID:19415899

Hozumi, Kentaro; Suzuki, Nobuharu; Uchiyama, Yoshihiko; Katagiri, Fumihiko; Kikkawa, Yamato; Nomizu, Motoyoshi

2009-06-16

260

Chain-Specific Heparin-Binding Sequences in the Laminin ? Chain LG45 Modules  

PubMed Central

Laminin ? chains contain five tandem globular modules (LG1-5) at the C-terminus. Here, we focused on the LG45 module, which play a critical biological role via binding to heparin/heparan sulfate, and examined their chain-specific heparin-binding affinity. The relative heparin-binding affinity of recombinant laminin ? chain LG45 proteins was ?5> ?4> ?1> ?2 and ?3. The ?5 chain LG45 module also promoted the strongest cell attachment. We screened heparin-binding sequences using the recombinant ?5LG45 protein and 43 synthetic peptides. Four peptides, A5G71 (GPLPSYLQFVGI) (IC50 = 91.8 µM), A5G77 (LVLFLNHGHFVA) (IC50 = 7.0 µM), A5G81 (AGQWHRVSVRWG) (IC50 = 5.9 µM), and A5G94 (KMPYVSLELEMR) (IC50 = 0.84 µM), inhibited the heparin-binding of rec-?5LG45. Additionally, the same four peptides exhibited dose-dependent heparin-binding activity in a solid-phase assay. We found that the ?5 chain LG45 module contains four heparin-binding sequences and this number is higher than that of the other LG45 modules (?2 and ?3, 1 sequence; ?1 and ?4, 2 sequences). The data suggest that the active sequences identified from the synthetic peptide screening contribute to the heparin-binding activity of the LG45 module. Most of the heparin-binding sequences in the LG45 modules are located in the N-terminal regions of the LG4 module within the loop regions in the proteins. The data suggest that the N-terminal loop regions of the LG4 module are mainly involved in the heparin/heparan sulfate-mediated biological functions. PMID:19415899

Hozumi, Kentaro; Suzuki, Nobuharu; Uchiyama, Yoshihiko; Katagiri, Fumihiko; Kikkawa, Yamato; Nomizu, Motoyoshi

2009-01-01

261

The Structure of the GM-CSF Receptor Complex Reveals a Distinct Mode of Cytokine Receptor Activation  

SciTech Connect

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that controls the production and function of blood cells, is deregulated in clinical conditions such as rheumatoid arthritis and leukemia, yet offers therapeutic value for other diseases. Its receptors are heterodimers consisting of a ligand-specific {alpha} subunit and a {beta}c subunit that is shared with the interleukin (IL)-3 and IL-5 receptors. How signaling is initiated remains an enigma. We report here the crystal structure of the human GM-CSF/GM-CSF receptor ternary complex and its assembly into an unexpected dodecamer or higher-order complex. Importantly, mutagenesis of the GM-CSF receptor at the dodecamer interface and functional studies reveal that dodecamer formation is required for receptor activation and signaling. This unusual form of receptor assembly likely applies also to IL-3 and IL-5 receptors, providing a structural basis for understanding their mechanism of activation and for the development of therapeutics.

Hansen, Guido; Hercus, Timothy R.; McClure, Barbara J.; Stomski, Frank C.; Dottore, Mara; Powell, Jason; Ramshaw, Hayley; Woodcock, Joanna M.; Xu, Yibin; Guthridge, Mark; McKinstry, William J.; Lopez, Angel F.; Parker, Michael W. (SVIMR-A); (Hanson)

2008-08-11

262

Time-dependent pericellular expression of collagen type IV, laminin, and heparan sulfate proteoglycan in myofibroblasts  

Microsoft Academic Search

Summary Human skin wounds (n = 62) with a wound age between 5 h and 6 weeks were investigated. The appearance of cell-associated pericellular basement membrane components collagen type IV, laminin and heparan sulfate proteoglycan (HSPG) in myofibroblasts was evaluated by immunohistochemistry. Laminin and HSPG were first detectable around myofibroblasts approximately 1.5 days after wounding. Collagen type IV did not

P. Betz; A. Nerlich; J. Wilske; J. Tiibel; I. Wiest; R. Penning; W. Eisenmengen

1992-01-01

263

Activity of new NOP receptor ligands in a rat peripheral mononeuropathy model: Potentiation of Morphine anti-allodynic activity by NOP receptor antagonists  

PubMed Central

The effect of new NOP receptor agonists and antagonists in the rat chronic constriction injury model was investigated. Intraperitoneally administered NOP receptor agonist SR14150 and antagonists SR16430 and SR14148, had no effect on mechanical allodynia when given alone. The nonselective NOP/mu-opioid receptor agonist SR16435, however, produced an anti-allodynic response, similar to morphine and reversible by naloxone. Notably, co-administration of the NOP receptor antagonists potentiated the anti-allodynic activity of both morphine and SR16435. Increased levels of the NOP receptor are implicated in the reduced efficacy of morphine in neuropathic pain. Our results suggest the utility of NOP receptor antagonists for potentiating opioid efficacy in chronic pain. PMID:19285491

Khroyan, Taline V.; Polgar, Willma E.; Orduna, Juan; Jiang, Faming; Olsen, Cris; Toll, Lawrence; Zaveri, Nurulain T.

2009-01-01

264

Effect of Cannabinoid Receptor Activation on Spreading Depression  

PubMed Central

Objective(s):The objective of this study was to evaluate the effect of cannabinoid on cortical spreading depression (CSD) in rat brain. Cannabis has been used for centuries for both symptomatic and prophylactic treatment of different types of headaches including migraine. CSD is believed to be a putative neuronal mechanism underlying migraine aura and subsequent pain. Materials and Methods:The effects of Delta9-tetrahydrocannabinol (THC), as well as, cannabinoid CB1 and CB2 receptor agonists on CSD in rat neocortical slices were investigated. Furthermore, the effect of cannabinoid CB1 agonist was tested on field excitatory postsynaptic potentials (fEPSP) and long-term potentiation (LTP). Results:HC (1-20 microM) dose dependently suppressed CSD amplitude, duration, and propagation velocity. Cannabinoid CB1 agonist, WIN 55,212-2 mesylate (1-10 microM), also significantly suppressed all characteristic features of CSD. However, cannabinoid CB2 agonist, JWH-133 (1-20 microM), did not affect CSD. FEPSP and induction of LTP were suppressed by application of WIN55212-2. Conclusion:Suppression of CSD by activation of CB1 receptors points to the potential therapeutic effects of cannabinoids in migraine with aura. More research is needed before we know whether cannabinoids may be helpful in treating migraine pain. PMID:23493641

Kazemi, Hadi; Rahgozar, Mehdi; Speckmann, Erwin-Josef; Gorji, Ali

2012-01-01

265

Determinants of the Heightened Activity of Glucocorticoid Receptor Translational Isoforms  

PubMed Central

Translational isoforms of the glucocorticoid receptor ? (GR-A, -B, -C1, -C2, -C3, -D1, -D2, and -D3) have distinct tissue distribution patterns and unique gene targets. The GR-C3 isoform-expressing cells are more sensitive to glucocorticoid killing than cells expressing other GR? isoforms and the GR-D isoform–expressing cells are resistant to glucocorticoid killing. Whereas a lack of activation function 1 (AF1) may underlie the reduced activity of the GR-D isoforms, it is not clear how the GR-C3 isoform has heightened activity. Mutation analyses and N-terminal tagging demonstrated that steric hindrance is probably the mechanism for the GR-A, -B, -C1, and -C2 isoforms to have lower activity than the GR-C3 isoform. In addition, truncation scanning analyses revealed that residues 98 to 115 are critical in the hyperactivity of the human GR-C3 isoform. Chimera constructs linking this critical fragment with the GAL4 DNA-binding domain showed that GR residues 98 to 115 do not contain any independent transactivation activity. Mutations at residues Asp101 or Gln106 and Gln107 all reduced the activity of the GR-C3 isoform. In addition, functional studies indicated that Asp101 is crucial for the GR-C3 isoform to recruit coregulators and to mediate glucocorticoid-induced apoptosis. Thus, charged and polar residues are essential components of an N-terminal motif that enhances the activity of AF1 and the GR-C3 isoform. These studies, together with the observations that GR isoforms have cell-specific expression patterns, provide a molecular basis for the tissue-specific functions of GR translational isoforms. PMID:23820903

Bender, Ingrid K.; Cao, Yun

2013-01-01

266

Histone deacetylase inhibitors equipped with estrogen receptor modulation activity.  

PubMed

We describe a set of novel histone deacetylase inhibitors (HDACi) equipped with either an antagonist or an agonist of the estrogen receptor (ER) to confer selective activity against breast cancers. These bifunctional compounds potently inhibit HDAC at nanomolar concentrations and either agonize or antagonize ER? and ER?. The ER antagonist activities of tamoxifen-HDACi conjugates (Tam-HDACi) are nearly identical to those of tamoxifen. Conversely, ethynyl-estradiol-HDACi conjugates (EED-HDACi) have attenuated ER agonist activities relative to the parent ethynyl-estradiol. In silico docking analysis provides structural basis for the trends of ER agonism/antagonism and ER subtype selectivity. Excitingly, lead Tam-HDACi conjugates show anticancer activity that is selectively more potent against MCF-7 (ER? positive breast cancer) compared to MDA-MB-231 (triple negative breast cancer), DU145 (prostate cancer), or Vero (noncancerous cell line). This dual-targeting approach illustrates the utility of designing small molecules with an emphasis on cell-type selectivity, not merely improved potency, working toward a higher therapeutic index at the earliest stages of drug development. PMID:23786452

Gryder, Berkley E; Rood, Michael K; Johnson, Kenyetta A; Patil, Vishal; Raftery, Eric D; Yao, Li-Pan D; Rice, Marcie; Azizi, Bahareh; Doyle, Donald F; Oyelere, Adegboyega K

2013-07-25

267

Histone Deacetylase Inhibitors Equipped with Estrogen Receptor Modulation Activity  

PubMed Central

We described a set of novel histone deacetylase inhibitors (HDACi) equipped with either an antagonist or an agonist of the estrogen receptor (ER) to confer selective activity against breast cancers. These bifunctional compounds potently inhibit HDAC at nanomolar concentrations, and either agonize or antagonize ER? and ER?. The ER antagonist activities of tamoxifen-HDACi conjugates (Tam-HDACi) are nearly identical to those of tamoxifen. Conversely, ethynyl-estradiol HDACi conjugates (EED-HDACi) have attenuated ER agonist activities relative to the parent ethynyl-estradiol. In silico docking analysis provides structural basis for the trends of ER agonism/antagonism and ER subtype selectivity. Excitingly, lead Tam-HDACi conjugates show anticancer activity that is selectively more potent against MCF-7 (ER? positive breast) compared to MDA-MB-231 (triple negative breast cancer), DU145 (prostate cancer) or Vero (non-cancerous cell line). This dual-targeting approach illustrates the utility of designing small molecules with an emphasis on cell-type selectivity, not merely improved potency, working towards a higher therapeutic index at the earliest stages of drug development. PMID:23786452

Gryder, Berkley E.; Rood, Michael K.; Johnson, Kenyetta A.; Patil, Vishal; Raftery, Eric D.; Yao, Li-Pan D.; Rice, Marcie; Azizi, Bahareh; Doyle, Donald F.; Oyelere, Adegboyega K.

2013-01-01

268

Structure-dependent Ah receptor agonist activities of chlorinated biphenylenes.  

PubMed

Polychlorinated biphenylenes (PCBP) have been identified as combustion by-products that bind the aryl hydrocarbon receptor (AhR) and exhibit 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like activity. This study investigates the Ah-responsiveness of 2,3,6,7-tetrachlorobiphenylene (2,3,6,7-CBP), 2,3,6-CBP, 2,3-CBP and 2-CBP in breast cancer cells. MCF-7 or ZR-75 cells were treated with different concentrations (1-100 nM) of the compounds alone to determine their activity as inducers of CYP1A1 protein expression or luciferase activity in cells transfected with a construct (pDRE(3)) containing three tandem dioxin responsive elements (DREs) linked to a luciferase reporter gene. In both assays, the order of potency was 2,3,6,7-CBP>2,3,6-CBP>2,3-CBP approximately 2-CBP, and 2,3,6,7-CBP and TCDD were equipotent. Similar results were also observed in an antiestrogenic assay in MCF-7 cells, confirming the high AhR agonist activity of 2,3,6,7-CBP in breast cancer cells. PMID:16759834

Khan, Shaheen; Konstantinov, Alex; Chittim, Brock; McAlees, Alan; Yeo, Brian; Safe, Stephen

2006-10-01

269

Protease-activated receptors in cancer: A systematic review  

PubMed Central

The traditional view of the role of proteases in tumor growth, progression and metastasis has significantly changed. Apart from their contribution to cancer progression, it is evident that a subclass of proteases, such as thrombin, serves as signal molecules controlling cell functions through the protease-activated receptors (PARs). Among the four types of PAR (PAR1-4; cloned and named in order of their discovery), PAR1, PAR3 and PAR4 are activated by thrombin, unlike PAR2, which is activated by trypsin-like serine proteases. Thrombin has been proven to be a significant factor in both the behavior of cancer in its involvement in hemostasis and blood coagulation. Thrombin is a key supporter of various cellular effects relevant to tumor growth and metastasis, as well as a potent activator of angiogenesis, which is essential for the growth and development of all solid tumor types. This review presents an overview of the role of PAR-mediated thrombin in angiogenesis and cancer, focusing on the ability of PAR1- and PAR4-mediated thrombin to affect tumorigenesis and angiogenesis. PMID:22848234

HAN, NA; JIN, KETAO; HE, KUIFENG; CAO, JIANG; TENG, LISONG

2011-01-01

270

SENESCENCE-ASSOCIATED DECLINE IN HEPATIC PEROXISOMAL ENZYME ACTIVITIES CORRESPONDS WITH DIMINISHED LEVELS OF RETINOID X RECEPTOR ALPHA, BUT NOT PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR ALPHA1  

EPA Science Inventory

Abstract Aging is associated with alterations in hepatic peroxisomal metabolism and susceptibility to hepatocarcinogenecity produced by agonists of peroxisome proliferator-activated receptor alpha (PPARa). Mechanisms involved in these effects are not well understood. Howev...

271

Differential effects of exercise on brain opioid receptor binding and activation in rats.  

PubMed

Physical exercise stimulates the release of endogenous opioid peptides supposed to be responsible for changes in mood, anxiety, and performance. Exercise alters sensitivity to these effects that modify the efficacy at the opioid receptor. Although there is evidence that relates exercise to neuropeptide expression in the brain, the effects of exercise on opioid receptor binding and signal transduction mechanisms downstream of these receptors have not been explored. Here, we characterized the binding and G protein activation of mu opioid receptor, kappa opioid receptor or delta opioid receptor in several brain regions following acute (7 days) and chronic (30 days) exercise. As regards short- (acute) or long-term effects (chronic) of exercise, overall, higher opioid receptor binding was observed in acute-exercise animals and the opposite was found in the chronic-exercise animals. The binding of [(35) S]GTP?S under basal conditions (absence of agonists) was elevated in sensorimotor cortex and hippocampus, an effect more evident after chronic exercise. Divergence of findings was observed for mu opioid receptor, kappa opioid receptor, and delta opioid receptor receptor activation in our study. Our results support existing evidence of opioid receptor binding and G protein activation occurring differentially in brain regions in response to diverse exercise stimuli. We characterized the binding and G protein activation of mu, kappa, and delta opioid receptors in several brain regions following acute (7 days) and chronic (30 days) exercise. Higher opioid receptor binding was observed in the acute exercise animal group and opposite findings in the chronic exercise group. Higher G protein activation under basal conditions was noted in rats submitted to chronic exercise, as visible in the depicted pseudo-color autoradiograms. PMID:25330347

Arida, Ricardo Mario; Gomes da Silva, Sérgio; de Almeida, Alexandre Aparecido; Cavalheiro, Esper Abrão; Zavala-Tecuapetla, Cecilia; Brand, Serge; Rocha, Luisa

2015-01-01

272

Screening of herbal extracts for activation of the human peroxisome proliferator-activated receptor.  

PubMed

The peroxisome proliferator-activated receptors play a pivotal role in metazoan lipid and glucose homeostasis. Synthetic activators of PPARalpha (fibrates) and PPARgamma (glitazones) are therefore widely used for treatment of dislipidemia and diabetes, respectively. There is growing evidence for herbal compounds to influence nuclear receptor signalling e.g. the PPARs. We recently reported carnosic acid and carnosol, both being diterpenes found in the labiate herbs sage and rosemary, to be activators of PPARgamma. The subsequent screening of a variety of ethanolic extracts, obtained from traditionally used herbs, for PPAR activation, led to an exceptionally high hit rate. Among 52 extracts nearly the half significantly activated PPARgamma and 14 activated PPARalpha in addition, whereas three of them were pan-PPAR activators, which also activated PPARdelta. The most active extracts, for which a concentration dependent effect could be shown, were the extracts of Alisma plantago aquatica (ze xie/european waterplantain), Catharanthus roseus (madagascar periwinkle), Acorus calamus (sweet calamus), Euphorbia balsamifera (balsam spurge), Jatropha curcas (barbados nut), Origanum majorana (marjoram), Zea mays (corn silk), Capsicum frutescens (chilli) and Urtica dioica (stinging nettle). The results of the present study provide a possible rationale for the traditional use of many herbs as antidiabetics. PMID:17152989

Rau, O; Wurglics, M; Dingermann, Th; Abdel-Tawab, M; Schubert-Zsilavecz, M

2006-11-01

273

A human vitamin D receptor mutant activated by cholecalciferol  

Microsoft Academic Search

The human vitamin D receptor (hVDR) is a member of the nuclear receptor superfamily, involved in calcium and phosphate homeostasis; hence implicated in a number of diseases, such as Rickets and Osteoporosis. This receptor binds 1?,25-dihydroxyvitamin D3 (also referred to as 1,25(OH)2D3) and other known ligands, such as lithocholic acid. Specific interactions between the receptor and ligand are crucial for

Amanda M. Ousley; Hilda S. Castillo; Anna Duraj-Thatte; Donald F. Doyle; Bahareh Azizi

2011-01-01

274

Regulation of GABA Receptor Activity by Neurosteroids and Phosphorylation  

NSDL National Science Digital Library

These two animations show two models for how neurosteroids regulate the flow of chloride ions (Cl-) through ionotropic gamma-aminobutyric acid (GABA) receptors. In the first model, binding of the neurosteroid allows a protein kinase C (PKC) phosphorylation site to become accessible. Phosphorylation of the channel increases flux through the channel. In the second model, phosphorylation by PKC allows the neurosteroid to bind and increase flux through the channel. The animations have two parts: (i) a diagrammatic representation of the sequence of events at the channel in the membrane and (ii) a representative current trace of data obtained using electrophysiological techniques. These animations would be useful in teaching how allosteric modulators (neurosteroids) and covalent modulators (kinases) can work together as regulators of protein activity.

Jeffrey Tasker (Tulane University;Department of Cell and Molecular Biology REV)

2004-05-25

275

Role of Peroxisome Proliferator-Activated Receptor ? in Diabetic Nephropathy  

PubMed Central

With a developing worldwide epidemic of diabetes mellitus, the renal complications associated with diabetes have become a serious health concern. Primary therapy for treating diabetic nephropathy is a multifactorial process. Peroxisome proliferator-activated receptor alpha (PPAR?) agonists have been used primarily in clinical practice for the treatment of dyslipidemia and insulin resistance. Given that PPAR? expression and regulation of metabolic pathways are involved in oxidative stress, inflammation, blood pressure regulation, and the renin-angiotensin aldosterone system, PPAR? likely influences the development and pathogenesis of diabetic nephropathy via indirect effects on glucose and lipid homeostasis and also by direct action on the kidneys. These findings suggest that PPAR? may become an important therapeutic target for treating diabetic renal complications. PMID:21977451

Chung, Sungjin

2011-01-01

276

Selective effects of ligands on vitamin D3 receptor- and retinoid X receptor-mediated gene activation in vivo.  

PubMed Central

Steroid/nuclear hormone receptors are ligand-regulated transcription f factors that play key roles in cell regulation, differentiation, and oncogenesis. Many nuclear receptors, including the human 1,25-dihydroxyvitamin D3 receptor (VDR), bind cooperatively to DNA either as homodimers or as heterodimers with the 9-cis retinoic acid (RA) receptor (retinoid X-receptor [RXR]). We have previously reported that the ligands for VDR and RXR can differentially modulate the affinity of the receptors' interaction with DNA in vitro, primarily by modulating the dimerization status of these receptors. These experiments suggested a complex interaction between VDR and RXR and their respective ligands on inducible target genes in vivo. To examine these effects in cells, we used a transient-transfection strategy whereby we simultaneously introduced two different reporter plasmids that are selectively inducible by each ligand. Although VDR can bind as a homodimer to the osteopontin gene vitamin D response element, we find that a RXR-VDR heterodimer must be the transactivating species from the element in vivo, since RXR enhances and 9-cis RA and other RXR-specific ligands attenuate this induction. Conversely, when VDR is overexpressed, vitamin D3 attenuates 9-cis RA induction from an RXR-responsive element. These effects, however, appear to be very sensitive to both the relative ratios of the two receptors and their respective target elements. Functional RXR-VDR complexes are strictly dependent on the DNA-binding polarity. Chimeric versions of VDR and RXR were also constructed to examine the putative activities of homodimeric receptors; a VDR chimera can transactivate in the absence of RXR, demonstrating that VDR has intrinsic transactivation properties. Taken together, these results establish a complex, sensitive cross talk in vivo between two ligands and their receptors that signal through two distinct endocrine pathways. PMID:8622645

Lemon, B D; Freedman, L P

1996-01-01

277

Inhibition of protein kinase activity of phorboid and ingenoid receptor by di(adenosine-5')oligophosphate.  

PubMed

Di(adenosine-5')oligophosphate nucleotides of general structure ApnA (n = 3-6) inhibited the protein kinase activity of homogeneous phorboid receptor. These nucleotides did not affect the phorboid binding activity. Ap4A competed for an ATP binding site on the phorboid receptor. Km for ATP was increased from 0.5 to 2 microM in the presence of 0.2 mM of Ap4A. KI was calculated to be approximately 0.1 mM. Ap4A-elicited inhibition of phorboid receptor kinase activity was independent of receptor concentration as well as of phosphoacceptor substrate concentration. PMID:3855354

Shoyab, M

1985-01-01

278

E3 protein of bovine coronavirus is a receptor-destroying enzyme with acetylesterase activity  

SciTech Connect

In addition to members of the Orthomyxoviridae and Paramyxoviridae, several coronaviruses have been shown to possess receptor-destroying activities. Purified bovine coronavirus (BCV) preparations have an esterase activity which inactivates O-acetylsialic acid-containing receptors on erythrocytes. Diisopropyl fluorophosphate (DFP) completely inhibits this receptor-destroying activity of BCV, suggesting that the viral enzyme is a serine esterase. Treatment of purified BCV with (/sup 3/H)DFP and subsequent sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins revealed that the esterase/receptor-destroying activity of BCV is associated with the E3 protein was specifically phosphorylated. This finding suggests that the esterase/receptor-destroying activity of BCV is associated with the E3 protein. Furthermore, treatment of BCV with DFP dramatically reduced its infectivity in a plaque assay. It is assumed that the esterase activity of BCV is required in an early step of virus replication, possible during virus entry or uncoating.

Vlasak, R.; Luytjes, W.; Leider, J.; Spaan, W.; Palese, P.

1988-12-01

279

Characterization and partial purification of solubilized active opiate receptors from toad brain.  

PubMed Central

Opiate receptors have been solubilized from toad brain membranes in active form by using digitonin. Between 40% and 50% of the stereospecific binding activity present in toad brain membranes is recoverable in the ultracentrifugal supernatant of digitonin extracts. Binding of opiates to the solubilized receptor is enhanced 4- to 5-fold by decreasing digitonin concentration to 0.1% or less prior to binding. The solubilized receptor is similar to the membrane-bound receptor in its affinity for various ligands and its sensitivity to heat, trypsin, and N-ethylmaleimide. Moreover, the sodium effect seen in membrane-bound receptor is retained in the solubilized preparation. Both membrane-bound and soluble toad receptors show weak binding of enkephalins, suggesting that they are predominantly of the mu type. The solubilized opiate receptor has an approximate molecular weight of 350,000-400,000. Purification of up to 20-fold has been achieved by gel filtration on Sepharose CL-6B. PMID:6270689

Ruegg, U T; Cuenod, S; Hiller, J M; Gioannini, T; Howells, R D; Simon, E J

1981-01-01

280

Investigating real-time activation of adenosine receptors by bioluminescence resonance energy transfer technique  

NASA Astrophysics Data System (ADS)

Adenosine receptors play important roles in many physiological and pathological processes, for example regulating myocardial oxygen consumption and the release of neurotransmitters. The activations of adenosine receptors have been studied by some kinds of techniques, such as western blot, immunohistochemistry, etc. However, these techniques cannot reveal the dynamical response of adenosine receptors under stimulation. In this paper, bioluminescence resonance energy transfer technique was introduced to study the real-time activation of adenosine receptors by monitoring the dynamics of cyclic adenosine monophosphate (cAMP) level. The results showed that there were significant differences between adenosine receptors on real-time responses under stimulation. Moreover, the dynamics of cAMP level demonstrated that competition between adenosine receptors existed. Taken together, our study indicates that monitoring the dynamics of cAMP level using bioluminescence resonance energy transfer technique could be one potential approach to investigate the mechanism of competitions between adenosine receptors.

Huang, Yimei; Yang, Hongqin; Zheng, Liqin; Chen, Jiangxu; Wang, Yuhua; Li, Hui; Xie, Shusen

2013-02-01

281

Flexible and sensitive method to functionally validate tumor-specific receptors via activation of NFAT.  

PubMed

Tumor-specific receptors may provide effective tools for anti-tumor immunogene therapy. However, the functional analysis of primary human T cells engrafted with tumor-specific receptors is laborious and emphasizes the need for a fast and sensitive method to validate such receptors. To this end, we have set up a Jurkat T cell-based reporter gene assay, and tested receptors with various formats, i.e., receptors based on either a monoclonal antibody (mAb), a full-length T cell receptor (fl-TCR)alphabeta or a chimeric (ch-)TCRalphabeta, and various antigen specificities for their ability to mediate tumor-specific activation of nuclear factor of activated T cells (NFAT). The mAb-based receptor specifically mediates NFAT activation after stimulation with tumor antigen-positive target cells. The observed receptor-mediated NFAT responses were validated by the use of ligand- and receptor-specific mAbs, as well as cyclosporin A (CsA) and a dominant negative mutant of NFAT. Furthermore, anti-TCR mAbs, peptide-loaded tumor cells and antigen-positive tumor cells all resulted in specific NFAT activation in TCR/CD8 co-transduced Jurkat T cells, irrespective of the TCR format used. Importantly, receptor-mediated NFAT responses parallel tumor-specific cytolysis and TNFalpha production of receptor-transduced primary human T lymphocytes. In fact, inhibition of NFAT activation compromises the immune responses of primary human T lymphocytes, pointing to a central involvement of NFAT in anti-tumor T cell responses. Taken together, receptor-mediated activation of NFAT constitutes a representative measure of anti-tumor T cell responses, and the genetically modified Jurkat T cells provide a flexible and sensitive tool with which to select rapidly tumor-specific (chimeric) receptors for immunogene therapy. PMID:12972184

Schaft, Niels; Lankiewicz, Birgit; Gratama, Jan Willem; Bolhuis, Reinder L H; Debets, Reno

2003-09-01

282

Two systems in vitro that show insulin-stimulated serine kinase activity towards the insulin receptor.  

PubMed Central

Two systems in vitro are described that show insulin-stimulated phosphorylation of the insulin receptor on serine residues. In the first system, insulin receptor was purified partially from Fao rat hepatoma cells by direct solubilization of the cells in Triton X-100 and chromatography on wheat-germ-agglutinin-agarose. Phosphorylation of these preparations with [gamma-32P]ATP in the presence or absence of insulin resulted in 32P incorporation exclusively into phosphotyrosine residues. Serine kinase activity towards the insulin receptor was reconstituted by adding extracts of Fao cells. Prior exposure of the cells to insulin stimulated serine kinase activity towards the insulin receptor in extracts 7.2-fold. A receptor serine kinase activity enhanced by treatment of cells with cyclic AMP analogues was also retained in the reconstituted system. In the second system, insulin receptor and insulin-sensitive serine kinase activity towards the insulin receptor were co-purified from human placenta. The protocol involved preparation of membranes, before solubilization and chromatography on wheat-germ-agglutinin-agarose, by using gentle procedures designed not to disrupt a potentially labile association between the insulin receptor and the serine kinase. Serine kinase activity in these preparations towards the insulin receptor was stimulated up to 10-fold by insulin, and the stoicheiometry of serine phosphorylation was estimated to be approx 0.8 mol/mol of insulin receptor for phosphorylations performed in the presence of insulin. Thus a preparation of insulin receptor is described for the first time that is phosphorylated to high stoicheiometry on serine in an insulin-dependent manner. Conditions that facilitate recovery and assay of serine kinase activity are defined and discussed. These systems provide a basis for characterizing the nature of the insulin-sensitive serine kinase that phosphorylates the insulin receptor, and defining its role in insulin action and control of receptor function. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. PMID:2965579

Smith, D M; King, M J; Sale, G J

1988-01-01

283

Ligand Affinity and Kinase Activity are Independent of Bacterial Chemotaxis Receptor Concentration: Insight into Signaling Mechanisms  

PubMed Central

Attractant binding to bacterial chemotaxis receptors initiates a transmembrane signal that inhibits the kinase CheA bound about 300 Å away at the other end of the receptor. Chemoreceptors form large clusters in many bacterial species, and the extent of clustering has been reported to vary with signaling state. To test whether ligand binding regulates kinase activity by modulating a clustering equilibrium, we measured the effects of two-dimensional receptor concentration on kinase activity in proteoliposomes containing the purified E. coli serine receptor reconstituted into vesicles at a range of lipid-to-protein molar ratios. The IC50 of kinase inhibition was unchanged despite a 10-fold change in receptor concentration. Such a change in concentration would have produced a measurable shift in the IC50 if receptor clustering were involved in kinase regulation, based on a simple model in which the receptor oligomerization and ligand binding equilibria are coupled. These results indicate that the primary signal, ligand control of kinase activity, does not involve a change in receptor oligomerization state. In combination with previous work on cytoplasmic fragments assembled on vesicle surfaces [Besschetnova et al. (2008) Proc. Nat. Acad. Sci. USA 105, 12289–12294], this suggests that ligand binding to chemotaxis receptors inhibits the kinase by inducing a conformational change that expands the membrane area occupied by the receptor cytoplasmic domain, without changing the number of associated receptors in the signaling complex. PMID:22870954

Sferdean, Fe C.; Weis, Robert M.; Thompson, Lynmarie K.

2013-01-01

284

Triclocarban mediates induction of xenobiotic metabolism through activation of the constitutive androstane receptor and the estrogen receptor alpha.  

PubMed

Triclocarban (3,4,4'-trichlorocarbanilide, TCC) is used as a broad-based antimicrobial agent that is commonly added to personal hygiene products. Because of its extensive use in the health care industry and resistance to degradation in sewage treatment processes, TCC has become a significant waste product that is found in numerous environmental compartments where humans and wildlife can be exposed. While TCC has been linked to a range of health and environmental effects, few studies have been conducted linking exposure to TCC and induction of xenobiotic metabolism through regulation by environmental sensors such as the nuclear xenobiotic receptors (XenoRs). To identify the ability of TCC to activate xenobiotic sensors, we monitored XenoR activities in response to TCC treatment using luciferase-based reporter assays. Among the XenoRs in the reporter screening assay, TCC promotes both constitutive androstane receptor (CAR) and estrogen receptor alpha (ER?) activities. TCC treatment to hUGT1 mice resulted in induction of the UGT1A genes in liver. This induction was dependent upon the constitutive active/androstane receptor (CAR) because no induction occurred in hUGT1Car(-/-) mice. Induction of the UGT1A genes by TCC corresponded with induction of Cyp2b10, another CAR target gene. TCC was demonstrated to be a phenobarbital-like activator of CAR in receptor-based assays. While it has been suggested that TCC be classified as an endocrine disruptor, it activates ER? leading to induction of Cyp1b1 in female ovaries as well as in promoter activity. Activation of ER? by TCC in receptor-based assays also promotes induction of human CYP2B6. These observations demonstrate that TCC activates nuclear xenobiotic receptors CAR and ER? both in vivo and in vitro and might have the potential to alter normal physiological homeostasis. Activation of these xenobiotic-sensing receptors amplifies gene expression profiles that might represent a mechanistic base for potential human health effects from exposure to TCC. PMID:22761658

Yueh, Mei-Fei; Li, Tao; Evans, Ronald M; Hammock, Bruce; Tukey, Robert H

2012-01-01

285

Activated scavenger receptor A promotes glial internalization of a?.  

PubMed

Beta-amyloid (A?) aggregates have a pivotal role in pathological processing of Alzheimer's disease (AD). The clearance of A? monomer or aggregates is a causal strategy for AD treatment. Microglia and astrocytes are the main macrophages that exert critical neuroprotective roles in the brain. They may effectively clear the toxic accumulation of A? at the initial stage of AD, however, their functions are attenuated because of glial overactivation. In this study, we first showed that heptapeptide XD4 activates the class A scavenger receptor (SR-A) on the glia by increasing the binding of A? to SR-A, thereby promoting glial phagocytosis of A? oligomer in microglia and astrocytes and triggering intracellular mitogen-activated protein kinase (MAPK) signaling cascades. Moreover, XD4 enhances the internalization of A? monomers to microglia and astrocytes through macropinocytosis or SR-A-mediated phagocytosis. Furthermore, XD4 significantly inhibits A? oligomer-induced cytotoxicity to glial cells and decreases the production of proinflammatory cytokines, such as TNF-? and IL-1?, in vitro and in vivo. Our findings may provide a novel strategy for AD treatment by activating SR-A. PMID:24718459

Zhang, He; Su, Ya-jing; Zhou, Wei-wei; Wang, Shao-wei; Xu, Peng-xin; Yu, Xiao-lin; Liu, Rui-tian

2014-01-01

286

A Mechanism of Intracellular P2X Receptor Activation*  

PubMed Central

P2X receptors (P2XRs) are ATP-activated calcium-permeable ligand-gated ion channels traditionally viewed as sensors of extracellular ATP during diverse physiological processes including pain, inflammation, and taste. However, in addition to a cell surface residency P2XRs also populate the membranes of intracellular compartments, including mammalian lysosomes, phagosomes, and the contractile vacuole (CV) of the amoeba Dictyostelium. The function of intracellular P2XRs is unclear and represents a major gap in our understanding of ATP signaling. Here, we exploit the genetic versatility of Dictyostelium to investigate the effects of physiological concentrations of ATP on calcium signaling in isolated CVs. Within the CV, an acidic calcium store, P2XRs are orientated to sense luminal ATP. Application of ATP to isolated vacuoles leads to luminal translocation of ATP and release of calcium. Mechanisms of luminal ATP translocation and ATP-evoked calcium release share common pharmacology, suggesting that they are linked processes. The ability of ATP to mobilize stored calcium is reduced in vacuoles isolated from P2XAR knock-out amoeba and ablated in cells devoid of P2XRs. Pharmacological inhibition of luminal ATP translocation or depletion of CV calcium attenuates CV function in vivo, manifesting as a loss of regulatory cell volume decrease following osmotic swelling. We propose that intracellular P2XRs regulate vacuole activity by acting as calcium release channels, activated by translocation of ATP into the vacuole lumen. PMID:22736763

Sivaramakrishnan, Venketesh; Fountain, Samuel J.

2012-01-01

287

Activated Scavenger Receptor A Promotes Glial Internalization of A?  

PubMed Central

Beta-amyloid (A?) aggregates have a pivotal role in pathological processing of Alzheimer’s disease (AD). The clearance of A? monomer or aggregates is a causal strategy for AD treatment. Microglia and astrocytes are the main macrophages that exert critical neuroprotective roles in the brain. They may effectively clear the toxic accumulation of A? at the initial stage of AD, however, their functions are attenuated because of glial overactivation. In this study, we first showed that heptapeptide XD4 activates the class A scavenger receptor (SR-A) on the glia by increasing the binding of A? to SR-A, thereby promoting glial phagocytosis of A? oligomer in microglia and astrocytes and triggering intracellular mitogen-activated protein kinase (MAPK) signaling cascades. Moreover, XD4 enhances the internalization of A? monomers to microglia and astrocytes through macropinocytosis or SR-A-mediated phagocytosis. Furthermore, XD4 significantly inhibits A? oligomer-induced cytotoxicity to glial cells and decreases the production of proinflammatory cytokines, such as TNF-? and IL-1?, in vitro and in vivo. Our findings may provide a novel strategy for AD treatment by activating SR-A. PMID:24718459

Zhou, Wei-wei; Wang, Shao-wei; Xu, Peng-xin; Yu, Xiao-lin; Liu, Rui-tian

2014-01-01

288

Neutrophil Serine Proteinases Activate Human Nonepithelial Cells to Produce Inflammatory Cytokines Through Protease-Activated Receptor 21  

Microsoft Academic Search

Protease-activated receptors (PARs) compose a family of G protein-coupled receptors activated by proteolysis with exposure of their tethered ligand. Recently, we reported that a neutrophil-derived serine proteinase, proteinase 3 (PR3), activated human oral epithelial cells through PAR-2. The present study examined whether other neutrophil serine proteinases, human leukocyte elastase (HLE), and cathepsin G (Cat G) activate nonepithelial cells, human gingival

Akiko Uehara; Koji Muramoto; Haruhiko Takada; Shunji Sugawara

289

Activation of Cannabinoid Receptor 2 Enhances Osteogenic Differentiation of Bone Marrow Derived Mesenchymal Stem Cells  

PubMed Central

Bone marrow derived mesenchymal stem cells (BM-MSCs) are considered as the most promising cells source for bone engineering. Cannabinoid (CB) receptors play important roles in bone mass turnover. The aim of this study is to test if activation of CB2 receptor by chemical agonist could enhance the osteogenic differentiation and mineralization in bone BM-MSCs. Alkaline phosphatase (ALP) activity staining and real time PCR were performed to test the osteogenic differentiation. Alizarin red staining was carried out to examine the mineralization. Small interference RNA (siRNA) was used to study the role of CB2 receptor in osteogenic differentiation. Results showed activation of CB2 receptor increased ALP activity, promoted expression of osteogenic genes, and enhanced deposition of calcium in extracellular matrix. Knockdown of CB2 receptor by siRNA inhibited ALP activity and mineralization. Results of immunofluorescent staining showed that phosphorylation of p38 MAP kinase is reduced by knocking down of CB2 receptor. Finally, bone marrow samples demonstrated that expression of CB2 receptor is much lower in osteoporotic patients than in healthy donors. Taken together, data from this study suggested that activation of CB2 receptor plays important role in osteogenic differentiation of BM-MSCs. Lack of CB2 receptor may be related to osteoporosis.

Sun, Yong-Xin; Xu, Ai-Hua; Yang, Yang; Zhang, Jia-Xing; Yu, Ai-Wen

2015-01-01

290

Linking receptor activation to changes in Sw I and II of G? proteins.  

PubMed

G-protein coupled receptors catalyze nucleotide exchange on G proteins, which results in subunit dissociation and effector activation. In the recent ?2AR-Gs structure, portions of Switch I and II of G? are not fully elucidated. We paired fluorescence studies of receptor-G?i interactions with the ?2AR-Gs and other Gi structures to investigate changes in Switch I and II during receptor activation and GTP binding. The ?2/?3 loop containing Leu194 of G?i is located between Switches I and II, in close proximity to IC2 of the receptor and the C-terminus of G?, thus providing an allosteric connection between these Switches and receptor activation. We compared the environment of residues in myristoylated G?i proteins in the heterotrimer to that upon receptor activation and subsequent GTP binding. Upon receptor activation, residues in both Switch regions are less solvent-exposed, as compared to the heterotrimer. Upon GTP?S binding, the environment of several residues in Switch I resemble the receptor-bound state, while Switch II residues display effects on their environment which are consistent with their role in GTP binding and G?? dissociation. The ability to merge available crystal structures with solution studies is a powerful tool to gain insight into conformational changes associated with receptor-mediated Gi protein activation. PMID:23466875

Hamm, Heidi E; Kaya, Ali I; Gilbert, James A; Preininger, Anita M

2013-10-01

291

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) and Its Receptors: Neuroendocrine and Endocrine Interaction  

Microsoft Academic Search

The recent progress of research on the functions of pituitary adenylate cyclase activating polypeptide (PACAP), especially endocrine and neuroendocrine interactions, is described. Studies of the genes encoding the PACAP precursor and the type I PACAP receptor provide information on the control of PACAP gene expression and on the relationship between the structure of the receptor subtypes and the activation of

Akira Arimura; Seiji Shioda

1995-01-01

292

Peroxisome proliferator-activated receptors (PPARs) in skin health, repair and disease  

Microsoft Academic Search

Peroxisome proliferator-activated receptors, PPAR?, PPAR?\\/? and PPAR?, are fatty acid activated transcription factors that belong to the nuclear hormone receptor family. While they are best known as transcriptional regulators of lipid and glucose metabolism, evidence has also accumulated for their importance in skin homeostasis. The three PPAR isotypes are expressed in rodent and human skin. Various cell culture and in

Liliane Michalik; Walter Wahli

2007-01-01

293

A homogenous assay to monitor the activity of the insulin receptor using Bioluminescence Resonance Energy Transfer.  

PubMed

Insulin exerts its biological effects through a plasma membrane receptor that possesses a tyrosine kinase activity. Binding of insulin to its receptor induces a conformational change that stimulates the autophosphorylation of the receptor on tyrosine residues. This autophosphorylation stimulates the tyrosine kinase activity of the receptor toward intracellular substrates involved in the transmission of the signal. The discovery of pharmacological agents that specifically activate the tyrosine kinase activity of the insulin receptor will be of great importance for the treatment of insulin-resistant or insulin-deficient patients. We have developed a procedure based on Bioluminescence Resonance Energy Transfer (BRET) to monitor the activation state of the insulin receptor. Human insulin receptor cDNA, was fused to either Renilla luciferase or yellow fluorescent protein coding sequences. Fusion insulin receptors were partially purified by wheat-germ lectin chromatography from HEK-293 cells co-transfected with these constructs. The conformational change induced by insulin on its receptor could be detected as an energy transfer (BRET signal) between Renilla luciferase and yellow fluorescent protein. BRET signal paralleled insulin-induced autophosphorylation of the fusion receptor. Dose-dependent effects of insulin, insulin-like growth factor 1 and epidermal growth factor on BRET signal were in agreement with known pharmacological properties of these ligands. Moreover, an antibody, which activated the autophosphorylation of the receptor, had similar effects on BRET signal. This methodology allows for rapid analysis of the effects of agonists on insulin receptor activity and could, therefore, be used in high-throughput screening for the discovery of molecules with insulin-like properties. PMID:12213574

Issad, Tarik; Boute, Nicolas; Pernet, Karine

2002-09-01

294

Stimulatory Effects of Peroxisome Proliferator-Activated Receptor-? on Fc? Receptor-Mediated Phagocytosis by Alveolar Macrophages  

PubMed Central

Alveolar macrophages abundantly express PPAR-?, with both natural and synthetic agonists maintaining the cell in a quiescent state hyporesponsive to antigen stimulation. Conversely, agonists upregulate expression and function of the cell-surface receptor CD36, which mediates phagocytosis of lipids, apoptotic neutrophils, and other unopsonized materials. These effects led us to investigate the actions of PPAR-? agonists on the Fc? receptor, which mediates phagocytosis of particles opsonized by binding of immunoglobulin G antibodies. We found that troglitazone, rosiglitazone, and 15-deoxy-?12,14-prostaglandin J2 increase the ability of alveolar, but not peritoneal, macrophages to carry out phagocytosis mediated by the Fc? receptor. Receptor expression was not altered but activation of the downstream signaling proteins Syk, ERK-1, and ERK-2 was observed. Although it was previously known that PPAR-? ligands stimulate phagocytosis of unopsonized materials, this is the first demonstration that they stimulate phagocytosis of opsonized materials as well. PMID:18253476

Aronoff, David M.; Serezani, Carlos H.; Carstens, Jennifer K.; Marshall, Teresa; Gangireddy, Srinivasa R.; Peters-Golden, Marc; Reddy, Raju C.

2007-01-01

295

Isolation and characterization of a specific receptor for biologically active phorbol and ingenol esters.  

PubMed

A high-affinity, specific receptor for biologically active phorbol and ingenol esters has been purified to electrophoretic homogeneity from murine brains using ammonium sulfate fractionation, and DEAE-cellulose, Sephadex G-200, Affi-Gel Blue, and phenyl-Sepharose chromatographies. The receptor is a single-chain hydrophobic protein with a molecular weight (Mr) of 81,500, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The receptor has a sedimentation coefficient of 5.2 S and Stokes radius of 30.3 A. It has an isoelectric point (pI) of 5.5. The receptor is heat and acid labile. The receptor absolutely depends upon phosphatidylserine or phosphatidylinositol (optimum concentration approximately 4-8 micrograms/ml) for its activity. A variety of divalent cations stimulates the binding activity of the receptor. A molecule of receptor binds 1-2 molecules of phorbol-12, 13-dibutyrate (PDBu) with a Kd value of 4.2 nM. Those phorbol and ingenol esters which stimulate cell growth in culture and have tumor-promoting activity in vivo inhibit the binding of labeled PDBu to its homogeneous receptor, while the biologically inactive derivatives fail to do so. The homogeneous receptor protein contains a protein kinase activity. PMID:6593003

Shoyab, M; Boaze, R

1984-10-01

296

Receptor-specific inhibition of GABAB-activated K+ currents by muscarinic and metabotropic glutamate receptors in immature rat hippocampus  

PubMed Central

It has been shown that the activation of Gq-coupled receptors (GqPCRs) in cardiac myocytes inhibits the G protein-gated inwardly rectifying K+ current (IGIRK) via receptor-specific depletion of phosphatidylinositol 4,5-bisphosphate (PIP2). In this study, we investigated the mechanism of the receptor-mediated regulation of IGIRK in acutely isolated hippocampal CA1 neurons by the muscarinic receptor agonist, carbachol (CCh), and the group I metabotropic glutamate receptor (mGluR) agonist, 3,5-dihydroxyphenylglycine (DHPG). IGIRK was activated by the GABAB receptor agonist, baclofen. When baclofen was repetitively applied at intervals of 2–3 min, the amplitude of the second IGIRK was 92.3 ± 1.7% of the first IGIRK in control. Pretreatment of neurons with CCh or DHPG prior to the second application of baclofen caused a reduction in the amplitude of the second IGIRK to 54.8 ± 1.3% and 51.4 ± 0.6%, respectively. In PLC?1 knockout mice, the effect of CCh on IGIRK was significantly reduced, whereas the effect of DHPG remained unchanged. The CCh-mediated inhibition of IGIRK was almost completely abolished by PKC inhibitors and pipette solutions containing BAPTA. The DHPG-mediated inhibition of IGIRK was attenuated by the inhibition of phospholipase A2 (PLA2), or the sequestration of arachidonic acid. We confirmed that DHPG eliminated the inhibition of IGIRK by arachidonic acid. These results indicate that muscarinic inhibition of IGIRK is mediated by the PLC/PKC signalling pathway, while group I mGluR inhibition of IGIRK occurs via the PLA2-dependent production of arachidonic acid. These results present a novel receptor-specific mechanism for crosstalk between GqPCRs and GABAB receptors. PMID:17255165

Sohn, Jong-Woo; Lee, Doyun; Cho, Hana; Lim, Wonil; Shin, Hee-Sup; Lee, Suk-Ho; Ho, Won-Kyung

2007-01-01

297

Activation of N-methyl-d-aspartate receptor downregulates inflammasome activity and liver inflammation via a ?-arrestin-2 pathway.  

PubMed

Activation of the cytosolic inflammasome machinery is responsible for acute and chronic liver inflammation, but little is known about its regulation. The N-methyl-d-aspartate (NMDA) receptor families are heterotetrameric ligand-gated ion channels that are activated by a range of metabolites, including aspartate, glutamate, and polyunsaturated fatty acids. In the brain NMDA receptors are present on neuronal and nonneuronal cells and regulate a diverse range of functions. We tested the role of the NMDA receptor and aspartate in inflammasome regulation in vitro and in models of acute hepatitis and pancreatitis. We demonstrate that the NMDA receptor is present on Kupffer cells, and their activation on primary mouse and human cells limits inflammasome activation by downregulating NOD-like receptor family, pyrin domain containing 3 and procaspase-1. The NMDA receptor pathway is active in vivo, limits injury in acute hepatitis, and can be therapeutically further activated by aspartate providing protection in acute inflammatory liver injury. Downregulation of inflammasome activation by NMDA occurs via a ?-arrestin-2 NF-k? and JNK pathway and not via Ca(2+) mobilization. We have identified the NMDA receptor as a regulator of inflammasome activity in vitro and in vivo. This has identified a new area of immune regulation associated by metabolites that may be relevant in a diverse range of conditions, including nonalcoholic steatohepatitis and total parenteral nutrition-induced immune suppression. PMID:25104498

Farooq, Ahmad; Hoque, Rafaz; Ouyang, Xinshou; Farooq, Ahsan; Ghani, Ayaz; Ahsan, Kaimul; Guerra, Mateus; Mehal, Wajahat Zafar

2014-10-01

298

Developmental and activity-dependent regulation of kainate receptors at thalamocortical synapses.  

PubMed

Most of the fast excitatory synaptic transmission in the mammalian brain is mediated by ionotrophic glutamate receptors, of which there are three subtypes: AMPA (alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate), NMDA (N-methyl-D-aspartate) and kainate. Although kainate-receptor subunits (GluR5-7, KA1 and 2) are widely expressed in the mammalian central nervous system, little is known about their function. The development of pharmacological agents that distinguish between AMPA and kainate receptors has now allowed the functions of kainate receptors to be investigated. The modulation of synaptic transmission by kainate receptors and their synaptic activation in a variety of brain regions have been reported. The expression of kainate receptor subunits is developmentally regulated but their role in plasticity and development is unknown. Here we show that developing thalamocortical synapses express postsynaptic kainate receptors as well as AMPA receptors; however, the two receptor subtypes do not colocalize. During the critical period for experience-dependent plasticity, the kainate-receptor contribution to transmission decreases; a similar decrease occurs when long-term potentiation is induced in vitro. This indicates that during development there is activity-dependent regulation of the expression of kainate receptors at thalamocortical synapses. PMID:10448859

Kidd, F L; Isaac, J T

1999-08-01

299

Glucocorticoid receptor activity regulates light adaptation in the zebrafish retina.  

PubMed

Glucocorticoids modulate diverse aspects of physiology and behavior, including energy homeostasis, stress response, and memory, through activation of the glucocorticoid receptor (GR). Light perception has profound effects on the production of glucocorticoids via functional connections of the retina to the hypothalamus-pituitary-adrenal axis. We report here that glucocorticoids can also signal in the reverse direction, i. e., regulate visual function in zebrafish, Danio rerio. The zebrafish GR mutant, gr (s357) , harbors a missense mutation that completely blocks the transcriptional activity of GR. In this mutant, visual behavior was abolished following a period of darkness and recovered sluggishly after return to the light. Electrophysiological measurements showed that the photoresponse of the dark-adapted retina was reduced in the mutant and re-adapted to light with a substantial delay. Several gene products, including some that are important for dopaminergic signaling, were misregulated in gr (s357) mutants. We suggest that GR controls a gene network required for visual adaptation in the zebrafish retina and potentially integrates neuroendocrine and sensory responses to environmental changes. PMID:24068988

Muto, Akira; Taylor, Michael R; Suzawa, Miyuki; Korenbrot, Juan I; Baier, Herwig

2013-01-01

300

Peroxisome proliferator-activated receptors, metabolic syndrome and cardiovascular disease  

PubMed Central

Metabolic syndrome (MetS) is a constellation of risk factors including insulin resistance, central obesity, dyslipidemia and hypertension that markedly increase the risk of Type 2 diabetes (T2DM) and cardiovascular disease (CVD). The peroxisome proliferators-activated receptor (PPAR) isotypes, PPAR?, PPAR?/? and PPAR? are ligand-activated nuclear transcription factors, which modulate the expression of an array of genes that play a central role in regulating glucose, lipid and cholesterol metabolism, where imbalance can lead to obesity, T2DM and CVD. They are also drug targets, and currently, PPAR? (fibrates) and PPAR? (thiazolodinediones) agonists are in clinical use for treating dyslipidemia and T2DM, respectively. These metabolic characteristics of the PPARs, coupled with their involvement in metabolic diseases, mean extensive efforts are underway worldwide to develop new and efficacious PPAR-based therapies for the treatment of additional maladies associated with the MetS. This article presents an overview of the functional characteristics of three PPAR isotypes, discusses recent advances in our understanding of the diverse biological actions of PPARs, particularly in the vascular system, and summarizes the developmental status of new single, dual, pan (multiple) and partial PPAR agonists for the clinical management of key components of MetS, T2DM and CVD. It also summarizes the clinical outcomes from various clinical trials aimed at evaluating the atheroprotective actions of currently used fibrates and thiazolodinediones. PMID:20932114

Azhar, Salman

2011-01-01

301

Glucocorticoid receptor activity regulates light adaptation in the zebrafish retina  

PubMed Central

Glucocorticoids modulate diverse aspects of physiology and behavior, including energy homeostasis, stress response, and memory, through activation of the glucocorticoid receptor (GR). Light perception has profound effects on the production of glucocorticoids via functional connections of the retina to the hypothalamus-pituitary-adrenal axis. We report here that glucocorticoids can also signal in the reverse direction, i. e., regulate visual function in zebrafish, Danio rerio. The zebrafish GR mutant, grs357, harbors a missense mutation that completely blocks the transcriptional activity of GR. In this mutant, visual behavior was abolished following a period of darkness and recovered sluggishly after return to the light. Electrophysiological measurements showed that the photoresponse of the dark-adapted retina was reduced in the mutant and re-adapted to light with a substantial delay. Several gene products, including some that are important for dopaminergic signaling, were misregulated in grs357 mutants. We suggest that GR controls a gene network required for visual adaptation in the zebrafish retina and potentially integrates neuroendocrine and sensory responses to environmental changes. PMID:24068988

Muto, Akira; Taylor, Michael R.; Suzawa, Miyuki; Korenbrot, Juan I.; Baier, Herwig

2013-01-01

302

Fish granulocytes express a constitutively active androgen receptor variant.  

PubMed

In humans, alternative splicing of androgen receptor (AR) is usually involved in some diseases. However, our knowledge about the presence of AR variants in other species and its importance for immunity is scant. Here, we report the identification of a constitutively active AR variant lacking the ligand-binding domain (LBD), AR?LBD, in the fish gilthead seabream. AR?LBD is expressed in the testis and the head-kidney (HK), and its expression varies with the reproductive stage and is correlated with plasma testosterone (T). In addition, AR?LBD is expressed in acidophilic granulocytes (AGs), which are the functional equivalent of mammalian neutrophils, but not in macrophages, and its expression is modulated by both T and immune stimuli. Notably, AR and AR?LBD were able to interact, being the activity of AR dominant at all concentrations tested of the ligand. These results reveal a new mechanism for the regulation of neutrophil biology in vertebrates and explain the conflicting results that suggest that androgens are less important than AR in human and mouse neutrophil homeostasis. PMID:24509065

Sánchez-Hernández, Miriam; Arizcun, Marta; García-Alcázar, Alicia; Sarropoulou, Elena; Mulero, Victoriano; García-Ayala, Alfonsa

2014-07-01

303

The antitussive activity of delta-opioid receptor stimulation in guinea pigs.  

PubMed

In this study, the activity of the delta-opioid receptor subtype-selective agonist, SB 227122, was investigated in a guinea pig model of citric acid-induced cough. Parenteral administration of selective agonists of the delta-opioid receptor (SB 227122), mu-opioid receptor (codeine and hydrocodone), and kappa-opioid receptor (BRL 52974) produced dose-related inhibition of citric acid-induced cough with ED(50) values of 7.3, 5.2, 5.1, and 5.3 mg/kg, respectively. The nonselective opioid receptor antagonist, naloxone (3 mg/kg, i.m.), attenuated the antitussive effects of codeine or SB 227122, indicating that the antitussive activity of both compounds is opioid receptor-mediated. The delta-receptor antagonist, SB 244525 (10 mg/kg, i.p.), inhibited the antitussive effect of SB 227122 (20 mg/kg, i.p.). In contrast, combined pretreatment with beta-funaltrexamine (mu-receptor antagonist; 20 mg/kg, s.c.) and norbinaltorphimine (kappa-receptor antagonist; 20 mg/kg, s.c.), at doses that inhibited the antitussive activity of mu- and kappa-receptor agonists, respectively, was without effect on the antitussive response of SB 227122 (20 mg/kg, i.p.). The sigma-receptor antagonist rimcazole (3 mg/kg, i.p.) inhibited the antitussive effect of dextromethorphan (30 mg/kg, i.p.), a sigma-receptor agonist, but not that of SB 227122. These studies provide compelling evidence that the antitussive effects of SB 227122 in this guinea pig cough model are mediated by agonist activity at the delta-opioid receptor. PMID:10640321

Kotzer, C J; Hay, D W; Dondio, G; Giardina, G; Petrillo, P; Underwood, D C

2000-02-01

304

Characterization of Peroxisome Proliferator-Activated Receptor a (PPARa) -Independent Effects of PPARa Activators in the Rodent Liver: Di-(2-ethylhexyl) phthalate Also Activates the Constitutive Activated Receptor  

EPA Science Inventory

Peroxisome proliferator chemicals (PPC) are thought to mediate their effects in rodents on hepatocyte growth and liver cancer through the nuclear receptor peroxisome proliferatoractivated receptor alpha (PPARa). Recent studies indicate that one such PPC, the plasticizer di2- et...

305

Electron microscopic structure of agrin and mapping of its binding site in laminin-1.  

PubMed Central

Agrin is a large, multidomain heparan sulfate proteoglycan that is associated with basement membranes of several tissues. Particular splice variants of agrin are essential for the formation of synaptic structures at the neuromuscular junction. The binding of agrin to laminin appears to be required for its localization to synaptic basal lamina and other basement membranes. Here, electron microscopy was used to determine the structure of agrin and to localize its binding site in laminin-1. Agrin appears as an approximately 95 nm long particle that consists of a globular, N-terminal laminin-binding domain, a central rod predominantly formed by the follistatin-like domains and three globular, C-terminal laminin G-like domains. In a few cases, heparan sulfate glycosaminoglycan chains were seen emerging from the central portion of the core protein. Moreover, we show that agrin binds to the central region of the three-stranded, coiled-coil oligomerization domain in the long arm of laminin-1, which mediates subunit assembly of the native laminin molecule. In summary, our data show for the first time a protein-protein interaction of the extracellular matrix that involves a coiled-coil domain, and they assign a novel role to this domain of laminin-1. Based on this, we propose that agrin associates with basal lamina in a polarized way. PMID:9430625

Denzer, A J; Schulthess, T; Fauser, C; Schumacher, B; Kammerer, R A; Engel, J; Ruegg, M A

1998-01-01

306

The impact of laminin on 3D neurite extension in collagen gels  

NASA Astrophysics Data System (ADS)

The primary goal of this research was to characterize the effect of laminin on three-dimensional (3D) neurite growth. Gels were formed using type I collagen at concentrations of 0.4-2.0 mg mL-1 supplemented with laminin at concentrations of 0, 1, 10, or 100 µg mL-1. When imaged with confocal microscopy, laminin was shown to follow the collagen fibers; however, the addition of laminin had minimal effect on the stiffness of the scaffolds at any concentration of collagen. Individual neurons dissociated from E9 chick dorsal root ganglia were cultured in the gels for 24 h, and neurite lengths were measured. For collagen gels without laminin, a typical bimodal response of neurite outgrowth was observed, with increased growth at lower concentrations of collagen gel. However, alteration of the chemical nature of the collagen gel by the laminin additive shifted, or completely mitigated, the bimodal neurite growth response seen in gels without laminin. Expression of integrin subunits, ?1, ?3, ?6 and ?1, were confirmed by PCR and immunolabeling in the 3D scaffolds. These results provide insight into the interplay between mechanical and chemical environment to support neurite outgrowth in 3D. Understanding the relative impact of environmental factors on 3D nerve growth may improve biomaterial design for nerve cell regeneration.

Swindle-Reilly, Katelyn E.; Papke, Jason B.; Kutosky, Hannah P.; Throm, Allison; Hammer, Joshua A.; Harkins, Amy B.; Kuntz Willits, Rebecca

2012-08-01

307

Ablation of astrocytic laminin impairs vascular smooth muscle cell function and leads to hemorrhagic stroke  

PubMed Central

Astrocytes express laminin and assemble basement membranes (BMs) at their endfeet, which ensheath the cerebrovasculature. The function of astrocytic laminin in cerebrovascular integrity is unknown. We show that ablation of astrocytic laminin by tissue-specific Cre-mediated recombination disrupted endfeet BMs and led to hemorrhage in deep brain regions of adult mice, resembling human hypertensive hemorrhage. The lack of astrocytic laminin led to impaired function of vascular smooth muscle cells (VSMCs), where astrocytes have a closer association with VSMCs in small arterioles, and was associated with hemorrhagic vessels, which exhibited VSMC fragmentation and vascular wall disassembly. Acute disruption of astrocytic laminin in the striatum of adult mice also impaired VSMC function, indicating that laminin is necessary for VSMC maintenance. In vitro, both astrocytes and astrocytic laminin promoted brain VSMC differentiation. These results show that astrocytes regulate VSMCs and vascular integrity in small vessels of deep brain regions. Therefore, astrocytes may be a possible target for hemorrhagic stroke prevention and therapy. PMID:23857767

Chen, Zu-Lin; Yao, Yao; Norris, Erin H.; Kruyer, Anna; Jno-Charles, Odella; Akhmerov, Akbarshakh

2013-01-01

308

Phytoceramide and sphingoid bases derived from brewer's yeast Saccharomyces pastorianus activate peroxisome proliferator-activated receptors  

PubMed Central

Background Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate lipid and glucose metabolism. PPAR? is highly expressed in the liver and controls genes involved in lipid catabolism. We previously reported that synthetic sphingolipid analogs, part of which contains shorter-length fatty acid chains than natural sphingolipids, stimulated the transcriptional activities of PPARs. Sphingosine and dihydrosphingosine (DHS) are abundant sphingoid bases, and ceramide and dihydroceramide are major ceramide species in mammals. In contrast, phytosphingosine (PHS) and DHS are the main sphingoid bases in fungi. PHS and phytoceramide exist in particular tissues such as the epidermis in mammals, and involvement of ceramide species in PPAR? activation in cultured keratinocytes has been reported. The purpose of the present study is to investigate whether natural sphingolipids with C18 fatty acid and yeast-derived sphingoid bases activate PPARs as PPAR agonists. Method Lipids of brewer's yeast contain PHS- and DHS-based sphingolipids. To obtain the sphingoid bases, lipids were extracted from brewer's yeast and acid-hydrolyzed. The sphingoid base fraction was purified and quantified. To assess the effects of sphingolipids on PPAR activation, luciferase reporter assay was carried out. NIH/3T3 and human hepatoma (HepG2) cells were transfected with expression vectors for PPARs and retinoid × receptors, and PPAR responsive element reporter vector. When indicated, the PPAR/Gal4 chimera system was performed to enhance the credibility of experiments. Sphingolipids were added to the cells and the dual luciferase reporter assay was performed to determine the transcriptional activity of PPARs. Results We observed that phytoceramide increased the transcriptional activities of PPARs significantly, whereas ceramide and dihydroceramide did not change PPAR activities. Phytoceramide also increased transactivation of PPAR/Gal4 chimera receptors. Yeast-derived sphingoid base fraction, which contained PHS and DHS, or authentic PHS or DHS increased PPAR-dependent transcription. Additionally, phytoceramide stimulated PPAR? activity in HepG2 hepatocytes, suggesting that phytoceramide activates genes regulated by PPAR?. Conclusions Phytoceramide and yeast-derived sphingoid bases activate PPARs, whereas ceramide and dihydroceramide do not change the PPAR activity. The present findings suggest that phytoceramide acts as a PPAR ligand that would regulate PPAR-targeted genes. PMID:21861924

2011-01-01

309

Epidermal Growth Factor Receptor Signal TransActivation  

Microsoft Academic Search

\\u000a Coordination of complex cell functions is achieved by the regulated information transfer along linear signalling pathways.\\u000a It has become apparent, however, that these linear pathways are not free-standing entities but parts of larger networks. Transactivation\\u000a of the epidermal growth factor receptor (EGFR) represents the paradigm for communication between G protein-coupled receptors\\u000a (GPCRs) and receptor tyrosine kinases (RTKs). Recent studies provided

Stefan Hart; Andreas Gschwind; Andreas Roidl; Axel Ullrich

310

Activation of calcineurin underlies altered trafficking of ?2 subunit containing GABAA receptors during prolonged epileptiform activity  

PubMed Central

Fast inhibitory signalling in the mammalian brain is mediated by gamma-aminobutyric acid type A receptors (GABAARs), which are targets for anti-epileptic therapy such as benzodiazepines. GABAARs undergo tightly regulated trafficking processes that are essential for maintenance and physiological modulation of inhibitory strength. The trafficking of GABAARs to and from the membrane is altered during prolonged seizures such as in Status Epilepticus (SE) and has been suggested to contribute to benzodiazepine pharmacoresistance in patients with SE. However, the intracellular signalling mechanisms that cause this modification in GABAAR trafficking remain poorly understood. In this study, we investigate the surface stability of GABAARs during SE utilising the low Mg2+ model in hippocampal rat neurons. Live-cell imaging of super ecliptic pHluorin (SEP)-tagged ?2 subunit containing GABAARs during low Mg2+ conditions reveals that the somatic surface receptor pool undergoes down-regulation dependent on N-methyl-d-aspartate receptor (NMDAR) activity. Analysis of the intracellular Ca2+ signal during low Mg2+ using the Ca2+-indicator Fluo4 shows that this reduction of surface GABAARs correlates well with the timeline of intracellular Ca2+ changes. Furthermore, we show that the activation of the phosphatase calcineurin was required for the decrease in surface GABAARs in neurons undergoing epileptiform activity. These results indicate that somatic modulation of GABAAR trafficking during epileptiform activity in vitro is mediated by calcineurin activation which is linked to changes in intracellular Ca2+ concentrations. These mechanisms could account for benzodiazepine pharmacoresistance and the maintenance of recurrent seizure activity, and reveal potential novel targets for the treatment of SE. This article is part of the Special Issue entitled ‘GABAergic Signaling in Health and Disease’. PMID:25245802

Eckel, Ramona; Szulc, Blanka; Walker, Matthew C.; Kittler, Josef T.

2015-01-01

311

Receptor-Drug Interaction: Europium Employment for Studying the Biochemical Pathway of G-Protein-Coupled Receptor Activation  

PubMed Central

In medicinal chemistry field, the biochemical pathways, involved in 7-transmembrane domains G-protein coupled receptors (GPCRs) activation, are commonly studied to establish the activity of ligands towards GPCRs. The most studied steps are the measurement of activated GTP-? subunit and stimulated intracellular cAMP. At the present, many researchers defined agonist or antagonist activity of potential GPCRs drugs employing [35S]GTP?S or [3H]cAMP as probes. Recently, the corresponding lanthanide labels Eu-GTP and Eu-cAMP as alternative to radiochemicals have been developed because they are highly sensitive, easy to automate, easily synthesized, they display a much longer shelf-life and they can be used in multilabel experiments. In the present review, the receptor-drug interaction by europium employment for studying the biochemical pathway of GPCR activation has been focused. Moreover, comparative studies between lanthanide label probes and the corresponding radiolabeled compounds have been carried out. PMID:18350113

Antonio, Colabufo Nicola; Grazia, Perrone Maria; Marialessandra, Contino; Francesco, Berardi; Roberto, Perrone

2007-01-01

312

cAMP-dependent protein kinase A activity modulates topiramate potentiation of GABA(A) receptors.  

PubMed

Activation of cAMP-dependent protein kinase A (PKA) prevents inhibition of non-NMDA glutamate receptors by the anticonvulsant topiramate. Using two-electrode voltage-clamp techniques, we demonstrate that PKA activity also modulates topiramate potentiation of recombinant GABA(A) receptors expressed in Xenpus laevis oocytes. PKA activators, dibutyryl-cAMP and forskolin, attenuate topiramate potentiation, whereas the PKA inhibitor H-89 increases topiramate potentiation. Thus, endogenous PKA activity and receptor phosphorylation states may contribute to topiramate treatment efficacy. PMID:21665439

Simeone, Timothy A; Wilcox, Karen S; White, H Steve

2011-09-01

313

Multiple Receptor Systems Promote CNS Neural Migration  

Microsoft Academic Search

To identify glial receptor systems in CNS migration, cere- bellar granule neuron migration was assayed on glass fibers coated with polylysine, astroglial membranes (AM fibers), or the extracellular matrix proteins collagen (COLL fibers), fi- bronectin (FN fibers), and laminin (LAM fibers). By video microscopy, granule cells migrated along AM fibers with the cytology, neuron-fiber apposition, and dynamics seen on living

Renata B. Fishman; Mary E. Hatten

1993-01-01

314

Aryl hydrocarbon receptor activity modulates prolactin expression in the pituitary  

PubMed Central

Pituitary tumors account for 15% of intracranial neoplasms, however the extent to which environmental toxicants contribute to the proliferation and hormone expression of pituitary cells is unknown. Aryl-hydrocarbon receptor (AhR) interacting protein (AIP) loss of function mutations cause somatotroph and lactotroph adenomas in humans. AIP sequesters AhR and inhibits its transcriptional function. Because of the link between AIP and pituitary tumors, we hypothesize that exposure to dioxins, potent exogenous ligands for AhR that are persistent in the environment, may predispose to pituitary dysfunction through activation of AhR. In the present study, we examined the effect of AhR activation on proliferation and endogenous pituitary hormone expression in the GH3 rat somato-lactotrope tumor cell line and the effect of loss of AhR action in knockout mice. GH3 cells respond to nM doses of the reversible AhR agonist ?-naphthoflavone with a robust induction of Cyp1a1. Although mRNA levels of the anti-proliferative signaling cytokine TGFbeta1 are suppressed upon ?-naphthoflavone treatment, we did not observe an alteration in cell proliferation. AhR activation with ?-naphthoflavone suppresses Ahr expression and impairs expression of prolactin (PRL), but not growth hormone (GH) mRNA in GH3 cells. In mice, loss of Ahr similarly leads to a reduction in Prl mRNA at P3, while Gh is unaffected. Additionally, there is a significant reduction pituitary hormones Lhb and Fshb in the absence of Ahr. Overall, these results demonstrate that AhR is important for pituitary hormone expression and suggests environmental dioxins can exert endocrine disrupting effects at the pituitary. PMID:22975028

Moran, Tyler B.; Brannick, Katherine E.; Raetzman, Lori T.

2012-01-01

315

Antileishmanial Activity of the Estrogen Receptor Modulator Raloxifene  

PubMed Central

Background The treatment of leishmaniasis relies mostly on parenteral drugs with potentially serious adverse effects. Additionally, parasite resistance in the treatment of leishmaniasis has been demonstrated for the majority of drugs available, making the search for more effective and less toxic drugs and treatment regimens a priority for the control of leishmaniasis. The aims of this study were to evaluate the antileishmanial activity of raloxifene in vitro and in vivo and to investigate its mechanism of action against Leishmania amazonensis. Methodology/Principal Findings Raloxifene was shown to possess antileishmanial activity in vitro against several species with EC50 values ranging from 30.2 to 38.0 µM against promastigotes and from 8.8 to 16.2 µM against intracellular amastigotes. Raloxifene's mechanism of action was investigated through transmission electron microscopy and labeling with propidium iodide, DiSBAC2(3), rhodamine 123 and monodansylcadaverine. Microscopic examinations showed that raloxifene treated parasites displayed autophagosomes and mitochondrial damage while the plasma membrane remained continuous. Nonetheless, plasma membrane potential was rapidly altered upon raloxifene treatment with initial hyperpolarization followed by depolarization. Loss of mitochondrial membrane potential was also verified. Treatment of L. amazonensis – infected BALB/c mice with raloxifene led to significant decrease in lesion size and parasite burden. Conclusions/Significance The results of this work extend the investigation of selective estrogen receptor modulators as potential candidates for leishmaniasis treatment. The antileishmanial activity of raloxifene was demonstrated in vitro and in vivo. Raloxifene produces functional disorder on the plasma membrane of L. amazonensis promastigotes and leads to functional and morphological disruption of mitochondria, which culminate in cell death. PMID:24810565

Reimão, Juliana Q.; Miguel, Danilo C.; Taniwaki, Noemi N.; Trinconi, Cristiana T.; Yokoyama-Yasunaka, Jenicer K. U.; Uliana, Silvia R. B.

2014-01-01

316

Quantitative structure-activity relationships of selective antagonists of glucagon receptor using QuaSAR descriptors.  

PubMed

In the present paper, quantitative structure activity relationship (QSAR) approach was applied to understand the affinity and selectivity of a novel series of triaryl imidazole derivatives towards glucagon receptor. Statistically significant and highly predictive QSARs were derived for glucagon receptor inhibition by triaryl imidazoles using QuaSAR descriptors of molecular operating environment (MOE) employing computer-assisted multiple regression procedure. The generated QSAR models revealed that factors related to hydrophobicity, molecular shape and geometry predominantly influences glucagon receptor binding affinity of the triaryl imidazoles indicating the relevance of shape specific steric interactions between the molecule and the receptor. Further, QSAR models formulated for selective inhibition of glucagon receptor over p38 mitogen activated protein (MAP) kinase of the compounds in the series highlights that the same structural features, which influence the glucagon receptor affinity, also contribute to their selective inhibition. PMID:17077558

Manoj Kumar, Palanivelu; Karthikeyan, Chandrabose; Hari Narayana Moorthy, Narayana Subbiah; Trivedi, Piyush

2006-11-01

317

Quantitative impedimetric NPY-receptor activation monitoring and signal pathway profiling in living cells.  

PubMed

Label-free and non-invasive monitoring of receptor activation and identification of the involved signal pathways in living cells is an ongoing analytic challenge and a great opportunity for biosensoric systems. In this context, we developed an impedance spectroscopy-based system for the activation monitoring of NPY-receptors in living cells. Using an optimized interdigital electrode array for sensitive detection of cellular alterations, we were able for the first time to quantitatively detect the NPY-receptor activation directly without a secondary or enhancer reaction like cAMP-stimulation by forskolin. More strikingly, we could show that the impedimetric based NPY-receptor activation monitoring is not restricted to the Y1-receptor but also possible for the Y2- and Y5-receptor. Furthermore, we could monitor the NPY-receptor activation in different cell lines that natively express NPY-receptors and proof the specificity of the observed impedimetric effect by agonist/antagonist studies in recombinant NPY-receptor expressing cell lines. To clarify the nature of the observed impedimetric effect we performed an equivalent circuit analysis as well as analyzed the role of cell morphology and receptor internalization. Finally, an antagonist based extensive molecular signal pathway analysis revealed small alterations of the actin cytoskeleton as well as the inhibition of at least L-type calcium channels as major reasons for the observed NPY-induced impedance increase. Taken together, our novel impedance spectroscopy based NPY-receptor activation monitoring system offers the opportunity to identify signal pathways as well as for novel versatile agonist/antagonist screening systems for identification of novel therapeutics in the field of obesity and cancer. PMID:25239555

Te Kamp, Verena; Lindner, Ricco; Jahnke, Heinz-Georg; Krinke, Dana; Kostelnik, Katja B; Beck-Sickinger, Annette G; Robitzki, Andrea A

2015-05-15

318

Peroxisomal bifunctional enzyme binds and activates the activation function-1 region of the peroxisome proliferator-activated receptor alpha.  

PubMed Central

The transcriptional activity of peroxisome proliferator-activated receptors (PPARs), and of nuclear hormone receptors in general, is subject to modulation by cofactors. However, most currently known co-activating proteins interact in a ligand-dependent manner with the C-terminal ligand-regulated activation function (AF)-2 domain of nuclear receptors. Since PPARalpha exhibits a strong constitutive transactivating function contained within an N-terminal AF-1 region, it can be speculated that a different set of cofactors might interact with this region of PPARs. An affinity purification approach was used to identify the peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (bifunctional enzyme, BFE) as a protein which strongly and specifically interacted with the N-terminal 92 amino acids of PPARalpha. Protein-protein interaction assays with the cloned BFE confirmed this interaction, which could be mapped to amino acids 307-514 of the BFE and the N-terminal 70 amino acids of PPARalpha. Moreover, transient transfection experiments in hepatoma cells revealed a 2.2-fold increase in the basal and ligand-stimulated transcriptional activity of PPARalpha in the presence of BFE. This stimulatory effect is preferentially observed for the PPARalpha isoform and it is significantly stronger (4.8-fold) in non-hepatic cells, which presumably express lower levels of endogenous BFE. Hence, the BFE represents the first known cofactor capable of activating the AF-1 domain of PPAR without requiring additional regions of this receptor. These data are compatible with a model whereby the PPAR-regulated BFE is able to modulate its own expression through an enhancement of the activity of PPARalpha, representing a novel peroxisomal-nuclear feed-forward regulatory loop. PMID:11139388

Juge-Aubry, C E; Kuenzli, S; Sanchez, J C; Hochstrasser, D; Meier, C A

2001-01-01

319

Probiotics Modulate Intestinal Expression of Nuclear Receptor and Provide Counter-Regulatory Signals to Inflammation-Driven Adipose Tissue Activation  

Microsoft Academic Search

BackgroundAdipocytes from mesenteric white adipose tissue amplify the inflammatory response and participate in inflammation-driven immune dysfunction in Crohn's disease by releasing proinflammatory mediators. Peroxisome proliferator-activated receptors (PPAR)-? and -?, pregnane x receptor (PXR), farnesoid x receptor (FXR) and liver x-receptor (LXR) are ligand-activated nuclear receptor that provide counter-regulatory signals to dysregulated immunity and modulates adipose tissue.AimsTo investigate the expression and

Andrea Mencarelli; Eleonora Distrutti; Barbara Renga; Claudio DAmore; Sabrina Cipriani; Giuseppe Palladino; Annibale Donini; Patrizia Ricci; Stefano Fiorucci

2011-01-01

320

Structural Sweet Spot for A1 Adenosine Receptor Activation by Truncated (N)- Methanocarba Nucleosides: Receptor Docking and Potent Anticonvulsant Activity  

PubMed Central

A1 adenosine receptor (AR) agonists display antiischemic and antiepileptic neuroprotective activity, but peripheral cardiovascular side effects impeded their development. SAR study of N6-cycloalkylmethyl 4?-truncated (N)-methanocarba-adenosines identified 10 (MRS5474, N6-dicyclopropylmethyl, Ki 47.9 nM) as a moderately A1AR-selective full agonist. Two stereochemically defined N6-methynyl group substituents displayed narrow SAR; larger than cyclobutyl greatly reduced AR affinity, and larger or smaller than cyclopropyl reduced A1AR selectivity. Nucleoside docking to A1AR homology model characterized distinct hydrophobic cyclopropyl subpockets, the larger “A” forming contacts with Thr270 (7.35), Tyr271 (7.36), Ile274 (7.39) and carbon chains of glutamates (EL2), and smaller subpocket “B” between TM6 and TM7. 10 suppressed minimal clonic seizures (6 Hz mouse model) without typical rotarod impairment of A1AR agonists. Truncated nucleosides, an appealing preclinical approach, have more drug-like physicochemical properties than other A1AR agonists. Thus, we identified highly restricted regions for substitution around N6 suitable for an A1AR agonist with anticonvulsant activity. PMID:22921089

Tosh, Dilip K.; Paoletta, Silvia; Deflorian, Francesca; Phan, Khai; Moss, Steven M.; Gao, Zhan-Guo; Jiang, Xiaohui; Jacobson, Kenneth A.

2012-01-01

321

A laminin and nerve growth factor-laden three-dimensional scaffold for enhanced neurite extension.  

PubMed

Agarose hydrogel scaffolds were engineered to stimulate and guide neuronal process extension in three dimensions in vitro. The extracellular matrix (ECM) protein laminin (LN) was covalently coupled to agarose hydrogel using the bifunctional cross-linking reagent 1,19- carbonyldiimidazole (CDI). Compared to unmodified agarose gels, LN-modified agarose gels significantly enhanced neurite extension from three-dimensionally (3D) cultured embryonic day 9 (E9) chick dorsal root ganglia (DRGs), and PC 12 cells. After incubation of DRGs or PC 12 cells with YIGSR peptide or integrin beta1 antibody respectively, the neurite outgrowth promoting effects in LN-modified agarose gels were significantly decreased or abolished. These results indicate that DRG/PC 12 cell neurite outgrowth promoting effect of LN-modified agarose gels involves receptors for YIGSR/integrin beta1 subunits respectively. 1,2-bis(10, 12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC)-based lipid microcylinders were loaded with nerve growth factor (NGF), and embedded into agarose hydrogels. The resulting trophic factor gradients stimulated directional neurite extension from DRGs in agarose hydrogels. A PC 12 cell-based bioassay demonstrated that NGF-loaded lipid microcylinders can release physiologically relevant amounts of NGF for at least 7 days in vitro. Agarose hydrogel scaffolds may find application as biosynthetic 3D bridges that promote regeneration across severed nerve gaps. PMID:10477852

Yu, X; Dillon, G P; Bellamkonda, R B

1999-08-01

322

Activity of ixabepilone in oestrogen receptor-negative and oestrogen receptor-progesterone receptor-human epidermal growth factor receptor 2-negative metastatic breast cancer  

Microsoft Academic Search

Oestrogen receptor (ER)-negative breast cancer, including oestrogen receptor-, progesterone receptor- and human epidermal growth factor receptor 2-negative (ER\\/PR\\/HER2-negative) breast cancer, is more aggressive than ER-positive disease. A major limitation in the treatment of ER-negative disease subtypes is the inherent insensitivity to hormonal agents (tamoxifen, aromatase inhibitors) that are widely used in the treatment of breast cancer. Thus, therapeutic options for

Xavier B. Pivot; Rubi K. Li; Eva S. Thomas; Hyun-Cheol Chung; Luis E. Fein; Valorie F. Chan; Jacek Jassem; Fernando Hurtado de Mendoza; Pralay Mukhopadyay; Henri H. Roché

2009-01-01

323

Discovery of novel, potent, and orally active spiro-urea human glucagon receptor antagonists.  

PubMed

A novel class of spiro-ureas has been discovered as potent human glucagon receptor antagonists in both binding and functional assays. Preliminary studies have revealed that compound 15 is an orally active human glucagon receptor antagonist in a transgenic murine pharmacodynamic model at 10 and 30 mpk. Compound 15 is orally bioavailable in several preclinical species and shows selectivity toward cardiac ion channels and other family B receptors, such as hGIP1 and hGLP. PMID:16102966

Shen, Dong-Ming; Zhang, Fengqi; Brady, Edward J; Candelore, Mari Rios; Dallas-Yang, Qing; Ding, Victor D-H; Dragovic, Jasminka; Feeney, William P; Jiang, Guoquiang; McCann, Peggy E; Mock, Steve; Qureshi, Sajjad A; Saperstein, Richard; Shen, Xiaolan; Tamvakopoulos, Constantin; Tong, Xinchun; Tota, Laurie M; Wright, Michael J; Yang, Xiaodong; Zheng, Song; Chapman, Kevin T; Zhang, Bei B; Tata, James R; Parmee, Emma R

2005-10-15

324

Structural Basis of Smad2 Recognition by the Smad Anchor for Receptor Activation  

Microsoft Academic Search

The Smad proteins mediate transforming growth factor-beta (TGFbeta) signaling from the transmembrane serine-threonine receptor kinases to the nucleus. The Smad anchor for receptor activation (SARA) recruits Smad2 to the TGFbeta receptors for phosphorylation. The crystal structure of a Smad2 MH2 domain in complex with the Smad-binding domain (SBD) of SARA has been determined at 2.2 angstrom resolution. SARA SBD, in

Geng Wu; Ye-Guang Chen; Barish Ozdamar; Cassie A. Gyuricza; P. Andrew Chong; Jeffrey L. Wrana; Joan Massagué; Yigong Shi

2000-01-01

325

Functional activity of 5HT 4 receptors in children with congenital heart disease  

Microsoft Academic Search

The effect of 5-methoxytryptamine (5-HT4 receptor agonist) on the inotropic function of atrial myocardium was studied in children aged 2 months to 17 years, operated\\u000a on for congenital heart disease. Functional activity of 5-HT4 receptors was 8.4 times higher in dysfunction of the atrial septum in comparison with other congenital heart diseases. The\\u000a positive inotropic effects of 5-HT4 receptor agonist

A. A. Mustafin; R. R. Nigmatullina; L. M. Mirolyubov

2006-01-01

326

Modulation of native GABA(A) receptor activity by triazolo 1,5-benzodiazepines.  

PubMed

In previous work our group described the synthesis and the activity on rat cerebellum granule cell GABAA receptors of new 1,5-benzodiazepine compounds. Here we are describing the synthesis of new triazolobenzodiazepines (mainly 1,5-benzodiazepine derivatives) and the evaluation of their biological activity in terms of effects on those GABAA receptors. Their effects were compared to those of 1,4-benzodiazepine agonists and some known 1,5-benzodiazepines. The activities were evaluated for the two GABAA receptor populations present in cerebellar granule cells, one mediating phasic inhibition and the other one mediating tonic inhibition. Some of the compounds displayed a profile of agonist at the component mediating phasic inhibition. This agonistic activity was prevented by the benzodiazepine site antagonist flumazenil. Interestingly, the active compounds displayed an agonistic activity at these receptors significantly greater than that of "classical" 1,4-benzodiazepine agonists, such as diazepam, flunitrazepam and alprazolam. PMID:23590909

Nikas, P; Gatta, E; Cupello, A; Di Braccio, M; Grossi, G; Pellistri, F; Robello, M

2013-07-23

327

Ligands Raise the Constraint That Limits Constitutive Activation in G Protein-coupled Opioid Receptors*  

PubMed Central

Using a cell-free bioluminescence resonance energy transfer strategy we compared the levels of spontaneous and ligand-induced receptor-G protein coupling in ? (DOP) and ? (MOP) opioid receptors. In this assay GDP can suppress spontaneous coupling, thus allowing its quantification. The level of constitutive activity was 4–5 times greater at the DOP than at the MOP receptor. A series of opioid analogues with a common peptidomimetic scaffold displayed remarkable inversions of efficacy in the two receptors. Agonists that enhanced coupling above the low intrinsic level of the MOP receptor were inverse agonists in reducing the greater level of constitutive coupling of the DOP receptor. Yet the intrinsic activities of such ligands are identical when scaled over the GDP base line of both receptors. This pattern is in conflict with the predictions of the ternary complex model and the “two state” extensions. According to this theory, the order of spontaneous and ligand-induced coupling cannot be reversed if a shift of the equilibrium between active and inactive forms raises constitutive activation in one receptor type. We propose that constitutive activation results from a lessened intrinsic barrier that restrains spontaneous coupling. Any ligand, regardless of its efficacy, must enhance this constraint to stabilize the ligand-bound complexed form. PMID:23836900

Vezzi, Vanessa; Onaran, H. Ongun; Molinari, Paola; Guerrini, Remo; Balboni, Gianfranco; Calò, Girolamo; Costa, Tommaso

2013-01-01

328

A bacterial tyrosine phosphatase inhibits plant pattern recognition receptor activation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Perception of pathogen-associated molecular patterns (PAMPs) by surface-localised pattern-recognition receptors (PRRs) is a key component of plant innate immunity. Most known plant PRRs are receptor kinases and initiation of PAMP-triggered immunity (PTI) signalling requires phosphorylation of the PR...

329

Inhibition of androgen receptor and ?-catenin activity in prostate cancer.  

PubMed

Androgen receptor (AR) is the major therapeutic target in aggressive prostate cancer. However, targeting AR alone can result in drug resistance and disease recurrence. Therefore, simultaneous targeting of multiple pathways could in principle be an effective approach to treating prostate cancer. Here we provide proof-of-concept that a small-molecule inhibitor of nuclear ?-catenin activity (called C3) can inhibit both the AR and ?-catenin-signaling pathways that are often misregulated in prostate cancer. Treatment with C3 ablated prostate cancer cell growth by disruption of both ?-catenin/T-cell factor and ?-catenin/AR protein interaction, reflecting the fact that T-cell factor and AR have overlapping binding sites on ?-catenin. Given that AR interacts with, and is transcriptionally regulated by ?-catenin, C3 treatment also resulted in decreased occupancy of ?-catenin on the AR promoter and diminished AR and AR/?-catenin target gene expression. Interestingly, C3 treatment resulted in decreased AR binding to target genes accompanied by decreased recruitment of an AR and ?-catenin cofactor, coactivator-associated arginine methyltransferase 1 (CARM1), providing insight into the unrecognized function of ?-catenin in prostate cancer. Importantly, C3 inhibited tumor growth in an in vivo xenograft model and blocked renewal of bicalutamide-resistant sphere-forming cells, indicating the therapeutic potential of this approach. PMID:24019458

Lee, Eugine; Madar, Aviv; David, Gregory; Garabedian, Michael J; Dasgupta, Ramanuj; Logan, Susan K

2013-09-24

330

Inhibition of androgen receptor and ?-catenin activity in prostate cancer  

PubMed Central

Androgen receptor (AR) is the major therapeutic target in aggressive prostate cancer. However, targeting AR alone can result in drug resistance and disease recurrence. Therefore, simultaneous targeting of multiple pathways could in principle be an effective approach to treating prostate cancer. Here we provide proof-of-concept that a small-molecule inhibitor of nuclear ?-catenin activity (called C3) can inhibit both the AR and ?-catenin–signaling pathways that are often misregulated in prostate cancer. Treatment with C3 ablated prostate cancer cell growth by disruption of both ?-catenin/T-cell factor and ?-catenin/AR protein interaction, reflecting the fact that T-cell factor and AR have overlapping binding sites on ?-catenin. Given that AR interacts with, and is transcriptionally regulated by ?-catenin, C3 treatment also resulted in decreased occupancy of ?-catenin on the AR promoter and diminished AR and AR/?-catenin target gene expression. Interestingly, C3 treatment resulted in decreased AR binding to target genes accompanied by decreased recruitment of an AR and ?-catenin cofactor, coactivator-associated arginine methyltransferase 1 (CARM1), providing insight into the unrecognized function of ?-catenin in prostate cancer. Importantly, C3 inhibited tumor growth in an in vivo xenograft model and blocked renewal of bicalutamide-resistant sphere-forming cells, indicating the therapeutic potential of this approach. PMID:24019458

Lee, Eugine; Madar, Aviv; David, Gregory; Garabedian, Michael J.; DasGupta, Ramanuj; Logan, Susan K.

2013-01-01

331

The effect of 17-N substituents on the activity of the opioid ? receptor in nalfurafine derivatives.  

PubMed

We have previously reported the essential structure of the opioid ? receptor agonist nalfurafine hydrochloride (TRK-820) for binding to the ? receptor. In the course of this study, we focused on the effect of the substituent at 17-N in nalfurafine on the binding affinity for the ? receptor. The exchange of the 17-N substituent in nalfurafine from cyclopropylmethyl to fluoro-substituted alkyl groups, which are strong electron withdrawing substituents, almost completely diminished the binding affinities for the ? and ? opioid receptors, but the binding affinity for the ? receptor was still maintained. As a result, nalfurafine derivatives with 17-fluoro-substituted alkyl groups showed higher selectivities for the ? receptor than did nalfurafine itself. With regard to the ? agonistic activities, the conversion of the 17-N substituent in nalfurafine from cyclopropylmethyl to fluoro-substituted alkyl groups led to the gradual decrease of the agonistic activities in the order corresponding to their binding affinities for the ? receptor. In contrast, the derivative with the bulky 17-isobutyl group showed lower affinity and agonistic activity for the ? receptor than the derivatives with the smaller functional groups. This research suggested that both the electronic property and the steric characteristics of the 17-N substituent would have a great influence on the binding property for the ? receptor. PMID:23200250

Nemoto, Toru; Yamamoto, Naoshi; Wada, Naohisa; Harada, Yukimasa; Tomatsu, Miyuki; Ishihara, Marina; Hirayama, Shigeto; Iwai, Takashi; Fujii, Hideaki; Nagase, Hiroshi

2013-01-01

332

Ligand interaction, binding site and G protein activation of the mu opioid receptor  

PubMed Central

With the recently solved crystal structure of the murine mu opioid receptor, the elucidation of the structure function relationships of the human mu receptor becomes feasible. In this study, we analyzed the available structural information along with ligand binding and G protein activation of human mu receptor. Affinity determinations were performed in a HEK293 cell line stably transfected with the human mu opioid receptor for 6 different agonists (morphine, DMAGO, and herkinorn) and antagonists (naloxone, beta-Funaltrexamine, and Norbinaltorphimine) based on the method. G protein activation was investigated in membrane preparations containing human mu receptors treated with the agonist, partial agonist, or antagonist compounds. 4DKL.pdb was utilized for structural analysis and docking calculations for 28 mu receptor ligands. The predicted affinities from docking were compared with those experimentally determined. While all known ligands bind to the receptor through the same binding site that is large enough to accommodate molecules of various sizes, interaction with D147 (D149 in human mu receptor) is essential for binding. No distinguishable interaction pattern in the binding site for agonist, partial agonist, or antagonist to predict pharmacological activities was found. The failure to reconcile the predicted affinities from docking with experimental values indicates that the receptor might undergo significant conformational changes from one state to the other states upon different ligand binding. A simplified model to understand the complicated system is proposed and further study on these multiple conformations using high resolution structural approaches is suggested. PMID:23415745

Cui, Xu; Yeliseev, Alexei; Liu, Renyu

2013-01-01

333

The role of NF-?B in SAA-induced peroxisome proliferator-activated receptor ? activation.  

PubMed

Serum amyloid A (SAA) is an acute phase protein whose expression increases markedly during bacterial infection, tissue damage, and inflammation. The potential beneficial roles of SAA include its involvement in the reverse cholesterol transport and possibly extracellular lipid deposition at sites of inflammation and tissue repair. It is an attractive therapeutic target for the treatment of atherosclerosis. Peroxisome proliferator-activated receptor ? (PPAR?) plays a major regulatory role in adipogenesis, and the expression of genes involved in lipid metabolism. Activation of PPAR? leads to multiple changes in gene expression, some of which are believed to be atherogenic while others are antiatherogenic. In this study, we demonstrated that SAA upregulated COX-2 expression and induced PPAR? activity through NF-?B pathway. The effect of SAA on NF-?B activity is mediated by FPRL-1 and TLR4. PMID:23340376

Li, Hongzhe; Ooi, Shu Qin; Heng, Chew-Kiat

2013-03-01

334

The transcriptional co-activator p\\/CIP binds CBP and mediates nuclear-receptor function  

Microsoft Academic Search

The functionally conserved proteins CBP and p300 act in conjunction with other factors to activate transcription of DNA. A new factor, p\\/CIP, has been discovered that is present in the cell as a complex with CBP and is required for transcriptional activity of nuclear receptors and other CBP\\/p300-dependent transcription factors. The highly related nuclear-receptor co-activator protein NCoA-1 is also specifically

Joseph Torchia; David W. Rose; Juan Inostroza; Yasutomi Kamei; Stefan Westin; Christopher K. Glass; Michael G. Rosenfeld

1997-01-01

335

A CBP Integrator Complex Mediates Transcriptional Activation and AP1 Inhibition by Nuclear Receptors  

Microsoft Academic Search

Nuclear receptors regulate gene expression by direct activation of target genes and inhibition of AP-1. Here we report that, unexpectedly, activation by nuclear receptors requires the actions of CREB-binding protein (CBP) and that inhibition of AP-1 activity is the apparent result of competition for limiting amounts of CBP\\/p300 in cells. Utilizing distinct domains, CBP directly interacts with the ligand-binding domain

Yasutomi Kamei; Lan Xu; Thorsten Heinzel; Joseph Torchia; Riki Kurokawa; Bernd Gloss; Sheng-Cai Lin; Richard A Heyman; David W Rose; Christopher K Glass; Michael G Rosenfeld

1996-01-01

336

Structural Basis for Ligand-Independent Activation of the Orphan Nuclear Receptor LRH1  

Microsoft Academic Search

The orphan nuclear receptors SF-1 and LRH-1 are constitutively active, but it remains uncertain whether their activation is hormone dependent. We report the crystal structure of the LRH-1 ligand binding domain to 2.4 Å resolution and find the receptor to be a monomer that adopts an active conformation with a large but empty hydrophobic pocket. Adding bulky side chains into

Elena P. Sablin; Irina N. Krylova; Robert J. Fletterick; Holly A. Ingraham

2003-01-01

337

Protease-activated receptor-1 in human brain: localization and functional expression in astrocytes  

Microsoft Academic Search

Protease-activated receptor-1 (PAR1) is a G-protein coupled receptor that is proteolytically activated by blood-derived serine proteases. Although PAR1 is best known for its role in coagulation and hemostasis, recent findings demonstrate that PAR1 activation has actions in the central nervous system (CNS) apart from its role in the vasculature. Rodent studies have demonstrated that PAR1 is expressed throughout the brain

Candice E. Junge; C. Justin Lee; Katherine B. Hubbard; Zhoabin Zhang; Jeffrey J. Olson; John R. Hepler; Daniel J. Brat; Stephen F. Traynelisa

2004-01-01

338

Activation of an Olfactory Receptor Inhibits Proliferation of Prostate Cancer Cells*  

PubMed Central

Olfactory receptors (ORs) are expressed not only in the sensory neurons of the olfactory epithelium, where they detect volatile substances, but also in various other tissues where their potential functions are largely unknown. Here, we report the physiological characterization of human OR51E2, also named prostate-specific G-protein-coupled receptor (PSGR) due to its reported up-regulation in prostate cancer. We identified androstenone derivatives as ligands for the recombinant receptor. PSGR can also be activated with the odorant ?-ionone. Activation of the endogenous receptor in prostate cancer cells by the identified ligands evoked an intracellular Ca2+ increase. Exposure to ?-ionone resulted in the activation of members of the MAPK family and inhibition of cell proliferation. Our data give support to the hypothesis that because PSGR signaling could reduce growth of prostate cancer cells, specific receptor ligands might therefore be potential candidates for prostate cancer treatment. PMID:19389702

Neuhaus, Eva M.; Zhang, Weiyi; Gelis, Lian; Deng, Ying; Noldus, Joachim; Hatt, Hanns

2009-01-01

339

Structural Determinants of Opioid and NOP Receptor Activity in Derivatives of Buprenorphine  

PubMed Central

The unique pharmacological profile of buprenorphine has led to its considerable success as an analgesic and as a treatment agent for drug abuse. Activation of nociceptin/orphanin FQ peptide (NOP) receptors has been postulated to account for certain aspects of buprenorphine’s behavioural profile. In order to investigate the role of NOP activation further, a series of buprenorphine analogues has been synthesised with the aim of increasing affinity for the NOP receptor. Binding and functional assay data on these new compounds indicate that the area around C20 in the orvinols is key to NOP receptor activity, with several compounds displaying higher affinity than buprenorphine. One compound, 1b, was found to be a mu opioid receptor partial agonist of comparable efficacy to buprenorphine, but with higher efficacy at NOP receptors. PMID:21866885

Cami-Kobeci, Gerta; Polgar, Willma E.; Khroyan, Taline V; Toll, Lawrence; Husbands, Stephen M.

2011-01-01

340

Protease-activated receptor-1: key player in the sepsis coagulation-inflammation crosstalk  

PubMed Central

Protease-activated receptors (PARs) belong to the family of G protein-coupled receptors. Among the four members, PAR1 plays a major role in orchestrating the interactions between coagulation and inflammation. PAR1 has opposing functions during sepsis, and PAR1 blockade or activation may be alternatively beneficial at early or late stages of different sepsis models. Studying molecular mechanisms of the crosstalk between inflammation and coagulation may lead to the identification of new targets for therapies in sepsis. However, the time-dependent switch of PAR1 from an exacerbating proinflammatory receptor to a protective anti-inflammatory receptor needs to be investigated before clinical trials can be recommended. Finally, as PAR1 seems to play a singular role in Streptococcus pneumoniae-induced sepsis through a crosstalk between PAR1 and platelet-activating factor receptor, the exact role of PAR1 needs to be investigated in other models of sepsis. PMID:23448515

2013-01-01

341

Inhibition of Opioid Receptor Mediated G-Protein Activity After Chronic Administration of Kynurenic Acid and its Derivative without Direct Binding to Opioid Receptors.  

PubMed

There is an increasing number of evidence showing analgesic properties of the kynurenic acid (KYNA), and also some studies demonstrate that kynurenine might interact with the opioid system. Therefore in this study, for the first time we investigated the direct binding affinity of KYNA and its structural analog KYNA-1 towards mu, kappa and delta opioid receptor in competition binding experiments applying opioid receptor specific radioligands. The binding affinity measurements were performed in Chinese hamster ovary cell lines overexpressing the corresponding opioid receptor (mu and kappa opioid receptor were rat, delta opioid receptor were mouse sequence). Additionally we also examined the chronic effect of these compounds on mu, kappa and delta opioid receptor and also nociceptin peptide receptor mediated G-protein activity in [(35)S]GTP?S binding assays performed in mouse cortex and striatum membranes. Our results showed that KYNA and KYNA-1 had no affinity towards any of the three classic opioid receptors. On the other hand the compounds significantly decreased opioid and nociceptin receptor mediated G-protein activity or in some cases enhanced the potency of the activating ligand. Moreover, the alterations were receptor and brain region specific. Accordingly, we conclude that KYNA and KYNA-1 do not interact directly with the opioid receptors, but more likely alter the receptor functions intracellularly. PMID:25478797

Zador, Ferenc; Samavati, Reza; Szlavicz, Eszter; Tuka, Bernadett; Bojnik, Engin; Fulop, Ferenc; Toldi, Jozsef; Vecsei, Laszlo; Borsodi, Anna

2014-01-01

342

Minireview: Lipid Metabolism, Metabolic Diseases, and Peroxisome Proliferator-Activated Receptors  

Microsoft Academic Search

Lipid and carbohydrate homeostasis in higher organisms is under the control of an integrated system that has the capac- ity to rapidly respond to metabolic changes. The peroxisome proliferator-activated receptors (PPARs) are nuclear fatty acid receptors that have been implicated to play an important role in obesity-related metabolic diseases such as hyperlipid- emia, insulin resistance, and coronary artery disease. The

CHIH-HAO LEE; PETER OLSON; RONALD M. EVANS

2003-01-01

343

Peroxisome proliferator-activated receptors: Lipid binding proteins controling gene expression  

Microsoft Academic Search

The peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily. Since their discovery in the beginning of the nineties the three isoforms (PPARa, ß\\/d and ?, encoded by different genes) have been implicated in the regulation of almost every single aspect of lipid metabolism and, consequently, in diseases that involve disturbances in lipid metabolism (obesity, diabetes, atherosclerosis,

Marc van Bilsen; Ger J. van der Vusse; Andries J. Gilde; Martijn Lindhout; Karin A. J. M. van der Lee

2002-01-01

344

CANNABINOID CB1 RECEPTORS ARE EXPRESSED IN THE MOUSE URINARY BLADDER AND THEIR ACTIVATION MODULATES  

E-print Network

CANNABINOID CB1 RECEPTORS ARE EXPRESSED IN THE MOUSE URINARY BLADDER AND THEIR ACTIVATION MODULATES of cannabinoid receptors in the urinary bladder and their potential role in reducing bladder inflam- matory pain. However, the localization of cannabinoid recep- tors in the urinary bladder remains unknown

Price, Theodore

345

G-1-activated membrane estrogen receptors mediate increased contractility of the human myometrium.  

PubMed

Estrogens are key mediators of increased uterine contractility at labor. We sought to determine whether membrane-associated estrogen receptors, such as the recently described seven-transmembrane receptor G protein-coupled receptor 30 (GPR30), mediated some of this effect. Using human myometrium obtained at term cesarean section before or after the onset of labor, we demonstrated the presence of GPR30 mRNA and protein using quantitative RT-PCR and Western blotting. GPR30 receptor was localized to the cell membrane and often colocalized with calveolin-1. Using the specific estrogen membrane receptor agonist G-1 and myometrial explants, we showed that membrane receptor activation led to phosphorylation of MAPK and the actin-modifying small heat shock protein 27. Using myometrial strips incubated with G-1 or vehicle we demonstrated that estrogen membrane receptor activation increased the myometrial contractile response to oxytocin. These data suggest that activation of the plasma membrane estrogen receptor GPR30 likely participates in the physiology of the human myometrium during pregnancy and identifies it as a potential target to modify uterine activity. PMID:21427217

Maiti, K; Paul, J W; Read, M; Chan, E C; Riley, S C; Nahar, P; Smith, R

2011-06-01

346

The role of 5HT 2A receptors in antipsychotic activity  

Microsoft Academic Search

The correlation between the clinical activity of antipsychotic agents and their affinity for the D2 dopamine receptor has been the mainstay of the hypothesis that schizophrenia is due to excessive dopaminergic function. More recently, the unique clinical profile of the atypical antipsychotic clozapine has been proposed to involve actions on additional receptor systems. In particular, the high affinity of clozapine

Christopher J. Schmidt; Stephen M. Sorensen; John H. Kenne; Albert A. Carr; Michael G. Palfreyman

1995-01-01

347

Discovery of a new series of potent prostacyclin receptor agonists with in vivo activity in rat.  

PubMed

The design and synthesis of two closely related series of prostacyclin receptor agonist compounds that showed excellent human IP receptor potency and efficacy is described. Compounds from this series showed in vivo activity after SC dosing in the monocrotaline model of PAH in rat. PMID:25666818

Tran, Thuy-Anh; Shin, Young-Jun; Kramer, Bryan; Choi, Juyi; Zou, Ning; Vallar, Pureza; Martens, Peter; Douglas Boatman, P; Adams, John W; Ramirez, Juan; Shi, Yunqing; Morgan, Michael; Unett, David J; Chang, Steve; Shu, Hsin-Hui; Tung, Shiu-Feng; Semple, Graeme

2015-03-01

348

Different Nuclear Signals Are Activated by the B Cell Receptor during Positive Versus Negative Signaling  

Microsoft Academic Search

It is not known how immunogenic versus tolerogenic cellular responses are signaled by receptors such as the B cell antigen receptor (BCR). Here we compare BCR signaling in naive cells that respond positively to foreign antigen and self-tolerant cells that respond negatively to self-antigen. In naive cells, foreign antigen triggered a large biphasic calcium response and activated nuclear signals through

James I. Healy; Ricardo E. Dolmetsch; Luika A. Timmerman; Jason G. Cyster; Mathew L. Thomas; Gerald R. Crabtree; Richard S Lewis; Christopher C Goodnow

1997-01-01

349

P2X4 receptors control the fate and survival of activated microglia.  

PubMed

Microglia, the resident immune cells of the central nervous system, responds to brain disarrangements by becoming activated to contend with brain damage. Here we show that the expression of P2X4 receptors is upregulated in inflammatory foci and in activated microglia in the spinal cord of rats with experimental autoimmune encephalomyelitis (EAE) as well as in the optic nerve of multiple sclerosis patients. To study the role of P2X4 receptors in microgliosis, we activated microglia with LPS in vitro and in vivo. We observed that P2X4 receptor activity in vitro was increased in LPS-activated microglia as assessed by patch-clamp recordings. In addition, P2X4 receptor blockade significantly reduced microglial membrane ruffling, TNF? secretion and morphological changes, as well as LPS-induced microglial cell death. Accordingly, neuroinflammation provoked by LPS injection in vivo induced a rapid microglial loss in the spinal cord that was totally prevented or potentiated by P2X4 receptor blockade or facilitation, respectively. Within the brain, microglia in the hippocampal dentate gyrus showed particular vulnerability to LPS-induced neuroinflammation. Thus, microglia processes in this region retracted as early as 2 h after injection of LPS and died around 24 h later, two features which were prevented by blocking P2X4 receptors. Together, these data suggest that P2X4 receptors contribute to controlling the fate of activated microglia and its survival. PMID:24254916

Vázquez-Villoldo, Nuria; Domercq, María; Martín, Abraham; Llop, Jordi; Gómez-Vallejo, Vanessa; Matute, Carlos

2014-02-01

350

Is receptor oligomerization causally linked to activation of the EGF receptor kinase?  

NASA Technical Reports Server (NTRS)

Transduction of a signal from an extracellular peptide hormone to produce an intracellular response is often mediated by a cell surface receptor, which is usually a glycoprotein. The secondary intracellular signal(s) generated after hormone binding to the receptor have been intensively studied. The nature of the primary signal generated by ligand binding to the receptor is understood less well in most cases. The particular case of the epidermal growth factor (EGF) receptor is analyzed, and evidence for or against two dissimilar models of primary signal transduction is reviewed. Evidence for the most widely accepted current model is found to be unconvincing. Evidence for the other model is substantial but indirect; a direct test of this model remains to be done.

Rintoul, D. A.; Spooner, B. S. (Principal Investigator)

1992-01-01

351

EPO-independent functional EPO receptor in breast cancer enhances estrogen receptor activity and promotes cell proliferation.  

PubMed

The main function of Erythropoietin (EPO) and its receptor (EPOR) is the stimulation of erythropoiesis. Recombinant human EPO (rhEPO) is therefore used to treat anemia in cancer patients. However, clinical trials have indicated that rhEPO treatment might promote tumor progression and has a negative effect on patient survival. In addition, EPOR expression has been detected in several cancer forms. Using a newly produced anti-EPOR antibody that reliably detects the full-length isoform of the EPOR we show that breast cancer tissue and cells express the EPOR protein. rhEPO stimulation of cultured EPOR expressing breast cancer cells did not result in increased proliferation, overt activation of EPOR (receptor phosphorylation) or a consistent activation of canonical EPOR signaling pathway mediators such as JAK2, STAT3, STAT5, or AKT. However, EPOR knockdown experiments suggested functional EPO receptors in estrogen receptor positive (ER?(+)) breast cancer cells, as reduced EPOR expression resulted in decreased proliferation. This effect on proliferation was not seen in ER? negative cells. EPOR knockdown decreased ER? activity further supports a mechanism by which EPOR affects proliferation via ER?-mediated mechanisms. We show that EPOR protein is expressed in breast cancer cells, where it appears to promote proliferation by an EPO-independent mechanism in ER? expressing breast cancer cells. PMID:24502950

Reinbothe, Susann; Larsson, Anna-Maria; Vaapil, Marica; Wigerup, Caroline; Sun, Jianmin; Jögi, Annika; Neumann, Drorit; Rönnstrand, Lars; Påhlman, Sven

2014-02-28

352

Expression of Protease-Activated Receptor 1 and 2 and Anti-Tubulogenic Activity of Protease-Activated Receptor 1 in Human Endothelial Colony-Forming Cells  

PubMed Central

Endothelial colony-forming cells (ECFCs) are obtained from the culture of human peripheral blood mononuclear cell (hPBMNC) fractions and are characterised by high proliferative and pro-vasculogenic potential, which makes them of great interest for cell therapy. Here, we describe the detection of protease-activated receptor (PAR) 1 and 2 amongst the surface proteins expressed in ECFCs. Both receptors are functionally coupled to extracellular signal-regulated kinase (ERK) 1 and 2, which become activated and phosphorylated in response to selective PAR1- or PAR2-activating peptides. Specific stimulation of PAR1, but not PAR2, significantly inhibits capillary-like tube formation by ECFCs in vitro, suggesting that tubulogenesis is negatively regulated by proteases able to stimulate PAR1 (e.g. thrombin). The activation of ERKs is not involved in the regulation of tubulogenesis in vitro, as suggested by use of the MEK inhibitor PD98059 and by the fact that PAR2 stimulation activates ERKs without affecting capillary tube formation. Both qPCR and immunoblotting showed a significant downregulation of vascular endothelial growth factor 2 (VEGFR2) in response to PAR1 stimulation. Moreover, the addition of VEGF (50–100 ng/ml) but not basic Fibroblast Growth Factor (FGF) (25–100 ng/ml) rescued tube formation by ECFCs treated with PAR1-activating peptide. Therefore, we propose that reduction of VEGF responsiveness resulting from down-regulation of VEGFR2 is underlying the anti-tubulogenic effect of PAR1 activation. Although the role of PAR2 remains elusive, this study sheds new light on the regulation of the vasculogenic activity of ECFCs and suggests a potential link between adult vasculogenesis and the coagulation cascade. PMID:25289673

Fortunato, Tiago M.; Vara, Dina S.; Wheeler-Jones, Caroline P.; Pula, Giordano

2014-01-01

353

Expression of protease-activated receptor 1 and 2 and anti-tubulogenic activity of protease-activated receptor 1 in human endothelial colony-forming cells.  

PubMed

Endothelial colony-forming cells (ECFCs) are obtained from the culture of human peripheral blood mononuclear cell (hPBMNC) fractions and are characterised by high proliferative and pro-vasculogenic potential, which makes them of great interest for cell therapy. Here, we describe the detection of protease-activated receptor (PAR) 1 and 2 amongst the surface proteins expressed in ECFCs. Both receptors are functionally coupled to extracellular signal-regulated kinase (ERK) 1 and 2, which become activated and phosphorylated in response to selective PAR1- or PAR2-activating peptides. Specific stimulation of PAR1, but not PAR2, significantly inhibits capillary-like tube formation by ECFCs in vitro, suggesting that tubulogenesis is negatively regulated by proteases able to stimulate PAR1 (e.g. thrombin). The activation of ERKs is not involved in the regulation of tubulogenesis in vitro, as suggested by use of the MEK inhibitor PD98059 and by the fact that PAR2 stimulation activates ERKs without affecting capillary tube formation. Both qPCR and immunoblotting showed a significant downregulation of vascular endothelial growth factor 2 (VEGFR2) in response to PAR1 stimulation. Moreover, the addition of VEGF (50-100 ng/ml) but not basic Fibroblast Growth Factor (FGF) (25-100 ng/ml) rescued tube formation by ECFCs treated with PAR1-activating peptide. Therefore, we propose that reduction of VEGF responsiveness resulting from down-regulation of VEGFR2 is underlying the anti-tubulogenic effect of PAR1 activation. Although the role of PAR2 remains elusive, this study sheds new light on the regulation of the vasculogenic activity of ECFCs and suggests a potential link between adult vasculogenesis and the coagulation cascade. PMID:25289673

Fortunato, Tiago M; Vara, Dina S; Wheeler-Jones, Caroline P; Pula, Giordano

2014-01-01

354

The angiotensin II type 1 receptor antagonist Losartan binds and activates bradykinin B2 receptor signaling  

Microsoft Academic Search

The angiotensin II type 1 receptor (AT1R) blocker (ARB) Losartan has cardioprotective effects during ischemia–reperfusion injury and inhibits reperfusion arrhythmias –effects that go beyond the benefits of lowering blood pressure. The renin–angiotensin and kallikrein–kinin systems are intricately connected and some of the cardioprotective effects of Losartan are abolished by blocking the bradykinin B2 receptor (B2R) signaling.In this study, we investigated

Marie Mi Bonde; Kristine Boisen Olsen; Niels Erikstrup; Tobias Speerschneider; Christina Lyngsø; Stig Haunsø; Morten Schak Nielsen; Søren P. Sheikh; Jakob Lerche Hansen

2011-01-01

355

Specific insulin/IGF1 hybrid receptor activation assay reveals IGF1 as a more potent ligand than insulin  

PubMed Central

This novel method enables specific measurement of the activation of hybrid receptors formed between the Insulin Receptor (IR) and the Insulin-like Growth Factor 1 Receptor (IGF1R). These hybrid receptors are present in tissues and cell lines expressing both IR and IGF1R. It is therefore challenging to separate the homodimer and hybrid receptor activation properties. This ELISA method enabled fast and quantitative measurements of activated hybrid receptors. The hybrid receptor specificity is obtained from a combination of two specific antibodies for IGF1R and for an IR tyrosine phosphorylation site. The specificity was shown by immunoprecipitations and Western blot analysis. IR exists as two splice variants; consequently, two splice variants of hybrid receptors can be expressed. It is reported here that both splice variants of insulin/IGF1 receptor hybrids are activated by IGF1 with >20-fold higher potency than insulin. PMID:25604425

Slaaby, Rita

2015-01-01

356

Tumor suppressive microRNA-218 inhibits cancer cell migration and invasion through targeting laminin-332 in head and neck squamous cell carcinoma  

PubMed Central

Recent our microRNA (miRNA) expression signature revealed that expression of microRNA-218 (miR-218) was reduced in cancer tissues, suggesting a candidate of tumor suppressor in head and neck squamous cell carcinoma (HNSCC). The aim of this study was to investigate the functional significance of miR-218 and its mediated moleculer pathways in HNSCC. Restoration of miR-218 in cancer cells led to significant inhibition of cell migration and invasion activities in HNSCC cell lines (FaDu and SAS). Genome-wide gene expression analysis of miR-218 transfectants and in silico database analysis showed that focal adhesion pathway was a promising candidate of miR-218 target pathways. The laminins are an important and biologically active part of the basal lamina, the function of that are various such as influencing cell differentiation, migration and adhesion as well as proliferation and cell survival. Interestingly, all components of laminin-332 (LAMA3, LAMB3 and LAMC2) are listed on the candidate genes in focal adhesion pathway. Furthermore, we focused on LAMB3 which has a miR-218 target site and gene expression studies and luciferase reporter assays showed that LAMB3 was directly regulated by miR-218. Silencing study of LAMB3 demonstrated significant inhibition of cell migration and invasion. In clinical specimens with HNSCC, the expression levels of laminin-332 were significantly upregulated in cancer tissues compared to adjacent non-cancerous tissues. Our analysis data showed that tumor suppressive miR-218 contributes to cancer cell migration and invasion through regulating focal adhesion pathway, especially laminin-332. Tumor suppressive miRNA-mediated novel cancer pathways provide new insights into the potential mechanisms of HNSCC oncogenesis. PMID:23159910

Kinoshita, Takashi; Hanazawa, Toyoyuki; Nohata, Nijiro; Kikkawa, Naoko; Enokida, Hideki; Yoshino, Hirofumi; Yamasaki, Takeshi; Hidaka, Hideo; Nakagawa, Masayuki; Okamoto, Yoshitaka; Seki, Naohiko

2012-01-01

357

Transcriptional integration of metabolism by the nuclear sterol-activated receptors LXR and FXR  

PubMed Central

Nuclear receptors are integrators of hormonal and nutritional signals, mediating changes to metabolic pathways within the body. Given that modulation of lipid and glucose metabolism has been linked to diseases including type 2 diabetes, obesity and atherosclerosis, a greater understanding of pathways that regulate metabolism in physiology and disease is crucial. The liver X receptors (LXRs) and the farnesoid X receptors (FXRs) are activated by oxysterols and bile acids, respectively. Mounting evidence indicates that these nuclear receptors have essential roles, not only in the regulation of cholesterol and bile acid metabolism but also in the integration of sterol, fatty acid and glucose metabolism. PMID:22414897

2013-01-01

358

Activity of SR 142801 at peripheral tachykinin receptors  

Microsoft Academic Search

The pharmacological profile of the novel tachykinin NK3 receptor antagonist SR 142801, ((S)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl) piperidin-3-yl) propyl)-4-phenylpiperidin-4-yl)-N-methylacetamide), was studied at tachykinin NK1, NK2 and NK3 receptors, in several in vitro bioassays. In the guinea-pig isolated ileum longitudinal muscle preparation, SR 142801 (10 nM–1 ?M) caused an insurmountable antagonism of tachykinin NK3 receptor-mediated contractions produced by senktide (apparent pKB = 9.27). The blockade

Riccardo Patacchini; Lorand Barthò; Peter Holzer; Carlo Alberto Maggi

1995-01-01

359

CANNABINOID RECEPTOR AGONISTS UPREGULATE AND ENHANCE SEROTONIN 2A (5-HT2A) RECEPTOR ACTIVITY VIA ERK1/2 SIGNALING  

PubMed Central

Recent behavioral studies suggest that non-selective agonists of cannabinoid receptors may regulate serotonin 2A (5-HT2A) receptor neurotransmission. Two cannabinoids receptors are found in brain, CB1 and CB2 receptors, but the molecular mechanism by which cannabinoid receptors would regulate 5-HT2A receptor neurotransmission remains unknown. Interestingly, we have recently found that certain cannabinoid receptor agonists can specifically upregulate 5-HT2A receptors. Here, we present experimental evidence that rats treated with a non-selective cannabinoid receptor agonist (CP 55,940, 50?g/kg, 7 days) showed increases in 5-HT2A receptor protein levels, 5-HT2A receptor mRNA levels, and 5-HT2A receptor-mediated phospholipase C Beta (PLC?) activity in prefrontal cortex (PFCx). Similar effects were found in neuronal cultured cells treated with CP 55,940 but these effects were prevented by selective CB2, but not selective CB1, receptor antagonists. CB2 receptors couple to the extracellular kinase (ERK) signaling pathway by G?i/o class of G-proteins. Noteworthy, GP 1a (selective CB2 receptor agonist) produced a strong upregulation of 5-HT2A receptor mRNA and protein, an effect that was prevented by selective CB2 receptor antagonists and by an ERK1/2 inhibitor, PD 198306. In summary, our results identified a strong cannabinoid-induced upregulation of 5-HT2A receptor signaling in rat PFCx. Our cultured cell studies suggest that selective CB2 receptor agonists upregulate 5-HT2A receptor signaling by activation of the ERK1/2 signaling pathway. Activity of cortical 5-HT2A receptors has been associated with several physiological functions and neuropsychiatric disorders such as stress response, anxiety & depression and schizophrenia. Therefore, these results might provide a molecular mechanism by which activation of cannabinoid receptors might be relevant to the pathophysiology of some cognitive and mood disorders in humans. PMID:23151877

Franklin, Jade M.; Carrasco, Gonzalo A.

2012-01-01

360

Discovery of a series of imidazo[4,5-b]pyridines with dual activity at angiotensin II type 1 receptor and peroxisome proliferator-activated receptor-?.  

PubMed

Mining of an in-house collection of angiotensin II type 1 receptor antagonists to identify compounds with activity at the peroxisome proliferator-activated receptor-? (PPAR?) revealed a new series of imidazo[4,5-b]pyridines 2 possessing activity at these two receptors. Early availability of the crystal structure of the lead compound 2a bound to the ligand binding domain of human PPAR? confirmed the mode of interaction of this scaffold to the nuclear receptor and assisted in the optimization of PPAR? activity. Among the new compounds, (S)-3-(5-(2-(1H-tetrazol-5-yl)phenyl)-2,3-dihydro-1H-inden-1-yl)-2-ethyl-5-isobutyl-7-methyl-3H-imidazo[4,5-b]pyridine (2l) was identified as a potent angiotensin II type I receptor blocker (IC(50) = 1.6 nM) with partial PPAR? agonism (EC(50) = 212 nM, 31% max) and oral bioavailability in rat. The dual pharmacology of 2l was demonstrated in animal models of hypertension (SHR) and insulin resistance (ZDF rat). In the SHR, 2l was highly efficacious in lowering blood pressure, while robust lowering of glucose and triglycerides was observed in the male ZDF rat. PMID:21557540

Casimiro-Garcia, Agustin; Filzen, Gary F; Flynn, Declan; Bigge, Christopher F; Chen, Jing; Davis, Jo Ann; Dudley, Danette A; Edmunds, Jeremy J; Esmaeil, Nadia; Geyer, Andrew; Heemstra, Ronald J; Jalaie, Mehran; Ohren, Jeffrey F; Ostroski, Robert; Ellis, Teresa; Schaum, Robert P; Stoner, Chad

2011-06-23

361

Grb2 controls phosphorylation of FGFR2 by inhibiting receptor kinase and Shp2 phosphatase activity  

PubMed Central

Constitutive receptor tyrosine kinase phosphorylation requires regulation of kinase and phosphatase activity to prevent aberrant signal transduction. A dynamic mechanism is described here in which the adaptor protein, growth factor receptor–bound protein 2 (Grb2), controls fibroblast growth factor receptor 2 (FGFR2) signaling by regulating receptor kinase and SH2 domain–containing protein tyrosine phosphatase 2 (Shp2) phosphatase activity in the absence of extracellular stimulation. FGFR2 cycles between its kinase-active, partially phosphorylated, nonsignaling state and its Shp2-dephosphorylated state. Concurrently, Shp2 cycles between its FGFR2-phosphorylated and dephosphorylated forms. Both reciprocal activities of FGFR2 and Shp2 were inhibited by binding of Grb2 to the receptor. Phosphorylation of Grb2 by FGFR2 abrogated its binding to the receptor, resulting in up-regulation of both FGFR2’s kinase and Shp2’s phosphatase activity. Dephosphorylation of Grb2 by Shp2 rescued the FGFR2–Grb2 complex. This cycling of enzymatic activity results in a homeostatic, signaling-incompetent state. Growth factor binding perturbs this background cycling, promoting increased FGFR2 phosphorylation and kinase activity, Grb2 dissociation, and downstream signaling. Grb2 therefore exerts constitutive control over the mutually dependent activities of FGFR2 and Shp2. PMID:23420874

Lin, Chi-Chuan; Suen, Kin M.; Melo, Fernando A.; Levitt, James A; Suhling, Klaus

2013-01-01

362

A2A Adenosine Receptor Antagonism Enhances Synaptic and Motor Effects of Cocaine via CB1 Cannabinoid Receptor Activation  

PubMed Central

Background Cocaine increases the level of endogenous dopamine (DA) in the striatum by blocking the DA transporter. Endogenous DA modulates glutamatergic inputs to striatal neurons and this modulation influences motor activity. Since D2 DA and A2A-adenosine receptors (A2A-Rs) have antagonistic effects on striatal neurons, drugs targeting adenosine receptors such as caffeine-like compounds, could enhance psychomotor stimulant effects of cocaine. In this study, we analyzed the electrophysiological effects of cocaine and A2A-Rs antagonists in striatal slices and the motor effects produced by this pharmacological modulation in rodents. Principal Findings Concomitant administration of cocaine and A2A-Rs antagonists reduced glutamatergic synaptic transmission in striatal spiny neurons while these drugs failed to produce this effect when given in isolation. This inhibitory effect was dependent on the activation of D2-like receptors and the release of endocannabinoids since it was prevented by L-sulpiride and reduced by a CB1 receptor antagonist. Combined application of cocaine and A2A-R antagonists also reduced the firing frequency of striatal cholinergic interneurons suggesting that changes in cholinergic tone might contribute to this synaptic modulation. Finally, A2A-Rs antagonists, in the presence of a sub-threshold dose of cocaine, enhanced locomotion and, in line with the electrophysiological experiments, this enhanced activity required activation of D2-like and CB1 receptors. Conclusions The present study provides a possible synaptic mechanism explaining how caffeine-like compounds could enhance psychomotor stimulant effects of cocaine. PMID:22715379

Tozzi, Alessandro; de Iure, Antonio; Marsili, Valentina; Romano, Rosaria; Tantucci, Michela; Di Filippo, Massimiliano; Costa, Cinzia; Napolitano, Francesco; Mercuri, Nicola Biagio; Borsini, Franco; Giampà, Carmen; Fusco, Francesca Romana; Picconi, Barbara; Usiello, Alessandro; Calabresi, Paolo

2012-01-01

363

Activation of liver X receptor decreases BACE1 expression and activity by reducing membrane cholesterol levels.  

PubMed

The synthetic Liver X receptor (LXR) activator T0901317 has been reported to exert neuroprotective effect in Alzheimer's disease, but the relationship between LXR activation and beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1) remains uncertain. This study investigated the effect of T0901317 on membrane cholesterol levels, BACE1 expression and activity. We found that T0901317 decreased membrane cholesterol levels, reduced BACE1 expression and activity as well as ?-secretase cleaved C-terminal fragment (?-CTF) levels in vivo and in vitro. Meanwhile, the expression of ATP-binding membrane cassette transport protein A1 (ABCA1) enhanced. Additionally, inhibition of ABCA1 abrogated the effects of T0901317 on membrane cholesterol levels and ?-secretase activity. Moreover, addition of LXR antagonist reversed the effect of T0901317 on ABCA1 mRNA expression, membrane cholesterol levels and ?-secretase activity. Our results suggest that activation of LXR may decrease BACE1 expression and activity through a pathway associated with ABCA1-mediated reduction in membrane cholesterol levels. PMID:21630010

Cui, Weigang; Sun, Yan; Wang, Zhongping; Xu, Chongchong; Xu, Li; Wang, Fei; Chen, Zulin; Peng, Yuwen; Li, Ruixi

2011-10-01

364

Alpinetin activates the ? receptor instead of the ? and ? receptor pathways to protect against rat myocardial cell apoptosis  

PubMed Central

Alpinetin is a natural flavonoid that protects cells against fatal injury in ischemia-reperfusion. ? receptor activation protects myocardial cells from trauma; however, the mechanism is unknown. The aim of this study was to explore the function of alpinetin in ? receptor-mediated myocardial apoptosis. The myocardial cells of newly born rats were cultivated and myocardial apoptosis was induced by serum deprivation. The MTT method was used to evaluate cell viability and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining was used to analyze apoptosis. The expression levels of opioid receptor mRNA and protein were tested using reverse transcription-polymerase reaction (RT-PCR) and western blot assays. In addition, an opioid receptor antagonist, as well as protein kinase C (PKC) and extracellular signal-regulated kinase (ERK) inhibitors, were used to determine the inferred signaling pathway. The results showed that that alpinetin reduced the myocardial apoptosis induced by serum deprivation in a concentration-dependent manner. However, the protection conferred to the myocardial cells by alpinetin was blocked by the ? opioid receptor antagonist naltrindole, as well as by PKC and ERK inhibitors (GF109203X and U0126, respectively). In addition, it was shown that alpinetin was able to maintain the stability of the mitochondrial membrane potential, lower the level of intracytoplasmic cytochrome c and reduce Bax displacement from the cytoplasm to the mitochondria. It was concluded that alpinetin was able to activate ? receptors to induce the endogenous protection of myocardial cells via the PKC/ERK signaling pathway. PMID:24348774

SUO, CHUANTAO; SUN, LIBO; YANG, SHUANG

2014-01-01

365

Alpinetin activates the ? receptor instead of the ? and ? receptor pathways to protect against rat myocardial cell apoptosis.  

PubMed

Alpinetin is a natural flavonoid that protects cells against fatal injury in ischemia-reperfusion. ? receptor activation protects myocardial cells from trauma; however, the mechanism is unknown. The aim of this study was to explore the function of alpinetin in ? receptor-mediated myocardial apoptosis. The myocardial cells of newly born rats were cultivated and myocardial apoptosis was induced by serum deprivation. The MTT method was used to evaluate cell viability and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining was used to analyze apoptosis. The expression levels of opioid receptor mRNA and protein were tested using reverse transcription-polymerase reaction (RT-PCR) and western blot assays. In addition, an opioid receptor antagonist, as well as protein kinase C (PKC) and extracellular signal-regulated kinase (ERK) inhibitors, were used to determine the inferred signaling pathway. The results showed that that alpinetin reduced the myocardial apoptosis induced by serum deprivation in a concentration-dependent manner. However, the protection conferred to the myocardial cells by alpinetin was blocked by the ? opioid receptor antagonist naltrindole, as well as by PKC and ERK inhibitors (GF109203X and U0126, respectively). In addition, it was shown that alpinetin was able to maintain the stability of the mitochondrial membrane potential, lower the level of intracytoplasmic cytochrome c and reduce Bax displacement from the cytoplasm to the mitochondria. It was concluded that alpinetin was able to activate ? receptors to induce the endogenous protection of myocardial cells via the PKC/ERK signaling pathway. PMID:24348774

Suo, Chuantao; Sun, Libo; Yang, Shuang

2014-01-01

366

A Hydrophobic Area of the GABA ?1 Receptor Containing Phenylalanine 124 Influences Both Receptor Activation and Deactivation.  

PubMed

Experimental evidence suggests that GABA ?1 receptors are potential therapeutic targets for the treatment of a range of neurological conditions, including anxiety and sleep disorders. Homology modelling of the GABA ?1 extracellular N-terminal domain has revealed a novel hydrophobic area that extends beyond, but not including the GABA-binding site. Phenylalanine 124 (F124) is predicted to be involved in maintaining the structural integrity of the orthosteric-binding site. We have assessed the activity of a series of GABA ?1 receptors that incorporate a mutation at F124. Wild-type and mutant human GABA ?1 subunits were expressed in Xenopus laevis oocytes and AD293 cells, and the pharmacology and kinetic properties of the receptors were measured using electrophysiological analysis. Mutation of F124 had minimal effect on receptor pharmacology. However, the rate of deactivation was significantly increased compared to wild type. This study provides further information about the role of residues within a novel hydrophobic area of the GABA ?1 receptor. This knowledge can help future studies into the design of potent and subtype-selective ligands with therapeutic value. PMID:24816654

Carland, J E; Yamamoto, I; Hanrahan, J R; Abdel-Halim, H; Lewis, T M; Absalom, N; Chebib, M

2015-02-01

367

Cinnabarinic acid, an endogenous metabolite of the kynurenine pathway, activates type 4 metabotropic glutamate receptors.  

PubMed

Cinnabarinic acid is an endogenous metabolite of the kynurenine pathway that meets the structural requirements to interact with glutamate receptors. We found that cinnabarinic acid acts as a partial agonist of type 4 metabotropic glutamate (mGlu4) receptors, with no activity at other mGlu receptor subtypes. We also tested the activity of cinnabarinic acid on native mGlu4 receptors by examining 1) the inhibition of cAMP formation in cultured cerebellar granule cells; 2) protection against excitotoxic neuronal death in mixed cultures of cortical cells; and 3) protection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice after local infusion into the external globus pallidus. In all these models, cinnabarinic acid behaved similarly to conventional mGlu4 receptor agonists, and, at least in cultured neurons, the action of low concentrations of cinnabarinic acid was largely attenuated by genetic deletion of mGlu4 receptors. However, high concentrations of cinnabarinic acid were still active in the absence of mGlu4 receptors, suggesting that the compound may have off-target effects. Mutagenesis and molecular modeling experiments showed that cinnabarinic acid acts as an orthosteric agonist interacting with residues of the glutamate binding pocket of mGlu4. Accordingly, cinnabarinic acid did not activate truncated mGlu4 receptors lacking the N-terminal Venus-flytrap domain, as opposed to the mGlu4 receptor enhancer, N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC). Finally, we could detect endogenous cinnabarinic acid in brain tissue and peripheral organs by high-performance liquid chromatography-tandem mass spectrometry analysis. Levels increased substantially during inflammation induced by lipopolysaccharide. We conclude that cinnabarinic acid is a novel endogenous orthosteric agonist of mGlu4 receptors endowed with neuroprotective activity. PMID:22311707

Fazio, F; Lionetto, L; Molinaro, G; Bertrand, H O; Acher, F; Ngomba, R T; Notartomaso, S; Curini, M; Rosati, O; Scarselli, P; Di Marco, R; Battaglia, G; Bruno, V; Simmaco, M; Pin, J P; Nicoletti, F; Goudet, C

2012-05-01

368

The expanding phenotype of laminin ?2 chain (merosin) abnormalities: case series and review  

PubMed Central

Initial reports of patients with laminin ?2 chain (merosin) deficiency had a relatively homogeneous phenotype, with classical congenital muscular dystrophy (CMD) characterised by severe muscle weakness, inability to achieve independent ambulation, markedly raised creatine kinase, and characteristic white matter hypodensity on cerebral magnetic resonance imaging. We report a series of five patients with laminin ?2 deficiency, only one of whom has this severe classical CMD phenotype, and review published reports to characterise the expanded phenotype of laminin ?2 deficiency, as illustrated by this case series. While classical congenital muscular dystrophy with white matter abnormality is the commonest phenotype associated with laminin ?2 deficiency, 12% of reported cases have later onset, slowly progressive weakness more accurately designated limb-girdle muscular dystrophy. In addition, the following clinical features are reported with increased frequency: mental retardation (~6%), seizures (~8%), subclinical cardiac involvement (3-35%), and neuronal migration defects (4%). At least 25% of patients achieve independent ambulation. Notably, three patients with laminin ?2 deficiency were asymptomatic, 10 patients had normal MRI (four with LAMA2 mutations reported), and between 10-20% of cases had maximum recorded creatine kinase of less than 1000 U/l. LAMA2 mutations have been identified in 25% of cases. Sixty eight percent of these have the classical congenital muscular dystrophy, but this figure is likely to be affected by ascertainment bias. We conclude that all dystrophic muscle biopsies, regardless of clinical phenotype, should be studied with antibodies to laminin ?2. In addition, the use of multiple antibodies to different regions of laminin ?2 may increase the diagnostic yield and provide some correlation with severity of clinical phenotype.???Keywords: congenital muscular dystrophy; laminin ?2 chain; merosin; skeletal muscle PMID:11584042

Jones, K.; Morgan, G.; Johnston, H.; Tobias, V.; Ouvrier, R.; Wilkinson, I.; North, K.

2001-01-01

369

Cell surface galactosyltransferase mediates the initiation of neurite outgrowth from PC12 cells on laminin  

Microsoft Academic Search

Neurite outgrowth from PC12 pheochromo- cytoma cells, as well as from peripheral and central nervous system neurons in vitro, is mediated by the extracellular matrix molecule, laminin. We have re- cently shown that mesenchymal cell spreading and migration on laminin is mediated, in part, by the cell surface enzyme,\\/~1,4 galactosyltransferase (GalTase). GalTase is localized on lamellipodia of migrating cells where

Paul C. Begovac; Barry D. Shur

1990-01-01

370

Epidermal Growth Factor Receptor Transactivation Is Required for Mitogen-Activated Protein Kinase Activation by Muscarinic Acetylcholine Receptors in HaCaT Keratinocytes  

PubMed Central

Non-neuronal acetylcholine plays a substantial role in the human skin by influencing adhesion, migration, proliferation and differentiation of keratinocytes. These processes are regulated by the Mitogen-Activated Protein (MAP) kinase cascade. Here we show that in HaCaT keratinocytes all five muscarinic receptor subtypes are expressed, but M1 and M3 are the subtypes involved in mitogenic signaling. Stimulation with the cholinergic agonist carbachol leads to activation of the MAP kinase extracellular signal regulated kinase, together with the protein kinase Akt. The activation is fully dependent on the transactivation of the epidermal growth factor receptor (EGFR), which even appears to be the sole pathway for the muscarinic receptors to facilitate MAP kinase activation in HaCaT cells. The transactivation pathway involves a triple-membrane-passing process, based on activation of matrix metalloproteases, and extracellular ligand release; whereas phosphatidylinositol 3-kinase, Src family kinases or protein kinase C do not appear to be involved in MAP kinase activation. Furthermore, phosphorylation, ubiquitination and endocytosis of the EGF receptor after cholinergic transactivation are different from that induced by a direct stimulation with EGF, suggesting that ligands other than EGF itself mediate the cholinergic transactivation. PMID:25421240

Ockenga, Wymke; Kühne, Sina; Bocksberger, Simone; Banning, Antje; Tikkanen, Ritva

2014-01-01

371

Epidermal growth factor receptor transactivation is required for mitogen-activated protein kinase activation by muscarinic acetylcholine receptors in HaCaT keratinocytes.  

PubMed

Non-neuronal acetylcholine plays a substantial role in the human skin by influencing adhesion, migration, proliferation and differentiation of keratinocytes. These processes are regulated by the Mitogen-Activated Protein (MAP) kinase cascade. Here we show that in HaCaT keratinocytes all five muscarinic receptor subtypes are expressed, but M1 and M3 are the subtypes involved in mitogenic signaling. Stimulation with the cholinergic agonist carbachol leads to activation of the MAP kinase extracellular signal regulated kinase, together with the protein kinase Akt. The activation is fully dependent on the transactivation of the epidermal growth factor receptor (EGFR), which even appears to be the sole pathway for the muscarinic receptors to facilitate MAP kinase activation in HaCaT cells. The transactivation pathway involves a triple-membrane-passing process, based on activation of matrix metalloproteases, and extracellular ligand release; whereas phosphatidylinositol 3-kinase, Src family kinases or protein kinase C do not appear to be involved in MAP kinase activation. Furthermore, phosphorylation, ubiquitination and endocytosis of the EGF receptor after cholinergic transactivation are different from that induced by a direct stimulation with EGF, suggesting that ligands other than EGF itself mediate the cholinergic transactivation. PMID:25421240

Ockenga, Wymke; Kühne, Sina; Bocksberger, Simone; Banning, Antje; Tikkanen, Ritva

2014-01-01

372

Stimulation of Wound Revascularization by Adenosine Receptor Activation  

Microsoft Academic Search

\\u000a Adenosine is an endogenous mediator implicated in wound healing. The exact mechanisms and receptors involved are still under\\u000a evaluation. We have observed that topical application of a selective adenosine A2A receptor agonist promotes wound healing in experimental animals, both healthy and with impaired healing. Histological analysis\\u000a revealed that adenosine promoted granulation tissue formation, with increased cellularity, matrix deposition, and vessel

M. Carmen Montesinos; María D. Valls

373

Proteinase-activated Receptor-2 Transactivation of Epidermal Growth Factor Receptor and Transforming Growth Factor-? Receptor Signaling Pathways Contributes to Renal Fibrosis*  

PubMed Central

Chronic kidney diseases cause significant morbidity and mortality in the population. During renal injury, kidney-localized proteinases can signal by cleaving and activating proteinase-activated receptor-2 (PAR2), a G-protein-coupled receptor involved in inflammation and fibrosis that is highly expressed in renal tubular cells. Following unilateral ureteric obstruction, PAR2-deficient mice displayed reduced renal tubular injury, fibrosis, collagen synthesis, connective tissue growth factor (CTGF), and ?-smooth muscle actin gene expression at 7 days, compared with wild-type controls. In human proximal tubular epithelial cells in vitro, PAR2 stimulation with PAR2-activating peptide (PAR2-AP) alone significantly up-regulated the expression of CTGF, a potent profibrotic cytokine. The induction of CTGF by PAR2-AP was synergistically increased when combined with transforming growth factor-? (TGF-?). Consistent with these findings, treating human proximal tubular epithelial cells with PAR2-AP induced Smad2/3 phosphorylation in the canonical TGF-? signaling pathway. The Smad2 phosphorylation and CTGF induction required signaling via both the TGF?-receptor and EGF receptor suggesting that PAR2 utilizes transactivation mechanisms to initiate fibrogenic signaling. Taken together, our data support the hypothesis that PAR2 synergizes with the TGF? signaling pathway to contribute to renal injury and fibrosis. PMID:24253040

Chung, Hyunjae; Ramachandran, Rithwik; Hollenberg, Morley D.; Muruve, Daniel A.

2013-01-01

374

Computational Modelling of the Receptor Tyrosine Kinase Activated MAPK Pathway Authors Names  

E-print Network

enzymes, receptors, transporters, docking and scaffolding proteins are regulated. The general layout. Gilbert * , and Walter Kolch ,§ Establishments * Bioinformatics Research Centre, Department of Computing Activated Protein Kinase (MAPK) pathway is one of the most important and intensively studied signalling

Calder, Muffy

375

A natural propenoic acid derivative activates peroxisome proliferator-activated receptor-?/? (PPAR?/?)  

PubMed Central

Aims: Previous studies showed that natural prenyloxyphenylpropanoid derivatives have potent biological properties in vivo. Given the structural similarities between these compounds and known peroxisome proliferator-activated receptor (PPAR) agonists, the present study examined the hypothesis that propenoic acid derivatives activate PPARs. Main methods: Chimeric reporter assays were performed to identify propenoic acid derivates that could activate PPARs. Quantitative polymerase chain reaction (qPCR) analysis of wild-type and Ppar?/?-null mouse primary keratinocytes was performed to determine if a test compound could specifically activate PPAR?/?. A human epithelial carcinoma cell line and primary mouse keratinocytes were used to determine the effect of the compound on cell proliferation. Key findings: Three of the propenoic acid derivatives activated PPARs, with the greatest efficacy being observed with prenyloxycinnamic acid derivatives 4?-geranyloxyferulic acid (compound 1) for PPAR?/?. Compound 1 increased expression of a known PPAR?/? target gene through a mechanism that requires PPAR?/?. Inhibition of cell proliferation by compound 1 was found in a human epithelial carcinoma cell line. Significance: Results from these studies demonstrate that compound 1 can activate PPAR?/? and inhibit cell proliferation of a human skin cancer cell line, suggesting that the biological effects of 4?-geranyloxyferulic acid may be mediated in part by activating this PPAR isoform. PMID:20153754

Genovese, Salvatore; Foreman, Jennifer E.; Borland, Michael G.; Epifano, Francesco; Gonzalez, Frank J.; Curini, Massimo; Peters, Jeffrey M.

2010-01-01

376

Activation of Peroxisome Proliferator-Activated Receptor-? During Hepatic Ischemia is Age-Dependent  

PubMed Central

Hepatic ischemia/reperfusion (I/R) injury is a complication of liver surgery, transplantation and shock and is known to be age-dependent. Our laboratory has recently shown that peroxisome proliferator-activated receptor-gamma (PPAR?) is downregulated during hepatic ischemia and that this exacerbates injury. Here we examined whether activation of PPAR? during ischemia was age-dependent. Male mice of different ages (young: 4–5 weeks; adult: 10–12 weeks; old: 10–12 months) were subjected to up to 90 minutes of hepatic ischemia. PPAR? activation occurred throughout ischemia in young mice, whereas activation in adult and old mice was lost after 30 minutes. No significant differences were noted in PPAR? ligand expression amongst the age groups. However, in young mice we observed a predominance of PPAR?1 in the nucleus, whereas in old mice this isoform remained largely in the cytoplasm. Finally, the degree of PPAR? activation was associated with autophagy in the liver, a mechanism of self-preservation. Conclusion PPAR? activation is prolonged in young mice as compared to older mice. This appears to be mediated by a selective retention of PPAR?1 in the nucleus and is associated with increased autophagy. The data suggest that PPAR? activation is an important component of the age-dependent response to hepatic I/R injury. PMID:18498870

Shin, Thomas; Kuboki, Satoshi; Huber, Nadine; Eismann, Thorsten; Galloway, Elizabeth; Schuster, Rebecca; Blanchard, John; Pritts, Timothy A.; Lentsch, Alex B.

2009-01-01

377

The Transmembrane Mutation G380R in Fibroblast Growth Factor Receptor 3 Uncouples Ligand-Mediated Receptor Activation from Down-Regulation  

Microsoft Academic Search

A point mutation, Gly380Arg, in the transmembrane domain of fibroblast growth factor receptor 3 (FGFR3) leads to achondroplasia, the most common form of genetic dwarfism in humans. This substitution was suggested to enhance mutant receptor dimerization, leading to constitutive, ligand-independent activation. We found that dimerization and activation of the G380R mutant receptor are predominantly ligand dependent. However, using both transient

E. Monsonego-Ornan; R. Adar; T. Feferman; O. Segev; A. Yayon

2000-01-01

378

Synergistic effect of laminin and mesenchymal stem cells on tracheal mucosal regeneration.  

PubMed

Although several studies have been successfully undertaken of tracheal reconstruction in terms of the maintaining the framework of the graft, most cases of reconstruction failure have resulted from delayed mucosal regeneration. The purposes of this study were to evaluate whether laminin-coated asymmetrically porous membrane (APM) scaffold enhances mucosal regeneration, to compare the mucosalization capability with mesenchymal stem cell (MSC) seeded APM, and to determine whether laminin coating and MSC seeding has a synergistic effect on mucosal regeneration. We reconstructed the full-thickness anterior tracheal defect of 36 New Zealand White rabbits with the APM scaffold. MSCs were isolated from the rabbit's inguinal fat. The animals were divided into 4 groups by the presence of laminin coating on APM and application of MSC [Group I, -/- (laminin/MSC); Group II, -/+; Group III, +/-; Group IV, +/+]. Endoscopy and histologic evaluation were performed and the results were compared among the groups. The results showed that ciliated columnar epithelium was regenerated earlier in groups II and III than in group I. Furthermore, the application of laminin and MSC had synergistic effects on tracheal epithelial regeneration. These results demonstrate that tracheal reconstruction by laminin-coated APM seeded with MSCs is most effective in enhancing tracheal mucosalization, and appears to be promising strategy in the regenerative treatment of tracheal defects. PMID:25617133

Lee, Doh Young; Lee, Jin Ho; Ahn, Hee-Jin; Oh, Se Heang; Kim, Tae Ho; Kim, Hee-Bok; Park, Seok-Won; Kwon, Seong Keun

2015-03-01

379

Neuronal migration in cerebellar microcultures is inhibited by antibodies against a neurite outgrowth domain of laminin.  

PubMed

The functional role of laminin in neuronal migration was investigated by using polyclonal antibodies or their divalent (Fab')2 fragments to a neurite outgrowth promoting domain of the B2 chain of laminin in a cerebellar microculture system widely recognized as a model for neuronal migration. We show here that these antibodies or their (Fab')2 fragments totally inhibit migration of the mouse cerebellar granule cells along the glial and other neuronal cell processes. Antibodies to native laminin or other control antibodies have no inhibitory effect. Immunocytochemical analysis of the cerebellar microcultures indicates that the functional role of these antibodies may relate to the fact that the punctate deposits of laminin and its neurite outgrowth promoting domain accumulate in between the migrating neurons and the glial cells. These data provide the first direct evidence for the functional role of laminin and its neurite outgrowth domain in neuronal migration in the mammals. They further suggest that a neuronal cell surface contact with the extracellular deposits of a neurite outgrowth domain of the B2 chain of laminin may mediate neuronal-glial interactions. PMID:1453481

Liesi, P; Seppälä, I; Trenkner, E

1992-09-01

380

The cellular origin of laminin determines its role in blood pressure regulation.  

PubMed

Laminin of different cellular sources has distinct functions. In addition to vascular smooth muscle cells (SMCs), aorta also contains a small population of