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1

Laminin receptor activation inhibits endothelial tissue factor expression.  

PubMed

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 to TNF-alpha (TNF-alpha) than those grown on fibronectin (n=6; p<0.001). EGCG (1-30 microM) inhibited TNF-alpha and histamine induced endothelial TF expression and activity in a concentration dependent manner resulting in 87% reduction of TF expression (n=5; p<0.001); in contrast, expression of tissue factor pathway inhibitor was not affected (n=4; p=NS). In vivo administration of EGCG (30 mg/kg/day) inhibited TF activity in carotid arteries of C57BL6 mice. Real-time PCR and promoter studies revealed that EGCG decreased TF expression at the transcriptional level and impaired activation of the mitogen activated protein (MAP) kinase JNK 1/2, but not ERK or p38. Similarly, the JNK 1/2 inhibitor SP600125 (1 microM) impaired TF promoter activity (n=4; p<0.001) and protein expression (n=4; p<0.001). 67LR blocking antibodies blunted the inhibitory effect of EGCG on both TF protein expression and JNK activation. In contrast, vascular cell adhesion molecule 1 (VCAM-1) was not affected by laminin nor EGCG, and its expression was not regulated by JNK. EGCG did not affect TNF-alpha stimulated NFkB activation. Laminin receptor activation inhibits endothelial TF expression by impairing JNK phosphorylation. Thus, 67LR may be a potential target for the development of novel anti-thrombotic therapies. PMID:19712679

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

2010-06-01

2

Laminin receptors for neurite formation.  

PubMed Central

Laminin, a basement membrane glycoprotein promotes both cell attachment and neurite outgrowth. Separate domains on laminin elicit these responses, suggesting that distinct receptors occur on the surface of cells. NG108-15 neuroblastoma-glioma cells rapidly extend long processes in the presence of laminin. We report here that 125I-labeled laminin specifically binds to these cells and to three membrane proteins of 67, 110, and 180 kDa. These proteins were isolated by affinity chromatography on laminin-Sepharose. The 67-kDa protein reacted with antibody to the previously characterized receptor for cell attachment to laminin. Antibodies to the 110-kDa and 180-kDa bands demonstrated that the 110-kDa protein was found in a variety of epithelial cell lines and in brain, whereas the 180-kDa protein was neural specific. Antibodies prepared against the 110-kDa and 180-kDa proteins inhibited neurite outgrowth induced by the neurite-promoting domain of laminin, whereas antibodies to the 67-kDa laminin receptor had no effect on neurite outgrowth. We conclude that neuronal cells have multiple cell-surface laminin receptors and that the 110-kDa and 180-kDa proteins are involved in neurite formation. Images PMID:2963341

Kleinman, H K; Ogle, R C; Cannon, F B; Little, C D; Sweeney, T M; Luckenbill-Edds, L

1988-01-01

3

Adhesion of platelets to laminin in the absence of activation  

PubMed Central

The binding of platelets to components in the subendothelial matrix is an initial event in hemostasis and thrombosis. The glycoprotein components of the matrix are considered important in this interaction. Of these, collagen binds and activates platelets and induces their aggregation. In this study we demonstrate that substrate-bound laminin causes time- and concentration-dependent adherence of human platelets to the substrate. The binding of platelets to laminin was found to be similar in some respects, but different in others, to their binding to surfaces coated with fibronectin or collagen. The binding of platelets to laminin or fibronectin was not associated with their activation under conditions in which type I collagen activates the platelets as measured by [14C]serotonin secretion. Platelets bound to laminin and fibronectin differed in their appearance; they remained rounded on laminin whereas they flattened completely on fibronectin. Binding of platelets to fibronectin, but not laminin, is inhibited by a recently described peptide (Pierschbacher, M., and E. Ruoslahti, 1984, Nature (Lond.), 309:30-33) containing the cell-attachment tetrapeptide sequence of fibronectin, which suggests that separate receptors exist for laminin and fibronectin. These studies establish laminin as a platelet-binding protein and suggest that laminin can contribute to the adhesiveness of exposed tissue matrices to platelets. Since laminin and fibronectin do not activate platelets, whereas collagen does, and laminin differs from fibronectin in that it does not induce spreading of the attached platelets, all three proteins appear to confer different signals to the platelets. Some of these may be related to platelet functions other than those necessary for the formation of a hemostatic plug. PMID:6501416

1984-01-01

4

Schwann cell myelination requires integration of laminin activities.  

PubMed

Laminins promote early stages of peripheral nerve myelination by assembling basement membranes (BMs) on Schwann cell surfaces, leading to activation of ?1 integrins and other receptors. The BM composition, structural bonds and ligands needed to mediate this process, however, are not well understood. Mice hypomorphic for laminin ?1-subunit expression that assembled endoneurial BMs with reduced component density exhibited an axonal sorting defect with amyelination but normal Schwann cell proliferation, the latter unlike the null. To identify the basis for this, and to dissect participating laminin interactions, LAMC1 gene-inactivated dorsal root ganglia were treated with recombinant laminin-211 and -111 lacking different architecture-forming and receptor-binding activities, to induce myelination. Myelin-wrapping of axons by Schwann cells was found to require higher laminin concentrations than either proliferation or axonal ensheathment. Laminins that were unable to polymerize through deletions that removed critical N-terminal (LN) domains, or that lacked cell-adhesive globular (LG) domains, caused reduced BMs and almost no myelination. Laminins engineered to bind weakly to ?6?1 and/or ?7?1 integrins through their LG domains, even though they could effectively assemble BMs, decreased myelination. Proliferation depended upon both integrin binding to LG domains and polymerization. Collectively these findings reveal that laminins integrate scaffold-forming and cell-adhesion activities to assemble an endoneurial BM, with myelination and proliferation requiring additional ?6?1/?7?1-laminin LG domain interactions, and that a high BM ligand/structural density is needed for efficient myelination. PMID:22767514

McKee, Karen K; Yang, Dong-Hua; Patel, Rajesh; Chen, Zu-Lin; Strickland, Sidney; Takagi, Junichi; Sekiguchi, Kiyotoshi; Yurchenco, Peter D

2012-10-01

5

Comprehensive proteomic analysis of nonintegrin laminin receptor interacting proteins.  

PubMed

Human nonintegrin laminin receptor is a multifunctional protein acting as an integral component of the ribosome and a cell surface receptor for laminin-1. The laminin receptor is overexpressed in several human cancers and is also the cell surface receptor for several viruses and pathogenic prion proteins, making it a pathologically significant protein. This study focused on the proteomic characterization of laminin receptor interacting proteins from Mus musculus. The use of affinity chromatography with immobilized recombinant laminin receptor coupled with mass spectrometry analysis identified 45 proteins with high confidence. Following validation through coimmunoprecipitation, the proteins were classified based on predicted function into ribosomal, RNA processing, signal transduction/metabolism, protein processing, cytoskeleton/cell anchorage, DNA/chromatin, and unknown functions. A significant portion of the identified proteins is related to functions or localizations previously described for laminin receptor. This work represents a comprehensive proteomic approach to studying laminin receptor and provides an essential stepping stone to a better mechanistic understanding of this protein's diverse functions. PMID:22909348

Venticinque, Lisa; Meruelo, Daniel

2012-10-01

6

67-kDa Laminin Receptor-dependent Protein Phosphatase 2A (PP2A) Activation Elicits Melanoma-specific Antitumor Activity Overcoming Drug Resistance.  

PubMed

The Ras/Raf/MEK/ERK pathway has been identified as a major, druggable regulator of melanoma. Mutational activation of BRAF is the most prevalent genetic alteration in human melanoma, resulting in constitutive melanoma hyperproliferation. A selective BRAF inhibitor showed remarkable clinical activity in patients with mutated BRAF. Unfortunately, most patients acquire resistance to the BRAF inhibitor, highlighting the urgent need for new melanoma treatment strategies. Green tea polyphenol (-)-epigallocatechin-3-O-gallate (EGCG) inhibits cell proliferation independently of BRAF inhibitor sensitivity, suggesting that increased understanding of the anti-melanoma activity of EGCG may provide a novel therapeutic target. Here, by performing functional genetic screening, we identified protein phosphatase 2A (PP2A) as a critical factor in the suppression of melanoma cell proliferation. We demonstrated that tumor-overexpressed 67-kDa laminin receptor (67LR) activates PP2A through adenylate cyclase/cAMP pathway eliciting inhibitions of oncoproteins and activation of tumor suppressor Merlin. Activating 67LR/PP2A pathway leading to melanoma-specific mTOR inhibition shows strong synergy with the BRAF inhibitor PLX4720 in the drug-resistant melanoma. Moreover, SET, a potent inhibitor of PP2A, is overexpressed on malignant melanoma. Silencing of SET enhances 67LR/PP2A signaling. Collectively, activation of 67LR/PP2A signaling may thus be a novel rational strategy for melanoma-specific treatment. PMID:25294877

Tsukamoto, Shuntaro; Huang, Yuhui; Umeda, Daisuke; Yamada, Shuhei; Yamashita, Shuya; Kumazoe, Motofumi; Kim, Yoonhee; Murata, Motoki; Yamada, Koji; Tachibana, Hirofumi

2014-11-21

7

Laminin-1-induced migration of multiple myeloma cells involves the high-affinity 67 kD laminin receptor  

PubMed Central

The 67?kD laminin receptor (67LR) binds laminin-1 (LN), major component of the basement membrane, with high affinity. In this study, we demonstrated that human multiple myeloma cell lines (HMCL) and murine 5T2MM cells express 67LR. CD38bright+ plasma cells in fresh multiple myeloma (MM) bone marrow (BM) samples showed weaker 67LR expression, but expression increased after direct exposure to a BM endothelial cell line (4LHBMEC). LN stimulated the in vitro migration of 3 HMCL (MM5.1, U266 and MMS.1), primary MM cells and the murine 5T2MM cells. 67LR has been shown to mediate the actions of LN through binding to CDPGYIGSR, a 9 amino acid sequence from the B1 chain of LN. MM cell migration was partially blocked by peptide 11, a synthetic nonapeptide derived from this amino sequence and also by a blocking antiserum against 67LR. Co-injection of peptide 11 with 5T2MM cells in a murine in vivo model of MM resulted in a decreased homing of 5T2MM cells to the BM compartment. In conclusion, LN acts as a chemoattractant for MM cells by interaction with 67LR. This interaction might be important during extravasation of circulating MM cells. © 2001 Cancer Research Campaign PMID:11720479

Vande Broek, I; Vanderkerken, K; De Greef, C; Asosingh, K; Straetmans, N; Van Camp, B; Van Riet, I

2001-01-01

8

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

PubMed

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 KRS, impinged on the interaction of KRS with 67LR and suppressed metastasis in three different mouse models. The compound inhibited the 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, Ameeq Ul; 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

9

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

10

Modulation of 5'-nucleotidase activity in plasma membranes and intact cells by the extracellular matrix proteins laminin and fibronectin.  

PubMed Central

Modulation of 5'-nucleotidase activity by the extracellular matrix proteins fibronectin, laminin and their fragments has been studied in plasma membrane preparations as well as in intact BCS-TC2 and Rugli cells. The ectoenzyme on plasma membranes is activated by laminin; fibronectin inhibits the AMPase activity on BCS-TC2 plasma membranes but no inhibitory effect is found in plasma membrane preparations from Rugli cells. These effects are dependent on the preincubation time and protein concentration. When the effect of the extracellular matrix proteins is studied on intact cells, both BCS-TC2 and Rugli cells show similar behaviour. A decrease in the enzyme activity is observed in the presence of fibronectin. The AMPase inhibitory activity is located on its 40 kDa fragment. No inhibitory activity is found in other fibronectin fragments, including the 140 kDa fragment which contains the RGDS cell-adhesion sequence. Laminin and its E1-4 and E8 fragments are able to activate the ecto-5'-nucleotidase activity of both BCS-TC2 and Rugli cells. The effect of the E1-4 fragment on intact cells is greater than that observed for the E8 fragment and uncleaved laminin. Our results suggest a bifunctional role for 5'-nucleotidase as ectoenzyme and cell receptor for extracellular matrix proteins. Images Fig. 1. PMID:1540133

Olmo, N; Turnay, J; Risse, G; Deutzmann, R; von der Mark, K; Lizarbe, M A

1992-01-01

11

Expression of the 67 kDa laminin receptor and the ?6 integrin subunit in serous ovarian carcinoma  

Microsoft Academic Search

The aim of this study was to analyze the expression of two laminin receptors, the 67kDa laminin receptor (LBP) precursor and\\u000a the ?6 integrin subunit, in effusions and solid tumors of patients diagnosed with serous ovarian carcinoma and to evaluate\\u000a their predictive role. Eighty-eight effusions and one hundred sixteen primary (= forty-one) and metastatic (= seventy-five)\\u000a ovarian carcinomas were evaluated

Vered Givant-Horwitz; Ben Davidson; Gregg van de Putte; Hiep Phuc Dong; Iris Goldberg; Sivan Amir; Gunnar B. Kristensen; Reuven Reich

2003-01-01

12

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

13

Putative role of 67 kDa elastin-laminin receptor in tumor invasion.  

PubMed

Cellular regulatory mechanisms normally maintain a delicate balance between cell proliferation, quiescence and death. The imbalance between these functions resulting from molecular intracellular changes is a key factor in tumorigenesis. Tumor cells detaching from the primary tumor possess a propension for invasion and metastasis formation. These tumor cells can attach, migrate, proliferate and grow in host tissue. The surrounding extracellular matrix (ECM) modulates these functions. It is now widely accepted that cell-matrix interactions play an important role in these processes. Most investigators concentrated their attention on the role of integrins in the above processes. There are, however, only scant data on the role of elastin and its receptors in tumor invasion. Nevertheless, experimental evidence indicates that the 67 kDa elastin-laminin receptor (ELR) subunit plays an important role in tumor invasion by mediating essential tumor cell functions leading to metastases. In this review we will concentrate on the putative role of the 67 kDa ELR subunit in tumor invasion. PMID:12083852

Fülöp, Tamas; Larbi, Anis

2002-06-01

14

Multiple Functions of the 37\\/67-kd Laminin Receptor Make It a Suitable Target for Novel Cancer Gene Therapy  

Microsoft Academic Search

The 37\\/67-kd laminin receptor, LAMR, is a multifunctional protein that associates with the 40S ribosomal subunit and also localizes to the cell membrane to interact with the extracellular matrix. LAMR is overexpressed in many types of cancer, playing important roles in tumor-cell migration and invasion. Here, we show that LAMR is also vital for tumor-cell proliferation, survival, and protein translation.

Jonathan Scheiman; Jen-Chieh Tseng; Yun Zheng; Daniel Meruelo

2010-01-01

15

Laminin ?2-Mediated Focal Adhesion Kinase Activation Triggers Alport Glomerular Pathogenesis  

PubMed Central

It has been known for some time that laminins containing ?1 and ?2 chains, which are normally restricted to the mesangial matrix, accumulate in the glomerular basement membranes (GBM) of Alport mice, dogs, and humans. We show that laminins containing the ?2 chain, but not those containing the ?1 chain activates focal adhesion kinase (FAK) on glomerular podocytes in vitro and in vivo. CD151-null mice, which have weakened podocyte adhesion to the GBM rendering these mice more susceptible to biomechanical strain in the glomerulus, also show progressive accumulation of ?2 laminins in the GBM, and podocyte FAK activation. Analysis of glomerular mRNA from both models demonstrates significant induction of MMP-9, MMP-10, MMP-12, MMPs linked to GBM destruction in Alport disease models, as well as the pro-inflammatory cytokine IL-6. SiRNA knockdown of FAK in cultured podocytes significantly reduced expression of MMP-9, MMP-10 and IL-6, but not MMP-12. Treatment of Alport mice with TAE226, a small molecule inhibitor of FAK activation, ameliorated fibrosis and glomerulosclerosis, significantly reduced proteinuria and blood urea nitrogen levels, and partially restored GBM ultrastructure. Glomerular expression of MMP-9, MMP-10 and MMP-12 mRNAs was significantly reduced in TAE226 treated animals. Collectively, this work identifies laminin ?2-mediated FAK activation in podocytes as an important early event in Alport glomerular pathogenesis and suggests that FAK inhibitors, if safe formulations can be developed, might be employed as a novel therapeutic approach for treating Alport renal disease in its early stages. PMID:24915008

Delimont, Duane; Dufek, Brianna M.; Meehan, Daniel T.; Zallocchi, Marisa; Gratton, Michael Anne; Phillips, Grady; Cosgrove, Dominic

2014-01-01

16

Laminin ?2-mediated focal adhesion kinase activation triggers Alport glomerular pathogenesis.  

PubMed

It has been known for some time that laminins containing ?1 and ?2 chains, which are normally restricted to the mesangial matrix, accumulate in the glomerular basement membranes (GBM) of Alport mice, dogs, and humans. We show that laminins containing the ?2 chain, but not those containing the ?1 chain activates focal adhesion kinase (FAK) on glomerular podocytes in vitro and in vivo. CD151-null mice, which have weakened podocyte adhesion to the GBM rendering these mice more susceptible to biomechanical strain in the glomerulus, also show progressive accumulation of ?2 laminins in the GBM, and podocyte FAK activation. Analysis of glomerular mRNA from both models demonstrates significant induction of MMP-9, MMP-10, MMP-12, MMPs linked to GBM destruction in Alport disease models, as well as the pro-inflammatory cytokine IL-6. SiRNA knockdown of FAK in cultured podocytes significantly reduced expression of MMP-9, MMP-10 and IL-6, but not MMP-12. Treatment of Alport mice with TAE226, a small molecule inhibitor of FAK activation, ameliorated fibrosis and glomerulosclerosis, significantly reduced proteinuria and blood urea nitrogen levels, and partially restored GBM ultrastructure. Glomerular expression of MMP-9, MMP-10 and MMP-12 mRNAs was significantly reduced in TAE226 treated animals. Collectively, this work identifies laminin ?2-mediated FAK activation in podocytes as an important early event in Alport glomerular pathogenesis and suggests that FAK inhibitors, if safe formulations can be developed, might be employed as a novel therapeutic approach for treating Alport renal disease in its early stages. PMID:24915008

Delimont, Duane; Dufek, Brianna M; Meehan, Daniel T; Zallocchi, Marisa; Gratton, Michael Anne; Phillips, Grady; Cosgrove, Dominic

2014-01-01

17

Deciphering the complex three-way interaction between the non-integrin laminin receptor, galectin-3 and Neisseria meningitidis  

PubMed Central

The non-integrin laminin receptor (LAMR1/RPSA) and galectin-3 (Gal-3) are multi-functional host molecules with roles in diverse pathological processes, particularly of infectious or oncogenic origins. Using bimolecular fluorescence complementation and confocal imaging, we demonstrate that the two proteins homo- and heterodimerize, and that each isotype forms a distinct cell surface population. We present evidence that the 37 kDa form of LAMR1 (37LRP) is the precursor of the previously described 67 kDa laminin receptor (67LR), whereas the heterodimer represents an entity that is distinct from this molecule. Site-directed mutagenesis confirmed that the single cysteine (C173) of Gal-3 or lysine (K166) of LAMR1 are critical for heterodimerization. Recombinant Gal-3, expressed in normally Gal-3-deficient N2a cells, dimerized with endogenous LAMR1 and led to a significantly increased number of internalized bacteria (Neisseria meningitidis), confirming the role of Gal-3 in bacterial invasion. Contact-dependent cross-linking determined that, in common with LAMR1, Gal-3 binds the meningococcal secretin PilQ, in addition to the major pilin PilE. This study adds significant new mechanistic insights into the bacterial–host cell interaction by clarifying the nature, role and bacterial ligands of LAMR1 and Gal-3 isotypes during colonization. PMID:25274119

Alqahtani, Fulwah; Mahdavi, Jafar; Wheldon, Lee M.; Vassey, Matthew; Pirinccioglu, Necmettin; Royer, Pierre-Joseph; Qarani, Suzan M.; Morroll, Shaun; Stoof, Jeroen; Holliday, Nicholas D.; Teo, Siew Y.; Oldfield, Neil J.; Wooldridge, Karl G.; Ala'Aldeen, Dlawer A. A.

2014-01-01

18

Deciphering the complex three-way interaction between the non-integrin laminin receptor, galectin-3 and Neisseria meningitidis.  

PubMed

The non-integrin laminin receptor (LAMR1/RPSA) and galectin-3 (Gal-3) are multi-functional host molecules with roles in diverse pathological processes, particularly of infectious or oncogenic origins. Using bimolecular fluorescence complementation and confocal imaging, we demonstrate that the two proteins homo- and heterodimerize, and that each isotype forms a distinct cell surface population. We present evidence that the 37 kDa form of LAMR1 (37LRP) is the precursor of the previously described 67 kDa laminin receptor (67LR), whereas the heterodimer represents an entity that is distinct from this molecule. Site-directed mutagenesis confirmed that the single cysteine (C(173)) of Gal-3 or lysine (K(166)) of LAMR1 are critical for heterodimerization. Recombinant Gal-3, expressed in normally Gal-3-deficient N2a cells, dimerized with endogenous LAMR1 and led to a significantly increased number of internalized bacteria (Neisseria meningitidis), confirming the role of Gal-3 in bacterial invasion. Contact-dependent cross-linking determined that, in common with LAMR1, Gal-3 binds the meningococcal secretin PilQ, in addition to the major pilin PilE. This study adds significant new mechanistic insights into the bacterial-host cell interaction by clarifying the nature, role and bacterial ligands of LAMR1 and Gal-3 isotypes during colonization. PMID:25274119

Alqahtani, Fulwah; Mahdavi, Jafar; Wheldon, Lee M; Vassey, Matthew; Pirinccioglu, Necmettin; Royer, Pierre-Joseph; Qarani, Suzan M; Morroll, Shaun; Stoof, Jeroen; Holliday, Nicholas D; Teo, Siew Y; Oldfield, Neil J; Wooldridge, Karl G; Ala'Aldeen, Dlawer A A

2014-10-01

19

Interactions between laminin and epithelial cells in intestinal health and disease.  

PubMed

Laminins are a multigene family of extracellular matrix molecules. Quantitatively, they are one of the most abundant glycoproteins present in basement membranes. Functionally, they can modulate several key biological activities, including cell adhesion and migration, gene expression and cell survival. Variability in the spatial and temporal expression of laminins, as well as of their specific receptors of the integrin family, in various tissues and organs, suggests that different laminins perform distinct functions. This article focuses on the human intestinal epithelium as a paradigm to illustrate the potential relationship between laminin-cell interactions and the cell state. This rapidly renewing epithelium consists of spatially separated proliferative and differentiated cell populations located in the crypts and on the villi, respectively. Differential distributions of the various laminins and laminin-binding integrins have been observed along the crypt-villus axis in both the developing and the adult intestine, and important alterations in the pattern of laminin expression have been reported in various intestinal pathologies, such as tufting enteropathy, Crohn's disease and ulcerative colitis, and colorectal cancer. More-direct approaches, including experimentation with in vitro and in vivo models, have provided evidence in support of a role for laminins in intestinal cell functions. Although further work is still needed, laminins emerge more and more as key regulators of specific cell functions important in both intestinal health and intestinal disease. PMID:14585148

Teller, I C; Beaulieu, J F

2001-09-01

20

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

21

Modulation of the Metastatic Activity of Melanoma Cells by Laminin and Fibronectin  

NASA Astrophysics Data System (ADS)

Metastatic mouse melanoma cells have a high affinity for the basement membrane and the ability to degrade it; these properties may allow tumor cells to invade the membrane and disseminate. In this study it was found that the metastatic potential of mouse melanoma cells varied when the cells were exposed in culture to fibronectin or laminin. After removal of fibronectin or exposure to laminin, the cells had an increased affinity for basement membrane collagen, were more invasive of basement membranes in vitro, and produced more lung colonies in vivo. These changes are correlated with and may be due to an increase in the laminin-binding capacity of the tumor cell surface.

Terranova, Victor P.; Williams, Jeannette E.; Liotta, Lance A.; Martin, George R.

1984-11-01

22

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

23

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

24

Expression of laminins and their integrin receptors in different conditions of synovial membrane and synovial membrane-like interface tissue  

PubMed Central

OBJECTIVE—To demonstrate the expression of laminins (Lns) and their integrin (Int) receptors in different synovial samples and synovial membrane-like interface tissues from well fixed and aseptically loosened total hip replacement (THR), and the potential role of Ln-Int interaction in the production of collagenases and cytokines.?METHODS—Immunohistochemical staining was done to detect the distribution of EHS Ln, Ln ?2, ?3, ?5, ?1, ?2 chains and Int ?1, ?2, ?3, ?6, ?1, ?4 subunits in different samples. Double immunofluorescence labelling was used to find colocalisation of Int ?6 subunit and collagenase-1/collagenase-3/TNF?/IL6.?RESULTS—General Ln immunoreactivity was detected in all specimens. Ln ?5, ?1 and ?2, but not ?2 and ?3 chains were seen in the synovial lining and the basement membrane of blood vessels with the intensity/extent of labelling in the following rank order: rheumatoid arthritis (RA) loosened prostheses, osteoarthritis, well fixed prostheses, traumatic knees. Among Int subunits, staining for ?1 was usually the strongest, followed by staining for Int ?6, ?1, ?3, and ?2 subunits, with the same rank order for overall expression of Lns. Int ?4 subunit was not detectable in most of the specimens. Double labelling focused on Int ?6 subunit disclosed its frequent colocalisation with collagenases 1 and 3 and with tumour necrosis factor ? and interleukin 6 in synovial lining.?CONCLUSION—Synovial lining contains Ln-10, Ln-11, and Int ?6?1 and ?1?1 receptors. In aseptic loosening of THR, interface tissue has a similar Ln subtype and Int receptor composition as RA synovium, which confirms its "lining-like" phenotype. Synovial lining does not contain Ln-5 (?3?3?2) or Int ?6?4, which are components of epithelial hemidesmosomes. The expression of Lns and their Int receptors is upregulated in inflammation. The close spatial relation between Ln and its Int receptors in synovial lining cells containing proteinases and cytokines suggests a potential role in joint destruction and prosthetic loosening.?? PMID:10531072

Konttinen, Y.; Li, T. F.; Xu, J. W.; Tagaki, M.; Pirila, L.; Silvennoinen, T.; Santavirta, S.; Virtanen, I.

1999-01-01

25

Dystrophin Glycoprotein Complex-associated G?? Subunits Activate Phosphatidyl Inositol-3-Kinase/Akt signaling in Skeletal Muscle in a Laminin-dependent Manner  

PubMed Central

Previously, we showed that laminin-binding to the dystrophin glycoprotein complex (DGC) of skeletal muscle causes a heterotrimeric G-protein, (G???) to bind, changing the activation state of the Gs? subunit. Others have shown that laminin-binding to the DGC also leads to Akt activation. G??, released when Gs? is activated, is known to bind phosphatidylinositol 3-kinase (PI3K), which activates Akt in other cells. Here, we investigate whether muscle Akt activation results from G??, using immunoprecipitation and immunoblotting, and purified G??. In the presence of laminin, PI3K-binding to the DGC increases and Akt becomes phosphorylated and activated (pAkt), and glycogen synthase kinase is phosphorylated. Antibodies, which specifically block laminin-binding to ?-dystroglycan, prevent PI3K-binding to the DGC. Purified bovine brain G?? also caused PI3K and Akt activation. These results show that DGC-G?? is binding PI3K and activating pAkt in a laminin-dependent manner. Mdx mice, which have greatly diminished amounts of DGC proteins, display elevated pAkt signaling and increased expression of integrin ?1 compared to normal muscle. This integrin binds laminin, G??, and PI3K. Collectively, these suggest that PI3K is an important target for the G??, which normally binds to DGC syntrophin, and activates PI3K/Akt signaling. Disruption of the DGC in mdx mouse is causing dis-regulation of the laminin-DGC-G??-PI3K-Akt signaling and is likely to be important to the pathogenesis of muscular dystrophy. Up-regulating integrin ?1 expression and activating the PI3K/Akt pathway in muscular dystrophy may partially compensate for the loss of the DGC. The results suggest new therapeutic approaches to muscle disease. PMID:19117013

Xiong, Yongmin; Zhou, Yanwen; Jarrett, Harry W.

2010-01-01

26

Green tea catechins potentiate the neuritogenic action of brain-derived neurotrophic factor: role of 67-kDa laminin receptor and hydrogen peroxide.  

PubMed

Delivery of optimal amounts of brain-derived neurotrophic factor (BDNF) to regions of the brain affected by neurodegenerative diseases is a daunting task. Using natural products with neuroprotective properties, such as green tea polyphenols, would be a highly useful complementary approach for inexpensive long-term treatment of these diseases. In this study, we used PC12(TrkB) cells which ectopically express TrkB, a high affinity receptor for BDNF. They differentiate and induce neurite outgrowth in response to BDNF. Using this model, we show for the first time that treatment with extremely low concentrations (<0.1 ?g/ml) of unfractionated green tea polyphenols (GTPP) and low concentrations (<0.5 ?M) of their active ingredient, epigallocatechin-3-gallate (EGCG), potentiated the neuritogenic ability of a low concentration (2 ng/ml) of BDNF. A synergistic interaction was observed between GTPP constituents, where epigallocatechin and epicatechin, both individually lacking this activity, promoted the action of EGCG. GTPP-induced potentiation of BDNF action required the cell-surface associated 67 kDa laminin receptor (67LR) to which EGCG binds with high affinity. A cell-permeable catalase abolished GTPP/EGCG-induced potentiation of BDNF action, suggesting the possible involvement of H2O2 in the potentiation. Consistently, exogenous sublethal concentrations of H2O2, added as a bolus dose (5 ?M) or more effectively through a steady-state generation (1 ?M), potentiated BDNF action. Collectively, these results suggest that EGCG, dependent on 67 LR and H2O2, potentiates the neuritogenic action of BDNF. Intriguingly, this effect requires only submicromolar concentrations of EGCG. This is significant as extremely low concentrations of polyphenols are believed to reach the brain after drinking green tea. PMID:24508265

Gundimeda, Usha; McNeill, Thomas H; Fan, Tiffany K; Deng, Ronald; Rayudu, David; Chen, Zachary; Cadenas, Enrique; Gopalakrishna, Rayudu

2014-02-28

27

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

PubMed Central

Systemic delivery of therapeutic agents to solid tumors is hindered by vascular and interstitial barriers. We hypothesized that prostate tumor specific epigallocatechin-gallate (EGCg) functionalized radioactive gold nanoparticles, when delivered intratumorally (IT), would circumvent transport barriers, resulting in targeted delivery of therapeutic payloads. The results described herein support our hypothesis. We report the development of inherently therapeutic gold nanoparticles derived from the Au-198 isotope; the range of the 198Au ?-particle (approximately 11 mm in tissue or approximately 1100 cell diameters) is sufficiently long to provide cross-fire effects of a radiation dose delivered to cells within the prostate gland and short enough to minimize the 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 approximately 72% retention of 198AuNP-EGCg in tumors 24 h after intratumoral administration. Therapeutic studies showed 80% reduction of tumor volumes after 28 d demonstrating significant inhibition of tumor growth compared to controls. This innovative nanotechnological approach serves as a basis for designing biocompatible 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. PMID:22802668

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

2012-01-01

28

Cloning and expression analysis of the 37-kDa laminin receptor precursor gene from Hyriopsis cumingii.  

PubMed

Hyriopsis cumingii is an economically important freshwater pearl mussel with high pearl quality that is endemic in China. Investigation of genes relevant to shell formation is important for increased pearl output. The substances that form mollusk shells are secreted by epithelial cells in the mantle, the proliferation of which influences secretion ability. This study focused on the proliferation-related 37-kDa laminin receptor precursor (37LRP) of H. cumingii. The full-length cDNA (1133 bp) encoding this 300-amino acid protein was cloned from the mantle. Quantitative fluorescence analysis showed that 37LRP expressed in eight tissues, with the highest expression observed in the liver, and its expression pattern in the mantle reflected shell repair. During repair, 37LRP expression was higher in the experimental shell repair group than that in the control group, exhibiting an initial increase followed by a decrease in expression, and returning to basal levels on completion of the repair. A similar trend was also observed with respect to immunity and cellular metabolism. Expression of the 37LRP protein in the experimental group was significantly higher than that in the control group at the first and second days after shell injury. After 4 days, 37LRP expression in the experimental group was lower than that in the control group. In situ hybridization revealed a strong positive signal corresponding to the 37LRP mRNA at the horny grooves of the mantle, evagination, and in epithelial cells of the velum, which implicated these areas in the repair and formation of the cuticle, prismatic layer, and nacre. PMID:24338406

Chang, X Z; Li, J L; Bai, Z Y; Li, X L

2013-01-01

29

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

30

Distinct and overlapping ligand specificities of the alpha 3A beta 1 and alpha 6A beta 1 integrins: recognition of laminin isoforms.  

PubMed Central

The ligand specificity of the alpha 3A beta 1 integrin was analyzed using K562 cells transfected with full-length alpha 3A cDNA and was compared with that of alpha 6A beta 1 in similarly transfected K562 cells. Clones were obtained that showed comparable surface expression of either alpha 3A beta 1 or alpha 6A beta 1 integrins. Those expressing alpha 3A beta 1 attached to and spread on immunopurified human kalinin and cellular matrices containing human kalinin, which is a particular isoform of laminin. In addition, alpha 3A transfectants adhered to bovine kidney laminins possessing a novel A chain variant. Binding to kalinin was blocked by a monoclonal antibody against the A chain constituent of kalinin and adhesion to both kalinin and kidney laminins by anti-alpha 3 and beta 1 monoclonal antibodies. The alpha 3A transfected cells bound more strongly to kalinin and bovine kidney laminins after treatment with the beta 1 stimulatory antibody TS2/16. A distinctly weaker and activation-dependent adhesion of alpha 3A transfectants was observed on human placental laminins possessing the Am chain variant (merosin), and no adhesion occurred on bovine heart laminins and murine EHS tumor laminin. Further inactive substrates were fibronectin, nidogen, and collagen types IV and VI, indicating that the alpha 3A beta 1 integrin is a much less promiscuous receptor than thought before. By contrast, alpha 6A transfected cells adhered to all laminin isoforms when stimulated with TS2/16. Adhesion also occurred only on bovine kidney laminins in the absence of TS2/16. These results demonstrate that both alpha 3A beta 1 and alpha 6A beta 1 integrins are typical laminin receptors but that their affinity and activation dependence for binding to various laminin isoforms differ considerably. Images PMID:8019006

Delwel, G O; de Melker, A A; Hogervorst, F; Jaspars, L H; Fles, D L; Kuikman, I; Lindblom, A; Paulsson, M; Timpl, R; Sonnenberg, A

1994-01-01

31

Laminin 5 processing and its integration into the ECM  

Microsoft Academic Search

Laminins are a family of multi-functional basement membrane proteins. Their C-terminal domain binds to cell surface receptors and is thereby responsible for cell anchorage and the initiation of specific outside-in and inside-out signals. With their N-terminal parts, laminins interact with proteins of the extracellular matrix scaffold to secure the basement membrane to the underlying mesenchymal tissue. Laminins 5A (?3A?3?2), 5B

Monique Aumailley; Abdallah El Khal; Naomi Knöss; Lucy Tunggal

2003-01-01

32

Plasmin-mediated degradation of laminin ?-1 is critical for ethanol-induced neurodegeneration  

PubMed Central

Background Alcoholism may result in severe neurological deficits and cognitive impairments. Many of central effects of ethanol (EtOH) can be explained by upregulation of NMDA and downregulation of GABA(A) receptors in response to a long-term EtOH consumption. Abrupt ethanol withdrawal (EW) may result in neuronal hyperexcitability leading to hallucinations, seizures, neurodegeneration and sometimes death. Methods Using a multidisciplinary approach in wild-type and genetically modified mice we have examined the contribution of the tissue-plasminogen activator, plasminogen and laminin to EW-induced cell death. Results Here we show that EW-induced neurodegeneration is mediated by the tissue plasminogen activator (tPA)/plasmin system. During EW, tPA is upregulated in the hippocampus, converts plasminogen to plasmin, which in turn degrades an extracellular matrix component laminin, leading to caspase-3-dependent cell death. Consequently, mice in which the tPA or plasminogen genes have been deleted do not show EW-induced laminin degradation, mitochondial dysfunction, and neurodegeneration. Finally we demonstrate, that disruption of the hippocampal laminin ?-1 renders the mice resistant to neurotoxic effects of EW. Conclusions Our data identify laminin ?-1 as a novel target to combat neurodegeneration. PMID:19577227

Skrzypiec, Anna; Maiya, Rajani; Chen, Zulin; Pawlak, Robert; Strickland, Sidney

2009-01-01

33

Association of Urinary Laminin G-Like 3 and Free K Light Chains with Disease Activity and Histological Injury in IgA Nephropathy  

PubMed Central

Summary Background and objectives IgA nephropathy has variable clinical presentation and progression. Its definitive diagnosis and prognosis require renal biopsy. The identification of new biomarkers allowing noninvasive diagnosis and monitoring of disease activity would be advantageous. This study analyzed the urine proteome of IgA nephropathy patients at an early stage of disease. Design, setting, participants, & measurements Urine from 49 IgA nephropathy patients, 42 CKD patients, and 40 healthy individuals was analyzed by surface-enhanced laser desorption/ionization time of flight/mass spectrometry. Differentially excreted proteins were identified by matrix-enhanced laser desorption/ionization time of flight/mass spectrometry, confirmed by immunologic methods, and validated in an independent set of patients (14 IgA nephropathy and 24 CKD). All patients were recruited at the Division of Nephrology of the University of Foggia from January of 2005 to March of 2007. Results Two proteins, with 21,598 and 23,458 m/z, were significantly decreased in IgA nephropathy and identified as Perlecan laminin G-like 3 peptide and Ig ? light chains, respectively. Western blot analysis confirmed the lower urinary excretion of laminin G-like 3 in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunonephelometry analysis confirmed the lower urinary excretion of free ? light chains in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunohistochemistry analysis justified the urinary excretion profile of such proteins in IgA nephropathy. Finally, urinary free ? light chains and laminin G-like 3 concentration inversely correlated with severity of clinical and histologic features of our IgA nephropathy cohort. Conclusions Laminin G-like 3 and free ? light chains can contribute to the noninvasive assessment of IgA nephropathy disease activity. PMID:23599406

Rocchetti, Maria Teresa; Papale, Massimo; d'Apollo, Anna Maria; Suriano, Ida Valentina; Di Palma, Anna Maria; Vocino, Grazia; Montemurno, Eustacchio; Varraso, Leonarda; Grandaliano, Giuseppe; Di Paolo, Salvatore

2013-01-01

34

The helper-component protease transmission factor of tobacco etch potyvirus binds specifically to an aphid ribosomal protein homologous to the laminin receptor precursor.  

PubMed

Potyviruses are plant pathogens transmitted by aphids in a non-persistent manner. During transmission, the virus-encoded factor helper-component protease (HCPro) is presumed to act as a molecular bridge, mediating the reversible retention of virions to uncharacterized binding sites in the vector mouthparts. Whilst the predicted interaction between HCPro and the coat protein (CP) of virions has been confirmed experimentally, the characterization of putative HCPro-specific receptors in aphids has remained elusive, with the exception of a report that described binding of HCPro of zucchini yellow mosaic virus to several cuticle proteins. To identify other aphid components that could play a role during transmission, this study used purified HCPro of tobacco etch virus (TEV) in far-Western blotting assays as bait to select interactors among proteins extracted from aphid heads. With this approach, new HCPro-interacting proteins were found, and several were identified after mass spectrometry analysis and searches in databases dedicated to aphid sequences. Among these interactors, a ribosomal protein S2 (RPS2) was chosen for further investigation due to its homology with the laminin receptor precursor, known to act as the receptor of several viruses. The specific interaction between RPS2 and TEV HCPro was confirmed after cloning and heterologous expression of the corresponding Myzus persicae gene. The possible involvement of RPS2 in the transmission process was further suggested by testing a variant of HCPro that was non-functional for transmission due to a mutation in the conserved KITC motif (EITC variant). This variant retained its ability to bind CP but failed to interact with RPS2. PMID:20631085

Fernández-Calvino, Lourdes; Goytia, Elisa; López-Abella, Dionisio; Giner, Ana; Urizarna, María; Vilaplana, Lluisa; López-Moya, Juan José

2010-11-01

35

Endocytic trafficking of laminin is controlled by dystroglycan and is disrupted in cancers.  

PubMed

The dynamic interactions between cells and basement membranes serve as essential regulators of tissue architecture and function in metazoans, and perturbation of these interactions contributes to the progression of a wide range of human diseases, including cancers. Here, we reveal the pathway and mechanism for the endocytic trafficking of a prominent basement membrane protein, laminin-111 (referred to here as laminin), and their disruption in disease. Live-cell imaging of epithelial cells revealed pronounced internalization of laminin into endocytic vesicles. Laminin internalization was receptor mediated and dynamin dependent, and laminin proceeded to the lysosome through the late endosome. Manipulation of laminin receptor expression revealed that the dominant regulator of laminin internalization is dystroglycan, a laminin receptor that is functionally perturbed in muscular dystrophies and in many cancers. Correspondingly, laminin internalization was found to be deficient in aggressive cancer cells displaying non-functional dystroglycan, and restoration of dystroglycan function strongly enhanced the endocytosis of laminin in both breast cancer and glioblastoma cells. These results establish previously unrecognized mechanisms for the modulation of cell-basement-membrane communication in normal cells and identify a profound disruption of endocytic laminin trafficking in aggressive cancer subtypes. PMID:25217627

Leonoudakis, Dmitri; Huang, Ge; Akhavan, Armin; Fata, Jimmie E; Singh, Manisha; Gray, Joe W; Muschler, John L

2014-11-15

36

YIGSR, a Synthetic Laminin Pentapeptide, Inhibits Experimental Metastasis Formation  

Microsoft Academic Search

The invasion of tumor cells through basement membranes is a critical step in the formation of metastases. The binding of the malignant cells to laminin in the basement membranes allows their attachment and activates their invasiveness. Recently a synthetic nonapeptide from the B1 chain sequence of laminin was identified as a major site for cell binding. A pentapeptide within the

Yukihide Iwamoto; Frank A. Robey; Jeannette Graf; Makoto Sasaki; Hynda K. Kleinman; Yoshihiko Yamada; George R. Martin

1987-01-01

37

Glycosylation of the laminin receptor (?3?1) regulates its association with tetraspanin CD151: Impact on cell spreading, motility, degradation and invasion of basement membrane by tumor cells.  

PubMed

Invasion is the key requirement for cancer metastasis. Expression of ?1,6 branched N-oligosaccharides associated with invasiveness, has been shown to promote adhesion to most Extra Cellular Matrix (ECM) and basement membrane (BM) components and haptotactic motility on ECM (fibronectin) but attenuate it on BM (laminin/matrigel) components. To explore the mechanism and to evaluate the significance of these observations in terms of invasion, highly invasive B16BL6 cells were compared with the parent (B16F10) cells or B16BL6 cells in which glycosylation was inhibited. We demonstrate that increased adhesion to matrix components induced secretion of MMP-9, important for invasion. Further, both the subunits of integrin receptors for fibronectin (?5?1) and laminin (?3?1) on B16BL6 cells were shown to carry these oligosaccharides. Although, glycosylation of receptors had no effect on their surface expression, it had same differential effect on cell spreading as haptotactic motility. Absence of correlation between invasiveness and expression of most tetraspanins (major regulators of integrin function) hints at an alternate mechanism. Here we show that glycosylation on ?3?1 impedes its association with CD151 and modulates spreading and motility of cells apparently to reach an optimum required for invasion of BM. These studies demonstrate the complex mechanisms used by cancer cells to be invasive. PMID:24530578

Ranjan, Amit; Bane, Sanjay M; Kalraiya, Rajiv D

2014-04-01

38

Molecular analysis of spontaneous nephrotropic anti-laminin antibodies in an autoimmune MRL-lpr/lpr mouse.  

PubMed

To explore the genetic relationship between anti-laminin and anti-DNA autoantibodies (autoAb), VH gene and gene family expression were determined among autoAb derived from an individual 6-mo-old MRL-lpr/lpr mouse. Whereas 85% of the anti-DNA Ig were identified by one of two VH family probes, 7183 and VHJ558, none of the anti-laminin antibodies (Ab) examined were recognized by these probes. Subsequent V region sequence analysis of three of the anti-laminin Ab revealed that they in fact utilized a J558 VH gene (VH50). Furthermore, FR2 and CDR2 oligonucleotide probes complementary to VH50 recognized multiple anti-laminin Ab by Northern blot analysis; the FR2 probe recognized two control anti-DNA Ab, but neither probe recognized anti-DNA Ab from the same mouse. Polymerase chain reaction amplification of MRL-lpr/lpr genomic liver DNA using primers generated from VH50 and Vk50 sequences indicated that all three anti-laminin Ig have a single replacement mutation in both their VH and Vk genes. Search of the nucleic acid databases revealed that both germline VH and Vk genes are expressed unmutated by murine lupus anti-dsDNA autoAb, previously sequenced in other laboratories. Sequence comparisons suggest that differences in anti-DNA and anti-laminin reactivity may be dependent upon somatically generated differences in the CDR3 regions of the H and L chains. The results indicate that lupus anti-laminin Ab can arise from distinct B cell populations but express the same unmutated germline V region genes as lupus anti-dsDNA autoAb. They further raise the possibility that these distinct B cell populations may be activated and expanded either: independently, by distinct Ig receptor ligands such as the Ag, laminin and DNA; or simultaneously, by a common ligand such as an anti-Id recognizing a common V region epitope. PMID:8335911

Foster, M H; Sabbaga, J; Line, S R; Thompson, K S; Barrett, K J; Madaio, M P

1993-07-15

39

Murine laminin binds to Histoplasma capsulatum. A possible mechanism of dissemination.  

PubMed Central

Histoplasmosis, an increasingly important opportunistic infection in immunosuppressed subjects, is characterized by hematogenous dissemination of the yeast from the lung. The mechanism of this dissemination is not fully understood. Laminin, the major glycoprotein of the extracellular matrix, is known to mediate the attachment of various invasive pathogens to host tissues. In the current study, laminin is demonstrated to bind to Histoplasma capsulatum in a rapid, specific, and saturable manner. Scatchard analysis with 125I-labeled laminin revealed an estimated 3.0 x 10(4) binding sites per yeast with an apparent Kd for laminin binding of 1.6 x 10(-9) M. Laminin binding to H. capsulatum was decreased from 62 +/- 1 to 17 +/- 1 ng (P < 0.001) in the presence of 3,000 nM of Ile-Lys-Val-Ala-Val, a pentapeptide within one major cell attachment site of laminin. A 50-kD H. capsulatum laminin-binding protein was demonstrated using an 125I-Ln blot of H. capsulatum cell wall proteins. The 50-kD protein is also recognized by antibodies directed at the 67-kD laminin receptor, suggesting they are related. This study proposes a possible mechanism for H. capsulatum attachment to laminin, an important first step required for the yeast to recognize and traverse the basement membrane. Images PMID:7635937

McMahon, J P; Wheat, J; Sobel, M E; Pasula, R; Downing, J F; Martin, W J

1995-01-01

40

Expression of the alpha 2-subunit of laminin correlates with increased cell adhesion and metastatic propensity.  

PubMed

Previous studies have indicated that laminin from neoplastic cells of high tumorigenicity is less active in promoting cell adhesion than aminin from normal cells or tissues. In the present study, we tested the hypothesis that laminin of metastatic tumor cells differs from that of nonmetastatic cells. Accordingly, we determined the subunit composition of laminin in highly metastatic, ras-transformed cells (4R) and compared it with laminin produced by nonmetastatic cells transformed with ras plus E1a (RE4). Metastatic 4R cells produced three to four times more of the alpha 2-subunit of laminin than RE4 cells did. Furthermore, the highly metastatic human melanoma cells (1205 and A2058) made and secreted into the medium, laminin containing significantly more of the alpha 2-subunit than laminin from the highly tumorigenic but nonmetastatic melanoma WM793 or HT1080 fibrosarcoma cells. Using HT1080 cells, laminin (250 ng/well) from 4R cells showed more adhesion promoting activity (68%) than laminin from RE4 cells (39%). Similarly, laminin isolated from human placenta, which expresses both the alpha 1 beta 1 gamma 1 and alpha 2 beta 1 gamma 1 isoforms, promoted cell adhesion better (63%) than EHS laminin (26%), which contains only the former isoform, at 250 ng/well. In addition, both 4R and RE4 cells attached more efficiently to 4R laminin-coated substratum than to RE4 laminin at 0.3 and 0.6 microgram/well.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7867894

Jenq, W; Wu, S J; Kefalides, N A

1994-11-01

41

Endothelial Cell Laminin Isoforms, Laminins 8 and 10, Play Decisive Roles in T Cell Recruitment across the Blood-Brain Barrier in Experimental Autoimmune Encephalomyelitis  

PubMed Central

An active involvement of blood–brain barrier endothelial cell basement membranes in development of inflammatory lesions in the central nervous system (CNS) has not been considered to date. Here we investigated the molecular composition and possible function of the extracellular matrix encountered by extravasating T lymphocytes during experimental autoimmune encephalomyelitis (EAE). Endothelial basement membranes contained laminin 8 (?4?1?1) and/or 10 (?5?1?1) and their expression was influenced by proinflammatory cytokines or angiostatic agents. T cells emigrating into the CNS during EAE encountered two biochemically distinct basement membranes, the endothelial (containing laminins 8 and 10) and the parenchymal (containing laminins 1 and 2) basement membranes. However, inflammatory cuffs occurred exclusively around endothelial basement membranes containing laminin 8, whereas in the presence of laminin 10 no infiltration was detectable. In vitro assays using encephalitogenic T cell lines revealed adhesion to laminins 8 and 10, whereas binding to laminins 1 and 2 could not be induced. Downregulation of integrin ?6 on cerebral endothelium at sites of T cell infiltration, plus a high turnover of laminin 8 at these sites, suggested two possible roles for laminin 8 in the endothelial basement membrane: one at the level of the endothelial cells resulting in reduced adhesion and, thereby, increased penetrability of the monolayer; and secondly at the level of the T cells providing direct signals to the transmigrating cells. PMID:11381080

Sixt, Michael; Engelhardt, Britta; Pausch, Friederike; Hallmann, Rupert; Wendler, Olaf; Sorokin, Lydia M.

2001-01-01

42

Regulation of TGF-? receptor activity  

PubMed Central

TGF-? signaling regulates diverse cellular processes, including cell proliferation, differentiation, apoptosis, cell plasticity and migration. Its dysfunctions can result in various kinds of diseases, such as cancer and tissue fibrosis. TGF-? signaling is tightly regulated at different levels along the pathway, and modulation of TGF-? receptor activity is a critical step for signaling regulation. This review focuses on our recent understanding of regulation of TGF-? receptor activity. PMID:22420375

2012-01-01

43

Ligand Affinity of the 67-kDElastin/Laminin Binding Protein Is Modulated bythe Protein'sLectinDomain: Visualization of  

E-print Network

Ligand Affinity of the 67-kDElastin/Laminin Binding Protein Is Modulated bythe Protein have revealed important aspects of the regu- lation of affinity of ligand-receptor interaction in situ decreased the affinity of the receptor(s) for both elastin and laminin. These findings were supported

Mecham, Robert

44

Sialic acid-dependent recognition of laminin and fibrinogen by Aspergillus fumigatus conidia.  

PubMed Central

In an attempt to define the molecular basis of the adherence of Aspergillus fumigatus conidia to the host tissues, a step which might be mediated by the recognition of basement membrane laminin or fibrinogen, we analyzed the binding of these glycoproteins by flow cytometry and a microtiter plate adherence assay. Flow cytometry revealed that the binding of fluorescein isothiocyanate-labeled laminin to conidia was saturable and specific. Moreover, the ability of conidia to bind laminin increased with their maturation. Competition experiments showed a cross-reactivity between laminin and fibrinogen binding and a lack of interactions with glycosaminoglycans. In addition, the binding of laminin was not inhibited by the different adhesive synthetic peptides tested. Furthermore, the microtiter plate assay of adherence to chymotrypsin degradation products of laminin or fibrinogen purified by gel filtration suggested a unique binding site common to sequential degradation fragments or the presence of multiple binding sites on the two ligands. Therefore, the role of carbohydrates in the recognition process was investigated. Among the carbohydrates tested, constitutive of the conidial wall or of the oligosaccharide side chains of laminin and fibrinogen, only N-acetylneuraminic acid and sialyllactose inhibited the binding of these glycoproteins to conidia. In conclusion, these results strengthen the idea that the laminin and fibrinogen receptors in A. fumigatus are identical and suggest an interaction mediated by a sialic acid-specific lectin of the conidial wall. PMID:9199441

Bouchara, J P; Sanchez, M; Chevailler, A; Marot-Leblond, A; Lissitzky, J C; Tronchin, G; Chabasse, D

1997-01-01

45

Fibronectin and laminin binding of urogenital and oral prevotella species.  

PubMed

88 strains of five Prevotella species--P. bivia, P. buccae, P. disiens, P. oralis, and P. oris--were examined for their fibronectin and laminin binding properties with the aid of latex particle agglutination assays. Beside single protein binding activities, all species showed strains that adhered to both fibronectin and laminin. The oral species, P. buccae, P. oralis, and P. oris were found to interact with laminin to a pronouncedly higher extent than with fibronectin. The urogenital species, P. bivia and P. disiens showed comparable activities of binding to fibronectin and laminin, with P. bivia exhibiting higher matrix protein binding rates than P. disiens. Within the oral species group, P. oralis showed a higher percentage of fibronectin and laminin reactive strains than did P. buccae and P. oris. The finding of species-related different binding properties may throw some light on the known differences in clinical relevance and pathogenicity of the urogenital species, P. bivia and P. disiens, but does so only in part concerning the oral species, P. buccae, P. oralis, and P. oris. Moreover, the observed differences in matrix protein binding of Prevotella species may have implications in chemotaxis and opsonization on the one hand and maintenance of colonization activities under antibiotic therapy on the other. PMID:9861680

Eiring, P; Waller, K; Widmann, A; Werner, H

1998-11-01

46

Laminins in the adult and aged brain  

Microsoft Academic Search

Only recently have we become aware of the diversity of laminins in adult brain. In vascular basement membranes, the expression\\u000a of at least five laminin chains has been demonstrated, suggesting the presence of several laminin variants. Recent ultrastructural\\u000a evidence for heterogeneity of laminin expression in vascular basement membranes is an exciting finding, and points to structural\\u000a and functional diversity of

Mathias Jucker; Min Tian; Donald K. Ingram

1996-01-01

47

Neuronal Death in the Hippocampus Is Promoted by Plasmin-Catalyzed Degradation of Laminin  

Microsoft Academic Search

Excess excitatory amino acids can provoke neuronal death i2n the hippocampus, and the extracellular proteases tissue plasminogen activator (tPA) and plasmin (ogen) have been implicated in this death. To investigate substrates for plasmin that might influence neuronal degeneration, extracellular matrix (ECM) protein expression was examined. Laminin is expressed in the hippocampus and disappears after excitotoxin injection. Laminin disappearance precedes neuronal

Zu-Lin Chen; Sidney Strickland

1997-01-01

48

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

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

49

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

50

A Novel Monoclonal Antibody to Human Laminin ?5 Chain Strongly Inhibits Integrin-Mediated Cell Adhesion and Migration on Laminins 511 and 521  

PubMed Central

Laminins, a large family of ??? heterotrimeric proteins mainly found in basement membranes, are strong promoters of adhesion and migration of multiple cell types, such as tumor and immune cells, via several integrin receptors. Among laminin ? (LM?) chains, ?5 displays the widest tissue distribution in adult life and is synthesized by most cell types. Here, we have generated and characterized five novel monoclonal antibodies (mAbs) to the human LM?5 chain to further study the biological relevance of ?5 laminins, such as laminins 511 (?5?1?1) and 521 (?5?2?1). As detected by ELISA, immunohistochemistry, immunoprecipitation and Western blotting, each antibody displayed unique properties when compared to mAb 4C7, the prototype LM?5 antibody. Of greatest interest, mAb 8G9, but not any other antibody, strongly inhibited ?3?1/?6?1 integrin-mediated adhesion and migration of glioma, melanoma, and carcinoma cells on laminin-511 and, together with mAb 4C7, on laminin-521. Accordingly, mAb 8G9 abolished the interaction of soluble ?3?1 integrin with immobilized laminins 511 and 521. Binding of mAb 8G9 to laminin-511 was unaffected by the other mAbs to the LM?5 chain but largely hindered by mAb 4E10 to a LM?1 chain epitope near the globular domain of laminin-511. Thus, mAb 8G9 defines a novel epitope localized at or near the integrin-binding globular domain of the LM?5 chain, which is essential for cell adhesion and migration, and identifies a potential therapeutic target in malignant and inflammatory diseases. PMID:23308268

Wondimu, Zenebech; Omrani, Shahin; Ishikawa, Taichi; Javed, Fawad; Oikawa, Yuko; Juronen, Erkki; Ingerpuu, Sulev; Patarroyo, Manuel

2013-01-01

51

Prostate specific membrane antigen produces pro-angiogenic laminin peptides downstream of matrix metalloprotease-2.  

PubMed

Prostate specific membrane antigen (PSMA) is a pro-angiogenic cell-surface protease that we previously demonstrated regulates blood vessel formation in a laminin and integrin ?1-dependent manner. Here, we examine the principal mechanism of PSMA activation of integrin ?1. We show that digesting laminin sequentially with recombinant matrix metalloprotease-2 (MMP-2) and PSMA generates small peptides that enhance endothelial cell adhesion and migration in vitro. We also provide evidence that these laminin peptides activate adhesion via integrin ?6?1 and focal adhesion kinase. Using an in vivo Matrigel implant assay, we show that these MMP/PSMA-derived laminin peptides also increase angiogenesis in vivo. Together, our results reveal a novel mechanism of PSMA activation of angiogenesis by processing laminin downstream of MMP-2. PMID:23775497

Conway, Rebecca E; Joiner, Kyle; Patterson, Alex; Bourgeois, David; Rampp, Robert; Hannah, Benjamin C; McReynolds, Samantha; Elder, John M; Gilfilen, Hannah; Shapiro, Linda H

2013-10-01

52

Oolemma receptors and oocyte activation.  

PubMed

At fertilization the sperm triggers a series of intracellular calcium oscillations that are pivotal to oocyte activation and development. Although the biological significance of the characteristic intracellular calcium (Ca(2+)(i)) oscillations is not fully understood, calcium ions are known to be involved in cortical granule release and in controlling cell cycle progression. Two different hypotheses attempt to explain how sperm initiate (Ca(2+)(i)) oscillations in mammalian oocytes. One hypothesis is that spermatozoa interact with a receptor located in the plasma membrane of the oocyte, which results in induction of pathways leading to activation. This receptor is coupled to a GTP-binding protein or to have tyrosine kinase activity and have the ability to induce activation of phospholipase C (PLC). In turn, PLC stimulates the hydrolysis of phosphatidyl inositol (4,5)-bisphosphate (PIP2) to produce diacylglycerol (DAG) and 1,4,5 inositol trisphosphate (IP3), a common Ca(2+) releasing compound. Most studies used to develop the mammalian model of oocyte activation have been performed in the mouse. There is a paucity of information from other mammalian models. The predominant mouse model of oocyte activation is that there is a soluble factor (PLC-zeta) delivered to the cytosol after fertilization that induces oocyte activation. However, as data in other mammals is collected, substantial evidence is beginning to support the existence of other more complex oocyte activation pathways in both murine and non-murine systems. Indeed, activation may involve redundant processes, each of which acting alone may be able to induce aspects of oocyte activation. Recent findings demonstrate the involvement of receptors that are known to associate in large, multimeric complexes. This fact leads one to speculate that the process of oocyte activation by the sperm cell is a highly complex and elaborate process that likely involves many more players than perhaps was initially expected. PMID:20397882

White, Kenneth L; Pate, Barry J; Sessions, Benjamin R

2010-10-01

53

Responses of cultured neural retinal cells to substratum-bound laminin and other extracellular matrix molecules.  

PubMed

The responses of cultured chick embryo retinal neurons to several extracellular matrix molecules are described. Retinal cell suspensions in serum-free medium containing the "N1" supplement (J. E. Bottenstein, S. D. Skaper, S. Varon, and J. Sato, 1980, Exp. Cell Res. 125, 183-190) were seeded on tissue culture plastic surfaces pretreated with polyornithine (PORN) and with one of the factors to be tested. Substantial cell survival could be observed after 72 hr in vitro on PORN pretreated with serum or laminin, whereas most cells appeared to be degenerating on untreated PORN, PORN-fibronectin, and PORN-chondronectin. Cell attachment, although quantitatively similar for all these substrata, was temperature-dependent on serum and laminin but not on fibronectin or untreated PORN. In a short-term bioassay, neurite development was abundant on laminin, scarce on serum and fibronectin, and absent on PORN. No positive correlation between cell spreading and neurite production could be seen: cell spreading was more extensive on PORN and fibronectin than on laminin or serum, while on laminin-treated dishes, spreading was similar for neurite-bearing and non-neurite-bearing cells. Laminin effects on retinal neurons were clearly substratum dependent. When bound to tissue culture plastic, laminin showed a dose-dependent inhibitory effect on cell attachment and did not stimulate neurite development. PORN-bound laminin, on the other hand, did not affect cell attachment but caused marked stimulation of neurite development, suggesting that laminin conformation and/or the spatial distribution of active sites play an important role in the neurite-promoting function of this extracellular matrix molecule. Investigation of the embryonic retina with ELISA and immunocytochemical methods showed that laminin is present in this organ during development. Therefore, in vivo and in vitro observations are consistent with the possibility that laminin might influence neuronal development in the retina. PMID:3902534

Adler, R; Jerdan, J; Hewitt, A T

1985-11-01

54

Laminin ?5 guides tissue patterning and organogenesis  

PubMed Central

Laminins (LM) are extracellular matrix molecules that contribute to and are required for the formation of basement membranes. They participate in the modulation of epithelial/mesenchymal interactions and are implicated in organogenesis and maintenance of organ homeostasis. Among the LM molecules, the LM ?5 chain (LM?5) is one of the most widely distributed LM in the developing and mature organism. Its presence in some basement membranes during embryogenesis is absolutely required for maintenance of basement membrane integrity and thus for proper organogenesis. LM?5 also regulates the expression of genes important for major biological processes, in part by repressing or activating signaling pathways, depending upon the physiological context. PMID:23076210

Spenle, Caroline; Simon-Assmann, Patricia; Orend, Gertraud; Miner, Jeffrey H.

2013-01-01

55

Dissecting the mechanism of torso receptor activation  

Microsoft Academic Search

Regulated activation of receptor tyrosine kinases depends both on the presence of the receptors at the cell surface and on the availability of their ligands. In Drosophila the torso (tor) tyrosine kinase receptor is distributed along the surface of the embryo but it is only activated at the poles by a diffusible extracellular ligand generated at each pole which is

Marc Furriols; Andreu Casali; Jordi Casanova

1998-01-01

56

Activation of peroxisome proliferator-activated receptors (PPARs) by their ligands and protein kinase A activators  

E-print Network

1 Activation of peroxisome proliferator-activated receptors (PPARs) by their ligands and protein title: PKA activators modulate PPAR activity Keywords: peroxisome-proliferator activated receptor electrophoresis; PKA, protein kinase A; PPAR, peroxisome proliferator-activated receptors; RXR, retinoid X

Paris-Sud XI, Université de

57

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; Bachinger, Hans Peter; Tonge, David

2010-01-01

58

Protein kinase activity of the insulin receptor.  

PubMed Central

The insulin receptor is an integral membrane glycoprotein (Mr approximately 300,000) composed of two alpha-subunits (Mr approximately 130,000) and two beta-subunits (Mr approximately 95,000) linked by disulphide bonds. This oligomeric structure divides the receptor into two functional domains such that alpha-subunits bind insulin and beta-subunits possess tyrosine kinase activity. The amino acid sequence deduced from cDNA of the single polypeptide chain precursor of human placental insulin receptor revealed that alpha- and beta-subunits consist of 735 and 620 residues, respectively. The alpha-subunit is hydrophilic, disulphide-bonded, glycosylated and probably extracellular. The beta-subunit consists of a short extracellular region which links the alpha-subunit through disulphide bridges, a hydrophobic transmembrane region and a longer cytoplasmic region which is structurally homologous with other tyrosine kinases like the src oncogene product and EGF receptor kinases. The cellular function of insulin receptors is dual: transmembrane signalling and endocytosis of hormone. The binding of insulin to its receptor on the cell membrane induces transfer of signal from extracellular to cytoplasmic receptor domains leading to activation of cell metabolism and growth. In addition, hormone-receptor complexes are internalized leading to intracellular proteolysis of insulin, whereas receptors are recycled to the membrane. These phenomena are kinetically well-characterized, but their molecular mechanisms remain obscure. Insulin receptor in different tissues and animal species are homologous in their structure and function, but show also significant differences regarding size of alpha-subunits, binding kinetics, insulin specificity and receptor-mediated degradation. We suggest that this heterogeneity of receptors may be linked to the diversity in insulin effects on metabolism and growth in various cell types. The purified insulin receptor phosphorylates its own beta-subunit and exogenous protein and peptide substrates on tyrosine residues, a reaction which is insulin-sensitive, Mn2+-dependent and specific for ATP. Tyrosine phosphorylation of the beta-subunit activates receptor kinase activity, and dephosphorylation with alkaline phosphatase deactivates the kinase. In intact cells or impure receptor preparations, a serine kinase is also activated by insulin. The cellular role of two kinase activities associated with the insulin receptor is not known, but we propose that the tyrosine- and serine-specific kinases mediate insulin actions on metabolism and growth either through dual-signalling or sequential pathways.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 3. Fig. 5. PMID:3017297

Gammeltoft, S; Van Obberghen, E

1986-01-01

59

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

60

Dystroglycan matrix receptor function in cardiac myocytes is important for limiting activity-induced myocardial damage  

PubMed Central

Rationale Genetic mutations in a number of putative glycosyltransferases lead to the loss of glycosylation of dystroglycan and loss of its laminin binding activity in genetic forms of human muscular dystrophy. Human patients and glycosylation defective myd mice develop cardiomyopathy with loss of dystroglycan matrix receptor function in both striated and smooth muscle. Objective To determine the functional role of dystroglycan in cardiac muscle and smooth muscle in the development of cardiomyopathy in muscular dystrophies. Methods and results Using Cre/lox mediated gene targeting, we show here that loss of dystroglycan function in ventricular cardiac myocytes is sufficient to induce a progressive cardiomyopathy in mice characterized by focal cardiac fibrosis, increase in cardiac mass, and dilatation ultimately leading to heart failure. In contrast, disruption of dystroglycan in smooth muscle is not sufficient to induce cardiomyopathy. The specific loss of dystroglycan function in cardiac myocytes causes the accumulation of large, clustered patches of myocytes with membrane damage, which increase in number in response to exercise induced cardiac stress, while exercised mice with normal dystroglycan expression accumulate membrane damage limited to individual myocytes. Conclusions Our findings suggest dystroglycan function as an extracellular matrix receptor in cardiac myocytes plays a primary role in limiting myocardial damage from spreading to neighboring cardiac myocytes, and loss of dystroglycan matrix receptor function in cardiac muscle cells is likely important in the development of cardiomyopathy in glycosylation-deficient muscular dystrophies. PMID:19797173

Michele, Daniel E.; Kabaeva, Zhyldyz; Davis, Sarah L.; Weiss, Robert M.; Campbell, Kevin P.

2009-01-01

61

Tethering a laminin peptide to a crosslinked collagen scaffold for biofunctionality.  

PubMed

Cell adhesion peptide regulates various cellular functions like proliferation, attachment, and spreading. The cellular response to laminin peptide (PPFLMLLKGSTR), a motif of laminin-5 alpha3 chain, tethered to type I collagen, crosslinked using microbial transglutaminase (mTGase) was investigated. mTGase is an enzyme that initiates crosslinking by reacting with the glutamine and lysine residues on the collagen fibers stabilizing the molecular structure. In this study that tethering of the laminin peptide in a mTGase crosslinked collagen scaffold enhanced cell proliferation and attachment. Laminin peptide tethered crosslinked scaffold showed unaltered cell morphology of 3T3 fibroblasts when compared with collagen and crosslinked scaffold. The triple helical structure of collagen remained unaltered by the addition of laminin peptide. In addition a dose-dependent affinity of the laminin peptide towards collagen was seen. The degree of crosslinking was measured by amino acid analysis, differential scanning calorimeter and fourier transform infrared spectroscopy. Increased crosslinking was observed in mTGase crosslinked group. mTGase crosslinking showed higher shrinkage temperature. There was alteration in the fibrillar architecture due to the crosslinking activity of mTGase. Hence, the use of enzyme-mediated linking shows promise in tethering cell adhesive peptides through biodegradable scaffolds. PMID:18478551

Damodaran, Gopinath; Collighan, Russell; Griffin, Martin; Pandit, Abhay

2009-06-15

62

Modulating Estrogen Receptor-related Receptor-? Activity Inhibits Cell Proliferation*  

PubMed Central

High expression of the estrogen receptor-related receptor (ERR)-? in human tumors is correlated to a poor prognosis, suggesting an involvement of the receptor in cell proliferation. In this study, we show that a synthetic compound (XCT790) that modulates the activity of ERR? reduces the proliferation of various cell lines and blocks the G1/S transition of the cell cycle in an ERR?-dependent manner. XCT790 induces, in a p53-independent manner, the expression of the cell cycle inhibitor p21waf/cip1 at the protein, mRNA, and promoter level, leading to an accumulation of hypophosphorylated Rb. Finally, XCT790 reduces cell tumorigenicity in Nude mice. PMID:19546226

Bianco, Stéphanie; Lanvin, Olivia; Tribollet, Violaine; Macari, Claire; North, Sophie; Vanacker, Jean-Marc

2009-01-01

63

Differential Activation of Peroxisome Proliferator-activated Receptors by Eicosanoids  

Microsoft Academic Search

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that regulate gene tran- scription in response to peroxisome proliferators and fatty acids. PPARs also play an important role in the regulation of adipocyte differentiation. It is unclear, however, what naturally occurring compounds activate each of the PPAR subtypes. To address this issue, a screening assay was established using heterologous fu- sions

W. Bayona; Caleb B. Kallen; Heather P. Harding; Christina P. Ravera; Gerald McMahon; Myles Browni; Mitchell A. Lazar

1995-01-01

64

Astrocytic laminin regulates pericyte differentiation and maintains blood brain barrier integrity  

PubMed Central

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. PMID:24583950

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

2014-01-01

65

Using Nuclear Receptor Activity to Stratify Hepatocarcinogens  

PubMed Central

Background Nuclear receptors (NR) are a superfamily of ligand-activated transcription factors that control a range of cellular processes. Persistent stimulation of some NR is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. Here we report on a systematic analysis of new in vitro human NR activity data on 309 environmental chemicals in relationship to their liver cancer-related chronic outcomes in rodents. Results The effects of 309 environmental chemicals on human constitutive androstane receptors (CAR/NR1I3), pregnane X receptor (PXR/NR1I2), aryl hydrocarbon receptor (AhR), peroxisome proliferator-activated receptors (PPAR/NR1C), liver X receptors (LXR/NR1H), retinoic X receptors (RXR/NR2B) and steroid receptors (SR/NR3) were determined using in vitro data. Hepatic histopathology, observed in rodents after two years of chronic treatment for 171 of the 309 chemicals, was summarized by a cancer lesion progression grade. Chemicals that caused proliferative liver lesions in both rat and mouse were generally more active for the human receptors, relative to the compounds that only affected one rodent species, and these changes were significant for PPAR (p0.001), PXR (p0.01) and CAR (p0.05). Though most chemicals exhibited receptor promiscuity, multivariate analysis clustered them into relatively few NR activity combinations. The human NR activity pattern of chemicals weakly associated with the severity of rodent liver cancer lesion progression (p0.05). Conclusions The rodent carcinogens had higher in vitro potency for human NR relative to non-carcinogens. Structurally diverse chemicals with similar NR promiscuity patterns weakly associated with the severity of rodent liver cancer progression. While these results do not prove the role of NR activation in human liver cancer, they do have implications for nuclear receptor chemical biology and provide insights into putative toxicity pathways. More importantly, these findings suggest the utility of in vitro assays for stratifying environmental contaminants based on a combination of human bioactivity and rodent toxicity. PMID:21339822

Shah, Imran; Houck, Keith; Judson, Richard S.; Kavlock, Robert J.; Martin, Matthew T.; Reif, David M.; Wambaugh, John; Dix, David J.

2011-01-01

66

Laminin ?1 is essential for mouse cerebellar development  

PubMed Central

Laminin ?1 (Lama1), which is a subunit of laminin-1 (laminin-111), a heterotrimeric ECM protein, is essential for embryonic development and promotes neurite outgrowth in culture. Because the deletion of Lama1 causes lethality at early embryonic stages in mice, the in vivo role of Lama1 in neural development and functions has not yet been possible to determine. In this study, we generated conditional Lama1 knockout (Lama1CKO) mice in the epiblast lineage using Sox2-Cre mice. These Lama1CKO mice survived, but displayed behavioral disorders and impaired formation of the cerebellum. Deficiency of Lama1 in the pial basement membrane of the meninges resulted in defects in the conformation of the meninges. During cerebellar development, Lama1 deficiency also caused a decrease in the proliferation and migration of granule cell precursors, disorganization of Bergmann glial fibers and endfeet, and a transient reduction in the activity of Akt. A marked reduction in numbers of dendritic processes in Purkinje cells was observed in Lama1CKO mice. Together, these results indicate that Lama1 is required for cerebellar development and functions. PMID:21983115

Ichikawa-Tomikawa, Naoki; Ogawa, Junko; Douet, Vanessa; Xu, Zhuo; Kamikubo, Yuji; Sakurai, Takashi; Kohsaka, Shinichi; Chiba, Hideki; Hattori, Nobutaka; Yamada, Yoshihiko; Arikawa-Hirasawa, Eri

2011-01-01

67

NMDA Receptor Activity in Neuropsychiatric Disorders  

PubMed Central

N-Methyl-d-aspartate (NMDA) receptors play a variety of physiologic roles and their proper signaling is essential for cellular homeostasis. Any disruption in this pathway, leading to either enhanced or decreased activity, may result in the manifestation of neuropsychiatric pathologies such as schizophrenia, mood disorders, substance induced psychosis, Huntington’s disease, Alzheimer’s disease, and neuropsychiatric systemic lupus erythematosus. Here, we explore the notion that the overlap in activity of at least one biochemical pathway, the NMDA receptor pathway, may be the link to understanding the overlap in psychotic symptoms between diseases. This review intends to present a broad overview of those neuropsychiatric disorders for which alternations in NMDA receptor activity is prominent thus suggesting that continued direction of pharmaceutical intervention to this pathway may present a viable option for managing symptoms. PMID:23772215

Lakhan, Shaheen E.; Caro, Mario; Hadzimichalis, Norell

2013-01-01

68

The Extracellular Matrix Protein Laminin ?2 Regulates the Maturation and Function of the Blood-Brain Barrier.  

PubMed

Laminins are major constituents of the gliovascular basal lamina of the blood-brain barrier (BBB); however, the role of laminins in BBB development remains unclear. Here we report that Lama2(-/-) mice, lacking expression of the laminin ?2 subunit of the laminin-211 heterotrimer expressed by astrocytes and pericytes, have a defective BBB in which systemically circulated tracer leaks into the brain parenchyma. The Lama2(-/-) vascular endothelium had significant abnormalities, including altered integrity and composition of the endothelial basal lamina, inappropriate expression of embryonic vascular endothelial protein MECA32, substantially reduced pericyte coverage, and tight junction abnormalities. Additionally, astrocytic endfeet were hypertrophic and lacked appropriately polarized aquaporin4 channels. Laminin-211 appears to mediate these effects at least in part by dystroglycan receptor interactions, as preventing dystroglycan expression in neural cells led to a similar set of BBB abnormalities and gliovascular disturbances, which additionally included perturbed vascular endothelial glucose transporter-1 localization. These findings provide insight into the cell and molecular changes that occur in congenital muscular dystrophies caused by Lama2 mutations or inappropriate dystroglycan post-translational modifications, which have accompanying brain abnormalities, including seizures. Our results indicate a novel role for laminin-dystroglycan interactions in the cooperative integration of astrocytes, endothelial cells, and pericytes in regulating the BBB. PMID:25392494

Menezes, Michael J; McClenahan, Freyja K; Leiton, Cindy V; Aranmolate, Azeez; Shan, Xiwei; Colognato, Holly

2014-11-12

69

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

70

Laminin-211 in skeletal muscle function  

PubMed Central

A chain is no stronger than its weakest link is an old idiom that holds true for muscle biology. As the name implies, skeletal muscle’s main function is to move the bones. However, for a muscle to transmit force and withstand the stress that contractions give rise to, it relies on a chain of proteins attaching the cytoskeleton of the muscle fiber to the surrounding extracellular matrix. The importance of this attachment is illustrated by a large number of muscular dystrophies caused by interruption of the cytoskeletal-extracellular matrix interaction. One of the major components of the extracellular matrix is laminin, a heterotrimeric glycoprotein and a major constituent of the basement membrane. It has become increasingly apparent that laminins are involved in a multitude of biological functions, including cell adhesion, differentiation, proliferation, migration and survival. This review will focus on the importance of laminin-211 for normal skeletal muscle function. PMID:23154401

Holmberg, Johan; Durbeej, Madeleine

2013-01-01

71

Bisecting GlcNAc Residues on Laminin-332 Down-regulate Galectin-3-dependent Keratinocyte Motility*  

PubMed Central

Laminin-332 (Lm332; formerly laminin-5) is a basement membrane protein in the skin, which promotes cell motility in wound healing and cancer invasion. In a previous study, we reported that the introduction of bisecting GlcNAc into Lm332 (GnT-III-Lm332), catalyzed by N-acetylglucosaminyltransferase III (GnT-III), reduced cell migration (Kariya, Y., Kato, R., Itoh, S., Fukuda, T., Shibukawa, Y., Sanzen, N., Sekiguchi, K., Wada, Y., Kawasaki, N., and Gu, J. (2008) J. Biol. Chem. 283, 33036–33045). However, the underlying molecular mechanism by which GnT-III-Lm332 suppresses the normal biological functions of Lm332 remains to be elucidated. In this study, we show that galectin-3, which is a ?-galactoside-binding protein, strongly bound to unmodified Lm332 but not to GnT-III-Lm332 and that binding of galectin-3 was completely blocked by lactose. Exogenous galectin-3 significantly enhanced keratinocyte cell motility on control Lm332 but not on GnT-III-Lm332. A functional blocking antibody against galectin-3 inhibited Lm332-induced ?3?1 and ?6?4 integrin clustering and focal contact formation. Co-immunoprecipitation revealed that galectin-3 associated with both ?4 integrin and epidermal growth factor receptor, thereby cross-linking the two molecules. The associations were inhibited by either the presence of lactose or expression of GnT-III. Moreover, galectin-3 consistently enhanced ERK activation. Taken together, the results of this study are the first to clearly identify the molecular mechanism responsible for the inhibitory effects of GnT-III on extracellular matrix-integrin-meditated cell adhesion, migration, and signal transduction. The findings presented herein shed light on the importance of N-glycosylation-mediated supramolecular complex formation on the cell surface. PMID:19940114

Kariya, Yoshinobu; Kawamura, Chihiro; Tabei, Toshiki; Gu, Jianguo

2010-01-01

72

Activation of insulin receptors by lagerstroemin.  

PubMed

Lagerstroemin, an ellagitannin isolated from the leaves of Lagerstroemia speciosa (L.) Pers. (Lythraceae), was examined for its biological activities. In rat adipocytes, the compound increased the rate of glucose uptake and decreased the isoproterenol-induced glycerol release. In Chinese hamster ovary cells expressing human insulin receptors, it increased the Erk activity. These insulin-like actions were accompanied by the increased tyrosine-phosphorylation of the beta-subunit of the insulin receptors. Tryptic digestion of the extracellular sites of the insulin receptors markedly increased the effective concentrations of insulin without changing those of lagerstroemin. Thus lagerstroemin was considered to cause its insulin-like actions by a mechanism different from that employed by insulin. PMID:14501154

Hattori, Katsuji; Sukenobu, Naoe; Sasaki, Tomo; Takasuga, Shunsuke; Hayashi, Takeo; Kasai, Ryoji; Yamasaki, Kazuo; Hazeki, Osamu

2003-09-01

73

Regeneration of Aplysia Bag Cell Neurons is Synergistically Enhanced by Substrate-Bound Hemolymph Proteins and Laminin  

NASA Astrophysics Data System (ADS)

We have investigated Aplysia hemolymph as a source of endogenous factors to promote regeneration of bag cell neurons. We describe a novel synergistic effect between substrate-bound hemolymph proteins and laminin. This combination increased outgrowth and branching relative to either laminin or hemolymph alone. Notably, the addition of hemolymph to laminin substrates accelerated growth cone migration rate over ten-fold. Our results indicate that the active factor is either a high molecular weight protein or protein complex and is not the respiratory protein hemocyanin. Substrate-bound factor(s) from central nervous system-conditioned media also had a synergistic effect with laminin, suggesting a possible cooperation between humoral proteins and nervous system extracellular matrix. Further molecular characterization of active factors and their cellular targets is warranted on account of the magnitude of the effects reported here and their potential relevance for nervous system repair.

Hyland, Callen; Dufrense, Eric R.; Forscher, Paul

2014-04-01

74

Regeneration of Aplysia Bag Cell Neurons is Synergistically Enhanced by Substrate-Bound Hemolymph Proteins and Laminin  

PubMed Central

We have investigated Aplysia hemolymph as a source of endogenous factors to promote regeneration of bag cell neurons. We describe a novel synergistic effect between substrate-bound hemolymph proteins and laminin. This combination increased outgrowth and branching relative to either laminin or hemolymph alone. Notably, the addition of hemolymph to laminin substrates accelerated growth cone migration rate over ten-fold. Our results indicate that the active factor is either a high molecular weight protein or protein complex and is not the respiratory protein hemocyanin. Substrate-bound factor(s) from central nervous system-conditioned media also had a synergistic effect with laminin, suggesting a possible cooperation between humoral proteins and nervous system extracellular matrix. Further molecular characterization of active factors and their cellular targets is warranted on account of the magnitude of the effects reported here and their potential relevance for nervous system repair. PMID:24722588

Hyland, Callen; Dufrense, Eric R.; Forscher, Paul

2014-01-01

75

Common mechanisms activate plant guard receptors and TLR4.  

PubMed

In metazoans, the innate immune system uses Pattern Recognition Receptors to detect conserved microbial products, whereas in plants Guard Receptors detect virulence factors or activities encoded by pathogens. In a recent study, Williams and colleagues report that plant Guard receptors can be activated by a mechanism remarkably similar to that of mammalian Toll-like Receptor 4. PMID:25224694

Kagan, Jonathan C

2014-10-01

76

Cytokine receptor dimerization and activation: prospects for small molecule agonists  

Microsoft Academic Search

Ligand-induced dimerization of cell surface receptors has emerged as a general mechanism for the initiation of signal transduction. A number of therapeutically important receptor families are believed to be activated by this process. Recently available structural information, particularly for the erythropoietin receptor, has provided insight into the mechanism of receptor activation. These findings have also revealed important constraints on the

Dale L. Boger; Joel Goldberg

2001-01-01

77

Laminin5 Inhibits Human Keratinocyte Migration  

Microsoft Academic Search

Laminin-5 (previously known as kalinin, epiligrin, and nicein) is an adhesive protein localized to the anchoring filaments within the lamina lucida space of the basement membrane zone lying between the epidermis and dermis of human skin. Anchoring filaments are structures within the lamina lucida and lie immediately beneath the hemidesmosomes of the overlying basal keratinocytes apposed to the basement membrane

Edel A. O'Toole; M. Peter Marinkovich; Warren K. Hoeffler; Heinz Furthmayr; David T. Woodley

1997-01-01

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

A Fractal Nature for Polymerized Laminin  

PubMed Central

Polylaminin (polyLM) is a non-covalent acid-induced nano- and micro-structured polymer of the protein laminin displaying distinguished biological properties. Polylaminin stimulates neuritogenesis beyond the levels achieved by ordinary laminin and has been shown to promote axonal regeneration in animal models of spinal cord injury. Here we used confocal fluorescence microscopy (CFM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize its three-dimensional structure. Renderization of confocal optical slices of immunostained polyLM revealed the aspect of a loose flocculated meshwork, which was homogeneously stained by the antibody. On the other hand, an ordinary matrix obtained upon adsorption of laminin in neutral pH (LM) was constituted of bulky protein aggregates whose interior was not accessible to the same anti-laminin antibody. SEM and AFM analyses revealed that the seed unit of polyLM was a flat polygon formed in solution whereas the seed structure of LM was highly heterogeneous, intercalating rod-like, spherical and thin spread lamellar deposits. As polyLM was visualized at progressively increasing magnifications, we observed that the morphology of the polymer was alike independently of the magnification used for the observation. A search for the Hausdorff dimension in images of the two matrices showed that polyLM, but not LM, presented fractal dimensions of 1.55, 1.62 and 1.70 after 1, 8 and 12 hours of adsorption, respectively. Data in the present work suggest that the intrinsic fractal nature of polymerized laminin can be the structural basis for the fractal-like organization of basement membranes in the neurogenic niches of the central nervous system. PMID:25296244

Hochman-Mendez, Camila; Cantini, Marco; Moratal, David; Salmeron-Sanchez, Manuel; Coelho-Sampaio, Tatiana

2014-01-01

80

A fractal nature for polymerized laminin.  

PubMed

Polylaminin (polyLM) is a non-covalent acid-induced nano- and micro-structured polymer of the protein laminin displaying distinguished biological properties. Polylaminin stimulates neuritogenesis beyond the levels achieved by ordinary laminin and has been shown to promote axonal regeneration in animal models of spinal cord injury. Here we used confocal fluorescence microscopy (CFM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize its three-dimensional structure. Renderization of confocal optical slices of immunostained polyLM revealed the aspect of a loose flocculated meshwork, which was homogeneously stained by the antibody. On the other hand, an ordinary matrix obtained upon adsorption of laminin in neutral pH (LM) was constituted of bulky protein aggregates whose interior was not accessible to the same anti-laminin antibody. SEM and AFM analyses revealed that the seed unit of polyLM was a flat polygon formed in solution whereas the seed structure of LM was highly heterogeneous, intercalating rod-like, spherical and thin spread lamellar deposits. As polyLM was visualized at progressively increasing magnifications, we observed that the morphology of the polymer was alike independently of the magnification used for the observation. A search for the Hausdorff dimension in images of the two matrices showed that polyLM, but not LM, presented fractal dimensions of 1.55, 1.62 and 1.70 after 1, 8 and 12 hours of adsorption, respectively. Data in the present work suggest that the intrinsic fractal nature of polymerized laminin can be the structural basis for the fractal-like organization of basement membranes in the neurogenic niches of the central nervous system. PMID:25296244

Hochman-Mendez, Camila; Cantini, Marco; Moratal, David; Salmeron-Sanchez, Manuel; Coelho-Sampaio, Tatiana

2014-01-01

81

Vimentin and laminin expression is associated with basal-like phenotype in both sporadic and BRCA1-associated breast carcinomas  

PubMed Central

Aims To determine whether basal?like phenotype and vimentin and/or laminin are related in both sporadic/familial (BRCA1 or BRCA2 mutated) tumours. Methods 230 non?familial and 28 hereditary node?negative invasive breast carcinomas were immunohistochemically analysed for oestrogen receptors (ER), progesterone receptors (PR), cytokeratin 5/6 (CK5/6), epidermal growth factor receptors (EGFR), Ki67, p53, vimentin and laminin, using tissue microarrays. Tumours were considered to have basal?like phenotype if they were ER negative and HER2 negative, but positive for CK5/6 and/or EGFR. Results In sporadic tumours, vimentin expression was found in 77.8% cases with basal?like phenotype and 15.5% of non?basal cases (p<0.001). In familial cases, vimentin was expressed in 83.3% basal?like cancers and 16.7% of non?basal tumours (p<0.001). Vimentin expression was more frequent in BRCA1 than BRCA2 mutation carriers. Vimentin expressing tumours were associated with poor prognosis (p?=?0.012) among patients not receiving adjuvant chemotherapy and showed a trend for local recurrence or visceral but not bone metastasis (p?=?0.021). Laminin expression was also related to basal?like phenotype in both sporadic/familial cases (p<0.001 and p?=?0.007, respectively), but neither with prognosis nor recurrence pattern in sporadic cancers. Conclusions Vimentin and laminin expression is associated with basal?like phenotype in breast cancer. Expression of vimentin and laminin is characteristic of BRCA1 associated tumours. Since vimentin and laminin staining is widely used by pathologists for diagnostic purposes, thus demonstrating the robustness of their specific antibodies, the immunohistochemical evaluation of these two molecules could be used in identification of basal?like breast tumours in both sporadic/familial cases. PMID:17105822

Rodriguez-Pinilla, Socorro Maria; Sarrio, David; Honrado, Emiliano; Moreno-Bueno, Gema; Hardisson, David; Calero, Francisco; Benitez, Javier; Palacios, Jose

2007-01-01

82

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

83

Peroxisome-Proliferator-Activated Receptor (PPAR)-? Activation Stimulates Keratinocyte Differentiation  

Microsoft Academic Search

Previous studies demonstrated that peroxisome-proliferator-activated receptor (PPAR)-? or PPAR-? activation stimulates keratinocyte differentiation, is anti-inflammatory, and improves barrier homeostasis. Here we demonstrate that treatment of cultured human keratinocytes with ciglitazone, a PPAR-? activator, increases involucrin and transglutaminase 1 mRNA levels. Moreover, topical treatment of hairless mice with ciglitazone or troglitazone increases loricrin, involucrin, and filaggrin expression without altering epidermal morphology.

Man Mao-Qiang; Ashley J. Fowler; Matthias Schmuth; Peggy Lau; Sandra Chang; Barbara E. Brown; Arthur H. Moser; Liliane Michalik; Beatrice Desvergne; Walter Wahli; Mei Li; Daniel Metzger; Pierre H. Chambon; Peter M. Elias; Kenneth R. Feingold

2004-01-01

84

Laminin in the male germ cells of Drosophila  

PubMed Central

To study genes that may be crucial for the male germ cell development of Drosophila we screened a cDNA expression library with a polyclonal antiserum against testis proteins of Drosophila hydei. We identified a cDNA fragment that exhibited a complete sequence similarity with the cDNA of the laminin B2 chain, an important component of the extracellular matrix. Transcripts of laminin B2 were detected in the RNA of male germ cells with the polymerase chain reaction and by in situ hybridization. We studied the reaction of different polyclonal antibodies including those against a Drosophila laminin B2-lac fusion protein, the entire Drosophila laminin complex, or against the mouse laminin complex and against laminin A and B1 chains with specific structures in developing male germ cells of Drosophila. Antigenic sites against laminin B2 were found in the lampbrush loops in primary spermatocyte nuclei, in nuclei of spermatids, and in heads of spermatozoa. The axonemes of elongating spermatids react with antibodies against the Drosophila laminin B1, B2 and laminin A chains. The possible biological functions of the laminin in the male germ cells of Drosophila are discussed. PMID:1429843

1992-01-01

85

Angiotensin Type 1 Receptor Blockers Induce Peroxisome Proliferator-Activated Receptor Activity  

Microsoft Academic Search

Background—Angiotensin type 1 receptor (AT1R) blockers (ARB) have been shown to reduce the incidence of type 2 diabetes mellitus by an unknown molecular mechanism. The peroxisome proliferator-activated receptor- (PPAR )i s the central regulator of insulin and glucose metabolism improving insulin sensitivity. We investigated the regulation of PPAR function by ARBs. Methods and Results—The ARBs irbesartan and telmisartan (10 mol\\/L)

Michael Schupp; Jürgen Janke; Ronald Clasen; Thomas Unger; Ulrich Kintscher

86

Peroxisome proliferator-activated receptors for hypertension.  

PubMed

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

2014-08-26

87

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.

Usuda, Daisuke; Kanda, Tsugiyasu

2014-01-01

88

Pregnenolone sulfate activates NMDA receptor channels.  

PubMed

Pregnenolone sulfate (PS), an endogenously occurring neurosteroid, has been shown to modulate the activity of several neurotransmitter-gated channels, including the NMDA receptor (NMDAR). NMDARs are glutamate-gated ion channels involved in excitatory synaptic transmission, synaptic plasticity, and excitotoxicity. In this study, we analyzed the effects of PS on calcium signaling in cultured hippocampal neurons and HEK293 cells expressing NMDAR. The cells were loaded with the Ca(2+) sensor Fura-2. In agreement with previous electrophysiological experiments, PS potentiated the increases in intracellular Ca(2+) induced by an exogenous application of glutamate; however, PS also increased intracellular Ca(2+) in the absence of exogenous NMDA agonist. The agonist-independent effect of PS was induced in all neurons studied and in HEK293 cells expressing GluN1/GluN2A-B receptors in a neurosteroid-specific manner. We conclude that PS is an endogenous NMDA agonist that activates the GluN1/GluN2A-B receptors. PMID:24359434

Adamusová, E; Cais, O; Vyklický, V; Kudová, E; Chodounská, H; Horák, M; Vyklický, L

2013-12-20

89

Activating and Inactivating Hormone Receptor Mutations  

Microsoft Academic Search

The unravelling of gene structures of hormones, their receptors and the various components of their signal transduction apparatus has enabled diagnosis of the aetiology of hormone resistance at the molecular level. Inactivating mutations can be found in hormone receptor genes or those encoding components of the post-receptor signal transduction cascade. Another category of receptor mutation is that causing constitutive receptor

Ilpo Huhtaniemi

2000-01-01

90

Protease-activated receptor 3 is a second thrombin receptor in humans  

Microsoft Academic Search

Thrombin is a coagulation protease that activates platelets, leukocytes, endothelial and mesenchymal cells at sites of vascular injury, acting partly through an unusual proteolytically activated G-protein-coupled receptor1-3. Knockout of the gene encoding this receptor provided definitive evidence for a second thrombin receptor in mouse platelets and for tissue-specific roles for different thrombin receptors4. We now report the cloning and characterization

Hiroaki Ishihara; Andrew J. Connolly; Dewan Zeng; Mark L. Kahn; Yao Wu Zheng; Courtney Timmons; Tracy Tram; Shaun R. Coughlin

1997-01-01

91

Angiogenic Laminin-Derived Peptides Stimulate Wound Healing  

PubMed Central

Acceleration of the wound healing process by using angiogenic peptides has been demonstrated previously. Here we used select laminin-111 peptides, A13 and C16, from the laminin ?1 and ?1 chain, respectively, to test whether they are able to stimulate wound healing in a rat full thickness wound model. The 12-mer peptides C16 and A13 are highly angiogenic and bind to integrins ?v?3 and ?5?1. We show that A13 increases wound reepithelialization as much as 17% over controls by day 4 and C16 increases coverage by 11%. Contraction of the treated wounds was increased as much as 11% for A13 and 8% for C16 at day 4. No differences were observed at day 7 with either peptide. The peptides also stimulated fibroblast migration in Boyden chamber assays. A13 increased cell migration as much as 2.4-fold on uncoated filters and as much as 16-fold on collagen type IV-coated filters over negative controls. Similarly, C16 also stimulated migration 1.8-fold on uncoated filters and as much as 12-fold on collagen-coated filters. A13 and C16 significantly decreased expression of the pro and active forms of matrix metalloproteinase 2 in foreskin fibroblasts indicating their role in collagen accumulation. We conclude that small bioactive angiogenic peptides can promote dermal wound healing and may offer a new class of stable and chemically manipulable therapeutics for wound healing. PMID:18603014

Malinda, Katherine M.; Wysocki, Annette B.; Koblinski, Jennifer E.; Kleinman, Hynda K.; Ponce, M. Lourdes

2008-01-01

92

Angiogenic laminin-derived peptides stimulate wound healing.  

PubMed

Acceleration of the wound healing process by using angiogenic peptides has been demonstrated previously. Here we used select laminin-111 peptides, A13 and C16, from the laminin alpha1 and gamma1 chain, respectively, to test whether they are able to stimulate wound healing in a rat full thickness wound model. The 12-mer peptides C16 and A13 are highly angiogenic and bind to integrins alphavbeta3 and alpha5beta1. We show that A13 increases wound re-epithelialization as much as 17% over controls by day 4 and C16 increases coverage by 11%. Contraction of the treated wounds was increased as much as 11% for A13 and 8% for C16 at day 4. No differences were observed at day 7 with either peptide. The peptides also stimulated fibroblast migration in Boyden chamber assays. A13 increased cell migration as much as 2.4-fold on uncoated filters and as much as 16-fold on collagen type IV-coated filters over negative controls. Similarly, C16 also stimulated migration 1.8-fold on uncoated filters and as much as 12-fold on collagen-coated filters. A13 and C16 significantly decreased expression of the pro and active forms of matrix metalloproteinase 2 in foreskin fibroblasts indicating their role in collagen accumulation. We conclude that small bioactive angiogenic peptides can promote dermal wound healing and may offer a new class of stable and chemically manipulable therapeutics for wound healing. PMID:18603014

Malinda, Katherine M; Wysocki, Annette B; Koblinski, Jennifer E; Kleinman, Hynda K; Ponce, M Lourdes

2008-01-01

93

Neuregulin and laminin stimulate phosphorylation of the NF2 tumor suppressor in Schwann cells by distinct protein kinase A and p21-activated kinase-dependent pathways  

Microsoft Academic Search

Mutations in the neurofibromatosis type 2 (NF2) gene cause formation of schwannomas and other tumors in the nervous system. The NF2 protein, Schwannomin\\/Merlin, is a cytoskeleton-associated tumor suppressor regulated by phosphorylation at serine 518 (S518). Unphosphorylated Schwannomin restricts cell proliferation in part by inhibiting Rac- and p21-activated kinase (Pak). In a negative-feedback loop, Pak phosphorylates Schwannomin inactivating its ability to

C Thaxton; J Lopera; M Bott; C Fernandez-Valle

2008-01-01

94

Laminin inhibits A ?42 fibril formation in vitro  

Microsoft Academic Search

In the present study, we investigated whether or not laminin inhibits A?42 fibril formation in the same manner as A?40. Both a thioflavine-T fluorometric assay and electron microscopy by negative staining demonstrated laminin to have a concentration-dependent inhibitory effect on A?42 fibril formation. The amyloid fibril formation was inhibited approximately by 70% due to the presence of 1.0 mg\\/ml laminin

Akira Monji; Ken-ichiro Tashiro; Ichiro Yoshida; Yoshihito Hayashi; Nobutada Tashiro

1998-01-01

95

Origin and evolution of laminin gene family diversity.  

PubMed

Laminins are a family of multidomain glycoproteins that are important contributors to the structure of metazoan extracellular matrices. To investigate the origin and evolution of the laminin family, we characterized the full complement of laminin-related genes in the genome of the sponge, Amphimedon queenslandica. As a representative of the Demospongiae, a group consistently placed within the earliest diverging branch of animals by molecular phylogenies, Amphimedon is uniquely placed to provide insight into early steps in the evolution of metazoan gene families. Five Amphimedon laminin-related genes possess the conserved molecular features, and most of the domains found in bilaterian laminins, but all display domain architectures distinct from those of the canonical laminin chain types known from model bilaterians. This finding prompted us to perform a comparative genomic analysis of laminins and related genes from a choanoflagellate and diverse metazoans and to conduct phylogenetic analyses using the conserved Laminin N-terminal domain in order to explore the relationships between genes with distinct architectures. Laminin-like genes appear to have originated in the holozoan lineage (choanoflagellates + metazoans + several other unicellular opisthokont taxa), with several laminin domains originating later and appearing only in metazoan (animal) or eumetazoan (placozoans + ctenophores + cnidarians + bilaterians) laminins. Typical bilaterian ?, ?, and ? laminin chain forms arose in the eumetazoan stem and another chain type that is conserved in Amphimedon, the cnidarian, Nematostella vectensis, and the echinoderm, Strongylocentrotus purpuratus, appears to have been lost independently from the placozoan, Trichoplax adhaerens, and from multiple bilaterians. Phylogenetic analysis did not clearly reconstruct relationships between the distinct laminin chain types (with the exception of the ? chains) but did reveal how several members of the netrin family were generated independently from within the laminin family by duplication and domain shuffling and by domain loss. Together, our results suggest that gene duplication and loss and domain shuffling and loss all played a role in the evolution of the laminin family and contributed to the generation of lineage-specific diversity in the laminin gene complements of extant metazoans. PMID:22319142

Fahey, Bryony; Degnan, Bernard M

2012-07-01

96

Peroxisome Proliferator-activated Receptor-/ Inhibits Epidermal Cell Proliferation by Down-regulation of Kinase Activity*  

E-print Network

Peroxisome Proliferator-activated Receptor- / Inhibits Epidermal Cell Proliferation by Down that peroxisome proliferator- activated receptor (PPAR ) attenuates cell prolifera- tion and skin carcinogenesis/or apoptosis. Peroxisome proliferator-activated receptors (PPARs)1 are members of the nuclear hormone receptor

Omiecinski, Curtis

97

A natural propenoic acid derivative activates peroxisome proliferator-activated receptor-/ (PPAR/)  

E-print Network

A natural propenoic acid derivative activates peroxisome proliferator-activated receptor-/ (PPAR 2010 Keywords: Peroxisome proliferator-activated receptor Natural ligand Cell proliferation Cancer Aims in vivo. Given the structural similarities between these compounds and known peroxisome proliferator

Omiecinski, Curtis

98

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 ...

99

Serotonin receptor activation leads to neurite outgrowth and neuronal survival  

Microsoft Academic Search

Serotonin 5-HT1 receptors are implicated in anxiety and depression. These receptors belong to the family A of G-protein-coupled receptors and couple to inhibitory G-proteins. Recent studies show that chronic activation of 5-HT1A receptors leads to proliferation of hippocampal neurons suggesting that neurogenesis contributes to the effects of antidepressants. However, the molecular mechanisms and pathways involved are not understood. We used

Ashwana D. Fricker; Carl Rios; Lakshmi A. Devi; Ivone Gomes

2005-01-01

100

Laminins affect T cell trafficking and allograft fate.  

PubMed

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

2014-05-01

101

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

102

Ligand Activation of Peroxisome ProliferatorActivated Receptor B Inhibits Colon Carcinogenesis  

E-print Network

Ligand Activation of Peroxisome Proliferator­Activated Receptor B Inhibits Colon Carcinogenesis, Maryland Abstract There is considerable debate whether peroxisome proliferator­ activated receptor B in the literature suggesting that peroxisome proliferator­activated receptor (PPAR)-h either poten- tiates

Omiecinski, Curtis

103

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

104

Nuclear Receptor Peroxisome Proliferator-activated Receptor (PPAR) Is Expressed in Resting Murine Lymphocytes  

Microsoft Academic Search

Peroxisome proliferator-activated receptors (PPARs) are transcription factors that belong to the nuclear hor- mone receptor superfamily. PPAR and PPAR ligands have been demonstrated to exert anti-inflammatory ac- tivities in macrophages by repressing the activities of several transcription factors. PPAR is expressed in T lymphocytes and may play a role in cytokine produc- tion, cellular proliferation, and susceptibility to apo- ptosis.

Dallas C. Jones; Xiaohong Ding; Raymond A. Daynes

2002-01-01

105

Structural insights into G-protein-coupled receptor activation?  

PubMed Central

G-protein-coupled receptors (GPCRs) are the largest family of eukaryotic plasma membrane receptors, and are responsible for the majority of cellular responses to external signals. GPCRs share a common architecture comprising seven transmembrane (TM) helices. Binding of an activating ligand enables the receptor to catalyze the exchange of GTP for GDP in a heterotrimeric G protein. GPCRs are in a conformational equilibrium between inactive and activating states. Crystallographic and spectroscopic studies of the visual pigment rhodopsin and two b-adrenergic receptors have defined some of the conformational changes associated with activation. PMID:18957321

Weis, William I; Kobilka, Brian K

2014-01-01

106

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 Chierici; Ono, Daisuke; Kobayashi, Fumio; Mustafa, Kamal; Wennerberg, Ann; Jimbo, Ryo

2012-01-01

107

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

108

Defining the metabolic effect of peroxisome proliferator-activated receptor ? activation  

E-print Network

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that function as ligand activated transcription factors. There are three identified isotypes: PPAR alpha, PPAR gamma and PPAR delta, together controlling the expression...

Roberts, Lee D

2010-06-08

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

Receptor-Mediated Activation of Heterotrimeric G-Proteins in  

E-print Network

Receptor-Mediated Activation of Heterotrimeric G-Proteins in Living Cells Chris Janetopoulos,* Tian Jin,* Peter Devreotes* Receptor-mediated activation of heterotrimeric GTP­binding proteins (G energy transfer (FRET) between - and - subunits fused to cyan and yellow fluorescent proteins. The G

Devreotes, Peter

111

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors. The three PPAR  

E-print Network

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors February 2012 Peroxisome proliferator- activated receptors (PPARs). This class of nuclear receptor acquired of the proliferation of peroxisomes observed in rodents given fibrates and other chemicals. The role of peroxisome

Cai, Long

112

Cell death sensitization of leukemia cells by opioid receptor activation  

PubMed Central

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

2013-01-01

113

Epidermal growth factor receptor kinase translocation and activation in vivo.  

PubMed

The rat liver epidermal growth factor (EGF) receptor was assessed for EGF-dependent autophosphorylation as well as phosphorylation of a defined exogenous substrate in purified plasmalemma and Golgiendosome fractions isolated from rat liver homogenates. While EGF-dependent kinase activity was readily detected in plasmalemma the corresponding activity in Golgi-endosome fractions required detergent. Consequent to the systemic injection of EGF in vivo, the majority (approximately 60%) of receptor as evaluated by 125I-EGF binding was rapidly lost (T 1/2 approximately 8 min) from the plasmalemma and correspondingly accumulated in the Golgi-endosome fraction in a dose-dependent manner. Electron microscope radioautography of 125I-EGF uptake into Golgi-endosome fractions identified internalization into lipoprotein-filled vesicles of heterogenous size and shape but not into stacked saccules of the Golgi apparatus. Evaluation of receptor kinase activity in plasmalemma fractions isolated at various times after EGF injection in vivo showed more rapid loss of EGF-dependent autophosphorylation activity (T 1/2 approximately 10 s) than of receptor content (T 1/2 approximately 8 min). In contrast to the EGF receptor kinase of the plasmalemma fraction, kinase activity accumulating in endosomes was activated, i.e. maximally stimulated, in the absence of EGF or Triton X-100 in vitro. Furthermore, following the peak time of accumulation of EGF receptor kinase in endosomes (5-15 min) EGF-dependent autophosphorylation activity and EGF receptor content were lost more slowly (T 1/2 approximately 27 and 87 min for the loss of autophosphorylation activity and receptor content, respectively). The rapidity of translocation of activated EGF receptor into endosomes (30 s) and the dose response to low levels (1 microgram) of EGF injected are consistent with a physiological role for internalized EGF receptor kinase activity. PMID:2424897

Kay, D G; Lai, W H; Uchihashi, M; Khan, M N; Posner, B I; Bergeron, J J

1986-06-25

114

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

115

Control of Peroxisome Proliferator-Activated Receptor 2 Stability and Activity by  

E-print Network

Control of Peroxisome Proliferator-Activated Receptor 2 Stability and Activity by SUMOylation Z of peroxisome proliferator-activated receptor 2 stability and activity by SUMOylation. Obes Res. 2004 in reg- ulating the activity of peroxisome proliferator-activated re- ceptor (PPAR ). Research Methods

Stephens, Jacqueline

116

Disruption of microfilaments alters laminin synthesis but not laminin trafficking in NHEK in vitro  

Microsoft Academic Search

Summary  Laminin synthesis and deposition are concomitant with the development of a basal lamina between the human epidermis and the\\u000a underlying dermis. One of the challenges in tissue engineering of human epidermal models is to develop substrates and conditions\\u000a that encourage the development of a basement membrane. The purpose of this study was to determine if actin filaments and\\/or\\u000a microtubules are

Jeffery R. Cook; Robert G. van Buskirk

1996-01-01

117

From laminin to lamin: regulation of tissue-specific gene expression by the ECM  

Microsoft Academic Search

Mammary epithelial cells need a laminin-rich extracellular matrix (ECM) to achieve a functionally differentiated phenotype that includes secretion of milk-specific proteins such as ?-casein. There is good evidence that ECM-induced expression of ?-casein involves an ‘ECM-response element’ in the promoter of the casein gene that is activated by integrin-mediated signalling. This article proposes that ECM-induced structural changes in the cytoskeleton,

Nancy Boudreau; Connie Myers; Mina J. Bissell

1995-01-01

118

Activation and dynamic network of the M2 muscarinic receptor.  

PubMed

G-protein-coupled receptors (GPCRs) mediate cellular responses to various hormones and neurotransmitters and are important targets for treating a wide spectrum of diseases. Although significant advances have been made in structural studies of GPCRs, details of their activation mechanism remain unclear. The X-ray crystal structure of the M2 muscarinic receptor, a key GPCR that regulates human heart rate and contractile forces of cardiomyocytes, was determined recently in an inactive antagonist-bound state. Here, activation of the M2 receptor is directly observed via accelerated molecular dynamics simulation, in contrast to previous microsecond-timescale conventional molecular dynamics simulations in which the receptor remained inactive. Receptor activation is characterized by formation of a Tyr206(5.58)-Tyr440(7.53) hydrogen bond and ?6-Å outward tilting of the cytoplasmic end of transmembrane ?-helix 6, preceded by relocation of Trp400(6.48) toward Phe195(5.47) and Val199(5.51) and flipping of Tyr430(7.43) away from the ligand-binding cavity. Network analysis reveals that communication in the intracellular domains is greatly weakened during activation of the receptor. Together with the finding that residue motions in the ligand-binding and G-protein-coupling sites of the apo receptor are correlated, this result highlights a dynamic network for allosteric regulation of the M2 receptor activation. PMID:23781107

Miao, Yinglong; Nichols, Sara E; Gasper, Paul M; Metzger, Vincent T; McCammon, J Andrew

2013-07-01

119

Tissue factor, protease activated receptors and pathologic heart remodelling.  

PubMed

Tissue factor is the primary initiator of coagulation cascade and plays an essential role in haemostasis and thrombosis. In addition, tissue factor and coagulation proteases contribute to many cellular responses via activation of protease activated receptors. The heart is an organ with high levels of constitutive tissue factor expression. This review focuses on the role of tissue factor, coagulation proteases and protease activated receptors in heart haemostasis and the pathological heart remodelling associated with myocardial infarction, viral myocarditis and hypertension. PMID:25104210

Antoniak, S; Sparkenbaugh, E; Pawlinski, R

2014-11-01

120

Laminin and biomimetic extracellular elasticity enhance functional differentiation in mammary  

E-print Network

EMBO open Laminin and biomimetic extracellular elasticity enhance functional differentiation mammary epithelial cells integrate biochemical and mechanical extra- cellular cues to maintain expression and non-biomimetic intracellular elasticity. Our data indicate that tissue-specific gene

Nelson, Celeste M.

121

Human receptor activation by aroclor 1260, a polychlorinated biphenyl mixture.  

PubMed

Polychlorinated biphenyls (PCBs) are persistent environmental toxicants, present in 100% of U.S. adults and dose-dependently associated with obesity and non-alcoholic fatty liver disease (NAFLD). PCBs are predicted to interact with receptors previously implicated in xenobiotic/energy metabolism and NAFLD. These receptors include the aryl hydrocarbon receptor (AhR), pregnane xenobiotic receptor (PXR), constitutive androstane receptor (CAR), peroxisome proliferator-activated receptors (PPARs), liver-X-receptor (LXR?), and farnesoid-X-receptor (FXR). This study evaluates Aroclor 1260, a PCB mixture with congener composition mimicking that of human adipose tissue, and selected congeners, as potential ligands for these receptors utilizing human hepatoma-derived (HepG2) and primate-derived (COS-1) cell lines, and primary human hepatocytes. Aroclor 1260 (20 ?g/ml) activated AhR, and PCB 126, a minor component, was a potent inducer. Aroclor 1260 activated PXR in a simple concentration-dependent manner at concentrations ?10 ?g/ml. Among the congeners tested, PCBs 138, 149, 151, 174, 183, 187, and 196 activated PXR. Aroclor 1260 activated CAR2 and CAR3 variants at lower concentrations and antagonize CAR2 activation by the CAR agonist, CITCO, at higher concentrations (?20 ?g/ml). Additionally, Aroclor 1260 induced CYP2B6 in primary hepatocytes. At subtoxic doses, Aroclor 1260 did not activate LXR or FXR and had no effect on LXR- or FXR-dependent induction by the agonists T0901317 or GW4064, respectively. Aroclor 1260 (20 ?g/ml) suppressed PPAR? activation by the agonist nafenopin, although none of the congeners tested demonstrated significant inhibition. The results suggest that Aroclor 1260 is a human AhR, PXR and CAR3 agonist, a mixed agonist/antagonist for CAR2, and an antagonist for human PPAR?. PMID:24812009

Wahlang, Banrida; Falkner, K Cameron; Clair, Heather B; Al-Eryani, Laila; Prough, Russell A; States, J Christopher; Coslo, Denise M; Omiecinski, Curtis J; Cave, Matthew C

2014-08-01

122

Dimerization with Cannabinoid Receptors Allosterically Modulates Delta Opioid Receptor Activity during Neuropathic Pain  

PubMed Central

The diversity of receptor signaling is increased by receptor heteromerization leading to dynamic regulation of receptor function. While a number of studies have demonstrated that family A G-protein-coupled receptors are capable of forming heteromers in vitro, the role of these heteromers in normal physiology and disease has been poorly explored. In this study, direct interactions between CB1 cannabinoid and delta opioid receptors in the brain were examined. Additionally, regulation of heteromer levels and signaling in a rodent model of neuropathic pain was explored. First we examined changes in the expression, function and interaction of these receptors in the cerebral cortex of rats with a peripheral nerve lesion that resulted in neuropathic pain. We found that, following the peripheral nerve lesion, the expression of both cannabinoid type 1 receptor (CB1R) and the delta opioid receptor (DOR) are increased in select brain regions. Concomitantly, an increase in CB1R activity and decrease in DOR activity was observed. We hypothesize that this decrease in DOR activity could be due to heteromeric interactions between these two receptors. Using a CB1R-DOR heteromer-specific antibody, we found increased levels of CB1R-DOR heteromer protein in the cortex of neuropathic animals. We subsequently examined the functionality of these heteromers by testing whether low, non-signaling doses of CB1R ligands influenced DOR signaling in the cortex. We found that, in cortical membranes from animals that experienced neuropathic pain, non-signaling doses of CB1R ligands significantly enhanced DOR activity. Moreover, this activity is selectively blocked by a heteromer-specific antibody. Together, these results demonstrate an important role for CB1R-DOR heteromers in altered cortical function of DOR during neuropathic pain. Moreover, they suggest the possibility that a novel heteromer-directed therapeutic strategy for enhancing DOR activity, could potentially be employed to reduce anxiety associated with chronic pain. PMID:23272051

Stockton, Steven D.; Miller, Lydia K.; Devi, Lakshmi A.

2012-01-01

123

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...

124

Avian pathogenic Escherichia coli bind fibronectin and laminin  

Microsoft Academic Search

Avian colisepticemia frequently occurs after respiratory tract damage, the primary site for infection allows bacteria to encounter\\u000a an exposed basement membrane, where laminin and fibronectin are important components. We investigated the ability of an isolate\\u000a of avian pathogenic Escherichia coli to bind fibronectin and laminin. Using Far-western dot blot analysis, we demonstrated the ability of this microorganism to\\u000a bind basement

Rosa María Ramírez; Yolanda Almanza; Rafael González; Santos García; Norma Heredia

2009-01-01

125

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

126

The inhibitory effect of laminin 1 and synthetic peptides deduced from the sequence in the laminin ?1 chain on A ?40 fibril formation in vitro  

Microsoft Academic Search

We investigated whether or not laminin 1 and the two different synthetic peptides deduced from the sequence in the laminin ?1 chain, both of which mediate cell attachment and neurite outgrowth in PC12 cells, have an effect on A?40 fibril formation in vitro. A thioflavine-T fluorometric assay showed a synthetic peptide containing the YFQRYLI sequence from the laminin ?1 chain

Akira Monji; Ken-ichiro Tashiro; Yosihito Hayashi; Ichiro Yoshida; Nobutada Tashiro

1998-01-01

127

Constitutively Active ALK2 Receptor Mutants Require Type II Receptor Cooperation  

PubMed Central

Constitutively activating mutations in receptor kinases recruit downstream effector pathways independently of upstream signaling, with consequences ranging from developmental syndromes to cancer. Classic fibrodysplasia ossificans progressiva (FOP) is a congenital syndrome resulting from highly conserved activating mutations of the glycine-serine-rich (GS) regulatory domain of ACVR1, encoding bone morphogenetic protein (BMP) type I receptor ALK2, which lead to inappropriate signaling and heterotopic ossification of soft tissues. It is unclear if constitutively active mutant ALK2 receptors (caALK2) can function independently of signaling complexes with type II receptors and ligands. We found that ablation of BmpRII and ActRIIa abrogated BMP ligand-mediated and caALK2-mediated signaling and transcription in cells and disrupted caALK2-induced heterotopic ossification in mice. Signaling via GS domain ALK2 mutants could be restored by the expression of either BMP type II receptor. The contribution of BMP type II receptors was independent of their ligand-binding or kinase function but was dependent upon an intact cytoplasmic domain. These data demonstrate that GS domain ALK2 mutants act independently of upstream signaling but may require a nonenzymatic scaffolding function provided by type II receptors to form functional, apparently ligand-independent signaling complexes. These findings define the minimal requirements for signaling of GS domain ALK2 mutants, with implications for the therapeutic targeting of their activity in disease. PMID:23572558

Bagarova, Jana; Vonner, Ashley J.; Armstrong, Kelli A.; Borgermann, Jan; Lai, Carol S. C.; Deng, Donna Y.; Beppu, Hideyuki; Alfano, Ivan; Filippakopoulos, Panagis; Morrell, Nicholas W.; Bullock, Alex N.; Knaus, Petra; Mishina, Yuji

2013-01-01

128

Constitutively active ALK2 receptor mutants require type II receptor cooperation.  

PubMed

Constitutively activating mutations in receptor kinases recruit downstream effector pathways independently of upstream signaling, with consequences ranging from developmental syndromes to cancer. Classic fibrodysplasia ossificans progressiva (FOP) is a congenital syndrome resulting from highly conserved activating mutations of the glycine-serine-rich (GS) regulatory domain of ACVR1, encoding bone morphogenetic protein (BMP) type I receptor ALK2, which lead to inappropriate signaling and heterotopic ossification of soft tissues. It is unclear if constitutively active mutant ALK2 receptors (caALK2) can function independently of signaling complexes with type II receptors and ligands. We found that ablation of BmpRII and ActRIIa abrogated BMP ligand-mediated and caALK2-mediated signaling and transcription in cells and disrupted caALK2-induced heterotopic ossification in mice. Signaling via GS domain ALK2 mutants could be restored by the expression of either BMP type II receptor. The contribution of BMP type II receptors was independent of their ligand-binding or kinase function but was dependent upon an intact cytoplasmic domain. These data demonstrate that GS domain ALK2 mutants act independently of upstream signaling but may require a nonenzymatic scaffolding function provided by type II receptors to form functional, apparently ligand-independent signaling complexes. These findings define the minimal requirements for signaling of GS domain ALK2 mutants, with implications for the therapeutic targeting of their activity in disease. PMID:23572558

Bagarova, Jana; Vonner, Ashley J; Armstrong, Kelli A; Börgermann, Jan; Lai, Carol S C; Deng, Donna Y; Beppu, Hideyuki; Alfano, Ivan; Filippakopoulos, Panagis; Morrell, Nicholas W; Bullock, Alex N; Knaus, Petra; Mishina, Yuji; Yu, Paul B

2013-06-01

129

The activation of the nicotinic acetylcholine receptor by the transmitter.  

PubMed

Experimental evidence has been published from isolated guinea pig muscle in vitro, and from direct ligand binding to receptors from T. californica, indicating that two agonist ions react with the nicotinic receptor by exchanging for one magnesium ion. It is the basis of the ion exchange receptor pair model, in which two acetylcholine ions exchange for one magnesium ion in contact with and between a pair of negatively charged receptor groups about 4 A apart. In the resting state the electrostatic attraction between the negatively charged receptor groups and the Mg2+ ion exerts a binding force. This binding force is opposed by the quantum mechanical repulsions of the electron clouds of the charged groups and ions in contact, together with the mutual repulsion of the pair of receptor oxyanions. When the Mg2+ ion is replaced by two acetylcholine ions the quaternary heads of the latter are positioned so that they form two mutually repelling ACh+ receptor group dipoles. As the Mg2+ ion leaves, its rehydration energy contributes to the sum of the electron cloud repulsions and the ACh+ receptor group dipole repulsions, causing the receptor groups to be forced apart activating the receptor macromolecule. The subsequent decrease in ACh+ concentration results in the reestablishment of the resting state. The coulombic electrostatic energy, the Born repulsion energy, the London attraction energy and the oxyanion ACh+ dipole repulsion energies have been calculated and shown to be consistent with the model. The displacement of the Mg2+ by two ACh+ ions makes several hundred kcals of energy available for receptor group separation and receptor activation. PMID:3982055

Taylor, D B; Spivak, C E

1985-02-01

130

Activation of the orphan receptor tyrosine kinase ALK by zinc.  

PubMed

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase essentially and transiently expressed during development of the central and peripheral nervous system. The nature of the cognate ligand of this receptor in Vertebrates is still a matter of debate. During synaptic transmission the release of ionic zinc found in vesicles of certain glutamatergic and gabaergic terminals may act as a neuromodulator by binding to pre- or post-synaptic receptors. Recently, zinc has been shown to activate the receptor tyrosine kinase, TrkB, independently of neurotrophins. This activation occurs via increasing the Src family kinase activity. In the present study, we investigated whether the ALK activity could be modulated by extracellular zinc. We first showed that zinc alone rapidly activates ALK. This activation is dependent of ALK tyrosine kinase activity and dimerization of the receptor but is independent of Src family kinase activity. In contrast, addition of sodium pyrithione, a zinc ionophore, led to a further activation of ALK. This stronger activation is dependent of Src family kinase but independent of ALK activity and dimerization. In conclusion, zinc could constitute an endogenous ligand of ALK in vertebrates. PMID:20621063

Bennasroune, Aline; Mazot, Pierre; Boutterin, Marie-Claude; Vigny, Marc

2010-08-01

131

Cell activation by glycated proteins. AGE receptors, receptor recognition factors and functional classification of AGEs.  

PubMed

Proteins modified by advanced glycation endproducts (AGE) bind to cell surface receptors and other AGE binding proteins. AGE-binding receptors are: scavenger receptors types I and II, the receptor for advanced glycation endproducts (RAGE), oligosaccharyl transferase-48 (OST-48, AGE-R1), 80K-H phosphoprotein (AGE-R2) and galectin-3 (AGE-R3). AGE receptors are found in monocytes, macrophages, endothelial cells, pericytes, podocytes, astrocytes and microglia. AGE-modified proteins also bind to lysozyme and lactoferrin. A critical review of the evidence for receptors binding AGE-modified protein binding in vivo is presented. Scavenger receptors have only been shown to bind proteins modified by AGE to a much higher extent than found in vivo. 80K-H phosphoprotein is involved in FGFR3 signal transduction to MAP kinase, and may be involved in AGE-receptor signal transduction. Whether all of these proteins bind AGE-modified proteins in vivo is not yet clear. Cell activation in response to AGE-modified proteins is associated with increased expression of extracellular matrix proteins, vascular adhesion molecules, cytokines and growth factors. Depending on the cell type and concurrent signaling, this is associated with chemotaxis, angiogenesis, oxidative stress, cell proliferation or programmed cell death (PCD). Receptor recognition factors for agonism at the AGE receptor have been little studied but to date hydroimidazolones appear to be the most likely candidates. Pharmacologic inhibition of AGE receptor-mediated cell activation with specific antagonists may provide the basis for therapeutic intervention in diseases where AGE accumulation is a suspected etiological factor vascular complications of diabetes, macrovascular disease, renal insufficiency and Alzheimer's disease. PMID:9846883

Thornalley, P J

1998-11-01

132

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

133

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.

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

2014-01-01

134

Physiologically active compounds interacting with serotonin (5-hydroxytryptamine) receptors  

NASA Astrophysics Data System (ADS)

The data on the structures of organic compounds active with respect to serotonin (5-hydroxytryptamine) receptors are systematised. Various aspects of their design are considered. The bibliography includes 296 references.

Zefirova, Ol'ga N.; Zefirov, Nikolai S.

2001-04-01

135

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

136

Differential trafficking of AMPA receptors following activation of NMDA receptors and mGluRs.  

PubMed

The removal of AMPA receptors from synapses is a major component of long-term depression (LTD). How this occurs, however, is still only partially understood. To investigate the trafficking of AMPA receptors in real-time we previously tagged the GluA2 subunit of AMPA receptors with ecliptic pHluorin and studied the effects of NMDA receptor activation. In the present study we have compared the effect of NMDA receptor and group I mGluR activation, using GluA2 tagged with super ecliptic pHluorin (SEP-GluA2) expressed in cultured hippocampal neurons. Surprisingly, agonists of the two receptors, which are both able to induce chemical forms of LTD, had clearly distinct effects on AMPA receptor trafficking. In agreement with our previous work we found that transient NMDA receptor activation results in an initial decrease in surface GluA2 from extrasynaptic sites followed by a delayed reduction in GluA2 from puncta (putative synapses). In contrast, transient activation of group I mGluRs, using DHPG, led to a pronounced but more delayed decrease in GluA2 from the dendritic shafts. Surprisingly, there was no average change in the fluorescence of the puncta. Examination of fluorescence at individual puncta, however, indicated that alterations did take place, with some puncta showing an increase and others a decrease in fluorescence. The effects of DHPG were, like DHPG-induced LTD, prevented by treatment with a protein tyrosine phosphatase (PTP) inhibitor. The electrophysiological correlate of the effects of DHPG in the SEP-GluA2 infected cultures was a reduction in mEPSC frequency with no change in amplitude. The implications of these findings for the initial mechanisms of expression of both NMDA receptor- and mGluR-induced LTD are discussed. PMID:21794146

Sanderson, Thomas M; Collingridge, Graham L; Fitzjohn, Stephen M

2011-01-01

137

Activation of Peroxisome Proliferator-Activated Receptor ?/? Induces Lung Cancer Growth via Peroxisome Proliferator-Activated Receptor Coactivator ?-1?  

PubMed Central

We previously demonstrated that a selective agonist of peroxisome proliferator–activated receptor ?/? (PPAR?/?), GW501516, stimulated human non–small cell lung carcinoma (NSCLC) growth, partly through inhibition of phosphatase and tensin homolog deleted on chromosome 10 expression. Here, we show that GW501516 also decreases the phosphorylation of AMP-activated protein kinase ? (AMPK?), a major regulator of energy metabolism. This was mediated through specific activation of PPAR?/?, as a PPAR?/? small interfering RNA inhibited the effect. However, AMPK? did not mediate the growth-promoting effects of GW501516, as silencing of AMPK? did not inhibit GW501516-induced cell proliferation. Instead, we found that GW501516 stimulated peroxisome proliferator–activated receptor coactivator ? (PGC)-1?, which activated the phosphatidylinositol 3 kinase (PI3-K)/Akt mitogenic pathway. An inhibitor of PI3-K, LY294002, had no effect on PGC-1?, consistent with PGC-1? being upstream of PI3-K/Akt. Of note, an activator of AMPK?, 5-amino-4-imidazole carboxamide riboside, inhibited the growth-promoting effects of GW501516, suggesting that although AMPK? is not responsible for the mitogenic effects of GW501516, its activation can oppose these events. This study unveils a novel mechanism by which GW501516 and activation of PPAR?/? stimulate human lung carcinoma cell proliferation, and suggests that activation of AMPK? may oppose this effect. PMID:18776129

Han, ShouWei; Ritzenthaler, Jeffrey D.; Sun, XiaoJuan; Zheng, Ying; Roman, Jesse

2009-01-01

138

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

139

Regulation of Neurite Outgrowth by Integrin Activation  

Microsoft Academic Search

During late-embryonic development, retinal neurons lose the ability to attach and extend neurites on the extracellular matrix molecule laminin-1 (LN-1), despite the fact that they retain ex- pression of integrin receptors for LN-1. Here we show that the developmental loss of responsiveness to LN-1 can be reversed by treatments that increase the activation state of integrins. Both extracellular application of

Jonathan K. Ivins; Peter D. Yurchenco; Arthur D. Lander

2000-01-01

140

Receptor activation of G proteins FJREVIEWS  

Microsoft Academic Search

G proteins are a highly conserved family of membrane- associated proteins composed of a, 3, and y subunits. The a subunit, which is unique for each G protein, binds GDP or GTP. Receptors such as those for \\/3- and a- adrenergic catecholamines, muscarinic agonists, and the retinal photoreceptor rhodopsin, catalyze the exchange of GDP for GTP binding to the a

ELLEN R. WEISS; DANIEL J. KELLEHER; SIDHARTHA SOPARKAR; SHOJI OSAWA; LYNN E. HEASLEY; GARY L. JOHNSON

141

Induction of Nuclear Translocation of Constitutive Androstane Receptor by Peroxisome Proliferator-activated  

E-print Network

Induction of Nuclear Translocation of Constitutive Androstane Receptor by Peroxisome Proliferator Peroxisome proliferators activate nuclear receptor peroxi- some proliferator-activated receptor (PPAR diverse synthetic compounds, desig- nated as peroxisome proliferators, induce a set of highly pre

Omiecinski, Curtis

142

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; Hubner, Harald; Pardon, Els; Valant, Celine; Sexton, Patrick M.; Christopoulos, Arthur; Felder, Christian C.; Gmeiner, Peter; Steyaert, Jan; Weis, William I.; Garcia, K. Christopher; Wess, Jurgen; Kobilka, Brian K.

2014-01-01

143

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

144

Activation and inhibition of erythropoietin receptor function: role of receptor dimerization.  

PubMed Central

Members of the cytokine receptor superfamily have structurally similar extracellular ligand-binding domains yet diverse cytoplasmic regions lacking any obvious catalytic domains. Many of these receptors form ligand-induced oligomers which are likely to participate in transmembrane signaling. A constitutively active (factor-independent) mutant of the erythropoietin receptor (EPO-R), R129C in the exoplasmic domain, forms disulfide-linked homodimers, suggesting that the wild-type EPO-R is activated by ligand-induced homodimerization. Here, we have taken two approaches to probe the role EPO-R dimerization plays in signal transduction. First, on the basis of the crystal structure of the ligand-bound, homodimeric growth hormone receptor (GH-R) and sequence alignment between the GH-R and EPO-R, we identified residues of the EPO-R which may be involved in intersubunit contacts in an EPO-R homodimer. Residue 129 of the EPO-R corresponds to a residue localized to the GH-R dimer interface region. Alanine or cysteine substitutions were introduced at four other residues of the EPO-R predicted to be in the dimer interface region. Substitution of residue E-132 or E-133 with cysteine renders the EPO-R constitutively active. Like the arginine-to-cysteine mutation at position 129 in the exoplasmic domain (R129C), E132C and E133C form disulfide-linked homodimers, suggesting that constitutive activity is due to covalent dimerization. In the second approach, we have coexpressed the wild-type EPO-R with inactive mutants of the receptor missing all or part of the cytosolic domain. These truncated receptors have a dominant inhibitory effect on the proliferative action of the wild-type receptor. Taken together, these results strengthen the hypothesis that an initial step in EPO- and EPO-R-mediated signal transduction is ligand-induced receptor dimerization. Images PMID:8196600

Watowich, S S; Hilton, D J; Lodish, H F

1994-01-01

145

HINT1 protein cooperates with cannabinoid 1 receptor to negatively regulate glutamate NMDA receptor activity  

PubMed Central

Background G protein-coupled receptors (GPCRs) are the targets of a large number of drugs currently in therapeutic use. Likewise, the glutamate ionotropic N-methyl-D-aspartate receptor (NMDAR) has been implicated in certain neurological disorders, such as neurodegeration, neuropathic pain and mood disorders, as well as psychosis and schizophrenia. Thus, there is now an important need to characterize the interactions between GPCRs and NMDARs. Indeed, these interactions can produce distinct effects, and whereas the activation of Mu-opioid receptor (MOR) increases the calcium fluxes associated to NMDARs, that of type 1 cannabinoid receptor (CNR1) antagonizes their permeation. Notably, a series of proteins interact with these receptors affecting their responses and interactions, and then emerge as novel therapeutic targets for the aforementioned pathologies. Results We found that in the presence of GPCRs, the HINT1 protein influences the activity of NMDARs, whereby NMDAR activation was enhanced in CNR1+/+/HINT1-/- cortical neurons and the cannabinoid agonist WIN55,212-2 provided these cells with no protection against a NMDA insult. NMDAR activity was normalized in these cells by the lentiviral expression of HINT1, which also restored the neuroprotection mediated by cannabinoids. NMDAR activity was also enhanced in CNR1-/-/HINT1+/+ neurons, although this activity was dampened by the expression of GPCRs like the MOR, CNR1 or serotonin 1A (5HT1AR). Conclusions The HINT1 protein plays an essential role in the GPCR-NMDAR connection. In the absence of receptor activation, GPCRs collaborate with HINT1 proteins to negatively control NMDAR activity. When activated, most GPCRs release the control of HINT1 and NMDAR responsiveness is enhanced. However, cannabinoids that act through CNR1 maintain the negative control of HINT1 on NMDAR function and their protection against glutamate excitotoxic insult persists. PMID:24093505

2013-01-01

146

Ligand Activation of Peroxisome Proliferator-Activated Receptor-/ Inhibits Cell Proliferation  

E-print Network

Ligand Activation of Peroxisome Proliferator-Activated Receptor- / Inhibits Cell Proliferation and is inconsis- tent with the notion that RA potentiates cell proliferation by acti- vating PPAR / . Peroxisome material. ABBREVIATIONS: PPAR, peroxisome proliferator-activated receptor; 9-cis RA, 9-cis retinoic a

Omiecinski, Curtis

147

Coupling of Receptor Conformation and Ligand Orientation Determine Graded Activity  

PubMed Central

SUMMARY Small molecules stabilize specific protein conformations from a larger ensemble, enabling molecular switches that control diverse cellular functions. We show here that the converse also holds true, where the conformational state of the estrogen receptor can direct distinct orientations of the bound ligand. “Gain of allostery” mutations that mimic the effects of ligand in driving protein conformation allowed crystallization of the partial agonist ligand WAY-169916 with both the canonical active and inactive conformations of the estrogen receptor. The intermediate transcriptional activity induced by WAY169916 is associated with the ligand binding differently to the active and inactive conformations of the receptor. Analyses of a series of chemical derivatives demonstrated that altering the ensemble of ligand binding orientations changes signaling output. The coupling of different ligand binding orientations to distinct active and inactive protein conformations defines a novel mechanism for titrating allosteric signaling activity. PMID:20924370

Bruning, John B.; Parent, Alex A.; Gil, German; Zhao, Min; Nowak, Jason; Pace, Margaret C.; Smith, Carolyn L.; Afonine, Pavel V.; Adams, Paul D.; Katzenellenbogen, John A.; Nettles, Kendall W.

2010-01-01

148

Receptor activity modifying proteins (RAMPs) interact with the VPAC2 receptor and CRF1 receptors and modulate their function  

PubMed Central

Background and Purpose Although it is established that the receptor activity modifying proteins (RAMPs) can interact with a number of GPCRs, little is known about the consequences of these interactions. Here the interaction of RAMPs with the glucagon-like peptide 1 receptor (GLP-1 receptor), the human vasoactive intestinal polypeptide/pituitary AC-activating peptide 2 receptor (VPAC2) and the type 1 corticotrophin releasing factor receptor (CRF1) has been examined. Experimental Approach GPCRs were co-transfected with RAMPs in HEK 293S and CHO-K1 cells. Cell surface expression of RAMPs and GPCRs was examined by elisa. Where there was evidence for interactions, agonist-stimulated cAMP production, Ca2+ mobilization and GTP?S binding to Gs, Gi, G12 and Gq were examined. The ability of CRF to stimulate adrenal corticotrophic hormone release in Ramp2+/– mice was assessed. Key Results The GLP-1 receptor failed to enhance the cell surface expression of any RAMP. VPAC2 enhanced the cell surface expression of all three RAMPs. CRF1 enhanced the cell surface expression of RAMP2; the cell surface expression of CRF1 was also increased. There was no effect on agonist-stimulated cAMP production. However, there was enhanced G-protein coupling in a receptor and agonist-dependent manner. The CRF1 : RAMP2 complex resulted in enhanced elevation of intracellular calcium to CRF and urocortin 1 but not sauvagine. In Ramp2+/– mice, there was a loss of responsiveness to CRF. Conclusions and Implications The VPAC2 and CRF1 receptors interact with RAMPs. This modulates G-protein coupling in an agonist-specific manner. For CRF1, coupling to RAMP2 may be of physiological significance. PMID:22946657

Wootten, D; Lindmark, H; Kadmiel, M; Willcockson, H; Caron, KM; Barwell, J; Drmota, T; Poyner, DR

2013-01-01

149

Dynamic regulation of Drosophila nuclear receptor activity in vivo.  

PubMed

Nuclear receptors are a large family of transcription factors that play major roles in development, metamorphosis, metabolism and disease. To determine how, where and when nuclear receptors are regulated by small chemical ligands and/or protein partners, we have used a 'ligand sensor' system to visualize spatial activity patterns for each of the 18 Drosophila nuclear receptors in live developing animals. Transgenic lines were established that express the ligand binding domain of each nuclear receptor fused to the DNA-binding domain of yeast GAL4. When combined with a GAL4-responsive reporter gene, the fusion proteins show tissue- and stage-specific patterns of activation. We show that these responses accurately reflect the presence of endogenous and exogenously added hormone, and that they can be modulated by nuclear receptor partner proteins. The amnioserosa, yolk, midgut and fat body, which play major roles in lipid storage, metabolism and developmental timing, were identified as frequent sites of nuclear receptor activity. We also see dynamic changes in activation that are indicative of sweeping changes in ligand and/or co-factor production. The screening of a small compound library using this system identified the angular psoralen angelicin and the insect growth regulator fenoxycarb as activators of the Ultraspiracle (USP) ligand-binding domain. These results demonstrate the utility of this system for the functional dissection of nuclear receptor pathways and for the development of new receptor agonists and antagonists that can be used to modulate metabolism and disease and to develop more effective means of insect control. PMID:16914501

Palanker, Laura; Necakov, Aleksandar S; Sampson, Heidi M; Ni, Ruoyu; Hu, Chun; Thummel, Carl S; Krause, Henry M

2006-09-01

150

Dynamic regulation of Drosophila nuclear receptor activity in vivo  

PubMed Central

Nuclear receptors are a large family of transcription factors that play major roles in development, metamorphosis, metabolism and disease. To determine how, where and when nuclear receptors are regulated by small chemical ligands and/or protein partners, we have used a ‘ligand sensor’ system to visualize spatial activity patterns for each of the 18 Drosophila nuclear receptors in live developing animals. Transgenic lines were established that express the ligand binding domain of each nuclear receptor fused to the DNA-binding domain of yeast GAL4. When combined with a GAL4-responsive reporter gene, the fusion proteins show tissue- and stage-specific patterns of activation. We show that these responses accurately reflect the presence of endogenous and exogenously added hormone, and that they can be modulated by nuclear receptor partner proteins. The amnioserosa, yolk, midgut and fat body, which play major roles in lipid storage, metabolism and developmental timing, were identified as frequent sites of nuclear receptor activity. We also see dynamic changes in activation that are indicative of sweeping changes in ligand and/or co-factor production. The screening of a small compound library using this system identified the angular psoralen angelicin and the insect growth regulator fenoxycarb as activators of the Ultraspiracle (USP) ligand-binding domain. These results demonstrate the utility of this system for the functional dissection of nuclear receptor pathways and for the development of new receptor agonists and antagonists that can be used to modulate metabolism and disease and to develop more effective means of insect control. PMID:16914501

Palanker, Laura; Necakov, Aleksandar S.; Sampson, Heidi M.; Ni, Ruoyu; Hu, Chun; Thummel, Carl S.; Krause, Henry M.

2007-01-01

151

COMMUNICATION Autocrine activation of adenosine A1 receptors blocks D1A but not D1B dopamine receptor desensitization  

Microsoft Academic Search

Adenosine is known to modulate dopamine responses in several brain areas. Here, we show that tonic activation of adenosine receptors is able to impede desensitization of D1 dopamine receptors. As measured by cAMP accumulation in transfected COS-7 cells, long-term exposure to dopamine agonists promoted desensitization of D1B receptor but not that of D1A receptor. The inability of D1A receptor to

Stephane Le Crom; Delphine Prou; Philippe Vernier

152

Transmembrane Interactions in the Activation of the Neu Receptor Tyrosine Kinase †  

Microsoft Academic Search

The Neu receptor tyrosine kinase is constitutively activated by a single amino acid change in the transmembrane domain of the receptor. The mutation of Val664 to glutamate or glutamine induces receptor dimerization and autophosphorylation of the receptor's intracellular kinase domain. The ability of this single mutation to activate the receptor is sequence-dependent, suggesting that specific helix - helix interactions stabilize

Steven O. Smith; Charles Smith; Srinivasan Shekar; Olve Peersen; Martine Ziliox; Saburo Aimoto

2002-01-01

153

Opportunistic activation of TRP receptors by endogenous lipids: Exploiting lipidomics to understand TRP receptor cellular communication  

PubMed Central

Transient receptor potential channels (TRPs) form a large family of ubiquitous non-selective cation channels that function as cellular sensors and in many cases regulate intracellular calcium. Identification of the endogenous ligands that activate these TRP receptors is still under intense investigation with the majority of these channels still remaining “orphans”. That these channels respond to a variety of external stimuli (e.g. plant-derived lipids, changes in temperature, and changes in pH) provides a framework for their abilities as cellular sensors, however, the mechanism of direct activation is still under much debate and research. In the cases where endogenous ligands (predominately lipids) have shown direct activation of a channel, multiple ligands have been shown to activate the same channel suggesting that these receptors are “promiscuous” in nature. Lipidomics of a growing class of endogenous lipids, N-acyl amides, the most famous of which is N-arachidonoyl ethanolamine (the endogenous cannabinoid, Anandamide) is providing a novel set of ligands that have been shown to activate some members of the TRP family and have the potential to deorphanize many more. Here it is argued that activation of TRPV receptors, a subset of the larger family of TRPs, by multiple endogenous lipids that are structurally analogous is a model system to drive our understanding that many TRP receptors are not promiscuous, but are more characteristically “opportunistic” in nature; exploiting the structural similarity and biosynthesis of a narrow range of analogous endogenous lipids. In addition, this manuscript will compare the activation properties of TRPC5 to the activity profile of an “orphan” lipid, N-palmitoyl glycine; further demonstrating that lipidomics aimed at expanding our knowledge of the family of N-acyl amides has the potential to provide novel avenues of research for TRP receptors. PMID:23178153

Bradshaw, Heather B.; Raboune, Siham; Hollis, Jennifer L.

2012-01-01

154

Diminished Hepatocellular Proliferation in Mice Humanized for the Nuclear Receptor Peroxisome Proliferator-Activated Receptor  

Microsoft Academic Search

Lipid-lowering fibrate drugs function as agonists for the nuclear re- ceptor peroxisome proliferator-activated receptor (PPAR). Sustained activation of PPAR leads to the development of liver tumors in rats and mice. However, humans appear to be resistant to the induction of perox- isome proliferation and the development of liver cancer by fibrate drugs. The molecular basis of this species difference is

Connie Cheung; Taro E. Akiyama; Jerrold M. Ward; Christopher J. Nicol; Lionel Feigenbaum; Charles Vinson; Frank J. Gonzalez

2004-01-01

155

Metal Binding Is Critical for the Folding and Function of Laminin Binding Protein, Lmb of Streptococcus agalactiae  

PubMed Central

Lmb is a 34 kDa laminin binding surface adhesin of Streptococcus agalactiae. The structure of Lmb reported by us recently has shown that it consists of a metal binding crevice, in which a zinc ion is coordinated to three highly conserved histidines. To elucidate the structural and functional significance of the metal ion in Lmb, these histidines have been mutated to alanine and single, double and triple mutants were generated. These mutations resulted in insolubility of the protein and revealed altered secondary and tertiary structures, as evidenced by circular dichroism and fluorescence spectroscopy studies. The mutations also significantly decreased the binding affinity of Lmb to laminin, implicating the role played by the metal binding residues in maintaining the correct conformation of the protein for its binding to laminin. A highly disordered loop, proposed to be crucial for metal acquisition in homologous structures, was deleted in Lmb by mutation (?Lmb) and its crystal structure was solved at 2.6 Å. The ?Lmb structure was identical to the native Lmb structure with a bound zinc ion and exhibited laminin binding activity similar to wild type protein, suggesting that the loop might not have an important role in metal acquisition or adhesion in Lmb. Targeted mutations of histidine residues confirmed the importance of the zinc binding crevice for the structure and function of the Lmb adhesin. PMID:23826314

Ragunathan, Preethi; Sridaran, Divya; Weigel, Anja; Shabayek, Sarah; Spellerberg, Barbara; Ponnuraj, Karthe

2013-01-01

156

Antipruritic activity of the ?-opioid receptor agonist, TRK-820  

Microsoft Academic Search

The effects of the ?-opioid receptor agonist, TRK-820, (?)-17-(cyclopropylmethyl)-3, 14?-dihydroxy-4, 5?-epoxy-6?-[N-methyl-trans-3-(3-furyl) acrylamido] morphinan hydrochloride, on the itch sensation were compared with those of histamine H1 receptor antagonists, using the mouse pruritogen-induced scratching model. Peroral administration of TRK-820 reduced the numbers of substance P- or histamine-induced scratches dose dependently. No obvious suppression of the spontaneous locomotor activity was observed at the

Yuko Togashi; Hideo Umeuchi; Kiyoshi Okano; Naoki Ando; Yoshitaka Yoshizawa; Toshiyuki Honda; Kuniaki Kawamura; Takashi Endoh; Jun Utsumi; Junzo Kamei; Toshiaki Tanaka; Hiroshi Nagase

2002-01-01

157

Activation of Group I Metabotropic Glutamate Receptors Potentiates Heteromeric Kainate Receptors  

PubMed Central

Kainate receptors (KARs), a family of ionotropic glutamate receptors, are widely expressed in the central nervous system and are critically involved in synaptic transmission. KAR activation is influenced by metabotropic glutamate receptor (mGlu) signaling, but the underlying mechanisms are not understood. We undertook studies to examine how mGlu modulation affects activation of KARs. Confocal immunohistochemistry of rat hippocampus and cultured rat cortex revealed colocalization of the high-affinity KAR subunits with group I mGlu receptors. In hippocampal and cortical cultures, the calcium signal caused by activation of native KARs was potentiated by activation of group I mGlu receptors. In Xenopus laevis oocytes, activation of group I mGlu receptors potentiated heteromeric but not homomeric KAR-mediated currents, with no change in agonist potency. The potentiation of heteromeric KARs by mGlu1 activation was attenuated by GDP?S, blocked by an inhibitor of phospholipase C or the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N?,N?-tetraacetic acid (BAPTA), prolonged by the phosphatase inhibitor okadaic acid, but unaffected by the tyrosine kinase inhibitor lavendustin A. Protein kinase C (PKC) inhibition reduced the potentiation by mGlu1 of GluK2/GluK5, and conversely, direct activation of PKC by phorbol 12-myristate,13-acetate potentiated GluK2/GluK5. Using site-directed mutagenesis, we identified three serines (Ser833, Ser836, and Ser840) within the membrane proximal region of the GluK5 C-terminal domain that, in combination, are required for mGlu1-mediated potentiation of KARs. Together, these data suggest that phosphorylation of key residues in the C-terminal domain changes the overall charge of this domain, resulting in potentiated agonist responses. PMID:23066089

Wetherington, Jonathon; Shaw, Renee; Serrano, Geidy; Swanger, Sharon; Dingledine, Raymond

2013-01-01

158

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

159

Isolation of laminin from human placental basement membranes: amnion, chorion and chorionic microvessels.  

PubMed

Laminin components were solubilized from basement membranes of amnion, chorion and chorionic microvessels of human placenta without prior protease digestion. These structures, after isolation, were initially processed in a sonicator bath containing a solution of Triton X-100, EDTA and 2M NaCl and the laminins extracted sequentially with 0.5M NaCl, 8 M urea, and 8 M urea + 2% 2-mercaptoethanol + 2% SDS. A high molecular weight (appr. 1 x 10(6)) complex containing laminins was purified by gel filtration on a Sepharose CL-2B column. This complex migrated as a single band on gel electrophoresis before reduction but resolved, after reduction, into four major laminin components, laminin A (350,000 M.W.), laminin M (240,000 M.W.) and laminins B1 and B2 (195,000 and 185,000 M.W.). Laminin M is a new molecular species of this protein. PMID:6847680

Ohno, M; Martinez-Hernandez, A; Ohno, N; Kefalides, N A

1983-05-16

160

Biological Effects of Thyrotropin Receptor Activation on Human Orbital Preadipocytes  

Microsoft Academic Search

PURPOSE. Thyrotropin receptor (TSHR) expression is upregu- lated in the orbits of patients with Graves ophthalmopathy (GO), most of whom have TSHR-stimulating antibodies. The authors investigated the biological effects of TSHR activation in vitro in adipose tissue, the site of orbital TSHR expression. METHODS. Activating mutant TSHR (TSHR*) or wild-type (WT) was introduced into human orbital preadipocytes using retro- viral

Lei Zhang; Glynn Baker; Dominika Janus; Carol A. Paddon; Dagmar Fuhrer; Marian Ludgate

2006-01-01

161

INFLAMMATORY BOWEL DISEASE Peroxisome proliferator activated receptor c in  

E-print Network

INFLAMMATORY BOWEL DISEASE Peroxisome proliferator activated receptor c in colonic epithelial cells . . . . . . . . . . . . . . . . . . . . . . . Gut 2006;55:1104­1113. doi: 10.1136/gut.2005.081745 Introduction: Peroxisome proliferator activated and an aberrant immune response to enteric flora, leading to intestinal inflammation. The role of peroxisome

Omiecinski, Curtis

162

Functional Interaction between Peroxisome Proliferator-Activated Receptor   and  -Catenin  

Microsoft Academic Search

Studies have demonstrated cross talk between -catenin and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Specifically, activation of PPAR induces the proteasomal degradation of -catenin in cells that express an adenomatous polyposis coli-containing destruction complex. In contrast, oncogenic -catenin is resistant to such degradation and inhibits the expression of PPAR target genes. In the present studies, we demonstrate a functional interaction

Jiajian Liu; Hong Wang; Ying Zuo; Stephen R. Farmer

2006-01-01

163

Original article Insulin receptor binding and tyrosine kinase activity  

E-print Network

.e., there was an impairment in insulin responsiveness in both glucose utilization and production in rats (Penicaud et aL, 1985Original article Insulin receptor binding and tyrosine kinase activity in liver and skeletal muscle Group, Clermont-Ferrand, 25-27 May 1988) Summary ― Insulin binding and tyrosine kinase activity

Boyer, Edmond

164

Chlorotriazines do not activate the aryl hydrocarbon receptor, the oestrogen receptor or the thyroid receptor in in vitro assays.  

PubMed

Atrazine, prometryn, propazine and simazine are chlorotriazines that are commonly employed as herbicides. However, their use is a major cause of concern, due to their reported endocrine disrupting effects in different taxa. Data from studies on the molecular and cellular processes underlying the hormonal action of these substances are contradictory. The ability of these chlorotriazines and the atrazine metabolites, desethyl-s-chlorotriazine and desisopropyl-s-chlorotriazine, to trigger responses mediated by the oestrogen receptor (ER), aryl hydrocarbon receptor (AhR) and thyroid receptor (TR), was studied by using in vitro approaches. Transcriptional activation assays were applied to observe the activation of ER and TR. The induction of ethoxyresorufin-O-deethylase (EROD) activity in the RTG-2 cell line served as an indicator of AhR activation. No responses were found in any of the assays, with any of the six chlorotriazines tested. Our observations indicate that the chlorotriazines tested are unlikely to cause their endocrine effects via these receptors. PMID:24773485

de la Casa-Resino, Irene; Navas, José M; Fernández-Cruz, María L

2014-03-01

165

Activation of b2-adrenergic receptor stimulates g-secretase activity and accelerates amyloid  

E-print Network

signaling pathways7,8 or by activation of the muscarinic acetylcholine receptor or estrogen recep- tor9 couple to heterotrimeric guanine nucleotide­binding proteins (G proteins) and modulate the levels of intracellular second messengers, such as cyclic AMP (cAMP)16,17. The activated receptor also undergoes clathrin

Tian, Weidong

166

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...

167

Conformational Changes Involved in G Protein-coupled Receptor Activation  

PubMed Central

Little is known about the nature of the conformational changes that convert G protein-coupled receptors (GPCRs), which bind diffusible ligands, from their resting into their active states. To gain structural insight into this process, various laboratories have used disulfide cross-linking strategies involving cysteine-substituted mutant GPCRs. Several recent disulfide cross-linking studies using the M3 muscarinic acetylcholine receptor as a model system have led to novel insights into the conformational changes associated with the activation of this prototypical class I GPCR. These structural changes are predicted to involve multiple receptor regions, primarily distinct segments of transmembrane helices III, VI, and VII, as well as helix 8. Given the high degree of structural homology found among most GPCRs, it is likely that these findings will be of considerable general relevance. A better understanding of the molecular mechanisms underlying GPCR activation may lead to novel strategies aimed at modulating GPCR function for therapeutic purposes. PMID:18838178

Wess, Jurgen; Han, Sung-Jun; Kim, Soo-Kyung; Jacobson, Kenneth A.; Li, Jian Hua

2012-01-01

168

Differential activation of intracellular versus plasmalemmal CB2 cannabinoid receptors.  

PubMed

The therapeutic and psychoactive properties of cannabinoids have long been recognized. The type 2 receptor for cannabinoids (CB2) has emerged as an important therapeutic target in several pathologies, as it mediates beneficial effects of cannabinoids while having little if any psychotropic activity. Difficulties associated with the development of CB2-based therapeutic agents have been related to its intricate pharmacology, including the species specificity and functional selectivity of the CB2-initiated responses. We postulated that a plasmalemmal or subcellular location of the receptor may contribute to the differential signaling pathways initiated by its activation. To differentiate between these two, we used extracellular and intracellular administration of CB2 ligands and concurrent calcium imaging in CB2-expressing U2OS cells. We found that extracellular administration of anandamide was ineffective, whereas 2-arachidonoyl glycerol (2-AG) and WIN55,212-2 triggered delayed, CB2-dependent Ca(2+) responses that were Gq protein-mediated. When microinjected, all agonists elicited fast, transient, and dose-dependent elevations in intracellular Ca(2+) concentration upon activation of Gq-coupled CB2 receptors. The CB2 dependency was confirmed by the sensitivity to AM630, a selective CB2 antagonist, and by the unresponsiveness of untransfected U2OS cells to 2-AG, anandamide, or WIN55,212-2. Moreover, we provide functional and morphological evidence that CB2 receptors are localized at the endolysosomes, while their activation releases Ca(2+) from inositol 1,4,5-trisphosphate-sensitive- and acidic-like Ca(2+) stores. Our results support the functionality of intracellular CB2 receptors and their ability to couple to Gq and elicit Ca(2+) signaling. These findings add further complexity to CB2 receptor pharmacology and argue for careful consideration of receptor localization in the development of CB2-based therapeutic agents. PMID:25033246

Brailoiu, G Cristina; Deliu, Elena; Marcu, Jahan; Hoffman, Nicholas E; Console-Bram, Linda; Zhao, Pingwei; Madesh, Muniswamy; Abood, Mary E; Brailoiu, Eugen

2014-08-01

169

Distribution and Function of Laminins in the Neuromuscular System of Developing, Adult, and Mutant Mice  

Microsoft Academic Search

Laminins, heterotrimers of a , b , and g chains, are prominent constituents of basal laminae (BLs) throughout the body. Previous studies have shown that laminins affect both myogenesis and synap- togenesis in skeletal muscle. Here we have studied the distribution of the 10 known laminin chains in muscle and peripheral nerve, and assayed the ability of several heterotrimers to

Bruce L. Patton; Jeffrey H. Miner; Arlene Y. Chiu; Joshua R. Sanes

1997-01-01

170

Interfering with mineralocorticoid receptor activation: the past, present, and future  

PubMed Central

Aldosterone is a potent mineralocorticoid produced by the adrenal gland. Aldosterone binds to and activates the mineralocorticoid receptor (MR) in a plethora of tissues, but the cardiovascular actions of aldosterone are of primary interest clinically. Although MR antagonists were developed as antihypertensive agents, they are now considered to be important therapeutic options for patients with heart failure. Specifically, blocking only the MR has proven to be a difficult task because of its similarity to other steroid receptors, including the androgen and progesterone receptors. This lack of specificity caused the use of the first-generation mineralocorticoid receptor antagonists to be fraught with difficulty because of the side effects produced by drug administration. However, in recent years, several advances have been made that could potentially increase the clinical use of agents that inhibit the actions of aldosterone. These will be discussed here along with some examples of the beneficial effects of these new therapeutic agents. PMID:25165560

2014-01-01

171

Allosteric Modulation of Protease-activated Receptor Signaling  

PubMed Central

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 the N-terminus that is exposed following proteolytic cleavage. The newly formed PAR N-terminus 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 the mechanisms that lead to allosteric modulation of PAR signaling. PMID:22681248

Canto, Isabel; Soh, Unice J. K.; Trejo, JoAnn

2014-01-01

172

New and selective ryanodine receptor activators for insect control.  

PubMed

Diamide insecticides have emerged as one of the most promising new classes of insecticide chemistry owing to their excellent insecticidal efficacy and high margins of mammalian safety. Chlorantraniliprole and flubendiamide, the first two insecticides from this class, demonstrate exceptional activity across a broad range of pests in the order Lepidoptera. This chemistry has been confirmed to control insects via activation of ryanodine receptors which leads to uncontrolled calcium release in muscle. The high levels of mammalian safety are attributed to a strong selectivity for insect over mammalian receptors. PMID:19186058

Lahm, George P; Cordova, Daniel; Barry, James D

2009-06-15

173

Protease-activated receptor 1-dependent neuronal damage involves NMDA receptor function  

PubMed Central

Protease-activated receptor 1 (PAR1) is a G-protein coupled receptor that is expressed throughout the central nervous system. PAR1 activation by brain-derived as well as blood-derived proteases has been shown to have variable and complex effects in a variety of animal models of neuronal injury and inflammation. In this study, we have evaluated the effects of PAR1 on lesion volume in wild-type or PAR1?/? C57Bl/6 mice subjected to transient occlusion of the middle cerebral artery or injected with NMDA in the striatum. We found that removal of PAR1 reduced infarct volume following transient focal ischemia to 57% of control. Removal of PAR1 or application of a PAR1 antagonist also reduced the neuronal injury associated with intrastriatal injection of NMDA to 60% of control. To explore whether NMDA receptor potentiation by PAR1 activation contributes to the harmful effects of PAR1, we investigated the effect of NMDA receptor antagonists on the neuroprotective phenotype of PAR1?/? mice. We found that MK801 reduced penumbral but not core neuronal injury in mice subjected to transient middle cerebral artery occlusion or intrastriatal NMDA injection. Lesion volumes in both models were not significantly different between PAR1?/? mice treated with and without MK801. Use of the NMDA receptor antagonist and dissociative anesthetic ketamine also renders NMDA-induced lesion volumes identical in PAR1?/? mice and wild-type mice. These data suggest that the ability of PAR1 activation to potentiate NMDA receptor function may underlie its harmful actions during injury. PMID:19416668

Hamill, Cecily E.; Mannaioni, Guido; Lyuboslavsky, Polina; Sastre, Aristide A.; Traynelis, Stephen F.

2009-01-01

174

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

175

Allosteric activation mechanism of the cys-loop receptors  

PubMed Central

Binding of a neurotransmitter to its ionotropic receptor opens a distantly located ion channel, a process termed allosteric activation. Here we review recent advances in the molecular mechanism by which the cys-loop receptors are activated with emphasis on the best studied nicotinic acetylcholine receptors (nAChRs). With a combination of affinity labeling, mutagenesis, electrophysiology, kinetic modeling, electron microscopy (EM), and crystal structure analysis, the allosteric activation mechanism is emerging. Specifically, the binding domain and gating domain are interconnected by an allosteric activation network. Agonist binding induces conformational changes, resulting in the rotation of a ? sheet of amino-terminal domain and outward movement of loop 2, loop F, and cys-loop, which are coupled to the M2–M3 linker to pull the channel to open. However, there are still some controversies about the movement of the channel-lining domain M2. Nine angstrom resolution EM structure of a nAChR imaged in the open state suggests that channel opening is the result of rotation of the M2 domain. In contrast, recent crystal structures of bacterial homologues of the cys-loop receptor family in apparently open state have implied an M2 tilting model with pore dilation and quaternary twist of the whole pentameric receptor. An elegant study of the nAChR using protonation scanning of M2 domain supports a similar pore dilation activation mechanism with minimal rotation of M2. This remains to be validated with other approaches including high resolution structure determination of the mammalian cys-loop receptors in the open state. PMID:19444220

Chang, Yong-chang; Wu, Wen; Zhang, Jian-liang; Huang, Yao

2009-01-01

176

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

177

GABAB Receptor Activation Modulates GABAA ReceptorMediated Inhibition in Chicken Nucleus Magnocellularis Neurons  

E-print Network

glutamatergic excitatory input solely from the eighth nerve and GABAergic inhibitory input primarily from the ipsilateral superior olivary nucleus. GABA activates both ligand-gated Cl channels [GABAA receptors (GABAARs is inhibitory, although depolarizing. Several studies have shown that this shunting, inhibitory GABAergic input

Rubel, Edwin

178

Structural basis for selective activation of ABA receptors.  

PubMed

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. PMID:20729860

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, George N; Volkman, Brian F

2010-09-01

179

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

180

Soluble extracts from Helicobacter pylori induce dome formation in polarized intestinal epithelial monolayers in a laminin-dependent manner.  

PubMed

Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid "dome" formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding alpha 6 beta 4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response. PMID:12819097

Terrés, A M; Windle, H J; Ardini, E; Kelleher, D P

2003-07-01

181

Extrasynaptic targeting of NMDA receptors following D1 dopamine receptor activation and cocaine self-administration  

PubMed Central

We previously showed that after repeated exposure to cocaine, D1-like dopamine receptor (D1DR) stimulation reverses plastic changes of AMPA receptor-mediated signaling in the nucleus accumbens shell. However, there is little information on the impact of cocaine self-administration on D1-NMDA receptor interactions in this brain region. Here, we assessed whether cocaine self-administration alters the effects of D1DR stimulation on synaptic and extrasynaptic NMDA receptors (NMDARs) using whole-cell patch-clamp recordings. In slices from cocaine-naïve rats, pre-treatment with a D1DR agonist decreased synaptic NMDAR receptor-mediated currents and increased the contribution of extrasynaptic NMDARs. In contrast, neither cocaine self-administration alone nor cocaine experience followed by D1DR stimulation had an effect on synaptic or extrasynaptic NMDAR signaling. Activation of extrasynaptic NMDARs relies on the availability of extracellular glutamate, which is regulated primarily by glutamate transporters. In cocaine-experienced animals, administration of a glutamate re-uptake blocker, DL-threo-?-benzyloxyaspartic acid (TBOA), revealed increased extrasynaptic NMDAR activity and stronger baseline activity of glutamate uptake transporters relative to cocaine-naïve rats. In cocaine-naïve rats, the D1DR-mediated increase in extrasynaptic NMDAR signaling was independent of the activity of glutamate re-uptake transporters. Taken together, these results indicate that cocaine experience blunts the influence of D1DRs on synaptic and extrasynaptic NMDAR signaling. Additionally, prior cocaine self-administration limits activation of the extrasynaptic NMDAR pool by increasing glutamate re-uptake. These findings outline a pattern of adaptive interactions between D1DRs and NMDARs in the nucleus accumbens shell and demonstrate up-regulation of extrasynaptic NMDAR signaling as a novel consequence of cocaine self-administration. PMID:23719812

Ortinski, Pavel I.; Turner, Jill R.; Pierce, R. Christopher

2013-01-01

182

Stimulation of Different Subtypes of Angiotensin II Receptors, AT1 and AT2 Receptors, Regulates STAT Activation by Negative Crosstalk  

Microsoft Academic Search

Angiotensin II type 2 (AT 2) receptor exerts an inhibitory action on cell growth. In the present study, we report that the stimulation of AT2 receptor in AT2 receptor cDNA-transfected rat adult vascular smooth muscle cells (VSMCs) inhibited angiotensin II type 1 (AT1) receptor-mediated tyrosine phosphorylation of STAT (signal transducers and activators of transcription) 1 a\\/b, STAT2, and STAT3 without

Masatsugu Horiuchi; Wataru Hayashida; Masahiro Akishita; Kouichi Tamura; Laurent Daviet; Jukka Y. A. Lehtonen; Victor J. Dzau

2010-01-01

183

Cofactoring and Dimerization of Proteinase-Activated Receptors  

PubMed Central

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.

2013-01-01

184

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

185

Peroxisome proliferator-activated receptors in the cardiovascular system  

PubMed Central

Peroxisome proliferator-activated receptor (PPAR)s are a family of three nuclear hormone receptors, PPAR?, -?, and -?, which are members of the steriod receptor superfamily. The first member of the family (PPAR?) was originally discovered as the mediator by which a number of xenobiotic drugs cause peroxisome proliferation in the liver. Defined functions for all these receptors, until recently, mainly concerned their ability to regulate energy balance, with PPAR? being involved in ?-oxidation pathways, and PPAR? in the differentiation of adipocytes. Little is known about the functions of PPAR?, though it is the most ubiquitously expressed. Since their discovery, PPARs have been shown to be expressed in monocytes/macrophages, the heart, vascular smooth muscle cells, endothelial cells, and in atherosclerotic lesions. Furthermore, PPARs can be activated by a vast number of compounds including synthetic drugs, of the clofibrate, and anti-diabetic thiazoldinedione classes, polyunsaturated fatty acids, and a number of eicosanoids, including prostaglandins, lipoxygenase products, and oxidized low density lipoprotein. This review will aim to introduce the field of PPAR nuclear hormone receptors, and discuss the discovery and actions of PPARs in the cardiovascular system, as well as the source of potential ligands. PMID:10696077

Bishop-Bailey, David

2000-01-01

186

Protease-activated receptors and prostaglandins in inflammatory lung disease  

PubMed Central

Protease-activated receptors (PARs) are a novel family of G protein-coupled receptors. Signalling through PARs typically involves the cleavage of an extracellular region of the receptor by endogenous or exogenous proteases, which reveals a tethered ligand sequence capable of auto-activating the receptor. A considerable body of evidence has emerged over the past 20 years supporting a prominent role for PARs in a variety of human physiological and pathophysiological processes, and thus substantial attention has been directed towards developing drug-like molecules that activate or block PARs via non-proteolytic pathways. PARs are widely expressed within the respiratory tract, and their activation appears to exert significant modulatory influences on the level of bronchomotor tone, as well as on the inflammatory processes associated with a range of respiratory tract disorders. Nevertheless, there is debate as to whether the principal response to PAR activation is an augmentation or attenuation of airways inflammation. In this context, an important action of PAR activators may be to promote the generation and release of prostanoids, such as prostglandin E2, which have well-established anti-inflammatory effects in the lung. In this review, we primarily focus on the relationship between PARs, prostaglandins and inflammatory processes in the lung, and highlight their potential role in selected respiratory tract disorders, including pulmonary fibrosis, asthma and chronic obstructive pulmonary disease. This article is part of a themed issue on Mediators and Receptors in the Resolution of Inflammation. To view this issue visit http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009 PMID:19845685

Peters, Terence; Henry, Peter J

2009-01-01

187

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

188

Covalent agonists for studying G protein-coupled receptor activation.  

PubMed

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

2014-07-22

189

Nuclear Receptor Activity and Liver Cancer Lesion Progression  

EPA Science Inventory

Nuclear receptors (NRs) are ligand-activated transcription factors that control diverse cellular processes. Chronic stimulation of some NRs is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. We explored this question using human CAR, PXR, PPARa,...

190

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; Hubner, Harald; Kobilka, Brian K.; Gmeiner, Peter

2014-01-01

191

Signaling by Committee: Receptor Clusters Determine Pathways of Cellular Activation  

E-print Network

in the allergic response mediated primarily by mast cells (5). The complex con- sists of four subunits BIOLOGY · VOL.2 NO.10 www.acschemicalbiology.org652 #12;lation of mast cells, releasing inflammatoSignaling by Committee: Receptor Clusters Determine Pathways of Cellular Activation Christopher W

Cairo, Christopher W.

192

Activation of Estrogen Receptor by Bavachin from Psoralea corylifolia  

PubMed Central

In this study, we examined the estrogenic activity of bavachin, a component of Psoralea corylifolia that has been used as a traditional medicine in Asia. Bavachin was purified from ethanolic extract of Psoralea corylifolia and characterized its estrogenic activity by ligand binding, reporter gene activation, and endogenous estrogen receptor (ER) target gene regulation. Bavachin showed ER ligand binding activity in competitive displacement of [3H] E2 from recombinant ER. The estrogenic activity of bavachin was characterized in a transient transfection system using ER? or ER? and estrogen-responsive luciferase plasmids in CV-1 cells with an EC50 of 320 nM and 680 nM, respectively. Bavachin increased the mRNA levels of estrogen-responsive genes such as pS2 and PR, and decreased the protein level of ER? by proteasomal pathway. However, bavachin failed to activate the androgen receptor in CV-1 cells transiently transfected with the corresponding receptor and hormone responsive reporter plasmid. These data indicate that bavachin acts as a weak phytoestrogen by binding and activating the ER. PMID:24116293

Park, Joonwoo; Kim, Do Hee; Ahn, Hye-Na; Song, Yun Seon; Lee, Young Joo; Ryu, Jae-Ha

2012-01-01

193

Activation of intestinal Peroxisome Proliferator-Activated Receptor increases HDL Sophie Colin1,2,3,4  

E-print Network

1 Activation of intestinal Peroxisome Proliferator-Activated Receptor increases HDL production, Peroxisome proliferator-activated receptor; Disclosures: No conflicts of interest exist inserm-00730530.1093/eurheartj/ehs227 #12;2 Abstract Aims: Peroxisome Proliferator-Activated Receptor (PPAR)1 is a transcription

Paris-Sud XI, Université de

194

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

195

Ligand binding and co-activator assembly of the peroxisome proliferator-activated receptor-?  

Microsoft Academic Search

The peroxisome proliferator-activated receptor-? (PPAR-?) is a ligand-dependent transcription factor that is important in adipocyte differentiation and glucose homeostasis and which depends on interactions with co-activators, including steroid receptor co-activating factor-1 (SRC-1). Here we present the X-ray crystal structure of the human apo-PPAR-? ligand-binding domain (LBD), at 2.2 ? resolution; this structure reveals a large binding pocket, which may explain

Robert T. Nolte; G. Bruce Wisely; Stefan Westin; Jeffery E. Cobb; Millard H. Lambert; Riki Kurokawa; Michael G. Rosenfeldk; Timothy M. Willson; Christopher K. Glass; Michael V. Milburn

1998-01-01

196

Protease-activated-receptor-2 affects protease-activated-receptor-1-driven breast cancer.  

PubMed

Mammalian protease-activated-receptor-1 and -2 (PAR1 and PAR2) are activated by proteases found in the flexible microenvironment of a tumor and play a central role in breast cancer. We propose in the present study that PAR1 and PAR2 act together as a functional unit during malignant and physiological invasion processes. This notion is supported by assessing pro-tumor functions in the presence of short hairpin; shRNA knocked-down hPar2 or by the use of a truncated PAR2 devoid of the entire cytoplasmic tail. Silencing of hPar2 by shRNA-attenuated thrombin induced PAR1 signaling as recapitulated by inhibiting the assembly of Etk/Bmx or Akt onto PAR1-C-tail, by thrombin-instigated colony formation and invasion. Strikingly, shRNA-hPar2 also inhibited the TFLLRN selective PAR1 pro-tumor functions. In addition, while evaluating the physiological invasion process of placenta extravillous trophoblast (EVT) organ culture, we observed inhibition of both thrombin or the selective PAR1 ligand; TFLLRNPNDK induced EVT invasion by shRNA-hPar2 but not by scrambled shRNA-hPar2. In parallel, when a truncated PAR2 was utilized in a xenograft mouse model, it inhibited PAR1-PAR2-driven tumor growth in vivo. Similarly, it also attenuated the interaction of Etk/Bmx with the PAR1-C-tail in vitro and decreased markedly selective PAR1-induced Matrigel invasion. Confocal images demonstrated co-localization of PAR1 and PAR2 in HEK293T cells over-expressing YFP-hPar2 and HA-hPar1. Co-immuno-precipitation analyses revealed PAR1-PAR2 complex formation but no PAR1-CXCR4 complex was formed. Taken together, our observations show that PAR1 and PAR2 act as a functional unit in tumor development and placenta-uterus interactions. This conclusion may have significant consequences on future breast cancer therapeutic modalities and improved late pregnancy outcome. PMID:24177339

Jaber, Mohammad; Maoz, Miriam; Kancharla, Arun; Agranovich, Daniel; Peretz, Tamar; Grisaru-Granovsky, Sorina; Uziely, Beatrice; Bar-Shavit, Rachel

2014-07-01

197

The Laminin 511/521-binding site on the Lutheran blood group glycoprotein is located at the flexible junction of Ig domains 2 and 3  

PubMed Central

The Lutheran blood group glycoprotein, first discovered on erythrocytes, is widely expressed in human tissues. It is a ligand for the ?5 subunit of Laminin 511/521, an extracellular matrix protein. This interaction may contribute to vaso-occlusive events that are an important cause of morbidity in sickle cell disease. Using x-ray crystallography, small-angle x-ray scattering, and site-directed mutagenesis, we show that the extracellular region of Lutheran forms an extended structure with a distinctive bend between the second and third immunoglobulin-like domains. The linker between domains 2 and 3 appears to be flexible and is a critical determinant in maintaining an overall conformation for Lutheran that is capable of binding to Laminin. Mutagenesis studies indicate that Asp312 of Lutheran and the surrounding cluster of negatively charged residues in this linker region form the Laminin-binding site. Unusually, receptor binding is therefore not a function of the domains expected to be furthermost from the plasma membrane. These studies imply that structural flexibility of Lutheran may be essential for its interaction with Laminin and present a novel opportunity for the development of therapeutics for sickle cell disease. PMID:17638854

Burton, Nicholas; Stefansdottir, Fanney O.; Spring, Frances A.; Parsons, Stephen F.; Pedersen, Jan S.; Oliveira, Cristiano L. P.; Lammie, Donna; Wess, Timothy; Mohandas, Narla; Chasis, Joel Anne; Anstee, David J.

2007-01-01

198

The Laminin 511/521 Binding Site on the Lutheran Blood Group Glycoprotein is Located at theFlexible Junction of Ig Domains 2 and 3  

SciTech Connect

The Lutheran blood group glycoprotein, first discovered on erythrocytes, is widely expressed in human tissues. It is a ligand for the {alpha}5 subunit of Laminin 511/521, an extracellular matrix protein. This interaction may contribute to vasocclusive events that are an important cause of morbidity in sickle cell disease. Using X-ray crystallography, small angle X-ray scattering and site directed mutagenesis we show that the extracellular region of Lutheran forms an extended structure with a distinctive bend between the second and third immunoglobulin-like domains. The linker between domains 2 and 3 appears to be flexible and is a critical determinant in maintaining an overall conformation for Lutheran that is capable of binding to Laminin. Mutagenesis studies indicate that Asp312 of Lutheran and the surrounding cluster of negatively charged residues in this linker region form the Laminin binding site. Unusually, receptor binding is therefore not a function of the domains expected to be furthermost from the plasma membrane. These studies imply that structural flexibility of Lutheran may be essential for its interaction with Laminin and present a novel opportunity for the development of therapeutics for sickle cell disease.

Mankelow, Tosti J.; Burton, Nicholas; Stedansdottir, Fanney O.; Spring, Frances A.; Parsons, Stephen F.; Pesersen, Jan S.; Oliveira, Cristiano L.P.; Lammie, Donna; Wess, Timothy; Mohandas, Narla; Chasis, Joel A.; Brady, R. Leo; Anstee, David J.

2007-07-01

199

Fast oscillatory activity induced by kainate receptor activation in the rat basolateral amygdala in vitro.  

PubMed

The basolateral amygdala (BLA) has a fundamental role in affective processing. In vivo studies have revealed rhythmic population activity of a similar type to that seen in the hippocampus and cortical areas during learning tasks. The amygdala contains densely interconnected networks of inhibitory interneurons similar to those responsible for fast network activity generation in the hippocampus and other cortical structures. Here we report that neuronal networks of the BLA in isolation generate persistent, gamma frequency (30-80 Hz) oscillations upon kainate receptor activation with kainic acid. We show that, like other cortical structures, BLA oscillations are completely dependent upon ?-aminobutyric acid (GABA)ergic inhibition. GABA(A) receptor blockade abolished all oscillations, and the activity was also sensitive to the barbiturate, pentobarbital. Blockade of ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors or N-methyl-D-aspartate (NMDA) receptors had no significant effect on gamma activity. However, the GluR5-containing kainate receptor-specific antagonist (S)-1-(2-amino-2-carboxyethyl)-3-(2-carboxybenzyl) pyrimidine-2,4-dione (UBP302) abolished oscillations-evidence that glutamatergic receptor involvement is predominantly kainate receptor mediated. The mixed AMPA/kainate receptor antagonist 6-nitro-7-sulphamoylbenzo[f]quinoxalone-2,3-dione disodium (NBQX) abolished all oscillatory activity in 8/14 of slices tested. In the remaining slices, gamma frequency activity was abolished to reveal a low-amplitude, NMDA receptor-dependent, beta frequency (10-20 Hz) oscillation. Gamma oscillations are abolished by gap junction blockade. While these data show the BLA capable of generating gamma rhythms in common with other cortical areas studied to date, the network mechanisms appear to be different, suggesting a unique network structure underlies amygdala rhythmogenesis. Understanding how BLA networks produce synchronous activity is paramount to understanding how the BLA executes influence on important cognitive processes such as emotional learning. PMID:21255131

Randall, Fiona E; Whittington, Miles A; Cunningham, Mark O

2011-03-01

200

Solubilization and characterization of active neurotensin receptors from mouse brain  

SciTech Connect

Neurotensin receptors were solubilized from mouse brain using the zwitterionic detergent 3-((3-cholamidopropyl)dimethylammonio)-1-propanesulfonic acid (CHAPS). The binding of /sup 125/I-labeled (Tyr/sup 3/)neurotensin to the soluble fraction was time-dependent, saturable, and reversible. Unlabeled neurotensin and its analogues acetylneurotensin (8-13), neurotensin (9-13), and neurotensin (1-12) competitively antagonized the binding of /sup 125/I-labeled (Tyr/sup 3/)neurotensin to CHAPS-solubilized extracts with relative potencies similar to those observed with membrane-bound receptors. Scatchard analysis of equilibrium binding data indicated that the soluble extract contained a single class of neurotensin binding sites with a K/sub d/ of 0.36 nM and a B/sub m/ of 63 fmol/mg. As already observed with membrane-bound receptors, the affinity of neurotensin for the soluble binding activity was decreased by Na/sup +/ ions. By contrast, soluble receptors were no longer sensitive to GTP and the antihistamine drug levocabastine. A molecular weight of about 100,000 was determined for soluble neurotensin receptors both under native conditions by gel filtration on Ultrogel AcA 34 and under denaturating conditions by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after photoaffinity labeling.

Mazella, J.; Chabry, J.; Kitabgi, P.; Vincent, J.P.

1988-01-05

201

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

202

Peroxisome proliferator-activated receptor ? and colorectal cancer  

PubMed Central

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily and ligand-activated transcription factors. PPAR? plays an important role in adipocyte differentiation, lipid storage and energy dissipation in adipose tissue, and is involved in the control of inflammatory reactions as well as in glucose metabolism through the improvement of insulin sensitivity. Growing evidence has demonstrated that activation of PPAR? has an antineoplastic effect in tumors, including colorectal cancer. High expression of PPAR? is detected in human colon cancer cell lines and adenocarcinoma. This review describes the molecular mechanisms by which PPAR? regulates tumorigenesis in colorectal cancer, and examines current clinical trials evaluating PPAR? agonists as therapeutic agents for colorectal cancer. PMID:21160824

Dai, Yun; Wang, Wei-Hong

2010-01-01

203

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; Muller, Michael; Kersten, Sander

2010-01-01

204

Laminin-?1 Impairs Spatial Learning through Inhibition of ERK/MAPK and SGK1 Signaling  

PubMed Central

Laminin is a major structural element of the basal lamina consisting of an ?-chain, a ?-chain, and a ?-chain arranged in a cross-like structure, with their C-terminal inter-coiled. Laminin is abundantly expressed in the hippocampus of mature brain and is implicated in several psychiatric disorders, but its possible role involved in learning and memory function is not known. This issue was examined here. Our results revealed that water maze training significantly decreased laminin-?1 (LB1) expression in the rat hippocampal CA1 area. Transfection of LB1 WT plasmid to hippocampal CA1 neurons impaired water maze performance in rats. Meanwhile, it decreased the phosphorylation level of ERK/MAPK and protein kinase serum- and glucocorticoid-inducible kinase-1 (SGK1). By contrast, knockdown of endogenous LB1 expression using RNA interference (LB1 siRNA) enhanced water maze performance. Meanwhile, it increased the phosphorylation level of ERK/MAPK and SGK1. The enhancing effect of LB1 siRNA on spatial learning and on the phosphorylation of ERK/MAPK and SGK1 was blocked by co-treatment with the MEK inhibitor U0126 at a concentration that did not apparently affect spatial learning and ERK/MAPK phosphorylation alone. Further, the enhancing effect of LB1 siRNA on spatial learning and SGK1 phosphorylation was similarly blocked by co-transfection with SGK1 siRNA at a concentration that did not markedly affect spatial learning and SGK1 expression alone. These results together indicate that LB1 negatively regulates spatial learning in rats. In addition, LB1 impairs spatial learning through decreased activation of the ERK/MAPK–SGK1 signaling pathway in the rat hippocampus. PMID:21849984

Yang, Ying C; Ma, Yun L; Liu, Wen T; Lee, Eminy HY

2011-01-01

205

Ligand mobility regulates B cell receptor clustering and signaling activation.  

PubMed

Antigen binding to the B cell receptor (BCR) induces receptor clustering, cell spreading, and the formation of signaling microclusters, triggering B cell activation. Although the biochemical pathways governing early B cell signaling have been well studied, the role of the physical properties of antigens, such as antigen mobility, has not been fully examined. We study the interaction of B cells with BCR ligands coated on glass or tethered to planar lipid bilayer surfaces to investigate the differences in B cell response to immobile and mobile ligands. Using high-resolution total internal reflection fluorescence (TIRF) microscopy of live cells, we followed the movement and spatial organization of BCR clusters and the associated signaling. Although ligands on either surface were able to cross-link BCRs and induce clustering, B cells interacting with mobile ligands displayed greater signaling than those interacting with immobile ligands. Quantitative analysis revealed that mobile ligands enabled BCR clusters to move farther and merge more efficiently than immobile ligands. These differences in physical reorganization of receptor clusters were associated with differences in actin remodeling. Perturbation experiments revealed that a dynamic actin cytoskeleton actively reorganized receptor clusters. These results suggest that ligand mobility is an important parameter for regulating B cell signaling. PMID:24411234

Ketchum, Christina; Miller, Heather; Song, Wenxia; Upadhyaya, Arpita

2014-01-01

206

Human peroxisome proliferator-activated receptor mRNA and protein expression during development  

EPA Science Inventory

The peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that regulate lipid and glucose homeostasis and are important in reproduction and development. PPARs are targets ofpharmaceuticals and are also activated by environmental contaminants, including ...

207

Influence of Peroxisome Proliferator-activated Receptor aaa on Ubiquinone Biosynthesis  

E-print Network

Influence of Peroxisome Proliferator-activated Receptor aaa on Ubiquinone Biosynthesis Mikael Institute NIH, Bethesda, Maryland 20892, USA The control of ubiquinone biosynthesis by peroxisome proliferators was investigated using peroxisome proliferator activated receptor a (PPARa)- null mice

Omiecinski, Curtis

208

alpha7 receptor-selective agonists and modes of alpha7 receptor activation.  

PubMed

The alpha7-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) alpha7-type receptor, to test a model for the concentration-dependent desensitization of alpha7-mediated responses. Our results confirm that 4OH-GTS-21 is a potent activator of neuronal alpha7 nicotinic-acetylcholine receptor. The rapid application of agonist leads to a brief period of maximal receptor-activation followed by desensitization. Rise rates, decay rates, and the degree to which current was desensitized were all concentration-dependent. Following the initial peak response to a 300-microM 4OH-GTS-21 application, current is reduced to baseline values within about 100 ms. Application of 30 microM 4OH-GTS-21 produced both a transient peak current and a sustained current that decayed only slowly after the removal of agonist. In the case of a 300-microM 4OH-GTS-21 application, after agonist was removed, we saw a rebound response up to the level of the 30-microM sustained current. The data, therefore, suggest that a sufficient level of agonist occupation can be retained on the receptor to promote activation for up to several hundred milliseconds. PMID:10771012

Papke, R L; Meyer, E; Nutter, T; Uteshev, V V

2000-03-30

209

Redox regulation of human protease-activated receptor-2 by activated factor X  

Microsoft Academic Search

Activated factor X (FXa) exerts coagulation-independent actions such as proliferation of vascular smooth muscle cells (SMCs) through the protease-activated receptors PAR-1 and PAR-2. Both receptors are upregulated upon vascular injury but the underlying mechanisms have not been defined. We examined if FXa regulates PAR-1 and PAR-2 in human vascular SMCs. FXa increased PAR-2 mRNA, protein, and cell-surface expression and augmented

Klaus Jobi; Bernhard H. Rauch; Seema Dangwal; Kerstin Freidel; Anke Doller; Wolfgang Eberhardt; Jens W. Fischer; Karsten Schrör; Anke C. Rosenkranz

2011-01-01

210

Laminin-database v.2.0: an update on laminins in health and neuromuscular disorders.  

PubMed

The laminin (LM)-database, hosted at http://www.lm.lncc.br, was published in the NAR database 2011 edition. It was the first database that provided comprehensive information concerning a non-collagenous family of extracellular matrix proteins, the LMs. In its first version, this database contained a large amount of information concerning LMs related to health and disease, with particular emphasis on the haemopoietic system. Users can easily access several tabs for LMs and LM-related molecules, as well as LM nomenclatures and direct links to PubMed. The LM-database version 2.0 integrates data from several publications to achieve a more comprehensive knowledge of LMs in health and disease. The novel features include the addition of two new tabs, 'Neuromuscular Disorders' and 'miRNA--LM Relationship'. More specifically, in this updated version, an expanding set of data has been displayed concerning the role of LMs in neuromuscular and neurodegenerative diseases, as well as the putative involvement of microRNAs. Given the importance of LMs in several biological processes, such as cell adhesion, proliferation, differentiation, migration and cell death, this upgraded version expands for users a panoply of information, regarding complex molecular circuitries that involve LMs in health and disease, including neuromuscular and neurodegenerative disorders. PMID:24106090

Golbert, Daiane C F; Santana-van-Vliet, Eliane; Mundstein, Alex S; Calfo, Vicente; Savino, Wilson; de Vasconcelos, Ana Tereza R

2014-01-01

211

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

212

Mechanism of A2 adenosine receptor activation. I. Blockade of A2 adenosine receptors by photoaffinity labeling  

SciTech Connect

It has previously been shown that covalent incorporation of the photoreactive adenosine derivative (R)-2-azido-N6-p-hydroxy-phenylisopropyladenosine ((R)-AHPIA) into the A1 adenosine receptor of intact fat cells leads to a persistent activation of this receptor, resulting in a reduction of cellular cAMP levels. In contrast, covalent incorporation of (R)-AHPIA into human platelet membranes, which contain only stimulatory A2 adenosine receptors, reduces adenylate cyclase stimulation via these receptors. This effect of (R)-AHPIA is specific for the A2 receptor and can be prevented by the adenosine receptor antagonist theophylline. Binding studies indicate that up to 90% of A2 receptors can be blocked by photoincorporation of (R)-AHPIA. However, the remaining 10-20% of A2 receptors are sufficient to mediate an adenylate cyclase stimulation of up to 50% of the control value. Similarly, the activation via these 10-20% of receptors occurs with a half-life that is only 2 times longer than that in control membranes. This indicates the presence of a receptor reserve, with respect to both the extent and the rate of adenylate cyclase stimulation. These observations require a modification of the models of receptor-adenylate cyclase coupling.

Lohse, M.J.; Klotz, K.N.; Schwabe, U.

1991-04-01

213

NMDA receptor activation strengthens weak electrical coupling in mammalian brain.  

PubMed

Electrical synapses are formed by gap junctions and permit electrical coupling, which shapes the synchrony of neuronal ensembles. Here, we provide a direct demonstration of receptor-mediated strengthening of electrical coupling in mammalian brain. Electrical coupling in the inferior olive of rats was strengthened by activation of NMDA-type glutamate receptors (NMDARs), which were found at synaptic loci and at extrasynaptic loci 20-100 nm proximal to gap junctions. Electrical coupling was strengthened by pharmacological and synaptic activation of NMDARs, whereas costimulation of ionotropic non-NMDAR glutamate receptors transiently antagonized the effect of NMDAR activation. NMDAR-dependent strengthening (1) occurred despite increased input conductance, (2) induced Ca(2+)-influx microdomains near dendritic spines, (3) required activation of the Ca(2+)/calmodulin-dependent protein-kinase II, (4) was restricted to neurons that were weakly coupled, and (5) thus strengthened coupling, mainly between nonadjacent neurons. This provided a mechanism to expand the synchronization of rhythmic membrane potential oscillations by chemical neurotransmitter input. PMID:24656255

Turecek, Josef; Yuen, Genevieve S; Han, Victor Z; Zeng, Xiao-Hui; Bayer, K Ulrich; Welsh, John P

2014-03-19

214

Bisphenol A and Its Analogues Activate Human Pregnane X Receptor  

PubMed Central

Background: Bisphenol A (BPA) is a base chemical used extensively in many consumer products. BPA and its analogues are present in environmental and human samples. Many endocrine-disrupting chemicals, including BPA, have been shown to activate the pregnane X receptor (PXR), a nuclear receptor that functions as a master regulator of xenobiotic metabolism. However, the detailed mechanism by which these chemicals activate PXR remains unknown. Objective: We investigated the mechanism by which BPA interacts with and activates PXR and examined selected BPA analogues to determine whether they bind to and activate PXR. Methods: Cell-based reporter assays, in silico ligand–PXR docking studies, and site-directed mutagenesis were combined to study the interaction between BPA and PXR. We also investigated the influence of BPA and its analogues on the regulation of PXR target genes in human LS180 cells. Results: We found that BPA and several of its analogues are potent agonists for human PXR (hPXR) but do not affect mouse PXR activity. We identified key residues within hPXR’s ligand-binding pocket that constitute points of interaction with BPA. We also deduced the structural requirements of BPA analogues that activate hPXR. BPA and its analogues can also induce PXR target gene expression in human LS180 cells. Conclusions: The present study advances our understanding of the mechanism by which BPA interacts with and activates human PXR. Activation of PXR by BPA may explain some of the adverse effects of BPA in humans. PMID:22214767

Sui, Yipeng; Ai, Ni; Park, Se-Hyung; Rios-Pilier, Jennifer; Perkins, Jordan T.; Welsh, William J.

2012-01-01

215

Mycobacterial laminin-binding histone-like protein mediates collagen-dependent cytoadherence.  

PubMed

When grown in the presence of exogenous collagen I, Mycobacterium bovis BCG was shown to form clumps. Scanning electron microscopy examination of these clumps revealed the presence of collagen fibres cross-linking the bacilli. Since collagen is a major constituent of the eukaryotic extracellular matrices, we assayed BCG cytoadherence in the presence of exogenous collagen I. Collagen increased the interaction of the bacilli with A549 type II pneumocytes or U937 macrophages, suggesting that BCG is able to recruit collagen to facilitate its attachment to host cells. Using an affinity chromatography approach, we have isolated a BCG collagen-binding protein corresponding to the previously described mycobacterial laminin-binding histone-like protein (LBP/Hlp), a highly conserved protein associated with the mycobacterial cell wall. Moreover, Mycobacterium leprae LBP/Hlp, a well-characterized adhesin, was also able to bind collagen I. Finally, using recombinant fragments of M. leprae LBP/Hlp, we mapped the collagen-binding activity within the C-terminal domain of the adhesin. Since this protein was already shown to be involved in the recognition of laminin and heparan sulphate-containing proteoglycans, the present observations reinforce the adhesive activities of LBP/Hlp, which can be therefore considered as a multifaceted mycobacterial adhesin, playing an important role in both leprosy and tuberculosis pathogenesis. PMID:23283469

Dias, André Alves; Raze, Dominique; de Lima, Cristiana Soares; Marques, Maria Angela de Melo; Drobecq, Hervé; Debrie, Anne-Sophie; Ribeiro-Guimarães, Michelle Lopes; Biet, Franck; Pessolani, Maria Cristina Vidal

2012-12-01

216

Peroxisome proliferator activated receptor-? and traumatic brain injury  

PubMed Central

Traumatic brain injury (TBI) represents a major health care problem and a significant socioeconomic challenge worldwide. No specific therapy for TBI is available. The peroxisome proliferator activated receptor-? (PPAR-?) belongs to the nuclear receptor superfamily. Although PPAR-? was originally characterized in adipose tissue as a regulator of lipid and glucose metabolism, recent studies showed that PPAR-? is present in most cell types and plays a central role in the regulation of adipogenesis, glucose homeostasis, cellular differentiation, apoptosis and inflammation. Here, we reviewed the current literature on the molecular mechanisms of PPAR-?-related neuroprotection after TBI. Growing evidence has indicated that the beneficial effects of PPAR-? activation in TBI appear to be mediated through downregulation of inflammatory responses, reduction of oxidative stress, inhibition of apoptosis, and promotion of neurogenesis. A thorough understanding of the PPAR-? pathway will be critical to the development of therapeutic interventions for the treatment of patients with TBI. PMID:21072262

Qi, Lei; Jacob, Asha; Wang, Ping; Wu, Rongqian

2010-01-01

217

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

218

Insect Repellents: Modulators of Mosquito Odorant Receptor Activity  

Microsoft Academic Search

BackgroundDEET, 2-undecanone (2-U), IR3535 and Picaridin are widely used as insect repellents to prevent interactions between humans and many arthropods including mosquitoes. Their molecular action has only recently been studied, yielding seemingly contradictory theories including odorant-dependent inhibitory and odorant-independent excitatory activities on insect olfactory sensory neurons (OSNs) and odorant receptor proteins (ORs).Methodology\\/Principal FindingsHere we characterize the action of these repellents

Jonathan D. Bohbot; Joseph C. Dickens; Mark A. Frye

2010-01-01

219

XAP2 inhibits glucocorticoid receptor activity in mammalian cells  

Microsoft Academic Search

XAP2 is member of a protein family sharing the TPR protein interaction motif. It displays close homology to the immunophilins FKBP51 and FKBP52 that act via the Hsp90 folding machinery to regulate the glucocorticoid receptor (GR). We show that XAP2 inhibits GR by reducing its responsiveness to hormone in transcriptional activation. The effect of XAP2 on GR requires its interaction

Anna Laenger; Isabelle Lang-Rollin; Christian Kozany; Jürgen Zschocke; Nicole Zimmermann; Joëlle Rüegg; Florian Holsboer; Felix Hausch; Theo Rein

2009-01-01

220

Alternative modes of GM-CSF receptor activation revealed using activated mutants of the common ?-subunit  

PubMed Central

Granulocyte/macrophage colony-stimulating factor promotes growth, survival, differentiation, and activation of normal myeloid cells and plays an important role in myeloid leukemias. The GM-CSF receptor (GMR) shares a signaling subunit, ?c, with interleukin-3 and interleukin-5 receptors and has recently been shown to induce activation of Janus kinase 2 (JAK2) and downstream signaling via formation of a unique dodecameric receptor complex. In this study we use 2 activated ?c mutants that display distinct signaling capacity and have differential requirements for the GMR ?-subunit (GMR-?) to dissect the signaling pathways associated with the GM-CSF response. The V449E transmembrane mutant selectively activates JAK2/signal transducer and activator of transcription 5 and extracellular signal-regulated kinase (ERK) pathways, resulting in a high level of sensitivity to JAK and ERK inhibitors, whereas the extracellular mutant (FI?) selectively activates the phosphoinositide 3-kinase/Akt and I?K?/nuclear factor?B pathways. We also demonstrate a novel and direct interaction between the SH3 domains of Lyn and Src with a conserved proline-rich motif in GMR-? and show a selective requirement for Src family kinases by the FI? mutant. We relate the nonoverlapping nature of signaling by the activated mutants to the structure of the unique GMR complex and propose alternative modes of receptor activation acting synergistically in the mature liganded receptor complex. PMID:20173116

Perugini, Michelle; Brown, Anna L.; Salerno, Diana G.; Booker, Grant W.; Stojkoski, Cvetan; Hercus, Timothy R.; Lopez, Angel F.; Hibbs, Margaret L.; Gonda, Thomas J.

2010-01-01

221

(Pro)Renin Receptor–Mediated Activation of Mitogen-Activated Protein Kinases in Human Vascular Smooth Muscle Cells  

Microsoft Academic Search

Blockade of (pro)renin receptor has benefits in diabetic angiotensin II type-1a-receptor–deficient mice, suggesting the importance of (pro)renin receptor–mediated intracellular signals. To determine the mechanism whereby the human (pro)renin receptor activates mitogen-activated protein kinases in human vascular smooth muscle cells (hVSMC), we treated the cells with recombinant human prorenin. Prorenin enhanced hVSMC proliferation and activated extracellular-signal–related protein kinase (ERK) in a

Mariyo Sakoda; Atsuhiro Ichihara; Yuki Kaneshiro; Tomoko Takemitsu; Yuichi Nakazato; A. H. M. Nurun NABI; Tsutomu Nakagawa; Fumiaki Suzuki; Tadashi Inagami; Hiroshi Itoh

2007-01-01

222

Ultrastructural and biochemical analysis of fibrinogen receptors on activated thrombocytes  

SciTech Connect

The present studies have been concerned with the role of fibrinogen and its receptor, GP IIb/IIIa, during the activation and early aggregation of pigeon thrombocytes. Thrombocytes were surface labeled with {sup 125}I then separated on SDS-PAGE. Analysis by gel autoradiography revealed major bands at MW 145 kd and 98 kd, which corresponded to human GPIIb and GPIIIa. Immunologic similarity of the pigeon and human receptor components was established by dot blot analysis using polyclonal antibodies directed against human GPIIb and GPIIIa. Pigeon fibrinogen, isolated by plasma precipitation with PEG-1000 and purified over Sepharose 4B, was used to study receptor-ligand interaction. Separation of pigeon fibrinogen on SDS-PAGE resulted in three peptides having apparent MW of 62kd, 55kd, and 47kd which are comparable to human fibrinogen. Further similarity of human and pigeon fibrinogen was verified by immonodiffusion against an antibody specific for the human protein. The role of fibrinogen and its receptor in thrombocyte function was established by turbidimetric aggregation using thrombin as an agonist under conditions requiring Ca++ and fibrinogen.

O'Toole, E.T.

1989-01-01

223

Cleavage and activation of a Toll-like receptor by microbial proteases.  

PubMed

Toll-like receptors (TLRs) are innate receptors that show high conservation throughout the animal kingdom. Most TLRs can be clustered into phylogenetic groups that respond to similar types of ligands. One exception is avian TLR15. This receptor does not categorize into one of the existing groups of TLRs and its ligand is still unknown. Here we report that TLR15 is a sensor for secreted virulence-associated fungal and bacterial proteases. Activation of TLR15 involves proteolytic cleavage of the receptor ectodomain and stimulation of NF-?B-dependent gene transcription. Receptor activation can be mimicked by the expression of a truncated TLR15 of which the entire ectodomain is removed, suggesting that receptor cleavage alleviates receptor inhibition by the leucine-rich repeat domain. Our results indicate TLR15 as a unique type of innate immune receptor that combines TLR characteristics with an activation mechanism typical for the evolutionary distinct protease-activated receptors. PMID:21383168

de Zoete, Marcel R; Bouwman, Lieneke I; Keestra, A Marijke; van Putten, Jos P M

2011-03-22

224

Activation of mitogen-activated protein kinases by a splice variant of GHRH receptor.  

PubMed

Hypothalamic GHRH controls the release of GH from the pituitary gland and also acts as a growth factor in a variety of cancers. The mitogenetic activity of GHRH is exerted through the binding to the pituitary type receptor (pGHRH-R) and its splice variants, mainly SV1. The intracellular signaling pathways that are activated upon the binding of GHRH to the SV1 receptor have not been elucidated. HeLa cervical cancer cells do not express GHRH or GHRH receptors (GHRHRs) and thus do not respond to GHRH or GHRH antagonists. In order to elucidate the mechanism of action of SV1 receptor, we transfected HeLa cells with plasmids for pcDNA3-GHRHR or pcDNA3-SV1. The transfected cells responded to both GHRH (1-29)NH(2) and GHRH antagonist MZ-5-156, as shown by an increase or decrease respectively in the proliferation rate in vitro and the expression of proliferative cell nuclear antigen. We also demonstrated that when the cells transfected with SV1 plasmid are stimulated with GHRH (1-29)NH(2), SV1 receptor activates the mitogen-activated protein kinases pathway (MAPKs), as shown previously for the cells that express pGHRH-R. Our results show, for the first time, the activation of the MAPKs cascade by the SV1 receptor. Since SV1 receptor is found in various tumors and mediates the responses to GHRH and synthetic antagonists, our findings shed light on the mechanism of action of SV1 receptor in cancer cells. PMID:19897610

Barabutis, Nektarios; Siejka, Agnieszka; Schally, Andrew V; Block, Norman L; Cai, Renzhi; Varga, Joseph L

2010-02-01

225

Acute Activation, Desensitization and Smoldering Activation of Human Acetylcholine Receptors  

PubMed Central

The behavioral effects of nicotine and other nicotinic agonists are mediated by AChRs in the brain. The relative contribution of acute activation versus chronic desensitization of AChRs is unknown. Sustained “smoldering activation” occurs over a range of agonist concentrations at which activated and desensitized AChRs are present in equilibrium. We used a fluorescent dye sensitive to changes in membrane potential to examine the effects of acute activation and chronic desensitization by nicotinic AChR agonists on cell lines expressing human ?4?2, ?3?4 and ?7 AChRs. We examined the effects of acute and prolonged application of nicotine and the partial agonists varenicline, cytisine and sazetidine-A on these AChRs. The range of concentrations over which nicotine causes smoldering activation of ?4?2 AChRs was centered at 0.13 µM, a level found in smokers. However, nicotine produced smoldering activation of ?3?4 and ?7 AChRs at concentrations well above levels found in smokers. The ?4?2 expressing cell line contains a mixture of two stoichiometries, namely (?4?2)2?2 and (?4?2)2?4. The (?4?2)2?2 stoichiometry is more sensitive to activation by nicotine. Sazetidine-A activates and desensitizes only this stoichiometry. Varenicline, cytisine and sazetidine-A were partial agonists on this mixture of ?4?2 AChRs, but full agonists on ?3?4 and ?7 AChRs. It has been reported that cytisine and varenicline are most efficacious on the (?4?2)2?4 stoichiometry. In this study, we distinguish the dual effects of activation and desensitization of AChRs by these nicotinic agonists and define the range of concentrations over which smoldering activation can be sustained. PMID:24244538

Campling, Barbara G.; Kuryatov, Alexander; Lindstrom, Jon

2013-01-01

226

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

227

Identification of intracellular receptor proteins for activated protein kinase C.  

PubMed Central

Protein kinase C (PKC) translocates from the cytosol to the particulate fraction on activation. This activation-induced translocation of PKC is thought to reflect PKC binding to the membrane lipids. However, immunological and biochemical data suggest that PKC may bind to proteins in the cytoskeletal elements in the particulate fraction and in the nuclei. Here we describe evidence for the presence of intracellular receptor proteins that bind activated PKC. Several proteins from the detergent-insoluble material of the particulate fraction bound PKC in the presence of phosphatidylserine and calcium; binding was further increased with the addition of diacylglycerol. Binding of PKC to two of these proteins was concentration-dependent, saturable, and specific, suggesting that these binding proteins are receptors for activated C-kinase, termed here "RACKs." PKC binds to RACKs via a site on PKC distinct from the substrate binding site. We suggest that binding to RACKs may play a role in activation-induced translocation of PKC. Images PMID:1850844

Mochly-Rosen, D; Khaner, H; Lopez, J

1991-01-01

228

Counter-regulatory role of bile acid activated receptors in immunity and inflammation.  

PubMed

In addition to their role in dietary lipid absorption bile acids are signaling modules activating nuclear receptors and at least one G-protein coupled receptors named the TGR5. With a different rank of potency primary and secondary bile acids activates a subset of nuclear receptors including the farnesoid-X-receptor (FXR, NR1H4); the constitutive androstane receptor (CAR, NR1H3), the pregnane-x- receptor (PXR, NR1H2), the vitamin D receptor (VDR, NR1H1). Originally, these receptors were characterized for their role as bile acid and xenobiotic sensors, emerging evidence, however, indicates that FXR, PXR and VDR and their ligands are important for the modulation of immune and inflammatory reactions in entero-hepatic tissues. The immune phenotype FXR deficient mice indicates that these receptors are essential for the maintenance of immune homeostasis. A common theme of all bile acid-activated receptor is their ability to counter-regulate effector activities of cells of innate immunity establishing that signals generated by these receptors and their ligands function as a braking signals for inflammation in entero-hepatic tissues. In this review, we will spotlight the molecular mechanisms of receptor/ligand function and how bile acid-activated receptors regulate the innate immunity in the gastrointestinal tract and liver. The ability of these receptors to integrate metabolic and inflammatory signaling makes them particularly attractive targets for intervention in immune-mediated diseases. PMID:20642438

Fiorucci, S; Cipriani, S; Mencarelli, A; Renga, B; Distrutti, E; Baldelli, F

2010-08-01

229

The Borrelia burgdorferi outer-surface protein ErpX binds mammalian laminin  

Microsoft Academic Search

The Lyme disease spirochaete, Borrelia burgdorferi, can invade and persistently infect its hosts' connective tissues. We now demonstrate that B. burgdorferi adheres to the extracellular matrix component laminin. The surface-exposed outer-membrane protein ErpX was identified as having affinity for laminin, and is the first laminin-binding protein to be identified in a Lyme disease spirochaete. The adhesive domain of ErpX was

Catherine A. Brissette; Ashutosh Verma; Amy Bowman; Anne E. Cooley; Brian Stevenson

2009-01-01

230

Tissue distribution of the laminin ?1 and ?2 chain during embryonic and fetal human development  

Microsoft Academic Search

Laminins are the major glycoproteins present in all basement membranes. Previously, we showed that perlecan is present during\\u000a human development. Although an overview of mRNA-expression of the laminin ?1 and ?2 chains in various developing fetal organs\\u000a is already available, a systematic localization of the laminin ?1 and ?2 chains on the protein level during embryonic and\\u000a fetal human development

Matthias Roediger; Nicolai Miosge; Nikolaus Gersdorff

2010-01-01

231

The Orphan Nuclear Receptor Constitutive Active\\/Androstane Receptor Is Essential for Liver Tumor Promotion by Phenobarbital in Mice  

Microsoft Academic Search

Hepatocellular carcinoma (HCC) is known to progress through a step often called tumor promotion. Phenobarbital (PB) is the prototype of nongenotoxic cacinogens that promote HCC in rodents. The molecular target of PB to elicit the promotion has been the subject of intense investigations over the last 30 years since it was discovered. The nuclear receptor constitutive active\\/androstane receptor (CAR) is

Yukio Yamamoto; Rick Moore; Thomas L. Goldsworthy; Masahiko Negishi; Robert R. Maronpot

2004-01-01

232

Reduced beta-adrenergic receptor activation decreases G-protein expression and beta-adrenergic receptor kinase activity in porcine heart.  

PubMed

To determine whether beta-adrenergic receptor agonist activation influences guanosine 5'-triphosphate-binding protein (G-protein) expression and beta-adrenergic receptor kinase activity in the heart, we examined the effects of chronic beta 1-adrenergic receptor antagonist treatment (bisoprolol, 0.2 mg/kg per d i.v., 35 d) on components of the myocardial beta-adrenergic receptor-G-protein-adenylyl cyclase pathway in porcine myocardium. Three novel alterations in cardiac adrenergic signaling associated with chronic reduction in beta-adrenergic receptor agonist activation were found. First, there was coordinate downregulation of Gi alpha 2 and Gs alpha mRNA and protein expression in the left ventricle; reduced G-protein content was also found in the right atrium. Second, in the left ventricle, there was a twofold increase in beta-adrenergic receptor-dependent stimulation of adenylyl cyclase and a persistent high affinity state of the beta-adrenergic receptor. Finally, there was a reduction in left ventricular beta-adrenergic receptor kinase activity, suggesting a previously unrecognized association between the degree of adrenergic activation and myocardial beta-adrenergic receptor kinase expression. The heart appears to adapt in response to chronic beta-adrenergic receptor antagonist administration in a manner that would be expected to offset reduced agonist stimulation. The mechanisms for achieving this extend beyond beta-adrenergic receptor upregulation and include alterations in G-protein expression, beta-adrenergic receptor-Gs interaction, and myocardial beta-adrenergic receptor kinase activity. PMID:7883975

Ping, P; Gelzer-Bell, R; Roth, D A; Kiel, D; Insel, P A; Hammond, H K

1995-03-01

233

Activation of lung vagal sensory receptors by circulatory endotoxin in rats  

Microsoft Academic Search

Although endotoxin is known to induce various pulmonary responses that are linked to the function of lung vagal sensory receptors, its effects on these pulmonary receptors are still not clear. This study investigated the effects of circulatory endotoxin on the afferent activity of lung vagal sensory receptors in rats. We recorded afferent activity arising from vagal pulmonary C fibers (CFs),

Ching Jung Lai; Ching-Yin Ho; Yu Ru Kou

2002-01-01

234

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

235

Cardiomyocyte lipids impair ?-adrenergic receptor function via PKC activation  

PubMed Central

Normal hearts have increased contractility in response to catecholamines. Because several lipids activate PKCs, we hypothesized that excess cellular lipids would inhibit cardiomyocyte responsiveness to adrenergic stimuli. Cardiomyocytes treated with saturated free fatty acids, ceramide, and diacylglycerol had reduced cellular cAMP response to isoproterenol. This was associated with increased PKC activation and reduction of ?-adrenergic receptor (?-AR) density. Pharmacological and genetic PKC inhibition prevented both palmitate-induced ?-AR insensitivity and the accompanying reduction in cell surface ?-ARs. Mice with excess lipid uptake due to either cardiac-specific overexpression of anchored lipoprotein lipase, PPAR?, or acyl-CoA synthetase-1 or high-fat diet showed reduced inotropic responsiveness to dobutamine. This was associated with activation of protein kinase C (PKC)? or PKC?. Thus, several lipids that are increased in the setting of lipotoxicity can produce abnormalities in ?-AR responsiveness. This can be attributed to PKC activation and reduced ?-AR levels. PMID:21139071

Drosatos, Konstantinos; Bharadwaj, Kalyani G.; Lymperopoulos, Anastasios; Ikeda, Shota; Khan, Raffay; Hu, Yunying; Agarwal, Rajiv; Yu, Shuiqing; Jiang, Hongfeng; Steinberg, Susan F.; Blaner, William S.; Koch, Walter J.

2011-01-01

236

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

237

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

PubMed

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, D; Ning, W; Xie, D; Guo, L; DuBois, R N

2012-02-23

238

SUMOYLATION OF THE HUMAN PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR INHIBITS ITS TRANS-ACTIVITY THROUGH THE RECRUITMENT OF THE NUCLEAR COREPRESSOR  

E-print Network

1 SUMOYLATION OF THE HUMAN PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR INHIBITS ITS TRANS receptor Peroxisome Proliferator-Activated Receptor alpha (PPAR) is a key regulator of genes implicated recruitment of NCoR. The nuclear receptor Peroxisome Proliferator-Activated Receptor alpha (PPAR) is a key

Paris-Sud XI, Université de

239

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

240

Inhibition of Peroxisome Proliferator-Activated Receptor? Increases Estrogen Receptor-Dependent Tumor Specification  

PubMed Central

PPAR? is a nuclear receptor that regulates gene transcription associated with intermediary metabolism, adipocyte differentiation, as well as tumor suppression and proliferation. To understand the role of PPAR? in tumorigenesis, transgenic mice were generated with mammary gland-directed expression of the dominant-negative transgene, Pax8PPAR?. Transgenic mice were phenotypically indistinguishable from wild-type mice, but mammary epithelial cells expressed a greater a high percentage of CD29hi/CD24neg, CK5+ and double positive CK14/CK18 cells. These changes correlated with reduced PTEN and increased Ras, ERK and AKT activation. Although spontaneous tumorigenesis did not occur, transgenic animals were highly susceptible to progestin/DMBA-induced mammary carcinogenesis, which in contrast to wild-type mice, resulted in a high tumor multiplicity and most importantly, in the appearance of predominantly estrogen receptor?-positive (ER+) ductal adenocarcinomas. Tumors expressed a similar PTENlo/pERKhi/pAKThi phenotype as mammary epithelium, and exhibited high activation of ERE-dependent reporter gene activity. Tumorigenesis in MMTV-Pax8PPAR? mice was insensitive to the chemopreventive effect of a PPAR? agonist, but was profoundly inhibited by the ER antagonist fulvestrant. These results reveal important new insights into the previously unrecognized role of PPAR? in the specification of mammary lineage and the development of ER+ tumors. PMID:19147585

Yin, Yuzhi; Yuan, Hongyan; Zeng, Xiao; Kopelovich, Levy; Glazer, Robert I.

2013-01-01

241

Farnesoid X receptor suppresses constitutive androstane receptor activity at the multidrug resistance protein-4 promoter.  

PubMed

Multidrug resistance protein-4 (MRP4) is a member of the multidrug resistance associated gene family that is expressed on the basolateral membrane of hepatocytes and undergoes adaptive up-regulation in response to cholestatic injury or bile acid feeding. In this study we demonstrate that farnesoid X receptor (FXR) regulates MRP4 in vivo and in vitro. In vivo deletion of FXR induces MRP4 gene expression. In vitro treatment of HepG2 cells with FXR ligands, chenodeoxycholic acid (CDCA), cholic acid (CA) and the synthetic ligand GW-4064 suppresses basal mRNA level of the MRP4 gene as well as the co-treatment with CDCA and 6-(4-Chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO), an activator of constitutive androstane receptor (CAR). We found in the human MRP4 promoter a CAR responsive element (CARE) embedded within an FXR responsive element (FXRE). We cloned this region and found that FXR suppresses CAR activity in luciferase assay. Finally, we demonstrated that FXR competes with CAR for binding to this overlapping binding site. Our results support the view that FXR activation in obstructive cholestasis might worsen liver injury by hijacking a protective mechanism regulated by CAR and provides a new molecular explanation to the pathophysiology of cholestasis. PMID:21296199

Renga, Barbara; Migliorati, Marco; Mencarelli, Andrea; Cipriani, Sabrina; D'Amore, Claudio; Distrutti, Eleonora; Fiorucci, Stefano

2011-03-01

242

NMDA receptor activation suppresses microtubule growth and spine entry.  

PubMed

Dynamic microtubules are important to maintain neuronal morphology and function, but whether neuronal activity affects the organization of dynamic microtubules is unknown. Here, we show that a protocol to induce NMDA-dependent long-term depression (LTD) rapidly attenuates microtubule dynamics in primary rat hippocampal neurons, removing the microtubule-binding protein EB3 from the growing microtubule plus-ends in dendrites. This effect requires the entry of calcium and is mediated by activation of NR2B-containing NMDA-type glutamate receptor. The rapid NMDA effect is followed by a second, more prolonged response, during which EB3 accumulates along MAP2-positive microtubule bundles in the dendritic shaft. MAP2 is both required and sufficient for this activity-dependent redistribution of EB3. Importantly, NMDA receptor activation suppresses microtubule entry in dendritic spines, whereas overexpression of EB3-GFP prevents NMDA-induced spine shrinkage. These results suggest that short-lasting and long-lasting changes in dendritic microtubule dynamics are important determinants for NMDA-induced LTD. PMID:21632941

Kapitein, Lukas C; Yau, Kah Wai; Gouveia, Susana Montenegro; van der Zwan, Wouter A; Wulf, Phebe S; Keijzer, Nanda; Demmers, Jeroen; Jaworski, Jacek; Akhmanova, Anna; Hoogenraad, Casper C

2011-06-01

243

DHEA metabolites activate estrogen receptors alpha and beta  

PubMed Central

Dehydroepiandrosterone (DHEA) levels were reported to associate with increased breast cancer risk in postmenopausal women, but some carcinogen-induced rat mammary tumor studies question this claim. The purpose of this study was to determine how DHEA and its metabolites affect estrogen receptors ? or ? (ER? or ER?) -regulated gene transcription and cell proliferation. In transiently transfected HEK-293 cells, androstenediol, DHEA, and DHEA-S activated ER?. In ER? transfected HepG2 cells, androstenedione, DHEA, androstenediol, and 7-oxo DHEA stimulated reporter activity. ER antagonists ICI 182,780 (fulvestrant) and 4-hydroxytamoxifen, general P450 inhibitor miconazole, and aromatase inhibitor exemestane inhibited activation by DHEA or metabolites in transfected cells. ER?-selective antagonist R,R-THC (R,R-cis-diethyl tetrahydrochrysene) inhibited DHEA and DHEA metabolite transcriptional activity in ER?-transfected cells. Expression of endogenous estrogen-regulated genes: pS2, progesterone receptor, cathepsin D1, and nuclear respiratory factor-1 was increased by DHEA and its metabolites in an ER-subtype, gene, and cell-specific manner. DHEA metabolites, but not DHEA, competed with 17?-estradiol for ER? and ER? binding and stimulated MCF-7 cell proliferation, demonstrating that DHEA metabolites interact directly with ER? and ER? in vitro, modulating estrogen target genes in vivo. PMID:23123738

Michael Miller, Kristy K.; Al-Rayyan, Numan; Ivanova, Margarita M.; Mattingly, Kathleen A.; Ripp, Sharon L.; Klinge, Carolyn M.; Prough, Russell A.

2012-01-01

244

Thiophene-Core Estrogen Receptor Ligands Having Superagonist Activity  

PubMed Central

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

2013-01-01

245

Peroxisome Proliferator-Activated Receptors (PPAR) and the Mitochondrial Aldehyde Dehydrogenase  

E-print Network

Peroxisome Proliferator-Activated Receptors (PPAR) and the Mitochondrial Aldehyde Dehydrogenase) and -5 (DR-5) element. Because DR-1 elements are preferred binding sites for peroxisome proliferator Receptor, Liver, Peroxisome Proliferator, Aldehyde Dehydrogenase. THE PEROXISOME proliferator

Omiecinski, Curtis

246

FEBS J . Author manuscript Visfatin is induced by peroxisome proliferator-activated receptor gamma in  

E-print Network

FEBS J . Author manuscript Page /1 11 Visfatin is induced by peroxisome proliferator/PBEF/NAMPT. The nuclear receptor Peroxisome Proliferator-Activated Receptor (PPAR) exerts anti-inflammatory effects

Boyer, Edmond

247

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

248

Dopamine Receptor Activation Increases HIV Entry into Primary Human Macrophages  

PubMed Central

Macrophages are the primary cell type infected with HIV in the central nervous system, and infection of these cells is a major component in the development of neuropathogenesis and HIV-associated neurocognitive disorders. Within the brains of drug abusers, macrophages are exposed to increased levels of dopamine, a neurotransmitter that mediates the addictive and reinforcing effects of drugs of abuse such as cocaine and methamphetamine. In this study we examined the effects of dopamine on HIV entry into primary human macrophages. Exposure to dopamine during infection increased the entry of R5 tropic HIV into macrophages, irrespective of the concentration of the viral inoculum. The entry pathway affected was CCR5 dependent, as antagonizing CCR5 with the small molecule inhibitor TAK779 completely blocked entry. The effect was dose-dependent and had a steep threshold, only occurring above 108 M dopamine. The dopamine-mediated increase in entry required dopamine receptor activation, as it was abrogated by the pan-dopamine receptor antagonist flupenthixol, and could be mediated through both subtypes of dopamine receptors. These findings indicate that the effects of dopamine on macrophages may have a significant impact on HIV pathogenesis. They also suggest that drug-induced increases in CNS dopamine may be a common mechanism by which drugs of abuse with distinct modes of action exacerbate neuroinflammation and contribute to HIV-associated neurocognitive disorders in infected drug abusers. PMID:25268786

Gaskill, Peter J.; Yano, Hideaki H.; Kalpana, Ganjam V.; Javitch, Jonathan A.; Berman, Joan W.

2014-01-01

249

Dopamine Receptor Activation Increases HIV Entry into Primary Human Macrophages.  

PubMed

Macrophages are the primary cell type infected with HIV in the central nervous system, and infection of these cells is a major component in the development of neuropathogenesis and HIV-associated neurocognitive disorders. Within the brains of drug abusers, macrophages are exposed to increased levels of dopamine, a neurotransmitter that mediates the addictive and reinforcing effects of drugs of abuse such as cocaine and methamphetamine. In this study we examined the effects of dopamine on HIV entry into primary human macrophages. Exposure to dopamine during infection increased the entry of R5 tropic HIV into macrophages, irrespective of the concentration of the viral inoculum. The entry pathway affected was CCR5 dependent, as antagonizing CCR5 with the small molecule inhibitor TAK779 completely blocked entry. The effect was dose-dependent and had a steep threshold, only occurring above 108 M dopamine. The dopamine-mediated increase in entry required dopamine receptor activation, as it was abrogated by the pan-dopamine receptor antagonist flupenthixol, and could be mediated through both subtypes of dopamine receptors. These findings indicate that the effects of dopamine on macrophages may have a significant impact on HIV pathogenesis. They also suggest that drug-induced increases in CNS dopamine may be a common mechanism by which drugs of abuse with distinct modes of action exacerbate neuroinflammation and contribute to HIV-associated neurocognitive disorders in infected drug abusers. PMID:25268786

Gaskill, Peter J; Yano, Hideaki H; Kalpana, Ganjam V; Javitch, Jonathan A; Berman, Joan W

2014-01-01

250

The third cytoplasmic loop of a yeast G-protein-coupled receptor controls pathway activation, ligand discrimination, and receptor internalization.  

PubMed Central

To identify functional domains of G-protein-coupled receptors that control pathway activation, ligand discrimination, and receptor regulation, we have used as a model the alpha-factor receptor (STE2 gene product) of the yeast Saccharomyces cerevisiae. From a collection of random mutations introduced in the region coding for the third cytoplasmic loop of Ste2p, six ste2sst alleles were identified by genetic screening methods that increased alpha-factor sensitivity 2.5- to 15-fold. The phenotypic effects of ste2sst and sst2 mutations were not additive, consistent with models in which the third cytoplasmic loop of the alpha-factor receptor and the regulatory protein Sst2p control related aspects of pheromone response and/or desensitization. Four ste2sst mutations did not dramatically alter cell surface expression or agonist binding affinity of the receptor; however, they did permit detectable responses to an alpha-factor antagonist. One ste2sst allele increased receptor binding affinity for alpha-factor and elicited stronger responses to antagonist. Results of competition binding experiments indicated that wild-type and representative mutant receptors bound antagonist with similar affinities. The antagonist-responsive phenotypes caused by ste2sst alleles were therefore due to defects in the ability of receptors to discriminate between agonist and antagonist peptides. One ste2sst mutation caused rapid, ligand-independent internalization of the receptor. These results demonstrate that the third cytoplasmic loop of the alpha-factor receptor is a multifunctional regulatory domain that controls pathway activation and/or desensitization and influences the processes of receptor activation, ligand discrimination, and internalization. PMID:8164685

Stefan, C J; Blumer, K J

1994-01-01

251

Structure-activity relationship of cinnamic acylsulfonamide analogues on the human EP3 prostanoid receptor.  

PubMed

Potent and selective antagonists of the human EP3 receptor have been identified. The structure-activity relationship of the chemical series was conducted and we found several analogues displaying sub-nanomolar K(i) values at the EP3 receptor and micromolar activities at the EP1, EP2 and EP4 receptors. The effect of added human serum albumin (HSA) on the binding affinity at the EP3 receptor was also investigated. PMID:11504634

Juteau, H; Gareau, Y; Labelle, M; Sturino, C F; Sawyer, N; Tremblay, N; Lamontagne, S; Carrière, M C; Denis, D; Metters, K M

2001-08-01

252

Aryl hydrocarbon receptor-independent activation of estrogen receptor-dependent transcription by 3-methycholanthrene  

SciTech Connect

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that stimulates transcription directed by xenobiotic response elements upstream of target genes. Recently, AhR ligands were reported to induce formation of an AhR-estrogen receptor (ER) complex, which can bind to estrogen response elements (EREs) and stimulate transcription of ER target genes. Presently, we investigate the effect of the AhR ligands 3-methylcholanthrene (3MC), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4',5-pentachlorobiphenyl (BZ126) on ERE-regulated luciferase reporter activity and endogenous ER target gene expression. In MCF-7 human breast cancer cells, 3MC induced transcription of ER reporter genes containing native promoter sequences of the ER-responsive genes complement 3 and pS2 and heterologous promoters regulated by isolated EREs. Dose-response studies revealed that the concentration of 3MC required to half-maximally activate transcription (EC{sub 5}) was >100-fold higher for an ER reporter (27-57 {mu}M) than for an AhR reporter (86-250 nM) in both MCF-7 cells and in human endometrial cancer Ishikawa cells. 3MC also stimulated expression of the endogenous ER target genes amphiregulin, cathepsin D and progesterone receptor, albeit to a much lower extent than was achieved following stimulation with 17{beta}-estradiol. In Ishikawa cells, 3MC, but not BZ126 or TCDD, stimulated ER{alpha}-dependent reporter activity but did not induce expression of endogenous ER target genes. Finally, studies carried out in the AhR-positive rat hepatoma cell line 5L and the AhR-deficient variant BP8 demonstrated that ER reporter activity could be induced by 3MC in a manner that was independent of AhR and thus distinct from the AhR-ER 'hijacking' mechanism described recently. 3MC may thus elicit estrogenic activity by multiple mechanisms.

Shipley, Jonathan M. [Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, 5 Cummington Street, MA 02215 (United States); Waxman, David J. [Division of Cell and Molecular Biology, Department of Biology, Boston University, Boston, 5 Cummington Street, MA 02215 (United States)]. E-mail: djw@bu.edu

2006-06-01

253

NK cell–activating receptors require PKC-? for sustained signaling, transcriptional activation, and IFN-? secretion  

PubMed Central

Natural killer (NK) cell sense virally infected cells and tumor cells through multiple cell surface receptors. Many NK cell–activating receptors signal through immunoreceptor tyrosine–based activation motif (ITAM)–containing adapters, which trigger both cytotoxicy and secretion of interferon-gamma (IFN-?). Within the ITAM pathway, distinct signaling intermediates are variably involved in cytotoxicity and/or IFN-? secretion. In this study, we have evaluated the role of protein kinase C-? (PKC-?) in NK-cell secretion of lytic mediators and IFN-?. We found that engagement of NK-cell receptors that signal through ITAMs results in prompt activation of PKC-?. Analyses of NK cells from PKC-?–deficient mice indicated that PKC-? is absolutely required for ITAM-mediated IFN-? secretion, whereas it has no marked influence on the release of cytolytic mediators. Moreover, we found that PKC-? deficiency preferentially impairs sustained extracellular-regulated kinase signaling as well as activation of c-Jun N-terminal kinase and the transcription factors AP-1 and NFAT but does not affect activation of NF-?B. These results indicate that NK cell–activating receptors require PKC-? to generate sustained intracellular signals that reach the nucleus and promote transcriptional activation, ultimately inducing IFN-? production. PMID:18784374

Tassi, Ilaria; Cella, Marina; Presti, Rachel; Colucci, Angela; Gilfillan, Susan; Littman, Dan R.

2008-01-01

254

Vitamin D receptor activation and survival in chronic kidney disease.  

PubMed

Replacement of activated vitamin D has been the cornerstone of therapy for secondary hyperparathyroidism (SHPT). Recent findings from several large observational studies have suggested that the benefits of vitamin D receptor activators (VDRA) may extend beyond the traditional parathyroid hormone (PTH)-lowering effect, and could result in direct cardiovascular and metabolic benefits. The advent of several new analogs of the activated vitamin D molecule has widened our therapeutic armamentarium, but has also made therapeutic decisions more complicated. Treatment of SHPT has become even more complex with the arrival of the first calcium-sensing receptor (CSR) agonist (cinacalcet hydrochloride) and with the uncovering of novel mechanisms responsible for SHPT. We provide a brief overview of the physiology and pathophysiology of SHPT, with a focus on vitamin D metabolism, and discuss various practical aspects of VDRA therapy and its reported association with survival in recent observational studies. A detailed discussion of the available agents is aimed at providing the practicing physician with a clear understanding of the advantages or disadvantages of the individual medications. A number of open questions are also analyzed, including the present and future roles of CSR agonists and 25(OH) vitamin D replacement. PMID:18288097

Kovesdy, C P; Kalantar-Zadeh, K

2008-06-01

255

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

256

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

257

A novel receptor involved in T-cell activation  

Microsoft Academic Search

OPTIMAL T-cell activation and T-cell expansion require triggering by T-cell antigen receptors and co-stimulatory signals provided by accessory cells1á¤-3. A major co-stimulatory pathway involves crosslinking the CD28 molecule on T cells by its ligands CD80 or CD86 expressed on antigen-presenting cells4á¤-7. But recent studies8,9 on CD28-deficient mice have indicated that CD28 is not required for all T-cell responses and that

Benjamin G. Cocks; Chia-Chun J. Chang; Hans Yssel; Jan E. de Vries; Gregorio Aversa

1995-01-01

258

Peroxisome Proliferator-Activated Receptors in Diabetic Nephropathy  

PubMed Central

Diabetic nephropathy is a leading cause of end-stage renal disease, which is increasing in incidence worldwide, despite intensive treatment approaches such as glycemic and blood pressure control in patients with diabetes mellitus. New therapeutic strategies are needed to prevent the onset of diabetic nephropathy. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that play important roles in lipid and glucose homeostases. These agents might prevent the progression of diabetic nephropathy, since PPAR agonists improve dyslipidemia and insulin resistance. Furthermore, data from murine models suggest that PPAR agonists also have independent renoprotective effects by suppressing inflammation, oxidative stress, lipotoxicity, and activation of the renin-angiotensin system. This review summarizes data from clinical and experimental studies regarding the relationship between PPARs and diabetic nephropathy. The therapeutic potential of PPAR agonists in the treatment of diabetic nephropathy is also discussed. PMID:19277201

Kume, Shinji; Uzu, Takashi; Isshiki, Keiji; Koya, Daisuke

2008-01-01

259

Reporter Mice for the Study of Intracellular Receptor Activity  

PubMed Central

During the past decade the remarkable progress in molecular genetics and the possibility to engineer cells to express genes reporting on the activity of specific promoters has produced major changes in biological research. The description and validation of reporter mice for non-invasive assessment of biological and biochemical processes in living subjects and the results obtained with the models reporting on the activity of estrogen and peroxisome proliferator receptors clearly showed that such technologies have the potential to enhance our understanding of disease and drug activity. Although reporter-gene technology is in its infancy, reporter animals already represent a valuable tool for biomedical investigation. The present chapter aims at critically illustrating the methodology to be applied when dealing with reporter systems and in vivo imaging. PMID:19763513

Maggi, Adriana; Rando, Gianpaolo

2010-01-01

260

Synaptic NMDA receptor activity boosts intrinsic antioxidant defences  

PubMed Central

Intrinsic antioxidant defences are important for neuronal longevity. We show that synaptic activity, acting via NMDA receptor (NMDAR) signaling, boosts antioxidant defences through changes to the thioredoxin-peroxiredoxin system. Synaptic activity enhances thioredoxin activity, facilitates the reduction of overoxidized peroxiredoxins, and promotes resistance to oxidative stress. Resistance is mediated by coordinated transcriptional changes: synaptic NMDAR activity inactivates a novel FOXO target gene, the thioredoxin inhibitor Txnip. Conversely, NMDAR blockade upregulates Txnip in vivo and in vitro, where it binds thioredoxin and promotes vulnerability to oxidative damage. Synaptic activity also up-regulates the peroxiredoxin re-activating genes Sestrin2 and Sulfiredoxin, via C/EBP? and AP-1 respectively. Mimicking these expression changes is sufficient to strengthen antioxidant defences. Trans-synaptic stimulation of synaptic NMDARs is crucial for boosting antioxidant defences: chronic bath activation of all (synaptic and extrasynaptic) NMDARs induces no antioxidative effects. Thus, synaptic NMDAR activity may influence the progression of pathological processes associated with oxidative damage. PMID:18344994

Papadia, Sofia; Soriano, Francesc X.; Leveille, Frederic; Martel, Marc-Andre; Dakin, Kelly A.; Hansen, Henrik H.; Kaindl, Angela; Sifringer, Marco; Fowler, Jill; Stefovska, Vanya; Mckenzie, Grahame; Craigon, Marie; Corriveau, Roderick; Ghazal, Peter; Horsburgh, Karen; Yankner, Bruce A.; Wyllie, David J. A.; Ikonomidou, Chrysanthy; Hardingham, Giles E.

2008-01-01

261

Kainate receptor activation induces glycine receptor endocytosis through PKC deSUMOylation.  

PubMed

Surface expression and regulated endocytosis of glycine receptors (GlyRs) play a critical function in balancing neuronal excitability. SUMOylation (SUMO modification) is of critical importance for maintaining neuronal function in the central nervous system. Here we show that activation of kainate receptors (KARs) causes GlyR endocytosis in a calcium- and protein kinase C (PKC)-dependent manner, leading to reduced GlyR-mediated synaptic activity in cultured spinal cord neurons and the superficial dorsal horn of rat spinal cord slices. This effect requires SUMO1/sentrin-specific peptidase 1 (SENP1)-mediated deSUMOylation of PKC, indicating that the crosstalk between KARs and GlyRs relies on the SUMOylation status of PKC. SENP1-mediated deSUMOylation of PKC is involved in the kainate-induced GlyR endocytosis and thus plays an important role in the anti-homeostatic regulation between excitatory and inhibitory ligand-gated ion channels. Altogether, we have identified a SUMOylation-dependent regulatory pathway for GlyR endocytosis, which may have important physiological implications for proper neuronal excitability. PMID:25236484

Sun, Hao; Lu, Li; Zuo, Yong; Wang, Yan; Jiao, Yingfu; Zeng, Wei-Zheng; Huang, Chao; Zhu, Michael X; Zamponi, Gerald W; Zhou, Tong; Xu, Tian-Le; Cheng, Jinke; Li, Yong

2014-01-01

262

Protease-activated receptor-1 (thrombin receptor) is expressed in mesenchymal portions of human hair follicle.  

PubMed

Protease nexin-1, a serine protease inhibitor, is expressed specifically in the dermal papilla (DP) of anagen hair follicles and is suggested to be one of the modulators of the cyclic growth of hair follicles. Accumulating evidence has shown that protease nexin-1 plays its biologic role by inhibiting thrombin action in various systems other than the hair follicle. Thrombin has various physiologic functions including blood coagulation cascade, mostly via activation of protease-activated receptors (PAR). In this study, we investigated the expression of PAR mRNA using RT-PCR in dissected human hair follicles. We showed that PAR-1 mRNA was expressed specifically in the mesenchymal portions, including DP and connective tissue sheath, of anagen hair follicles. Furthermore, immunoreactivity for PAR-1 was detected in the DP and lower portion of connective tissue sheath in the anagen and catagen phases and in the DP of telogen hair follicles. Because only a pharmacologic level (100 nM) of thrombin significantly stimulated cell proliferation and DNA synthesis of the cultured dermal papilla cells, thrombin does not seem to have a mitogenic effect on dermal papilla cells physiologically. These results raise the possibility that thrombin is involved in the cyclic hair growth through its receptor of PAR-1. PMID:14632180

Anan, T; Sonoda, T; Asada, Y; Kurata, S; Takayasu, S

2003-10-01

263

Kainate receptor activation induces glycine receptor endocytosis through PKC deSUMOylation  

PubMed Central

Surface expression and regulated endocytosis of glycine receptors (GlyRs) play a critical function in balancing neuronal excitability. SUMOylation (SUMO modification) is of critical importance for maintaining neuronal function in the central nervous system. Here we show that activation of kainate receptors (KARs) causes GlyR endocytosis in a calcium- and protein kinase C (PKC)-dependent manner, leading to reduced GlyR-mediated synaptic activity in cultured spinal cord neurons and the superficial dorsal horn of rat spinal cord slices. This effect requires SUMO1/sentrin-specific peptidase 1 (SENP1)-mediated deSUMOylation of PKC, indicating that the crosstalk between KARs and GlyRs relies on the SUMOylation status of PKC. SENP1-mediated deSUMOylation of PKC is involved in the kainate-induced GlyR endocytosis and thus plays an important role in the anti-homeostatic regulation between excitatory and inhibitory ligand-gated ion channels. Altogether, we have identified a SUMOylation-dependent regulatory pathway for GlyR endocytosis, which may have important physiological implications for proper neuronal excitability. PMID:25236484

Sun, Hao; Lu, Li; Zuo, Yong; Wang, Yan; Jiao, Yingfu; Zeng, Wei-Zheng; Huang, Chao; Zhu, Michael X.; Zamponi, Gerald W.; Zhou, Tong; Xu, Tian-Le; Cheng, Jinke; Li, Yong

2014-01-01

264

Phosphorylation of the Human Leukemia Inhibitory Factor (LIF) Receptor by Mitogen-Activated Protein Kinase and the Regulation of LIF Receptor Function by Heterologous Receptor Activation  

Microsoft Academic Search

We used a bacterially expressed fusion protein containing the entire cytoplasmic domain of the human leukemia inhibitory factor (LIF) receptor to study its phosphorylation in response to LIF stimulation. The dose- and time-dependent relationships for phosphorylation of this construct in extracts of LIF-stimulated 3T3-L1 cells were super-imposable with those for the stimulation of mitogen-activated protein kinase (MAPK). Indeed, phosphorylation of

William P. Schiemann; Lee M. Graves; Heinz Baumann; Karen K. Morella; David P. Gearing; Mark D. Nielsen; Edwin G. Krebs; Neil M. Nathanson

1995-01-01

265

The Environmental Estrogen, Nonylphenol, Activates the Constitutive Androstane Receptor  

PubMed Central

Nonylphenol (NP) and its parent compounds, the nonylphenol ethoxylates are some of the most prevalent chemicals found in U.S. waterways. NP is also resistant to biodegradation and is a known environmental estrogen, which makes NP a chemical of concern. Our data show that NP also activates the constitutive androstane receptor (CAR), an orphan nuclear receptor important in the induction of detoxification enzymes, including the P450s. Transactivation assays demonstrate that NP increases murine CAR (mCAR) transcriptional activity, and NP treatment can overcome the inhibitory effects of the inverse agonist, androstanol, on mCAR activation. Treatment of wild-type (CAR +/+) mice with NP at 50 or 75 mg/kg/day increases Cyp2b protein expression in a dose-dependent manner as demonstrated by Western blotting, and was confirmed by quantitative reverse transcription–PCR of Cyp2b10 transcript levels. CAR-null (CAR ?/?) mice show no increased expression of Cyp2b following NP treatment, indicating that CAR is required for NP-mediated Cyp2b induction. In addition, NP increases the translocation of CAR into the nucleus, which is the key step in the commencement of CAR's transcriptional activity. NP also induced CYP2B6 in primary human hepatocytes, and increased Cyp2b10 messenger RNA and protein expression in humanized CAR mice, indicating that NP is an activator of human CAR as well. In conclusion, NP is a CAR activator, and this was demonstrated in vitro with transactivation assays and in vivo with transgenic CAR mouse models. PMID:17483497

Hernandez, Juan P.; Huang, Wendong; Chapman, Laura M.; Chua, Steven; Moore, David D.; Baldwin, William S.

2007-01-01

266

Influence of plasma and ultraviolet treatment of zirconia on initial attachment of human oral keratinocytes: Expressions of laminin ?2 and integrin ?4.  

PubMed

Initial attachment of human oral keratinocytes cultured on yttria-stabilized tetragonal zirconia polycrystal (TZP) surfaces that were subjected to UV or oxygen plasma (O2-plasma) treatment was investigated. The viability of the attached cells, mRNA expression of laminin ?2 and integrin ?4, distribution of laminin ?2 and integrin ?4, cell area, and cell morphology were assessed. The results showed that no differences in the viability of attached cells were recognized among the conditions. However, expression of laminin ?2 and integrin ?4 as well as cell morphology were promoted only in O2-plasma specimens even though superhydrophilicity was obtained in both the UV and O2-plasma specimens compared with the untreated control specimen. The photocatalytic activity was believed to be closely involved in the above-mentioned differences. The results of this study suggest that TZP surface treated with oxygen plasma promotes the initial attachment capability of human oral keratinocytes with enhancing the extracellular matrix such as laminin ?2. PMID:25273051

Kobune, Kazuhiro; Miura, Tadashi; Sato, Toru; Yotsuya, Mamoru; Yoshinari, Masao

2014-01-01

267

Sperm Epidermal Growth Factor Receptor (EGFR) Mediates ?7 Acetylcholine Receptor (AChR) Activation to Promote Fertilization  

PubMed Central

To attain fertilization the spermatozoon binds to the egg zona pellucida (ZP) via sperm receptor(s) and undergoes an acrosome reaction (AR). Several sperm receptors have been described in the literature; however, the identity of this receptor is not yet certain. In this study, we suggest that the ?7 nicotinic acetylcholine receptor (?7nAChR) might be a sperm receptor activated by ZP to induce epidermal growth factor receptor (EGFR)-mediated AR. We found that isolated ZP or ?7 agonists induced the AR in sperm from WT but not ?7-null spermatozoa, and the induced AR was inhibited by ?7 or EGFR antagonists. Moreover, ?7-null sperm showed very little binding to the egg, and microfluidic affinity in vitro assay clearly showed that ?7nAChR, as well as EGFR, interacted with ZP3. Induction of EGFR activation and the AR by an ?7 agonist was inhibited by a Src family kinase (SFK) inhibitor. In conclusion we suggest that activation of ?7 by ZP leads to SFK-dependent EGFR activation, Ca2+ influx, and the acrosome reaction. PMID:22577141

Jaldety, Yael; Glick, Yair; Orr-Urtreger, Avi; Ickowicz, Debby; Gerber, Doron; Breitbart, Haim

2012-01-01

268

Receptor Interacting Protein 140 Regulates Expression of Uncoupling Protein 1 in Adipocytes through Specific Peroxisome Proliferator Activated Receptor Isoforms and Estrogen-Related Receptor ?  

PubMed Central

Expression of uncoupling protein 1 (Ucp1) mRNA is elevated in differentiated adipocytes derived from brown or white adipose tissue devoid of the nuclear receptor corepressor receptor interacting protein 140 (RIP140). Increased expression is mediated in part by the recruitment of peroxisome proliferator activated receptors ? and ?, together with estrogen-related receptor ?, which functions through a novel binding site on the Ucp1 enhancer. This demonstrates that regulation of Ucp1 expression in the absence of RIP140 involves derepression of at least three different nuclear receptors. The ability to increase expression of Ucp1 by ?-adrenergic signaling is independent of RIP140, as shown by the action of the ?3-adrenergic agonist CL 316,243 to stimulate expression in both brown and white adipocytes in the presence and absence of the corepressor. Therefore, the expression of this metabolic uncoupling protein in adipose cells is regulated by inhibition as well as activation of distinct signaling pathways. PMID:17456798

Debevec, Darja; Christian, Mark; Morganstein, Daniel; Seth, Asha; Herzog, Birger; Parker, Malcolm; White, Roger

2007-01-01

269

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...

270

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

271

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

272

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; Blazquez, Cristina; Resel, Eva; Soria-Gomez, Edgar; Cannich, Astrid; Ferrero, Jose J.; Sagredo, Onintza; Benito, Cristina; Romero, Julian; Sanchez-Prieto, Jose; Lutz, Beat; Fernandez-Ruiz, Javier; Galve-Roperh, Ismael; Guzman, Manuel

2014-01-01

273

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

274

Pristanic acid and phytanic acid: naturally occurring ligands for the nuclear receptor peroxisome proliferator-activated receptor a  

Microsoft Academic Search

Phytanic acid and pristanic acid are branched- chain fatty acids, present at micromolar concentrations in the plasma of healthy individuals. Here we show that both phytanic acid and pristanic acid activate the peroxisome proliferator-activated receptor a (PPAR a ) in a concentration- dependent manner. Activation is observed via the ligand- binding domain of PPAR a as well as via a

Anna W. M. Zomer; Bart van der Burg; Gerbert A. Jansen; Ronald J. A. Wanders; Paul T. van der Saag

275

Activation of NMDA receptors reverses desensitization of mGluR5 in native and recombinant systems  

Microsoft Academic Search

The metabotropic glutamate receptor, mGluR5, has a critical role in induction of NMDA-receptor-dependent forms of synaptic plasticity and excitotoxicity. This is likely mediated by a reciprocal positive-feedback interaction between these two glutamate receptor subtypes in which activation of mGluR5 potentiates NMDA receptor currents and NMDA receptor activation potentiates mGluR5-mediated responses. We have investigated the mechanism by which NMDA receptor activation

S. Alagarsamy; M. J. Marino; S. T. Rouse; R. W. Gereau; S. F. Heinemann; P. J. Conn

1999-01-01

276

[Activators, receptors and signal transduction pathways of blood platelets].  

PubMed

Platelet participation in hemostatic plug formation requires transition into an activated state (or, rather, variety of states) upon action of agonists like ADP, thromboxane A , collagen, thrombin, and others. The mechanisms of action for different agonists, their receptors and signaling pathways associated with them, as well as the mechanisms of platelet response inhibition are the subject of the present review. Collagen exposed upon vessel wall damage induced initial platelet attachment and start of thrombus formation, which involves numerous processes such as aggregation, activation of integrins, granule secretion and increase of intracellular Ca2+. Thrombin, ADP, thromboxane A , and ATP activated platelets that were not initially in contact with the wall and induce additional secretion of activating substances. Vascular endothelium and secretory organs also affect platelet activation, producing both positive (adrenaline) an d negative (prostacyclin, nitric oxide) regulators, thereby determining the relation of activation and inhibition signals, which plays a significant role in the formation of platelet aggregate under normal and pathological conditions. The pathways of platelet signaling are still incompletely understood, and their exploration presents an important objective both for basic cell biology and for the development of new drugs, the methods of diagnostics and of treatment of hemostasis disorders. PMID:24837309

Shaturny?, V I; Shakhidzhanov, S S; Sveshnikova, A N; Panteleev, M A

2014-01-01

277

Tonic GABAA receptor conductance in medial subnucleus of the tractus solitarius neurons is inhibited by activation of ?-opioid receptors  

PubMed Central

Our laboratory previously reported that gastric activity is controlled by a robust GABAA receptor-mediated inhibition in the medial nucleus of the tractus solitarius (mNTS) (Herman et al. 2009), and that ?-opioid receptor activation inhibits gastric tone by suppression of this GABA signaling (Herman et al. 2010). These data raised two questions: 1) whether any of this inhibition was due to tonic GABAA receptor-mediated conductance in the mNTS; and 2) whether ?-opioid receptor activation suppressed both tonic and phasic GABA signaling. In whole cell recordings from rat mNTS neurons, application of three GABAA receptor antagonists (gabazine, bicuculline, and picrotoxin) produced a persistent reduction in holding current and decrease in population variance or root mean square (RMS) noise, suggesting a blockade of tonic GABA signaling. Application of gabazine at a lower concentration abolished phasic currents, but had no effect on tonic currents or RMS noise. Application of the ?-subunit preferring agonist gaboxadol (THIP) produced a dose-dependent persistent increase in holding current and RMS noise. Pretreatment with tetrodotoxin prevented the action of gabazine, but had no effect on the THIP-induced current. Membrane excitability was unaffected by the selective blockade of phasic inhibition, but was increased by blockade of both phasic and tonic currents. In contrast, activation of tonic currents decreased membrane excitability. Application of the ?-opioid receptor agonist DAMGO produced a persistent reduction in holding current that was not observed following pretreatment with a GABAA receptor antagonist and was not evident in mice lacking the ?-subunit. These data suggest that mNTS neurons possess a robust tonic inhibition that is mediated by GABAA receptors containing the ?-subunit, that determines membrane excitability, and that is partially regulated by ?-opioid receptors. PMID:22114164

Herman, Melissa A.; Gillis, Richard A.; Vicini, Stefano; Dretchen, Kenneth L.

2012-01-01

278

Proteinase-activated receptor 2 sensitizes transient receptor potential vanilloid 1, transient receptor potential vanilloid 4, and transient receptor potential ankyrin 1 in paclitaxel-induced neuropathic pain.  

PubMed

Paclitaxel chemotherapy is limited by a long-lasting painful neuropathy that lacks an effective therapy. In this study, we tested the hypothesis that paclitaxel may release mast cell tryptase, which activates protease-activated receptor 2 (PAR2) and, subsequently, protein kinases A and C, resulting in mechanical and thermal (both heat and cold) hypersensitivity. Correlating with the development of neuropathy after repeated administration of paclitaxel, mast cell tryptase activity was found to be increased in the spinal cord, dorsal root ganglia, and peripheral tissues in mice. FSLLRY-amide, a selective PAR2 antagonist, blocked paclitaxel-induced neuropathic pain behaviors in a dose- and time-dependent manner. In addition, blocking downstream signaling pathways of PAR2, including phospholipase C (PLC), protein kinase A (PKA), and protein kinase C? (PKC), effectively attenuated paclitaxel-induced mechanical, heat, or cold hypersensitivity. Furthermore, sensitized pain response was selectively inhibited by antagonists of transient receptor potential (TRP) V1, TRPV4, or TRPA1. These results revealed specific cellular signaling pathways leading to paclitaxel-induced neuropathy, including the activation of PAR2 and downstream enzymes PLC, PKC?, and PKA and resultant sensitization of TRPV1, TRPV4, and TRPA1. Targeting one or more of these signaling molecules may present new opportunities for the treatment of paclitaxel-induced neuropathy. PMID:21763756

Chen, Y; Yang, C; Wang, Z J

2011-10-13

279

Engineered repressors are potent inhibitors of androgen receptor activity  

PubMed Central

Prostate cancer growth is dependent upon the Androgen Receptor (AR) pathway, hence therapies for this disease often target this signalling axis. Such therapies are successful in the majority of patients but invariably fail after a median of 2 years and tumours progress to a castrate resistant stage (CRPC). Much evidence exists to suggest that the AR remains key to CRPC growth and hence remains a valid therapeutic target. Here we describe a novel method to inhibit AR activity, consisting of an interaction motif, that binds to the AR ligand-binding domain, fused to repression domains. These ‘engineered repressors’ are potent inhibitors of AR activity and prostate cancer cell growth and importantly inhibit the AR under circumstances in which conventional therapies would be predicted to fail, such as AR mutation and altered cofactor levels. PMID:24659630

Brooke, Greg N.; Powell, Sue M.; Lavery, Derek N.; Waxman, Jonathan; Buluwela, Laki; Ali, Simak; Bevan, Charlotte L.

2014-01-01

280

Development/Plasticity/Repair Schwann Cell-Specific Ablation of Laminin 1 Causes  

E-print Network

the laminin 1 gene in Schwann cells. Disruption of laminin 1 gene expression resulted in depletion of all important. In vitro stud- ies using Schwann cell/neuronal coculture have shown that lami- nin deposition system using the calcium/calmodulin-dependent protein kinase II promoter to drive Cre expression (Ca

281

Laminin ?2 deficiency and muscular dystrophy; genotype-phenotype correlation in mutant mice  

Microsoft Academic Search

Deficiency of laminin ?2 is the cause of one of the most severe muscular dystrophies in humans and other species. It is not yet clear how particular mutations in the laminin ?2 chain gene affect protein expression, and how abnormal levels or structure of the protein affect disease. Animal models may be valuable for such genotype-phenotype analysis and for determining

L. T. Guo; X. U. Zhang; W. Kuang; H. Xu; L. A. Liu; J.-T. Vilquin; Y. Miyagoe-Suzuki; S. Takeda; M. A. Ruegg; U. M. Wewer; E. Engvall

2003-01-01

282

Laminin and Bullous Pemphigoid Antigen Are Distinct Basement Membrane Proteins Synthesized by Epidermal Cells  

Microsoft Academic Search

We sought to determine if laminin, a high molecular weight glycoprotein of basement membrane, is synthesized by epidermal cells and whether it is distinct from bullous pemphigoid (BP) antigen, another high molecular weight-protein of basement membrane. By indirect immunofluorescence we detected laminin in cultures of Pam cells (a mouse keratinocyte cell line) and normal human epidermal cells. To directly demonstrate

John R. Stanley; Pamela Hawley-Nelson; Mina Yaar; George H. Martin; Stephen I. Katz

1982-01-01

283

Essential and overlapping roles for laminin ? chains in notochord and blood vessel formation  

Microsoft Academic Search

Laminins are major constituents of basement membranes and have wide ranging functions during development and in the adult. They are a family of heterotrimeric molecules created through association of an ?, ? and ? chain. We previously reported that two zebrafish loci, grumpy (gup) and sleepy (sly), encode laminin ?1 and ?1, which are important both for notochord differentiation and

Steven M. Pollard; Michael J. Parsons; Makoto Kamei; Ross N. W. Kettleborough; Kevin A. Thomas; Van N. Pham; Moon-Kyoung Bae; Annabelle Scott; Brant M. Weinstein; Derek L. Stemple

2006-01-01

284

The chicken leukocyte receptor complex encodes a primordial, activating, high-affinity IgY Fc receptor  

PubMed Central

Fc receptors are key players of the immune system that link the fine specificity of immunoglobulins and innate effector responses. Here, we describe a nonmammalian Fc? receptor, CHIR-AB1, a member of the leukocyte receptor complex, that binds IgY with high affinity with its single Ig domain. It is expressed on immature and mature B lymphocytes, monocytes, macrophages, and natural killer cells and harbors motifs of activating and inhibitory Fc receptors. In the absence of Fc?RI?, CHIR-AB1 can be expressed on B cells but cross-linking does not induce intracellular calcium release. In contrast, cells expressing CHIR-AB1 and Fc?RI? are triggered to release intracellular calcium upon stimulation with heat-aggregated IgY. CHIR-AB1 thus represents a primordial Fc receptor that combines features of different mammalian counterparts. PMID:17606923

Viertlboeck, Birgit C.; Schweinsberg, Sonja; Hanczaruk, Matthias A.; Schmitt, Ramona; Du Pasquier, Louis; Herberg, Friedrich W.; Gobel, Thomas W.

2007-01-01

285

Adenosine A1 receptor activation inhibits LTP in sympathetic ganglia.  

PubMed

The effects of adenosine on long-term potentiation of sympathetic ganglia was studied in the isolated superior cervical ganglion of the rat, using extracellularly recorded compound action potential as an index of synaptic transmission. Adenosine in a small concentration (2 microM) blocked the post-tetanic potentiation without affecting long-term potentiation. Higher concentrations blocked both responses with no significant effect on basal transmission. The inhibitory effect appears to be due to activation of adenosine A1 receptors. This was indicated by results from experiments with the A1 agonist N6-cyclopentyladenosine (1 microM) which caused inhibition of the basal transmission as well as long-term potentiation and post-tetanic potentiation. This inhibition was readily antagonized by 8-phenyltheophylline (1 microM), an A1 receptor antagonist. A small enhancement of basal transmission was seen on treatment with 8-phenyltheophylline. The inhibitory effect of N6-cyclopentyladenosine on long-term potentiation was totally prevented when the Ca2+ concentration in the superfusate was doubled (from 2.2 to 4.4 mM). The adenosine A2 receptor agonist 5'-(N-cyclopropyl)-carboxamidoadenosine (1 microM), although caused a slight potentiation of basal transmission, had no significant effect on the post-tetanic potentiation or long-term potentiation. The adenosine transport inhibitors, dipyridamole (2 microM) and S-(4-nitorobenzyl)-6-thioinosine (2 microM) caused significant inhibition of the basal ganglionic transmission without affecting post-tetanic potentiation or long-term potentiation. The effect of dipyradimole on basal transmission was not antagonized in the presence of 8-phenyltheophylline suggesting a non-specific action. The results suggest that exogenous adenosine can inhibit both post-tetanic potentiation and long-term potentiation in sympathetic ganglia, probably by activation of presynaptic A1 receptors. The results also suggest that endogenous adenosine, which is probably released in minute amounts, may only modulate basal transmission without influencing induction or maintenance of long-term potentiation in the superior cervical ganglion. PMID:9756986

Hogan, Y H; Hawkins, R; Alkadhi, K A

1998-10-01

286

Cyclic AMP-receptor protein activates aerobactin receptor IutA expression in Vibrio vulnificus.  

PubMed

The ferrophilic bacterium Vibrio vulnificus can utilize the siderophore aerobactin of Escherichia coli for iron acquisition via its specific receptor IutA. This siderophore piracy by V. vulnificus may contribute to its survival and proliferation, especially in mixed bacterial environments. In this study, we examined the effects of glucose, cyclic AMP (cAMP), and cAMP-receptor protein (Crp) on iutA expression in V. vulnificus. Glucose dose-dependently repressed iutA expression. A mutation in cya encoding adenylate cyclase required for cAMP synthesis severely repressed iutA expression, and this change was recovered by in trans complementing cya or the addition of exogenous cAMP. Furthermore, a mutation in crp encoding Crp severely repressed iutA expression, and this change was recovered by complementing crp. Accordingly, glucose deprivation under iron-limited conditions is an environmental signal for iutA expression, and Crp functions as an activator that regulates iutA expression in response to glucose availability. PMID:22538662

Kim, Choon-Mee; Kim, Seong-Jung; Shin, Sung-Heui

2012-04-01

287

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

288

?-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

289

Androgen receptor polyglutamine repeat length affects receptor activity and C2C12 cell development  

PubMed Central

Testosterone (T) has an anabolic effect on skeletal muscle and is believed to exert its local effects via the androgen receptor (AR). The AR harbors a polymorphic stretch of glutamine repeats demonstrated to inversely affect receptor transcriptional activity in prostate and kidney cells. The effects of AR glutamine repeat length on skeletal muscle are unknown. In this study we examined the effect of AR CAG repeat length on AR function in C2C12 cells. AR expression vectors harboring 14, 24, and 33 CAG repeats were used to assess AR transcriptional activity. C2C12 cell proliferation, differentiation, gene expression, myotube formation, and myonuclear fusion index were assessed. Transcriptional activity increased with increasing repeat length and in response to testosterone (AR14 = 3.91 ± 0.26, AR24 = 25.21 ± 1.72, AR33 = 36.08 ± 3.22 relative light units; P < 0.001). Ligand activation was increased for AR33 (2.10 ± 0.04) compared with AR14 (1.54 ± 0.09) and AR24 (1.57 ± 0.05, P < 0.001). AR mRNA expression was elevated in each stably transfected line. AR33 cell proliferation (20,512.3 ± 1,024.0) was decreased vs. AR14 (27,604.17 ± 1,425.3; P < 0.001) after 72 h. Decreased CK activity in AR14 cells (54.9 ± 2.9 units/?g protein) in comparison to AR33 (70.8 ± 8.1) (P < 0.05) was noted. The myonuclear fusion index was lower for AR14 (15.21 ± 3.24%) and AR33 (9.97 ± 3.14%) in comparison to WT (35.07 ± 5.60%, P < 0.001). AR14 and AR33 cells also displayed atypical myotube morphology. RT-PCR revealed genotype differences in myostatin and myogenin expression. We conclude that AR polyglutamine repeat length is directly associated with transcriptional activity and alters the growth and development of C2C12 cells. This polymorphism may contribute to the heritability of muscle mass in humans. PMID:21828246

Sheppard, Ryan L.; Spangenburg, Espen E.; Chin, Eva R.

2011-01-01

290

Activation of Protease-Activated Receptor 2 Induces VEGF Independently of HIF-1  

PubMed Central

Background Human adipose stem cells (hASCs) can promote angiogenesis through secretion of proangiogenic factors such as vascular endothelial growth factor (VEGF). In other cell types, it has been shown that induction of VEGF is mediated by both protease activated receptor 2 (PAR2) and hypoxia inducible factor 1(HIF-1). The present study hypothesized that PAR2 stimulation through activation of kinase signaling cascades lead to induction of HIF-1 and secretion of VEGF. Methodology/Principal Findings Immunohistochemistry revealed the expression of PAR2 receptors on the surface of hASCs. Blocking the PAR2 receptors with a specific antibody prior to trypsin treatment showed these receptors are involved in trypsin-evoked increase in VEGF secretion from hASCs. Blocking with specific kinase inhibitors suggested that that activation of MEK/ERK and PI3-kinase/Akt pathways are involved in trypsin-eveoked induction of VEGF. The effect of the trypsin treatment on the transcription of VEGF peaked at 6 hours after the treatment and was comparable to the activation observed after keeping hASCs for 24 hours at 1% oxygen. In contrast to hypoxia, trypsin alone failed to induce HIF-1 measured with ELISA, while the combination of trypsin and hypoxia had an additive effect on both VEGF transcription and secretion, results which were confirmed by Western blot. Conclusion In hASCs trypsin and hypoxia induce VEGF expression through separate pathways. PMID:23049945

Rasmussen, Jeppe Gr?ndahl; Riis, Simone Elkjaer; Fr?bert, Ole; Yang, Sufang; Kastrup, Jens; Zachar, Vladimir; Simonsen, Ulf; Fink, Trine

2012-01-01

291

Kinase-active signaling complexes of bacterial chemoreceptors do not contain proposed receptor-receptor contacts observed in crystal structures †  

PubMed Central

The receptor dimers that mediate bacterial chemotaxis form high-order signaling complexes with CheW and the kinase CheA. From the packing arrangement in two crystal structures of different receptor cytoplasmic fragments, two different models have been proposed for receptor signaling arrays: the trimers-of-dimers and hedgerow models. Here we identified an inter-dimer distance that differs substantially in the two models, labeled the atoms defining this distance through isotopic enrichment, and measured it with 19F-13C REDOR. This was done in two types of receptor samples: isolated bacterial membranes containing overexpressed, intact receptor and soluble receptor fragments reconstituted into kinase-active signaling complexes. In both cases, the distance found was not compatible with the receptor dimer-dimer contacts observed in the trimers-of-dimers or in the hedgerow models. Comparisons of simulated and observed REDOR dephasing were used to deduce a closest-approach distance at this interface, which provides a constraint for the possible arrangements of receptor assemblies. PMID:20088541

Fowler, Daniel J.; Weis, Robert M.; Thompson, Lynmarie K.

2010-01-01

292

Reaching out for signals: filopodia sense EGF and respond by directed retrograde transport of activated receptors  

Microsoft Academic Search

rbB1 receptors situated on cellular filopodia un- dergo systematic retrograde transport after binding of the epidermal growth factor (EGF) and activation of the receptor tyrosine kinase. Specific inhibitors of the erbB1 receptor tyrosine kinase as well as cytochalasin D, a disruptor of the actin cytoskeleton, abolish transport but not free diffusion of the receptor-ligand complex. Diffu- sion constants and transport

Diane S. Lidke; Keith A. Lidke; Bernd Rieger; Thomas M. Jovin; Donna J. Arndt-Jovin

2005-01-01

293

A human cell surface receptor activated by free fatty acids and thiazolidinedione drugs  

Microsoft Academic Search

Fatty acids, which are essential nutritional components, are also involved in cardiovascular and metabolic diseases. Here we report a human cell surface receptor that we name free fatty acid receptor (FFAR), because it is specifically activated by medium to long-chain free fatty acids. The receptor belongs to the class of seven-transmembrane, G-protein coupled receptors (GPCRs) and also mediates responses to

Knut Kotarsky; Niclas E. Nilsson; Erik Flodgren; Christer Owman; Björn Olde

2003-01-01

294

High-affinity benzodiazepine receptor ligands among benzodiazepines and betacarbolines with different intrinsic activity  

SciTech Connect

Structural and electrostatic features of diazepam, flumazenil, and methyl betacarboline-3-carboxylate (BCCM) have been investigated using the molecular superimposition method. These high-affinity benzodiazepine (BZ) receptor ligands are structurally unrelated and they have different intrinsic activity. These ligands are superimposed in such a way that common structural and electrostatic features essential for the high receptor binding affinity overlap. In addition to this binding pharmacophore, there are roughly three separate binding zones in the BZ receptor, one for each class of ligands. The intrinsic activity of BZ receptor ligands depends on the molecular structures and the way the ligand approaches the receptor.

Yliniemelae, A.; Gynther, J. (Univ. of Kuopio (Finland)); Konschin, H.; Tylli, H. (Univ. of Helsinki (Finland)); Rouvinen, J. (Univ. of Joensuu (Finland))

1989-01-01

295

Enhancer transcripts mark active estrogen receptor binding sites  

PubMed Central

We have integrated and analyzed a large number of data sets from a variety of genomic assays using a novel computational pipeline to provide a global view of estrogen receptor 1 (ESR1; a.k.a. ER?) enhancers in MCF-7 human breast cancer cells. Using this approach, we have defined a class of primary transcripts (eRNAs) that are transcribed uni- or bidirectionally from estrogen receptor binding sites (ERBSs) with an average transcription unit length of ?3–5 kb. The majority are up-regulated by short treatments with estradiol (i.e., 10, 25, or 40 min) with kinetics that precede or match the induction of the target genes. The production of eRNAs at ERBSs is strongly correlated with the enrichment of a number of genomic features that are associated with enhancers (e.g., H3K4me1, H3K27ac, EP300/CREBBP, RNA polymerase II, open chromatin architecture), as well as enhancer looping to target gene promoters. In the absence of eRNA production, strong enrichment of these features is not observed, even though ESR1 binding is evident. We find that flavopiridol, a CDK9 inhibitor that blocks transcription elongation, inhibits eRNA production but does not affect other molecular indicators of enhancer activity, suggesting that eRNA production occurs after the assembly of active enhancers. Finally, we show that an enhancer transcription “signature” based on GRO-seq data can be used for de novo enhancer prediction across cell types. Together, our studies shed new light on the activity of ESR1 at its enhancer sites and provide new insights about enhancer function. PMID:23636943

Hah, Nasun; Murakami, Shino; Nagari, Anusha; Danko, Charles G.; Kraus, W. Lee

2013-01-01

296

Constitutive Somatostatin Receptor Subtype 2 Activity Attenuates GH Synthesis  

PubMed Central

Somatostatin signals predominantly through somatostatin receptor (SSTR) subtype 2 to attenuate GH release. However, the independent role of the receptor in regulating GH synthesis is unclear. Because we had previously demonstrated constitutive SSTR2 activity in mouse corticotrophs, we now analyzed GH regulation in rat pituitary somatotroph (GC) tumor cells, which express SSTR2 exclusively and are devoid of endogenous somatostatin ligand. We demonstrate that moderately stable SSTR2 overexpression (GpSSTR2WT cells) was associated with decreased GH promoter activity, GH mRNA, and hormone levels compared with those of control transfectants (GpCon cells). In contrast, levels of GH mRNA and peptide and GH promoter activity were unchanged in GpSSTR2DRY stable transfectants moderately expressing DRY motif mutated SSTR2 (R140A). GpSSTR2DRY did not exhibit an enhanced octreotide response as did GpSSTR2WT cells; however, both SSTR2WT-enhanced yellow fluorescent protein (eYFP) and SSTR2DRY-eYFP internalized on octreotide treatment. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, increased GH synthesis in wild-type GC cells and primary pituitary cultures. GpSSTR2WT cells induced GH synthesis more strongly on SAHA treatment, evident by both higher GH peptide and mRNA levels compared with the moderate but similar GH increase observed in GpCon and GpSSTR2DRY cells. In vivo SAHA also increased GH release from GpSSTR2WT but not from control xenografts. Endogenous rat GH promoter chromatin immunoprecipitation showed decreased baseline acetylation of the GH promoter with exacerbated acetylation after SAHA treatment in GpSSTR2WT compared with that of either GpSSTR2DRY or control cells, the latter 2 transfectants exhibiting similar GH promoter acetylation levels. In conclusion, modestly increased SSTR2 expression constitutively decreases GH synthesis, an effect partially mediated by GH promoter histone deacetylation. PMID:23696564

Ben-Shlomo, Anat; Pichurin, Oxana; Khalafi, Ramtin; Zhou, Cuiqi; Chesnokova, Vera; Ren, Song-Guang; Liu, Ning-Ai

2013-01-01

297

The glucagon-like peptide 1 receptor agonist enhances intrinsic peroxisome proliferator-activated receptor ? activity in endothelial cells.  

PubMed

Recent studies have suggested glucagon-like peptide-1 (GLP-1) signaling to exert anti-inflammatory effects on endothelial cells, although the precise underlying mechanism remains to be elucidated. In the present study, we investigated whether PPAR? activation is involved in the GLP-1-mediated anti-inflammatory action on endothelial cells. When we treated HUVEC cells with 0.2ng/ml exendin-4, a GLP-1 receptor agonist, endogenous PPAR? transcriptional activity was significantly elevated, by approximately 20%, as compared with control cells. The maximum PPAR? activity enhancing effect of exendin-4 was observed 12h after the initiation of incubation with exendin-4. As H89, a PKA inhibitor, abolished GLP-1-induced PPAR? enhancement, the signaling downstream from GLP-1 cross-talk must have been involved in PPAR? activation. In conclusion, our results suggest that GLP-1 has the potential to induce PPAR? activity, partially explaining the anti-inflammatory effects of GLP-1 on endothelial cells. Cross-talk between GLP-1 signaling and PPAR? activation would have major impacts on treatments for patients at high risk for cardiovascular disease. PMID:25109805

Onuma, Hirohisa; Inukai, Kouichi; Kitahara, Atsuko; Moriya, Rie; Nishida, Susumu; Tanaka, Toshiaki; Katsuta, Hidenori; Takahashi, Kazuto; Sumitani, Yoshikazu; Hosaka, Toshio; Ishida, Hitoshi

2014-08-22

298

Protective effects of a peroxisome proliferator-activated receptor-h/y agonist in experimental autoimmune encephalomyelitis  

E-print Network

Protective effects of a peroxisome proliferator-activated receptor-h/y agonist in experimental Agonists of the peroxisome proliferator-activated receptor gamma (PPARg) exert anti-inflammatory and anti. Introduction Peroxisome Proliferator-Activated Receptors (PPARs) are nuclear hormone receptors. In response

Omiecinski, Curtis

299

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

300

Peroxisome Proliferator-activated Receptor ( )-dependent Regulation of Ubiquitin C Expression Contributes to Attenuation of  

E-print Network

Peroxisome Proliferator-activated Receptor ( )-dependent Regulation of Ubiquitin C Expression 21702 The role of peroxisome proliferator-activated recep- tor- (PPAR ) in the molecular regulation cycle control, which could lead to skin cancer (1, 2). Peroxisome proliferator-activated receptors

Omiecinski, Curtis

301

ACTIVATION OF A DIMERIC METABOTROPIC GLUTAMATE RECEPTOR BY INTER-SUBUNIT REARRANGEMENT  

E-print Network

ACTIVATION OF A DIMERIC METABOTROPIC GLUTAMATE RECEPTOR BY INTER-SUBUNIT REARRANGEMENT Carsten contribute to GPCR activation. Here we examined this possibility using a dimeric metabotropic glutamate in the activation of a dimeric GPCR, we chose a metabotropic glutamate receptor (mGluR) as a model. These GPCRs

Boyer, Edmond

302

SHP-1 phosphatase activity counteracts increased T cell receptor affinity  

PubMed Central

Anti-self/tumor T cell function can be improved by increasing TCR-peptide MHC (pMHC) affinity within physiological limits, but paradoxically further increases (Kd < 1 ?M) lead to drastic functional declines. Using human CD8+ T cells engineered with TCRs of incremental affinity for the tumor antigen HLA-A2/NY-ESO-1, we investigated the molecular mechanisms underlying this high-affinity–associated loss of function. As compared with cells expressing TCR affinities generating optimal function (Kd = 5 to 1 ?M), those with supraphysiological affinity (Kd = 1 ?M to 15 nM) showed impaired gene expression, signaling, and surface expression of activatory/costimulatory receptors. Preferential expression of the inhibitory receptor programmed cell death-1 (PD-1) was limited to T cells with the highest TCR affinity, correlating with full functional recovery upon PD-1 ligand 1 (PD-L1) blockade. In contrast, upregulation of the Src homology 2 domain-containing phosphatase 1 (SHP-1/PTPN6) was broad, with gradually enhanced expression in CD8+ T cells with increasing TCR affinities. Consequently, pharmacological inhibition of SHP-1 with sodium stibogluconate augmented the function of all engineered T cells, and this correlated with the TCR affinity–dependent levels of SHP-1. These data highlight an unexpected and global role of SHP-1 in regulating CD8+ T cell activation and responsiveness and support the development of therapies inhibiting protein tyrosine phosphatases to enhance T cell–mediated immunity. PMID:23391724

Hebeisen, Michael; Baitsch, Lukas; Presotto, Danilo; Baumgaertner, Petra; Romero, Pedro; Michielin, Olivier; Speiser, Daniel E.; Rufer, Nathalie

2013-01-01

303

Regulation of DNA Binding Activity of the Ligand-Activated Aryl Hydrocarbon Receptor by Tyrosine Phosphorylation  

Microsoft Academic Search

Aryl hydrocarbon receptor (AhR), a member of the bHLH–PAS family, is a ligand-activated transcription factor which plays an important role in normal liver development and in mediating the toxicity of polycyclic and halogenated aromatic hydrocarbon pollutants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin. Phosphorylation is known to regulate the transformation process of unliganded AhR into functionally active AhR\\/ARNT heterodimer that has high affinity for

Sang-ki Park; Ellen C. Henry; Thomas A. Gasiewicz

2000-01-01

304

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

305

Modulation of cardiac ryanodine receptor activity by ROS and RNS.  

PubMed

Calcium release through cardiac ryanodine receptors (RyR2) triggers heart muscle contraction. Reactive oxygen/nitrogen species (ROS/RNS), normally produced in the heart, promote endogenous RyR2 S-nitrosylation and S-glutathionylation. These reversible redox modifications increase RyR2 activity in vitro, and presumably also in vivo. RyR2 S-glutathionylation increases under physiologically relevant conditions (tachycardia and exercise), suggesting that cardiac cells utilize this redox modification to increase RyR2 activity under increased demand. In contrast, in vivo changes in RyR2 S-nitrosylation in response to physiological stimuli remain uncharacterized. The number and identity of the highly reactive RyR2 cysteine residues and the nature of the redox modification they undergo are presently unknown. Likewise, the physiological sources of ROS/RNS responsible for functionally relevant RyR2 redox modifications have not been completely identified. The redox state of RyR2 is altered in heart failure leading to enhanced RyR2 activity, which presumably contributes to decrease SR calcium content and induce other calcium release abnormalities observed in heart failure. Greater understanding of RyR2 redox modulation is necessary to counteract the deleterious consequences of RyR2 activity deregulation caused by oxidative stress. PMID:21196188

Donoso, Paulina; Sanchez, Gina; Bull, Ricardo; Hidalgo, Cecilia

2011-01-01

306

Phosphorylation and Activation of Androgen Receptor by Aurora-A*  

PubMed Central

Aurora-A kinase is frequently overexpressed/activated in various types of human malignancy, including prostate cancer. In this study, we demonstrate elevated levels of Aurora-A in androgen-refractory LNCaP-RF but not androgen-sensitive LNCaP cells, which prompted us to examine whether Aurora-A regulates the androgen receptor (AR) and whether elevated Aurora-A is involved in androgen-independent cell growth. We show that ectopic expression of Aurora-A induces AR transactivation activity in the presence and absence of androgen. Aurora-A interacts with AR and phosphorylates AR at Thr282 and Ser293 in vitro and in vivo. Aurora-A induces AR transactivation activity in a phosphorylation-dependent manner. Ectopic expression of Aurora-A in LNCaP cells induces prostate-specific antigen expression and cell survival, whereas knockdown of Aurora-A sensitizes LNCaP-RF cells to apoptosis and cell growth arrest. These data indicate that AR is a substrate of Aurora-A and that elevated Aurora-A could contribute to androgen-independent cell growth by phosphorylation and activation of AR. PMID:20713353

Shu, Shao-Kun; Liu, Qiyuan; Coppola, Domenico; Cheng, Jin Q.

2010-01-01

307

RSUME Enhances Glucocorticoid Receptor SUMOylation and Transcriptional Activity  

PubMed Central

Glucocorticoid receptor (GR) activity is modulated by posttranslational modifications, including phosphorylation, ubiquitination, and SUMOylation. The GR has three SUMOylation sites: lysine 297 (K297) and K313 in the N-terminal domain (NTD) and K721 within the ligand-binding domain. SUMOylation of the NTD sites mediates the negative effect of the synergy control motifs of GR on promoters with closely spaced GR binding sites. There is scarce evidence on the role of SUMO conjugation to K721 and its impact on GR transcriptional activity. We have previously shown that RSUME (RWD-containing SUMOylation enhancer) increases protein SUMOylation. We now demonstrate that RSUME interacts with the GR and increases its SUMOylation. RSUME regulates GR transcriptional activity and the expression of its endogenous target genes, FKBP51 and S100P. RSUME uncovers a positive role for the third SUMOylation site, K721, on GR-mediated transcription, demonstrating that GR SUMOylation acts positively in the presence of a SUMOylation enhancer. Both mutation of K721 and small interfering RNA-mediated RSUME knockdown diminish GRIP1 coactivator activity. RSUME, whose expression is induced under stress conditions, is a key factor in heat shock-induced GR SUMOylation. These results show that inhibitory and stimulatory SUMO sites are present in the GR and at higher SUMOylation levels the stimulatory one becomes dominant. PMID:23508108

Druker, Jimena; Liberman, Ana C.; Antunica-Noguerol, María; Gerez, Juan; Paez-Pereda, Marcelo; Rein, Theo; Iñiguez-Lluhí, Jorge A.; Holsboer, Florian

2013-01-01

308

RSUME enhances glucocorticoid receptor SUMOylation and transcriptional activity.  

PubMed

Glucocorticoid receptor (GR) activity is modulated by posttranslational modifications, including phosphorylation, ubiquitination, and SUMOylation. The GR has three SUMOylation sites: lysine 297 (K297) and K313 in the N-terminal domain (NTD) and K721 within the ligand-binding domain. SUMOylation of the NTD sites mediates the negative effect of the synergy control motifs of GR on promoters with closely spaced GR binding sites. There is scarce evidence on the role of SUMO conjugation to K721 and its impact on GR transcriptional activity. We have previously shown that RSUME (RWD-containing SUMOylation enhancer) increases protein SUMOylation. We now demonstrate that RSUME interacts with the GR and increases its SUMOylation. RSUME regulates GR transcriptional activity and the expression of its endogenous target genes, FKBP51 and S100P. RSUME uncovers a positive role for the third SUMOylation site, K721, on GR-mediated transcription, demonstrating that GR SUMOylation acts positively in the presence of a SUMOylation enhancer. Both mutation of K721 and small interfering RNA-mediated RSUME knockdown diminish GRIP1 coactivator activity. RSUME, whose expression is induced under stress conditions, is a key factor in heat shock-induced GR SUMOylation. These results show that inhibitory and stimulatory SUMO sites are present in the GR and at higher SUMOylation levels the stimulatory one becomes dominant. PMID:23508108

Druker, Jimena; Liberman, Ana C; Antunica-Noguerol, María; Gerez, Juan; Paez-Pereda, Marcelo; Rein, Theo; Iñiguez-Lluhí, Jorge A; Holsboer, Florian; Arzt, Eduardo

2013-06-01

309

Activation of Ah receptor by pure humic acids.  

PubMed

Humic substances (HS) are ubiquitous in the environment. However, some studies indicate that HS could induce direct adverse effects on human health and hormone-like effects in fish, amphibians, and invertebrates. In this study we investigated a possible biochemical mechanism of HS toxicity via activation of the aryl hydrocarbon receptor (AhR). AhR mediates the toxic and biological effects of environmental contaminants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but a number of structurally diverse compounds has also been found to activate AhR. Alkali solutions of humic acids (HA) were prepared, and subsequently, lipophilic compounds (including parts of HA) were extracted by liquid-liquid extraction with hexane/dichloromethane. Organic extract of HA was further treated with sulfuric acid to study the role of possible trace persistent contaminants. In vitro dioxin-like activities of obtained extract and HA solutions have been evaluated using H4IIE.luc cells by determining the ethoxyresorufin-O-deethylase (EROD) activity and induction of AhR-dependent reporter luciferase. Traces of nonpersistent residues in HA with known AhR activity were identified and quantified by GC-MS. Our results show that an alkali solution as well as organic extract of HA were active in both EROD and luciferase assays, while H2SO4-treated extract activity was negligible. Only nonsignificant levels of AhR-inducing contaminants (PAHs and PCBs) were found in the HA samples. Our results indicate that HA or their fragments can elicit significant inductions of AhR-mediated effects in vitro. To our best knowledge, this study is the first in providing direct evidence of dioxin-like effects of HA. Further efforts should focus on detailed characterization of potential toxic effects of various HSs. PMID:16841312

Bittner, Michal; Janosek, Jaroslav; Hilscherová, Klára; Giesy, John; Holoubek, Ivan; Bláha, Lud?k

2006-08-01

310

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

311

Novel protein interactors of urokinase-type plasminogen activator receptor.  

PubMed

The urokinase-type plasminogen activator receptor (uPAR) has been implicated in tumor growth and metastasis. The crystal structure of uPAR revealed that the external surface is largely free to interact with a number of proteins. Additionally, due to absence of an intracellular cytoplasmic protein domain, many of the biological functions of uPAR necessitate interactions with other proteins. Here, we used yeast two-hybrid screening of breast cancer cDNA library to identify hSpry1 and HAX1 proteins as putative candidate proteins that interact with uPAR bait constructs. Interaction between these two candidates and uPAR was confirmed by GST-pull down, co-immunoprecipitation assays and confocal microscopy. These novel interactions that have been identified may also provide further evidence that uPAR can interact with a number of other proteins which may influence a range of biological functions. PMID:20696135

Mekkawy, Ahmed H; De Bock, Charles E; Lin, Zhen; Morris, David L; Wang, Yao; Pourgholami, Mohammad H

2010-09-01

312

Targeting the Urokinase Plasminogen Activator Receptor Inhibits Ovarian Cancer Metastasis  

PubMed Central

Purpose To understand the functional and preclinical efficacy of targeting urokinase plasminogen activator receptor (u-PAR) in ovarian cancer. Experimental Design Expression of u-PAR was studied in 162 epithelial ovarian cancers, including 77 pairs of corresponding primary and metastatic tumors. The effect of an antibody against u-PAR (ATN-658) on proliferation, adhesion, invasion, apoptosis, and migration was assessed in three (SKOV3ip1, HeyA8, and CaOV3) ovarian cancer cell lines. The impact of the u-PAR antibody on tumor weight, number, and survival was examined in corresponding ovarian cancer xenograft models and the mechanism by which ATN-658 blocks metastasis was explored. Results Only 8% of all ovarian tumors were negative for u-PAR expression. Treatment of SKOV3ip1, HeyA8, and CaOV3 ovarian cancer cells with the u-PAR antibody inhibited cell invasion, migration and adhesion. In vivo, anti-u-PAR treatment reduced the number of tumors and tumor weight in CaOV3 and SKOV3ip1 xenografts, and reduced tumor weight and increased survival in HeyA8 xenografts. Immunostaining of CaOV3 xenograft tumors and ovarian cancer cell lines showed an increase in active-caspase 3 and TUNEL staining. Treatment with u-PAR antibody inhibited ?5-integrin and u-PAR colocalization on primary human omental ECM. Anti-u-PAR treatment also decreased the expression of urokinase, u-PAR, ?3-integrin and fibroblast growth factor receptor-1 both in vitro and in vivo. Conclusions This study shows that an antibody against u-PAR reduces metastasis, induces apoptosis, and reduces the interaction between u-PAR and ?5-integrin. This provides a rationale for targeting the u-PAR pathway in patients with ovarian cancer and for further testing of ATN-658 in this indication. PMID:21149615

Kenny, Hilary A.; Leonhardt, Payton; Ladanyi, Andras; Yamada, S. Diane; Montag, Anthony; Im, Hae Kyung; Jagadeeswaran, Sujatha; Shaw, David E.; Mazar, Andrew P.; Lengyel, Ernst

2010-01-01

313

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...

314

Mechanism of kinase activation in the receptor for colony-stimulating factor 1.  

PubMed Central

Receptor tyrosine kinases remain dormant until activated by ligand binding to the extracellular domain. Two mechanisms have been proposed for kinase activation: (i) ligand binding to the external domain of a receptor monomer may induce a conformational change that is transmitted across the cell membrane (intramolecular model) or (ii) the ligand may facilitate oligomerization, thereby allowing interactions between the juxtaposed kinase domains (intermolecular model). The receptor for colony-stimulating factor 1 was used to test these models. Large insertions at the junction between the external and transmembrane domains of the receptor, introduced by site-directed mutagenesis of the cDNA, were positioned to isolate the external domain and prevent transmembrane conformational propagation while allowing for receptor oligomerization. Such mutant receptors were expressed on the cell surface, bound ligand with high affinity, exhibited ligand-stimulated autophosphorylation, and signaled mitogenesis and cellular proliferation in the presence of ligand. A second experimental strategy directly tested the intermolecular model of ligand activation. A hybrid receptor composed of the external domain of human glycophorin A and the transmembrane and cytoplasmic domains of the colony-stimulating factor 1 receptor exhibited anti-glycophorin antibody-induced kinase activity that supported mitogenesis. Our data strongly support a mechanism of receptor activation based on ligand-induced receptor oligomerization. Images PMID:2169623

Lee, A W; Nienhuis, A W

1990-01-01

315

Trigeminal Medullary Dorsal Horn Neurons Activated by Nasal Stimulation Coexpress AMPA, NMDA, and NK1 Receptors  

PubMed Central

Afferent information initiating the cardiorespiratory responses during nasal stimulation projects from the nasal passages to neurons within the trigeminal medullary dorsal horn (MDH) via the anterior ethmoidal nerve (AEN). Central AEN terminals are thought to release glutamate to activate the MDH neurons. This study was designed to determine which neurotransmitter receptors (AMPA, kainate, or NMDA glutamate receptor subtypes or the Substance P receptor NK1) are expressed by these activated MDH neurons. Fos was used as a neuronal marker of activated neurons, and immunohistochemistry combined with epifluorescent microscopy was used to determine which neurotransmitter receptor subunits were coexpressed by activated MDH neurons. Results indicate that, during nasal stimulation with ammonia vapors in urethane-anesthetized Sprague-Dawley rats, activated neurons within the superficial MDH coexpress the AMPA glutamate receptor subunits GluA1 (95.8%) and GluA2/3 (88.2%), the NMDA glutamate receptor subunits GluN1 (89.1%) and GluN2A (41.4%), and NK1 receptors (64.0%). It is therefore likely that during nasal stimulation the central terminals of the AEN release glutamate and substance P that then produces activation of these MDH neurons. The involvement of AMPA and NMDA receptors may mediate fast and slow neurotransmission, respectively, while NK1 receptor involvement may indicate activation of a nociceptive pathway. PMID:24967301

McCulloch, P. F.; DiNovo, K. M.; Westerhaus, D. J.; Vizinas, T. A.; Peevey, J. F.; Lach, M. A.; Czarnocki, P.

2013-01-01

316

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

317

Activation of transient receptor potential ankyrin 1 by eugenol.  

PubMed

Eugenol is a bioactive plant extract used as an analgesic agent in dentistry. The structural similarity of eugenol to cinnamaldehyde, an active ligand for transient receptor potential ankyrin 1 (TRPA1), suggests that eugenol might produce its effect via TRPA1, in addition to TRPV1 as we reported previously. In this study, we investigated the effect of eugenol on TRPA1, by fura-2-based calcium imaging and patch clamp recording in trigeminal ganglion neurons and in a heterologous expression system. As the result, eugenol induced robust calcium responses in rat trigeminal ganglion neurons that responded to a specific TRPA1 agonist, allyl isothiocyanate (AITC), and not to capsaicin. Capsazepine, a TRPV1 antagonist failed to inhibit eugenol-induced calcium responses in AITC-responding neurons. In addition, eugenol response was observed in trigeminal ganglion neurons from TRPV1 knockout mice and human embryonic kidney 293 cell lines that express human TRPA1, which was inhibited by TRPA1-specific antagonist HC-030031. Eugenol-evoked TRPA1 single channel activity and eugenol-induced TRPA1 currents were dose-dependent with EC50 of 261.5?M. In summary, these results demonstrate that the activation of TRPA1 might account for another molecular mechanism underlying the pharmacological action of eugenol. PMID:24384226

Chung, G; Im, S T; Kim, Y H; Jung, S J; Rhyu, M-R; Oh, S B

2014-03-01

318

Corticothalamic Activation Modulates Thalamic Firing Through Glutamate "Metabotropic" Receptors  

NASA Astrophysics Data System (ADS)

The mammalian thalamus forms an obligatory relay for nearly all sensory information that reaches the cerebral cortex. The transmission of sensory information by the thalamus varies in a state-dependent manner, such that during slow wave sleep or drowsiness thalamic responsiveness is markedly reduced, whereas during the waking, attentive state transmission is enhanced. Although activation of brainstem inputs to thalamic neurons has long been assumed to underlie this gating of sensory transfer through the thalamus, numerically the largest input to thalamic relay neurons derives from layer VI cells of the cerebral cortex. Here we report that activation of corticothalamic fibers causes a prolonged excitatory postsynaptic potential in guinea pig dorsal lateral geniculate relay neurons resulting from the reduction of a potassium conductance, consistent with the activation of glutamatergic "metabotropic" receptors. This slow depolarization can switch firing of thalamic neurons from the burst firing mode, which is prevalent during slow wave sleep, to the single spike mode, which is prevalent during waking, thereby facilitating transmission of sensory information through the thalamus. This prolonged enhancement of thalamic transfer may allow the cerebral cortex to gate or control selective fields of sensory inputs in a manner that facilitates arousal, attention, and cognition.

McCormick, David A.; von Krosigk, Marcus

1992-04-01

319

Odorant receptor-mediated sperm activation in disease vector mosquitoes  

PubMed Central

Insects, such as the malaria vector mosquito, Anopheles gambiae, depend upon chemoreceptors to respond to volatiles emitted from a range of environmental sources, most notably blood meal hosts and oviposition sites. A subset of peripheral signaling pathways involved in these insect chemosensory-dependent behaviors requires the activity of heteromeric odorant receptor (OR) ion channel complexes and ligands for numerous A. gambiae ORs (AgOrs) have been identified. Although AgOrs are expressed in nonhead appendages, studies characterizing potential AgOr function in nonolfactory tissues have not been conducted. In the present study, we explore the possibility that AgOrs mediate responses of spermatozoa to endogenous signaling molecules in A. gambiae. In addition to finding AgOr transcript expression in testes, we show that the OR coreceptor, AgOrco, is localized to the flagella of A. gambiae spermatozoa where Orco-specific agonists, antagonists, and other odorant ligands robustly activate flagella beating in an Orco-dependent process. We also demonstrate Orco expression and Orco-mediated activation of spermatozoa in the yellow fever mosquito, Aedes aegypti. Moreover, we find Orco localization in testes across distinct insect taxa and posit that OR-mediated responses in spermatozoa may represent a general characteristic of insect reproduction and an example of convergent evolution. PMID:24550284

Pitts, R. Jason; Liu, Chao; Zhou, Xiaofan; Malpartida, Juan C.; Zwiebel, Laurence J.

2014-01-01

320

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

321

Triclocarban Mediates Induction of Xenobiotic Metabolism through Activation of the Constitutive Androstane Receptor and the Estrogen Receptor Alpha  

PubMed Central

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

322

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

323

The role of ECL2 in CGRP receptor activation: a combined modelling and experimental approach  

PubMed Central

The calcitonin gene-related peptide (CGRP) receptor is a complex of a calcitonin receptor-like receptor (CLR), which is a family B G-protein-coupled receptor (GPCR) and receptor activity modifying protein 1. The role of the second extracellular loop (ECL2) of CLR in binding CGRP and coupling to Gs was investigated using a combination of mutagenesis and modelling. An alanine scan of residues 271–294 of CLR showed that the ability of CGRP to produce cAMP was impaired by point mutations at 13 residues; most of these also impaired the response to adrenomedullin (AM). These data were used to select probable ECL2-modelled conformations that are involved in agonist binding, allowing the identification of the likely contacts between the peptide and receptor. The implications of the most likely structures for receptor activation are discussed. PMID:24047872

Woolley, Michael. J.; Watkins, Harriet A.; Taddese, Bruck; Karakullukcu, Z. Gamze; Barwell, James; Smith, Kevin J.; Hay, Debbie L.; Poyner, David R.; Reynolds, Christopher A.; Conner, Alex C.

2013-01-01

324

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

325

Peroxisome Proliferator-Activated Receptor Gamma Activators Inhibit Gene Expression and Migration in Human Vascular Smooth Muscle Cells  

Microsoft Academic Search

Migration of vascular smooth muscle cells (VSMCs) plays an important role in atherogenesis and restenosis after arterial interventions. The expression of matrix metalloproteinases (MMPs), particularly MMP-9, contributes to VSMC migration. This process requires degradation of basal laminae and other components of the arterial extracellular matrix. Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor family, regulate gene expression after activation

Nikolaus Marx; Uwe Schonbeck; Mitchell A. Lazar; Peter Libby; Jorge Plutzky

326

Anti-laminin reactivity and glomerular immune deposition by in vitro recombinant antibodies.  

PubMed

Growing evidence suggests that recombinatorial events prior to antigen contact can generate pathogenic autoantibodies in the nonautoimmune individual, thus providing potential disease mediators if conditions arise that permit bypass of tolerance and activation of autoreactive lymphocytes. To examine the disease potential of selected germline antibody genes, Ig were created de novo by in vitro recombination of Ig H and L chains. H chain loss variant (i.e., L-chain only) cell lines were transfected with a DNA construct encoding the variable region and regulatory sequences (LamH) of a nephrotropic murine lupus anti-laminin Ig, and the resultant Ig were examined for in vitro antigen reactivity and in vivo glomerular immune deposition. The results indicate that two light chains, LamL (Vk8, Jk5) and 238L (Vk4, Jk5), expressing unrelated germline V1 genes, combine with LamH to generate Ig that bind basement membrane laminin in vitro, diverge in their capacity to bind ssDNA, and produce two distinct patterns of glomerular immune deposits in vivo: dense mesangial matrix (LamH/LamL) and dramatic linear glomerular basement membrane (LamH/238L) deposits. The Ig genes used by both LamH and 238L are present in nonautoimmune mice as well as in lupus-prone strains. We conclude that certain unmutated Ig genes can contribute to multiple distinct disease associated specificities, including binding to intrinsic kidney antigens, and that mutation is not essential to generate these Ig. Collectively, these observations suggest that pathogenic autoantibodies can be generated in the normal preimmune repertoire by random recombinatorial and somatic events in the absence of mutation. PMID:9543184

Foster, M H; Liu, Q; Chen, H; Nemazee, D; Cooperstone, B G

1997-01-01

327

Disease-associated Mutations in the Prion Protein Impair Laminin-induced Process Outgrowth and Survival*  

PubMed Central

Prions, the agents of transmissible spongiform encephalopathies, require the expression of prion protein (PrPC) to propagate disease. PrPC is converted into an abnormal insoluble form, PrPSc, that gains neurotoxic activity. Conversely, clinical manifestations of prion disease may occur either before or in the absence of PrPSc deposits, but the loss of normal PrPC function contribution for the etiology of these diseases is still debatable. Prion disease-associated mutations in PrPC represent one of the best models to understand the impact of PrPC loss-of-function. PrPC associates with various molecules and, in particular, the interaction of PrPC with laminin (Ln) modulates neuronal plasticity and memory formation. To assess the functional alterations associated with PrPC mutations, wild-type and mutated PrPC proteins were expressed in a neural cell line derived from a PrPC-null mouse. Treatment with the laminin ?1 chain peptide (Ln ?1), which mimics the Ln binding site for PrPC, increased intracellular calcium in cells expressing wild-type PrPC, whereas a significantly lower response was observed in cells expressing mutated PrPC molecules. The Ln ?1 did not promote process outgrowth or protect against staurosporine-induced cell death in cells expressing mutated PrPC molecules in contrast to cells expressing wild-type PrPC. The co-expression of wild-type PrPC with mutated PrPC molecules was able to rescue the Ln protective effects, indicating the lack of negative dominance of PrPC mutated molecules. These results indicate that PrPC mutations impair process outgrowth and survival mediated by Ln ?1 peptide in neural cells, which may contribute to the pathogenesis of genetic prion diseases. PMID:23132868

Machado, Cleiton F.; Beraldo, Flavio H.; Santos, Tiago G.; Bourgeon, Dominique; Landemberger, Michele C.; Roffe, Martin; Martins, Vilma R.

2012-01-01

328

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

329

Shift in Kiss1 cell activity requires estrogen receptor ?.  

PubMed

Reproductive function requires timely secretion of gonadotropin-releasing hormone, which is controlled by a complex excitatory/inhibitory network influenced by sex steroids. Kiss1 neurons are fundamental players in this network, but it is currently unclear whether different conditions of circulating sex steroids directly alter Kiss1 neuronal activity. Here, we show that Kiss1 neurons in the anteroventral periventricular and anterior periventricular nuclei (AVPV/PeN) of males and females exhibit a bimodal resting membrane potential (RMP) influenced by K(ATP) channels, suggesting the presence of two neuronal populations defined as type I (irregular firing patterns) and type II (quiescent). Kiss1 neurons in the arcuate nucleus (Arc) are also composed of firing and quiescent cells, but unlike AVPV/PeN neurons, the range of RMPs did not follow a bimodal distribution. Moreover, Kiss1 neuronal activity in the AVPV/PeN, but not in the Arc, is sexually dimorphic. In females, estradiol shifts the firing pattern of AVPV/PeN Kiss1 neurons and alters cell capacitance and spontaneous IPSCs amplitude of AVPV/PeN and Arc Kiss1 populations in an opposite manner. Notably, mice with selective deletion of estrogen receptor ? (ER?) from Kiss1 neurons show cellular activity similar to that observed in ovariectomized females, suggesting that estradiol-induced changes in Kiss1 cellular properties require ER?. We also show that female prepubertal Kiss1 neurons are under higher inhibitory influence and all recorded AVPV/PeN Kiss1 neurons were spontaneously active. Collectively, our findings indicate that changes in cellular activity may underlie Kiss1 action in pubertal initiation and female reproduction. PMID:23407940

Frazão, Renata; Cravo, Roberta M; Donato, Jose; Ratra, Dhirender V; Clegg, Deborah J; Elmquist, Joel K; Zigman, Jeffrey M; Williams, Kevin W; Elias, Carol F

2013-02-13

330

Shift in Kiss1 cell activity requires estrogen receptor ?  

PubMed Central

Summary Reproductive function requires timely secretion of gonadotropin releasing hormone, which is controlled by a complex excitatory/inhibitory network influenced by sex steroids. Kiss1 neurons are fundamental players in this network, but it is currently unclear whether different conditions of circulating sex steroids directly alters Kiss1 neuronal activity. Here, we show that Kiss1 neurons in the anteroventral periventricular and anterior periventricular nuclei (AVPV/PeN) of males and females exhibit a bimodal resting membrane potential (RMP) influenced by KATP channels, suggesting the presence of two neuronal populations defined as Type I (irregular firing patterns) and Type II (quiescent). Kiss1 neurons in the arcuate nucleus (Arc) are also composed of firing and quiescent cells, but unlike AVPV/PeN neurons, the range of RMPs did not follow a bimodal distribution. Moreover, Kiss1 neuronal activity in the AVPV/PeN, but not in the Arc, is sexually dimorphic. In females, estradiol shifts the firing pattern of AVPV/PeN Kiss1 neurons and alters cell capacitance and spontaneous inhibitory postsynaptic potentials (IPSCs) amplitude of AVPV/PeN and Arc Kiss1 populations in an opposite manner. Notably, mice with selective deletion of estrogen receptor ? (ER?) from Kiss1 neurons show cellular activity similar to that observed in ovariectomized females, suggesting that estradiol-induced changes in Kiss1 cellular properties require ER?. We also show that female prepubertal Kiss1 neurons are under higher inhibitory influence while all AVPV/PeN Kiss1 neurons are spontaneously active. Collectively, our findings indicate that changes in cellular activity may underlie Kiss1 action in pubertal initiation and female reproduction. PMID:23407940

Frazao, Renata; Cravo, Roberta M.; Donato, Jose; Ratra, Dhirender; Clegg, Deborah; Elmquist, Joel K.; Zigman, Jeffrey M.; Williams, Kevin W.; Elias, Carol F.

2013-01-01

331

Activation of peroxisome proliferator-activated receptor beta/delta induces lung cancer growth via peroxisome proliferator-activated receptor coactivator gamma-1alpha.  

PubMed

We previously demonstrated that a selective agonist of peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta), GW501516, stimulated human non-small cell lung carcinoma (NSCLC) growth, partly through inhibition of phosphatase and tensin homolog deleted on chromosome 10 expression. Here, we show that GW501516 also decreases the phosphorylation of AMP-activated protein kinase alpha (AMPKalpha), a major regulator of energy metabolism. This was mediated through specific activation of PPARbeta/delta, as a PPARbeta/delta small interfering RNA inhibited the effect. However, AMPKalpha did not mediate the growth-promoting effects of GW501516, as silencing of AMPKalpha did not inhibit GW501516-induced cell proliferation. Instead, we found that GW501516 stimulated peroxisome proliferator-activated receptor coactivator gamma (PGC)-1alpha, which activated the phosphatidylinositol 3 kinase (PI3-K)/Akt mitogenic pathway. An inhibitor of PI3-K, LY294002, had no effect on PGC-1alpha, consistent with PGC-1alpha being upstream of PI3-K/Akt. Of note, an activator of AMPKalpha, 5-amino-4-imidazole carboxamide riboside, inhibited the growth-promoting effects of GW501516, suggesting that although AMPKalpha is not responsible for the mitogenic effects of GW501516, its activation can oppose these events. This study unveils a novel mechanism by which GW501516 and activation of PPARbeta/delta stimulate human lung carcinoma cell proliferation, and suggests that activation of AMPKalpha may oppose this effect. PMID:18776129

Han, Shouwei; Ritzenthaler, Jeffrey D; Sun, Xiaojuan; Zheng, Ying; Roman, Jesse

2009-03-01

332

Structural determinants of adenophostin A activity at inositol trisphosphate receptors.  

PubMed

Adenophostin A is the most potent known agonist of inositol 1,4,5-trisphosphate (InsP(3)) receptors. Ca(2+) release from permeabilized hepatocytes was 9.9 +/- 1.6-fold more sensitive to adenophostin A (EC(50), 14.7 +/- 2.4 nM) than to InsP(3) (145 +/- 10 nM), consistent with the greater affinity of adenophostin A for hepatic InsP(3) receptors (K(d) = 0.48 +/- 0.06 and 3.09 +/- 0.33 nM, respectively). Here, we systematically modify the structures of the glucose, ribose, and adenine moieties of adenophostin A and use Ca(2+) release and binding assays to define their contributions to high-affinity binding. Progressive trimming of the adenine of adenophostin A reduced potency, but it fell below that of InsP(3) only after complete removal of the adenine. Even after substantial modifications of the adenine (to uracil or even unrelated aromatic rings, retaining the beta-orientation), the analogs were more potent than InsP(3). The only analog with an alpha-ribosyl linkage had massively decreased potency. The 2'-phosphate on the ribose ring of adenophostin A was essential and optimally active when present on a five-membered ring in a position stereochemically equivalent to its location in adenophostin A. Xylo-adenophostin, where xylose replaces the glucose ring of adenophostin A, was only slightly less potent than adenophostin A, whereas manno-adenophostin (mannose replacing glucose) had similar potency to InsP(3). These results are consistent with the relatively minor role of the 3-hydroxyl of InsP(3) (the equivalent is absent from xylo-adenophostin) and greater role of the equatorial 6-hydroxyl (the equivalent is axial in manno-adenophostin). This is the first comprehensive analysis of all the key structural elements of adenophostin A, and it provides a working model for the design of related high-affinity ligands of InsP(3) receptors. PMID:11306705

Correa, V; Riley, A M; Shuto, S; Horne, G; Nerou, E P; Marwood, R D; Potter, B V; Taylor, C W

2001-05-01

333

SHP-1 phosphatase activity counteracts increased T cell receptor affinity.  

PubMed

Anti-self/tumor T cell function can be improved by increasing TCR-peptide MHC (pMHC) affinity within physiological limits, but paradoxically further increases (K(d) < 1 ?M) lead to drastic functional declines. Using human CD8(+) T cells engineered with TCRs of incremental affinity for the tumor antigen HLA-A2/NY-ESO-1, we investigated the molecular mechanisms underlying this high-affinity-associated loss of function. As compared with cells expressing TCR affinities generating optimal function (K(d) = 5 to 1 ?M), those with supraphysiological affinity (K(d) = 1 ?M to 15 nM) showed impaired gene expression, signaling, and surface expression of activatory/costimulatory receptors. Preferential expression of the inhibitory receptor programmed cell death-1 (PD-1) was limited to T cells with the highest TCR affinity, correlating with full functional recovery upon PD-1 ligand 1 (PD-L1) blockade. In contrast, upregulation of the Src homology 2 domain-containing phosphatase 1 (SHP-1/PTPN6) was broad, with gradually enhanced expression in CD8(+) T cells with increasing TCR affinities. Consequently, pharmacological inhibition of SHP-1 with sodium stibogluconate augmented the function of all engineered T cells, and this correlated with the TCR affinity-dependent levels of SHP-1. These data highlight an unexpected and global role of SHP-1 in regulating CD8(+) T cell activation and responsiveness and support the development of therapies inhibiting protein tyrosine phosphatases to enhance T cell-mediated immunity. PMID:23391724

Hebeisen, Michael; Baitsch, Lukas; Presotto, Danilo; Baumgaertner, Petra; Romero, Pedro; Michielin, Olivier; Speiser, Daniel E; Rufer, Nathalie

2013-03-01

334

Mutations of CB1 T210 Produce Active and Inactive Receptor Forms  

PubMed Central

Human cannabinoid receptor 1 (CB1) has attracted substantial interest as a potential therapeutic target for treating obesity and other obsessive disorders. An understanding of the mechanism governing the transition of the CB1 receptor between its inactive and active states is critical for understanding how therapeutics can selectively regulate receptor activity. We have examined the importance of the Thr at position 210 in CB1 in this transition, a residue predicted to be on the same face of the helix as the Arg of the DRY motif highly conserved in the G protein-coupled receptor superfamily. This Thr was substituted with Ile and Ala via mutagenesis, and the receptors, T210I and T210A, were expressed in HEK 293 cells. The T210I receptor exhibited enhanced agonist and diminished inverse agonist affinity relative to the wild type, consistent with a shift toward the active form. However, treatment with GTP?S to inhibit G protein coupling diminished the affinity change for the inverse agonist SR141716A. The decreased thermal stability of the T210I receptor and increased level of internalization of a T210I receptor—GFP chimera were also observed, consistent with constitutive activity. In contrast, the T210A receptor exhibited the opposite profile: diminished agonist and enhanced inverse agonist affinity. The T210A receptor was found to be more thermally stable than the wild type, and high levels of a T210A receptor—GFP chimera were localized to the cell surface as predicted for an inactive receptor form. These results suggest that T210 plays a key role in governing the transition between inactive and active CB1 receptor states. PMID:16634642

D'Antona, Aaron M.; Ahn, Kwang H.; Kendall, Debra A.

2008-01-01

335

A quantitative study of the dependence of feline cold receptor activity on the calcium concentration  

Microsoft Academic Search

An isolated preparation of the cat tongue was developed to study quantitatively the relation between single cold receptor activity and calcium concentration. The activity recorded from lingual cold fibres of the isolated preparation was identical to that observed by previous authors in lingual cold receptors of whole animals. A perfusing solution containing excess calcium (5 mmol\\/l) suppressed discharge at constant

Klaus Schfifer

1987-01-01

336

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 Institute, Bethesda, Maryland 20892 Received September 21, 2005; accepted November 28, 2005 Peroxisome to toxicity will be highlighted. Key Words: peroxisome proliferator-activated receptors (PPAR); toxicity

Omiecinski, Curtis

337

Expression of the Peroxisome Proliferator-Activated Receptor (PPAR) in the Mouse Colonic Mucosa  

Microsoft Academic Search

The peroxisome proliferator-activated receptor (PPAR), a member of the steroid nuclear receptor superfamily, has been shown to be activated by various compounds such as fibrates, thiazolidinediones, prostaglandins, and fatty acids. Here we demonstrate expression of PPAR in mouse colonic and small intestinal mucosa by Western blot analysis and immunohistochemistry, indicating a higher expression level in the differentiated colonic epithelial cells

Anethe Mansén; Hebé Guardiola-Diaz; Joseph Rafter; Christina Branting; Jan-Åke Gustafsson

1996-01-01

338

Protein phosphatase 5 mediates lipid metabolism through reciprocal control of glucocorticoid receptor and peroxisome proliferator-activated receptor-? (PPAR?).  

PubMed

Glucocorticoid receptor-? (GR?) and peroxisome proliferator-activated receptor-? (PPAR?) regulate adipogenesis by controlling the balance between lipolysis and lipogenesis. Here, we show that protein phosphatase 5 (PP5), a nuclear receptor co-chaperone, reciprocally modulates the lipometabolic activities of GR? and PPAR?. Wild-type and PP5-deficient (KO) mouse embryonic fibroblast cells were used to show binding of PP5 to both GR? and PPAR?. In response to adipogenic stimuli, PP5-KO mouse embryonic fibroblast cells showed almost no lipid accumulation with reduced expression of adipogenic markers (aP2, CD36, and perilipin) and low fatty-acid synthase enzymatic activity. This was completely reversed following reintroduction of PP5. Loss of PP5 increased phosphorylation of GR? at serines 212 and 234 and elevated dexamethasone-induced activity at prolipolytic genes. In contrast, PPAR? in PP5-KO cells was hyperphosphorylated at serine 112 but had reduced rosiglitazone-induced activity at lipogenic genes. Expression of the S112A mutant rescued PPAR? transcriptional activity and lipid accumulation in PP5-KO cells pointing to Ser-112 as an important residue of PP5 action. This work identifies PP5 as a fulcrum point in nuclear receptor control of the lipolysis/lipogenesis equilibrium and as a potential target in the treatment of obesity. PMID:21994940

Hinds, Terry D; Stechschulte, Lance A; Cash, Harrison A; Whisler, Donald; Banerjee, Ananya; Yong, Weidong; Khuder, Saja S; Kaw, Meenakshi K; Shou, Weinian; Najjar, Sonia M; Sanchez, Edwin R

2011-12-16

339

Complement activation triggered by chondroitin sulfate released by thrombin receptor-activated platelets  

PubMed Central

Summary Background Chondroitin sulfate (CS) is a glycosaminoglycan released by activated platelets. Objective Herewe test the hypothesis that CS released by activated platelets can trigger complement activation in the fluid phase. Methods and results Thrombin receptor-activating peptide (TRAP)-6 was used to activate platelets in platelet-rich plasma and blood, anticoagulated with the thrombin inhibitor lepirudin. TRAP activation induced fluid-phase complement activation, as reflected by the generation of C3a and sC5b-9, which could be attenuated by the C3 inhibitor compstatin. Chondroitinase ABC treatment of supernatants from activated platelets totally inhibited the activation, indicating that platelet-derived CS had initiated the complement activation. Furthermore, addition of purified CS to plasma strongly triggered complement activation. C1q was identified as the recognition molecule, as it bound directly to CS, and CS-triggered complement activation could be restored in C1q-depleted serum by adding purified C1q. TRAP activation of whole blood increased the expression of CD11b on leukocytes and generation of leukocyte–platelet complexes. It was demonstrated that these leukocyte functions were dependent on C3 activation and signaling via C5a, as this expression could be inhibited by compstatin and by a C5aR antagonist. Conclusions We conclude that platelets trigger complement activation in the fluid phase by releasing CS, which leads to inflammatory signals mediated by C5a. PMID:18503629

HAMAD, O. A.; EKDAHL, K. N.; NILSSON, P. H.; ANDERSSON, J.; MAGOTTI, P.; LAMBRIS, J. D.; NILSSON, B.

2009-01-01

340

Activation of NMDA receptor of glutamate influences MMP-2 activity and proliferation of glioma cells.  

PubMed

Glioblastoma multiforme (GBM) is the most common malignant glioma, which has high proliferative rate and an extremely invasive phenotype. Major limitations in the effective treatment of malignant gliomas are the proliferation and infiltration into the surrounding brain tissue. Although studies have shown that various stimuli promote glioma cell proliferation and invasion, the underlying mechanisms remain largely unknown. Glioma cells secrete significant amount of glutamate into surrounding tissue and intracellular signaling is thought to be initiated upon glutamate-induced modulation of the ion channels in GBM cells. The objective of the study was to investigate the effect of activation of NMDA (N-methyl-D-aspartate) receptors of glutamate on gelatinase subfamily MMPs and on proliferation of glioma cells. U251MG and U87MG cell lines were maintained in Dulbecco's Modified Eagle's Medium. Proliferation assay was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a yellow tetrazole (MTT) assay. Matrix metalloproteinase (MMP)-2 and MMP-9 activity was investigated by gelatin zymography assay. We demonstrate that activated NMDA receptors (NMDAR) increased the activity of MMP-2 only in U251MG glioma cells at concentrations of 100 and 200 ?M and increased the proliferation of both U87MG and U251MG glioma cells at concentrations of 50, 100, 150 and 200 ?M. Inhibition of NMDAR using MK-801, a non-competitive antagonist of the NMDAR, significantly inhibited the effect of activation of NMDAR on MMP-2 activity and on proliferation. We conclude that NMDA receptor activation has role in activity of MMP-2 and proliferation of glioma cells. PMID:24374786

Ramaswamy, Palaniswamy; Aditi Devi, N; Hurmath Fathima, K; Dalavaikodihalli Nanjaiah, Nandakumar

2014-06-01

341

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

342

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

343

Multiple activities of insect repellents on odorant receptors in mosquitoes.  

PubMed

Several lines of evidence suggest that insect repellent molecules reduce mosquito-host contacts by interacting with odorants and odorant receptors (ORs), thereby ultimately affecting olfactory-driven behaviours. We describe the molecular effects of 10 insect repellents and a pyrethroid insecticide with known repellent activity on two highly specific Aedes aegypti (Diptera: Culicidae) ORs, AaOR2 + AaOR7 and AaOR8 + AaOR7, exquisitely sensitive to key mosquito attractants indole and (R)-(-)-1-octen-3-ol, expressed in oocytes of Xenopus (Anura: Pipidae). Our study demonstrates that insect repellents can both inhibit odorant-evoked currents mediated by ORs and independently elicit currents in the absence of odorants. All of the repellents had effects on one or both ORs; most of these compounds were selective inhibitors and showed a high degree of specificity in their capacity to activate the two ORs. These results show that a range of insect repellents belonging to structurally diverse chemical classes modulate the function of mosquito ORs through multiple molecular mechanisms. PMID:21395633

Bohbot, J D; Fu, L; LE, T C; Chauhan, K R; Cantrell, C L; Dickens, J C

2011-12-01

344

Activation of ?7-containing nicotinic receptors on astrocytes triggers AMPA receptor recruitment to glutamateric synapses  

PubMed Central

Astrocytes, an abundant form of glia, are known to promote and modulate synaptic signaling between neurons. They also express ?7-containing nicotinic acetylcholine receptors (?7-nAChRs), but the functional relevance of these receptors is unknown. We show here that stimulation of ?7-nAChRs on astrocytes releases components that induce hippocampal neurons to acquire more a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors post-synaptically at glutamatergic synapses. The increase is specific in that no change is seen in synaptic NMDA receptor clusters or other markers for glutamatergic synapses, or in markers for GABAergic synapses. Moreover, the increases in AMPA receptors on the neuron surface are accompanied by increases in the frequency of spontaneous miniature synaptic currents mediated by the receptors and increases in the ratio of evoked synaptic currents mediated by AMPA versus NMDA receptors. This suggests that stimulating ?7-nAChRs on astrocytes can convert ‘silent’ glutamatergic synapses to functional status. Astrocyte-derived thrombospondin is necessary but not sufficient for the effect, while tumor necrosis factor-? is sufficient but not necessary. The results identify astrocyte ?7-nAChRs as a novel pathway through which nicotinic cholinergic signaling can promote the development of glutamatergic networks, recruiting AMPA receptors to post-synaptic sites and rendering the synapses more functional. PMID:24032433

Wang, Xulong; Lippi, Giordano; Carlson, David M.; Berg, Darwin K.

2014-01-01

345

How does angiotensin AT2 receptor activation help neuronal differentiation and improve neuronal pathological situations?  

PubMed Central

The angiotensin type 2 (AT2) receptor of angiotensin II has long been thought to be limited to few tissues, with the primary effect of counteracting the angiotensin type 1 (AT1) receptor. Functional studies in neuronal cells have demonstrated AT2 receptor capability to modulate neuronal excitability, neurite elongation, and neuronal migration, suggesting that it may be an important regulator of brain functions. The observation that the AT2 receptor was expressed in brain areas implicated in learning and memory led to the hypothesis that it may also be implicated in cognitive functions. However, linking signaling pathways to physiological effects has always proven challenging since information relative to its physiological functions has mainly emerged from indirect observations, either from the blockade of the AT1 receptor or through the use of transgenic animals. From a mechanistic standpoint, the main intracellular pathways linked to AT2 receptor stimulation include modulation of phosphorylation by activation of kinases and phosphatases or the production of nitric oxide and cGMP, some of which are associated with the Gi-coupling protein. The receptor can also interact with other receptors, either G protein-coupled such as bradykinin, or growth factor receptors such as nerve growth factor or platelet-derived growth factor receptors. More recently, new advances have also led to identification of various partner proteins, thus providing new insights into this receptor’s mechanism of action. This review summarizes the recent advances regarding the signaling pathways induced by the AT2 receptor in neuronal cells, and discussed the potential therapeutic relevance of central actions of this enigmatic receptor. In particular, we highlight the possibility that selective AT2 receptor activation by non-peptide and selective agonists could represent new pharmacological tools that may help to improve impaired cognitive performance in Alzheimer’s disease and other neurological cognitive disorders. PMID:23267346

Guimond, Marie-Odile; Gallo-Payet, Nicole

2012-01-01

346

Constitutive activity of G-protein-coupled receptors: cause of disease and common property of wild-type receptors  

Microsoft Academic Search

The aim of this review is to provide a systematic overview on constitutively active G-protein-coupled receptors (GPCRs), a rapidly evolving area in signal transduction research. We will discuss mechanisms, pharmacological tools and methodological approaches to analyze constitutive activity. The two-state model defines constitutive activity as the ability of a GPCR to undergo agonist-independent isomerization from an inactive (R) state to

Roland Seifert; Katharina Wenzel-Seifert

2002-01-01

347

Activity-induced and developmental downregulation of the Nogo receptor  

Microsoft Academic Search

The three axon growth inhibitory proteins, myelin associated glycoprotein, oligodendrocyte-myelin glycoprotein and Nogo-A, can all bind to the Nogo-66 receptor (NgR). This receptor is expressed by neurons with high amounts in regions of high plasticity where Nogo expression is also high. We hypothesized that simultaneous presence of high levels of Nogo and its receptor in neurons confers a locked state

Anna Josephson; Alexandra Trifunovski; Camilla Schéele; Johan Widenfalk; Claes Wahlestedt; Stefan Brené; Lars Olson; Christian Spenger

2003-01-01

348

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...

349

A selective metabotropic glutamate receptor 7 agonist: Activation of receptor signaling via an allosteric site modulates stress parameters in vivo  

PubMed Central

Metabotropic glutamate receptor (mGluR) subtypes (mGluR1 to mGluR8) act as important pre- and postsynaptic regulators of neurotransmission in the CNS. These receptors consist of two domains, an extracellular region containing the orthosteric agonist site and a transmembrane heptahelical domain involved in G protein activation and recognition of several recently synthesized pharmacological modulators. The presynaptic receptor mGluR7 shows the highest evolutionary conservation within the family, but no selective pharmacological tool was known. Here we characterize an mGluR7-selective agonist, N,N?-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082), which directly activates receptor signaling via an allosteric site in the transmembrane domain. At transfected mammalian cells expressing mGluR7, AMN082 potently inhibits cAMP accumulation and stimulates GTP?S binding (EC50-values, 64-290 nM) with agonist efficacies comparable with those of l-2-amino-4-phosphonobutyrate (L-AP4) and superior to those of l-glutamate. AMN082 (?10 ?M) failed to show appreciable activating or inhibitory effects at other mGluR subtypes and selected ionotropic GluRs. Chimeric receptor studies position the binding site of AMN082 in the transmembrane region of mGluR7, and we demonstrate that this allosteric agonist has little, if any, effect on the potency of orthosteric ligands. Here we provide evidence for full agonist activity mediated by the heptahelical domain of family 3 G protein-coupled receptors (which have mGluR-like structure) that may lead to drug development opportunities. Further, AMN082 is orally active, penetrates the blood-brain barrier, and elevates the plasma stress hormones corticosterone and corticotropin in an mGluR7-dependent fashion. Therefore, AMN082 is a valuable tool for unraveling the role of mGluR7 in stress-related CNS disorders. PMID:16339898

Mitsukawa, Kayo; Yamamoto, Rina; Ofner, Silvio; Nozulak, Joachim; Pescott, Oliver; Lukic, Snezana; Stoehr, Natacha; Mombereau, Cedric; Kuhn, Rainer; McAllister, Kevin H.; van der Putten, Herman; Cryan, John F.; Flor, Peter J.

2005-01-01

350

Impact of human autoantibodies on ?1-adrenergic receptor conformation, activity, and internalization  

PubMed Central

Aims Autoantibodies against second extracellular loops of ?1-adrenergic receptors frequent in dilated cardiomyopathy confer myocardial dysfunction presumably via cAMP stimulation. Here, we investigate the autoantibody impact on receptor conformation and function. Methods and results IgG was prepared from patients with dilated cardiomyopathy, matched healthy donors (10 each) or commercial IgG preparations (2). IgG binding to ?1-adrenergic receptor peptides was detected in 5 of 10 patients and 2 of 10 controls. IgG colocalization with the native receptor was detected in 8 of 10 patients and 1 of 10 controls (10 of 10 patients and 7 of 10 controls at >30 mg IgG/L). All IgGs exhibiting receptor colocalization triggered changes in receptor conformation (determined with fluorescent sensors) not stringently correlated to cAMP stimulation, suggesting the induction of more or less active receptor conformations. Receptor-activating IgG was detected in 8 of 10 patients but only 1 of 10 controls. In addition, IgG from 8 of 10 patients and 3 of 10 controls attenuated receptor internalization (measured by total internal reflection fluorescence microscopy). IgG-inducing inactive receptor conformations had no effect on subsequent cAMP stimulation by isoproterenol. IgG-inducing active receptor conformations dampened or augmented subsequent cAMP stimulation by isoproterenol, depending on whether receptor internalization was attenuated or not. Corresponding IgG effects on the basal beating rate and chronotropic isoproterenol response of embryonic human cardiomyocytes were observed. Conclusions (i) Autoantibodies trigger conformation changes in the ?1-adrenergic receptor molecule. (ii) Some also attenuate receptor internalization. (iii) Combinations thereof increase the basal beating rate of cardiomyocytes and optionally entail dampening of their chronotropic catecholamine responses. (iv) The latter effects seem specific for patient autoantibodies, which also have higher levels. PMID:23208588

Bornholz, Beatrice; Weidtkamp-Peters, Stefanie; Schmitmeier, Stephanie; Seidel, Claus A. M.; Herda, Lars R.; Felix, Stephan B.; Lemoine, Horst; Hescheler, Jurgen; Nguemo, Filomain; Schafer, Christoph; Christensen, Morten O.; Mielke, Christian; Boege, Fritz

2013-01-01

351

Modulation of receptors and adenylate cyclase activity during sucrose feeding, food deprivation, and cold exposure  

SciTech Connect

Thermogenesis in brown adipose tissue (BAT) serves as a regulator of body temperature and weight maintenance. Thermogenesis can be stimulated by catecholamine activation of adenylate cyclase through the {beta}-adrenergic receptor. To investigate the effects of sucrose feeding, food deprivation, and cold exposure on the {beta}-adrenergic pathway, adenylate cyclase activity and {beta}-adrenergic receptors were assessed in rat BAT after 2 wk of sucrose feeding, 2 days of food deprivation, or 2 days of cold exposure. {beta}-Adrenergic receptors were identified in BAT using ({sup 125}I)iodocyanopindolol. Binding sites had the characteristics of mixed {beta}{sub 1}- and {beta}{sub 2}-type adrenergic receptors at a ratio of 60/40. After sucrose feeding or cold exposure, there was the expected increase in BAT mitochondrial mass as measured by total cytochrome-c oxidase activity but a decrease in {beta}-adrenergic receptor density due to a loss of the {beta}{sub 1}-adrenergic subtype. This BAT {beta}-adrenergic receptor downregulation was tissue specific, since myocardial {beta}-adrenergic receptors were unchanged with either sucrose feeding or cold exposure. Forskolin-stimulated adenylate cyclase activity increased in BAT after sucrose feeding or cold exposure but not after food deprivation. These data suggest that in BAT, sucrose feeding or cold exposure result in downregulation of {beta}-adrenergic receptors and that isoproterenol-stimulated adenylate cyclase activity was limited by receptor availability.

Scarpace, P.J.; Baresi, L.A.; Morley, J.E. (Veterans Administration Medical Center, Los Angeles, CA (USA) Univ. of California, Los Angeles (USA))

1987-12-01

352

Activation of serotonin 3 receptors changes in vivo auditory responses in the mouse inferior colliculus  

PubMed Central

Metabotropic serotonin receptors such as 5-HT1A and 5-HT1B receptors shape the level, selectivity, and timing of auditory responses in the inferior colliculus (IC). Less is known about the effects of ionotropic 5-HT3 receptors, which are cation channels that depolarize neurons. In the current study, the influence of the 5-HT3 receptor on auditory responses in vivo was explored by locally iontophoresing a 5-HT3 receptor agonist and antagonists onto single neurons recorded extracellularly in mice. Three main findings emerge from these experiments. First, activation of the 5-HT3 receptor can either facilitate or suppress auditory responses, but response suppressions are not consistent with 5-HT3 effects on presynaptic GABAergic neurons. Both response facilitations and suppressions are less pronounced in neurons with high precision in response latency, suggesting functional differences in the role of receptor activation for different classes of neuron. Finally, the effects of 5-HT3 activation vary across repetition rate within a subset of single neurons, suggesting that the influence of receptor activation sometimes varies with the level of activity. These findings contribute to the view of the 5-HT3 receptor as an important component of the serotonergic infrastructure in the IC, with effects that are complex and neuron- selective. PMID:19236912

Bohorquez, Alexander; Hurley, Laura M.

2009-01-01

353

Activation of peroxisome proliferators-activated receptor ? (PPAR?) promotes blastocyst hatching in mice.  

PubMed

Prostaglandins participate in a variety of female reproductive processes, including ovulation, fertilization, embryo implantation and parturition. In particular, maternal prostacyclin (PGI(2)) is critical for embryo implantation and the action of PGI(2) is not mediated via its G-protein-coupled membrane receptor, IP, but its nuclear receptor, peroxisome-proliferator-activated receptor ? (PPAR?). Recently, several studies have shown that PGI(2) enhances blastocyst development and/or hatching rate in vitro, and subsequently implantation and live birth rates in mice. However, the mechanism by which PGI(2) improves preimplantation embryo development in vitro remains unclear. Using molecular, pharmacologic and genetic approaches, we show that PGI(2)-induced PPAR? activation accelerates blastocyst hatching in mice. mRNAs for PPAR?, retinoid X receptor (heterodimeric partners of PPAR?) and PGI(2) synthase (PGIS) are temporally induced after zygotic gene activation, and their expression reaches maximum levels at the blastocyst stage, suggesting that functional complex of PPAR? can be formed in the blastocyst. Carbaprostacyclin (a stable analogue of PGI(2)) and GW501516 (a PPAR? selective agonist) significantly accelerated blastocyst hatching but did not increase total cell number of cultured blastocysts. Whereas U51605 (a PGIS inhibitor) interfered with blastocyst hatching, GW501516 restored U51605-induced retarded hatching. In contrast to the improvement of blastocyst hatching by PPAR? agonists, PPAR antagonists significantly inhibited blastocyst hatching. Furthermore, deletion of PPAR? at early stages of preimplantation mouse embryos caused delay of blastocyst hatching, but did not impair blastocyst development. Taken together, PGI(2)-induced PPAR? activation accelerates blastocyst hatching in mice. PMID:21511721

Kang, Hee Jung; Hwang, Soo Jin; Yoon, Jung Ah; Jun, Jin Hyun; Lim, Hyunjung Jade; Yoon, Tae Ki; Song, Haengseok

2011-10-01

354

Lens Extrusion from Laminin Alpha 1 Mutant Zebrafish  

PubMed Central

We report analysis of the ocular lens phenotype of the recessive, larval lethal zebrafish mutant, lama1a69/a69. Previous work revealed that this mutant has a shortened body axis and eye defects including a defective hyaloid vasculature, focal corneal dysplasia, and loss of the crystalline lens. While these studies highlight the importance of laminin ?1 in lens development, a detailed analysis of the lens defects seen in these mutants was not reported. In the present study, we analyze the lenticular anomalies seen in the lama1a69/a69 mutants and show that the lens defects result from the anterior extrusion of lens material from the eye secondary to structural defects in the lens capsule and developing corneal epithelium associated with basement membrane loss. Our analysis provides further insights into the role of the lens capsule and corneal basement membrane in the structural integrity of the developing eye. PMID:24526906

Semina, Elena V.; Duncan, Melinda K.

2014-01-01

355

UVB Increases Urokinase-Type Plasminogen Activator Receptor (uPAR) Expression1  

Microsoft Academic Search

Keratinocytes synthesize and secrete urokinase-type plasminogen activator, which binds to its specific receptor on keratinocytes. When bound to urokinase-type plasminogen activator receptor, urokinase-type plasminogen activator proteolytically converts surface bound plasminogen to plasmin, which in turn cleaves many extracellular components leading to pericellular proteolysis. The activation of the urokinase system has been observed during re-epithelialization of skin wounds and in lesions

Christoph Marschall; Ernst Lengyel; Toshiko Nobutoh; Evelyn Braungart; Kathrin Douwes; Aleksandra Simon; Viktor Magdolen; Ute Reuning; Klaus Degitz

1999-01-01

356

Crystal structure of the mouse interleukin-3 ?-receptor: insights into interleukin-3 binding and receptor activation.  

PubMed

Interleukin-3 (IL-3) is a cytokine secreted by mast cells and activated T-cells known to be an important regulator of differentiation, survival, proliferation and activation of a range of haemopoietic lineages. The effects of IL-3 on target cells are mediated by a transmembrane receptor system composed of a cytokine-specific ?-subunit and a ?-subunit, the principal signalling entity. In the mouse, two ?-subunits have co-evolved: a common ?-subunit (?c) shared between IL-3 and the related cytokines IL-5 and granulocyte/macrophage colony-stimulating factor (GM-CSF); and an IL-3-specific ?-subunit (?IL-3). ?IL-3 differs from ?c in its specificity for IL-3 and its capacity to bind IL-3 directly in the absence of an ?-subunit, and, in the absence of structural information, the basis for these properties has remained enigmatic. In the present study, we have solved the crystal structure of the ?IL-3 ectodomain at 3.45 Å (1 Å=0.1 nm) resolution. This structure provides the first evidence that ?IL-3 adopts an arch-shaped intertwined homodimer with similar topology to the paralogous ?c structure. In contrast with apo-?c, however, the ligand-binding interface of ?IL-3 appears to pre-exist in a conformation receptive to IL-3 engagement. Molecular modelling of the IL-3-?IL-3 interface, in conjunction with previous mutational studies, suggests that divergent evolution of both ?IL-3 and IL-3 underlies their unique capacity for direct interaction and specificity. PMID:25137390

Carr, Paul D; Ewens, Cameron L; Dai, Jin; Ollis, David L; Murphy, James M; Jackson, Colin J; Young, Ian G

2014-11-01

357

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

358

Protease-activated receptors differentially regulate human platelet activation through a phosphatidic acid-dependent pathway.  

PubMed

Pathological conditions such as coronary artery disease are clinically controlled via therapeutic regulation of platelet activity. Thrombin, through protease-activated receptor (PAR) 1 and PAR4, plays a central role in regulation of human platelet function in that it is known to be the most potent activator of human platelets. Currently, direct thrombin inhibitors used to block platelet activation result in unwanted side effects of excessive bleeding. An alternative therapeutic strategy would be to inhibit PAR-mediated intracellular platelet signaling pathways. To elucidate the best target, we are studying differences between the two platelet thrombin receptors, PAR1 and PAR4, in mediating thrombin's action. In this study, we show that platelet activation by PAR1-activating peptide (PAR1-AP) requires a phospholipase D (PLD)-mediated phosphatidic acid (PA) signaling pathway. We show that this PAR1-specific PA-mediated effect is not regulated through differential granule secretion after PAR-induced platelet activation. Perturbation of this signaling pathway via inhibition of lipid phosphate phosphatase-1 (LPP-1) by propranolol or inhibition of the phosphatidylcholine-derived phosphatidic acid (PA) formation by PLD with a primary alcohol significantly attenuated platelet activation by PAR1-AP. Platelet activation by thrombin or PAR4-AP was insensitive to these inhibitors. Furthermore, these inhibitors significantly attenuated activation of Rap1 after stimulation by PAR1-AP but not thrombin or PAR4-AP. Because PA metabolites such as diacylglycerol play an important role in intracellular signaling, identifying crucial differences in PA regulation of PAR-induced platelet activation may lead to a greater understanding of the role of PAR1 versus PAR4 in progression of thrombosis. PMID:17151288

Holinstat, Michael; Voss, Bryan; Bilodeau, Matthew L; Hamm, Heidi E

2007-03-01

359

Acutely increasing ?GABAA receptor activity impairs memory and inhibits synaptic plasticity in the hippocampus  

PubMed Central

Extrasynaptic ?-aminobutyric acid type A (GABAA) receptors that contain the ? subunit (?GABAA receptors) are expressed in several brain regions including the dentate gyrus (DG) and CA1 subfields of the hippocampus. Drugs that increase ?GABAA receptor activity have been proposed as treatments for a variety of disorders including insomnia, epilepsy and chronic pain. Also, long-term pretreatment with the ?GABAA receptor–preferring agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) enhances discrimination memory and increases neurogenesis in the DG. Despite the potential therapeutic benefits of such treatments, the effects of acutely increasing ?GABAA receptor activity on memory behaviors remain unknown. Here, we studied the effects of THIP (4 mg/kg, i.p.) on memory performance in wild-type (WT) and ?GABAA receptor null mutant (Gabrd?/?) mice. Additionally, the effects of THIP on long-term potentiation (LTP), a molecular correlate of memory, were studied within the DG and CA1 subfields of the hippocampus using electrophysiological recordings of field potentials in hippocampal slices. The results showed that THIP impaired performance in the Morris water maze, contextual fear conditioning and object recognition tasks in WT mice but not Gabrd?/? mice. Furthermore, THIP inhibited LTP in hippocampal slices from WT but not Gabrd?/? mice, an effect that was blocked by GABAA receptor antagonist bicuculline. Thus, acutely increasing ?GABAA receptor activity impairs memory behaviors and inhibits synaptic plasticity. These results have important implications for the development of therapies aimed at increasing ?GABAA receptor activity. PMID:24062648

Whissell, Paul D.; Eng, Dave; Lecker, Irene; Martin, Loren J.; Wang, Dian-Shi; Orser, Beverley A.

2013-01-01

360

Activation of Purinergic Receptor Subtypes Modulates Odor Sensitivity  

Microsoft Academic Search

Purinergic nucleotides, including ATP and adenosine, are important neuromodulators of peripheral auditory and visual sensory systems (Thorne and Housley, 1996). ATP released by the olfactory epithelium (OE) after noxious stimuli provides a physiological source for a neuromodulatory substance independent of efferent innervation. Here we show that multiple subtypes of purinergic receptors are differentially expressed in olfactory receptor neurons and sustentacular

Colleen C. Hegg; Denise Greenwood; Wei Huang; Pengcheng Han; Mary T. Lucero

2003-01-01

361

Nicotinic alpha 7 receptor clusters on hippocampal GABAergic neurons: regulation by synaptic activity and neurotrophins.  

PubMed

Nicotinic acetylcholine receptors containing the alpha7 gene product are expressed at substantial levels in the hippocampus. Because of their specific locations and their high relative calcium permeability, the receptors not only mediate cholinergic transmission in the hippocampus but also influence signaling at noncholinergic synapses. We have used fluorescently labeled alpha-bungarotoxin to image alpha7-containing receptors on hippocampal neurons and to examine their regulation in culture. The highest levels of staining for such receptors were most commonly found on GABAergic interneurons identified immunohistochemically. The receptors were distributed in clusters on the soma and dendrites and were localized in part at GABAergic synapses. A 3 d blockade of electrical activity with tetrodotoxin or NMDA receptors with APV dramatically reduced the proportion of GABAergic neurons expressing high levels of receptor staining and reduced the mean number of distinguishable receptor clusters on individual neurons. Blockade of either GABA(A) receptors with bicuculline or nicotinic receptors with d-tubocurarine had no effect, although exposure to nicotine could increase the level of receptor staining. Anti-BDNF and anti-NGF antibodies produced decrements equivalent to those of tetrodotoxin and APV, whereas addition of BDNF and NGF each increased staining levels and increased the number of distinguishable receptor clusters on GABAergic neurons. The exogenous neurotrophins could not, however, overcome the effects of either tetrodotoxin or APV. The results indicate that both NMDA receptor activation and the neurotrophins BDNF and NGF are necessary to sustain the distribution patterns of alpha7-containing nicotinic receptors on GABAergic hippocampal neurons. PMID:12223543

Kawai, Hideki; Zago, Wagner; Berg, Darwin K

2002-09-15

362

The oxidative stress mediator 4-hydroxynonenal is an intracellular agonist of the nuclear receptor peroxisome proliferator-activated receptor-?/? (PPAR?/?)  

PubMed Central

Liver insufficiency and damage is a major cause of death and disease worldwide and may result from exposure to environmental toxicants, specific combinations or dosages of pharmaceuticals and microbial metabolites. The generation of reactive intermediates, in particular 4-hydroxynonenal (4-HNE), is a common event in liver damage caused by a variety of hepatotoxic drugs and solvents. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that are involved in the transcriptional regulation of lipid metabolism as well as other biological functions. Importantly, we have observed that the PPAR?/??/? mouse is more susceptible to chemically-induced hepatotoxicity than its wildtype counterpart, and our objective in this study was to elucidate the mechanism(s) by which PPAR?/? confers protection to hepatocytes. We hypothesized that PPAR?/? plays a protective role by responding to toxic lipids and altering gene expression accordingly. In support, oxidized-VLDL and constituents including 13-S-hydroxyoctadeca-dienoic acid (13(S)-HODE) and 4-HNE are PPAR?/? ligands. A structure-activity relationship was established where 4-HNE and 4-hydroperoxynonenal (4-HpNE) enhanced the activity of the PPAR?/? subtype while 4-hyroxy-hexenal (4-HHE), 4-oxo-2-Nonenal (4-ONE), and trans-4,5-epoxy-2(E)-decenal did not activate this receptor. Increasing PPAR?/? activity with a synthetic agonist decreased sensitivity of hepatocytes to 4-HNE and other toxic agents, whereas inhibition of this receptor had the opposite result. Gene expression microarray analysis identified several important PPAR?/?-regulated detoxification enzymes involved in 4-HNE metabolism that are regulated at the transcript level. This research established 4-HNE as an endogenous modulator of PPAR?/? activity and raises the possibility that agonists of this nuclear receptor may be utilized to prevent or treat liver disease associated with oxidative damage. PMID:17382197

Coleman, Jeffrey D.; Prabhu, K. Sandeep; Thompson, Jerry T.; Reddy, P. Sreenivasula; Peters, Jeffrey M.; Peterson, Blake R.; Reddy, C. Channa; Vanden Heuvel, John P.

2007-01-01

363

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

364

Hesperetin glucuronides induce adipocyte differentiation via activation and expression of peroxisome proliferator-activated receptor-?.  

PubMed

In previous reports, hesperidin, a flavonoid glucoside from citrus fruit, is hydrolyzed to hesperetin, an aglycone of hesperidin, and converted to the hesperetin glucuronides (H7-OG and H3'-OG) in vivo and depresses blood glucose levels. But there are no reports on the activity of hesperetin glucuronides. To determine the activity of hesperetin glucuronides, H7-OG and H3'-OG were synthesized and peroxisome proliferator-activated receptor-? (PPAR?) agonist activity was observed at 250 ?M. These glucuronides accelerated the differentiation of 3T3-L1 cells into adipocytes at 10 ?M. Furthermore, H7-OG showed additive effects in reporter gene assays and caused noncompetitive reactions in time-resolved fluorescence resonance energy transfer assays with a thiazolidinedione derivative. Our results indicated that hesperetin glucuronides activated PPAR?, accelerated adipocyte differentiation. PMID:25036134

Gamo, Kanae; Miyachi, Hiroyuki; Nakamura, Kayoko; Matsuura, Nobuyasu

2014-01-01

365

Activation of D2 dopamine receptors inhibits estrogen response element-mediated estrogen receptor transactivation in rat pituitary lactotrophs.  

PubMed

Estrogen and dopamine are major opposing regulators of the endocrine functions of pituitary lactotrophs. Dopamine inhibits estrogen-induced changes in the synthesis and secretion of prolactin, and lactotroph proliferation. We studied the mechanism of the inhibitory effects of dopaminergic stimulation on estrogen-induced functional changes of rat lactotrophs in primary culture. The dopaminergic agonist, bromocriptine (BC), suppressed 17?-estradiol-stimulated lactotroph proliferation, prolactin promoter activity, and mRNA expression of some estrogen-responsive genes. In lactotroph-enriched pituitary cells, BC treatment inhibited the estrogen response element (ERE) DNA sequence-mediated estrogen receptor (ER) transcriptional activity. Using a lactotroph-specific ERE transcriptional assay, we found that BC inhibition of the ERE-mediated ER transcriptional activity partly involved D2 dopamine receptor-mediated, pertussis toxin-sensitive G protein-coupled, cAMP/protein kinase A-dependent signaling. BC treatment had no effect on the cellular concentration of ER? or its phosphorylation status at Ser-118. Similar transcriptional inhibition by BC was also found in GH4ZR7 cells, a D2 dopamine receptor-expressing somatomammotrophic cell line. These results suggest that activation of the D2 dopamine receptors inhibits estrogen-dependent lactotroph functions in part via attenuation of ERE-mediated ER transactivation. PMID:23701824

Ishida, Maho; Mitsui, Tetsuo; Izawa, Michi; Arita, Jun

2013-08-15

366

The oxidative stress mediator 4-hydroxynonenal is an intracellular agonist of the nuclear receptor peroxisome proliferator-activated receptor-?\\/? (PPAR?\\/?)  

Microsoft Academic Search

Liver insufficiency and damage are major causes of death and disease worldwide and may result from exposure to environmental toxicants, specific combinations or dosages of pharmaceuticals, and microbial metabolites. The generation of reactive intermediates, in particular 4-hydroxynonenal (4-HNE), is a common event in liver damage caused by a variety of hepatotoxic drugs and solvents. The peroxisome proliferator-activated receptors (PPARs) are

Jeffrey D. Coleman; K. Sandeep Prabhu; Jerry T. Thompson; P. Sreenivasula Reddy; Jeffrey M. Peters; Blake R. Peterson; C. Channa Reddy; John P. Vanden Heuvel

2007-01-01

367

Activation of type-2 cannabinoid receptor inhibits neuroprotective and antiinflammatory actions of glucocorticoid receptor ?: when one is better than two.  

PubMed

Endocannabinoids (eCBs) and glucocorticoids (GCs) are two distinct classes of signaling lipids that exert both neuroprotective and immunosuppressive effects; however, the possibility of an actual interaction of their receptors [i.e., type-2 cannabinoid (CB2) and glucocorticoid receptor ? (GR?), respectively] remains unexplored. Here, we demonstrate that the concomitant activation of CB2 and GR? abolishes the neuroprotective effects induced by each receptor on central neurons and on glial cells in animal models of remote cell death. We also show that the ability of eCBs and GCs, used individually, to inhibit tumour necrosis factor-? (TNF-?) and interferon-? (IFN-?) production from activated human T lymphocytes is lost when CB2 and GR? are activated simultaneously. In addition, signal transduction pathways triggered by concomitant activation of both receptors led to increased levels of GR?, heat-shock proteins-70 and -90, and p-JNK, as well as to reduced levels of p-STAT6. These effects were reversed only by selectively antagonizing CB2, but not GR?. Overall, our study demonstrates for the first time the existence of a CB2-driven negative cross-talk between eCB and GC signaling in both rats and humans, thus paving the way to the possible therapeutic exploitation of CB2 as a new target for chronic inflammatory and neurodegenerative diseases. PMID:23296125

Bisicchia, Elisa; Chiurchiù, Valerio; Viscomi, Maria Teresa; Latini, Laura; Fezza, Filomena; Battistini, Luca; Maccarrone, Mauro; Molinari, Marco

2013-06-01

368

Terminal Differentiation of Human Liposarcoma Cells Induced by Ligands for Peroxisome Proliferator-Activated Receptor gamma and the Retinoid X Receptor  

Microsoft Academic Search

Induction of terminal differentiation represents a promising therapeutic approach to certain human malignancies. The peroxisome proliferator-activated receptor gamma (PPARgamma ) and the retinoid X receptor alpha (RXRalpha ) form a heterodimeric complex that functions as a central regulator of adipocyte differentiation. Natural and synthetic ligands for both receptors have been identified. We demonstrate here that PPARgamma is expressed at high

Peter Tontonoz; Samuel Singer; Barry M. Forman; Pasha Sarraf; Jonathan A. Fletcher; Christopher D. M. Fletcher; Regina P. Brun; Elisabetta Mueller; Soner Altiok; Heather Oppenheim; Ronald M. Evans; Bruce M. Spiegelman

1997-01-01

369

The phosphoproteome of toll-like receptor-activated macrophages  

PubMed Central

Recognition of microbial danger signals by toll-like receptors (TLR) causes re-programming of macrophages. To investigate kinase cascades triggered by the TLR4 ligand lipopolysaccharide (LPS) on systems level, we performed a global, quantitative and kinetic analysis of the phosphoproteome of primary macrophages using stable isotope labelling with amino acids in cell culture, phosphopeptide enrichment and high-resolution mass spectrometry. In parallel, nascent RNA was profiled to link transcription factor (TF) phosphorylation to TLR4-induced transcriptional activation. We reproducibly identified 1850 phosphoproteins with 6956 phosphorylation sites, two thirds of which were not reported earlier. LPS caused major dynamic changes in the phosphoproteome (24% up-regulation and 9% down-regulation). Functional bioinformatic analyses confirmed canonical players of the TLR pathway and highlighted other signalling modules (e.g. mTOR, ATM/ATR kinases) and the cytoskeleton as hotspots of LPS-regulated phosphorylation. Finally, weaving together phosphoproteome and nascent transcriptome data by in silico promoter analysis, we implicated several phosphorylated TFs in primary LPS-controlled gene expression. PMID:20531401

Weintz, Gabriele; Olsen, Jesper V; Fruhauf, Katja; Niedzielska, Magdalena; Amit, Ido; Jantsch, Jonathan; Mages, Jorg; Frech, Cornelie; Dolken, Lars; Mann, Matthias; Lang, Roland

2010-01-01

370

Function of the cytoplasmic tail of human calcitonin receptor-like receptor in complex with receptor activity-modifying protein 2  

SciTech Connect

Receptor activity-modifying protein 2 (RAMP2) enables calcitonin receptor-like receptor (CRLR) to form an adrenomedullin (AM)-specific receptor. Here we investigated the function of the cytoplasmic C-terminal tail (C-tail) of human (h)CRLR by co-transfecting its C-terminal mutants into HEK-293 cells stably expressing hRAMP2. Deleting the C-tail from CRLR disrupted AM-evoked cAMP production or receptor internalization, but did not affect [{sup 125}I]AM binding. We found that CRLR residues 428-439 are required for AM-evoked cAMP production, though deleting this region had little effect on receptor internalization. Moreover, pretreatment with pertussis toxin (100 ng/mL) led to significant increases in AM-induced cAMP production via wild-type CRLR/RAMP2 complexes. This effect was canceled by deleting CRLR residues 454-457, suggesting Gi couples to this region. Flow cytometric analysis revealed that CRLR truncation mutants lacking residues in the Ser/Thr-rich region extending from Ser{sup 449} to Ser{sup 467} were unable to undergo AM-induced receptor internalization and, in contrast to the effect on wild-type CRLR, overexpression of GPCR kinases-2, -3 and -4 failed to promote internalization of CRLR mutants lacking residues 449-467. Thus, the hCRLR C-tail is crucial for AM-evoked cAMP production and internalization of the CRLR/RAMP2, while the receptor internalization is dependent on the aforementioned GPCR kinases, but not Gs coupling.

Kuwasako, Kenji, E-mail: kuwasako@fc.miyazaki-u.ac.jp [Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan)] [Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan); Kitamura, Kazuo; Nagata, Sayaka; Hikosaka, Tomomi [Division of Circulation and Body Fluid Regulation, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan)] [Division of Circulation and Body Fluid Regulation, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan); Kato, Johji [Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan)] [Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692 (Japan)

2010-02-12

371

A Corepressor and Chicken Ovalbumin Upstream Promoter Transcriptional Factor Proteins Modulate Peroxisome ProliferatorActivated Receptor 2\\/Retinoid X Receptor  Activated Transcription from the Murine Lipoprotein Lipase Promoter  

Microsoft Academic Search

Complex physiological stimuli differentially regulate the tissue- specific transcription of the lipoprotein lipase (LPL) gene. A conserved DNA recognition element (2171 to 2149 bp) within the promoter functions as a transcriptional enhancer when bound by the peroxi- some proliferator-activated receptor-g2 (PPARg2)\\/retinoid X receptor a (RXRa) heterodimer, but serves as a transcriptional silencer in the presence of unidentified double and single

CLAUDIUS E. ROBINSON; XIYING WU; ZAFAR NAWAZ; SERGIO A. ONATE; JEFFREY M. GIMBLE

1999-01-01

372

Isolated dorsal root ganglion neurones inhibit receptor-dependent adenylyl cyclase activity in associated glial cells  

PubMed Central

Background and Purpose Hyper-nociceptive PGE2 EP4 receptors and prostacyclin (IP) receptors are present in adult rat dorsal root ganglion (DRG) neurones and glial cells in culture. The present study has investigated the cell-specific expression of two other Gs-protein coupled hyper-nociceptive receptor systems: ?-adrenoceptors and calcitonin gene-related peptide (CGRP) receptors in isolated DRG cells and has examined the influence of neurone–glial cell interactions in regulating adenylyl cyclase (AC) activity. Experimental Approach Agonist-stimulated AC activity was determined in mixed DRG cell cultures from adult rats and compared with activity in DRG neurone-enriched cell cultures and pure DRG glial cell cultures. Key Results Pharmacological analysis showed the presence of Gs-coupled ?2-adrenoceptors and CGRP receptors, but not ?1-adrenoceptors, in all three DRG cell preparations. Agonist-stimulated AC activity was weakest in DRG neurone-enriched cell cultures. DRG neurones inhibited IP receptor-stimulated glial cell AC activity by a process dependent on both cell–cell contact and neurone-derived soluble factors, but this is unlikely to involve purine or glutamine receptor activation. Conclusions and Implications Gs-coupled hyper-nociceptive receptors are readily expressed on DRG glial cells in isolated cell cultures and the activity of CGRP, EP4 and IP receptors, but not ?2-adrenoceptors, in glial cells is inhibited by DRG neurones. Studies using isolated DRG cells should be aware that hyper-nociceptive ligands may stimulate receptors on glial cells in addition to neurones, and that variable numbers of neurones and glial cells will influence absolute measures of AC activity and affect downstream functional responses. PMID:22924655

Ng, KY; Yeung, BHS; Wong, YH; Wise, H

2013-01-01

373

Laminin and Type IV Collagen Isoform Substitutions Occur in Temporally and Spatially Distinct Patterns in Developing Kidney Glomerular Basement Membranes  

PubMed Central

Kidney glomerular basement membranes (GBMs) undergo laminin and type IV collagen isoform substitutions during glomerular development, which are believed to be required for maturation of the filtration barrier. Specifically, GBMs of earliest glomeruli contain laminin ?1?1?1 and collagen ?1?2?1(IV), whereas mature glomeruli contain laminin ?5?2?1 and collagen ?3?4?5(IV). Here, we used confocal microscopy to simultaneously evaluate expression of different laminin and collagen IV isoforms in newborn mouse GBMs. Our results show loss of laminin ?1 from GBMs in early capillary loop stages and continuous linear deposition of laminin bearing the ?5 chain thereafter. In contrast, collagen ?1?2?1(IV) persisted in linear patterns into late capillary loop stages, when collagen ?3?4?5(IV) first appeared in discontinuous, non-linear patterns. This patchy pattern for collagen ?3?4?5(IV) continued into maturing glomeruli where there were lengths of linear, laminin ?5-positive GBM entirely lacking either isoform of collagen IV. Relative abundance of laminin and collagen IV mRNAs in newborn and 5-week-old mouse kidneys also differed, with those encoding laminin ?1, ?5, ?1, ?2, and ?1, and collagen ?1(IV) and ?2(IV) chains all significantly declining at 5 weeks, but ?3(IV) and ?4(IV) were significantly upregulated. We conclude that different biosynthetic mechanisms control laminin and type IV collagen expression in developing glomeruli. PMID:23896970

St. John, Patricia L.; Stroganova, Larysa; Zelenchuk, Adrian; Steenhard, Brooke M.

2013-01-01

374

Receptor activity modifying protein-3 mediates the protumorigenic activity of lysyl oxidase-like protein-2.  

PubMed

Lysyl oxidase-like protein-2 (LOXL2) induces epithelial to mesenchymal transition and promotes invasiveness. To understand the mechanisms involved, we examined the effect of LOXL2 overexpression in MCF-7 cells on gene expression. We found that LOXL2 up-regulated the expression of receptor activity modifying protein-3 (RAMP3). Expression of RAMP3 in MDA-MB-231 cells in which LOXL2 expression was inhibited restored vimentin expression, invasiveness, and tumor development. Inhibition of RAMP3 expression in MDA-MB-231 cells mimicked the effects produced by inhibition of LOXL2 expression and was accompanied by inhibition of p38 phosphorylation. LOXL2 overexpression in these cells did not restore invasiveness, suggesting that RAMP3 functions downstream to LOXL2. LOXL2 and RAMP3 are strongly coexpressed in human colon, breast, and gastric carcinomas but not in normal colon or gastric epithelial cells. RAMP3 associates with several G-protein-coupled receptors forming receptors for peptides, such as adrenomedullin and amylin. We hypothesized that RAMP3 could function as a transducer of autocrine signals induced by such peptides. However, the proinvasive effects of RAMP3 could not be abrogated following inhibition of the expression or activity of these peptides. Our experiments suggest that the protumorigenic effects of LOXL2 are partially mediated by RAMP3 and that RAMP3 inhibitors may function as antitumorigenic agents. - PMID:20802105

Brekhman, Vera; Lugassie, Jennie; Zaffryar-Eilot, Shelly; Sabo, Edmond; Kessler, Ofra; Smith, Victoria; Golding, Hana; Neufeld, Gera

2011-01-01

375

Sigma-1 receptor activation prevents intracellular calcium dysregulation in cortical neurons during in vitro ischemia.  

PubMed

Sigma receptors are putative targets for neuroprotection following ischemia; however, little is known on their mechanism of action. One of the key components in the demise of neurons following ischemic injury is the disruption of intracellular calcium homeostasis. Fluorometric calcium imaging was used to examine the effects of sigma receptor activation on changes in intracellular calcium concentrations ([Ca(2+)](i)) evoked by in vitro ischemia in cultured cortical neurons from embryonic rats. The sigma receptor agonist, 1,3-di-o-tolyl-guanidine (DTG), was shown to depress [Ca(2+)](i) elevations observed in response to ischemia induced by sodium azide and glucose deprivation. Two sigma receptor antagonists, metaphit [1-(1-(3-isothiocyanatophenyl)-cyclohexyl)-piperidine] and BD-1047 (N-[2-3,4-dichlorophenyl)-ethyl]-N-methyl-2-(dimethylamino)ethylamine), were shown to blunt the ability of DTG to inhibit ischemia-evoked increases in [Ca(2+)](i), revealing that the effects are mediated by activation of sigma receptors and not via the actions of DTG on nonspecific targets such as N-methyl-d-aspartate receptors. DTG inhibition of ischemia-induced increases in [Ca(2+)](i) was mimicked by the sigma-1 receptor-selective agonists, carbetapentane, (+)-pentazocine and PRE-084 [2-(4-morpholinethyl) 1-phenylcyclohexanecarboxylate hydrochloride], but not by the sigma-2-selective agonist, ibogaine, showing that activation of sigma-1 receptors is responsible for the effects. In contrast, DTG, carbetapentane, and ibogaine blocked spontaneous, synchronous calcium transients observed in our preparation at concentrations consistent with sigma receptor-mediated effects, indicating that both sigma-1 and sigma-2 receptors regulate events that affect [Ca(2+)](i) in cortical neurons. Our studies show that activation of sigma receptors can ameliorate [Ca(2+)](i) dysregulation associated with ischemia in cortical neurons and, thus, identify one of the mechanisms by which these receptors may exert their neuroprotective properties. PMID:16988055

Katnik, Christopher; Guerrero, Waldo R; Pennypacker, Keith R; Herrera, Yelenis; Cuevas, Javier

2006-12-01

376

Tonically active GABA A receptors: modulating gain and maintaining the tone  

Microsoft Academic Search

GABAA receptors not only respond to the local release of GABA from presynaptic terminals, but can also mediate a persistent ‘tonic current’. This reflects the activation of high-affinity GABAA receptors by ambient GABA concentrations. Tonic GABAA-receptor-mediated signalling occurs in different brain regions, shows cell-type-specific differences in magnitude and pharmacology, and changes during brain development. Some clues to the adaptive significance

Alexey Semyanov; Matthew C. Walker; Dimitri M. Kullmann; R. Angus Silver

2004-01-01

377

New insight into active muscarinic receptors with the novel radioagonist [³H]iperoxo.  

PubMed

Activation of G protein-coupled receptors involves major conformational changes of the receptor protein ranging from the extracellular transmitter binding site to the intracellular G protein binding surface. GPCRs such as the muscarinic acetylcholine receptors are commonly probed with radioantagonists rather than radioagonists due to better physicochemical stability, higher affinity, and indifference towards receptor coupling states of the former. Here we introduce tritiated iperoxo, a superagonist at muscarinic M? receptors with very high affinity. In membrane suspensions of transfected CHO-cells, [³H]iperoxo - unlike the common radioagonists [³H]acetylcholine and [³H]oxotremorine M - allowed labelling of each of the five muscarinic receptor subtypes in radioagonist displacement and saturation binding studies. [³H]iperoxo revealed considerable differences in affinity between the even- and the odd-numbered muscarinic receptor subtypes with affinities for the M? and M? receptor in the picomolar range. Probing ternary complex formation on the M? receptor, [³H]iperoxo dissociation was not influenced by an archetypal allosteric inverse agonist, reflecting activation-related rearrangement of the extracellular loop region. At the inner side of M?, the preferred Gi protein acted as a positive allosteric modulator of [³H]iperoxo binding, whereas Gs and Gq were neutral in spite of their robust coupling to the activated receptor. In intact CHO-hM? cells, endogenous guanylnucleotides promoted receptor/G protein-dissociation resulting in low-affinity agonist binding which, nevertheless, was still reported by [³H]iperoxo. Taken together, the muscarinic superagonist [³H]iperoxo is the best tool currently available for direct probing activation-related conformational transitions of muscarinic receptors. PMID:24863257

Schrage, Ramona; Holze, Janine; Klöckner, Jessica; Balkow, Aileen; Klause, Anne S; Schmitz, Anna-Lena; De Amici, Marco; Kostenis, Evi; Tränkle, Christian; Holzgrabe, Ulrike; Mohr, Klaus

2014-08-01

378

Oleylethanolamide regulates feeding and body weight through activation of the nuclear receptor PPAR-alpha  

Microsoft Academic Search

Oleylethanolamide (OEA) is a naturally occurring lipid that regulates satiety and body weight. Although structurally related to the endogenous cannabinoid anandamide, OEA does not bind to cannabinoid receptors and its molecular targets have not been defined. Here we show that OEA binds with high affinity to the peroxisome-proliferator-activated receptor-alpha (PPAR-alpha), a nuclear receptor that regulates several aspects of lipid metabolism.

Jin Fu; Silvana Gaetani; Fariba Oveisi; Jesse Lo Verme; Antonia Serrano; Fernando Rodríguez de Fonseca; Anja Rosengarth; Hartmut Luecke; Barbara Di Giacomo; Giorgio Tarzia; Daniele Piomelli

2003-01-01

379

Anandamide activation of CB1 receptors increases spontaneous bursting and oscillatory activity in the thalamus.  

PubMed

The endocannabinoid system is a modulatory system that has been strongly associated with the regulation of functions as learning and memory, pain perception and sensory physiology in many areas of the central nervous system. However, although a role in sensory processing has been demonstrated at the level of the thalamus, the influence of the endocannabinoid system on thalamic rhythms and oscillations has been less studied, despite the fact that such activities are significant characteristics of the thalamic state. The present work aimed to characterize the role of anandamide (AEA) - one of the endogenous CB1 receptor agonists - and AM251 - a CB1 antagonist - in the modulation of burst firing and oscillatory activity present in the dLGN of the anesthetized rat. Administration of AEA (0.5mg/kg iv) increased the number of bursts in the majority of the cells tested and induced the appearance of a slow delta-like (1.5Hz) oscillatory activity. These effects were CB1-mediated, as demonstrated by the complete antagonism during the co-application of AM251 (0.5mg/kg iv). Thus, by demonstrating that the AEA-mediated activation of CB1 receptors increases spontaneous bursting and oscillatory activity in the thalamus our study infers that endocannabinoids could have a role in processes controlling the sleep-wake cycle and level of arousal. PMID:24508153

Dasilva, M; Grieve, K L; Cudeiro, J; Rivadulla, C

2014-04-18

380

Regulation of Proteome Maintenance Gene Expression by Activators of Peroxisome Proliferator-Activated Receptor ?  

PubMed Central

The nuclear receptor peroxisome proliferator-activated receptor ? (PPAR?) is activated<