Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Gene expression of platelet-derived growth factor (PDGF) and its receptors in cultured human retinal pigment epithelial (RPE) cells was studied by using semiquantitative polymerase chain reaction. The RPE cells were found to express PDGF A- and B-chain genes as well as alpha- and beta-receptor genes with dominant expression of B-chain and beta-receptor isoforms. Phorbol myristate acetate (PMA) and thrombin increased the expression of PDGF B-chain gene to 19.8 +/- 1.75 and 15.9 +/- 1.84 fold (n = 3) of the control without affecting beta-receptor gene expression. PDGF produced by the RPE cells may play an important role in the pathogenesis of some ocular proliferative diseases.
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PMID:Platelet-derived growth factor gene expression in cultured human retinal pigment epithelial cells. 128 Apr 33

Thrombin elicits multiple biological effects on a variety of cells. We have previously shown that thrombin is a potent mitogen for human glomerular mesangial cells. This mitogenic effect of thrombin is associated with activation of phospholipase C (PLC) and induction of platelet-derived growth factor (PDGF) gene expression. The thrombin receptor, which belongs to the guanine nucleotide binding protein (G protein)-coupled receptor family, has recently been shown to induce rapid tyrosine phosphorylation of cellular proteins. In the present study, we investigated the role of protein-tyrosine phosphorylation in mediating the cellular responses elicited by thrombin in human glomerular mesangial cells. Amino acid labeling followed by immunoprecipitation with phosphotyrosine antibodies demonstrate that thrombin stimulates tyrosine phosphorylation of a set of cellular proteins. Treatment of mesangial cells with thrombin followed by immunoblotting with phosphotyrosine antibodies showed three major bands of tyrosine-phosphorylated proteins approximately 130, 70, and 44-42 kDa. Phosphorylation of these proteins was inhibited by two tyrosine kinase inhibitors, herbimycin A and genistein. Both compounds inhibited DNA synthesis and PDGF B-chain gene expression but had no effect on inositol phosphates production or increases in cytosolic calcium in response to thrombin. These data demonstrate that protein-tyrosine phosphorylation is not required for thrombin-induced PLC activation with inositol phosphate formation and subsequent intracellular calcium release, but it is an absolute requirement for thrombin-induced DNA synthesis and PDGF B-chain gene expression.
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PMID:Mitogenic signaling of thrombin in mesangial cells: role of tyrosine phosphorylation. 752 56

Thrombin is a potent mitogen for mesangial cells and stimulates PDGF B-chain gene expression in these cells. It also activates phospholipase C (PLC) resulting in an increase in cytosolic Ca2+ and diacylglycerol (DAG) that are the physiological activators of protein kinase C (PKC). Immunoprecipitation of specific PKC isotypes from thrombin-stimulated mesangial cells with subsequent measurement of their enzymatic activity shows activation of Ca(2+)-dependent PKC alpha and Ca(2+)-independent PKC zeta in a time dependent manner. Optimum activation of both of these isozymes was obtained at 60 minutes. PKC alpha activity increased 83% over basal while activity of PKC zeta increased 104%. Prolonged exposure of mesangial cells to phorbol myristate acetic acid (PMA) inhibited the enzymatic activity of PKC alpha but not PKC zeta. This inhibition of PKC alpha had no effect on thrombin-induced DNA synthesis but abolished PDGF B-chain gene expression induced by thrombin. These data provide the first evidence that PKC alpha activation is necessary for thrombin-induced PDGF B-chain gene expression but not for thrombin-induced DNA synthesis.
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PMID:PKC alpha regulates thrombin-induced PDGF-B chain gene expression in mesangial cells. 758 54

Thrombin is a coagulation system protease that also serves as a potent stimulator of gene expression in several cell types, including endothelial cells (EC). We and others have previously demonstrated that the transcription of platelet-derived growth factor (PDGF) B-chain (c-sis) by EC is stimulated severalfold by thrombin. Here we examine the molecular mechanism of this regulatory process using bovine aortic EC transiently transfected with a vector containing the chloramphenicol acetyltransferase (CAT) gene under the control of a 400-base pair fragment of the human PDGF B-chain promoter. Thrombin treatment of these cells caused a severalfold increase in CAT expression. Deletion analysis and site-directed mutagenesis revealed that the region spanning nucleotides -61 to -53 from the transcription initiation site (referred to as the thrombin response, or ThR, region) was critical for the transcriptional response to thrombin. Electrophoretic mobility shift assays with an oligonucleotide corresponding to the region -64 to -44, which contained the ThR region, led to the identification of a thrombin-inducible nuclear factor (TINF) in extracts from thrombin-treated, but not control, EC. TINF was formed as early as 40 min post-thrombin treatment, persisted for at least 7 h, but was no longer present after 24 h. TINF appeared in the absence of de novo protein synthesis. The ThR region consists of a repeat of a CCACCC element in an ABBA configuration, which, based on mutation analysis and transfection assays, appears to be critical in mediating thrombin stimulation of the PDGF B-chain gene. The conservation of the ThR region in the promoter of the PDGF B-chain among three species (human, feline, and murine) further supports the importance of this region as a cis-acting regulatory element.
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PMID:Identification of a thrombin response element in the human platelet-derived growth factor B-chain (c-sis) promoter. 862 96

The proteolytic enzyme thrombin is produced during activation of the coagulation pathway. Intraglomerular fibrin deposition and thrombosis are common pathologic features of several glomerular diseases, including transplant rejection. The effect of thrombin on platelet-derived growth factor (PDGF) production and DNA synthesis in well characterized bovine glomerular endothelial cells (G/endo) was studied. DNA synthesis was measured as the amount of [3H]thymidine incorporated into acid-insoluble material. PDGF released in the supernatant was measured by Western blotting and by a radioreceptor assay. PDGF mRNA expression was analyzed by solution hybridization, using human genomic PDGF B-chain (c-sis) and A-chain cDNA probes. G/endo constitutively secrete PDGF activity in serum-free medium. Thrombin stimulates PDGF production and increases the expression of mRNA that hybridizes with labeled B-chain but not A-chain probe, whereas epidermal growth factor and transforming growth factor-alpha stimulate the expression of PDGF A-chain mRNA. In addition, thrombin stimulates DNA synthesis with a peak effect at 24 h. Unlike endothelial cells from other microvascular beds, G/endo did not respond to any of the three PDGF isoforms BB, AB, or AA. These data demonstrate that bovine G/endo produce PDGF and that thrombin stimulates de novo synthesis of PDGF from these cells. Because mesangial, but not bovine, G/endo express PDGF receptors, PDGF released by G/endo is likely to modulate mesangial cell functions such as proliferation and matrix production by means of a paracrine mechanism.
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PMID:Thrombin regulates PDGF expression in bovine glomerular endothelial cells. 955 60

Thrombin stimulates the expression of multiple genes in endothelial cells (ECs), but the trans-acting factors responsible for this induction remain undefined. We have previously described a thrombin-inducible nuclear factor (TINF), which binds to an element in the PDGF B promoter and is responsible for the thrombin inducibility of this gene. Inactive cytoplasmic TINF is rapidly activated and translocated to nuclei of ECs upon stimulation with thrombin. We have now purified TINF from thrombin-treated ECs. Amino acid sequencing revealed it to be a member of the Y-box protein family, and the sole Y-box protein-encoding cDNA we detected in human or bovine ECs corresponded to DNA-binding protein B (dbpB). DbpB translocated to the nucleus after thrombin stimulation of ECs as shown by FACS analysis of nuclei from ECs expressing GFP-dbpB fusion proteins. During thrombin activation, dbpB was found to be cleaved, yielding a 30-kDa NH(2)-terminal fragment that recognized the thrombin-response element sequence, but not the Y-box consensus sequence. Preincubation of ECs with protein tyrosine phosphatase inhibitors completely blocked dbpB activation by thrombin and blocked induction of endogenous PDGF B-chain mRNA and promoter activation by thrombin. Y-box proteins are known to act constitutively to regulate the expression of several genes. Activation of this class of transcription factors in response to thrombin or any other agonist represents a novel signaling pathway.
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PMID:Thrombin activates a Y box-binding protein (DNA-binding protein B) in endothelial cells. 1095 33