Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have identified a novel cellular action of thrombin on cultured rat adrenal medullary endothelial cells (RAMEC). Five-minute incubation of RAMEC with physiological concentrations of thrombin (<1 U/ml) caused within 3 h an increase in the basolateral deposition of the extracellular matrix (ECM) proteins fibronectin, laminin, and collagens IV and I, concomitant with a corresponding decrease in the apical release of these proteins into the medium. This shift in vectorial secretion of ECM proteins, quantitated with enzyme-linked immunoassays, was time dependent. Maximal stimulation of ECM protein deposition was observed after incubation of cells with thrombin for 5-15 min. Prolonged exposure (>1 h) to thrombin resulted in loss of proteins from the ECM. Thrombin-stimulated ECM protein deposition exhibited a bell-shaped dose dependence, peaking for all proteins at 0.25 U/ml of thrombin, and was independent of de novo mRNA or protein synthesis. Maximal amounts of deposited proteins increased between 2.5-fold (fibronectin) and 4-fold (collagen I) over baseline values. Similar results were obtained with thrombin receptor agonist peptide (TRAP), proteolytically active gamma-thrombin, and, to a lesser extent, other serine proteases such as trypsin and plasmin. A scrambled TRAP, proteolytically inactive PPACK-thrombin, DIP-thrombin, and type IV collagenase were ineffective. Together, these results suggest that the thrombin effects are mediated by proteolytic activation of the thrombin receptor. Possible involvement of the phospholipase C-signaling pathway in thrombin-mediated ECM protein deposition was also investigated. Inhibition or downregulation of protein kinase C (PKC) and chelation of intracellular or extracellular Ca2+ did not suppress, but rather enhanced, basal and thrombin-stimulated ECM protein deposition. Quantitative differences in augmentation of basolateral deposition by these treatments suggest differential regulatory pathways for individual ECM proteins. Our data indicate that, in cultured RAMEC, short-term activation of the thrombin receptor causes an increase in amounts of deposited ECM protein by a cellular signaling pathway that is independent of PKC activation and/or elevation of intracellular Ca2+.
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PMID:Thrombin modulates vectorial secretion of extracellular matrix proteins in cultured endothelial cells. 914 35

Our prior work shows that cultured BR cells derived from dog mastocytomas secrete the 92-kDa proenzyme form of gelatinase B. We provided a possible link between mast cell activation and metalloproteinase-mediated matrix degradation by demonstrating that alpha-chymase, a serine protease released from secretory granules by degranulating mast cells, converts progelatinase B to an enzymatically active form. The current work shows that these cells also secrete gelatinase A. Furthermore, gelatinases A and B both colocalize to alpha-chymase-expressing cells of canine airway, suggesting that normal mast cells are a source of gelatinases in the lung. In BR cells, gelatinase B and alpha-chymase expression are regulated, whereas gelatinase A expression is constitutive. Progelatinase B mRNA and enzyme expression are strongly induced by the critical mast cell growth factor, kit ligand, which is produced by fibroblasts and other stromal cells. Induction of progelatinase B is blocked by U-73122, Ro31-8220, and thapsigargin, implicating phospholipase C, protein kinase C, and Ca2+, respectively, in the kit ligand effect. The profibrotic cytokine TGF-beta virtually abolishes the gelatinase B mRNA signal and also attenuates kit ligand-mediated induction of gelatinase B expression, suggesting that an excess of TGF-beta in inflamed or injured tissues may alter mast cell expression of gelatinase B, which is implicated in extracellular matrix degradation, angiogenesis, and apoptosis. In summary, these data provide the first evidence that normal mast cells express gelatinases A and B and suggest pathways by which their regulated expression by mast cells can influence matrix remodeling and fibrosis.
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PMID:Mast cell expression of gelatinases A and B is regulated by kit ligand and TGF-beta. 1022 34