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)

We made serial measurements of the platelet intracellular free calcium concentration in 167 patients with non-insulin-dependent diabetes mellitus (77 males and 90 females) over a two-year period, and investigated the relationship between this parameter and diabetic angiopathy. We measured both the basal and thrombin-stimulated platelet free calcium concentrations using fura-2/AM as a fluorescent indicator. The patients were grouped according to the severity of nephropathy, retinopathy, and hypertension and their hemoglobin A1c levels. The basal platelet calcium level of the diabetic patients was higher than that of a healthy control group. There were high levels in the patients with mild nephropathy and retinopathy, but low levels in those with severe disease, and the platelet calcium level reflected the degree of progression of diabetic angiopathy. Stimulated platelet calcium varied with the progression of nephropathy, being highest in early nephropathy and lowest after proteinuria developed. Our findings suggested that abnormalities of calcium handling may be related to the onset of diabetic vascular complications, especially diabetic nephropathy.
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PMID:Platelet free Ca2+ concentration in non-insulin-dependent diabetes mellitus. 184 17

Mast cells appear to promote fibroblast proliferation, presumably through secretion of growth factors, although the molecular mechanisms underlying this mitogenic potential have not been explained fully by known mast cell-derived mediators. We report here that tryptase, a trypsin-like serine proteinase of mast cell secretory granules, is a potent mitogen for fibroblasts in vitro. Nanomolar concentrations of dog tryptase strongly stimulate thymidine incorporation in Chinese hamster lung and Rat-1 fibroblasts and increase cell density in both subconfluent and confluent cultures of these cell lines. Tryptase-induced cell proliferation appears proteinase-specific, as this response is not mimicked by pancreatic trypsin or mast cell chymase. In addition, low levels of tryptase markedly potentiate DNA synthesis stimulated by epidermal growth factor, basic fibroblast growth factor, or insulin. Inhibitors of catalytic activity decrease the mitogenic capacity of tryptase, suggesting, though not proving, the participation of the catalytic site in cell activation by tryptase. Differences in Ca++ mobilization and sensitivity to pertussis toxin suggest that tryptase and thrombin activate distinct signal transduction pathways in fibroblasts. These data implicate mast cell tryptase as a potent, previously unrecognized fibroblast growth factor, and may provide a molecular link between mast cell activation and fibrosis.
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PMID:Mast cell tryptase is a mitogen for cultured fibroblasts. 186 60

Two preparations of bovine thrombin were found to stimulate DNA synthesis in cultured human retinal pigment epithelial cells. DNA synthesis was assessed by both [3H]thymidine incorporation into TCA precipitable material and nuclear labeling with [3H]thymidine. Cultures grown in the presence of thrombin for 48 hr showed a significant increase in cell number. When the concentrations of the two thrombin preparations were normalized for clotting activity, they had almost identical dose-response curves and both caused a tenfold maximal stimulation of [3H]thymidine incorporation. The EC50 for the preparation with higher specific activity was 20 ng ml(-1). Hirudin, a specific high affinity inhibitor of thrombin, completely blocked the mitogenic effect. When a maximally effective concentration of thrombin was used in combination with maximally effective concentrations of other growth factors (insulin, acidic fibroblast growth factor, platelet-derived growth factor, epidermal growth factor), they were found to be strongly synergistic in stimulating DNA synthesis. These data suggest that thrombin may act as an endocrine mediator of retinal pigment epithelial cell proliferation and participate in normal and exaggerated ocular wound healing.
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PMID:Thrombin is a stimulator of retinal pigment epithelial cell proliferation. 187 7

Enhanced platelet functions have been reported in patients with diabetes mellitus. Our recent study demonstrated that phosphoinositide turnover is increased in platelets from diabetic patients. In the present study, we evaluated the abnormality in platelet intracellular calcium mobilization in patients with Type 2 (non-insulin-dependent) diabetes mellitus using fura-2, a fluorescent calcium indicator. Washed platelets were prepared from six diabetic patients with increased platelet aggregation rates (DM-A group), seven diabetic patients with normal platelet aggregation rates (DM-B group), and eight age-matched healthy control subjects. The basal intracellular free calcium concentrations in platelets were similar among the three groups. Thrombin (0.025-0.1 U/ml) induced a dose-dependent increase in intracellular calcium in both the presence and the absence of extracellular calcium. This increase in the presence of extracellular calcium, which depends on calcium influx and release, was significantly higher in the DM-A group than in the DM-B and control groups. However, there was no significant difference between the control group and the DM-B group. In the absence of extracellular calcium, thrombin-induced calcium increase, which depends only on calcium release, was also significantly enhanced in the DM-A group. Furthermore, the calcium increase stimulated by platelet-activating factor (10 nmol/l) with and without extracellular calcium was significantly higher in the DM-A group than in the other groups. Additionally, calcium ionophore A23187 (100 nmol/l) caused a significantly higher calcium increase in the DM-A group with extracellular calcium, while the calcium increase without extracellular calcium showed no significant difference among the three groups. These observations suggest that enhanced intracellular calcium mobilization due to increased calcium influx and release may be closely related to platelet hyperfunctions in diabetes mellitus.
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PMID:Increased intracellular calcium mobilization in platelets from patients with type 2 (non-insulin-dependent) diabetes mellitus. 190 85

An anticoagulant proteinase, lebetase, was isolated from the venom of Vipera lebetina by gel filtration and anion-exchange chromatography. The proteinase consists of a single polypeptide chain with a molecular weight of 23,700. Amino acid analysis indicates that lebetase contains 214 residues. It consists of several isoforms in the pH range 4.6-5.4, all having fibrinolytic activity. Lebetase hydrolyzes casein, fibrinogen and fibrin, and oxidized insulin B-chain in the positions Ala14-Leu15 and Tyr16-Leu17. Its fibrinolytic activity is inhibited by EDTA and lost upon heating at 70 degrees C for 10 min. The enzyme readily hydrolyzes the A alpha-chain and more slowly the B beta-chain of fibrinogen. In fibrin, the same chains are attacked. Thus, the enzyme is an A alpha, B beta-fibrinogenase. The fibrinolytic activity of lebetase is direct, without any plasminogen activation. E280 1% is 13.0 for lebetase. The enzyme showed low hemorrhagic activity.
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PMID:Purification and characterization of lebetase, a fibrinolytic enzyme from Vipera lebetina (snake) venom. 206 76

Glucose-dependent insulinotropic polypeptide (GIP) is a forty-two amino acid hormone that stimulates the secretion of insulin from the pancreatic B-cells in the presence of elevated glucose concentrations. The human GIP gene with the human A alpha-fibrinopeptide sequence was synthesized and linked to the Staphylococcus aureus protein A gene in the vector pRIT2T. This plasmid was expressed in Escherichia coli, and the resulting fusion protein consisted of three domains: protein A for ease of purification, fibrinopeptide sequence for thrombin cleavage and human GIP. The GIP was subsequently cleaved from the fusion protein with alpha-thrombin. The identity of the recombinant human GIP was confirmed by SDS-PAGE, ELISA, HPLC and amino-terminal amino acid sequence analysis. This recombinant product was shown to have comparable insulinotropic activity to porcine GIP in the isolated perfused pancreas.
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PMID:Expression of recombinant human glucose-dependent insulinotropic polypeptide in Escherichia coli by sequence-specific proteolysis of a protein A fusion protein. 208 31

Genistein has been shown to inhibit specifically in vitro the epidermal growth factor (EGF)-receptor tyrosine protein kinase activity (Akiyama et al., J Biol Chem 262: 5592-5597, 1987). When the effects of genistein on NIH-3T3 cells were studied, a cytostatic effect was observed at low concentration (less than 40 microM) and a cytotoxic effect at higher concentration (greater than 40 microM). Genistein was able to block the mitogenic effect mediated by EGF on NIH-3T3 cells (IC50 = 12 microM) or by insulin (IC50 = 19 microM). Genistein was also able to block the mitogenic effect mediated by thrombin (IC50 = 20 microM) although the thrombin receptor does not involve a protein tyrosine kinase activity. Genistein at cytostatic concentration (less than 40 microM) did not prevent the induction of c-myc mRNA synthesis caused by the activation of EGF receptor by EGF. Therefore the cytostatic effect of genistein on NIH-3T3 cells did not appear to be mediated by EGF receptor tyrosine kinase inhibition. This hypothesis was also supported by the absence of effect of genistein on the EGF-stimulated phosphorylation of several proteins and particularly of a cytosolic 80 kD protein. The stimulation of S6 kinase activity of cells treated by EGF was prevented by genistein. The stimulation by EGF of in situ S6 phosphorylation was also prevented by genistein. In addition, S6 kinase extracted from cells treated by EGF was inhibited by genistein. These effects occur at similar doses and maximal inhibition of S6 kinase was obtained at about 15 microM.
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PMID:Mechanisms of action in NIH-3T3 cells of genistein, an inhibitor of EGF receptor tyrosine kinase activity. 215 78

Platelet intracellular Ca2+ concentration ([Ca2+]i) and its response to stimuli (ADP and thrombin) were studied in 15 insulin-dependent and 22 non-insulin-dependent diabetes mellitus patients with the fluorescent probe Fura 2. The activity of Ca2(+)-ATPase and Na(+)-K(+)-ATPase, membrane fluidity, and cholesterol and phospholipid content were also determined in platelet membranes. Compared with control subjects, diabetic patients showed 1) increased platelet [Ca2+]i in the resting state, 2) higher Ca2+ levels after stimulation with thrombin and ADP, due entirely to increased resting concentrations, 3) reduced activity of Na(+)-K(+)-ATPase, 4) increased activity of Ca2(+)-ATPase, 5) higher fluidity of the platelet membrane, and 6) increased membrane concentration of total phospholipids. Na(+)-K(+)-ATPase activity was inversely related to platelet [Ca2+]i in each group studied, whereas Ca2(+)-ATPase activity was positively correlated with intracellular Ca2+ levels. The data obtained in diabetic subjects suggest an abnormality in Ca2+ and Na+ transport across the platelet membrane that might be responsible for the reported platelet hyperreactivity to stimuli in diabetes.
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PMID:Altered cellular Ca2+ and Na+ transport in diabetes mellitus. 216 3

Enhanced platelet functions have been demonstrated in patients with non-insulin-dependent diabetes mellitus (NIDDM). This study evaluated abnormalities in platelet signal transduction in diabetic patients, including turnover of phosphoinositides, mobilization of intracellular Ca2+, and phosphorylation of 20,000- and 47,000-Mr proteins (P20 and P47). Washed platelets were obtained from 6 patients with NIDDM whose platelet aggregation rates were abnormally elevated (DM-A group), 11 NIDDM patients with normal platelet aggregation rates (DM-B group), and 8 age-matched healthy control subjects. The mass and specific radioactivity of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), and phosphatidic acid (PA) in 32P-labeled platelets were not different among the three groups. Hydrolysis of PIP2, PIP, and PI; accumulation of PA; and phosphorylation of P20 in platelets stimulated by 0.05 U/ml thrombin were significantly increased in the DM-A group compared with the control or DM-B group. There was no difference in P47 phosphorylation among the three groups. On the contrary, P20 and P47 phosphorylation induced by 50 nM of 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, was significantly decreased in the DM-A group. Additionally, the intracellular free Ca2+ concentration [( Ca2+]i) was measured with the fluorescent Ca2+ indicator fura 2. Although the basal [Ca2+]i value was similar in the three groups, the rise in [Ca2+]i induced by 0.05 U/ml thrombin in the presence and the absence of extracellular Ca2+ was significantly higher in the DM-A group than the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in phosphoinositide turnover, Ca2+ mobilization, and protein phosphorylation in platelets from NIDDM patients. 217 10

In order to evaluate the role of phosphoinositide turnover in growth factor action, we expressed human M1 muscarinic acetylcholine (Hm1) receptors in Chinese hamster lung fibroblasts (CCL39 cell line). In the transfected cells (39M1-81 clone), but not in wild type fibroblasts, the muscarinic agonist carbachol induced a release of inositol phosphates as strong as alpha-thrombin, a very potent growth factor and activator of phosphoinositide-specific phospholipase C (PLC) in this cell system. In contrast to thrombin, carbachol-stimulated PLC activity was not inhibited by pertussis toxin treatment of cells. At concentrations that elicited a comparable initial rate of inositol phosphate release (10 nM for thrombin and 0.1 mM for carbachol), both agents gave rise to an identical calcium signal and equally stimulated Na+/H+ exchange and the transcription of the early genes c-jun, c-fos, and c-myc. Surprisingly, however, carbachol is not a mitogen for 39M1-81 cells, and even if tested in association with insulin or fibroblast growth factor, its effects on cell proliferation remained weak when compared with thrombin. Also, the muscarinic agonist did not stimulate soft agar colony forming capacity and did not prevent growth arrest in Go upon serum deprivation of cycling 39M1-81 cells. The failure of carbachol to induce cell proliferation could not be attributed to rapid and complete desensitization of Hm1 receptors nor to the activation of inhibitory pathways like adenylyl cyclase stimulation. We conclude that strong and persistent activation of phosphoinositide turnover elicits early biochemical events generally associated with mitogenesis, but is not sufficient to stimulate or maintain continuous cell proliferation. On the basis of our results, we postulate that thrombin mitogenesis depends critically on signaling events different from phosphoinositide turnover, possibly the stimulation of a receptor tyrosine kinase or a Gi protein-activated tyrosine kinase.
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PMID:Strong and persistent activation of inositol lipid breakdown induces early mitogenic events but not Go to S phase progression in hamster fibroblasts. Comparison of thrombin and carbachol action in cells expressing M1 muscarinic acetylcholine receptors. 217 13


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