Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.7 (plasmin)
9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasmin is known to activate platelets. However, it is not clear whether plasminogen activators as used in thrombolytic therapy can aggregate platelets and how this relates to the ability of each activator to convert plasminogen to plasmin. Urokinase (UK) and streptokinase (SK) activated purified plasminogen (2 microM) in a concentration-dependent manner. The rates of aggregation of washed platelets by the above plasminogen activators and plasminogen were similar to the extent of activation of plasminogen to plasmin in the absence of platelets. UK or SK (0.2 microM) and plasminogen (2 microM) aggregated platelets modified by an ADP affinity analog, 5'-p-fluorosulfonylbenzoyladenosine (FSBA), and cleaved aggregin, a putative ADP receptor, in [3H]FSBA-modified platelets. These results suggest that the effect was independent of ADP. In contrast, incubation mixtures containing only plasminogen (2 microM) and single chain tissue plasminogen activator (sc-tPA) (less than or equal to 0.12 microM) neither activated the zymogen to an appreciable extent nor aggregated platelets. But, in the presence of fibrin(ogen) fragments (tPA-stimulator), a mixture of plasminogen and sc-tPA aggregated unmodified and FSBA-modified platelets, and cleaved aggregin. The results imply that platelets, in the presence of t-PA stimulator, potentiate activation of plasminogen to plasmin by t-PA, as previously reported. P1, Phe-Gln-Val-Val-Cys-(NpyS)-Gly-NH2, (NpyS = 3-nitro-2-thiopyridine), a synthetic hexapeptide capable of binding to and inhibiting calpain, has been shown to inhibit platelet aggregation induced by purified plasmin. P1 inhibited platelet aggregation by plasminogen and any of the three plasminogen activators. Our results show that at plasma concentrations of plasminogen and at levels of UK and SK attained after infusion of these agents during thrombolysis, these mixtures can cause maximum aggregation which may contribute to reocclusion and stenosis following infarct therapy. P1 can effectively inhibit platelet aggregation under such conditions.
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PMID:Aggregation of washed platelets by plasminogen and plasminogen activators is mediated by plasmin and is inhibited by a synthetic peptide disulfide. 153 63

Covalently cross-linked multimers of lipocortin I are shown to be present in human epidermoid carcinoma A431 cells treated with epidermal growth factor or the calcium ionophore A23187. This intracellular cross-linking of lipocortin I is suggested to be mediated by the action of tissue transglutaminase, a Ca2(+)-dependent protein cross-linking enzyme. Cross-linking of lipocortin I competes with proteolytic digestion of the protein, and pretreatment of the cells with inhibitors for calpain (Ca2(+)-dependent intracellular protease) markedly enhanced the cross-linking of lipocortin I. Cross-linked lipocortin I is shown to be present in the soluble fraction of A431 cells as well as in the particulate fraction; a 34-kDa fragment of lipocortin I was solubilized successfully by plasmin digestion of the latter fraction. Immunofluorescence microscopy using specific antilipocortin-I antibody showed that cross-linked lipocortin I forms an envelope-like structure, which is not extracted with [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA) or Triton X-100. In vitro incubation of purified lipocortin I with tissue transglutaminase resulted in the formation of covalently cross-linked lipocortin I dimer, tetramer, and so on. Amine incorporation and cross-linking studies using lipocortin I and its N-terminal truncated derivatives indicated that the cross-linking site is localized within the plasmin-susceptible N-terminal 29 amino acids of lipocortin I. The cross-linking of lipocortin I is shown to be accelerated more than 10 times by the addition of phosphatidylserine vesicles, on which lipocortin I molecules are most likely aligned in a conformation suitable for cross-linking. Collectively, these findings suggest that an increase of intracellular calcium concentration results in the attachment of lipocortin I onto the plasma membrane phospholipids through the C-terminal domain of the molecule where the membrane-bound lipocortin I is cross-linked by the action of tissue transglutaminase through the N-terminal domain.
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PMID:Calcium-induced intracellular cross-linking of lipocortin I by tissue transglutaminase in A431 cells. Augmentation by membrane phospholipids. 167 Jul 73

We recently reported that thrombin-induced platelet aggregation 1) is accompanied by cleavage of aggregin, a 100-kDa membrane protein and a putative ADP receptor, 2) is indirectly mediated by intracellularly activated calpain, and 3) requires the occupancy of high-affinity thrombin receptors. Because of the similarities between responses after platelet activation induced by thrombin and plasmin (greater than or equal to 1.0 casein unit/ml), we investigated whether or not plasmin-induced platelet aggregation proceeds by the same mechanism that underlies thrombin-induced platelet aggregation. We found that the rate of plasmin-induced aggregation of washed intact platelets and that of platelets modified by 5'-p-fluorosulfonylbenzoyladenosine (FSBA, an affinity analogue of ADP, which covalently modifies aggregin) were similar, indicating that the aggregation is independent of the ADP effect. Plasmin completely cleaved [3H]FSBA-labeled aggregin in intact platelets. A mixture of metabolic inhibitors (2-deoxy-D-glucose, gluconolactone, and antimycin A) completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin, demonstrating that an energy-requiring step is involved in the reaction. The synthetic hexapeptide affinity reagent Phe-Gln-Val-Val-Cys(NpyS)-Gly-NH2 (NpyS = 3-nitro-2-thiopyridine), a potent and specific inhibitor of thrombin-induced platelet aggregation and platelet calpain, completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin. These results suggest that, like thrombin, plasmin-induced platelet aggregation is accompanied by the cleavage of aggregin and these responses are indirectly mediated by the intracellularly activated calpain.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasmin-induced platelet aggregation is accompanied by cleavage of aggregin and indirectly mediated by calpain. 214 55

1. A synthetic peptide disulfide, Gln-Val-Val-Cys(NpyS)-Gly-NH2 (P1) inhibited thrombin and plasmin-induced platelet aggregation and cleavage of aggregin. P1 did not inhibit platelet aggregation induced by other agonists nor did it inhibit shape change. 2. P1 also inhibited purified platelet calpain II. 3. The correspondence between the molecular structure of P1 and inhibitory sequence of the peptide in domain 2 of high molecular weight kininogen has shed light on the molecular nature of the cellular mechanism underlying thrombin- and plasmin-induced platelet aggregation and the inhibition by P1. 4. P1 may prove to be useful in designing and improving future protocols of thrombolytic therapy to prevent reocclusion. P1 may also have a role in inhibiting thrombin formed during angioplasty and thus preventing restenosis.
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PMID:Selective inhibition of thrombin- and plasmin-induced platelet aggregation by a synthetic peptide disulfide. 256 38

Amyloid beta protein (beta/A4) is deposited in senile plaques of patients with Alzheimer's disease. This protein is derived from a larger membrane-associated protein, termed amyloid precursor protein (APP). The constitutive processing of APP occurs at the central portion of beta/A4, resulting in the release of large N-terminal peptides. We have purified these peptides from the culture medium of cDNA-transfected COS-1 cells. Some of the isoforms contain the Kunitz-type protease inhibitor (KPI) domain and strongly inhibit trypsin, chymotrypsin and plasmin, but do not inhibit kallikrein, prolyl endopeptidase or granzyme A. The peptides also do not inhibit cysteine proteases such as cathepsin B or calpain. Soluble APPs lacking the KPI domain fail to inhibit any of these proteases. The results indicate that the KPI domain in soluble APPs has protease inhibitory activity against certain serine proteases.
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PMID:Inhibitory spectra of purified protease nexin-II and related proteins towards cellular proteinases. 790 50

Platelet glycocalicin (GC) is the extramembranous portion of GPIb alpha that can be rapidly cleaved by enzymes such as calpain, plasmin, trypsin, elastase, etc. Quantitative cleavage will ultimately result in an acquired Bernard-Soulier-like bleeding disorder, and circulating GC may act as a potential inhibitor of platelet adhesion. We have developed and standardized a new enzyme-linked immunosorbent assay (ELISA), which uses two monoclonal antibodies (mAbs), both of which bind to the amino-terminal 45-kD fragment of GC and inhibit platelet-von Willebrand interactions and the streptavidin-biotin system. First, the methodology was evaluated and standardized with special emphasis on the anticoagulant and the inhibitors (EDTA, prostaglandin E1 [PGE1], aprotinin, N-ethyl-maleimide), the mode of high-speed centrifugation (to avoid platelet microparticles), and the standards used (purified GPIb and GC). This assay was then used to analyze the GC levels of healthy subjects (2.04 +/- 0.46 micrograms/mL) and of patients with selected diseases. The results of patients with aplastic anemia and thrombocytosis confirmed that GC levels are clearly dependent on the platelet count, which was the basis for the introduction of the GC index, the standardization of GC for a platelet count of 250 x 10(9)/L. The GC index discriminates reliably patients with active immune thrombocytopenic purpura from those in remission. GC levels are elevated in patients on hemodialysis (3.62 +/- 0.75 micrograms/mL, P < .001). The high GC index (6.93 +/- 4.21, P < .001) in cirrhosis patients suggests an increased platelet turnover and/or abnormal proteolysis. In contrast to other groups, we have not found that recombinant tissue plasminogen activator (rtPA) treatment of patients with myocardial infarction increases GC levels. However, concentrations are elevated in leukemia and the highest levels found are approximately 40 micrograms/mL. These studies suggest that GC is a useful platelet marker in certain diseases, which directly reflects platelet damage and possibly platelet dysfunction.
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PMID:Glycocalicin: a new assay--the normal plasma levels and its potential usefulness in selected diseases. 829 32

The use of first generation plasminogen activators, urokinase, streptokinase and tissue plasminogen activator has revolutionized thrombolytic therapy for myocardial infarction and ischaemia, and potentially stroke. However, thrombolytic therapy employing these activators is limited by reocclusion of the very arteries being opened, which follows in a small but significant number of patients. The development of second generation plasminogen activators, e.g. staphylokinase and anisoylated plasminogen streptokinase activator complex, has not alleviated the problems encountered with classical plasminogen activators. It is now widely recognized that aberrant platelet aggregation induced primarily by thrombin, rather than plasmin, is one of the major causes of recurrent thrombosis following pharmacologic thrombolysis. Agents that (a) inhibit enzymatic and/or coagulant activity of thrombin, (b) block binding of thrombin to its receptor, and (c) interfere with the generation of thrombin by the prothrombinase complex may compromise haemostasis resulting in haemorrhage. We recently demonstrated that thrombin-induced platelet aggregation is accompanied by cleavage of aggregin, a putative ADP-receptor on the platelet surface, and that these events are indirectly mediated by intracellularly activated calpain expressed on the surface. In this review, we discuss the known mechanisms of thrombin-induced platelet aggregation and suggest relative advantages of potential pharmacological agents, being developed in our laboratory, over those that have been previously developed and tested. These inhibitors selectively prevent aggregation of platelets induced by thrombin by inhibiting calpain expressed on the surface. Moreover, one of these inhibitors which blocks thrombin-induced platelet aggregation does not interfere with other platelet responses mediated by thrombin or platelet aggregation induced by other agonists, such as, ADP, collagen, phorbol myristate acetate and thromboxane A2 mimetics. This selectivity could reduce the chances of perturbing the formation of a haemostatic plug.
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PMID:Reocclusion after thrombolytic therapy: strategies for inhibiting thrombin-induced platelet aggregation. 832 74

Coagulation factor V (FV) and factor VIII (FVIII) are usually decreased in septicemic DIC. Low doses of endotoxin administered to healthy volunteers stimulate activation of the fibrinolytic, contact and coagulation systems, but not clinical DIC. Following the administration of endotoxin (4 ng/kg) to normal volunteers (n = 15), we applied new assays for FV antigens using monoclonal antibodies to the activation peptide (C1) and to the light chain of FV. At 5 hours, FV coagulant activity was significantly decreased (64 +/- 9%), as was the FV light chain antigen (74 +/- 6%), without a change in factor V C1 antigen or total protein C. In contrast, FVIII coagulant activity was greater than preinfusion levels at 2-5 hours. The decrease in FV activity may be due to APC cleavage of FV heavy chain, but the loss of light chain antigen suggests that plasmin and/or calpain also contribute. APC may not be the only enzyme responsible for cofactor inactivation. FV is one of the most sensitive markers, even reflecting subclinical activation of coagulation.
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PMID:Cofactors V and VIII after endotoxin administration to human volunteers. 858 99

Transforming growth factor-beta (TGF-beta) is normally secreted in a latent form, and plasmin-mediated proteolytic cleavage of latency-associated peptide (LAP), a component of latent TGF-beta complex that makes the complex inactive, activates latent TGF-beta. In the present study, we investigated the possible involvement of calpain, one of the cysteine proteases, in the activation of latent TGF-beta. When recombinant latent TGF-beta was incubated with calpain (1-10 u/ml) in a test tube, calpain cleaved LAP and released mature TGF-beta from the latent complex. When calpain was applied to cultured bovine capillary endothelial (BCE) cells, a low concentration of calpain (0.05-0.1 u/ml) inhibited the migration and proliferation of the cells, and these inhibitory effects were abrogated by anti-TGF-beta antibody as well as by calpain inhibitor peptide, but not by alpha2-antiplasmin, a specific inhibitor of plasmin. Active TGF-beta was detected in the conditioned medium of BCE cells collected in the presence of calpain. Chemical cross-linking of (125)I-calpain to BCE cells followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that calpain bound to the cell surface through chondroitinase ABC-sensitive proteoglycan. In addition, treatment of the BCE cells with chondroitinase ABC abrogated the inhibitory effect of calpain on the migration of these cells. Our data thus suggest that calpain is able to activate latent TGF-beta through a mechanism independent of plasmin. This activation is efficient in the presence of cells, and calpain binds to the cell surface via proteoglycan and activates latent TGF-beta, which is targeted to the same surface.
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PMID:Cell-associated activation of latent transforming growth factor-beta by calpain. 942 5

Much attention has been paid to proteinases derived from not only neurons but also microglia in relation to neuronal death. There is accumulating evidence that intra- and extracellular proteinases in these cells are part of the basic machinery of neuronal death pathways. Some members of the ced-3/interleukin-1 beta converting enzyme (ICE) (caspase) family of cysteine proteinases have been thought to play a major role in apoptosis of not only non-neuronal cells but also neurons. Calpain has also been demonstrated to be a mediator of the neurodegenerative response. Recent studies have shown that excitotoxic and ischemic neuronal injury could be attenuated by inhibitors of caspases and calpain. Several recent studies have suggested the involvement of endosomal/lysosomal proteinases, including cathepsins B, D and E, in neuronal death induced by excitotoxins and ischemia. Furthermore, it has been reported that the extracellular tissue-type plasminogen activator/plasmin proteolytic cascade is involved in excitotoxic injury of the hippocampal neurons. In addition to such neuronal proteinases, microglial proteinases are believed to be important for the modification of neuronal functions positively or negatively. Cathepsins E and S derived from microglia have been suggested to contribute to neuronal survival through degradation and removal of beta-amyloid, damaged neurons and cellular debris. On the other hand, 6-hydroxydopamine-induced microglial cell death was inhibited by inhibitors of aspartic proteinases and caspases, suggesting the involvement of cathepsins E and D and caspases in microglial cell death. Therefore, identification of which proteinases play a causative role in neuronal death execution and clarification of the regulators and substrates for such proteinases is very important for understanding the molecular basis of the neuronal death pathways and to develop novel neuroprotective agents.
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PMID:[Involvement of proteinases produced by both neurons and microglia in neuronal lesion and death pathways]. 978 98


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