Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasminogen activation has been shown to be inhibited by the cell-specific production of a number of protease inhibitors belonging to the serine protease inhibitor family. In the bovine testis this inhibitor production is induced by glucocorticoids. Monospecific antibodies raised against the three known classes of plasminogen activator inhibitor were used to identify which type of inhibitor was secreted by bovine Sertoli cell-enriched cultures. Immunoblot analysis and [35S]methionine labelling of newly synthesized proteins revealed that a novel protein with an apparent molecular weight of 49 kDa, which shares antigenic determinants with placental and macrophage PAI and fibroblast protease nexin, is secreted in response to dexamethasone stimulation. This protein was shown by immunoadsorption to be a functionally active inhibitor of both tissue-type and urokinase-type plasminogen activators.
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PMID:Characterization of a plasminogen activator inhibitor induced by glucocorticoids in immature bovine Sertoli cell-enriched cultures. 325 23

This study was designed to evaluate major fibrinolytic parameters in relation to parameters of inflammation associated with different kinds of pleural effusion. Sixty patients with pleural effusion were studied. The underlying aetiology was empyema in 10 cases, tuberculosis in 9, cancer in 31, cardiac failure in 7, and undetermined in 3. Plasminogen, plasminogen activator inhibitor 1 (PAI-1) and 2 (PAI-2), tissue type plasminogen activator (t-PA), urokinase (u-PA) and D-dimers (D-D) were quantified in plasma samples and pleural effusion specimens. These data were then correlated with inflammatory or infectious parameters, i.e. fibrinogen, von Willebrand factor (vWF), erythrocyte sedimentation rate (ESR), protein concentration, and white blood cell count. D-D levels were higher in pleural fluid than in plasma. D-D levels were not correlated with either plasminogen activator or plasminogen activator inhibitor levels, suggesting the presence of other fibrinolytic pathways. PAI levels (PAI activity, PAI-1 antigenicity, PAI-2 antigenicity) and vWF levels were significantly higher in patients with tuberculosis and empyema than in patients with cancer or cardiac failure. Regression analysis between inflammatory and fibrinolytic parameters showed that pleural PAI levels were significantly correlated with pleural neutrophil count, vWF levels, and plasma fibrinogen levels. D-D levels were correlated with blood ESR. No significant difference in pleural t-PA, u-PA and D-D levels was observed between aetiologies. The highest pleural t-PA and u-PA values were noted in patients with cancer, especially lymphoma. Plasma t-PA levels were higher inpatients with pleural effusion secondary to congestive heart failure, but this difference did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fibrinolytic and inflammatory processes in pleural effusions. 748 3

Endothelial cell-derived proteases can be classified according to their physiological role. The proteases involved in extracellular matrix degradation are important in endothelial cell migration and thereby in angiogenesis. They include the urokinase-type plasminogen activator (uPA) and the metalloproteases, collagenases, gelatinases and stromelysin. uPA secreted from endothelial cells remains associated with the cell membrane, on specific receptors localized in the vicinity of the receptors for plasminogen. This favours the local activation of plasminogen into plasmin. Plasmin, generated on the cell surface, is fully active as it is not inhibited by alpha 2-antiplasmin. Plasmin acts directly by degrading some components of the extracellular matrix and indirectly by activating the prometalloproteases. Secretion of PAI by migrating cells is generally stimulated by the same factors that induce uPA secretion, limiting the degradation of the matrix to the pericellular path. The degradation of the fibrin clot involves the tissue-type plasminogen activator tPA, which like the uPA activates plasminogen to plasmin. This system is also regulated by two different mechanisms. On the one hand, fibrin itself favours its own degradation by formation of a ternary complex, fibrin-plasminogen-tPA, in which the affinity of tPA for plasminogen is markedly increased, as compared to the affinity of unbound tPA. In addition, plasmin generated on the clot is protected from inhibition by alpha 2-antiplasmin. On the other hand, as for uPA, tPA is inhibited by PAI-1. The importance of the regulation of this system is illustrated by the thrombotic risk observed when there is either a decrease in tPA or an increase in PAI-1, and inversely by haemorrhages in the case of increase in tPA.
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PMID:Endothelial cell proteases: physiological role and regulation. 751 36

Limited proteolysis in vivo of insulin-like growth factor-binding protein-3 (IGFBP-3) by as yet unidentified serine proteases plays a key role in controlling the bioavailability of IGFBP-3-associated insulin-like growth factors (IGFs). Both the IGF system and the system of plasminogen activators (PAs) and their inhibitors (PAIs) are involved in bone remodeling, and plasmin has been shown to provoke dissociation of IGFBP-IGF complexes in cultured MG-63 human osteoblasts. The aim of this work was to investigate interactions between IGF-I and the PA/PAI system and their influence on IGFBP-3 production and proteolysis in this cell model. At confluency, MG-63 cells maintained for 3 days in serum-free medium constitutively secreted IGFBP-2 and small amounts of IGFBP-3 and IGFBP-4. As shown by Western ligand and immunoblot analyses of the culture medium and Northern blot analysis of IGFBP-3 messenger RNA, production of these IGFBPs, and of IGFBP-3 in particular, was dose dependently stimulated by the addition of 12.5-100 ng/ml recombinant human (rh) IGF-I. Increasing concentrations of plasminogen (0.05-3.5 micrograms/ml) added during the final 12 h of culture reduced the amounts of IGFBP detectable by Western ligand blotting, especially IGFBP-3. This reduction reflected proteolysis, as shown by immunoblotting, which revealed 30-, 20-, and 16-kilodalton fragments of IGFBP-3. In the presence of 25 ng/ml IGF-I, which stimulated IGFBP-3 production, proteolysis was reduced by approximately half. Incubation of glycosylated [125I]rh-IGFBP-3 as substrate in cell-free conditioned medium gave the same results. Addition of 50 ng/ml rhIGF-I to conditioned medium (to promote IGFBP-3-rhIGF-I complex formation) failed to diminish plasmin-induced proteolysis of IGFBP-3. Urokinase PA activity in the conditioned medium decreased significantly when the cells were cultured with rhIGF-I, indicating a direct action of IGF-I on urokinase PA and/or PAI production. Our results support the notion of a regulation loop whereby IGF-I controls its own bioavailability via its action on both IGFBP-3 production and the PA/PAI system, which regulates IGFBP-3 proteolysis. The proteolytic cleavages of IGFBP-3 caused by plasmin were the same as those caused in vivo by serine protease acting on this IGFBP.
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PMID:Interactions between insulin-like growth factor-I (IGF-I) and the system of plasminogen activators and their inhibitors in the control of IGF-binding protein-3 production and proteolysis in human osteosarcoma cells. 752 30

The prerequisite for a curative resection of metastases is their restriction to the key organs, the liver and lungs, in the sense of a limited dissemination. For long-term prognosis, the type of primary tumor as well as the radical resection of lung and liver metastases is essential. To improve the process of surgical indication and therapy of tumors, clear definitions for the terms "tumor recurrence" and "metastases" have been agreed upon. Research and clinical investigation have led to a better understanding of tumor-regulating factors, some of which are briefly described: Metastasis promoting factors include the lack of E-cadherin, which leads to a local penetration of basal membranes by tumor cells; CD44 seems to play an important role in cell-cell and cell-matrix interactions, apparently increasing the metastatic potential of tumors and reducing the long-term survival of patients. High levels of urokinase in primary tumors are also associated with a poorer prognosis, as well as plasminogen inactivator inhibitor PAI II, which plays a crucial role in tumor growth. Positive findings in bone marrow aspirates of patients with different malignancies, stained for cytokeratin 18, either are associated with higher recurrence rates in colon and breast cancer or can be correlated to the prognosis of patients with gastric cancer. Technical aspects of surgery for hepatic, pulmonary and skeletal metastases are presented and discussed with respect to curative and palliative indications.
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PMID:Surgical treatment of tumor metastases: general considerations and results. 753 64

Urokinase (u-PA) is synthesized and secreted as a single-chain polypeptide (single-chain u-PA, scu-PA), which has such little enzymatic activity in solution that it has been considered essentially enzymatically inert. We found that plasminogen activator inhibitor type 1 (PAI-1), the major PAI in plasma, demonstrated concentration-dependent inhibition of this solution-phase scu-PA enzymatic activity. 125I-scu-PA formed complexes with PAI-1 in a concentration- and time-dependent manner, as detected by SDS-polyacrylamide gel electrophoresis under reducing conditions. Among a given population of scu-PA molecules, all measurable enzymatic activity was inhibited by a 10-fold molar excess of PAI-1. However, at this stoichiometry, only a minority of 125I-scu-PA molecules formed SDS-stable complexes with PAI-1 (i.e. complexes that formed a covalent bond upon denaturation), even though the uncomplexed PAI-1 molecules remained competent to inhibit u-PA enzymatic activity. Neither the extent nor the time course of complex formation was altered by using PAI-1 that had been pre-incubated with native human vitronectin, compared with native PAI-1 alone. 125I-scu-PA.PAI-1 complexes that would form a covalent bond if denatured were reversible and existed in equilibrium with either non-complexed or loosely complexed reactants. These data suggest that scu-PA has more enzyme-like properties than previously appreciated and raises the possibility that it resembles single-chain tissue type-plasminogen activator in lacking a complete zymogen conformation.
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PMID:Interaction of single-chain urokinase and plasminogen activator inhibitor type 1. 754 49

The Tyr-SV40E transgenic mouse model of malignant skin melanoma has been used here to generate melanomas in genetically identical (C57BL/6) mice for analysis of the plasminogen activator (PA) system during tumor development and progression. Twenty-two melanocytic lesions were examined by in situ zymography for PA activity and by immunohistochemistry for concomitant visualization of PA proteins; these lesions encompassed 3 nevi and 19 primary melanomas ranging from melanotic through mixed tumors to amelanotic tumors. Although urokinase-type plasminogen activator (u-Pa) activity was not detected at premalignant stages, it began to appear early in tumorigenesis and became more prominent in later stages of a majority of the tumors. The activity was largely attributable to the endothelium of sprouting capillaries and to a lesser degree to granulocytes, fibroblastic cells, and occasional melanoma cells within tumors. Tissue-type plasminogen activator (t-PA) was undetectable or low in all cases. Of the inhibitors (PAI), PAI-1 was seen in endothelial and fibroblastic cells and in the extracellular matrix, whereas PAI-2 occurred in only one case and was melanoma cell associated. Eleven additional melanomas were analyzed by reverse transcription-PCR for PA expression in RNA extracts from relatively large tumor samples. These were obtained from eight primary melanomas and three metastases, again spanning melanotic, mixed, and amelanotic cases. From four of the mixed primary tumors with distinct melanotic and amelanotic zones, the respective components were propagated separately in transgenic hosts as s.c. transplants to obtain data for clearly identifiable melanotic versus amelanotic parts. u-PA and PAI-1 mRNAs were expressed in all. t-PA expression varied greatly and was notably high in several amelanotic tumors or tumor components, possibly as a result of large blood vessels, as such vessels were seen to be t-PA positive in normal tissue. The u-PA activity in sprouting capillaries may indicate a role in neoangiogenesis. Therefore, according to these mouse models, u-PA may indirectly be a potential therapeutic target against melanoma progression.
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PMID:Expression of plasminogen activators and plasminogen activator inhibitors in cutaneous melanomas of transgenic melanoma-susceptible mice. 755 49

Increased expression of plasminogen activator inhibitor-1 (PAI-1) has been demonstrated in the human atherosclerotic vessel wall and may contribute to the impaired plasma fibrinolytic capacity in patients at high risk of atherothrombotic events. In addition, the mural PA/plasmin system may have important pathobiologic functions during atherogenesis. We quantitatively analyzed PAs of the tissue type (TPA) and urokinase type (UPA), PAIs, and plasminogen in protein extracts from different layers of human aorta in relation to the presence and severity of atherosclerotic lesions. In comparison with normal control vessels, intimal and neointimal TPA concentrations were reduced in atherosclerotic aortas except in the necrotic core areas of advanced plaques, where TPA was mainly complexed to PAI-1 in extracellular matrix deposits. In the media, TPA antigen was higher in lesional segments and closely associated with smooth muscle cells. UPA antigen was increased in the intima of atherosclerotic lesions and colocalized with tissue-infiltrating macrophages and neointimal smooth muscle cells. By spectrophotometric assay, neither TPA nor UPA activity could be detected in intimal or medial extracts. PAI-1 concentrations increased significantly in the intima of atherosclerotic segments compared with adjacent uninvolved areas or control aortas. The immunohistochemical distribution of PAI-1 was similar to that observed for TPA. A large excess of PAI-1 over PA concentrations, particularly in the intimal layer, characterizes atherosclerotic lesions of the human aorta and suggests that PA action is locally confined and counterbalanced by enhanced PAI expression and accumulation.
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PMID:Quantification of plasminogen activators and their inhibitors in the aortic vessel wall in relation to the presence and severity of atherosclerotic disease. 760 Jan 21

It has been shown that a 90-kDa protein (90K), with an as yet unknown function, is expressed in the majority of human breast-cancer tissues. In addition, the serum level of this 90K antigen is elevated in a certain proportion of breast-cancer patients, and high serum levels are associated with a poor overall survival. It was therefore of interest to determine whether levels of 90K in tumor tissues could be used as a prognostic variable in breast cancer. In the present study, the levels of 90K in primary breast tumor cytosols were studied with respect to the length of relapse-free or overall survival in 547 patients (median follow-up, 81.4 months), and the relationship with response to first-line tamoxifen therapy and the length of progression-free survival in 184 patients with recurrent disease (median follow-up, 59.8 months). 90K levels in tumor cytosols were determined with an immunoradiometric assay. The cytosolic contents of 90K were not significantly correlated with age, menopausal status, tumor size, nodal status or differentiation grade. On the other hand, the levels of 90K were positively correlated with those of cytosolic estrogen receptor, progesterone receptor, urokinase-type plasminogen activator, its inhibitor PAI-I, cathepsin D and PS2. The cytosolic tumor level of 90K was not associated with the rate of relapse or death in primary breast cancer, nor with response to first-line therapy with tamoxifen or the length of progression-free survival in recurrent disease.
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PMID:Expression of tumor-associated 90K-antigen in human breast cancer: no correlation with prognosis and response to first-line therapy with tamoxifen. 761 55

Degradation of the extracellular matrix plays a crucial role in cancer invasion. This degradation is accomplished by the concerted action of several enzyme systems, including generation of the serine protease plasmin by the urokinase pathway of plasminogen activation, different types of collagenases and other metalloproteinases, and other extracellular enzymes. The degradative enzymes are involved also in tissue remodelling under non-malignant conditions, and the main difference appears to be that mechanisms which regulates these processes under normal conditions are defective in cancer. Specific inhibitors have been identified for most of the proteolytic enzymes, e.g. plasminogen activator inhibitors (PAI's) and tissue inhibitors of metalloproteinases (TIMP's). It has been contemplated that these inhibitors counteracted the proteolytic activity of the enzymes, thereby inhibiting extracellular tissue degradation which in turn should prevent tumor cell invasion. This review focuses on plasminogen inhibitor type 1 (PAI-1). It is described that PAI-1 is not produced by the epithelial cancer cell but by the stromal cells in the tumors, suggesting a concerted action between stroma and tumor cells in the processes controlling proteolysis in cancer. The specific localization of PAI-1 to the tumor stroma and in many cases to areas surrounding the tumor vessels has lead us to suggest that PAI-1 serves to protect the tumor stroma from the ongoing uPA-mediated proteolysis. This hypothesis is supported by recent clinical data showing increased levels of PAI-1 in metastases as compared to the primary tumor as well as data demonstrating that high levels of PAI-1 in tumor extracts from breast, lung, gastric and ovarian cancer is associated with a shorter overall survival.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasminogen activator inhibitor type 1 in cancer: therapeutic and prognostic implications. 766 68


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