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)

Vitronectin (VN) stabilizes plasminogen activator inhibitor type 1 (PAI-1) activity and prevents the fibrin(ogen)-induced acceleration of plasminogen activation by t-PA. These antifibrinolytic activities as well as other functions are mediated by the glycosaminoglycan (GAG) binding domain of VN. Since the GAG binding region is rich in arginyl and lysyl residues, it is a potential target for enzymes such as plasmin. In this paper, the dose and time-dependent proteolysis of VN by plasmin is demonstrated. The addition of urokinase or streptokinase (200 units/ml) to plasma also produced proteolysis of VN. With minimal proteolysis, the 75 kDa band was degraded to a 62-65 kDa form of VN. This minimal proteolysis destroyed the binding of [3H]-heparin to VN and reversed the neutralization of heparin by VN. Thus, the plasmin-mediated proteolysis of the GAG binding activity of VN could destroy the antifibrinolytic activity of VN during physiologic conditions and during thrombolytic therapy. Furthermore, other functions of VN in complement and coagulation systems that are mediated by the GAG binding domain may be destroyed by plasmin proteolysis.
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PMID:Limited proteolysis of vitronectin by plasmin destroys heparin binding activity. 172 Sep 4

Vitronectin endows plasminogen activator inhibitor 1 (PAI-1), the fast-acting inhibitor of both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), with additional thrombin inhibitory properties. In view of the apparent association between PAI-1 and vitronectin in the endothelial cell matrix (ECM), we analyzed the interaction between PAI-1 and thrombin in this environment. Upon incubating 125I-labeled alpha-thrombin with endothelial cell matrix (ECM), the protease formed SDS-stable complexes exclusively with PAI-1, with subsequent release of these complexes into the supernatant. Vitronectin was required as a cofactor for the association between PAI-1 and thrombin in ECM. Metabolic labeling of endothelial cell proteins, followed by incubation of ECM with t-PA, u-PA, or thrombin, indicated that all three proteases depleted PAI-1 from ECM by complex formation and proteolytic cleavage. Proteolytically inactive thrombin as well as anticoagulant thrombin, i.e., thrombin in complex with its endothelial cell surface receptor thrombomodulin, did not neutralize PAI-1, emphasizing that the procoagulant moiety of thrombin is required for a functional interaction with PAI-1. A physiological implication of our findings may be related to the mutual neutralization of both PAI-1 and thrombin, providing a new link between plasminogen activation and the coagulation system. Evidence is provided that in ECM, procoagulant thrombin may promote plasminogen activator activity by inactivating PAI-1.
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PMID:Thrombin neutralizes plasminogen activator inhibitor 1 (PAI-1) that is complexed with vitronectin in the endothelial cell matrix. 172 12

Fetal rat osteoblast-enriched calvarial cells were used to study the effects of various growth factors and cytokines on plasminogen activator (PA) and plasminogen activator inhibitor (PAI) activities and the possible relationship of these effects to bone resorption. Confluent cultures were exposed to various factors under serum-free conditions, and levels of PA and PAI activities were examined in both conditioned medium (CM) and cell layer using the 125I-fibrin plate assay, fibrin zymogram, and reverse fibrin zymogram. According to the 125I-fibrin plate assay or zymogram, incubation of cells with acidic fibroblast growth factor (aFGF), basic FGF (bFGF), epidermal growth factor (EGF), and platelet-derived growth factor (PDGF) elevated the PA activity in the CM as well as in the cell layer extract. Incubation with interleukin 1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF alpha), and insulin-like growth factor I (IGF-I) produced no change in PA activity in either CM or cell layer. Addition of transforming growth factor beta (TGF beta) to calvarial cells resulted in nearly undetectable PA activity in CM with the fibrin plate assay but increased PA activity on the fibrin zymogram after PAI was separated from PA by SDS-PAGE. A reverse fibrin zymogram indicated that PAI activity was greatly enhanced in TGF beta-treated CM. TGF beta treatment also increased PA activity in the cell layer of calvarial cells. Treatment of calvarial cells with bFGF and PDGF slightly increased PAI secretion into medium. This increase, however, was not as dramatic as the increase of PA induced by these two agents. IL-1 alpha and TNF alpha did not change PAI concentration in CM. No detectable PAI activity was found in the cell layer in control and treated groups. The PA found in the CM and cell layer of rat calvarial cells was the urokinase type; the PAI stimulated by TGF beta was the endothelial cell type, PAI-1. The regulation of PA activity by growth factors and cytokines did not correlate with their resorption-stimulating activities. Thus, PA secreted by osteoblasts may not be the only factor involved in the initiation of bone resorption. Delineation of the function of PA and PAI in the physiology of bone tissue awaits further studies.
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PMID:Regulation of plasminogen activator and plasminogen activator inhibitor production by growth factors and cytokines in rat calvarial cells. 172 49

The human U373 glioblastoma/astrocytoma cell line was found to constitutively produce and secrete a plasminogen activator and a plasminogen activator inhibitor. The plasminogen activator was identified as urokinase based on apparent molecular weight, immunoblotting with anti-urokinase antibodies, and Northern blotting with a human urokinase cDNA probe. The inhibitor secreted by U373 cells was found to be related to the PAI-1 molecule based on reactivity with anti-human PAI-1 antibodies, apparent molecular weight, and Northern blot analysis with a human PAI-1 cDNA probe. The expression of both urokinase and the PAI-1-like molecule by U373 cells could be modulated by phorbol myristate acetate or by inflammatory mediators such as interferon-gamma and interleukin-1. In the case of interleukin-1, the alpha form exhibited no detectable effect while the beta form not only elevated inhibitor levels, it also appeared to induce the production of tissue plasminogen activator. Thus, in these cells interleukin-1 beta induces alterations in PA and PAI expression and interleukin-1 alpha does not, even though the two forms are reported to utilize the same cellular receptor.
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PMID:Modulation of plasminogen activator and plasminogen activator inhibitor expression in the human U373 glioblastoma/astrocytoma cell line by inflammatory mediators. 172 61

Tumor necrosis factor (TNF) has a profound capacity to alter the endothelial cell phenotype that includes morphologic and functional changes that may be central for proinflammatory processes. Recent observations have indicated that TNF can promote the synthesis and secretion of urokinase plasminogen activator (uPA) in low passage human endothelial cells that normally release little uPA. In this report we have confirmed and expanded upon these initial observations in human endothelial cells and describe the ability of gamma-interferon (gamma-IFN) to inhibit TNF-induced uPA synthesis and secretion in a dose-dependent manner (0.025 to 25 ng/mL). Analysis of cell-free conditioned medium derived from gamma-IFN-treated cultures by micro-enzyme-linked immunosorbent assay (ELISA) methodologies using uPA- and plasminogen activator inhibitor type 1 (PAI-1)-specific monoclonal antibodies (MoAbs) indicate that the decrease in uPA activity observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) zymography is a direct result of a decrease in extracellular uPA antigen and is not a consequence of increased PAI-1 antigen. These findings are supported by Northern blot analyses that indicate that gamma-IFN treatment of endothelial cells resulted in a decreased steady state level of uPA messenger RNA (mRNA) with no measurable change in PAI-1 mRNA. This inhibitory response is specific for gamma-IFN because alpha-IFN fails to elicit a similar inhibitory response. In addition, TNF augmented extracellular proteolysis of radiolabeled subendothelial extracellular matrix (ECM) in a dose-dependent manner. The observed increase in ECM degradation mediated by TNF treatment of endothelial cells was dependent on the presence of plasminogen and could be inhibited by an anticatalytic uPA MoAb implying the requirement of proteolytically active uPA in this process. gamma-IFN (25 ng/mL) treatment of endothelial cells antagonized TNF-promoted degradation of radiolabeled ECM at a concentration that completely inhibited TNF-mediated uPA expression and activity. In addition, endothelial cells treated with TNF (18 hours) displayed the ability to invade ECM and reorganize individual cells into tube-like structures that were not evident in untreated control cultures when grown on Matrigel-coated culture dishes. gamma-IFN treatment of endothelial cells propagated on Matrigel was observed to inhibit TNF-mediated ECM invasion and tube formation at concentrations that were analogous to those required for the inhibition of uPA expression and activity. In summary, these observations suggest a novel homeostatic control mechanism for endothelial cell regulation of subendothelial ECM degradation promoted by TNF and inhibited by gamma-IFN.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Tumor necrosis factor induction of endothelial cell urokinase-type plasminogen activator mediated proteolysis of extracellular matrix and its antagonism by gamma-interferon. 173 9

We measured antigen levels of 2 kinds of plasminogen activator, tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (UK), as well as those of their primary inhibitors, type-I plasminogen activator inhibitor (PAI-1) and type-2 plasminogen activator inhibitor (PAI-2), in tissue extracts from benign and malignant breast tumors. Tumor tissue samples from 40 fibroadenomas and 40 breast cancers were examined. t-PA antigen levels were the same in the 2 groups. Malignant tumors contained higher levels of UK antigen than did benign tumors. In the case of breast cancer, UK antigen levels of tumors with axillary lymph-node involvement were significantly higher than those of tumors without lymph-node involvement. PAI-1 and PAI-2 antigen levels of breast-cancer tissue samples were higher than those of fibroadenoma samples. PAI-1 antigen levels of carcinomas with lymph-node involvement were also significantly higher than those of carcinomas without node involvement. PAI-2 antigen levels, on the contrary, were higher in carcinomas without node involvement. UK, PAI-1 and PAI-2 antigen levels are potentially excellent independent factors for prediction of the metastatic potential of breast cancers.
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PMID:Plasminogen activator system in human breast cancer. 173 2

The correlation between the production of plasminogen activators (PA), especially urokinase-type PA (u-PA), by cancer cells and their metastatic potential was studied. For this purpose, cells from the human rectal adenocarcinoma tumor line (RCM-l/nu) originally maintained by serial passage in nude mice as the solid subcutaneous tumor, were injected into the spleen. Cancer cells from liver metastatic foci were suspended and then injected into the spleen. After 10 cycles of this selection, a highly metastatic liver tumor line termed L-10 was obtained. The amount of u-PA in the supernatant of the tumor homogenate of L-10 was larger than that of RCM-l/nu. Using an in vitro culture system, the media conditioned by L-10 cells had a higher PA activity and a higher u-PA antigen level than by RCM-l/nu cells. The apparent difference in u-PA activity and antigen levels of these two lines was not due to the difference in the production of plasminogen activator inhibitor (PAI), because PAI antigen level and PAI activity in the culture media were almost equal between them. No tissue-type PA production was detectable in these tumor lines. From these results we deduce that u-PA may play an important role in tumor metastasis.
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PMID:Correlation between urokinase-type plasminogen activator production and the metastatic ability of human rectal cancer cells. 176 31

In the present study 57 consecutive patients with a first episode of venographically proven deep vein thrombosis were investigated to evaluate the release of tissue-type plasminogen activator (t-PA) and of urokinase-type plasminogen activator (u-PA) in response to DDAVP stimulation as well as the resting plasminogen activator inhibitor (PAI) concentration, comparing this to the results obtained in 66 similar patients with a clinical suspicion of thrombosis but with a normal venogram. All assays were performed without knowledge of the patient's status. Four patients in the deep vein thrombosis-group (7%) had an absent u-PA antigen response upon DDAVP infusion, while a normal response was observed in all control subjects. Patients and controls showed similar increases in t-PA antigen level upon DDAVP. High resting PAI antigen levels were encountered in 5 patients in the deep vein thrombosis-group (9%) and in 6 subjects in the control group (9%). The results from this controlled study indicate that a defective release of u-PA may occur in patients with deep vein thrombosis and may have pathogenetic significance. Furthermore it is concluded that elevation of PAI levels cannot be considered as a specific risk factor for venous thrombosis.
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PMID:Deep vein thrombosis and fibrinolysis. Defective urokinase type plasminogen activator release. 179 91

We determined the plasma levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI) activity and their antigen levels including urokinase plasminogen activator (u-PA) in 33 male and 27 female normal subjects. Males had mean t-PA activity of 0.50 iu/ml which was significantly lower (p less than 0.01) than the females 0.64 iu/ml. Males had higher (p less than 0.001) mean PAI activity (15.5 AU/ml) as compared to females 10.3 AU/ml. The respective mean levels of t-PA and PAI antigen were significantly higher (p less than 0.01) in males (8.1 ng/ml and 17.6 ng/ml) than in females (6.2 ng/ml and 12.1 ng/ml). The mean u-PA level in males was 1.54 ng/ml which was significantly higher (p less than 0.01) than in females with 1.02 ng/ml. In post-venous occlusion studies, females had a greater mean response of 8.6 fold in t-PA activity as compared to males with a mean of 4.5 fold increase. The mean t-PA antigen response in males was 2.0 fold increase as compared to 2.6 fold increase in the females. No significant responses were seen in both sexes in either PAI activity or antigen levels when compared with the resting state. In zymography studies, free t-PA, its inhibitor complexes and u-PA were demonstrated in the euglobulin fractions of stored plasma. This study demonstrates that significant differences in t-PA, u-PA and PAI exist between male and female subjects which should be taken into account when determining their levels in clinical conditions.
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PMID:Plasminogen activators t-PA, u-PA and its inhibitor (PAI) in normal males and females. 180 23

A model system consisting of thrombin-stimulated bovine platelet releasates (PRthr) and bovine aortic endothelial cells (BAEs) was developed to determine if the interaction between platelets and endothelial cells regulates fibrinolysis. Zymographic analysis indicated that PRthr treatment of BAEs decreases urokinase and increases type 1 plasminogen activator inhibitor (PAI-1) activity. Although PRthr did not affect the overall rate of BAE protein synthesis, it increased PAI-1 biosynthesis within 6 hours. This increase was complete by 12 hours, with maximum stimulation at 10 to 15 micrograms/mL PRthr (1 microgram approximately 10(7) platelets). Neutralizing antibodies to transforming growth factor beta (TGF beta) reduced this effect by 75%. Treatments that activate latent TGF beta (eg, acidification or plasmin) increased this effect approximately fivefold, suggesting that TGF beta in PRthr exists in both a latent (approximately 80%) and an active (approximately 20%) form. In contrast to PRthr, adenosine diphosphate-prepared platelet releasates did not increase PAI-1 synthesis before acidification, indicating that they contain only the latent form of TGF beta. These results suggest that platelets can modulate the fibrinolytic system of the endothelium through the release of TGF beta, and that the mechanism by which the platelets are activated can influence the relative amount of active TGF beta.
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PMID:Platelets stimulate endothelial cells to synthesize type 1 plasminogen activator inhibitor. Evaluation of the role of transforming growth factor beta. 182 86


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