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 activator inhibitor-1 (PAI-1) binds to the somatomedin B (SMB) domain of vitronectin. It inhibits the adhesion of U937 cells to vitronectin by competing with the urokinase receptor (uPAR; CD87) on these cells for binding to the same domain. Although the inhibitor also blocks integrin-mediated cell adhesion, the molecular basis of this effect is unclear. In this study, the effect of the inhibitor on the adhesion of a variety of cells (e.g., U937, MCF7, HT-1080, and HeLa) to vitronectin was assessed, and the importance of the SMB domain in these interactions was determined. Although PAI-1 blocked the adhesion of all of these cells to vitronectin-coated wells, it did not block adhesion to a variant of vitronectin which lacked the SMB domain. Interestingly, HT-1080 and U937 cells attached avidly to microtiter wells coated with purified recombinant SMB (which does not contain the RGD sequence), and this adhesion was again blocked by the inhibitor. These results affirm that PAI-1 can inhibit both uPAR- and integrin-mediated cell adhesion, and demonstrate that the SMB domain of vitronectin is required for these effects. They also show that multiple cell types can employ uPAR as an adhesion receptor. The use of purified recombinant SMB should help to further define this novel adhesive pathway, and to delineate its relationship with integrin-mediated adhesive events.
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PMID:Plasminogen activator inhibitor-1 regulates cell adhesion by binding to the somatomedin B domain of vitronectin. 1157 1

The effect of wound fluids collected from acute well-healing wounds and chronic nonhealing venous leg ulcers on the plasminogen activation system of keratinocyte and fibroblast cell cultures was studied in a simplified wound-healing model. Acute wound fluid was collected from donor sites of split skin grafts at different time points representing the progressive healing of the wound. Urokinase-type plasminogen activator, tissue-type plasminogen activator, urokinase-type plasminogen activator receptor, and plasminogen activator inhibitor 1 expression were studied. The methods used were immunocapture assay and immunocytochemistry. The results indicated that the later the acute wound fluid was collected, the greater the urokinase-type plasminogen activator and the lower the plasminogen inhibitor-1 level in treated cells. In contrast, the level of urokinase-type plasminogen activator receptor remained stable irrespective of wound fluid treatment. Immunostaining for urokinase-type plasminogen activator of acute wound fluid-treated cells showed a disseminated punctate pattern over the cell surface, but with chronic wound fluid, urokinase-type plasminogen activator was localized to focal contacts. Our findings support the view that in the acute wound environment the plasminogen activator system is proteolytically active and that in chronic leg ulcers urokinase-type plasminogen activator and urokinase-type plasminogen activator receptor may also be organized for cell adhesion and migration.
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PMID:Differential effects of acute and chronic wound fluids on urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor, and tissue-type plasminogen activator in cultured human keratinocytes and fibroblasts. 1167 40

Plasminogen activators are serine proteases induced in the brain by electrical activity leading to synaptic remodelling. They are classified into two distinct subtypes, tissue plasminogen activating factor and urokinase plasminogen activating factor (tPA and uPA, respectively), which are both expressed in brain areas thought to be important in learning and memory. Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of tPA and uPA activity, and is expressed in corresponding brain areas. Mice lacking tPA show a deficit in the acquisition of a 15 s differential reinforcement of low rate of responding (DRL15") task relative to their wild types (WTs) under certain conditions. The current set of experiments were designed to investigate further the role of tPA and to extend our knowledge to uPA and PAI-1, using mice with the respective genes deleted (uPA -/- and PAI-1 -/- mice) in the DRL15" task. uPA -/- mice showed no disruption of DRL acquisition, but PAI-1 -/- mice showed a deficit similar to that seen in tPA -/- mice. In an attempt to compensate for this deficit, experiments using a fixed number of reinforcers or a signalled-DRL15" schedule, similar to that used in rat lesion studies of DRL, were performed. tPA -/- mice were able to complete the signalled-DRL task as well as their WTs, and, similarly, PAI-1 -/- mice were able to learn the fixed-number-of-reinforcers-DRL15" schedule and the signalled-DRL schedule. These data indicate that uPA deletion does not affect performance of a standard DRL15" task, whereas deletion of PAI-1 has the same behavioural consequences in these tasks as deletion of tPA. Deficits of both genotypes can be attenuated by providing either external information on completion of the delay or by equalizing the number of reinforcers obtained.
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PMID:DRL performance in mice with deletion of tPA, uPA or PAI-1 genes. 1174 43

Plasminogen activator inhibitor-1 (PAI-1) is a serine protease inhibitor (SERPIN) specific for tissue-type and urokinase-like plasminogen activators. High plasma PAI-1 activity is a risk factor for thrombotic diseases. Due to the short half-life of PAI-1, regulation of PAI-1 gene expression and secretion of active PAI-1 into the blood stream is important for hemostatic balance. We have investigated transcriptional control of PAI-1 gene expression in bovine aortic endothelial cells (BAECs) and human cell lines using PAI-1 5' promoter-luciferase reporter assays. Contrary to the cytokine-induced up-regulation of PAI-1 mRNA and protein levels, we found that only transforming growth factor-beta (TGF-beta) was efficient in inducing PAI-1 promoter activation. Tissue necrosis factor-alpha (TNF-alpha) induced a small luciferase activity with the 2.5 kb PAI-1 promoter, but not with the PAI-800/4G/5G and p3TP-lux promoters. Next we investigated whether a lack of response to TNF-alpha was due to deficient signaling pathways. BAECs responded to TNF-alpha with robust NFkappaB promoter activation. TGF-beta activated the p38 MAP kinase, while TNF-alpha activated both the SAPK/JNK and p38 MAP kinases. The ERK1/2 MAP kinases were constitutively activated in BAECs. BAEC therefore responded to TNF-alpha stimulation with activation of the MAP kinases and the NFkappaB transcriptional factors. We further measured the messenger RNA stability under the influence by TGF-beta and TNF-alpha and found no difference. PAI-1 gene activation by TNF-alpha apparently is yet to be defined for the location of the response element and/or the signaling pathway, while TGF-beta is the most important cytokine for PAI-1 transcriptional activation through its 5' proximal promoter.
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PMID:Differential mechanisms of plasminogen activator inhibitor-1 gene activation by transforming growth factor-beta and tumor necrosis factor-alpha in endothelial cells. 1177 28

Different extracellular matrix proteins have been described as binding proteins for growth factors, influencing their storage or presentation towards cellular receptors. The multifunctional adhesive glycoprotein vitronectin (VN), which is found in the circulation and widely distributed throughout different tissues, has been implicated in the regulation of vascular cell functions, and these activities could be related to interactions with various growth factors. In vitro, soluble VN interfered with transforming growth factor-beta (TGF-beta) binding to isolated extracellular matrix and was found to associate with TGF-beta1 and TGF-beta2 as well as with other growth factors such as vascular endothelial growth factor, epidermal growth factor, or basic fibroblast growth factor in a saturable manner. In particular, binding of TGF-beta was maximal for the heparin-binding multimeric isoform of VN, whereas VN in a ternary complex with thrombin and antithrombin or plasma VN exhibited weaker binding. Plasminogen activator inhibitor-1 (PAI-1) or heparin, but not desulfated glycosaminoglycans, interfered with binding of VN to TGF-beta, and soluble PAI-1 was able to dissociate VN-bound TGF-beta. Upon limited plasmin proteolysis of VN, only the fragments comprising the intact aminoterminal portion of VN bound to TGF-beta as did a synthetic peptide (amino acids 43 to 62), indicating that TGF-beta and PAI-1 share common binding site(s) on VN. Although VN did not influence TGF-beta bioactivity for mink lung epithelial cells, TGF-beta dose dependently inhibited both urokinase-receptor as well as alpha(v)-integrin-dependent adhesion to VN. This activity of TGF-beta was reminiscent of the antiadhesive function of PAI-1. In atherosclerotic tissue sections, staining patterns of VN and TGF-beta indicated their colocalization. These findings describe VN as a new binding protein for TGF-beta, whereby specific functions of both factors become modulated by this interaction.
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PMID:Molecular interactions and functional interference between vitronectin and transforming growth factor-beta. 1179 24

Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of both tissue- and urokinase-type plasminogen activators (t-PA, u-PA). PAI-1 also regulates the attachment of cells to the adhesive glycoprotein vitronectin (VN). PAI-1 gene expression has been observed in various cell types, and many regulatory factors have been identified to play a role in PAI-1 gene transcription. The complete picture of how the PAI-1 gene is expressed when cells adhere to a culture plate has not been fully elucidated. We found that in anchorage-dependent cells, PAI-1 gene was up-regulated when cells were beginning to attach to a culture dish and was down-regulated when cells had attached completely. The PAI-1 gene expression was induced only in adhered cells but not in non-adhered cells. The regulation of PAI-1 protein was also found in both culture medium and cell lysate when cells were attached to a culture dish. Our experiment indicates that vitronectin and fibronectin, as components of ECM, may be the factors involved in the regulation of PAI-1 gene expression. PAI-1, as an inhibitor of the interaction between vitronectin and integrin alphavbeta3, may also be a regulator of its own expression.
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PMID:Cell adhesion regulates the plasminogen activator inhibitor-1 gene expression in anchorage-dependent cells. 1182 81

Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of fibrinolysis by its inhibition of both tissue-type and urokinase plasminogen activators. PAI-1 levels are elevated in type II diabetes and this elevation correlates with macro- and microvascular complications of diabetes. Insulin increases PAI-1 production in several experimental systems, but the mechanism of insulin-activated PAI-1 transcription remains to be determined. Deletion analysis of the PAI-1 promoter revealed that the insulin response element is between -117 and -7. Mutation of the AT-rich site at -52/-45 abolished the insulin responsiveness of the PAI-1 promoter. This sequence is similar to the inhibitory sequence found in the phosphoenolpyruvate carboxylkinase/insulin-like growth factor-I-binding protein I promoters. Gel-mobility shift assays demonstrated that the forkhead bound to the PAI-1 promoter insulin response element. Expression of the DNA-binding domain of FKHR acted as a dominant negative to block insulin-increased PAI-1-CAT expression. A LexA-FKHR construct was also insulin responsive. These data suggested that a member of the Forkhead/winged helix family of transcription factors mediated the effect of insulin on PAI-1 transcription. Inhibition of phosphatidylinositol 3-kinase reduced the effect of insulin on PAI-1 gene expression, a result consistent with activation through FKHR. However, it was likely that a different member of the FKHR family (not FKHR) mediated this effect since FKHR was present in both insulin-responsive and non-responsive cell lines.
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PMID:A Forkhead/winged helix-related transcription factor mediates insulin-increased plasminogen activator inhibitor-1 gene transcription. 1191 88

Plasminogen activator inhibitor-1 (PAI-1) is a serine protease inhibitor that was isolated 20 years ago. First recognized as an inhibitor of intravascular fibrinolysis, it is now evident that PAI-1 is a multifunctional protein with actions that may be dependent on or independent of its protease inhibitory effects. The latter often involve interactions between PAI-1 and vitronectin or the urokinase receptor. The protease-inhibitory actions of PAI-1 extend beyond fibrinolysis and include extracellular matrix turnover and activation of several proenzymes and latent growth factors. PAI-1 has been implicated in several renal pathogenetic processes, including thrombotic microangiopathies and proliferative and/or crescentic glomerulopathies. Most recently, it has become clear that PAI-1 also plays a pivotal role in progressive renal disease, both glomerulosclerosis and tubulointerstitial fibrosis. An active area of present research interest, untold stories are likely to be uncovered soon.
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PMID:Plasminogen activator inhibitor-1 and the kidney. 1211 May 4

Plasminogen activator inhibitor-1 (PAI-1), the primary physiological inhibitor of both tissue-type plasminogen activator and urokinase-type plasminogen activator in plasma, is a well established risk factor in thrombotic diseases. Reduction of active PAI-1 levels may lead to a decreased tendency of thrombosis. Compounds that can suppress pharmacologically active PAI-1 levels are therefore considered as putative drugs. In the present study, we describe the PAI-1 neutralizing properties and mechanism of a newly selected compound (i.e. fendosal, HP129) in comparison to four previously reported compounds (i. e. AR-H029953XX, XR1853, XR5118 and the peptide TVASS) using different assays. The inhibitory effect of these compounds on active PAl-1 was analyzed by a plasmin-coupled chromogenic assay (Coaset t-PA), direct chromogenic assays (t-PA, u-PA) and quantification of complex formation by ELISA, SDS-PAGE and surface plasmon resonance. Comparative evaluation of the obtained IC50 values reveals large differences [i.e. IC50 of 15 microM (HP129) vs. >1000 microM (XR5118) determined at 37 degrees C using SDS-PAGE] between the compounds studied. Importantly, the relative potency of the various compounds is also dependent on the method used (10 to 170-fold differences in IC50 values). Characterization of the PAI-1 forms (i.e. active, non-reactive and substrate) generated upon inactivation reveals that the newly described compound HP129 induces a unique pathway (i.e. active to non-reactive conversion via a substrate-behaving intermediate) of inactivation compared to the other compounds. Taken together, these data strongly suggest that the various compounds act through different mechanisms. In addition, the results stress the necessity for a careful selection of the method used for the evaluation of PAI-1 inhibitors, preferably requiring a panel of screening methods.
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PMID:Characterization and comparative evaluation of a novel PAI-1 inhibitor. 1215 54

Lipid abnormalities and dysregulation of the plasminogen activator (PA)/plasmin system may be involved in the development of glomerulosclerosis. We investigated the effects of low-density lipoprotein (LDL) on PA inhibitor-1 (PAI-1), urokinase-type PA (uPA), and tissue-type PA (tPA) in relationship to protein kinase C (PKC) in cultured human mesangial cells (HMC). LDL (200 microg/ml) induced two peaks of PKC activation at hours 0.25 and 6, with translocation of PKC-alpha, -beta(1), and -delta from cytosol to the membrane. The second increase in PKC activity gradually decreased to the control value by hour 18. LDL downregulated 2.4-kb PAI-1, uPA, and tPA mRNA expression within 6 h of incubation with HMC. On the other hand, after 12-48 h, LDL-treated cells showed a significant increase in PAI-1, tPA, and uPA mRNA levels. LDL induced up to a twofold increase in PAI-1 antigen levels in the extracellular matrix of HMC after 24-48 h as well as increased PA inhibitory activity in the culture medium. Analysis of the adhesion plaques from cells incubated with LDL for 48 h by zymography showed increased intensity of lysis near molecular weights of approximately 55,000 and 100,000. LDL slightly increased tPA release at hours 24 and 48 but did not increase PA activity in culture medium. The stimulatory effects of LDL on PAI-1, tPA, and uPA gene regulation in HMC were blocked by the inhibition of PKC using GF-109203X 12 h after treatment with LDL or downregulation of PKC using phorbol myristate acetate. In summary, LDL regulates PAI-1, uPA, and tPA in biphasic patterns in HMC, and the upregulation of PAI-1, uPA, and tPA after long-term LDL exposure seems to be mediated by a delayed PKC activation associated with an increased PA inhibitory activity. These results suggest that LDL, after prolonged incubations with HMC, causes a PA/inhibitor imbalance favoring accumulation of matrix.
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PMID:Biphasic regulation of plasminogen activator/inhibitor by LDL in mesangial cells. 1216 92


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