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

The authors examined the effect of insulin-like growth factor 1 (IGF 1), epidermal growth factor (EGF), and acidic fibroblast growth factor (AFGF) on the synthesis by human retinal endothelial cell (HREC) of plasminogen activators (PA; tissue-type [t-PA] and urokinase-type [u-PA]) and plasminogen activator inhibitor (PAI). Immunologic and functional assays for t-PA, u-PA, and PA1 were conducted with cell lines derived from three diabetics and three nondiabetic controls. Confluent HREC of nondiabetic origin did not respond to IGF I (100 ng/ml) with any change of t-PA antigen in the medium (10.7 +/- 1.1 ng/ml unstimulated versus 10.1 +/- 0.8 ng/ml) stimulated, P = not significant). Likewise AFGF and EGF caused no significant change of t-PA levels. Both IGF I and EGF caused a significant increase of t-PA from HREC of diabetic origin (9.6 +/- 0.8 ng/ml unstimulated versus 16.6 +/- 1.9 ng/ml IGF I-stimulated, P less than 0.001, and 14.6 +/- 2.7 ng/ml EGF-stimulated P less than 0.005). Supplementation of AFGF had no effect on HREC of diabetic origin. In confluent cultures, only small quantities of u-PA were detected. After wounding confluent cultures, u-PA activity was associated with cells migrating from the wound edges. Functional PA activity was also measured by chromogenic assay. Results further supported a predominance of t-PA activity being produced by confluent HREC in culture. These results suggest that modulation of PA production by HREC is influenced by exposure to growth factors, by the state of confluency, and the origin of the cells (diabetic vesus nondiabetic).
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PMID:Plasminogen activator production by human retinal endothelial cells of nondiabetic and diabetic origin. 170 73

Plasminogen activator inhibitor type 1 (PAI-1), the fast-acting inhibitor of tissue-type plasminogen activator (t-PA) and urokinase (u-PA), is a member of the serpin superfamily of proteins. Both in plasma and in the growth substratum of cultured endothelial cells, PAI-1 is associated with its binding protein vitronectin, resulting in a stabilization of active PAI-1. Recently, it has been demonstrated that the PAI-1-binding site on vitronectin is adjacent to a heparin-binding site (Preissner et al., 1990). Furthermore, it can be deduced that the amino acid residues, proposed to mediate heparin binding in the serpins antithrombin III and heparin cofactor II, are conserved in PAI-1. Consequently, here we have investigated whether PAI-1 also interacts with heparin. At pH 7.4, PAI-1 quantitatively binds to heparin-Sepharose and can be eluted with increasing [NaCl]. Binding of PAI-1 to heparin-Sepharose can be efficiently competed with heparin in solution (IC50, 7 microM). In the presence of heparin, the protease specificity of PAI-1 toward thrombin is substantially increased. This is shown by (i) quenching of thrombin activity of PAI-1 in the presence of heparin and (ii) induction of the formation of SDS-stable complexes between thrombin and PAI-1 by heparin. In a dose response curve, both effects reached a maximum at approximately 1 unit/mL and then diminished again upon further increasing the heparin concentration, strongly suggesting a template mechanism as an explanation for the observed effect. In contrast to vitronectin, heparin does not stabilize the active conformation of PAI-1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Functional interaction of plasminogen activator inhibitor type 1 (PAI-1) and heparin. 170 36

A transcriptional silencer has been identified in the 5' regulatory region of the human urokinase plasminogen activator (uPA) gene. This region is able to block transcription from the human u-PA as well as the rabbit beta-globin promoters in a cell type specific and orientation independent way. The silencer is enhancer dependent and is active in two cell lines (HeLa and CV-1) which produce little if any uPA, but not in the high uPA producer PC3. Silencing activity and enhancer dependence can be separated: the silencing activity has been localized to the DNA fragment -660 to -536, while the enhancer dependence is located in the -536 to -308 fragment. The DNA sequence of the silencer region contains an element that closely resembles the TGF-beta responsive negative element TIE.
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PMID:A cell-type specific and enhancer-dependent silencer in the regulation of the expression of the human urokinase plasminogen activator gene. 171 Mar 52

The present in vitro study investigated dose-, time- and temperature-dependent effects of two-chain urokinase plasminogen activator (u-PA, urokinase) on normal citrated plasma. When 10 micrograms/ml u-PA were added to pooled normal plasma and incubated for 30 min at an ambient temperature (25 degrees C), alpha 2-antiplasmin decreased to 8% of the control value. Incubation on ice yielded a decrease to 45% of control, whereas alpha 2-antiplasmin was fully consumed at 37 degrees C. Fibrinogen and plasminogen fell to 46% and 39%, respectively, after a 30 min incubation at 25 degrees C. Thrombin time prolonged to 190% of control. Various inhibitors were studied with respect to their suitability and efficacy to prevent these in vitro effects. Aprotinin exhibited a good protective effect on fibrinogen at concentrations exceeding 500 KIU/ml plasma. Its use, however, was limited due to interferences with some haemostatic assays. We could demonstrate that L-Glutamyl-L-Glycyl-L-Arginyl chloromethyl ketone (GGACK) and a specific polyclonal anti-u-PA-antibody (anti-u-PA-IgG) effectively inhibited urokinase-induced plasmin generation without interfering with haemostatic assays. The anti-u-PA-antibody afforded full protection of alpha 2-antiplasmin at therapeutic levels of u-PA. It is concluded that u-PA in plasma samples from patients during thrombolytic therapy may induce in vitro effects which should be prevented by the use of a suitable inhibitor such as GGACK or specific anti-u-PA-antibody.
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PMID:In vitro effects of urokinase--prevention by different inhibitors. 171 Aug 33

Several human melanoma cell lines produced tissue-type plasminogen activator (t-PA), as detected by zymography and immunocapture assay of culture media and cell lysates. Urokinase (u-PA) was found at only less than or equal to 1% the level of t-PA. Acid eluates of the cell surface indicated that the melanoma cells had t-PA bound on their surface, but no u-PA, and also had a very low capacity to bind exogenous u-PA. After incubation of the melanoma cells with 10% plasminogen-depleted fetal calf serum and human plasminogen, bound plasmin activity could be eluted from the cell surface with tranexamic acid, an analogue of lysine. This indicated that plasminogen was activated on the cell surface. The cell-surface plasmin formation was inhibited by an anti-catalytic monoclonal antibody to human t-PA, and not by an anti-catalytic antibody to u-PA. The melanoma cells also synthesized and secreted alpha 2-macroglobulin (alpha 2M), as shown by alpha 2M-specific mRNA in Northern blotting and detection of alpha 2M protein in conditioned cell culture media. The media were found to inhibit u-PA but not t-PA. This inhibition was related to their alpha 2M content, and immunoabsorption of alpha 2M removed the inhibitory activity. These studies suggest that t-PA can bind to the surface of melanoma cells and generate surface-bound plasmin. Because t-PA and cell-bound plasmin are unaffected by alpha 2M, t-PA may, in the case of melanoma cells, serve an analogous function to u-PA in supporting tumor cell invasion.
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PMID:Plasminogen activation by t-PA on the surface of human melanoma cells in the presence of alpha 2-macroglobulin secretion. 171 33

Plasminogen activator inhibitor 1 (PAI-1), an essential regulatory protein of the fibrinolytic system, harbors interaction sites for plasminogen activators (tissue-type [t-PA] and urokinase-type [u-PA]) and for fibrin. In this study, anti-PAI-1 monoclonal antibodies (MoAbs) were used to identify interaction sites of PAI-1 with these components. The binding sites of 18 different MoAbs were established and are located on five distinct "linear" areas of PAI-1. MoAbs, binding to two distinct areas of PAI-1, are able to prevent the inhibition of t-PA by PAI-1. In addition, two interaction sites for fibrin were identified on PAI-1. The area located between amino acids 110 and 145 of PAI-1 contains a binding site for both components and its significance is discussed in the context of the t-PA inhibition by fibrin-bound PAI-1. Subsequently, the MoAbs were used to assess the role of platelet-PAI-1 in clot-lysis. An in vitro clot-lysis system was used to demonstrate that clot-lysis resistance is dependent on the presence of activated platelets and that PAI-1 is a major determinant for lysis-resistance. We propose that, upon activation of platelets, PAI-1 is fixed within the clot by binding to fibrin and retains its full capacity to inhibit t-PA and u-PA.
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PMID:The interaction of plasminogen activator inhibitor 1 with plasminogen activators (tissue-type and urokinase-type) and fibrin: localization of interaction sites and physiologic relevance. 171 49

Plasminogen activator inhibitor 1 (PAI-1) is the fast-acting inhibitor of both tissue-type and urokinase-type plasminogen activators (t-PA, u-PA) and is an essential regulatory protein of the fibrinolytic system. In the presence of either the protein vitronectin or the glycosaminoglycan heparin, PAI-1 is also an efficient inhibitor of thrombin. To assess whether these cofactors turn PAI-1 into a general protease inhibitor or whether their influence is restricted to thrombin, the second-order association rate constants between PAI-1 and the human plasma proteases t-PA, u-PA, plasmin, thrombin, Factor Xa (FXa), and Factor XIIa (FXIIa) in the absence and in the presence of either vitronectin or heparin are determined. In addition, the role of the PAI-1 reactive site P3 to P3' residues for the specificity of inhibition was studied by using PAI-1 reactive site mutants. Our results show that: (1) Heparin exclusively increases the rate of inhibition of thrombin by PAI-1, whereas in the presence of heparin the rate of inhibition of the other proteases is not altered; (2) Vitronectin is an obligatory cofactor for the inhibition of thrombin by PAI-1. In addition, vitronectin moderately increases the rate of inhibition by PAI-1 of u-PA and of plasmin, but does not alter the rate of inhibition of t-PA, FXa, or FXIIa; (3) Apart from the important role of the P1 residue, no consensus can be presented on the nature of other residues within the P3 to P3' region with regard to target protease specificity.
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PMID:On the target specificity of plasminogen activator inhibitor 1: the role of heparin, vitronectin, and the reactive site. 171 20

The mesothelial cells obtained from human omental adipose tissue showed a typical cobblestone monolayer and reacted strongly with keratin, but did not have Von Willebrand factor. Ultrastructurally these cells revealed the existence of desmosome-like cell junctions as well as intracellular canaliculi, tubular structures surrounded by microvilli, and tonofilament-like filaments. The mesothelial cells grew much faster in the medium containing epidermal growth factor, actively took up acetylated-low density lipoprotein into their cytoplasm, and released angiotensin-converting enzyme. They also released urokinase-type plasminogen activator, but only half as much as do human umbilical vein endothelial cells; release of tissue-type plasminogen activator was not observed. Inasmuch as the mesothelial cells also released plasminogen activator inhibitor-1, as do human umbilical vein endothelial cells, we could not detect u-PA activity in culture medium. u-Pa may play a role in the protection against adhesion among visceral organs. These observations indicate that cultured human mesothelial cells have characteristics closely related to those found in human endothelial cells.
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PMID:Close similarity between cultured human omental mesothelial cells and endothelial cells in cytochemical markers and plasminogen activator production. 171 52

Extravascular coagulation and fibrinolysis are intimately involved in and modulate cancer cell growth, invasion and metastasis. Samples from resection specimens of patients with primary lung cancer (adenocarcinomas) were tested with monoclonal (MAb) and polyclonal (PAb) antibodies against various factors of the coagulation or fibrinolysis systems, or against antigens of inflammatory or proliferating cells. MAb Ki-67 specific to nuclear antigens of proliferating cells showed a distinct but variable staining of cell nuclei throughout the tumor tissue. Nests of tumor tissue stained with cytokeratin-specific antibodies (PKK1), whereas other parts were negative. Fibrin(ogen) and fibronectin were found throughout the tumor tissue stroma and in the alveolar lining, and the most densely stained areas were at the transition zone between normal and tumor tissue. Fibrinolytic system components like tissue plasminogen activators (t-PA), and urokinase (u-PA), and their inhibitors PAI-1 and PAI-2 were all studied. All specimens were negative for t-PA (except endothelial linings), whereas urokinase-specific antibodies stained loosely packed tumor cells and macrophages within the tumor stromal tissue and alveolar septa. Both PAI-1 and PAI-2 were most prominently expressed within interstitial and alveolar macrophages. A weaker staining of tumor tissue cells was demonstrated. Inflammatory cells like macrophages and T lymphocytes were located in aggregates or diffusely spread within tumor stromal tissue. The inflammatory reaction was most intense at the border between normal lung and tumor tissue.
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PMID:Immunohistochemical localization of coagulation, fibrinolytic and antifibrinolytic markers in adenocarcinoma of the lung. 172 Mar 19

Flow cytofluorometric protocols (FACScan) are described for the rapid and quantitative real-time analysis of binding of FITC-pro-u-PA to cell surface receptors (u-PAR) on living, resting, and also on PMA-stimulated human monocytic U937 cells. Binding of pro-u-PA was visualized by CLSM. This fairly new technique is superior over conventional fluorescence microscopy and is an alternative to electron microscopic approaches. Both flow cytofluorometry and confocal laser scanning microscopy allow the analysis quantitatively and with high-sensitivity binding of FITC-pro-u-PA to single suspended or adherent cells. By CLSM u-PA/u-PAR were found to be located in heterogeneously distributed discrete patches at the cell surface on U937 and not inside the cell. This is in agreement with previous studies by Hansen et al, who applied radioiodinated u-PA and electron microscopy to locate u-PAR on microvilli of fixed U937 cells. By flow cytofluorometry, it was possible to quantify the time-dependent and temperature-dependent binding of FITC-pro-u-PA to living single U937. Apparent saturation of u-PAR was achieved at 5 nM FITC-pro-u-PA for both nonstimulated and PMA-stimulated U937 cells. Half saturation of u-PAR was also determined. Nonstimulated U937 was 0.7 nM, and PMA-stimulated U937 was 1.1 nM of FITC-pro-u-PA. This increase in half-saturation concentration in PMA-stimulated cells is paralleled by a steep increase in binding sites (3.6-fold). The use of fluoresceinated reference beads is recommended to verify changes in affinity and binding sites. Using CLSM or flow cytofluorometry, it is also possible to study the structure relationship of u-PA/u-PAR in the presence of competitive binding analogues or inhibitors. Fluorescence techniques will also permit the identification of u-PAR-positive cells in blood, ascitic fluid, or biopsies obtained from cancer patients.
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PMID:Fluorescent probes as tools to assess the receptor for the urokinase-type plasminogen activator on tumor cells. 172 74


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