Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The potential contribution of serine/threonine-specific protein phosphatases in the transcriptional regulation of plasminogen activator and plasminogen activator inhibitor gene expression was explored in human HT-1080 fibrosarcoma and U-937 monocyte-like cells using okadaic acid, a potent and specific inhibitor of phosphatases 1 and 2A (PP1 and PP2A). In both cell types okadaic acid induced plasminogen activator type 2 (PAI-2) gene transcription and mRNA and potentiated induction mediated by phorbol-12-myristate-13-acetate and tumor necrosis factor. Okadaic acid-mediated induction of PAI-2 was inhibited by 8-bromo-cAMP in HT-1080 cells but not in U-937 cells. Okadaic acid had opposite effects on urokinase (u-PA) gene expression in the two cell lines; u-PA mRNA and gene transcription was suppressed in HT-1080 cells but transiently induced in U-937 cells. Tissue-type PA (t-PA) mRNA, although undetectable in U-937 cells, was also suppressed by okadaic acid in HT-1080 cells. This effect was selective, as constitutive and phorbol-12-myristate-13-acetate-mediated expression of plasminogen activator inhibitor type 1 mRNA was not modulated by okadaic acid in either cell type. These results indicate that PP1 and PP2A protein phosphatases are involved in signal transduction pathways modulating PAI-2, u-PA, and t-PA, and furthermore, that okadaic acid interaction with the protein kinase C and A pathways are gene- and cell type-specific.
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PMID:Cell- and gene-specific interactions between signal transduction pathways revealed by okadaic acid. Studies on the plasminogen activating system. 131 13

Hyperthermia is a clinical sign of inflammation and constitutes in itself an adaptive defense mechanism. The fibrinolytic system, a highly regulated proteolytic system, is involved in inflammatory processes. Plasminogen activator inhibitor 1 (PAI-1) is the principal inhibitor of the two activators of the fibrinolytic system: tissue- and urokinase-type PAs (t-PA and u-PA). Our present paper provides the first evidence that hyperthermia can directly induce PAI-1. A moderate heat stress, sufficient to induce heat shock protein 70 mRNA approximately 100-fold, resulted in a two- to three-fold increase in functionally active PAI-1 in the conditioned medium of human HT-1080 fibrosarcoma and Hep G2 hepatoma cells. Exposure of these cells to 42 degrees C led to a similar two-fold and two- to five-fold induction of PAI-1 mRNA expression in HT-1080 and Hep G2 cells, respectively, as has been determined by using both oligo d(T) selected and total RNA preparations. These results suggest that the observed increase in PAI-1 accumulation is due to an induction of PAI-1 biosynthesis. Run-on transcription analysis indicates that the induction of PAI-1 biosynthesis by hyperthermia is mediated by a stimulation of PAI-1 gene transcription. No significant effect of hyperthermia was found on t-PA or u-PA at the level of antigen accumulation, mRNA, and gene transcription in human HT-1080 fibrosarcoma cells. These results point to an additional regulatory mechanism of fibrinolysis in the context of inflammation.
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PMID:Induction of plasminogen activator inhibitor 1 biosynthesis by hyperthermia. 165 90

We have studied the effect of the adenylate cyclase-stimulating agent forskolin on expression of components of the plasminogen activation system in the human fibrosarcoma cell line HT-1080. By enzyme-linked immunosorbent assays, forskolin was found to cause a 2 to 4-fold decrease in intracellular and culture medium levels of type-1 inhibitor of plasminogen activators (PAI-1) and tissue-type plasminogen activator (t-PA). This was true for cells not treated with other agents and for cells, in which the PAI-1 and t-PA levels had been increased 5 to 10-fold by treatment with dexamethasone. This down-regulation could be traced back to corresponding decreases in the cellular levels of PAI-1 and t-PA mRNAs. Of the two PAI-1 mRNAs, the 2.4 kb species was 5-fold decreased by forskolin in cells treated with dexamethasone, while the 3.4 kb transcript was unaffected; in cells not treated with dexamethasone, forskolin affected the two PAI-1 transcripts in parallel. These studies show that in addition to the many inducers of PAI-1, PAI-1 gene expression is also subject to negative modulation by cyclic AMP. They also show that t-PA gene expression, in contrast to the induction by cyclic AMP observed in many other cell lines, may also be subject to negative regulation by cyclic AMP. Thus, hormonal agents acting with cyclic AMP as a second messenger may be involved in down-regulating PAI-1 and t-PA expression in vivo.
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PMID:Forskolin down-regulates type-1 plasminogen activator inhibitor and tissue-type plasminogen activator and their mRNAs in human fibrosarcoma cells. 170 20

Plasminogen activation on the cell surface is regulated by a variety of modulators which balance surface-bound plasminogen activators (PAs) and plasminogen activator inhibitors (PAIs). In this study, we developed as assay system to assess modulation of cell-associated plasminogen activation. Plasmin generation by endogenous plasminogen activators was measured with a combination of exogenously added plasminogen and a chromogenic substrate, S-2251, in the presence of living cells. A cell surface PA activity was quantitated by adopting a rate of plasmin generation. We used HT-1080, a human fibrosarcoma cell line, as representative of cells which have both PAs and PAIs on their cell surface. A basal level of cell surface PA activity was specifically reduced by anti-urokinase-type PA IgG and enhanced by anti-PAI-1 IgG, suggesting that the basal level is determined by a balance between uPA and PAI-1 on the cell surface. We examined effects of dexamethasone and thrombin on cell surface PA activity in the assay system. Dexamethasone appeared to suppress the cell surface PA activity by enhancing de novo synthesis of PAI-1, whereas thrombin suppressed it by inactivating single-chain urokinase-type plasminogen activators. These results indicate that our assay system can be adapted for the screening of various types of PA modulators.
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PMID:An assay system for the modulators of plasminogen activation on the cell surface. 189 67

The effects of dexamethasone on protein synthesis were studied in human fibrosarcoma (HT-1080) cells. Dexamethasone induced a new protein of 46 kD which was rapidly secreted into the medium, while neither progesterone nor estradiol would induce the synthesis of this protein and only a small increase in its amount could be seen in the presence of testosterone. The 46 kD protein was partially purified by ammonium sulfate precipitation and gel filtration and mouse monoclonal antibodies to it were produced in mouse hybrid cells. Altogether 13 positive clones were found, of which six reacted only with native and seven reacted with the unreduced 46 kD protein in Western blotting. It was possible by using polyclonal antibodies to plasminogen activator inhibitor type I (PAI-1) and purified plasminogen activator inhibitor type I to confirm that the 46 kD protein purified and characterized here was PAI-1. In addition, the 46 kD protein clearly inhibited plasminogen activation, thus further confirming that protein isolated was an inhibitor of plasminogen activator. Since the induction of PAI-1 by dexamethasone was very extensive, it is possible that glucocorticoids regulate proteolysis and fibrinolysis in vivo by increasing the amount of the inhibitor of plasminogen activator and thus preventing the activation of plasminogen to plasmin. The reduction of activation of plasminogen to plasmin by glucocorticoid-induced inhibitor could be of great importance, e.g., in various blistering diseases, in metastases from malignant cells, and in the migration of inflammatory cells.
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PMID:Dexamethasone-induced plasminogen activator inhibitor: characterization, purification, and preparation of monoclonal antibodies. 214 2

We have analyzed the role of plasminogen-activator inhibitor type 1 (PAI-1) in the regulation of tumor cell-mediated extracellular matrix degradation. Immunocytochemical analysis revealed PAI-1 associated with microgranular and fibrillar material of the extracellular matrix and demonstrated the presence of PAI-1 as a cell surface-associated antigen. Transforming growth factor beta significantly reduced matrix degradation mediated by HT-1080 human fibrosarcoma cells. This inhibition was correlated with an increase in PAI-1 antigen expression, whereas urinary-type plasminogen activator (u-PA) secretion was unaffected. In this experimental system, PAI-1 regulated extracellular matrix breakdown, as added PAI-1 inhibited matrix solubilization, whereas monoclonal antibodies to PAI-1 increased it. A cell line (LPAI) producing high levels of biologically active PAI-1 was established by transfection of a human PAI-1 cDNA clone into mouse L cells. Coculture experiments demonstrated that LPAI cells prevented matrix degradation by Lu-PA cells (L cells expressing high levels of u-PA) or Co-115 human colon carcinoma cells (expressing tissue-type plasminogen activator). These results indicate that PAI-1 may play a critical role in the regulation of extracellular matrix degradation during tumor cell invasion.
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PMID:Plasminogen-activator inhibitor type 1 is a potent natural inhibitor of extracellular matrix degradation by fibrosarcoma and colon carcinoma cells. 216 14

Tumor necrosis factor-alpha (TNF-alpha) was found to induce type-1 plasminogen activator inhibitor (PAI-1) antigen in the human fibrosarcoma cell line HT-1080, and PAI-1 and urokinase-type plasminogen activator (u-PA) antigens in the human carcinoma cell line T-CAR1; tissue-type plasminogen activator (t-PA) antigen was not affected or slightly decreased. The effects in HT-1080 and T-CAR1 cells were preceded by increases in the cellular levels of the corresponding mRNAs. Cycloheximide caused an increase of PAI-1 mRNA in T-CAR1 cells, but not in HT-1080 cells; during this increase the relative abundance of the two PAI-1 mRNA species, of 2.3 kb and 3.4 kb, respectively, changed strongly in favor of the longer transcript. We conclude that TNF-alpha may affect proteolytic activity in the microenvironment of cells in malignant tumors by affecting gene expression of u-PA and PAI-1.
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PMID:Tumor necrosis factor-alpha regulates mRNA for urokinase-type plasminogen activator and type-1 plasminogen activator inhibitor in human neoplastic cell lines. 250 Nov 20

A cosmid (cos pUK0322) harboring the complete human urokinase-type plasminogen activator (u-PA) gene and Geneticin resistance as a selectable marker was isolated from a human genomic library and characterized. After transfection of cos pUK0322 into mouse L cells and selection, several plasminogen activator (PA)-expressing clones were obtained and one (LuPA) was chosen for additional study. The PA expressed was identical to human pro-u-PA in enzymatic, electrophoretic, and antigenic properties. The expression of PA was stable over 50 population doublings. The regulation of the transfected gene was studied by treatment of the cells with various hormones and other effectors. Expression of PA activity was inhibited fivefold by dexamethasone and stimulated two- to threefold by agonists of the adenylate cyclase dependent pathway of signal transduction, such as dibutyryl cyclic AMP and cholera and pertussis toxins. The modulation of PA activity was associated with corresponding changes in mRNA steady-state levels. The phenotypic changes associated with pro-u-PA expression were analyzed in vitro by degradation of 3H-labeled extracellular matrix (ECM), invasion of a matrigel basement membrane analogue, and by light and electron microscopy. LuPA cells and reference HT-1080 fibrosarcoma cells, in contrast to control Lneo cells transfected with the neomycin resistance gene, degraded the ECM and invaded the matrigel basement membrane. Matrix degradation correlated with the modulation of pro-u-PA gene expression as it was inhibited by dexamethasone and promoted by dibutyryl cyclic AMP. Inhibition of PA or plasmin using anti-u-PA IgG or aprotinin prevented ECM degradation and invasion. These results demonstrate that u-PA expression alone is sufficient to confer to a cell an experimental invasive phenotype.
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PMID:Mouse L cells expressing human prourokinase-type plasminogen activator: effects on extracellular matrix degradation and invasion. 250 27

We have studied the regulation by glucocorticoids and dibutyryl cAMP of the amounts of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and a Mr approximately 54000 plasminogen activator inhibitor accumulated in serum-free conditioned culture fluid by a human fibrosarcoma, a human glioblastoma and a human melanoma cell line (HT-1080, UCT/gl-1 and Bowes). For the quantitation of u-PA and t-PA, we used sandwich-type ELISA with a combination of polyclonal and monoclonal antibodies. For an estimation of variations in the amount of the inhibitor, we used sodium dodecyl sulphate-polyacrylamide gel electrophoresis followed by Coomassie blue staining of conditioned culture fluid proteins, the inhibitor protein band being identified by its selective removal by passage of the conditioned culture fluids through a column with monoclonal antibodies against the inhibitor. The modulation of the 3 proteins by the hormonal agents varied greatly between the cell lines. The proteins were independently regulated, in the sense that the hormonal agents did not concomitantly change their levels in the direction expected either to increase or decrease total extracellular plasminogen activator activity. In conditioned culture fluids containing both t-PA and inhibitor, the two were present in the medium as a Mr approximately 120 000 complex. In contrast, no u-PA inhibitor complexes were found in conditioned culture fluid from any of the cell lines; this is likely to be due to the occurrence of u-PA in the culture fluid in the one-chain proenzyme form, which, unlike active u-PA, does not react with the inhibitor. These findings illustrate the complexity of the regulation of extracellular plasminogen activator activity, and imply that the presumed functional diversity of u-PA and t-PA may be related to their independent regulation.
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PMID:Hormonal regulation of extracellular plasminogen activators and Mr approximately 54,000 plasminogen activator inhibitor in human neoplastic cell lines, studied with monoclonal antibodies. 301 58

An approximately 75% pure form of a human Mr approximately 54,000 plasminogen activator inhibitor from conditioned culture fluid of the fibrosarcoma cell line HT-1080 was obtained by a single step of chromatography on concanavalin A-Sepharose. The inhibitor inhibited human urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator, but not plasmin. Rabbit antibodies against this plasminogen activator inhibitor also reacted with a plasminogen activator inhibitor with identical electrophoretic mobility in extracts of human blood platelets, indicating that the HT-1080-inhibitor is of the same type as the inhibitor of blood platelets. As revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by fibrin-agarose zymography, incubation of HT-1080-inhibitor with the active form of human u-PA led to the formation of an equimolar sodium dodecyl sulfate-resistant complex between them; in contrast, no complex formation was observed between the inhibitor and the proenzyme form of human u-PA (pro-u-PA). Likewise, using a column of anti-inhibitor antibodies coupled to Sepharose for removal of excess inhibitor and activator-inhibitor complexes, the potential enzymatic activity of pro-u-PA was found to be unaffected by incubation with inhibitor under conditions in which more than 95% of the active u-PA had formed complex with inhibitor.
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PMID:Plasminogen activator inhibitor from human fibrosarcoma cells binds urokinase-type plasminogen activator, but not its proenzyme. 308 13


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