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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

How heparin inhibits vascular smooth muscle cell proliferation and migration has not been established. We have investigated the hypothesis that heparin inhibits vascular smooth muscle cell proliferation and migration by interfering with the expression and activity of proteases such as plasminogen activators. In an in vitro mitogenesis model, tissue-type plasminogen activator (tPA) mRNA and protein increase in baboon smooth muscle cells stimulated with fetal bovine serum or phorbol esters. Heparin inhibits smooth muscle cell proliferation and suppresses the induction of tPA mRNA and protein while it has little effect on the mRNA of urokinase-type plasminogen activator, plasminogen activator inhibitor type I, and a number of genes that are also modulated by serum and phorbol esters. The inhibitory effect on tPA mRNA is specific to heparin-like molecules and does not depend on the anticoagulation activity of heparin. The increase in tPA mRNA is due to increased transcription, which is suppressed by heparin. The induction of tPA by serum and phorbol esters is diminished by protein kinase C inhibitors such as H7 or staurosporine and by protein kinase C depletion. Since heparin suppresses the induction of the tPA gene by phorbol esters, these results suggest that heparin may interfere with the protein kinase C pathway.
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PMID:Heparin selectively inhibits the transcription of tissue-type plasminogen activator in primate arterial smooth muscle cells during mitogenesis. 131 Jun 87

Heparin is a potent inhibitor of arterial smooth muscle cell (SMC) migration and proliferation in vivo and in vitro. We propose that heparin affects these SMC functions by interfering with either the expression or the activity of secreted proteases required for cell movement. We have reported that heparin selectively inhibits the expression of tissue-type plasminogen activator in SMCs during mitogenesis. In this study we show that the gene expression of another kind of protease, interstitial collagenase, is induced by fetal bovine serum and is also suppressed by heparin. The inhibitory effect on the induced collagenase mRNA is specific to heparin-like molecules and does not depend on the anticoagulant activity of heparin. The induction of the collagenase gene depends on the protein kinase C pathway, since it can be induced by phorbol esters such as phorbol 12-myristate 13-acetate and blocked by inhibitors such as H-7 and staurosporine. In transient transfection assays with chloramphenicol acetyltransferase constructs containing the phorbol ester-responsive element introduced into baboon SMCs, heparin inhibits transcription induced by serum or phorbol 12-myristate 13-acetate. These results support the conclusion that, in primate SMCs, interstitial collagenase gene transcription mediated by the phorbol ester-responsive element is blocked by heparin.
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PMID:Heparin inhibits collagenase gene expression mediated by phorbol ester-responsive element in primate arterial smooth muscle cells. 131 15

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

We investigated the effect of phorbol myristate acetate (PMA), dexamethasone (Dex) and reagents which raise intracellular cyclic AMP, on the production of plasminogen activator inhibitor type-2 (PAI-2) in human promyelocytic leukemia cell line, PL-21 and on the production of urinary type plasminogen activator (u-PA) in human pre-B cell lymphoma cell line, RC-K8. Cells were cultured in fetal bovine serum free RPMI-1640 containing the test-reagents for 48 hours. PAI-2 and u-PA antigens were measured by ELISA kits. PMA, an activator of protein kinase C (PKC), markedly increased both PAI-2 and u-PA production in each cell line. On the other hand, cAMP increased PAI-2 production in PL-21 cells, but decreased u-PA synthesis in RC-K8 cells. Similar to cAMP, Dex also increased PAI-2 production but decreased u-PA production in RC-K8 cells. Moreover, PMA and cAMP synergistically increased the PAI-2 production. This was verified by Western blot, using a monoclonal antibody against the PAI-2. These two cell lines are, therefore, useful for clarifying the role of A kinase and C kinase on PAI-2 and u-PA synthesis in human hemopoietic cells.
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PMID:[Effect of cyclic AMP and phorbol ester on PAI-2 synthesis in a leukemic cell line PL-21 and on u-PA secretion in a pre-B cell lymphoma cell line RC-K8]. 131 13

Two plasminogen activators (PAs): tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), as well as the type-1 plasminogen activator inhibitor (PAI-1) are synthesized and secreted by rat astrocytes. Preliminary studies suggest that PA activity plays a role in astrocyte development and differentiation. We have examined the regulation of the PA system by the cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) in purified rat astrocyte cultures. PKA activity was increased by exposing cultured astrocytes to forskolin or dibutyryl cyclic AMP, whereas PKC activity was stimulated with phorbol-12-myristate 13-acetate (PMA). Activation of both second-messenger pathways produced a time- and dose-dependent increase in the total PA activity. However, based on SDS-PAGE/zymography we found that forskolin increased t-PA activity and reduced u-PA activity, whereas PMA treatment caused a significant increase in u-PA activity without altering t-PA activity. Reverse zymography analysis revealed that astrocyte PAI-1 activity is decreased by forskolin and increased by PMA. Together, these results demonstrate that the components of the PA system in rat astrocytes are independently and reciprocally regulated by PKA and PKC. Our findings raise the possibility that the plasminogen activator system could be involved in some of the actions of growth factors and/or neuromodulators that modulate PKC or PKA in astrocytes.
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PMID:Regulation of plasminogen activators and type-1 plasminogen activator inhibitor by cyclic AMP and phorbol ester in rat astrocytes. 133 67

We have previously shown that alpha-thrombin exerted a mitogenic effect on human glomerular epithelial cells and stimulated the synthesis of urokinase-type (u-PA) and tissue-type plasminogen activator (t-PA) and of their inhibitor, plasminogen activator inhibitor 1 (PAI-1). In the present study, we investigate the signal transduction mechanisms of thrombin in these cultured cells. Thrombin induced an increase in intracellular free calcium concentrations ([Ca2+]i) in a dose-dependent manner, a plateau being reached at 1 U/ml thrombin. A 60% inhibition of this effect was produced by 300 nM nicardipine, a dihydroperidine agent, or by 4 mM EGTA, indicating that increase in [Ca2+]i was due in part to extracellular Ca2+ entry through L-type voltage-sensitive calcium channels. Thrombin also induced an increase in inositol trisphosphate (IP3), suggesting that phospholipase C activation and phosphatidylinositides breakdown were stimulated. Interestingly thrombin-stimulated cell proliferation measured by 3H thymidine incorporation was inhibited by 300 nM nicardipine, and restored by addition of 10(-8) M ionomycin, indicating that calcium entry was critical for the mitogenic signal of thrombin. Conversely, nicardipine did not modify thrombin-stimulated synthesis of u-PA, t-PA, and PAI-1. Both thrombin-stimulated cell proliferation and protein synthesis required protein kinase C activation since these effects were blocked by 10 microM H7, an inhibitor of protein kinases, and by desensitization of protein kinase C by phorbol ester pretreatment of the cells. Interestingly, DFP-inactivated thrombin which binds the thrombin receptor and gamma-thrombin, which has some enzymatic activity but does not bind to thrombin receptor, had no effect when used alone. Simultaneous addition of these two thrombin derivatives had no effect on [Ca2+]i, and 3H thymidine incorporation but stimulated u-PA, t-PA, and PAI-1 synthesis although to a lesser extent than alpha-thrombin. This effect also required protein kinase C activation to occur, presumably by a pathway distinct from phosphoinositoside turnover since it was not associated with IP3 generation. In conclusion, multiple signalling pathways can be activated by alpha-thrombin in glomerular epithelial cells: 1) Ca2+ influx through a dihydroperidine-sensitive calcium channel, which seems critical for mitogenesis; 2) protein kinase C activation by phosphoinositide breakdown, which stimulates both mitogenesis and synthesis of u-PA, t-PA, and PAI-1; 3) protein kinase C activation by other phospholipid breakdown can stimulate u-PA, t-PA, and PAI-1 synthesis but not mitogenesis.
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PMID:Thrombin signal transduction mechanisms in human glomerular epithelial cells. 153 79

Human mesangial cells in culture synthesize and secrete plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator (t-PA). Phorbol myristate acetate (PMA), a known activator of protein kinase C, induces a three to four-fold increase in t-PA and PAI-1 release over a period of 24 h, whereas cell-associated t-PA and PAI-1 levels remain relatively stable. A similar effect is obtained with oleylacetyl glycerol, a more physiologic protein kinase C activator. The effect of PMA is suppressed in the presence of H7, an inhibitor of cellular protein kinases, and by cycloheximide and actinomycin D, indicating a requirement for de novo protein and RNA synthesis, respectively. Northern blot analysis of PMA-treated cells reveals a rapid and transient increase in PAI-1 mRNA reaching a maximum after 4-8 h, whereas increase in t-PA mRNA levels requires 24 h. Activation of protein kinase A by addition of 8-bromocyclic AMP (8-bromo cAMP) has no significant effect on PAI-1 release but inhibits the PMA-mediated increases in PAI-1 antigen and mRNA. Addition of 8-bromo cAMP alone does not affect t-PA release. When added to PMA-stimulated cells, 8-bromo cAMP inhibits t-PA release in a dose-dependent manner, but causes a superinduction of t-PA mRNA. 8-bromo cAMP also induces a decrease in PMA-stimulated intracellular t-PA release. Similar inhibition is observed after stimulation of endogenous adenylate cyclase with prostaglandin E1 or isoproterenol. This indicates that protein kinase A activation may inhibit PMA-stimulated t-PA release via a post-transcriptional effect, e.g. inhibition of protein synthesis or activation of protein degradation. In conclusion, hormones or mediators which activate protein kinase C can stimulate t-PA and PAI-1 synthesis in human mesangial cells. Protein kinase A activation has no effect on the basal release of PAI-1 and t-PA by human mesangial cells, and, in contrast to endothelial cells, it inhibits both PMA-stimulated PAI-1 and t-PA releases. This cell-specific regulation of t-PA and PAI-1 seems to be mediated by differential transcriptional and post transcriptional mechanisms.
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PMID:Cell-specific regulation of plasminogen activator inhibitor 1 and tissue type plasminogen activator release by human kidney mesangial cells. 155 43

Transfection of mouse Y1 adrenal tumor cells with DNA encoding mutant type I regulatory subunit generated stable transformants in which the basal activity of cAMP-dependent protein kinase was repressed. As expected, steroidogenesis in these kinase-deficient cells was no longer stimulated by corticotropin or cAMP analogues, and the expression of three cAMP-regulated genes (ornithine decarboxylase, urokinase-type plasminogen activator, and P450 side-chain cleavage) could no longer be induced. However, in addition to the loss of hormone responsiveness, the basal level of steroidogenesis and the constitutive expression of these cAMP-inducible genes was also repressed in kinase-defective mutant clones. To verify that functional cA-PK would revert this repressed phenotype, we transfected a cA-PK defective subclone of Y1 cells, Kin 8, with DNA encoding the C alpha and C beta subunits of cAMP-dependent protein kinase. Basal levels of steroid production were restored to normal in stable transformants, and the elevation of kinase activity following induction of the C-subunit expression vectors elicited a steroidogenic response. Gene transcription was also shown to be regulated by either C alpha or C beta as measured by the induction of plasminogen activator and ornithine decarboxylase mRNA levels and transcription rates. The dominant role played by cAMP-dependent protein kinase in these adrenal cells was demonstrated by experiments showing the regulation of ornithine decarboxylase gene expression by protein kinase C requires basal cAMP-dependent protein kinase activity.
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PMID:Cyclic AMP-dependent protein kinase controls basal gene activity and steroidogenesis in Y1 adrenal tumor cells. 156 25

Activation of protein kinase C leads to a strong induction of tissue-type plasminogen activator (t-PA) expression in endothelial cells. Using endothelial cells from human umbilical vein (HUVECs) and human aorta (HAECs), we have studied this regulation of t-PA and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), at the mRNA level and have compared their induction with the expression of platelet-derived growth factors A and B (PDGF-A and PDGF-B) and the proto-oncogenes c-jun and c-fos. Treatment of HUVECs with exogenous bacterial phospholipase C or the synthetic diacylglycerol 1-oleoyl-2-acetylglycerol led to a threefold and a twofold increase, respectively, in t-PA concentrations in 24-hour-conditioned medium. Similarly, the more stable protein kinase C activator 4 beta-phorbol-12-myristate-13-acetate (PMA) caused about a 10-fold increase in t-PA antigen levels. This effect of PMA is maximal between 8 and 16 hours at a concentration of 10 nM and is fully accounted for by parallel increases in t-PA mRNA levels. An increase in intracellular cyclic adenosine monophosphate levels by forskolin (10 microM) slightly diminished t-PA expression but further enhanced the PMA-induced increases in t-PA synthesis and mRNA levels by at least twofold. PMA also enhanced the mRNA levels of two other important endothelium-expressed genes, PDGF-A and PDGF-B, with a time profile similar to that of t-PA, with peak values about fivefold higher than control values. Forskolin did not further stimulate this PMA-induced PDGF expression in HUVECs, which suggests a regulatory mechanism different from that of t-PA. Qualitatively very similar induction patterns of t-PA, PDGF-A, and PDGF-B were seen with HAECs. In contrast to t-PA and PDGF, PAI-1 mRNA and antigen levels increased only slightly after PMA treatment of HUVECs or HAECs; forskolin alone or in combination with PMA diminished the expression of PAI-1. The induction of t-PA mRNA by PMA was dependent on protein synthesis and was preceded by a strong transient increase in c-jun and c-fos mRNA levels; the induction of c-fos but not of c-jun was potentiated by forskolin. Because the products of these two proto-oncogenes form dimeric complexes for which specific binding sites are present in the t-PA promoter region, they may mediate the protein kinase C-dependent increase in t-PA gene expression, including the stimulating action of cyclic adenosine monophosphate.
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PMID:Role of protein kinase C and cyclic adenosine monophosphate in the regulation of tissue-type plasminogen activator, plasminogen activator inhibitor-1, and platelet-derived growth factor mRNA levels in human endothelial cells. Possible involvement of proto-oncogenes c-jun and c-fos. 164 85

Epidermal growth factor (EGF) induces tissue-type plasminogen activator (t-PA) biosynthesis in HeLa cells. Based on nuclear run-on transcription assays, t-PA biosynthesis is modulated by EGF on the level of gene transcription. The effect of EGF is slow, requiring 4-8 h to induce t-PA gene transcription and up to 24 h to induce t-PA mRNA and antigen secretion. An additive response is observed when cells are treated with both phorbol 12-myristate 13-acetate and EGF, suggesting that the two pathways converge and act independently to implement their respective effects. cAMP has previously been shown to potentiate phorbol 12-myristate 13-acetate-mediated induction of t-PA biosynthesis in HeLa cells and in human endothelial cells. Akin to this observation, cAMP also potentiates the EGF-mediated increase in t-PA mRNA. Maximal levels of t-PA mRNA is seen in the presence of all three agonists. The regulation of t-PA by EGF alone and in the presence of either PMA or cAMP is consistent with a role of t-PA during growth and development, and further indicates a functional interplay between protein kinase C-, tyrosine kinase, - and cAMP-dependent signal transduction pathways during regulation of t-PA gene expression.
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PMID:Regulation of human tissue-type plasminogen activator gene transcription by epidermal growth factor and 3',5'-cyclic adenosine monophosphate. 166 1


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