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

The regulation of tissue-plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) synthesis was studied in cultured human mesothelial cells derived from omentum (HOMC). Heparin (100 U/ml) as well as pentosan polysulfate (300 micrograms/ml) stimulated tPA synthesis by HOMC 2.9-4.5-fold. Heparin-induced tPA production was dose- and time-dependent and was inhibited by cycloheximide. tPA production by HOMC was also stimulated by phorbol 12-myristate 13-acetate (2.6-fold), fibrin clots (1.9-fold), or batroxobin (1.9-fold). Heparin and pentosan polysulfate did not stimulate PAI-1 production by HOMC, while phorbol 12-myristate 13-acetate (100 nM) increased the concentration of PAI-1 in the conditioned medium by 2.6-fold over 24 h. The interaction of heparin with HOMC was studied by direct binding experiments. Dose-dependent specific binding of biotinylated heparin to HOMC was saturable at about 10 micrograms/ml, the KD was estimated to about 0.15 microM. Biotinylated heparin bound rapidly to HOMC and reached a plateau within 60 min. Unlabeled heparin as well as pentosan polysulfate inhibited binding of biotinylated heparin in a dose-dependent fashion. These data demonstrate that heparin interacts with HOMC, and increases the fibrinolytic capacity in these cells by selectively increasing the production of tPA.
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PMID:Heparin stimulates fibrinolysis in mesothelial cells by selective induction of tissue-plasminogen activator but not plasminogen activator inhibitor-1 synthesis. 212 72

Tissue-type plasminogen activator (PA) activity and antigen was measured in nine different tissues from healthy rats (brain, lung, heart, liver, spleen, kidney, adrenal, aorta and skeletal muscle). After extraction in a KSCN buffer (for kidney) or in an acid acetate buffer (for all other tissues), total PA activity was determined by an improved spectrophotometric procedure, and tissue-type PA (tPA) activity was determined by quenching with anti-rat tPA Ig; tPA antigen was determined by an ELISA procedure. tPA was the major PA (greater than 90%) in all tissues, except kidney and liver (65%) and spleen (40%). Lung yielded the highest tPA activity (1400 U/g), followed by kidney, brain, heart and adrenal (150-300 U/g), and then by liver, aorta, spleen and muscle (15-30 U/g). In agreement with fibrin autographic studies, which demonstrated the presence of tPA-PAI complexes in the tissue extracts, the tPA antigen/activity ratio was generally greater than one. Free PA inhibitor activity could not be demonstrated in any tissue.
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PMID:Distribution of tissue-type plasminogen activator (activity and antigen) in rat tissues. 213 39

The transplacental effect of lead compounds (lead acetate and tetraethyl lead) on the tissue plasminogen activator activity (PAA), plasminogen activator inhibition (PAI) and plasmin inhibition (PI) was studied in the rat. The concentration of lead in organs of the newborn showed a great variation; the distribution of lead in the organs studied depended on the dose and the stage of gestation at injection. In each organ the concentration of lead was dose-dependent. In control specimens no lead could be detected. The tissue response of PAA, PAI and PI to the lead compounds also showed a great variation; however, there was no correlation between lead concentrations and PAA, PAI or PI responses. Changes of one or more of the parameters studied (PAA, PAI or PI) were noticed in lungs, liver, heart, brain and kidneys. The PAA was due to the tissue type plasminogen activator in all organs studied; in kidneys and lungs the urokinase type of plasminogen activator was also detected. Therefore, fetal tissue PAA, PAI and PI can be affected transplacentally by lead compounds.
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PMID:Transplacental effect of lead compounds on tissue plasminogen activator activity, plasminogen activator inhibition and plasmin inhibition. 214 47

Secretion of urokinase-type plasminogen activator (uPA) by chicken embryo fibroblasts (CEF) is increased approximately 50-fold following transformation by Rous sarcoma virus (RSV). Using a cloned and fully sequenced chicken uPA cDNA probe, we have established that this increase in plasminogen activator production can be largely accounted for by an increase in cellular uPA mRNA. CEF contained on average less than 1 molecule of uPA mRNA/cell, whereas RSV-CEF contained 25-60 molecules/cell. The increase in cellular uPA mRNA levels was dependent on the activity of the RSV-encoded transforming protein, protein-tyrosine kinase pp60v-src. Cells infected with an RSV mutant encoding a temperature-sensitive form of the src protein (ts-NY68) contained low uPA mRNA levels when cultured at the nonpermissive temperature and high uPA mRNA levels when maintained at the permissive temperature. Temperature shift studies with tsNY68-CEF demonstrated that changes in pp60v-src activity rapidly altered uPA mRNA levels; the uPA mRNA content of total RNA extracts increased and decreased with half-time kinetics of 3-5 h. Serine/threonine-specific protein kinases also appear to modulate uPA mRNA levels in CEF cultures. Exposure of CEF and RSV-CEF for 24 h to the protein kinase C activating agent phorbol myristate acetate (PMA) increased cellular uPA mRNA levels to 20 and 260 molecules/cell, respectively. These data are consistent with the previously observed synergism between RSV and PMA in increasing plasminogen activator secretion. Nuclear run-on transcription analyses established that both RSV and PMA increase cellular uPA mRNA levels by way of increased uPA gene expression.
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PMID:Plasminogen activator gene expression is induced by the src oncogene product and tumor promoters. 215 28

Urokinase-type plasminogen activator (uPA) binds to a specific receptor on various cell types, the bound molecule retaining its enzymatic activity against plasminogen. We have now investigated whether receptor-bound uPA also retains the ability to react with and be inhibited by plasminogen activator inhibitors (PAI-1 and PAI-2). uPA bound to its receptor on human U937 monocyte-like cells was inhibited by PAI-1 (in its active form in the presence of vitronectin fragments) with an association rate constant of 4.5 x 10(6) M-1 s-1, which was 40% lower than that obtained for uPA in solution (7.9 x 10(6) M-1 s-1). The inhibition of uPA by PAI-2 was decreased to a similar extent by receptor binding, falling from 5.3 x 10(5) to 3.3 x 10(5) M-1 s-1. Stimulation of U937 cells with phorbol 12-myristate 13-acetate was accompanied by a further reduction in receptor-bound uPA inhibition by PAI-1 and PAI-2 to 1.7 x 10(6) and 1.1 x 10(5) M-1 s-1, respectively. These constants although lower than those for uPA in solution still represent rather rapid inhibition of the enzyme, and demonstrate that uPA bound to its specific cellular receptor remains available for efficient inhibition by PAI's, which may therefore play a major role in controlling cell-surface plasminogen activation and extracellular proteolytic activity.
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PMID:Inhibition of receptor-bound urokinase by plasminogen-activator inhibitors. 216 46

Tissue-type plasminogen activator (t-PA) gene expression is regulated by the tumor-promoting phorbol ester, phorbol-12-myristate 13-acetate (PMA), by cyclic AMP analogues, and the cAMP agonist, forskolin. Based on nuclear "run-on" transcription assays, t-PA expression is modulated by PMA on the level of transcription. 8-Bromo-cyclic AMP and forskolin do not induce t-PA gene transcription alone but act synergistically with PMA. These effects are confirmed by transient expression assays in HeLa cells employing deletion mutants of the t-PA gene promoter fused to the chloramphenicol acetyltransferase (CAT) reporter gene. Constitutive expression and most of the PMA-mediated induction requires sequences downstream of position -145. DNase I protection ("footprint") analysis of this region reveals two protein-binding sites: one between position -102 and -115, differing from the consensus sequence of the cAMP-responsive element (CRE) by the substitution of an adenine for a guanine in the middle of the core motif (TGACATCA), and another, located in the first exon (between position +60 and +74), displaying homology to the consensus sequence of the activator protein 2- (AP-2) binding site (CCCCACCCCC). Base substitutions in the core of either the CRE-like element or the AP-2 site suppress constitutive CAT expression by over 80%, whereas the relative PMA- and PMA plus cAMP-mediated responses are retained. CAT expression is below the detection limit when both elements are mutagenized together. Hence, the CRE-like element and the exon-located AP-2-binding site have a cooperative impact on basal transcription, but each element can independently convey the effect of activators of the protein kinase C- and A-dependent pathways of signal transduction. The results of band-shift analysis and competition titration experiments demonstrate that the CRE-like element acts as a low affinity binding site for the same proteins which recognize the authentic CRE.
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PMID:A DNA motif related to the cAMP-responsive element and an exon-located activator protein-2 binding site in the human tissue-type plasminogen activator gene promoter cooperate in basal expression and convey activation by phorbol ester and cAMP. 216 21

The hormonal regulation of the human urokinase type plasminogen activator (uPA) gene has been studied by introducing into mouse and rat Sertoli cell primary cultures a recombinant plasmid, in which the transcription regulatory elements of the cloned human uPA gene drive the expression of the bacterial chloramphenicol-acetyl-transferase gene. It was found to be expressed and regulated by FSH and (Bu)2cAMP in the mouse cells only, in agreement with data on the expression of the endogenous gene in rat and mouse gonads. The stimulation of transcription by FSH was evident in cultures from 13-day-old but not from 18-day-old mice, even though (Bu)2cAMP induction could be observed at both ages. Phorbol-myristate acetate was found to activate the human uPA promoter in Sertoli cell cultures from mice of both ages, even though the effect was less evident in cultures of 18-day-old animals. Deletion analysis of the human uPA 5'-flanking region showed that the distal enhancer element is not needed for (Bu)2cAMP induction, and that at least two promoter regions are involved in (Bu)2cAMP induced transcription. One of these cAMP responsive regions lies between nucleotides -72 and -29 from the CAP site. The sequence of this region would suggest the binding of transcription factor AP-2, a cell-specific mediator of both cAMP and phorbol esters action on gene expression. However, these sequences do not mediate phorbol ester activation of human uPA promoter in mouse Sertoli cells.
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PMID:Follicle-stimulating hormone and cyclic AMP induce transcription from the human urokinase promoter in primary cultures of mouse Sertoli cells. 217 96

Human neuronal brain cultures established from 12- and 14-week-old fetuses synthesize and secrete urokinase-type plasminogen activator (uPA) and limited amounts of tissue-type plasminogen activator (tPA). These cells also produce and secrete the endothelial cell-type PA inhibitor (PAI-1), which forms sodium dodecyl sulfate-stable tPA/PAI-1 complexes in the culture medium. Immunocytochemistry shows a predominant localization of uPA, tPA, and PAI-1 in neuronal cells, with only a very weak positivity detectable in the few glial cells present in these cultures. The protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulates the synthesis of both uPA and PAI-1, resulting in a final increase in the plasmin-generating capacity of neuronal cell cultures. No significant effect is observed, however, when cells are treated with the TPA analogue 4 alpha-phorbol 12,13-didecanoate, which is inactive as a PKC inducer, or with the neurotrophic polypeptide basic fibroblast growth factor. These data represent the first characterization of the plasmin-generating system in human fetal brain neurons and suggest a role for PKC in the modulation of uPA and PAI-1 synthesis.
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PMID:Synthesis of urokinase-type plasminogen activator and of type-1 plasminogen activator inhibitor in neuronal cultures of human fetal brain: stimulation by phorbol ester. 221 17

We studied blood coagulation and fibrinolysis in 19 patients during surgery with cardiopulmonary bypass (CPB). CPB was performed with a rotating pump and a membrane oxygenator. Heparinization was achieved with heparin 3 mg.kg-1 and the ACT value was kept above 400 seconds throughout the CPB. Heparin was neutralized by protamine at a ratio of 1:1-1.5 of the total amount of heparin. Blood was collected four times from an indwelling arterial line. We obtained the first sample immediately after induction of anesthesia, the second sample before heparinization, the third sample before protamine administration, and the fourth sample at the end of the operation. FPA, FPB beta 15-42, alpha 2PI-Pl-C, D-dimer, and the t-PA activity were measured. A statistically significant elevation of FPA was observed during the operation. FPB beta 15-42, alpha 2PI-Pl-C, and the D-dimer rose significantly immediately after the beginning of the CPB and these elevations continued until the end of the operation. The t-PA activity was elevated significantly only during the CPB. In conclusion, the t-PA is released from the endothelial cells during CPB by some undetermined mechanism (primary fibrinolysis). Then, plasmin is generated by the t-PA and this dissolves the fibrin clots formed by thrombin before the beginning of the CPB (secondary fibrinolysis). Enhanced fibrinolytic activity before and after the CPB is physiological secondary fibrinolysis.
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PMID:[Increased fibrinolytic activity during surgery with cardiopulmonary bypass]. 238 94

A crucial event during angiogenesis is the invasion of the perivascular extracellular matrix by sprouting endothelial cells. To investigate the possible role of proteases in endothelial cell invasiveness in vitro, bovine microvascular endothelial cells (BMEC) grown on collagen gels were treated with phorbol myristate acetate (PMA), a tumor promoter that markedly increases their production of collagenase and plasminogen activator. Whereas control BMEC were confined to the surface of the gels, PMA-treated BMEC invaded the underlying collagen matrix, where they formed an extensive network of capillary-like tubular structures. This phenomenon, which mimics some of the events occurring during angiogenesis in vivo, required protein synthesis and intercellular contact, was accompanied by collagen degradation, and was prevented by the metalloprotease inhibitor 1,10-phenanthroline.
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PMID:Tumor-promoting phorbol esters induce angiogenesis in vitro. 241 23


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