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 formation and release of covalent complexes between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) limits the application of equilibrium radioligand binding analysis to characterize the interaction between t-PA and human umbilical vein endothelial cell (HUVEC) monolayers. To avoid this difficulty, we used a recombinant mutant of t-PA, S478A rt-PA, in which alanine has been substituted for the active-site serine. Although the mutant is incapable of covalently reacting with PAI-1, 125I-labeled S478A rt-PA binding to HUVEC monolayers is specific and reversible and is characterized by a high affinity (Kd of 1.5 nM) and a large number of sites (1.5 x 10(6)/cell). This binding was shown to occur through noncovalent interaction with PAI-1 in the HUVEC monolayer by the fact that a monoclonal anti-PAI-1 antibody (MA-7D4) completely blocked S478A rt-PA binding. Two solution-phase assays with recombinant PAI-1 (rPAI-1) confirmed this noncovalent interaction: complexes between 125I-S478A rt-PA and rPAI-1 could be isolated by immunoprecipitation with anti-PAI-1 antibodies, and S478A rt-PA competed with rt-PA for inactivation by rPAI-1. In contrast diisopropylphosphate rt-PA (in which the active site serine is chemically modified) showed minimal binding to HUVEC monolayers, as a result of impaired interaction with PAI-1, in the two assays. Thus, both wild-type rt-PA and S478A rt-PA interact with the HUVEC monolayer through PAI-1. With rt-PA this results in the formation of covalent rt-PA.PAI-1 complexes that are released from the monolayer into the supernatant. With S478A rt-PA this results in the formation of noncovalent complexes that remain associated with the HUVEC monolayer, thereby identifying a large pool of reactive PAI-1 molecules in the monolayer.
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PMID:Binding of tissue-type plasminogen activator with human endothelial cell monolayers. Characterization of the high affinity interaction with plasminogen activator inhibitor-1. 210 30

In contrast to most other serine proteases, tissue-type plasminogen activator (t-PA) possesses enzymatic activity as the one-chain zymogen form. The hypothesis that lysine residues 277 or 416 may be involved in stabilization of an active conformation of one-chain t-PA via salt-bridge formation with aspartic acid residue 477 was tested by site-directed mutagenesis. Four recombinant t-PA mutants were constructed. The amidolytic activities of these analogues were compared to that of authentic t-PA. Substitution of arginine-275 provided an analogue [( R275G]t-PA) resistant to plasmin cleavage. The amidolytic activity of [R275G]t-PA was comparable to that of authentic one-chain t-PA, and so was the activity of [R275L,K277L]t-PA, in which additional substitution of lysine residue 277 was carried out. This suggested that its presence was nonessential for obtaining one-chain t-PA activity. In contrast, substitution of lysine residue 416 to obtain [K416S]t-PA and [K416S,H417T]t-PA resulted in substantial quenching of amidolytic one-chain activity. As expected, the amidolytic activities of the two-chain forms were less affected by the substitution. Involvement of lysine residue 416 in one-chain t-PA activity was also indicated by decreased activities of [K416S]t-PA and [K416S,H417T]t-PA with plasminogen as the substrate. The one-chain activity of the lysine residue 416 substitution analogues was partially restored in the presence of fibrin. This could indicate that strong ligands such as fibrin might provide an alternative stabilization of the active conformation of one-chain t-PA.
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PMID:Quenching of the amidolytic activity of one-chain tissue-type plasminogen activator by mutation of lysine-416. 211 46

Increasing attention is being paid to alterations of the hemostatic balance in tumors, in general, and brain tumors, in particular. Apparently divergent results, showing excess fibrinolysis (i.e., increased plasminogen activator activity) or its inhibition (i.e., increased inhibitor activity), have been reported. The 9L rat brain tumor is a gliosarcoma and a model used to study treatment paradigms for human gliomas. To study the roles of fibrin and fibrinolysis in this brain tumor model, we used these features to investigate the nature of the plasminogen activator (PA) and thrombin inhibitors in normal rat brain and in the 9L rat brain tumor, growing both in vitro and in vivo in rat brain. The results indicate that cells cultured from the tumor in vitro express PA inhibitory activity which is both of the protease nexin I and PA inhibitor 1 types. However, the serpin PA inhibitory activity in extracts of both the normal brain and tumor is of the protease nexin I/PA inhibitor 3 type. This activity is higher in the tumor than in the surrounding "normal" tissue. In addition, we present evidence for a novel thrombin inhibitor which (a) is present only in the tumor growing in rat brain and undetectable either in the normal brain tissue or in vitro, (b) is in a latent, but sodium dodecyl sulfate-activatable, state, and (c) does not bind urokinase. In current studies, investigators are exploring the roles of these molecules and the target serine proteases they inhibit in the pathogenesis of gliomas.
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PMID:Serpin inhibitors of urokinase and thrombin in normal rat brain and the 9L brain tumor: evidence for elevated expression of protease nexin I-like inhibitor and a novel sodium dodecyl sulfate-activated tumor antithrombin. 211 23

Urokinase (UK, Mr 55,000) and tissue-type plasminogen activator (tPA, Mr 74,000) are serine proteinases involved in many biological processes, ie, cell migration, neoplastic transformation, and extracellular proteolysis. Cutaneous fibrinolytic activity (dependent on the activity of UK and tPA) was studied with the autohistographic fibrin film method in 40 patients affected by psoriasis vulgaris before and after topical (anthralin, betamethasone valerate, hydrocolloid occlusive dressing) or systemic psoralen-ultraviolet-light (PUVA) treatments. Autohistographic studies also were performed after apposition of monoclonal antibodies directed against the catalytic site of UK and tPA. Finally, UK and tPA were localized immunohistochemically in the psoriatic plaques and in controls using the immunoperoxidase procedure based on the biotin/avidin system. UK and tPA immunoreactivity was present in the cytoplasm and around the outlines of keratinocytes in the psoriatic patches before treatment and in the patches not cleared after treatment, while it was not detectable in normal epidermis, in the unaffected psoriatic epidermis, and in the cleared psoriatic skin. Cutaneous fibrinolytic activity was present in the cases in which UK and tPA were detected histochemically and, in the psoriatic epidermis, it was abolished by preincubation with anti-tPA but not with anti-UK antibodies. This study suggests that established topical and systemic treatments for psoriasis possess UK and tPA antagonist activity.
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PMID:Antipsoriatic therapies inhibit epidermal plasminogen activator activity. 212 55

The human T cell-associated serine proteinase-1 (HuTSP-1) is expressed by activated T lymphocytes and is exocytosed upon their interaction with target cells. Here, we report that HuTSP-1 is able to convert single-chain human pro-urokinase into the active two-chain enzyme. Time-dependent activation by HuTSP-1 of recombinant human pro-urokinase as well as natural pro-urokinase derived from human melanoma cells was demonstrated in a chromogenic assay specific for active urokinase type plasminogen activator and in immunoblotting experiments revealing the conversion of single-chain into two-chain urokinase. Control experiments excluded plasmin as the activating agent. These data suggest a novel pathway for plasmin generation during T cell-mediated processes such as immune responses and extravasation of immune cells.
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PMID:Activation of pro-urokinase by the human T cell-associated serine proteinase HuTSP-1. 213 93

The presence of plasminogen activator (PA) with a Mr of about 35,000 was detected by SDS-PAGE in extract from Guerin epithelioma. The activator, which is a serine proteinase, was partially purified on Sephadex G-50 followed by Lys-Sepharose. Rat plasma, both of healthy and epithelioma-bearing animals, inhibited the activity of such isolated PA. However, the difference between these plasmas in their antiactivator action was observed after inactivation of plasma proteinase inhibitors. In such conditions, the control plasma lost the ability to inhibit the examined PA, whereas the plasma of epithelioma bearing rats retained this ability.
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PMID:Plasminogen activator (PA) in Guerin epithelioma. Additional PA inhibitor in plasma of rats bearing the epithelioma. 214 18

We studied a role of plasminogen activator and plasmin in keratinocyte migration. First we examined the effects of various proteinase inhibitors on keratinocyte migration using wound healing model in cultured keratinocyte. Among the proteinase inhibitors tested, only an inhibitor of serine proteinases, camostat mesilate showed a concentration-dependent inhibition on the migration. Anti urokinase IgG was also able to suppress the migration. On the other hand exogenous plasminogen enhanced it. These results strongly suggest that PA/plasmin system is involved in keratinocyte migration.
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PMID:[Effects of plasminogen activator on epidermal cell migration]. 214 79

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

In the course of studies on the regulation of plasminogen activator-mediated extracellular matrix degradation in muscle we found the presence of a factor, a cellular inhibitor of serine proteases having features similar to the serpin protease nexin I (PNI). This factor was present in the medium and at maximum concentration following fusion of skeletal muscle cells in culture. The ability of the PNI homologue in mouse muscle to inhibit ECM degradation by urokinase in myoblast medium was compared to that of human PNI purified from human fibroblasts. Stable (to SDS) 1:1 molar ratio complex formation between PNI and proteases, the proposed means by which these enzymes are regulated and removed, was also detected. Cell surface receptors for protease:PNI complexes, the specific binding sites for inactive complex internalization, were found on multinucleated myotubes, while little or no receptor activity was detected on myoblasts. These data suggest that developmental regulation of a) increased PNI proteolytic inhibitory activity expression and b) the appearance of protease:inhibitor complex receptors on muscle cell surfaces during myogenesis may constitute important regulatory features of muscle surface proteolytic activity. They complement previous studies of proteoglycan metabolism in muscle, which itself contains molecules capable of regulating the activity of myotube surface proteases.
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PMID:Plasminogen activators and their inhibitors in the neuromuscular system: II. Serpins and serpin: protease complex receptors increase during in vitro myogenesis. 216 58

Complexes between tissue-type plasminogen activator (t-PA) and its rapidly acting inhibitor plasminogen activator inhibitor type 1 (PAI-1) are bound, internalized, and degraded by HepG2 cells. The mechanism involves endocytosis mediated by a specific high-affinity receptor. However, the particular domains of the complex that are recognized by the receptor have not been elucidated. To identify the determinants involved in ligand binding to the receptor, several variants of t-PA were assessed for their ability to form complexes with PAI-1 and thereby to inhibit specific cellular binding of complexes between structurally unmodified 125I-t-PA and PAI-1. Catalytically active variants lacking selected structural domains form complexes with PAI-1 and inhibit 125I-t-PA.PAI-1 binding to HepG2 cells. In addition, several forms of the plasminogen activator urokinase (u-PA), which shares partial structural homology with t-PA, were evaluated as competitors of cellular binding. The catalytically active two-chain forms of u-PA, but not the inactive proenzyme single-chain form, complex with PAI-1 and inhibit specific binding of 125I-t-PA.PAI-1, suggesting that the serine protease domain, rather than other domains, may confer the determinants required for cellular binding. However, a mutant t-PA with markedly reduced catalytic activity, resulting from replacement of the active site serine with threonine, not only forms complexes with PAI-1 but also inhibits specific cellular binding of unmodified 125I-t-PA.PAI-1. These data indicate that specific binding of t-PA.PAI-1 to HepG2 cells does not require a serine-containing catalytic site in the protease domain. To determine whether binding of the complex is mediated through other components of t-PA or through structural elements of PAI-1, both t-PA and PAI-1 were examined separately for capacity to bind directly to HepG2 cells. To exclude potential interactions with components of the extracellular matrix which contains binding sites for PAI-1, ligand binding to HepG2 cells in suspension was assessed. Although neither t-PA nor PAI-1 alone binds specifically to HepG2 cells, the preformed t-PA.PAI-1 complexes do. These findings suggest that specific binding of t-PA.PAI-1 requires elements of the PAI-1 moiety and/or parts of the protease domain of t-PA.
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PMID:Identification of determinants involved in binding of tissue-type plasminogen activator-plasminogen activator inhibitor type 1 complexes to HepG2 cells. 216 6


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