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)

Five rat thyroid cell lines were tested for the expression of the cell surface receptor for urokinase type plasminogen activator (uPA). All tested lines were found to bind uPA, but transformed 1-5G and Ki-Mol cells, which are also high uPA producers, bound at least ten times more uPA, as compared to non-producers, 'normal' TL5 cells. Moreover, it was possible to remove membrane-bound uPA by treating the cells with phosphatidylinositol-specific phospholipase C, suggesting that rat uPAR, like its human counterpart, is linked to the membrane by a glucosyl-phosphatidylinositol anchor. The specificity of the binding was tested by competition with three different synthetic peptides corresponding to amino acids 14-37 of human, rat and mouse uPA. The results indicate also that the receptor binding region of rat uPA is located within the growth factor domain of the molecule and that its expression may be dependent on the transformed state of the cells.
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PMID:The receptor for the plasminogen activator of urokinase type is up-regulated in transformed rat thyroid cells. 132 34

The binding of tissue-type plasminogen activator (t-PA) to membranes prepared from human liver was investigated, and a specific, saturable, high-affinity binding site (Kd = 3.4 nM) was identified. The binding of t-PA to liver membranes was not affected by an excess of D-mannose or D-galactose, or by active urokinase (u-PA), whereas binding of t-PA to membranes prepared from human HepG2 hepatoma cells was inhibited by u-PA. HepG2-membrane-bound t-PA was fully complexed to PA inhibitor 1 (PAI-1), whereas liver-membrane-bound t-PA was not complexed. Gel filtration on Sephacryl S300 of membrane proteins solubilized in deoxycholate revealed that high-affinity t-PA binding activity elutes at an apparent molecular mass of 40 kDa. Monoclonal antibodies specific for the growth factor and the kringle 2 domains inhibited the binding of t-PA to liver membranes and the catabolism of t-PA by rat hepatoma cells. Human liver membranes also bound u-PA; binding was inhibited by pro-u-PA, the N-terminal fragment of u-PA, but not by the 33 kDa form of u-PA or by t-PA. Our results show that human liver membranes contain a specific 40 kDa binding protein for t-PA that is different from the PAI-1-dependent receptor described on HepG2 cells and the mannose receptor isolated from human liver.
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PMID:Characterization of the binding of plasminogen activators to plasma membranes from human liver. 144 49

Bartonella bacilliformis, a gram-negative, flagellated, motile bacterium, is the etiologic agent of verruca peruana. It is found within the verruca, where it can form large cytoplasmic (Rocha-Lima) inclusions in endothelial cells. Previously, an activity has been described in homogenates of B. bacilliformis that in vitro increases the proliferation of endothelial cells and their production of tissue-type plasminogen activator (t-PA) and in vivo is angiogenic. The aim of the present study was to determine if live B. bacilliformis similarly stimulated endothelial cells and produced the Rocha-Lima inclusion. By measuring proliferation of cells and the production of t-PA in vitro, it was found that the live bacteria increased both parameters in a fashion similar to the homogenates of B. bacilliformis. Interaction between the bacteria and endothelial cells appeared to be necessary for proliferation. On electron microscopy, bacteria penetrated the endothelial cell within 1 h, forming a small membrane-bound inclusion. By 12 h, a large membrane-bound inclusion, similar to the Rocha-Lima inclusion, containing numerous bacteria was present. These data provide further evidence that B. bacilliformis has an angiogenic activity and that the bacteria are at least in part responsible for the vascular proliferation of the verruca.
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PMID:Interactions between live Bartonella bacilliformis and endothelial cells. 158 35

The Escherichia coli outer-membrane phospholipase A (OM PLA) is a membrane-bound acyl hydrolase with a broad substrate specificity. In order to obtain more insight into the mechanism of action of this enzyme, we designed an active-site-directed inhibitor for OM PLA on the basis of the known substrate specificity as a first step in the elucidation of the catalytic mechanism of this enzyme. The inhibitor, hexadecanesulfonyl fluoride, consists of a long hydrocarbon chain for high-affinity binding by the enzyme and a sulfonyl fluoride moiety as a reactive group. The kinetics of the inactivation of OM PLA by hexadecanesulfonyl fluoride were studied in Triton X-100 micelles. Inactivation is very fast, specific and shows the same characteristics with respect to acyl specificity, pH profile and metal ion requirement as the activity of OM PLA on substrates. Incubation of OM PLA with a stoichiometric amount of hexadecanesulfonyl fluoride leads to a total and irreversible loss of enzyme activity, resulting from the sulfonylation of Ser144. This Ser144, which we suggest to be the active-site serine of OM PLA, is part of the sequence HDSNG, whereas in the water-soluble serine proteases and lipases the structural motif GXSXG is normally encountered. On the basis of the kinetics of inactivation of OM PLA by hexadecanesulfonyl fluoride, we discuss a possible catalytic mechanism of the enzyme.
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PMID:Inactivation of Escherichia coli outer-membrane phospholipase A by the affinity label hexadecanesulfonyl fluoride. Evidence for an active-site serine. 204 Feb 86

Cell lines established from the Lepidopteran insect Spodoptera frugiperda (e.g., Sf9) are used routinely as hosts for the expression of foreign proteins by baculovirus vectors. Previously, we showed that human tissue plasminogen activator (t-PA) was expressed, N-glycosylated, and secreted by Sf9 cells infected with a recombinant baculovirus (Jarvis DL, Summers MD: Mol Cell Biol 9:214-223, 1989). We also showed that t-PA secretion was blocked by tunicamycin (TM), an inhibitor of N-glycosylation, but not by castanospermine (CS) or N-methyldeoxynojirimycin, inhibitors of the initial steps in N-linked oligosaccharide processing. This suggested that the addition, but not the processing, of N-linked oligosaccharides is required for the secretion of recombinant t-PA from baculovirus-infected Sf9 cells. In this study, we present a more generalized evaluation of the role of N-glycosylation in the transport of recombinant glycoproteins through the Sf9 cell secretory pathway. Several different secretory or membrane-bound glycoproteins were expressed in control, TM-treated, or CS-treated Sf9 cells, and their appearance in the medium or on the cell surface was measured. The results showed that TM blocked the transport of some, but not all, of these proteins, whereas CS did not block the transport of any. This suggests that N-glycosylation is sometimes required for the transport of recombinant glycoproteins through the Sf9 secretory pathway, while processing of the oligosaccharides is not. At least two other proteins, p80 and p31, consistently coimmunoprecipitated with the nonglycosylated precursors of recombinant glycoproteins expressed in TM-treated Sf9 cells. Neither was antigenically related to any of the recombinant proteins. Relatively larger amounts of p80 and p31 were coprecipitated when transport was completely blocked by TM compared to when transport was only reduced or was unaffected. These results suggest that p80 and p31 block the transport of some nonglycosylated glycoprotein precursors in TM-treated Sf9 cells by binding to them and producing transport-incompetent heterooligomeric complexes. If this speculation is correct, then p80 and p31 are functionally analogous to the mammalian immunoglobulin heavy chain binding/glucose-regulated 78 kilodalton protein (BiP/GRP78).
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PMID:Role of glycosylation in the transport of recombinant glycoproteins through the secretory pathway of lepidopteran insect cells. 234 87

The clot-lysing ability of streptokinase (SK) was examined using membrane-bound thrombi. Encapsulation of SK in large unilamellar phospholipid vesicles (liposomes) resulted in entrapping approximately 30% of its original activity. Measurements of streptokinase activity for liposomal-encapsulated streptokinase (LESK) indicated little loss of activity or leakage in Tris-buffered saline over a 24-hr period at temperatures of 4 and 23 degrees C. However, incubation of free SK and LESK in platelet-poor plasma (PPP) at 37 degrees C resulted in a decrease of SK activity. The retention of SK activity in LESK was considerably higher than that of unentrapped SK. Clot-dissolving time (CDT) was measured by monitoring the pressure drop during slow filtration in plasma through membrane-bound thrombi. The results indicated that both LESK and free SK were able to activate the fibrinolytic system. Without prior incubation in PPP at 37 degrees C, the CDT of a SK and PPP mixture (SK/PPP) was 10.7 +/- 1.9 min (n = 12), while that of a LESK and PPP mixture (LESK/PPP) was 12.4 +/- 1.7 min (n = 12). The CDT-detected clot-lysing abilities of both SK and LESK were diminished by incubation in PPP, but to different extents. After 15- and 30-min incubations, the CDT of SK/PPP increased significantly to 15.5 +/- 1.5 and 24.1 +/- 2.4 min (n = 5, P less than 0.05), respectively. In contrast, the CDT of LESK/PPP increased to 13.3 +/- 0.8 min (n = 5) after 15 min of incubation and to 16.0 +/- 1.1 min (n = 5, P less than 0.05) after a 30-min incubation. These results suggest that entrapment of SK in liposomes preserves the thrombolytic potential of the plasminogen activator by limiting its exposure to the components of the plasma.
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PMID:Thrombolysis using liposomal-encapsulated streptokinase: an in vitro study. 260 91

Cardiac rat myocytes in primary culture exhibit a membrane-bound and a secreted form of plasminogen activator (PA). Growth of the cells in presence of 2 X 10(-8) M or 10(-7) M dexamethasone markedly reduced both the membrane-bound and the secreted activities of PA. The extent of reduction depended on the time of addition as well as on the length of exposure to the hormone. A similar concentration of estradiol had no effect on PA activity of the myocytes. Cardiac rat fibroblasts in primary culture showed only the particulate form of the enzyme. Exposure of the fibroblasts to 10(-7) M dexamethasone produced a marked inhibition of this activity. The inhibition of PA activity in medium conditioned by dexamethasone-treated myocytes could be relieved by treatment of the medium with 1% (v/v) sodium dodecyl sulphate (SDS). Digestion with 3.3 micrograms/ml bovine trypsin caused an increase in PA activity of media conditioned with control or dexamethasone-treated cells. The present results indicate that cardiac myocytes and fibroblasts produce PA, and that the modulation of PA by glucocorticoid either involves formation of an inactive PA-protein complex or production of an inactive proenzyme. Since glucocorticoids are often administered in conjunction with fibrinolytic enzymes to re-establish cardial perfusion after thrombosis, the present findings indicate further research to assess potential clinical effects of glucocorticoids through suppression of endogenous PA activity in the heart.
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PMID:Suppression of plasminogen activator activity by dexamethasone in cultured cardiac myocytes. 294 22

Phorbol ester (12-O-tetradecanoyl-phorbol 13-acetate) stimulates the secretion of tissue-type plasminogen activator by the melanoma cell line, Bowes. This effect is associated with increased levels of mRNAs for both tissue-type plasminogen activator and a 48 kDa-protein. Labelling of melanoma cells with L-[35S]methionine allowed to identify an intracellular protein which, by 3 criteria, was identical with the in vitro translation product of the 48kDa-protein mRNA: a Mr of 48,000 on electrophoresis in the presence of sodium dodecyl sulphate; inducibility by phorbol ester and failure of reducing agents to affect electrophoretic mobility. As detectable by L-[35S]methionine labelling, the protein was mainly localized in the cytosol. In vitro phosphorylation reactions, carried out on subcellular fractions revealed a membrane-associated protein which also had the three characteristics of the aforementioned 48 kDa-protein. Phosphorylation did not require Ca2+-ions. Addition of phorbol ester to the reaction mixtures increased the phosphorylation. Reconstitution experiments between membrane and cytosol fractions of phorbol ester-treated and untreated cells showed that the 48kDa protein occurs in a cytosolic, unphosphorylated and a membrane-bound, phosphorylated form and that the former is converted to the latter by a phorbol ester activated, membrane-associated protein kinase.
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PMID:Phorbol ester stimulates the synthesis and phosphorylation of a 48 kDa-intracellular protein in plasminogen activator secreting melanoma cells. 308 56

Human aortic (HAE), human umbilical vein (HUVE), and bovine aortic (BAE) endothelial cells were compared in their synthesis and release of fibrinolytic components during culturing. After isolation, the cultures were grown to confluency and then studied under identical conditions for release of tissue plasminogen activator (t-PA) antigen and plasminogen activator inhibitor (PAI) into serum-free medium. HAE cells released 10 times more t-PA antigen than HUVE cells, and the respective cell lysates also contained comparably higher values. Free PAI capacity was found in the conditioned media of both HAE and HUVE cells. BAE cell t-PA release was much lower than that of the HAE cells, and free inhibitor capacity was not found in the conditioned medium. BAE cells contained significant amounts of PA activity in cell membrane-bound form. This PA activity on the cell surface was not stimulated by addition of CNBr fibrinogen fragments but could be partially inhibited by activated bovine PAI and antibodies against human t-PA and urokinase PA, respectively.
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PMID:Comparison of fibrinolytic activities of human and bovine endothelial cells. 313 61

The specificities of six monoclonal antibodies produced against plasminogen activator of the human Bowes melanoma cell line are described. They have been used to detect membrane-bound plasminogen activator on cultured human lymphoid cell lines and in neoplastic human lymphocytic and myeloid cells of leukemic patients. These studies indicate that only certain phenotypic subsets of the T-cell lineage derived from patients with chronic lymphocytic leukemia or with Szezary syndrome express plasminogen activator on their surface membrane.
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PMID:Monoclonal antibodies detecting plasminogen activators on the membrane of leukemic lymphoid cells of T-cell origin. 350 Jul 78


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