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)

Macrophages were obtained by peritoneal lavage from untreated mice or from mice which had received either Brewer's thioglycollate broth or a suspension of streptococcus A cell walls intraperitoneally 4 days before. 3 h after harvesting, adherent cells from untreated mice were allowed to phagocytose zymosan, formaldehyde-treated sheep erythrocytes, or latex beads. Phagocytosis was stopped after 1 h and culture was continued for up to 10 days. Phagocytosis of zymosan or sheep erythrocytes triggered the immediate release of lysosomal glycosidases, stimulated the synthesis of cellular lactate dehydrogenase, and induced the delayed production and secretion of plasminogen activator . No such changes were observed upon phagocytosis of latex. Although all three particles used were phagocytosed, only zymosan and sheep erythrocytes stimulated glucose oxidation via the hexose monophosphate shunt. Similar findings were obtained in macrophages elicited with streptococcus A cell walls after zymosan phagocytosis. Thioglycollate-elicited macrophages, however, which were already secreting lysosomal hydrolases and plasminogen activator, could not be activated further by zymosan. The results of this study show that macrophages become activated after phagocytosis of particles that stimulate the activity of their hexose monophosphate shunt. The triggering event appears to be the burst of shunt activity itself or shunt-related biochemical reactions rather than phagocytic uptake per se or particle-dependent complement activation by the alternative pathway. Once initiated, macrophage activation proceeds independently of the intracellular fate of the ingested material .
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PMID:Role of phagocytosis in the activation of macrophages. 72 42

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

Various studies have shown that mannose receptors rapidly eliminate glycoproteins and microorganisms bearing high mannose-type carbohydrate chains from the blood circulation. The purpose of this study was to characterize the mannose receptor in the liver, which in vivo is involved in the rapid clearance of tissue-type plasminogen activator from the circulation. Human liver membranes were solubilized in Triton X-100, and the solution was applied to a tissue-type plasminogen activator Sepharose column. Bound proteins were eluted with ethylenediaminetetraacetate (10 mmol/L). A second, similar purification step rendered a single liver protein of 175,000 daltons. A combination of ligand blotting and a chromogenic assay for tissue-type plasminogen activator demonstrated that the identified liver protein is a mannose receptor because it bound tissue-type plasminogen activator, this tissue-type plasminogen activator binding being fully inhibited by 0.2 mol/L D-mannose. Western-blot analysis revealed that the isolated liver protein is immunologically identical to the human mannose receptor from placenta. Treatment of the liver protein and the placenta mannose receptor with trypsin yielded the same pattern of proteolytic degradation products as identified on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We conclude that the physiologically relevant mannose receptor for tissue-type plasminogen activator clearance isolated from human liver is immunologically and structurally similar to or identical with the human mannose receptor isolated from placenta.
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PMID:Isolation and characterization of the mannose receptor from human liver potentially involved in the plasma clearance of tissue-type plasminogen activator. 161 83

Previous studies have shown that tissue-type plasminogen activator (t-PA) in blood is cleared by the liver partially through a mannose-specific uptake system. The present study was undertaken to investigate, in a purified system, whether t-PA is recognized by the mannose receptor which is expressed on macrophages and liver sinusoidal cells. The mannose receptor was isolated and purified from bovine alveolar macrophages and migrated as a single protein band at Mr 175,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Ligand blotting revealed that this protein specifically bound t-PA. The t-PA-receptor interaction was further characterized in a binding assay, which showed saturable binding with an apparent dissociation constant of 1 nM. t-PA binding required calcium ions and was negligible in the presence of EDTA or at acid pH. Mannose-albumin was an effective inhibitor, whereas galactose-albumin did not have a significant effect. From a series of monosaccharides tested, D-mannose and L-fucose were the most potent inhibitors, N-acetyl-D-glucosamine was a moderate inhibitor, whereas D-galactose and N-acetyl-D-galactosamine were ineffective. t-PA, deglycosylated by endoglycosidase H, did not interact with the receptor. It is concluded that the mannose receptor specifically binds t-PA, probably through its high mannose-type oligosaccharide.
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PMID:Binding of tissue-type plasminogen activator by the mannose receptor. 190 88

A simple and sensitive chromogenic microtitre plate assay for glycoprotein enzymes is described, using melanoma tissue plasminogen activator (t-PA) as a model enzyme. The assay is based on the binding of t-PA to immobilised lectin and quantitating the bound enzyme with plasminogen, fibrinogen fragments and chromogenic substrate S-2251 on an ELISA plate reader. Seven different lectins were examined for the binding of t-PA, and of these, concanavalin A was chosen for subsequent studies. The specificity of this binding can be inhibited dose-dependently in the presence of D-mannose and methyl alpha-D-mannoside, but not by D-glucose and D-lactose. The lower limit of the sensitivity of this assay is about 0.5 IU/ml. Comparison of the dose-response curves indicates that the sensitivity of this assay method is very similar to that of bioimmunoassay using anti-t-PA IgG to capture the antigen. The applicability of this method to other glycoprotein enzymes was also evaluated using alkaline phosphatase from bovine mucosa. The specificity of this method was related to the choice of substrate and this was shown by analysis of a mixture of t-PA and alkaline phosphatase. It is suggested that this assay can be adapted for the analysis of complex glycoprotein mixtures with the appropriate choice of lectin and substrate.
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PMID:Lectin affinity bioassay: an assay method for glycoprotein enzyme. 249 37

We have examined the phosphorylation state of five proteins known to become phosphorylated on tyrosine during transformation by Rous sarcoma virus by using cells infected with a panel of partially transforming mutant viruses. Situations of viral mutant and growth temperature were found in which phosphorylation of some proteins occurred more extensively than that of others, indicating that mutations in the src gene had affected the specificity of pp60src for some of its substrates as well as affecting the activity of the enzyme. To obtain insight into the biological functions of these phosphorylations, comparisons were made between the degree of phosphorylation of these proteins and the expression of various indicators of the transformed phenotype. The data suggest that phosphorylation of proteins l, p, and q (Mr of 46,000, 39,000 and 28,000, respectively) is not sufficient to induce changes in adhesiveness, hexose transport or morphology. The phosphorylation of protein p or l or total phosphotyrosine content correlated well with the production of plasminogen activator, and the phosphorylation of proteins l and q correlated well with increased hexose transport. However, even when good correlations were observed, significant exceptions were sometimes noted. It thus remains possible that some phosphorylations on tyrosine observed in Rous sarcoma virus-transformed cells are not causally related to the expression of the measured parameters of transformation.
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PMID:Phosphotyrosine-containing proteins and expression of transformation parameters in cells infected with partial transformation mutants of Rous sarcoma virus. 618 22

Fifteen transformation defective sensitive mutants of Rous sarcoma virus have been investigated to see if the expression of the pp60src-associated protein kinase activity correlated with other parameters of transformation such as altered growth control, morphological changes, increased hexose transport, and increased plasminogen activator protease synthesis. The expression of a protein kinase activity paralleled or preceded the onset of other parameters of transformation with but one exception: altered control of cell growth. The stability of the pp60src molecule in mutant-infected cells at the nonpermissive temperature was investigated with the finding that mutant pp60src did not show an increased turnover at the nonpermissive temperature as compared to wild type virus pp60src. Furthermore, it could be shown that pre-existing pp60src in mutant-infected cells maintained at the non-permissive temperature became activated after temperature shift to the permissive temperature. Temperature shift performed under conditions of inhibition of new protein synthesis with cycloheximide, puromycin, or emetine was followed by greatly increased protein kinase activity, and a parallel phosphorylation of pp60src itself in tyrosine residues. Morphological features of transformation could be demonstrated likewise under conditions of inhibition of protein synthesis.
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PMID:In vitro transformation with Rous sarcoma virus and the pp60src-associated protein kinase. 626 96

In order to investigate a possible correlation between in vitro transformation and tumorigenicity in ovo, a new temperature-sensitive class T mutant of Rous Sarcoma Virus was isolated with a lower (39 degrees 5C) restrictive temperature for morphological transformation. This lower restrictive temperature was compatible with the survival of chicken and duck eggs for the tumorigenicity studies. In chicken embryo fibroblasts (CEF) infected by this new mutant, PA 17, and cultured at 39 degrees 5C, increase of hexose uptake, plasminogen activator production and anchorage-independent growth were only partially restricted, requiring incubation at 41 degrees 5C for a complete shut-off. Tumorigenicity in chicken and duck eggs inoculated with CEF infected and transformed by PA 17 was restricted at 39 degrees 5C, correlating well with the restriction of morphological transformation at this temperature. The kinase activity of the transforming protein pp60src in lysates of PA 17 infected cells cultured at permissive or restrictive temperatures was labile in RIPA buffer, as in the case of some previously examined ts T mutants. In the non-ionic detergent NP40 buffer, the kinase activity of PA17 infected cell lysates was better conserved and showed a moderate temperature dependence. These results suggest that, in spite of the correlations between the transformed cell phenotype in vitro and cell tumorigenicity in ovo, it is difficult to establish a quantitative relationship.
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PMID:A ts T mutant of Schmidt Ruppin strain of Rous sarcoma virus restricted at 39.5 degrees C for the morphological transformation and the tumorigenicity of chicken embryo fibroblasts. 627 5

We have isolated and characterized mutants of Rous sarcoma virus which induce some parameters of transformation but fail to fully induce other parameters. We believe these mutants code for a pp60src which phosphorylates some targets well but phosphorylates others poorly. Using these mutants, we examined the phosphorylation of a 36,000 Mr protein which is phosphorylated on a tyrosine in cells transformed by Rous sarcoma virus, in an attempt to correlate this phosphorylation with the expression of specific transformation parameters. We found that phosphorylation of the 36,000 Mr protein was neither necessary nor sufficient for loss of fibronectin or for loss of density-dependent inhibition of growth. Phosphorylation of the protein was not sufficient for morphological alterations, increased hexose transport, or loss of adhesiveness. For the parameters measured, the best correlation was with increased plasminogen activator. In addition, it is noteworthy that cells infected with the mutant CU2 displayed low levels of phosphorylation of the 36,000 Mr protein and also were deficient in anchorage-independent growth and tumorigenicity, raising the possibility that the phosphorylation of the 35,000 Mr protein may be required for malignant growth properties.
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PMID:Phosphorylation of a 36,000 Mr cellular protein in cells infected with partial transformation mutants of rous sarcoma virus. 628 26

Under conditions employed in our laboratory, tumors which are induced by avian sarcoma virus (ASV) usually grow progressively for several weeks and then regress. In order to further understand the basis for tumor regression in this model, we compared avian sarcoma cells which were cultured from tumors at different stages of development in terms of various phenotypic properties. The results indicate that tumor cells which are derived from progressively-growing sarcomas are rapidly growing, produce large quantities of the enzyme plasminogen activator, and have much in common generally with chicken embryo fibroblast (CEF) cells that have been transformed by ASV. In contrast, tumor cells that are obtained from regressors have elevated levels of hexose transport, grow very slowly, are greatly enlarged and display properties that are characteristic of senescent cells in culture.
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PMID:Phenotypic differences between tumor cells derived from different stages of neoplastic growth. 628 92


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