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)

To identify factors potentially influencing expression of type 1 plasminogen activator inhibitor (PAI-1), we characterized the human tissue-specific distribution of PAI-1 mRNA and the influence of epidermal growth factor (EGF) on expression of steady state levels of PAI-1 mRNA and secretion of PAI-1 by Hep G2 cells. Two species of PAI-1 mRNA (3.2 and 2.2 kilobases) were detected, and the ratio of the two varied among tissues (3 to 5:1) in contrast to the 1:1 ratio detected in Hep G2 cells. Expression of PAI-1 mRNA was inversely related to the distribution of tissue-type plasminogen activator mRNA (2.3 kilobases). Nu-Serum, a growth media supplement, increased steady state levels of PAI-1 mRNA 5-fold within 3 h. Factors responsible were found to be trypsin-sensitive and dialysis-resistant. Antisera to EGF attenuated Nu-Serum-induced increases of PAI-1 mRNA by 57%, suggesting that EGF or EGF homologous peptides contributed to the response. EGF elicited increases of PAI-1 mRNA levels in a dose-dependent manner. Induction was rapid (7-fold at 3 h with 5 ng/ml) and complete within 10 h. The response was not attenuated by cycloheximide (25 micrograms/ml). Factor X and glyceraldehyde-3-phosphate dehydrogenase mRNA did not increase. Increased levels of PAI-1 antigen were detected in conditioned media of Hep G2 cells by 4 h and were maximal at 8 h (6-fold). We conclude that the expression of PAI-1 mRNA is tissue-specific and regulated by epidermal growth factor in Hep G2 cells.
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PMID:Regulation of the expression of type 1 plasminogen activator inhibitor in Hep G2 cells by epidermal growth factor. 284 25

Tumor cells from a murine fibrosarcoma (FSa) produce plasminogen activator (PA), a protease that converts the zymogen plasminogen into the trypsin-like enzyme plasmin. Several studies indicate that tumor cell invasion is accompanied by proteolysis and that PA, generated by highly malignant cells, is by far the most ubiquitous protease associated with malignant transformation. Subpopulations of FSa cells were isolated by using density gradient centrifugation and the ability of these populations to form lung colonies was compared with their associated levels of PA production. Five populations of cells from a murine fibrosarcoma were separated in continuous gradients of Renografin in the density range 1.05-1.18 g/cm2. The PA activities of an unseparated control cell lysate and cell lysates of the five separated populations were determined by using [125I]fibrin as a substrate in a reaction between cell lysate and plasminogen. The assay was based on the release of digested [125I]fibrin from the surface of Petri dishes into the supernatant solution, and the results were expressed as a percentage of the total radioactivity. The cell populations collected at densities of 1.05 and 1.09 (B1, B2) were the more clonogenic with relative clonogenic efficiencies of 2.6 and 3.3 times that of the unseparated tumor population, respectively. Analysis for PA demonstrated that enzyme formation was restricted mostly to these two populations. Cells from populations 4 and 5 did not secrete increased amounts of PA and had reduced clonogenic efficiencies compared with the unseparated FSa control population. These results are consistent with the hypothesis that PA activity is correlated with the clonogenicity of tumor subpopulations isolated from a heterogeneous and complex tumor system such as the FSa.
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PMID:Plasminogen activator activity in clonogenic cell populations separated from a murine fibrosarcoma. 292 Apr 77

Expression of plasminogen activator (PA) activity may be an important factor in the ability of tumour cells to metastasize; however, not all metastatic cells produce detectable PA activity. Conditioned culture media from revertant metastatic clones of cells derived by fusion of metastatic and non-metastatic rat mammary adenocarcinoma cells were found to contain a potent inhibitor of PA. This inhibited thrombin, human urokinase (UK) and tumour-derived PA, but not plasmin or trypsin. Inhibition was still obtained after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE) of mixtures of PA and inhibitor, followed by development of PA activity on fibrin overlays. The PA inhibitor eluted from Sephadex G-200 over a broad M.wt. range (35,000-80,000) and was inactivated by heating to 70 degrees for 30 min. The appearance of inhibitory activity in the culture media was time-dependent and could be reduced by incubation of cells with cycloheximide. Because of these findings, the possible presence of inhibitors should be considered in investigations into the role of PA in the metastatic process.
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PMID:An inhibitor of plasminogen activator produced by tumour cell fusion hybrids. 293 23

Incubation of HTC rat hepatoma cells with the synthetic glucocorticoid dexamethasone rapidly inhibits plasminogen activator (PA) activity secondary to the induction of a specific acid-stable inhibitor of plasminogen activation (Cwikel, B. J., Barouski-Miller, P.A., Coleman, P.L., and Gelehrter, T.D. (1984) J. Biol. Chem. 259, 6847-6851). We have further characterized this inhibitor with respect to its interaction with both urokinase and tissue plasminogen activator, and its protease specificity. The HTC PA inhibitor rapidly inhibits urokinase and tissue plasminogen activator with an apparent second-order rate constant of 3-5 x 10(7) M-1 X s-1. The inhibitor forms stable covalent complexes with both urokinase and tissue plasminogen activator, with which plasmin, trypsin, and factor Xa apparently do not compete. Complex formation is saturable and requires the active site of the PA. The mass of the inhibitor-PA complex is 50,000 daltons greater than that of PA alone, consistent with an Mr for the PA inhibitor of 50,000 as demonstrated directly by reverse fibrin autography. The HTC PA inhibitor does not inhibit thrombin and differs in its kinetic and biochemical properties from protease nexin.
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PMID:Characterization of the dexamethasone-induced inhibitor of plasminogen activator in HTC hepatoma cells. 293 42

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

Previous studies of alkali burns have provided evidence for an important role of the plasminogen activator (PA)/plasmin system in corneal ulceration. Current studies have utilized a sensitive, plasminogen-dependent fluorescent assay to demonstrate that PA is present mostly in a latent (trypsin- or plasmin-activatable) form (proactivator) in cultures of rabbit corneal epithelial cells or normal corneas. Cultures of ulcerating corneas demonstrate only active PA early in organ culture, whereas, latent PA levels increase later in culture. Thus, ulceration is correlated with the apparent conversion of latent to active PA. Moreover, profiles of proactivator and latent collagenase and of active PA and active collagenase in vitro, respectively, are similar, suggesting that activator and collagenase are under coordinate control. Cultures of normal epithelial cells and nonulcerating corneas contain PA molecular weight species of 72,000 and 46,000 MW, and ulcer corneas, species of 72,000, 46,000, and 35,000 MW. Double-diffusion analysis indicates that rabbit epithelial cells, fibroblasts, and ulcer corneas produce urokinase (UK)-like PA; and human cornea extracts and tears also contain PA immunoreactive with anti-UK antibodies. The existence of PA in a latent form identifies another level of regulation in the cascades that lead to stromal ulceration.
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PMID:Latent and active plasminogen activator in corneal ulceration. 298 39

Human foreskin cells possess sites on their surfaces that specifically bind both active and diisopropylphosphofluoridate-inactivated 2 chain 54 K Da [125I]-urokinase, but do not bind the 54 K Da single chain form of urokinase. 125I-urokinase bound to these sites is not internalized and is very slow to dissociate. There are about 40,000 available binding sites per cell. Brief incubation with pH 2.5 buffer at 5 degrees C unmasks another two to six fold more sites and also extracts plasminogen activator that, based on its accessibility to trypsin, appears to be at the cell surface. This suggests that the cryptic urokinase binding sites could be sites occupied with endogenous plasminogen activator.
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PMID:Cryptic urokinase binding sites on human foreskin fibroblasts. 300 45

The intense stromal response to some human tumors is termed the desmoplastic reaction. It is found with most human breast carcinomas. Dissolution of this response, containing predominantly fibrous proteins such as collagen and elastin, can occur with treatment. We have undertaken a study of the collagenases of the breast tumor desmoplastic reaction using a tissue culture model composed of human breast tumor cell lines and various human fibroblasts. The breast tumor cells had the higher collagenase activity, particularly the ZR75-31A cell line. Activity was 10-fold higher than that of the stromal cells. The enzyme was secreted into the media and required trypsin pretreatment for activity to be manifest. Partial purification was achieved of the major collagenase species. The protein was a metalloprotease and, like other mammalian collagenases, had a relative molecular weight of 60,000. Classical 3/4 and 1/4 cleavage products of the triple helical collagen substrate were demonstrated, typical of most mammalian collagenases. Only types I and III collagens were suitable substrates for this enzyme, with no apparent preference between the two. The breast tumor collagenases were not responsive to hormones; however, stimulation of activity was apparent in the absence of proteolytic pretreatment. This may represent conversion of the procollagenases of the breast tumor cells to the active form by an estrogen-sensitive plasminogen activator secreted by the same tumor cells.
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PMID:Collagenases in human breast carcinoma cell lines. 300 15

The purpose of these studies was to identify some of the extracellular proteolytic enzymes associated with the development and healing of acute inflammatory lesions. Lesions were produced in the skin of rabbits by the topical application of the military vesicant, sulfur mustard (SM). Full-thickness, 1-cm2 central biopsies of the lesions were organ-cultured for one to three days, and the culture fluids were assayed for proteases with a variety of substrates. When compared to culture fluids from normal skin, the culture fluids from both developing and healing SM lesions had three to six times the levels of proteases hydrolyzing two synthetic peptide substrates: (1) t-butyloxycarbonyl-Leu-Gly-Arg-4-trifluoromethylcoumarin-7-amide(Boc-Leu -Gly- Arg-AFC, herein abbreviated LGA-AFC), and (2) N-benzoyl-phenylalanine-beta-naphthyl ester (BPN). LGA-AFC is a substrate for trypsin, plasmin, plasminogen activator, thrombin, kallikrein, and the C3 and C5 convertases; BPN is a chymotrypsin and cathepsin G substrate. The culture fluids did not consistently hydrolyze four other synthetic peptide substrates or the proteins [14C]-casein and [14C]elastin. In order to determine the likely sources of LGA-AFCase and BPNase activity, we counted the number of granulocytes (PMNs), macrophages (MNs) and activated fibroblasts in histologic sections of developing and healing SM lesions, and we measured the levels of these enzymes in serum, in culture fluids of PMN and MN peritoneal exudate cells, and in culture fluids of two fibroblast cell lines. In SM lesions, serum and fibroblasts seemed to be the major source of LGA-AFCase, and serum alone the major source of BPNase. Tissue PMNs and MNs seemed to be only minor sources. The crusts of healing lesions, which were full of dead PMNs, seemed to be a rich source of both enzymes. In the SM lesion culture fluids, whether LGA-AFC and BPN were hydrolyzed by endopeptidases or only by exopeptidases could be determined by evaluating complex formation with alpha-macroglobulin proteinase inhibitors (alpha M). Endopeptidases, but not exopeptidases, are entrapped and inhibited by alpha M, because an internal peptide band in alpha M must first be hydrolyzed before molecular rearrangement (required for proteinase inhibition) occurs. The catalytic site of endopeptidases that are entrapped and inhibited by alpha M is known to remain active on (and reachable by) small synthetic peptide substrates such as LGA-AFC and BPN.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Proteases released in organ culture by acute dermal inflammatory lesions produced in vivo in rabbit skin by sulfur mustard: hydrolysis of synthetic peptide substrates for trypsin-like and chymotrypsin-like enzymes. 304 42

An immunosorption procedure is developed for quantitative estimation of plasminogen activator of the urokinase type in human blood serum. The procedure involved sorption of urokinase from blood serum using polyclonal antibodies to the enzyme as a sorbent at the first step of the assay. Concentration of the immunoreactive urokinase in a preparation correlated with the absorbed fraction of standard urokinase added into the sample at the second step after washing of the sorbent. The residual fibrinolytic activity of the standard dose was detected in fibrin-agar gel. Results of the assay were not altered in presence of high molecular (bovine blood serum, soy bean inhibitor of trypsin) and low molecular inhibitors of urokinase (benzamidine, arginine, epsilon-aminocapronic acid). Sensitivity of the assay constituted 0.05 IU/sample (2.5 IU/ml, 0.25 ng/sample) and might be increased by a decimal order after addition of plasminogen into fibrin-agar gel. Content of urokinase in blood serum of healthy men (21-48 years old) was equal to 166 +/- 8.9 IU/ml with individual variations from 107 to 260 IU/ml.
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PMID:[Immunosorption method of urokinase determination]. 307 Sep 32


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