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 continuous cell line, J774.2, exhibits many macrophage-like functions such as latex and Fc-mediated phagocytosis, antibody mediated phagocytosis, antibody mediated cytotoxicity, chemotaxis, and lysozyme secretion. Cyclic AMP stimulates Fc-mediated phagocytosis and inhibits the growth of J774.2. To further evaluate the relationship between cyclic AMP and the specialized functions exhibited by these cells. Variants deficient in phagocytosis, adenylate cyclase and cyclic AMP-dependent protein kinase were derived. We have now shown that J774.2 also secretes plasminogen activator and that this secretion is rapidly and specifically inhibited by 8-bromoadenosine 3':5'-cyclic monophosphoric acid (8 Br--cAMP) or cholera toxin under conditions where lysozyme secretion is unaltered. Utilizing protein kinase-deficient variants, the ability of cyclic AMP to inhibit plasminogen activator secretion was shown to be mediated by a cyclic AMP-dependent protein kinase. We conclude that cyclic AMP has diametrically opposing effects on two macrophage-like functions: Fc-mediated phagocytosis and plasminogen activator secretion.
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PMID:Inhibition of plasminogen activator secretion by cyclic AMP in a macrophage-like cell line. 21 71

Studies in the past 10 years have shown that there are two different, but related pathways for the acceleration of tissue-type plasminogen activator (t-PA) catalysis: (1) fibrin-dependent enhancement of t-PA amidolytic activity by fibrin binding; (2) fibrin-mediated stimulation of plasminogen activation by t-PA via the formation of a ternary complex of fibrin, t-PA and plasminogen. The common characteristic of both phenomena is the affinity of t-PA for fibrin, which is realized by the same enzyme binding site. However, a comparison of the kinetic data, the participating fibrin structures and the differences between single-chain and two-chain t-PA (sct-PA and tct-PA, respectively) shows that both phenomena have different causes. Fibrin-mediated stimulation of plasminogen activation involves both sct-PA and tct-PA and different fibrinogen derivatives such as fibrin, fibrinogen cyanogen bromide fragment FCB-2, fibrin alpha-chain and poly-lysine. This mechanism is described by a marked apparent decrease in the KM value. In contrast, fibrin-dependent enhancement of t-PA activity against low molecular weight peptides is exclusive to sct-PA and is characterized by an increase in the kcat value and, depending on the nature of the substrate, by an increase in kcat and a decrease in KM. Thus, sct-PA activity modulation depends strictly on the correct three-dimensional folding of fibrin and is not mediated by fibrinogen fragment FCB-2 or isolated fibrin chains.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of fibrin-mediated stimulation of plasminogen activation by tissue-type plasminogen activator (t-PA) and fibrin-dependent enhancement of amidolytic activity of t-PA. 160 92

The rate of activation of plasminogen by tissue-type plasminogen activator (t-PA) is greatly increased by fibrin, but much less by fibrinogen. Fibrin(ogen) fragments such as the fibrin(ogen) cyanogen bromide fragment FCB-2 and FCB-5, and a synthetic peptide with the sequence of fibrinogen A alpha-(148-160), a constituent of FCB-2, also have rate-enhancing properties. In order to find a possibly smaller, still stimulating site within A alpha-(148-160) we synthesized successive linear amino-terminally acylated hexapeptides [i.e. A alpha-(148-153), A alpha-(149-154)'d, .... A alpha-(155-160)] from the sequence A alpha-(148-160). The only hexapeptide within the sequence A alpha-(148-160) capable of enhancing the rate of plasminogen-to-plasmin conversion by t-PA appears to be the amino-terminally acylated peptide comprising the sequence A alpha-(154-159). This peptide enhances the plasminogen activation rate six-fold; half-maximal activation rate is reached at a peptide concentration of 56 microM.
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PMID:The sequence A alpha-(154-159) of fibrinogen is capable of accelerating the t-PA catalysed activation of plasminogen. 193 32

Intact fibrin monomer, the early fibrin degradation product (X-fragment), late fibrinogen degradation products (fragments D and E), fibrinogen cyanogen bromide fragment FCB-2, and isolated peptide chains of fibrinogen and fibrin were investigated for their ability to replace fibrin in the stimulation of one-chain tissue-type plasminogen activator. They were also investigated for their ability to stimulate plasminogen activation by one-chain tissue-type plasminogen activator, which occurs via ternary complex formation. The stimulatory effect of the different fibrin/ogen products decreased in the order: fibrin X-fragment greater than fibrin monomer greater than CNBr-fragment FCB-2 greater than fibrin alpha-chain. Fibrin beta/gamma-chains and fibrinogen peptide chains were found to be weak stimulators. Fibrinogen fragments D and E have almost no effect. The amidolytic activity of one-chain tissue-type plasminogen activator was stimulated by intact fibrin monomer and somewhat more strongly by fibrin X-fragment. This stimulation by fibrin monomer, which occurred via an increase in the kcat value, was competitively inhibited by isolated fibrin alpha-chain (Ki = 0.12 mumol/l). The results show that the fibrin-mediated stimulation of plasminogen activation occurs when both one-chain tissue-type plasminogen activator and plasminogen are bound to fibrin, and that this process is essentially independent of the conformation of the fibrin molecule. In comparison, the fibrin-dependent stimulation of the amidolytic activity of one-chain tissue-type plasminogen activator is a more complex process, which depends on the correct conformation of the fibrin molecule.
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PMID:Comparison of the effects of fibrinogen and fibrin products and isolated peptide chains on the fibrin-mediated stimulation of plasminogen activation by tissue-type plasminogen activator, and on the fibrin-dependent enhancement of the amidolytic activity of one-chain tissue-type plasminogen activator. 212 81

HTC rat hepatoma cells synthesize and secrete tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1). Incubation with 8-bromo-cAMP increases tPA activity more than 50-fold and, in combination with dexamethasone, causes an additional 4-fold increase. We have investigated the mechanism of the regulation of tPA activity by cyclic nucleotides, both alone and in combination with dexamethasone, by examining the effects of these agents on tPA and PAI-1 mRNA and protein. 8-Bromo-cAMP induces only a 2-fold increase in tPA mRNA and a 5-fold increase in tPA protein which is not sufficient to account for the increase in tPA activity. However, 8-bromo-cAMP causes a 90% decrease in PAI-1 mRNA and a 60-70% decrease in PAI-1 protein, which, taken together with the modest increase in tPA mRNA and protein, can account for the increase in tPA activity. Incubation with 8-bromo-cAMP plus dexamethasone also results in an 80-90% decrease in PAI-1 mRNA, but causes a synergistic 10- to 20-fold increase in tPA mRNA and protein. Regulation of both mRNAs by 8-bromo-cAMP requires concomitant RNA synthesis. Inhibition of protein synthesis by cycloheximide totally blocks the 8-bromo-cAMP-induced decrease in PAI-1 mRNA. Cycloheximide alone causes a 5- to 10-fold increase in tPA mRNA, and no further hormonal effect is observed. Thus, 8-bromo-cAMP increases tPA activity primarily by decreasing PAI-1 mRNA accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cyclic nucleotide regulation of plasminogen activator and plasminogen activator-inhibitor messenger RNAs in rat hepatoma cells. 215 75

The fibrinolytic (fibrin dissolving) properties of several anionic, cationic, nonionic and zwitterionic detergents were assessed in an in vitro fibrin agarose assay. Of the 4 anionic detergents tested, only sodium dodecyl sulfate (SDS) was found to be fibrinolytic. SDS was fibrinolytic either in the absence or presence of factor XIII. Four other cationic detergents were found to possess similar fibrinolytic properties. These cationic detergents were cetyltrimethylammonium bromide (CTAB), mix alkyltrimethyl ammonium bromide (MTAB), hexadecyltrimethylammonium bromide (HTAB) and cetylpyridium chloride (CPC). The nonionic (digitonin, triton X-100/tween 20) and zeitterionic (CHAPS, zeittergent 3-08) detergents were not fibrinolytic. Detergents mediated fibrinolysis, unlike that of tissue type plasminogen activator and urokinase, was independent of the presence of plasminogen. Non-detergents such as polyethylene glycol and highly charged compounds such as poly-1-lysine and poly-1-glutamic acid were not fibrinolytic. Fibrinolytic activity was observed for SDS and the cationic detergents at concentrations ranging from 0.1-10 percent. The effects of these fibrinolytic detergents (SDS, CTAB, MTAB, HTAB and CPC) on clot formation and on pre-formed clots were then assessed, using freshly drawn human venous blood. Incorporation of these detergents into blood inhibited the formation of clots in a concentration dependent manner. The detergents were also able to dissolve pre-formed clots in a similar fashion. SDS was found to be most potent in these properties.
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PMID:Fibrin solubilizing properties of certain anionic and cationic detergents. 251 Mar 56

Full-length human parathyroid hormone-related protein (PTHrP-(1-141] as well as a carboxyl-terminal shortened form (PTHrP-(1-108] have been expressed from recombinant DNA-derived clones. These proteins were expressed in Escherichia coli as fusion proteins so that cyanogen bromide cleavage yields the desired product. Both proteins were purified and then characterized by sodium dodecyl sulfate gel electrophoresis, amino-terminal amino acid sequencing, peptide mapping, and mass spectral analysis. Recombinant PTHrP-(1-141), PTHrP-(1-108), synthetic PTHrP-(1-34), and naturally derived PTHrP are all equipotent in the stimulation of cyclic AMP levels in the osteoblast-like cell line UMR 106-01. However, PTHrP-(1-141) and -(1-108) are two to four times more active than PTHrP-(1-34) in the stimulation of plasminogen activator activity from this cell line. PTHrP-(1-141) reacts equipotently with PTHrP-(1-34) in a radioimmunoassay using an antiserum prepared against PTHrP-(1-34). PTHrP-(1-141), -(1-108), and -(1-84) were used as PTHrP-specific mobility standards on sodium dodecyl sulfate gel electrophoresis to determine the approximate length of two forms of naturally derived PTHrP. The data show that PTHrP purified from the lung tumor cell line BEN contains a major form of about 108 amino acids and another form of about 141 amino acids.
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PMID:Purification and characterization of recombinant human parathyroid hormone-related protein. 254 37

Tissue-type plasminogen activator (t-pa) is a serine protease comprising four different putative structural domains with homologies to fibronectin finger-like structures (finger), epidermal growth factor, kringle structures, and the active site of serine proteases. Only the finger and epidermal growth factor domain are each entirely encoded by unique single exons. We assessed the functional contribution of these two structural domains by making mutants precisely deleted for one or both of the relevant exons. The three mutant genes were expressed in monkey cells, and the variant proteins, purified from the culture medium, were characterized for their fibrinolytic activity, fibrinogenolytic potential, and affinity for fibrin. No significant difference in any biochemical property was observed among the variants. All three variants retained a catalytic dependence on cyanogen bromide fragments of fibrinogen which could not be distinguished from the wild-type enzyme. The activities of the variants were also very similar to that of wild-type t-pa, showing no detectable fibrinogenolytic potential in human plasma at activator concentrations of 500 IU/ml, or when their fibrinolytic activity was tested in human plasma using the 125I-labeled fibrin clot lysis assay at activator concentrations of 150 IU/ml or greater. However, the variants were markedly defective in fibrinolysis at low activator concentrations such that essentially no fibrinolysis was detected at 15 IU/ml. Measurement of fibrin binding showed that the variants lacked the high fibrin binding characteristic of wild-type t-pa. These results demonstrate that the fibrin specificity and fibrin-dependent activity of t-pa are independent of the protein's high affinity for fibrin. The implication of these results is that the t-pa variants would be ineffective activators at a physiological concentration of approximately 2 IU/ml but would be expected to behave similarly to wild-type t-pa at the steady-state plasma concentrations of 0.75-1.25 micrograms/ml (approximately 500 IU/ml) currently required for coronary reperfusion in patients receiving t-pa for acute myocardial infarction (Garabedian, H.D., Gold, H.K., Leinbach, R.C., Yasuda, T., Johns, J.A., and Collen, D. (1986) Am. J. Cardiol. 58, 673-679).
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PMID:Variants of human tissue-type plasminogen activator. Fibrin binding, fibrinolytic, and fibrinogenolytic characterization of genetic variants lacking the fibronectin finger-like and/or the epidermal growth factor domains. 312 18

In order to localize the binding site(s) for tissue-type plasminogen activator (t-PA) in the fibrin(ogen) molecule, the following binding assay was developed. Two-chain t-PA was immobilized onto microtitration plates. The t-PA-coated plates were then incubated with fibrinogen and various fibrinogen fragments. The extent of binding was quantified with enzyme-labelled antibodies against fibrin(ogen) and its fragments. Hardly any binding to t-PA was observed with fibrinogen or fragments X, Y and E; a moderate binding was observed with fragments Dcate and DEGTA and a strong binding with the cyanogen bromide fragment FCB-2 (Kd apparent = 140 nM). The binding of fibrinogen and its fragments to immobilized Lys-plasminogen was measured by the same method as a control for the binding assay. Results were in line with literature data: virtually no binding to Lys-plasminogen with fibrinogen or fragments X and Y, a moderate binding with fragments Dcate, DEGTA and E and a strong binding with FCB-2 (Kd apparent = 70 nM). The stimulatory capacity of the various fragments on the Lys-plasminogen activation by t-PA, as studied in a spectrophotometric assay, was found to be absent for fragment E, low for fibrinogen, fragments X, Y, Dcate and DEGTA, and high for FCB-2. It is concluded that a t-PA-binding site resides in the C-terminal globular domains of fibrinogen from which fragments D and FCB-2 originate. The site is hidden in the native fibrinogen molecule and in early fibrinogen degradation products. Binding of both Lys-plasminogen and t-PA appears to be required for a stimulator of the plasminogen activation, as illustrated by fragment E which only binds Lys-plasminogen and has no stimulatory capacity.
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PMID:Binding of tissue-type plasminogen activator to fibrinogen fragments. 312 7

Activation of human plasminogen by human tissue-type plasminogen activator (t-PA) is accelerated in the presence of cyanogen bromide digests of human fibrin(ogen). In the present study a possible species specificity of this phenomenon was investigated. All combinations of the plasminogens, fibrin monomers and cyanogen bromide digests of the fibrinogens of man, pig, rat, cat and monkey (Macaca mulatta), and three t-PA species (man, rat and pig) were studied. No species differences were noted with the fibrin monomers i.e. the activation rate of all five plasminogens increased more than 20-fold in the presence of all five fibrin monomer species, irrespective if man, rat or pig t-PA was used. However, we found that species specificities come to expression when cyanogen bromide digests of the corresponding fibrinogens were used as accelerators. Our results indicate that the plasminogen species and not the source of t-PA or fibrinogen dictates if accelerated activation occurs in the presence of a fibrinogen CNBr digest. The plasminogens can be roughly divided in two groups: --One group, comprising human, monkey and cat plasminogen, which are activated at a higher rate by all three t-PA species in the presence of fibrinogen digest independent on the fibrinogen species from which the digest was prepared. --Another group, comprising pig and rat plasminogen, which is not or only marginally more quickly activated by the 3 t-PA species, irrespective of the fibrinogen species from which the CNBr digest was prepared.
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PMID:Species specificity in the acceleration of tissue-type plasminogen activator-mediated activation of plasminogens, by fibrinogen cyanogen bromide fragments. 404 Jun 60


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