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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two types of plasminogen activator (PAs) are present in human endometrium, and their contents vary with the different phases of menstrual cycle, i.e. high in the proliferative phase and low in the secretory phase. In the present study by immunohistochemical technique, both uPA and tPA antigens were demonstrated in the stromal and glandular cells of the endometrium. In cell culture, tPA was released only from stromal cells and uPA only from glandular cells as determined by SDS-PAGE followed by fibrin overlay technique, but PA inhibitor type-1 (PAI-1) was secreted by both stromal and glandular cells. Furthermore, secretion of PAs from endometrial cells was enhanced by adding estradiol and markedly inhibited by progesterone in a dose dependent manner, while the PAI reacted just in the opposite way. The effect of the peptide hormones, hCG, GnRH, PRL, as well as cAMP in cell culture on the secretion of PAs and PAI was similar to that of estradiol, while forskolin demonstrated definitely more stimulative effect on tPA than uPA. Taking into account of the finding of the present study, it appears that, under hormonal control, a balance between PAs and PAI in the endometrium exists. The physiological roles of the PAs and PAI in the endometrium were discussed.
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PMID:[Plasminogen activators and plasminogen activator inhibitor type-1 in human endometrium]. 129 66

The human sarcoma cell line HT1080 was found, by in situ hybridization, to consist of cells expressing various levels of urokinase (uPA) and tissue type (tPA) plasminogen activator (PA) suggesting clonal variation of expression of these genes. Colonies originating from single HT1080 cells were, therefore, established and screened for PA activity using a fibrin agarose overlay. Colonies inducing lysis (clone C+ and H+) or no lysis (clones B- and M-) were isolated and tested for mRNA levels of uPA, tPA, uPA receptor (uPAR) and the 3 PA inhibitors (PAI), PAI-1, PAI-2 and protease-nexin I. The different clones revealed considerable variation of expression of the different PA and PAI genes, with lysis-inducing clones expressing mainly the PA genes, whereas non-lysing clones demonstrated higher expression of the PAI genes. Amplification or loss of specific genes was excluded by Southern blotting. The protein levels of cellular and secreted PA and PAI determined by ELISA and Western blots demonstrated a pattern similar to that observed for PA and PAI mRNA concentrations, suggesting clonal differences either on the level of transcription or in RNA processing and/or stability. Due to complex interactions between PA and PAI, neither mRNA nor protein levels of the different genes were predictive for the amount of functional PA activity present in the supernatant or on the cell surface of the different clones. Receptor-bound uPA activity was found to be considerably higher in lysis-inducing than in non-lysing clones and the activity was dependent on neutralization by PAI-1 rather than on the level of uPAR mRNA.
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PMID:Clonal variation of expression of the genes coding for plasminogen activators, their inhibitors and the urokinase receptor in HT1080 sarcoma cells. 132 52

Recombinant tissue-plasminogen activator (r-tPA), expressed in Escherichia coli cells in an aggregated form, was solubilized with a strong chaotrope in the absence of any reducing agent. The solubilized molecule was reactivated by a procedure that was developed to mimic the physiological conditions optimal for the functional folding and activity of the native protein. The use of partially purified fibrinogen, as a source of fibrin (the effector), is shown to facilitate the reactivation process and increase its yield by at least a factor of two. The yield of the process is also shown to be particularly dependent on the recombinant protein concentration. At a concentration level of 3-3.7 mg r-tPA/L in the reactivation mixture, up to a 90% yield of activity was obtained. Purification of the activated form of r-tPA was achieved with a two-step column-chromatography scheme. This included a gel filtration step on a Sephadex G-50 column followed by an affinity chromatography step on a lysine-sepharose column. The product was composed of roughly equal amounts of one-chain and two-chain t-PA. The feasibility of using a two water-soluble polymeric phase system, with a centrifugal partition chromatography (CPC), in scaling up the reactivation process or the purification step was also evaluated.
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PMID:Effector-assisted refolding of recombinant tissue-plasminogen activator produced in Escherichia coli. 138 Jul 90

Parotid saliva from 12 healthy volunteers was collected prior to and after 5 and 25 min of stimulation at a constant flow rate of 0.25 or 1.0 ml min-1. In the salivary samples the concentrations of tPA (tissue-type plasminogen activator), PAI-1 (plasminogen activator inhibitor type-1), albumin and total protein were determined and the activity of amylase, tPA and PAI assessed. Presence of both tPA and PAI-1 antigen was demonstrated in all samples, and in unstimulated saliva the ratio between the activator and its inhibitor was 1:7. Upon stimulation we found a significantly increased concentration of PAI-1, a less pronounced increase in tPA concentration, unchanged amylase and total protein levels and significantly decreased albumin concentration. tPA activity was significantly reduced after prolonged stimulation which had no effect on PAI activity. In stimulated saliva a significant positive correlation between concentration of tPA and PAI-1 was demonstrated. Stimulation with citric acid had no effect on output of albumin which is passively filtered from blood, whereas the increase in flow rate corresponded to the significantly increased secretion rate of total protein and amylase which is secreted by gland cells. The secretion pattern of tPA and PAI-1 differed significantly from that of albumin in showing markedly increased output rate during the stimulation period, and the relative increase in output of PAI-1 was significantly higher than that of amylase and total protein. Thus, the results from this study suggest an active release of both tPA and its main inhibitor PAI-1 into saliva.
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PMID:Increased release of tissue plasminogen activator and its inhibitor in human parotid saliva upon stimulation. 138 46

Urokinase-type (uPA) and tissue-type (tPA) plasminogen activators were identified by fibrinolytic autography in the sulcus epithelium of human gingival mucosa but not in the orthokeratinized gingival epithelium. Fibrinolytic activity was present only over blood vessels in frozen sections of oral squamous cell carcinomas, the malignant epithelial cells showing no plasminogen activator activity. Plasminogen activators could not be demonstrated in either the sulcus or gingival epithelium by immunofluorescence, but both uPA and tPA were found in occasional squamous carcinoma cells. Fibrinolytic activity of culture fluids from epithelial explants grown in vitro from human gingival mucosa showed marked variation, but activity was much higher in the culture supernatants than in the cell lysates. Fibrinolytic activity of culture fluids from epithelial explants of squamous cell carcinomas was low both in supernatants and lysates. Zymogram overlays of sodium dodecyl sulphate-polyacrylamide electrophoretic gels from culture supernatants showed that the low fibrinolytic activity of culture supernatants of oral squamous cell carcinomas was due to the associated presence of plasminogen activator inhibitors. The fibrinolytic activity in the zymogram was due predominantly to uPA but some lysis was due also to tPA.
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PMID:Plasminogen activators in normal and malignant oral epithelium in vivo and in vitro. 141 24

Rat ovarian cells produce not only plasminogen activator (tPA) but also plasminogen activator inhibitor type 1 (PAI-1), and their coordinated geneexpression induced by gonadotropins are thought to be responsible for follicular rupture. In this study, it was demonstrated that (1) theca-interstitial compartment synthesizes the majority of PAI-1 activity in the ovary before ovulation, the follicular wall may therefore serve as a specific barrier to prevent the secretion of PA into the extrafollicular compartment; (2) Granulosa cells contribute only small amount of ovarian PAI-1 activity, but synthesize most of tissue-type plasminogen activator activity involved in the process leading to ovulation: (3) Since only matured cumulus-oocyte complexes secrete high level of tPA and PAI-1, both tPA and PAI-1 activity in the conditioned medium may be used as reliable markers for evaluating oocyte quality for in vitro fertilization.
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PMID:[Hormonal regulation of PAI-1 secretion by cultured rat ovarian cells]. 145 60

A rabbit ear model of blood loss was developed to compare the effects of an active form of recombinant plasminogen activator inhibitor-1 (rPAI-1) with epsilon amino caproic acid (EACA) in antagonizing tissue-type plasminogen activator (r-tPA)-induced blood loss. The antagonism of both rebleeding, which occurs as a result of hemostatic plug degradation, and r-tPA-induced hemorrhage, where rabbits lose approximately 30% of their blood volume, was studied. rPAI-1 (1 mg/kg i.v.) or EACA (70 mg/kg i.v.) antagonized the rebleeding induced by r-tPA (10 micrograms kg-1 min-1) to a similar extent. In the hemorrhagic studies, rPAI-1 effectively antagonized the r-tPA-induced hemorrhage with an ED50 of 3 mg/kg i.v., while the ED50 obtained for EACA was 230 mg/kg i.v. rPAI-1 may be of value in reversing r-tPA-induced blood loss during thrombolytic therapy or in clinical situations where excessive fibrinolysis contributes to bleeding.
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PMID:Comparison of recombinant plasminogen activator inhibitor-1 and epsilon amino caproic acid in a hemorrhagic rabbit model. 150 11

In order to establish a mammalian cell expression system with a minimum of selection steps and a stable expression of microgram amounts of recombinant protein (human tissue-type plasminogen activator mutants and chimeric proteins) per 10(6) cells per day, we investigated Chinese hamster ovary cells and the dihydrofolate reductase-deficient Chinese hamster ovary cell line CHO(dhfr-). The 1tPA expression vector pCMVtPA was cotransfected either with the SV40 enhancer sequence containing dhfr expression vector pMT2 or with the enhancerless dhfr expression vector pAdD26SV(A) into CHO(dhfr-) cells. With both dhfr expression plasmids, selection for dhfr+ transformants followed by single dilution cloning was sufficient to generate cell lines with a production level of up to 4.6 micrograms tPA/10(6) cells.day. This approach is useful if gene amplification procedures are time-consuming and impracticable because of a large number of recombinant proteins. In order to establish CHO cell lines with a tPA expression level as high as that in the case of CHO(dhfr-) cells, repeated dilution cloning is necessary.
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PMID:Generation of recombinant CHO(dhfr-) cell lines by single selection for dhfr+ transformants. 152 11

Osteoblasts produce proteolytic enzymes and their production is regulated by osteotropic agents. It has been suggested that these proteases play a role in bone resorption by removing the superficial collagenous layer from the bone matrix and indirectly inducing migration of osteoclast precursors towards the bone matrix. We examined the effect of the plasminogen activator tPA on osteoclastic resorption using 17-day-old mouse embryonic long bone explants representing different stages of osteoclast development, that is, radii containing already mature osteoclasts and metacarpals containing no mature osteoclasts but only osteoclast precursors/progenitors which are still confined to the periosteum. Tissue type PA stimulated osteoclastic resorption (measured as 45Ca-release) in 17-day-old fetal metacarpals but not in radii of the same animal. Blocking the enzymatic activity of tPA did not inhibit its effect on osteoclastic resorption. Plasmin, the direct product of PA enzymatic activity, did not induce osteoclastic resorption. However, a tPA-mutant missing the growth-factor-like domain of the molecule, failed to stimulate 45Ca-release from the metacarpals. In addition, in both systems tPA and transforming growth factor alpha had similar effects on osteoclastic resorption. The finding that tPA stimulated 45Ca-release only in the metacarpals suggests that tPA has an effect on osteoclast formation rather than on the activity of already mature osteoclasts. Under the experimental conditions used this effect seems to be mediated by the growth factor domain of tPA rather than by the enzymatic activity of the molecule.
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PMID:The effect of tissue type plasminogen activator (tPA) on osteoclastic resorption in embryonic mouse long bone explants: a possible role for the growth factor domain of tPA. 153 5

Plasmin is known to activate platelets. However, it is not clear whether plasminogen activators as used in thrombolytic therapy can aggregate platelets and how this relates to the ability of each activator to convert plasminogen to plasmin. Urokinase (UK) and streptokinase (SK) activated purified plasminogen (2 microM) in a concentration-dependent manner. The rates of aggregation of washed platelets by the above plasminogen activators and plasminogen were similar to the extent of activation of plasminogen to plasmin in the absence of platelets. UK or SK (0.2 microM) and plasminogen (2 microM) aggregated platelets modified by an ADP affinity analog, 5'-p-fluorosulfonylbenzoyladenosine (FSBA), and cleaved aggregin, a putative ADP receptor, in [3H]FSBA-modified platelets. These results suggest that the effect was independent of ADP. In contrast, incubation mixtures containing only plasminogen (2 microM) and single chain tissue plasminogen activator (sc-tPA) (less than or equal to 0.12 microM) neither activated the zymogen to an appreciable extent nor aggregated platelets. But, in the presence of fibrin(ogen) fragments (tPA-stimulator), a mixture of plasminogen and sc-tPA aggregated unmodified and FSBA-modified platelets, and cleaved aggregin. The results imply that platelets, in the presence of t-PA stimulator, potentiate activation of plasminogen to plasmin by t-PA, as previously reported. P1, Phe-Gln-Val-Val-Cys-(NpyS)-Gly-NH2, (NpyS = 3-nitro-2-thiopyridine), a synthetic hexapeptide capable of binding to and inhibiting calpain, has been shown to inhibit platelet aggregation induced by purified plasmin. P1 inhibited platelet aggregation by plasminogen and any of the three plasminogen activators. Our results show that at plasma concentrations of plasminogen and at levels of UK and SK attained after infusion of these agents during thrombolysis, these mixtures can cause maximum aggregation which may contribute to reocclusion and stenosis following infarct therapy. P1 can effectively inhibit platelet aggregation under such conditions.
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PMID:Aggregation of washed platelets by plasminogen and plasminogen activators is mediated by plasmin and is inhibited by a synthetic peptide disulfide. 153 63


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