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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Incubation of HTC rat hepatoma cells with the synthetic glucocorticoid dexamethasone rapidly inhibits plasminogen activator (PA) activity and reveals the presence of a specific PA inhibitor (PAI-1). To determine whether the hormonal inhibition of PA activity reflects a decrease in the amount of PA or an increased amount of the inhibitor, or both, we have assayed PA and PAI-1 immunologically. HTC PA was determined to be entirely of the tissue type (tPA), and both free and complexed antigen was quantified by a RIA using rabbit antirat tPA, with rat insulinoma tPA as tracer and standard. PAI-1 was quantified by a Western blot assay using rabbit anti-HTC PAI-1 antibody and purified HTC PAI-1 as standard. Under conditions in which dexamethasone inhibited PA activity by 90%, there was no decrease in the cellular content of tPA antigen. Paradoxically, dexamethasone increased tPA antigen approximately 1.5-fold. Under these same conditions, dexamethasone increased PAI-1 antigen 4- to 5-fold. We conclude that the glucocorticoid inhibition of tPA activity in HTC cells is not secondary to a decrease in the amount of tPA but is secondary to the induction of a specific PA inhibitor.
Mol Endocrinol 1987 Jan
PMID:Dexamethasone inhibition of tissue-type plasminogen activator (tPA) activity: paradoxical induction of both tPA antigen and plasminogen activator inhibitor. 313 52

FSH and GnRH both stimulate rat granulosa cells to produce tissue-type plasminogen activator (tPA). We have studied the molecular mechanisms involved in the action of these hormones by measuring tPA mRNA levels in primary cultures of rat granulosa cells. When granulosa cells were cultured in the presence of FSH or GnRH the level of tPA mRNA was increased 20- and 12-fold, respectively. The induction of tPA mRNA by FSH and GnRH was additive and the kinetics of induction differed. The effect of FSH could be mimicked by bromo-cAMP or forskolin, and was drastically enhanced by cotreatment with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine. These findings are consistent with the notion that FSH mediates its effect through the protein kinase A pathway. GnRH is believed to augment phospholipid turnover in granulosa cells, leading to the activation of the protein kinase C pathway. Like GnRH, the protein kinase C activator phorbol myristate acetate also induced tPA mRNA in granulosa cells. In the presence of the protein synthesis inhibitor, cycloheximide, FSH-stimulated tPA message levels were enhanced by 30-fold, revealing superinduction of tPA mRNA levels by this pathway. In contrast the induction of tPA mRNA by GnRH was inhibited by cycloheximide indicating that the synthesis of an intermediate protein is required for the GnRH effect. Our data suggest that FSH and GnRH increase the tPA mRNA levels by two distinct pathways in cultured granulosa cells, providing a model system for studying the hormonal regulation of tPA gene expression.
Mol Endocrinol 1988 Sep
PMID:Hormonal regulation of tissue-type plasminogen activator messenger ribonucleic acid levels in rat granulosa cells: mechanisms of induction by follicle-stimulating hormone and gonadotropin releasing hormone. 313 93

Poly(A)+-RNA from human kidney and human embryonal lung fibroblasts fractionated by sucrose gradient centrifugation was translated in Xenopus oocytes. Assay for plasminogen-dependent fibrinolytic activity detected synthesis of secreted plasminogen activator and revealed the active fraction of poly(A)+-RNA with a sedimentation coefficient of approximately 23S. Translation products of the active fraction were immunoadsorbed by antiurokinase monoclonal antibodies immobilized on sepharose. Gel electrophoretic analysis of the protein products showed that the 23S fraction of poly(A)+-RNA from human kidney contains mRNA for single-chain urokinase-type plasminogen activator with apparent molecular weight of approximately 50 kDa.
Mol Biol (Mosk)
PMID:[mRNA for the plasminogen activator of the urokinase type: translation in oocytes of Xenopus laevis]. 339 55

Primary cultures of skeletal muscle cells secrete plasminogen activator (PA) activity to the conditioning medium and display membrane-bound PA. Growth of these cells in culture in presence of 10(-7) M dexamethasone resulted in a marked reduction of the membranal and secreted PA activity. The hormone also reduced cytosolic creatine phosphokinase (CPK) activity and cytosolic protein content. However, cell viability and their ability to undergo fusion were uneffected. The extent of hormone-induced reduction in PA activity depended on the time and extend of exposure. Maximal suppression was obtained by exposing the cells to dexamethasone during the first 4 days of culture. The medium conditioned with dexamethasone-treated cells did not inhibit plasmin, endogenous PA or exogenous PA. Exposure of the conditioned medium from hormone-treated cells to sodium dodecyl sulphate (SDS) or trypsin restored the activity to values observed in media from cells not exposed to the hormone. Acidification of the medium failed to reactivate the enzyme. The myogenic cell line L-8 also displayed membrane-bound PA activity, which was of a comparable magnitude in both fusing and non-fusing L-8 cells. However, in contrast to the primary cultures, exposure of L-8 cells to dexamethasone had no effect on their PA activity whether studied under conditions which allowed or prohibited fusion. The present findings imply that PA has no conducive role in the process of fusion associated with maturation of skeletal muscle cells.
Mol Cell Biochem 1986 Feb
PMID:Plasminogen activator activity in differentiating rat myoblasts. 351 60

Human carcinoma HEp-3 lost its tumorigenic and metastatic potential upon prolonged culture in vitro. This change was accompanied by a reduced production of plasminogen activator (PA) of the urokinase type (uPA), which is secreted by HEp-3 cells, a change in response to effectors that modulate uPA production, and an alteration of cell morphology. Similar but more rapid changes occurred when malignant HEp-3 cells were exposed to dimethyl sulfoxide (DMSO). uPA activity in the culture medium dropped below 50% of the control level within 6 h after the addition of DMSO and became undetectable after 24 h of treatment. This drop in uPA activity was not caused by an increased production of PA inhibitors. The cell-associated uPA decreased to 25 to 30% of the control level within 6 h of DMSO treatment and remained at this level for at least 96 h; the reduced uPA production was partially accounted for by a rapid decrease in the functional and chemical concentration of uPA mRNA. In contrast, the concentrations of most of the abundant mRNA species did not appear to be significantly affected, and cell growth was only slightly inhibited in the presence of DMSO. Malignant HEp-3 cells treated with DMSO responded to cholera toxin with an enhanced production of uPA, and their morphology became indistinguishable from that of nonmalignant HEp-3 cells grown in vitro for prolonged periods of time. All of the above changes were fully and rapidly reversible. The inhibitory effect of DMSO on PA production appears to be specific for uPA of human cell lines.
Mol Cell Biol 1985 Dec
PMID:Effect of dimethyl sulfoxide on human carcinoma cells, inhibition of plasminogen activator synthesis, change in cell morphology, and alteration of response to cholera toxin. 383 48

Hypersensitivity granulomas induced by infection with Schistosoma mansoni were isolated from the livers of BALB/c mice after 7, 8, 10, and 12 weeks. The parasite egg-granulomas were sequentially extracted with a Tris-buffered saline (soluble fraction) and 2 M KSCN (bound fraction). Fibrinolytic enzyme activity measured with both synthetic substrates and fibrin plates demonstrated an elevated level of plasminogen activator activity in the bound fraction 7-8 weeks after infection when mature granulomas first began to appear, followed by a gradual decrease 10-12 weeks after infection. An electrophoretic enzymography technique revealed multiple molecular species of plasminogen activator at Mr = 95K, 74K, 60K, 45K, and 24K. The bands with Mr = 45K and 24K were found compatible with the electrophoretic pattern of macrophage-plasminogen activator. When the granulomas reached maximum size after 10 to 12 weeks, the plasminogen activator with 45K and 24K diminished, while plasminogen activator activity at Mr = 95K, 74K, and 60K remained unchanged suggesting the presence of both vascular and tissue types of plasminogen activators. There was no urokinase-type plasminogen activator detectable in granulomas at any time. In the soluble fraction no enzymatic activity was found, whereas regulating inhibitor activity for plasminogen activator was consistently detectable.
Exp Mol Pathol 1985 Aug
PMID:Detection of granuloma-associated plasminogen activator in experimental murine schistosomiasis. 404 36

Expression of human tissue-type plasminogen activator (t-PA) at high levels has been achieved in Chinese hamster ovary (CHO) cells by cotransfection and subsequent coamplification of the transfected sequences. Expression vectors containing the t-PA cDNA gene and dihydrofolate reductase (DHFR) cDNA gene were cotransfected into CHO DHFR-deficient cells. Transformants expressing DHFR were selected by growth in media lacking nucleosides and contained low numbers of t-PA genes and DHFR genes. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate generated cells which had amplified both DHFR genes and t-PA genes over 100-fold. These cell lines expressed elevated levels of enzymatically active t-PA. To optimize both t-PA sequence amplification and t-PA expression, various modifications of the original procedure were used. These included alterations to the DHFR expression vector, optimization of the molar ratio of t-PA to DHFR sequences in the cotransfection, and modification of the methotrexate resistance selection procedure. The structure of the amplified DNA, its chromosomal location, and its stability during growth in the absence of methotrexate are reported.
Mol Cell Biol 1985 Jul
PMID:Coamplification and coexpression of human tissue-type plasminogen activator and murine dihydrofolate reductase sequences in Chinese hamster ovary cells. 404 Jun 3

Our studies first demonstrated that established hamster cell lines transformed in vitro by herpesviruses activate plasminogen more effectively than normal hamster fibroblasts. This ability is probably due to increased levels of the enzyme plasminogen activator (PA). In the studies described here, the 333-8-9 cell line, originally transformed by herpes simplex virus type 2 strain 333, was used to derive subclonal lines that maintained stable PA phenotypes over the course of long in vitro passage. We were interested in correlating tumor formation by the subclones with their fibrinolytic capacity. Cells were, therefore, single-cell subcloned twice, and resulting cultures were tested for ability to activate plasminogen in vitro. PA activity was then quantitated by [125I]fibrin lysis assay, and high- and low-activity subclones were isolated; these retained high- or low-activity phenotypes. Syngeneic newborn hamsters were inoculated with these subclones and observed for the appearance of palpable tumors. A strong correlation between enzyme activity and tumor formation was observed in four separate trials; animals receiving high-PA subclones developed tumors more rapidly than those inoculated with the parental cell line. Tumors were also excised from test animals, and the cell lines established from the tumors were tested in vitro at different passages for their ability to activate plasminogen. These tumor cells were then reinoculated into syngeneic animals to confirm the tumorigenicity of cell lines with high fibrinolytic activity. In these experiments, the positive correlation between PA production and tumorigenicity was confirmed.
Mol Cell Biol 1981 May
PMID:Tumorigenicity of herpesvirus-transformed cells correlates with production of plasminogen activator. 610 Sep 64

Sertoli cells in primary cultures produce plasminogen activator activity, and release it into the medium at rates greatly influenced by a variety of factors, including cell density, the presence of hormones, incubation temperature and duration of culture. In Sertoli cells maintained in culture in the presence of dibutyryl cAMP, the amounts of plasminogen activator activity secreted per cells were maximal at cell densities up to 2.5 microgram DNA/cm2 (350 units/microgram cell DNA), and declined to 40 units/microgran cell DNA at a density of 22 micrograms DNA/cm2. Concentrations of follicle-stimulating hormone (FSH) required to elicit half-maximal stimulation of the production of plasminogen activator activity were 0.37 micrograms/ml for oFSH-NIH S12 and 8 ng/ml for the more purified of SH-S1528C2. The ED50 for dibutyryl cAMP was found to be 0.08 mM. Addition of an inhibitor of phosphodiesterase (3-isobutyl-l-methylxanthine) enhanced the formation of plasminogen activator by cells cultured in the presence of FSH. Addition to the culture medium of testosterone, epidermal growth factor, insulin, human chorionic gonadotropin or prostaglandins (E1, E2 or F1 alpha) did not result in increased production of PA activity by Sertoli cells. Cells in culture for as long as 14 days remained responsive to FSH or dibutyryl cAMP. Increases in cellular levels of plasminogen activator became evident within 2-4 after addition of either FSH or dibutyryl cAMP to the medium. The stimulation of FSH or dibutyryl cAMP of the production of plasminogen activator activity was shown to be dependent upon de novo synthesis of RNA and protein. Levels of enzyme activity released by Sertoli cells maintained in culture for 48 h at 37 degrees C were approx. 50% higher than plasminogen activator released by cells cultured at 32 degrees C. The control of the production of plasminogen activator activity by Sertoli cells was discussed in relation to the control of plasminogen activator production by granulose cells, and the possible role of plasminogen activator in gonadal functions.
Mol Cell Endocrinol 1982 May
PMID:The control of the synthesis and secretion of plasminogen activator by rat sertoli cells in culture. 617 77

Macrophages which are intimately involved in acute and chronic inflammatory reactions are functionally heterogeneous not only with regard to the expression of constitutive functions but also in their response to lymphokine signals. The biological basis of this heterogeneity is poorly understood. Whether we are dealing with true subpopulations or with intermediately stable phenotypes has not been resolved. To study these questions we adopted a bone marrow liquid culture system in which bone marrow cells--in the presence of a colony-stimulating factor--proliferate and differentiate into macrophages. This culture system was taken here as a model to study the expression of various functions by macrophages in the course of maturation. Several tests were performed daily and in parallel from the same batch of cells. It was found that certain functions were expressed early and were also characteristic for mature macrophages such as Fc receptors, phagocytosis of latex beads and unspecific esterase. Other functions appeared and disappeared in an ordered sequence, such as the response to macrophage migration inhibitory factor and chemotactic factor as well as the production of interferon and plasminogen activator. The time course of functional expression was strongly dependent on proliferation of precursor cells as well as on proliferation of differentiated macrophages. It is concluded that the transient phenotypic expression of functions during differentiation is the basis for the functional heterogeneity of macrophages.
Mol Immunol 1982 Oct
PMID:Heterogeneity of macrophages in response to lymphokines and other signals. 618 13


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