Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The urokinase-type plasminogen activator receptor (u-PAR) facilitates extracellular matrix degradation in part by accelerating plasmin formation at the cell surface. We previously reported that u-PAR expression is elevated in colon cancer cell lines characterized by their in vitro invasive capacity. Since, u-PAR expression is increased by a variety of growth factors, which signal through the extracellular signal-regulated kinases 1 and 2 (ERK1/ERK2), we determined if these mitogen-activated protein kinases (MAPKs) regulate u-PAR expression in two cultured colon cancer cell lines. An in-gel kinase assay showed that ERK1 activity was considerably higher in RKO cells, which display > or = 10(5) receptors/cell, than the GEO cells which have approximately 10(4) urokinase receptors per cell. The expression of either an ERK-inactivating phosphatase (CL100), or a kinase-defective ERK1, decreased the activity of a u-PAR promoter-driven CAT reporter in RKO cells. Immune complex kinase assays indicated that the constitutive ERK1 activity in RKO cells was largely a result of an activated MEK1. Further, treatment of RKO cells with a specific inhibitor (PD 098059) of MEK1 activation, which diminished ERK1 activity, reduced the amount of urokinase specifically bound to the cell surface and this was associated with reduced laminin degradation. The expression of a dominant negative c-Raf-1 also reduced u-PAR promoter activity suggesting that MEK1 activation involved an activator at, or upstream, of this serine-threonine kinase. Transfection of the u-PAR-deficient GEO cells with a constitutively activated MEK1 expression construct up-regulated u-PAR promoter activity. Similarly treatment of GEO cells with a phosphatase inhibitor (sodium vanadate) caused a dose-dependent increase in ERK1 activity which paralleled increased cell surface binding of urokinase. Taken together, these data suggest that elevated u-PAR expression, in at least a sub-population of colon cancer, is partly a consequence of a constitutively activated ERK-1-dependent signaling cascade.
 ...
PMID:Elevated urokinase-type plasminogen activator receptor expression in a colon cancer cell line is due to a constitutively activated extracellular signal-regulated kinase-1-dependent signaling cascade. 919 Oct 56

The low density lipoprotein receptor-related protein (LRP) has been reported to regulate cellular migration. In this study, an antisense RNA expression strategy was used to reduce LRP to undetectable levels in HT 1080 fibrosarcoma cells. The LRP-deficient cells demonstrated increased levels of cell-surface uPAR, higher levels of uPA in conditioned medium, increased migration on vitronectin-coated surfaces, and increased invasion of Matrigel. LRP-deficient cells also demonstrated increased levels of phosphorylated extracellular signal-regulated kinase (ERK) in the absence of exogenous stimulants. Antibodies which block binding of endogenously produced uPA to uPAR reduced ERK phosphorylation and migration of LRP-deficient cells to the levels observed with control cells. Inhibitors of ERK activation, including PD098059 and dominant-negative MEK1, also decreased the migration of LRP-deficient but not control cells. By contrast, constitutively active MEK1 stimulated the migration of control but not LRP-deficient cells. Although Matrigel invasion by LRP-deficient cells was inhibited by the proteinase inhibitor, aprotinin, PD098059 in combination with aprotinin was necessary for an optimal effect. Expression of the VLDL receptor in LRP-deficient cells reversed the changes in cellular migration and invasion. These studies demonstrate that binding of endogenously produced uPA to uPAR may serve as a major determinant of basal levels of activated ERK and, by this mechanism, regulate cellular migration and invasion. By regulating the uPA/uPAR system, LRP may also regulate ERK activation, cellular migration, and invasion.
 ...
PMID:Extracellular signal-regulated kinase functions in the urokinase receptor-dependent pathway by which neutralization of low density lipoprotein receptor-related protein promotes fibrosarcoma cell migration and matrigel invasion. 1059 31

We have previously reported a constitutively activated form of the Flt-1 kinase (BCR-FLTm) molecularly engineered based on the structural backbone of the activated tyrosine kinase BCR-ABL. Here we show that it can induce not only growth stimulation but also tubulogenic differentiation of non-tubulogenic NP31 (non parenchymal) sinusoidal endothelial cells of rat liver in basement membrane matrix. Tubules formed in vitro were accompanied by fenestration structures and allowed circulation when transplanted into syngeneic animals. This biological response was not observed in other activated forms of kinases constructed in a similar fashion, which include Trk (BCR-TRK), KDR (BCR-KDR), and the parental BCR-ABL. Interestingly, formation of fine tubules was accomplished with lower but not higher expression levels of BCR-FLTm. Compared to NP cells in primary culture NP31 is deficient in expression of alpha1 integrin subunit, which was restored by expression of BCR-FLTm that had tubulogenic ability. Matrix-induced tyrosine phosphorylation of an adaptor protein Shc with recruitment of Grb-2 was observed even when tubulogenesis was nearly completed at G1 stage of the cell cycle in 2-3 weeks. Activation of matrix metalloproteinase 2 (MMP-2) and expression of urokinase type plasminogen activator (uPA) was observed with cellular invasion into matrix at the depth of 200-300 microm. Inhibitors for MAP kinase activator MEK1 and for serine proteases showed deleterious effects on the tubulogenesis. We suppose that matrix ligand-induced integrin signals cooperate with a low level of Flt-1 kinase activity to promote tubulogenic behaviors of endothelial cells in this system.
 ...
PMID:An oncogenic form of the Flt-1 kinase has a tubulogenic potential in a sinusoidal endothelial cell line. 1072 21

In a previous work we have reported evidences on the mitogenic activity of urokinase-type and tissue-type plasminogen activator (u-PA, t-PA) on serum-deprived human dermal fibroblasts. In this work we have studied the transcription-dependent changes of some cell-cycle related genes associated with the biological activity of PAs, as well as the possible involvement of protein tyr kinases (PTK) and/or protein kinase C (PKC) in the mitogenic signal transduction. The data obtained demonstrate that the growth factor activity of PAs is associated with: - a rapid transient activation of early response genes, c-fos, c-jun and c-myc; - the subsequent coordinated down-regulation of p53 and p21CIP1; - the constant expression of the MEK1 mRNA in every phase of the cell cycle. Quiescent (G0) cells did not express c-fos, c-jun, c-myc and cyclin A, but upon stimulation with mitogens (fetal calf serum (FCS), u-PA, t-PA) the cyclin A mRNA expression was observed in concomitance with the activation of DNA synthesis. Therefore u-PA, t-PA and FCS similarly modulate the expression of c-fos, c-jun, c-myc, p53, p21CIP1 and cyclin A with only slight differences likely related to the time required for activation of DNA synthesis. The PAs mitogenic stimulation of serum-starved cells was associated with the internalization of their molecules, as revealed by immunostaining. The biological activity of u-PA, t-PA, as well as that of limiting concentration of FCS (1%), was mediated by PTK and PKC. Conversely, PTK, but not PKC, was involved in the activation of the proliferative response of basic fibroblast growth factor in the same experimental conditions. In conclusion, u-PA and t-PA can utilize two different pathways, one depending on PTK and the other on PKC in a way similar to the mitogenic activity induced by low concentration of FCS (1%).
 ...
PMID:Gene response of human skin fibroblasts to urokinase- and tissue-type plasminogen activators. 1080 Oct 75

Increased urokinase plasminogen activator (u-PA) production is associated with tumor invasion and metastasis in several malignancies, including breast cancer. The mechanisms underlying constitutive u-PA expression are not well understood. We examined the relationship between the signal strength of the ERK pathway and the level of u-PA expression in the metastatic human breast cancer cell line MDA-MB-231. Treatment with the MEK1 inhibitor PD98059 resulted in decreased ERK1/2 phosphorylation and decreased u-PA mRNA and protein expression. Inhibition of ERK1/2 activity also led to decreased cell proliferation and to decreased cyclin D1 expression. Less than 5% of total ERK1/2 was phosphorylated in exponentially growing MDA-MB-231 cells, and ERK1/2 activity could be stimulated by okadaic acid. Okadaic acid did not stimulate u-PA expression, but induced strong expression of the cdk-inhibitor p21Cip1. These findings suggest that ERK1/2 signaling is tuned to a level which results in high u-PA expression and rapid cell proliferation.
 ...
PMID:ERK signalling in metastatic human MDA-MB-231 breast carcinoma cells is adapted to obtain high urokinase expression and rapid cell proliferation. 1091 9

Urinary trypsin inhibitor (UTI), a Kunitz-type protease inhibitor, interacts with cells as a negative modulator of the invasive cells. Human ovarian cancer cell line, HRA, was treated with phorbol ester (PMA) to evaluate the effect on expression of urokinase-type plasminogen activator (uPA), since the action of uPA has been implicated in matrix degradation and cell motility. Preincubation of the cells with UTI reduced the ability of PMA to trigger the uPA expression at the gene level and at the protein level. UTI-induced down-regulation of PMA-stimulated uPA expression is irreversible and is independent of a cytotoxic effect. Down-regulation of uPA by UTI is mediated by its binding to the cells. We next asked whether the mechanism of inhibition of uPA expression by UTI was due to interference with the protein kinase C second messenger system. An assay for PKC activity demonstrated that UTI does not directly inhibit the catalytic activity of PKC and that PMA translocation of PKC from cytosol to membrane was inhibited by UTI, indicating that UTI inhibits the activation cascade of PKC. PMA could also activate a signaling pathway involving MEK1/ERK2/c-Jun-dependent uPA expression. When cells were preincubated with UTI, we could detect suppression of phosphorylation of these proteins. Like several types of PKC inhibitor, UTI inhibited PMA-stimulated invasiveness. We conclude that UTI markedly suppresses the cell motility possibly through negative regulation of PKC- and MEK/ERK/c-Jun-dependent mechanisms, and that these changes in behavior are correlated with a coordinated down-regulation of uPA which is likely to contribute to the cell invasion processes.
 ...
PMID:Suppression of urokinase expression and invasiveness by urinary trypsin inhibitor is mediated through inhibition of protein kinase C- and MEK/ERK/c-Jun-dependent signaling pathways. 1105 91

Our previous works demonstrated that ligands of macrophage scavenger receptor (MSR) induce protein kinases (PKs) including protein-tyrosine kinase (PTK) and up-regulate urokinase-type plasminogen activator expression (Hsu, H. Y., Hajjar, D. P., Khan, K. M., and Falcone, D. J. (1998) J. Biol. Chem. 273, 1240--1246). To continue to investigate MSR ligand-mediated signal transductions, we focus on ligands, oxidized low density lipoprotein (OxLDL), and fucoidan induction of the cytokines tumor necrosis factor-alpha (TNF) and interleukin 1 beta (IL-1). In brief, in murine macrophages J774A.1, OxLDL and fucoidan up-regulate TNF production; additionally, fucoidan but not OxLDL induces IL-1 secretion, prointerleukin 1 (proIL-1, precursor of IL-1) protein, and proIL-1 message. Simultaneously, fucoidan stimulates activity of interleukin 1-converting enzyme. We further investigate the molecular mechanism by which ligand binding-induced PK-mediated mitogen-activated protein kinase (MAPK) in regulation of expression of proIL-1 and IL-1. Specifically, fucoidan stimulates activity of p21-activated kinase (PAK) and of the MAPKs extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38. Combined with PK inhibitors and genetic mutants of Rac1 and JNK in PK activity assays, Western blotting analyses, and IL-1 enzyme-linked immunosorbent assay, the role of individual PKs in the regulation of proIL-1/IL-1 was extensively dissected. Moreover, tyrosine phosphorylation of pp60Src as well as association between pp60Src and Hsp90 play important roles in fucoidan-induced proIL-1 expression. We are the first to establish two fucoidan-mediated signaling pathways: PTK(Src)/Rac1/PAK/JNK and PTK(Src)/Rac1/PAK/p38, but not PTK/phospholipase C-gamma 1/PKC/MEK1/ERK, playing critical roles in proIL-1/IL-1 regulation. Our current results indicate and suggest a model for MSR ligands differentially modulating specific PK signal transduction pathways, which regulate atherogenesis-related inflammatory cytokines TNF and IL-1.
 ...
PMID:Ligands of macrophage scavenger receptor induce cytokine expression via differential modulation of protein kinase signaling pathways. 1139 Mar 74

Binding of the urokinase-type plasminogen activator (uPA) to its receptor activates diverse cell signaling pathways. How these signals are integrated so that cell physiology is altered remains unclear. In this study, we demonstrated that migration of MCF-7 breast cancer cells and HT-1080 fibrosarcoma cells on serum-coated surfaces is stimulated by agents that activate ERK, including uPA, epidermal growth factor, and constitutively active MEK1. The promigratory activity of these agents was entirely blocked not only by the MEK-specific antagonist PD098059, but also by antagonists of the Rho-Rho kinase pathway, including Y-27632 and dominant-negative RhoA (RhoA-N19). uPA did not significantly increase the level of GTP-bound RhoA, suggesting that the constitutive activity of the Rho-Rho kinase pathway may be sufficient to support ERK-stimulated cell migration. Paradoxically, Y-27632 and RhoA-N19 increased ERK phosphorylation in MCF-7 cells, providing further evidence that ERK activation alone does not promote cell migration when Rho kinase is antagonized. When MCF-7 cell migration was stimulated by ERK-independent processes such as expression of the beta(3) integrin subunit or changing the substratum to type I collagen, Y-27632 and RhoA-N19 failed to inhibit the response. This study supports a model in which the Ras-ERK and Rho-Rho kinase pathways cooperate to promote cell migration. Neutralizing either pathway is sufficient to block the response to agents that stimulate cell migration by activating ERK.
 ...
PMID:Cooperativity between the Ras-ERK and Rho-Rho kinase pathways in urokinase-type plasminogen activator-stimulated cell migration. 1180 8

Calcitonin (CT) is a polypeptide hormone and has a variety of functions including regulation of urinary calcium excretion. By using a cDNA subtraction hybridization method, we identified that NF-IL3A and urokinase-type plasminogen activator (uPA) genes were up-regulated by CT in porcine renal cell line LLC-PK1. CT-mediated induction of these genes was not inhibited by cycloheximide. These data suggest that these up-regulations are not induced by increased synthesis of regulating proteins; therefore, they are immediately response early (IE). We also found that CT treatment led to the phosphorylation of Erk1/2. We demonstrated that PD98059, a MEK1 inhibitor, inhibited CT-induced mRNA expressions of uPA, but had no obvious influence on the NF-IL3A induction. These results demonstrated the inductions of uPA by CT involve Erk1/2 phosphorylation. We provide the first evidence that NF-IL3A expression is up-regulated by CT. The present findings suggest that the transcriptions of the NF-IL3A and uPA could be induced by CT and might be important mediators of CT function in renal cells.
 ...
PMID:Induction of uPA but not NF-IL3A by calcitonin is dependent on Erk1/2 phosphorylation in porcine renal cell line LLC-PK1. 1182 Jul 89

Our laboratory showed that bikunin, a Kunitz-type protease inhibitor, suppresses 4beta-phorbol 12-myristate 13-acetate (PMA)- or tumor necrosis factor-alpha (TNFalpha)-induced urokinase-type plasminogen activator (uPA) expression in different cell types. In addition to its effects on protease inhibition, bikunin could be modulating other cellular events associated with the metastatic cascade. To test this hypothesis, we examined whether bikunin was able to suppress the expression of uPA receptor (uPAR) mRNA and protein in a human chondrosarcoma cell line, HCS-2/8, and two human ovarian cancer cell lines, HOC-I and HRA. The present study showed that (a) bikunin suppresses the expression of constitutive and PMA-induced uPAR mRNA and protein in a variety of cell types; (b) an extracellular signal-regulated kinase (ERK) activation system is necessary for the PMA-induced increase in uPAR expression, as PD098059 and U0126, which prevent the activation of MEK1, reduce the uPAR expression; (c) bikunin markedly suppresses PMA-induced phosphorylation of ERK1/2 at the concentration that prevents uPAR expression, but does not reduce total ERK1/2 antigen level; (d) bikunin has no ability to inhibit overexpression of uPAR in cells treated with sodium vanadate; and (e) we further studied the inhibition of uPAR expression by stable transfection of HRA cells with bikunin gene, demonstrating that bikunin secretion is necessary for inhibition of uPAR expression. We conclude that bikunin downregulates constitutive and PMA-stimulated uPAR mRNA and protein possibly through suppression of upstream targets of the ERK-dependent cascade, independent of whether cells were treated with exogenous bikunin or transfected with bikunin gene.
 ...
PMID:Suppression of urokinase receptor expression by bikunin is associated with inhibition of upstream targets of extracellular signal-regulated kinase-dependent cascade. 1218 Sep 71


1 2 3 Next >>