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)

Interstitial fibrosis is one of the most deleterious events during the progression of renal deterioration after renal mass reduction. In vivo, hydroxymethylglutaryl CoA reductase inhibitors (HRI) were shown to reduce progression of glomerulosclerosis, but the mechanisms are still unclear. The present study investigates, in vivo, whether lovastatin, a potent HRI, was able to modulate the plasminogen-plasmin pathway, one of the most efficient systems involved in extracellular matrix remodeling, and characterizes in vitro the cellular mechanisms of these effects. Proximal tubules freshly isolated from rats treated for 2 d with lovastatin (4 mg/kg per d) showed increased tissue-type plasminogen activator (tPA) and urokinase (uPA) activities and antigens. Incubation with lovastatin (5 microM) of proximal tubules isolated from untreated rats induced an increase in tPA and uPA and a decrease in plasminogen activator inhibitor-1 (PAI-1) activities. In vitro, supernatants, cytosols, and membranes of renal proximal tubular cells in primary cultures had no detectable uPA activity, and lovastatin (0.1 to 10 microM) induced an increase in tPA and a decrease in PAI-1 activities and antigens. These effects were reversed by mevalonate and geranylgeranyl-pyrophosphate (GGPP) but not by farnesyl-pyrophosphate or LDL cholesterol. C3 exoenzyme, an inhibitor of the geranylgeranylated-activated Rho protein, reproduced the effect of lovastatin on tPA and PAI- activity and blocked its reversion by GGPP. The effect of lovastatin was associated with a disruption of cellular actin stress fibers, which was reversed by GGPP and reproduced by C3 exoenzyme. In conclusion, HRI can modify the fibrinolytic potential of proximal tubules, most likely via inhibition of geranylgeranylated Rho protein and disruption of the cytoskeleton. The resulting increase of proteolytic activity of tubular cells may serve to prevent extracellular matrix deposition and renal interstitial fibrosis.
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PMID:Lovastatin modulates in vivo and in vitro the plasminogen activator/plasmin system of rat proximal tubular cells: role of geranylgeranylation and Rho proteins. 969 59

Liver regeneration after partial hepatectomy (PHx) of the liver serves as a model for studying normal growth factor signals that become aberrant in cancer. Growth factor signals that may play a role in initiating the proliferation of hepatocytes after 70% PHx in the rat were investigated immediately after surgical resection of the liver. Presumptive activity was evaluated by determining the tyrosine phosphorylation state of receptors for epidermal growth factor (EGF) and hepatocyte growth factor (HGF) in the liver after PHx and after sham operation as a control. Under these conditions, it was determined that the EGF receptor was constitutively phosphorylated. EGF receptor tyrosine phosphorylation, however, was increased over basal levels by 60 min after resection. The HGF receptor, c-Met, was minimally phosphorylated in control livers, but a biphasic increase in phosphorylation was observed at 1-5 min after PHx and 60 min postsurgery. A slight increase in c-Met phosphorylation was observed in the sham-operated livers, but the signal was significantly less when compared with that in resected livers. Furthermore, 1 min after PHx, but not sham operation, urokinase-type plasminogen activator (u-PA) and u-PA receptor were observed in the immunoprecipitates of c-Met. Signaling downstream of growth factor receptor activation was also examined. There were no discernible phosphorylation changes in focal adhesion kinase during the early events after surgery in PHx; however, a rapid and sustained increase in the tyrosine phosphorylation of paxillin beginning 1 min after PHx, and a gradual increase in the phosphorylation beginning 5 min postsham operation, were observed. Changes in the activated state of the small GTP-binding protein Rho A and its associated proteins were seen but only after 3 h after PHx. The results indicate that HGF-related signal transduction cascades, which contribute to hepatocyte proliferation, are initiated within one min after PHx.
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PMID:Growth factor signal transduction immediately after two-thirds partial hepatectomy in the rat. 1046 91

The urokinase-type plasminogen activator receptor (uPAR) is involved in the regulation of cell motility in a variety of cell types. We show here that expression of human uPAR in growing murine fibroblasts leads to a dramatic reorganization of the actin cytoskeleton. uPAR expression induces multiple rapidly advancing protrusions that resemble the leading edge of migrating cells. The cytoskeletal changes are independent of uPA and activation of the RGD-binding activity of integrins but require uPAR binding to vitronectin (VN). The actin reorganization is blocked by coexpression of dominant negative versions of either Rac (N17Rac) or p130Cas, but not by inhibitors of Cdc42 or Rho, and is accompanied by a Rac-dependent increase in cell motility. In addition, a fourfold increase in the level of activated Rac is induced by uPAR expression. We conclude that uPAR interacts with VN both to initiate a p130Cas/Rac-dependent signaling pathway leading to actin reorganization and increased cell motility and to act as an adhesion receptor required for these responses. This mechanism may play a role in uPAR-mediated regulation of cell motility at sites where VN and uPAR are co-expressed, such as malignant tumors.
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PMID:Rac mediates cytoskeletal rearrangements and increased cell motility induced by urokinase-type plasminogen activator receptor binding to vitronectin. 1125 16

Cerivastatin is used in the treatment of hypercholesterolemia to inhibit 3-hydroxy 3-methylglutaryl coenzyme A reductase and thus prevent the synthesis of cholesterol precursors, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), responsible, respectively, for translocation of Ras and Rho to the cell membrane, a step required for their cell signaling, leading to cell proliferation and migration. Recently, it has been suggested that non lipid-related effects of statins could play a beneficial role in cancer therapy. In this study, we have investigated the mechanisms by which statins inhibit cancer and the types of cancers which could benefit from this therapy. In MDA-MB-231 cells, an aggressive breast cancer cell line with spontaneous activation of Ras and NFkappaB and overexpression of RhoA, cerivastatin induced inhibition of both cell proliferation and invasion through Matrigel. This anti-proliferative effect was related to G(1)/S arrest due to an increase in p21(Waf1/Cip1). The anti-invasive effect was observed from 18 h and could be explained by RhoA delocalization from the cell membrane, resulting in disorganization of the actin fibers and disappearance of focal adhesion sites. The importance of RhoA inactivation in both these inhibitory effects was proved by their reversion by GGPP but not by FPP. Moreover, cerivastatin was also shown to induce inactivation of NFkappaB, in a RhoA inhibition-dependent manner, resulting in a decrease in urokinase and metalloproteinase-9 expression, two proteases involved in cell migration. The participation of Ras inactivation is considered a subsidiary mechanism for the effects of cerivastatin, as they were not rescued by FPP. Prolonged treatment of MDA-MB-231 cells with high doses of cerivastatin induced a loss of cell attachment. Interestingly, the effect of cerivastatin was considerably lower on poorly invasive MCF-7 cells. In conclusion, our results suggest that cerivastatin inhibits cell signaling pathways involved in the invasiveness and metastatic properties of highly invasive cancers.
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PMID:Cerivastatin, an inhibitor of HMG-CoA reductase, inhibits the signaling pathways involved in the invasiveness and metastatic properties of highly invasive breast cancer cell lines: an in vitro study. 1147 Jul 41

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.
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PMID:Cooperativity between the Ras-ERK and Rho-Rho kinase pathways in urokinase-type plasminogen activator-stimulated cell migration. 1180 8

The membrane receptor for the neuropeptide bombesin/gastrin-releasing peptide (GRP) is expressed by a large fraction of human colorectal carcinoma cells. We reported previously a stimulation of cell adhesion and lamellipodia formation by the neuropeptide bombesin in the human, bombesin/GRP receptor-expressing, Isreco1 colorectal cancer cell line (J. C. Saurin et al., Cancer Res., 59: 962-967, 1999). Using invasion and motility assays, we demonstrate in this report that bombesin can both enhance the invasive capacity of Isreco1 cells in a dose-dependent manner (maximal effect at 1 nM) and stimulate the closure of wounds performed on confluent Isreco1 cells. These effects were reversed fully by the specific bombesin/GRP receptor antagonist D-Phe(6)-Bn(6-13)OMe used at 1 micro M. MMP-9 and urokinase-type plasminogen activator were expressed by Isreco1 cells, and bombesin did not significantly alter their level of secretion. Interestingly, exoenzyme C3 (10 micro g/ml) decreased cell invasiveness induced by bombesin by 70% and completely inhibited the migration of Isreco1 cells. Similarly, the Rho-kinase inhibitor Y-27632 dose-dependently reduced the effect of bombesin on cell invasion. Moreover, pull-down assays for GTP-bound RhoA demonstrated that bombesin was able to activate the small G-protein in Isreco1 cells. These results show that the neuropeptide bombesin is able to modulate invasiveness of Isreco1 colorectal carcinoma cells in vitro through a Rho-dependent pathway, leading to an increase in cell locomotion without a significant effect on tumor-cell associated proteolytic activity. These findings indicate that bombesin/GRP receptor expression may contribute to the cellular events that are critical for invasion/migration of colorectal carcinoma cells.
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PMID:Bombesin stimulates invasion and migration of Isreco1 colon carcinoma cells in a Rho-dependent manner. 1218 43

Lovastatin is a competitive inhibitor of 3-hydroxy 3-methylglutaryl coenzyme A reductase, the key regulatory enzyme of cholesterol biosynthesis. This enzyme catalyzes the formation of mevalonate, which is also the precursor of isoprenoid moieties, such as farnesol and geraniol, that are incorporated into several molecules essential for tumor cell signaling. Here, we describe that pretreatment with a non-cytotoxic concentration of lovastatin (10 microM) dramatically inhibited the metastatic ability of F311 mammary carcinoma cells in syngeneic BALB/c mice. Similarly, daily i.p. treatment of animals with a well-tolerated dose of lovastatin (10 mg/kg/day) significantly reduced the number of experimental lung metastases. In vitro, incubation of F3II monolayers in the presence of lovastatin caused a rounded-cell morphology. Immunofluorescence analysis revealed a lack of cortical actin organization, micrutubule disruption and inhibition of integrin-mediated focal contacts in lovastatin-treated cells. Exposure of F3II cells to lovastatin significantly inhibited tumor cell adhesion and migration, and coincubation with the cholesterol precursor mevalonate prevented these effects. Lovastatin reduced membrane localization of Rho protein, a signaling molecule involved in the regulation of actin-based cell motility that needs geranylation for membrane association and activation. In addition, lovastatin induced a dose-dependent inhibition in the secretion of urokinase, a key proteolytic enzyme during tumor invasion and metastasis, and a significant increase of tissue-type plasminogen activator, a marker of good prognosis in mammary cancer. These data suggest that antimetastatic properties of lovastatin are strongly associated with alterations in cytoskeleton organization and the consequent modulation of adhesion, motility and proteolysis.
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PMID:Lovastatin alters cytoskeleton organization and inhibits experimental metastasis of mammary carcinoma cells. 1240 93

Zoledronic acid (ZOL) is a nitrogen-containing bisphosphonate and its use in reducing osteoporosis and cancer-induced osteolysis is increasing. Recent findings indicated that ZOL has a direct effect on cancer cells. In this study, the effect of ZOL was examined on the aggressive MDA-MB-231 breast cancer cell line. ZOL induces an important inhibition of cell invasion at low concentrations (1 microM). This is not explained by modifications of proteases involved in cell invasiveness (matrix metalloproteinases and urokinase-type plasminogen activator), but by a disorganisation of actin cytoskeleton due to RhoA inhibition related to its defective prenylation as it was reversed by geranylgeraniol (GGOH) and mimicked by the Rho selective inhibitor C3 exoenzyme. In addition, ZOL inhibits the chemotactic effect induced by stromal cell-derived factor 1(SDF-1), a chemokine greatly involved in cancer metastasis to bone. This effect is related to both reduction of cell motility induced by RhoA inhibition and to a decreased expression of CXCR-4, the SDF-1 receptor. Finally, ZOL reduces Cox-2 expression and, consequently, the secretion of prostaglandins E2 (PGE2) in a RhoA-independent manner. This inhibition could contribute to bone protection in breast cancers because PGE2 stimulates osteoclast-mediated bone resorption. In summary, new insights in the mechanism of ZOL action on aggressive breast cancer cells are demonstrated and could explain its beneficial action in both the reduction of osteolysis and prevention of metastasis.
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PMID:New insights into the actions of bisphosphonate zoledronic acid in breast cancer cells by dual RhoA-dependent and -independent effects. 1277 33

Rho GTPases are overexpressed in human tumors and are involved in a variety of cellular processes such as organization of the actin cytoskeleton, cell-cell contact and malignant transformation. EGFR activation plays a key role in the acquisition of motile properties in carcinoma cells, and it has been proposed that downregulation of FAK activity is one of its most relevant consequences. In the present study, using mammary MCF-7 cells, we demonstrated that overexpression of the active form of the small GTPase RhoA induced the activation of EGFR by a phenomenon that depends on the activity of a metalloproteinase (MMP), which presumably cleaves a membrane-bound EGFR ligand. The EGFR tyrosine phosphorylation correlates with ERK1,2 activation and the stimulation of urokinase production. An aggressive mammary cell line (MDA-MB-231) that overexpresses both RhoA and EGFR in their active forms also displayed an MMP-dependent activation mechanism of EGFR. RhoA-GTP-transfected cells showed a cortical array of F-actin, rounded morphology, reduced spreading potential and a dephosphorylation of FAK that was released by integrin-dependent fibronectin adhesion and a specific EGFR tyrosine kinase inhibitor. Our results suggest that the MMP-dependent EGFR activation observed in V14 RhoA cells represents the starting point of a signaling route that promotes cell motility by activation of ERK1,2 and further enhancement of proteases production.
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PMID:Overexpression of RhoA-GTP induces activation of the Epidermal Growth Factor Receptor, dephosphorylation of focal adhesion kinase and increased motility in breast cancer cells. 1596 82

A large number of chronic lung diseases such as asthma bronchiale are associated with alveolar and/or bronchial inflammation accompanied by a damage of the alveolocapillary barrier. In this process proteolytic mechanisms may play a crucial role. The aim of the present study was to assess the role of TNF-alpha on the proteolytic activity of pulmonary epithelial cells and to find possible intracellular signaling pathways which may mediate the effect of TNF-alpha. For our studies we have used the A549 human lung epithelial cell line. Plasminogen activator and metalloproteinase activity was measured using zymography. TNF-alpha induced a time and concentration dependent activation of the urokinase type plasminogen activator (u-PA) and tissue type plasminogen activator (t-PA) activity in A549 cells. This effect could be blocked completely by dexamethasone and was reduced significantly by the Rho-kinase inhibitor Y27632. Similarly, an increased activity in the culture medium of the 72 kDa MMP-2 in response to TNF-alpha could be observed as well. This could be reduced by dexamethasone and Y27632. Our results show that TNF-alpha is at least partly responsible for an increased proteolytic activity and beside corticosteroids Rho-kinase may constitute a potential target for future therapeutical approaches.
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PMID:Regulation of proteolytic activity induced by inflammatory stimuli in lung epithelial cells. 1617 72


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