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

Plasminogen activator inhibitor 1 (PAI-1) is a major inhibitor of urokinase-type plasminogen activator (uPA). In this study, we explored the role of PAI-1 in cell signaling. In MCF-7 cells, PAI-1 did not directly activate the mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase (ERK) 1 and ERK2, but instead altered the response to uPA so that ERK phosphorylation was sustained. This effect required the cooperative function of uPAR and the very low density lipoprotein receptor (VLDLr). When MCF-7 cells were treated with uPA-PAI-1 complex in the presence of the VLDLr antagonist, receptor-associated protein, or with uPA-PAI-1(R76E) complex, which binds to the VLDLr with greatly decreased affinity, transient ERK phosphorylation (<5 min) was observed, mimicking the uPA response. ERK phosphorylation was not induced by tissue-type plasminogen activator-PAI-1 complex or by uPA-PAI-1 complex in the presence of antibodies that block uPA binding to uPAR. uPA-PAI-1 complex induced tyrosine phosphorylation of focal adhesion kinase and Shc and sustained association of Sos with Shc, whereas uPA caused transient association of Sos with Shc. By sustaining ERK phosphorylation, PAI-1 converted uPA into an MCF-7 cell mitogen. This activity was blocked by receptor-associated protein and not observed with uPA-PAI-1(R76E) complex, demonstrating the importance of the VLDLr. uPA promoted the growth of other cells in which ERK phosphorylation was sustained, including beta3 integrin overexpressing MCF-7 cells and HT 1080 cells. The MEK inhibitor, PD098059, blocked the growth-promoting activity of uPA and uPA-PAI-1 complex in these cells. Our results demonstrate that PAI-1 may regulate uPA-initiated cell signaling by a mechanism that requires VLDLr recruitment. The kinetics of ERK phosphorylation in response to uPAR ligation determine the function of uPA and uPA-PAI-1 complex as growth promoters.
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PMID:Plasminogen activator inhibitor 1 functions as a urokinase response modifier at the level of cell signaling and thereby promotes MCF-7 cell growth. 1126 65

Vitronectin (VN) and pro-urokinase (pro-uPA) stimulated migration of rat smooth muscle cells in a dose-dependent and additive way, and induced motile-type changes in cell morphology together with a complete reorganization of the actin filaments and of the microtubules. All these effects were inhibited by pertussis toxin, or by antibodies directed against the urokinase receptor (uPAR) or against the VN receptor alpha(v)beta(3) suggesting that an association between the two receptors is required to mediate both signals. Investigation of the signaling pathways showed that increasing the intracellular cAMP resulted in a selective inhibition of VN-induced cell migration. On the other hand, PD 98059, an inhibitor of MEK, differentially inhibited the pro-uPA- but not the VN-induced cell migration. Phosphorylation and nuclear translocation of Erk by pro-uPA was directly observed. We conclude that the signaling pathways of pro-uPA and VN must be at least in part different.
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PMID:Urokinase/urokinase receptor and vitronectin/alpha(v)beta(3) integrin induce chemotaxis and cytoskeleton reorganization through different signaling pathways. 1136 Jan 87

Bone metastases from prostate origin generate an osteoblastic reaction that is expressed in vitro by increased osteoblast proliferation. The urokinase-like plasminogen activator (u-PA) present in the media conditioned by tumoral prostatic cells acting as a ligand of the cellular membrane receptor (u-PAR), has been identified as the specific factor that modulates this proliferative reaction. The present study represents an effort to unravel the intracellular pathway by which u-PA activates osteoblastic proliferation and to evaluate the role of cellular receptor u-PAR in this proliferative phenomenon. Our results show that in vitro u-PA stimulates proliferation of SaOS-2 osteoblastic cells by activating the MAP kinase route of ERK 1 and 2 and the p38 pathway. These results are in accordance with the inhibition of intermediate activation and cell proliferation by PD 098059 and SB 203580, specific inhibitors of MEK and p38, respectively. We also show that SaOS-2 cells increase their proliferative response when cells are plated onto vitronectin, the second natural ligand of u-PAR, and that culturing SaOS-2 cells in the presence of u-PA represents a stimuli for u-PAR expression. On the basis of these results we propose that osteoblastic cells respond to the prostate-derived u-PA stimuli in a very efficient manner that includes the utilization of two different signaling routes and the stimulation of the expression of the u-PA receptor.
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PMID:ERK 1,2 and p38 pathways are involved in the proliferative stimuli mediated by urokinase in osteoblastic SaOS-2 cell line. 1150 Sep 57

Bikunin (bik, also known as 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) in order to evaluate the effect on expression of urokinase-type plasminogen activator (uPA). Preincubation of the cells with bik reduced the ability of PMA to trigger the uPA expression at the gene level and at the protein level. We next asked whether the mechanism of inhibition of uPA expression by bik is due to interference with MAP kinase, since PMA could also activate a signaling pathway involving MEK/ERK/c-Jun-dependent uPA expression. When cells were preincubated with bik, we could detect suppression of phosphorylation of these proteins, demonstrating that bik markedly suppresses the cell motility possibly through negative regulation of 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. To clarify the role of bik on tumor metastasis, HRA cells were transfected with an expression vector harboring a cDNA encoding for human bik. Transfection of HRA with the bik cDNA resulted in five variants stably expressing functional bik and significantly reduced invasion, but not proliferation, adhesion, or migration relative to the parental cells. Animals with bik* transfectants induced reduced peritoneal dissemination and long term survival. These results suggest that transfection with the bik gene induces the suppression of tumor cell invasion and peritoneal dissemination, and can prolong survival. This pre-clinical animal model offers the possibility to explore gene therapy as a new treatment modality for ovarian cancer.
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PMID:Suppression of urokinase expression and tumor metastasis by bikunin overexpression [mini-review]. 1177 42

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

Altered expression of alphav integrins plays a critical role in tumor growth, invasion, and metastasis. In this study, we show that normal human epithelial ovarian cell line, HOSE, and ovarian cancer cell lines, OVCA 429, OVCA 433, and OVHS-1, expressed alphav integrin and associated beta1, beta3, and beta5 subunits, but only ovarian cancer cell lines OVCA 429 and OVCA 433 expressed alphavbeta6 integrin. The expression of alphavbeta6 in OVCA 429 and OVCA 433 was far higher than alphavbeta3 and alphavbeta5 integrin and correlated with high p42/p44 mitogen activated protein kinase (MAPK) activity and high secretion of high molecular weight urokinase plasminogen activator (HMW-uPA), pro-metalloproteinase 2 and 9 (pro-MMP-9 and pro-MMP-2). In contrast to HOSE and OVHS 1, OVCA 433 and OVCA 429 exhibited approximately 2-fold more plasminogen-dependent [3H]-collagen type IV degradation. Plasminogen-dependent [3H]-collagen IV degradation was inhibited by inhibitor of uPA (amiloride) and MMP (phenanthroline) and by antibodies against uPA or MMP-9 or alphavbeta6 integrin, indicating the involvement of alphavbeta6 integrin, uPA and MMP-9 in the process. The alphavbeta6 correlated increase in HMW-uPA and pro-MMP secretion could be inhibited by tyrosine kinase inhibitor genistein or the MEK 1 inhibitor U0126, consistent with a role of active p42/44 MAPK in the elevation of uPA, MMP-9, and MMP-2 secretion. Under similar conditions, genistein and U0126 inhibited plasminogen-dependent [3H]-collagen type IV degradation. These data suggest that sustained elevation of p42/44 MAPK activity may be required for the co-expression of alphavbeta6 integrin, which in turn may regulate the malignant potential of ovarian cancer cells via proteolytic mechanisms.
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PMID:Association between alphavbeta6 integrin expression, elevated p42/44 kDa MAPK, and plasminogen-dependent matrix degradation in ovarian cancer. 1183 93

The anti-invasive ability of the mitogen-activated protein kinase (MAPK) kinase inhibitor, U0126, was examined in human A375 melanoma cells in vitro. The effect was compared to that of PD98059, another commonly used MEK (MAPK kinase) inhibitor. U0126 or PD98059 showed a dose-dependent inhibition of A375 cell invasion through growth factor-reduced Matrigel. U0126 was more potent than PD98059 in suppressing tumor cell invasion. Both compounds significantly decreased urokinase plasminogen activator (uPA) and matrix metalloproteinases-9 (MMP-9) concentrations in conditioned media. At 5 microM, U0126 inhibited phosphorylation of the MEK 1/2 to a non-detectable level within 24 h. The phosphorylation of extracellular signal-related kinase 1/2 was also dramatically suppressed by the treatment with 10 microM U0126 or 40 microM PD98059. Both compounds suppressed the protein expression of c-Jun, but not c-Fos. The expression of uPA and MMP-9 was also inhibited. Our data suggest that U0126 is an effective agent in inhibiting human A375 melanoma cell invasion and that the effect is partially due to the decreased production of uPA and MMP-9.
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PMID:U0126, a mitogen-activated protein kinase kinase inhibitor, inhibits the invasion of human A375 melanoma cells. 1188 67

A lot of parallels have been described between invasion of malignant tumor cells and leukocyte movement during inflammatory responses. Concerning these similarities, we investigated the function of cytokine-suppressive anti-inflammatory drugs (CSAIDs), which act via inhibition of stress-activated MAP-kinases, in regulation of expression of proteolytic enzymes and in vitro invasion of malignant melanoma cells. The p38MAPK inhibitor SB203580 reduced matrigel invasion of MeWo cells by 60%, while the MEK-1 inhibitor PD98059 did not have any effect on invasion. Active p38MAPK was detected in MeWo cells by immunoblotting and confocal microscopy. Cells showed a constitutive expression of matrix-metalloproteinase (MMP)-2 as well as tissue inhibitor of metalloproteinases (TIMP)-1 and TIMP-2 mRNAs. Expression of MMP-1 or urokinase-type plasminogen activator (uPA) was not detected by Northern blot. Inhibition of p38MAPK by the specific inhibitor SB203580 resulted in downregulation of MMP-2 mRNA and protein levels as well as gelatinolytic activity, while expression levels of TIMP-1 and TIMP-2 mRNAs were not changed. The specific MEK-1 inhibitor PD98059 did not change expression of MMP-2 or TIMPs. Neither SB203580 nor PD98059 changed proliferation of cells. The results suggest that stress-activated protein kinases like p38MAPK are involved in regulation of expression of MMP-2 as well as in vitro invasion of malignant melanoma cells. Inhibitors of p38MAPK may be promising substances to interfere with a signaling cascade associated with invasion of malignant tumor cells.
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PMID:An inhibitor of stress-activated MAP-kinases reduces invasion and MMP-2 expression of malignant melanoma cells. 1191 86

The tumor suppressor PTEN possesses lipid and protein phosphatase activities. It has been well established that the lipid phosphatase activity is essential for its tumor-suppressive function via the phosphoinositide 3-kinase (PI3K) and Akt pathways. The precise role of the protein phosphatase activity is still unclear. In the current study, we demonstrate that overexpression of wild-type PTEN in the MCF-7 breast cancer line results in phosphatase activity-dependent decreases in the phosphorylation of ETS-2, which is a transcription factor whose DNA-binding ability is controlled by phosphorylation. Exposure of MCF-7 cells to insulin, insulin-like growth factor 1 (IGF-1) or epidermal growth factor (EGF) can lead to the phosphorylation of ETS-2, Akt and ERK1/2. The MEK inhibitor PD590089 abrogates insulin-stimulated phosphorylation of ETS-2. In contrast, the PI3K inhibitor LY492002 has no effect on insulin-stimulated phosphorylation of ETS-2, despite the fact that it diminishes insulin-stimulated phosphorylation of Akt. Interestingly, overexpression of PTEN in MCF-7 leads to blockade of insulin-stimulated, but not EGF-stimulated, phosphorylation of ERK, accompanied by dramatic decreases in ETS-2 phosphorylation. We further show that the relationship of PTEN and ETS-2 has functional significance by demonstrating that PTEN abrogates activation of the uPA Ras-responsive enhancer, a target of ETS-2 action, in a phosphatase-dependent manner, irrespective of the presence or absence of insulin. Our observations, therefore, suggest that PTEN blocks insulin-stimulated ETS-2 phosphorylation through inhibition of the ERK members of the MAP kinase family independently of PI3K, and that the PTEN effect on the phosphorylation status of ETS-2 may be mediated through PTEN's protein phosphatase activity.
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PMID:PTEN blocks insulin-mediated ETS-2 phosphorylation through MAP kinase, independently of the phosphoinositide 3-kinase pathway. 1209 11

Changes in cellular morphology induced as a consequence of direct perturbation of cytoskeletal structure with network-specific targeting agents (i.e. microfilament- or microtubule-disrupting drugs) results in the stimulated expression of a specific subset of genes. Transcription of c-fos, collagenase, transforming growth factor-beta, actin, urokinase plasminogen activator and its type-1 inhibitor (PAI-1) appears to be particularly responsive to shape-activated signaling pathways. Cytochalasin D (CD) or colchicine treatment of contact-inhibited and serum-deprived vascular smooth muscle (R22) cells was used, therefore, as a model system to evaluate morphology-associated controls on PAI-1 gene regulation in the absence of added growth factors. PAI-1 transcript levels in quiescent R22 cells increased rapidly and in a CD-concentration-dependent fashion, with kinetics of expression paralleling the morphological changes. Colchicine concentrations that effectively disrupted microtubule structure and reduced the cellular 'footprint' area (to approximately that of CD treatment) also stimulated PAI-1 synthesis. Shape-related increases in PAI-1 mRNA synthesis were ablated by prior exposure to actinomycin D. Unlike the mechanism of induction in growth-factor-stimulated cells, CD- and colchicine-induced PAI-1 expression required on-going protein synthesis (i.e. it was a secondary response). Although PAI-1 is a TGF-beta-regulated gene and TGF-beta expression is also shape dependent, an autocrine TGF-beta loop was not a factor in CD-initiated PAI-1 transcription. Since CD exposure resulted in actin microfilament disruption and subsequent morphological changes, with uncertain effects on interactions between signaling intermediates or 'scaffold' structures, a pharmacological approach was selected to probe the pathways involved. Signaling events leading to PAI-1 induction were compared with colchicine-treated cells. CD- as well as colchicine-stimulated PAI-1 expression was effectively and dose dependently attenuated by the MEK inhibitor PD98059 (in the 10 to 25 microM concentration range), consistent with the known MAP kinase dependency of PAI-1 synthesis in growth-factor-stimulated cells. Reduced PAI-1 mRNA levels upon exposure to genistein prior to CD addition correlated with inhibition of ERK1/2 activity, implicating a tyrosine kinase in shape-dependent MEK activation. Src-family kinases, moreover, appeared to be specific upstream elements in the CD- and colchicine-dependent pathways of PAI-1 transcription since both agents effectively activated pp60(c-src) kinase activity in quiescent R22 cells. The restrictive (src-family) kinase inhibitor PP1 completely inhibited induced, as well as basal, ERK activity in a coupled immunoprecipitation myelin-basic-protein-phosphorylation assay and ablated shape-initiated PAI-1 mRNA expression. These data suggest that PP1-sensitive tyrosine kinases are upstream intermediates in cell-shape-associated signaling pathways resulting in ERK1/2 activation and subsequent PAI-1 transcription. In contrast to the rapid and transient kinetics of ERK activity typical of serum-stimulated cells, the ERK1/2 response to CD and colchicine is both delayed and relatively sustained. Collectively, these data support a model in which MEK is a focal point for the convergence of shape-initiated signaling events leading to induced PAI-1 transcription.
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PMID:MEK/ERK pathway mediates cell-shape-dependent plasminogen activator inhibitor type 1 gene expression upon drug-induced disruption of the microfilament and microtubule networks. 1211 65


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