Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 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.
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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 urokinase-type plasminogen activator receptor (u-PAR) has been implicated in tumor progression, and previous studies have shown that the expression of this gene is strongly up-regulated by PMA. Although the signaling mechanism by which PMA modulates u-PAR expression is not known, the effect of this phorbol ester on the expression of other genes has been ascribed to activation of the c-Raf-1-ERK signaling pathway. However, in the current study we examined an alternate possibility that the inductive effect of PMA on u-PAR expression also required a JNK1-dependent signaling cascade usually associated with stress-inducing stimuli. PMA treatment of the u-PAR-deficient OVCAR-3 ovarian cancer cells, which contain low JNK activities, resulted in a rapid (5 min) increase in JNK activity. Maximal JNK activity (12-fold induction) occurred after 30 min; this preceding the earliest detected rise in u-PAR protein (2 h). Dose-response studies with PMA also indicated that the increased JNK activity was tightly correlated with elevated u-PAR protein levels. The stimulation of u-PAR promoter activity by PMA required an intact upstream AP-1 motif (-184) and in PMA-treated cells this motif was bound with c-Jun as indicated from mobility shift assays. PMA up-regulated the c-Jun trans acting activity as indicated by the higher activity of a GAL4-regulated luciferase reporter in phorbol-ester-treated cells co-transfected with an expression vector encoding the c-Jun transactivation domain fused to the GAL4 DNA-binding domain. The ability of PMA to stimulate u-PAR promoter activity was effectively titrated out by the co-expression of either a kinase-defective JNK1 or a dominant negative MEKK1 the latter being an upstream activator of JNK1. Conversely, u-PAR promoter activity was stimulated by the co-expression of a constitutively active MEKK1 and this induction was antagonized by the inclusion of the kinase-defective JNK1 plasmid. We also determined the biological significance of the JNK1-dependent signaling cascade in regulating u-PAR promoter activity by c-Ha-ras since this oncogene is activated and/or overexpressed in a variety of tumors including ovarian cancer. Transfection of an activated c-Ha-ras into OVCAR-3 cells stimulated u-PAR promoter activity over 20-fold and this could be countered by the individual expression of dominant negative expression constructs to Rac-1, MEKK1 or JNK1. Taken together, these data suggest that the PMA- or c-Ha-Ras-dependent stimulation of u-PAR gene expression requires a JNK1-dependent signaling module and that, at least for PMA, the concurrent stimulation of a JNK1-independent signaling module is also required. Thus, caution should be exercised in invoking linear signaling modules to account for the regulation of inducible gene expression.
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PMID:Stimulation of urokinase-type plasminogen activator receptor expression by PMA requires JNK1-dependent and -independent signaling modules. 967 6

Cell signaling by coagulation factor Xa (Xa) contributes to pro-inflammatory responses in vivo. This study characterizes the signaling mechanism of Xa in a HeLa cell line that expresses protease-activated receptor 1 (PAR-1) but not PAR-2, -3, or -4. Xa induced NF-kappaB in HeLa cells efficiently but with delayed kinetics compared to thrombin. This delay caused no difference in gene expression patterns, as determined by high-density microarray analysis. Both proteases prominently induced the angiogenesis-promoting gene Cyr61 and connective tissue growth factor. Inhibition of PAR-1 cleavage abolished MAP kinase phosphorylation and gene induction by Xa, demonstrating that Xa signals through PAR-1 and not through a novel member of the PAR family. Activation of cell surface prothrombin with the snake venom enzyme Ecarin also produced PAR-1-dependent signaling. However, though the response to Ecarin was completely blocked by the thrombin inhibitor hirudin, the response to Xa was not. This suggests that the Xa response is not mediated by locally generated thrombin. The concentration dependence of Xa for PAR-1 activation is consistent with previously characterized Xa-mediated PAR-2 signaling, suggesting that local concentration of Xa on the cell surface, rather than sequence-specific recognition of the PAR scissile bond, determines receptor cleavage. This study demonstrates that PAR-1 cleavage by Xa can elicit the same cellular response as thrombin, but mechanistic differences in receptor recognition may be crucial for specific roles for Xa in signaling during spatial or temporal separation from thrombin generation.
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PMID:Gene induction by coagulation factor Xa is mediated by activation of protease-activated receptor 1. 1134 37

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

The coagulation protease Factor Xa (Xa)(1) triggers a variety of cellular responses that may be important for inflammatory reactions to tissue injury. Protease-activated receptors (PAR1, PAR2, and PAR4) can mediate Xa signaling in heterologous expression systems. However, other candidate Xa receptors have been described, and the extent to which one or more PARs account for Xa signaling in relevant differentiated cells is unknown. We examined Xa signaling in endothelial cells from wild-type and PAR-deficient mice. Wild-type endothelial cells responded to agonists for PAR1, PAR2, and PAR4. Relative to wild-type, Xa-triggered phosphoinositide hydrolysis was reduced by 60-75% in Par2 -/- endothelial cells, by 20-30% in Par1 -/- endothelial cells, and by approximately 90% in Par2 -/- endothelial cells treated with a PAR1 antagonist. Similar results were obtained when ERK1/2 phosphorylation was used to assess Xa signaling. Thus PAR2 is the main endogenous Xa receptor in these endothelial cell preparations and, together, PAR2 and PAR1 appear to account for approximately 90% of endothelial Xa signaling. By contrast, in fibroblasts, PAR1 by itself accounted for virtually all Xa-induced phosphoinositide hydrolysis. This information is critical for the design and interpretation of knockout mouse studies to probe the possible roles of Xa signaling in vivo.
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PMID:Genetic evidence that protease-activated receptors mediate factor Xa signaling in endothelial cells. 1185 Apr 18

In C. elegans embryos, a Wnt/MAPK signaling pathway downregulates the TCF/LEF transcription factor POP-1, resulting in a lower nuclear level in signal-responsive cells compared to their sisters. Although the beta-catenin WRM-1 is required for POP-1 downregulation, a direct interaction between these two proteins does not seem to be required, as the beta-catenin-interacting domain of POP-1 is dispensable for both POP-1 downregulation and function in early embryos. We show here that WRM-1 downregulates POP-1 by promoting its phosphorylation by the MAP kinase LIT-1 and subsequent nuclear export via a 14-3-3 protein, PAR-5. In signal-responsive cells, we also detect a concurrent upregulation of nuclear LIT-1 that is dependent on Wnt/MAPK signaling. Our results suggest a model whereby Wnt/MAPK signaling downregulates POP-1 levels in responsive cells, in part by increasing nuclear LIT-1 levels, thereby increasing POP-1 phosphorylation and PAR-5-mediated nuclear export.
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PMID:Phosphorylation by the beta-catenin/MAPK complex promotes 14-3-3-mediated nuclear export of TCF/POP-1 in signal-responsive cells in C. elegans. 1506 85

The growth rate of vascular smooth muscle cells (VSMCs), which were derived from aorta of mice deficient in the fibrinolytic factors tissue-type plasminogen activator (t-PA(-/-)), urokinase (u-PA(-/-)), u-PA receptor (u-PAR(-/-)) and type 1 plasminogen activator inhibitor (PAI-1(-/-)), as well as wild-type (WT) mice, was investigated in the presence of mouse melanoma cells (B16). In the VSMCs cultured with a basal medium supplemented with 10% fetal calf serum (FCS), there was no difference in the growth rate among the gene-lacking VSMCs and WT VSMCs, indicating that these fibrinolytic factors were not involved in the FCS-mediated cell proliferation. On the other hand, when these VSMCs were cultured with B16 cells in either the mixed culture or a double-chamber, only u-PAR(-/-) VSMCs showed a significantly lower growth rate. In addition, these suppressive effects on u-PAR(-/-) VSMCs were also observed in the presence of B16-derived conditioned medium (B16/CM). The growth rate of all the VSMCs except u-PAR(-/-) VSMCs was increased in the presence of B16/CM. The degree of the increase in cell number was comparable to that obtained with FCS. These effects on growth activity were partially associated with the levels of mitogen-activated protein kinase (MAPK, p42/p44) activity. The findings suggest that u-PAR plays an important role in the proliferative response of VSMCs and that without u-PAR, there is no intracellular signaling for cell proliferation.
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PMID:Growth inhibition of vascular smooth muscle cells derived from urokinase receptor (u-PAR)-deficient mice in the presence of carcinoma cells. 1508 64

We characterized the tracheal and bronchial relaxation caused by proteinase-activated receptor-2 (PAR-2) activation in ddY mice and/or in wild-type and PAR-2-knockout mice of C57BL/6 background. Ser-Leu-Ile-Gly-Arg-Leu-amide (SLIGRL-NH(2)) and Thr-Phe-Leu-Leu-Arg-amide, PAR-2- and PAR-1-activating peptides, respectively, caused relaxation in the isolated ddY mouse trachea and main bronchus. The relaxation was abolished by specific inhibitors of cyclooxygenase (COX)-1, COX-2, mitogen-activated protein kinase kinase (MEK), and p38 MAP kinase. The MEK and p38 MAP kinase inhibitors did not affect prostaglandin E(2)-induced relaxation. Inhibitors of cytosolic Ca(2+)-dependent phospholipase A(2) (PLA), Ca(2+)-independent PLA(2), diacylglycerol lipase, tyrosine kinase, and protein kinase C exhibited no or only minor inhibitory effects on the PAR-mediated relaxation. Trypsin, a PAR-2 activator, and 2-furoyl-Leu-Ile-Gly-Arg-Leu-amide, a potent PAR-2-activating peptide, in addition to SLIGRL-NH(2), caused airway relaxation in wild-type C57BL/6 mice, as in ddY mice. In PAR-2-knockout mice, the peptide effects were absent and the potency of trypsin decreased. Desensitization of PAR-2 and/or PAR-1 greatly suppressed the relaxant effect of trypsin. The bronchial and tracheal tissues displayed distinct sensitivities toward trypsin and the PAR-2-activating peptides. Our data indicate an involvement of both COX-1 and COX-2, and the MEK-extracellular signal-regulated kinase and p38 MAP kinase signaling pathways in the PAR-2- and PAR-1-triggered relaxation of mouse airway tissue, and substantiate a role for PAR-2 in regulating both the trachea and bronchial responsiveness in the mouse lung.
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PMID:Proteinase-activated receptor-2-mediated relaxation in mouse tracheal and bronchial smooth muscle: signal transduction mechanisms and distinct agonist sensitivity. 1519 93

Tannins are plant-derived water-soluble polyphenols with wide-ranging biological activities. The mechanisms underlying the anti-inflammatory effect of tannins are not fully understood and may be the result of inhibition of poly(ADP-ribose) (PAR) glycohydrolase (PARG), the main catabolic enzyme of PAR metabolism. Therefore, we set out to investigate the mechanism of the anti-inflammatory effect of gallotannin (GT) in A549 cells with special regard to the role of poly(ADP-ribosyl)ation. Using an inflammation-focused low-density array and reverse transcription-polymerase chain reaction, we found that GT suppressed the expression of most cytokines and chemokines in cytokine-stimulated A549 cells, whereas the PARP inhibitor PJ-34 only inhibited few transcripts. Activation of the transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1), was blocked by GT, whereas PJ-34 only suppressed NF-kappaB activation but not AP-1 activation. GT also inhibited IkappaB phosphorylation and nuclear translocation of NF-kappaB, but PJ-34 had no effect on these upstream events. In the AP-1 pathway, GT treatment, even in the absence of cytokines, caused maximal phosphorylation of c-Jun N-terminal kinase and c-Jun. GT also caused a low-level phosphorylation of p38, extracellular signal-regulated kinases 1 and 2, activating transcription factor2, and cAMP-response element-binding protein but inhibited cytokine-induced phosphorylation of these kinases and transcription factors. GT inhibited protein phosphatases 1 and 2A, which may explain the increased phosphorylation of mitogen-activated protein kinase and their substrates. GT exerted potent antioxidant effect but failed to cause PAR accumulation. In summary, the potent inhibitory effects of GT on the transcription of cytokine and chemokine genes are probably not related to PARG inhibition. Inhibition of AP-1 activation and upstream signaling events may be responsible for the effects of GT.
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PMID:Gallotannin inhibits the expression of chemokines and inflammatory cytokines in A549 cells. 1597 37

We investigated proteinase-activated receptor-2 (PAR(2))-triggered signal transduction pathways causing increased prostaglandin E(2) (PGE(2)) formation in human lung-derived A549 epithelial cells. The PAR(2) agonist, SLIGRL-NH(2) (Ser-Leu-Ile-Gly-Arg-Leu-amide), evoked immediate cytosolic Ca(2+) mobilization and delayed (0.5-3 h) PGE(2) formation. The PAR(2)-triggered PGE(2) formation was attenuated by inhibition of the following signal pathway enzymes: cyclooxygenases 1 and 2 (COX-1 and COX-2, respectively), cytosolic Ca(2+)-dependent phospholipase A(2) (cPLA(2)), the mitogen-activated protein kinases (MAPKs), mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) and p38 MAPK, Src family tyrosine kinase, epidermal growth factor (EGF) receptor tyrosine kinase (EGFRK), and protein kinase C (PKC), but not by inhibition of matrix metalloproteinases. SLIGRL-NH(2) caused prompt (5 min) and transient ERK phosphorylation, blocked in part by inhibitors of PKC and tyrosine kinases but not by an EGFRK inhibitor. SLIGRL-NH(2) also evoked a relatively delayed (15 min) and persistent (30 min) phosphorylation of p38 MAPK, blocked by inhibitors of Src and EGFRK but not by inhibitors of COX-1 or COX-2. SLIGRL-NH(2) elicited a Src inhibitor-blocked prompt (5 min) and transient phosphorylation of the EGFRK. SLIGRL-NH(2) up-regulated COX-2 protein and/or mRNA levels that were blocked by inhibition of p38 MAPK, EGFRK, Src, and COX-2 but not MEK-ERK. SLIGRL-NH(2) also caused COX-1-dependent up-regulation of microsomal PGE synthase-1 (mPGES-1). We conclude that PAR(2)-triggered PGE(2) formation in A549 cells involves a coordinated up-regulation of COX-2 and mPGES-1 involving cPLA(2), increased cytosolic Ca(2+), PKC, Src, MEK-ERK, p38 MAPK, Src-mediated EGF receptor trans-activation, and also metabolic products of both COX-1 and COX-2.
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PMID:Signal transduction for proteinase-activated receptor-2-triggered prostaglandin E2 formation in human lung epithelial cells. 1612 Aug 14


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