Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study we examined the contribution of MAPK1 and 2 [also known as extracellular signal-regulated kinases (ERK)-1 and 2] to the induction of zif268 mRNA in PC12D cells by using two methods to block the activation of these kinases. In one set of experiments, we inhibited the activation of MAPK by pretreating cells with PD098059, a specific inhibitor of MEK (MAPKK), the immediate upstream activator of MAPK. In the second set of experiments, we blocked the activation of MAPK by overexpressing N17Ras, a dominant-negative form of Ha-Ras. These two approaches yielded similar results and showed that inhibition of MAPK blocks less than half of the induction of zif268 mRNA by NGF. Much of the residual induction of zif268 mRNA is blocked by low concentrations of wortmannin, an inhibitor of phosphatidylinositol (PI) 3-kinase. Since PI 3-kinase was previously shown to function upstream in epidermal growth factor (EGF)-mediated activation of c-Jun N-terminal kinase (JNK), and JNK is known to phosphorylate and activate transcription factors that regulate the expression of zif268, we investigated the role of JNK in the induction of zif268 mRNA by NGF. Stimulation of PC12D cells with NGF weakly activates JNK, but this activation is enhanced rather than inhibited by pretreatment with wortmannin, suggesting that JNK does not function downstream of PI 3-kinase in the induction of zif268 mRNA. A role for JNK in the induction of the zif268 gene is indicated, however, by the fact that cotransfection of expression vectors encoding JIP-1 or the JNK binding domain of JIP-1, which act as dominant-negative inhibitors of JNK, partially blocks the NGF-mediated induction of a luciferase reporter gene linked to the zif268 promoter. Together, these results suggest that MAPK, PI-3 kinase and JNK each play a role in the induction of zif268 gene expression by NGF in PC12D cells.
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PMID:Nerve growth factor induces zif268 gene expression via MAPK-dependent and -independent pathways in PC12D cells. 1005 43

The Met receptor tyrosine kinase and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), have been implicated in human tumor development and metastasis. HGF/SF induces the expression of urokinase plasminogen activator (uPA) and the uPA receptor (uPAR), important mediators of cell invasion and metastasis. We have developed a cell-based assay to screen for inhibitors of this signaling system using the induction of endogenous uPA and uPAR and the subsequent conversion of plasminogen to plasmin as the biological end point. Assay validation was established using a neutralizing antiserum to HGF/SF and a uPA inhibitor (B428), as well as inhibitors of the MKK-MAPK1/2 pathway, shown previously to be important in the induction of uPA and uPAR. Using this assay, we found several classes of molecules that exhibited inhibition of HGF/SF-dependent plasmin activation. However, we discovered that certain members of the geldanamycin family of anisamycin antibiotics are potent inhibitors of HGF/SF-mediated plasmin activation, displaying inhibitory properties at femtomolar concentrations and nine orders of magnitude below their growth inhibitory concentrations. At nanomolar concentrations, the geldanamycins down-regulate Met protein expression, inhibit HGF/SF-mediated cell motility and invasion, and also revert the phenotype of both autocrine HGF/SF-Met transformed cells as well as those transformed by Met proteins with activating mutations. Thus, the geldanamycins may have important therapeutic potential for the treatment of cancers in which Met activity contributes to the invasive/metastatic phenotype.
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PMID:The geldanamycins are potent inhibitors of the hepatocyte growth factor/scatter factor-met-urokinase plasminogen activator-plasmin proteolytic network. 1066 86

Little is known about the genetic regulation of medulloblastoma dissemination, but metastatic medulloblastoma is highly associated with poor outcome. We obtained expression profiles of 23 primary medulloblastomas clinically designated as either metastatic (M+) or non-metastatic (M0) and identified 85 genes whose expression differed significantly between classes. Using a class prediction algorithm based on these genes and a leave-one-out approach, we assigned sample class to these tumors (M+ or M0) with 72% accuracy and to four additional independent tumors with 100% accuracy. We also assigned the metastatic medulloblastoma cell line Daoy to the metastatic class. Notably, platelet-derived growth factor receptor alpha (PDGFRA) and members of the downstream RAS/mitogen-activated protein kinase (MAPK) signal transduction pathway are upregulated in M+ tumors. Immunohistochemical validation on an independent set of tumors shows significant overexpression of PDGFRA in M+ tumors compared to M0 tumors. Using in vitro assays, we show that platelet-derived growth factor alpha (PDGFA) enhances medulloblastoma migration and increases downstream MAP2K1 (MEK1), MAP2K2 (MEK2), MAPK1 (p42 MAPK) and MAPK3 (p44 MAPK) phosphorylation in a dose-dependent manner. Neutralizing antibodies to PDGFRA blocks MAP2K1, MAP2K2 and MAPK1/3 phosphorylation, whereas U0126, a highly specific inhibitor of MAP2K1 and MAP2K2, also blocks MAPK1/3. Both inhibit migration and prevent PDGFA-stimulated migration. These results provide the first insight into the genetic regulation of medulloblastoma metastasis and are the first to suggest a role for PDGFRA and the RAS/MAPK signaling pathway in medulloblastoma metastasis. Inhibitors of PDGFRA and RAS proteins should therefore be considered for investigation as possible novel therapeutic strategies against medulloblastoma.
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PMID:Expression profiling of medulloblastoma: PDGFRA and the RAS/MAPK pathway as therapeutic targets for metastatic disease. 1459 98

Activation of the mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)-mitogen-activated protein kinase (MAPK) pathway is a frequent event in tumorigenesis, and analysis of human breast carcinomas demonstrates that 25-50% of these tumors express elevated levels of activated MAPK1/2. However, a direct role for MEK1 in regulating the invasive and metastatic potential of mammary epithelial cells remains to be established. To directly address the role of constitutive MEK1 signaling in transformation, we have selected the murine mammary epithelial cell line, EpH4, as a model system. EpH4 cells expressing constitutively activated MEK1 display invasive growth in 3-dimensional collagen gels and enhanced motility, and metastatic potential in modified Boyden chamber assays. Furthermore, analysis of markers of normal epithelial morphology by immunofluorescence revealed reorganization of the actin cytoskeleton, and mislocalization of beta-catenin and ZO-1 away from sites of cell-cell contact. However, in contrast to expectations, these changes occurred independently of an epithelial to mesenchymal transition, a change seen frequently in transformed epithelial cells. Moreover, transplantation of EpH4 cells expressing constitutively activated MEK1 into the cleared mammary fat pads of immune-competent hosts rapidly produced tumors that were highly invasive, well vascularized, and readily metastasized to distant organs. Gene expression profiling was performed to identify the downstream targets of MEK1 signaling. Constitutive MEK1 induced the expression of genes involved in proliferation and of matrix metalloproteinases, which regulate invasion and metastasis. These results demonstrate that constitutively activated MEK1 brings about robust tumorigenic changes in murine mammary epithelial cells, and mediates their invasiveness and metastasis in vivo without a requirement for epithelial to mesenchymal transition.
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PMID:MEK1 signaling mediates transformation and metastasis of EpH4 mammary epithelial cells independent of an epithelial to mesenchymal transition. 1218 38

Aldosterone plays a pathological role in cardiac fibrosis by directly affecting cardiac fibroblasts. Understanding of the cellular mechanisms of aldosterone action in cardiac fibroblasts, however, is rudimentary. One possibility is that aldosterone promotes proliferation of cardiac fibroblasts by activating specific cellular signaling cascades. The current study tests whether aldosterone stimulates proliferation of isolated adult rat cardiac myofibroblasts (RCF) by activating Kirsten Ras (Ki-RasA) and its effector, the MAPK1/2 cascade. Aldosterone (10 nM) significantly increased RCF proliferation. This action was sensitive to the mineralocorticoid receptor (MR) antagonist spironolactone. Expression of MR in RCF and the whole rat heart was confirmed by immunoblotting. Aldosterone significantly increased absolute and active (GTP bound) Ki-RasA levels in RCF. Aldosterone, in addition, significantly increased phospho-c-Raf and phospho-MAPK1/2. The effects of aldosterone on Ki-RasA and phospho-c-Raf proteins were inhibited by spironolactone but not RU-486, suggesting that aldosterone acts via MR. Inhibitors of MEK1/2 and c-Raf prevented aldosterone-induced activation of MAPK1/2 and proliferation. These results show that aldosterone directly increases RCF proliferation through MR-dependent activation of Ki-RasA and its effector, the MAPK1/2 cascade. Activation of cardiac fibroblasts through such a cascade may play a role in the pathological actions exerted by aldosterone on the heart.
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PMID:Aldosterone stimulates proliferation of cardiac fibroblasts by activating Ki-RasA and MAPK1/2 signaling. 1238 14

We describe here the construction of a library of small interfering RNA expression vectors targeted to a few hundred apoptosis-related genes and the application of this library to an investigation of thapsigargin (TG)-induced apoptosis. Thapsigargin triggers endoplasmic reticulum stress, with subsequent apoptosis, but the molecular mechanisms underlying this process are incompletely understood. Using our library, we identified three anti-apoptotic genes, namely, NOXA, E2F1, and MAPK1, in addition to already characterized genes in the apoptotic pathway. In contrast to proposals by others, our data revealed (i) that TG-induced apoptosis is associated with Apaf1 in a caspase-3- and caspase-9-independent manner; (ii) that the E2F1-PUMA pathway might be involved; and (iii) that the ERK pathway, via MAP3K8 (mitogen-activated protein kinase kinase 8), is required for the induction by TG of apoptosis. Our study demonstrates clearly that unexpected and novel genes can be identified effectively by our method, and it provides evidence for the efficacy and utility of the comprehensive analysis of signaling networks and pathways using a library of small interfering RNA expression vectors.
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PMID:Identification of a network involved in thapsigargin-induced apoptosis using a library of small interfering RNA expression vectors. 1548 92

Recently, attention has been focused on the role of aldosterone in the pathophysiology of hypertension and cardiovascular disease. Several clinical and experimental data support the hypothesis that aldosterone contributes to the progression of renal injury. However, the molecular mechanisms of the effects of aldosterone in signal transduction and the cell-cycle progression of mesangial cells are not well known. For determining the signaling pathway of aldosterone in cultured mesangial cells, the effects of aldosterone on the mitogen-activated protein kinase 1/2 (MAPK1/2) pathway and the promoter activities of cyclin D1, cyclin A, and cyclin E were investigated. First, it was shown that the mineralocorticoid receptor (MR) was expressed in rat mesangial cells and glomeruli and that aldosterone stimulated the proliferation of mesangial cells via the MR and MAPK1/2 pathway. Next, it was demonstrated that aldosterone stimulated Ki-RasA, c-Raf kinase, MEK1/2, and MAPK1/2 in rat mesangial cells. Aldosterone induced cyclin D1 and cyclin A promoter activities and protein expressions, as well as the increments of CDK2 and CDK4 kinase activities. The presence of CYP11B2 and 11beta-HSD2 mRNA in rat mesangial cells also was shown. In conclusion, aldosterone seems to exert mainly MR-induced effects that stimulate c-Raf, MEK1/2, MAPK1/2, the activities of CDK2 and CDK4, and the cell-cycle progression in mesangial cells. MR antagonists may serve as a potential therapeutic approach to mesangial proliferative disease.
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PMID:Aldosterone stimulates proliferation of mesangial cells by activating mitogen-activated protein kinase 1/2, cyclin D1, and cyclin A. 1597 97

Disrupted ERK1/2 (MAPK3/MAPK1) MAPK signaling has been associated with several developmental syndromes in humans; however, mutations in ERK1 or ERK2 have not been described. We demonstrate haplo-insufficient ERK2 expression in patients with a novel approximately 1 Mb micro-deletion in distal 22q11.2, a region that includes ERK2. These patients exhibit conotruncal and craniofacial anomalies that arise from perturbation of neural crest development and exhibit defects comparable to the DiGeorge syndrome spectrum. Remarkably, these defects are replicated in mice by conditional inactivation of ERK2 in the developing neural crest. Inactivation of upstream elements of the ERK cascade (B-Raf and C-Raf, MEK1 and MEK2) or a downstream effector, the transcription factor serum response factor resulted in analogous developmental defects. Our findings demonstrate that mammalian neural crest development is critically dependent on a RAF/MEK/ERK/serum response factor signaling pathway and suggest that the craniofacial and cardiac outflow tract defects observed in patients with a distal 22q11.2 micro-deletion are explained by deficiencies in neural crest autonomous ERK2 signaling.
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PMID:Mouse and human phenotypes indicate a critical conserved role for ERK2 signaling in neural crest development. 1895 47

Pulsatile GNRH regulates the gonadotropin subunit genes in a differential manner, with faster frequencies favoring Lhb gene expression and slower frequencies favoring Fshb. Early growth response 1 (EGR1) is critical for Lhb gene transcription. We examined GNRH regulation of EGR1 and its two corepressors, Ngfi-A-binding proteins 1 and 2 (NAB1 and NAB2), both in vivo and in cultured rat pituitary cells. In rats, fast GNRH pulses (every 30 min) stably induced Egr1 primary transcript (PT) and mRNA 2-fold (P < 0.05) for 1-24 h. In contrast, slow GNRH pulses (every 240 min) increased Egr1 PT at 24 h (6-fold; P < 0.05) but increased Egr1 mRNA 4- to 5-fold between 4 and 24 h. Both GNRH pulse frequencies increased EGR1 protein 3- to 4-fold. In cultured rat pituitary cells, GNRH pulses (every 60 min) increased Egr1 (PT, 2.5- to 3-fold; mRNA, 1.5- to 2-fold; P < 0.05). GNRH pulses had little effect on Nab1/2 PT/mRNAs either in vivo or in vitro. We also examined specific intracellular signaling cascades activated by GNRH. Inhibitors of mitogen-activated protein kinase 8/9 (MAPK8/9 [also known as JNK]; SP600125) and MAP Kinase Kinase 1 (MAP2K1 [also known as MEK1]; PD98059) either blunted or totally suppressed the GNRH induction of Lhb PT and Egr1 PT/mRNA, whereas the MAPK14 (also known as p38) inhibitor SB203580 did not. In summary, pulsatile GNRH stimulates Egr1 gene expression and protein in vivo but not in a frequency-dependent manner. Additionally, GNRH-induced Egr1 gene expression is mediated by MAPK8/9 and MAPK1/3, and both are critical for Lhb gene transcription.
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PMID:Regulation of Lhb and Egr1 gene expression by GNRH pulses in rat pituitaries is both c-Jun N-terminal kinase (JNK)- and extracellular signal-regulated kinase (ERK)-dependent. 1971 May 10

The mitogen-activated protein kinase (MAPK) signaling cascade plays an important role in cell life. Herein we show that small interfering RNAs targeting MAPK1 can inhibit HeLa cell growth and induce apoptosis along with up-regulation of signal transducers and activator 1 and 2 (STAT1/2). However, across-talk between the ras-raf-ERK1/2 signalling cascade and the JAK-STAT pathway remain largely unknown. Using MEK inhibitor U0126 and JAK-2 inhibitor AG490, we analyzed the relationship between ERK1/2 and STAT1/2 in HeLa cells. U0126 inhibited HeLa cell growth, arrested the cell cycle at G1/G0, and induced cell apoptosis, and AG490 partially reversed the effects of U0126. U0126 induced up-regulation of ERK1/2 and down-regulation of phosphorylated ERK1/2, increased STAT1 and STAT2 expression in a dose-dependent manner, and activated STAT1/2 via their phosphorylation. AG490 markedly inhibited the phosphorylation of STAT1 and STAT2 and slightly increased that of ERK1/2 inhibited by U0126. We suggest that STAT1/2 is involved in the inhibition of cell growth induced by U0126 in HeLa cells.
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PMID:STAT1/2 is involved in the inhibition of cell growth induced by U0126 in HeLa cells. 2000 11


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