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)

Overexpression of catalase, but not manganese superoxide dismutase (MnSOD), inhibited glucose deprivation-induced cytotoxicity and c-Jun N-terminal kinase 1 (JNK1) activation in human prostate adenocarcinoma DU-145 cells. Suppression of JNK1 activation by catalase overexpression resulted from inhibition of apoptosis signal-regulating kinase 1 (ASK1) activation by preventing dissociation of thioredoxin (TRX) from ASK1. Overexpression of catalase also inhibited relocalization of Daxx from the nucleus to the cytoplasm as well as association of Daxx with ASK1 during glucose deprivation. Taken together, hydrogen peroxide (H(2)O(2)) rather than superoxide anion (O(2) (*-)) acts as a second messenger of metabolic oxidative stress to activate the ASK1-MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)-mitogen-activated protein kinase (MAPK) signal transduction pathway.
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PMID:Catalase, but not MnSOD, inhibits glucose deprivation-activated ASK1-MEK-MAPK signal transduction pathway and prevents relocalization of Daxx: hydrogen peroxide as a major second messenger of metabolic oxidative stress. 1450 47

To define the mechanism of arsenite-induced tumor promotion, we examined the role of reactive oxygen species (ROS) in the signaling pathways of cells exposed to arsenite. Arsenite treatment resulted in the persistent activation of p70(s6k) and extracellular signal-regulated kinase 1/2 (ERK1/2) which was accompanied by an increase in intracellular ROS production. The predominant produced appeared to be H(2)O(2), because the arsenite-induced increase in dichlorofluorescein (DCF) fluorescence was completely abolished by pretreatment with catalase but not with heat-inactivated catalase. Elimination of H(2)O(2) by catalase or N-acetyl-L-cysteine inhibited the arsenite-induced activation of p70(s6k) and ERK1/2, indicating the possible role of H(2)O(2) in the arsenite activation of the p70(s6k) and the ERK1/2 signaling pathways. A specific inhibitor of p70(s6k), rapamycin, and calcium chelators significantly blocked the activation of p70(s6k) induced by arsenite. While the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002 completely abrogated arsenite activation of p70(s6k), ERK1/2 activation by arsenite was not affected by these inhibitors, indicating that H(2)O(2) might act as an upstream molecule of PI3K as well as ERK1/2. Consistent with these results, none of the inhibitors impaired H(2)O(2) production by arsenite. DNA binding activity of AP-1, downstream of ERK1/2, was also inhibited by catalase, N-acetyl-L-cysteine, and the MEK inhibitor PD98059, which significantly blocked arsenite activation of ERK1/2. Taken together, these studies provide insight into mechanisms of arsenite-induced tumor promotion and suggest that H(2)O(2) plays a critical role in tumor promotion by arsenite through activation of the ERK1/2 and p70(s6k) signaling pathways.
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PMID:Hydrogen peroxide mediates arsenite activation of p70(s6k) and extracellular signal-regulated kinase. 1451 95

Epidermal keratinocyte differentiation is a tightly regulated stepwise process that requires protein kinase C (PKC) activation. Studies on cultured mouse keraitnocytes induced to differentiate with Ca2+ have indirectly implicated the involvement of PKCa isoform. When PKCalpha was overexpressed in undifferentiated keratinocytes using adenoviral system, expressions of differentiation markers such as loricrin, filaggrin, keratin 1 (MK1) and keratin 10 (MK10) were increased, and ERK1/2 phosphorylation was concurrently induced without change of other MAPK such as p38 MAPK and JNK1/2. Similarly, transfection of PKCalpha kinase active mutant (PKCalpha- CAT) in the undifferentiated keratinocyte, but not PKCbeta-CAT, also increased differentiation marker expressions. On the other hand, PKCalpha dominant negative mutant (PKCbeta-KR) reduced Ca2+ -mediated differentiation marker expressions, while PKCbeta-KR did not, suggesting that PKCalpha is responsible for keratinocyte differentiation. When downstream pathway of PKCalpha in Ca2+ -mediated differentiation was examined, ERK1/2, p38 MAPK and JNK1/2 phosphorylations were increased by Ca2+ shift. Treatment of keratinocytes with PD98059, MEK inhibitor, and SB20358, p38 MAPK inhibitor, before Ca2+ shift induced morphological changes and reduced expressions of differentiation markers, but treatment with SP60012, JNK1/2 inhibitor, did not change at all. Dominant negative mutants of ERK1/2 and p38 MAPK also inhibited the expressions of differentiation marker expressions in Ca2+ shifted cells. The above results indicate that both ERK1/2 and p38 MAPK may be involved in Ca2+ -mediated differentiation, and that only ERK1/2 pathway is specific for PKCalpha-mediated differentiation in mouse keratinocytes.
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PMID:PKCalpha induces differentiation through ERK1/2 phosphorylation in mouse keratinocytes. 1536 48

Syndecan-4, a heparan sulfate proteoglycan that is widely expressed in the vascular wall and as a cell surface receptor, modulates events relevant to acute tissue repair, including cell migration and proliferation, cell-substrate interactions, and matrix remodeling. While syndecan-4 expression is regulated in response to acute vascular wall injury, its regulation under chronic proatherogenic conditions such as those characterized by prolonged exposure to oxidized lipids has not been defined. In this investigation, arterial smooth muscle cells were treated with 13-hydroperoxy-9,11-octadecadienoic acid (HPODE) and 13-hydroperoxy-10,12-octadecadienoic acid, oxidized products of linoleic acid, which is the major oxidizable fatty acid in LDL. Both oxidized fatty acids induced a dose-dependent, rapid upregulation of syndecan-4 mRNA expression that was not attenuated by cycloheximide. This response was inhibited by pretreatment with N-acetylcysteine, catalase, or MEK1/2 inhibitors, but not by curcumin or lactacystin, known inhibitors of NF-kappaB. These data suggest that oxidized linoleic acid induces syndecan-4 mRNA expression through the initial generation of intracellular hydrogen peroxide with subsequent activation of the extracellular signal-regulated kinase signaling pathway via MEK1/2. Notably, the HPODE-induced enhancement of syndecan-4 mRNA was accompanied by accelerated shedding of syndecan-4. In principle, alterations in both the cell surface expression and shedding of syndecan-4 may augment a variety of proatherogenic events that occur in response to oxidized lipids.
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PMID:Oxidized linoleic acid regulates expression and shedding of syndecan-4. 1546 57

Epithelial-mesenchymal transition (EMT) plays an important role in renal tubulointerstitial fibrosis and TGF-beta1 is the key inducer of EMT. Phosphorylation of Smad proteins and/or mitogen-activated protein kinases (MAPK) is required for TGF-beta1-induced EMT. Because reactive oxygen species (ROS) are involved in TGF-beta1 signaling and are upstream signaling molecules to MAPK, this study examined the role of ROS in TGF-beta1-induced MAPK activation and EMT in rat proximal tubular epithelial cells. Growth-arrested and synchronized NRK-52E cells were stimulated with TGF-beta1 (0.2 to 20 ng/ml) or H(2)O(2) (1 to 500 microM) in the presence or absence of antioxidants (N-acetylcysteine or catalase), inhibitors of NADPH oxidase (diphenyleneiodonium and apocynin), mitochondrial electron transfer chain subunit I (rotenone), and MAPK (PD 98059, an MEK [MAP kinase/ERK kinase] inhibitor, or p38 MAPK inhibitor) for up to 96 h. TGF-beta1 increased dichlorofluorescein-sensitive cellular ROS, phosphorylated Smad 2, p38 MAPK, extracellular signal-regulated kinases (ERK)1/2, alpha-smooth muscle actin (alpha-SMA) expression, and fibronectin secretion and decreased E-cadherin expression. Antioxidants effectively inhibited TGF-beta1-induced cellular ROS, phosphorylation of Smad 2, p38 MAPK, and ERK, and EMT. H(2)O(2) reproduced all of the effects of TGF-beta1 with the exception of Smad 2 phosphorylation. Chemical inhibition of ERK but not p38 MAPK inhibited TGF-beta1-induced Smad 2 phosphorylation, and both MAPK inhibitors inhibited TGF-beta1- and H(2)O(2)-induced EMT. Diphenyleneiodonium, apocynin, and rotenone also significantly inhibited TGF-beta1-induced ROS. Thus, this data suggest that ROS play an important role in TGF-beta1-induced EMT primarily through activation of MAPK and subsequently through ERK-directed activation of Smad pathway in proximal tubular epithelial cells.
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PMID:Role of reactive oxygen species in TGF-beta1-induced mitogen-activated protein kinase activation and epithelial-mesenchymal transition in renal tubular epithelial cells. 1567 11

The role of reactive oxygen species (ROS) in regulating the expression of the inducible nitric oxide synthase (iNOS) was studied in rat aortic vascular smooth muscle cells (VSMC). We hypothesized that ROS regulate iNOS expression through the mitogen-activated protein kinases ERK and p38(MAPK). We found that interleukin-1beta (IL-1beta) stimulated the production of hydrogen peroxide (H2O2) which could be inhibited by loading the cells with the H2O2-scavenging enzyme catalase. Inhibition of the upstream ERK1,2 activator MEK1,2 with U0126 prevented IL-1beta-stimulated iNOS expression, while the p38MAPK inhibitor SB03580 potentiated iNOS expression. Loading the cells with catalase enhanced ERK activation and iNOS expression but had no effect on p38MAPK activation or PDGF-induced ERK activation. These data indicated that H2O2 negatively regulates iNOS expression through ERK inhibition independently of p38MAPK. The present results outline a novel role for H2O2 in suppressing signaling pathways leading to gene expression such as iNOS in VSMC in response to cytokines.
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PMID:Catalase potentiates interleukin-1beta-induced expression of nitric oxide synthase in rat vascular smooth muscle cells. 1568 16

Reactive oxygen species (ROS) play a critical role in cardiac hypertrophy. We have recently shown that the serotonin-degrading enzyme monoamine oxidase A (MAO A) is an important source of hydrogen peroxide in rat heart. In the present study, we investigated the potential role of hydrogen peroxide generated by MAO A in cardiomyocyte hypertrophy by serotonin. Serotonin (5 microM, 48 h) induced hypertrophy in cultured adult rat ventricular myocytes, as reflected by increased 3H-leucine incorporation (+43%, P<0.001) and total protein content (+22%, P<0.001). Serotonin also increased intracellular hydrogen peroxide and oxidative stress production, measured respectively by DCF fluorescence intensity and GSH/GSSG ratio, and promoted ERK1/2 phosphorylation (P<0.001). Serotonin effects were only partially inhibited by the 5-HT2B receptor antagonist SB 206553. In contrast, they were extensively (>80%) prevented by the amine uptake inhibitor imipramine, the MAO inhibitor pargyline and the MEK inhibitor PD 98059. Cardiomyocyte hypertrophy and ERK activation were also inhibited by decreasing intracellular ROS by adenoviral overexpression of catalase or cardiomyocytes treatment with the iron chelator deferoxamine. These data suggest that part of cardiac hypertrophic effect of serotonin requires hydrogen peroxide production by MAO A and ERK1/2 activation. This newly recognized, receptor-independent mechanism of serotonin may contribute to myocardial remodeling and failure.
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PMID:A new hypertrophic mechanism of serotonin in cardiac myocytes: receptor-independent ROS generation. 1570 74

Previous microarray expression analyses have indicated autocrine human growth hormone (hGH) regulation of genes involved in the oxidative stress response. Expression analysis of antioxidant enzymes revealed that autocrine hGH increased both the mRNA and protein levels of catalase, superoxide dismutase 1 (SOD1), glutathione peroxidase and glutamylcysteine synthetase but not that of SOD2. As a consequence, autocrine hGH increased the antioxidant capacity of mammary carcinoma cells and protected against oxidative stress-induced apoptosis. Catalase activity was increased by autocrine production of hGH in mammary carcinoma cells and a catalase inhibitor abrogated protection from oxidative stress afforded by autocrine hGH. Autocrine hGH transcriptionally regulated catalase gene expression in a p44/42 MAP kinase-dependent manner and inhibition of MEK concordantly abrogated the protective effect of autocrine hGH against oxidative stress-induced apoptosis. Given that increased cellular oxidative stress is a key effector mechanism of specific chemotherapeutic agents, we propose that antagonism of autocrine hGH will improve the efficacy of chemotherapeutic regimes utilized for human mammary carcinoma.
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PMID:p44/42 MAP kinase-dependent regulation of catalase by autocrine human growth hormone protects human mammary carcinoma cells from oxidative stress-induced apoptosis. 1578 23

Benzene (BZ) is a class I carcinogen and its oxidation to reactive intermediates is a prerequisite of hematoxicity and myelotoxicity. The generated metabolites include hydroquinone, which is further oxidized to the highly reactive 1,4-benzoquinone (BQ) in bone marrow. Therefore, we explored the mechanisms underlying BQ-induced HL-60 cell proliferation by studying the role of BQ-induced reactive oxygen species (ROS) in the activation of the ERK-MAPK signaling pathway. BQ treatment (0.01-30 microM) showed that doses below 10 microM did not significantly reduce viability. ROS production after 3 microM BQ treatment increased threefold; however, catalase addition reduced ROS generation to basal levels. FACS analysis showed that BQ induced a fivefold increase in the proportion of cells in S-phase. We also observed a high proportion of Bromodeoxyuridine (BrdU) stained cells, indicating a higher DNA synthesis rate. BQ also produced rapid and prolonged phosphorylation of ERK1/2 proteins. Simultaneous treatment with catalase or PD98059, a potent MEK protein inhibitor, reduced cell recruitment into the S-phase and also abolished the ERK1/2 protein phosphorylation induced by BQ, suggesting that MEK/ERK is an important pathway involved in BQ-induced ROS mediated proliferation. The prolonged activation of ERK1/2 contributes to explain the increased S-phase cell recruitment and to understand the leukemogenic processes associated with exposure to benzene metabolites. Thus, the possible mechanism by which BQ induce HL-60 cells to enter the cell cycle and proliferate is linked to ROS production and its growth promoting effects by specific activation of regulating genes known to be activated by redox mechanisms.
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PMID:Benzoquinone activates the ERK/MAPK signaling pathway via ROS production in HL-60 cells. 1579 63

Oxidative stress is known to induce cell death in a wide variety of cell types, apparently by modulating intracellular signaling pathways. Activation of extracellular signal-regulated kinase (ERK) in oxidative stress remains controversial. In some cellular systems, the ERK activation is associated with protection against oxidative stress, while in other system, the ERK activation is involved in apoptotic cell death. The present study was undertaken to examine the role of ERK activation in H2O2-induced cell death of human glioma (A172) cells. H2O2 resulted in a time- and dose-dependent cell death, which was largely attributed to apoptosis. H2O2 treatment caused marked sustained activation of ERK. The ERK activation and cell death induced by H2O2 was prevented by catalase, the hydrogen peroxide scavenger, and U0126, an inhibitor of ERK upstream kinase MEK1/2. Transient transfection with constitutive active MEK1, an upstream activator of ERK1/2, increased H2O2-induced cell death, whereas transfection with dominant-negative mutants of MEK1 decreased the cell death. The ERK activation and cell death caused by H2O2 was inhibited by antioxidants (N-acetylcysteine and trolox), Ras inhibitor, and suramin. H2O2 produced depolarization of mitochondrial membrane potential and its effect was prevented by catalase and U0126. Taken together, these findings suggest that growth factor receptor/Ras/MEK/ERK signaling pathway plays an active role in mediating H2O2-induced apoptosis of human glioma cells and functions upstream of mitochondria-dependent pathway to initiate the apoptotic signal.
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PMID:Role of ERK in hydrogen peroxide-induced cell death of human glioma cells. 1589 30


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