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

---

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

In Con8 rat mammary epithelial tumor cells, indirect immunofluorescence revealed that Sgk (serum- and glucocorticoid-regulated kinase) and Erk/MAPK (extracellular signal-regulated protein kinase/mitogen activated protein kinase) co-localized to the nucleus in serum-treated cells and to the cytoplasmic compartment in cells treated with the synthetic glucocorticoid dexamethasone. Moreover, the subcellular distribution of the importin-alpha nuclear transport protein was similarly regulated in a signal-dependent manner. In vitro GST-pull down assays revealed the direct interaction of importin-alpha with either Sgk or Erk/MAPK, while RNA interference knockdown of importin-alpha expression disrupted the localization of both Sgk and Erk into the nucleus of serum-treated cells. Wild type or kinase dead forms of Sgk co-immunoprecipitated with Erk/MAPK from either serum- or dexamethasone-treated mammary tumor cells, suggesting the existence of a protein complex containing both kinases. In serum-treated cells, nucleus residing Sgk and Erk/MAPK were both hyperphosphorylated, indicative of their active states, whereas, in dexamethasone-treated cells Erk/MAPK, but not Sgk, was in its inactive hypophosphorylated state. Treatment with a MEK inhibitor, which inactivates Erk/MAPK, caused the relocalization of both Sgk and ERK to the cytoplasm. We therefore propose that the signal-dependent co-localization of Sgk and Erk/MAPK mediated by importin-alpha represents a new pathway of signal integration between steroid and serum/growth factor-regulated pathways.
...
PMID:The stimulus-dependent co-localization of serum- and glucocorticoid-regulated protein kinase (Sgk) and Erk/MAPK in mammary tumor cells involves the mutual interaction with the importin-alpha nuclear import protein. 1769 13

Evidence suggests that mitogen-activated protein kinase kinase (MEK) plays a role in cell transformation and tumor development and might be a significant target for chemoprevention. 3,5,4'-Trihydroxy-trans-stilbene (resveratrol), a non-flavonoid polyphenol found in various foods and beverages, including red wines, is reported to be a natural chemopreventive agent. However, the concentrations required to exert these effects might be difficult to achieve by drinking only one or two glasses of red wine a day. On the other hand, the flavonol content of red wine is approximately 30 times higher than that of resveratrol. Here we demonstrated that 3,3',4',5,5',7-hexahydroxyflavone (myricetin), one of the major flavonols in red wine, is a novel inhibitor of MEK1 activity and transformation of JB6 P+ mouse epidermal cells. Myricetin (10 microM) inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA) or epidermal growth factor (EGF)-induced cell transformation by 76 or 72%, respectively, compared with respective reductions of 26 or 19% by resveratrol (20 microM). A combination of myricetin and resveratrol exerted additive but not synergistic effects on either TPA- or EGF-induced transformation. Myricetin, but not resveratrol, attenuated tumor promoter-induced activation of c-fos or activator protein-1. Myricetin strongly inhibited MEK1 kinase activity and suppressed TPA- or EGF-induced phosphorylation of extracellular signal-regulated kinase (ERK) or p90 ribosomal S6 kinase, downstream targets of MEK. Moreover, myricetin inhibited H-Ras-induced cell transformation more effectively than either PD098059, a MEK inhibitor, or resveratrol. Myricetin directly bound with glutathione S-transferase-MEK1 but did not compete with ATP. Overall, these results indicated that myricetin has potent anticancer-promoting activity and mainly targets MEK signaling, which may contribute to the chemopreventive potential of several foods including red wines.
...
PMID:Myricetin is a novel natural inhibitor of neoplastic cell transformation and MEK1. 1769 61

Daidzein and genistein are isoflavones found in soybean. Genistein is known to exhibit anticarcinogenic activities and inhibit tyrosine kinase activity. However, the underlying molecular mechanisms of the chemopreventive activities of daidzein and its metabolite, equol, are not understood. Here we report that equol inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced neoplastic transformation of JB6 P+ mouse epidermal cells by targeting the MEK/ERK/p90RSK/activator protein-1 signaling pathway. TPA-induced neoplastic cell transformation was inhibited by equol, but not daidzein, at noncytotoxic concentrations in a dose-dependent manner. Equol dose-dependently attenuated TPA-induced activation of activator protein-1 and c-fos, whereas daidzein did not exert any effect when tested at the same concentrations. The TPA-induced phosphorylation of ERK1/2, p90RSK, and Elk, but not MEK or c-Jun N-terminal kinase, was inhibited by equol but not by daidzein. In vitro kinase assays revealed that equol greatly inhibited MEK1, but not Raf1, kinase activity, and an ex vivo kinase assay also demonstrated that equol suppressed TPA-induced MEK1 kinase activity in JB6 P+ cell lysates. Equol dose-dependently inhibited neoplastic transformation of JB6 P+ cells induced by epidermal growth factor or H-Ras. Both in vitro and ex vivo pull-down assays revealed that equol directly bound with glutathione S-transferase-MEK1 to inhibit MEK1 activity without competing with ATP. These results suggested that the antitumor-promoting effect of equol is due to the inhibition of cell transformation mainly by targeting a MEK signaling pathway. These findings are the first to reveal a molecular basis for the anticancer action of equol and may partially account for the reported chemopreventive effects of soybean.
...
PMID:Equol, a metabolite of the soybean isoflavone daidzein, inhibits neoplastic cell transformation by targeting the MEK/ERK/p90RSK/activator protein-1 pathway. 1772 30

Here we use a large-scale RNAi suppression screen to identify additional kinases playing a role in the activation of SKN-1 in response to oxidative stress. The SKN-1 transcription factor specifies cell fate of the EMS blastomere at the four-cell stage in the nematode Caenorhabditis elegans and also directs transcription of many genes responding to oxidative stress, including glutathione S-transferase, NAD(P)H:quinone oxidoreductase, and superoxide dismutase. SKN-1 localizes to the nucleus and directs transcription following exposure to paraquat, heat, hyperbaric oxygen, and sodium azide. Previous studies have identified GSK-3 as an inhibitor of SKN-1 nuclear localization, in the absence of stress, and PMK-1 as an activator of SKN-1 during periods of oxidative stress. Through this screen we have identified four kinases, MKK-4, IKK epsilon-1, NEKL-2, and PDHK-2, which are necessary for the nuclear localization of SKN-1 in response to oxidative stress. Inhibition of two of these kinases results in shorter life span and increased sensitivity to stress.
...
PMID:Activation of SKN-1 by novel kinases in Caenorhabditis elegans. 1796 27

The Ser/Thr kinase ribosomal S6 kinase 2 (RSK2) has been demonstrated to phosphorylate transcription factor CREB (cyclic AMP-responsive-binding protein) and histone H3 in response to mitogenic stimulation by epidermal growth factor (EGF). EGF activates the MEK/ERK pathway to activate RSK2. We recently reported that receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) directly tyrosine phosphorylates RSK2 at Tyr-529, which consequently regulates RSK2 activation by facilitating inactive ERK binding to RSK2 that is required for ERK-dependent phosphorylation and activation of RSK2 (Kang, S., Dong, S., Gu, T. L., Guo, A., Cohen, M. S., Lonial, S., Khoury, H. J., Fabbro, D., Gilliland, D. G., Bergsagel, P. L., Taunton, J., Polakiewicz, R. D., and Chen, J. (2007) Cancer Cell 12, 201-214). Here we report that upon treatment of EGF, RSK2 was tyrosine-phosphorylated at Tyr-529 and activated in 293T and COS7 cells that do not express FGFR3. In contrast to FGFR3, the receptor tyrosine kinase EGF receptor did not directly phosphorylate RSK2 at Tyr-529 in an in vitro kinase assay using recombinant RSK2 and active EGF receptor or FGFR3. By mass spectroscopy-based studies, we identified Src tyrosine kinase family members Src and Fyn as upstream kinases of RSK2 Tyr-529. Treatment of Src inhibitor PP2 effectively attenuated EGF-dependent activation and Tyr-529 phosphorylation of RSK2, suggesting that Src family members are the kinases that phosphorylate RSK2 at Tyr-529 in response to EGF. Src and Fyn were able to directly phosphorylate RSK2 at Tyr-529 in the in vitro kinase assay. In vitro reconstitution of Tyr-529 phosphorylation by Src in glutathione S-transferase-tagged RSK2 enhanced inactive ERK binding to RSK2 wild type, but not the Y529F mutant. Together, our findings suggest that Src-dependent phosphorylation at Tyr-529 facilitates inactive ERK binding to RSK2, which might be a general requirement for RSK2 activation by EGF through the MEK/ERK pathway.
...
PMID:Epidermal growth factor stimulates RSK2 activation through activation of the MEK/ERK pathway and src-dependent tyrosine phosphorylation of RSK2 at Tyr-529. 1815 74

The therapeutic effects of alpha-lipoic acid (alpha-LA) via NF-kappa B down regulation were demonstrated on joint inflammation and erosion in an animal model. In this study, we investigated how alpha-LA inhibits the pathway of NF-kappa B activation by TNF-alpha via the mitogen-activated protein kinase (MAPK) pathway in rheumatoid arthritis (RA) fibroblast-like synovial cells (FLS). FLS were stimulated with TNF-alpha following pre-treatment with or without alpha-LA. Electrophoretic mobility shift assays (EMSA) revealed that TNF-alpha activates NF-kappa B in FLS. This was inhibited by alpha-LA at concentrations of 1 mM. TNF-alpha induced IKK mediated phosphorylation of GST-I kappa B and pre-treatment with alpha-LA inhibited this pathway. FLS constitutively express MEKK1, MEKK2, MEKK3, and TAK1 and that their levels are unaffected by TNF-alpha or alpha-LA. Immunoprecipitation using anti-MEKK1 antibody phosphorylated GST-I kappa B and pre-treating the cells with alpha-LA could abolish the reaction. FLS were immunoprecipitated using an antibody to MEKK1, and MKK4 was coprecipitated with MEKK1. In addition, immune complexes precipitated with anti-MKK4 antibody phosphorylated GST-I kappa B, and pre-treatment with alpha-LA inhibited the phosphorylation. Immunoprecipitation assay showed that MEKK1, MKK4, IKK-alpha, IKK-beta, I kappa B, and NF-kappa B comprised immunocomplex. It can be concluded that TNF-alpha activates NF-kappa B in FLS through MEKK1-MKK4-IKK signaling complex, and alpha-LA inhibits this signaling at the level of or upstream of IKK-alpha and IKK-beta.
...
PMID:Alpha-lipoic acid inhibits TNF-alpha induced NF-kappa B activation through blocking of MEKK1-MKK4-IKK signaling cascades. 1818 52

The present studies defined the biological effects of a GST fusion protein of melanoma differentiation-associated gene-7 (mda-7), GST-MDA-7 (1 and 30 nmol/L), on cell survival and cell signaling in primary human glioma cells in vitro. GST-MDA-7, in a dose- and time-dependent fashion killed glioma cells with diverse genetic characteristics; 1 nmol/L caused arrest without death, whereas 30 nmol/L caused arrest and killing after exposure. Combined inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT function was required to enhance 1 nmol/L GST-MDA-7 lethality in all cell types, whereas combined activation of MEK1 and AKT was required to suppress 30 nmol/L GST-MDA-7 lethality; both effects are mediated in part by modulating c-Jun NH(2)-terminal kinase (JNK) 1-3 activity. The geldanamycin 17AAG inhibited AKT and ERK1/2 in GBM cells and enhanced GST-MDA-7 lethality. JNK1-3 signaling promoted BAX activation and mitochondrial dysfunction. In GBM6 cells, GST-MDA-7 (30 nmol/L) transiently activated p38 mitogen-activated protein kinase, which was modestly protective against JNK1-3-induced toxicity, whereas GST-MDA-7 (300 nmol/L) caused prolonged intense p38 mitogen-activated protein kinase activation, which promoted cell death. In GBM12 cells that express full-length mutant activated ERBB1, inhibition of ERBB1 did not modify GST-MDA-7 lethality; however, in U118 established glioma cells, stable overexpression of wild-type ERBB1 and/or truncated active ERBB1vIII suppressed GST-MDA-7 lethality. Our data argue that combined inhibition of ERK1/2 and AKT function, regardless of genetic background, promotes MDA-7 lethality in human primary human glioma cells via JNK1-3 signaling and is likely to represent a more ubiquitous approach to enhancing MDA-7 toxicity in this cell type than inhibition of ERBB1 function.
...
PMID:Regulation of GST-MDA-7 toxicity in human glioblastoma cells by ERBB1, ERK1/2, PI3K, and JNK1-3 pathway signaling. 1828 16

Twenty human proteins encode Phox/Bem1p (PB1) domains, which are involved in forming protein heterodimers. MEKK2, MEKK3, and MEK5 are 3 serine-threonine protein kinases that have PB1 domains. MEKK2, MEKK3, and MEK5 are the MAP3Ks and the MAP2K in the ERK5 mitogen-activated protein kinase (MAPK) signaling module. ERK5 is a critical MAPK for both development of the vasculature and vascular homeostasis in the adult, but no other MAPK has been shown to be critical in vascular maintenance in the adult animal. MEKK2 and MEKK3 are the only MAP3Ks shown to physically interact with and activate the MEK5-ERK5 signaling module. Interaction of MEKK2 or MEKK3 with MEK5 is mediated by heterodimerization of the MEKK2 (or MEKK3) PB1 and MEK5 PB1 domains. The authors have developed a homogeneous, time-resolved fluorescence resonance energy transfer (TR-FRET) assay to monitor PB1-PB1 domain heterodimerization. The assay uses a europium-chelate conjugated GST-MEK5 PB1 domain chimera, biotinylated MEKK2 PB1 domain, and streptavidin-Cy5. Interaction of the MEKK2 and MEK5 PB1 domains gives a robust FRET signal (Z' factor = 0.93), which is completely abrogated by mutation of 2 acidic residues (64D65E-->AA) within the MEK5 PB1 domain that causes loss of stable PB1-PB1 domain interaction. This assay can be used to study the specificity of PB1-PB1 domain interactions and to screen for molecules that can regulate MEKK2/MEKK3-MEK5 interactions. Disruption of PB1 domain interactions represents a novel approach for selectively regulating the ERK5 signaling pathway independent of kinase active site-directed adenosine triphosphate competitive inhibitors.
...
PMID:Homogeneous time-resolved fluorescence resonance energy transfer assay for measurement of Phox/Bem1p (PB1) domain heterodimerization. 1848 Apr 72

Resveratrol, present in grapes and red wine, is reported to be a natural chemopreventive agent against cancer. However, the concentrations required to exert these effects may be difficult to achieve by drinking only 1 or 2 glasses of red wine a day. Therefore, developing more potent, nontoxic analogues of resveratrol may provide a feasible means of achieving an effective physiologic concentration. Here we report that the resveratrol analogue, 3,5,3',4',5'-pentahydroxy-trans-stilbene (RSVL2), inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced neoplastic transformation in JB6 P+ mouse epidermal cells. Further, we identified MEK/ERK signaling as the direct molecular target for the anticancer effects of RSVL2 and demonstrated that RSVL2 inhibited MEK1, but not Raf1 or ERK2 kinase activity. RSVL2 also dose-dependently suppressed MEK1 kinase activity induced by TPA and the inhibition of H-Ras-induced cell transformation was much stronger for RSVL2 than for PD098059 or resveratrol. Both in vitro and ex vivo pull-down assays indicated that RSVL2, but not resveratrol, directly bound with GST-MEK1, but did not compete with ATP for binding. Docking data indicated that the low inhibitory activity of resveratrol might be due to the lack of the hydroxyl group at the meta position of the B ring, thereby preventing resveratrol from forming a hydrogen bond with the backbone amide group of Ser212, which is the key interaction for stabilizing the inactive conformation of the activation loop.
...
PMID:The resveratrol analogue 3,5,3',4',5'-pentahydroxy-trans-stilbene inhibits cell transformation via MEK. 1876 48

Tumor necrosis factor-alpha (TNF-alpha) is a mediator of multiple inflammatory diseases. Vascular endothelial growth factor (VEGF) plays a critical role in TNF-alpha-mediated diseases. We investigated the inhibitory effects of 3,3',4',5,5',7-hexahydroxyflavone (myricetin), an abundant natural flavonoid, on TNF-alpha-induced VEGF upregulation and the underlying molecular mechanism. Myricetin is a direct inhibitor of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase 1 (MEK1) and inhibits neoplastic cell transformation. We found that myricetin inhibited TNF-alpha-induced VEGF expression in JB6 P+ mouse epidermal cells by targeting MAPK kinase 4 (MKK4), as well as MEK1. The activation of activator protein-1 by TNF-alpha was inhibited by myricetin in a dose-dependent manner. The phosphorylation of c-Jun N-terminal kinase (JNK) and ERK was inhibited by myricetin, but not the phosphorylation of their upstream kinases MKK4 and MEK1. TNF-alpha-induced VEGF expression was inhibited by SP600125 and U0126, which are inhibitors of JNK and MEK, respectively. Myricetin inhibited TNF-alpha-induced MKK4 activity and bound glutathione S-transferase-MKK4 directly by competing with ATP. Computer modeling suggested that myricetin docks onto the ATP-binding site in MKK4, which is located between the N- and C-lobes of the kinase domain. Overall, our results indicate that myricetin has potent chemopreventive effects against TNF-alpha-related disease, mainly by targeting MKK4 and MEK1.
...
PMID:MKK4 is a novel target for the inhibition of tumor necrosis factor-alpha-induced vascular endothelial growth factor expression by myricetin. 1902 90


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---