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)

Endochondral bone growth is regulated through the rates of proliferation and differentiation of growth plate chondrocytes. While little is known about the intracellular events controlling these processes, the protein kinase c-Raf, a central component of the cellular signal transduction machinery, has recently been shown to be expressed only by differentiated, hypertrophic chondrocytes. The involvement of c-Raf in the transcriptional regulation of the hypertrophic chondrocyte-specific collagen X gene was investigated using cotransfections of collagen X reporter plasmids and expression vectors for mutant c-Raf proteins. Both activated and dominant-negative forms of c-Raf reduced the activity of the collagen X promoter to approximately 30%. The element mediating the repressing effect of activated c-Raf was located between nucleotides -2864 and -2410 of the promoter, whereas the effect of the dominant-negative form of c-Raf was conferred by the 462 nucleotides immediately upstream of the transcription start site. Inhibition of MEK1/2 and ERK1/2, downstream components of Raf-signaling, also caused repression of basal collagen X promoter activity. These data suggest that c-Raf regulates collagen X promoter activity positively and negatively through different cis-acting elements and represent the first evidence of c-Raf activity described in hypertrophic chondrocytes.
...
PMID:Raf signaling stimulates and represses the human collagen X promoter through distinguishable elements. 1002 14

Mitogen-activated protein kinase (MAPK) cascades underlie long-term mitogenic, morphogenic, and secretory activities of purinergic receptors. In HEK-293 cells, N-ethylcarboxamidoadenosine (NECA) activates endogenous A2BARs that signal through Gs and Gq/11. UTP activates P2Y2 receptors and signals only through Gq/11. The MAPK isoforms, extracellular-signal regulated kinase 1/2 (ERK), are activated by NECA and UTP. H-89 blocks ERK activation by forskolin, but weakly affects the response to NECA or UTP. ERK activation by NECA or UTP is unaffected by a tyrosine kinase inhibitor (genistein), attenuated by a phospholipase C inhibitor (U73122), and is abolished by a MEK inhibitor (PD098059) or dominant negative Ras. Inhibition of protein kinase C (PKC) by GF 109203X failed to block ERK activation by NECA or UTP, however, another PKC inhibitor, Ro 31-8220, which unlike GF 109203X, can block the zeta-isoform, and prevents UTP- but not NECA-induced ERK activation. In the presence of forskolin, Ro 31-8220 loses its ability to block UTP-stimulated ERK activation. PKA has opposing effects on B-Raf and c-Raf-1, both of which are found in HEK-293 cells. The data are explained by a model in which ERK activity is modulated by differential effects of PKC zeta and PKA on Raf isoforms.
...
PMID:A2B adenosine and P2Y2 receptors stimulate mitogen-activated protein kinase in human embryonic kidney-293 cells. cross-talk between cyclic AMP and protein kinase c pathways. 1002 23

Mitogenic signals initiated at the plasma membrane are transmitted to the nucleus through an intricate signalling network. We identified the protooncoprotein Cot as a new component of mitogenic signalling cascades, which activates both the classic cytoplasmic cascade and the SAPK stress pathway. Wildtype and activated Cot phosphorylate and activate MEK-1 and SEK-1 in vitro. These findings are consistent with the sequence homology between Cot and the rat gene Tpl-2. Expression of oncogenic Cot in 293, NIH3T3 and PC12 cells leads to in vivo phosphorylation of endogenous c-Jun and Erk-1/2 suggesting that the serine/threonine kinase Cot functions beside c-Raf-1 and Mos as a direct activator of MEK-1. Furthermore, we have examined the biological effects of Cot on the phenotype of fibroblastic and neuronal cells. In order to test a potential c-Raf-1 dependency of Cot transformation, the effect of oncogenic Cot on Raf revertant CHP25 cells was determined. Cot could restore the transformed phenotype indicating that Cot transformation is not dependent on active c-Raf-1 and that Cot is not a target for the putative Raf inhibitor, which is presumably active in the revertant cell line. Expression of oncogenic versions of Raf as well as v-Mos leads to differentiation of PC12 cells. Cot also induces neurite outgrowth of PC12 cells. These data are consistent with the role of Cot in the classic mitogenic cascade and suggest that the simultaneously activated JNK/SAPK stress pathway has no antagonistic effects in this context.
...
PMID:Cot protooncoprotein activates the dual specificity kinases MEK-1 and SEK-1 and induces differentiation of PC12 cells. 1005 Aug 76

We have developed a quantitative scintillation proximity assay (SPA) that reproduces the Raf/MEK/ERK signal transduction pathway. The components of this assay include human cRaf1, MEK1, and ERK2 and a biotinylated peptide substrate for ERK2. cRaf1 was expressed as a his-tagged protein in insect cells in an active form. MEK1 and ERK2 were expressed in Escherichia coli as glutathione S-transferase (GST)-fusion proteins in their inactive forms. ERK2 was removed from the GST portion of the fusion protein by cleavage with thrombin protease. When the purified components are incubated together, cRaf-1 phosphorylates and activates MEK1, MEK1 phosphorylates and activates ERK2, and ERK2 phosphorylates the peptide, biotin-AAATGPLSPGPFA. Phosphorylation of the peptide using [gamma-33P]ATP is detected following binding to streptavidin-coated SPA beads. The assay detects inhibitors of cRaf1, MEK1, or ERK2, and has been used to screen large numbers of compounds. The specific target of inhibition was subsequently identified with secondary assays described herein.
...
PMID:A scintillation proximity assay for the Raf/MEK/ERK kinase cascade: high-throughput screening and identification of selective enzyme inhibitors. 1007 22

Protein kinase C (PKC) isoforms constitute an important component of the signal transduction pathway used by cardiomyocytes to respond to a variety of extracellular stimuli. Translocation to distinct intracellular sites represents an essential step in the activation of PKC isoforms, presumably as a prerequisite for stable access to substrate. Caveolae are specialized subdomains of the plasma membrane that are reported to concentrate key signaling proteins and may represent a locus for PKC action, given that PKC activators have been reported to dramatically alter caveolae morphology. Accordingly, this study examines whether PKC isoforms initiate signaling in cardiomyocyte caveolae. Phorbol ester-sensitive PKC isoforms were detected at very low levels in caveolae fractions prepared from unstimulated cardiomyocytes; phorbol 12-myristate 13-acetate (PMA) (but not 4alpha-PMA, which does not activate PKC) recruited calcium-sensitive PKCalpha and novel PKCdelta and PKCepsilon to this compartment. The subcellular localization of the phorbol ester-insensitive PKClambda isoform was not influenced by PMA. Endothelin also induced the selective translocation of PKCalpha and PKCepsilon (but not PKCdelta or PKClambda) to caveolae. Multiple components of the extracellular signal-regulated protein kinase (ERK) cascade, including A-Raf, c-Raf-1, mitogen-activated protein kinase kinase, and ERK, were detected in caveolae under resting conditions. Although levels of these proteins were not altered by PMA, translocation of phorbol ester-sensitive PKC isoforms to caveolae was associated with the activation of a local ERK cascade as well as the phosphorylation of a approximately 36-kDa substrate protein in this fraction. Finally, a minor fraction of a protein that has been designated as a receptor for activated protein kinase C resides in caveolae and (along with caveolin-3) could represent a mechanism to target PKC isoforms to cardiomyocyte caveolae. These studies identify cardiomyocyte caveolae as a meeting place for activated PKC isoforms and their downstream target substrates.
...
PMID:Activated protein kinase C isoforms target to cardiomyocyte caveolae : stimulation of local protein phosphorylation. 1032 35

In several neuronal cell systems, fibroblast-derived growth factor (FGF) and nerve growth factor (NGF) act as neurogenic agents, whereas epidermal growth factor (EGF) acts as a mitogen. The mechanisms responsible for these different cellular fates are unclear. We report here that although FGF, NGF, and EGF all activate mitogen-activated protein (MAP) kinase (extracellular signal-related kinase [ERK]) in rat hippocampal (H19-7) and pheochromocytoma (PC12) cells, the activation of ERK by the neurogenic agents FGF and NGF is dependent upon protein kinase Cdelta (PKCdelta), whereas ERK activation in response to the mitogenic EGF is independent of PKCdelta. Antisense PKCdelta oligonucleotides or the PKCdelta-specific inhibitor rottlerin inhibited FGF- and NGF-induced, but not EGF-induced, ERK activation. In contrast, EGF-induced ERK activation was inhibited by the phosphatidylinositol-3-kinase inhibitor wortmannin, which had no effect upon FGF-induced ERK activation. Rottlerin also inhibited the activation of MAP kinase kinase (MEK) in response to activated Raf, but had no effect upon c-Raf activity or ERK activation by activated MEK. These results indicate that PKCdelta functions either downstream from or in parallel with c-Raf, but upstream of MEK. Inhibition of PKCdelta also blocked neurite outgrowth induced by FGF and NGF in PC12 cells and by activated Raf in H19-7 cells, indicating a role for PKCdelta in the neurogenic effects of FGF, NGF, and Raf. Interestingly, the PKCdelta requirement is apparently cell type specific, since FGF-induced ERK activation was independent of PKCdelta in NIH 3T3 murine fibroblasts, in which FGF is a mitogen. These data demonstrate that PKCdelta contributes to growth factor specificity and response in neuronal cells and may also promote cell-type-specific differences in growth factor signaling.
...
PMID:Protein kinase Cdelta mediates neurogenic but not mitogenic activation of mitogen-activated protein kinase in neuronal cells. 1033 Jan 61

In mouse embryo NIH 3T3 fibroblasts, ethanol (60-80 mM) was found to enhance the stimulatory effects of sphingosine 1-phosphate (S1P) on both DNA synthesis and cell proliferation. Well-detectable potentiating effects of ethanol on S1P-induced mitogenesis required the presence of calcium (>1 mM) and zinc (20-40 microM) in the incubation medium. The amphibian tetrapeptide bombesin, which is known to mobilize intracellular calcium in fibroblasts, had no effect alone, but it approximately doubled the combined stimulatory effects of ethanol and S1P on DNA synthesis. The synergistic mitogenic effects of ethanol and S1P were also slightly enhanced, rather than inhibited, by the alcohol dehydrogenase inhibitor 4-methylpyrazole (5 mM). Of the various growth regulatory enzymes examined, ethanol detectably enhanced the stimulatory effects of S1P on the phosphosphorylation (activation) of p42/p44 mitogen-activated protein (MAP) kinases, but not of p38 MAP kinase. Cotreatment of fibroblasts with ethanol for 10 min also enhanced the stimulatory effects of S1P on the activities of c-Raf-1 kinase and p70 S6 kinase, but neither S1P nor ethanol had effects on phosphatidylinositol 3'-kinase and Akt/PKB kinase activities. Ethanol-plus-S1P-induced DNA synthesis was partially inhibited by both PD 98059 (50 microM) and rapamycin (10 nM), inhibitors of p42/p44 MAP kinase kinase and mTOR/p70 S6 kinases, respectively. The results indicate that in NIH 3T3 fibroblasts, ethanol can enhance the mitogenic effects of S1P by a zinc- and calcium-dependent mechanism involving both the rapamycin-sensitive p70 S6 kinase-dependent and the c-Raf-1/MAP kinase-dependent growth regulatory pathways.
...
PMID:Ethanol potentiates the mitogenic effects of sphingosine 1-phosphate by a zinc- and calcium-dependent mechanism in fibroblasts. 1033 73

The mechanism of Taxol-induced apoptosis was investigated in MCF-7 human breast carcinoma cells. Taxol-induced apoptosis was associated with phosphorylation of both c-Raf-1 and Bcl-2 and activation of ERK and JNK MAP kinases. The serine protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) effectively blocked apoptosis, but N-p-tosyl-L-lysine chloromethyl ketone (TLCK), another serine protease inhibitor, was without effect. TPCK treatment also prevented phosphorylation of c-Raf-1 and Bcl-2 in response to Taxol treatment. The serine protease inhibitor did not alter JNK activity, but it enhanced Taxol-induced activation of ERK1/2. Treatment of cells with the inhibitor of MEK activation, PD98059, prevented Taxol-induced ERK activation both in the presence and absence of TPCK, but did not influence survival of either Taxol- or Taxol plus TPCK-treated cells. In addition, PD98059 had no effect on c-Raf-1 or Bcl-2 phosphorylation. Thus, while the Taxol-induced phosphorylations of c-Raf-1 and Bcl-2 proteins appear to be coupled, these events can be disassociated from ERK1/2 activation. In summary, these findings suggest that phosphorylation of c-Raf-1 and Bcl-2, but not ERK1/2, are important signaling events in Taxol-induced apoptosis of MCF-7 breast cancer cells and that a TPCK inhibitable protease(s) is required for these processes.
...
PMID:Serine protease inhibitor TPCK prevents Taxol-induced cell death and blocks c-Raf-1 and Bcl-2 phosphorylation in human breast carcinoma cells. 1037 21

The collagen X gene is expressed exclusively by differentiated, hypertrophic chondrocytes. The mechanisms controlling collagen X expression remain largely unknown. Here we show that collagen X promoter activity can be induced by serum stimulation of chondrogenic MCT cells. The serum response is conferred by a 462 nucleotide promoter fragment. Both the c-Raf/MEK/ERK and p38 MAP kinase pathways are required for this effect, whereas phosphatidylinositol-3-kinase and protein kinase A repress promoter activation. These data are the first to demonstrate serum inducibility of the collagen X promoter and to identify signal transduction pathways involved.
...
PMID:Serum induction of the collagen X promoter requires the Raf/MEK/ERK and p38 pathways. 1044 66

Multiple biological functions have been ascribed to the Ras-related G protein R-Ras. These include the ability to transform NIH 3T3 fibroblasts, the promotion of cell adhesion, and the regulation of apoptotic responses in hematopoietic cells. To investigate the signaling mechanisms responsible for these biological phenotypes, we compared three R-Ras effector loop mutants (S61, G63, and C66) for their relative biological and biochemical properties. While the S61 mutant retained the ability to cause transformation, both the G63 and the C66 mutants were defective in this biological activity. On the other hand, while both the S61 and the C66 mutants failed to promote cell adhesion and survival in 32D cells, the G63 mutant retained the ability to induce these biological activities. Thus, the ability of R-Ras to transform cells could be dissociated from its propensity to promote cell adhesion and survival. Although the transformation-competent S61 mutant bound preferentially to c-Raf, it only weakly stimulated the mitogen-activated protein kinase (MAPK) activity, and a dominant negative mutant of MEK did not significantly perturb R-Ras oncogenicity. Instead, a dominant negative mutant of phosphatidylinositol 3-kinase (PI3-K) drastically inhibited the oncogenic potential of R-Ras. Interestingly, the ability of the G63 mutant to induce cell adhesion and survival was closely associated with the PI3-K-dependent signaling cascades. To further delineate R-Ras downstream signaling events, we observed that while a dominant negative mutant of Akt/protein kinase inhibited the ability of R-Ras to promote cell survival, both dominant negative mutants of Rac and Ral suppressed cell adhesion stimulated by R-Ras. Thus, the biological actions of R-Ras are mediated by multiple effectors, with PI3-K-dependent signaling cascades being critical to its functions.
...
PMID:Differential roles of Akt, Rac, and Ral in R-Ras-mediated cellular transformation, adhesion, and survival. 1045 80


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

---