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 cultured chick skeletal muscle cells loaded with Fura-2, the tyrosine kinase inhibitors herbimycin A and genistein abolished both the fast inositol 1,4,5-trisphosphatedependent Ca(2+) release from internal stores and extracellular Ca(2+) influx induced by 1alpha, 25(OH)(2)-vitamin D(3) (1alpha,25(OH)(2)D(3)). Daidzein, an inactive analog of genistein, was without effects. Tyrosine phosphatase inhibition by orthovanadate increased cytosolic Ca(2+). Anti-phosphotyrosine immunoblot analysis revealed that 1alpha, 25(OH)(2)D(3) rapidly (0.5-10 min) stimulates in a concentrationdependent fashion (0.1-10 nm) tyrosine phosphorylation of several myoblast proteins, among which the major targets of the hormone could be immunochemically identified as phospholipase Cgamma (127 kDa), which mediates intracellular store Ca(2+) mobilization and external Ca(2+) influx, and the growth-related proteins mitogen-activated protein (MAP) kinase (42/44 kDa) and c-myc (65 kDa). Genistein suppressed the increase in phosphorylation and concomitant elevation of MAPK activity elicited by the sterol. Both genistein and the MAPK kinase (MEK) inhibitor PD98059 abolished stimulation of DNA synthesis by 1alpha,25(OH)(2)D(3). The sterol-induced increase in tyrosine phosphorylation of c-myc, a finding not reported before for cell growth regulators, was totally suppressed by the specific Src inhibitor PP1. These results demonstrate that tyrosine phosphorylation is a previously unrecognized mechanism involved in 1alpha,25(OH)(2)D(3) regulation of Ca(2+) homeostasis in hormone target cells. In addition, the data involve tyrosine kinase cascades in the mitogenic effects of 1alpha, 25(OH)(2)D(3) on skeletal muscle cells.
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PMID:Involvement of tyrosine kinase activity in 1alpha,25(OH)2-vitamin D3 signal transduction in skeletal muscle cells. 1096 10

This article reviews recent results of studies aiming to elucidate modes of integrating signals initiated in ACTH receptors and FGF2 receptors, within the network system of signal transduction found in Y1 adrenocortical cells. These modes of signal integration should be central to the mechanisms underlying the regulation of the G0-->G1-->S transition in the adrenal cell cycle. FGF2 elicits a strong mitogenic response in G0/G1-arrested Y1 adrenocortical cells, that includes a) rapid and transient activation of extracellular signal-regulated kinases-mitogen-activated protein kinases (ERK-MAPK) (2 to 10 min), b) transcription activation of c-fos, c-jun and c-myc genes (10 to 30 min), c) induction of c-Fos and c-Myc proteins by 1 h and cyclin D1 protein by 5 h, and d) onset of DNA synthesis stimulation within 8 h. ACTH, itself a weak mitogen, interacts with FGF2 in a complex manner, blocking the FGF2 mitogenic response during the early and middle G1 phase, keeping ERK-MAPK activation and c-Fos and cyclin D1 induction at maximal levels, but post-transcriptionally inhibiting c-Myc expression. c-Fos and c-Jun proteins are mediators in both the strong and the weak mitogenic responses respectively triggered by FGF2 and ACTH. Induction of c-Fos and stimulation of DNA synthesis by ACTH are independent of PKA and are inhibited by the PKC inhibitor GF109203X. In addition, ACTH is a poor activator of ERK-MAPK, but c-Fos induction and DNA synthesis stimulation by ACTH are strongly inhibited by the inhibitor of MEK1 PD98059.
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PMID:Proliferative signaling initiated in ACTH receptors. 1100 13

Epidemiological evidence suggests that smoking is a major cause of human lung cancer. However, the mechanism by which cigarette smoke induces the cancer remains unestablished. To evaluate the effects of cigarette smoke on the expression of inducible nitric oxide synthase (iNOS), nuclear protooncogenes and related mitogen-activated protein kinases (MAPKs) in rat lung tissue, a histopathological study of the effects of gas-phase cigarette smoke on rat lung tissue were carried out. The terminal bronchioles were found to be infiltrated predominantly by lymphocytes in the peribronchiolar region and a mild to moderate degree of emphysema was noted in the alveolar spaces. The terminal bronchioles also showed marked lipid peroxidation, dilatation, and peribronchiolar fibrosis. Immunohistochemical evaluation showed that the expression of iNOS, NF-kappa B, MAPKs (MEK1, ERK2), phosphotyrosine protein and c-fos was increased in the terminal bronchioles but protein kinase C (PKC), MEKK-1, c-jun, p38 and c-myc showed no change. These results provide evidence to suggest that exposure to cigarette smoke results in oxidant stress which leads to the stimulation of iNOS and c-fos together with the induction of protein tyrosine phosphorylation and MEK1/ERK2 which in turn may promote lung pathogenesis.
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PMID:Increased expression of iNOS and c-fos via regulation of protein tyrosine phosphorylation and MEK1/ERK2 proteins in terminal bronchiole lesions in the lungs of rats exposed to cigarette smoke. 1135 18

Erythropoietin (Epo) stimulation of erythroid cells results in the activation of several kinases and a rapid induction of c-myc expression. Protein kinase C is necessary for Epo up-regulation of c-myc by promoting elongation at the 3'-end of exon 1. PKCepsilon mediates this signal. We now show that Epo triggers two signaling pathways to c-myc. Epo rapidly up-regulated Myc protein in BaF3-EpoR cells. The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 blocked Myc up-regulation in a concentration-dependent manner but had no effect on the Epo-induced phosphorylation of ERK1 and ERK2. LY294002 also had no effect on Epo up-regulation of c-fos. MEK1 inhibitor PD98059 blocked both the c-myc and the c-fos responses to Epo. PD98059 and the PKC inhibitor H7 also blocked the phosphorylation of ERK1 and ERK2. PD98059 but not LY294002 inhibited Epo induction of ERK1 and ERK2 phosphorylation in normal erythroid cells. LY294002 blocked transcription of c-myc at exon 1. PD98059 had no effect on transcription from exon 1 but, rather, blocked Epo-induced c-myc elongation at the 3'-end of exon 1. These results identify two Epo signaling pathways to c-myc, one of which is PI3K-dependent operating on transcriptional initiation, whereas the other is mitogen-activated protein kinase-dependent operating on elongation.
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PMID:Erythropoietin activates two distinct signaling pathways required for the initiation and the elongation of c-myc. 1148 13

Initiation of translation of the proto-oncogene c-myc can occur by either the cap-dependent scanning mechanism or by internal ribosome entry. The latter mechanism requires a complex RNA structural element that is located in the 5' untranslated region of c-myc, termed an internal ribosome entry segment (IRES). Recent work has shown that IRESs are used to maintain protein expression under conditions when cap-dependent translation initiation is compromised; for example, during mitosis, apoptosis and under conditions of cell stress, such as hypoxia or heat shock. Induction of genotoxic stress also results in a large reduction in global protein synthesis rates and therefore we investigated whether the c-myc IRES was active following DNA damage. As expected, in cells treated with either ethylmethane sulphonate or mitomycin C there was a large reduction in protein synthesis, although this was brought about by two different mechanisms. However, in each case the c-myc IRES was active and c-Myc protein expression was maintained. Finally we showed that the proteins required for this process are downstream of the p38 mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated protein kinase (ERK)/MEK(MAPK/ERK kinase) signalling pathways, since pre-treatment of cells with inhibitors of these pathways before DNA damage is initiated inhibits both c-myc IRES activity and expression of c-Myc protein.
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PMID:Internal ribosome entry segment-mediated initiation of c-Myc protein synthesis following genotoxic stress. 1156 82

Examination of the expression of proteins linked with signaling pathways commanding cell death and cell survival has been carried out to increase understanding on the mechanisms leading to cell death in the cerebellum in Creutzfeldt-Jakob disease (CJD). Expression of Fas, Fas ligand (Fas-L), ERK, MEK, Bcl-2, Bax, N-myc, c-myc, pro-caspase-2 and active caspase-3 was examined by immunohistochemistry in the cerebellum of six patients with sporadic CJD, three patients with olivopontocerebellar atrophy (OPCA) and six age-matched controls. No modifications in the expression of these proteins were observed in granule cells in CJD and OPCA when compared with controls, except in a few cells in the molecular and granular layers in CJD that displayed dense homogeneous active caspase-3 immunostaining. This suggests selective activation of caspase-3 in association with increased cellular vulnerability in CJD. No modifications in pro-caspase-2 and c-myc immunoreactivity were observed in Purkinje cells in diseased brains when compared with controls. However, increased diffuse Fas, Fas-L, MEK, ERK and Bax expression, and enhanced granular active caspase-3 immunoreactivity was found in the cytoplasm of Purkinje cells in CJD. Increase in Bcl-2 and N-myc occurred in Purkinje cells in CJD and OPCA. These results indicate that enhanced Fas, Fas-L, MERK, ERK, Bax and granular active caspase-3 expression is not lethal to Purkinje cells in CJD, whereas increased Bcl-2 and N-myc does not preclude per se cell death or death survival in CJD and OPCA. These findings point to the likelihood that expression of these cell death proteins in neurodegeneration has functional roles differing from those related with apoptosis.
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PMID:Cell death signaling in the cerebellum in Creutzfeldt-Jakob disease. 1158 44

Retinoids have been shown to promote vascular smooth muscle cell differentiation, although the underlying mechanism is unclear. In fact, treatment of rat aortic smooth muscle cells with all-trans retinoic acid (ATRA) has been shown to markedly elevate the mRNA and protein levels of smooth muscle alpha-actin. Considering that an exit from the cell cycle is a prerequisite for cell differentiation, we examined the effect of ATRA on cellular events during the progression from Go to S phase. Pretreatment with ATRA dose-dependently inhibited DNA synthesis induced by basic fibroblast growth factor. However, ATRA did not inhibit transient activation of mitogen-activated protein kinase (MAPK) in response to mitogenic stimulation. And ATRA consistently failed to influence the phosphorylation of MAPK kinase (MEK) and the expression of MAPK-specific dual phosphatase (MKP-1). ATRA did not interfere with other early mitogenic signals either, such as the phosphorylation of FGF-1 receptor or the induction of immediate early genes c-fos, c-jun, and c-myc. In contrast, ATRA strongly suppressed the pRb kinase activities of the cyclin-dependent kinases (Cdks) Cdk4, Cdk6, and Cdk2. ATRA did not influence the expressions of Cip/Kip family Cdk inhibitors or those of cyclins D1 and D2, whereas it strongly inhibited the expressions of cyclins D3 and E, Cdk4, Cdk6, and Cdk2. These results suggest that ATRA targets multiple genes essential for entry into the cell cycle and for the subsequent progression to G1 phase, but without interrupting early mitogenic signals upstream of MAPK.
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PMID:All-trans retinoic acid inhibits vascular smooth muscle cell proliferation targeting multiple genes for cyclins and cyclin-dependent kinases. 1167 54

MKK7 is a recently discovered mitogen-activated protein kinase (MAPK) kinase that is unique in that it specifically activates only the c-JUN NH(2)-terminal protein kinase (JNK) family of enzymes. Very little is known about the biological role of MKK7. We generated inducible cell lines from the human embryonal kidney carcinoma cell line, HEK293, by stable transfection with a constitutively active mutant of MKK7, MKK7(3E), fused to green fluorescent protein (GFP), under the control of an ecdysone-inducible promoter. Treatment of cells with the synthetic ecdysone analog ponasterone A induced expression of GFP-MKK7(3E) and resulted in sustained activation of endogenous JNK, but neither of the other endogenous MAPKs, ERK or p38. Red and green fluorescing cDNA copies of mRNA extracted from cells obtained before and after induction of GFP-MKK7(3E) were hybridized to microarrays containing more than 6,000 cDNAs in eight independent experiments. By selection criteria, 23 genes were differentially regulated after 24 h of induction of GFP-MKK7(3E) and 16 after 48 h. The expression of 9 genes was consistently changed after both 24 and 48 h of induction. These changes included down-regulation of three genes, c-myc, angiopoietin-2, and glucose-regulated protein 58, and up-regulation of 6 genes, tissue factor pathway inhibitor-2, GRP78, autotaxin, PPP1R7, the DKFZ cDNA p434D0818, and 1 unknown gene. Consistent with previously described roles of several of the altered genes, MKK7(3E) inhibited cell proliferation. These data implicate active MKK7 in the negative regulation of cell proliferation and provide evidence for a new role for this kinase in the regulation of a distinct, hitherto unrecognized set of genes.
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PMID:Inducible expression of a constitutively active mutant of mitogen-activated protein kinase kinase 7 specifically activates c-JUN NH2-terminal protein kinase, alters expression of at least nine genes, and inhibits cell proliferation. 1171 98

Macrophages exposed to receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*) demonstrate increased DNA synthesis and cell division. In the current study, we have probed the role of cytosolic phospholipase A(2) (cPLA(2)) activity in the cellular response to alpha(2)M*. Ligation of the alpha(2)M* signaling receptor by alpha(2)M*, or its receptor binding fragment, increased cPLA(2) activity 2-3-fold in a concentration and time-dependent manner. This activation required a pertussis toxin-insensitive G protein. Cellular binding of alpha(2)M* also induced transient translocation of cPLA(2) activity to nuclei and membrane fractions. Inhibition of protein kinase C activity or chelation of Ca(2+) inhibited alpha(2)M*-induced increased cPLA(2) activity. Binding of alpha(2)M* to macrophages, moreover, increased phosphorylation of MEK 1/2, ERK 1/2, p38 MAPK, and JNK. Incubation of macrophages with inhibitors of MEK 1/2 or p38 MAPK before stimulation with alpha(2)M* profoundly decreased phosphorylation of MAPKs, blocking cPLA(2) activation. alpha(2)M*-induced increase in [(3)H]thymidine uptake and cell proliferation was completely abolished if activation of cPLA(2) was prevented. The response of macrophages to alpha(2)M* requires transcription factors nuclear factor kappaB, and cAMP-responsive element-binding protein as well as expression of the proto-oncogenes c-fos and c-myc. These studies indicate that the activation of cPLA(2) plays a crucial role in alpha(2)M*-induced mitogenesis and cell proliferation.
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PMID:Regulation of cytosolic phospholipase A2 activity in macrophages stimulated with receptor-recognized forms of alpha 2-macroglobulin: role in mitogenesis and cell proliferation. 1173 96

We studied the effect of beryllium fluoride on murine peritoneal macrophages and determined its effects on signal transduction and genetic regulation. At low concentration (1-5 nM), BeF(2) caused an approximate twofold increase in [(3)H]thymidine uptake and cell number, but above 5 nM, it showed cytotoxic effects. BeF(2) increased cellular inositol (1,4,5)trisphosphate (IP(3)) and [Ca(2)(+)](i) about twofold. The rise in [Ca(2)(+)](i) occurred consequent to release from IP(3)-sensitive Ca(2)(+) stores and from influx, mainly via L-type channels. A significant increase in the levels of MEK1, ERK1, p38 MAPK, and JNK phosphorylation was observed in BeF(2)-exposed macrophages. The levels of NF-kappaB and CREB transcription factors and the proto-oncogenes c-fos and c-myc were also elevated significantly. Intracellular Ca(2)(+) chelation blocked the effect of BeF(2). We conclude that BeF(2) at low concentration exerts its mitogenic effects in peritoneal macrophages by elevating [Ca(2)(+)](i), which triggers the activation of p21(ras)-dependent MAPK signaling cascades.
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PMID:Beryllium fluoride-induced cell proliferation: a process requiring P21(ras)-dependent activated signal transduction and NF-kappaB-dependent gene regulation. 1186 86


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