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)

The Grb2-associated binder-1 (Gab1) is one of the major adapter molecules downstream of growth factor receptor signaling. Even though insulin causes tyrosine phosphorylation of Gab1, its role in insulin signaling has not been identified yet. We have demonstrated that insulin increased expression of early growth response gene-1 (egr-1), which is one of the most important transcription factors involved in cell proliferation and differentiation. In the present study, the possible role of Gab1 in insulin-induced egr-1 expression was studied using Rat1 fibroblasts expressing human insulin receptors and wildtype Gab1 (HIRc/Gab1(WT)), Gab1 with three tyrosines in the phosphatidylinositol (PI) 3'-kinase binding domain mutated to phenylalanine (HIRc/Gab1(DeltaPI3K)), or histidinol resistance only (HIRc/HIS). Insulin-induced egr-1 expression in HIRc/Gab1(DeltaPI3K) cells was much lower than in the other cells, as determined by Northern blot analysis. These results suggest that Gab1 is involved in the signaling pathway for insulin-induced egr-1 expression through increasing PI3'-kinase activity. The MAP kinase activity increased less with insulin treatment in HIRc/Gab1(DeltaPI3K) cells than in other cells. Inhibition of MAP kinase by the MEK inhibitor completely abolished insulin-induced egr-1 expression. These results suggest that Gab1 increases MAP kinase activity through its PI3'-kinase binding site, which then leads to egr-1 expression. Our results indicate that Gab1 is involved in the control of egr-1 expression regulated by insulin.
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PMID:Grb-2-associated binder-1 is involved in insulin-induced egr-1 gene expression through its phosphatidylinositol 3'-kinase binding site. 1140 19

beta -adrenergic agonists stimulate neonatal rat cardiac fibroblast growth, albeit the identity of the signaling event(s) remains equivocal. Isoproterenol (ISO) treatment increased intracellular cyclic AMP levels; however, cyclic AMP-elevating agents had no effect on protein synthesis. The tyrosine kinase inhibitor tyrphostin A25, and the inhibition of ras processing by the farnesyltransferase inhibitor BMS-191563 attenuated ISO-stimulated protein synthesis. Concomitant with increased protein synthesis, ISO stimulated extracellular signal-regulated protein kinase (ERK) and phosphatidylinositol 3-kinase (PI3-K) activity. The MEK1/2 inhibitor PD098059 abrogated ISO-stimulated ERK activity, albeit the increase in protein synthesis was unaffected. By contrast, LY294002 inhibited both ISO-stimulated PI3-K activity, and protein synthesis. ISO treatment did not increase the expression of transforming growth factor-beta(1)(TGF-beta(1)) mRNA, whereas a significant decrease in the steady-state mRNA level of TGF- beta(3)was observed. This latter effect was mimicked by cyclic AMP-elevating agents. Angiotensin II (AII) activation of the AT(1)receptor increased protein synthesis, but in contrast to ISO, the growth response was not inhibited by either tyrphostin A25 or BMS-191563, and was associated with the concomitant expression of both TGF-beta(1)and TGF-beta(3)mRNAs. Analogous to ISO, AII treatment increased ERK and PI3-K activity, and PI3-K was required for protein synthesis. These findings are the first to highlight the activation of PI3-K by a Gs(alpha)-coupled receptor, and its essential role in beta -adrenergic as well as AT(1)receptor-mediated protein synthesis in neonatal rat cardiac fibroblasts. However, despite the conserved role of PI3-K, additional disparate signaling pathways are recruited by ISO and AII, which may differentially influence fibroblast phenotype.
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PMID:beta-Adrenergic stimulation of rat cardiac fibroblasts promotes protein synthesis via the activation of phosphatidylinositol 3-kinase. 1144 12

The mechanisms underlying the anti-apoptotic action of interleukin (IL)-6 on hematopoietic cells have been extensively studied, but those in the case of neuronal cells have been poorly reported. We investigated the effect of IL-6 on the survival of rat PC12 pheochromocytoma cells and analyzed the signaling pathways of the cytokine by means of some kinase inhibitors. IL-6 protects PC12 cells from the death induced by serum deprivation or anticancer agents, such as cisplatin, paclitaxel and 5-fluorouracil. Phosphatidylinositol (PI)3-kinase inhibitors (LY294002 and wortmannin) but not a mitogen-activated protein kinase kinase inhibitor (PD98059) completely suppressed the IL-6-promoted survival of the cells. A Janus tyrosine kinase 2 inhibitor (tyrphostin AG490) suppressed the phosphorylation of signal transducers and activators of transcription (STAT)3 and only partially inhibited the anti-apoptotic activity of IL-6. IL-6 stimulated phosphorylation of Akt, a downstream effector of PI3 kinase, and in the presence of LY294002, the phosphorylation of Akt was reduced to basal level. These results suggest that the signaling pathway for the anti-apoptotic effect of IL-6 in PC12 cells is mediated in major part by activation of the PI3-kinase/Akt pathway and thus is different from that in hematopoietic cells.
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PMID:Interleukin-6 protects rat PC12 cells from serum deprivation or chemotherapeutic agents through the phosphatidylinositol 3-kinase and STAT3 pathways. 1148 35

Recent advances in defining neurotrophin signaling mediators have provided insights into the signal transduction mechanisms that underlie axon growth. Evidence is accumulating that major Trk effectors regulate the morphological development of embryonic peripheral neurons. Less is known about signaling related to the robust axon extension that follows peripheral axotomy of adult neurons. Regenerative axon growth can be mimicked in vitro by a "conditioning" lesion performed 2 weeks before culture (Smith and Skene, 1997). Previous work has implicated both neurotrophins and cytokines in this response. Because signal transduction mediators of both of these families of growth factors are well characterized, we have compared the role of neurotrophin and cytokine signaling in developmental versus regenerative sensory axon growth. Chemical inhibitors were administrated to embryonic and axotomized sensory neurons in vitro to block the activation of Erk kinase (MEK)-extracellular signal-regulated kinase (ERK), phosphatidylinositol-3 kinase (PI3-K), and janus kinase (JAK) signaling. As expected, both MEK and PI3-K inhibition blocked axon growth from both naive and NGF-stimulated embryonic day 13 sensory neurons, whereas inhibition of JAK phosphorylation had no effect. In contrast, neither MEK nor PI3-K inhibitors blocked elongation of adult sensory neurons after a conditioning lesion. However, the addition of a JAK2 inhibitor prevented the regenerative axon response. Consistent with these pharmacological results, the percentage of neurons showing intense nuclear signal transducers and activators of transcription 3 phosphorylation after a conditioning lesion was markedly increased compared with controls. These observations demonstrate that the signaling mediators that underlie regenerative axon growth are distinct from those used during development and suggest that cytokine signaling may be critical to peripheral nervous system regeneration.
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PMID:Different signaling pathways mediate regenerative versus developmental sensory axon growth. 1151 95

Oncogenic ras upregulates the expression of VEGF through the activation of the transcriptional enhancer hypoxia inducible factor-1alpha (HIF-1alpha) by a still poorly understood mechanism. Here, we demonstrate that both the Raf/MEK/MAPK and the PI3 kinase/Akt signaling pathways potently and additively stimulate the expression from a hypoxia response element (HRE) within the 5'flanking region of the VEGF promoter. Interestingly, while MAPK appears to specifically upregulate the transactivation activity of HIF-1alpha through direct phosphorylation of its regulatory/inhibitory domain, GSK-3, a downstream target of Akt, directly phosphorylates the HIF-1alpha oxygen-dependent degradation domain. These results suggest a novel mechanism whereby two divergent signaling pathways emerging from Ras may cooperatively but independently regulate the activity of a HIF-1alpha, thereby promoting the expression of a potent angiogenic mediator.
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PMID:MAPK and Akt act cooperatively but independently on hypoxia inducible factor-1alpha in rasV12 upregulation of VEGF. 1154 90

We investigated the attachment and spreading of v-Crk-transformed cells, v-Crk3Y1, on fibronectin. Transformation by v-Crk virtually suppressed the spreading, but not the attachment, of cells on fibronectin. This suppression of cell spreading was not correlated with the suppression of integrin alpha5 and beta1 expression. However, the spreading of v-Crk3Y1 on fibronectin was dramatically restored by either expression of dominant-negative Ras or treatment with manumycin A, a Ras farnesyltransferase inhibitor. Moreover, both expression of dominant-negative MEK1 and treatment of cells with U0126, a MEK1 inhibitor, restored the cell spreading of v-Crk3Y1. In contrast, neither treatment with LY294002, a PI3K inhibitor, nor expression of dominant-negative C3G showed no effect on cell spreading on fibronectin. Taken together, our results suggest that, among multiple signaling pathways activated by v-Crk, the Ras-MEK1-MAP kinase cascade plays a pivotal role in the suppression of cell spreading on fibronectin, but C3G and the PI3 kinase do not.
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PMID:Suppression of cell spreading by v-Crk requires Ras-MEK-MAP kinase signaling. 1159 97

Previous studies demonstrate that interleukin-6 (IL-6) mediates growth and survival in human multiple myeloma (MM) cells via the MEK/MAPK and JAK/STAT signaling pathways, respectively. IL-6 also confers protection against Dexamethasone (Dex)-induced apoptosis via activation of protein tyrosine phosphatase (SHP2). In the current study, we characterized IL-6 triggered phophatidylinositol-3 kinase/Akt kinase (PI3-K/Akt) signaling in MM cells. IL-6 induces Akt/PKB phosphorylation in a time and dose dependent manner in MM.1S MM cells. IL-6 also induced phosphorylation of downstream targets of Akt, including Bad, GSK-3beta, and FKHR, confirming Akt activation. Inhibition of Akt activation by the PI3-K inhibitor LY294002 partially blocked IL-6 triggered MEK/MAPK activation and proliferation in MM.1S cells, suggesting cross-talk between PI3-K and MEK signaling. We demonstrate that Dex-induced apoptosis in MM.1S cells is mediated by downstream activation of caspase-9, with resultant caspase-3 cleavage; and conversely, that IL-6 triggers activation of PI3-K and its association with SHP2, inactivates caspase-9, and protects against Dex-induced apoptosis. LY294002 completely abrogates this signaling cascade, further confirming the importance of PI3-K/Akt signaling in conferring the protective effect of IL-6 against Dex-induced apoptosis. Finally, we show that IL-6 triggered PI3-K/Akt signaling in MM.1S cells inactivates forkhead transcriptional factor (FKHR), with related G1/S phase transition, whereas LY294002 blocks this signaling, resulting in upregulation of p27(KIP1) and G1 growth arrest. Our data therefore suggest that PI3-K/Akt signaling mediates growth, survival, and cell cycle regulatory effects of IL-6 in MM.
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PMID:Biologic sequelae of interleukin-6 induced PI3-K/Akt signaling in multiple myeloma. 1159 6

We investigated the role of H-Ras in chemokine-induced integrin regulation in leukocytes. Stimulation of Jurkat T cells with the CXC chemokine stromal cell-derived factor-1alpha (SDF-1alpha) resulted in a rapid increase in the phosphorylation, i.e., activation of extracellular signal receptor-activated kinase (ERK) but not c-Jun NH(2)-terminal kinase or p38 kinase, and phosphorylation of Akt, reflecting phosphatidylinositol 3-kinase (PI3-K) activation. Phosphorylation of ERK in Jurkat cells was enhanced and attenuated by expression of dominant active (D12) or inactive (N17) forms of H-Ras, respectively, while N17 H-Ras abrogated SDF-1alpha-induced Akt phosphorylation. SDF-1alpha triggered a transient regulation of adhesion to intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 mediated by lymphocyte function antigen-1 (LFA-1) and very late antigen-4 (VLA-4), respectively, and a rapid increase in LFA-1 binding to soluble ICAM-1.Ig, which was inhibited by D12 but not N17 H-Ras. Both D12 and N17 H-Ras abrogated the regulation of LFA-1 but not VLA-4 avidity, and impaired LFA-1-mediated transendothelial chemotaxis but not VLA-4-dependent transmigration induced by SDF-1alpha. Analysis of the mutant Jurkat J19 clone revealed LFA-1 with constitutively high affinity and reduced ERK phosphorylation, which were partially restored by expression of active H-Ras. Inhibition of PI3-K blocked the up-regulation of Jurkat cell adhesion to ICAM-1 by SDF-1alpha, whereas inhibition of mitogen-activated protein kinase kinase impaired the subsequent down-regulation and blocking both pathways abrogated LFA-1 regulation. Our data suggest that inhibition of initial PI3-K activation by inactive H-Ras or sustained activation of an inhibitory ERK pathway by active H-Ras prevail to abolish LFA-1 regulation and transendothelial migration induced by SDF-1alpha in leukocytes, establishing a complex and bimodal involvement of H-Ras.
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PMID:Dual role of H-Ras in regulation of lymphocyte function antigen-1 activity by stromal cell-derived factor-1alpha: implications for leukocyte transmigration. 1159 92

We assessed the effect of signalling through CXCR4 on the proliferation and differentiation of human megakaryocytic progenitor cells (CFU-Meg) in the presence or absence of stem cell factor (SCF) and/or thrombopoietin (TPO), using peripheral blood-derived CD34(+)IL-6R(-) cells as a target. TPO alone induced a significant number of CFU-Meg colonies. Although stromal cell-derived factor-1 (SDF-1) or SCF alone did not support CFU-Meg colony formation, these factors had a synergistic effect on CFU-Meg colony formation in the presence of TPO. The combination of SDF-1, SCF and TPO induced twice as many CFU-Meg colonies as TPO alone. To investigate the mechanism of this synergistic action, we examined the effects of various protein kinase inhibitors on CFU-Meg colony formation. LY294002 and GF109203X (inhibitors of PI3-K and PKC respectively) completely or partially inhibited this synergistic action. In contrast, a MEK inhibitor (PD98059) did not inhibit CFU-Meg colony formation. It significantly increased the higher ploidy classes (16N to 64N) of megakaryocytes supported by TPO, TPO + SCF, TPO + SDF-1, and TPO + SCF + SDF-1, whereas it abolished the effect of SDF-1 on the increase of higher ploidy classes of megakaryocytes supported by TPO. These results suggest that MAPK may negatively or positively regulate the nuclear maturation of megakaryocytes, known as endomitosis. In the presence of PD98059, proplatelet formation (PPF) was significantly augmented, suggesting that the MAPK pathway may also inhibit the initiation of PPF. In conclusion, simultaneous activation of three signals through c-mpl, c-kit and CXCR4 can induce the in vitro proliferation and differentiation of CFU-Meg, and SDF-1 is a potentiator of human megakaryocytopoiesis.
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PMID:Simultaneous signalling through c-mpl, c-kit and CXCR4 enhances the proliferation and differentiation of human megakaryocyte progenitors: possible roles of the PI3-K, PKC and MAPK pathways. 1172 31

Cardiotrophin-1 protects cardiac myocytes from ischaemic re-oxygenation (IR) injury. CT-1 activates MEK1/2,p42/44MAPK as well as the phosphatidylinositol (PI) 3-OH kinase (PI3) protein kinase B (PKB/Akt) pathway. In this study we investigate the signalling pathways that mediate the anti-apoptotic cell survival effect of CT-1 in IR. Dominant negative gene based inhibitors of MEK1/2, PI3-kinase and Akt inhibited CT-1 mediated cardioprotection in re-oxygenation as did chemical inhibitors of the PI3-kinase pathway. Hence the PI3-kinase/Akt pathway is required in addition to MEK1/2 to mediate CT-1 cardioprotection in IR.
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PMID:CT-1 mediated cardioprotection against ischaemic re-oxygenation injury is mediated by PI3 kinase, Akt and MEK1/2 pathways. 1174 48


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