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)

Exposure of neutrophils to a variety of agonists including soluble chemoattractant peptides and cytokines results in degranulation and activation of the oxidative burst (effector functions) that are required for bacterial killing. At present, the signaling pathways regulating these important functions are incompletely characterized. Mitogen-activated protein (MAP) kinases (MAPK) as well as members of a family of "renaturable kinases" are rapidly activated in neutrophils in response to diverse physiological agonists, suggesting that they may regulate cell activation. Antagonists of phosphatidyl inositol-3-(OH) kinase (PI3-kinase) such as wortmannin (Wtmn) inhibit these effector responses as well as certain of the above-mentioned kinases, leading to the suggestion that these enzymes lie downstream of PI3-kinase in the pathway regulating the oxidative burst and granule secretion. However, an apparent discrepancy exists in that, while virtually obliterating activity of PI3-kinase and the oxidase at low concentrations (ID50 < 20 nM), Wtmn has only variable inhibitory effects on MAPK even at substantially higher concentrations (75-100 nM). This raises the possibility that the inhibitory effects of Wtmn are mediated via other enzyme systems. The purpose of the current study was therefore to compare the effects of Wtmn on PI3-kinase activity and on the chemoattractant-activated kinases, and to determine the potential relationship of these pathways to microbicidal responses. In human neutrophils, both the oxidative burst and granule secretion induced by fMLP were inhibited by Wtmn but at markedly different concentrations: the oxidative burst was inhibited with an ID50 of < 5 nM while granule secretion was only partially inhibited at concentrations exceeding 75 nM. Activation of both MEK-1 and MAPK in response to fMLP was only partially inhibited by high doses of Wtmn (ID50 of > 100 nM and approximately 75 nM, respectively). In contrast, Wtmn potently inhibited fMLP-induced activation of the 63 and 69 kDa renaturable kinases (ID50 approximately 5-10 nM). We speculate that the renaturable kinases may be involved in the regulation of the oxidative burst, whereas the MAPK pathway may play a role in other neutrophil functions such as granule secretion.
...
PMID:Inhibition of neutrophil oxidative burst and granule secretion by wortmannin: potential role of MAP kinase and renaturable kinases. 920 30

The alphavbeta3 integrin plays a fundamental role during the angiogenesis process by inhibiting endothelial cell apoptosis. However, the mechanism of inhibition is unknown. In this report, we show that integrin-mediated cell survival involves regulation of nuclear factor-kappa B (NF-kappaB) activity. Different extracellular matrix molecules were able to protect rat aorta- derived endothelial cells from apoptosis induced by serum withdrawal. Osteopontin and beta3 integrin ligation rapidly increased NF-kappaB activity as measured by gel shift and reporter activity. The p65 and p50 subunits were present in the shifted complex. In contrast, collagen type I (a beta1-integrin ligand) did not induce NF-kappaB activity. The alphavbeta3 integrin was most important for osteopontin-mediated NF-kappaB induction and survival, since adding a neutralizing anti-beta3 integrin antibody blocked NF-kappaB activity and induced endothelial cell death when cells were plated on osteopontin. NF-kappaB was required for osteopontin- and vitronectin-induced survival since inhibition of NF-kappaB activity with nonphosphorylatable IkappaB completely blocked the protective effect of osteopontin and vitronectin. In contrast, NF-kappaB was not required for fibronectin, laminin, and collagen type I-induced survival. Activation of NF-kappaB by osteopontin depended on the small GTP-binding protein Ras and the tyrosine kinase Src, since NF-kappaB reporter activity was inhibited by Ras and Src dominant-negative mutants. In contrast, inhibition of MEK and PI3-kinase did not affect osteopontin-induced NF-kappaB activation. These studies identify NF-kappaB as an important signaling molecule in alphavbeta3 integrin-mediated endothelial cell survival.
...
PMID:NF-kappaB mediates alphavbeta3 integrin-induced endothelial cell survival. 958 25

Members of the erbB family of receptor tyrosine kinases are commonly overexpressed in human breast cancer. However, the relative contribution of particular signalling pathways activated downstream of these receptors to the mitogenic response of transformed breast epithelial cells remains poorly characterized. Administration of heregulin-beta2 (HRG), a ligand for erbB3 and erbB4, to growth arrested T-47D human breast cancer cells leads to activation of both the PI3-kinase and MAP kinase signalling pathways and potent stimulation of cell cycle progression. Specific inhibitors were used to assess the role of these pathways in HRG-induced mitogenesis and to identify underlying mechanisms in terms of regulation of gene expression. Treatment with the MEK inhibitor PD98059 led to a complete block of HRG-induced entry into S-phase, whilst administration of the PI3-kinase inhibitor wortmannin resulted in only modest inhibition. In addition, administration of PD98059 8 h after HRG was equipotent with simultaneous administration in inhibiting entry into S-phase. However, delaying addition for 14-16 h after HRG, when the cells were entering S-phase, was without effect. HRG stimulation led to sequential induction of c-myc, cyclin D1, cyclin E and cyclin A gene expression and hyperphosphorylation of the retinoblastoma protein pRB. p21 (WAF1/CIP1/SDI1) gene expression was rapidly induced by HRG, but significant changes in p27 (KIP1) protein levels were not detected. Preincubation with PD98059 blocked the HRG-dependent induction of cyclin D1 mRNA, p21 and c-Myc protein and pRB phosphorylation. These findings demonstrate that MEK activation is critical to HRG-induced S-phase entry in these cells whilst PI3-kinase plays a minor role. Moreover, these data are compatible with HRG-induced activation of MEK being critical for a mid-G1 transition point and implicate c-myc and cyclin D1 as key targets of the MAP kinase pathway involved in this response.
...
PMID:Inhibition of the MAP kinase cascade blocks heregulin-induced cell cycle progression in T-47D human breast cancer cells. 965 48

HC11 mouse mammary epithelial cells are capable of differentiating in vitro. By growing cells in EGF-containing medium, and upon confluence withdrawing EGF, these cells become competent at responding to lactogenic hormone treatment and expressing milk proteins. We found that during proliferation and at confluence STAT5A and STAT5B proteins were expressed at equal levels or with STAT5B being predominant. In competent cells, expression levels of STAT5A and STAT5B increased markedly with STAT5A now being the predominant form, an expression pattern resembling the expression patterns of STAT5 proteins seen during mammary gland differentiation in vivo. This suggests that EGF has a suppressive effect on STAT5 expression, in particular, STAT5A, which we conclude to be mediated through ras/raf/MEK/MAPK pathway and to a lesser extent through a PI3-kinase-mediated pathway. Furthermore, we also found that EGF regulated a nuclear phosphatase capable of dephosphorylating tyrosine-phosphorylated STAT5. Our data show that HC11 cells have retained the expression patterns of STAT5 proteins seen in vivo. This makes HC11 cells useful for studying molecular mechanisms regulating expression of STAT factors and their participation in differentiation processes of mammary gland.
...
PMID:EGF modulates expression of STAT5 in mammary epithelial cells. 974 94

In our present studies utilizing a well characterized proximal tubule cell line, LLCPKcl4, we determined that all four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) stimulated [3H]thymidine incorporation, with 14,15-EET being the most potent. In contrast, no mitogenic effects were seen with arachidonic acid, other cP450 arachidonate metabolites (12R-hydroxyeicosatetraenoic acid (12R-HETE), 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), or 20-HETE), or lipoxygenase metabolites (5S-HETE, leukotriene B4, or lipoxin A4). We found that their metabolically more stable sulfonimide (SI) analogs (11,12-EET-SI and 14,15-EET-SI) were also potent mitogens. In addition 14,15-EET-SI also increased cell proliferation as well as expression of both c-fos and egr-1 mRNA. The protein kinase C and A inhibitors, H-7 and H-8, or the cyclooxygenase inhibitor, indomethacin, had no effect upon 14, 15-EET-induced [3H]thymidine incorporation, but the selective tyrosine kinase inhibitor, genistein, significantly inhibited it. Immunoprecipitation and immunoblotting demonstrated increased tyrosine phosphorylation of PI3-kinase and epidermal growth factor receptor (EGFR) within 1 min of EET administration. EETs also stimulated association of PI3-kinase with EGFR. PI3-kinase inhibitors, wortmannin and LY 294002, markedly inhibited 14, 15-EET-SI-stimulated [3H]thymidine incorporation. In addition, 14, 15-EET-SI administration stimulated tyrosine phosphorylation of src homologous and collagen-like protein (SHC) and association of SHC with both growth factor receptor-binding protein (GRB2) and EGFR. Mitogen-activated protein kinase was also activated within 5 min. Pretreatment of the cells with the mitogen-activated protein kinase kinase inhibitor, PD98059, inhibited the 14,15-EET-SI-stimulated [3H]thymidine incorporation. Moreover, immunoblotting indicated that 14,15-EET stimulated tyrosine phosphorylation of the specific pp60(c-src) substrate p120 and c-Src association with EGFR. 14, 15-EET increased src kinase activity within 1 min. Our data indicate that EETs are potent mitogens for renal epithelial cells, and the mitogenic effects of the EETs are mediated, at least in part, by the activation of Src kinase and initiation of a tyrosine kinase phosphorylation cascade.
...
PMID:Epoxyeicosatrienoic acids and their sulfonimide derivatives stimulate tyrosine phosphorylation and induce mitogenesis in renal epithelial cells. 978 38

To examine the molecular mechanism of insulin receptor trafficking, we investigated the intracellular signaling molecules that regulate this process in Rat1 fibroblasts overexpressing insulin receptors. Cellular localization of insulin receptors was assessed by confocal laser microscopy with indirect immunofluorescence staining. Insulin receptors were visualized diffusely in the basal state. Insulin treatment induced the change of insulin receptor localization to perinuclear compartment. This insulin-induced insulin receptor trafficking was not affected by treatment of the cells with PI3-kinase inhibitor (wortmannin), whereas treatment with MEK [mitogen-activated protein (MAP) kinase-Erk kinase] inhibitor (PD98059) partly inhibited the process in a dose-dependent manner. Interestingly, treatment with both wortmannin and PD98059 almost completely inhibited insulin receptor trafficking. The functional importance of PI3-kinase and MAP kinase in the trafficking process was directly assessed by using single cell microinjection analysis. Microinjection of p85-SH2 and/or catalytically inactive MAP kinase ([K71A]Erk1) GST fusion protein gave the same results as treatment with wortmannin and PD98059. Furthermore, to determine the crucial step for the requirement of PI3-kinase and MAP kinase pathways, the effect of wortmannin and PD98059 on insulin receptor endocytosis was studied. Insulin internalization from the plasma membrane and subsequent insulin degradation were not affected by treatment with wortmannin and PD98059. In contrast, insulin receptor down-regulation from the cell surface and insulin receptor degradation, after prolonged incubation with insulin, were markedly impaired by the treatment. These results suggest that PI3-kinase and MAP kinase pathways synergistically regulate insulin receptor trafficking at a step subsequent to the receptor internalization.
...
PMID:Synergistic role of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase cascade in the regulation of insulin receptor trafficking. 1043 44

Replacement of external NaCl with LiCl induced cytoplasmic alkalinization in CCL-39 cells and rat L6 myoblasts expressing the endogenous Na+/H+ exchanger isoform NHE1. This Li+-induced alkalinization is due to activation of the Na+/H+ exchanger because it was completely inhibited by 100 microM ethylisopropylamiloride (apparent Kd=1 microM) and because it did not occur in exchanger-deficient PS120 cells. The effect of Li+ was not mimicked by Na+, K+, Cs+ and choline+. Li+ caused cytoplasmic alkalinization in PS120 cells expressing NHE1 or NHE2, but not NHE3, when Li+ was added to cells at a concentration high enough to saturate their external transport sites as predicted from Li+ affinities. Li+ did not induce phosphatidylinositol (PI) turnover or intracellular Ca2+ mobilization. Li+-induced alkalinization was not affected by protein kinase C down-regulation, loss of glycogen synthase kinase 3beta caused by antisense oligonucleotide treatment, or pretreatment with calphostin C, pertussis toxin, MEK inhibitor PD98059 and PI3-kinase inhibitor LY294002. However, it was markedly suppressed by the tyrosine kinase inhibitor genistein (10 microM). Thus, externally added Li+ activates NHE1 and NHE2 via a mechanism possibly involving a tyrosine kinase, causing an increase in cytoplasmic pH that could potentially affect various cell functions.
...
PMID:Lithium activates mammalian Na+/H+ exchangers: isoform specificity and inhibition by genistein. 1067 42

Recent studies suggest that hepatocyte growth factor (HGF) functions as a neurotrophic factor in the central nervous system. In this study, we investigated the neuroprotective effect of HGF and its mechanism of action. We used cultured cerebellar granule neurons that underwent apoptosis when the culture medium was changed from that containing serum with 25 mM K(+) to serum-free medium containing 5 mM K(+), and HGF prevented apoptotic cell death. HGF stimulated both mitogen-activated protein (MAP) kinase and phosphatidylinositol-3 (PI3)-kinase activity in cerebellar granule neurons. Two specific inhibitors of PI3-kinase, wortmannin and LY294002, efficiently blocked this neuroprotective effect of HGF. In contrast, PD98059, a selective inhibitor of MAP kinase kinase (MEK), did not affect the anti-apoptotic effect of HGF. The downstream signal of PI3-kinase in this protection was further investigated. HGF-induced phosphorylation of Akt and pretreatment of the cells with wortmannin completely impaired Akt activation. These results suggest that HGF prevents apoptosis in cerebellar granule neurons via the PI3-kinase/Akt pathway.
...
PMID:Hepatocyte growth factor protects cultured rat cerebellar granule neurons from apoptosis via the phosphatidylinositol-3 kinase/Akt pathway. 1067 87

Neuregulin can trigger morphogenetic signals in cells both in vivo and in culture through the activation of receptors from the ErbB family. We have ectopically expressed various ErbB-receptors in 32D myeloid cells lacking endogenous ErbB-proteins, and in CHO cells, which express only ErbB-2. We show here that activation of ErbB-3/ErbB-2 heterodimeric receptors triggers PI3-kinase-dependent lamellipodia formation and spreading, while individual ErbB-receptor homodimers as well as ErbB-3/ErbB-1 heterodimers are much less effective. CHO cells expressing ErB-3/ErbB-2 together with N-cadherin, an adhesion receptor, form epithelioid colonies. Neuregulin activates cell motility leading to transition of these colonies into ring-shaped multicellular arrays, similar to those induced by neuregulin in epithelial cells of different types (Chausovsky et al., 1998). This process requires both PI3-kinase and MAP kinase kinase activity and depends on coordinated changes in the actin- and microtubule-based cytoskeleton. Transactivation of ErbB-2 is not sufficient for the activation of cell motility and ring formation, and the C-terminal domain of ErbB-3 bearing the docking sites for the p85 subunit of PI3-kinase is essential for these morphogenetic effects. Thus, ErbB-3 in conjunction with ErbB-2 mediates, via its C-terminal domain, cytoskeletal and adhesion alterations which activate cell spreading and motility, leading to the formation of complex structures such as multicellular rings. Oncogene (2000) 19, 878 - 888.
...
PMID:Molecular requirements for the effect of neuregulin on cell spreading, motility and colony organization. 1070 96

In an experimental model of in vivo hyperthermia, we investigated the involvement of a number of signalling events in rat liver. We report that in vivo heat shock causes a powerful activation of c-Jun N-terminal kinase and p38 kinase but does not trigger poly(ADP-ribose) polymerase cleavage, a signature event of apoptosis. Among the upstream regulators of the kinases, we show that stress-activated protein kinase/extracellular signal-regulated kinase/nitrogen-activated protein kinase kinase 4 SEK1/MKK4 is not involved whereas MKK3 and/or MKK6 are activated. PAK activity displays a transient rise, whereas GCK does not change. PI3-kinase activity increases in anti-phosphotyrosine immunoprecipitates, suggesting a tyrosine kinase-dependent induction mechanism, and the co-immunoprecipitation of PI3-kinase with p60 Src kinase supports the involvement of this latter. GSK3, which may act downstream to PI3-kinase through AKT, undergoes hyperphosphorylation, thus playing a possible role in the protection from apoptosis and in the modulation of heat-shock transcription factor activity.
...
PMID:Cellular signalling after in vivo heat shock in the liver. 1077 75


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

---