Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.25 (MEKK1)
 1,856 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oncoprotein Ras transforms cells by binding to one or more effector proteins. Effector proteins have been identified by their ability to bind to Ras in the GTP but not GDP form, and by their requirement for the Ras effector domain for binding. The best understood Ras effectors are serine/threonine kinases of the Raf family, but other candidate Ras effectors, including a Ral guanine nucleotide dissociation stimulator and phosphatidylinositol 3-kinase (PI3 kinase) have also been identified. To investigate the mechanism of binding of cRaf-1 to Ras, and to investigate the roles of other candidate Ras effectors in transformation, we have isolated and characterized mutants of activated Ras with decreased binding to cRaf-1 relative to other candidate effectors. Examination of these mutants indicates that surface-exposed residues of Ras outside the minimal effector domain interact differentially with cRaf-1 and other Ras-binding proteins, and that fibroblast transformation correlates with cRaf-1 binding and mitogen-activated protein (MAP) kinase activation. Furthermore, activation of PI3 kinase can occur in the absence of significant MAP kinase activation, suggesting that PI3 kinase activation is a primary effect of Ras.
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PMID:Identification and characterization of mutations in Ha-Ras that selectively decrease binding to cRaf-1. 930 99

Apoptosis of vascular smooth muscle cells (SMCs) has been described in culture and also during remodelling of the artery following injury. However, the mediators that regulate apoptosis in SMCs are unknown. Because neurotrophins, a family of related polypeptide growth factors, including nerve growth factor (NGF) and its cognate receptor TrkA have been shown to be strongly expressed in atherosclerotic lesions, the present study was undertaken to evaluate in vitro, the activity of NGF with regard to apoptosis of confluent cultures of human aortic SMCs. We report here that NGF induced apoptosis of SMCs in a dose-dependent manner. This effect was detected from the concentration of 1 ng/ml and reached a maximum at 100 ng/ml. The concentration that induced a half-maximum effect was 8.8 ng/ml. The pro-apoptotic activity of NGF was time dependent and was significant after 3 h of incubation. The pro-apoptotic activity of NGF was blocked in a dose-dependent manner by K-252a, an inhibitor of TrkA tyrosine phosphorylation, suggesting that a NGF/TrkA signal transduction pathway could activate apoptotic cell death programs in human SMCs. Significantly, NGF-induced apoptosis was inhibited by wortmannin and PD 98059, showing that both PI3 kinase and MEK kinase were involved. At a NGF concentration that strongly induced apoptosis (100 ng/ml), TGFbeta1 which has been identified several times as a protective factor, dose dependently inhibited the pro-apoptotic effect of NGF. The IC50 value was 1.5 ng/ml. These results indicate that, at least in vitro, TGFbeta1 can inhibit the pro-apoptotic activity of NGF for SMCs therefore suggesting that TGFbeta1 has the capacity to diminish the deleterious consequences of an excitotoxic or ischemic injury that might occur during atherogenesis or following angioplasty.
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PMID:NGF exhibits a pro-apoptotic activity for human vascular smooth muscle cells that is inhibited by TGFbeta1. 937 61

Neurotrophins promote multiple actions on neuronal cells including cell survival and differentiation. The best-studied neurotrophin, nerve growth factor (NGF), is a major survival factor in sympathetic and sensory neurons and promotes differentiation in a well-studied model system, PC12 cells. To mediate these actions, NGF binds to the TrkA receptor to trigger intracellular signaling cascades. Two kinases whose activities mediate these processes include the mitogen-activated protein (MAP) kinase (or extracellular signal-regulated kinase [ERK]) and phosphoinositide 3-kinase (PI3-K). To examine potential interactions between the ERK and PI3-K pathways, we studied the requirement of PI3-K for NGF activation of the ERK signaling cascade in dorsal root ganglion cells and PC12 cells. We show that PI3-K is required for TrkA internalization and participates in NGF signaling to ERKs via distinct actions on the small G proteins Ras and Rap1. In PC12 cells, NGF activates Ras and Rap1 to elicit the rapid and sustained activation of ERKs respectively. We show here that Rap1 activation requires both TrkA internalization and PI3-K, whereas Ras activation requires neither TrkA internalization nor PI3-K. Both inhibitors of PI3-K and inhibitors of endocytosis prevent GTP loading of Rap1 and block sustained ERK activation by NGF. PI3-K and endocytosis may also regulate ERK signaling at a second site downstream of Ras, since both rapid ERK activation and the Ras-dependent activation of the MAP kinase kinase kinase B-Raf are blocked by inhibition of either PI3-K or endocytosis. The results of this study suggest that PI3-K may be required for the signals initiated by TrkA internalization and demonstrate that specific endocytic events may distinguish ERK signaling via Rap1 and Ras.
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PMID:Role of phosphoinositide 3-kinase and endocytosis in nerve growth factor-induced extracellular signal-regulated kinase activation via Ras and Rap1. 1102 77

The Akt family of serine/threonine-directed kinases promotes cellular survival in part by phosphorylating and inhibiting death-inducing proteins. Here we describe a novel functional interaction between Akt and apoptosis signal-regulating kinase 1 (ASK1), a mitogen-activated protein kinase kinase kinase. Akt decreased ASK1 kinase activity stimulated by both oxidative stress and overexpression in 293 cells by phosphorylating a consensus Akt site at serine 83 of ASK1. Activation of the phosphoinositide 3-kinase (PI3-K)/Akt pathway also inhibited the serum deprivation-induced activity of endogenous ASK1 in L929 cells. An association between Akt and ASK1 was detected in cells by coimmunoprecipitation. Phosphorylation by Akt inhibited ASK1-mediated c-Jun N-terminal kinase and activating transcription factor 2 activities in intact cells. Finally, activation of the PI3-K/Akt pathway reduced apoptosis induced by ASK1 in a manner dependent on phosphorylation of serine 83 of ASK1. These results provide the first direct link between Akt and the family of stress-activated kinases.
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PMID:Akt phosphorylates and negatively regulates apoptosis signal-regulating kinase 1. 1115 76

Proapoptotic nuclear receptor family member Nur77 translocates from the nucleus to the mitochondria, where it interacts with Bcl-2 to trigger apoptosis. Nur77 translocation is induced by certain apoptotic stimuli, including the synthetic retinoid-related 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN)/CD437 class. In this study, we investigated the molecular mechanism by which AHPN/CD437 analog (E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces Nur77 nuclear export. Our results demonstrate that 3-Cl-AHPC effectively activated Jun N-terminal kinase (JNK), which phosphorylates Nur77. Inhibition of JNK activation by a JNK inhibitor suppressed 3-Cl-AHPC-induced Nur77 nuclear export and apoptosis. In addition, several JNK upstream activators, including the phorbol ester TPA, anisomycin and MAPK kinase kinase-1 (MEKK1), phosphorylated Nur77 and induced its nuclear export. However, Nur77 phosphorylation by JNK, although essential, was not sufficient for inducing Nur77 nuclear export. Induction of Nur77 nuclear export by MEKK1 required a prolonged MEKK1 activation and was attenuated by Akt activation. Expression of constitutively active Akt prevented MEKK1-induced Nur77 nuclear export. Conversely, transfection of dominant-negative Akt or treatment with a phosphatidylinositol 3-kinase (PI3-K) inhibitor accelerated MEKK1-induced Nur77 nuclear export. Furthermore, mutation of an Akt phosphorylation residue Ser351 in Nur77 abolished the effect of Akt or the PI3-K inhibitor. Together, our results demonstrate that both activation of JNK and inhibition of Akt play a role in translocation of Nur77 from the nucleus to the cytoplasm.
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PMID:Regulation of Nur77 nuclear export by c-Jun N-terminal kinase and Akt. 1643 70

Calreticulin is an endoplasmic reticulum protein important in cardiovascular development. Deletion of the calreticulin gene leads to defects in the heart and the formation of omphaloceal. These defects could both be due to changes in the extracellular matrix composition. Matrix metalloproteinases (MMP)-2 and MMP-9 are two of the MMPs which are essential for cardiovascular remodelling and development. Here, we tested the hypothesis that the defects observed in the heart and body wall of the calreticulin null embryos are due to alterations in MMP-2 and MMP-9 activity. Our results demonstrate that there is a significant decrease in the MMP-9 and increase in the MMP-2 activity and expression in the calreticulin deficient cells. We also showed that there is a significant increase in the expression level of membrane type-1 matrix metalloproteinase (MT1-MMP). In contrast, there was no change in the tissue inhibitor of matrix metalloproteinase (TIMP)-1 or -2 in the calreticulin deficient cells as compared to the wild type cells. Interestingly, the inhibition of the MEK kinase pathway using PD98059 attenuated the decrease in the MMP-9 mRNA with no effect on the MMP-2 mRNA level in the calreticulin deficient cells. Furthermore, PI3 kinase inhibitor decreased the expression of both the MMP-2 and MMP-9. This study is the first report on the role of calreticulin in regulating MMP activity.
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PMID:Differential expression and activity of matrix metalloproteinase-2 and -9 in the calreticulin deficient cells. 1741 77

Resveratrol (trans-3,5,4'-trihydroxystilbene), a compound found largely in the skins of red grapes and wines, possesses anti-cancer and anti-angiogenic properties and protects the cardiovascular system. However, the molecular mechanisms by which resveratrol inhibits angiogenesis are currently subjects of intense investigation. The purpose of this study was to examine whether FOXO transcription factors mediate anti-angiogenic effects of resveratrol, and whether vascular endothelial growth factor (VEGF) neutralizing antibody can enhance these effects of resveratrol. Inhibition of PI3 kinase (PI3K)/AKT and MEK/ERK pathways synergistically inhibited migration and capillary tube formation of Human Umbilical Vein Endothelial Cells (HUVECs) and further enhanced the anti-angiogenic effects of resveratrol. Inhibitors of AKT and MEK kinase synergistically inhibited cytoplasmic FOXO3a phosphorylation, which was accompanied by its nuclear translocation in HUVECs. Interestingly, inhibition of PI3K/AKT and MEK/ERK pathways synergistically induced FOXO transcriptional activity and inhibited cell migration and capillary tube formation. Antiangiogenic effects of resveratrol were enhanced by inhibitors of AKT and MEK. Phosphorylation-deficient mutants of FOXOs induced FOXO transcriptional activity, inhibited HUVEC cell migration, and capillary tube formation, and also enhanced antiangiogenic effects of resveratrol. Finally, VEGF neutralizing antibody enhanced the anti-proliferative and anti-angiogenic effects of resveratrol. In conclusion, regulation of FOXO transcription factors by resveratrol may play an important role in angiogenesis which is critical for cancer, diabetic retinopathy, rheumatoid arthritis, psoriasis, and cardiovascular disorders.
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PMID:FOXO transcription factors and VEGF neutralizing antibody enhance antiangiogenic effects of resveratrol. 2001 70

Using a multidimensional genomic data set on glioblastoma from The Cancer Genome Atlas, we identified hsa-miR-26a as a cooperating component of a frequently occurring amplicon that also contains CDK4 and CENTG1, two oncogenes that regulate the RB1 and PI3 kinase/AKT pathways, respectively. By integrating DNA copy number, mRNA, microRNA, and DNA methylation data, we identified functionally relevant targets of miR-26a in glioblastoma, including PTEN, RB1, and MAP3K2/MEKK2. We demonstrate that miR-26a alone can transform cells and it promotes glioblastoma cell growth in vitro and in the mouse brain by decreasing PTEN, RB1, and MAP3K2/MEKK2 protein expression, thereby increasing AKT activation, promoting proliferation, and decreasing c-JUN N-terminal kinase-dependent apoptosis. Overexpression of miR-26a in PTEN-competent and PTEN-deficient glioblastoma cells promoted tumor growth in vivo, and it further increased growth in cells overexpressing CDK4 or CENTG1. Importantly, glioblastoma patients harboring this amplification displayed markedly decreased survival. Thus, hsa-miR-26a, CDK4, and CENTG1 comprise a functionally integrated oncomir/oncogene DNA cluster that promotes aggressiveness in human cancers by cooperatively targeting the RB1, PI3K/AKT, and JNK pathways.
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PMID:Integrative genome analysis reveals an oncomir/oncogene cluster regulating glioblastoma survivorship. 2008 Jun 66