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

We demonstrate here a novel role for the I kappa B kinase complex-associated protein (IKAP) in the regulation of activation of the mammalian stress response via the c-Jun N-terminal kinase (JNK)-signaling pathway. We cloned IKAP as a JNK-associating protein using the Ras recruitment yeast two-hybrid system. IKAP efficiently and specifically enhanced JNK activation induced by ectopic expression of MEKK1 and ASK1, upstream activators of JNK. Importantly, IKAP also enhanced JNK activation induced by ultraviolet light irradiation as well as treatments with tumor necrosis factor or epidermal growth factor. The JNK association site in IKAP was mapped to the C-terminal part of IKAP. Interestingly, this region is deleted from IKAP expressed in the autonomous nervous system of the patients affected by familial dysautonomia. Ectopic expression of this C-terminal fragment of IKAP was sufficient to support JNK activation. Taken together, our data demonstrate a novel role for IKAP in the regulation of the JNK-mediated stress signaling. Additionally, our results point to a role of JNK signaling in familial dysautonomia and, thus, further support the involvement of JNK signaling in the development, survival, and degeneration of the sensory and autonomic nervous system.
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PMID:A novel specific role for I kappa B kinase complex-associated protein in cytosolic stress signaling. 1205 26

Nuclear factor kappaB-inducing kinase (NIK) is a member of the MAP kinase kinase kinase family that was first identified as a component of the TNF-R1-induced NF-kappaB activation pathway (TNF, tumor necrosis factor; nuclear factor kappaB, NF-kappaB). Gene knockout study, however, suggests that NIK is dispensable for TNF-R1- but required for lymphotoxin-beta receptor-induced NF-kappaB activation. A NIK kinase inactive mutant is a potent inhibitor of NF-kappaB activation triggered by various stimuli, suggesting that NIK is involved in a broad range of NF-kappaB activation pathways. To unambiguously identify signaling pathways that NIK participates in, we screened antibody arrays for proteins that are associated with NIK. This effort identified ErbB4, one of the EGF/heregulin receptors, and Grb7, an adapter protein associated with ErbB4 (ErbB, epidermal growth factor receptor family protein; EGF, epidermal growth factor; Grb, growth factor receptor bound). Coimmunoprecipitation experiments demonstrated that NIK interacted with Grb7, as well as Grb10 and Grb14, but not Grb2. Domain mapping experiments indicated that the central GM domain of Grb7 was sufficient for its interaction with NIK. Coimmunoprecipitation experiments also indicated that Grb7 and NIK could be simultaneously recruited into signaling complexes of all known EGF/heregulin receptors, including EGFR, ErbB2, ErbB3, and ErbB4. In reporter gene assays, NIK could potentiate Grb7, ErbB2/ErbB4, and EGF-induced NF-kappaB activation. A NIK kinase inactive mutant could block ErbB2/ErbB4 and EGF-induced NF-kappaB activation. Moreover, EGF/heregulin receptors activated NF-kappaB in wild-type, but not NIK-/- embryonic fibroblasts. Our findings suggest that NIK is a component of the EGF/heregulin receptor signaling complexes and involved in NF-kappaB activation triggered by these receptors.
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PMID:NIK is a component of the EGF/heregulin receptor signaling complexes. 1285 71

TR3, also known as NGFI-B or nur77, is an immediate-early response gene and an orphan member of the steroid/thyroid/retinoid receptor superfamily. We previously reported that TR3 expression was induced by apoptotic stimuli and was required for their apoptotic effect in lung cancer cells. Here, we present evidence that TR3 was also induced by epidermal growth factor (EGF) and serum and was required for their mitogenic effect in lung cancer cells. Ectopic expression of TR3 in both H460 and Calu-6 lung cancer cell lines promoted their cell cycle progression and BrdU incorporation, while inhibition of TR3 expression by the small interfering RNA approach suppressed the mitogenic effect of EGF and serum. Analysis of TR3 mutants showed that both TR3 DNA binding and transactivation were required for its mitogenic effect. In contrast, they were dispensable for its apoptotic activity. Furthermore, confocal microscopy analysis demonstrated that TR3 functioned in the nucleus to induce cell proliferation, whereas it acted on mitochondria to induce apoptosis. In examining the signaling that regulates the mitogenic function of TR3, we observed that coexpression of constitutive-active MEKK1 inhibited TR3 transcriptional activity and TR3-induced proliferation. The inhibitory effect of MEKK1 was mediated through activation of Jun N-terminal kinase, which efficiently phosphorylated TR3, resulting in loss of its DNA binding. Together, our results demonstrate that TR3 is capable of inducing both proliferation and apoptosis in the same cells depending on the stimuli and its cellular localization.
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PMID:Mitogenic effect of orphan receptor TR3 and its regulation by MEKK1 in lung cancer cells. 1461 8

WNK1 belongs to a unique protein kinase family that lacks the catalytic lysine in its normal position. Mutations in human WNK1 and WNK4 have been implicated in causing a familial form of hypertension. Here we report that overexpression of WNK1 led to increased activity of cotransfected ERK5 in HEK293 cells. ERK5 activation was blocked by the MEK5 inhibitor U0126 and expression of a dominant negative MEK5 mutant. Expression of dominant negative mutants of MEKK2 and MEKK3 also blocked activation of ERK5 by WNK1. Moreover, both MEKK2 and MEKK3 coimmunoprecipitated with endogenous WNK1 from cell lysates. WNK1 phosphorylated both MEKK2 and -3 in vitro, and MEKK3 was activated by WNK1 in 293 cells. Finally, ERK5 activation by epidermal growth factor was attenuated by suppression of WNK1 expression using small interfering RNA. Taken together, these results place WNK1 in the ERK5 MAP kinase pathway upstream of MEKK2/3.
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PMID:WNK1 activates ERK5 by an MEKK2/3-dependent mechanism. 1468 Dec 16

Previously, no member of the mixed-lineage kinase (MLK) protein family was known to function as an oncogene. Here, we demonstrate that MLK-like mitogen-activated protein triple kinase (MLTK)-alpha, a member of the MLK family, induced neoplastic cell transformation and tumorigenesis in athymic nude mice. Introduction of small interference RNA (siRNA)-MLTK-alpha into MLTK-alpha-overexpressing cells dramatically suppressed cell transformation. Nuclear accumulation of the pHisG-MLTK-alpha fusion protein was observed after epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate treatment. Phosphorylation of downstream mitogen-activated protein kinase-targeted transcription factors including c-Myc, Elk-1, c-Jun, and activating transcription factor (ATF) 2 was also differentially enhanced in MLTK-alpha-overexpressing cells exposed to epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate stimulation compared with cells expressing mock vector or siRNA-MLTK-alpha. Very importantly, MLTK-alpha-overexpressing cells formed fibrosarcomas when injected s.c. into athymic nude mice, whereas almost no tumor formation was observed in mice that received injections of mock or siRNA-MLTK-alpha stably transfected cells. These results are the first to indicate that MLTK-alpha plays a key role in neoplastic cell transformation and cancer development.
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PMID:A novel role for mixed-lineage kinase-like mitogen-activated protein triple kinase alpha in neoplastic cell transformation and tumor development. 1517 94

Mitogen-activated protein kinase (MAPK) cascades are central components of the intracellular signaling networks used by eukaryotic cells to respond to a wide spectrum of extracellular stimuli. An MAPK is activated by an MAPK kinase, which in turn is activated by an MAPK kinase kinase (MAP3K). However, little is known about the molecular aspects of the regulation and activation of large numbers of MAP3Ks that are crucial in relaying upstream receptor-mediated signals through the MAPK cascades to induce various physiological responses. In this study, we identified a novel MEKK2-interacting protein, Mip1, that regulates MEKK2 dimerization and activation by forming a complex with inactive and nonphosphorylated MEKK2. In particular, Mip1 prevented MEKK2 activation by blocking MEKK2 dimer formation, which in turn blocked JNKK2, c-Jun N-terminal kinase 1 (JNK1), extracellular signal-regulated kinase 5, and AP-1 reporter gene activation by MEKK2. Furthermore, we found that the endogenous Mip1-MEKK2 complex was dissociated transiently following epidermal growth factor stimulation. In contrast, the knockdown of Mip1 expression by siRNA augmented the MEKK2-mediated JNK and AP-1 reporter activation. Together, our data suggest a novel model for MEKK2 regulation and activation.
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PMID:Mip1, an MEKK2-interacting protein, controls MEKK2 dimerization and activation. 1598 11

Aberrant epidermal growth factor receptor (EGFR, ErbB1) signaling is implicated in cell transformation, motility, and invasion in a variety of cell types, and EGFR is the target of several anticancer drugs. However, the kinetics of EGFR signaling and the individual contributions of site-specific phosphorylation events remain largely unknown. A peptide-based, multiplex immunoassay approach was developed to simultaneously measure both total and phosphorylated protein in a single sample. The approach involves the proteolytic digestion of proteins prior to the isolation and quantitation of site-specific phosphorylation events within an individual protein. Quantitation of phosphorylated and total proteins, in picomolar to nanomolar concentrations, were interpolated from standard curves generated with synthetic peptides that correspond to the peptide targets used in the immunoassays. In this study, a bead-based, nine-plex immunoassay measuring total and phosphorylated protein was constructed to measure temporal, site-specific phosphorylation of key members of the EGFR pathway (ErbB1 receptor, MEK1, MEK2, ERK1, and ERK2) in A431 cells stimulated with epidermal growth factor. The effect of MEK inhibition on this pathway was determined using a known MEK kinase inhibitor, SL327. The results reported herein are the first quantitative measurements of site-specific phosphorylation events and total proteins in a single sample, at the same time representing a new paradigm for standardized protein and phosphorylation analysis using multiplexed, peptide-based, sandwich immunoassays.
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PMID:Quantitative measurement of epidermal growth factor receptor-mitogen-activated protein kinase signal transduction using a nine-plex, peptide-based immunoassay. 1827 35

Tumor progression locus-2 (Tpl-2) kinase is a member of the mitogen-activated protein kinase kinase kinase family that has been implicated in cellular transformation. The enhanced expression of this protein has been shown to activate both the mitogen-activated protein kinase and c-Jun N-terminal kinase pathways. However, the molecular mechanisms responsible for the oncogenic potential of Tpl-2 are still largely unknown. Here, we showed that Tpl-2 interacted with p53 both in vitro and ex vivo. The overexpression of Tpl-2 inhibited the epidermal growth factor (EGF)-induced p53 phosphorylation (Ser15) through upregulating the activity of protein phosphatase 2A, which interacted with p53 stimulated by EGF. Also, the EGF-induced p53 activity was suppressed in the Tpl-2 wild-type (WT)-transfected HEK 293 cells, but had no effect in the Tpl-2-mutant (S413A)-transfected cells. Furthermore, introduction of small interfering RNA-Tpl-2 into HEK 293 cells resulted in decreased cell viability compared with only adenovirus-p53-infected cells. In addition, the Tpl-2 WT, but not Tpl-2 mutant (S413A), showed increased EGF-induced c-fos promoter activity, followed by activator protein 1 (AP-1) transactivation activity, which was associated with the cell transformation prompted by the H-Ras-Tpl-2-AP-1 signaling axis. These results indicated that the Ser413 of Tpl-2 plays an important role in EGF-induced carcinogenesis as well as inactivation of the p53.
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PMID:Tpl-2 kinase downregulates the activity of p53 and enhances signaling pathways leading to activation of activator protein 1 induced by EGF. 1922 Oct 2

We investigated the physiological role of endogenous MAPK-activating death domain-containing protein (MADD), a splice variant of the IG20 gene, that can interact with TNFR1 in tumor necrosis factor-alpha (TNFalpha)-induced activation of NF-kappaB, MAPK, ERK1/2, JNK, and p38. Using exon-specific short hairpin RNAs expressing lentiviruses, we knocked down the expression of all IG20 splice variants or MADD, which is overexpressed in cancer cells. Abrogation of MADD expression rendered cells highly susceptible to TNFalpha-induced apoptosis in the absence of cycloheximide. It also resulted in a dramatic loss in TNFalpha-induced activation of MAPK without any apparent effect on NF-kappaB activation. This observation was substantiated by an accompanying loss in the activation of p90RSK, a key downstream target of MAPK, whereas the NF-kappaB-regulated interleukin 6 levels remained unaffected. Endogenous MADD knockdown, however, did not affect epidermal growth factor-induced MAPK activation thereby demonstrating the specific requirement of MADD for TNF receptor-mediated MAPK activation. Re-expression of short hairpin RNA-resistant MADD in the absence of endogenous IG20 expression rescued the cells from TNFalpha-induced apoptosis. The requirement for MADD was highly specific for TNFalpha-induced activation of MAPK but not the related JNK and p38 kinases. Loss of MADD expression resulted in reduced Grb2 and Sos1/2 recruitment to the TNFR1 complex and decreased Ras and MEKK1/2 activation. These results demonstrate the essential role of MADD in protecting cancer cells from TNFalpha-induced apoptosis by specifically activating MAPKs through Grb2 and Sos1/2 recruitment, and its potential as a novel cancer therapeutic target.
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PMID:MADD, a splice variant of IG20, is indispensable for MAPK activation and protection against apoptosis upon tumor necrosis factor-alpha treatment. 1928 68

Extracellular signal-regulated kinase 5 (ERK5) is also known as big MAPK (BMK1) or MAPK7. ERK5 is 115 kDa in mass and therefore larger than the other MAPKs such as ERK1/2, JNK, and p38. Like other MAPKs, ERK5 is ubiquitously expressed in mammalian cells and is part of a three kinase cascade involving a MAPK kinase (MEK5) and MAPK kinase kinase (primarily MEKK2 and MEKK3). ERK5 is important for proliferative responses to growth factors like epidermal growth factor and stress responses such as hyperosmolarity. Upon stimulation, ERK5 rapidly translocates to the nucleus for the control of transcription. ERK5 is also critical for maintenance of vascular integrity and endothelial cell survival. In this chapter, we define methods used to measure the activation of ERK5 using different biochemical and cell-based assays.
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PMID:Activity assays for extracellular signal-regulated kinase 5. 2081 78


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