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)

Lipopolysaccharide (LPS)-activated macrophages are pivotal in innate immunity. With LPS treatment, extracellular signals are transduced into macrophages via Toll-like receptor 4 and induce inflammatory mediator production by activating signaling pathways, including the nuclear factor-kappaB (NF-kappaB) pathway and the mitogen-activated protein kinase (MAPK) pathway. However, the mechanisms by which the intracellular free Ca2+ concentration ([Ca2+]i) increases and protein kinase C (PKC) is activated remain unclear. Therefore, we investigated the signaling pathway for Ca2+- and PKC-dependent NF-kappaB activation, inducible nitric-oxide synthase expression, and tumor necrosis factor-alpha (TNF-alpha) production in LPS-stimulated rat peritoneal macrophages. The results demonstrated that the LPS-induced transient [Ca2+]i increase is due to Ca2+ release and influx. Extracellular and intracellular Ca2+ chelators inhibited phosphorylation of PKCalpha and PKCbeta. A PKCbeta-specific and a general PKC inhibitor blunted phosphorylation of serine in mitogen-activated/extracellular signal-regulated kinase kinase kinase (MEKK) 1. Moreover, a MEKK inhibitor reduced activation of inhibitorykappaB kinase and NF-kappaB. Upstream of the [Ca2+]i increase, a protein-tyrosine kinase inhibitor reduced phosphorylation of phospholipase C (PLC) gamma. Furthermore, a PLC inhibitor eliminated the transient [Ca2+]i increase and decreased the amount of activated PKC. Therefore, these results revealed the following roles of Ca2+ and PKC in the signaling pathway for NF-kappaB activation in LPS-stimulated macrophages. After LPS treatment, protein-tyrosine kinase mediates PLCgamma1/2 phosphorylation, which is followed by a [Ca2+]i increase. Several PKCs are activated, and PKCbeta regulates phosphorylation of serine in MEKK1. Moreover, MEKKs regulate inhibitory kappaB kinase activation. Sequentially, NF-kappaB is activated, and inducible nitric-oxide synthase and tumor necrosis factor-alpha production is promoted.
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PMID:Ca2+- and protein kinase C-dependent signaling pathway for nuclear factor-kappaB activation, inducible nitric-oxide synthase expression, and tumor necrosis factor-alpha production in lipopolysaccharide-stimulated rat peritoneal macrophages. 1692 14

In a previous study, we showed that the Ca2+/calmodulin-dependent protein kinase IIdelta (CaMKIIdelta) activates the mouse Per1 (mPer1) promoter through a 5'-GAGGGG-3' motif near exon1B. Here we use luciferase reporter gene assays to document additive activation of the mPer1 promoter by CaMKIIdelta and mitogen-activated protein kinase (MAPK) pathways. Transfection of constitutively active MEKK markedly increased mPer1 promoter activity in NB2A cells. Experiments using MAPK inhibitors and dominant-negative c-Jun NH2-terminal kinase 1 (JNK1) showed that extracellular signal-regulated kinase (ERK) accounts for MEKK-induced mPer1 gene activation. We next defined the ERK-responsive region in the mPer1 promoter. A region from -1735 to -1721 was required for ERK-induced promoter activation. We also identified a CaMKII-responsive element near exon 1B. Although mutation of the CaMKII-responsive element has no effect on the ERK responsiveness, elimination of a GC-rich sequence downstream of the CaMKII-responsive region totally abolished ERK responsiveness. Finally, ERK-induced promoter activation was additively potentiated by co-transfection with active CaMKIIdelta. These results suggest that additive activation by ERK and CaMKII, most likely as a result of photic stimulation in the suprachiasmatic nucleus, plays a critical role in activating the mPer1 gene promoter.
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PMID:MAP kinase additively activates the mouse Per1 gene promoter with CaM kinase II. 1702 Jul 48

IkappaB kinase beta (IKKbeta) subunit of IKK complex is essential for the activation of NF-kappaB in response to various proinflammatory signals. Cys-179 in the activation loop of IKKbeta is known to be the target site for IKK inhibitors such as cyclopentenone prostaglandins, arsenite, and antirheumatic gold compounds. Here we show that a mutant IKKbeta in which Cys-179 is substituted with alanine had decreased activity when it was expressed in HEK-293 cells, and TNF stimulation did not restore the activity. Phosphorylation of activation loop serines (Ser-177 and Ser-181) which is required for IKKbeta activation was reduced in the IKKbeta (C179A) mutant. The activity of IKKbeta (C179A) was partially recovered when its phosphorylation was enforced by coexpression with mitogen-activated protein kinase kinase kinases (MAPKKK) such as NF-kappaB inducing kinase (NIK) and MAPK/extracellular signal-regulated kinase kinase kinase 1(MEKK1) or when the serine residues were replaced with phospho-mimetic glutamate. The IKKbeta (C179A) mutant was normal in dimer formation, while its activity abnormally responded to the change in the concentration of substrate ATP in reaction mixture. Our results suggest that Cys-179 of IKKbeta plays a critical role in enzyme activation by promoting phosphorylation of activation-loop serines and interaction with ATP.
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PMID:Cysteine-179 of IkappaB kinase beta plays a critical role in enzyme activation by promoting phosphorylation of activation loop serines. 1707 71

The DNA damage checkpoint pathway governs how cells regulate cell cycle progression in response to DNA damage. A screen for suppressors of a fission yeast chk1 mutant defective in the checkpoint pathway identified a novel Schizosaccharomyces pombe protein, Msc1. Msc1 contains 3 plant homeodomain (PHD) finger motifs, characteristically defined by a C4HC3 consensus similar to RING finger domains. PHD finger domains in viral proteins and in the cellular protein kinase MEKK1 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1) have been implicated as ubiquitin E3 protein ligases that affect protein stability. The close structural relationship of PHD fingers to RING fingers suggests that other PHD domain-containing proteins might share this activity. We show that each of the three PHD fingers of Msc1 can act as ubiquitin E3 ligases, reporting for the first time that PHD fingers from a nuclear protein exhibit E3 ubiquitin ligase activity. The function of the PHD fingers of Msc1 is needed to rescue the DNA damage sensitivity of a chk1Delta strain. Msc1 co-precipitates Rhp6, the S. pombe homologue of the human ubiquitin-conjugating enzyme Ubc2. Strikingly, deletion of msc1 confers complete suppression of the slow growth phenotype, UV and hydroxyurea sensitivities of an rhp6 deletion strain and restores deficient histone H3 methylation observed in the rhp6Delta mutant. We speculate that the target of the E3 ubiquitin ligase activity of Msc1 is likely to be a chromatin-associated protein.
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PMID:The plant homeodomain fingers of fission yeast Msc1 exhibit E3 ubiquitin ligase activity. 1745 68

Tumor progression locus 2 (TPL-2) kinase is essential for Toll-like receptor 4 activation of the mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) and for upregulation of the inflammatory cytokine tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-stimulated macrophages. LPS activation of ERK requires TPL-2 release from associated NF-kappaB1 p105, which blocks TPL-2 access to its substrate, the ERK kinase MEK. Here we demonstrate that TPL-2 activity is also regulated independently of p105, since LPS stimulation was still needed for TPL-2-dependent activation of ERK in Nfkb1(-/-) macrophages. In wild-type macrophages, LPS induced the rapid phosphorylation of serine (S) 400 in the TPL-2 C-terminal tail. Mutation of this conserved residue to alanine (A) blocked the ability of retrovirally expressed TPL-2 to induce the activation of ERK in LPS-stimulated Nfkb1(-/-) macrophages. TPL-2(S400A) expression also failed to reconstitute LPS activation of ERK and induction of TNF in Map3k8(-/-) macrophages, which lack endogenous TPL-2. Consistently, the S400A mutation was found to block LPS stimulation of TPL-2 MEK kinase activity. Thus, induction of TPL-2 MEK kinase activity by LPS stimulation of macrophages requires TPL-2 phosphorylation on S400, in addition to its release from NF-kappaB1 p105. Oncogenic C-terminal truncations of TPL-2 that remove S400 could promote its transforming potential by eliminating this critical control step.
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PMID:Phosphorylation of TPL-2 on serine 400 is essential for lipopolysaccharide activation of extracellular signal-regulated kinase in macrophages. 1770 78

Estradiol-17beta (E(2)) induces rodent hippocampal neural progenitor cell (NPC) proliferation in vitro, in vivo, and after brain injury. The purpose of the present investigation was to determine whether E(2)-induced proliferation observed in rodent model systems generalized to cells of human neural origin and the signaling pathway by which E(2) promotes mitosis of human NPCs (hNPCs). Results of these analyses indicate that E(2) induced a significant increase in hNPC proliferation in a time- and dose-dependent manner. E(2)-induced hNPC DNA replication was paralleled by elevated cell cycle protein expression and centrosome amplification, which was associated with augmentation of total cell number. To determine whether estrogen receptor (ER) and which ER subtype were required for E(2)-induced hNPC proliferation, ER expression was first determined by real-time RT-PCR, followed by Western blot analysis, and subsequently verified pharmacologically using ERalpha or beta-selective ligands. Results of these analyses indicated that ERbeta expression was predominant relative to ERalpha, which was barely detectable in hNPCs. Activation of ERbeta by the ERbeta-selective ligand, diarylpropionitrile, led to an increase in phosphorylated extracellular signal-regulated kinase, and subsequent centrosome amplification and hNPC proliferation, which were blocked by the MEKK antagonist, UO126, but not its inactive analog, UO124. These findings, for the first time, demonstrate the molecular cascade and related cell biology events involved in E(2)-induced hNPC proliferation in vitro. Therapeutic implications of these findings relevant to hormone therapy and prevention of neurodegenerative disease are discussed.
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PMID:Estradiol-17beta-induced human neural progenitor cell proliferation is mediated by an estrogen receptor beta-phosphorylated extracellularly regulated kinase pathway. 1796 44

Parathyroid hormone-related peptide (PTHrP) and the parathyroid hormone-PTHrP receptor increase chondrocyte proliferation and delay chondrocyte maturation in endochondral bone development at least partly through cyclic AMP (cAMP)-dependent signaling pathways. Because data suggest that the ability of cAMP to stimulate cell proliferation involves the mitogen-activated protein kinase kinase kinase B-Raf, we hypothesized that B-Raf might mediate the proliferative action of PTHrP in chondrocytes. Though B-Raf is expressed in proliferative chondrocytes, its conditional removal from cartilage did not affect chondrocyte proliferation and maturation or PTHrP-induced chondrocyte proliferation and PTHrP-delayed maturation. Similar results were obtained by conditionally removing B-Raf from osteoblasts. Because A-raf and B-raf are expressed similarly in cartilage, we speculated that they may fulfill redundant functions in this tissue. Surprisingly, mice with chondrocytes deficient in both A-Raf and B-Raf exhibited normal endochondral bone development. Activated extracellular signal-regulated kinase (ERK) was detected primarily in hypertrophic chondrocytes, where C-raf is expressed, and the suppression of ERK activation in these cells by PTHrP or a MEK inhibitor coincided with a delay in chondrocyte maturation. Taken together, these results demonstrate that B-Raf and A-Raf are dispensable for endochondral bone development and they indicate that the main role of ERK in cartilage is to stimulate not cell proliferation, but rather chondrocyte maturation.
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PMID:A-raf and B-raf are dispensable for normal endochondral bone development, and parathyroid hormone-related peptide suppresses extracellular signal-regulated kinase activation in hypertrophic chondrocytes. 1796 76

The activation of mitogen-activated protein/extracellular signal-regulated kinase (MEK) is well known to be associated with tumor invasion and metastasis. We previously reported that a polymethoxyflavonoid, nobiletin (5,6,7,8,3',4'-hexamethoxyflavone), derived from Citrus depressa (Hayata), inhibits the phosphorylation of MEK and thereby suppresses matrix metalloproteinase (MMP) expression in a tumor-metastasis stimulator, 12-O-tetradecanoyl phorbol 13-acetate (TPA)-stimulated human fibrosarcoma HT-1080 cells [Mol. Cancer Ther. 3 (2004) 839-847]. In the present study, we investigated whether or not nobiletin might directly influence MEK activity to exhibit the antitumor metastatic activity in vitro. MEK kinase assay using myelin basic protein (MBP) revealed that TPA-augmented MEK activity in HT-1080 cells and that the augmented MEK activity was diminished by nobiletin treatment. In addition, the decrease in MEK activity caused by nobiletin was found to inhibit the phosphorylation of extracellular regulated kinases (ERK), a downstream signaling factor for MEK. Furthermore, when an immunoprecipitated active MEK was incubated with nobiletin under cell-free conditions, nobiletin was found to inhibit the MEK-mediated MBP phosphorylation. In contrast, other citrus polymethoxyflavonoids such as 3-hydroxy-5,6,7,8,3',4'-hexamethoxyflavone (natsudaidain) and 3,5,6,7,8,3',4'-heptamethoxyflavone, did not directly inhibit MEK activity. Moreover, natsudaidain and 3,5,6,7,8,3',4'-heptamethoxyflavone exhibited no or less inhibitory effect than nobiletin on the proMMP-9/progelatinase B production in HT-1080 cells. Therefore, these results provide novel evidence that nobiletin directly inhibits MEK activity and decreases the sequential phosphorylation of ERK, exhibiting the antitumor metastatic activity by suppressing MMP expression in HT-1080 cells.
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PMID:A citrus polymethoxyflavonoid, nobiletin, is a novel MEK inhibitor that exhibits antitumor metastasis in human fibrosarcoma HT-1080 cells. 1805 6

Clinical and basic science data support an integral role of calcitonin gene-related peptide (CGRP) in the pathophysiology of temporomandibular joint disorders. Recently, we have shown that CGRP can stimulate the synthesis and release of nitric oxide (NO) from trigeminal ganglion glial cells. The goal of this study was to determine the role of mitogen-activated protein kinase (MAPK) signaling pathways in CGRP regulation of iNOS expression and NO release from cultured trigeminal ganglion glial cells from Sprague-Dawley rats. CGRP treatment for 2 h significantly increased activity of the MAPK reporter genes, Elk, ATF-2, and CHOP. In addition, CGRP increased nuclear staining for the active forms of the MAPKs: extracellular signal-regulated kinase, c-Jun amino-terminal kinase, and p38. This stimulatory event was not observed in cultures pre-treated with the CGRP receptor antagonist peptide CGRP(8-37). Similarly, pre-treatment with selective MAPK inhibitors repressed increases in reporter gene activity as well as CGRP-induced increases in iNOS expression and NO release mediated by MAPKs. In addition, over-expression of MAPK kinase 1 (MEK1), MEK3, MEK6, and MEK kinase significantly increased iNOS expression and NO production in glial cells. Results from our study provide evidence that CGRP binding to its receptor can stimulate iNOS gene expression via activation of MAPK pathways in trigeminal ganglion glial cells.
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PMID:CGRP stimulation of iNOS and NO release from trigeminal ganglion glial cells involves mitogen-activated protein kinase pathways. 1945 95

The purpose of the present study was to examine the signal transduction pathways involved in follistatin gene expression induced by GnRH in the LbetaT2 cell line. The LHbeta-subunit was predominantly increased by high frequency GnRH pulses (30 min interval); whereas low frequency pulses (120 min) increased FSHbeta. In a static culture, follistatin expression was significantly increased at 12 h (2.35 +/- 0.80-fold) after the addition of GnRH. Following pulsatile stimulation, follistatin mRNA was increased by high frequency GnRH pulses, but not by low frequency pulses. In a static culture, GnRH maximally activated extracellular signal-regulated kinase (ERK) 10 min (3.2 +/- 0.55-fold) after treatment. In addition, intracellular cAMP accumulated up to 2.1 +/- 0.76-fold. Follistatin promoter activity was significantly increased following transfection with either a constitutively active cAMP dependent protein kinase (PKA) or a constitutively active MEK kinase (MEKK). The induction of follistatin gene expression by GnRH was completely inhibited by H89, a protein kinase A inhibitor, and U0126, a MEK inhibitor. Follistatin gene expression was also activated by both PACAP and CPT-cAMP under static culture conditions. Maximal ERK activation levels were nearly identical regardless of GnRH pulse frequency; however, high frequency GnRH pulses elevated both the intracellular cAMP level as well as cAMP-response element (Cre) promoter activity. These results suggest that both the PKA and ERK pathways are necessary for the induction of the follistatin promoter. Furthermore, the intracellular cAMP level, but not ERK activity, determined whether follistatin was induced following high frequency GnRH pulses.
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PMID:Follistatin gene expression by gonadotropin-releasing hormone: a role for cyclic AMP and mitogen-activated protein kinase signaling pathways in clonal gonadotroph LbetaT2 cells. 1953 41


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