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 involvement of serine/threonine protein phosphatases in signaling pathways that control the expression of the cyclooxygenase-2 (COX-2) gene in human chondrocytes was examined. Okadaic acid (OKA), an inhibitor of protein phosphatases 1 (PP-1) and 2A (PP-2A), induced a delayed, time-dependent increase in the rate of COX-2 gene transcription (runoff assay) resulting in increased steady-state mRNA levels and enzyme synthesis. The latter response was dose dependent over a narrow range of 1-30 nmol/L with declining expression and synthesis of COX-2 at higher concentrations due to cell toxicity. The delayed increase in COX-2 mRNA expression was accompanied by the induction of the proto-oncogenes c-jun, junB, junD, and c-fos (but not FosB or Fra-1). Increased phosphorylation of CREB-1/ATF-1 transcription factors was observed beginning at 4 h and reached a zenith at 8 h. Gel-shift analysis confirmed the up-regulation of AP-1 and CRE nuclear binding proteins, though there was little or no OKA-induced nuclear protein binding to SP-1, AP-2, NF-kappaB or NF-IL-6 regulatory elements. OKA-induced nuclear protein binding to 32P-CRE oligonucleotides was abrogated by a pharmacological inhibitor of protein kinase A (PKA), KT-5720; the latter compound also inhibited OKA-induced COX-2 enzyme synthesis. Calphostin C (CalC), an inhibitor of PKC isoenzymes, had little effect in this regard. Inhibition of 12P-CRE binding was also observed in the presence of an antibody to CREB-binding protein (265-kDa CBP), an integrator and coactivator of cAMP-responsive genes. The binding to 32P-CRE was unaffected in the presence of excess radioinert AP-1 and COX-2 NF-IL-6 oligonucleotides, although a COX-2 CRE-oligo competed very efficiently. 32P-AP-1 consensus sequence binding was unaffected by incubation of chondrocytes with KT-5720 or CalC, but was dramatically diminished by excess radioinert AP-1 and CRE-COX-2 oligos. Supershift analysis in the presence of antibodies to c-Jun, c-Fos, JunD, and JunB suggested that AP-1 complexes were composed of c-Fos, JunB, and possibly c-Jun. OKA has no effect on total cellular PKC activity but caused a delayed time-dependent increase in total PKA activity and synthesis. OKA suppressed the activity of the MAP kinases, ERK1/2 in a time-dependent fashion, suggesting that the Raf-1/MEKK1/MEK1/ERK1,2 cascade was compromised by OKA treatment. By contrast, OKA caused a dramatic increase in SAPK/JNK expression and activity, indicative of an activation of MEKK1/JNKK/SAPK/JNK pathway. OKA stimulated a dose-dependent activation of CAT activity using transfected promoter-CAT constructs harboring the regulatory elements AP-1 (c-jun promoter) and CRE (CRE-tkCAT). We conclude that in primary phenotypically stable human chondrocytes, COX-2 gene expression may be controlled by critical phosphatases that interact with phosphorylation dependent (e.g., MAP kinases:AP-1, PKA:CREB/ATF) signaling pathways. AP-1 and CREB/ATF families of transcription factors may be important substrates for PP-1/PP-2A in human chondrocytes.
 ...
PMID:Transcriptional induction of cyclooxygenase-2 gene by okadaic acid inhibition of phosphatase activity in human chondrocytes: co-stimulation of AP-1 and CRE nuclear binding proteins. 962 Jan 67

Upon transforming growth factor-beta (TGF-beta) binding to its cognate receptor, Smad3 and Smad4 form heterodimers and transduce the TGF-beta signal to the nucleus. In addition to the Smad pathway, another pathway involving a member of the mitogen-activated protein kinase kinase kinase family of kinases, TGF-beta-activated kinase-1 (TAK1), is required for TGF-beta signaling. However, it is unknown how these pathways function together to synergistically amplify TGF-beta signaling. Here we report that the transcription factor ATF-2 (also called CRE-BP1) is bound by a hetero-oligomer of Smad3 and Smad4 upon TGF-beta stimulation. ATF-2 is one member of the ATF/CREB family that binds to the cAMP response element, and its activity is enhanced after phosphorylation by stress-activated protein kinases such as c-Jun N-terminal kinase and p38. The binding between ATF-2 and Smad3/4 is mediated via the MH1 region of the Smad proteins and the basic leucine zipper region of ATF-2. TGF-beta signaling also induces the phosphorylation of ATF-2 via TAK1 and p38. Both of these actions are shown to be responsible for the synergistic stimulation of ATF-2 trans-activating capacity. These results indicate that ATF-2 plays a central role in TGF-beta signaling by acting as a common nuclear target of both Smad and TAK1 pathways.
 ...
PMID:ATF-2 is a common nuclear target of Smad and TAK1 pathways in transforming growth factor-beta signaling. 1008 40

Antineoplasic agents such as cisplatin and adriamycin execute their pharmacological role by triggering apoptosis. We have studied the mechanism of apoptosis induction by cisplatin and adriamycin. Both drugs activated JNK with slow and persistent kinetics. Adriamycin activated caspase-3 before the rise in JNK activity, while the response to cisplatin occurs hours after JNK activation. The increase in JNK activity was necessary for cisplatin-mediated apoptosis but it was dispensable for adriamycin-induced cell death. Cells derived from c-jun knock out mice were more resistant to cisplatin cell death than normal cells, but no difference was observed in response to adriamycin. Activation of JNK and cell death by cisplatin is mediated by the MEKK1/SEK1 cascade, since expression of dominant negative expression vectors of these kinases blocked both processes. p38 was also activated by cisplatin with similar kinetics as JNK. AP-1 complexes were activated by cisplatin including mainly c-jun/ATF-2 heterodimers suggesting that AP-1-dependent transcription partially mediated cisplatin-induced apoptosis.
 ...
PMID:Lack of c-Jun activity increases survival to cisplatin. 1040 93

Transforming growth factor-beta (TGF-beta)-activated kinase 1 (TAK1), a member of the mitogen-activated protein kinase kinase kinase family, is suggested to be involved in TGF-beta-induced gene expression, but the signaling mechanism from TAK1 to the nucleus remains largely undefined. We have found that p38 mitogen-activated protein kinase, and its direct activator MKK6 are rapidly activated in response to TGF-beta. Expression of dominant negative MKK6 or dominant negative TAK1 inhibited the TGF-beta-induced transcriptional activation as well as the p38 activation. Constitutive activation of the p38 pathway in the absence of TGF-beta induced the transcriptional activation, which was enhanced synergistically by coexpression of Smad2 and Smad4 and was inhibited by expression of the C-terminal truncated, dominant negative Smad4. Furthermore, we have found that activating transcription factor-2 (ATF-2), which is known as a nuclear target of p38, becomes phosphorylated in the N-terminal activation domain in response to TGF-beta, that ATF-2 forms a complex with Smad4, and that the complex formation is enhanced by TGF-beta. In addition, expression of a nonphosphorylatable form of ATF-2 inhibited the TGF-beta-induced transcriptional activation. These results show that the p38 pathway is activated by TGF-beta and is involved in the TGF-beta-induced transcriptional activation by regulating the Smad-mediated pathway.
 ...
PMID:Involvement of the p38 mitogen-activated protein kinase pathway in transforming growth factor-beta-induced gene expression. 1048 Sep 32

Activated Transcription Factor-2 (ATF-2) is important during development of and during injury to the brain. Both Jun N-terminal Kinases (JNKs) and p38 Mitogen-Activated Protein Kinases (p38MAPKs) may phosphorylate ATF-2, but the contribution of these two pathways in cells has never been investigated. We have assayed endogenous p38MAPK activity in SK-N-MC and SH-SY5Y human neuroblastoma cells for activation of a GAL4/ATF-2 fusionprotein, by means of titrations of transfected expression plasmids and by using the p38MAPK inhibitor SB203580. It was found that basal activation of ATF-2 was independent of p38MAPK and that whereas MAPK kinase-3 (MKK3) was a weak inducer of ATF-2 activation, it was a potent activator of the stress activated transcription factor CHOP. In contrast, ATF-2 was very potently activated by the JNK pathway activator MAPK kinase kinase-1 (MEKK1). Thus, kinases downstream of MEKK1 appear relevant, but it is unlikely that p38MAPKs contribute quantitatively to activation of ATF-2 in these cells.
 ...
PMID:Contribution of MAP kinase pathways to the activation of ATF-2 in human neuroblastoma cells. 1082 86

Ca(2+)-sensitive tyrosine kinase Pyk2 was shown to be involved in angiotensin (Ang) II-mediated activation of extracellular signal-regulated kinase (ERK) via transactivation of epidermal growth factor receptor (EGF-R). In this study, we tested the involvement of Pyk2 and EGF-R in Ang II-induced activation of JNK and c-Jun in cardiac fibroblasts. Ang II markedly stimulated JNK activities, which were abolished by genistein and intracellular Ca(2+) chelators but partially by protein kinase C depletion. Inhibition of EGF-R did not affect Pyk2 and JNK activation by Ang II. Stable transfection with a dominant negative (DN) mutant for Pyk2 (PKM) completely blocked JNK activation by Ang II. DN mutants of Rac1 (DN-Rac1) and MEK kinase (DN-MEKK1) also abolished it, whereas those of Cdc42, RhoA, and Ha-Ras had no effect. Induction of c-Jun gene transcription by Ang II was abolished in PKM, DN-Rac1, and DN-MEKK1, in which Ang II-induced binding of ATF2/c-Jun heterodimer to the activator protein-1 sequence at -190 played a key role. These results suggest that 1) in cardiac fibroblasts activation of JNK and c-Jun by Ang II is initiated by Pyk2-dependent signalings but not by downstream signals of EGF-R or Ras, 2) Rac1 but not Cdc42 is required for JNK activation by Ang II upstream of MEKK1, and 3) ATF-2/c-Jun binding to the activator protein-1 sequence at -190 plays a key role for induction of c-Jun gene by Ang II.
 ...
PMID:Angiotensin II initiates tyrosine kinase Pyk2-dependent signalings leading to activation of Rac1-mediated c-Jun NH2-terminal kinase. 1085 8

We previously demonstrated that bone morphogenetic proteins (BMPs) induce cardiomyocyte differentiation through the mitogen-activated protein kinase kinase kinase TAK1. Transcription factors Smads mediate transforming growth factor-beta signaling and the ATF/CREB family transcription factor ATF-2 has recently been shown to act as a common target of the Smad and the TAK1 pathways. We here examined the role of Smads and ATF-2 in cardiomyocyte differentiation of P19CL6, a clonal derivative of murine P19 cells. Although P19CL6 efficiently differentiates into cardiomyocytes when treated with dimethyl sulfoxide, P19CL6noggin, a P19CL6 cell line constitutively overexpressing the BMP antagonist noggin, did not differentiate into cardiomyocytes. Cooverexpression of Smad1, a ligand-specific Smad, and Smad4, a common Smad, restored the ability of P19CL6noggin to differentiate into cardiomyocytes, whereas stable overexpression of Smad6, an inhibitory Smad, completely blocked differentiation of P19CL6, suggesting that the Smad pathway is necessary for cardiomyocyte differentiation. ATF-2 stimulated the betaMHC promoter activity by the synergistic manner with Smad1/4 and TAK1 and promoted terminal cardiomyocyte differentiation of P19CL6noggin, whereas overexpression of the dominant negative form of ATF-2 reduced the promoter activities of several cardiac-specific genes and inhibited differentiation of P19CL6. These results suggest that Smads, TAK1, and their common target ATF-2 cooperatively play a critical role in cardiomyocyte differentiation.
 ...
PMID:Smads, TAK1, and their common target ATF-2 play a critical role in cardiomyocyte differentiation. 1135 31

The immediate-early (IE) promoter of human cytomegalovirus (HCMV) constitutes a primary genetic switch, which determines the progression of viral infection. Earlier reports by others have shown mitogen-activated protein kinase kinase kinase-1 (MEKK1) to be able to up-regulate HCMV-IE promoter through downstream mitogen-activated protein kinase (MAPK) pathways. However, we noticed that the activation of the HCMV-IE promoter by constitutively active MEKK1 (MEKK1-TRU) might not be through the MAPK pathways. Using a HCMV-IE enhancer/promoter (- 522 to + 72) driving a luciferase reporter, we demonstrated that the downstream MAPK activation actually repressed the up-regulation of the promoter by MEKK1 in CHO-K1 and human 293 cells. We further found that the up-regulation of HCMV-IE promoter by MEKK1 could be in great extent suppressed by over-expression of IkappaBalpha. Deletion of the NFkappaB/rel sites in the HCMV-IE enhancer region by mutagenesis proportionally reduced the transcriptional activation by MEKK1-TRU, whereas deletion of the ATF/CREB binding sites or cyclic AMP response elements (CRE) had no effects. Furthermore, the NFkappaB/rel deletion mutant also showed repression on the basic transcription activity of the HCMV-IE promoter. Our results indicate that the NFkappaB/rel sites are not only responsible for the modulation of HCMV-IE enhancer activity by MEKK1 but also control the basic transcription activity of the HCMV-IE promoter. On the other hand, the four consensus CRE sites were found to have no function in the activation of the promoter by MEKK1.
 ...
PMID:Modulation of human cytomegalovirus immediate-early gene enhancer by mitogen-activated protein kinase kinase kinase-1. 1174

Mammalian cells have a remarkable diverse repertoire of response to genotoxic stress that damage DNA. Cellular responses to DNA damaging agents will initially exhibit gene induction, which is regulated by complex mechanism(s) and probably involves multiple signaling pathways. In this paper, we demonstrate that induction of ATF3 protein, a member of the ATF/CREB family of transcription factors, by ionizing radiation (IR) requires normal cellular p53 function. In contrast, induction of ATF3 after UV radiation (UV) or Methyl methanesulphonate (MMS) is independent of p53 status. Induction of ATF3 by DNA damage is rapid, transient, and through a transcriptional mechanism. The ATF3 promoter is induced by UV and MMS, but not by IR. In addition, ATF3 promoter can be activated by MEKK1, an upstream activator of the ERK and JNK kinase pathway, but not induced following p53 expression. Those results indicate that regulation of ATF3 induction after DNA damage utilizes both the p53-dependent and -independent pathways, and may also involve MAP kinase signaling pathways. Using the tetracycline-inducible system (tet-off), we have found that over-expression of ATF3 protein moderately suppresses cell growth. Interestingly, over-expression of ATF3 protein is able to slow down progression of cells from G1 to S phase, indicating that ATF3 protein might play a negative role in the control of cell cycle progression.
 ...
PMID:ATF3 induction following DNA damage is regulated by distinct signaling pathways and over-expression of ATF3 protein suppresses cells growth. 1238 11

Activator protein 1 (AP-1) transcription factor dimers are composed of Jun, Fos, and ATF member proteins, but the mechanisms that determine AP-1 composition are not clearly defined and the function of specific dimers is not well understood. MEKK1 is a mitogen-activated protein kinase (MAPK) kinase kinase and an ubiquitin ligase that regulates both the extracellular signal-regulated kinase 1/2 and the c-Jun amino-terminal kinase. Herein, we demonstrate that MEKK1 regulates the AP-1 protein repertoire. Both FGF-2 and phorbol ester-inducible urokinase-type plasminogen activator (uPA) expression requires AP-1 binding to an enhancer element in the uPA promoter, and we have previously shown that FGF-2 or PMA induction of uPA expression is strongly dependent on MEKK1. JunB mRNA is significantly increased in MEKK1-/- cells, demonstrating that MEKK1 suppresses JunB mRNA expression. Upregulation of JunB expression in MEKK1-/- cells forms an inhibitory AP-1 complex that binds to the uPA promoter and inhibits uPA transcription. MEKK1 also regulates Fra-2 protein stability by inducing Fra-2 ubiquitination and degradation. MEKK1 regulates AP-1-dependent gene expression by regulating the expression, activity and degradation of component members of the AP-1 complex. Controlling the repertoire of a transcription factor complex is a newly defined function for an MAPK kinase kinase.
 ...
PMID:MEKK1 regulates the AP-1 dimer repertoire via control of JunB transcription and Fra-2 protein stability. 1555 21


1 2 Next >>