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)

We have investigated the early in vivo signaling events triggered by serum that lead to activation of the c-fos proto-oncogene in HeLa cells. Both RAF-1 and MEK kinase activities are fully induced within 3 min of serum treatment and quickly decrease thereafter, slightly preceding the activation and inactivation of p42MAPK/ERK2. ERK2 activity correlates tightly with a transient phosphatase-sensitive modification of ternary complex factor (TCF), manifested by the slower electrophoretic mobility of TCF-containing protein-DNA complexes. These induced complexes in turn correlate with the activity of the c-fos, egr-1, and junB promoters. Phorbol ester treatment induces the same events but with slower and prolonged kinetics. Inhibition of serine/threonine phosphatase activities by okadaic acid treatment reverses the repression of the c-fos promoter either after induction or without induction. This corresponds to the presence of the induced complexes and of ERK2 activity, as well as to the activation of a number of other kinases. Inhibition of tyrosine phosphatase activities by sodium vanadate treatment delays but does not block ERK2 inactivation, TCF dephosphorylation, and c-fos repression. The tight linkage in vivo between the activity of MAP kinase, TCF phosphorylation, and immediate-early gene promoter activity is consistent with the notion that a stable ternary complex over the serum response element is a direct target for the MAP kinase signaling cascade. Furthermore, serine/threonine phosphatases are implicated in regulating the kinase cascade, as well as the state of TCF modification and c-fos promoter activity, in vivo.
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PMID:Transient activation of RAF-1, MEK, and ERK2 coincides kinetically with ternary complex factor phosphorylation and immediate-early gene promoter activity in vivo. 806 54

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.
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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

POU domain proteins have been implicated as key regulators during development and lymphocyte activation. The POU domain protein T-cell factor beta1 (TCFbeta1), which binds octamer and octamer-related sequences, is a potent transactivator. In this study, we showed that TCFbeta1 is phosphorylated following activation via the T-cell receptor or by stress-induced signals. Phosphorylation of TCFbeta1 occurred predominantly at serine and threonine residues. Signals which upregulate Jun kinase (JNK)/stress-activated protein kinase activity also lead to association of JNK with TCFbeta1. JNK associates with the activation domain of TCFbeta1 and phosphorylates its DNA binding domain. The phosphorylation of recombinant TCFbeta1 by recombinant JNK enhances the ability of TCFbeta1 to bind to a consensus octamer motif. Consistent with this conclusion, TCFbeta1 upregulates reporter gene transcription in an activation- and JNK-dependent manner. In addition, inhibition of JNK activity by catalytically inactive MEKK (in which methionine was substituted for the lysine at position 432) also inhibits the ability of TCFbeta1 to drive inducible transcription from the interleukin-2 promoter. These results suggest that stress-induced signals and T-cell activation induce JNK, which then acts on multiple cis sequences by modulating distinct transactivators like c-Jun and TCFbeta1. This demonstrates a coupling between the JNK activation pathway and POU domain proteins and implicates TCFbeta1 as a physiological target in the JNK signal transduction pathway leading to coordinated biological responses.
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PMID:Jun kinase phosphorylates and regulates the DNA binding activity of an octamer binding protein, T-cell factor beta1. 1002 89

In mammals, TAK1, a MAPKKK kinase, is implicated in multiple signaling processes, including the regulation of NF-kappaB activity via the IL1-R/TLR pathways. TAK1 function has largely been studied in cultured cells, and its in vivo function is not fully understood. We have isolated null mutations in the Drosophila dTAK1 gene that encodes dTAK1, a homolog of TAK1. dTAK1 mutant flies are viable and fertile, but they do not produce antibacterial peptides and are highly susceptible to Gram-negative bacterial infection. This phenotype is similar to the phenotypes generated by mutations in components of the Drosophila Imd pathway. Our genetic studies also indicate that dTAK1 functions downstream of the Imd protein and upstream of the IKK complex in the Imd pathway that controls the Rel/NF-kappaB like transactivator Relish. In addition, our epistatic analysis places the caspase, Dredd, downstream of the IKK complex, which supports the idea that Relish is processed and activated by a caspase activity. Our genetic demonstration of dTAK1's role in the regulation of Drosophila antimicrobial peptide gene expression suggests an evolutionary conserved role for TAK1 in the activation of Rel/NF-kappaB-mediated host defense reactions.
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PMID:Mutations in the Drosophila dTAK1 gene reveal a conserved function for MAPKKKs in the control of rel/NF-kappaB-dependent innate immune responses. 1148 85

In Drosophila, the immune deficiency (Imd) pathway controls antibacterial peptide gene expression in the fat body in response to Gram-negative bacterial infection. The ultimate target of the Imd pathway is Relish, a transactivator related to mammalian P105 and P100 NF-kappaB precursors. Relish is processed in order to translocate to the nucleus, and this cleavage is dependent on both Dredd, an apical caspase related to caspase-8 of mammals, and the fly Ikappa-B kinase complex (dmIKK). dTAK1, a MAPKKK, functions upstream of the dmIKK complex and downstream of Imd, a protein with a death domain similar to that of mammalian receptor interacting protein (RIP). Finally, the peptidoglycan recognition protein-LC (PGRP-LC) acts upstream of Imd and probably functions as a receptor for the Imd pathway. Using inducible expression of dFADD double-stranded RNA, we demonstrate that dFADD is a novel component of the Imd pathway: dFADD double-stranded RNA expression reduces the induction of antibacterial peptide-encoding genes after infection and renders the fly susceptible to Gram-negative bacterial infection. Epistatic studies indicate that dFADD acts between Imd and Dredd. Our results reinforce the parallels between the Imd and the TNF-R1 pathways.
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PMID:Inducible expression of double-stranded RNA reveals a role for dFADD in the regulation of the antibacterial response in Drosophila adults. 1212 72