Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cross-linking membrane Ig (mIg) on B cells stimulates tyrosine phosphorylation of proteins involved in signal transduction including the mIg-associated proteins Ig-alpha and Ig-beta, the tyrosine kinases p53/p56lyn, p55blk, p59fyn, and PTK72, phosphatidylinositol 3-kinase, phospholipase C gamma 1 and gamma 2, and the mitogen-activated protein kinase. We now show that the p21ras GTPase-activating protein (GAP) is also a substrate for mIg-activated tyrosine kinases. p21ras is a key regulator of cell growth and GAP may act as both a regulator of p21ras activity and as a downstream effector of p21ras. We found that mIg cross-linking caused a rapid increase in tyrosine phosphorylation of GAP in the immature B cell line WEHI-231, the mature B cell lines BAL 17 and Daudi, and the IgG-bearing B cell line A20. In fibroblasts, tyrosine kinase activation causes GAP to associate with two other tyrosine-phosphorylated proteins, p62 and p190, which have homologies to an RNA-binding protein and a transcriptional repressor, respectively. Similarly, mlg cross-linking induced the association of GAP with a 62-kDa tyrosine-phosphorylated protein in BAL 17, WEHI-231, and Daudi cells. Anti-Ig treatment also increased the amount of a 190-kDa tyrosine-phosphorylated protein associated with GAP in WEHI-231 and Daudi cells. After separation by SDS-PAGE and transfer to nitrocellulose, the tyrosine-phosphorylated p62 and p190 present in anti-GAP immunoprecipitates from B cells were capable of binding radiolabeled recombinant GAP, as previously reported for the GAP-associated p62 and p190 from fibroblasts. The amount of p62 that could be detected in this way after immunoprecipitation with antiphosphotyrosine antibodies was much greater from anti-IgM-treated BAL 17 cells than from unstimulated BAL 17 cells. This probably reflects anti-Ig-induced tyrosine phosphorylation of p62. In any case, GAP, p62, and/or p190 may be involved in signal transduction by mIg in B cells.
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PMID:Targets of B lymphocyte antigen receptor signal transduction include the p21ras GTPase-activating protein (GAP) and two GAP-associated proteins. 841 71

Stimulation of the B cell Ag receptor (BCR), a multimeric complex containing heterodimers of Ig-alpha and Ig-beta, initiates a cascade of tyrosine phosphorylation that results in cellular activation. One of the earliest substrates phosphorylated is Ig-alphabeta, and it appears that kinase activation emanates from this structure with the most proximal kinases themselves, and some of their immediate substrates, associating with the heterodimer. To identify other molecules that may be involved in proximal BCR signaling, we examined the substrates that were tyrosine phosphorylated following stimulation with either anti-IgG Abs or pervanadate in the murine B cell lymphoma A20 IIA1.6 and in resting splenic B cells. Immunoblotting with anti-phosphotyrosine Abs revealed that a doublet of 40 and 42 kDa was phosphorylated within 1 min of stimulation with either agonist. The phosphorylation of p40/42 in A20 cells induced by anti-IgG was rapid and transient, peaking at 2 min after stimulation and becoming almost undetectable after 10 min. Furthermore, at least 25% of phosphorylated p40/42 co-immunoprecipitated with Ig-alphabeta, but none precipitated with MHC II, CD40, Fc(gamma)RII, Fyn, HS-1, or Syk, suggesting that this protein complex specifically associates with the Ig-alphabeta heterodimer. p40/42 did not react with Abs to Ig-alpha, Ig-beta, mitogen-activated protein kinase, or Lnk. Furthermore, and in contrast to Ig-alphabeta, p40/42 was highly acidic and not part of a disulfide-linked complex. Finally, p40/42 was demonstrated to be a glycosylated surface protein that was constitutively associated with Ig-alphabeta. These results suggest that p40/42 is a novel constituent of the resting B cell Ag receptor complex.
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PMID:A novel complex, p40/42, is constitutively associated with the B cell antigen receptor and phosphorylated upon receptor stimulation. 889 12

The transforming Epstein-Barr virus-encoded latent membrane protein 1 (LMP1) activates signalling on the NF-kappaB axis through two distinct domains in its cytoplasmic C terminus, namely, CTAR1 (amino acids [aa] 187 to 231) and CTAR2 (aa 351 to 386). The ability of CTAR1 to activate NF-kappaB appears to be attributable to the direct interaction of tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2), while recent work indicates that CTAR2-induced NF-kappaB is mediated through its association with TNF receptor-associated death domain (TRADD). LMP1 expression also results in activation of the c-Jun N-terminal kinase (JNK) (also known as stress-activated protein kinase) cascade, an effect which is mediated exclusively through CTAR2 and can be dissociated from NF-kappaB induction. The organization and signalling components involved in LMP1-induced JNK activation are not known. In this study we have dissected the extreme C terminus of LMP1 and have identified the last 8 aa of the protein (aa 378 to 386) as being important for JNK signalling. Using a series of fine mutants in which single amino acids between codons 379 and 386 were changed to glycine, we have found that mutations of Pro379, Glu381, Ser383, or Tyr384 diminish the ability of LMP1 CTAR2 to engage JNK signalling. Interestingly, this region was also found to be essential for CTAR2-mediated NF-kappaB induction and coincides with the LMP1 amino acid sequences shown to bind TRADD. Furthermore, we have found that LMP1-mediated JNK activation is synergistically augmented by low levels of TRADD expression, suggesting that this adapter protein is critical for LMP1 signalling. TRAF2 is known to associate with TRADD, and expression of a dominant-negative N-terminal deletion TRAF2 mutant was found to partially inhibit LMP1-induced JNK activation in 293 cells. In addition, the TRAF2-interacting protein A20 blocked both LMP1-induced JNK and NF-kappaB activation, further implicating TRAF2 in these phenomena. While expression of a kinase-inactive mutated NF-kappaB-inducing kinase (NIK), a mitogen-activated protein kinase kinase kinase which also associates with TRAF2, impaired LMP1 signalling on the NF-kappaB axis, it did not inhibit LMP1-induced JNK activation, suggesting that these two pathways may bifurcate at the level of TRAF2. These data further define a role for TRADD and TRAF2 in JNK activation and confirm that LMP1 utilizes signalling mechanisms used by the TNF receptor/CD40 family to elicit its pleiotropic activities.
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PMID:Epstein-Barr virus-encoded latent membrane protein 1 activates the JNK pathway through its extreme C terminus via a mechanism involving TRADD and TRAF2. 988 3

The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) interacts with the tumor necrosis factor receptor (TNFR)-associated factor (TRAF) molecules, which are important for LMP1-mediated signaling. Two domains of LMP1 can independently activate NF-kB, carboxyl-terminal activating region 1 (CTAR1) and CTAR2. The activation of NF-kB by CTAR1 occurs through direct interaction of LMP1 with the TRAF molecules, whereas CTAR2 interacts with the TNFR-associated death domain protein (TRADD) to activate NF-kB and the c-Jun N-terminal kinase (JNK). A20, which is induced by LMP1 through NF-kB, can block NF-kB activation from both domains of LMP1 and inhibit JNK activation from CTAR2. A20 also has been shown to associate with TRAF1 and TRAF2. In this study, an interaction between LMP1 and A20 was detected that was increased by TRAF2 overexpression. A20 did not affect the association of TRAF1 with TRAF2 but did displace TRAF1 from the LMP1 complex. The interaction of LMP1 and TRADD was decreased in the presence of A20, and the LMP1-A20 association was decreased by TRADD, suggesting that A20 and TRADD both interact with LMP1 and may compete for binding. These data indicate that A20 alters the interactions between LMP1 and the TRAF molecules and TRADD, affecting the activation of NF-kB, JNK, and perhaps other TRAF-mediated signaling events.
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PMID:The A20 protein interacts with the Epstein-Barr virus latent membrane protein 1 (LMP1) and alters the LMP1/TRAF1/TRADD complex. 1054 41

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are involved in signaling pathways triggered by members of the TNF receptor (TNFR) family and other cell surface proteins. After recruitment to a receptor, TRAFs initiate formation of multiprotein complexes that induce downstream events, such as translocation of transcription factor nuclear factor kappaB (NF-kappaB) and activation of c-Jun N-terminal kinase (JNK). Several proteins in these complexes play important roles in regulation of apoptosis. However, the fate of TRAF-containing complexes once assembled in response to receptor multimerization is not understood. In this report, we demonstrate that crosslinking of TNFR family members or interaction of TRAF2 with the cytoplasmic protein A20 leads to intracellular translocation of TRAF2. This redistribution leads to depletion of the cytoplasmic pool of TRAF2. The ratio between soluble and insoluble TRAF2 determines the sensitivity of cells to TNF-alpha-induced apoptosis and may play an important role in limiting further TRAF-dependent signal transduction.
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PMID:Translocation of TRAF proteins regulates apoptotic threshold of cells. 1086 Aug 54

A20 zinc finger protein is a negative regulator of tumor necrosis factor (TNF)-induced signaling pathways leading to apoptosis, stress response and inflammation. A20 has been shown to bind to TNF-receptor-associated factor 2 (TRAF2) and 14-3-3 chaperone proteins. Our data indicate that the zinc finger domain of A20 is sufficient and that neither TRAF2 nor 14-3-3 binding is necessary for the inhibitory effects of A20. Mutations in the 14-3-3 binding site of A20 did, however, result in a partial cleavage of A20 protein suggesting that 14-3-3 chaperone proteins may stabilize A20. Furthermore, we show that A20 acts early in TNF-induced signaling cascades blocking both TNF-induced rapid activation of c-Jun N-terminal kinase and processing of the receptor-associated caspase-8. Taken together our data indicate that the zinc finger domain of A20 contains all necessary functional domains required for the inhibition of TNF signaling and that A20 may function at the level of the receptor signaling complex.
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PMID:A20 zinc finger protein inhibits TNF-induced apoptosis and stress response early in the signaling cascades and independently of binding to TRAF2 or 14-3-3 proteins. 1131 9

A20, a TNF inducible gene, inhibits TNF-mediated apoptosis as well as NF-kappa B induced by this cytokine. Reporter assay experiments revealed that A20 is a very effective inhibitor of NF-kappa B signaling induced by TRAFs and several Map3 kinases, including NIK, MEKK1, COT, and TAK1. Similarly, the NF-kappa B inducing activity of TAX, an activator of the I kappa B kinase complex, is also abrogated by A20. Inhibition of NF-kappa B is specific as A20 has no effect on TNF-alpha-induced JNK activation. These results suggest that the molecular target of A20 is more distal to the receptor than TRAFs as previously proposed. A20 inhibits NF-kappa B-dependent transcription without a concomitant decrease in nuclear NF-kappa B DNA binding activity or nuclear translocation of p65. This apparent discrepancy between transcriptional readout and gel shift experiments is observed with a variety of stimuli, including expression of IKK beta. Therefore, in addition to the phosphorylation of I kappa B, another signal is needed for transcriptional activation of NF-kappa B. A20 inhibits this non-redundant signal. The observation that A20 associates with IKK alpha and is phosphorylated upon IKK beta co-expression may suggest that A20 interferes with some aspects of signalosome function.
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PMID:A20 inhibits NF-kappa B activation downstream of multiple Map3 kinases and interacts with the I kappa B signalosome. 1159 95

We have shown that carbon monoxide (CO) generated by heme oxygenase-1 (HO-1) protects endothelial cells (EC) from tumor necrosis alpha (TNF-alpha)-mediated apoptosis. This effect relies on the activation of p38 MAPK. We now demonstrate that HO-1/CO requires the activation of the transcription factor NF-kappaB to exert this anti-apoptotic effect. Our data suggest that EC have basal levels of NF-kappaB activity that sustain the expression of NF-kappaB-dependent anti-apoptotic genes required to support the anti-apoptotic effect of HO-1/CO. Over-expression of the inhibitor of NF-kappaB alpha (IkappaBalpha) suppresses the anti-apoptotic action of HO-1/CO. Reconstitution of NF-kappaB activity, by co-expression of IkappaBalpha with different members of the NF-kappaB family, i.e. p65/RelA or p65/RelA plus c-Rel, restores the anti-apoptotic effect of HO-1/CO. Expression of the NF-kappaB family members p65/RelA or p65/RelA with p50 or c-Rel up-regulates the expression of the anti-apoptotic genes A1, A20, c-IAP2, and manganese superoxide dismutase (MnSOD). Inhibition of NF-kappaB activity by over-expression of IkappaBalpha suppresses the expression of some of these anti-apoptotic genes, i.e. c-IAP2. Under inhibition of NF-kappaB, co-expression of some of these anti-apoptotic genes, i.e. c-IAP2 and A1, restores the anti-apoptotic action of HO-1/CO, whereas expression of A20 or MnSOD cannot. The ability of c-IAP2 and/or A1 to restore the anti-apoptotic action of HO-1/CO is abolished when p38 MAPK activation is blocked by over-expression of a p38 MAPK dominant negative mutant. In conclusion, we demonstrate that HO-1/CO cooperates with NF-kappaB-dependent anti-apoptotic genes, i.e. c-IAP2 and A1, to protect EC from TNF-alpha-mediated apoptosis. This effect is dependent on the ability of HO-1/CO to activate the p38 MAPK signal transduction pathway.
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PMID:Heme oxygenase-1-derived carbon monoxide requires the activation of transcription factor NF-kappa B to protect endothelial cells from tumor necrosis factor-alpha-mediated apoptosis. 1188 Mar 64

The proteolytic activity of caspases is involved in apoptosis and inflammation. In this regard, caspase-1 is required for pro-interleukin (IL)-1beta and pro-IL-18 maturation. We report here on a novel function of caspase-1 as an activator of nuclear factor of the kappa-enhancer in B-cells (NF-kappaB) and p38 mitogen-activated protein kinase (MAPK). This function is not shared by the murine caspase-1 homologues caspase-11 and -12. In contrast to pro-IL-1beta maturation, caspase-1-induced NF-kappaB activation is not inhibited by the virus-derived caspase-1 inhibitor cytokine response modifier A and is equally induced by the enzymatically inactive caspase-1 C285A mutant. Although the general NF-kappaB-inhibiting protein A20 inhibits caspase-1-derived activation of NF-kappaB, dominant-negative forms of TRAF2 and RIP1 have no effect. We demonstrate that caspase-1 interacts with RIP2 and that dominant-negative forms of RIP2 and IkappaB kinase complex-beta inhibit caspase-1-mediated NF-kappaB activation. Structure-function analysis shows that the caspase recruitment domain of caspase-1 mediates the activation of NF-kappaB and p38 MAPK. These data demonstrate that caspase-1 contributes to inflammation by two distinct pathways: proteolysis of pro-IL-1beta, and RIP2-dependent activation of NF-kappaB and p38 MAPK mediated by the caspase recruitment domain.
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PMID:Caspase-1 activates nuclear factor of the kappa-enhancer in B cells independently of its enzymatic activity. 1503 21

NF-kappa B1 p105 forms a high-affinity, stoichiometric interaction with TPL-2, a MEK kinase essential for TLR4 activation of the ERK mitogen-activated protein kinase cascade in lipopolysaccharide (LPS)-stimulated macrophages. Interaction with p105 is required to maintain TPL-2 metabolic stability and also negatively regulates TPL-2 MEK kinase activity. Here, affinity purification identified A20-binding inhibitor of NF-kappa B 2 (ABIN-2) as a novel p105-associated protein. Cotransfection experiments demonstrated that ABIN-2 could interact with TPL-2 in addition to p105 but preferentially formed a ternary complex with both proteins. Consistently, in unstimulated bone marrow-derived macrophages (BMDMs), a substantial fraction of endogenous ABIN-2 was associated with both p105 and TPL-2. Although the majority of TPL-2 in these cells was complexed with ABIN-2, the pool of TPL-2 which could activate MEK after LPS stimulation was not, and LPS activation of TPL-2 was found to correlate with its release from ABIN-2. Depletion of ABIN-2 by RNA interference dramatically reduced steady-state levels of TPL-2 protein without affecting levels of TPL-2 mRNA or p105 protein. In addition, ABIN-2 increased the half-life of cotransfected TPL-2. Thus, optimal TPL-2 stability in vivo requires interaction with ABIN-2 as well as p105. Together, these data raise the possibility that ABIN-2 functions in the TLR4 signaling pathway which regulates TPL-2 activation.
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PMID:ABIN-2 forms a ternary complex with TPL-2 and NF-kappa B1 p105 and is essential for TPL-2 protein stability. 1516 88


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