Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.10 (IKK)
 4,900 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NF-kappaB comprises a family of cellular transcription factors that are involved in the inducible expression of a variety of cellular genes that regulate the inflammatory response. NF-kappaB is sequestered in the cytoplasm by inhibitory proteins, I(kappa)B, which are phosphorylated by a cellular kinase complex known as IKK. IKK is made up of two kinases, IKK-alpha and IKK-beta, which phosphorylate I(kappa)B, leading to its degradation and translocation of NF-kappaB to the nucleus. IKK kinase activity is stimulated when cells are exposed to the cytokine TNF-alpha or by overexpression of the cellular kinases MEKK1 and NIK. Here we demonstrate that the anti-inflammatory agents aspirin and sodium salicylate specifically inhibit IKK-beta activity in vitro and in vivo. The mechanism of aspirin and sodium salicylate inhibition is due to binding of these agents to IKK-beta to reduce ATP binding. Our results indicate that the anti-inflammatory properties of aspirin and salicylate are mediated in part by their specific inhibition of IKK-beta, thereby preventing activation by NF-kappaB of genes involved in the pathogenesis of the inflammatory response.
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PMID:The anti-inflammatory agents aspirin and salicylate inhibit the activity of I(kappa)B kinase-beta. 981 96

Interleukin-1 (IL-1) and tumor necrosis factor (TNF-alpha) stimulate transcription factors AP-1 and NF-kappaB through activation of the MAP kinases JNK and p38 and the IkappaB kinase (IKK), respectively. The TNF-alpha and IL-1 signals are transduced through TRAF2 and TRAF6, respectively. Overexpressed TRAF2 or TRAF6 activate JNK, p38, or IKK in the absence of extracellular stimulation. By replacing the carboxy-terminal TRAF domain of TRAF2 and TRAF6 with repeats of the immunophilin FKBP12, we demonstrate that their effector domains are composed of their amino-terminal Zn and RING fingers. Oligomerization of the TRAF2 effector domain results in specific binding to MEKK1, a protein kinase capable of JNK, p38, and IKK activation, and induction of TNF-alpha and IL-1 responsive genes. TNF-alpha also enhances the binding of native TRAF2 to MEKK1 and stimulates the kinase activity of the latter. Thus, TNF-alpha and IL-1 signaling is based on oligomerization of TRAF2 and TRAF6 leading to activation of effector kinases.
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PMID:Signaling by proinflammatory cytokines: oligomerization of TRAF2 and TRAF6 is sufficient for JNK and IKK activation and target gene induction via an amino-terminal effector domain. 1034 18

NF-kappa B is a key regulator of inflammatory gene transcription and is activated in the rheumatoid arthritis (RA) synovium. In resting cells, NF-kappa B is retained as an inactive cytoplasmic complex by its inhibitor, I kappa B. Phosphorylation of I kappa B targets it for proteolytic degradation, thereby releasing NF-kappa B for nuclear translocation. Recently, two related I kappa B kinases (IKK-1 and IKK-2) were identified in immortalized cell lines that regulate NF-kappa B activation by initiating I kappa B degradation. To determine whether IKK regulates NF-kappa B in primary cells isolated from a site of human disease, we characterized IKK in cultured fibroblast-like synoviocytes (FLS) isolated from synovium of patients with RA or osteoarthritis. Immunoreactive IKK protein was found to be abundant in both RA and osteoarthritis FLS by Western blot analysis. Northern blot analysis showed that IKK-1 and IKK-2 genes were constitutively expressed in all FLS lines. IKK function in FLS extracts was determined by measuring phosphorylation of recombinant I kappa B in vitro. IKK activity in both RA and osteoarthritis FLS was strongly induced by TNF-alpha and IL-1 in a concentration-dependent manner. Activity was significantly increased within 10 min of stimulation and declined to near basal levels within 80 min. Activation of IKK in FLS was accompanied by phosphorylation and degradation of endogenous I kappa B alpha as determined by Western blot analysis. Concomitant activation and nuclear translocation of NF-kappa B was documented by EMSA and immunohistochemistry. Transfection with a dominant negative IKK-2 mutant prevented TNF-alpha-mediated NF-kappa B nuclear translocation, whereas a dominant negative IKK-1 mutant had no effect. This is the first demonstration that IKK-2 is a pivotal regulator of NF-kappa B in primary human cells.
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PMID:NF-kappa B regulation by I kappa B kinase in primary fibroblast-like synoviocytes. 1038 45

The IkappaB kinases (IKKs) lie downstream of the NF-kappaB-inducing kinase (NIK) and activate NF-kappaB by phosphorylation of IkappaBalpha. This leads to IkappaBalpha degradation and release of NF-kappaB. In U937 monocytic cells, interleukin (IL)-1beta (1 ng/ml) and tumor necrosis factor (TNF)-alpha; 10 ng/ml) induced kappaB-dependent transcription equally. However, IKK activity was strongly induced by TNF-alpha but not by IL-1beta. This was consistent with IkappaBalpha phosphorylation and degradation, yet TNF-alpha-induced NF-kappaB DNA binding was only 30-40% greater than for IL-1beta. This was not explained by degradation of IkappaBbeta, IkappaBepsilon, or p105 nor nuclear translocation of NF-kappaB. IkappaBalpha complexes or degradation-independent release of NF-kappaB. Dominant negative (NIK) repressed TNF-alpha and IL-1beta-induced kappaB-dependent transcription by approximately 60% and approximately 35%, respectively. These data reveal an imprecise relationship between IKK activation, IkappaBalpha degradation, and NF-kappaB DNA binding, suggesting the existence of additional mechanisms that regulate NF-kappaB activation. Finally, the lack of correlation between DNA binding and transcriptional activation plus the fact that PP1 and genistein both inhibited kappaB-dependent transcription without affecting DNA binding activity demonstrate the existence of regulatory steps downstream of NF-kappaB DNA binding. Therapeutically these data are important as inhibition of the NIK-IKK-IkappaBalpha cascade may not produce equivalent reductions in NF-kappaB-dependent gene expression.
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PMID:Differential IkappaB kinase activation and IkappaBalpha degradation by interleukin-1beta and tumor necrosis factor-alpha in human U937 monocytic cells. Evidence for additional regulatory steps in kappaB-dependent transcription. 1039 45

The NF-kappaB precursor p105 has dual functions: cytoplasmic retention of attached NF-kappaB proteins and generation of p50 by processing. It is poorly understood whether these activities of p105 are responsive to signalling processes that are known to activate NF-kappaB p50-p65. We propose a model that p105 is inducibly degraded, and that its degradation liberates sequestered NF-kappaB subunits, including its processing product p50. p50 homodimers are specifically bound by the transcription activator Bcl-3. We show that TNFalpha, IL-1beta or phorbolester (PMA) trigger rapid formation of Bcl-3-p50 complexes with the same kinetics as activation of p50-p65 complexes. TNF-alpha-induced Bcl-3-p50 formation requires proteasome activity, but is independent of p50-p65 released from IkappaBalpha, indicating a pathway that involves p105 proteolysis. The IkappaB kinases IKKalpha and IKKbeta physically interact with p105 and inducibly phosphorylate three C-terminal serines. p105 is degraded upon TNF-alpha stimulation, but only when the IKK phospho-acceptor sites are intact. Furthermore, a p105 mutant, lacking the IKK phosphorylation sites, acts as a super-repressor of IKK-induced NF-kappaB transcriptional activity. Thus, the known NF-kappaB stimuli not only cause nuclear accumulation of p50-p65 heterodimers but also of Bcl-3-p50 and perhaps further transcription activator complexes which are formed upon IKK-mediated p105 degradation.
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PMID:NF-kappaB p105 is a target of IkappaB kinases and controls signal induction of Bcl-3-p50 complexes. 1046 55

Recent investigations have elucidated the cytokine-induced NF-kappaB activation pathway. IkappaB kinase (IKK) phosphorylates inhibitors of NF-kappaB (IkappaBs). The phosphorylation targets them for rapid degradation through a ubiquitin-proteasome pathway, allowing the nuclear translocation of NF-kappaB. We have examined the possibility that IKK can phosphorylate the p65 NF-kappaB subunit as well as IkappaB in the cytokine-induced NF-kappaB activation. In the cytoplasm of HeLa cells, the p65 subunit was rapidly phosphorylated in response to TNF-alpha in a time dependent manner similar to IkappaB phosphorylation. In vitro phosphorylation with GST-fused p65 showed that a p65 phosphorylating activity was present in the cytoplasmic fraction and the target residue was Ser-536 in the carboxyl-terminal transactivation domain. The endogenous IKK complex, overexpressed IKKs, and recombinant IKKbeta efficiently phosphorylated the same Ser residue of p65 in vitro. The major phosphorylation site in vivo was also Ser-536. Furthermore, activation of IKKs by NF-kappaB-inducing kinase induced phosphorylation of p65 in vivo. Our finding, together with previous observations, suggests dual roles for IKK complex in the regulation of NF-kappaB.IkappaB complex.
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PMID:IkappaB kinases phosphorylate NF-kappaB p65 subunit on serine 536 in the transactivation domain. 1052 9

The activation of NF-kappaB by receptors in the tumor necrosis factor (TNF) receptor and Toll/interleukin-1 (IL-1) receptor families requires the TRAF family of adaptor proteins. Receptor oligomerization causes the recruitment of TRAFs to the receptor complex, followed by the activation of a kinase cascade that results in the phosphorylation of IkappaB. TANK is a TRAF-binding protein that can inhibit the binding of TRAFs to receptor tails and can also inhibit NF-kappaB activation by these receptors. However, TANK also displays the ability to stimulate TRAF-mediated NF-kappaB activation. In this report, we investigate the mechanism of the stimulatory activity of TANK. We find that TANK interacts with TBK1 (TANK-binding kinase 1), a novel IKK-related kinase that can activate NF-kappaB in a kinase-dependent manner. TBK1, TANK and TRAF2 can form a ternary complex, and complex formation appears to be required for TBK1 activity. Kinase-inactive TBK1 inhibits TANK-mediated NF-kappaB activation but does not block the activation mediated by TNF-alpha, IL-1 or CD40. The TBK1-TANK-TRAF2 signaling complex functions upstream of NIK and the IKK complex and represents an alternative to the receptor signaling complex for TRAF-mediated activation of NF-kappaB.
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PMID:NF-kappaB activation by a signaling complex containing TRAF2, TANK and TBK1, a novel IKK-related kinase. 1058 Dec 43

CD40 belongs to the tumor necrosis factor (TNF) receptor family. CD40 signaling involves the recruitment of TNF receptor-associated factors (TRAFs) to its cytoplasmic domain. We have identified a novel intracellular CD40-binding protein termed TRAF and TNF receptor-associated protein (TTRAP) that also interacts with TNF-R75 and CD30. The region of the CD40 cytoplasmic domain that is required for TTRAP association overlaps with the TRAF6 recognition motif. Association of TTRAP with CD40 increases profoundly in response to treatment of cells with CD40L. Interestingly, TTRAP also associates with TRAFs, with the highest affinity for TRAF6. In transfected cells, TTRAP inhibits in a dose-dependent manner the transcriptional activation of a nuclear factor-kappaB (NF-kappaB)-dependent reporter mediated by CD40, TNF-R75 or Phorbol 12-myristate 13-acetate (PMA) and to a lesser extent by TRAF2, TRAF6, TNF-alpha, or interleukin-1beta (IL-1beta). TTRAP does not affect stimulation of NF-kappaB induced by overexpression of the NF-kappaB-inducing kinase (NIK), the IkappaB kinase alpha (IKKalpha), or the NF-kappaB subunit P65/RelA, suggesting it acts upstream of the latter proteins. Our results indicate that we have isolated a novel regulatory factor that is involved in signal transduction by distinct members of the TNF receptor family.
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PMID:TTRAP, a novel protein that associates with CD40, tumor necrosis factor (TNF) receptor-75 and TNF receptor-associated factors (TRAFs), and that inhibits nuclear factor-kappa B activation. 1076 46

Interleukin (IL)-1beta signals through various adapter proteins and kinases that lead to activation of numerous downstream targets, including the transcription factors including NF-kappaB. In this study, we analyzed and characterized the effect of the differentiation of intestinal epithelial cells on IL-1beta-mediated NF-kappaB activation and IL-8 gene expression. We report that IL-8 mRNA accumulation and protein secretion were down-regulated in IL-1beta- and lipopolysaccharide-stimulated differentiated HT-29 cells (HT-29/MTX, where MTX is methotrexate) compared with undifferentiated cells (HT-29/p), whereas no differential effects were found following tumor necrosis factor (TNF)-alpha or phorbol myristate acetate stimulation. Cross-linking and affinity binding studies reveal that IL-1beta exclusively binds the type I receptor (IL-1RI) and not IL-1RII in both HT-29/p and HT-29/MTX cells. IL-1beta-mediated IkappaB kinase and c-Jun N-terminal kinase (JNK) activity were both diminished in differentiated HT-29 cells. DNA binding activity in differentiated HT-29 cells relative to HT-29/p cells was strongly reduced following IL-1beta exposure but not after TNF-alpha stimulation. The proximal IL-1 signaling molecule IL-1 receptor-associated kinase was not degraded in IL-1beta-stimulated HT-29 cells, in contrast to Caco-2 cells. kappaB-luciferase reporter gene activity was 16-fold higher following TNF receptor-associated factor-6 transfection after IL-1beta stimulation in HT-29/MTX cells. We conclude that cellular differentiation of HT-29 cells selectively impairs the IL-1beta signaling pathway inhibiting both NF-kappaB and JNK activity in response to IL-1beta. This relative unresponsiveness to IL-1beta may represent an important regulatory mechanism of differentiated intestinal epithelial cells.
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PMID:Cellular differentiation causes a selective down-regulation of interleukin (IL)-1beta-mediated NF-kappaB activation and IL-8 gene expression in intestinal epithelial cells. 1076 57

The inflammatory cytokine, TNF-alpha, induces IL-8 gene transcription via a mechanism involving proteasome-mediated IkappaBalpha degradation and NF-kappaB activation. Here, we investigated whether arsenic, which has been shown to inhibit the ubiquitin-proteasome pathway, could inhibit TNF-alpha-mediated increases in IL-8 expression. Using RT-PCR, we show that the addition of TNF-alpha to human bronchial epithelial (BEAS 2B) or embryonic kidney (HEK293) cells resulted in increased steady-state levels of IL-8 mRNA. This was preceded by a rapid decrease in cellular IkappaBalpha levels, as demonstrated by Western analysis, and an increase in nuclear levels of NF-kappaB, as demonstrated by gel shift analysis. Further demonstrating the activation of NF-kappaB, TNF-alpha induced the transcription of a NF-kappaB-dependent reporter gene. Exposing the cells to 500 microM arsenite, prior to adding TNF-alpha, completely inhibited IkappaBalpha degradation, NF-kappaB translocation, NF-kappaB-dependent gene transcription, and transcription of the endogenous gene for IL-8. In comparison with the proteasome inhibitor MG-132, which does not affect the phosphorylation and ubiquitination of IkappaBalpha, arsenite inhibited the phosphorylation of IkappaBalpha. Furthermore, arsenite directly blocked the activity of IKK, the kinase responsible for IkappaBalpha phosphorylation. These studies demonstrate that high levels of arsenic may inhibit NF-kappaB-mediated gene transcription by specifically blocking IKK activity, thereby limiting the phosphorylation and subsequent degradation of the NF-kappaB inhibitor, IkappaBalpha.
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PMID:Arsenic inhibits NF-kappaB-mediated gene transcription by blocking IkappaB kinase activity and IkappaBalpha phosphorylation and degradation. 1077 61


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