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)

The zinc finger protein A20 is a tumor necrosis factor (TNF)- and interleukin 1 (IL-1)-inducible protein that negatively regulates nuclear factor-kappa B (NF-kappaB)-dependent gene expression. However, the molecular mechanism by which A20 exerts this effect is still unclear. We show that A20 does not inhibit TNF- induced nuclear translocation and DNA binding of NF-kappaB, although it completely prevents the TNF- induced activation of an NF-kappaB-dependent reporter gene, as well as TNF-induced IL-6 and granulocyte macrophage-colony stimulating factor gene expression. Moreover, NF-kappaB activation induced by overexpression of the TNF receptor-associated proteins TNF receptor-associated death domain protein (TRADD), receptor interacting protein (RIP), and TNF recep- tor-associated factor 2 (TRAF2) was also inhibited by expression of A20, whereas NF-kappaB activation induced by overexpression of NF-kappaB-inducing kinase (NIK) or the human T cell leukemia virus type 1 (HTLV-1) Tax was unaffected. These results demonstrate that A20 inhibits NF-kappaB-dependent gene expression by interfering with a novel TNF-induced and RIP- or TRAF2-mediated pathway that is different from the NIK-IkappaB kinase pathway and that is specifically involved in the transactivation of NF-kappaB. Via yeast two-hybrid screening, we found that A20 binds to a novel protein, ABIN, which mimics the NF-kappaB inhibiting effects of A20 upon overexpression, suggesting that the effect of A20 is mediated by its interaction with this NF-kappaB inhibiting protein, ABIN.
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PMID:The zinc finger protein A20 inhibits TNF-induced NF-kappaB-dependent gene expression by interfering with an RIP- or TRAF2-mediated transactivation signal and directly binds to a novel NF-kappaB-inhibiting protein ABIN. 1038 26

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

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by persistent joint swelling and progressive destruction of cartilage and bone. Current RA treatments are largely empirical in origin and their precise mechanism of action is uncertain. Increasing evidence shows that chronic inflammatory diseases such as RA are caused by prolonged production of proinflammatory cytokines including tumor necrosis factor (TNF) and interleukin 1 (IL-1). The nuclear factor kappaB (NF-kappaB) plays an essential role in transcriptional activation of TNF and IL-1. NF-kappaB is induced by many stimuli including TNF and IL-1, forming a positive regulatory cycle that may amplify and maintain RA disease process. NF-kappaB and enzymes involved in its activation can be a target for anti-inflammatory treatment. Aspirin and sodium salicylate inhibit activation of NF-KB by blocking IkappaB kinase, a key enzyme in NF-kappaB activation. Glucocorticoids suppress expression of inflammatory genes by binding glucocorticoid receptor with NF-kappaB, and increasing expression of inhibitory protein of NF-kappaB, IkappaBalpha. Sulfasalazine and gold compounds also inhibit NF-kappaB activation. Continuing advances in our understanding of action mechanism of antirheumatic agents will benefit the future development of RA regimens with greater efficacy and less toxicity.
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PMID:Nuclear factor kappaB (NF-kappaB) pathway as a therapeutic target in rheumatoid arthritis. 1040 63

The adenovirus E1A protein has been implicated in increasing cellular susceptibility to apoptosis induced by tumor necrosis factor (TNF); however, its mechanism of action is still unknown. Since activation of nuclear factor kappaB (NF-kappaB) has been shown to play an anti-apoptotic role in TNF-induced apoptosis, we examined apoptotic susceptibility and NF-kappaB activation induced by TNF in the E1A transfectants and their parental cells. Here, we reported that E1A inhibited activation of NF-kappaB and rendered cells more sensitive to TNF-induced apoptosis. We further showed that this inhibition was through suppression of IkappaB kinase (IKK) activity and IkappaB phosphorylation. Moreover, deletion of the p300 and Rb binding domains of E1A abolished its function in blocking IKK activity and IkappaB phosphorylation, suggesting that these domains are essential for the E1A function in down-regulating IKK activity and NF-kappaB signaling. However, the role of E1A in inhibiting IKK activity might be indirect. Nevertheless, our results suggest that inhibition of IKK activity by E1A is an important mechanism for the E1A-mediated sensitization of TNF-induced apoptosis.
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PMID:E1A sensitizes cells to tumor necrosis factor-induced apoptosis through inhibition of IkappaB kinases and nuclear factor kappaB activities. 1041 49

Flavonoids are a group of naturally-occurring phenolic compounds in the plant kingdom, and many flavonoids are found with vascular protective properties. Nevertheless how the protective response is exerted by flavonoids is not well characterized. In view of the nuclear factor-kappaB (NFkappaB) may play a central role in the initiation of atherosclerosis, prevention of the activation of NFkappaB represents an important role in protecting vascular injury. In this study, the effects of flavonoids on NFkappaB/inhibitor-kappaB (IkappaB) system in ECV304 cells activated with tumor necrosis factor-alpha (TNFalpha) were examined. We investigated the inhibitory action of six flavonoids on IkappaB kinase (IKK) activity, an enzyme recently found to phosphorylate critical serine residues of IkappaB for degradation. Of six flavonoids tested, myricetin was found to strongly inhibit IKK kinase activity, and prevent the degradation of IkappaBalpha and IkappaBbeta in activated endothelial cells. Furthermore, myricetin was also found to inhibit NFkappaB activity correlated with suppression of monocyte adhesion to ECV304 cells. Therefore we conclude that flavonoids may be of therapeutic value for vascular disease through down regulation of NFkappaB/IkappaB system.
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PMID:Suppression of TNFalpha-mediated NFkappaB activity by myricetin and other flavonoids through downregulating the activity of IKK in ECV304 cells. 1044 Sep 30

The inflammatory mediators lipopolysaccharide (LPS) and tumor necrosis factor (TNF) are potent activators of NF-kappaB. This study compared the effect of these stimuli on endogenous IkappaB kinase (IKK) signalsome activation and IkappaB phosphorylation/proteolysis in human monocytic cells and investigated the role of the signalsome proteins IKK-alpha, IKK-beta, NF-kappaB-inducing kinase (NIK), IKK-gamma (NF-kappaB essential modulator), and IKK complex-associated protein. Kinase assays showed that TNF elicited a rapid but short-lived induction of IKK activity with a 3-fold greater effect on IKK-alpha than on IKK-beta, peaking at 5 min. In contrast, LPS predominantly stimulated IKK-beta activity, which slowly increased, peaking at 30 min. A second peak was observed at a later time point following LPS stimulation, which consisted of both IKK-alpha and -beta activity. The endogenous levels of the signalsome components were unaffected by stimulation. Furthermore, our studies showed association of the IKK-alpha/beta heterodimer with NIK, IkappaB-alpha and -epsilon in unstimulated cells. Exposure to LPS or TNF led to differential patterns of IkappaB-alpha and IkappaB-epsilon disappearance from and reassembly with the signalsome, whereas IKK-alpha, IKK-beta, and NIK remained complex-associated. NIK cannot phosphorylate IkappaB-alpha directly, but it appears to be a functionally important subunit, because mutated NIK inhibited stimulus-induced kappaB-dependent transcription more effectively than mutated IKK-alpha or -beta. Overexpression of IKK complex-associated protein inhibited stimulus-mediated transcription, whereas NF-kappaB essential modulator enhanced it. The understanding of LPS- and TNF-induced signaling may allow the development of specific strategies to treat sepsis-associated disease.
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PMID:Differential effects of lipopolysaccharide and tumor necrosis factor on monocytic IkappaB kinase signalsome activation and IkappaB proteolysis. 1045 28

Endotoxic lipopolysaccharide (LPS) is a proinflammatory agonist produced by gram-negative bacteria and a contributor to the majority of the 400,000 septic shock cases recorded annually in US hospitals. The primary target cells for LPS are monocytes and macrophages. Their response consists of massive production of proinflammatory cytokines, reactive oxygen- and nitrogen-intermediates, procoagulants, and cell adhesion molecules. In turn, expression of these LPS-responsive factors contributes to collapse of the circulatory system, to disseminated intravascular coagulation, and to a 30% mortality rate. A common intracellular mechanism responsible for the expression of septic shock genes in monocytes and macrophages involves the activation of NF-kappaB. This transcription factor is regulated by a family of structurally related inhibitors including IkappaBalpha, IkappaBbeta, and IkappaBepsilon, which trap NF-kappaB in the cytoplasm. In this report, the investigators show that LPS derived from different gram-negative bacteria activates cytokine-responsive IkappaB kinases containing catalytic subunits termed IKKalpha (IKK1) and IKKbeta (IKK2). The kinetics of IKKalpha and IKKbeta activation in LPS-stimulated human monocytic cells differ from that recorded on their stimulation with tumor necrosis factor-alpha, thereby implying a distinct activation mechanism. LPS-activated IKK complexes phosphorylate all 3 inhibitors of NF-kappaB: IkappaBalpha, IkappaBbeta, and IkappaBepsilon. Moreover, LPS activates IKKbeta preferentially, relative to IKKalpha. Thus, IKK complex constitutes the main intracellular target for LPS-induced NF-kappaB signaling to the nucleus in human monocytic cells to activate genes responsible for septic shock.
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PMID:IkappaB kinase complex is an intracellular target for endotoxic lipopolysaccharide in human monocytic cells. 1047 96

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family that interacts with several receptors, including TRAIL-R1, TRAIL-R2, and TRAIL-R4. TRAIL-R1 and TRAIL-R2 can induce apoptosis of cancer cells and activate the transcription factor NF-kappaB. TRAIL-R4 can activate NF-kappaB and protect cells from TRAIL-induced apoptosis. Here we show that TRAIL-R1-, TRAIL-R2-, and TRAIL-R4-induced NF-kappaB activation are mediated by a TRAF2-NIK-IkappaB kinase alpha/beta signaling cascade but is MEKK1 independent. TRAIL receptors also activate the protein kinase JNK. JNK activation by TRAIL-R1 is mediated by a TRAF2-MEKK1-MKK4 but not the TRAF2-NIK/IkappaB kinase alpha/beta signaling pathway. We also show that activation of NF-kappaB or overexpression of TRAIL-R4 does not protect TRAIL-R1-induced apoptosis. Moreover, inhibition of NF-kappaB by IkappaBalpha sensitizes cells to tumor necrosis factor- but not TRAIL-induced apoptosis. These findings suggest that TRAIL receptors induce apoptosis, NF-kappaB and JNK activation through distinct signaling pathways, and activation of NF-kappaB is not sufficient for protecting cells from TRAIL-induced apoptosis.
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PMID:Tumor necrosis factor-related apoptosis-inducing ligand receptors signal NF-kappaB and JNK activation and apoptosis through distinct pathways. 1052 44

The transcription factor nuclear factor kappaB (NF-kappaB) coordinates the activation of numerous genes in response to pathogens and proinflammatory cytokines and is, therefore, pivotal in the development of acute and chronic inflammatory diseases. In its inactive state, NF-kappaB is constitutively present in the cytoplasm as a p50-p65 heterodimer bound to its inhibitory protein IkappaB. Proinflammatory cytokines, such as tumor necrosis factor (TNF), activate NF-kappaB by stimulating the activity of the IkappaB kinases (IKKs) which phosphorylate IkappaBalpha on serine residues 32 and 36, targeting it for rapid degradation by the 26 S proteasome. This enables the release and nuclear translocation of the NF-kappaB complex and activation of gene transcription. Interleukin-10 (IL-10) is a pleiotropic cytokine that controls inflammatory processes by suppressing the production of proinflammatory cytokines which are known to be transcriptionally controlled by NF-kappaB. Conflicting data exists on the effects of IL-10 on TNF- and LPS-induced NF-kappaB activity in human monocytes and the molecular mechanisms involved have not been elucidated. In this study, we show that IL-10 functions to block NF-kappaB activity at two levels: 1) through the suppression of IKK activity and 2) through the inhibition of NF-kappaB DNA binding activity. This is the first evidence of an anti-inflammatory protein inhibiting IKK activity and demonstrates that IKK is a logical target for blocking inflammatory diseases.
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PMID:Interleukin-10 signaling blocks inhibitor of kappaB kinase activity and nuclear factor kappaB DNA binding. 1054 12

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


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