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)

This study demonstrates that the engagement of CD40 results in the activation of the recently described IkappaB kinase (IKK) in a human B cell line. The kinase appears to reside within the cell in a cytosolic signalsome complex consisting of IKK, IkappaB, and an MKP-1-like molecule. While the binding of CD154 to CD40 induces the assembly of a CD40-TRAF receptor complex, IKK is not recruited to this complex. Nonetheless, a functional link between TRAF2 and IKK activity in B cells is demonstrated by the fact that overexpression of TRAF2 constitutively induces IKK activity, NF-kappaB luciferase and Fas expression. Synergy in the activation of IKK and NF-kappaB-dependent gene expression was observed by the simultaneous engagement of the B cell receptor and CD40, establishing an early means for cross-talk between these two B cell activation pathways. This study discusses the sequential biochemical events that transpire upon CD40 engagement by its ligand in human B cells.
 ...
PMID:Activation and regulation of the IkappaB kinase in human B cells by CD40 signaling. 1022 3

Fas-associated death domain protein (FADD), caspase-8-related protein (Casper), and caspase-8 are components of the tumor necrosis factor receptor type 1 (TNF-R1) and Fas signaling complexes that are involved in TNF-R1- and Fas-induced apoptosis. Here we show that overexpression of FADD and Casper potently activates NF-kappaB. In the presence of caspase inhibitors, overexpression of caspase-8 also activates NF-kappaB. A caspase-inactive point mutant, caspase-8(C360S), activates NF-kappaB as potently as wild-type caspase-8, suggesting that caspase-8-induced apoptosis and NF-kappaB activation are uncoupled. NF-kappaB activation by FADD and Casper is inhibited by the caspase-specific inhibitors crmA and BD-fmk, suggesting that FADD- and Casper-induced NF-kappaB activation is mediated by caspase-8. FADD, Casper, and caspase-8-induced NF-kappaB activation are inhibited by dominant negative mutants of TRAF2, NIK, IkappaB kinase alpha, and IkappaB kinase beta. A dominant negative mutant of RIP inhibits FADD- and caspase-8-induced but not Casper-induced NF-kappaB activation. A mutant of Casper and the caspase-specific inhibitors crmA and BD-fmk partially inhibit TNF-R1-, TRADD, and TNF-induced NF-kappaB activation, suggesting that FADD, Casper, and caspase-8 function downstream of TRADD and contribute to TNF-R1-induced NF-kappaB activation. Moreover, activation of caspase-8 results in proteolytic processing of NIK, which is inhibited by crmA. When overexpressed, the processed fragments of NIK do not activate NF-kappaB, and the processed C-terminal fragment inhibits TNF-R1-induced NF-kappaB activation. These data indicate that FADD, Casper, and pro-caspase-8 are parts of the TNF-R1-induced NF-kappaB activation pathways, whereas activated caspase-8 can negatively regulate TNF-R1-induced NF-kappaB activation by proteolytically inactivating NIK.
 ...
PMID:Activation of NF-kappaB by FADD, Casper, and caspase-8. 1075 78

Stimulation of T cells by antigens or mitogens triggers multiple signaling pathways leading to activation of genes encoding interleukin-2 and other growth-regulatory cytokines. The same stimuli also activate the gene encoding an apoptosis-inducing molecule, Fas ligand (FasL), which contributes to activation-induced cell death. It has been proposed that the signaling pathways involved in cytokine gene induction also contribute to activation-induced FasL expression; however, genetic evidence for this proposal is lacking. In the present study, the role of the NF-kappaB signaling pathway in FasL gene expression was examined using a mutant T cell line deficient in an essential NF-kappaB signaling component, IkappaB kinase gamma. These mutant cells have a blockade in signal-induced activation of NF-kappaB but remained normal in the activation of NF-AT and AP-1 transcription factors. Interestingly, the NF-kappaB signaling defect has no effect on mitogen-stimulated FasL gene expression, although it completely blocks the interleukin-2 gene induction. We further demonstrate that NF-kappaB activation is required for protecting T cells from apoptosis induction by mitogens and an agonistic anti-Fas antibody. These genetic results suggest that the NF-kappaB signaling pathway is not required for activation-induced FasL expression but rather mediates cell growth and protection from activation-induced cell death.
 ...
PMID:The NF-kappa B signaling pathway is not required for Fas ligand gene induction but mediates protection from activation-induced cell death. 1083 65

We explored the role of the NF-kappa B pathway in the survival of primary human CD4+ T lymphocytes during CD28 costimulation. Transduction of proliferating CD4+ T cells with a tetracycline-regulated retrovirus encoding for a dominant-interfering, degradation-resistant I-kappaBalpha (inhibitor of kappa B alpha factor) mutant induced apoptosis. Using DNA arrays, we show that Bcl-xL features as a prominent anti-apoptotic member among a number of early CD28-inducible genes. A 1.2-kb segment of the proximal Bcl-xL promoter, linked to a luciferase reporter, responded to CD3/CD28 stimulation in Jurkat cells. Mutation of an NF-kappa B site around -840 decreased, while ectopic expression of I-kappa B kinase-beta (IKK beta) enhanced reporter gene activity. Na+-salicylate and cyclopentenone PGs, direct inhibitors of IKK beta, interfered in the activation of the Bcl-xL promoter and induced apoptosis in CD28-costimulated CD4+ T cells. Moreover, salicylate blocked nuclear localization of NF-kappa B factors that bind to the NF-kappa B binding site in the Bcl-xL promoter, as well as the expression of Bcl-xL protein. HuT-78, a lymphoblastoid T cell line with constitutive NF-kappa B activity, contained elevated levels of Bcl-xL protein and, similar to proliferating CD4+ T cells, was resistant to apoptotic stimuli such as anti-Fas and TNF-alpha. In contrast, the same stimuli readily induced apoptosis in a Jurkat T cell clone with no detectable Bcl-xL expression. Jurkat BMS2 cells also differed from HuT-78 in collapse of mitochondrial membrane potential and superoxide generation in the mitochondrium. Taken together, these data demonstrate that CD3/CD28-induced activation of IKK beta and expression of Bcl-xL promote the survival of primary human CD4+ T lymphocytes.
 ...
PMID:The NF-kappa B cascade is important in Bcl-xL expression and for the anti-apoptotic effects of the CD28 receptor in primary human CD4+ lymphocytes. 1092 51

We have recently shown that 5-Fluorouracil (5-FU) suppresses the transcription factor NF-kappaB in human salivary gland cancer cells (cl-1) by mediating upregulation of IkappaB-alpha expression. However, the precise mechanism involved in this action has not yet been elucidated. IkappaB kinases (IKK-alpha and IKK-beta) are the key components of the IKK complex that mediates activation of NF-kappaB in response to external stimuli such as cytokines. In addition, NF-kappaB-inducing kinase (NIK) and mitogen-activated protein kinase kinase kinase 1 (MEKK-1), both of which are the upstream kinases for the IKKs, interact with and activate the IKKs. Thus, we investigated the molecular mechanisms involved in the suppression of NF-kappaB by 5-FU. Although 5-FU did not affect the expression levels of IKKs, NIK, or MEKK-1, IKK activity in cl-1 cells was suppressed at both 6 h and 12 h after treatment with 2 microgram/ml 5-FU. Moreover, when cells were treated with various concentrations of 5-FU for 12 h, the concentration of 2 microgram/ml efficiently inhibited the IKK activity as compared to 1, 5, or 10 microgram/ml. The expression of Fas-associated death domain-like interleukin 1-converting enzyme-inhibitory protein (FLIP), which acts as an inhibitor of an initiator caspase (caspase-8), was down-regulated by 5-FU treatment in cl-1 cells. Apoptosis, as evidenced by cleavage of poly(ADP-ribose) polymerase through the action of an executioner caspase (caspase-3), was also clearly observed. Thus, these results suggest that 5-FU induction of apoptosis in cl-1 cells may be mediated by suppression of NF-kappaB via inhibition of IKK activity.
 ...
PMID:5-Fluorouracil suppression of NF-KappaB is mediated by the inhibition of IKappab kinase activity in human salivary gland cancer cells. 1126 6

Mechanisms underlying radiation and chemotherapy resistance, the hallmark of human melanoma, are not well understood. Here we demonstrate that expression levels of signal adaptor protein TRAF2 coincide with melanoma resistance to UV-irradiation. Altered TRAF2 signaling by a form of TRAF2, which lacks the ring finger domain (TRAF2DeltaN), increases activities of p38 MAPK, ATF2, and the level of TNFalpha expression. Forced expression of TRAF2DeltaN in HHMSX highly metastatic melanoma cells that lack Fas expression and thus utilize the TNFalpha-TNFR1 as the major apoptotic pathway sensitized cells to UV-induced apoptosis. An over twofold increase in degree of apoptosis was observed in TRAF2DeltaN expressing cells that were treated with actinomycin D, anisomycin or with the radiomimetic drug neocarzinostatin. Sensitization by TRAF2DeltaN is selective since it was not observed in response to either Taxol or cis-platinum treatment. TRAF2DeltaN effects are primarily mediated via p38 since inhibition of p38 reduces, whereas activation of p38 promotes the level of UV-induced apoptosis. Conversely, activation of IKK attenuates the sensitization of melanoma by TRAF2DeltaN, indicating that p38-mediated suppression of NF-kappaB activity is among TRAF2DeltaN effects. Our finding identifies p38, TNFalpha and NF-kappaB among key players that efficiently sensitizes melanoma cells to UV-, ribotoxic (anisomycin) and radiomimetic chemicals-induced programmed cell death in response to aberrant TRAF2 signaling.
 ...
PMID:Expression of ring finger-deleted TRAF2 sensitizes metastatic melanoma cells to apoptosis via up-regulation of p38, TNFalpha and suppression of NF-kappaB activities. 1140 19

Nuclear Factor-kappaB (NF-kappaB) is known to be one of the key regulators of genes involved in survival signaling. The purpose of this study is to investigate the role of NF-kappaB activity in signaling events related to cell survival in hepatocytes, which has been supposed to be one of the most sensitive organs against Fas-induced cytotoxicity. The functions of NF-kappaB activity on Fas-mediated apoptosis in different human cell lines were investigated by a magnetic concentration system for cells with exogenous protein production. We demonstrated that the activation of NF-kappaB was triggered by anti-Fas treatment in hepatocyte derived cell lines, HepG2 and Huh-7 cells. Overexpression of kinase-inactive NF-kappaB-inducing kinase (NIK) and IkappaB kinase (IKK) inhibited the activation of NF-kappaB introduced by anti-Fas treatment in these cells. Notably, inactivation of NF-kappaB by the production of IkappaB-alpha protein made these cells more susceptible to apoptosis induced by Fas stimulation. In contrast, transient expression of NIK showed a suppressive effect on Fas-mediated apoptosis in the same cell lines. These findings suggest the involvement of NF-kappaB in suppression of Fas-mediated apoptosis in human hepatocyte derived cell lines, in which concomitant activation of this transcriptional factor was observed through the stimulation of Fas signaling.
 ...
PMID:Regulation of Fas-mediated apoptosis by NF-kappaB activity in human hepatocyte derived cell lines. 1149 24

Stimulation of cells with tumor necrosis factor alpha (TNFalpha) triggers NF-kappaB1 p105 proteolysis, releasing associated Rel subunits to translocate into the nucleus and modulate target gene expression. Phosphorylation of serine 927 within the p105 PEST region by the IkappaB kinase (IKK) complex is required to promote p105 proteolysis in response to TNFalpha stimulation. In this study, the role of the p105 death domain (DD) in signal-induced p105 proteolysis is investigated. Endogenous p105 is shown to interact with the IKK complex in HeLa cells, and transient transfection experiments in 293 cells indicate that each of the catalytic components of the IKK complex, IKK1 and IKK2, can bind to p105. Interaction of p105 with both IKK1 and IKK2 is substantially reduced by deletion of the p105 DD or introduction of a specific point mutation (L841A) into the p105 DD homologous to the lpr mutation in Fas. Phosphorylation of immunoprecipitated p105 on serine 927 by purified recombinant IKK1 or IKK2 protein in vitro is dramatically reduced in both DD mutants relative to wild type. Furthermore, both of the DD mutations significantly impair the ability of low concentrations of IKK2 to induce p105 serine 927 phosphorylation and proteolysis in transiently transfected 3T3 cells. However, high levels of transiently expressed IKK2 bypass the requirement for the p105 DD to induce p105 serine 927 phosphorylation. Finally, p105 serine 927 phosphorylation by the endogenous IKK complex after TNFalpha stimulation and subsequent p105 proteolysis is blocked in both p105 DD mutants when stably expressed in HeLa cells. Thus, the p105 DD acts as a docking site for IKK, increasing its local concentration in the vicinity of the p105 PEST region and facilitating efficient serine 927 phosphorylation.
 ...
PMID:The death domain of NF-kappa B1 p105 is essential for signal-induced p105 proteolysis. 1197 29

In this study, we examined the role of the nuclear factor-kappaB (NF-kappaB)-inducing kinase (NIK) in distinct signaling pathways leading to NF-kappaB activation. We show that a dominant-negative form of NIK (dnNIK) delivered by adenoviral (Ad5dnNIK) vector inhibits Fas-induced IkappaBalpha phosphorylation and NF-kappaB-dependent gene expression in HT-29 and HeLa cells. Interleukin (IL)-1beta- and tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation and kappaB-dependent gene expression are inhibited in HeLa cells but not in Ad5dnNIK-infected HT-29 cells. Moreover, Ad5dnNIK failed to sensitize HT-29 cells to TNF-alpha-induced apoptosis at an early time point. However, cytokine- and Fas-induced signals to NF-kappaB are finally integrated by the IkappaB kinase (IKK) complex, since IkappaBalpha phosphorylation, NF-kappaB DNA binding activity, and IL-8 gene expression were strongly inhibited in HT-29 and HeLa cells overexpressing dominant-negative IKKbeta (Ad5dnIKKbeta). Our findings support the concept that cytokine signaling to NF-kappaB is redundant at the level of NIK. In addition, this study demonstrates for the first time the critical role of NIK and IKKbeta in Fas-induced NF-kappaB signaling cascade.
 ...
PMID:Differential requirement for NF-kappaB-inducing kinase in the induction of NF-kappaB by IL-1beta, TNF-alpha, and Fas. 1205 4

Signals emanating from receptors of the tumor necrosis factor/nerve growth factor (TNF/NGF) family control practically all aspects of immune defense and, as such, constitute potential targets for therapeutic intervention through rational drug design. Indeed, arrest of these signals by blocking ligand-receptor interactions enables effective suppression of a variety of activities that are implicated in various pathologies, such as T and B lymphocyte activation and growth, inflammation, fibroblast proliferation, and cell death. To be therapeutically useful, however, inhibition of signaling should be restricted by determinants of specificity, at least to the same degree observed when blocking activation of individual receptors. In spite of their broad range of functions, receptors of the TNF/NGF family are known to activate just a few signaling pathways. Of these, the most extensively studied are the activation of the caspase protease cascade, which leads to cell death, and the activation of NF-kappaB (nuclear factor-kappaB) transcription factors through protein phosphorylation cascades. Until recently, most studies of the two pathways have solely focused on the core signaling complexes that are shared by the different receptors: death-inducing complexes containing the cysteine proteases caspase-8 and caspase-10, bound to the adapter protein MORT1/FADD (mediator of receptor-induced toxicity/Fas-associated DD protein), and the NF-kappaB-activating complex, composed of the protein kinases IKK1 (IkappaB kinase 1) and IKK2 (IkappaB kinase 2) and the regulatory subunit NEMO (NF-kappaB essential modulator; the 'IKK signalosome'). Knowledge has begun to emerge of additional molecules and mechanisms that affect these basic signaling complexes and impose specificity on their function.
 ...
PMID:How are the regulators regulated? The search for mechanisms that impose specificity on induction of cell death and NF-kappaB activation by members of the TNF/NGF receptor family. 1211 Jan 39


1 2 3 Next >>