Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.10 (IKK)
4,900 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mononuclear phagocytes play a major role in immune and inflammatory responses. Bacterial lipopolysaccharide (LPS) induces monocytes to express a variety of genes by activating the NF-kappaB/Rel transcription factor family. Recently, we have reported that the tumor necrosis factor and interleukin 1 signaling pathways activate two kinases, IKK1 and IKK2. Phosphorylation of the IkappaB cytoplasmic inhibitors, IkappaBalpha, IkappaBbeta, and IkappaBepsilon, by these kinases triggers proteolytic degradation and the release of NF-kappaB/Rel proteins into the nucleus. At present, the role of the IKKs in LPS signaling has not been investigated. Here, we report that LPS induces IKK activity in human monocytes and THP-1 monocytic cells. The kinetics of activation of kinase activity in monocytic cells are relatively slow with maximal activity observed at 60 min, which coincides with the degradation of IkappaBs and the nuclear translocation of NF-kappaB. In transfection experiments, overexpression of wild type IKK1, a dominant negative mutant IKK1 (K44M), or wild type IKK2 did not affect LPS-induced kappaB-dependent transcription in monocytic cells. In contrast, a dominant negative mutant of IKK2 inhibited LPS induction of kappaB-dependent transcription in a dose-dependent manner. These results indicate that LPS induction of kappaB-dependent gene expression in human monocytic cells requires activation of IKK2.
...
PMID:Role of IKK1 and IKK2 in lipopolysaccharide signaling in human monocytic cells. 980 6

Activation of the transcription factor NF-kappaB depends on the specific dual phosphorylation of its inhibitor protein IkappaB by the homologous cytokine-inducible IkappaB kinases 1 and 2 (IKK1/2). Various IkappaB isoforms exist: IkappaBalpha, IkappaBbeta1/2 (two alternative splice variants), and IkappaBepsilon. However, the individual relevance and the specific regulation of these isoforms is not well-understood. We have studied the direct interaction of recombinant IkappaBalpha, IkappaBbeta1, IkappaBbeta2, and IkappaBepsilon with the recombinant homodimeric IKK2. Fluorescence-based active site titration revealed that each IKK2 dimer contains two binding sites for IkappaB. By using surface plasmon resonance analysis, we found that all IkappaB proteins interact with the IKK2 dimer following a noncooperative binding mechanism. Further, the four IkappaB proteins bind to the kinase with equilibrium dissociation constants (KD) in the range of 50-300 nM; the association rate constants for all IkappaB isoforms with IKK2 were between 6.0 x 10(3) and 22.5 x 10(3) M-1 s-1, and the dissociation rate constants were between 1.25 x 10(-3) and 1.75 x 10(-3) s-1. This high-affinity binding suggests that the previously observed preassociation of all analyzed IkappaB proteins with the biochemically purified 700 kDa IkappaB kinase (IKK) complex is based on a direct enzyme-substrate association between the various IkappaB isoforms and the IKK proteins. The apparent catalytic efficiencies (kcat/KM) of IKK2 for IkappaBalpha, IkappaBbeta1, IkappaBbeta2, and IkappaBepsilon were 22 x 10(3), 10 x 10(3), 5.4 x 10(3), and 8.5 x 10(3) s-1 M-1, respectively, with KM values ranging between 1.7 x 10(-6) and 3.2 x 10(-6) M and kcat values ranging between 1.5 x 10(-2) and 3.7 x 10(-2) s-1. The relative affinities and catalytic efficiencies of IKK2 for the IkappaB isoforms were also reflected by the kinetics observed for the TNF-induced, phosphorylation-dependent degradation of the alpha, beta1, beta2, and epsilon isoforms of IkappaB in human umbilical vein endothelial cells. Therefore, differential regulation of the IkappaB isoforms in some cell types is not a direct result of the IKK activity, but appears to be due to parallel events.
...
PMID:The kinetics of association and phosphorylation of IkappaB isoforms by IkappaB kinase 2 correlate with their cellular regulation in human endothelial cells. 1032 Mar 52

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.
...
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

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.
...
PMID:IkappaB kinase complex is an intracellular target for endotoxic lipopolysaccharide in human monocytic cells. 1047 96

Insulin-dependent diabetes mellitus (IDDM) is characterized by the T cell-mediated destruction of insulin-producing beta cells. Accordingly, APCs, such as macrophage, have also been shown to be important in the disease process. However, the role(s) of dendritic cells (DCs) that exhibit potent APC function remains undefined in IDDM. Here we demonstrate that DCs derived from nonobese diabetic (NOD) mice, a model for IDDM, are more sensitive to various forms of stimulation compared with those from C57BL/6 and BALB/c mice, resulting in increased IL-12 secretion. This property is a consequence of hyperactivation of NF-kappaB, a transcription factor known to regulate IL-12 gene expression. Specifically, NOD DCs exhibit persistent hyperactivation of both IkappaB kinase and NF-kappaB in response to stimuli, in addition to selective degradation of IkappaBepsilon. Transfection of NOD DCs with a modified form of IkappaBalpha significantly reduced IL-12 secretion, suggesting that hyperactivation of NF-kappaB was in part responsible for increased IL-12 production. An enhanced capacity of NOD DCs to secrete IL-12 would be expected to contribute to the development of pathogenic Th1 (Tc1) cells during the diabetogenic response.
...
PMID:Dendritic cells from nonobese diabetic mice exhibit a defect in NF-kappa B regulation due to a hyperactive I kappa B kinase. 1146 66

In this study, tolerance induction by preexposure of murine macrophages to Toll-like receptor (TLR)2 and TLR4 agonists was revisited, focusing on the major signaling components associated with NF-kappaB activation. Pretreatment of macrophages with a pure TLR4 agonist (protein-free Escherichia coli (Ec) LPS) or with TLR2 agonists (Porphyromonas gingivalis LPS or synthetic lipoprotein Pam3Cys) led to suppression of TNF-alpha secretion, IL-1R-associated kinase-1, and IkappaB kinase (IKK) kinase activities, c-jun N-terminal kinase, and extracellular signal-regulated kinase phosphorylation, and to suppression of NF-kappaB DNA binding and transactivation upon challenge with the same agonist (TLR4 or TLR2 "homotolerance," respectively). Despite inhibited NF-kappaB DNA binding, increased levels of nuclear NF-kappaB were detected in agonist-pretreated macrophages. For all the intermediate signaling elements, heterotolerance was weaker than TLR4 or TLR2 homotolerance with the exception of IKK kinase activity. IKK kinase activity was unperturbed in heterotolerance. TNF-alpha secretion was also suppressed in P. gingivalis LPS-pretreated, Ec LPS-challenged cells, but not vice versa, while Pam3Cys and Ec LPS did not induce a state of cross-tolerance at the level of TNF-alpha. Experiments designed to elucidate novel mechanisms of NF-kappaB inhibition in tolerized cells revealed the potential contribution of IkappaBepsilon and IkappaBxi inhibitory proteins and the necessity of TLR4 engagement for induction of tolerance to Toll receptor-IL-1R domain-containing adapter protein/MyD88-adapter-like-dependent gene expression. Collectively, these data demonstrate that induction of homotolerance affects a broader spectrum of signaling components than in heterotolerance, with selective modulation of specific elements within the NF-kappaB signaling pathway.
...
PMID:Induction of in vitro reprogramming by Toll-like receptor (TLR)2 and TLR4 agonists in murine macrophages: effects of TLR "homotolerance" versus "heterotolerance" on NF-kappa B signaling pathway components. 1249 38

Interleukin-10 (IL-10) has potent immunoregulatory effects on the maturation and the antigen-presenting cell (APC) function of dendritic cells (DCs). The molecular basis underlying these effects in DCs, however, is ill defined. It is well established that the transcription factor NF-kappaB is a key regulator of DC development, maturation, and APC function. This study was initiated to determine the effects of IL-10 on the NF-kappaB signaling pathway in immature DCs. IL-10 pretreatment of myeloid DCs cultured from bone marrow resulted in reduced DNA binding and nuclear translocation of NF-kappaB after anti-CD40 antibody or lipopolysaccharide (LPS) stimulation. Furthermore, inhibited NF-kappaB activation was characterized by reduced degradation, phosphorylation, or both of IkappaBalpha and IkappaBepsilon but not IkappaBbeta and by reduced phosphorylation of Ser536, located in the trans-activation domain of p65. Notably, IL-10-mediated inhibition of NF-kappaB coincided with suppressed IkappaB kinase (IKK) activity in vitro. Furthermore, IL-10 blocked inducible Akt phosphorylation, and inhibitors of phosphatidylinositol 3-kinase (PI3K) effectively suppressed the activation of Akt, IKK, and NF-kappaB. These findings demonstrate that IL-10 targets IKK activation in immature DCs and that suppressing the PI3K pathway in part mediates blockade of the pathway.
...
PMID:Immunoregulation of dendritic cells by IL-10 is mediated through suppression of the PI3K/Akt pathway and of IkappaB kinase activity. 1511 57

NF-kappaB is the generic name of a family of transcription factors which play a critical role in the immune, inflammatory and anti-apoptotic responses. Homo- or heterodimers between the five members of the family are retained in the cytoplasm by inhibitory molecules of the IkappaB family, which mask their nuclear localization signal. Three of these inhibitory molecules have been described: IkappaBalpha, IkappaBbeta and IkappaBepsilon. Following cellular stimulation, IkappaB proteins become phosphorylated by the IkappaB kinase (IKK) complex, ubiquitinated and finally degraded by the proteasome. NF-kappaB is then released and translocated to the nucleus, where it activates its target genes by binding to specific sites in their regulatory regions. The IKK complex is constituted of at least three subunits: two kinases, IKKalpha and IKKbeta, and one regulatory subunit (NEMO/IKKgamma), and it constitutes an integrator of most if not all signals which activate NF-kappaB. Although the mechanisms leading to the degradation of the IkappaB proteins are relatively well understood, the precise molecular mechanisms which result in the activation of the high-molecular-weight kinase complex remain to be elucidated. The central role of the IKK complex is consistent with its involvement in a series of human pathologies. We describe here four pathologies: two are due to mutations in the gene encoding the NEMO molecule, a third one in the gene encoding the IkappaBalpha inhibitor, while the fourth one is due to mutations in a gene which had been described as a tumor suppressor. This gene encodes a protein which interacts with NEMO and exhibits deubiquitinase activity, therefore strengthening the recent hypothesis of the role of non-degradation-linked ubiquitination in NF-kappaB activation.
...
PMID:[Human pathologies associated with NF-kappaB defects]. 1536 56

NF-kappaB is a family of essential transcription factors involved in both embryonic development and inflammatory responses of the immune system. NF-kappaB can be activated by two pathways, i.e. the canonical (NF-kappaB1) pathway, which acts through the catalytic components of the IkappaB kinase complex and leads to IkappaB phosphorylation, degradation, and subsequent NF-kappaB nuclear translocation, or the non-canonical (NF-kappaB2) pathway, which involves NF-kappaB-induced kinase-dependent proteolytic processing of p100/p52 to yield translocation-competent p52-containing NF-kappaB complexes. We examined the relative roles of the NF-kappaB1 and NF-kappaB2 pathways in TCR/CD28 costimulation. We found that TCR/CD28 costimulation activates the canonical but not the non-canonical NF-kappaB pathway and that the serine/threonine kinase protein kinase C (PKC) is essential for TCR/CD28-mediated canonical NF-kappaB activation in T cells. Importantly, TCR/CD28 costimulation induces higher p52 protein levels in T cells, but this effect is secondary to enhanced de novo synthesis of p100, not to enhanced processing of extant p100; PKC deficiency impairs signal-dependent p52 accumulation because of defects in p100 production. Finally, we found that TCR/CD28 costimulation induces IkappaBalpha, IkappaBbeta, and IkappaBepsilon degradation, and PKC is required for IkappaBalpha and IkappaBepsilon but not IkappaBbeta degradation. PKC acts solely within the canonical pathway to activate NF-kappaB, and PKC deficiency impacts upon p100/p52 processing in a manner that is independent of NF-kappaB-induced kinase.
...
PMID:Role for protein kinase Ctheta (PKCtheta) in TCR/CD28-mediated signaling through the canonical but not the non-canonical pathway for NF-kappaB activation. 1553 66

It has become increasingly clear that hyaluronan is more than the simple matrix molecule it was once thought to be but instead takes part in a multitude of biological functions. Three genes encode for hyaluronan synthases (HAS). We demonstrated earlier that HAS2 and HAS3 are constitutively activated in type-B synoviocytes (fibroblast-like synoviocytes) and, furthermore, that the only gene that readily responds to stimulation with a series of proinflammatory cytokines is HAS1. Here we probe the involvement of the transcription factor NF-kappaB in induced and noninduced HAS activation. Transforming growth factor (TGF) beta1 as well as interleukin (IL)-1beta are both strong inducers of HAS1 transcription. Stimulation of fibroblast-like synoviocytes with IL-1beta resulted in rapid degradation of IkappaBalpha, an event that was preceded by IkappaBalpha phosphorylation. Interestingly, TGFbeta1 neither affected IkappaBalpha levels, nor did it cause phosphorylation of IkappaBalpha. In addition, TGFbeta1 had no effect on IkappaBbeta and IkappaBepsilon levels. Electrophorectic mobility shift assays demonstrate that IL-1beta is a potent inducer of NF-kappaB translocation; however, TGFbeta1 treatment did not result in shifting bands. Two adenovirus constructs were used to further clarify differences in TGFbeta1- and IL-1beta-induced HAS1 activation. Overexpressing IkappaBalpha completely abolished the IL-1beta effect on HAS1 but did not interfere with TGFbeta1-induced HAS1 mRNA accumulation. Identical results were obtained when a dominant negative IKK was overexpressed. Interestingly, neither overexpression of IkappaBalpha nor of IKK had any effect on HAS2 and HAS3 mRNA levels. Taken together, HAS1 can be activated by distinct pathways; IL-1beta utilizes NF-kappaB, and TGFbeta1 does not. Furthermore, HAS2 and HAS3 are activated without the involvement of NF-kappaB.
...
PMID:Adenovirus-mediated gene transfer of mutated IkappaB kinase and IkappaBalpha reveal NF-kappaB-dependent as well as NF-kappaB-independent pathways of HAS1 activation. 1625 73


1 2 Next >>

---