Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of the macrophage cell line RAW 264.7 with lipopolysaccharide (LPS) and gamma interferon (IFN-gamma) induces the expression of gene products involved in host defense, among them type 2 nitric oxide synthase. Treatment of cells with 15-deoxy-Delta(12,14)-prostaglandin J(2) (15dPGJ(2)) inhibited the LPS- and IFN-gamma-dependent synthesis of NO, a process that was not antagonized by similar concentrations of prostaglandin J(2), prostaglandin E(2), or rosiglitazone, a peroxisomal proliferator-activated receptor gamma ligand. Incubation of activated macrophages with 15dPGJ(2) inhibited the degradation of IkappaBalpha and IkappaBbeta and increased their levels in the nuclei. NF-kappaB activity, as well as the transcription of NF-kappaB-dependent genes, such as those encoding type 2 nitric oxide synthase and cyclooxygenase 2, was impaired under these conditions. Analysis of the steps leading to IkappaB phosphorylation showed an inhibition of IkappaB kinase by 15dPGJ(2) in cells treated with LPS and IFN-gamma, resulting in an impaired phosphorylation of IkappaBalpha, at least in the serine 32 residue required for targeting and degradation of this protein. Incubation of partially purified activated IkappaB kinase with 2 microM 15dPGJ(2) reduced by 83% the phosphorylation in serine 32 of IkappaBalpha, suggesting that this prostaglandin exerts direct inhibitory effects on the activity of the IkappaB kinase complex. These results show rapid actions of 15dPGJ(2), independent of peroxisomal proliferator receptor gamma activation, in macrophages challenged with low doses of LPS and IFN-gamma.
Mol Cell Biol 2000 Mar
PMID:Inhibition of IkappaB kinase and IkappaB phosphorylation by 15-deoxy-Delta(12,14)-prostaglandin J(2) in activated murine macrophages. 1066 46

The phosphorylation of IkappaB by the multiprotein IkappaB kinase complex (IKC) precedes the activation of transcription factor NF-kappaB, a key regulator of the inflammatory response. Here we identified the mixed-lineage group kinase 3 (MLK3) as an activator of NF-kappaB. Expression of the wild-type form of this mitogen-activated protein kinase kinase kinase (MAPKKK) induced nuclear immigration, DNA binding, and transcriptional activity of NF-kappaB. MLK3 directly phosphorylated and thus activated IkappaB kinase alpha (IKKalpha) and IKKbeta, revealing its function as an IkappaB kinase kinase (IKKK). MLK3 cooperated with the other two IKKKs, MEKK1 and NF-kappaB-inducing kinase, in the induction of IKK activity. MLK3 bound to components of the IKC in vivo. This protein-protein interaction was dependent on the central leucine zipper region of MLK3. A kinase-deficient version of MLK3 strongly impaired NF-kappaB-dependent transcription induced by T-cell costimulation but not in response to tumor necrosis factor alpha or interleukin-1. Accordingly, endogenous MLK3 was phosphorylated and activated by T-cell costimulation but not by treatment of cells with tumor necrosis factor alpha or interleukin-1. A dominant negative version of MLK3 inhibited NF-kappaB- and CD28RE/AP-dependent transcription elicited by the Rho family GTPases Rac and Cdc42, thereby providing a novel link between these GTPases and the IKC.
Mol Cell Biol 2000 Apr
PMID:Mixed-lineage kinase 3 delivers CD3/CD28-derived signals into the IkappaB kinase complex. 1071 78

The activity of the NF-kappaB family of transcription factors is regulated principally by phosphorylation and subsequent degradation of their inhibitory IkappaB subunits. Site-specific serine phosphorylation of IkappaBs by two IkappaB kinases (IKKalpha [also known as CHUK] and IKKbeta) targets them for proteolysis. IKKalpha and -beta have a unique structure, with an amino-terminal serine-threonine kinase catalytic domain and carboxy-proximal helix-loop-helix (HLH) and leucine zipper-like (LZip) amphipathic alpha-helical domains. Here, we describe the properties of two novel cellular isoforms of IKKalpha: IKKalpha-DeltaH and IKKalpha-DeltaLH. IKKalpha-DeltaH and IKKalpha-DeltaLH are differentially spliced isoforms of the IKKalpha mRNA lacking its HLH domain and both its LZip and HLH domains, respectively. IKKalpha is the major RNA species in most murine cells and tissues, except for activated T lymphocytes and the brain, where the alternatively spliced isoforms predominate. Remarkably, IKKalpha-DeltaH and IKKalpha-DeltaLH, like IKKalpha, respond to tumor necrosis factor alpha stimulation to potentiate NF-kappaB activation in HEK293 cells. A mutant, catalytically inactive form of IKKalpha blocked IKKalpha-, IKKalpha-DeltaH-, and IKKalpha-DeltaLH-mediated NF-kappaB activation. Akin to IKKalpha, its carboxy-terminally truncated isoforms associated with the upstream activator NIK (NF-kappaB-inducing kinase). In contrast to IKKalpha, IKKalpha-DeltaLH failed to associate with either itself, IKKalpha, IKKbeta, or NEMO-IKKgamma-IKKAP1, while IKKalpha-DeltaH complexed with IKKbeta and IKKalpha but not with NEMO. Interestingly, each IKKalpha isoform rescued HEK293 cells from the inhibitory effects of a dominant-negative NEMO mutant, while IKKalpha could not. IKKalpha-DeltaCm, a recombinant mutant of IKKalpha structurally akin to IKKalpha-DeltaLH, was equally functional in these assays, but in sharp contrast, IKKbeta-DeltaCm, a structurally analogous mutant of IKKbeta, was inactive. Our results demonstrate that the functional roles of seemingly analogous domains in IKKalpha and IKKbeta need not be equivalent and can also exhibit different contextual dependencies. The existence of cytokine-inducible IKKalpha-DeltaH and IKKalpha-DeltaLH isoforms illustrates potential modes of NF-kappaB activation, which are not subject to the same in vivo regulatory constraints as either IKKalpha or IKKbeta.
Mol Cell Biol 2000 Apr
PMID:Functional isoforms of IkappaB kinase alpha (IKKalpha) lacking leucine zipper and helix-loop-helix domains reveal that IKKalpha and IKKbeta have different activation requirements. 1073 66

The NF-kappaB/Rel family of eukaryotic transcription factors plays an essential role in the regulation of inflammatory, antiapoptotic, and immune responses. NF-kappaB is activated by many stimuli including costimulation of T cells with ligands specific for the T-cell receptor (TCR)-CD3 complex and CD28 receptors. However, the signaling intermediates that transduce these costimulatory signals from the TCR-CD3 and CD28 surface receptors leading to nuclear NF-kappaB expression are not well defined. We now show that protein kinase C-theta (PKC-theta), a novel PKC isoform, plays a central role in a signaling pathway induced by CD3-CD28 costimulation leading to activation of NF-kappaB in Jurkat T cells. We find that expression of a constitutively active mutant of PKC-theta potently induces NF-kappaB activation and stimulates the RE/AP composite enhancer from the interleukin-2 gene. Conversely, expression of a kinase-deficient mutant or antisense PKC-theta selectively inhibits CD3-CD28 costimulation, but not tumor necrosis factor alpha-induced activation of NF-kappaB in Jurkat T cells. The induction of NF-kappaB by PKC-theta is mediated through the activation of IkappaB kinase beta (IKKbeta) in the absence of detectable IKKalpha stimulation. PKC-theta acts directly or indirectly to stimulate phosphorylation of IKKbeta, leading to activation of this enzyme. Together, these results implicate PKC-theta in one pathway of CD3-CD28 costimulation leading to NF-kappaB activation that is apparently distinct from that involving Cot and NF-kappaB-inducing kinase (NIK). PKC-theta activation of NF-kappaB is mediated through the selective induction of IKKbeta, while the Cot- and NIK-dependent pathway involves induction of both IKKalpha and IKKbeta.
Mol Cell Biol 2000 Apr
PMID:Protein kinase C-theta participates in NF-kappaB activation induced by CD3-CD28 costimulation through selective activation of IkappaB kinase beta. 1073 97

Two related kinases, IkappaB kinase alpha (IKKalpha) and IKKbeta, phosphorylate the IkappaB proteins, leading to their degradation and the subsequent activation of gene expression by NF-kappaB. IKKbeta has a much higher level of kinase activity for the IkappaB proteins than does IKKalpha and is more critical than IKKalpha in modulating tumor necrosis factor alpha activation of the NF-kappaB pathway. These results indicate an important role for IKKbeta in activating the NF-kappaB pathway but leave open the question of the role of IKKalpha in regulating this pathway. In the current study, we demonstrate that IKKalpha directly phosphorylates IKKbeta. Moreover, IKKalpha either directly or indirectly enhances IKKbeta kinase activity for IkappaBalpha. Finally, transfection studies to analyze NF-kappaB-directed gene expression suggest that IKKalpha is upstream of IKKbeta in activating the NF-kappaB pathway. These results indicate that IKKalpha, in addition to its previously described ability to phosphorylate IkappaBalpha, can increase the ability of IKKbeta to phosphorylate IkappaBalpha.
Mol Cell Biol 2000 May
PMID:IkappaB kinase alpha (IKKalpha) regulation of IKKbeta kinase activity. 1077 55

The pathway by which atypical protein kinase C (aPKC) contributes to nerve growth factor (NGF) signaling is poorly understood. We previously reported that in PC12 cells NGF-induced activation of mitogen-activated protein kinase (MAPK) occurs independently of classical and nonclassical PKC isoforms, whereas aPKC isoforms were shown to be required for NGF-induced differentiation. NGF-induced activation of PKC-iota was observed to be dependent on phosphatidylinositol 3-kinase (PI3K) and led to coassociation of PKC-iota with Ras and Src. Expression of dominant negative mutants of either Src (DN2) or Ras (Asn-17) impaired activation of PKC-iota by NGF. At the level of Raf-1, neither PKC-iota nor PI3 kinase was required for activation; however, PKC-iota could weakly activate MEK. Inhibitors of PKC-iota activity and PI3K had no effect on NGF-induced MAPK or p38 activation but reduced NGF-stimulated c-Jun N-terminal kinase activity. Src, PI3K, and PKC-iota were likewise required for NGF-induced NF-kappaB activation and cell survival, whereas Ras was not required for either survival or NF-kappaB activation but was required for differentiation. IKK existed as a complex with PKC-iota, Src and IkappaB. Consistent with a role for Src in regulating NF-kappaB activation, an absence of Src activity impaired recruitment of PKC-iota into an IKK complex and markedly impaired NGF-induced translocation of p65/NF-kappaB to the nucleus. These findings reveal that in PC12 cells, aPKCs comprise a molecular switch to regulate differentiation and survival responses coupled downstream to NF-kappaB. On the basis of these findings, Src emerges as a critical upstream regulator of both PKC-iota and the NF-kappaB pathway.
Mol Cell Biol 2000 Jul
PMID:Mapping of atypical protein kinase C within the nerve growth factor signaling cascade: relationship to differentiation and survival of PC12 cells. 1084 76

The interferon (IFN)-induced double-stranded RNA-activated protein kinase PKR mediates inhibition of protein synthesis through phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) and is also involved in the induction of the IFN gene through the activation of the transcription factor NF-kappaB. NF-kappaB is retained in the cytoplasm through binding to its inhibitor IkappaBalpha. The critical step in NF-kappaB activation is the phosphorylation of IkappaBalpha by the IkappaB kinase (IKK) complex. This activity releases NF-kappaB from IkappaBalpha and allows its translocation to the nucleus. Here, we have studied the ability of PKR to activate NF-kappaB in a reporter assay and have shown for the first time that two catalytically inactive PKR mutants, PKR/KR296 and a deletion mutant (PKR/Del42) which lacks the potential eIF2alpha-binding domain, can also activate NF-kappaB. This result indicated that NF-kappaB activation by PKR does not require its kinase activity and that it is independent of the PKR-eIF2alpha relationship. Transfection of either wild-type PKR or catalytically inactive PKR in PKR(0/0) mouse embryo fibroblasts resulted in the activation of the IKK complex. By using a glutathione S-transferase pull-down assay, we showed that PKR interacts with the IKKbeta subunit of the IKK complex. This interaction apparently does not require the integrity of the IKK complex, as it was found to occur with extracts from cells deficient in the NF-kappaB essential modulator, one of the components of the IKK complex. Therefore, our results reveal a novel pathway by which PKR can modulate the NF-kappaB signaling pathway without using its kinase activity.
Mol Cell Biol 2000 Jul
PMID:PKR stimulates NF-kappaB irrespective of its kinase function by interacting with the IkappaB kinase complex. 1084 80

The transcription factor NF-kappaB plays critical roles in immune and inflammatory responses. Here we show that filarial parasitic sheath proteins cause activation of NF-kappaB in the airway epithelial HEp-2 cell line. This activation was transient and saturable, and involved degradation of the cytoplasmic inhibitor protein IkappaBalpha. Stable expression of IkappaBalpha mutated at Ser32 and Ser36 to Ala caused inhibition of NF-kappaB activation, indicating that this activation involves the IkappaB kinase-mediated pathway. Moreover, while it did not influence the HEp-2 cell survival, selective blockade of NF-kappaB activation resulted in inhibition of the expression and the secretion of pro-inflammatory cytokines, tumor necrosis factor-alpha, interleukin-6 and interleukin-8. Thus, initial transient activation of NF-kappaB resulted in profound and long-term effects on epithelial cell responses to filarial parasitic proteins. These findings implicate an important role for NF-kappaB in orchestrating inflammatory reactions associated with tropical pulmonary eosinophilia.
Mol Immunol
PMID:NF-kappaB is essential for induction of pro-inflammatory cytokine genes by filarial parasitic sheath proteins. 1086 10

Beta-transducing repeat-containing protein (betaTrCP) targets the ubiquitination and subsequent degradation of both beta-catenin and IkappaB, thereby playing an important role in beta-catenin/Tcf and NF-kappaB-dependent signaling. Here evidence is presented that beta-catenin/Tcf signaling elevates the expression of betaTrCP mRNA and protein in a Tcf-dependent manner, which does not require betaTrCP transcription. Induction of betaTrCP expression by the beta-catenin/Tcf pathway results in an accelerated degradation of the wild-type beta-catenin, suggesting that the negative feedback loop regulation may control the beta-catenin/Tcf pathway. This signaling also upregulated NF-kappaB transactivation without affecting the activity of IkappaB kinase, thereby establishing that the maintenance of the betaTrCP level is important for coordination between beta-catenin/Tcf and NF-kappaB signaling.
Mol Cell 2000 May
PMID:Wnt/beta-catenin signaling induces the expression and activity of betaTrCP ubiquitin ligase receptor. 1088 23

Here we report the identification of a novel PMA-inducible IkappaB kinase complex, distinct from the well-characterized high-molecular weight IkappaB kinase complex containing IKKalpha, IKKbeta, and IKKgamma. We have characterized one kinase from this complex, which we designate IKKepsilon. Although recombinant IKKepsilon directly phosphorylates only serine 36 of IKBalpha, the PMA-activated endogenous IKKepsilon complex phosphorylates both critical serine residues. Remarkably, this activity is due to the presence of a distinct kinase in this complex. A dominant-negative mutant of IKKepsilon blocks induction of NF-kappaB by both PMA and activation of the T cell receptor but has no effect on the activation of NF-KB by TNFalpha or IL-1. These observations indicate that the activation of NF-kappaB requires multiple distinct IkappaB kinase complexes, which respond to both overlapping and discrete signaling pathways.
Mol Cell 2000 Mar
PMID:IKKepsilon is part of a novel PMA-inducible IkappaB kinase complex. 1088 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>