Article

Inducible Phosphorylation of NF- B p65 at Serine 468 by T Cell Costimulation Is Mediated by IKK

Hannover Medical School, Hanover, Lower Saxony, Germany
Journal of Biological Chemistry (Impact Factor: 4.57). 04/2006; 281(10):6175-83. DOI: 10.1074/jbc.M508045200
Source: PubMed

ABSTRACT

Here we identify IKKepsilon as a novel NF-kappaB p65 kinase that mediates inducible phosphorylation of Ser468 and Ser536 in response to T cell costimulation. In addition, the kinase activity of IKKepsilon contributes to the control of p65 nuclear uptake. Serines 468 and 536 are evolutionarily conserved, and the surrounding amino acids display sequence homology. Down-regulation of IKKepsilon levels by small interfering RNA does not affect inducible phosphorylation of Ser536 but largely prevents Ser468 phosphorylation induced by T cell costimulation. Ser536-phosphorylated p65 is found predominantly in the cytosol. In contrast, the Ser468 phosphorylated form of this transcription factor occurs mainly in the nucleus, suggesting a function for transactivation. Reconstitution of p65-/- cells with either wild type p65 or point-mutated p65 variants showed that inducible phosphorylation of Ser468 serves to enhance p65-dependent transactivation. These results also provide a mechanistic link that helps to explain the relevance of IKKepsilon for the expression of a subset of NF-kappaB target genes without affecting cytosolic IkappaBalpha degradation.

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    • "At least twelve p65 serine or threonine residues have been identified whose phosphorylation regulates its nuclear localization and/or transcriptional activation (13,15,22,23,26272830,48495051525354. We therefore asked whether Ca 2+ regulates p65 nuclear translocation by controlling phosphorylation of any of these residues. "
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    ABSTRACT: T cell activation following antigen binding to the T cell receptor (TCR) involves the mobilization of intracellular calcium (Ca2+) to activate the key transcription factors NFAT and NF-kB. The mechanism of NFAT activation by Ca2+ has been determined; however, the role of Ca2+ in controlling NF-kB signaling is poorly understood and the source of Ca2+ required for NF-kB activation is unknown. We demonstrate that TCR- but not TNF-induced NF-kB signaling upstream of IκB kinase (IKK) activation absolutely requires the influx of extracellular Ca2+ via STIM1-dependent CRAC/Orai channels. We further show that Ca2+ influx controls phosphorylation of the NF-kB protein p65 on Ser536 and that this post-translational modification controls its nuclear localization and transcriptional activation. Notably our data reveal that this role for Ca2+ is entirely separate from its upstream control of IkBa degradation, thereby identifying a novel Ca2+-dependent distal step in TCR-induced NF-kB activation. Finally, we demonstrate that this control of distal signaling occurs via Ca2+-dependent PKCa-mediated phosphorylation of p65. Thus, we establish the source of Ca2+ required for TCR induced NF-kB activation and, define new distal Ca2+-dependent checkpoints in TCR-induced NF-kB signaling that have broad implications for the control of immune cell development and T cell functional specificity.
    Preview · Article · Jan 2016 · Journal of Biological Chemistry
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    • "The expression vectors for Tax-1 and Tax-2B full length and Tax-1 truncated mutants were previously described (Lamsoul et al., 2005;Tosi et al., 2011;Turci et al., 2009Turci et al., , 2012). The pcDNA3- Flag-IKKε, pcDNA3-Flag-IKKεΔC, pCDNA3-Flag-TBK1, pEGFP-C1- DDX3, p55C1B-Luc, pIRF3-GFP, pcDNA3-TBK1-Myc, pcDNA3- TRAF3-Flag, HA-TRAF3 plasmids were kindly provided by Schmitz (Mattioli et al., 2006), Lin (Breiman et al., 2005), Kracht (Buss et al., 2004), Tarn (Lai et al., 2008), Fujita (Yoneyama et al., 1996), Hiscott (Lin et al., 1998), Chariot (Gatot et al., 2007), Servant (vanZuylen et al., 2012) and Harhaj (Charoenthongtrakul et al., 2013), respectively. "

    Full-text · Article · Jan 2014 · Retrovirology
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    • "Substitution of Ser468 with an alanine impedes this interaction and almost completely prevents COMMD1-mediated RELA ubiquitination and proteasomal degradation. Upon NF-κB activation , RELA S468A substitution results in prolonged binding of RELA to a selective set of NF-κB target genes [49] [50] [51]. Interestingly, after removal of RELA from the promoter site, COMMD1 was detected at the same "
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    ABSTRACT: NF-κB is an important regulator of immunity and inflammation, and its activation pathway has been studied extensively. The mechanisms that downregulate the activity of NF-κB have also received a lot of attention, particularly since its activity needs to be terminated to prevent chronic inflammation and subsequent tissue damage. The COMMD family has been identified as a new group of proteins involved in NF-κB termination. All ten COMMD members share the structurally conserved carboxy-terminal motif, the COMM domain, and are ubiquitously expressed. They seem to play distinct and non-redundant roles in various physiological processes, including NF-κB signaling. In this review, we describe the mechanisms and proteins involved in the termination of canonical NF-κB signaling, with a specific focus on the role of the COMMD family in the down-modulation of NF-κB.
    Full-text · Article · Sep 2013 · Biochimica et Biophysica Acta
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