Positive regulation of IκB kinase signaling by protein serine/threonine phosphatase 2A
Positive regulation of IκB kinase signaling by protein serine/threonine phosphatase 2A
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DOI：
10.1074/jbc.m506093200
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发表时间：
2005-10-28
影响因子：
4.8
通讯作者：
Wadzinski, BE
中科院分区：
文献类型：
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作者：
Kray, AE;Carter, RS;Wadzinski, BE
转录因子NF-κ B在对促炎细胞因子如肿瘤坏死因子-α（TNF）的细胞应答中起关键调节作用。在没有TNF的情况下，NF-κ B被抑制性I κ B蛋白隔离在细胞质中。IKK（一种多组分I κ B激酶）的β-催化亚基磷酸化I κ B，靶向蛋白水解破坏抑制剂，促进NF-κ B的核转位。该途径由IKK β中T环丝氨酸的TNF依赖性磷酸化启动，其极大地刺激I κ B激酶活性。先前的体外混合实验表明，蛋白质丝氨酸/苏氨酸磷酸酶2A（PP 2A）可以使这些T环丝氨酸和IKK去磷酸化，表明PP 2A在IKK信号传导中的负调节作用。在这里，我们提供了几个在体内的证据表明，PP 2A在IKK的调节中起着积极的作用，而不是消极的作用。首先，TNF诱导的I κ B降解在用冈田酸或fostriecin（两种有效的PP 2A抑制剂）处理的细胞中减弱。第二，PP 2A在未转染的哺乳动物细胞中与IKK形成稳定的复合物。这种相互作用严重依赖于IKK γ调节亚基的氨基酸残基121 - 179。第三，IKK γ中PP 2A结合位点的缺失减弱了TNF处理的细胞中IKK β的T环磷酸化和催化活化。综上所述，这些数据提供了强有力的证据，IKK中心点PP 2A复合物的形成是体内I κ B激酶活性的适当诱导所必需的。
Transcription factor NF-kappa B plays a key regulatory role in the cellular response to pro-inflammatory cytokines such as tumor necrosis factor-alpha(TNF). In the absence of TNF, NF-kappa B is sequestered in the cytoplasm by inhibitory I kappa B proteins. Phosphorylation of I kappa B by the beta-catalytic subunit of IKK, a multicomponent I kappa B kinase, targets the inhibitor for proteolytic destruction and facilitates nuclear translocation of NF-kappa B. This pathway is initiated by TNF-dependent phosphorylation of T loop serines in IKK beta, which greatly stimulates I kappa B kinase activity. Prior in vitro mixing experiments indicate that protein serine/threonine phosphatase 2A (PP2A) can dephosphorylate these T loop serines and inactivate IKK, suggesting a negative regulatory role for PP2A in IKK signaling. Here we provided several in vivo lines of evidence indicating that PP2A plays a positive rather than a negative role in the regulation of IKK. First, TNF-induced degradation of I kappa B is attenuated in cells treated with okadaic acid or fostriecin, two potent inhibitors of PP2A. Second, PP2A forms stable complexes with IKK in untransfected mammalian cells. This interaction is critically dependent on amino acid residues 121 - 179 of the IKK gamma regulatory subunit. Third, deletion of the PP2A-binding site in IKK gamma attenuates T loop phosphorylation and catalytic activation of IKK beta in cells treated with TNF. Taken together, these data provide strong evidence that the formation of IKK center dot PP2A complexes is required for the proper induction of I kappa B kinase activity in vivo.