Liu Xiaohong, Berry Corbett T, Ruthel Gordon, Madara Jonathan J, MacGillivray Katelyn, Gray Carolyn M, Madge Lisa A, McCorkell Kelly A, Beiting Daniel P, Hershberg Uri, May Michael J, Freedman Bruce D
From the Departments of Pathobiology and.
From the Departments of Pathobiology and the School of Biomedical Engineering, Drexel University, Philadelphia, Pennsylvania 19104.
J Biol Chem. 2016 Apr 15;291(16):8440-52. doi: 10.1074/jbc.M115.713008. Epub 2016 Jan 29.
T cell activation following antigen binding to the T cell receptor (TCR) involves the mobilization of intracellular Ca(2+) to activate the key transcription factors nuclear factor of activated T lymphocytes (NFAT) and NF-κB. The mechanism of NFAT activation by Ca(2+) has been determined. However, the role of Ca(2+) in controlling NF-κB signaling is poorly understood, and the source of Ca(2+) required for NF-κB activation is unknown. We demonstrate that TCR- but not TNF-induced NF-κB signaling upstream of IκB kinase activation absolutely requires the influx of extracellular Ca(2+) via STIM1-dependent Ca(2+) release-activated Ca(2+)/Orai channels. We further show that Ca(2+) influx controls phosphorylation of the NF-κB protein p65 on Ser-536 and that this posttranslational modification controls its nuclear localization and transcriptional activation. Notably, our data reveal that this role for Ca(2+) is entirely separate from its upstream control of IκBα degradation, thereby identifying a novel Ca(2+)-dependent distal step in TCR-induced NF-κB activation. Finally, we demonstrate that this control of distal signaling occurs via Ca(2+)-dependent PKCα-mediated phosphorylation of p65. Thus, we establish the source of Ca(2+) required for TCR-induced NF-κB activation and define a new distal Ca(2+)-dependent checkpoint in TCR-induced NF-κB signaling that has broad implications for the control of immune cell development and T cell functional specificity.
抗原与T细胞受体（TCR）结合后，T细胞活化涉及细胞内Ca（2+）的动员，以激活关键转录因子活化T淋巴细胞核因子（NFAT）和NF-κB。Ca（2+）激活NFAT的机制已被确定。然而，Ca（2+）在控制NF-κB信号传导中的作用尚不清楚，NF-κB激活所需的Ca（2+）来源也未知。我们证明，在IκB激酶激活上游，TCR诱导而非TNF诱导的NF-κB信号传导绝对需要细胞外Ca（2+）通过STIM1依赖性Ca（2+）释放激活的Ca（2+）/Orai通道流入。我们进一步表明，Ca（2+）内流控制NF-κB蛋白p65在Ser-536位点的磷酸化，这种翻译后修饰控制其核定位和转录激活。值得注意的是，我们的数据表明，Ca（2+）的这一作用与其对IκBα降解的上游控制完全分开，从而确定了TCR诱导的NF-κB激活中一个新的Ca（2+）依赖性远端步骤。最后，我们证明这种远端信号传导的控制是通过Ca（2+）依赖性PKCα介导的p65磷酸化实现的。因此，我们确定了TCR诱导的NF-κB激活所需的Ca（2+）来源，并定义了TCR诱导的NF-κB信号传导中一个新的远端Ca（2+）依赖性检查点，这对免疫细胞发育和T细胞功能特异性的控制具有广泛影响。
