Joshi Rubin N, Binai Nadine A, Marabita Francesco, Sui Zhenhua, Altman Amnon, Heck Albert J R, Tegnér Jesper, Schmidt Angelika
Unit of Computational Medicine, Center for Molecular Medicine, Department of Medicine Solna, Karolinska University Hospital, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden.
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, Netherlands.
Front Immunol. 2017 Sep 25;8:1163. doi: 10.3389/fimmu.2017.01163. eCollection 2017.
Regulatory T cells (Tregs) control key events of immune tolerance, primarily by suppression of effector T cells. We previously revealed that Tregs rapidly suppress T cell receptor (TCR)-induced calcium store depletion in conventional CD4CD25 T cells (Tcons) independently of IP levels, consequently inhibiting NFAT signaling and effector cytokine expression. Here, we study Treg suppression mechanisms through unbiased phosphoproteomics of primary human Tcons upon TCR stimulation and Treg-mediated suppression, respectively. Tregs induced a state of overall decreased phosphorylation as opposed to TCR stimulation. We discovered novel phosphosites (T595_S597) in the DEF6 (SLAT) protein that were phosphorylated upon TCR stimulation and conversely dephosphorylated upon coculture with Tregs. Mutation of these DEF6 phosphosites abrogated interaction of DEF6 with the IP receptor and affected NFAT activation and cytokine transcription in primary Tcons. This novel mechanism and phosphoproteomics data resource may aid in modifying sensitivity of Tcons to Treg-mediated suppression in autoimmune disease or cancer.
调节性T细胞（Tregs）主要通过抑制效应T细胞来控制免疫耐受的关键事件。我们之前发现，Tregs能独立于IP水平快速抑制常规CD4CD25 T细胞（Tcons）中T细胞受体（TCR）诱导的钙库耗竭，从而抑制NFAT信号传导和效应细胞因子表达。在此，我们分别通过对受TCR刺激和Treg介导抑制的原代人Tcons进行无偏磷酸化蛋白质组学研究，来探究Treg的抑制机制。与TCR刺激相反，Tregs诱导了整体磷酸化水平降低的状态。我们在DEF6（SLAT）蛋白中发现了新的磷酸化位点（T595_S597），该位点在TCR刺激时被磷酸化，而在与Tregs共培养时则相反地发生去磷酸化。这些DEF6磷酸化位点的突变消除了DEF6与IP受体的相互作用，并影响了原代Tcons中的NFAT激活和细胞因子转录。这种新机制和磷酸化蛋白质组学数据资源可能有助于改变Tcons在自身免疫性疾病或癌症中对Treg介导抑制的敏感性。
