Docking protein Gab2 is phosphorylated by ZAP-70 and negatively regulates T cell receptor signaling by recruitment of inhibitory molecules
Docking protein Gab2 is phosphorylated by ZAP-70 and negatively regulates T cell receptor signaling by recruitment of inhibitory molecules
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DOI：
10.1074/jbc.m105384200
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发表时间：
2001-11-30
影响因子：
4.8
通讯作者：
Saito, T
中科院分区：
文献类型：
--
作者：
Yamasaki, S;Nishida, K;Saito, T
为了维持各种T细胞应答和免疫平衡，T细胞抗原受体（TCR）触发的激活信号必须受到抑制信号的调节。Gab 2是胰岛素受体底物-1家族的一种衔接蛋白，参与细胞因子受体的下游信号传导。我们研究了Gab 2在TCR介导的信号转导中的功能作用。在TCR刺激后，Gab 2被ZAP-70磷酸化并与磷蛋白如ZAP-70、LAT和CD 3 ζ共沉淀。Gab 2在Jurkat细胞或抗原特异性T细胞杂交瘤中的过表达导致NF-AT活化、白细胞介素-2产生和酪氨酸磷酸化的抑制。通过突变体分析Gab 2的结构与功能关系。缺乏SHP-2结合位点的Gab 2突变体大多废除了Gab 2的抑制活性，但其抑制功能通过融合到活性SHP-2作为嵌合蛋白而恢复。具有缺陷性磷脂酰肌醇3-激酶结合能力的突变体也损害了抑制活性，而普列克底物蛋白同源结构域缺失突变体揭示了普列克底物蛋白同源结构域定位于质膜的关键功能。这些结果表明，Gab 2是ZAP-70的底物，并且通过介导抑制性分子向TCR信号传导复合物的募集而充当朝向TCR信号传导抑制的开关分子。
To maintain various T cell responses and immune equilibrium, activation signals triggered by T cell antigen receptor (TCR) must be regulated by inhibitory signals. Gab2, an adaptor protein of the insulin receptor substrate-1 family, has been shown to be involved in the downstream signaling from cytokine receptors. We investigated the functional role of Gab2 in TCR-mediated signal transduction. Gab2 was phosphorylated by ZAP-70 and co-precipitated with phosphoproteins, such as ZAP-70, LAT, and CD3 zeta, upon TCR stimulation. Overexpression of Gab2 in Jurkat cells or antigen-specific T cell hybridomas resulted in the inhibition of NF-AT activation, interleukin-2 production, and tyrosine phosphorylation. The structure-function relationship of Gab2 was analyzed by mutants of Gab2. The Gab2 mutants lacking SHP-2-binding sites mostly abrogated the inhibitory activity of Gab2, but its inhibitory function was restored by fusing to active SHP-2 as a chimeric protein. A mutant with defective phosphatidylinositol 3-kinase binding capacity also impaired the inhibitory activity, and the pleckstrin homology domain-deletion mutant revealed a crucial function of the pleckstrin homology domain for localization to the plasma membrane. These results suggest that Gab2 is a substrate of ZAP-70 and functions as a switch molecule toward inhibition of TCR signal transduction by mediating the recruitment of inhibitory molecules to the TCR signaling complex.