Marengère L E, Mirtsos C, Kozieradzki I, Veillette A, Mak T W, Penninger J M
Amgen Institute, and Department of Medical Biophysics, University of Toronto, Ontario, Canada.
J Immunol. 1997 Jul 1;159(1):70-6.
The molecular adapter c-Cbl is rapidly tyrosine phosphorylated following stimulation through the TCR and associates with Src homology domain-2 (SH2)/SH3 domain-containing adapters such as Grb2, Crk, and Crk-L, which interact with guanine nucleotide exchange factors specific for the Ras family. This suggests that c-Cbl may link TCR activation to molecules that regulate GTP binding proteins. The SH2/SH3-containing protein Vav also contains a guanine nucleotide exchange factor domain, and Vav has a crucial role in thymocyte development and activation of peripheral T cells following stimulation through the TCR. Here we show that Vav and c-Cbl form inducible molecular complexes in TCR-activated murine thymocytes and peripheral T cells as well as pervanadate-treated T cells. Vav/c-Cbl interactions are also detectable in freshly isolated T cells from gene-targeted mice that lack the T cell-specific inhibitory receptor CTLA-4, in which c-Cbl is hyperphosphorylated on tyrosine residues. The interaction between Vav and c-Cbl is directly mediated via the SH2 domain of Vav and is dependent on tyrosine phosphorylation of c-Cbl. In addition, we show that the conserved motif Y699 MTP present in c-Cbl is the binding site for the Vav SH2 domain in vitro. These data imply that c-Cbl is a molecular adapter that regulates the function of Vav in thymocytes and peripheral T cells.
分子衔接蛋白c-Cbl在通过TCR刺激后迅速发生酪氨酸磷酸化，并与含有Src同源结构域2（SH2）/SH3结构域的衔接蛋白（如Grb2、Crk和Crk-L）结合，这些衔接蛋白与Ras家族特异性的鸟嘌呤核苷酸交换因子相互作用。这表明c-Cbl可能将TCR激活与调节GTP结合蛋白的分子联系起来。含有SH2/SH3的蛋白Vav也含有一个鸟嘌呤核苷酸交换因子结构域，并且Vav在胸腺细胞发育以及TCR刺激后外周T细胞的激活中起关键作用。在此我们表明，Vav和c-Cbl在TCR激活的小鼠胸腺细胞和外周T细胞以及过钒酸钠处理的T细胞中形成可诱导的分子复合物。在缺乏T细胞特异性抑制性受体CTLA-4的基因靶向小鼠的新鲜分离T细胞中也可检测到Vav/c-Cbl相互作用，其中c-Cbl在酪氨酸残基上发生了过度磷酸化。Vav和c-Cbl之间的相互作用直接通过Vav的SH2结构域介导，并且依赖于c-Cbl的酪氨酸磷酸化。此外，我们表明c-Cbl中存在的保守基序Y699MTP在体外是Vav SH2结构域的结合位点。这些数据表明c-Cbl是一种调节胸腺细胞和外周T细胞中Vav功能的分子衔接蛋白。
