Berry D M, Benn S J, Cheng A M, McGlade C J
The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Toronto, Ontario, Canada.
Oncogene. 2001 Mar 8;20(10):1203-11. doi: 10.1038/sj.onc.1204218.
Gads is a SH2 and SH3 domain-containing, hematopoietic-specific adaptor protein that functions in signalling from the T cell receptor. Gads acts by linking SLP-76, bound by the carboxy-terminal Gads SH3 domain, to tyrosine phosphorylated LAT which contains binding sites for the Gads SH2 domain. Gads is distinguished from Grb2 and the closely related Grap protein by the presence of a 120 amino acid unique region between the SH2 domain and the carboxy terminal SH3 domain. Here we demonstrate that the unique region of Gads contains a capase cleavage site. Induction of apoptosis in lymphocytes results in detectable Gads cleavage by 60 min. Gads cleavage is blocked in vivo by treating cells with a caspase 3 inhibitor. A putative caspase 3 cleavage site was identified within the unique region and mutation of this site prevented Gads cleavage in vitro, and in vivo. The Gads cleavage products retained the predicted binding specificity for SLP-76 and LAT. Expression of the Gads cleavage products in Jurkat T cells inhibited NFAT activation following TCR cross linking. These findings indicate that cleavage of Gads in vivo could function to alter signalling downstream of the T cell receptor by disrupting cross talk between SLP-76 and LAT.
Gads是一种含有SH2和SH3结构域的造血特异性衔接蛋白，在T细胞受体信号传导中发挥作用。Gads的作用是将羧基末端Gads SH3结构域结合的SLP-76与酪氨酸磷酸化的LAT连接起来，LAT含有Gads SH2结构域的结合位点。Gads与Grb2和密切相关的Grap蛋白的区别在于，在SH2结构域和羧基末端SH3结构域之间存在一个120个氨基酸的独特区域。在这里，我们证明Gads的独特区域包含一个半胱天冬酶切割位点。淋巴细胞凋亡的诱导导致60分钟内可检测到Gads的切割。通过用半胱天冬酶3抑制剂处理细胞，Gads的切割在体内被阻断。在独特区域内鉴定出一个假定的半胱天冬酶3切割位点，该位点的突变阻止了Gads在体外和体内的切割。Gads切割产物保留了对SLP-76和LAT的预测结合特异性。Gads切割产物在Jurkat T细胞中的表达抑制了TCR交联后NFAT的激活。这些发现表明，体内Gads的切割可能通过破坏SLP-76和LAT之间的串扰来改变T细胞受体下游的信号传导。
