Caspase-dependent cleavage of the hematopoietic specific adaptor protein Gads alters signalling from the T cell receptor

Gads is a SH2 and SH3 domain-containing, hematopoietic-specific adaptor pro tein that functions in signalling from the T cell receptor. Gads acts by li nking SLP-76, bound by the carboxy-terminal Gads SH3 domain, to tyrosine ph osphorylated LAT which contains binding sites for the Gads SH2 domain. Gads is distinguished from Grb2 and the closely related Grap protein by the pre sence of a 120 amino acid unique region between the SH2 domain and the carb oxy terminal SH3 domain. Here we demonstrate that the unique region of Gads contains a capase cleavage site. Induction of apoptosis in lymphocytes res ults in detectable Gads cleavage by 60 min. Gads cleavage is blocked in viv o by treating cells with a caspase 3 inhibitor. A putative caspase 3 cleava ge site was identified within the unique region and mutation of this site p revented Gads cleavage in vitro, and in vivo. The Gads cleavage products re tained the predicted binding specificity for SLP-76 and LAT, Expression of the Gads cleavage products in Jurkat T cells inhibited NFAT activation foll owing TCR cross linking. These findings indicate that cleavage of Gads in v ivo could function to alter signalling downstream of the T cell receptor by disrupting cross talk between SLP-76 and LAT.