Functional association between SLAP-130 and SLP-76 in Jurkat T cells

T cell antigen receptor (TCR) engagement results in protein-tyrosine kinase activation which initiates signaling cascades leading to induction of the interleukin-2 gene. Previous studies identified two substrates of the TCR-i nduced protein-tyrosine kinases, SH2 domain-containing leukocyte specific p rotein of 76 kDa (SLP-76) and SLP-76-associated phosphoprotein of 130 kDa ( SLAP-130). While SLP-76 appears to couple the TCR. with downstream signals, SLAP-130 may play a negative regulatory role in T cell activation. In this study, we demonstrate that consistent with its ability to abrogate the SLP -76 augmentation of TCR-induced activation of the NFAT/AP1 region of the in terleukin-2 promoter, overexpression of SLAP-130 also interferes with the r escue of signaling in SLP-76-deficient Jurkat cells in cotransfection exper iments. The effect of SLAP-130 on SLP-76 function is specific for regulatin g TCR-induced ERK activation, but not phospholipase C gamma 1 phosphorylati on, By generating both deletion and point mutants of SLAP-130, we identifie d tyrosine 559 as critical for the interaction between SLP-76 and SLAP-130. We show that mutation of this residue in context of full-length SLAP-130 d iminishes the ability of SLAP-130 to abrogate SLP-76 function, These data s uggest that the SLAP-130/SLP-76 association is important for the negative r egulatory role that SLAP-130 appears to play in T cell signaling.