Requirement of the Src homology 2 domain protein Shb for T cell receptor-dependent activation of the interleukin-2 gene nuclear factor for activationof T cells element in Jurkat T cells

Stimulation of the T cell antigen receptor (TCR) induces tyrosine phosphory lation of numerous intracellular proteins. We have recently investigated th e role of the adaptor protein Shb in the early events of T cell signaling a nd observed that Shb associates with Grb2, linker for activation of T cells (LAT) and the TCR zeta-chain in Jurkat cells. We now report that Shb also associates with phospholipase C-gamma 1 (PLC-gamma 1) in these cells. Overe xpression of Src homology 2 domain defective Shb caused diminished phosphor ylation of LAT and consequently the activation of mitogen-activated protein kinases was decreased upon TCR stimulation. In addition, the Shb mutant al so blocked phosphorylation of PLC-gamma 1 and the increase in cytoplasmic C a2+ following TCR stimulation. Nuclear factor for activation of T cells is a major target for Ras and calcium signaling pathways in T cells following TCR stimulation, and the overexpression of the mutant Shb prevented TCR-dep endent activation of the nuclear factor for activation of T cells. Conseque ntly, endogenous interleukin-2 production was decreased under these conditi ons. The results indicate a role for Shb as a link between the TCR and down stream signaling events involving LAT and PLC-gamma 1 and resulting in the activation of transcription of the interleukin-2 gene.