LCP2,also named as SLP76,is an adapter protein that acts as a substrate of the T cell antigen receptor (TCR)-activated protein tyrosine kinase pathway. It contains an N-terminal leucine Zip motif,a tyrosine-rich domain,a proline-rich domain and a C-terminal SH2 domain. It is constitutively associated with the growth factor receptor-bound protein 2 (Grb2)-related adapter protein 2 (Grap2,a.k.a. GADS) through the interaction of its proline residues with one of the SH3 domains of Grap2. SLP76 associates with growth factor receptor bound protein 2 (Grap2),and is thought to play a role TCR-mediated intracellular signal transduction. SLP76 is also expressed by mast cells,and mast cell activation was markedly impaired in SLP76-deficient mice.