Positively regulates T-cell receptor signaling by enhancing the MAP kinase pathway. Required for optimal conjugation between T- cells and antigen-presenting cells by promoting the clustering of integrin ITGAL on the surface of T-cells. May be involved in high affinity immunoglobulin epsilon receptor signaling in mast cells. {ECO:0000269|PubMed:10856234, ECO:0000269|PubMed:11909961, ECO:0000269|PubMed:12652296, ECO:0000269|PubMed:15939789, ECO:0000269|PubMed:16980616}. This is the function of SKAP1 (src kinase associated phosphoprotein 1, ENSG00000141293).