Adapter protein primarily involved in signaling pathways within T-cells, as well as other immune cells such as platelets, mast cells, and natural killer (NK) cells (PubMed:11313406, PubMed:33159816). Plays a crucial role for transducing signal from the T-cell receptor (TCR) after antigen recognition leading to T-cell activation. Mechanistically, once phosphorylated by the kinase ZAP70, mediates interactions with the guanine-nucleotide exchange factor VAV1, the adapter protein NCK and the kinase ITK (PubMed:8673706, PubMed:8702662). In turn, stimulates the activation of PKC-theta/PRKCQ and NF-kappa-B transcriptional activity in response to CD3 and CD28 costimulation (PubMed:11313406). Also plays an essential role in AGER- induced signaling pathways including p38 MAPK and ERK1/2 activation leading to cytokine release and pro-inflammatory responses (PubMed:33436632). {ECO:0000269|PubMed:11313406, ECO:0000269|PubMed:33436632, ECO:0000269|PubMed:8673706, ECO:0000269|PubMed:8702662}. This is the function of LCP2 (lymphocyte cytosolic protein 2, Ensembl gene identifier ENSG00000043462).