GRAP2 (GRB2 related adaptor protein 2), a divergent member of the GRB2/Sem5/Drk family, is an adaptor protein involved in leukocyte-specific protein-tyrosine kinase signaling. GRAP2 shares similar structural organization as GRB2 and GRAP with a central SH2 domain flanked by 2 SH3 domains. However, unlike GRB2 and GRAP, the SH2 domain and the C-terminal SH3 domain of GRAP2 contains a unique 120 amino acid glutamine/proline rich sequence. In T lymphocytes, GRAP2 interacts with LAT and SLP-76 to regulate NF-AT (nuclear factor of activated T cells) and form a signaling complex with HPK1 to mediate the JNK signaling pathway. GRAP2 also interacts with M-CSFR and the activated T cell co-stimulatory receptor CD28.