Adapter protein which acts downstream of several membrane receptors including cytokine, antigen, hormone, cell matrix and growth factor receptors to regulate multiple signaling pathways. Regulates osteoclast differentiation mediating the TNFRSF11A/RANK signaling. In allergic response, it plays a role in mast cells activation and degranulation through PI-3-kinase regulation. Also involved in the regulation of cell proliferation and hematopoiesis. Interacts with SHC1; may mediate interaction with receptors (By similarity). Interacts with SYK (By similarity). Interacts with PI-3 kinase. Interacts with GRB2 (via SH3 2 domain). Interacts (phosphorylated) with PTPN11. Interacts with TNFRSF11A (via cytoplasmic domain). Interacts (phosphorylated) with 14-3-3 family proteins SFN, YWHAB, YWHAE, YWHAG, YWHAH, YWHAQ and YWHAZ; prevents interaction with GRB2 and attenuates GAB2 signaling. Interacts with HCK. The SH3-binding motifs mediate interaction with SHC1 and GRB2. The PH domain mediates phosphatidylinositol 3,4,5-trisphosphate and phosphatidylinositol 3,4-bisphosphate binding. Phosphorylated on tyrosine residue(s) by the thrombopoietin receptor (TPOR), stem cell factor receptor (SCFR), and T-cell and B-cell antigen receptors, gp130, IL-2R and IL-3R (By similarity). Phosphorylated upon stimulation of TNFRSF11A/RANK by TNFSF11/RANKL (By similarity). Phosphorylated upon EGF stimulation. Phosphorylated on tyrosine residues by HCK upon IL6 signaling. Dephosphorylated by PTPN11. Belongs to the GAB family. Extended N-terminus.