Adapter protein that binds F-actin and DNM1, and thereby plays a role in receptor-mediated endocytosis. Required for the formation of organized podosome rosettes. May act as a common effector of antigen receptor-signaling pathways in leukocytes. Acts as a key component of the immunological synapse that regulates T-cell activation by bridging TCRs and the actin cytoskeleton to gene activation and endocytic processes (By similarity). Plays a role in the reorganization of the actin cytoskeleton, formation of cell projections, such as neurites, in neuron morphogenesis and synapse formation via its interaction with WASL and COBL. Does not bind G-actin and promote actin polymerization by itself. Interacts with FGD1, MAP4K1 and PRAM1 (By similarity). Interacts with ANKRD54. Interacts with WASL and WIPF1 (By similarity). Interacts with SHANK2 and SHANK3. Interacts with both COBL and PACSIN1. Interacts with DNM1 and SYN1. Associates with lamellipodial actin and membrane ruffles. Colocalizes with actin and cortactin at podosome dots and podosome rosettes. Detected in brain (at protein level). Widely expressed in brain with highest levels in hippocampus and cerebral cortex. Located primarily in dendrites and, in moderate amounts, in cell bodies. Isoform 1 and isoform 3 are the predominant isoforms in brain. The SH3 domain mediates interaction with SHANK2, SHANK3 and PRAM1. Belongs to the ABP1 family.