Has an important role in stress fiber formation induced by active diaphanous protein homolog 1 (DRF1). Induces microspike formation, in vivo (By similarity). In vitro, stimulates N-WASP-induced ARP2/3 complex activation in the absence of CDC42 (By similarity). May play an important role in the maintenance of sarcomeres and/or in the assembly of myofibrils into sarcomeres. Implicated in regulation of actin polymerization and cell adhesion. Plays a role in angiogenesis. Associates with the intermediate filaments, vimentin and desmin. Binds the first and third SH3 domains of NCK. Binds the proline-rich domains of N-WASP through its SH3 domain (By similarity). Similarly, binds diaphanous protein homolog 1 (DRF1). Binds the SH3 domains of GRB2 through its proline-rich domains. Interacts with Helicobacter pylori toxin vacA. Isoform 4 interacts with FHOD1. Interacts with FASLG. Interacts with TMIGD2. Colocalizes with DRF1 at membrane ruffles, and with Nck at Z-disks in mature cardiac myocytes. Highest expression in heart, brain, skeletal muscle, kidney and liver. Lower levels in placenta, lung, small intestine and leukocytes. Weak expression in colon, thymus and spleen. A chromosomal aberration involving NCKIPSD/AF3p21 is found in therapy-related leukemia. Translocation t(3;11)(p21;q23) with KMT2A/MLL1. Found in a brain affected by Alzheimer disease. May be due to intron retention. Truncated N-terminus.