Involved in cytoskeletal rearrangements required for phagocytosis of apoptotic cells and cell motility. Along with DOCK1, mediates CRK/CRKL regulation of epithelial and endothelial cell spreading and migration on type IV collagen (PubMed:19004829). Functions as a guanine nucleotide exchange factor (GEF), which activates Rac Rho small GTPases by exchanging bound GDP for free GTP. Its GEF activity may be enhanced by ELMO1 (PubMed:8657152). Interacts with the SH3 domains of CRK and NCK2 via multiple sites (PubMed:8657152, PubMed:8662907, PubMed:11240126). Interacts with nucleotide-free RAC1 via its DOCKER domain (PubMed:9808620, PubMed:12134158). Interacts with ELMO1, ELMO2 and probably ELMO3 via its SH3 domain (PubMed:12134158). Interacts with ADGRB1. Identified in a complex with AUTS2 and ELMO2 (By similarity). Recruited to membranes via its interaction with phosphatidylinositol 3,4,5-trisphosphate. Highly expressed in placenta, lung, kidney, pancreas and ovary. Expressed at intermediate level in thymus, testes and colon. The DOCKER domain is necessary and sufficient for the GEF activity. Belongs to the DOCK family.