Acts as guanine nucleotide exchange factor (GEF) for RHOA, RAC1 and CDC42 GTPases. Regulates cell migration and adhesion assembly and disassembly through a RAC1, PI3K, RHOA and AKT1-dependent mechanism. Increases both RAC1 and CDC42 activity, but decreases the amount of active RHOA. Required for MMP9 up-regulation via the JNK signaling pathway in colorectal tumor cells. Involved in tumor angiogenesis and may play a role in intestinal adenoma formation and tumor progression. Both the ABR and the SH3 domains contribute to maintaining the protein in an inhibited conformation by associating with the C-terminal tail. Binding of these domains to the C-terminal tail inhibits the activity of the protein by blocking a region that is required for its GEF activity. Interacts (via ABR and SH3 domain) with APC. The binding of APC enhances its GEF activity by relieving it from an autoinhibitory conformation, in which the ABR and SH3 domains are associated with the C-terminal tail. Interacts (via C-terminal tail) with PPP1R9B (via C-terminus). Interacts with RAC1. Accumulates in the lamellipodium and ruffle membrane in response to hepatocyte growth factor (HGF) treatment. Additional isoforms seem to exist. Expressed at high levels in the placenta, spleen and kidney, at moderate levels in lung, small intestine, liver, brain and heart, and at low levels in skeletal muscle. Expression is aberrantly enhanced in most colorectal tumors. The C-terminal tail is required for its GEF activity. Truncated N-terminus.