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.