ARHGEF4 (Rho guanine nucleotide exchange factor 4), also known as ASEF1 (Adenomatous polyposis coli - stimulated guanine nucleotide exchange factor 1) is an approximately 80 kDa cytoplasmic protein important for growth factor-mediated regulation of cell morphology and migration. Besides N-terminal adenomatous polyposis coli (APC)-binding region (ABR) it contains Dbl homology (DH), Pleckstrin homology (PH) and SH3 domains. The SH3 domain inhibits GEF activity of ARHGEF4 by intramolecular interaction with the DH domain, whereas binding of APC stimulates the GEF activity. Activated ARHGEF4 stimulates the small GTPase Cdc42, which leads to decreased cell-cell adherence and enhanced cell migration.