EPHEXIN is a 710 amino acid protein that localizes to both the membrane and the cytoplasm and contains one SH3 domain, one PH domain and one DH domain. Expressed at high levels in brain and present at lower levels in lung tissue, EPHEXIN interacts with EphA4 and functions as a guanine nucleotide exchange factor (GEF) that is capable of activating Rho A, Rac 1 and Cdc42 and is thought to play a role in axon guidance and growth cone collapse. EPHEXIN is subject to Src-dependent phosphorylation, an event that increases the GEF activity of EPHEXIN toward Rho A. Human EPHEXIN, which exists as multiple alternatively spliced isoforms, shares a high degree of sequence homology with its mouse counterpart, suggesting a conserved role between species.