Guanine nucleotide exchange factor for the Rho family of Ras-related GTPases. Plays an important role in angiogenesis. Its recruitment by phosphorylated EPHA2 is critical for EFNA1-induced RAC1 GTPase activation and vascular endothelial cell migration and assembly. Interacts (via SH2 domains) with the phosphorylated form of EPHA2. Interacts with NEK3 and PRLR and this interaction is prolactin-dependent (By similarity). Interacts with SSX2IP. Phosphorylated on tyrosine residues in response to FGR activation.