Rho GTPase-activating protein involved in the signal transduction pathway that regulates endothelial cell capillary tube formation during angiogenesis. Acts as a GTPase activator for the RAC1 by converting it to an inactive GDP-bound state. Inhibits RAC1-dependent lamellipodia formation. May also play a role in transcription regulation via its interaction with VEZF1, by regulating activity of the endothelin-1 (EDN1) promoter. Interacts with VEZF1. Mainly cytoplasmic. Some fraction is nuclear. Predominantly present in endothelial cells (at protein level).