Activates CDC42, a member of the Ras-like family of Rho- and Rac proteins, by exchanging bound GDP for free GTP. Activates JNK1 via CDC42 but not RAC1. Binds to phosphatidylinositol 4,5-bisphosphate, phosphatidylinositol 3,4,5-trisphosphate, phosphatidylinositol 5-monophosphate, phosphatidylinositol 4-monophosphate and phosphatidylinositol 3-monophosphate (By similarity). Recruitment to the endosome and ruffle membrane requires the presence of phosphoinositides. The FYVE-type zinc-finger is necessary for early endosome localization. Recruitment to endosomal membranes via this domain requires the presence of phosphatidylinositol 3-phosphate or other phosphatidylinositides (By similarity). The PH domain is necessary for localization to the ruffle membrane. Recruitment to ruffle membrane occurs through binding of phosphoinositides by the PH domain. This domain also contributes to the lipid-binding properties of the protein (By similarity). The DH domain is necessary for its ability to activate JNK1 via CDC42. May be due to an intron retention. Extended N-terminus.