Involved in cell shape and neuronal morphogenesis, positively regulating the establishment and maintenance of dendritic spines. Plays a role in cellular protein transport, including protein transport away from primary cilia. May function via activation of RAC1 and PAK1 (By similarity). Homodimer (By similarity). Interacts with RAC1 (By similarity). Interacts (via N-terminus) with MYO5A, the interaction is required for its role in dendrite formation (By similarity). Interacts with RAB8A; interaction is dependent on the phosphorylation of RAB8A on 'Thr-72' (By similarity). Interacts with RAB10 and RAB12; interaction is dependent on the phosphorylation of 'Thr-73' on RAB10 and 'Ser-105' on RAB12 (By similarity). Belongs to the RILPL family.