Functions as guanine nucleotide exchange factor for RAC1. May play a role in semaphorin signaling. Plays a role in the assembly and disassembly of dendritic filopodia, the formation of dendritic spines, regulation of dendrite length and ultimately the formation of synapses (By similarity). Interacts with CADM1. Interacts with RAC1 (By similarity). Recruited to the cell membrane via interaction with CADM1. Intramolecular interaction between the DH domain and the PH domains can stabilize the protein in an autoinhibited conformation.