Stimulates GTP hydrolysis of members of the Rho family. Its action on RHOA activity and signaling is implicated in growth and stabilization of dendritic spines, and therefore in synaptic function. Critical for the stabilization of AMPA receptors at postsynaptic sites. Critical for the regulation of synaptic vesicle endocytosis at pre-synaptic terminals. Required for the localization of NR1D1 to dendrites, can suppress its repressor activity and protect it from proteasomal degradation (By similarity). Interacts with HOMER1. Interacts with AMPA receptor complexes. Interacts with SH3GL2 (endophilin-A1) (By similarity). Interacts (via C-terminus) with NR1D1 (By similarity).