Postsynaptic RAC1 GTPase activating protein (GAP) that plays a key role in neuronal morphogenesis and migration mainly during development of the cerebral cortex. Regulates excitatory and inhibitory synapse maturation and density in cortical pyramidal neurons. SRGAP2/SRGAP2A limits excitatory and inhibitory synapse density through its RAC1-specific GTPase activating activity, while it promotes maturation of both excitatory and inhibitory synapses through its ability to bind to the postsynaptic scaffolding protein HOMER1 at excitatory synapses, and the postsynaptic protein GPHN at inhibitory synapses. Mechanistically, acts by binding and deforming membranes, thereby regulating actin dynamics to regulate cell migration and differentiation. Promotes cell repulsion and contact inhibition of locomotion: localizes to protrusions with curved edges and controls the duration of RAC1 activity in contact protrusions. In non-neuronal cells, may also play a role in cell migration by regulating the formation of lamellipodia and filopodia. Homodimer. Forms a heterooligomer with SRGAP1 and SRGAP3 through its F-BAR domain. Interacts (via SH3 domain) with GPHN. Interacts (via SH3 domain) with FMNL1 (activated by RAC1); regulates the actin filament severing activity of FMNL1 and actin dynamics. Interacts (via SH3 domain) with FMNL3. Interacts with RAC1; specifically stimulates RAC1 GTPase activity. Interacts (via F-BAR domain) with HOMER1. Interacts with ROBO1 and ROBO2 (By similarity). Interacts with FASLG. Interacts with PRMT5 (By similarity). Recruited to actin-rich phagosomes during phagocytosis (By similarity). Translocates from nucleus to cytoplasm during development (PubMed:17710530). Expressed in brain during neonatal period. Not detected in adult brain (at protein level). The F-BAR domain mediates oligomerization, binds membranes, and induces plasma membrane protrusions. Methylation at Arg-927 is required for the stimulation of cell migration, dimerization and localization at the plasma membrane protrusions.