Major constituent of the PSD essential for postsynaptic signaling. Inhibitory regulator of the Ras-cAMP pathway. Member of the NMDAR signaling complex in excitatory synapses, it may play a role in NMDAR-dependent control of AMPAR potentiation, AMPAR membrane trafficking and synaptic plasticity. Regulates AMPAR-mediated miniature excitatory postsynaptic currents. Exhibits dual GTPase-activating specificity for Ras and Rap. May be involved in certain forms of brain injury, leading to long-term learning and memory deficits (By similarity). Interacts KLHL17, CAMK2A and CAMK2B (By similarity). Interacts with MPDZ. Additional isoforms seem to exist. The C2 domain is required for RapGAP activity. Phosphorylated by CaM-kinase II. Dephosphorylated upon NMDA receptor activation or SYNGAP1/MPDZ complex disruption. Phosphorylation by PLK2 promotes its activity (By similarity). The disease is caused by variants affecting the gene represented in this entry. It is uncertain whether Met-1 or Met-16 is the initiator methionine. Extended N-terminus. Leiden Open Variation Database (LOVD)