May regulate AMPA receptor content at nascent synapses, and have a role in postsynaptic development and maturation. Homodimer. Interacts with GRIA1 and GRIA2. Shuttles between the cell surface and early endosome membrane. Brain-specific. Expressed in Purkinje neurons in cerebellum. Also detected in the hippocampus. Found at excitatory synapses and postsynaptic cells. Expressed during synaptogenesis. Found at the cell surface of excitatory synapses. Belongs to the CD225/Dispanin family.