Enables ionotropic glutamate receptor binding activity and scaffold protein binding activity. Involved in several processes, including dendritic spine morphogenesis; locomotory exploration behavior; and neurotransmitter receptor localization to postsynaptic specialization membrane. Acts upstream of or within protein localization to synapse; regulation of long-term neuronal synaptic plasticity; and synaptic vesicle maturation. Located in several cellular components, including axon; postsynaptic density membrane; and synaptic vesicle. Is extrinsic component of cytoplasmic side of plasma membrane. Part of AMPA glutamate receptor complex. Is active in glutamatergic synapse. Colocalizes with postsynaptic membrane. Is expressed in central nervous system; dorsal root ganglion; olfactory epithelium; and retina. Used to study Williams-Beuren syndrome and autism spectrum disorder. Human ortholog(s) of this gene implicated in autosomal dominant non-syndromic intellectual disability. Orthologous to human DLG4 (discs large MAGUK scaffold protein 4). [provided by Alliance of Genome Resources, Apr 2022]