Members of the postsynaptic density-95 (PSD-95)/SAP90 family of membrane-associated guanylate kinase (MAGUK) proteins function as multimodular scaffolds that organize protein-signaling complexes at neuronal synapses. SAPAP3 (PSD-95/SAP90-binding protein 3), also known as DLGAP3 (disks large-associated protein 3) or DAP3, is a 979 amino acid protein that belongs to the SAPAP family of PSD-95/SAP90-associated proteins. Localized to the cell junction, as well as to the peripheral membrane and the cell synapse, SAPAP3 is thought to play a role in the organization of neuronal cell signaling and synapses, and may also function as an adaptor protein, possibly linking ion channels with the cytoskeleton.