SAP102 (G670) Antibody #3733

Synapse-associated protein 102 (SAP102, DLG3) belongs to the membrane-associated guanylate kinase (MAGUK) protein family and is a homolog of the Drosophila disc large (dlg) tumor suppressor protein. SAP102 consists of three PDZ domains, a Src homology 3 (SH3) domain, and a guanylate kinase (GK) domain (1). The SAP102 protein is more highly expressed in nonproliferating cells than in proliferating cells, indicating a role in the negative regulation of cell growth. SAP102 interacts with the carboxy terminus of the adenomatous polyposis coli (APC) tumor suppressor protein. Furthermore, SAP102 associates with PSD95 in the presence of calcium while the SH3 domain of SAP102 binds calmodulin (2,3). All three PDZ domains of SAP102 participate in binding to the NMDA receptor, interacting specifically with the carboxy-terminal domain of the N-methyl-D-aspartate receptor 2B (NR2B). This SAP102-NR2B interaction may facilitate AMPA receptor withdrawal from the postsynaptic membrane by inhibiting the Erk/MAPK pathway (1,4). Neuronal SAP102 is concentrated at dendritic shafts and spines, axons, and synaptic junctions. At excitatory synapses, SAP102 is involved in NMDA receptor clustering and immobilization and links NMDA receptors to the submembraneous cytomatrix (4). SAP102 and the NMDA receptor function together to mediate plasticity, behavior, and signal transduction (1). A nonsyndromic form of X-linked mental retardation is caused by loss-of-function mutations to the SAP102 gene. The SAP102 protein may be involved in autism since MAGUK proteins in the NMDA receptor complex bind directly to the autism susceptibility gene, neuroligin (1,5).