Synapse-associated protein 102 belongs to the membrane-associated guanylate kinase protein family and is a homolog of the Drosophila dis large tumor suppressor protein. SAP102 has extensive sequence homology to the PSD 95 family of proteins that facilitate ion channel clustering at synaptic terminal (1, 2). SAP102 consists of three 90 amino acids PDZ domains at its amino terminus, a Src homology 3 domain and a guanylate kinase domain (3). All three PDZ domains of SAP102 participate in binding to the NMDA reception, interacting specifically with the carboxy-terminal domain of the N-methyl-D-aspartate receptor 2B (NR2B). The interaction may facilitate AMPA receptor withdrawal from the postsynaptic membrane by inhibiting the ERK/MAPK pathway (3, 4). SAP102 also interacts with synaptic ras-GTPase activating protein synGAP through its PDZ domains (3). In general, the SAP102 protein is more highly expressed in non-proliferating cells than in proliferating cells, indicating a role in the negative regulation of cell growth.