Emerging roles of Dlg-like PDZ proteins in the organization of the NMDA-type glutamatergic synapse.

A group of proteins found at cell-cell junctions have a common structural domain, called PDZ-a stretch of 80-90 amino acid residues initially identified in the three proteins PSD-95, Dlg, and ZO-1. This domain is found in various proteins from bacteria to mammals and is involved in protein-protein interaction. Recently, many proteins containing this domain were identified in the nervous system by molecular cloning and shown to interact with other synaptic proteins, including various transmitter receptors, ion channels, and signal transducers. These PDZ-containing proteins are mostly located near the synaptic membrane and are, therefore, speculated to transport associated proteins to the synapse and/or anchor them at the synaptic sites. Alternatively, as a single molecule often contains multiple PDZ domains that can interact with each other, it may cluster all these synaptic molecules and facilitate their signaling at synaptic sites. This review focuses on the best characterized PDZ-containing proteins that interact with N-methyl-D-aspartate (NMDA)-type glutamate receptors and discusses their functions in synaptic organization.