and neuroligins/neur-exins indicates that the PSD may bridge with the “active zone” of the presynaptic terminal. The Homer family of scaffolding proteins is encoded by 3 genes (Homer1, Homer2, and Homer3). Homer scaffolding proteins interact with the C-terminus of Group I mGluRs, bind to Shank/PSD-95/ NMDA-receptor complexes, and can also interact with a number of downstream effectors of mGlu1/5 including: IP3 receptors, diacylglycerol lipase-2, and PI3K enhancer (PIKE). Homer proteins are best characterized for their role in regulating mGlu1/5 trafficking, PSD localization, and signaling of mGlu1/5 and NMDA receptors, but are also critical in the regulation of actin and dendritic morphology.93 Furthermore, through their ability to associate with Shank, Homers facilitate cross-talk between mGlu1/5 and NMDA receptors and the integration of their calcium-dependent intracel-lular events underpinning synaptic plasticity.94
