Homer-binding domain of metabotropic glutamate receptor
This is the proline-rich region of metabotropic glutamate receptor proteins that binds Homer-related synaptic proteins. The Homer proteins form a physical tether linking mGluRs with the inositol trisphosphate receptors (IP3R) that appears to be due to the proline-rich "Homer ligand" (PPXXFr). Activation of PI turnover triggers intracellular calcium release. MGluR function is altered in the mouse model of human Fragile X syndrome mental retardation, a disorder caused by loss of function mutations in the Fragile X mental retardation gene Fmr1. Homer 3 (and to a lesser extent Homer 1b/c) has been shown to form a multimeric complex with mGlu1a and the IP3 receptor, indicating that Homers may play a role in the localization of receptors to their signalling partners.