Postsynaptic density scaffolding protein. Binds and cross-links cytoplasmic regions of GRM1, GRM5, ITPR1, DNM3, RYR1, RYR2, SHANK1 and SHANK3. By physically linking GRM1 and GRM5 with ER-associated ITPR1 receptors, it aids the coupling of surface receptors to intracellular calcium release. May also couple GRM1 to PI3 kinase through its interaction with AGAP2 (By similarity). Isoforms can be differently regulated and may play an important role in maintaining the plasticity at glutamatergic synapses (By similarity) Required for normal hearing (PubMed:25816005). Negatively regulates T cell activation by inhibiting the calcineurin-NFAT pathway. Acts by competing with calcineurin/PPP3CA for NFAT protein binding, hence preventing NFAT activation by PPP3CA (By similarity). Forms coiled-coil structures coiled-coil structures that mediate homo- and heteromultimerization. Interacts with NFATC2; interaction is reduced by AKT activation. Interacts with NFATC1 and NFATC4 (By similarity). Interacts with DAGLA (via PPXXF motif); this interaction is required for the cell membrane localization of DAGLA (By similarity). Postsynaptic density of neuronal cells. The stabilization and clustering of the metabotropic glutamate receptors appears to be mediated by isoform 1 and isoform 2 at the cell surface. Expressed in olfactory bulb, hippocampus, thalamus and heart (PubMed:9808459). Expressed in the cochlea, organ of Corti. Expression is particularly enriched in the tips of stereocilia of both inner and outer hair cells (PubMed:25816005). Homozygous knockout mice exhibit early onset progressive hearing loss. Belongs to the Homer family.