Distribution of members of the PSD-95 family of MAGUK proteins at the synaptic region of inner and outer hair cells of the guinea pig cochlea

PDZ-domain containing proteins of the MAGUK (membrane-associated guanylate kinase) family target, anchor, and cluster receptors and channels to subcel lular sites. Among the MAGUK proteins, the members of the PSD-95 family (MA GUKs: PSD-95, PSD-93, SAP-97, and SAP-102) target and anchor glutamate rece ptors to the synaptic terminals. Associations of glutamate receptors with M AGUKs have been described in the brain but not in the cochlea. In this stud y, RT-PCR, immunofluorescence microscopy, and immunoelectron microscopy wer e used to investigate the presence and distribution of MAGUK proteins in th e organ of Corti. The presence of the mRNA for PSD-95, PSD-93, SAP-97, and SAP-102 in the organ of Corti was confirmed by RT-PCR, Immunocytochemistry using a "pan-MAGUK" antibody, which recognizes all four MAGUK proteins, and selective antibodies against these proteins revealed that all four MAGUKs are present within the base of inner hair cells while all except SAP-97 are found within the base of the outer hair cells. In addition, PSD-93 and PSD -95 are found in postsynaptic afferent terminals on inner hair cells, while postsynaptic afferent terminals on outer hair cells have PSD-93. Synapse 4 0:258-268, 2001, (C) 2001 Wiley-Liss, Inc.dagger