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 subcellular sites. Among the MAGUK proteins, the members of the PSD-95 family (MAGUKs: PSD-95, PSD-93, SAP-97, and SAP-102) target and anchor glutamate receptors to the synaptic terminals. Associations of glutamate receptors with MAGUKs have been described in the brain but not in the cochlea. In this study, RT-PCR, immunofluorescence microscopy, and immunoelectron microscopy were used to investigate the presence and distribution of MAGUK proteins in the 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.
Davies
C
C
Section on Structural Cell Biology, NIDCD, NIH, Bethesda, Maryland, USA.
Tingley
D
D
Kachar
B
B
Wenthold
R J
RJ
Petralia
R S
RS
D000818:Animals; D051528:Guanylate Kinases; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000737:chemistry* / Q000648:ultrastructure; D018072:Hair Cells, Auditory, Outer / Q000737:chemistry* / Q000648:ultrastructure; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009479:Neuropeptides / Q000032:analysis; D009703:Nucleoside-Phosphate Kinase / Q000032:analysis*; D015221:Potassium Channels / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism; D013136:Spiral Ganglion / Q000737:chemistry / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000737:chemistry* / Q000648:ultrastructure
D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D015221:Potassium Channels; D017470:Receptors, Glutamate; C033652:postsynaptic density proteins; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases