title: Presynaptic localization of G protein isoforms in the efferent nerve terminals of the mammalian cochlea.
abstract: Heterotrimeric guanine nucleotide binding proteins (G proteins) are known to be involved in receptor-mediated synaptic activity. In order to determine which G protein isoforms, if any, are involved in synaptic regulation in the organ of Corti, we performed an extensive immunocytochemical screening. We localized a Galpha(q/11) isoform to the efferent nerve terminals using antibodies specific against the alpha subunit of these proteins. The label was observed in the efferent boutons contacting either the outer hair cells or the afferent fibers at the inner spiral bundle. We compared the localization of this isoform to that of the presynaptic protein SNAP-25 in double labeling experiments. Galpha(q/11) immunoreactivity was present predominantly in the cytoplasm of the presynaptic boutons in a region of high density of synaptic vesicles, while SNAP-25 was localized predominantly in the plasma membrane of the boutons. No label for these proteins was found at the afferent synapses, including the presynaptic terminals on hair cells. These results suggest that an isoform of the Gq subfamily of the G proteins might be involved in presynaptic modulation of neurotransmitter release at the cochlear efferents.
authors.affiliation: Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: M
authors.initials: M
authors.lastname: Kurc
authors.forename: V
authors.initials: V
authors.lastname: Dodane
authors.forename: D S
authors.initials: DS
authors.lastname: Pinto
authors.forename: B
authors.initials: B
authors.lastname: Kachar
mesh_terms: D000818:Animals; D003051:Cochlea / Q000294:innervation* / Q000378:metabolism*; D004525:Efferent Pathways / Q000378:metabolism; D005260:Female; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009925:Organ of Corti / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D015398:Signal Transduction; D050825:Synaptosomal-Associated Protein 25
chemical_list: D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050825:Synaptosomal-Associated Protein 25; D019204:GTP-Binding Proteins