title: Rabconnectin3α promotes stable activity of the H+ pump on synaptic vesicles in hair cells.
abstract: Acidification of synaptic vesicles relies on the vacuolar-type ATPase (V-ATPase) and provides the electrochemical driving force for neurotransmitter exchange. The regulatory mechanisms that ensure assembly of the V-ATPase holoenzyme on synaptic vesicles are unknown. Rabconnectin3α (Rbc3α) is a potential candidate for regulation of V-ATPase activity because of its association with synaptic vesicles and its requirement for acidification of intracellular compartments. Here, we provide the first evidence for a role of Rbc3α in synaptic vesicle acidification and neurotransmission. In this study, we characterized mutant alleles of rbc3α isolated from a large-scale screen for zebrafish with auditory/vestibular defects. We show that Rbc3α is localized to basal regions of hair cells in which synaptic vesicles are present. To determine whether Rbc3α regulates V-ATPase activity, we examined the acidification of synaptic vesicles and localization of the V-ATPase in hair cells. In contrast to wild-type hair cells, we observed that synaptic vesicles had elevated pH, and a cytosolic subunit of the V-ATPase was no longer enriched in synaptic regions of mutant hair cells. As a consequence of defective acidification of synaptic vesicles, afferent neurons in rbc3α mutants had reduced firing rates and reduced accuracy of phase-locked action potentials in response to mechanical stimulation of hair cells. Collectively, our data suggest that Rbc3α modulates synaptic transmission in hair cells by promoting V-ATPase activity in synaptic vesicles.
authors.affiliation: Oregon Hearing Research Center and Vollum Institute, Howard Hughes Medical Institute, Oregon Health and Science University, Portland, Oregon 97239, USA.
authors.forename: Zev
authors.initials: Z
authors.lastname: Einhorn
authors.forename: Josef G
authors.initials: JG
authors.lastname: Trapani
authors.forename: Qianyong
authors.initials: Q
authors.lastname: Liu
authors.forename: Teresa
authors.initials: T
authors.lastname: Nicolson
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects; D000200:Action Potentials / Q000235:genetics; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006198:Hair Cells, Auditory / Q000166:cytology*; D007814:Larva; D053403:Lateral Line System / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008967:Molecular Biology; D009154:Mutation / Q000235:genetics; D010812:Physical Stimulation; D017494:Proton Pumps / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012678:Sensation Disorders / Q000235:genetics; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism; D014741:Video Recording; D014786:Vision Disorders / Q000235:genetics; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004791:Enzyme Inhibitors; D018942:Macrolides; D026901:Membrane Transport Proteins; D017494:Proton Pumps; D012333:RNA, Messenger; D029961:Zebrafish Proteins; C057620:bafilomycin A; D049452:Green Fluorescent Proteins; C520788:V-ATPase subunit A, zebrafish; D025262:Vacuolar Proton-Translocating ATPases