Tryptophan‐rich basic protein (WRB) mediates insertion of the tail‐anchored protein otoferlin and is required for hair cell exocytosis and hearing |
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| Authors: | Rosamaria Santarelli Montserrat Rodriguez‐Ballesteros Thomas Weber Sangyong Jung Elena Cardenas Xudong Wu Sonja M Wojcik Kelvin Y Kwan Ignacio del Castillo Blanche Schwappach Nicola Strenzke David P Corey Shuh‐Yow Lin Tobias Moser |
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| Affiliation: | 1. Department of Neurosciences, University of Padova, Padova, Italy;2. Audiology and Phoniatrics Service, Treviso Regional Hospital, Treviso, Italy;3. Servicio de Genetica, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain;4. Institute for Auditory Neuroscience and InnerEarLab, University Medical Center G?ttingen, G?ttingen, Germany;5. Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, G?ttingen, Germany;6. Otolaryngology Division, Department of Surgery, School of Medicine, University of California San Diego, La Jolla, CA, USA;7. Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA;8. Department of Molecular Neurobiology, Max‐Planck‐Institute for Experimental Medicine, G?ttingen, Germany;9. W. M. Keck Center for Collaborative Neuroscience, Nelson Lab‐D250, Rutgers University, Piscataway, NJ, USA;10. Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain;11. Institute of Molecular Biology, University Medical Center G?ttingen, G?ttingen, Germany;12. Collaborative Research Center 889, University of G?ttingen, G?ttingen, Germany;13. Auditory Systems Physiology Group and InnerEarLab, Department of Otolaryngology, University of G?ttingen Medical Center, G?ttingen, Germany;14. Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center G?ttingen, G?ttingen, Germany |
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| Abstract: | The transmembrane recognition complex (TRC40) pathway mediates the insertion of tail‐anchored (TA) proteins into membranes. Here, we demonstrate that otoferlin, a TA protein essential for hair cell exocytosis, is inserted into the endoplasmic reticulum (ER) via the TRC40 pathway. We mutated the TRC40 receptor tryptophan‐rich basic protein (Wrb) in hair cells of zebrafish and mice and studied the impact of defective TA protein insertion. Wrb disruption reduced otoferlin levels in hair cells and impaired hearing, which could be restored in zebrafish by transgenic Wrb rescue and otoferlin overexpression. Wrb‐deficient mouse inner hair cells (IHCs) displayed normal numbers of afferent synapses, Ca2+ channels, and membrane‐proximal vesicles, but contained fewer ribbon‐associated vesicles. Patch‐clamp of IHCs revealed impaired synaptic vesicle replenishment. In vivo recordings from postsynaptic spiral ganglion neurons showed a use‐dependent reduction in sound‐evoked spiking, corroborating the notion of impaired IHC vesicle replenishment. A human mutation affecting the transmembrane domain of otoferlin impaired its ER targeting and caused an auditory synaptopathy. We conclude that the TRC40 pathway is critical for hearing and propose that otoferlin is an essential substrate of this pathway in hair cells. |
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| Keywords: | deafness endoplasmic reticulum protein targeting synapse tail‐anchored protein |
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