Structure and function of otoferlin, a synaptic protein of sensory hair cells essential for hearing
Hearing relies upon speedy synaptic transmission of sound information from inner hair cells (IHCs) to spiral ganglion neurons. To accomplish this, IHCs use a sophisticated presynaptic machinery including the multi-C<sub>2</sub> domain protein otoferlin that is affected by human deafness mutations. Otoferlin is essential for IHC exocytosis, but how it binds Ca<sup>2+</sup> and the target membrane to serve synaptic vesicle (SV) tethering, docking, and fusion remained unclear. Here, we obtained cryo-electron microscopy structures of otoferlin and employed molecular dynamics simulations of membrane binding. We show that membrane binding by otoferlin involves C<sub>2</sub>B-C<sub>2</sub>G domains and repositions C<sub>2</sub>F and C<sub>2</sub>G domains. Disruption of Ca<sup>2+</sup>-binding sites of the C<sub>2</sub>D domain in mice altered synaptic sound encoding and eliminated the Ca<sup>2+</sup> cooperativity of IHC exocytosis, indicating that it requires the binding of several Ca<sup>2+</sup>-ions by otoferlin. Together, our findings elucidate molecular mechanisms underlying otoferlin-mediated SV docking and support the role of otoferlin as Ca<sup>2+</sup> sensor of SV fusion in IHCs.
Authors
- Julia Preobraschenski (ORCID: https://orcid.org/0000-0002-1825-0433)
- Nicola Strenzke (ORCID: https://orcid.org/0000-0003-1673-1046)
- Constantin Pape (ORCID: https://orcid.org/0000-0001-6562-7187)
- Norbert Babai (ORCID: https://orcid.org/0000-0002-9348-0546)
- Vladimir Peña (ORCID: https://orcid.org/0000-0002-7013-5504)
- Klara Esch (ORCID: https://orcid.org/0000-0002-0729-4713)
- Helmut Grubmüller (ORCID: https://orcid.org/0000-0002-3270-3144)
- Lisa Feldmann (ORCID: https://orcid.org/0009-0002-3404-2869)
- Constantin Cretu (ORCID: https://orcid.org/0000-0002-6466-176X)
- Tobias Moser (ORCID: https://orcid.org/0000-0001-7145-0533)
- Fritz Benseler (ORCID: https://orcid.org/0009-0006-3846-9447)
- Florian Leidner (ORCID: https://orcid.org/0000-0002-0048-889X)
- Csaba Zoltán Kibédi Szabó
- Nils Brose (ORCID: https://orcid.org/0000-0003-0938-8534)
- Carolin Wichmann (ORCID: https://orcid.org/0000-0001-8868-8716)
- Han Chen (ORCID: https://orcid.org/0009-0003-1357-5161)
- Natalia Evdokimova
- Sophia Mutschall
- Abigail Trebilcock
Institutions
- Cancer Research UK (GB)
- German Center for Neurodegenerative Diseases (DE)
- Universitätsmedizin Göttingen (DE)
- European Neuroscience Institute Göttingen (DE)
- Nanoscale Microscopy and Molecular Physiology of the Brain Cluster of Excellence 171 — DFG Research Center 103 (DE)
- Max Planck Institute for Biophysical Chemistry (DE)
- Max Planck Institute of Experimental Medicine (DE)
- Artificial Intelligence in Medicine (Canada) (CA)
- Max Planck Institute for Multidisciplinary Sciences (DE)
- University of Göttingen (DE)
Publication Details
- Journal
- Science Advances
- Published
- 2025-10-15
- DOI
- https://doi.org/10.1126/sciadv.ady8532
- Citations
- 2
- Primary Topic
- Hearing, Cochlea, Tinnitus, Genetics
- Type
- article
- Field-Weighted Citation Impact
- 2.93