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Journal Article

Endophilin-A regulates presynaptic Ca2+ influx and synaptic vesicle recycling in auditory hair cells.

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Jaime Tobon,  L. M.
Research Group of Synaptic Nanophysiology, MPI for Biophysical Chemistry, Max Planck Society;

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Neef,  J.
Research Group of Synaptic Nanophysiology, MPI for Biophysical Chemistry, Max Planck Society;

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Moser,  T.
Research Group of Synaptic Nanophysiology, MPI for Biophysical Chemistry, Max Planck Society;

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Citation

Kroll, J., Jaime Tobon, L. M., Vogl, C., Neef, J., Kondratiuk, I., König, M., et al. (2019). Endophilin-A regulates presynaptic Ca2+ influx and synaptic vesicle recycling in auditory hair cells. The EMBO Journal, 38(5): e100116. doi:10.15252/embj.2018100116.


Cite as: http://hdl.handle.net/21.11116/0000-0002-FAC3-8
Abstract
Ribbon synapses of cochlear inner hair cells (IHCs) operate with high rates of neurotransmission; yet, the molecular regulation of synaptic vesicle (SV) recycling at these synapses remains poorly understood. Here, we studied the role of endophilins-A1-3, endocytic adaptors with curvature-sensing and curvature-generating properties, in mouse IHCs. Single-cell RT-PCR indicated the expression of endophilins-A1-3 in IHCs, and immunoblotting confirmed the presence of endophilin-A1 and endophilin-A2 in the cochlea. Patch-clamp recordings from endophilin-A-deficient IHCs revealed a reduction of Ca2+ influx and exocytosis, which we attribute to a decreased abundance of presynaptic Ca2+ channels and impaired SV replenishment. Slow endocytic membrane retrieval, thought to reflect clathrin-mediated endocytosis, was impaired. Otoferlin, essential for IHC exocytosis, co-immunoprecipitated with purified endophilin-A1 protein, suggestive of a molecular interaction that might aid exocytosis-endocytosis coupling. Electron microscopy revealed lower SV numbers, but an increased occurrence of coated structures and endosome-like vacuoles at IHC active zones. In summary, endophilins regulate Ca2+ influx and promote SV recycling in IHCs, likely via coupling exocytosis to endocytosis, and contributing to membrane retrieval and SV reformation.