Exocytotic Machineries of Vestibular Type I and Cochlear Ribbon Synapses Display Similar Intrinsic Otoferlin-Dependent Ca2+ Sensitivity But a Different Coupling to Ca2+ Channels - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Neuroscience Année : 2014

Exocytotic Machineries of Vestibular Type I and Cochlear Ribbon Synapses Display Similar Intrinsic Otoferlin-Dependent Ca2+ Sensitivity But a Different Coupling to Ca2+ Channels

Résumé

The hair cell ribbon synapses of the mammalian auditory and vestibular systems differ greatly in their anatomical organization and firing properties. Notably, vestibular Type I hair cells (VHC-I) are surrounded by a single calyx-type afferent terminal that receives input from several ribbons, whereas cochlear inner hair cells (IHCs) are contacted by several individual afferent boutons, each facing a single ribbon. The specificity of the presynaptic molecular mechanisms regulating transmitter release at these different sensory ribbon synapses is not well understood. Here, we found that exocytosis during voltage activation of Ca2+ channels displayed higher Ca2+ sensitivity, 10 mV more negative half-maximum activation, and a smaller dynamic range in VHC-I than in IHCs. VHC-I had a larger number of Ca2+ channels per ribbon (158 vs 110 in IHCs), but their Ca2+ current density was twofold smaller because of a smaller open probability and unitary conductance. Using confocal and stimulated emission depletion immunofluorescence microscopy, we showed that VHC-I had fewer synaptic ribbons (7 vs 17 in IHCs) to which Cav1.3 channels are more tightly organized than in IHCs. Gradual intracellular Ca2+ uncaging experiments revealed that exocytosis had a similar intrinsic Ca2+ sensitivity in both VHC-I and IHCs (KD of 3.3 ± 0.6 μm and 4.0 ± 0.7 μm, respectively). In otoferlin-deficient mice, exocytosis was largely reduced in VHC-I and IHCs. We conclude that VHC-I and IHCs use a similar micromolar-sensitive otoferlin Ca2+ sensor and that their sensory encoding specificity is essentially determined by a different functional organization of Ca2+ channels at their synaptic ribbons.
Fichier principal
Vignette du fichier
10853.full.pdf (4.08 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte
Licence : CC BY - Paternité

Dates et versions

hal-04160516 , version 1 (18-07-2023)

Licence

Paternité

Identifiants

Citer

P. Vincent, Y. Bouleau, S. Safieddine, Christine Petit, D. Dulon. Exocytotic Machineries of Vestibular Type I and Cochlear Ribbon Synapses Display Similar Intrinsic Otoferlin-Dependent Ca2+ Sensitivity But a Different Coupling to Ca2+ Channels. Journal of Neuroscience, 2014, 34 (33), pp.10853-10869. ⟨10.1523/JNEUROSCI.0947-14.2014⟩. ⟨hal-04160516⟩
33 Consultations
3 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More