Compartmentalization of antagonistic Ca2+ signals in developing cochlear hair cells.

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Compartmentalization of antagonistic Ca2+ signals in developing cochlear hair cells.

Proc Natl Acad Sci U S A. 2018 02 27;115(9):E2095-E2104

Authors: Moglie MJ, Fuchs PA, Elgoyhen AB, Goutman JD

Abstract
During a critical developmental period, cochlear inner hair cells (IHCs) exhibit sensory-independent activity, featuring action potentials in which Ca2+ ions play a fundamental role in driving both spiking and glutamate release onto synapses with afferent auditory neurons. This spontaneous activity is controlled by a cholinergic input to the IHC, activating a specialized nicotinic receptor with high Ca2+ permeability, and coupled to the activation of hyperpolarizing SK channels. The mechanisms underlying distinct excitatory and inhibitory Ca2+ roles within a small, compact IHC are unknown. Making use of Ca2+ imaging, afferent auditory bouton recordings, and electron microscopy, the present work shows that unusually high intracellular Ca2+ buffering and "subsynaptic" cisterns provide efficient compartmentalization and tight control of cholinergic Ca2+ signals. Thus, synaptic efferent Ca2+ spillover and cross-talk are prevented, and the cholinergic input preserves its inhibitory signature to ensure normal development of the auditory system.

PMID: 29439202 [PubMed - indexed for MEDLINE]

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