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The concentrations of calcium buffering proteins in mammalian cochlear hair cells

journal contribution
posted on 2023-06-08, 23:37 authored by Caroline M Hackney, Shanthini Mahendrasingam, Andrew PennAndrew Penn, Robert Fettiplace
Calcium buffers are important for shaping and localizing cytoplasmic Ca2+ transients in neurons. We measured the concentrations of the four main calcium-buffering proteins (calbindin-D28k, calretinin, parvalbumin-α, and parvalbumin-β) in rat cochlear hair cells in which Ca2+ signaling is a central element of fast transduction and synaptic transmission. The proteins were quantified by calibrating immunogold tissue counts against gels containing known amounts of each protein, and the method was verified by application to Purkinje cells in which independent estimates exist for some of the protein concentrations. The results showed that, in animals with fully developed hearing, inner hair cells had 1/10 of the proteinaceous calcium buffer of outer hair cells in which the cell body contained parvalbumin-β (oncomodulin) and calbindin-D28k at levels equivalent to 5 mM calcium-binding sites. Both proteins were partially excluded from the hair bundles, which may permit fast unbuffered Ca2+ regulation of the mechanotransducer channels. The sum of the calcium buffer concentrations decreased in inner hair cells and increased in outer hair cells as the cells developed their adult properties during cochlear maturation. The results suggest that Ca2+ has distinct roles in the two types of hair cell, reflecting their different functions in auditory transduction. Ca 2+ is used in inner hair cells primarily for fast phase-locked synaptic transmission, whereas Ca2+ may be involved in regulating the motor capability underlying cochlear amplification of the outer hair cell. The high concentration of calcium buffer in outer hair cells, similar only to skeletal muscle, may protect against deleterious consequences of Ca2+ loading after acoustic overstimulation. Copyright © 2005 Society for Neuroscience.

History

Publication status

  • Published

Journal

Journal of Neuroscience

ISSN

0270-6474

Publisher

Society for Neuroscience

Issue

34

Volume

25

Page range

7867-7875

Department affiliated with

  • Neuroscience Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2015-12-03

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