TRPC-like conductance mediates restoration of intracellular Ca2+ in cochlear outer hair cells in the guinea pig and rat

Nicholas P Raybould, Daniel J Jagger, Refik Kanjhan, Denise Greenwood, Peter Laslo, Noriyuki Hoya, Christian Soeller, Mark B Cannell, Gary D Housley

Research output: Contribution to journalArticle (Academic Journal)

25 Citations (Scopus)

Abstract

Ca2+ signalling is central to cochlear sensory hair cell physiology through its influence on sound transduction, membrane filter properties and neurotransmission. However, the mechanism for establishing Ca2+ homeostasis in these cells remains unresolved. Canonical transient receptor potential (TRPC) Ca2+ entry channels provide an important pathway for maintaining intracellular Ca2+ levels. TRPC3 subunit expression was detected in guinea pig and rat organ of Corti by RT-PCR, and localized to the sensory and neural poles of the inner and outer hair cells (OHCs) by confocal immunofluorescence imaging. A cation entry current with a TRPC-like phenotype was identified in guinea pig and rat OHCs by whole-cell voltage clamp. This slowly activating current was induced by the lowering of cytosolic Ca2+ levels ([Ca2+]i) following a period in nominally Ca2+-free solution. Activation was dependent upon the [Ca2+]o and was sustained until [Ca(2+)]i was restored. Ca2+ entry was confirmed by confocal fluorescence imaging, and rapidly recruited secondary charybdotoxin- and apamin-sensitive K(Ca) currents. Dual activation by the G protein-coupled receptor (GPCR)-phospholipase C-diacylglycerol (DAG) second messenger pathway was confirmed using the analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG). Ion substitution experiments showed that the putative TRPC Ca2+ entry current was selective for Na+ > K+ with a ratio of 1: 0.6. The Ca2+ entry current was inhibited by the TRPC channel blocker 2-aminoethyl diphenylborate (2APB) and the tyrosine kinase inhibitor, erbstatin analogue. We conclude that TRPC Ca2+ entry channels, most likely incorporating TRPC3 subunits, support cochlear hair cell Ca2+ homeostasis and GPCR signalling.
Original languageEnglish
Pages (from-to)101-113
Number of pages13
JournalJournal of Physiology
Volume579
Issue numberPt 1
Publication statusPublished - 15 Jan 2007

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    Raybould, N. P., Jagger, D. J., Kanjhan, R., Greenwood, D., Laslo, P., Hoya, N., Soeller, C., Cannell, M. B., & Housley, G. D. (2007). TRPC-like conductance mediates restoration of intracellular Ca2+ in cochlear outer hair cells in the guinea pig and rat. Journal of Physiology, 579(Pt 1), 101-113.