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Eur J Neurosci. 2001 Dec;14(12):1947-52.

The voltage-sensitive motor protein and the Ca2+-sensitive cytoskeleton in developing rat cochlear outer hair cells.

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Laboratoire de Biologie Cellulaire et Moléculaire de l'Audition, EMI INSERM 99-27, Université de Bordeaux 2, Hôpital Pellegrin, Bat PQR, 33076 Bordeaux, France.


Cochlear outer hair cells (OHCs) possess a unique fast voltage-driven motility associated with a voltage-sensitive motor protein embedded in the basolateral membrane. This mechanism is believed to underlie the cochlear amplification in mammals. OHCs also have a Ca2+/calmodulin-dependent mechanical pathway which involves a submembranous circumferential cytoskeleton. The purpose of this study was to compare the functional appearance of the voltage-sensitive motor proteins with that involving the Ca2+-sensitive cytoskeleton during postnatal development of rat OHCs. We demonstrate that whole-cell electromotility and Ca2+-voked mechanical responses, by ionomycin, develop concomitantly after postnatal day 5 (P5). These two mechanical properties also develop simultaneously in OHCs isolated from two-week-old cultures of P0-P1 organs of Corti. This excludes the participation of neural innervation in the postnatal maturation of the OHCs' motile properties. In addition, we show that the expression of the membranous voltage-sensitive motor protein precedes, by several days, the appearance of whole-cell electromotility. The concomitant development of whole-cell electromotility and Ca2+-sensitive motility, both in vivo and in vitro, underlines the cytoskeleton as an important factor in the functional organization of the voltage-sensitive motor proteins within the plasma membrane.

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