The voltage-sensitive motor protein and the Ca2+-sensitive cytoskeleton in developing rat cochlear outer hair cells.
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.
Beurg
M
M
Laboratoire de Biologie Cellulaire et Moléculaire de l'Audition, EMI INSERM 99-27, Université de Bordeaux 2, Hôpital Pellegrin, Bat PQR, 33076 Bordeaux, France.
Bouleau
Y
Y
Dulon
D
D
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D018072:Hair Cells, Auditory, Outer / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D006309:Hearing / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D020409:Molecular Motor Proteins / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D007473:Ion Channels; D007476:Ionophores; D020409:Molecular Motor Proteins; D015759:Ionomycin