MOTILITY VOLTAGE SENSOR OF THE OUTER HAIR CELL RESIDES WITHIN THE LATERAL PLASMA-MEMBRANE

The outer hair cell (OHC) from the organ of Corti is believed to be re sponsible for the mammal's exquisite sense of hearing. A membrane-base d motile response of this cell underlies the initial processing of aco ustic energy. The voltage-dependent capacitance of the OHC, possibly r eflecting charge movement of the motility voltage sensor, was measured in cells during intracellular dialysis of trypsin under whole cell vo ltage clamp. Within 10 min after dialysis, light and electron microsco pic examination revealed that the subplasmalemmal structures, includin g the cytoskeletal framework and subsurface cisternae, were disrupted and/or detached from adjacent plasma membrane. Dialysis of heat-inacti vated trypsin produced no changes in cell structure, Simultaneous meas ures of linear and nonlinear membrane capacitance revealed minimal cha nges, indicating that contributions by subsurface structures to the ge neration of the nonlinear capacitance are unlikely, This study strongl y suggests that voltage-dependent charge movement in the OHC reflects properties of the force generator's voltage sensor and that the sensor /motor resides solely within the lateral plasma membrane.