MAPPING THE DISTRIBUTION OF THE OUTER HAIR CELL MOTILITY VOLTAGE SENSOR BY ELECTRICAL AMPUTATION

The outer hair cell (OHC) possesses a nonlinear charge movement whose characteristics indicate that it represents the voltage sensor respons ible for OHC mechanical activity. OHC mechanical activity is known to exist along a restricted extent of the cell's length. We have used a s imultaneous partitioning microchamber and whole cell voltage clamp tec hnique to electrically isolate sections of the OHC membrane and find t hat the nonlinear charge movement is also restricted along the cell's length. Apical and basal portions of the OHC are devoid of voltage sen sors, corresponding to regions of the cell where the subsurface cister nae and/or the mechanical responses are absent. We conclude that the p hysical domain of the motility voltage sensor corresponds to that of t he mechanical effector and speculate that sensor and effector reside w ithin one intra membranous molecular species, perhaps an evolved nonco nducting or poorly conducting voltage-dependent ion channel.