Non-uniform mapping of stress-induced, motility-related charge movement in the outer hair cell plasma membrane.

There is a growing consensus that outer hair cell (OHC) electromotility underlies the mammalian cochlear amplifier. This voltage-dependent motility is mirrored by a gating current, which along with motility can be altered by tension applied to the cell's plasma membrane. We used localized tension application along the length of the OHC to induce gating currents from membrane microdomains; with this information we mapped the distribution of the OHC's sensitivity to membrane stress before and after disrupting the cytoskeleton with intracellular Pronase. Mechanically induced gating currents, which were susceptible to salicylate, lanthanides and turgor pressure, evidenced a bell-shaped distribution that was restricted to the lateral membrane where the electromotile response resides. After Pronase treatment, gating currents remained intact and restricted. These results confirm that the molecular motors are intrinsically and bi-directionally susceptible to voltage and tension, and provide evidence for limited mobility of OHC motors within the cell's lateral membrane.