Coupling between outer hair cell electromotility and prestin sensor charge depends on voltage operating point

The OHC drives cochlear amplification, and prestin activity is the basis. The frequency response of nonlinear capacitance (NLC), which is a ratiometric measure of prestin's voltage-sensor charge movement (dQ_p/dV_m), depends on the location of AC voltage excitation along prestin's operating voltage range, being slowest at the voltage (V_h) where NLC peaks. Here we directly investigate the coupling between prestin charge movement (Q_p) and electromotility (eM) at frequencies up to 6.25 kHz, and find tight correspondence between the two at operating voltages displaced from V_h. Near V_h, however, eM shows a slower frequency response than Q_p. We reason that coupling is more susceptible to molecular/cellular loads at V_h, where prestin compliance is expected to be maximal. Recent cryo-EM studies have begun to shed light on structural features of prestin that impact its performance against loads. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.