Prestin and the cochlear amplifier

Abstract

In non-mammalian, hair cell-bearing sense organs amplification is associated with mechano-electric transducer channels in the stereovilli (commonly called stereocilia). Because mammals possess differentiated outer hair cells (OHC), they also benefit from a novel electromotile process, powered by the motor protein, prestin. Here we consider new work pertaining to this protein and its potential role as the mammalian cochlear amplifier.

Figure 1. Two models of prestin gating by voltage, in which the presence of intracellular chloride is an essential factor in both, but the gating mechanisms are different

The long (or extended) state of the molecule corresponds to hyperpolarization of the cell; the short (or compact) state to depolarization. The no-chloride case is arbitrarily modelled as long. In A, Cl⁻ is assumed to associate with a positive binding site and the combination is translocated across the membrane. In B, chloride binding enables a positive gating particle to unlock and be translocated. The cartoons depict incomplete transporters. If full anion transport is demonstrated, a pore region needs to be incorporated.