A prestin motor in chicken auditory hair cells: active force generation in a nonmammalian species.

Active force generation by outer hair cells (OHCs) underlies amplification and frequency tuning in the mammalian cochlea but whether such a process exists in nonmammals is unclear. Here, we demonstrate that hair cells of the chicken auditory papilla possess an electromechanical force generator in addition to active hair bundle motion due to mechanotransducer channel gating. The properties of the force generator, its voltage dependence and susceptibility to salicylate, as well as an associated chloride-sensitive nonlinear capacitance, suggest involvement of the chicken homolog of prestin, the OHC motor protein. The presence of chicken prestin in the hair cell lateral membrane was confirmed by immunolabeling studies. The hair bundle and prestin motors together create sufficient force to produce fast lateral displacements of the tectorial membrane. Our results imply that the first use of prestin as a motor protein occurred early in amniote evolution and was not a mammalian invention as is usually supposed.