Transduction channels' gating can control friction on vibrating hair-cell bundles in the ear

Significance
In this work, we developed a dynamic force assay to characterize frictional forces that impede sound-evoked vibrations of hair-cell bundles, the mechanosensory antennas of the inner ear. We find that opening and closing of mechanosensitive ion channels in the hair bundle produce frictional forces that can dominate viscous drag on the hair-bundle structure. We show that channel friction can be understood quantitatively using a physical theory of hair-bundle mechanics that includes channel kinetics. Friction originating from gating of ion channels is a concept that is relevant to all mechanosensitive channels. In the context of hearing, this channel friction may contribute to setting the characteristic frequency of the hair cell.