Perception of sound and gravity by TMC1 and TMC2

Abstract

Central to our ability to hear and sense gravity is a cellular process known as mechanotransduction, which is initiated by the opening of mechanosensitive cation channels located near the tips of the stereocilia of auditory and vestibular inner ear hair cells. The molecular identity of the mechanotransduction channels has eluded researchers despite intensive investigations over the years. In this issue of the JCI, Kawashima et al. report their results obtained using mice with targeted deletion of both transmembrane channel-like 1 (Tmc1) and Tmc2. The use of inner ear hair cells isolated from these mice provided a nearly perfect system for testing the mechanotransduction channels without disrupting functions of other accessory proteins needed in the complicated molecular apparatus, and it allowed the authors to show that the proteins encoded by these genes are integral components of the mechanotransduction complex.

Figure 1. The mechanotransduction process in mammalian hair cells.

Displacement of the stereocilia creates tension in tip links that open the mechanotransduction channels located near the tips of stereocilia. The mechanotransduction channel is coupled to an adaptation motor so tension of the tip link can be properly adjusted.