TMC1 confers a leak conductance to modulate excitability of auditory hair cells in mammals

Hearing sensation relies on the mechanoelectrical transducer (MET) channel of cochlear hair cells, in which Transmembrane channel-like 1 (TMC1) and TMC2 have been proposed to be the pore-forming subunits. Meanwhile it has been reported that TMCs regulate other biological processes in a variety of lower organisms ranging from sensations to motor functions. However, it is still an open question whether TMCs play roles other than their function in MET in mammals. In this study, we report that in mouse hair cells TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitution, 4 amino acids of TMC1 are characterized critical for the leak conductance. The leak conductance is essential for action potential firing and tonotopic along the cochlear coil. Taken together, our results suggest that TMC1 confers a background leak conductance that modulates membrane excitability in cochlear hair cells.