Pairwise coupling of hair cell transducer channels links auditory sensitivity and dynamic range

Hair cells in the inner ear provide the basis for the exquisite hearing capabilities of mammals. These cells transduce sound-induced displacements of their mechanosensitive hair bundle into electrical currents within a fraction of a millisecond and with nanometer fidelity. Excitatory displacements of the hair cell’s bundle tense tip links that open transducer channels. These channels are located either at one or at both ends of the links, where the latter possibility was thought to compromise sensitivity via negative cooperativity, and discarded for quantitatively describing the transduction process. Here, we show instead that this series mode of activation accurately explains measured transduction in hair cells. It enhances both sensitivity and dynamic range of hair cell transduction, by one channel that is extremely sensitive at small displacements while the other responds best to larger stimuli. Our results provide a new framework for exploring the dynamics of hair cell activation.