Two Interdependent TRPV Channel Subunits, Inactive and Nanchung, Mediate Hearing inDrosophila

Hearing inDrosophiladepends on the transduction of antennal vibration into receptor potentials by ciliated sensory neurons in Johnston's organ, the antennal chordotonal organ. We previously found that aDrosophilaprotein in the vanilloid receptor subfamily (TRPV) channel subunit, Nanchung (NAN), is localized to the chordotonal cilia and required to generate sound-evoked potentials (Kim et al., 2003). Here, we show that the only otherDrosophilaTRPV protein is mutated in the behavioral mutantinactive(iav). The IAV protein forms a hypotonically activated channel when expressed in cultured cells; in flies, it is specifically expressed in the chordotonal neurons, localized to their cilia and required for hearing. IAV and NAN are each undetectable in cilia of mutants lacking the other protein, indicating that they both contribute to a heteromultimeric transduction channelin vivo. A functional green fluorescence protein-IAV fusion protein shows that the channel is restricted to the proximal cilium, constraining models for channel activation.