TRPV5, TRPV6, TRPM6, and TRPM7 do not contribute to hair-cell mechanotransduction
The hair-cell mechanotransduction channel remains unidentified. We tested whether four transient receptor channel (TRP) family members, TRPV5, TRPV6, TRPM6, and TRPM7, participated in transduction. Using cysteine-substitution mouse knock-ins and methanethiosulfonate reagents selective for those alleles, we found that inhibition of TRPV5 or TRPV6 had no effect on transduction in mouse cochlear hair cells. TRPM6 and TRPM7 each interacted with the tip-link component PCDH15 in cultured eukaryotic cells, which suggested they could participate in transduction. Cochlear hair cell transduction was insensitive to shRNA knockdown of Trpm6 or Trpm7, however, and was not affected by manipulations of Mg2+, which normally perturbs TRPM6 and TRPM7. To definitively examine the role of these two channels in transduction, we showed that deletion of either or both of their genes selectively in hair cells had no effect on auditory function. We suggest that TRPV5, TRPV6, TRPM6, and TRPM7 are unlikely to be the pore-forming subunit of the hair-cell transduction channel.