What is the hair cell transduction channel?

In contrast to nearly all other sensory systems, the mechanically sensitive ion channel carrying the receptor current into hair cells of the inner ear has not been identified in molecular terms. A number of candidates from at least two different ion channel families have been considered: these include the epithelial sodium channel (ENaC) and acid-sensing ion channel (ASIC) members of the DEG/ENaC superfamily of amiloride-sensitive sodium channels, as well as the TRP channels TRPN1, TRPV4, TRPML3 and TRPA1. For each, initial supportive results were followed by further studies that cast doubts on their involvement. No promising candidates have recently emerged, but the TRP family continues to be attractive in general.