A bundle of stereocilia from a rat earFLICKR, ZEISS MICROSCOPYFor decades, scientists have been trying to pin down the channel in ears’ hair cells that converts mechanical energy from sound waves to an electrical message in the brain. Yet for all the work numerous labs have put toward identifying this so-called mechanotransduction channel, it has remained out of reach. Scientists have now identified another piece of the puzzle, a protein called TMIE that is essential for mechanotransduction and that localizes to just the right spot in the cell. Their results were published in Neuron last week (November 20).
“This new paper locks down that TMIE is involved in mechanotransduction,” said Peter Barr-Gillespie of Oregon Health & Science University who did not participate in the study. What remains unknown, however, is whether TMIE is an accessory to the pore-forming part of the channel or actually part of that elusive conductance pathway.
The basic structure of hair cells includes a finger-like protrusion called a stereocilium. Each stereocilium is connected to its neighbor stereocilium by a “tip link,” an extracellular filament that triggers the activity of the mechanotransduction channel when the tip link moves in response to sound waves coursing through the cochlea. At one end of the tip link is the protein cadherin 23; at the other end—adjacent to the channel—is the protein protocadherin 15.
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