Finally, scientists have discovered a key molecular mechanism behind human hearing

Scientists have finally discovered the structure of a mysterious protein complex inside the inner ear that enables hearing in humans.

To solve this decades-old puzzle, researchers had to grow 60 million roundworms (Caenorhabditis elegans), which use a protein complex very similar to that of humans to detect touch.

Since humans only have a tiny amount of this protein in their inner ear, they turn to another source. was the only way for the team to accumulate enough protein to study.

“We spent several years optimizing methods for growing worms and isolating proteins, and we had many ‘low points’ when we considered giving up,” says co-first author Sarah Clark. , a biochemist from Oregon Health and Science University (OHSU). in Portland.

Researchers have known for some time that the transmembrane channel-like protein 1 (TMC1) complex plays an important role in hearing, but the exact composition has remained elusive.

“This is the last sensory system in which this fundamental molecular machinery has remained unknown,” says lead author Eric Gouaux, senior biochemist at OHSU.

Thanks to this new research, published in Naturewe now know that this protein complex functions as a voltage-sensitive ion channel that opens and closes based on the movement of hairs inside the inner ear.

Using electron microscopy, the researchers found that the protein complex “looks like an accordion”, with subunits “supported like handles” on either side.

Sound waves passing through the ear strike the eardrum (tympanic membrane), then the inner ear where they shake the ossicles; three of the smallest bones in the body. The ossicles strike the snail-like cochlea, which in turn brushes microscopic finger-like hairs called stereocilia against the membranes.

These stereocilia are embedded in cells that have ion channels formed by the TMC1 complex that open and close as the hairs move, sending electrical signals along the auditory nerve to the brain to be interpreted as sound.

“The field of auditory neuroscience has been waiting for these results for decades, and now that they’re here, we’re thrilled,” says OSHU otolaryngologist Peter Barr-Gillespie, a national leader in heart disease research. hearing who did not participate in the study.

This discovery could one day help researchers develop treatments for hearing loss.

Hearing loss and deafness affect more than 460 million people worldwide. By understanding the nature of hearing, researchers can continue to find various ways to support, treat or prevent hearing loss in our community.

This article was published in Nature.