The discovery of molecular “springs” reveals how hearing is caused

Auditation begins with the elongation of the elastic molecule “springs,” which open ion channels to the sensory hair cells of the ear. For decades, researchers knew that these gating springs had to exist, but they couldn’t find them. The team at Göttingen’s Cluster of Excellence Multiscale Bioimaging (MBEXC) has now discovered such a spring for the first time. Their findings shed new light on our understanding of hearing sensation and the function of ion channels.

The results are displayed in Natural Neuroscience.

When a sound hits your ear, it causes small movements inside. “Audible cells” register these movements with the help of special molecules known as ion channels. Auditory cells have pores with normally closed phyla. Any movement detected inside the ear must be sent to the ion channel gate to open.

This is done by gating springs. This is elastic and resilient, like a ballpoint pen spring. As these gating springs extend, they open the channel gate and allow ions to flow through the channel pores.

Researchers have been searching for these springs for over 40 years. They previously discovered promising structures in the ears of fruit flys. In addition to the gates and pores, there are ion channels with areas that are spirally wound, like ballpoint pen springs. Therefore, researchers suspected that this spiral could become a gating spring.

The research team, led by Professor Martin Gepfert, director of the Department of Cell Neurobiology at the University of Goettingen, tested it.

“Our assumption would be to double the spiral and cut the stiffness of the gating spring by halving it. That wasn’t,” says Dr. Thomas Effertz, one of the two lead authors of the University Medical Center.

Researchers found that the coiled spiral is stiff but flexible to the channel gate via a bent hinge. When researchers doubled the hinges and placed the two hinges in the tandem, the opening spring was halved. This indicates that the hinge is a gating spring.

“In fact, we were able to observe that at the molecular level it is a flexible joint that bends under mechanical tension, not a spiral,” says Professor Bert de Groot of the Max Planck Institute in Goettingen.

“We have doubts,” says Dr. Philip Herat, Department of Cell Neurobiology and co-leader author at the University of Goettingen.

These results not only provide important new insights into how auditory processes are initiated at the molecular level, but also contribute to a better understanding of the basic functions of ion channels, which are key components of all cells and the basis of all senses.