Protein found in both taste buds and inner ear

Protein found in both taste buds and inner ear

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Otop1 is a gene that has been linked to balance and coordination and is also found in taste cells. 

 

Functions in the body are commonly interconnected, but many of them often have unusual connective networks. Recently researchers at the University of Southern California (USC) Dornsife College of Letters, Arts and Sciences discovered that cells responsible for detecting sour foods are functionally connected to the vestibular system in the ear. 

The researchers stumbled upon a new family of ion channels, known as the otopetrin family of genes, that linked these two systems together.

Ion channels play an important role in the body. In short, they are membrane proteins that allow for specific ions to pass through, thereby creating an action potential — or electrical impulse — to be sent across the cell membrane. 

These action potentials happen on an all-or-none basis, kind of like flipping a light switch. They either occur fully or not at all. Action potentials take place when a stimulus temporarily causes a shift in the neuron’s membrane potential due to a sudden movements of ions moving in and out of a neuron. 

At resting potential, the inside of the neuron is negative compared to the outside because of the large amount of positive sodium ions present on the outside. When the sodium ion channels open, an influx of sodium ions rush into the neuron. If the depolarizing current reaches the threshold level, an action potential occurs. 

In 2010, Emily Liman, a professor of biological sciences at USC Dornsife, showed that a specific proton channel was responsible for the cells that detect sour taste. However, the genes responsible for expressing this proton channel were unknown at that time. 

With RNA sequencing, RNAseq for short, Liman and her team were able to determine the genes responsible for expressing only sour taste cells. 

According to ScienceDaily, Yu-Hsiang Tu, a graduate student in Liman’s lab, tested each gene individually in order to find the one that produced a proton-conducting protein in cells that did not have any proton-conducting channels. They identified this gene to be the otopetrin 1 (Otop1) gene.

The otopetrin family, specifically Otop1, has been proven to be essential for people to maintain their balance. This is because Otop1 is required for the proper development of the otoconia, which are calcium carbonate crystals that provide the sense of acceleration and gravity. Mutations in Otop1 have been shown to compromise balancing ability in mice.

Investigators speculated that pH may be the underlying factor that connects the taste system to the vestibular system.

The pH scale is influenced by the presence of positive hydrogen ions. A higher concentration of positive hydrogen ions may indicate a low pH, or an acidic solution, whereas a lower concentration of ions would show a high pH, or a basic solution.

Liman and her team hypothesized that, in the vestibular system, a specific pH condition may be necessary to ensure proper formation of otoconia crystals. By compromising the necessary pH conditions, the ability to balance may also be affected.

“We never in a million years expected that the molecule that we were looking for in taste cells would also be found in the vestibular system,” Liman said in a press release. 

Liman believes that this discovery highlights the power of fundamental research in science.

Kavya Boyapati, a sophomore molecular and cellular biology major at Hopkins, said during an interview with The News-Letter that she would have never guessed that there would be a connection between what seems to be two completely different systems.

“There’s no doubt that more connections like these will be discovered in the future, and I can’t wait to see what two systems will get linked together next time,” Boyapati said.

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