Protein sends message to brain that tongue has detected sweet, bitter or umami flavor

By Rachel Ehrenberg

Web edition: March 6, 2013

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When something hits a taste bud (cross sections mouse taste buds shown), it kicks off a chain of events: Detectors of bitter, sweet or umami (yellow-green cells) ultimately open a newly pinpointed gateway, releasing molecules that send the taste signal to the brain.

Credit: Akiyuki Taruno

When something leaves a bad taste in your mouth — or a good one — you might blame a newly pinpointed protein. Experiments using mice have revealed a key player in the chain of events that lets the brain know what the tongue has tasted.

Kevin Foskett of the University of Pennsylvania and colleagues found that the protein Calhm1 sits on bitter, sweet and umami taste cells. It serves as a gateway, releasing a flood of molecules from the cell when alerted to the taste of one of the three flavors. Those released molecules — ATP, typically an energy source for cells — may be the final of several messengers in a chain that activates the brain’s taste-sensing nerves, the researchers found.

Mice that couldn’t make Calhm1 were neither turned off by bitter tastes nor fond of sweet or umami ones. Instead, they treated those flavors as if they were water, the researchers report March 7 in Nature.