Biological complexity: specialized taste proteins (Introduction)

by David Turell , Tuesday, January 09, 2018, 17:40 (2510 days ago) @ David Turell

There are two specialized proteins necessary to send taste signals to the brain for interpretation:

https://medicalxpress.com/news/2018-01-chemical-pathway-brain-sweet-savory.html

"Until now, many scientists believed that a single protein—TRPM5—acted as a gatekeeper for tasting these delectable foods. Remove TRPM5 from a person's taste cells, and they would no longer be able to identify sweet, bitter or savory (also called umami) foods.

"A new study challenges this thinking. The research, published on Jan. 8 finds that a second protein—TRPM4—performs a similar role in the taste system.

In experiments, mice who had TRPM4 drank sugar water enthusiastically and enjoyed a savory treat. They also recoiled from quinine, a bitter compound. Mice who were missing the protein on their taste cells had a more difficult time detecting sweet, bitter and savory flavors.

"'Our research shows that there is redundancy in the taste system," says lead researcher Kathryn Medler, Ph.D., associate professor of biological sciences in the University at Buffalo College of Arts and Sciences. "This is important because taste is actually central to our survival. If you can't taste something bitter, you might gobble up something that's poisonous without ever knowing that it could be harmful."

***

"Like TRPM5, TRPM4 is a special kind of protein called an ion channel. Found on taste cells, TRPM5 and TRPM4 channels open when sweet, bitter or savory foods land on the tongue. This sets off a chain reaction in which the cells produce an electrical signal that travels to the brain, notifying the organ of which flavors have been detected.

"Banik and Medler's new study found that mice were most sensitive to sweet, bitter and umami stimuli when the animals had both TRPM5 and TRPM4 on their taste cells. Removing either protein caused a decrease in sensitivity, and removing both left the mice unable to detect the flavors at all.

"Though the study was done on mice, the research is likely relevant to humans, Medler says. TRPM5 and TRPM4 are both present in human taste cells, and TRPM5 is known to play a role in how people taste."

Comment: How did evolution as a chance process find these two specific proteins? But more to the point is the magical way the particular stimuli are identified as electrical impulses which can be specifically identified by the brain neurons. All of our sensory input is really a second-hand representation of reality. But it works.