PHILADELPHIA (March 6, 2013) -- Working with a multidisciplinary consortium of 19 researchers from nine institutions, Monell scientists have provided critical information to identify CALHM1, a channel in the walls of taste receptor cells, as a necessary component in the process of sweet, bitter, and umami (savory) taste perception.
When sweet, bitter and umami molecules reach the tongue, they activate taste receptors in specialized cells called Type II taste cells. "The question that the consortium wanted to answer is, 'how do these taste cells tell the brain that they have detected something?' said Monell taste biologist Michael G. Tordoff, PhD. "This question has been a longstanding missing link in our understanding of taste perception."
The scientists already knew that activation of taste receptors on Type II cells initiates a complex chain of events inside the taste cells. What they found, as reported in the current issue of Nature, is that the final step involves the opening of a pore formed by CALHM1 in the taste cell membrane. The open channel allows molecules of the neurotransmitter ATP to leave the taste cell and relay a signal to adjacent nerve cells connected to the brain.
Monell molecular neurobiologist Ichiro Matsumato, PhD, contributed to the work by showing that the gene for CALHM1 is expressed in Type II taste cells, but not in other types of taste tissue. "Our findings demonstrate that the CALHM1 pore is localized specifically in cells that detect sweet, bitter and umami taste," said Matsumato.
The necessity of CALHM1 for the ability to taste sweet, bitter, and umami was demonstrated in behavioral tests performed by Tordoff. Reasoning that mice lacking the CALMH1 channel would not be able to release ATP to send information about sweet, bitter and umami taste detection to the brain, Tordoff tested the taste preferences of Calhm1 'knockout' mice. Engineered by co-author Philippe Marambaud, PhD, of the
|Contact: Leslie Stein|
Monell Chemical Senses Center