A team headed by biologists from the University of California, San Diego has discovered the cells and the protein that enable us to detect sour, one of the five basic tastes. The scientists, who included researchers from the National Institute of Dental and Craniofacial Research, suggest that this protein is also the long-sought sensor of acidity in the cerebrospinal fluid.
The study, featured on the cover of the August 24 issue of the journal Nature, reports that each of the five basic tastes is detected by distinct taste receptors--proteins that detect taste molecules--in distinct cells. The team previously discovered the sweet, bitter and umami (savory) receptors and showed that they are found in separate cells, but some researchers have argued that sour and salty tastes, which depend on the detection of ions, would not be wired in the same way.
"Our results show that each of the five basic taste qualities is exquisitely segregated into different taste cells" explained Charles Zuker, a professor of biology at UCSD and a Howard Hughes Medical Institute Investigator, who headed the study. "Taken together, our work has also shown that all taste qualities are found in all areas of the tongue, in contrast with the popular view that different tastes map to different areas of the tongue."
To determine if the taste cells and receptors for sour were separate from the receptors for the other basic tastes, the researchers tested mice in which they had genetically ablated the cells containing the sour taste receptors. The mice could not taste sour, but had completely normal sweet, bitter, umami and salty tastes. Therefore, although the salt taste receptor has not yet been discovered, it and the four identified receptors must each be segregated into distinct taste cells.
In addition to being found in the taste buds, the researchers discovered that the sour protein receptor, PKD2L1, is also found along the entire length of the spin
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Contact: Sherry Seethaler
sseethaler@ucsd.edu
858-534-4656
University of California - San Diego
23-Aug-2006