Mammals taste using a sensory palette consisting of only 5 basic taste modalities: sweet, bitter, sour, salty, and umami (the taste of monosodium glutamate). Sour taste detection provides important sensory input to warn against the ingestion of acidic foods such as spoiled or unripe fruit. Huang, et al in a study published in the August 24, 2006 issue of Nature, have for the first time identified the sour taste sensor. Called PKD2L1, in the tongue it is expressed in a subset of taste receptor cells distinct from those responsible for sweet, bitter, and umami taste. The study results now establish independent cellular substrates for 4 of the 5 basic taste modalities (all except salty). PKD2L1 is also expressed in specific neurons surrounding the central canal of the spinal cord. The authors of the study propose that these cells correspond to the long-sought components of the cerebrospinal fluid chemosensory system, suggesting a common basis for acid sensing in disparate physiological settings.
(Source: National Institute of Dental and Craniofacial Research Web site, Science News in Brief, accessed September 8, 2006)
