The Cells and Logic for Mammalian Sour Taste detection

In recent years the molecular mechanisms of three of the five basic taste sensations in mammals have been identified: sweet, bitter and umami (monosodium glutamate). The others, sour (or 'acid') and salt, were elusive. Now the cells and a candidate receptor mediating sour taste have been identified. PKD2L1, a polycystic kidney disease-like ion channel, is proposed to act as part of the mammalian sour taste receptor, and shown to define the population of cells on the tongue required for sour taste. PKD2L1 is also found in neurons around the central canal of the spinal cord that trigger action potentials in response to a fall in extracellular pH. These cells could be long-sought components of the cerebrospinal fluid chemosensory system. This work points to a common basis for acid sensing in very different physiological settings. On the cover, tongue tissue with taste receptor cells labelled red for sour sensing and green for sweet, umami and bitter.