Bidirectional temperature-sensing by a single  thermosensory neuron in C. elegans.
Humans and other animals can sense temperature changes as small as 0.1 degree C. How animals achieve such exquisite sensitivity is poorly understood. By recording from the C. elegans thermosensory neurons AFD in vivo, we found that cooling closes and warming opens ion channels. We found that AFD thermosensitivity, which exceeds that of most biological processes by many orders of magnitude, is achieved by nonlinear signal amplification. Mutations in genes encoding subunits of a cyclic guanosine monophosphate (cGMP)-gated ion channel (tax-4 and tax-2) and transmembrane guanylate cyclases (gcy-8, gcy-18 and gcy-23) eliminated both cooling- and warming-activated thermoreceptor currents, indicating that a cGMP-mediated pathway links variations in temperature to changes in ionic currents. The resemblance of C. elegans thermosensation to vertebrate photosensation and the sequence similarity between TAX-4 and TAX-2 and subunits of the rod phototransduction channel raise the possibility that nematode thermosensation and vertebrate vision are linked by conserved evolution.
Ramot
Daniel
D
Program in Neuroscience, Stanford University, 279 Campus Dr., Stanford, California 94305, USA.
MacInnis
Bronwyn L
BL
Goodman
Miriam B
MB
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D003080:Cold Temperature; D006152:Cyclic GMP / Q000378:metabolism; D006162:Guanylate Cyclase / Q000235:genetics / Q000502:physiology; D006358:Hot Temperature; D007473:Ion Channels / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009475:Neurons, Afferent / Q000502:physiology*; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013696:Temperature; D013697:Thermosensing / Q000235:genetics / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; D007473:Ion Channels; D021122:Protein Subunits; C102183:tax-2 protein, C elegans; C102184:tax-4 protein, C elegans; C511738:GCY-18 protein, C elegans; C511739:GCY-23 protein, C elegans; C511737:GCY-8 protein, C elegans; D006162:Guanylate Cyclase; D006152:Cyclic GMP