title: Environmental alkalinity sensing mediated by the transmembrane guanylyl cyclase GCY-14 in C. elegans.
abstract: Survival requires that living organisms continuously monitor environmental and tissue pH. Animals sense acidic pH using ion channels and G-protein-coupled receptors (GPCRs), but monitoring of alkaline pH is not well understood. We report here that in the nematode Caenorhabditis elegans, a transmembrane receptor-type guanylyl cyclase (RGC), GCY-14, of the ASEL gustatory neuron, plays an essential role in the sensing of extracellular alkalinity. Activation of GCY-14 opens a cGMP-gated cation channel encoded by tax-2 and tax-4, resulting in Ca(2+) entry into ASEL. Ectopic expression of GCY-14 in other neurons indicates that it accounts for the alkalinity sensing capability. Domain-swapping and site-directed mutagenesis of GCY-14 reveal that GCY-14 functions as a homodimer, in which histidine of the extracellular domains plays a crucial role in alkalinity detection. These results argue that in addition to ion channels and GPCRs, RGCs also play a role in pH sensation in neurons.
authors.affiliation: Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Murayama
authors.forename: Jun
authors.initials: J
authors.lastname: Takayama
authors.forename: Mayuki
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Ichiro N
authors.initials: IN
authors.lastname: Maruyama
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D020013:Calcium Signaling; D006152:Cyclic GMP / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000378:metabolism; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D007473:Ion Channels; C102183:tax-2 protein, C elegans; C102184:tax-4 protein, C elegans; D006162:Guanylate Cyclase; D006152:Cyclic GMP