title: Water taste transduction pathway is calcium dependent in Drosophila.
abstract: In mammals, detection of osmolarity by the gustatory system was overlooked until recently. In insects, specific taste receptor neurons detect hypoosmotic stimuli and are commonly called "W" (water) cells. W cells are easy to access in vivo and represent a good model to study the transduction of hypoosmotic stimuli. Using pharmacological and genetic approaches in Drosophila, we show that tarsal W cell firing activity depends on the concentration of external calcium bathing the dendrite. This dependence was confirmed by the strong inhibition of W cell responses to hypoosmotic stimuli by lanthanum (IC(50) = 8 nM), an ion known to inhibit calcium-permeable channels. Downstream, the transduction pathway likely involves calmodulin because calmodulin antagonists such as W-7 (IC(50) = 2 microM) and fluphenazine (IC(50) = 30 microM) prevented the activation of the W cell by hypoosmotic stimuli. A protein kinase C (PKC) may also be involved as W cell responses were blocked by PKC inhibitors, chelerythrine (IC(50) = 20 microM) and staurosporine (IC(50) = 30 microM). It was also reduced when expressing an inhibitory pseudosubstrate of PKC in gustatory receptor neurons. In the rat, the transduction pathway underlying low osmolarity detection involves aquaporin and swelling-activated ion channels. Our study suggests that the transduction pathway of hypoosmotic stimuli in insects differs from mammals.
authors.affiliation: Institut National de Recherche Agronomique, Unité Mixte de Recherche, 1272 Physiologie de l'Insecte-Signalisation et Communication, Versailles, France. nicolas.meunier@jouy.inra.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Meunier
authors.forename: Frédéric
authors.initials: F
authors.lastname: Marion-Poll
authors.forename: Philippe
authors.initials: P
authors.lastname: Lucas
mesh_terms: D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism; D018118:Chloride Channels / Q000187:drug effects; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005476:Fluphenazine / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D009994:Osmolar Concentration; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D053119:Benzophenanthridines; D002147:Calmodulin; D018118:Chloride Channels; D029721:Drosophila Proteins; D011956:Receptors, Cell Surface; D013449:Sulfonamides; C405956:gustatory receptor, Drosophila; C017967:W 7; D007811:Lanthanum; C016299:chelerythrine; D011493:Protein Kinase C; D019311:Staurosporine; D005476:Fluphenazine; D002118:Calcium