title: Bestrophin-encoded Ca²⁺-activated Cl⁻ channels underlie a current with properties similar to the native current in the moth Spodoptera littoralis olfactory receptor neurons.
abstract: Responses of insect olfactory receptor neurons (ORNs) involve an entry of Ca²⁺ through olfactory heterodimeric receptor complexes. In moths, the termination of ORN responses was found to strongly depend on the external Ca²⁺ concentration through the activation of unknown Ca²⁺-dependent Cl⁻ channels. We thus investigated the molecular identity of these Cl⁻ channels. There is compelling evidence that bestrophins form Cl⁻ channels when expressed in heterologous systems. Here we provide evidence that antennae of the moth Spodoptera littoralis express three transcripts encoding proteins with hallmarks of bestrophins. One of these transcripts, SlitBest1b, is expressed in ORNs. The heterologous expression of SlitBest1b protein in CHO-K1 cells yielded a Ca²⁺-activated Cl⁻ current that shares electrophysiological properties with the native Ca²⁺-activated Cl⁻ current of ORNs. Both currents are anionic, present similar dependence on the intracellular Ca²⁺ concentration, partly inactivate over time, have the same anion permeability sequence, the same sequence of inhibitory efficiency of blockers, the same almost linear I-V relationships and finally both currents do not depend on the cell volume. Therefore, our data suggest that SlitBest1b is a good candidate for being a molecular component of the olfactory Ca²⁺-activated Cl⁻ channel and is likely to constitute part of the insect olfactory transduction pathway. A different function (e.g. regulation of other proteins, maintenance of the anionic homeostasis in the sensillar lymph) and a different role (e.g. involvement in the olfactory system development) cannot be excluded however.
authors.affiliation: Institut National de la Recherche Agronomique, UMR 1272 Physiologie de l'Insecte: Signalisation et Communication, Versailles, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: François
authors.forename: Marta
authors.initials: M
authors.lastname: Grauso
authors.forename: Elodie
authors.initials: E
authors.lastname: Demondion
authors.forename: Françoise
authors.initials: F
authors.lastname: Bozzolan
authors.forename: Stéphane
authors.initials: S
authors.lastname: Debernard
authors.forename: Philippe
authors.initials: P
authors.lastname: Lucas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D057506:Arthropod Antennae / Q000294:innervation / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D006224:Cricetinae; D005439:Flufenamic Acid / Q000494:pharmacology; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D019476:Insect Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009544:Niflumic Acid / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D018034:Olfactory Receptor Neurons / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009928:Organ Specificity; D018408:Patch-Clamp Techniques; D010539:Permeability; D061251:Primary Cell Culture; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera / Q000166:cytology / Q000235:genetics / Q000378:metabolism
chemical_list: D018118:Chloride Channels; D019476:Insect Proteins; D009579:Nitrobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D009544:Niflumic Acid; D005439:Flufenamic Acid; D002118:Calcium