title: Bestrophin-2 is a candidate calcium-activated chloride channel involved in olfactory transduction.
abstract: Ca-activated Cl channels are an important component of olfactory transduction. Odor binding to olfactory receptors in the cilia of olfactory sensory neurons (OSNs) leads to an increase of intraciliary Ca concentration by Ca entry through cyclic nucleotide-gated (CNG) channels. Ca activates a Cl channel that leads to an efflux of Cl from the cilia, contributing to the amplification of the OSN depolarization. The molecular identity of this Cl channel remains elusive. Recent evidence has indicated that bestrophins are able to form Ca-activated Cl channels in heterologous systems. Here we have analyzed the expression of bestrophins in the mouse olfactory epithelium and demonstrated that only mouse bestrophin-2 (mBest2) was expressed. Single-cell RT-PCR showed that mBest2 was expressed in OSNs but not in supporting cells. Immunohistochemistry revealed that mBest2 was expressed on the cilia of OSNs, the site of olfactory transduction, and colocalized with the main CNGA2 channel subunit. Electrophysiological properties of Ca-activated Cl currents from native channels in dendritic knob/cilia of mouse OSNs were compared with those induced by the expression of mBest2 in HEK-293 cells. We found the same anion permeability sequence, small estimated single-channel conductances, a Ca sensitivity difference of one order of magnitude, and the same side-specific blockage of the two Cl channel blockers commonly used to inhibit the odorant-induced Ca-activated Cl current in OSNs, niflumic acid, and 4-acetamido-4'-isothiocyanato-stilben-2,2'-disulfonate (SITS). Therefore, our data suggest that mBest2 is a good candidate for being a molecular component of the olfactory Ca-activated Cl channel.
authors.affiliation: Sector of Neurobiology, International School for Advanced Studies (SISSA), Via Beirut 2-4, 34014 Trieste, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Pifferi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pascarella
authors.forename: Anna
authors.initials: A
authors.lastname: Boccaccio
authors.forename: Andrea
authors.initials: A
authors.lastname: Mazzatenta
authors.forename: Stefano
authors.initials: S
authors.lastname: Gustincich
authors.forename: Anna
authors.initials: A
authors.lastname: Menini
authors.forename: Silvia
authors.initials: S
authors.lastname: Zucchelli
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000075002:Bestrophins; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism; D004594:Electrophysiology; D006801:Humans; D015640:Ion Channel Gating; D051379:Mice; D008810:Mice, Inbred C57BL; D009544:Niflumic Acid / Q000494:pharmacology; D009831:Olfactory Mucosa / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D014162:Transfection
chemical_list: D000906:Antibodies; C497463:Best2 protein, mouse; D000075002:Bestrophins; D018118:Chloride Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D009544:Niflumic Acid; D002118:Calcium