title: Chloride accumulation in mammalian olfactory sensory neurons.
abstract: The generation of an excitatory receptor current in mammalian olfactory sensory neurons (OSNs) involves the sequential activation of two distinct types of ion channels: cAMP-gated Ca(2+)-permeable cation channels and Ca(2+)-gated Cl(-) channels, which conduct a depolarizing Cl(-) efflux. This unusual transduction mechanism requires an outward-directed driving force for Cl(-), established by active accumulation of Cl(-) within the lumen of the sensory cilia. We used two-photon fluorescence lifetime imaging microscopy of the Cl(-)-sensitive dye 6-methoxy-quinolyl acetoethyl ester to measure the intracellular Cl(-) concentration in dendritic knobs of OSNs from mice and rats. We found a uniform intracellular Cl(-) concentration in the range of 40-50 mm, which is indicative of active Cl(-) accumulation. Functional assays and PCR experiments revealed that NKCC1-mediated Cl(-) uptake through the apical membrane counteracts Cl(-) depletion in the sensory cilia, and thus maintains the responsiveness of OSNs to odor stimulation. To permit Cl(-) accumulation, OSNs avoid the "chloride switch": they do not express KCC2, the main Cl(-) extrusion cotransporter operating in neurons of the adult CNS. Cl(-) accumulation provides OSNs with the driving force for the depolarizing Cl(-) current that is the basis of the low-noise receptor current in these neurons.
authors.affiliation: Institute for Biological Information Processing (IBI-1), Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kaneko
authors.forename: Ilva
authors.initials: I
authors.lastname: Putzier
authors.forename: Stephan
authors.initials: S
authors.lastname: Frings
authors.forename: U Benjamin
authors.initials: UB
authors.lastname: Kaupp
authors.forename: Thomas
authors.initials: T
authors.lastname: Gensch
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D002923:Cilia / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D006706:Homeostasis; D017136:Ion Transport / Q000502:physiology; D051379:Mice; D008856:Microscopy, Fluorescence / Q000379:methods; D018034:Olfactory Receptor Neurons / Q000378:metabolism* / Q000502:physiology; D016133:Polymerase Chain Reaction; D011804:Quinolines / Q000493:pharmacokinetics; D051381:Rats; D011955:Receptors, Drug / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction; D049992:Sodium Chloride Symporters; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism*; D064506:Solute Carrier Family 12, Member 2; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters / Q000235:genetics* / Q000378:metabolism*; D000096922:K Cl- Cotransporters
chemical_list: D002712:Chlorides; D000242:Cyclic AMP; D005456:Fluorescent Dyes; D011804:Quinolines; D011955:Receptors, Drug; D049992:Sodium Chloride Symporters; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters; D000096922:K Cl- Cotransporters; C578878:Slc12a2 protein, mouse; C578879:Slc12a2 protein, rat; C578875:Slc12a3 protein, mouse; C578876:Slc12a3 protein, rat; C064415:thiazide receptor; C078229:N-(6-methoxyquinolyl)acetoethyl ester