A cyclic nucleotide-gated conductance in olfactory receptor cilia

@article{Nakamura1987ACN,
  title={A cyclic nucleotide-gated conductance in olfactory receptor cilia},
  author={Tadashi Nakamura and Geoffrey H. Gold},
  journal={Nature},
  year={1987},
  volume={325},
  pages={442-444}
}
Olfactory transduction is thought to be initiated by the binding of odorants to specific receptor proteins in the cilia of olfactory receptor cells (reviewed in refs 1–3). The mechanism by which odorant binding could initiate membrane depolarization is unknown, but the recent discovery of an odorant-stimulated adenylate cyclase in purified olfactory cilia4,5 suggests that cyclic AMP may serve as an intracellular messenger for olfactory transduction. If so, then there might be a conductance in… 

Single odor-sensitive channels in olfactory receptor neurons are also gated by cyclic nucleotides

Recording from on-cell patches provides a direct demonstration that the cyclic nucleotide-gated channel is the conductance pathway for the odor- elicited current.

Primary structure and functional expression of a cyclic nucleotide-activated channel from olfactory neurons

The molecular cloning, functional expression and characterization of a channel that is likely to mediate olfactory transduction are reported, suggesting that the two systems might use homologous channels.

Transduction mechanisms in vertebrate olfactory receptor cells.

A comprehensive review of the biophysical and electrophysiological evidence regarding the transduction processes as well as subsequent signal processing and spike generation in ORNs is presented.

The cyclic nucleotide-activated conductance in olfactory cilia: Effects of cytoplasmic Mg2+ and Ca2+

The effects of cytoplasmic Ca2+ and Mg2+ on the cAMP-activated current were measured in single olfactory cilia and it is unlikely that an influx of divalent cations terminates the odorant response by a direct effect on thecAMP-gated channels.

The electrochemical basis of odor transduction in vertebrate olfactory cilia.

Most vertebrate olfactory receptor neurons share a common G-protein-coupled pathway for transducing the binding of odorant into depolarization, and the relation between stimulus strength and receptor current shows positive cooperativity.

Direct modulation by Ca2+–calmodulin of cyclic nucleotide-activated channel of rat olfactory receptor neurons

Ca2+ reduces the apparent affinity of the channel for cAMP by up to 20-fold in the presence of calmodulin, an abundant protein in olfactory cilia, suggesting that it may be a key component of the Ca2+ -triggered Olfactory adaptation.

Calcium-Sensitive Particulate Guanylyl Cyclase as a Modulator of cAMP in Olfactory Receptor Neurons

A small, localized, odorant-induced cAMP response may be amplified to modulate downstream transduction enzymes or transcriptional events, demonstrating the existence of a regulatory loop in which cGMP can augment a cAMP signal, and in turn cAMP negatively regulates cG MP production via PKA.

Presence of Ca2+-dependent K+ channels in chemosensory cilia support a role in odor transduction.

The presence of K+ channels in the ORN cilia is demonstrated and supports their participation in odor transduction.

Both external and internal calcium reduce the sensitivity of the olfactory cyclic-nucleotide-gated channel to CAMP.

It was found that cytoplasmic Ca2+ above 1 microM made the channels less sensitive to cAMP, and an unexpected result was that externalCa2+ could also greatly reduce the sensitivity of the channels to camp.

Odor stimuli trigger influx of calcium into olfactory neurons of the channel catfish.

Data suggest that an influx of calcium triggered by odor stimulation of phosphoinositide turnover may be an alternate or additional mechanism of olfactory transduction.
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References

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The results suggest a role for cyclic nucleotides in olfactory transduction13,20–22, and point to a molecular analogy between olfaction and visual15,16, hormone17,18 and neurotransmitter19 reception, and reveal new ways to identify and isolate Olfactory receptor proteins.

Cyclic GMP-sensitive conductance of retinal rods consists of aqueous pores

Recordings of cGMP-activated single-channel currents from excised rod outer segment patches bathed in solutions low in divalent cations suggest that opening of the pore is triggered by cooperative binding of at least three cG MP molecules.

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Several lines of evidence support the hypothesis that the initial molecular events and subsequent stages of transduction are mediated by odorant receptor sites and associated ion channels located in the membrane of the cilia and apical dendritic knob of the olfactory receptor neuron.

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It is reported that, as expected, single cGMP-activated channel activity can be detected from an excised rod membrane patch in the absence of divalent cations, and a puzzle about the light-sensitive conductance is resolved by demonstrating that it is an aqueous pore rather than a carrier.

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Biochemical studies of olfaction: isolation, characterization, and odorant binding activity of cilia from rainbow trout olfactory rosettes.

  • L. RheinR. H. Cagan
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1980
This study provides direct biochemical evidence that olfactory cilia bind odorant molecules and supports the hypothesis that odorant recognition sites are integral parts of the cilia.