Muscarinic acetylcholine receptor M3 modulates odorant receptor activity via inhibition of β-arrestin-2 recruitment.

Yue Jiang,Minghong Ma,Yun Rose Li,Huikai Tian,Hiroaki Matsunami

doi:10.1038/ncomms7448

Abstract

The olfactory system in rodents serves a critical function in social, reproductive, and survival behaviors. Processing of chemosensory signals in the brain is dynamically regulated in part by an animal's physiological state. We previously reported that type 3 muscarinic acetylcholine receptors (M3-Rs) physically interact with odorant receptors (ORs) to promote odor-induced responses in a heterologous expression system. However, it is not known how M3-Rs affect the ability of olfactory sensory neurons (OSNs) to respond to odors. Here, we show that an M3-R antagonist attenuates odor-induced responses in OSNs from wild-type, but not M3-R-null mice. Using a novel molecular assay, we demonstrate that the activation of M3-Rs inhibits the recruitment of β-arrestin-2 to ORs, resulting in a potentiation of odor-induced response in OSNs. These results suggest a role for acetylcholine in modulating olfactory processing at the initial stages of signal transduction in the olfactory system.

Highlights

The olfactory system in rodents serves a critical function in social, reproductive and survival behaviours
olfactory sensory neurons (OSNs) cilia obtained from M3-R KO mice did not show detectable M3-R staining (Fig. 1b; n 1⁄4 6 sections from two animals), supporting our previous find that M3-Rs are expressed in OSNs
We noted that the gross anatomy of the olfactory epithelium (OE) as well as the cilia morphology in whole-mount OE attached to the septal wall from M3-R KO mice is indistinguishable from that of WT littermates (Supplementary Fig. 1; n 1⁄4 4 epithelial preparations from two animals for each condition)

Summary

Introduction

The olfactory system in rodents serves a critical function in social, reproductive and survival behaviours. We previously reported that type 3 muscarinic acetylcholine receptors (M3-Rs) physically interact with odorant receptors (ORs) to promote odour-induced responses in a heterologous expression system. It is not known how M3-Rs affect the ability of olfactory sensory neurons (OSNs) to respond to odours. Application of the muscarinic agonist carbachol or the physiological M3-R ligand acetylcholine resulted in increased odour-induced responses in OSNs. To identify the mechanism, we used a novel b-arrestin-2 recruitment assay for ORs expressed in heterologous cells to show that M3-R inhibits b-arrestin-2 recruitment in ORs in an activity-dependent manner. Our results demonstrate that M3-Rs modulate OR activity by regulating b-arrestin-2 recruitment, revealing a novel mechanism for acetylcholine in regulating olfactory sensory processing at the peripheral level

Methods

Results

Conclusion