Abstract
Odorants and pheromones are essential to insects as chemical cues for finding food or an appropriate mating partner. These volatile compounds bind to olfactory receptors (Ors) expressed by olfactory sensory neurons. Each insect Or functions as a ligand-gated ion channel and is a heteromeric complex that comprises one type of canonical Or and a highly conserved Orco subunit. Because there are many Or types, insect Ors can recognize with high specificity a myriad of chemical cues. Cyclic nucleotides can modulate the activity of insect Or-Orco complexes; however, the mechanism of action of these nucleotides is under debate. Here, we show that cyclic nucleotides, including cAMP and cGMP, interact with the silkmoth sex pheromone receptor complex, BmOr-1-BmOrco, from the outside of the cell and that these nucleotides act as antagonists at low concentrations and weak agonists at high concentrations. These cyclic nucleotides do not compete with the sex pheromone, bombykol, for binding to the BmOr-1 subunit. ATP and GTP also weakly inhibited BmOr-1-BmOrco activity, but D-ribose had no effect; these findings indicated that the purine moiety was crucial for the inhibition. Only the bombykol receptors have been so far shown to be subject to modulation by nucleotide-related compounds, indicating that this responsiveness to these compounds is not common for all insect Or-Orco complexes.
Highlights
Olfactory receptors (Ors) play a pivotal role in sensing volatile chemicals in the external environment
We have previously shown that HEK293T cells expressing BmOr-1-BmOrco or Or47a-Orco were weakly sensitive to extracellular applications of membrane-permeable cyclic nucleotide analogs, 8-Br-cGMP and 8-Br-cAMP [2]
We demonstrated that cyclic nucleotides and related compounds acted as non-competitive inhibitors of the bombykol receptor, BmOr-1-BmOrco
Summary
Olfactory receptors (Ors) play a pivotal role in sensing volatile chemicals in the external environment. Both vertebrate and invertebrate Ors possess a seven-transmembrane topology, mammalian Ors are G protein-coupled receptors, whereas insect Ors are heteromeric cation channel complexes that are directly gated by chemosignals, including general odorants and pheromones [1,2,3]. Every type of heteromeric complex exhibits specific, distinct ligand selectivity and distinct channel properties. Given that there are 60–400 potential ligand-binding Or genes in each insect species [8,15,16,17,18,19,20], the insect Or complex represent a large family of ion-channel receptors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
