Cargando…

Insect odorant receptor trafficking requires calmodulin

BACKGROUND: Like most animals, insects rely on their olfactory systems for finding food and mates and in avoiding noxious chemicals and predators. Most insect olfactory neurons express an odorant-specific odorant receptor (OR) along with Orco, the olfactory co-receptor. Orco binds ORs and permits th...

Descripción completa

Detalles Bibliográficos
Autores principales: Bahk, Suhyoung, Jones, Walton D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5043534/
https://www.ncbi.nlm.nih.gov/pubmed/27686128
http://dx.doi.org/10.1186/s12915-016-0306-x
_version_ 1782456769742635008
author Bahk, Suhyoung
Jones, Walton D.
author_facet Bahk, Suhyoung
Jones, Walton D.
author_sort Bahk, Suhyoung
collection PubMed
description BACKGROUND: Like most animals, insects rely on their olfactory systems for finding food and mates and in avoiding noxious chemicals and predators. Most insect olfactory neurons express an odorant-specific odorant receptor (OR) along with Orco, the olfactory co-receptor. Orco binds ORs and permits their trafficking to the dendrites of antennal olfactory sensory neurons (OSNs), where together, they are suggested to form heteromeric ligand-gated non-selective cation channels. While most amino acid residues in Orco are well conserved across insect orders, one especially well-conserved region in Orco’s second intracellular loop is a putative calmodulin (CaM) binding site (CBS). In this study, we explore the relationship between Orco and CaM in vivo in the olfactory neurons of Drosophila melanogaster. RESULTS: We first found OSN-specific knock-down of CaM at the onset of OSN development disrupts the spontaneous firing of OSNs and reduces Orco trafficking to the ciliated dendrites of OSNs without affecting their morphology. We then generated a series of Orco CBS mutant proteins and found that none of them rescue the Orco-null Orco(1) mutant phenotype, which is characterized by an OR protein trafficking defect that blocks spontaneous and odorant-evoked OSN activity. In contrast to an identically constructed wild-type form of Orco that does rescue the Orco(1) phenotype, all the Orco CBS mutants remain stuck in the OSN soma, preventing even the smallest odorant-evoked response. Last, we found CaM’s modulation of OR trafficking is dependent on activity. Knock-down of CaM in all Orco-positive OSNs after OR expression is well established has little effect on olfactory responsiveness alone. When combined with an extended exposure to odorant, however, this late-onset CaM knock-down significantly reduces both olfactory sensitivity and the trafficking of Orco only to the ciliated dendrites of OSNs that respond to the exposed odorant. CONCLUSIONS: In this study, we show CaM regulates OR trafficking and olfactory responses in vivo in Drosophila olfactory neurons via a well-conserved binding site on the olfactory co-receptor Orco. As CaM’s modulation of Orco seems to be dependent on activity, we propose a model in which the CaM/Orco interaction allows insect OSNs to maintain appropriate dendritic levels of OR regardless of environmental odorant concentrations.
format Online
Article
Text
id pubmed-5043534
institution National Center for Biotechnology Information
language English
publishDate 2016
publisher BioMed Central
record_format MEDLINE/PubMed
spelling pubmed-50435342016-10-05 Insect odorant receptor trafficking requires calmodulin Bahk, Suhyoung Jones, Walton D. BMC Biol Research Article BACKGROUND: Like most animals, insects rely on their olfactory systems for finding food and mates and in avoiding noxious chemicals and predators. Most insect olfactory neurons express an odorant-specific odorant receptor (OR) along with Orco, the olfactory co-receptor. Orco binds ORs and permits their trafficking to the dendrites of antennal olfactory sensory neurons (OSNs), where together, they are suggested to form heteromeric ligand-gated non-selective cation channels. While most amino acid residues in Orco are well conserved across insect orders, one especially well-conserved region in Orco’s second intracellular loop is a putative calmodulin (CaM) binding site (CBS). In this study, we explore the relationship between Orco and CaM in vivo in the olfactory neurons of Drosophila melanogaster. RESULTS: We first found OSN-specific knock-down of CaM at the onset of OSN development disrupts the spontaneous firing of OSNs and reduces Orco trafficking to the ciliated dendrites of OSNs without affecting their morphology. We then generated a series of Orco CBS mutant proteins and found that none of them rescue the Orco-null Orco(1) mutant phenotype, which is characterized by an OR protein trafficking defect that blocks spontaneous and odorant-evoked OSN activity. In contrast to an identically constructed wild-type form of Orco that does rescue the Orco(1) phenotype, all the Orco CBS mutants remain stuck in the OSN soma, preventing even the smallest odorant-evoked response. Last, we found CaM’s modulation of OR trafficking is dependent on activity. Knock-down of CaM in all Orco-positive OSNs after OR expression is well established has little effect on olfactory responsiveness alone. When combined with an extended exposure to odorant, however, this late-onset CaM knock-down significantly reduces both olfactory sensitivity and the trafficking of Orco only to the ciliated dendrites of OSNs that respond to the exposed odorant. CONCLUSIONS: In this study, we show CaM regulates OR trafficking and olfactory responses in vivo in Drosophila olfactory neurons via a well-conserved binding site on the olfactory co-receptor Orco. As CaM’s modulation of Orco seems to be dependent on activity, we propose a model in which the CaM/Orco interaction allows insect OSNs to maintain appropriate dendritic levels of OR regardless of environmental odorant concentrations. BioMed Central 2016-09-29 /pmc/articles/PMC5043534/ /pubmed/27686128 http://dx.doi.org/10.1186/s12915-016-0306-x Text en © Bahk and Jones. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research Article
Bahk, Suhyoung
Jones, Walton D.
Insect odorant receptor trafficking requires calmodulin
title Insect odorant receptor trafficking requires calmodulin
title_full Insect odorant receptor trafficking requires calmodulin
title_fullStr Insect odorant receptor trafficking requires calmodulin
title_full_unstemmed Insect odorant receptor trafficking requires calmodulin
title_short Insect odorant receptor trafficking requires calmodulin
title_sort insect odorant receptor trafficking requires calmodulin
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5043534/
https://www.ncbi.nlm.nih.gov/pubmed/27686128
http://dx.doi.org/10.1186/s12915-016-0306-x
work_keys_str_mv AT bahksuhyoung insectodorantreceptortraffickingrequirescalmodulin
AT joneswaltond insectodorantreceptortraffickingrequirescalmodulin