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Deciphering the molecular determinants of cholinergic anthelmintic sensitivity in nematodes: When novel functional validation approaches highlight major differences between the model Caenorhabditis elegans and parasitic species

Deciphering the molecular determinants of cholinergic anthelmintic sensitivity in nematodes: When novel functional validation approaches highlight major differences between the model Caenorhabditis elegans and parasitic species
Deciphering the molecular determinants of cholinergic anthelmintic sensitivity in nematodes: When novel functional validation approaches highlight major differences between the model Caenorhabditis elegans and parasitic species
Cholinergic agonists such as levamisole and pyrantel are widely used as anthelmintics to treat parasitic nematode infestations. These drugs elicit spastic paralysis by activating acetylcholine receptors (AChRs) expressed in nematode body wall muscles. In the model nematode Caenorhabditis elegans, genetic screens led to the identification of five genes encoding levamisole-sensitive-AChR (L-AChR) subunits: unc-38, unc-63, unc-29, lev-1 and lev-8. These subunits form a functional L-AChR when heterologously expressed in Xenopus laevis oocytes. Here we show that the majority of parasitic species that are sensitive to levamisole lack a gene orthologous to C. elegans lev-8. This raises important questions concerning the properties of the native receptor that constitutes the target for cholinergic anthelmintics. We demonstrate that the closely related ACR-8 subunit from phylogenetically distant animal and plant parasitic nematode species functionally substitutes for LEV-8 in the C. elegans L-AChR when expressed in Xenopus oocytes. The importance of ACR-8 in parasitic nematode sensitivity to cholinergic anthelmintics is reinforced by a ‘model hopping’ approach in which we demonstrate the ability of ACR-8 from the hematophagous parasitic nematode Haemonchus contortus to fully restore levamisole sensitivity, and to confer high sensitivity to pyrantel, when expressed in the body wall muscle of C. elegans lev-8 null mutants. The critical role of acr-8 to in vivo drug sensitivity is substantiated by the successful demonstration of RNAi gene silencing for Hco-acr-8 which reduced the sensitivity of H. contortus larvae to levamisole. Intriguingly, the pyrantel sensitivity remained unchanged thus providing new evidence for distinct modes of action of these important anthelmintics in parasitic species versus C. elegans. More broadly, this highlights the limits of C. elegans as a predictive model to decipher cholinergic agonist targets from parasitic nematode species and provides key molecular insight to inform the discovery of next generation anthelmintic compounds.
1553-7366
Blanchard, Alexandra
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Guégnard, Fabrice
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Charvet, Claude L.
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Crisford, Anna
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Courtot, Elise
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Sauvé, Christine
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Harmache, Abdallah
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Duguet, Thomas
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O’Connor, Vincent
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Castagnone-Sereno, Philippe
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Reaves, Barbara
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Wolstenholme, Adrian J.
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Beech, Robin N.
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Holden-Dye, Lindy
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Neveu, Cedric
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Lok, James B.
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Blanchard, Alexandra
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Guégnard, Fabrice
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Charvet, Claude L.
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Crisford, Anna
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Courtot, Elise
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Sauvé, Christine
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Harmache, Abdallah
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Duguet, Thomas
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O’Connor, Vincent
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Castagnone-Sereno, Philippe
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Reaves, Barbara
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Wolstenholme, Adrian J.
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Beech, Robin N.
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Holden-Dye, Lindy
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Neveu, Cedric
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Lok, James B.
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Blanchard, Alexandra, Guégnard, Fabrice, Charvet, Claude L., Crisford, Anna, Courtot, Elise, Sauvé, Christine, Harmache, Abdallah, Duguet, Thomas, O’Connor, Vincent, Castagnone-Sereno, Philippe, Reaves, Barbara, Wolstenholme, Adrian J., Beech, Robin N., Holden-Dye, Lindy and Neveu, Cedric , Lok, James B. (ed.) (2018) Deciphering the molecular determinants of cholinergic anthelmintic sensitivity in nematodes: When novel functional validation approaches highlight major differences between the model Caenorhabditis elegans and parasitic species. PLoS Pathogens, 14 (5). (doi:10.1371/journal.ppat.1006996).

Record type: Article

Abstract

Cholinergic agonists such as levamisole and pyrantel are widely used as anthelmintics to treat parasitic nematode infestations. These drugs elicit spastic paralysis by activating acetylcholine receptors (AChRs) expressed in nematode body wall muscles. In the model nematode Caenorhabditis elegans, genetic screens led to the identification of five genes encoding levamisole-sensitive-AChR (L-AChR) subunits: unc-38, unc-63, unc-29, lev-1 and lev-8. These subunits form a functional L-AChR when heterologously expressed in Xenopus laevis oocytes. Here we show that the majority of parasitic species that are sensitive to levamisole lack a gene orthologous to C. elegans lev-8. This raises important questions concerning the properties of the native receptor that constitutes the target for cholinergic anthelmintics. We demonstrate that the closely related ACR-8 subunit from phylogenetically distant animal and plant parasitic nematode species functionally substitutes for LEV-8 in the C. elegans L-AChR when expressed in Xenopus oocytes. The importance of ACR-8 in parasitic nematode sensitivity to cholinergic anthelmintics is reinforced by a ‘model hopping’ approach in which we demonstrate the ability of ACR-8 from the hematophagous parasitic nematode Haemonchus contortus to fully restore levamisole sensitivity, and to confer high sensitivity to pyrantel, when expressed in the body wall muscle of C. elegans lev-8 null mutants. The critical role of acr-8 to in vivo drug sensitivity is substantiated by the successful demonstration of RNAi gene silencing for Hco-acr-8 which reduced the sensitivity of H. contortus larvae to levamisole. Intriguingly, the pyrantel sensitivity remained unchanged thus providing new evidence for distinct modes of action of these important anthelmintics in parasitic species versus C. elegans. More broadly, this highlights the limits of C. elegans as a predictive model to decipher cholinergic agonist targets from parasitic nematode species and provides key molecular insight to inform the discovery of next generation anthelmintic compounds.

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Accepted/In Press date: 18 April 2018
e-pub ahead of print date: 2 May 2018
Published date: 2 May 2018

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Local EPrints ID: 420454
URI: https://eprints.soton.ac.uk/id/eprint/420454
ISSN: 1553-7366
PURE UUID: 7097f0bb-57ed-4cd8-b6a7-1aab21e98063
ORCID for Anna Crisford: ORCID iD orcid.org/0000-0001-5775-643X

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Date deposited: 08 May 2018 16:30
Last modified: 14 Mar 2019 01:39

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Contributors

Author: Alexandra Blanchard
Author: Fabrice Guégnard
Author: Claude L. Charvet
Author: Anna Crisford ORCID iD
Author: Elise Courtot
Author: Christine Sauvé
Author: Abdallah Harmache
Author: Thomas Duguet
Author: Philippe Castagnone-Sereno
Author: Barbara Reaves
Author: Adrian J. Wolstenholme
Author: Robin N. Beech
Author: Cedric Neveu
Editor: James B. Lok

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