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Communication Dans Un Congrès Année : 2020

Kill two birds with one stone: novel levamisole and pyrantel receptors and mechanisms of resistance in Haemonchus contortus

Résumé

Levamisole and pyrantel are important drugs of the anthelmintic arsenal used in livestock and humans. Anthelmintic resistance is a growing issue and we do believe that unravelling anthelmintic target sites of action constitutes a pre-requisite step towards the identification of drug-resistance mechanisms. Levamisole-sensitive acetylcholine receptors (L-AChRs), are hetero-pentameric ligandgated ion-channels that mediate fast excitatory neurotransmission at the nematode neuromuscular junctions. The canonical Caenorhabditis elegans L-AChR is made up of five different subunits, the three α-type UNC-63, UNC-38, LEV-8 and the two non-α UNC-29 and LEV-1. In contrast to C. elegans, three main subunit changes occurred in the gastrointestinal nematode of small ruminants Haemonchus contortus: the UNC-29 subunit duplicated in four copies, the LEV-1 subunit had no signal peptide and there was no orthologue of LEV-8. We previously characterized several L-AChR subtypes of H. contortus using the Xenopus oocyte expression system. The L-AChR subtype 1.1 is composed of the UNC-29.1, UNC-38, UNC-63 and ACR-8 subunits and is more sensitive to levamisole than acetylcholine. The replacement of UNC-29.1 by the UNC-29.3 or UNC-29.4 copies gave rise to the respective L-AChR subtypes 1.3 and 1.4, which both exhibited dissimilar pharmacology patterns than the L-AChR subtype 1.1. Interestingly, the omission of ACR-8 led to the L-AChR subtype 2.1 which was more sensitive to pyrantel than levamisole. However the UNC-29.2 copy failed to replace UNC-29.1 and LEV-1 was never proven to be functional. In addition, we identified the expression of a truncated form of UNC-63 (Hco-UNC-63b) in the levamisole- and pyrantel-resistant isolate RHS6 evidencing a strong dominant negative effect on the functioning of the L-AChR. Taking the C. elegans L-AChR as a reference receptor led us to assemble new subunit combinations including both Hco-UNC-29.2 and Hco-LEV-1 subunits. Hence, we reconstituted two novel subtypes of H. contortus L-AChRs showing distinct pharmacologies. These data reinforced the critical role for Hco-ACR-8 in levamisole sensitivity. Furthermore, we identified a truncated spliced form of Hco-LEV-1 in the Kokstadt multidrug-resistant isolate and showed that it hampered the function of L-AChRs when co-expressed with its full-length counterpart. Altogether, these studies highlight the wide repertoire of L-AChR subtypes in parasitic nematodes and bring new insight to our understanding of levamisole resistance.
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Dates et versions

hal-03154806 , version 1 (01-03-2021)

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  • HAL Id : hal-03154806 , version 1

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Claude L. Charvet, Elise Courtot, Thomas B. Duguet, Eléonore Charrier, Margot Lacouette-Rata, et al.. Kill two birds with one stone: novel levamisole and pyrantel receptors and mechanisms of resistance in Haemonchus contortus. Anthelminitics IV : from discovery to ressitance, Feb 2020, Santa Monica, United States. ⟨hal-03154806⟩
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