Pharmacological characterization of a homomeric nicotinic acetylcholine receptor formed by Ancylostoma caninum ACR-16
Parasitic nematode infections are treated using anthelmintic drugs, some of which target nicotinic acetylcholine receptors (nAChRs) located in different parasite tissues. The limited arsenal of anthelmintic agents and the prevalence of drug resistance imply that future defense against parasitic infections will depend on the discovery of novel targets and therapeutics. Previous studies have suggested that Ascaris suum ACR-16 nAChRs are a suitable target for the development of antinematodal drugs. In this study, we characterized the pharmacology of the Ancylostoma caninum ACR-16 receptor using two-electrode voltage-clamp electrophysiology. This technique allowed us to study the effects of cholinergic agonists and antagonists on the nematode nAChRs expressed in Xenopus laevis oocytes. Aca-ACR-16 was not sensitive to many of the existing cholinomimetic anthelmintics (levamisole, oxantel, pyrantel, and tribendimidine). 3-Bromocytisine was the most potent agonist (> 130% of the control acetylcholine current) on the Aca-ACR-16 nAChR but, unlike Asu-ACR-16, oxantel did not activate the receptor. The mean time constants of desensitization for agonists on Aca-ACR-16 were longer than the rates observed in Asu-ACR-16. In contrast to Asu-ACR-16, the A. caninum receptor was completely inhibited by DHβE and moderately inhibited by α-BTX. In conclusion, we have successfully reconstituted a fully functional homomeric nAChR, ACR-16, from A. caninum, a model for human hookworm infections. The pharmacology of the receptor is distinct from levamisole-sensitive nematode receptors. The ACR-16 homologue also displayed some pharmacological differences from Asu-ACR-16. Hence, A. caninum ACR-16 may be a valid target site for the development of anthelmintics against hookworm infections.
KeywordsnAChR Hookworms Aca-ACR-16 Anthelmintic Xenopus oocyte
This research was funded by NIH R21AI092185 to APR, NIH RO1AI047194 and the E. A. Benbrook Foundation for Pathology and Parasitology to RJM. We would like to thank Dr. Claude L. Charvet, INRA, Université Tours, Nouzilly, France for the generous gift of pTB207 vector.
Compliance with ethical standards
Conflict of interest
The authors declare that this work has no conflict of interest.
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