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Shaver AO, Miller IR, Schaye ES, Moya ND, Collins JB, Wit J, Blanco AH, Shao FM, Andersen EJ, Khan SA, Paredes G, Andersen EC. Quantifying the fitness effects of resistance alleles with and without anthelmintic selection pressure using Caenorhabditis elegans. PLoS Pathog 2024; 20:e1012245. [PMID: 38768235 PMCID: PMC11142691 DOI: 10.1371/journal.ppat.1012245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 05/31/2024] [Accepted: 05/07/2024] [Indexed: 05/22/2024] Open
Abstract
Albendazole (a benzimidazole) and ivermectin (a macrocyclic lactone) are the two most commonly co-administered anthelmintic drugs in mass-drug administration programs worldwide. Despite emerging resistance, we do not fully understand the mechanisms of resistance to these drugs nor the consequences of delivering them in combination. Albendazole resistance has primarily been attributed to variation in the drug target, a beta-tubulin gene. Ivermectin targets glutamate-gated chloride channels (GluCls), but it is unknown whether GluCl genes are involved in ivermectin resistance in nature. Using Caenorhabditis elegans, we defined the fitness costs associated with loss of the drug target genes singly or in combinations of the genes that encode GluCl subunits. We quantified the loss-of-function effects on three traits: (i) multi-generational competitive fitness, (ii) fecundity, and (iii) development. In competitive fitness and development assays, we found that a deletion of the beta-tubulin gene ben-1 conferred albendazole resistance, but ivermectin resistance required the loss of two GluCl genes (avr-14 and avr-15). The fecundity assays revealed that loss of ben-1 did not provide any fitness benefit in albendazole conditions and that no GluCl deletion mutants were resistant to ivermectin. Next, we searched for evidence of multi-drug resistance across the three traits. Loss of ben-1 did not confer resistance to ivermectin, nor did loss of any single GluCl subunit or combination confer resistance to albendazole. Finally, we assessed the development of 124 C. elegans wild strains across six benzimidazoles and seven macrocyclic lactones to identify evidence of multi-drug resistance between the two drug classes and found a strong phenotypic correlation within a drug class but not across drug classes. Because each gene affects various aspects of nematode physiology, these results suggest that it is necessary to assess multiple fitness traits to evaluate how each gene contributes to anthelmintic resistance.
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Affiliation(s)
- Amanda O. Shaver
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Isabella R. Miller
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Etta S. Schaye
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Nicolas D. Moya
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - J. B. Collins
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Janneke Wit
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Alyssa H. Blanco
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Fiona M. Shao
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Elliot J. Andersen
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Sharik A. Khan
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Gracie Paredes
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Erik C. Andersen
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
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2
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Shaver AO, Miller IR, Schaye ES, Moya ND, Collins J, Wit J, Blanco AH, Shao FM, Andersen EJ, Khan SA, Paredes G, Andersen EC. Quantifying the fitness effects of resistance alleles with and without anthelmintic selection pressure using Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.01.578300. [PMID: 38370666 PMCID: PMC10871296 DOI: 10.1101/2024.02.01.578300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Albendazole and ivermectin are the two most commonly co-administered anthelmintic drugs in mass-drug administration programs worldwide. Despite emerging resistance, we do not fully understand the mechanisms of resistance to these drugs nor the consequences of delivering them in combination. Albendazole resistance has primarily been attributed to variation in the drug target, a beta-tubulin gene. Ivermectin targets glutamate-gated chloride channel (GluCl) genes, but it is unknown whether these genes are involved in ivermectin resistance in nature. Using Caenorhabditis elegans, we defined the fitness costs associated with loss of the drug target genes singly or in combinations of the genes that encode GluCl subunits. We quantified the loss-of function effects on three traits: (i) multi-generational competitive fitness, (ii) fecundity, and (iii) development. In competitive fitness and development assays, we found that a deletion of the beta-tubulin gene ben-1 conferred albendazole resistance, but ivermectin resistance required loss of two GluCl genes (avr-14 and avr-15) or loss of three GluCl genes (avr-14, avr-15, and glc-1). The fecundity assays revealed that loss of ben-1 did not provide any fitness benefit in albendazole and that no GluCl deletion mutants were resistant to ivermectin. Next, we searched for evidence of multi-drug resistance across the three traits. Loss of ben-1 did not confer resistance to ivermectin, nor did loss of any single GluCl subunit or combination confer resistance to albendazole. Finally, we assessed the development of 124 C. elegans wild strains across six benzimidazoles and seven macrocyclic lactones to identify evidence of multi-drug resistance between the two drug classes and found a strong phenotypic correlation within a drug class but not across drug classes. Because each gene affects various aspects of nematode physiology, these results suggest that it is necessary to assess multiple fitness traits to evaluate how each gene contributes to anthelmintic resistance.
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Affiliation(s)
- Amanda O. Shaver
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Isabella R. Miller
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Etta S. Schaye
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Nicolas D. Moya
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - J.B. Collins
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Janneke Wit
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Alyssa H. Blanco
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Fiona M. Shao
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Elliot J. Andersen
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Sharik A. Khan
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Gracie Paredes
- Molecular Biosciences, Northwestern University, Evanston, Illinois, United States of America
| | - Erik C. Andersen
- Dept. of Biology, Johns Hopkins University, Baltimore, Maryland, United States of America
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3
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Habibi S, Nazareth K, Nichols J, Varley S, Forrester SG. The Haemonchus contortus LGC-39 subunit is a novel subtype of an acetylcholine-gated chloride channel. Int J Parasitol Drugs Drug Resist 2023; 22:20-26. [PMID: 37054482 PMCID: PMC10122009 DOI: 10.1016/j.ijpddr.2023.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 03/27/2023] [Accepted: 04/02/2023] [Indexed: 04/15/2023]
Abstract
The nematode genome exhibits a vast array of Cys-loop receptors that are activated by a diverse set of neurotransmitters and anthelmintic drugs such as ivermectin and levamisole. While many Cys-loop receptors have been functionally and pharmacologically characterized, there remains a large subset of orphan receptors where the agonist remains unknown. We have identified an orphan Cys-loop receptor, LGC-39, from the parasitic nematode Haemonchus contortus that is a novel type of cholinergic-sensitive ligand-gated chloride channel. This receptor groups outside of the acetylcholine-gated chloride channel family, in the previously named GGR-1 (GABA/Glycine Receptor-1) group of Cys-loop receptors. We found that LGC-39 forms a functional homomeric receptor when expressed in Xenopus laevis oocytes and is activated by several cholinergic ligands including acetylcholine, methacholine and surprisingly, atropine with an EC50 for atropine on the low μM range. A homology model was generated which revealed some key features of the LGC-39 ligand-binding pocket that may explain some of the elements important for atropine recognition of the LGC-39 receptor. Overall these results suggest that the GGR-1 family (now called LGC-57) of Cys-loop receptors includes novel acetylcholine-gated chloride channel subtypes and may represent important future drug targets.
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Affiliation(s)
- Sarah Habibi
- Faculty of Science, Ontario Tech University, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Kristen Nazareth
- Faculty of Science, Ontario Tech University, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Jennifer Nichols
- Faculty of Science, Ontario Tech University, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Sierra Varley
- Faculty of Science, Ontario Tech University, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Sean G Forrester
- Faculty of Science, Ontario Tech University, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada.
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4
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Choudhary S, Kashyap SS, Martin RJ, Robertson AP. Advances in our understanding of nematode ion channels as potential anthelmintic targets. Int J Parasitol Drugs Drug Resist 2022; 18:52-86. [PMID: 35149380 PMCID: PMC8841521 DOI: 10.1016/j.ijpddr.2021.12.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 12/15/2022]
Abstract
Ion channels are specialized multimeric proteins that underlie cell excitability. These channels integrate with a variety of neuromuscular and biological functions. In nematodes, the physiological behaviors including locomotion, navigation, feeding and reproduction, are regulated by these protein entities. Majority of the antinematodal chemotherapeutics target the ion channels to disrupt essential biological functions. Here, we have summarized current advances in our understanding of nematode ion channel pharmacology. We review cys-loop ligand gated ion channels (LGICs), including nicotinic acetylcholine receptors (nAChRs), acetylcholine-chloride gated ion channels (ACCs), glutamate-gated chloride channels (GluCls), and GABA (γ-aminobutyric acid) receptors, and other ionotropic receptors (transient receptor potential (TRP) channels and potassium ion channels). We have provided an update on the pharmacological properties of these channels from various nematodes. This article catalogs the differences in ion channel composition and resulting pharmacology in the phylum Nematoda. This diversity in ion channel subunit repertoire and pharmacology emphasizes the importance of pursuing species-specific drug target research. In this review, we have provided an overview of recent advances in techniques and functional assays available for screening ion channel properties and their application.
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Affiliation(s)
- Shivani Choudhary
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Sudhanva S Kashyap
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Richard J Martin
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Alan P Robertson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
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5
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Lamassiaude N, Courtot E, Corset A, Charvet CL, Neveu C. Pharmacological characterization of novel heteromeric GluCl subtypes from C. elegans and parasitic nematodes. Br J Pharmacol 2021; 179:1264-1279. [PMID: 34623639 PMCID: PMC9306661 DOI: 10.1111/bph.15703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 08/30/2021] [Accepted: 09/01/2021] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Macrocyclic lactones (MLs) are the most widely used broad-spectrum anthelmintic drugs for the treatment of parasitic nematodes impacting both human and animal health. MLs are known to act as agonist of the nematode glutamate-gated chloride channels (GluCls). However, for many important nematode species, the GluCls subunit composition and pharmacological properties remain largely unknown. In order to get new insights about the GluCl diversity and MLs mode of action, we identified and pharmacologically characterized receptors made of highly conserved GluCl subunits from the model nematode Caenorhabditis elegans, the human filarial nematode Brugia malayi and the horse parasite Parascaris univalens. EXPERIMENTAL APPROACH AVR-14, GLC-2, GLC3 and GLC-4 are the most conserved GluCl subunits throughout the Nematoda phylum. For each nematode species, we investigated the ability of these subunits to form either homomeric or heteromeric GluCls when expressed in Xenopus laevis oocytes and performed the detailed pharmacological characterization of the functional channels. KEY RESULTS Here, a total of 14 GluCls have been functionally reconstituted and heteromers formation was inferred from pharmacological criteria. Importantly, we report that the GLC-2 subunit plays a pivotal role in the composition of heteromeric GluCls in nematodes. In addition, we describe a novel GluCl subtype, made of the GLC-2/GLC-3 subunit combination, for which a high concentration of the anthelmintics ivermectin and moxidectin reversibly potentiate glutamate-induced response. CONCLUSION AND IMPLICATIONS This study brings new insights into the diversity of GluCl subtypes in nematodes and promote novel drug targets for the development of next generation anthelmintic compounds.
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Affiliation(s)
| | | | | | | | - Cédric Neveu
- INRAE, Université de Tours, ISP, Nouzilly, France
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6
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Buckingham SD, Mann HJ, Hearnden OK, Sattelle DB. Turning a Drug Target into a Drug Candidate: A New Paradigm for Neurological Drug Discovery? Bioessays 2020; 42:e2000011. [PMID: 32776366 DOI: 10.1002/bies.202000011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/26/2020] [Indexed: 11/11/2022]
Abstract
The conventional paradigm for developing new treatments for disease mainly involves either the discovery of new drug targets, or finding new, improved drugs for old targets. However, an ion channel found only in invertebrates offers the potential of a completely new paradigm in which an established drug target can be re-engineered to serve as a new candidate therapeutic agent. The L-glutamate-gated chloride channels (GluCls) of invertebrates are absent from vertebrate genomes, offering the opportunity to introduce this exogenous, inhibitory, L-glutamate receptor into vertebrate neuronal circuits either as a tool with which to study neural networks, or a candidate therapy. Epileptic seizures can involve L-glutamate-induced hyper-excitation and toxicity. Variant GluCls, with their inhibitory responses to L-glutamate, when engineered into human neurons, might counter the excitotoxic effects of excess L-glutamate. In reviewing recent studies on model organisms, it appears that this approach might offer a new paradigm for the development of candidate therapeutics for epilepsy.
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Affiliation(s)
- Steven D Buckingham
- School of Biological and Chemical Sciences, Queen Mary University London, Mile End Road, London, E1 4NS, UK.,UCL Respiratory, University College London, 5 University Street, London, WC1E 6JF, UK
| | - Harry-Jack Mann
- UCL Respiratory, University College London, 5 University Street, London, WC1E 6JF, UK
| | - Olivia K Hearnden
- UCL Respiratory, University College London, 5 University Street, London, WC1E 6JF, UK
| | - David B Sattelle
- UCL Respiratory, University College London, 5 University Street, London, WC1E 6JF, UK
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7
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Habibi SA, Blazie SM, Jin Y, Forrester SG. Isolation and characterization of a novel member of the ACC ligand-gated chloride channel family, Hco-LCG-46, from the parasitic nematode Haemonchus contortus. Mol Biochem Parasitol 2020; 237:111276. [DOI: 10.1016/j.molbiopara.2020.111276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 03/24/2020] [Accepted: 03/25/2020] [Indexed: 10/24/2022]
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8
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Choudhary S, Buxton SK, Puttachary S, Verma S, Mair GR, McCoy CJ, Reaves BJ, Wolstenholme AJ, Martin RJ, Robertson AP. EAT-18 is an essential auxiliary protein interacting with the non-alpha nAChR subunit EAT-2 to form a functional receptor. PLoS Pathog 2020; 16:e1008396. [PMID: 32243475 PMCID: PMC7173930 DOI: 10.1371/journal.ppat.1008396] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 04/21/2020] [Accepted: 02/11/2020] [Indexed: 11/19/2022] Open
Abstract
Nematode parasites infect approximately 1.5 billion people globally and are a significant public health concern. There is an accepted need for new, more effective anthelmintic drugs. Nicotinic acetylcholine receptors on parasite nerve and somatic muscle are targets of the cholinomimetic anthelmintics, while glutamate-gated chloride channels in the pharynx of the nematode are affected by the avermectins. Here we describe a novel nicotinic acetylcholine receptor on the nematode pharynx that is a potential new drug target. This homomeric receptor is comprised of five non-α EAT-2 subunits and is not sensitive to existing cholinomimetic anthelmintics. We found that EAT-18, a novel auxiliary subunit protein, is essential for functional expression of the receptor. EAT-18 directly interacts with the mature receptor, and different homologs alter the pharmacological properties. Thus we have described not only a novel potential drug target but also a new type of obligate auxiliary protein for nAChRs. Soil-transmitted helminths affect about a quarter of the worlds’ population. Chemical anthelmintics not only alleviate the threat to human and animal health but also improve agricultural economics and food security. Here we have identified a “druggable” nicotinic acetylcholine receptor (nAChR) subunit, EAT-2, that constitutes the pharyngeal cholinergic receptor in nematodes. The receptor is required for feeding and possibly for reproductive behavior in worms. A selective therapeutic compound targeting this nAChR should either starve the worms or make them sluggish, helping with faster expulsion from the host. The EAT-2 pharyngeal nAChR is a unique receptor formed by five non-α subunits that lack vicinal cysteines in the ligand binding loop-C. To date, all cation selective nAChRs contain at least two α subunits. It is possible that EAT-2 subunits have retained functionality without the vicinal cysteines due to evolutionary modifications and expresses as a new nAChR subtype which doesn’t fit the established dogma based on the study of vertebrate receptors. Our findings also identified a new type of auxiliary protein subunit, which is essential for functional expression of the pharyngeal nAChR and also modulates its pharmacology. To the best of our knowledge, this is the first report of an auxiliary protein that is essential for functional expression in any cys-loop ligand-gated ion channel.
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Affiliation(s)
- Shivani Choudhary
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Samuel K. Buxton
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Sreekanth Puttachary
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Saurabh Verma
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Gunnar R. Mair
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Ciaran J. McCoy
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Barbara J. Reaves
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Adrian J. Wolstenholme
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Richard J. Martin
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
| | - Alan P. Robertson
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa, United States of America
- * E-mail:
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9
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Callanan MK, Habibi SA, Law WJ, Nazareth K, Komuniecki RL, Forrester SG. Investigating the function and possible biological role of an acetylcholine-gated chloride channel subunit (ACC-1) from the parasitic nematode Haemonchus contortus. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2018; 8:526-533. [PMID: 30401619 PMCID: PMC6287539 DOI: 10.1016/j.ijpddr.2018.10.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/25/2018] [Accepted: 10/26/2018] [Indexed: 01/30/2023]
Abstract
The cys-loop superfamily of ligand-gated ion channels are well recognized as important drug targets for many invertebrate specific compounds. With the rise in resistance seen worldwide to existing anthelmintics, novel drug targets must be identified so new treatments can be developed. The acetylcholine-gated chloride channel (ACC) family is a unique family of cholinergic receptors that have been shown, using Caenorhabditis elegans as a model, to have potential as anti-parasitic drug targets. However, there is little known about the function of these receptors in parasitic nematodes. Here, we have identified an acc gene (hco-acc-1) from the sheep parasitic nematode Haemonchus contortus. While similar in sequence to the previously characterized C. elegans ACC-1 receptor, Hco-ACC-1 does not form a functional homomeric channel in Xenopus oocytes. Instead, co-expression of Hco-ACC-1 with a previously characterized subunit Hco-ACC-2 produced a functional heteromeric channel which was 3x more sensitive to acetylcholine compared to the Hco-ACC-2 homomeric channel. We have also found that Hco-ACC-1 can be functionally expressed in C. elegans. Overexpression of both cel-acc-1 and hco-acc-1 in both C. elegans N2 and acc-1 null mutants decreased the time for worms to initiate reversal avoidance to octanol. Moreover, antibodies were generated against the Hco-ACC-1 protein for use in immunolocalization studies. Hco-ACC-1 consistently localized to the anterior half of the pharynx, specifically in pharyngeal muscle tissue in H. contortus. On the other hand, expression of Hco-ACC-1 in C. elegans was restricted to neuronal tissue. Overall, this research has provided new insight into the potential role of ACC receptors in parasitic nematodes. Isolation of an ACC-1 orthologue from Haemonchus contortus. Hco-ACC-1 may play a role in pharyngeal pumping. Hco-ACC-1 forms a sensitive ACh heteromeric channel when co-expressed with Hco-ACC-2.
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Affiliation(s)
- Micah K Callanan
- Faculty of Science, University of Ontario Institute of Technology, 2000, Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Sarah A Habibi
- Faculty of Science, University of Ontario Institute of Technology, 2000, Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Wen Jing Law
- Department of Biological Sciences, University of Toledo, Toledo, OH, 43606, USA
| | - Kristen Nazareth
- Faculty of Science, University of Ontario Institute of Technology, 2000, Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | | | - Sean G Forrester
- Faculty of Science, University of Ontario Institute of Technology, 2000, Simcoe Street North, Oshawa, ON, L1H 7K4, Canada.
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10
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Molecular and pharmacological characterization of an acetylcholine-gated chloride channel (ACC-2) from the parasitic nematode Haemonchus contortus. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2018; 8:518-525. [PMID: 30266440 PMCID: PMC6287471 DOI: 10.1016/j.ijpddr.2018.09.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 09/17/2018] [Accepted: 09/17/2018] [Indexed: 12/05/2022]
Abstract
Nematode cys-loop ligand-gated ion channels (LGICs) have been shown to be attractive targets for the development of novel anti-parasitic drugs. The ACC-1 family of receptors are a unique group of acetylcholine-gated chloride channels present only in invertebrates, and sequence analysis suggests that they contain a novel binding site for acetylcholine. We have isolated a novel member of this family, Hco-ACC-2, from the parasitic nematode Haemonchus contortus and using site-directed mutagenesis, electrophysiology and molecular modelling examined how two aromatic amino acids in the binding site contributed to agonist recognition. It was found that instead of a tryptophan residue in binding loop B, which essential for ligand binding in mammalian nAChRs, there is a phenylalanine (F200) in Hco-ACC-2. Amino acid changes at F200 to either a tyrosine or tryptophan were fairly well tolerated, where a F200Y mutation resulted in a channel hypersensitive to ACh and nicotine as well as other cholinergic agonists such as carbachol and methacholine. In addition, both pyrantel and levamisole were partial agonists at the wild-type receptor and like the other agonists showed an increase in sensitivity at F200Y. On the other hand, in Hco-ACC-2 there is a tryptophan residue at position 248 in loop C that appears to be essential for receptor function, as mutations to either phenylalanine or tyrosine resulted in a marked decrease in agonist sensitivity. Moreover, mutations that swapped the residues F200 and W248 (ie. F200W/W248F) produced non-functional receptors. Overall, Hco-ACC-2 appears to have a novel cholinergic binding site that could have implications for the design of specific anthelmintics that target this family of receptors in parasitic nematodes. Isolation of an ACC-2 orthologue from Haemonchus contortus. Hco-ACC-2 responds to several cholinergic agonists including levamisole and pyrantel. W248 in loop C plays an essential role in agonist recognition.
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11
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Abstract
The free-living nematode Caenorhabditis elegans is the simplest animal model organism to work with. Substantial knowledge and tools have accumulated over 50 years of C. elegans research. The use of C. elegans relating to parasitic nematodes from a basic biology standpoint or an applied perspective has increased in recent years. The wealth of information gained on the model organism, the use of the powerful approaches and technologies that have advanced C. elegans research to parasitic nematodes and the enormous success of the omics fields have contributed to bridge the divide between C. elegans and parasite nematode researchers. We review key fields, such as genomics, drug discovery and genetics, where C. elegans and nematode parasite research have convened. We advocate the use of C. elegans as a model to study helminth metabolism, a neglected area ready to advance. How emerging technologies being used in C. elegans can pave the way for parasitic nematode research is discussed.
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12
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Renahan T, Hong RL. A species-specific nematocide that results in terminal embryogenesis. ACTA ACUST UNITED AC 2017; 220:3238-3247. [PMID: 28684461 DOI: 10.1242/jeb.159665] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 06/29/2017] [Indexed: 01/20/2023]
Abstract
Nematode-insect interactions are ubiquitous, complex and constantly changing as the host and nematode coevolve. The entomophilic nematode Pristionchus pacificus is found on a myriad beetle species worldwide, although the molecular dynamics of this relationship are largely unknown. To better understand how host cues affect P. pacificus embryogenesis, we characterized the threshold of sensitivity to the pheromone (Z)-7-tetradecen-2-one (ZTDO) by determining the minimum exposure duration and developmental window that results in P. pacificus embryonic lethality. We found early-stage embryos exposed to volatile ZTDO for as few as 4 h all display terminal embryogenesis, characterized by punctuated development up to 48 h later, with abnormal morphology and limited cavity formation. To determine if the pheromone arrests pre-hatching development by suffocating or permeabilizing the eggshells, we raised embryos under anoxic conditions and also examined eggshell permeability using the lipophilic dye FM4-64. We found that asphyxiating the embryos arrested embryogenesis in a reversible manner but did not phenocopy the effects of ZTDO exposure, whereas the ZTDO-induced disruption of embryogenesis did correlate with increased eggshell permeability. The effects of ZTDO are also highly specific, as other lipid insect compounds do not produce any detectable embryocidal effect. The high specificity and unusual teratogenic effect of ZTDO may be important in mediating the host-nematode relationship by regulating P. pacificus development.
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Affiliation(s)
- Tess Renahan
- California State University, Northridge, Department of Biology, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA
| | - Ray L Hong
- California State University, Northridge, Department of Biology, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA
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Evolution, Expression, and Function of Nonneuronal Ligand-Gated Chloride Channels in Drosophila melanogaster. G3-GENES GENOMES GENETICS 2016; 6:2003-12. [PMID: 27172217 PMCID: PMC4938653 DOI: 10.1534/g3.116.029546] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ligand-gated chloride channels have established roles in inhibitory neurotransmission in the nervous systems of vertebrates and invertebrates. Paradoxically, expression databases in Drosophila melanogaster have revealed that three uncharacterized ligand-gated chloride channel subunits, CG7589, CG6927, and CG11340, are highly expressed in nonneuronal tissues. Furthermore, subunit copy number varies between insects, with some orders containing one ortholog, whereas other lineages exhibit copy number increases. Here, we show that the Dipteran lineage has undergone two gene duplications followed by expression-based functional differentiation. We used promoter-GFP expression analysis, RNA-sequencing, and in situ hybridization to examine cell type and tissue-specific localization of the three D. melanogaster subunits. CG6927 is expressed in the nurse cells of the ovaries. CG7589 is expressed in multiple tissues including the salivary gland, ejaculatory duct, malpighian tubules, and early midgut. CG11340 is found in malpighian tubules and the copper cell region of the midgut. Overexpression of CG11340 increased sensitivity to dietary copper, and RNAi and ends-out knockout of CG11340 resulted in copper tolerance, providing evidence for a specific nonneuronal role for this subunit in D. melanogaster Ligand-gated chloride channels are important insecticide targets and here we highlight copy number and functional divergence in insect lineages, raising the potential that order-specific receptors could be isolated within an effective class of insecticide targets.
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