1
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Sanders VR, Millar NS. Potentiation and allosteric agonist activation of α7 nicotinic acetylcholine receptors: binding sites and hypotheses. Pharmacol Res 2023; 191:106759. [PMID: 37023990 DOI: 10.1016/j.phrs.2023.106759] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/27/2023] [Accepted: 03/30/2023] [Indexed: 04/07/2023]
Abstract
Considerable progress has been made in recent years towards the identification and characterisation of novel subtype-selective modulators of nicotinic acetylcholine receptors (nAChRs). In particular, this has focussed on modulators of α7 nAChRs, a nAChR subtype that has been identified as a target for drug discovery in connection with a range of potential therapeutic applications. This review focusses upon α7-selective modulators that bind to receptor sites other than the extracellular 'orthosteric' agonist binding site for the endogenous agonist acetylcholine (ACh). Such compounds include those that are able to potentiate responses evoked by orthosteric agonists such as ACh (positive allosteric modulators; PAMs) and those that are able to activate α7 nAChRs by direct allosteric activation in the absence of an orthosteric agonist (allosteric agonists or 'ago-PAMs'). There has been considerable debate about the mechanism of action of α7-selective PAMs and allosteric agonists, much of which has centred around identifying the location of their binding sites on α7 nAChRs. Based on a variety of experimental evidence, including recent structural data, there is now clear evidence indicating that at least some α7-selective PAMs bind to an inter-subunit site located in the transmembrane domain. In contrast, there are differing hypotheses about the site or sites at which allosteric agonists bind to α7 nAChRs. It will be argued that the available evidence supports the conclusion that direct allosteric activation by allosteric agonists/ago-PAMs occurs via the same inter-subunit transmembrane site that has been identified for several α7-selective PAMs.
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Affiliation(s)
- Victoria R Sanders
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
| | - Neil S Millar
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.
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2
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Ihara M. Ligand-gated ion channels as targets of neuroactive insecticides. Biosci Biotechnol Biochem 2022; 86:157-164. [PMID: 34849545 DOI: 10.1093/bbb/zbab202] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 11/16/2021] [Indexed: 11/14/2022]
Abstract
The Cys-loop superfamily of ligand-gated ion channels (Cys-loop receptors) is one of the most ubiquitous ion channel families in vertebrates and invertebrates. Despite their ubiquity, they are targeted by several classes of pesticides, including neonicotinoids, phenylpyrazols, and macrolides such as ivermectins. The current commercialized compounds have high target site selectivity, which contributes to the safety of insecticide use. Structural analyses have accelerated progress in this field; notably, the X-ray crystal structures of acetylcholine binding protein and glutamate-gated Cl channels revealed the details of the molecular interactions between insecticides and their targets. Recently, the functional expression of the insect nicotinic acetylcholine receptor (nAChR) has been described, and detailed evaluations using the insect nAChR have emerged. This review discusses the basic concepts and the current insights into the molecular mechanisms of neuroactive insecticides targeting the ligand-gated ion channels, particularly Cys-loop receptors, and presents insights into target-based selectivity, resistance, and future drug design.
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Affiliation(s)
- Makoto Ihara
- Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
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3
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Yokoi K, Nakamura Y, Jouraku A, Akiduki G, Uchibori-Asano M, Kuwazaki S, Suetsugu Y, Daimon T, Yamamoto K, Noda H, Sanada-Morimura S, Matsumura M, Cuong LQ, Van Chien H, Estoy GF, Shinoda T. Genome-wide assessment and development of molecular diagnostic methods for imidacloprid-resistance in the brown planthopper, Nilaparvata lugens (Hemiptera; Delphacidae). PEST MANAGEMENT SCIENCE 2021; 77:1786-1795. [PMID: 33249740 DOI: 10.1002/ps.6200] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/20/2020] [Accepted: 11/28/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND The brown planthopper, Nilaparvata lugens (Stål), is one of the most notorious pests of rice throughout Asia. The brown planthopper has developed high resistance to imidacloprid, a member of neonicotinoid insecticides. Several genes and mutations conferring imidacloprid resistance in N. lugens, especially in eastern and southeastern Asia populations, have been reported. Thus, the key mechanisms of imidacloprid resistance need to be examined. RESULTS RNA-seq analyses revealed that only one cytochrome P450 monooxygenase gene, CYP6ER1, was commonly upregulated in the five resistant strains tested. Sequences of CYP6ER1, which were highly expressed in the imidacloprid-resistant strains, contained a three-nucleotide deletion in the coding region, and amino acid substitutions and deletion, compared to that in an imidacloprid-susceptible strain. RNAi-mediated gene knockdown of CYP6ER1 increased imidacloprid susceptibility in a resistant strain. Further, we established two simple and convenient PCR-based molecular diagnostic methods to detect the CYP6ER1 locus with the three-nucleotide deletion. Using these methods, the resistance of F2 progenies derived from the crosses of F1 siblings from susceptible and resistant parents was analyzed, showing that the imidacloprid resistance had a relationship to the CYP6ER1 locus with the three-nucleotide deletion. CONCLUSION The overexpression of a variant CYP6ER1 with amino acid substitutions and deletion was involved in imidacloprid resistance in N. lugens. Based on these findings, molecular diagnostic methods have been developed and are promising tools for monitoring imidacloprid resistance in paddy fields. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Kakeru Yokoi
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Yuki Nakamura
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Akiya Jouraku
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Gaku Akiduki
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
- Kyushu Okinawa Agriculture Research Center, National Agriculture and Food Research Organization (NARO), Koshi, Japan
| | - Miwa Uchibori-Asano
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Seigo Kuwazaki
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Yoshitaka Suetsugu
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Takaaki Daimon
- Department of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kimiko Yamamoto
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Hiroaki Noda
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Sachiyo Sanada-Morimura
- Kyushu Okinawa Agriculture Research Center, National Agriculture and Food Research Organization (NARO), Koshi, Japan
| | - Masaya Matsumura
- Kyushu Okinawa Agriculture Research Center, National Agriculture and Food Research Organization (NARO), Koshi, Japan
| | - Le Quoc Cuong
- Southern Regional Plant Protection Center, Tien Giang, Vietnam
| | - Ho Van Chien
- Southern Regional Plant Protection Center, Tien Giang, Vietnam
| | - Gerardo F Estoy
- Philippine Rice Research Institute (PhilRice) - Agusan Experiment Station at Basilisa, Remedios T. Romualdez,, Philippines
| | - Tetsuro Shinoda
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
- Faculty of Food and Agricultural Sciences, Fukushima University, Fukushima, Japan
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4
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Maloney EM, Taillebois E, Gilles N, Morrissey CA, Liber K, Servent D, Thany SH. Binding properties to nicotinic acetylcholine receptors can explain differential toxicity of neonicotinoid insecticides in Chironomidae. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2021; 230:105701. [PMID: 33249296 DOI: 10.1016/j.aquatox.2020.105701] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 11/16/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Neonicotinoids are neuroactive insecticides commonly detected in freshwater ecosystems. Recent studies have indicated that these compounds are markedly toxic to Chironomidae, a widespread family of ecologically important aquatic insects. However, despite their sensitivity, the pharmacological mechanisms driving neonicotinoid toxicity have yet to be characterized in these insect species. Here, we used a combination of saturation and competition binding studies to characterize neonicotinoid binding properties to nicotinic acetylcholine receptors (nAChR) in two different Chironomidae (Chironomus riparius and Chironomus dilutus) at two different life stages (larval and adult). Using radiolabeled imidacloprid ([3H]-IMI), we characterized and compared receptor density (Bmax), imidacloprid binding affinity (KD), and receptor binding affinity (Ki) to three different neonicotinoid competitors (imidacloprid, clothianidin, and thiamethoxam). We then compared receptor density and binding affinity parameters derived for Chironomidae to data previously generated for other dipterans and agricultural pests. We found that there were limited differences in neonicotinoid binding between C. riparius and C. dilutus, with both organisms demonstrating high affinities for imidacloprid (KD = 0.22-0.87 nM) and high receptor densities (Bmax = 0.92-6.53 pmol/mg). However, there were significant differences between life-stages, with larvae expressing higher densities of nicotinic acetylcholine receptors and higher imidacloprid affinities than adults. Moreover, there were compound-specific differences in receptor affinity, with larval stages displaying relative affinities (Ki) that generally correlated with acute neonicotinoid toxicity (e.g. clothianidin ≥ imidacloprid >>> thiamethoxam). Finally, compared to other dipterans and agricultural pests, Chironomidae display very high densities of high affinity nicotinic acetylcholine receptors, which likely contribute to their sensitivity. Results indicated that receptor-level differences in neonicotinoid binding may be responsible for ecotoxicological differences amongst distinct insect species, and they likely play a role in life stage-, and compound-level toxicity differences previously observed for Chironomidae. Overall, this study highlights the value of understanding the toxicological mechanisms of action of neonicotinoids in sensitive, non-target aquatic insects, to better predict adverse effects associated with unintentional neonicotinoid exposure.
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Affiliation(s)
- E M Maloney
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
| | - E Taillebois
- Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), USC INRAE 1328, Université d'Orléans, Orléans, France
| | - N Gilles
- Université Paris Saclay, CEA, Département Médicaments et Technologies pour la Santé, SIMoS, 91191 Gif-sur-Yvette, France
| | - C A Morrissey
- School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - K Liber
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - D Servent
- Université Paris Saclay, CEA, Département Médicaments et Technologies pour la Santé, SIMoS, 91191 Gif-sur-Yvette, France
| | - S H Thany
- Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), USC INRAE 1328, Université d'Orléans, Orléans, France
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5
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Marquart LA, Turner MW, McDougal OM. Qualitative Assay to Detect Dopamine Release by Ligand Action on Nicotinic Acetylcholine Receptors. Toxins (Basel) 2019; 11:toxins11120682. [PMID: 31757080 PMCID: PMC6949981 DOI: 10.3390/toxins11120682] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/14/2019] [Accepted: 11/18/2019] [Indexed: 11/16/2022] Open
Abstract
A pheochromocytoma of the rat adrenal medulla derived (a.k.a. PC12) cell-based assay for dopamine measurement by luminescence detection was customized for the qualitative evaluation of agonists and antagonists of nicotinic acetylcholine receptors (nAChRs). The assay mechanism begins with ligand binding to transmembrane nAChRs, altering ion flow into the cell and inducing dopamine release from the cell. Following release, dopamine is oxidized by monoamine oxidase generating hydrogen peroxide that catalyzes a chemiluminescence reaction involving luminol and horseradish peroxidase, thus producing a detectable response. Results are presented for the action of nAChR agonists (acetylcholine, nicotine, and cytisine), and antagonists (α-conotoxins (α-CTxs) MII, ImI, LvIA, and PeIA) that demonstrate a luminescence response correlating to the increase or decrease of dopamine release. A survey of cell growth and treatment conditions, including nerve growth factor, nicotine, ethanol, and temperature, led to optimal assay requirements to achieve maximal signal intensity and consistent response to ligand treatment. It was determined that PC12 cells treated with a combination of nerve growth factor and nicotine, and incubated at 37 °C, provided favorable results for a reduction in luminescence signal upon treatment of cells with α-CTxs. The PC12 assay is intended for use as a fast, efficient, and economic qualitative method to assess the bioactivity of molecules that act on nAChRs, in which testing of ligand-nAChR binding hypotheses and computational predictions can be validated. As a screening method for nAChR bioactivity, lead compounds can be assessed for their likelihood of exhibiting desired bioactivity prior to being subjected to more complex quantitative methods, such as electrophysiology or live animal studies.
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Affiliation(s)
- Leanna A. Marquart
- Department of Chemistry and Biochemistry, Boise State University, Boise, ID 83725, USA;
| | - Matthew W. Turner
- Biomolecular Sciences PhD Program, Boise State University, Boise, ID 83725, USA;
| | - Owen M. McDougal
- Biomolecular Sciences PhD Program, Boise State University, Boise, ID 83725, USA;
- Correspondence:
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6
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Taillebois E, Cartereau A, Jones AK, Thany SH. Neonicotinoid insecticides mode of action on insect nicotinic acetylcholine receptors using binding studies. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2018; 151:59-66. [PMID: 30704714 DOI: 10.1016/j.pestbp.2018.04.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Revised: 04/14/2018] [Accepted: 04/17/2018] [Indexed: 06/09/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are the main target of neonicotinoid insecticides, which are widely used in crop protection against insect pests. Electrophysiological and molecular approaches have demonstrated the presence of several nAChR subtypes with different affinities for neonicotinoid insecticides. However, the precise mode of action of neonicotinoids on insect nAChRs remains to be elucidated. Radioligand binding studies with [3H]-α-bungarotoxin and [3H]-imidacloprid have proved instructive in understanding ligand binding interactions between insect nAChRs and neonicotinoid insecticides. The precise binding site interactions have been established using membranes from whole body and specific tissues. In this review, we discuss findings concerning the number of nAChR binding sites against neonicotinoid insecticides from radioligand binding studies on native tissues. We summarize the data available in the literature and compare the binding properties of the most commonly used neonicotinoid insecticides in several insect species. Finally, we demonstrate that neonicotinoid-nAChR binding sites are also linked to biological samples used and insect species.
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Affiliation(s)
- Emiliane Taillebois
- Université François Rabelais de Tours, Laboratoire Nutrition, Croissance et Cancer, INSERM 1069, 37032 Tours, France
| | - Alison Cartereau
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France
| | - Andrew K Jones
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Steeve H Thany
- Université d'Orléans, LBLGC USC INRA 1328, 1 rue de Chartres, 45067 Orléans, France.
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7
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Crespi A, Plutino S, Sciaccaluga M, Righi M, Borgese N, Fucile S, Gotti C, Colombo SF. The fifth subunit in α3β4 nicotinic receptor is more than an accessory subunit. FASEB J 2018; 32:4190-4202. [PMID: 29505300 DOI: 10.1096/fj.201701377r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The α3β4 subtype is the predominant neuronal nicotinic acetylcholine receptor present in the sensory and autonomic ganglia and in a subpopulation of brain neurons. This subtype can form pentameric receptors with either 2 or 3 β4 subunits that have different pharmacologic and functional properties. To further investigate the role of the fifth subunit, we coexpressed a dimeric construct coding for a single polypeptide containing the β4 and α3 subunit sequences, with different monomeric subunits. With this strategy, which allowed the formation of single populations of receptors with unique stoichiometry, we demonstrated with immunofluorescence and biochemical and functional assays that only the receptors with 3 β4 subunits are efficiently expressed at the plasma membrane. Moreover, the LFM export motif of β4 subunit in the fifth position exerts a unique function in the regulation of the intracellular trafficking of the receptors, their exposure at the cell surface, and consequently, their function, whereas the same export motif present in the β4 subunits forming the acetylcholine binding site is dispensable.-Crespi, A., Plutino, S., Sciaccaluga, M., Righi, M., Borgese, N., Fucile, S., Gotti, C., Colombo, S. F. The fifth subunit in α3β4 nicotinic receptor is more than an accessory subunit.
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Affiliation(s)
- Arianna Crespi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Simona Plutino
- Dipartimento di Fisiologia e Farmacologia, Università di Roma La Sapienza, Rome, Italy; and
| | - Miriam Sciaccaluga
- Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Neuromed, Istituto Neurologico Mediterraneo, Pozzilli, Italy
| | - Marco Righi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Nica Borgese
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Sergio Fucile
- Dipartimento di Fisiologia e Farmacologia, Università di Roma La Sapienza, Rome, Italy; and.,Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Neuromed, Istituto Neurologico Mediterraneo, Pozzilli, Italy
| | - Cecilia Gotti
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
| | - Sara Francesca Colombo
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.,Consiglio Nazionale delle Ricerche (CNR) Institute of Neuroscience, Milan, Italy
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8
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Shelukhina I, Spirova E, Kudryavtsev D, Ojomoko L, Werner M, Methfessel C, Hollmann M, Tsetlin V. Calcium imaging with genetically encoded sensor Case12: Facile analysis of α7/α9 nAChR mutants. PLoS One 2017; 12:e0181936. [PMID: 28797116 PMCID: PMC5552293 DOI: 10.1371/journal.pone.0181936] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 07/10/2017] [Indexed: 11/17/2022] Open
Abstract
Elucidation of the structural basis of pharmacological differences for highly homologous α7 and α9 nicotinic acetylcholine receptors (nAChRs) may shed light on their involvement in different physiological functions and diseases. Combination of site-directed mutagenesis and electrophysiology is a powerful tool to pinpoint the key amino-acid residues in the receptor ligand-binding site, but for α7 and α9 nAChRs it is complicated by their poor expression and fast desensitization. Here, we probed the ligand-binding properties of α7/α9 nAChR mutants by a proposed simple and fast calcium imaging method. The method is based on transient co-expression of α7/α9 nAChR mutants in neuroblastoma cells together with Ric-3 or NACHO chaperones and Case12 fluorescent calcium ion sensor followed by analysis of their pharmacology using a fluorescence microscope or a fluorometric imaging plate reader (FLIPR) with a GFP filter set. The results obtained were confirmed by electrophysiology and by calcium imaging with the conventional calcium indicator Fluo-4. The affinities for acetylcholine and epibatidine were determined for human and rat α7 nAChRs, and for their mutants with homologous residues of α9 nAChR incorporated at positions 117-119, 184, 185, 187, and 189, which are anticipated to be involved in ligand binding. The strongest decrease in the affinity was observed for mutations at positions 187 and 119. The L119D mutation of α7 nAChR, showing a larger effect for epibatidine than for acetylcholine, may implicate this position in pharmacological differences between α7 and α9 nAChRs.
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Affiliation(s)
- Irina Shelukhina
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Ekaterina Spirova
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Denis Kudryavtsev
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Lucy Ojomoko
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Markus Werner
- Department of Biochemistry I, Ruhr University Bochum, Bochum, Germany
| | | | - Michael Hollmann
- Department of Biochemistry I, Ruhr University Bochum, Bochum, Germany
| | - Victor Tsetlin
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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9
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Ray C, Soderblom EJ, Bai Y, Carroll FI, Caron MG, Barak LS. Probing the Allosteric Role of the α5 Subunit of α3β4α5 Nicotinic Acetylcholine Receptors by Functionally Selective Modulators and Ligands. ACS Chem Biol 2017; 12:702-714. [PMID: 28045487 DOI: 10.1021/acschembio.6b01117] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nicotinic acetylcholine receptors regulate the nicotine dependence encountered with cigarette smoking, and this has stimulated a search for drugs binding the responsible receptor subtypes. Studies link a gene cluster encoding for α3β4α5-D398N nicotinic acetylcholine receptors to lung cancer risk as well as link a second mutation in this cluster to an increased risk for nicotine dependence. However, there are currently no recognized drugs for discriminating α3β4α5 signaling. In this study, we describe the development of homogeneous HEK-293 cell clones of α3β4 and α3β4α5 receptors appropriate for drug screening and characterizing biochemical and pharmacological properties of incorporated α5 subunits. Clones were assessed for plasma membrane expression of the individual receptor subunits by mass spectrometry and immunochemistry, and their calcium flux was measured in the presence of a library of kinase inhibitors and a focused library of acetylcholine receptor ligands. We demonstrated an incorporation of two α3 subunits in approximately 98% of plasma membrane receptor pentamers, indicating a 2/3 subunit expression ratio of α3 to β4 alone or to coexpressed β4 and α5. With prolonged nicotine exposure, the plasma membrane expression of receptors with and without incorporated α5 increased. Whereas α5 subunit expression decreased the cell calcium response to nicotine and reduced plasma membrane receptor number, it partially protected receptors from nicotine mediated desensitization. Hit compounds from both libraries suggest the α5 and α5-D398N subunits allosterically modify the behavior of nicotine at the parent α3β4 nicotinic acetylcholine receptor. These studies identify pharmacological tools from two distinct classes of drugs, antagonists and modifiers that are α5 and α5-D398N subtype selective that provide a means to characterize the role of the CHRNA5/A3/B4 gene cluster in smoking and cancer.
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Affiliation(s)
| | | | | | - F. Ivy Carroll
- Departments
of Pharmacology and Toxicology, RTI International, 3040 E. Cornwallis Road, Durham, North Carolina 27709, United States
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10
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Wang J, Wang X, Lansdell SJ, Zhang J, Millar NS, Wu Y. A three amino acid deletion in the transmembrane domain of the nicotinic acetylcholine receptor α6 subunit confers high-level resistance to spinosad in Plutella xylostella. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 71:29-36. [PMID: 26855198 PMCID: PMC4821178 DOI: 10.1016/j.ibmb.2016.02.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 01/28/2016] [Accepted: 02/03/2016] [Indexed: 05/13/2023]
Abstract
Spinosad is a macrocyclic lactone insecticide that acts primarily at the nicotinic acetylcholine receptors (nAChRs) of target insects. Here we describe evidence that high levels of resistance to spinosad in the diamondback moth (Plutella xylostella) are associated with a three amino acid (3-aa) deletion in the fourth transmembrane domain (TM4) of the nAChR α6 subunit (Pxα6). Following laboratory selection with spinosad, the SZ-SpinR strain of P. xylostella exhibited 940-fold resistance to spinosad. In addition, the selected insect population had 1060-fold cross-resistance to spinetoram but, in contrast, no cross-resistance to abamectin was observed. Genetic analysis indicates that spinosad resistance in SZ-SpinR is inherited as a recessive and autosomal trait, and that the 3-aa deletion (IIA) in TM4 of Pxα6 is tightly linked to spinosad resistance. Because of well-established difficulties in functional expression of cloned insect nAChRs, the analogous resistance-associated deletion mutation was introduced into a prototype nAChR (the cloned human α7 subunit). Two-electrode voltage-clamp recording with wild-type and mutated nAChRs expressed in Xenopus laevis oocytes indicated that the mutation causes a complete loss of agonist activation. In addition, radioligand binding studies indicated that the 3-aa deletion resulted in significantly lower-affinity binding of the extracellular neurotransmitter-binding site. These findings are consistent with the 3-amino acid (IIA) deletion within the transmembrane domain of Pxα6 being responsible for target-site resistance to spinosad in the SZ-SpinR strain of P. xylostella.
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Affiliation(s)
- Jing Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
| | - Xingliang Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
| | - Stuart J Lansdell
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom.
| | - Jianheng Zhang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
| | - Neil S Millar
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom.
| | - Yidong Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
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11
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Qu Y, Chen J, Li C, Wang Q, Guo W, Han Z, Jiang W. The subunit gene Ldα1 of nicotinic acetylcholine receptors plays important roles in the toxicity of imidacloprid and thiamethoxam against Leptinotarsa decemlineata. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2016; 127:51-58. [PMID: 26821658 DOI: 10.1016/j.pestbp.2015.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 09/16/2015] [Accepted: 09/16/2015] [Indexed: 06/05/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ACh-gated ion channels. It is believed that nAChRs composed of different subunits may vary in their function and toxicological characteristics. Neonicotinoids are activators of nAChRs and important insecticides that are extensively used for crop protection and resistance has been developed by some pests. They are also major insecticides for the control of Leptinotarsa decemlineata, which is a destructive defoliator pest that invaded the Xinjiang region of China in the 1990s. However, little is known about the constitution or subunits of the target in this pest. In this study, the full-length cDNAs encoding four new nAChR subunits (named Ldα3, Ldα6, Ldα10, and Ldβ1) were cloned from L. decemlineata. These genes encode 822-, 753-, 672-, and 759-amino acid proteins, respectively, which share typical features of insect nAChRs subunits and closely resemble the corresponding subunits of the nAChRs from Tribolium castaneum. Temporal and spatial expression analyses showed that these genes, as well as the previously identified Ldα1, Ldα2, and Ldα8 genes, are widely expressed in all developmental stages, including eggs, larvae of various instars, pupae, and adults. All genes monitored were expressed at higher levels in the head than in the thorax and abdomen, except for Ldα10. Dietary ingestion of double-stranded RNA bacterially expressed for Ldα1 (dsLdα1) significantly reduced the mRNA level of Ldα1 in treated larvae and adults by 48.0% and 78.6%, respectively. Among the non-target genes, Ldα3, Ldα9, and Ldβ1 were significantly up-regulated in larvae. A toxicity bioassay showed that dsLdα1 treatment greatly decreased the sensitivity to imidacloprid and thiamethoxam in adults. The larval susceptibility to thiamethoxam but not to imidacloprid was also reduced because of the lower down-regulation of Ldα1. Thus, our results suggest that Ldα1 encodes a subunit of a functional nAChR that mediates the toxicity of imidacloprid and thiamethoxam against L. decemlineata and that the down-regulation of Ldα1 might be an important mechanism for resistance and/or tolerance of L. decemlineata to neonicotinoids.
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Affiliation(s)
- Yang Qu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Jinhua Chen
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Chenge Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Qiang Wang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Wenchao Guo
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi 830000, China
| | - Zhaojun Han
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Weihua Jiang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
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Kim GR, Yoon TH, Park WG, Park JY, Kang JH, Kim HW. Five nicotinic acetylcholine receptor subunits from the Morotoge shrimp,Pandalopsis japonica: cloning, tissue distribution, and functional expression inXenopusoocytes. Anim Cells Syst (Seoul) 2015. [DOI: 10.1080/19768354.2015.1109547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Crespin L, Legros C, List O, Tricoire-Leignel H, Mattei C. Injection of insect membrane in Xenopus oocyte: An original method for the pharmacological characterization of neonicotinoid insecticides. J Pharmacol Toxicol Methods 2015; 77:10-6. [PMID: 26391340 DOI: 10.1016/j.vascn.2015.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 09/04/2015] [Accepted: 09/15/2015] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Insect nicotinic acetylcholine receptors (nAChRs) represent a major target of insecticides, belonging to the neonicotinoid family. However, the pharmacological profile of native nAChRs is poorly documented, mainly because of a lack of knowledge of their subunit stoichiometry, their tissue distribution and the weak access to nAChR-expressing cells. In addition, the expression of insect nAChRs in heterologous systems remains hard to achieve. Therefore, the structure-activity characterization of nAChR-targeting insecticides is made difficult. The objective of the present study was to characterize insect nAChRs by an electrophysiological approach in a heterologous system naturally devoid of these receptors to allow a molecular/cellular investigation of the mode of action of neonicotinoids. Methods To overcome impediments linked to the expression of insect nAChR mRNA or cDNA, we chose to inject insect membranes from the pea aphid (Acyrthosiphon pisum) into Xenopus oocytes. This microtransplantation technique was designed to gain access to native nAChRs embedded in their membrane, through direct stimulation with nicotinic agonists. Results We provide evidence that an enriched-nAChR membrane allows us to characterize native receptors. The presence of such receptors was confirmed with fluorescent α-BgTX labeling. Electrophysiological recordings of nicotine-induced inward currents allowed us to challenge the presence of functional nAChR. We compared the effect of nicotine (NIC) with clothianidin (CLO) and we assessed the effect of thiamethoxam (TMX). Discussion This technique has been recently highlighted with mammalian and human material as a powerful functional approach, but has, to our knowledge, never been used with insect membrane. In addition, the use of the insect membrane microtransplantation opens a new and original way for pharmacological screening of neurotoxic insecticides, including neonicotinoids. Moreover, it might also be a powerful tool to investigate the pharmacological properties of insect nAChR.
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Affiliation(s)
- Lucille Crespin
- Laboratoire de Biologie Neurovasculaire et Mitochondriale Intégrée CNRS UMR6214, INSERM U1083, Univ. Angers Faculté de Médecine, rue Haute de Reculée, 49045 Angers cedex 01, France
| | - Christian Legros
- Laboratoire de Biologie Neurovasculaire et Mitochondriale Intégrée CNRS UMR6214, INSERM U1083, Univ. Angers Faculté de Médecine, rue Haute de Reculée, 49045 Angers cedex 01, France
| | - Olivier List
- Récepteurs et Canaux Ioniques Membranaires, UPRES-EA 2647 USC INRA 1330, SFR 4207 QUASAV, Univ. Angers, 2 Bd Lavoisier, 49045 Angers cedex 01, France
| | - Hélène Tricoire-Leignel
- INRA/Université d'Angers, Neuroéthologie-RCIM, UPRES-EA 2647 USC INRA 1330, SFR 4207 QUASAV, 42, rue Georges Morel, 49071 Beaucouzé, France.
| | - César Mattei
- Laboratoire de Biologie Neurovasculaire et Mitochondriale Intégrée CNRS UMR6214, INSERM U1083, Univ. Angers Faculté de Médecine, rue Haute de Reculée, 49045 Angers cedex 01, France.
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Zhang Y, Wang X, Yang B, Hu Y, Huang L, Bass C, Liu Z. Reduction in mRNA and protein expression of a nicotinic acetylcholine receptor α8 subunit is associated with resistance to imidacloprid in the brown planthopper, Nilaparvata lugens. J Neurochem 2015; 135:686-94. [DOI: 10.1111/jnc.13281] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 08/02/2015] [Accepted: 08/04/2015] [Indexed: 12/30/2022]
Affiliation(s)
- Yixi Zhang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
| | - Xin Wang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
| | - Baojun Yang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
| | - Yuanyuan Hu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
| | - Lixin Huang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
| | - Chris Bass
- Department of Biological Chemistry and Crop Protection; Rothamsted Research; Harpenden Hertfordshire UK
| | - Zewen Liu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education); College of Plant Protection; Nanjing Agricultural University; Nanjing China
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Allosteric modulation of nicotinic acetylcholine receptors. Biochem Pharmacol 2015; 97:408-417. [PMID: 26231943 DOI: 10.1016/j.bcp.2015.07.028] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/24/2015] [Indexed: 12/12/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are receptors for the neurotransmitter acetylcholine and are members of the 'Cys-loop' family of pentameric ligand-gated ion channels (LGICs). Acetylcholine binds in the receptor extracellular domain at the interface between two subunits and research has identified a large number of nAChR-selective ligands, including agonists and competitive antagonists, that bind at the same site as acetylcholine (commonly referred to as the orthosteric binding site). In addition, more recent research has identified ligands that are able to modulate nAChR function by binding to sites that are distinct from the binding site for acetylcholine, including sites located in the transmembrane domain. These include positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), silent allosteric modulators (SAMs) and compounds that are able to activate nAChRs via an allosteric binding site (allosteric agonists). Our aim in this article is to review important aspects of the pharmacological diversity of nAChR allosteric modulators and to describe recent evidence aimed at identifying binding sites for allosteric modulators on nAChRs.
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Wang X, Bao H, Sun H, Zhang Y, Fang J, Liu Q, Liu Z. Selective actions of Lynx proteins on different nicotinic acetylcholine receptors in the locust, Locusta migratoria manilensis. J Neurochem 2015; 134:455-62. [PMID: 25951893 DOI: 10.1111/jnc.13151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/22/2015] [Accepted: 04/22/2015] [Indexed: 12/27/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are major neurotransmitter receptors and targets of neonicotinoid insecticides in the insect nervous system. The full function of nAChRs is often dependent on associated proteins, such as chaperones, regulators and modulators. Here, three Lynx (Ly-6/neurotoxin) proteins, Loc-lynx1, Loc-lynx2 and Loc-lynx3, were identified in the locust, Locusta migratoria manilensis. Co-expression with Lynx resulted in a dramatic increase in agonist-evoked macroscopic currents on nAChRs Locα1/β2 and Locα2/β2 in Xenopus oocytes, but no changes in agonist sensitivity. Loc-lynx1 and Loc-lynx3 only modulated nAChRs Locα1/β2 while Loc-lynx2 modulated Locα2/β2 specifically. Meanwhile, Loc-lynx1 induced a more significant increase in currents evoked by imidacloprid and epibatidine than Loc-lynx3, and the effects of Loc-lynx1 on imidacloprid and epibatidine were significantly higher than those on acetylcholine. Among three lynx proteins, only Loc-lynx1 significantly increased [(3) H]epibatidine binding on Locα1/β2. The results indicated that Loc-lynx1 had different modulation patterns in nAChRs compared to Loc-lynx2 and Loc-lynx3. Taken together, these findings indicated that three Lynx proteins were nAChR modulators and had selective activities in different nAChRs. Lynx proteins might display their selectivities from three aspects: nAChR subtypes, various agonists and different modulation patterns. Insect Lynx (Ly-6/neurotoxin) proteins act as the allosteric modulators on insect nicotinic acetylcholine receptors (nAChRs), the important targets of insecticides. We found that insect lynx proteins showed their selectivities from at least three aspects: nAChR subtypes, various agonists and different modulation patterns.
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Affiliation(s)
- Xin Wang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Haibo Bao
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China.,Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Huahua Sun
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Yixi Zhang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Jichao Fang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Qinghong Liu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Zewen Liu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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Elmore CS, Landvatter S, Dorff PN, Powell ME, Killick D, Blake T, Hall J, Heys JR, Harding J, Urbanek R, Ernst G. Synthesis of three alpha 7 agonists in labeled form. J Labelled Comp Radiopharm 2014; 57:342-9. [DOI: 10.1002/jlcr.3186] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 01/14/2014] [Accepted: 01/14/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Charles S. Elmore
- Isotope Chemistry; DMPK, AstraZeneca Pharmaceuticals LP; 43183 Mölndal Sweden
| | | | - Peter N. Dorff
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - Mark E. Powell
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - David Killick
- Isotope Chemistry; DMPK, AstraZeneca Pharmaceuticals LP; Alderley Park UK
| | - Timothy Blake
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - James Hall
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - J. Richard Heys
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - John Harding
- Isotope Chemistry; DMPK, AstraZeneca Pharmaceuticals LP; Alderley Park UK
| | - Rebecca Urbanek
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
| | - Glen Ernst
- CNS-Chemistry; AstraZeneca Pharmaceuticals LP; Wilmington DE 19850 USA
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Shi M, Yue Z, Kuryatov A, Lindstrom JM, Sehgal A. Identification of Redeye, a new sleep-regulating protein whose expression is modulated by sleep amount. eLife 2014; 3:e01473. [PMID: 24497543 PMCID: PMC3912633 DOI: 10.7554/elife.01473] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In this study, we report a new protein involved in the homeostatic regulation of sleep in Drosophila. We conducted a forward genetic screen of chemically mutagenized flies to identify short-sleeping mutants and found one, redeye (rye) that shows a severe reduction of sleep length. Cloning of rye reveals that it encodes a nicotinic acetylcholine receptor α subunit required for Drosophila sleep. Levels of RYE oscillate in light-dark cycles and peak at times of daily sleep. Cycling of RYE is independent of a functional circadian clock, but rather depends upon the sleep homeostat, as protein levels are up-regulated in short-sleeping mutants and also in wild type animals following sleep deprivation. We propose that the homeostatic drive to sleep increases levels of RYE, which responds to this drive by promoting sleep. DOI: http://dx.doi.org/10.7554/eLife.01473.001.
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Affiliation(s)
- Mi Shi
- Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, United States
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Large scale expression and purification of the mouse 5-HT3 receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2544-52. [DOI: 10.1016/j.bbamem.2013.05.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/22/2013] [Accepted: 05/27/2013] [Indexed: 02/08/2023]
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Molgó J, Aráoz R, Benoit E, Iorga BI. Physical and virtual screening methods for marine toxins and drug discovery targeting nicotinic acetylcholine receptors. Expert Opin Drug Discov 2013; 8:1203-23. [DOI: 10.1517/17460441.2013.822365] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Rinkevich FD, Scott JG. Limitations of RNAi of α6 nicotinic acetylcholine receptor subunits for assessing the in vivo sensitivity to spinosad. INSECT SCIENCE 2013; 20:101-108. [PMID: 23955830 DOI: 10.1111/j.1744-7917.2012.01523.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Spinosad is a widely used insecticide that exerts its toxic effect primarily through interactions with the nicotinic acetylcholine receptor. The α6 nicotinic acetylcholine receptor subunit is involved in spinosad toxicity as demonstrated by the high levels of resistance observed in strains lacking α6. RNAi was performed against the Dα6 nicotinic acetylcholine receptor subunit in Drosophila melanogaster using the Gal4-UAS system to examine if RNAi would yield results similar to those of Dα6 null mutants. These Dα6-deficient flies were subject to spinosad contact bioassays to evaluate the role of the Dα6 nicotinic acetylcholine receptor subunit on spinosad sensitivity. The expression of Dα6 was reduced 60%-75% as verified by quantitative polymerase chain reaction. However, there was no change in spinosad sensitivity in D. melanogaster. We repeated RNAi experiments in Tribolium castaneum using injection of dsRNA for Tcasα6. RNAi of Tcasα6 did not result in changes in spinosad sensitivity, similar to results obtained with D. melanogaster. The lack of change in spinosad sensitivity in both D. melanogaster and T. castaneum using two routes of dsRNA administration shows that RNAi may not provide adequate conditions to study the role of nicotinic acetylcholine receptor subunits on insecticide sensitivity due to the inability to completely eliminate expression of the α6 subunit in both species. Potential causes for the lack of change in spinosad sensitivity are discussed.
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Affiliation(s)
- Frank D Rinkevich
- Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853-0901, USA
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The Drosophila nicotinic acetylcholine receptor subunits Dα5 and Dα7 form functional homomeric and heteromeric ion channels. BMC Neurosci 2012; 13:73. [PMID: 22727315 PMCID: PMC3444433 DOI: 10.1186/1471-2202-13-73] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 05/17/2012] [Indexed: 11/29/2022] Open
Abstract
Background Nicotinic acetylcholine receptors (nAChRs) play an important role as excitatory neurotransmitters in vertebrate and invertebrate species. In insects, nAChRs are the site of action of commercially important insecticides and, as a consequence, there is considerable interest in examining their functional properties. However, problems have been encountered in the successful functional expression of insect nAChRs, although a number of strategies have been developed in an attempt to overcome such difficulties. Ten nAChR subunits have been identified in the model insect Drosophila melanogaster (Dα1-Dα7 and Dβ1-Dβ3) and a similar number have been identified in other insect species. The focus of the present study is the Dα5, Dα6 and Dα7 subunits, which are distinguished by their sequence similarity to one another and also by their close similarity to the vertebrate α7 nAChR subunit. Results A full-length cDNA clone encoding the Drosophila nAChR Dα5 subunit has been isolated and the properties of Dα5-, Dα6- and Dα7-containing nAChRs examined in a variety of cell expression systems. We have demonstrated the functional expression, as homomeric nAChRs, of the Dα5 and Dα7 subunits in Xenopus oocytes by their co-expression with the molecular chaperone RIC-3. Also, using a similar approach, we have demonstrated the functional expression of a heteromeric ‘triplet’ nAChR (Dα5 + Dα6 + Dα7) with substantially higher apparent affinity for acetylcholine than is seen with other subunit combinations. In addition, specific cell-surface binding of [125I]-α-bungarotoxin was detected in both Drosophila and mammalian cell lines when Dα5 was co-expressed with Dα6 and RIC-3. In contrast, co-expression of additional subunits (including Dα7) with Dα5 and Dα6 prevented specific binding of [125I]-α-bungarotoxin in cell lines, suggesting that co-assembly with other nAChR subunits can block maturation of correctly folded nAChRs in some cellular environments. Conclusion Data are presented demonstrating the ability of the Drosophila Dα5 and Dα7 subunits to generate functional homomeric and also heteromeric nAChRs.
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Pohanka M. Alpha7 nicotinic acetylcholine receptor is a target in pharmacology and toxicology. Int J Mol Sci 2012; 13:2219-2238. [PMID: 22408449 PMCID: PMC3292018 DOI: 10.3390/ijms13022219] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 01/26/2012] [Accepted: 02/14/2012] [Indexed: 01/18/2023] Open
Abstract
Alpha7 nicotinic acetylcholine receptor (α7 nAChR) is an important part of the cholinergic nerve system in the brain. Moreover, it is associated with a cholinergic anti-inflammatory pathway in the termination of the parasympathetic nervous system. Antagonists of α7 nAChR are a wide group represented by conotoxin and bungarotoxin. Even Alzheimer's disease drug memantine acting as an antagonist in its side pathway belongs in this group. Agonists of α7 nAChR are suitable for treatment of multiple cognitive dysfunctions such as Alzheimer's disease or schizophrenia. Inflammation or even sepsis can be ameliorated by the agonistic acting compounds. Preparations RG3487, SEN34625/WYE-103914, SEN12333, ABT-107, Clozapine, GTS-21, CNI-1493, and AR-R17779 are representative examples of the novel compounds with affinity toward the α7 nAChR. Pharmacological, toxicological, and medicinal significance of α7 nAChR are discussed throughout this paper.
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Affiliation(s)
- Miroslav Pohanka
- Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 50001 Hradec Kralove, Czech Republic; E-Mail: ; Tel.: +420-973253091; Fax: +420-973253091
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Jindrichova M, Lansdell SJ, Millar NS. Changes in temperature have opposing effects on current amplitude in α7 and α4β2 nicotinic acetylcholine receptors. PLoS One 2012; 7:e32073. [PMID: 22359659 PMCID: PMC3281115 DOI: 10.1371/journal.pone.0032073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 01/19/2012] [Indexed: 11/19/2022] Open
Abstract
We have examined the effect of temperature on the electrophysiological properties of three neuronal nicotinic acetylcholine receptor (NACHR) subtypes: the rapidly desensitizing homomeric α7 nAChR, the more slowly desensitizing heteromeric α4β2 nAChR and on α7 nAChRs containing a transmembrane mutation (L247T) that results in dramatically reduced desensitization. In all cases, the functional properties of receptors expressed in Xenopus oocytes at room temperature (RT; 21°C) were compared to those recorded at either physiological temperature (37°C) or at lower temperature (4°C). Alterations in temperature had dramatically differing effects on the amplitude of whole-cell responses detected with these three nAChR subtypes. Compared to responses at RT, the amplitude of agonist-evoked responses with α4β2 nAChRs was increased at high temperature (125±9%, n = 6, P<0.01) and reduced at low temperature (47±5%, n = 6, P<0.01), whereas the amplitude of α7 responses was reduced at high temperature (27±7%, n = 11, P<0.001) and increased at low temperatures (224±16%, n = 10, P<0.001). In contrast to the effects of temperature on α4β2 and wild type α7 nAChRs, the amplitude of α7 nAChRs containing the L247T mutation was unaffected by changes in temperature. In addition, changes in temperature had little or no effect on current amplitude when α7 nAChRs were activated by the largely non-desensitizing allosteric agonist 4BP-TQS. Despite these differing effects of temperature on the amplitude of agonist-evoked responses in different nAChRs, changes in temperature had a consistent effect on the rate of receptor desensitization on all subtypes examined. In all cases, higher temperature resulted in increased rates of desensitization. Thus, it appears that the differing effects of temperature on the amplitudes of whole-cell responses cannot be explained by temperature-induced changes in receptor desensitization rates.
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Affiliation(s)
- Marie Jindrichova
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Stuart J. Lansdell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Neil S. Millar
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- * E-mail:
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Dederer H, Werr M, Ilg T. Differential sensitivity of Ctenocephalides felis and Drosophila melanogaster nicotinic acetylcholine receptor α1 and α2 subunits in recombinant hybrid receptors to nicotinoids and neonicotinoid insecticides. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 41:51-61. [PMID: 20933086 DOI: 10.1016/j.ibmb.2010.09.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/22/2010] [Accepted: 09/29/2010] [Indexed: 05/30/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are the binding sites for nicotinoid drugs, such as nicotine and epibatidine, and are the molecular targets of the selectively insecticidal neonicotinoids. In this study we report the full length cDNA cloning of the three Ctenocephalides (C.) felis (cat flea) nAChR α subunits Cfα1, Cfα2, and Cfα3. When expressed in Xenopus oocytes as hybrid receptors with the Gallus gallus (chicken) β2 (Ggβ2) subunit, these cat flea α subunits formed acetylcholine-responsive ion channels. Acetylcholine-evoked currents of Cfα2/Ggβ2 were resistant to α-bungarotoxin, while those of Cfα1/Ggβ2 were sensitive to this snake toxin. The pharmacological profiles of Cfα1/Ggβ2, Cfα2/Ggβ2 and the chicken neuronal receptor Ggα4/Ggβ2 for acetylcholine, two nicotinoids and 6 insecticidal neonicotinoids were determined and compared. Particularly remarkable was the finding that Cfα1/Ggβ2 was far more sensitive to acetylcholine, nicotine and neonicotinoid agonists than either Cfα2/Ggβ2 or Ggα4/Ggβ2: for the anti flea neonicotinoid market compound imidacloprid the respective EC₅₀s were 0.02 μM, 1.31 μM and 10 μM. These results were confirmed for another insect species, Drosophila melanogaster, where the pharmacological profile of the Dmα1 and Dmα2 subunits as hybrid receptors with Ggβ2 in Xenopus oocyte expressions resulted in a similar sensitivity pattern as those identified for the C. felis orthologs. Our results show that at least in a Ggβ2 hybrid receptor setting, insect α1 subunits confer higher sensitivity to neonicotinoids than α2 subunits, which may contribute in vivo to the insect-selective action of this pesticide class.
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Affiliation(s)
- Helene Dederer
- Intervet Innovation GmbH, Zur Propstei, 55270 Schwabenheim, Germany
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