title: The Ascaris suum nicotinic receptor, ACR-16, as a drug target: Four novel negative allosteric modulators from virtual screening.
abstract: Soil-transmitted helminth infections in humans and livestock cause significant debility, reduced productivity and economic losses globally. There are a limited number of effective anthelmintic drugs available for treating helminths infections, and their frequent use has led to the development of resistance in many parasite species. There is an urgent need for novel therapeutic drugs for treating these parasites. We have chosen the ACR-16 nicotinic acetylcholine receptor of Ascaris suum (Asu-ACR-16), as a drug target and have developed three-dimensional models of this transmembrane protein receptor to facilitate the search for new bioactive compounds. Using the human α7 nAChR chimeras and Torpedo marmorata nAChR for homology modeling, we defined orthosteric and allosteric binding sites on the Asu-ACR-16 receptor for virtual screening. We identified four ligands that bind to sites on Asu-ACR-16 and tested their activity using electrophysiological recording from Asu-ACR-16 receptors expressed in Xenopus oocytes. The four ligands were acetylcholine inhibitors (SB-277011-A, IC50, 3.12 ± 1.29 μM; (+)-butaclamol Cl, IC50, 9.85 ± 2.37 μM; fmoc-1, IC50, 10.00 ± 1.38 μM; fmoc-2, IC50, 16.67 ± 1.95 μM) that behaved like negative allosteric modulators. Our work illustrates a structure-based in silico screening method for seeking anthelmintic hits, which can then be tested electrophysiologically for further characterization.
authors.affiliation: Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA.
authors.forename: Fudan
authors.initials: F
authors.lastname: Zheng
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
authors.forename: Alan P
authors.initials: AP
authors.lastname: Robertson
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Abongwa
authors.affiliation: Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA; Department of Physics and Astronomy, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA.
authors.forename: Edward W
authors.initials: EW
authors.lastname: Yu
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA. Electronic address: rjmartin@iastate.edu.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Martin
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site / Q000235:genetics; D000818:Animals; D017165:Ascaris suum / Q000033:anatomy & histology* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D002069:Butaclamol / Q000494:pharmacology; D003198:Computer Simulation; D016503:Drug Delivery Systems; D055808:Drug Discovery / Q000379:methods*; D005449:Fluorenes / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D020128:Inhibitory Concentration 50; D007540:Isonipecotic Acids / Q000378:metabolism / Q000494:pharmacology; D008024:Ligands; D008958:Models, Molecular; D018722:Nicotinic Agonists / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000378:metabolism*; D044005:Tetrahydroisoquinolines / Q000494:pharmacology; D014101:Torpedo / Q000235:genetics / Q000502:physiology; D014981:Xenopus / Q000235:genetics
chemical_list: C000612063:9-fluorenylmethoxycarbonyl-4-(naphthalen-1-yl)-piperidine-4-carboxylic acid; C000612064:9-fluorenylmethoxycarbonyl-4-(naphthalen-2-yl)piperidine-4-carboxylic acid; D005449:Fluorenes; D007540:Isonipecotic Acids; D008024:Ligands; D018722:Nicotinic Agonists; D009570:Nitriles; D011978:Receptors, Nicotinic; C409982:SB 277011; D044005:Tetrahydroisoquinolines; D002069:Butaclamol
keywords: (+), principal subunit; (−), complementary subunit; AChBP, acetylcholine-binding protein; Allosteric modulator; Asu-ACR-16; ECD, extracellular domain; Homology modeling; NAM, negative allosteric modulator; Orthosteric site; Structure-based drug discovery; TID, transmembrane and intracellular domain; Xenopus expression; nAChR, nicotinic acetylcholine receptor