title: A constitutively active G protein-coupled acetylcholine receptor regulates motility of larval Schistosoma mansoni.
abstract: The neuromuscular system of helminths controls a variety of essential biological processes and therefore represents a good source of novel drug targets. The neuroactive substance, acetylcholine controls movement of Schistosoma mansoni but the mode of action is poorly understood. Here, we present first evidence of a functional G protein-coupled acetylcholine receptor in S. mansoni, which we have named SmGAR. A bioinformatics analysis indicated that SmGAR belongs to a clade of invertebrate GAR-like receptors and is related to vertebrate muscarinic acetylcholine receptors. Functional expression studies in yeast showed that SmGAR is constitutively active but can be further activated by acetylcholine and, to a lesser extent, the cholinergic agonist, carbachol. Anti-cholinergic drugs, atropine and promethazine, were found to have inverse agonist activity towards SmGAR, causing a significant decrease in the receptor's basal activity. An RNAi phenotypic assay revealed that suppression of SmGAR activity in early-stage larval schistosomulae leads to a drastic reduction in larval motility. In sum, our results provide the first molecular evidence that cholinergic GAR-like receptors are present in schistosomes and are required for proper motor control in the larvae. The results further identify SmGAR as a possible candidate for antiparasitic drug targeting.
authors.affiliation: Institute of Parasitology, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Ste. Anne de Bellevue Quebec, H9X 3V9, Canada.
authors.forename: Kevin
authors.initials: K
authors.lastname: MacDonald
authors.affiliation: Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kimber
authors.affiliation: Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA.
authors.forename: Tim A
authors.initials: TA
authors.lastname: Day
authors.affiliation: Institute of Parasitology, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Ste. Anne de Bellevue Quebec, H9X 3V9, Canada. Electronic address: paula.ribeiro@mcgill.ca.
authors.forename: Paula
authors.initials: P
authors.lastname: Ribeiro
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D018680:Cholinergic Antagonists / Q000494:pharmacology; D018509:DNA, Helminth / Q000235:genetics / Q000378:metabolism; D005260:Female; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009043:Motor Activity / Q000502:physiology; D011398:Promethazine / Q000494:pharmacology; D011487:Protein Conformation; D011950:Receptors, Cholinergic / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012550:Schistosoma mansoni / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: D000977:Antiparasitic Agents; D018679:Cholinergic Agonists; D018680:Cholinergic Antagonists; D018509:DNA, Helminth; D011950:Receptors, Cholinergic; D043562:Receptors, G-Protein-Coupled; D001285:Atropine; D002217:Carbachol; D011398:Promethazine; D000109:Acetylcholine
keywords: Acetylcholine (ACh); Constitutive activity; G protein-coupled acetylcholine receptor (GAR); G protein-coupled receptor (GPCR); RNA interference (RNAi); Schistosome