TY - JOUR T1 - Activation of <em>Caenorhabditis elegans</em> levamisole-sensitive and mammalian nicotinic receptors by the antiparasitic bephenium JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.118.113357 SP - mol.118.113357 AU - Ornella Turani AU - Guillermina Hernando AU - Jeremias Corradi AU - Cecilia Bouzat Y1 - 2018/01/01 UR - http://molpharm.aspetjournals.org/content/early/2018/09/05/mol.118.113357.abstract N2 - Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels involved in neuromuscular transmission. In nematodes, muscle nAChRs are targets of antiparasitic drugs. Bephenium is an anthelmintic compound whose molecular action at the free-living nematode Caenorhabditis elegans, which is a model for anthelmintic drug discovery, is poorly known. We explored its effect on C. elegans locomotion and applied single-channel recordings to identify its molecular target, mechanism of action, and selectivity between mammalian and C. elegans nAChRs. As in parasites, bephenium paralyzes C. elegans. A mutant strain lacking the muscle levamisole-sensitive nAChR (L-AChR) shows full resistance to bephenium, indicating that this receptor is the target site. Bephenium activates L-AChR channels from larvae muscle cells in the micromolar range. Channel activity is similar to that elicited by levamisole, appearing mainly as isolated brief openings. Our analysis revealed that bephenium is an agonist of L-AChR and an open-channel blocker at higher concentrations. It also activates mammalian muscle nAChRs. Opening events are significantly briefer than those elicited by ACh and do not appear in activation episodes at a range of concentrations, indicating that it is a very weak agonist of mammalian nAChRs. Recordings in the presence of ACh showed that bephenium acts as a voltage-dependent channel blocker and a low-affinity agonist. Molecular docking into homology modeled binding-site interfaces proposed binding modes for bephenium that explain its partial agonism. Given the great diversity of helminth nAChRs and the overlap of their pharmacological profiles, unravelling drug selectivity basis is required for rational design of anthelmintic drugs. ER -