Determinants of Subtype-Selectivity of the Anthelmintic Paraherquamide A on Caenorhabditis elegans Nicotinic Acetylcholine Receptors

  • Mol Pharmacol. 2023 Jun;103(6):299-310. doi: 10.1124/molpharm.122.000601.
Wataru Koizumi  1 ,  Shuya Otsubo  1 ,  Shogo Furutani  1 ,  Kunihiro Niki  1 ,  Koichi Takayama  1 ,  Shota Fujimura  1 ,  Takanobu Maekawa  1 ,  Ryosuke Koyari  1 ,  Makoto Ihara  1 ,  Kenji Kai  1 ,  Hideo Hayashi  1 ,  Mohammad Shaokat Ali  1 ,  Eriko Kage-Nakadai  1 ,  David B Sattelle  1 ,  Kazuhiko Matsuda  2
Affiliations
  • 1. Department of Applied Biological Chemistry, Faculty of Agriculture (W.K., S.O., S.Fur., K.N., K.T., S.Fuj., T.M., R.K., M.I., K.M.) and Agricultural Technology and Innovation Research Institute (K.M.), Kindai University, Nara, Japan; Graduate School of Agriculture (K.K., H.H.) and Graduate School of Human Life and Ecology (M.S.A., E.K-N.), Osaka Metropolitan University, Osaka, Japan; Faculty of Food Science and Technology, Chattogram Veterinary and Animal Sciences University, Chattogram, Bangladesh (M.S.A.); and Centre for Respiratory Biology, UCL Respiratory, Division of Medicine, University College London, London, UK (D.B.S.).
  • 2. Department of Applied Biological Chemistry, Faculty of Agriculture (W.K., S.O., S.Fur., K.N., K.T., S.Fuj., T.M., R.K., M.I., K.M.) and Agricultural Technology and Innovation Research Institute (K.M.), Kindai University, Nara, Japan; Graduate School of Agriculture (K.K., H.H.) and Graduate School of Human Life and Ecology (M.S.A., E.K-N.), Osaka Metropolitan University, Osaka, Japan; Faculty of Food Science and Technology, Chattogram Veterinary and Animal Sciences University, Chattogram, Bangladesh (M.S.A.); and Centre for Respiratory Biology, UCL Respiratory, Division of Medicine, University College London, London, UK (D.B.S.) [email protected].
PMID: 36948535 DOI: 10.1124/molpharm.122.000601
Abstract

The anthelmintic paraherquamide A acts selectively on the nematode L-type nicotinic acetylcholine receptors (nAChRs), but the mechanism of its selectivity is unknown. This study targeted the basis of paraherquamide A selectivity by determining an X-ray crystal structure of the acetylcholine binding protein (AChBP), a surrogate nAChR ligand-binding domain, complexed with the compound and by measuring its actions on wild-type and mutant Caenorhabditis elegans nematodes and functionally expressed C. elegans nAChRs. Paraherquamide A showed a higher efficacy for the levamisole-sensitive [L-type (UNC-38/UNC-29/UNC-63/LEV-1/LEV-8)] nAChR than the nicotine-sensitive [N-type (ACR-16)] nAChR, a result consistent with in vivo studies on wild-type worms and worms with mutations in subunits of these two classes of receptors. The X-ray crystal structure of the Ls-AChBP-paraherquamide A complex and site-directed amino acid mutation studies showed for the first time that loop C, loop E, and loop F of the orthosteric receptor binding site play critical roles in the observed L-type nAChR selective actions of paraherquamide A. SIGNIFICANCE STATEMENT: Paraherquamide A, an oxindole alkaloid, has been shown to act selectively on the L-type over N-type nAChRs in nematodes, but the mechanism of selectivity is unknown. We have co-crystallized paraherquamide A with the acetylcholine binding protein, a surrogate of nAChRs, and found that structural features of loop C, loop E, and loop F contribute to the L-type nAChR selectivity of the alkaloid. The results create a new platform for the design of anthelmintic drugs targeting cholinergic neurotransmission in parasitic nematodes.

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