TY - JOUR
T1 - Studies on an acetylcholine binding protein identify a basic residue in loop G on the β1 strand as a new structural determinant of neonicotinoid actions
AU - Ihara, Makoto
AU - Okajima, Toshihide
AU - Yamashita, Atsuko
AU - Oda, Takuma
AU - Asano, Takuya
AU - Matsui, Mikana
AU - Sattelle, David B.
AU - Matsuda, Kazuhiko
N1 - Funding Information:
This study was supported by the Ministry of Agriculture, Forestry, and Fisheries of Japan Genomics-based Technology for Agricultural Improvement [Grant PRM-3002], and the Strategic Project to Support the Formation of Research Bases at Private Universities: Matching Fund Subsidy from the Ministry of Education, Culture, Sports, Science and Technology of Japan [Grant S1101035]. M.I., To.O., and A.Y. contributed equally to this study. Primary laboratory of origin: Department of Applied Biological Chemistry, Faculty of Agriculture, Kinki University dx.doi.org/10.1124/mol.114.094698. s This article has supplemental material available at molpharm. aspetjournals.org.
PY - 2014
Y1 - 2014
N2 - Neonicotinoid insecticides target insect nicotinic acetylcholine receptors (nAChRs). Their widespread use and possible risks to pollinators make it extremely urgent to understand the mechanisms underlying their actions on insect nAChRs. We therefore elucidated X-ray crystal structures of the Lymnaea stagnalis acetylcholine binding protein (Ls-AChBP) and its Gln55Arg mutant, more closely resembling insect nAChRs, in complex with a nitromethylene imidacloprid analog (CH-IMI) and desnitro-imidacloprid metabolite (DN-IMI) as well as commercial neonicotinoids, imidacloprid, clothianidin, and thiacloprid. Unlike imidacloprid, clothianidin, and CH-IMI, thiacloprid did not stack with Tyr185 in the wild-type Ls-AChBP, but did in the Gln55Arg mutant, interacting electrostatically with Arg55. In contrast, DN-IMI lacking the NO2 group was directed away from Lys34 and Arg55 to form hydrogen bonds with Tyr89 in loop A and the main chain carbonyl of Trp143 in loop B. Unexpectedly, we found that several neonicotinoids interacted with Lys34 in loop G on the β1 strand in the crystal structure of the Gln55Arg mutant. Basic residues introduced into the α7 nAChR at positions equivalent to AChBP Lys34 and Arg55 enhanced agonist actions of neonicotinoids, while reducing the actions of acetylcholine, (-)-nicotine, and DN-IMI. Thus, not only the basic residues in loop D, but also those in loop G determine the actions of neonicotinoids. These novel findings provide new insights into the modes of action of neonicotinoids and emerging derivatives.
AB - Neonicotinoid insecticides target insect nicotinic acetylcholine receptors (nAChRs). Their widespread use and possible risks to pollinators make it extremely urgent to understand the mechanisms underlying their actions on insect nAChRs. We therefore elucidated X-ray crystal structures of the Lymnaea stagnalis acetylcholine binding protein (Ls-AChBP) and its Gln55Arg mutant, more closely resembling insect nAChRs, in complex with a nitromethylene imidacloprid analog (CH-IMI) and desnitro-imidacloprid metabolite (DN-IMI) as well as commercial neonicotinoids, imidacloprid, clothianidin, and thiacloprid. Unlike imidacloprid, clothianidin, and CH-IMI, thiacloprid did not stack with Tyr185 in the wild-type Ls-AChBP, but did in the Gln55Arg mutant, interacting electrostatically with Arg55. In contrast, DN-IMI lacking the NO2 group was directed away from Lys34 and Arg55 to form hydrogen bonds with Tyr89 in loop A and the main chain carbonyl of Trp143 in loop B. Unexpectedly, we found that several neonicotinoids interacted with Lys34 in loop G on the β1 strand in the crystal structure of the Gln55Arg mutant. Basic residues introduced into the α7 nAChR at positions equivalent to AChBP Lys34 and Arg55 enhanced agonist actions of neonicotinoids, while reducing the actions of acetylcholine, (-)-nicotine, and DN-IMI. Thus, not only the basic residues in loop D, but also those in loop G determine the actions of neonicotinoids. These novel findings provide new insights into the modes of action of neonicotinoids and emerging derivatives.
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U2 - 10.1124/mol.114.094698
DO - 10.1124/mol.114.094698
M3 - Article
C2 - 25267717
AN - SCOPUS:84925548930
VL - 86
SP - 736
EP - 746
JO - Molecular Pharmacology
JF - Molecular Pharmacology
SN - 0026-895X
IS - 6
ER -