title: IPPA08 allosterically enhances the action of imidacloprid on nicotinic acetylcholine receptors.
abstract: Our previous study showed that IPPA08, a cis-configuration neonicotinoid compound with unique oxabridged substructure, acted as a specific synergist to neonicotinoid insecticides targeting nicotinic acetylcholine receptors (nAChRs). Heteropentamer nAChRs have diverse characteristics and can form canonical and noncanonical subunit interfaces. While canonical interfaces have been exploited as targets of many drugs, noncanonical interfaces have received less attention. In this study, the mechanism of IPPA08 synergism was evaluated on hybrid nAChRs consisting of three α1 subunits from the brown planthopper and two rat β1 subunits (Nlα1/rβ2) expressed in Xenopus oocytes. IPPA08 alone evoked inward currents, but only at very high concentrations, greater than 1 mM. However, at concentrations below 200 μM, IPPA08 slowed the decay of inward currents evoked by imidacloprid, but not by acetylcholine, and also increased the sensitivity of Nlα1/rβ2 to imidacloprid. Both modulations by IPPA08 were concentration-dependent in the same concentration range of 10-150 μM. Experimentally induced mutations in canonical (α+/β-) and noncanonical (β+/α-) interfaces of Nlα1/rβ2 receptors were also examined to evaluate the presence of possible binding sites for IPPA08 on the receptors. Our results showed that mutations in the canonical interfaces affected only the potency of IPPA08 as an agonist, while mutations in the noncanonical interfaces affected only the synergistic action of IPPA08. Based on these results, we propose that at low concentrations IPPA08 can act as a positive allosteric modulator of noncanonical interfaces, and likely slow the decay of currents through stabilizing the open-channel state caused by the action of imidacloprid on canonical interfaces.
authors: Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, St. Zhongling 50, Nanjing 210014, China; Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Weigang 1, Nanjing 210095, China.
authors: Haibo
authors: H
authors: Bao
authors: Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China.
authors: Xusheng
authors: X
authors: Shao
authors: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Weigang 1, Nanjing 210095, China; Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China.
authors: Yixi
authors: Y
authors: Zhang
authors: Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China.
authors: Jiagao
authors: J
authors: Cheng
authors: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Weigang 1, Nanjing 210095, China.
authors: Yunchao
authors: Y
authors: Wang
authors: Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China.
authors: Xiaoyong
authors: X
authors: Xu
authors: Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, St. Zhongling 50, Nanjing 210014, China.
authors: Jichao
authors: J
authors: Fang
authors: Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Weigang 1, Nanjing 210095, China. Electronic address: liuzewen@njau.edu.cn.
authors: Zewen
authors: Z
authors: Liu
authors: Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China. Electronic address: lizhong@ecust.edu.cn.
authors: Zhong
authors: Z
authors: Li
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006430:Hemiptera / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D021122:Protein Subunits; D011978:Receptors, Nicotinic
keywords: IPPA08; Nicotinic acetylcholine receptors; Noncanonical interface; Synergistic mechanism