靶向昆虫烟碱乙酰胆碱受体的C-25型苦木素作用机制与其杀虫功能导向的理性设计

昆虫烟碱乙酰胆碱受体广泛分布于昆虫中枢神经系统，是重要的杀虫剂作用靶标，如靶向该受体的新烟碱类杀虫剂，因其高效广谱的杀虫效果，占据了全球25%以上的销售份额。但近年来，随着抗性害虫的出现以及对益虫的误杀等问题，寻找和发现结构新颖、选择性更强的靶向该受体的先导化合物变得日益紧迫。前期，我们从苦木科植物牛筋果中分离得到具有杀虫活性的新骨架C-25型苦木素，细胞水平的电生理实验显示，它对模式生物黑腹果蝇该受体有强烈的抑制活性，解离常数与吡虫啉相当，但它们对受体亚型选择性及相应的结合位点并不清楚。因此，本申请拟采用光亲和标记、点击化学以及SWATH技术联用的方法，通过合成小分子探针，定量分析蛋白差异，阐明其作用靶标、位点及机制；通过构建活性筛选库，研究构效关系，优化药效团模型，探讨以该受体为靶标构建新型活性先导物的可行性。本申请项目研究对发现和发展新型的、更具应用前景的杀虫先导化合物具有重要的意义

Insect nicotinic acetylcholine receptors (nAChRs) are molecular targets of insecticides widely expressed in the central nervous system. Neonicotinoid insecticides are highly selective agonists of insect nAChRs and supply farmers with invaluable, highly effective tools against some of the world’s most destructive crop pests. This class of insecticides comprises a market share of more than 25% of total global insecticide sales. Their popularity has imposed a mounting selection pressure for resistance, along with the unexpected harmful effects to beneficial insects. Thus, it is urgent to search more promising candidates focusing on major and ubiquitous nAChRs target for insecticide action. Valuable inspirations could be provided from our previous work on the C-25 quassinoids as novel lead compounds for pesticides in this challenging field, which exhibited notable biological properties, including insecticidal activity against Aphis medicaginis Koch and antagonist activity at the nAChRs of Drosophila melanogaster (with Kd value approximating that of the positive reference imidacloprid). We propose to further investigate these quassinoids through the combinational methods of photoaffinity probes, click chemistry, and SWATH mass spectrometry, with the aim to study the relating mechanisms within the exact acting-sites of the monomers. Derived from the natural products, their analogues with modified structures such as ring conjugate systems, different substituted chain lengths, or simplified motifs will be prepared, to find the relation between the chemical structure and the activity of the compounds of this series by detailed assays evaluating their corresponding activities. Such information should be useful for designing and synthesizing novel derivatives as potential insecticides.