No abstract

Ryanodine receptors (RyRs) are homotetrameric intracellular calcium (Ca 2+ ) release channels responsible for excitation−contraction coupling of muscle cells. Diamide insecticides specifically act on RyRs of Lepidoptera and Coleoptera pests and are safe for nontargeted organisms, generating big worldwide sales. Despite their popularity, several devastating agricultural pests have been reported to be resistant to them because of mutations in a small transmembrane region of their RyRs, hinting a binding pocket nearby. A potential solution to overcome resistance is to develop new insecticides targeting different binding sites in pest RyRs. Based on a high-resolution crystal structure of diamondback moth (DBM) RyR N-terminal domain (NTD) determined by our group, we carried out extensive structure-based insecticide screening targeting the intersubunit interface. We identified eight lead compounds that selectively target the open conformation of DBM RyR, which are predicted to act as channel activators similar to diamide insecticides. Binding mode analysis shows selective binding to a hydrophobic pocket of DBM NTD-A but not to the pocket of its mammalian counterpart. We tested three available compounds on the HEK293 cell lines stably expressing DBM or mammalian RyR, one of which shows good potency and selectivity against DBM RyR. The insecticidal effect of the compound was also confirmed using fruit flies. The detailed binding mode, toxicity, absorption, distribution, metabolism, and excretion, and reactivity of the compound were predicted by bioinformatic methods. Together, our study lays a foundation for developing a new class of selective RyR-targeting insecticides to control both wild-type and resistant pests.

: Ryanodine receptor (RyR) is one of the primary targets of commercial insecticides. The diamide insecticide family, including flubendiamide, chlorantraniliprole, cyantraniliprole, etc, targets insect RyRs and can be used to control a wide range of destructive agricultural pests. The diamide insecticides are highly selective against lepidopteran and coleopteran pests with relatively low toxicity for non-target species, such as mammals, fishes, and beneficial insects. However, recently mutations identified on insect RyRs have emerged and caused resistance in several major agricultural pests throughout different continents. This review paper summarizes the recent findings on structure and function of insect RyRs as insecticide target. Specifically, we examine the structures of RyRs from target and non-target species, which reveals the molecular basis for insecticide action and selectivity. We also examine the structural and functional changes of RyR caused by the resistance mutations. Finally, we examine the progress in RyR structure-based insecticide design, and discuss how this might help the development of new generation of green insecticides.