Diamide insecticides target insect ryanodine receptors (RYRs) and cause dysregulation of calcium signaling in insect muscles and neurons, generating worldwide sales over 2 billion US dollars annually. Several resistance mutations have been reported to reduce the efficacy of the diamides, but the exact binding sites and mechanism of resistance mutations were not clear. Recently, we solved the cryo-electron microscopy (cryo-EM) structure of RYR in complex with the anthranilic diamide chlorantraniliprole (CHL). CHL binds to the pseudo–voltage-sensor domain (pVSD) of RYR, a site in proximity to the previously identified resistance mutations. Mutagenesis studies in silico, in mutant cell lines, and in transgenic Drosophila strains revealed the key residues involved in diamide coordination and the molecular mechanism under species-selectivity and resistance mutations. We also proposed that CHL may alleviate the loss-of-function effects of some central core disease (CCD) mutations by increasing the opening probability (Po) of RYR1. In addition, we solved the crystal structures of several RYR domains from the diamondback moth and the bee, revealing insect-specific structural features which could be potentially targeted by novel insecticides. Interestingly, we found that the phosphorylation of insect RYR is temperature dependent, facilitated by the low thermal stability and dynamic structure of the insect RYR. Our structures provide a foundation for developing novel pesticides to overcome the resistance crisis.
This research was funded by the National Natural Science Foundation of China (grants no. 32022073 and 31972287, to Z. Yuchi), the National Key Research and Development Program of China (grants no. 2017YFD0201400 and 2017YFD0201403, to Z. Yuchi), Canadian Institutes of Health Research (grant no. PJT-159601, to F. Van Petegem), Basis for Supporting Innovative Drug Discovery and Life Science Research from the Japan Agency for Medical Research and Development (no. JP20am0101080j0004, to T. Murayama), Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (grant no. 19H03404, to T. Murayama) and fellowships from the Canadian Institutes of Health Research and Michael Smith Foundation for Health Research (to O. Haji-Ghassemi).