Structural basis for the interaction of diapause hormone with its receptor in the silkworm, Bombyx mori

Diapause hormone (DH) is a 24-aa amidated neuropeptide that elicits the embryonic diapause of the silkworm, Bombyx mori ( Bommo), via sensitive and selective interaction with its receptor, Bommo DH receptor ( Bommo-DHR). Previous studies of the structure-activity relationship of Bommo-DH were all based on an in vivo diapause-induction bioassay, which has provided little information on the structure of Bommo-DHR or its iteration with DH. Here, to unveil the interaction of Bommo-DH with its receptor, N-terminally truncated analogs and alanine-scanning mutants of Bommo-DH were chemically synthesized and functionally evaluated by using a Cy5.5-labeled Bommo-DH competitive binding assay and Bommo-DHR-based functional assays, including cAMP assay and Ca²⁺ mobilization assay. Our study demonstrates that the C-terminal residues of Arg23 and Leu24 of Bommo-DH are essential for the binding and activation of Bommo-DHR, and that Trp19 and Phe20 also contribute to the functional activity of Bommo-DH. In contrast, when Gly21 or Pro22 were replaced with alanine, both mutants exhibited binding and signaling activities that were indistinguishable from the wild-type peptide. Furthermore, our homology modeling and molecular dynamics simulations, together with experimental validations, have identified the residues of Glu89, Phe172, Phe194, and Tyr299 in Bommo-DHR that are critically involved in the interaction with Bommo-DH. These results may deepen our understanding of the interactions of class-A GPCRs with their peptidic ligands, particularly those between pheromone biosynthesis-activating neuropeptide/DH family neuropeptides and their cognate receptors.-Shen, Z., Jiang, X., Yan, L., Chen, Y., Wang, W., Shi, Y., Shi, L., Liu, D., Zhou, N. Structural basis for the interaction of diapause hormone with its receptor in the silkworm, Bombyx mori.