化蛹是全变态昆虫在长期进化过程中形成的一种环境适应方式，受胰岛素和蜕皮激素双重调控。我们在前一个国家基金资助下，阐明了G-蛋白偶联受体（GPCR）在细胞膜上传导蜕皮激素（20E）信号，并发现蜕皮激素促进胰岛素途径的拮抗基因表达，抑制胰岛素途径的关键基因表达，但分子机理尚不清楚。本项目拟用棉铃虫为材料继续研究：GPCR在蜕皮激素促进胰岛素拮抗基因(磷酯酰肌醇三磷酸酶PTEN和转录因子FoxO)表达中的作用及分子机理；GPCR在蜕皮激素抑制胰岛素途径关键基因（胰岛素受体InR、蛋白激酶Akt、PI3K和PDK）表达、蛋白质磷酸化、蛋白质互作及亚细胞定位中的作用及分子机理；蜕皮激素激活GPCR的分子机制；以及参与蜕皮激素信号转导的不同的GPCR之间的关系及其激活的信号途径。通过这些研究，阐明蜕皮激素通过GPCR拮抗胰岛素功能并促进昆虫化蛹的分子机理，为害虫控制提供新的重要靶标基因。

Pupation is an adaptive manner of holometabolous insects to the cold environment variation in winter. Pupation is regulated by insulin and 20-hydroxyecdysone (20E), with insulin promoting cell growth and proliferation, and 20E counteracting insulin activity and promoting apoptosis. In our previous studies, we have demonstrated that G-protein-coupled receptor (GPCR) transmits 20E signal on the cell membrane; 20E promotes the insulin-counteractive gene expression; represses insulin-critical gene expression and protein phosphorylation, however, the molecular mechanism is unclear. Based on these studies, we are going to further study: the role and mechanism of GPCR in 20E promoting insulin-counteractive gene expression, including phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN) and transcription factor FoxO; the role and mechanism of GPCR in 20E repressing insulin-critical gene expression (including insulin receptor InR, protein kinases Akt,PI3K and PDK）, protein phosphorylation, protein interaction and subcellular localization; mechanism of 20E activating GPCR; the relationship and the signal pathways of the GPCRs that transmit 20E signal. By this study, we are going to demonstrate the mechanism that 20E via GPCRs counteracts insulin function and promotes pupation. The results may demonstrate the function and mechanism of GPCR in 20E signaling and insect pupation, reveal the 20E nongenomic pathway, and present new gene targets for pest control.