The Steroid Hormone 20-hydroxyecdysone Promotes Or Represses Insulin Receptor Expression And Phosphorylation Based Concentration

Research background,research progress,scientific problemsThe growth and metabolism of organisms are regulated by both growth factors and other hormones,and their activity is mediated by the corresponding receptors.The life cycle of insects is mainly regulated by three hormones:ecdysone(20E),juvenile hormone(JH),and insulin like peptide(?ps).The insulin signaling pathway mainly controls the growth and development,while the 20E and JH interactions control the molting metamorphosis signals.When insulin regulates the growth of larvae to reach critical body weight,PTTH is released to promote the synthesis and release of ecdysteroids,and finally procesed into active metabolite 20E in tissues.In Drosophila,insulin is synthesized by pancreatic ?-cells,stimulating the growth of tissue and PG,and allowing PG to secrete large amounts of 20E and initiate metamorphosis.In D.melanogaster fatbodies,20E fights insulin-promoting growth by promotingthe nuclear localization of the transcription factor dFOXO(forkheadbox O,FoxO)and translationof the translational repressor 4E-BP.In silkworm,20E has different regulatory effects on receptor complexes EcRB1/USP1 and insulin receptor under different physiological conditions.Previous studies on Helicoverpa armigera showed that there is a cyclin-dependent kinase regulatory subunit 1(CKS1),insulin up-regulates CKS1 expression,and high concentrations of 20E inhibit CKS1 expression.In addition,a GTPase-Rab4b was found to be involved in the transcriptional regulation of related genes in the 20E and insulin pathways.20E can upregulate the expressionofPhosphatidylinositol-3,4,5-trisphosphate 3-phosphatase(PTEN)and Forkhead box protein FoxO,while PTEN can inhibit Phosphorylation of AKT achieves inhibition of FoxO phosphorylation,leading to nuclear localization of FoxO and antagonism of the insulin pathway.The above studies have shown that 20E is involved in the regulation of insulin pathways,but the mechanism of action is still not clear.In this dissertation,Lepidoptera insect Helicoverpa armigera was used as a model.Insulin receptor(IR)was selected as the target.Through hormone stimulation,double-stranded RNA interference,constructionofoverexpression plasmids and other experimental techniques,the regulation of IR by 20E was studied,and the regulation of insulin signaling by 20E was elucidated.The molecular mechanism provides a theoretical basis and target gene for pest control.Research results and conclusionsCompared with the control group,interfering IR with dsRNAonlarvae showed high mortality rate,delayed pupation,and small pupae phenotype.The interferenceofIR on the larvae could inhibits the expression of related genes downstream of the insulin signaling pathway.The results show that IR promotes larval growth and development.During the larval to adult development stage,IR was highly expressed during the feeding period and the molting metaphase was lowly expressed.In insect tissues and in H.armigera epidermal cell lines,insulin up-regulated IR expression in a concentration-and time-dependent manner.20E,on the other hand,relies on concentration gradient to adjust the expression of IR in both directions.Low concentration of 20E promotes the expression of IR,and high concentration of 20E inhibits the expressionofIR.The same results were obtainedby superimposing insulin and different concentrations of 20EonHaEpi cell lines.Low concentrations of 20Epromoted insulin-induced IR expression and phosphorylation,while high concentrations of 20E inhibited insulin-induced IR expression and phosphorylation.Ilps were expressed in the developmental stages of the larvae to midges of cotton bollworm,and showed up-regulated expression in the late instar larvae and pupal stages,indicating that late-instar larvae and pupal 20E didnot inhibit IR phosphorylationby inhibiting the expressionof IlPs.The protein translation inhibitor cycloheximide and phosphatase inhibitors experiments showed that 20E may dephosphorylate IR by up-regulating phosphatase expression.After the cell line interfered with PTEN,the effect of high concentration of 20E on inhibiting IR phosphorylation was reduced.On the contrary,overexpression of PTEN did not result in dephosphorylation of IR in the presence of high concentration of 20E,explain that high concentration of 20E dephosphorylates IR by up-regulating PTEN expression Dephosphorylation did not detect the interaction between PTEN and IR induced by 20E,suggesting that PTEN indirectly regulates IR phosphorylation.The study draws the following conclusions:IR-mediated insulin signaling promotes larval growth and development,and IR expression and phosphorylation are up-regulated by insulin.High concentration of 20E promoted the expression of Ilps,and high concentration of 20E inhibited IR phosphorylation by up-regulating the expression of PTEN.These studies revealed that 20E participates in the regulation of insulin signaling through bidirectional regulation of IR expression and phosphorylation.Innovative and meaningfulIn this dissertation,we found for the first time that the 20E-dependent concentration of bidirectional regulation of IR expression and phosphorylation involved in the regulation of insulin signaling pathway provided new data support for 20E and insulin co-regulation of the growth and development of H.armigera.