The Functions Of Protein Kinase C Delta And Stromal Interaction Molecule 1 During Metamorphosis In Helicoverpa Armigera

Background,scientific questions and significanceDuring the development of insects,ecdysone?20E?and juvenile hormone?JH?counteractively regulate the molting and metamorphosis of insect insects.JH has higher titer during feeding stage,which promotes larval feeding and tissues growth.20E has higher titer in molting and metamorphosis,which promoted molting and metamorphosis.Metamorphic insects have very distinct changes in their bodies,including the apoptosis of larval tissues and the formation of adult tissues.After the adults are formed,the midgut of the larvae are completely degraded and disappeared.A series of signal transduction pathways are involved in metamorphsis.This is the focus of current research on the development of insects.The 20E signaling pathway plays a key role in promoting larval tissue apoptosis.20E has also been determined to induce apoptosis through non-genomic and genomic pathways.Protein kinase C?PKC?,a member of the serine/threonine protein kinase superfamily,can promote the phosphorylation of multiple proteins at the serine or threonine sites and participate in a variety of cellular metabolic activities.PKC also plays a key role in insect 20E-induced gene transcription.The phosphorylation of cell cycle-dependent protein kinase 10?CDK 10?by PKC-mediated superoxide valve protein?USP?determines 20E-induced gene expression and the occurrence of insect metamorphosis.However,there are many types of PKC in the body,and it is not specifically reported which PKC is involved in the apoptosis induced by the 20E pathway.Calcium ion acts as an intracellular second messenger and is closely related to apoptosis.High concentration of calcium ions leads to the apoptosis of mitochondria through the activation of protein kinase C?PKC?and downstream caspase-3.During the metamorphic development of insects,20E rapidly increases the intracellular calcium concentration through non-genomic pathways,including the release of calcium and the influx of extracellular calcium.Although there have been researches to prove that 20E increases the intracellular calcium ion concentration by store-operated calcium entry?SOCE?,the specific mechanism of action is not perfect.Stromal interaction molecule 1?STIM1?plays an important role in the involvement of SOCE.The mechanism of responding to 20E pro-apoptotic signaling in the metaphase is unclearn By studying the function of PKC and STIM1 in promoting apoptosis signaling pathway in 20E,we further clarify and improve the non-genomic signaling pathway and the non-genomic and genomic signaling pathways of insect ecdysteroids.Results and ConclusionsThrough activation of the EcRB1/USP1 transcription complex by 20E,PKC8 expression was upregulated in several tissues during the metamorphic stage.Knockdown of PKC? caused failure to transition from larvae to pupae,prevented tissues from undergoing programmed cell death?PCD?,and downregulated the expression of the transcription factor Brz-7 and the apoptosis executors caspase-3 and caspase-6.The threonine residue at position 1343 of PKC? was phosphorylated and was critical for its pro-apoptotic function.Overexpression of the PKC? catalytic domain was localized to the nuclei in HaEpi cells,which increased caspase-3 activity and apoptosis.PKC? directly phosphorylated a threonine residue at position 468 in the amino acid sequence of EcRB 1.The phosphorylation of EcRB1 was critical for its heterodimeric interaction with the USP1 protein and for binding to the ecdysone response element.The data suggested that 20E upregulates PKC? expression to regulate EcRB1 phosphorylation for EcRB1/USP1 transcription complex formation,apoptotic gene transcription and apoptosis.20E improved the expression of STIM1 through GPCRs?ErGPCR-1 and ErGPCR-2?and nuclear transcription factors?EcRB1 and USP1?during metamorphosis.20E promoted EcRB1 binding to EcRE to regulate STIM1 transcription.KnockdownofSTIM1 expression in larvae caused pupation delay,prevented the separation of larvae midgut from imaginal midgut and suppressed 20E-induced gene transcription.STIM1 located inlarvae midgut during metamorphosis and participated the apoptosis of larvae midgut.20E induced STIM1 translocation to ER-PM junctions and clustered into puncta to promote calcium ion influx through SOCE.STIM1 was phosphorylated in tissues of H.armigera.20E induced PKC phosphorylated STIM1 at Ser485 through GPCR,PLC and IP3R.The phosphorylation of STIM1 plays an important role in the formation of STIM1 puncta and SOCE.These results suggest that 20E via GPCR to regulate PKC phosphorylation of STIM1 to promote calcium influx and 20E-induced apoptosis.Scientific significancesThis study clarified that 20E up-regulates the expression of PKC8,promotes the phosphorylation of EcRB1,promotes the formation of EcRB1/USP transcription complex,promotes the 20E pathway gene expression and apoptosis,completes the metamorphosis development,and deepens the understanding of 20E genomic signal pathway.It had been demonstrated that 20E induces STIM1 phosphorylation and aggregation through GPCR-mediated non-genomic pathways,promotes the induction of intracellular Ca²⁺increase through SOCE,and upregulates the expression of PKC?S to promote apoptosis.,enriched the 20E non-genomic pathway induced calcium influx knowledge.The full text deepens and consolidates the basic model for the 20E to regulate the metamorphic development of insects through membrane receptors and nuclear receptors.Provides new target genes for pest control.