The Function Of G Protein Beta Subunit (G β) In Ecdysone Signal Pathway

BackgroundThe progress of insects’ development will always need to get through the growth, reproduction and death. And the insects must be molting, which was induced by the20-hydroxyecdysone (20E) before they could grow up. A whole generation of holometabolous contains four main stages, the eggs, the larvae, the pupa and the adult. During one stage to another, and during the intervals between larvae, insects need to molt in order to grow up.Helicoverpa armigera is a kind of insect, which also have the molting behavior, provides a good experimental platform for the study of life processes such as apoptosis, differentiation, and tissue reconstructionCurrently one of the hot topics in the field of life sciences research is steroid hormone membrane receptor. And the hotspots in this field are mainly focusing on the seeking of steroid hormone membrane receptor and the process of signal transduction mechanisms in the early stages. Whether there is a kind of steroid hormone membrane receptor and the mechanisms of their interactions between the steroid hormone and the receptor and how the signal was transferred into the cell. An increasing number of reports indicate the presence of the steroid hormone membrane receptor and preliminary explorations focusing on the membrane signaling pathways have been done.This research mainly focused on the downstream molecular G protein beta subunit of GPCR signaling pathways.The purpose of this study is to explore the ways that Gβ involved in20E signaling pathways and the functions Gβ showed up.Research progressGβ is a subunit of heterotrimeric G protein, and its main function is to form a Gβγ dimer with the G protein γ subunit (Gγ), then formed a heterotrimeric G protein with G protein a subunit (Ga). Heterotrimeric G protein could receive the signal transferred by GPCR and pass the signal to the downstream molecules. It has been reported that, as a membrane receptor, the G protein-coupled receptors (GPCRs) involved in20E signaling pathways and transferred the signal into intracellular and opened the calcium channels, causing programmed cell death.Scientific questionsThe mechanisms of the interaction between20E and the downstream molecules remain unclear. Whether the G protein participant in the20E signaling pathway by functioning as the primary signaling molecule or performing as a regulator, which transcription levels could be regulated by20E. Whether the G protein could regulate the transcription factors in20E signaling pathway is remain unknown.Methods and ResultsWe conducted a preliminary exploration about the distribution as well as the transcription levels of Gβ in the different tissues during larvae stages. By adding exogenous ecdysone, we explored the impact of ecdysone to the transcription levels of the gene. After the RNA interference of Gβ, we examined the transcription levels of the crucial transcription factors in the downstream of20E signaling.Transcription levels in different tissues and during different stages demonstrate that Gβ performance a high transcription level during the molting stage in the larvae, while the20E titers is at the peak.The hormone induction experiments demonstrate that Gβ could be upregulated by20E.After the RNA interference, several crucial transcription factors showed a downregulated transcription level, which demonstrated that Gp could participant in the20E signaling. Furthermore, after the interference on the larvae, most of the larvae could not survive. Overexpressing experiments demonstrate that the gene could respond to20E through a nongenomic pathway.Conclusion and SignificanceIn summary, Gβ could respond to the signal that GPCR accepted from ecdysone, and transfer the signal into the intracellular, initiating the cascades downstream and regulating the transcription factors in20E signaling. And it is crucial for the larvae growth and metamorphosis. This gene could respond to the induction of20E through a nongenomic pathway.Our research explored the participation of Gβ into the20E signaling pathway, providing the preliminary evidence for GPCR working as the membrane receptor molecules of20E.