| Description: |
20-Hydroxyecdysone (20E) is a naturally occurring ecdysteroid hormone which controls the ecdysis (moulting) and metamorphosis of arthropods. 20E could as ingredients in nutritional supplements for various sports, particularly bodybuilding; it
induces autophagy and caspase activity, it slowly reduces food consumption and then indirectly induces a state of starvation resulting in the elevation of the mRNA levels of InR , IRS , PI3K110 , and PDK in the Bombyx fat body during molting and pupation, and it inhibits innate immunity in the fat body during Bombyx postembryonic development. |
| In vivo: |
| Insect Mol Biol. 2014 Aug;23(4):407-16. | | 20-hydroxyecdysone mediates non-canonical regulation of mosquito vitellogenins through alternative splicing.[Pubmed: 24720618] |
Vitellogenesis is one of the most well-studied physiological processes in mosquitoes. Expression of mosquito vitellogenin genes is classically described as being restricted to female adult reproduction.
METHODS AND RESULTS:
We report premature vitellogenin transcript expression in three vector mosquitoes: Culex tarsalis, Aedes aegypti and Anopheles gambiae. Vitellogenins expressed during non-reproductive stages are alternatively spliced to retain their first intron and encode premature termination codons. We show that intron retention results in transcript degradation by translation-dependent nonsense-mediated mRNA decay. This is probably an example of regulated unproductive splicing and translation (RUST), a mechanism known to regulate gene expression in numerous organisms but which has never been described in mosquitoes. We demonstrate that the hormone 20-hydroxyecdysone (20E) is responsible for regulating post-transcriptional splicing of vitellogenin. After exposure of previtellogenic fat bodies to 20E, vitellogenin expression switches from a non-productive intron-retaining transcript to a spliced protein-coding transcript. This effect is independent of factors classically known to influence transcription, such as juvenile hormone-mediated competence and amino acid signalling through the target of rapamycin pathway.
CONCLUSIONS:
Non-canonical regulation of vitellogenesis through RUST is a novel role for the multifunctional hormone 20E, and may have important implications for general patterns of gene regulation in mosquitoes. | | Insect Biochem Mol Biol. 2014 Feb;45:30-9. | | E93 predominantly transduces 20-hydroxyecdysone signaling to induce autophagy and caspase activity in Drosophila fat body.[Pubmed: 24316411] | During the larval-prepupal transition in Drosophila, a balancing crosstalk occurs between autophagy and caspase activity in the remodeling fat body: the inhibition of autophagy induces caspase activity and the inhibition of caspases induces autophagy.
Both autophagy and caspase activity are induced by a pulse of molting hormone (20-hydroxyecdysone, 20E) via the 20E nuclear receptor complex, EcR-USP.
METHODS AND RESULTS:
We here demonstrate that E93, a 20E primary-response gene encoding an HTH transcription factor, predominantly transduces 20E signaling to induce autophagy and caspase activity in the remodeling fat body. RNAi knockdown or mutation of E93 blocks autophagy and caspase activity, E93 overexpression induces them both, while E93 overexpression has a better rescuing effect on the inhibition of autophagy than caspase activity caused by EcR(DN) overexpression. At the transcriptional level, E93 not only greatly impacts the 20E-triggered transcriptional cascade, but also upregulates essential autophagy and apoptosis genes. Meanwhile, at the phosphorylational level, E93 blocks the PI3K-TORC1 signaling to initiate autophagy.
CONCLUSIONS:
Taken together, we conclude that autophagy and caspase activity are induced by 20E and predominantly transduced by E93 in the remodeling fat body of Drosophila. |
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