Conversion of 3-oxo steroids into ecdysteroids triggers molting and expression of 20E-inducible genes in Drosophila melanogaster
Conversion of 3-oxo steroids into ecdysteroids triggers molting and expression of 20E-inducible genes in Drosophila melanogaster
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DOI：
10.1016/j.bbrc.2012.04.045
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发表时间：
2012-05-11
影响因子：
3.1
通讯作者：
Nishida, Ritsuo
中科院分区：
文献类型：
--
作者：
Ono, Hajime;Morita, Sayo;Nishida, Ritsuo
蜕皮甾体是昆虫体内的一种甾体激素，它协调昆虫的主要发育转变。在胚后发育期间，蜕皮激素在前胸腺（PG）中由膳食胆固醇生物合成。尽管进行了广泛的研究，但最初的转换过程，即所谓的“黑匣子”，尚未得到定性。细胞色素P450酶，Spookier（Spok），被推测为黑腹果蝇幼虫-蛹转变过程中黑匣子中的限速酶。RNAi介导的PG中spok表达的敲低导致蜕皮停滞。因为发育停滞可以通过应用适当的中间体来挽救，所以我们检查了候选中间体在RNAi处理的幼虫中的潜在活性。我们发现两种3-氧代类固醇，胆甾-4，7-二烯-3，6-二酮-14 α-醇（δ（4）-二酮醇）和5 β [H]胆甾-7-烯-3，6-二酮-14 α-醇（二酮醇），触发了RNAi处理的幼虫的蜕皮。我们还检测到通过喂食δ（4）-二酮醇或二酮醇，RNAi处理的幼虫中蜕皮类固醇的量增加，表明饮食3-氧代类固醇被掺入并在体内转化为蜕皮类固醇。此外，通过饲喂δ（4）-二酮醇或二酮醇，在RNAi处理的幼虫中诱导了20-羟基蜕皮激素诱导基因。这些结果表明，Δ（4）-二酮醇和二酮醇是蜕皮甾体生物合成途径的组分，并且位于Spok催化的步骤的下游。(C)2012 Elsevier Inc. All rights reserved.
Ecdysteroids, steroid hormones in insects, coordinate major developmental transitions. During postembryonic development, ecdysone is biosynthesized from dietary cholesterol in the prothoracic gland (PG). Despite extensive studies, the initial conversion process, the so-called "Black Box", has not been characterized. A cytochrome P450 enzyme, Spookier (Spok), is speculated as a rate limiting enzyme in the Black Box during larval-pupal transitions in Drosophila melanogaster. RNAi mediated knockdown of spok expression in the PG results in arrest of molting. Because the developmental arrest can be rescued by application of an appropriate intermediate, we examined potential activities of candidate intermediates in the RNAi-treated larvae. We found that two 3-oxo steroids, cholesta-4,7-diene-3,6-dione-14 alpha-ol (Delta(4)-diketol) and 5 beta[H]cholesta-7-ene-3,6-dione-14 alpha-ol (diketol), triggered molting of the RNAi-treated larvae. We also detected an enhancement of the amounts of ecdysteroids in the RNAi-treated larvae by feeding the Delta(4)-diketol or diketol, indicating that the dietary 3-oxo steroids were incorporated and converted into ecdysteroids in vivo. Furthermore, 20-hydroxyecdysone inducible genes were induced in the RNAi-treated larvae by feeding the Delta(4)-diketol or diketol. These results indicate that Delta(4)-diketol and diketol are components of the ecdysteroid biosynthetic pathway and lie downstream of a step catalyzed by Spok. (C) 2012 Elsevier Inc. All rights reserved.