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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Locust retinoid X receptors: 9-Cis-retinoic acid in embryos from a primitive insect
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Locust retinoid X receptors: 9-Cis-retinoic acid in embryos from a primitive insect

机译：蝗虫类视黄醇X受体：原始昆虫胚胎中的9-Cis-视黄酸

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摘要

The retinoid X receptor (RXR) is activated by its often elusive cognate ligand, 9-cis-retinoic acid (9-cis-RA). In flies and moths, molting is mediated by a heterodimer ecdysone receptor consisting of the ecdysone monomer (EcR) and an RXR homolog, ultraspiracle (USP); the latter is believed to have diverged from its RXR origin. In the more primitive insect, Locusta migratoria (Lm), RXR is more similar to human RXRs than to USPs. LmRXR was detected in early embryos when EcR transcripts were absent, suggesting another role apart from ecdysone signaling. Recombinant LmRXRs bound 9-cis-RA and all-trans-RA with high affinity (IC50 = 61.2–107.7 nM; Kd = 3 nM), similar to human RXR. To determine whether specific binding had functional significance, the presence of endogenous retinoids was assessed. Embryos were extracted by using modified Bligh and Dyer and solid-phase protocols to avoid the oily precipitate that makes this material unsuitable for assay. These extracts contained retinoids (5.4 nM) as assessed by RA-inducible Cyp26A1-promoter luciferase reporter cell lines. Furthermore, the use of HPLC and MS confirmed the presence of retinoids and identified in any embryo, 9-cis-RA, in addition to all-trans-RA. We estimate that whole embryos contain 3 nM RA, including 9-cis-RA at a concentration of 1.6 nM. These findings strongly argue for a functional role for retinoids in primitive insects and favor a model where signaling through the binding of 9-cis-RA to its RXR is established relatively early in evolution and embryonic development.
机译：类视黄醇X受体（RXR）被其通常难以捉摸的同源配体9-顺-视黄酸（9-顺-RA）激活。在蝇类和飞蛾中，蜕皮是由异二聚体蜕皮激素受体介导的，该受体由蜕皮激素单体（EcR）和RXR同系物超螺旋体（USP）组成。后者被认为与RXR起源背道而驰。在更原始的昆虫中，Locusta migratoria（Lm）的RXR与人类RXR的相似性比与USP的相似。当缺少EcR转录本时，在早期胚胎中检测到LmRXR，这暗示着蜕皮激素信号传导以外的另一种作用。重组LmRXR与人RXR相似，具有高亲和力（IC50 = 61.2-107.7 nM； Kd = 3 nM）结合9-cis-RA和全反式RA。为了确定特异性结合是否具有功能重要性，评估了内源性类维生素A的存在。通过使用改良的Bligh和Dyer和固相规程提取胚胎，以避免油状沉淀物，使该物质不适合测定。这些提取物含有类维生素A（5.4 nM），经RA诱导的Cyp26A1启动子荧光素酶报告细胞株评估。此外，HPLC和MS的使用证实了类维生素A的存在，并在除全反式RA之外的任何胚胎9-顺式-RA中进行了鉴定。我们估计整个胚胎含有3 nM RA，包括浓度为1.6 nM的9-cis-RA。这些发现强烈证明了类维生素A在原始昆虫中的功能作用，并支持这样一种模型，其中通过9-顺式-RA与其RXR结合的信号传导是在进化和胚胎发育中相对较早地建立的。

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