Petruccelli Emily, Li Qi, Rao Yi, Kitamoto Toshihiro
Interdisciplinary Program in Genetics, Graduate College.
Peking University School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Beijing 100871, China.
J Neurosci. 2016 Apr 20;36(16):4647-57. doi: 10.1523/JNEUROSCI.3774-15.2016.
Steroids profoundly influence behavioral responses to alcohol by activating canonical nuclear hormone receptors and exerting allosteric effects on ion channels. Accumulating evidence has demonstrated that steroids can also trigger biological effects by directly binding G-protein-coupled receptors (GPCRs), yet physiological roles of such unconventional steroid signaling in controlling alcohol-induced behaviors remain unclear. The dopamine/ecdysteroid receptor (DopEcR) is a GPCR that mediates nongenomic actions of ecdysteroids, the major steroid hormones in insects. Here, we report that Drosophila DopEcR plays a critical role in ethanol-induced sedation.DopEcR mutants took longer than control flies to become sedated during exposure to ethanol, despite having normal ethanol absorption or metabolism. RNAi-mediated knockdown of DopEcR expression revealed that this receptor is necessary after eclosion, and is required in particular neuronal subsets, including cholinergic and peptidergic neurons, to mediate this behavior. Additionally, flies ubiquitously overexpressing DopEcR cDNA had a tendency to become sedated quickly upon ethanol exposure. These results indicate that neuronal subset-specific expression of DopEcR in adults is required for normal sedation upon exposure to ethanol. We also obtained evidence indicating that DopEcR may promote ethanol sedation by suppressing epidermal growth factor receptor/extracellular signal-regulated kinase signaling. Last, genetic and pharmacological analyses suggested that in adult flies ecdysone may serve as an inverse agonist of DopEcR and suppress the sedation-promoting activity of DopEcR in the context of ethanol exposure. Our findings provide the first evidence for the involvement of nongenomic G-protein-coupled steroid receptors in the response to alcohol, and shed new light on the potential roles of steroids in alcohol-use disorders.
Alcohol abuse is an alarming personal and societal burden. The improvement of prevention and treatment strategies for alcohol-use disorders requires a better understanding of their biological basis. Steroid hormones profoundly affect alcohol-induced behaviors, but the contribution of their unconventional, nongenomic actions during these responses has not yet been elucidated. We found that Drosophila DopEcR, a unique G-protein-coupled receptor (GPCR) with dual specificity for dopamine and steroids, mediates noncanonical steroid actions to promote ethanol-induced sedation. Because steroid signaling and the behavioral response to alcohol are evolutionarily well conserved, our findings suggest that analogous mammalian receptors likely play important roles in alcohol-use disorders. Our work provides a foundation for further characterizing the function and mechanisms of action of nonclassical steroid GPCR signaling.
类固醇通过激活经典核激素受体并对离子通道产生变构效应，深刻影响对酒精的行为反应。越来越多的证据表明，类固醇还可通过直接结合G蛋白偶联受体（GPCR）触发生物学效应，然而这种非传统类固醇信号在控制酒精诱导行为中的生理作用仍不清楚。多巴胺/蜕皮类固醇受体（DopEcR）是一种GPCR，介导昆虫主要类固醇激素蜕皮类固醇的非基因组作用。在此，我们报告果蝇DopEcR在乙醇诱导的镇静中起关键作用。尽管DopEcR突变体的乙醇吸收或代谢正常，但在接触乙醇期间，它们比对照果蝇需要更长时间才能进入镇静状态。RNA干扰介导的DopEcR表达敲低表明，该受体在羽化后是必需的，并且在特定的神经元亚群中是必需的，包括胆碱能和肽能神经元，以介导这种行为。此外，普遍过表达DopEcR cDNA的果蝇在接触乙醇后往往会迅速进入镇静状态。这些结果表明，成体中DopEcR在神经元亚群中的特异性表达是接触乙醇后正常镇静所必需的。我们还获得了证据表明DopEcR可能通过抑制表皮生长因子受体/细胞外信号调节激酶信号传导来促进乙醇诱导的镇静。最后，遗传和药理学分析表明，在成年果蝇中，蜕皮激素可能作为DopEcR的反向激动剂，并在乙醇暴露的情况下抑制DopEcR的镇静促进活性。我们的研究结果为非基因组G蛋白偶联类固醇受体参与酒精反应提供了首个证据，并为类固醇在酒精使用障碍中的潜在作用提供了新的线索。
酒精滥用是一个令人担忧的个人和社会负担。改善酒精使用障碍的预防和治疗策略需要更好地了解其生物学基础。类固醇激素深刻影响酒精诱导的行为，但其在这些反应中的非传统、非基因组作用的贡献尚未阐明。我们发现果蝇DopEcR是一种对多巴胺和类固醇具有双重特异性的独特G蛋白偶联受体（GPCR），介导非经典类固醇作用以促进乙醇诱导的镇静。由于类固醇信号传导和对酒精的行为反应在进化上高度保守，我们的研究结果表明类似的哺乳动物受体可能在酒精使用障碍中起重要作用。我们的工作为进一步表征非经典类固醇GPCR信号传导的功能和作用机制奠定了基础。
