Chandra Ramesh, Francis T Chase, Konkalmatt Prasad, Amgalan Ariunzaya, Gancarz Amy M, Dietz David M, Lobo Mary Kay
Department of Anatomy and Neurobiology and.
Department of Medicine, Division of Nephrology, University of Maryland School of Medicine Baltimore, Maryland 21201, and.
J Neurosci. 2015 May 20;35(20):7927-37. doi: 10.1523/JNEUROSCI.0548-15.2015.
An imbalance in molecular signaling cascades and transcriptional regulation in nucleus accumbens (NAc) medium spiny neuron (MSN) subtypes, those enriched in dopamine D1 versus D2 receptors, is implicated in the behavioral responses to psychostimulants. To provide further insight into the molecular mechanisms occurring in MSN subtypes by cocaine, we examined the transcription factor early growth response 3 (Egr3). We evaluated Egr3 because it is a target of critical cocaine-mediated signaling pathways and because Egr3-binding sites are found on promoters of key cocaine-associated molecules. We first used a RiboTag approach to obtain ribosome-associated transcriptomes from each MSN subtype and found that repeated cocaine administration induced Egr3 ribosome-associated mRNA in NAc D1-MSNs while reducing Egr3 in D2-MSNs. Using Cre-inducible adeno-associated viruses combined with D1-Cre and D2-Cre mouse lines, we observed that Egr3 overexpression in D1-MSNs enhances rewarding and locomotor responses to cocaine, whereas overexpression in D2-MSNs blunts these behaviors. miRNA knock-down of Egr3 in MSN subtypes produced opposite behavioral responses from those observed with overexpression. Finally, we found that repeated cocaine administration altered Egr3 binding to promoters of genes that are important for cocaine-mediated cellular and behavioral plasticity. Genes with increased Egr3 binding to promoters, Camk2α, CREB, FosB, Nr4a2, and Sirt1, displayed increased mRNA in D1-MSNs and, in some cases, a reduction in D2-MSNs. Histone and the DNA methylation enzymes G9a and Dnmt3a displayed reduced Egr3 binding to their promoters and reduced mRNA in D1-MSNs. Our study provides novel insight into an opposing role of Egr3 in select NAc MSN subtypes in cocaine action.
伏隔核（NAc）中棘状神经元（MSN）亚型（即富含多巴胺D1受体与D2受体的亚型）的分子信号级联和转录调控失衡，与对精神兴奋剂的行为反应有关。为了进一步深入了解可卡因作用于MSN亚型时发生的分子机制，我们研究了转录因子早期生长反应3（Egr3）。我们评估Egr3是因为它是关键的可卡因介导信号通路的靶点，且在关键的可卡因相关分子的启动子上发现了Egr3结合位点。我们首先使用RiboTag方法从每个MSN亚型中获取核糖体相关转录组，发现重复给予可卡因会诱导NAc D1-MSNs中Egr3核糖体相关mRNA的表达，同时降低D2-MSNs中的Egr3表达。利用Cre诱导型腺相关病毒结合D1-Cre和D2-Cre小鼠品系，我们观察到D1-MSNs中Egr3的过表达增强了对可卡因的奖赏和运动反应，而D2-MSNs中Egr3的过表达则减弱了这些行为。MSN亚型中Egr3的miRNA敲低产生了与过表达相反的行为反应。最后，我们发现重复给予可卡因会改变Egr3与对可卡因介导的细胞和行为可塑性很重要的基因启动子的结合。Egr3与启动子结合增加的基因，如Camk2α、CREB、FosB、Nr4a2和Sirt1，在D1-MSNs中的mRNA水平升高，在某些情况下，在D2-MSNs中则降低。组蛋白以及DNA甲基化酶G9a和Dnmt3a在D1-MSNs中显示出Egr3与它们启动子的结合减少以及mRNA水平降低。我们的研究为Egr3在可卡因作用的特定NAc MSN亚型中的相反作用提供了新的见解。
