Post-transcriptional regulation of energy usage: glucose and lipid metabolism

本项目的研究重点是了解影响能量代谢的RNA结合蛋白(RBPs)和非编码(NC)RNA，因为产生能量的过程随着年龄的增长而受损。特别是，我们研究了RBPs和ncRNAs对胰岛素产生、脂肪生成和肌肉生成的调节。 葡萄糖动态平衡。随着人们越来越认识到葡萄糖代谢在转录后水平受到广泛调控，我们最近与Lee实验室(韩国首尔天主教大学)合作进行了研究，发现HUD是一种RNA结合蛋白，通过HUD作为胰岛素诱导基因1表达增强剂的影响而减少胰腺细胞中甘油三酯的产生(Kim等人，Biochim BiPhys Acta gene Regulatory Machines，2016)。在与Auburger实验室的合作中，我们发现细胞质蛋白Aaxin-2(ATXN2)与翻译启动因子有关，其缺陷会导致肥胖。据报道(Lastres-Becker等人，Biochimica BiPhysica Acta，2016)，ATXN2是一种营养应激诱导的mRNA翻译调节剂，影响起始前复合体。 线粒体。在过去的报告期间，我们在理解长非编码(LNC)RNA在线粒体功能中的作用和代谢方面取得了重要进展。一些线粒体lncRNAs是由核DNA编码的，但其转运到线粒体的机制尚不清楚。一种这样的核DNA编码的lncRNA，RMRP，被发现是与RMRP相关的限制性商业惯例Hur和GRSF1的靶标，并将其动员到线粒体上。在培养的人类细胞中，HUR与细胞核中的RMRP结合并将其输出到胞浆中；随后，GRSF1促进了线粒体中RMRP的功能。因此，沉默GRSF1削弱了RMRP进入线粒体的作用，并降低了耗氧率。我们的发现描绘了一种限制性商业惯例介导核DNA编码的lncRNAs到线粒体的运输的机制(Noh等人，基因和发展，2016)。 与德卡波实验室合作(Di Francesco等人自由基生物学和医学，2016)，我们报道了证据表明，NAD(P)H：醌氧化还原酶(NQO1)除了在防御活性氧化物种方面发挥作用外，还能够结合RNA并形成核糖核蛋白(RNP)复合体。它的主要靶点之一是SERPINA1基因，编码丝氨酸蛋白酶抑制物-1-抗胰蛋白酶，A1AT与肥胖相关的代谢性炎症、慢性阻塞性肺疾病(COPD)、肝硬变和肝细胞癌等疾病有关。NQO1结合了SERPINA1的mRNA，但不影响SERPINA1的mRNA水平；相反，它促进了SERPINA1的翻译。NQO1作为一种RNA结合蛋白的这种新的作用机制可能有助于解释它的多效性生物学效应。 与玻尔实验室合作，我们研究了Cockayne综合征蛋白CsA和CSB在DNA修复中的作用(Scheibai-Knudsen等人，Proc Natl Acad Sci，2017)，并与Auburger实验室合作，确定了Aaxin-2在饥饿期间翻译控制中的作用(Lastres-Becker等人，Biochim BiPhys Acta，2016)。 肌肉发生。其他能量代谢。在此期间，我们还发现，在肌祖细胞(卫星细胞)和肌细胞中发挥转录因子功能的生肌调节因子(MRF)MYF5显示了一种新的RNA结合功能。MYF5的一个重要靶点是Ccnd1mRNA，它编码关键的细胞周期调节因子CCND1(Cyclin D1)。沉默MYF5在增殖期成肌细胞中的表达表明，MYF5促进了CCND1的翻译，并适度增加了Ccnd1mRNA的转录。在C2C12细胞中过表达MYF5上调了CCND1的表达，而沉默MYF5则降低了成肌细胞的增殖和成肌细胞向肌管的分化。这些发现导致我们提出MYF5促进早期肌肉发生的部分原因是通过协同上调Ccnd1转录和Ccnd1 mRNA翻译(Panda等人，2016年核酸研究)。

The studies in this Project focus on understanding the RNA-binding proteins (RBPs) and noncoding (nc)RNAs that influence energy metabolism, since the processes that generate energy become impaired with aging. In particular, we have studied the regulation of insulin production, adipogenesis, and myogenesis by RBPs and ncRNAs. GLUCOSE HOMEOSTASIS. With rising appreciation that glucose metabolism is extensively regulated at the post-transcriptional level, we recently collaborated with the Lee laboratory (Catholic University, Seoul, Korea) in studies that found HuD to be an RNA-binding protein responsible for reducing triglyceride production in pancreatic cells through the influence of HuD as an enhancer of expression of insulin-induced gene 1 (Kim et al., Biochim Biophys Acta Gene Regulatory Mechanisms, 2016). In collaboration with the Auburger laboratory, we found that the cytoplasmic protein Ataxin-2 (ATXN2), whose deficiency leads to obesity, associates with translation initiation factors. As reported (Lastres-Becker et al., Biochimica Biophysica Acta, 2016), ATXN2 is a nutritional stress-inducible modulator of mRNA translation that affects the pre-initiation complex. MITOCHONDRIA. Over the past reporting period, we have made important progress towards understanding the role and metabolism of long noncoding (lnc)RNA in mitochondrial function. Some mitochondrial lncRNAs are encoded by nuclear DNA, but the mechanisms that mediate their transport to mitochondria are poorly characterized. One such nuclear DNA-encoded lncRNA, RMRP, was found to be the target of RBPs HuR and GRSF1, which associated with RMRP and mobilized it to mitochondria. In cultured human cells, HuR bound RMRP in the nucleus and exported it to the cytosol; subsequently, GRSF1 facilitated the function of RMRP in the mitochondria. Accordingly, silencing GRSF1 impaired the import of RMRP into mitochondria and lowered oxygen consumption rates. Our findings delineate a mechanism whereby RBPs mediate the transport of nuclear DNA-encoded lncRNAs into the mitochondria (Noh et al., Genes and Development, 2016). In collaboration with the de Cabo laboratory (Di Francesco et al. Free Radical Biology and Medicine, 2016), we reported evidence that the NAD(P)H: quinone oxidoreductase (NQO1), besides its role in defense against reactive oxidative species, was also capable of binding RNA and forming ribonucleoprotein (RNP) complexes. One of its main targets, SERPINA1 mRNA, encodes the serine protease inhibitor -1-antitrypsin, A1AT, which is associated with disorders including obesity-related metabolic inflammation, chronic obstructive pulmonary disease (COPD), liver cirrhosis and hepatocellular carcinoma. NQO1 bound SERPINA1 mRNA but did not affect SERPINA1 mRNA levels; instead, it enhanced the translation of SERPINA1 mRNA. This novel mechanism of action of NQO1 as an RNA-binding protein may help explain its pleiotropic biological effects. In collaboration with the Bohr Laboratory, we investigated the roles of Cockayne Syndrome proteins CSA and CSB on DNA Repair (Scheibye-Knudsen et al., Proc Natl Acad Sci, 2017), and in collaboration with the Auburger lab we identified the role of Ataxin-2 on translational control during starvation (Lastres-Becker et al., Biochim Biophys Acta, 2016). MYOGENESIS. Other energy metabolism. During this review period, we also discovered that the myogenic regulatory factor (MRF) MYF5, which functions as a transcription factor in muscle progenitor cells (satellite cells) and myocytes, displayed a novel RNA-binding function. One prominent MYF5 target was Ccnd1 mRNA, which encodes the key cell cycle regulator CCND1 (Cyclin D1). Silencing MYF5 expression in proliferating myoblasts revealed that MYF5 promoted CCND1 translation and modestly increased transcription of Ccnd1 mRNA. Overexpression of MYF5 in C2C12 cells upregulated CCND1 expression while silencing MYF5 reduced myoblast proliferation as well as differentiation of myoblasts into myotubes. Thes findings led us to propose that MYF5 enhances early myogenesis in part by coordinately elevating Ccnd1 transcription and Ccnd1 mRNA translation (Panda et al., Nucleic Acids Research 2016).