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（RBP）和非编码（NC）RNA，因为产生能量的过程会随着衰老而受损。特别是，我们研究了RBP和ncRNA对胰岛素产生、脂肪形成和肌形成的调节。 葡萄糖稳态。随着葡萄糖代谢在转录后水平上被广泛调节的认识的提高，我们最近与Lee实验室（Catholic University，首尔，韩国）合作进行研究，发现HuD是一种RNA结合蛋白，通过HuD作为胰岛素诱导基因1表达的增强剂的影响，负责减少胰腺细胞中甘油三酯的产生（Kim et al.，Biochim Biophys Acta Gene Regulatory Mechanisms，2016）。在与Auburger实验室的合作中，我们发现细胞质蛋白Ataxin-2（ATXN 2）与翻译起始因子有关，ATXN 2的缺乏导致肥胖。据报道（Lastres-Becker等人，根据Biochimica Bioproteica Acta，2016），ATXN 2是影响前起始复合物的mRNA翻译的营养应激诱导型调节剂。 线粒体。在过去的报告期间，我们已经取得了重要进展，了解线粒体功能中的长非编码（lnc）RNA的作用和代谢。一些线粒体lncRNA由核DNA编码，但介导其转运至线粒体的机制的特征很差。一种这样的核DNA编码的lncRNA，RMRP，被发现是RBP HuR和GRSF 1的靶标，其与RMRP结合并将其动员到线粒体。在培养的人类细胞中，HuR在细胞核中结合RMRP并将其输出到胞质溶胶;随后，GRSF 1促进RMRP在线粒体中的功能。因此，沉默GRSF 1削弱了RMRP向线粒体的输入，并降低了耗氧速率。我们的发现描绘了RBP介导核DNA编码的lncRNA转运到线粒体中的机制（Noh等人，基因与发育，2016）。 与de卡波实验室合作（Di Francesco et al. Free Radical Biology and Medicine，2016），我们报告了NAD（P）H：醌氧化还原酶（NQO 1）除了在防御反应性氧化物质中的作用外，还能够结合RNA并形成核糖核蛋白（RNP）复合物的证据。其主要靶标之一SERPINA 1 mRNA编码丝氨酸蛋白酶抑制剂-1-抗胰蛋白酶A1 AT，其与包括肥胖相关的代谢性炎症、慢性阻塞性肺病（COPD）、肝硬化和肝细胞癌在内的疾病相关。NQO 1结合SERPINA 1 mRNA，但不影响SERPINA 1 mRNA水平;相反，它增强SERPINA 1 mRNA的翻译。NQO 1作为RNA结合蛋白的这种新的作用机制可能有助于解释其多效性生物学效应。 与Bohr实验室合作，我们研究了Cockayne综合征蛋白CSA和CSB对DNA修复的作用（Scheibye-Knudsen等人，Proc Natl Acad Sci，2017），并与Auburger实验室合作，我们确定了Ataxin-2在饥饿期间对翻译控制的作用（Lastres-Becker et al.，Biochim Biophys Acta，2016）。 肌生成。 其他能量代谢。在这一审查期间，我们还发现，肌生成调节因子（MRF）MYF 5，作为一个转录因子在肌肉祖细胞（卫星细胞）和肌细胞中发挥作用，显示了一种新的RNA结合功能。一个重要的MYF 5靶点是Ccnd 1 mRNA，它编码关键的细胞周期调节因子CCND 1（细胞周期蛋白D1）。在增殖的成肌细胞中沉默MYF 5的表达表明，MYF 5促进CCND 1的翻译和适度增加CCND 1 mRNA的转录。MYF 5在C2 C12细胞中的过表达上调CCND 1表达，而沉默MYF 5则降低成肌细胞增殖以及成肌细胞向肌管的分化。这些发现使我们提出MYF 5部分地通过协同提高Ccnd 1转录和Ccnd 1 mRNA翻译来增强早期肌生成（Panda et al.，Nucleic Acids Research 2016）。

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).