RNA编辑酶 ADAR2 在调控葡萄糖代谢平衡中的生理学功能
文献类型：学位论文
| 作者 | 赵丽韵 |
| 学位类别 | 博士 |
| 答辩日期 | 2010-05 |
| 授予单位 | 中国科学院上海生命科学研究院营养科学研究所 |
| 授予地点 | 中国科学院上海生命科学研究院 |
| 导师 | 刘勇 |
| 关键词 | RNA编辑 ADAR2 胞外分泌 β 细胞 血糖平衡 |
| 学位专业 | 生物化学与分子生物学 |
| 中文摘要 | 作用于RNA上的腺苷酸脱氨酶ADAR蛋白家族催化一类将腺苷酸转变为肌苷酸的RNA编辑作用。这种基因重编码作用因其对神经递质受体和离子通道性能的修饰在中枢神经系统中起着极为重要的作用。之前的研究中我们发现了ADAR2介导的RNA编辑在胰腺胰岛和β细胞中受到代谢状况的调控。然而关于ADAR2在葡萄糖代谢调控中生理学功能仍然知之甚少。本论文首先探讨了ADAR2在专业分泌细胞中的调控功能。我们发现在大鼠胰岛瘤细胞系INS-1中降低ADAR2的表达会导致会损害细胞葡萄糖诱导胰岛素分泌能力。同样在ADAR2表达缺陷的大鼠嗜铬细胞瘤细胞系PC12中内源蛋白分泌也会明显降低。此外，ADAR2的表达缺陷还会显著抑制钙离子引发的细胞膜电容增加过程，并降低囊泡分泌调控蛋白Munc18-1与synaptotagmin7的表达水平。这些发现揭示了RNA编辑作用是细胞囊泡分泌途径中一种全新的调控机制，并阐述了ADAR2基因在细胞分泌事件中的重要功能。为了进一步阐释ADAR2在体内葡萄糖代谢调节过程中的生理功能，我们使用RIP-cre小鼠建立了ADAR2条件性敲除模型，在胰腺β细胞和部分下丘脑细胞中敲除ADAR2基因表达（简称βA2KO小鼠）。虽然βA2KO小鼠表现出胰岛素分泌能力一定程度的下降，但是血糖水平、胰岛素水平和糖耐受性并没有发生变化。更重要的是，在代谢压力存在的情况下，高脂食物引起的高血糖症在βA2KO小鼠中得到缓解，同时糖耐受情况也得到明显改善。进一步的实验发现，βA2KO小鼠中这种葡萄糖代谢情况的改善很有可能是源自肝脏糖异生水平的显著下降。这些数据都说明βA2KO小鼠能够抵抗肥胖引起的葡萄糖不耐受症。同时我们推测ADAR2在下丘脑神经元中的基因功能对于代谢压力下体内葡萄糖代谢平衡的调控至关重要。 |
| 索取号 | D2010-189 |
| 英文摘要 | RNA editing via the conversion of adenosine (A) to inosine (I) is catalyzed by two major families of adenosine deaminases acting on RNA (ADARs), ADAR1 and ADAR2. This genetic recoding process is known to play essential roles in the central nerve system (CNS) through functional modifications of neurotransmitter receptors and ion channels. Previously, we have shown that RNA editing by ADAR2 is metabolically regulated in pancreatic islets and β-cells. However, it remains unknown whether ADAR2 acts in the physiological regulation of systemic glucose metabolism. To investigate the function of ADAR2 in professional secretory cells, we found that specific knockdown of ADAR2 expression not only markedly impaired glucose-stimulated insulin secretion in the rat insulinoma INS-1 cells but also significantly reduced the secretion of endogenous cellular protein upon KCl stimulation in the rat adrenal pheochromocytoma PC12 cells. Complementation studies demonstrated that the deaminase activity of ADAR2 was required to exert its regulatory effects on insulin secretion in β-cells. Moreover, deficiency in ADAR2 significantly attenuated Ca2+-evoked membrane capacitance increases. Interestingly, the secretory defects in ADAR2-deficient INS-1 and PC12 cells were coupled to decreased expression of Munc18-1 and synaptotagmin VII, two key molecules in the regulation of vesicle exocytosis. Thus, these results reveal an important aspect of ADAR2 actions in cellular exocytosis, implicating RNA editing as a novel mechanism in the control of cellular secretory machinery. Pancreatic islet β-cells are central to the maintenance of glucose homeostasis in mammals, sensing and responding to the glucose changes in the blood by regulated insulin biosynthesis and secretion. The CNS, particularly the hypothalamus, is known to play pivotal roles in the control of energy balance and fuel metabolism through integrating body’s nutritional and hormonal signals. To further determine the physiological function of ADAR2 in glucose homeostasis, we generated conditional ADAR2 knockout mice (denoted βA2KO) using transgenic RIP-cre mice. Depletion of ADAR2 occurred not only in pancreatic β cells but also in cre-expressing neurons within the hypothalamus of βA2KO animals. Whereas the isolated pancreatic islets exhibited mild impairment in glucose-stimulated insulin secretion, the βA2KO mice showed normal blood glucose and serum insulin levels with unaltered glucose tolerance. Importantly, when challenged with a high-fat diet, βA2KO mice manifested marked alleviation of hyperglycemia and glucose intolerance. This improvement of glucose metabolism in βA2KO mice under metabolic stress could be, at least in large part, attributable to pronounced suppression of hepatic gluconeogenesis as revealed by pyruvate tolerance tests. These data demonstrate that βA2KO mice are resistant to obesity-induced glucose intolerance, raising the possibility that ADAR2 in select hypothalamic neurons plays critical roles in the regulation of glucose homeostasis under metabolic stress. It remains to be deciphered whether and/or how ADAR2 exerts its metabolic actions through the hypothalamic neurons in controlling hepatic glucose production. |
| 语种 | 中文 |
| 公开日期 | 2015-12-24 |
| 源URL | [http://202.127.25.144/handle/331004/316]  |
| 专题 | 中国科学院上海生命科学研究院营养科学研究所_糖脂代谢与调控研究组 |
| 推荐引用方式 GB/T 7714 | 赵丽韵. RNA编辑酶 ADAR2 在调控葡萄糖代谢平衡中的生理学功能[D]. 中国科学院上海生命科学研究院. 中国科学院上海生命科学研究院营养科学研究所. 2010. |
入库方式： OAI收割
来源：上海营养与健康研究所
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