In-Vivo Regulation of ADAR2 Activity by Autoediting

突触信号的多样性部分是由多种受体亚型的存在产生的，这些受体亚型通过激活单独的下游信号来响应神经递质。在哺乳动物的中枢神经系统中，通过一种被称为A-to-I RNA编辑的过程，受体的谱系被扩展到基因组编码集之外。已经发现，腺苷在编码几个离子型谷氨酸受体亚基的前递归-mRNAs和5-羟色胺受体(5-HT2cR)的2C亚型形成的双链中被转化为肌苷，由此产生的改变的mRNAs编码不同功能的受体。两个被称为ADAR1和ADAR2的双链RNA结合的腺苷脱氨酶负责对这些神经元转录进行精确的A-to-I编辑。最近的研究表明，ADAR2表达的适当调节对于维持编辑位点的选择性至关重要，而ADAR2表达的错误调节会导致小鼠极端肥胖(Emeson，未发表的结果)。新发现的在编码ADAR2的前mRNA中发生的A-to-I编辑事件表明，ADAR2活性发生了一种相当独特的调节形式，其中ADAR2可能通过编辑自己的转录本来负向调节自己的表达。这项建议的最终目的是测试ADAR2自动编辑的重要性。这将通过研究在基因工程中缺乏ADAR2自动编辑的小鼠的ADAR2 mRNA和蛋白质表达来实现，并将检查ADAR2已知底物中编辑模式的结果变化。

The diversity of synaptic signaling is partly generated by the presence of multiple receptor isoforms that respond to a neurotransmitter by activating separate downstream signals. In the mammalian central nervous system, the repertoire of receptors is expanded beyond the genomically encoded set by a process known as A-to-I RNA editing. It has been discovered that adenosines are converted to inosines within duplexes formed by precurser-mRNAs that code for several ionotropic glutamate receptor subunits and the 2C-subtype of the serotonin receptor (5-HT2cR), and the resulting altered mRNAs code for functionally distinct receptors. Two double-stranded RNA binding adenosine deaminases called ADAR1 and ADAR2 are responsible for precise A-to-I editing of those neuronal transcripts. Recent studies suggest that the appropriate regulation of the expression of ADAR2 is critical for maintaining editing site selectivity, and misregulation of ADAR2 expression in mice leads to extreme obesity (Emeson, unpublished results). A newly discovered A-to-I editing event in the pre-mRNA encoding ADAR2 itself suggests that a quite unique form of regulation of ADAR2 activity occurs, where ADAR2 may negatively regulate its own expression by editing its own transcript. The ultimate aim of this proposal is to test the significance of ADAR2 autoediting. This will be accomplished by studying ADAR2 mRNA and protein expression in mice genetically engineered to lack ADAR2 autoediting, and the resulting changes of editing patterns in known substrates of ADAR2 will be examined.