In-Vivo Regulation of ADAR2 Activity by Autoediting

突触信号的多样性部分是由多种受体同种异构体的存在产生的，这些受体同种异构体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，受体的库被扩展到基因组编码集之外。已经发现，腺苷在由前体mrna形成的双链内转化为肌苷，这些前体mrna编码几种嗜离子性谷氨酸受体亚基和5-HT2cR受体的2c亚型，并且由此产生的改变的mrna编码功能不同的受体。两种名为ADAR1和ADAR2的双链RNA结合腺苷脱氨酶负责这些神经元转录物的精确A-to-I编辑。最近的研究表明，适当调节ADAR2的表达对于维持编辑位点的选择性至关重要，而小鼠中ADAR2表达的错误调节会导致极度肥胖（Emeson，未发表的结果）。在编码ADAR2本身的前mrna中新发现的A-to- i编辑事件表明，ADAR2活性的调节存在一种相当独特的形式，其中ADAR2可能通过编辑其自身的转录物负向调节其自身的表达。本提案的最终目的是测试ADAR2自动编辑的意义。这将通过在缺乏ADAR2自编辑的基因工程小鼠中研究ADAR2 mRNA和蛋白表达来完成，并将检查已知ADAR2底物中编辑模式的变化。

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maintaining editing site selectivity, and misregulation of ADAR2 expression in mice leads to extreme obesity (Emeson, unpublished results).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.