RNA editing of AMPA receptor subunit GluR2 in ischemia

在发达国家，缺血性中风是第三大死亡原因。这种疾病的一个重要特征是 一种高度选择性的神经元丢失模式；某些可识别的神经元亚群，特别是CA1 海马区的锥体神经元严重受损，而其他神经元则完好无损。这是其中的一步 选择性神经元损伤涉及钙离子通过钙离子通透性的AMPA受体通道进入。AMPA 受体是谷氨酸受体(GluRs)的一个主要亚型，由GluR1-4亚基组装而成。 通道的钙离子通透性主要由Q/R部位的GluR2 RNA编辑决定；编辑的GluR2(R) 亚基形成钙离子不通透通道，而未经编辑的GluR2(Q)通道允许钙离子进入。在……里面 大多数CA1神经元、AMPA受体通道都含有GluR2(R)，因此对钙离子流是不通透的。 最近，我们发现短暂性前脑缺血选择性地干扰GluR2Q/R位点编辑和 从而通过AMPA受体通道诱导损伤性钙离子进入脆弱的CA1神经元。我们 还表明GluR2Q/R位点编辑受损与GluR2Q/R位点表达减少密切相关 ADAR2(作用于RNA的腺苷脱氨酶)基因，与GluR2 Q/R相关的核酶 站点编辑。因此，我们假设ADAR2基因的表达减少是导致受损的原因 GluR2 Q/R站点编辑。为了直接解决这一假设，我们将确定ADAR2基因的恢复 表达挽救GluR2 Q/R位点编辑，进而阻断AMPA受体的钙通透性 通道，导致缺血后大鼠易受伤害的神经元存活。总体而言，该项目将 有两个具体目标： 特定目的1：确定ADAR2基因表达的恢复是否通过 AMPA受体通道和挽救缺血后大鼠易损神经元。 特异性目的2：确定稳定的ADAR2基因沉默是否会导致细胞退行性变 缺血不敏感神经元，以及如果编辑RNA导致ADAR2缺陷神经元变性 一个或多个谷氨酸受体亚基缺失。 总而言之，该项目将确定依赖ADAR2的GluR2 Q/R站点编辑决定了 神经元对缺血的影响。因此，这项工作将为卒中治疗定义一个有前景的靶点。

Ischemic stroke is the third leading cause of death in developed countries. A critical feature of the disease is a highly selective pattern of neuronal loss; certain identifiable subsets of neurons, particularly CA1 pyramidal neurons in the hippocampus, are severely damaged while others remain intact. A step in this selective neuronal injury involves Ca2+ entry through Ca2+-permeable AMPA receptor channels. AMPA receptors are a major subtype of glutamate receptors (GluRs) that are assembled from GluR1-4 subunits. Ca2+ permeability of the channels is dominated by GluR2 RNA editing at the Q/R site; edited GluR2(R) subunits form Ca2+-impermeable channels, whereas unedited GluR2(Q) channels allow Ca2+ entry. In most CA1 neurons, AMPA receptor channels contain GluR2(R), and thus are impermeable to Ca2+ flow. Recently, we have identified that transient forebrain ischemia selectively disrupts GluR2 Q/R site editing and hence induces injurious Ca2+ entry through AMPA receptor channels into vulnerable CA1 neurons. We have also shown that impaired GluR2 Q/R site editing is closely correlated with reduced expression of ADAR2 (short for adenosine deaminase acting on RNA) gene, a nuclear enzyme responsible for GluR2 Q/R site editing. We thus hypothesize that reduced expression of ADAR2 gene is responsible for the impaired GluR2 Q/R site editing. To address this hypothesis directly, we will determine if restoration of ADAR2 gene expression rescues GluR2 Q/R site editing and in turn blocks Ca2+ permeability of AMPA receptor channels, leading to the survival of vulnerable neurons in the post-ischemic rats. Overall, this project will have two specific aims: Specific Aim 1: To determine whether restoration of ADAR2 gene expression blocks Ca2+ entry through AMPA receptor channels and rescues vulnerable neurons in the post-ischemic rats. Specific Aim 2: To determine if generation of stable ADAR2 gene silencing induces degeneration of ischemia-insensitive neurons, and if degeneration of ADAR2-deficient neurons results from RNA editing deficits of one or more glutamate receptor subunits. Together, this project will identify that ADAR2-dependent GluR2 Q/R site editing determines vulnerability of neurons to ischemia. Thus, this work will define a promising target for stoke therapy.