下调磷酸酯酶2A抑制因子降低Abeta的机制及其神经保护作用的研究

Abeta protein deposits is one of pathological markers of Alzheimer's disease (AD). Both the phosphorylated level of amyloid precursor protein (APP) at Thr668 and beta-/gamma-secretase activities promote Abeta production. So, decreasing the level of Thr668-pAPP and/or beta-/gamma- secretase activities have potent application values. The preliminary data have shown that downregulation of I2PP2A by intracranial infusion of lentivirus (Lenti-siI2PP2A) remarkably reduces abeta accumulation in Tg2576 mice. The project will investigate the effects of knockdown I2PP2A on phosphorylated Thr668-APP level and beta-/gamma- secretase activities and the underlying mechanisms in cell lines. We will also study ameliorative effects of knockdown I2PP2A on AD like pathophysiology and cognitive deficits of Tg2576 mice and a triple transgenic model of AD (3×Tg-AD) harboring three mutant genes: β-amyloid precursor protein (βAPPSwe), presenilin-1 (PS1M146V), and tauP301L, through intracranial infusion of lenti-siI2PP2A. Knockdown I2PP2A could attenuate tau phosphorylation and decrease Abeta level, so the results provide I2PP2A as a new target for drug research and development in AD.

beta淀粉样肽（Abeta）沉积是老年性痴呆(AD)的病理标志，APP Thr668位点磷酸化、beta-/gamma-分泌酶活性均可促进Abeta生成。因此，降低Thr668-pAPP水平和/或降低beta-/gamma-分泌酶活性对防治AD有潜在应用价值。申请者最近研究显示：针对PP2A抑制因子-2（I2PP2A）的 siRNA 慢病毒表达载体转染Tg2576转基因鼠，可降低Abeta水平。本项目拟在细胞水平进一步确定下调 I2PP2A 对APP磷酸化水平及分泌酶活性的影响及相关分子机制；采用慢病毒表达载体转染Tg2576和APPSwe×PS1M126V×TauP301L转基因鼠，研究下调 I2PP2A 表达水平对转基因鼠的AD-样病理和行为异常的改善作用。基于下调I2PP2A可同时逆转tau过度磷酸化和减少Abeta，该项目研究结果有望使I2PP2A成为AD有效药物研发的新靶点。

beta淀粉样肽（Abeta）沉积是老年性痴呆(AD)的病理标志，APP Thr668位点磷酸化、beta-/gamma-分泌酶活性均可促进Abeta生成。因此，降低Thr668-pAPP水平和/或降低beta-/gamma-分泌酶活性对防治AD有潜在应用价值。本项目拟在细胞水平进一步确定下调 I2PP2A对APP磷酸化水平及分泌酶活性的影响及相关分子机制；采用慢病毒表达载体转染tau及Tg2576转基因鼠，研究下调 I2PP2A表达水平对转基因鼠的AD-样病理和行为异常的改善作用。.本研究发现：（1）I2PP2A在tg2576鼠脑内水平呈年龄依赖性的升高，伴有PP2A活性下降；（2）下调I2PP2A降低A和tau蛋白过度磷酸化水平；（3）下调I2PP2A可激活PP2A，从而调节由下调I2PP2A所导致的A积聚减少；（4）PP2A可调控APP磷酸化水平和-分泌酶活性；（5）下调I2PP2A改善学习记忆能力，是通过升高学习记忆相关蛋白水平，而不是通过PP2A介导的；（6）高浓度OA引起细胞和动物样本内APP磷酸化水平升高，且在N2a/APP细胞中引起总APP蛋白水平升高；（7）抑制PP1的活性可以降低APP的磷酸化水平；（8）OA可上调N2a/APP细胞中的β、γ分泌酶活性，并且减少α、β-CTF的产生量；（9）下调ANP32A改善htau转基因鼠学习记忆能力和突触可塑性。.本研究在细胞和整体水平上首次揭示下调I2PP2A表达水平，可能通过降低APP Thr668位点磷酸化修饰水平和/或调节α-、β-、γ-分泌酶活性，从而降低Aβ水平，由于下调I2PP2A可逆转tau的过度磷酸化及抑制Abeta的生成，而改善动物的学习记忆与认知功能障碍；揭示了I2PP2A是一个潜在的治疗AD的有效靶点。