蛋白激酶A和磷酸酶2A影响脊髓小脑运动失调症1型的机制

Spinocerebellar ataxia type 1 (SCA1) is a lethal neurodegenerative disorder caused by expansion of a polyglutamine tract in ATAXIN-1 protein. It is an autosomal dominant inherited disease. Yet, considerable data indicate that ATAXIN-1 residues outside of the glutamine tract have a substantial impact on severity of disease. In SCA1, phosphorylation of ATAXIN-1 at S776 modulates disease and the interaction of ATAXIN-1 with many other proteins. The phosphorylation state of ATAXIN-1 is a dynamic process dictated by both protein kinase A (PKA) and protein phosphatase 2A (PP2A). Due to the importance of ATAXIN-1 phosphorylation at S776, the regulatory mechanism of this site's phosphorylation is critical for understanding the disease pathogenesis and developing avenues for disease therapeutics. The project is focused on the regulation of PKA and PP2A on ATAXIN-1 phosphorylation at S776, ATAXIN-1's function and cellular properties, and focused on PKA and PP2A's roles in SCA1 as well. The results would demonstrate the mechanism of SCA1's pathogenesis in the aspect of phosphorylation regulation and the signaling pathway regulating ATAXIN-1's phosphorylation. The results will also provide some new avenues for SCA1's therapeutics.

脊髓小脑运动失调症1型是一种遗传性神经退化性疾病，治疗困难，目前尚无特异性治疗。此病由于失调症蛋白1基因突变引起但受别的机制调控。失调症蛋白1丝氨酸776位点的磷酸化直接影响蛋白功能和特性及脊髓小脑运动失调症1型疾病的发生发展。因此如何调控此位点的磷酸化是深入理解疾病发生机理和防治的重要突破口。本项目主要研究调控失调症蛋白1磷酸化的蛋白激酶PKA和磷酸酶PP2A对失调症蛋白1磷酸化的作用机制，蛋白功能和特性的调节，及在脊髓小脑运动失调症1型中所起的作用，以阐明PKA和PP2A与失调症蛋白1及疾病的内在联系，从而揭示失调症蛋白1磷酸化对脊髓小脑运动失调症1型发病的机理和信号传导途径，从新的视觉揭示脊髓小脑运动失调症1型的发生机制，并为脊髓小脑运动失调症1型的防治提供新靶点。

研究脊髓小脑运动失调症1型（Spinocerebellar Ataxia Type 1, SCA1）其发病机理及其防治是目前国内外的热点。目前国内外尤其是国内对其发病机理，疾病防治和药物筛选方面的论文数量甚少。失调症蛋白1(ATAXIN-1)S776位点的磷酸化对疾病的发生发展具重要影响，研究表明磷酸化S776位点的激酶是蛋白激酶A(Protein Kinase A, PKA), 而磷酸酶是蛋白磷酸酶2A(Protein Phosphatase 2A, PP2A)。本课题研究调控ATAXIN-1磷酸化的两种酶，PKA和PP2A，在正常的表达ATAXIN-1[30Q]和SCA1小鼠各个脑部位的表达分布和活性,对揭示疾病选择性特定的发病部位提供理论和实验的依据。结果表明PKA蛋白在SCA1小鼠的疾病发生发展的重要部位，小脑和脑干，相比ATAXIN-1[30Q]小鼠，表达大幅度增强而PP2A蛋白的表达减少。mRNA的表达与蛋白表达并不完全一致，表明mRNA的翻译和翻译后调控可能在疾病的发生发展中发挥作用。同时纯化异常的ATAXIN-1[82Q]和正常ATAXIN-1[30Q]蛋白，并各自和PKA，PP2A进行酶动力学反应，结果显示异常的ATAXIN-1[82Q]比正常ATAXIN-1[30Q]蛋白更容易被PKA磷酸化，而不易被PP2A脱磷酸化。这些结果提示了突变的ATAXIN-1[82Q]的致病机理及PKA和PP2A在其中的作用机制。并利用酶动力学筛选出抑制PKA磷酸化S776-ATAXIN-1的小分子，为疾病的防治和药物的合成提供初期的研究成果。