Mortalin泛素化修饰异常在氧化应激导致帕金森病发病中的作用及其机制

Oxidative stress plays a crucial role in the pathogenesis of Parkinson's disease (PD). Mitochondria is the place where the major products of oxidative stress reactive oxygen species(ROS) is generated and cleared. Mortalin can translocate into mitochondria to reduce the ROS level when cells are attacked by oxidative stress. The early studies have shown the linkage between mortalin deficiency and imparied anti-oxidative ability of cells. The mutations of mortalin gene were also identified in PD patients. It indicated that abnormal mortalin function may closely related to the pathogenesis of PD. Our previous experiments showed that the ubiquitination of mortalin is involved in the mitochondrial translocation of mortalin instead of its degradation. We proposed that the mortalin abnormalities may affect its ubiquitination and the following mitochondrial translocation, thus affect cellular anti-oxidative stress function, leading to the neuronal degeneration. This study aims to screen the specific E3 ligase of mortalin, and observe whether the abnornal ubiquitination of mortalin or the abnormal interaction of mortalin-E3 liagase would affect the mitochondrial translocation of mortalin, anti-oxidative stress function of cells and survival of cells. This study will help to further illustrate the pathogenesis of PD.

氧化应激在帕金森病发病过程中起重要作用，线粒体是氧化应激主要产物活性氧（ROS）的主要产生场所和清除场所。Mortalin可在抗氧化应激过程中转位入线粒体，降低ROS的生成。前期的研究证明mortalin功能缺失会导致细胞抗氧化应激能力受损；在帕金森病(PD)患者中也发现了mortalin基因的突变，提示mortalin的异常可能与帕金森病的发病密切相关。我们前期的实验表明，mortalin的泛素化修饰不影响蛋白的降解途径，而参与其线粒体的转位。由此我们设想mortalin的异常可能影响其泛素化修饰及线粒体转位，影响其抗氧化应激功能，最终导致神经元的变性死亡。本研究拟通过体内外实验筛选修饰mortalin泛素化的E3连接酶，观察泛素化修饰以及mortalin与特异性连接酶E3间相互作用对mortalin线粒体转位、细胞抗氧化应激功能及细胞存活的影响，从而帮助我们进一步了解PD的发病机制。

帕金森病是一种常见的神经退行性疾病，其主要临床表现为静止性震颤、肌强直、运动迟缓、姿势步态异常等运动症状。作为PD的致病基因之一，UCHL1可导致常染色体显性遗传性PD。另外，在散发性PD中也发现UCHL1蛋白水平的下降。目前UCHL1的致病机制尚不明确。.为了进一步研究UCHL1的功能，我们通过小干扰RNA技术对UCHL1蛋白进行下调表达，实验发现细胞对神经毒物MPP+的刺激更为敏感，表现为细胞活力下降、凋亡蛋白产生以及线粒体膜电位的下降，而UCHL1过表达可以挽救上述过程。我们通过免疫共沉淀实验，发现UCHL1与Mortalin蛋白存在相互作用，并且UCHL1可以对Mortalin发挥泛素连接酶作用，介导Mortalin的线粒体定位。