alpha-Synuclein Inhibition of Mitochondrial Protein Import

 描述(申请人提供)：帕金森病(PD)是一种常见的神经退行性疾病，导致运动障碍、认知和精神症状以及自主神经功能障碍。遗传和环境因素与帕金森病的发病机制有关，线粒体缺陷和突触蛋白α-突触核蛋白的积聚似乎是大多数形式的帕金森病的共同特征。此外，有证据表明线粒体功能障碍和α-突触核蛋白积累之间存在双向相互作用。抑制线粒体复合体I会导致α-突触核蛋白的聚集和寡聚，而α-突触核蛋白水平的增加会导致线粒体损伤和产生活性氧(ROS)。α-突触核蛋白与线粒体之间的相互作用的性质尚不清楚，也不清楚这些作用是否由未经修饰的单体α-突触核蛋白引起，也不清楚参与发病的翻译后修饰是否重要，如寡聚化、多巴胺修饰、磷酸化或硝化。线粒体有自己的基因组，但它只编码13种蛋白质，因此它们必须进口大约99%的&gt；1000蛋白质。线粒体蛋白质的输入是通过复杂和高度调控的系统进行的，其中最被理解的是识别蛋白质上的N末端线粒体靶向信号(MTS)。虽然没有一致的序列，但MTS形成了一个两亲性螺旋，可由受体蛋白TOM20识别，TOM20是线粒体膜外转位酶复合体(TOM)的一个亚单位。尽管单体α-突触核蛋白在溶液中是一种本质上无序的蛋白质，但与膜上的阴离子脂类结合在一起，它形成了一个两亲性螺旋。 与已知的MTS基序相似。在此背景下，我们有强有力的证据表明，某些形式的翻译后修饰的α-突触核蛋白与TOM20特异结合，并干扰线粒体靶标蛋白的输入。我们建议研究α-突触核蛋白与线粒体导入机制的相互作用，目的如下：(1)定义抑制线粒体蛋白导入的α-突触核蛋白的特定形式；(2)定义关键的结合伙伴和结合参数；(3)确定α-突触核蛋白诱导的线粒体蛋白导入障碍的功能后果；(4)研究阻断线粒体蛋白导入是否会导致类似于α-突触核蛋白过表达的黑质纹状体神经变性；以及(5)研究基因操作线粒体导入以防止α-突触核蛋白在黑质过度表达的可能性。

 DESCRIPTION (provided by applicant): Parkinson disease (PD) is a common neurodegenerative disorder resulting in motor impairment, cognitive and psychiatric symptoms and autonomic dysfunction. Genetic and environmental factors have been implicated in PD pathogenesis, and it appears that mitochondrial defects and accumulation of the synaptic protein, α- synuclein, are common to most forms of the disease. Moreover, there is evidence of a bidirectional interaction between mitochondrial dysfunction and α-synuclein accumulation. Inhibition of mitochondrial complex I leads to accretion and oligomerization of α-synuclein, and increased levels of α-synuclein cause mitochondrial impairment and production of reactive oxygen species (ROS). The nature of the interaction between α- synuclein and mitochondria remains obscure, and it is unclear whether unmodified monomeric α-synuclein is responsible for these effects, or whether posttranslational modifications which have been implicated in pathogenesis, such as oligomerization, dopamine modification, phosphorylation or nitration are important. Mitochondria contain their own genome, but it encodes only 13 proteins, so they must import about 99% of the >1000 proteins they contain. Mitochondrial protein import occurs through complex and highly regulated systems, the best understood of which recognizes N-terminal mitochondrial targeting signals (MTS) on proteins destined for import. While there is no consensus sequence, MTS characteristically form an amphipathic helix that is recognized by a receptor protein, TOM20, which is a subunit of the translocase complex of the outer mitochondrial membrane (TOM). Although monomeric α-synuclein is an intrinsically disordered protein in solution, in association with anionic lipids in membranes, it forms an amphipathic helix similar to known MTS motifs. In this context, we have strong evidence that certain forms of posttranslationally-modified α-synuclein bind specifically to TOM20 and interfere with import of mitochondrially-targeted proteins. We propose to study the interaction of α-synuclein with mitochondrial import machinery in the following aims: (1) Define the specific forms of α-synuclein that inhibit mitochondrial protein import; (2) Define key binding partners and binding parameters; (3) Determine functional consequences of α-synuclein-induced impairment of mitochondrial protein import; (4) Investigate whether blockade of mitochondrial protein import causes nigrostriatal neurodegeneration similar to α-synuclein overexpression; and (5) Examine the potential for genetic manipulation of mitochondrial import to protect against AAV2-mediated α-synuclein overexpression in substantia nigra.