ROLE OF THE PINK1/PARKIN PATHWAY IN MITOCHONDRIAL DYNAMICS AND TISSUE INTEGRITY

描述（由申请人提供）：线粒体功能障碍是帕金森病的常见特征，但我们对潜在的分子机制的了解是初步的。最近，一种影响线粒体完整性的遗传途径已经从PINK 1和parkin基因的研究中出现，这些基因的功能丧失突变是导致大多数早发性隐性形式帕金森病的原因。PINK 1基因编码丝氨酸/苏氨酸激酶，其定位于线粒体内膜空间和细胞质，而parkin编码泛素蛋白连接酶，其广泛定位于整个细胞，包括细胞质和线粒体。对PINK 1和parkin的高度保守的果蝇直系同源物的突变分析表明，PINK 1在一个共同的途径中作用于Parkin的上游，该途径促进组织子集中的线粒体完整性，包括间接飞行肌和中枢神经系统中的多巴胺能神经元。我们最近的工作表明PINK 1/Parkin通路通过促进线粒体分裂影响线粒体和组织的完整性。我们从这一发现和其他研究结果推测，PINK 1/Parkin通路通过磷酸化和/或泛素化线粒体形态发生机制的特定组分来促进线粒体分裂。我们进一步假设，细胞死亡伴随着减少线粒体分裂parkin和PINK 1突变体来源于低效率的交付损坏的线粒体自噬体，有缺陷的运输扩大（融合）线粒体突触前神经末梢，和/或过量的活性氧产生扩大线粒体。提出了两个具体的目标来解决这些假设：第一个目标将测试是否PINK 1/帕金通路激活线粒体分裂或抑制线粒体融合，通过使用已建立的线粒体融合和裂变测定系统，并通过测试PINK 1/帕金通路的候选底物。第二个目标涉及遗传，分子和细胞生物学实验，以区分PINK 1和parkin突变体中受损的线粒体分裂影响组织完整性的特定模型。从这些实验中，我们希望推进我们的长期目标，阐明帕金森病中线粒体功能障碍和选择性细胞死亡的机制。公共卫生相关性：帕金或PTEN诱导的激酶1（PINK 1）基因的功能丧失突变是常染色体隐性遗传家族性帕金森病的最常见原因。我们的提案旨在了解Parkin和PINK 1的生物学作用以及它们的突变失活如何导致神经元丢失。我们对PINK 1和Parkin的研究的见解可能与更常见的帕金森病的特发性形式有关，这种见解可能导致这种衰弱性疾病的预防性治疗的发展。

DESCRIPTION (provided by applicant): Mitochondrial dysfunction is a common feature of Parkinson's disease, but our knowledge of the underlying molecular mechanisms is rudimentary. Recently, a genetic pathway that influences mitochondrial integrity has emerged from studies of the PINK1 and parkin genes, loss-of-function mutations of which are responsible for the majority of early-onset recessive forms of parkinsonism. The PINK1 gene encodes a serine/threonine kinase that localizes to the mitochondrial inner membrane space and to the cytoplasm, whereas parkin encodes a ubiquitin-protein ligase that localizes broadly throughout the cell, including the cytoplasm and mitochondria. Mutational analyses of highly-conserved Drosophila orthologs of PINK1 and parkin indicate that PINK1 acts upstream of Parkin in a common pathway that promotes mitochondrial integrity in a subset of tissues, including indirect flight muscle and dopaminergic neurons in the central nervous system. Our recent work indicates that the PINK1/Parkin pathway influences mitochondrial and tissue integrity by promoting mitochondrial fission. We hypothesize from this and other findings that the PINK1/Parkin pathway promotes mitochondrial fission by phosphorylating and/or ubiquitinating particular components of the mitochondrial morphogenesis machinery. We further hypothesize that the cell death accompanying reduced mitochondrial fission in parkin and PINK1 mutants derives from inefficient delivery of damaged mitochondria to autophagosomes, defective trafficking of enlarged (fused) mitochondria to presynaptic nerve terminals, and/or excessive reactive oxygen species production by enlarged mitochondria. Two specific aims are proposed to address these hypotheses: the first aim will test whether the PINK1/Parkin pathway activates mitochondrial fission or inhibits mitochondrial fusion by using established mitochondrial fusion and fission assay systems, and by testing candidate substrates of the PINK1/Parkin pathway. The second aim involves genetic, molecular and cell biological experiments to distinguish between specific models by which impaired mitochondrial fission in PINK1 and parkin mutants influences tissue integrity. From these experiments, we hope to advance our long-term goal of elucidating the mechanisms underlying mitochondrial dysfunction and selective cell death in Parkinson's disease. PUBLIC HEALTH RELEVANCE: Loss-of-function mutations in the parkin or PTEN-induced kinase 1 (PINK1) genes are collectively the most frequent cause of autosomal recessive familial Parkinson's disease. Our proposal aims to understand the biological roles of Parkin and PINK1 and how their mutational inactivation results in neuronal loss. Insight from our studies of PINK1 and Parkin are likely to be relevant to more common idiopathic forms of Parkinson's disease and this insight could lead to the development of preventative treatments for this debilitating disorder.