LRRK2 and mitochondrial dysfunction

描述(由申请人提供)：富含亮氨酸的重复蛋白激酶2(LRRK2)的突变是迄今为止发现的家族性和特发性帕金森病(PD)的最常见原因。大多数LRRK2相关病例表现为典型的特发性或散发性帕金森病的临床症状。因此，了解LRRK诱导的神经变性的机制可能会为帕金森病的发病机制提供新的见解，并为治疗干预开辟新的途径。令人信服的证据表明，线粒体功能障碍可能是帕金森病发病机制中的一个关键事件。然而，帕金森病患者线粒体功能障碍的机制仍不清楚。鉴于有几条证据表明LRRK2存在于线粒体，LRRK2作用的一个可能机制是在线粒体。线粒体是动态细胞器，经历着连续的分裂和融合事件，具有重要的生理功能，并受一种机制的调节，该机制涉及到发挥相反作用的大的动力蛋白相关的GTP酶。这些线粒体分裂和融合蛋白不仅控制线粒体的数量和形态，而且还控制线粒体的分布和功能。值得注意的是，线粒体动力学改变在PD相关毒素处理的细胞和表达致病突变PINK-1、Parkin或DJ-1的细胞中起作用，提示线粒体动力学改变可能是导致PD发病过程中线粒体功能障碍的常见途径。最近的研究表明，LRRK2与PINK1/Parkin之间存在潜在的功能相互作用，这表明LRRK2也可能参与了这一途径。事实上，在我们的初步研究中，我们发现LRRK2(G2019S)突变的过表达导致SHSY-5Y人神经母细胞瘤细胞和原代大鼠皮质神经元线粒体断裂和异常分布，以及DLP1/OPA1表达减少和线粒体功能障碍。基于这些观察，我们的总体假设是LRRK2突变导致线粒体动力学异常，进而导致线粒体超微结构缺陷、功能障碍和重新分布，从而对神经元功能产生不利影响，包括导致帕金森病患者的突触异常。为了解决这一假设，将追求以下两个具体目标。目的1确定突变型LRRK2是否导致神经元线粒体分裂/融合异常和功能障碍；目的2：确定突变型LRRK2对线粒体分裂/融合的影响。 公共卫生相关性：了解LRRK2突变如何导致家族性帕金森病具有极其重要的意义。根据该领域的最新发展和我们的初步结果，我们建议研究LRRK2突变是否通过对线粒体分裂和融合平衡的毒性作用而导致线粒体异常。该项目的完成将使我们能够为更深入的机制研究收集数据，这可能有助于确定新的治疗靶点

DESCRIPTION (provided by applicant): Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause thus far identified for both familial and idiopathic Parkinson's disease (PD). The majority of LRRK2 linked cases present clinical symptoms typical of idiopathic or sporadic PD. Therefore, understanding of mechanisms underlying LRRK-induced neurodegeneration will likely provide new insights into pathogenesis of PD and open new avenues for therapeutic intervention. Compelling evidence suggest that mitochondrial dysfunction could represent a critical event in the pathogenesis of PD. However, the mechanisms underlying mitochondrial dysfunction in PD remain elusive. Given that several lines of evidence suggested the mitochondrial presence of LRRK2, a possible mechanism of LRRK2 action is at mitochondria. Mitochondria are dynamic organelles that undergo continual fission and fusion events which serve crucial physiological function and are regulated by a machinery involving large dynamin- related GTPase that exert opposing effects. These mitochondria fission and fusion proteins control not only mitochondrial number and morphology but also mitochondrial distribution and function. Notably, an altered mitochondrial dynamics plays a role in mitochondrial dysfunction in cells treated with PD-related toxins and in cells expressing pathogenic mutant PINK-1, Parkin or DJ-1, suggesting that an altered mitochondrial dynamics may be a common pathway leading to mitochondrial dysfunction during PD pathogenesis. More recent studies demonstrated a potential functional interaction between LRRK2 and PINK1/Parkin suggesting that LRRK2 could also be involved in this pathway. Indeed, in our preliminary studies, we found that overexpression of LRRK2 (G2019S) mutant causes mitochondrial fragmentation and abnormal distribution and reduced expression of DLP1/OPA1 along with mitochondrial dysfunction in SHSY-5Y human neuroblastoma cells and primary rat cortical neurons. Based on these observations, our overall hypothesis is that LRRK2 mutations cause abnormal mitochondrial dynamics which in turn causes mitochondrial ultrastructural defects, dysfunction and redistribution which adversely affects neuronal function including causing synaptic abnormalities in PD. To address this hypothesis, the following two specific aims will be pursued. Aim 1 To determine whether mutant LRRK2 cause abnormal mitochondrial fission/fusion and dysfunction in neurons; Aim 2: To determine how mutant LRRK2 affects mitochondrial fission/fusion. PUBLIC HEALTH RELEVANCE: It is of paramount significance to understand how LRRK2 mutations cause familial Parkinson disease. Based on recent development in the field and our preliminary results, we propose to investigate whether LRRK2 mutants cause mitochondrial abnormalities via its toxic effect on the balance of mitochondrial fission and fusion. The completion of this project will enable us to collect data for a more in-depth mechanistic study that may help identify novel therapeutic targets