The role of Parkin in selective dopamine neuronal degeneration

描述（由申请人提供）：黑质纹状体（NS）多巴胺（DA）神经元的进行性变性是帕金森病（PD）运动症状的基础，缺乏减缓进展的治疗。DA代谢异常被认为是NSDA神经元选择性变性的机制。然而，所有DA神经元在PD中并没有受到相同程度的影响。虽然中脑NSDA神经元严重丢失，但下丘脑结节漏斗（TI）DA神经元保持完整。当这些DA神经元群体暴露于线粒体复合物I抑制剂在体外和体内时，可以看到类似的易感性模式。虽然NSDA和TIDA神经元对复合物I抑制具有类似的初始反应，但只有TIDA神经元能够使用依赖于新蛋白质合成的机制恢复。我们的初步数据还表明，帕金参与了这种差异的敏感性，因为它是显着上调TIDA，但不是NSDA神经元后，急性中毒性损伤。Parkin是一种多功能蛋白，支持正常的线粒体功能，具有E3连接酶，标记错误折叠的蛋白质进行蛋白质体降解，并似乎保护DA神经元免受各种毒性损伤。Parkin还具有重要的蛋白体独立功能，可以促进DA神经元的存活。本项目的总体目标是阐明帕金森介导的分子机制，使NSDA神经元敏感和TIDA神经元抵抗外源性神经毒素暴露。我们假设parkin主要通过蛋白酶体非依赖性机制起作用，保护TIDA神经元，并可以拯救NSDA神经元免受PD相关病理应激、线粒体复合物I抑制诱导的损伤。 为了解决中心假设，将在野生型小鼠和具有parkin无效背景的小鼠中进行rAAV介导的空间限制的parkin表达操纵。将评估外源性调节parkin表达对TIDA和NSDA神经元对急性和慢性神经毒性应激的反应的影响，以确认parkin在允许DA神经元在初始损伤后恢复中的中心作用。分子和药理学方法将被用来阐明帕金神经保护作用的初始下游介质。尽管观察到在临床上可观察到的PD症状发作时，DA神经元的显著部分已经丢失，但似乎有可能存在处于风险和功能障碍的神经元，但如果提供必要的恢复机制，则可以恢复。由于TIDA神经元在DA神经元中是独特的，它们能够从由PD相关病理性应激源诱导的损伤中恢复，因此它们提供了一个强大的平台来剖析帕金森介导的DA神经元恢复机制，并且可以产生用于神经保护治疗开发的新靶点。 公共卫生相关性：帕金蛋白似乎有利于神经元暴露于帕金森病中所见的病理性应激源后的恢复。帕金的保护机制将被确定为开发帕金森病新疗法的策略。

DESCRIPTION (provided by applicant): Progressive degeneration of nigrostriatal (NS) dopamine (DA) neurons underlies the motor symptoms of Parkinson's disease (PD) and therapies that slow progression are lacking. Abnormal DA metabolism has been proposed as a mechanism for the selective degeneration of NSDA neurons. All DA neurons, however, are not affected to the same extent in PD. While there is severe loss of midbrain NSDA neurons, the hypothalamic tuberoinfundibular (TI) DA neurons remain intact. A similar pattern of susceptibility can be seen in these DA neuronal populations when they are exposed to mitochondrial complex I inhibitors in vitro and in vivo. Although NSDA and TIDA neurons have a similar initial response to complex I inhibition, only TIDA neurons are able to recover using a mechanism that is dependent on new protein synthesis. Our preliminary data also implicate that parkin is involved in this differential susceptibility since it is markedly upregulated in TIDA, but not NSDA neurons following an acute toxic injury. Parkin is a multifunctional protein that supports normal mitochondrial function, has an E3 ligase that tags misfolded proteins for proteosomal degradation and appears to protect DA neurons from a variety of toxic insults. Parkin also has important proteosome independent functions that could promote DA neuronal survival. The overall goal of this project is to elucidate the parkin-mediated molecular mechanisms that render NSDA neurons sensitive and TIDA neurons resistant to exogenous neurotoxin exposure. We hypothesize that parkin, acting primarily via proteosome-independent mechanisms, protects TIDA neurons and can rescue NSDA neurons from injury induced by a PD relevant pathological stress, mitochondrial complex I inhibition. To address the central hypothesis, rAAV-mediated, spatially restricted manipulation of parkin expression will be performed in wild-type mice and on mice with a parkin null background. The impact of exogenously modulating parkin expression on the TIDA and NSDA neuronal responses to both acute and chronic neurotoxic stress will be assessed to confirm the central role of parkin in allowing DA neurons to recover following an initial insult. Molecular and pharmacological methods will be used to elucidate the initial downstream mediators of the neuroprotective effects of parkin. Despite the observation that a significant portion of DA neurons have been lost at the onset of clinically observable symptoms of PD, it is plausible that there are neurons that are at risk and dysfunctional, but that could recover if provided the necessary machinery for recovery. Since TIDA neurons are unique amongst DA neurons in their ability to recover from an injury induced by a PD relevant pathological stressor, they provide a powerful platform to dissect the parkin-mediated mechanisms of DA neuronal recovery and could yield novel targets for neuroprotective therapy development. PUBLIC HEALTH RELEVANCE: Parkin protein appears to facilitate the recovery of neurons following exposure to pathological stressors seen in Parkinson's disease. The protective mechanisms of parkin will be determined as a strategy to develop new therapies for Parkinson's disease.