alpha-synuclein and protein degradation

描述(申请人提供)：帕金森氏病(PD)是美国和其他地方老龄化人口的主要健康负担。在罕见的家系中识别导致这种疾病的基因缺陷可能会导致对更常见的散发性形式的病理生理学有新的见解。与帕金森病相关的一个特殊基因是α-突触核蛋白(ASYN)，因为它的蛋白产物是路易小体的主要成分。此外，ASYN基因的倍增足以引起人类的帕金森病。因此，阐明ASYN的正常和异常功能及其调控方式，可能有助于更好地理解PD的发病机制和开发新的治疗方法。我们先前已经发现，突变的ASYN可以通过溶酶体和泛素-蛋白酶体系统来损害蛋白质的降解。蛋白质处理缺陷也可能出现在其他遗传性或散发形式的帕金森病中，并可能形成这种疾病的共同病理生理学基础。我们提出，对溶酶体的影响可能是通过突变ASYN抑制伴侣介导的自噬(CMA)途径来实现的，而CMA通常会降解ASYN。然而，这些结果在很大程度上是在人工环境中实现的，ASYN的降解及其对蛋白质分解系统的影响存在争议。我们建议首先通过操纵CMA的受体LAMP2A及其限速步骤，以及通过检测当ASYN不针对CMA途径时ASYN的降解，来确定ASYN在神经细胞中被CMA降解。不影响CMA的突变ASYN也将被检查它们的相对毒性效应，以确定ASYN毒性是否部分由CMA阻断所介导。我们最近发现ASYN可以分泌并发挥毒性作用，我们将研究这种可能与生理相关的毒性是否与抑制神经细胞中的UPS和/或溶酶体功能有关。最后，我们将研究ASYN对神经元细胞系中蛋白质降解系统的影响是否适用于原代神经元细胞培养。这些研究将有助于破译ASYN水平的翻译后调节，这对其稳态水平及其对神经元生理学的影响至关重要，以及它对蛋白质降解途径的影响，这可能是其致病作用的关键。

DESCRIPTION (provided by applicant): Parkinson's Disease (PD) is a major health burden on the ageing population in the United States and elsewhere. The identification of gene defects that cause the disease in rare families may lead to new insights into the pathophysiology of the more common sporadic forms. One particular gene linked to PD that is especially relevant to the sporadic disease is alpha-synuclein (ASYN), as its protein product is the major component of Lewy Bodies. Furthermore, multiplication of the ASYN locus is sufficient to cause PD in humans. Therefore, elucidating the normal and aberrant functions of ASYN, as well as the manner of its regulation, may lead to a better understanding of the pathophsyiology of PD and the development of novel therapies. We have previously found that mutant ASYN can impair protein degradation through the lysosomes and the ubiquitin-proteasome system. Defects of protein handling may also occur in other genetic or sporadic forms of PD, and may form a common pathophysiological basis for this disorder. We have proposed that the impact on the lysosomes may be mediated by an inhibition by mutant ASYN of the pathway of Chaperone-Mediated Autophagy (CMA), which normally degrades ASYN. However, these results were largely achieved in an artificial setting, and the degradation of ASYN and its impact on proteolytic systems is controversial. We propose to first establish that ASYN is degraded by CMA in neuronal cells, by manipulating Lamp2a, the receptor for CMA and its rate-limiting step, and by examining the degradation of ASYN when it is not targeted to the CMA pathway. Mutant ASYNs that do not affect CMA will also be examined for their relative toxic effects, to ascertain whether ASYN toxicity is mediated in part by CMA blockade. We have recently found that ASYN can be secreted and exert toxic effects, and we will examine whether such toxicity, which may be physiologically relevant, is related to the inhibition of UPS and/or lysosomal function in neuronal cells. Lastly, we will examine whether the effects of ASYN on protein degradation systems in neuronal cell lines are applicable in primary neuronal cell cultures. These studies will help to decipher the post-translational regulation of ASYN levels, which is critical for its steady-state levels and its impact on neuronal physiology, and its effects on protein degradation pathways, which may be critical for its pathogenic effects.