The role of the Fe/S cluster protein CISD1 in Parkinson’s disease

帕金森病（PD）是一种神经系统疾病，由中脑结构中称为黑质的多巴胺能神经元变性引起。其特征在于线粒体功能障碍、氧化应激、铁代谢改变和线粒体质量控制缺陷;将PD与CDGSH铁硫结构域1（CISD 1）功能障碍联系起来的病理生理学改变，CISD 1是一种锚定在面向细胞溶质的线粒体外膜中的含二聚2Fe-2S（Fe/S）簇的蛋白质。CISD 1能够响应于氧化刺激将其Fe/S簇转移到其他蛋白质，在线粒体生物能量学和形态学的调节中是重要的，并且参与线粒体质量控制，其中它是PTEN诱导的神经元激酶1（PINK 1）的靶点并且被E3泛素连接酶Parkin泛素化，这是PD病理生理学中必不可少的途径。重要的是，小鼠中的CISD 1敲除导致类似于PD的运动表型。自己的初步数据也暗示了CISD 1在PD的病理生理学中的作用;我们观察到，神经元敲除果蝇CISD 1增加了PINK 1敲除果蝇和暴露于鱼藤酮（一种药理学PD模型）的果蝇的寿命。我们还发现CISD 1在缺乏PINK 1的人中脑多巴胺能神经元中上调。基于这些观察结果，我们假设CISD 1在响应PINK 1/Parkin激活时被泛素化和降解，从而将其Fe/S簇转移到其他蛋白质。这有助于保留Fe/S簇并作为存活信号。在没有PINK 1（可能还有Parkin）的情况下，CISD 1在线粒体外膜上积累，并且不会将其Fe/S簇转移到其他地方，这会扰乱细胞的稳态。在缺乏CISD 1的情况下，Fe/S簇不能转移到其他蛋白质上，这也会干扰细胞内稳态和线粒体质量控制的正确执行。我们认为，这一途径的功能障碍使多巴胺能神经元衰弱。为了证明或反驳这一假设，我们将产生果蝇品系和人类多巴胺能神经元，缺乏CISD 1或表达影响Fe/S簇稳定性的突变等位基因，并使用这些工具来阐明CISD 1及其Fe/S簇的存在，不存在或稳定性如何影响线粒体的形状，功能和质量控制。我们将干扰CISD 1在PD苍蝇模型中的表达，并研究其在从患有PD的患者获得的样品中的表达。我们将最终确定在线粒体功能障碍时与CISD 1发生物理和遗传相互作用的蛋白质，并作为铁硫簇的潜在受体。这项工作是最感兴趣的，因为它全面评估了这种有趣的蛋白质在体外和体内的多个方面，并将揭示其在破坏性人类疾病的病理生理学中的作用。

Parkinson’s disease (PD) is a neurological disorder caused by degeneration of dopaminergic neurons in a midbrain structure called the substantia nigra pars compacta. It is characterized by mitochondrial dysfunction, oxidative stress, altered iron metabolism and defective mitochondrial quality control; pathophysiological alterations which connect PD with dysfunction of CDGSH Iron Sulfur Domain 1 (CISD1), a dimeric 2Fe-2S (Fe/S) cluster-containing protein anchored in the outer mitochondrial membrane facing the cytosol. CISD1 is capable of transferring its Fe/S cluster to other proteins in response to oxidative stimuli, is important in the regulation of mitochondrial bioenergetics and morphology, and is involved in mitochondrial quality control where it is a target of PTEN-induced neuronal kinase 1 (PINK1) and ubiquitylated by the E3 ubiquitin ligase Parkin, a pathway essential in PD pathophysiology. Importantly, CISD1 knockout in mice results in a motor phenotype that resembles PD. Own preliminary data also imply a role for CISD1 in the pathophysiology of PD; we observed that neuronal knockdown of fly CISD1 increases lifespan of PINK1 knockout flies and of flies exposed to rotenone, a pharmacological PD model. We also found CISD1 to be upregulated in human midbrain dopaminergic neurons lacking PINK1. Based on these observations, we hypothesize that CISD1 transfers its Fe/S cluster to other proteins when it is ubiquitylated and degraded in response to PINK1/Parkin activation. This serves to preserve the Fe/S cluster and acts as a survival signal. In the absence of PINK1 (and probably also Parkin), CISD1 accumulates at the outer mitochondrial membrane and does not transfer its Fe/S cluster elsewhere which disturbs cellular homeostasis. In the absence of CISD1, the Fe/S cluster cannot be transferred to other proteins which also disturbs cellular homeostasis and the correct execution of mitochondrial quality control. We posit that dysfunction of this pathway debilitates dopaminergic neurons. To prove or disprove this hypothesis, we will generate Drosophila melanogaster lines and human dopaminergic neurons that lack CISD1 or express mutant alleles that affect the stability of the Fe/S cluster and use these tools to illuminate how CISD1 and the presence, absence or stability of its Fe/S cluster affects mitochondrial shape, function and quality control. We will perturb CISD1 expression in fly models of PD and study its expression in samples obtained from patients suffering from PD. We will finally identify proteins that physically and genetically interact with CISD1 in response to mitochondrial dysfunction and serve as potential acceptors for the iron-sulfur cluster. This work is of utmost interest as it comprehensively assesses multiple facets of this interesting protein in vitro and in vivo and will shed light on its role in the pathophysiology of a devastating human disease.