ROLE AND MECHANISMS OF EFFLUX IN MANGANESE HOMEOSTASIS AND DETOXIFICATION

描述（由申请人提供） 锰是一种必需元素，在细胞水平升高时变得有毒，导致无法治愈的神经毒性综合征的发作。到目前为止，在哺乳动物的锰稳态和中毒的研究集中在锰流入的机制，但确定的流入转运蛋白既不特定的锰，也不受细胞锰水平的调节。 与此相反，虽然外排在维持其他金属的稳态中起着重要作用，但胞质锰外排的作用尚未得到充分研究。 研究人员现在已经确定了一个重要的作用，通过摄取到高尔基体的锰流出，然后分泌在维持细胞锰水平和防止过量的锰积累在升高的暴露。在此基础上，他们的目标是阐明由高尔基体的锰流出的调节机制，以便更好地理解这个基本过程中的锰稳态和锰诱导的神经毒性的发展中的作用。 研究人员的结果表明，高尔基体对Mn的吸收需要SPCA 1，这是一个高尔基体定位的Ca/Mn泵，并且SPCA 1在高尔基体和内体之间快速运输。 由于亚细胞贩运的离子泵调节其活性，他们的第一个目标是阐明SPCA 1贩运调节锰外流的作用。 调查人员还 发现增加的高尔基体内Mn诱导高尔基体蛋白GPP 130的快速降解，并且GPP 130水平影响Mn流出和毒性。因此，第二个目的是阐明GPP 130调节Mn流出和毒性的机制。 最后，作为额外的因素调节锰流出仍有待确定，第三个目标是进行全基因组RNAi筛选的蛋白质，改变控制锰的高尔基体。 在筛选中，GPP 130的修饰版本将作为高尔基体内腔Mn的新型传感器。 拟议的研究将提供一个关键的，但未探索的方面锰稳态，这是直接相关的锰诱导的神经毒性的病理生物学机制的理解。 公共卫生相关性：锰是一种环境和职业毒素，导致帕金森样神经系统疾病的发作，无法治愈。拟议的工作将确定Mn从人体细胞中去除的机制。这将为今后研制提高细胞锰清除率的药物治疗锰中毒奠定基础。 这也将使我们能够确定是否存在遗传或后天缺陷，在锰去除人口中，增加发展锰诱导的神经毒性的风险。

DESCRIPTION (provided by applicant) Mn is an essential element that becomes toxic at elevated cellular levels leading to the onset of an incurable neurotoxic syndrome. To date, research on Mn homeostasis and toxicosis in mammals has focused on the mechanisms of Mn influx but the identified influx transporters are neither specific for Mn nor regulated by cellular Mn levels. In contrast, the role of efflux of cytosolic Mn is understudied although efflux plays a significant role in maintaining homeostasis of other metals. The investigators have now identified an important role for efflux of Mn via uptake into the Golgi apparatus followed by secretion in maintaining cellular Mn levels and protecting against excess Mn accumulation during elevated exposure. Based on this, their goal is to elucidate the regulatory mechanisms governing Mn efflux by the Golgi to so as to better understand the role of this fundamental process in Mn homeostasis and in the development of Mn-induced neurotoxicity. The investigators' results indicate that uptake of Mn into the Golgi requires SPCA1, a Golgi-localized Ca/Mn pump and that SPCA1 rapidly traffics between the Golgi and endosomes. As subcellular trafficking of ion pumps regulate their activity, their first aim is to elucidate the role of SPCA1 trafficking in regulating Mn efflux. The investigators also discovered that increased intra-Golgi Mn induces rapid degradation of the Golgi protein GPP130 and that GPP130 levels impact Mn efflux and toxicity. Therefore, the second aim is to elucidate the mechanism by which GPP130 regulates Mn efflux and toxicity. Finally, as additional factors regulating Mn efflux remain to be identified, the third aim is to perform a genome wide RNAi screen for proteins that alter control of Mn by the Golgi. In the screen, a modified version of GPP130 will serve as a novel sensor of Golgi lumenal Mn. The proposed studies will provide mechanistic understanding of a crucial but unexplored aspect of Mn homeostasis that is directly relevant to the pathobiology of Mn-induced neurotoxicity. Public Health Relevance: Manganese is an environmental and occupational toxin that leads to the onset of a Parkinson-like neurologic disease with no cure. The proposed work will determine the mechanism by which Mn is removed from human cells. This will lay the foundation for making drugs that increase removal of cellular Mn for the treatment of Mn toxicity in the future. It will also enable us to determine if genetic or acquired defects in Mn removal exist in the population that increases the risk of developing Mn-induced neurotoxicity.