Function and dysfunction of prion protein in cellular iron metabolism

描述(由申请人提供)：Pron病发病机制涉及的因素的复杂性和多样性阻碍了对有效治疗策略的探索。尽管每一篇报道都加深了我们对Pron病发病机制的理解，但PrPC的正常功能和疾病相关构象PrPSc的毒性机制都不完全清楚。有报道称，在普恩病毒感染的神经母细胞瘤细胞和小鼠模型中，铁代谢异常表明氧化还原铁介导的神经毒性与其他几种神经退行性疾病有关，包括阿尔茨海默病、帕金森氏病、亨廷顿病等。来自我的实验室的最新数据表明，PrPC在人类神经母细胞瘤细胞中作为铁感应、摄取或运输蛋白发挥作用，PrPC的致病突变以每种突变特有的方式改变细胞铁状态。我们还注意到了PrPC通过调节铁的摄取或运输来调节细胞铁状态的证据，这一证据表明PrPC在感染病毒的仓鼠和人脑中存在铁代谢异常，而这种功能的改变是由于疾病状态下的点突变或聚集引起的，从而导致神经毒性。在拟议的研究中，我们将在两个具体目标上检验这一假设。在目标1中，我们将研究PrPC是否参与细胞铁的摄取、外排或转移到铁蛋白，并确定PrP相互作用的蛋白质或影响其铁调节功能的因素。在目标2中，将评估PrP致病突变对细胞铁状态和对自由基损伤的敏感性的影响。表现出对自由基敏感性增加的细胞系将被用来评估铁络合剂和清除自由基的化合物的保护作用。这些研究将在两个不同的领域提高对PrP疾病发病机制的理解：1)阐明PrP在PrP疾病进展过程中改变脑内铁稳态的作用；2)验证铁螯合作用在减轻PrP疾病相关神经毒性方面的有效性。公共卫生相关性：Pron病是一种致命的神经退行性疾病，目前还没有治疗方法。这些疾病具有传染性、家族性和散发性。PrP-scrapie(PrPSc)是所有Prion疾病的主要感染性和病原体，由一种富含β-折叠的Prion蛋白亚型组成，称为PrP-scrapie。我们的数据表明，脑铁稳态的失衡有助于PrPSc的产生和传播，并有助于在这些疾病中观察到神经退行性变。在拟议的研究中，我们将在细胞模型中测试这一假说，并调查铁螯合是否可以作为一种治疗措施来减轻普里恩病相关的神经毒性。

DESCRIPTION (provided by applicant): The complexity and multiplicity of factors involved in prion disease pathogenesis has hampered the search for an effective therapeutic strategy. Though each report has improved our understanding of prion disease pathogenesis, neither the normal function of prion protein (PrPC) nor the mechanism of toxicity by the disease associated conformer PrPSc is entirely clear. Reports of abnormal iron metabolism in prion infected neuroblastoma cells and mouse models implicate redox-iron mediated neurotoxicity in these disorders as has been proposed for several other neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and others. Recent data from my laboratory indicate that PrPC functions as an iron sensing, uptake, or transport protein in human neuroblastoma cells, and pathogenic mutations in PrPC alter cellular iron status in ways that are specific to each mutation. We have also noted evidence of abnormal iron metabolism in prion disease affected hamster and human brains, leading us to hypothesize that PrPC modulates cellular iron status by regulating iron uptake or transport, and alteration of this function due to point mutations or aggregation in the diseased state induces neurotoxicity. In the proposed studies we will check this hypothesis in two specific aims. In aim 1 we will investigate whether PrPC is involved in cellular iron uptake, efflux, or transfer to ferritin, and identify PrP-interacting proteins or factors responsible for its iron modulating function. In aim 2, the influence of pathogenic mutations of PrP on cellular iron status and susceptibility to free radical damage will be assessed. Cell lines exhibiting increased susceptibility to free radicals will be used to evaluate the protective effect of iron chelators and free radical scavenging compounds. These studies will improve understanding of prion disease pathogenesis in two distinct areas: 1) clarify the role of PrP in altering brain iron homeostasis during prion disease progression, and 2) validate the effectiveness of iron chelation in alleviating prion disease associated neurotoxicity. PUBLIC HEALTH RELEVANCE: Prion diseases are fatal neurodegenerative disorders for which there is currently no treatment. These disorders are infectious, familial, and sporadic in nature. The principal infectious and pathogenic agent in all prion disorders comprises of a beta-sheet rich isoform of the prion protein termed PrP-scrapie (PrPSc). Our data suggest that imbalance in brain iron homeostasis helps in the generation and propagation of PrPSc and contributes to the neurodegeneration observed in these disorders. In the proposed studies we will test this hypothesis in cell models, and investigate whether iron chelation can be used as a therapeutic measure to alleviate prion disease associated neurotoxicity.