Mitochondrial iron-sulfur mechanisms in Friedreich's ataxia

描述（由申请人提供）：弗里德赖希共济失调（FRDA）是一种遗传性线粒体神经退行性和脱髓鞘疾病，在美国影响数千人，在全球影响数千人。弗里德赖希共济失调是由于线粒体共济失调蛋白表达不足所致。在上一个资助期，我们通过证明frataxin与线粒体的铁-硫簇机制密切接触并特异性改变铁-硫转录物来实现我们的目标，并且铁-硫簇缺陷是frataxin缺陷细胞中最早可观察到的问题，并且随之而来的缺陷包括血红素缺乏和炎症。在目前的建议中，我们将扩展我们对铁硫簇合成缺陷如何导致神经变性，脱髓鞘和心脏变性的理解。目的1：研究frataxin与ISCU、ISD 11、GRP 75和Hsc 20的结合位点。目的2的重点是确定在背根神经节和雪旺细胞系的铁硫缺乏症的病理生理后果，在β-氧化，蛋白质不溶性，生物能量学，血红素缺乏症和炎症。目标3是针对确认目标2中观察到的最强缺陷，通过测量来自弗里德赖希共济失调的最佳小鼠模型的原代DRG神经元和许旺细胞中的这些参数，并通过微阵列。目的4将研究两个最可能的病理生理机制的心脏变性是致命的大多数弗里德赖希的患者，即β-氧化和桥粒假说。目的5是在细胞系、原代细胞和整个动物中测试用于挽救目的2、3和4中观察到的病理生理学后果的基于机制的化合物。这些目标紧紧集中在弗里德赖希共济失调的病理生理机制和抑制这些过程的治疗手段上。公共卫生相关性：弗里德赖希共济失调是最常见的常染色体隐性共济失调，发生频率为1/50，000个体。数千名美国人被诊断出患有弗里德赖希共济失调。Friedreich的结果是线粒体蛋白共济失调蛋白的表达减少。我们的工作主要集中在frataxin的功能，以及由frataxin缺乏引起的神经和心脏变性的病理生理机制。我们的工作（目标5）是专门集中在筛选和测试潜在的弗里德赖希共济失调治疗机制为基础的药物的翻译目标。

DESCRIPTION (provided by applicant): Friedreich's ataxia (FRDA) is an inherited mitochondrial neurodegenerative and demyelinating disease that affects thousands in the US, and several thousands more worldwide. Friedreich's ataxia results from a deficiency in the expression of the mitochondrial frataxin protein. In the previous grant period, we achieved our aims by demonstrating that frataxin makes intimate contact with the iron-sulfur cluster machinery of the mitochondria and alters iron-sulfur transcripts specifically, and that iron-sulfur cluster defects are the earliest observable problems in frataxin-deficient cells, and that consequent defects include heme deficiency and inflammation. In the current proposal, we will extend our understanding of how the defect in iron-sulfur cluster synthesis causes neurodegeneration, demyelination, and cardiodegeneration. Aim 1 is focused on site directed mutagenesis and binding studies to determine the contacts of frataxin with ISCU, ISD11, GRP75 and Hsc20. Aim 2 is focused on determining pathophysiological consequences of iron-sulfur deficiency in dorsal root ganglial and Schwann cell lines, in terms of beta-oxidation, protein insolubility, bioenergetics, heme deficiency and inflammation. Aim 3 is directed at the confirmation of the strongest defects observed in Aim 2, by measuring these parameters in primary DRG neurons and Schwann cells from the best mouse model of Friedreich's ataxia, and by microarray. Aim 4 will investigate the two most likely pathophysiological mechanisms for the cardiodegeneration that is lethal to most Friedreich's patients, i.e. the beta-oxidative and desmosomal hypotheses. Aim 5 is to test mechanism-based compounds for rescue of the pathophysiological consequences observed in Aims 2, 3, and 4, in cell lines, primary cells, and whole animals. These aims are tightly focused on the pathophysiological mechanism(s) of Friedreich's ataxia, and therapeutic means to inhibit these processes. PUBLIC HEALTH RELEVANCE: Friedreich's Ataxia is the most common autosomal recessive ataxia, and occurs with a frequency of 1/50,000 individuals. Several thousand Americans have been diagnosed with Friedreich's ataxia. Friedreich's results in a decreased expression of the mitochondrial protein frataxin. Our work is tightly focused on the function of frataxin, and the pathophysiologic mechanisms of neuro- and cardio-degeneration that result from frataxin-deficiency. Our work (Aim 5) is specifically focused on the translational goal of screening and testing mechanism-based drugs for potential Friedreich's ataxia therapy.