Mitochondrial iron-sulfur mechanisms in Friedreich's ataxia

描述(申请人提供)：Friedreich‘s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，影响美国数千人，全球数千人。Friedreich‘s共济失调是由于线粒体Frataxin蛋白表达不足所致。在之前的资助期间，我们实现了我们的目标，证明了Frataxin与线粒体的铁-硫簇机制密切接触，并特异性地改变铁-硫转录本，铁-硫簇缺陷是Frataxin缺陷细胞中最早可观察到的问题，由此导致的缺陷包括血红素缺乏和炎症。在目前的提案中，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重点是定点突变和结合研究，以确定Frataxin与ISCU、ISD11、GRP75和Hsc20的接触。目的2从β-氧化、蛋白质不解性、生物能量学、血红素缺乏和炎症等方面探讨铁硫缺乏对背根神经节细胞和雪旺细胞的病理生理影响。目标3旨在通过测量Friedreich‘s共济失调最佳小鼠模型的原代DRG神经元和雪旺细胞中的这些参数，并通过微阵列来确认在目标2中观察到的最强烈的缺陷。目的4研究大多数Friedreich‘s患者致死的心脏变性的两种最可能的病理生理机制，即β氧化假说和桥粒假说。目标5是在细胞系、原代细胞和整个动物中测试用于挽救在目标2、3和4中观察到的病理生理后果的基于机制的化合物。这些目标紧紧地集中在弗里德里希共济失调的病理生理机制(S)以及抑制这些过程的治疗方法上。公共卫生相关性：Friedreich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人。数千名美国人被诊断出患有弗里德里希共济失调。Friedreich的研究结果导致线粒体蛋白Frataxin的表达减少。我们的工作主要集中在Frataxin的功能，以及由于Frataxin缺乏而导致的神经和心脏退化的病理生理机制。我们的工作(目标5)专门专注于筛选和测试潜在Friedreich共济失调治疗的基于机制的药物的翻译目标。

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.