p38 MAPK activation as a therapeutic target for Friedreich ataxia

项目概要/摘要 对于常染色体隐性遗传的神经和心脏退行性疾病Friedreich， 共济失调（FA）。FA是由编码蛋白质共济失调蛋白的基因中的亚型突变引起的。Frataxin定位 线粒体基质和铁硫簇（ISCs）的生物发生中的功能，这是重要的 线粒体内和线粒体外酶的辅基。我们发现p38 MAP激酶应激- 反应途径在FA细胞中组成性过度活化，可能是由于持续的氧化应激和/或 DNA损伤反应（DDR）我们的假设是p38蛋白的慢性过度激活 调节ISC生物发生复合体中一个关键蛋白的信号通路是适应不良反馈回路的一部分 进一步抑制FA细胞中ISC的生物发生;因此，抑制p38途径，或其活化， 抵消共济失调蛋白功能降低的有害作用。我们的初步研究表明脂质 脂质过氧化和端粒损伤在FA发病机制，这两个激活p38，这两个都是 ISC缺陷的后果。我们假设FA细胞中的ISC生物合成将增加，并且FA- 通过（i）抑制p38和/或MK2改善相关缺陷，其将p38与ISC生物发生联系起来;或（ii） p38激活的减少，通过氧化应激（特别是脂质过氧化）的减少或 DDR减少（特别是继发于临界端粒缩短）。与基因互补 方法，我们将测试已知靶向这些途径的化合物，使我们能够阐明这些途径的作用。 这些途径在FA发病机制，同时推进我们的总体目标， 优先考虑潜在的临床开发化合物。我们的具体目标是：目标1。利用成纤维细胞 探讨p38-MAPK通路、氧化应激和DNA相互作用的模型 FA发病机制中的损害，并测试相关药物和药物靶点以改善 与FA相关的缺陷。我们将检验我们的假设，即p38通路的组成性过度激活在 FA细胞代表了一个适应不良的反馈回路，抑制这一通路可以抵消有害的 降低共济失调蛋白功能的作用，从而改善FA相关缺陷。结合使用 基因和小分子方法，我们将测试抗氧化剂，抗DDR剂和p38/MK2的作用 抑制p38活化、ISC生物发生和FA相关缺陷。目标2和3。使用FA iPSC- 衍生的心肌细胞和感觉神经元（Aim 2）和FA斑马鱼（Aim 3），以测试我们的 在体外和体内受影响的细胞类型的假设。利用基因和小分子的结合 方法，我们将测试抗氧化剂、抗DDR剂和p38/MK2抑制对p38活化的影响， ISC生物发生和FA相关缺陷在这些模型中得到验证。我们预计将产生重大的积极影响： 我们的初步研究已经将这些途径与FA病理生理学联系起来， 已经开发了一些途径，在某些情况下，已经在其他疾病的临床试验中。

PROJECT SUMMARY/ABSTRACT There are no approved therapies for the autosomal-recessive neuro- and cardio-degenerative disorder Friedreich ataxia (FA). FA is caused by hypomorphic mutations in the gene encoding the protein frataxin. Frataxin localizes to the mitochondrial matrix and functions in the biogenesis of iron-sulfur-clusters (ISCs), which are important prosthetic groups for both intra- and extra-mitochondrial enzymes. We found that the p38 MAP kinase stress- response pathway is constitutively hyperactivated in FA cells, likely as a result of ongoing oxidative stress and/or an ongoing DNA damage response (DDR). Our working hypothesis is that chronic hyperactivation of the p38 pathway, which modulates a key protein in the ISC biogenesis complex, is part of a maladaptive feedback loop that further suppresses ISC biogenesis in FA cells; hence, inhibition of the p38 pathway, or of its activation, counteracts the deleterious effects of decreased frataxin function. Our preliminary studies have implicated lipid peroxidation and telomere damage in FA pathogenesis, both of which activate p38, and both of which are consequences of ISC deficiency. We hypothesize that ISC biogenesis in FA cells will be increased, and FA- associated defects ameliorated, by (i) inhibition of p38 and/or MK2, which links p38 to ISC biogenesis; or (ii) a reduction in p38 activation, either through a decrease in oxidative stress (particularly lipid peroxidation) or a decrease in the DDR (particularly secondary to critical telomere shortening). Complemented by genetic approaches, we will test compounds that are known to target these pathways, allowing us to elucidate the roles of these pathways in FA pathogenesis while simultaneously advancing our overall goal of identifying and prioritizing compounds for potential clinical development. Our Specific Aims are: Aim 1. To use fibroblast models to interrogate the interrelated roles of the p38-MAPK pathway, oxidative stress, and DNA damage in the pathogenesis of FA, and to test relevant drugs and drug targets for amelioration of FA-associated defects. We will test our hypothesis that constitutive hyperactivation of the p38 pathway in FA cells represents a maladaptive feedback loop, and that inhibiting this pathway counteracts the deleterious effects of decreased frataxin function, thereby ameliorating FA-associated defects. Using a combination of genetic and small-molecule approaches, we will test the effects of antioxidants, anti-DDR agents, and p38/MK2 inhibition on p38 activation, ISC biogenesis, and FA-associated defects. Aims 2 and 3. To use FA iPSC- derived cardiomyocytes and sensory neurons (Aim 2), and FA zebrafish (Aim 3), to test our hypotheses in affected cell types in vitro and in vivo. Using a combination of genetic and small-molecule approaches, we will test the effects of antioxidants, anti-DDR agents, and p38/MK2 inhibition on p38 activation, ISC biogenesis, and FA-associated defects validated in these models. We anticipate a significant positive impact: our preliminary studies already link these pathways to FA pathophysiology, and compounds targeting these pathways have been developed and, in some cases, are already in clinical trials for other disorders.