Protein Succination as a Mediator of Neuropathology in Mitochondrial Disease

 描述(由申请人提供)： 摘要以脑病为表现的线粒体疾病以5000例活产儿中1例发生，通常在5岁以下死亡。线粒体疾病是一种呼吸链疾病，线粒体不再有效地运行以产生ATP，通常是由于电子传输链(ETC)的一个或多个组件出现问题。幸运的是，基因测序已经确定了导致这些脑肌病的线粒体或核DNA的大量突变。然而，在大多数情况下，遗传缺陷和神经病理之间仍然没有明确的代谢联系，有效的治疗方法也很少。这项提案中描述的创新研究有望揭示ETC活性降低和神经病理之间的一种新的代谢联系。此前，我们已经检测到一种新的蛋白质翻译后修饰，S-(2-琥珀酸)半胱氨酸(2SC)，它是由Krebs环中间体富马酸与蛋白质中的活性半胱氨酸残基反应形成的。糖尿病患者脂肪细胞中富马酸和琥珀酸化的蛋白质增加，从而干扰蛋白质的功能和周转。富马酸的增加是燃料供应过剩、NADH积累和反馈抑制Krebs循环的结果。在一个新的，这些观察的横向扩展中，我们提出了类似的ETC抑制，例如在Leigh综合征期间复合体I缺乏时，将导致线粒体疾病中NADH、富马酸和琥珀酸化的增加。在初步研究中，我们证明了在Leigh综合征小鼠模型(Ndufs4基因敲除(KO)小鼠)的脑干中可以检测到与神经退行性变相关的几种蛋白质琥珀酸化增加。我们假设线粒体应激导致富马酸的积累，琥珀酸化改变蛋白质的结构或功能，从而导致疾病病理。我们将在特定的目标1中确认这一点。我们已经确定了几个琥珀酸化的靶点，我们计划在特定的目标2中机械地解决这些琥珀酸化如何导致线粒体功能的进一步降低。在特定的目标3中，我们将使用分子策略来区分生物能量缺陷和蛋白质琥珀酸化，并研究旨在减少延胡索酸和琥珀酸化的治疗策略，从而改善线粒体功能和疾病表型。总体而言，这些基础研究将证明琥珀酸化是线粒体应激和神经病理学之间的机械联系，对于阐明治疗线粒体疾病的新的治疗途径具有重要意义。

 DESCRIPTION (provided by applicant): ABSTRACT Mitochondrial diseases manifesting as encephalopathies occur at a rate of 1 in 5000 live births and are often fatal by ~5 years old. Mitochondrial diseases are respiratory chain disorders in which the mitochondria are no longer operating efficiently to produce ATP, usually due to a problem with one or more components of the electron transport chain (ETC). Fortunately, genetic sequencing has identified a large number of the mutations in mitochondrial or nuclear DNA which cause these encephalomyopathies. However, in most cases there is still no clear metabolic link between the genetic defect and the neuropathology, and very few effective treatments. The innovative studies described in this proposal are expected to reveal a novel metabolic link between reduced ETC activity and neural pathology. Previously, we have detected a new post-translational modification of proteins, S-(2-succino)cysteine (2SC), which is formed by reaction of the Krebs cycle intermediate fumarate with reactive cysteine residues in protein. Both fumarate and succination of proteins are increased in adipocytes in diabetes, disturbing protein function and turnover. The increase in fumarate develops as a result of excess fuel supply, accumulation of NADH, and feedback inhibition of the Krebs cycle. In a novel, lateral extension of these observations we propose that a similar inhibition of the ETC, e.g. in Complex I deficiency during Leigh Syndrome, would result in increased NADH, fumarate and succination in mitochondrial disease. In Preliminary Studies, we demonstrate that increased succination of proteins is detectable on several proteins in the brainstem of a mouse model of Leigh syndrome (Ndufs4 knockout (KO) mouse) in association with neurodegeneration. We hypothesize that mitochondrial stress results in the accumulation of fumarate and that succination alters protein structure or function contributing to disease pathology. We will confirm this in Specific Aim 1. We have identified several succinated targets already and we plan to mechanistically address how succination of these leads to further reductions in mitochondrial function in Specific Aim 2. In Specific Aim 3 we will use a molecular strategy to distinguish the bioenergetic defect from protein succination and investigate therapeutic strategies designed to reduce fumarate and succination leading to improvements in mitochondrial function and the disease phenotype. Overall, these foundational studies will demonstrate that succination is a mechanistic link between mitochondrial stress and neuropathology, with important implications for the elucidation of novel therapeutic avenues for the treatment of mitochondrial diseases.