Charcot Marie Tooth disease 4A - GDAP1-mediated redox-dependent interaction of mitochondria with the cytoskeleton

Charcot-Marie-Tooth病4A是一种常染色体隐性遗传性多发性神经病，由线粒体蛋白GDAP1(神经节苷脂诱导分化相关蛋白1)突变引起。到目前为止，还没有专门的疗法来治疗这种毁灭性的疾病。我们最近发现，携带GDAP1突变的患者来源的运动神经元显示出更多的管状线粒体，降低的线粒体钙水平，以及抑制的丙酮酸脱氢酶复合体(PDC)。PDC功能障碍导致细胞代谢重新连接，以谷氨酰胺依赖和增加对脂肪酸β氧化的依赖来为三羧酸循环提供乙酰辅酶A。我们确定肌动蛋白聚合蛋白cofilin-1(CFL1)和肌动蛋白细胞骨架的其他蛋白是GDAP1新的相互作用伙伴。GDAP1-CFL1相互作用的中断会导致线粒体附近丝状肌动蛋白的减少，从而阻止主要裂变因子Drp1进入线粒体。因此，这种新的相互作用可以解释在各种GDAP1功能丧失模型中观察到的有缺陷的线粒体分裂和更管状的线粒体形状，但尚不清楚这是否也介导了代谢变化。由于GDAP1是一种潜在的谷胱甘肽转移酶，我们推测GDAP1在与细胞骨架蛋白相互作用时，通过细胞骨架蛋白的翻译后修饰来调节肌动蛋白的动态。根据这一假设，我们已经通过氧化还原蛋白质组学确定了可能的靶蛋白；大约四分之一的蛋白与相互作用组重叠。在这个项目中，我们将专注于这些潜在的相互作用因子的一个子集，并研究GDAP1是否调节它们的氧化还原状态和功能，以及这是否介导了线粒体钙水平的降低和对PDC的抑制。我们还旨在确定可以逆转GDAP1功能丧失引发的代谢功能障碍的饮食和化合物，并在(患者来源的)GDAP1缺乏模型和最近建立的Fly模型中研究它们的效果。总而言之，该项目旨在进一步描述人类疾病的病理生理学特征，并确定其治疗的潜在药物靶点。

Charcot-Marie-Tooth disease 4A is an autosomal-recessive polyneuropathy caused by mutation of the mitochondrial protein GDAP1 (Ganglioside-induced differentiation associated protein 1). To date, no specific therapy exists to treat this devastating disease. We recently showed that patient-derived motoneurons carrying GDAP1 mutations display more tubular mitochondria, reduced mitochondrial Ca2+ levels, and an inhibited pyruvate dehydrogenase complex (PDC). The PDC dysfunction results in a rewired cellular metabolism characterized by glutamine dependence and increased reliance on fatty acid β-oxidation to supply acetyl-CoA for the tricarboxylic acid cycle. We identified Cofilin-1 (CFL1), an actin-polymerizing protein, and other proteins of the actin cytoskeleton as novel interaction partners of GDAP1. Disrupted GDAP1-CFL1 interaction leads to a reduced presence of filamentous actin in the proximity of mitochondria, precluding access of the major fission factor DRP1 to mitochondria. Thus, this novel interaction can explain the defective mitochondrial fission and the more tubular mitochondrial shape observed in various GDAP1 loss of function models but it is unclear if this also mediates the metabolic changes. As GDAP1 is a putative glutathione transferase, we hypothesize that GDAP1, upon interacting with proteins of the cytoskeleton, regulates actin dynamics via post-translational modification of cytoskeletal proteins. In line with this hypothesis, we have identified putative target proteins by redox proteomics; about a fourth of which overlap with the interactome. In this project, we will concentrate on a subset of these potential interactors and study if GDAP1 regulates their redox state and function and if this mediates the reduced mitochondrial Ca2+ levels and inhibition of the PDC. We also aim to identify diets and compounds that can revert the metabolic dysfunction instigated by GDAP1 loss of function and study their effect in (patient-derived) models of GDAP1 deficiency and in a recently established fly model. Together, this project aims to further characterize the pathophysiology of a human disease and identify potential drug targets for its treatment.