Dynamin-related protein 1, neurodegeneration and Huntington's disease

描述(申请人提供)：亨廷顿病(HD)是一种致命的常染色体显性遗传性神经退行性疾病，由亨廷顿蛋白基因第一外显子内编码谷氨酰胺的CAG扩张引起。尽管与该病相关的基因突变已被确定，但HD的分子和细胞基础尚不清楚，成功治疗该病仍难以捉摸。基础研究和临床研究表明，线粒体功能障碍在HD的发病机制中起重要作用。线粒体以高度动态的管状网络组织起来，通过相反的融合和分裂过程不断重塑。动力蛋白相关蛋白1(Dynamin-Related Protein 1，Drp1)是一个大的GTP酶，是控制线粒体分裂的关键蛋白。最近的研究强调了DRp1介导的过度线粒体分裂在HD细胞培养模型中神经元死亡中的原因作用。然而，目前尚不清楚Drp1过度激活如何介导HD患者线粒体损伤和神经变性，以及药物抑制Drp1激活是否足以减轻突变型Htt(MtHtt)引起的神经毒性和神经变性。我们最近的工作表明，在HD细胞培养和体内HD R6/2转基因小鼠脑中，Drp1被转移到线粒体并高度激活。重要的是，利用我们团队最近开发的一种新型的选择性DRp1多肽抑制剂p110，我们发现抑制依赖于Drp1的线粒体损伤可以纠正HD细胞培养中的线粒体功能障碍和神经细胞死亡，并减少HD R6/2转基因小鼠的行为缺陷和纹状体神经元的丢失。此外，p110治疗纠正了线粒体的形态，减少了HD患者诱导的多能干细胞(HD-iPS细胞)来源的GABA能纹状体神经元的轴突丢失和细胞死亡。此外，使用无偏倚的蛋白质组学分析，我们最近描述了来自HD Patient-iPS细胞的神经元培养中Drp1的相互作用组。我们的初步研究确定了两个机制上不同的候选蛋白(线粒体AAA-ATPase家族成员ATADA3和丝氨酸/苏氨酸激酶MAPK1)，它们参与了DRp1介导的神经元损伤。这些证据表明，Drp1过度激活是HD神经退行性变的主要原因。因此，我们假设，在体外和体内，抑制Drp1介导的线粒体损伤是减少HD模型神经病理的一种新方法。利用生化、成像、生物能量学、蛋白质组学和药理学方法，从动物到患者神经元，我们在这一应用中的目标是从机制和治疗细节两个方面揭开Drp1介导的线粒体功能障碍在神经退行性变中的复杂性。这项研究将为DRp1介导的线粒体分裂在HD发病机制中的作用提供新的信息，并为研究纹状体神经元的线粒体病理学提供一个有用的模型系统。我们还将开发抑制HD发病机制的药理学工具，作为开发HD新疗法的第一步。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a fatal, autosomal dominant, neurodegenerative disorder caused by a glutamine-coding CAG expansion within exon 1 of the huntingtin gene. Although the genetic mutation associated with the disease has been identified, the molecular and cellular basis of HD is not yet understood and successful treatment for this disease remains elusive. Basic research and clinical studies indicate that mitochondrial dysfunction plays an important role in the pathogenesis of HD. Mitochondria are organized in a highly dynamic tubular network that is continuously reshaped by opposing processes of fusion and fission. Dynamin-related protein 1 (Drp1) is a large GTPase and a key protein governing mitochondrial fission. Recent studies have highlighted the causal role of Drp1-mediated excessive mitochondrial fission in neuronal death in HD cell culture models. However, how Drp1 hyperactivation mediates mitochondrial damage and neurodegeneration in HD and whether pharmacological inhibition of Drp1 activation is sufficient to reduce mutant Htt (mtHtt)-induced neurotoxicity and neurodegeneration are not known. Our recent work showed that Drp1 is translocated to the mitochondria and hyper-activated in both HD cell cultures and in vivo in the HD R6/2 transgenic mouse brain. Importantly, using a novel and selective peptide inhibitor of Drp1, P110, recently developed in our group, we found that inhibition of Drp1-dependent mitochondrial impairment corrected mitochondrial dysfunction and neuronal cell death in HD cell cultures, and reduced behavioral deficits and loss of striatal neurons in HD R6/2 transgenic mice. Moreover, treatment with P110 corrected mitochondrial morphology and reduced neurite loss and cell death in GABAergic striatal neurons derived from HD patient- induced pluripotent stem cells (HD-iPS cells). Further, using unbiased proteomic analysis, we recently profiled the interactome of Drp1 in neuronal cultures derived from HD patient-iPS cells. Our preliminary studies identified two mechanistically distinct candidate proteins (ATADA3, a member of mitochondrial AAA-ATPase family, and MAPK1, a serine/threonine kinase) that are involved in Drp1-mediated neuronal damage. These lines of evidence indicate that Drp1 hyperactivation is a predominant cause of neurodegeneration in HD. Thus, we hypothesize that inhibition of Drp1-mediated mitochondrial damage is a novel approach for reducing neuropathology in HD models in vitro and in vivo. Using biochemical, imaging, bio-energetic, proteomic and pharmacological approaches ranging from animals to patient neurons, our goal in this application is to unravel the complexity of Drp1-mediated mitochondrial dysfunction in neurodegeneration in both mechanistic and therapeutic detail. The proposed study will produce novel information on the role of Drp1-mediated mitochondrial fission in the pathogenesis of HD and provide a useful model system in which to study mitochondrial pathology in striatal neurons. We will also generate pharmacological tools to inhibit HD pathogenesis as a first step towards the development of novel therapeutics for HD.