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

描述（由申请人提供）：亨廷顿舞蹈病（HD）是一种致命的常染色体显性神经退行性疾病，由亨廷顿基因1外显子内谷氨酰胺编码CAG扩增引起。虽然与疾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，而且这种疾病的成功治疗仍然难以捉摸。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。线粒体组织在一个高度动态的管状网络中，通过相反的融合和裂变过程不断重塑。动力蛋白相关蛋白1 （Drp1）是一个较大的GTPase，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的因果作用。然而，Drp1过度激活如何介导HD的线粒体损伤和神经退行性变，以及药物抑制Drp1激活是否足以减少突变型Htt （mtHtt）诱导的神经毒性和神经退行性变尚不清楚。我们最近的研究表明，在HD细胞培养和HD R6/2转基因小鼠大脑中，Drp1被转移到线粒体并被超激活。重要的是，使用我们小组最近开发的一种新的选择性Drp1肽抑制剂P110，我们发现抑制Drp1依赖的线粒体损伤纠正了HD细胞培养中的线粒体功能障碍和神经元细胞死亡，并减少了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治疗可以纠正线粒体形态，减少来自HD患者诱导的多能干细胞（HD- ips细胞）的gaba能纹状体神经元的神经突损失和细胞死亡。此外，利用无偏倚的蛋白质组学分析，我们最近分析了来自HD患者ips细胞的神经元培养物中Drp1的相互作用组。我们的初步研究确定了两种机制不同的候选蛋白（线粒体aaa - atp酶家族成员ATADA3和丝氨酸/苏氨酸激酶MAPK1），它们参与drp1介导的神经元损伤。这些证据表明，Drp1过度激活是HD患者神经退行性变的主要原因。因此，我们假设抑制drp1介导的线粒体损伤是一种减少体内和体外HD模型神经病理的新方法。利用从动物到患者神经元的生化、成像、生物能量、蛋白质组学和药理学方法，我们的目标是揭示drp1介导的线粒体功能障碍在神经退行性变中的复杂性，包括机制和治疗细节。本研究将对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.