Oxidation-dependent mutant huntingtin oligomers and Huntington's disease pathogen

描述（申请人提供）：亨廷顿舞蹈病（HD）是一种进行性、最终致命的神经退行性疾病，在美国约有3万人患有该疾病，目前尚无有效治疗方法。HD是由亨廷顿蛋白基因内CAG扩增引起的。HD的病理特征是可溶性和聚集性错误折叠的亨廷顿蛋白的神经元积聚和主要累及纹状体和新皮层的神经元变性。越来越多的证据表明突变型亨廷顿蛋白（mhtt）的可溶性寡聚物是HD发病的重要介质。我们的长期目标是确定mhtt低聚物在HD中的作用，并确定降低低聚物水平的干预措施是否对HD小鼠具有神经保护作用，并为治疗人类HD提供有效的靶点。我们有初步的数据表明，突变亨廷顿蛋白的一些低聚物是通过半胱氨酸残基的位点特异性氧化形成的。这些发现使我们假设氧化依赖性mhtt低聚物是HD的重要介质。在本提案中，我们计划解决这些寡聚物种在HD发病机制中的作用。在目的1中，我们将确定如何通过阻断或加速小鼠纹状体中突变的亨廷顿蛋白二聚化来改变HD的进展。我们的假设是突变的亨廷顿蛋白二聚化促进了HD的进展。我们将使用慢病毒系统来产生表达突变型N171-82Q亨廷顿蛋白二聚化或二聚化抗性的小鼠，并评估行为，生化和解剖疾病结果。在目标2中，我们将使用细胞培养系统筛选促进可溶性低聚亨廷顿蛋白转化为单体的硫醇转移酶。我们假设促进这种转化的硫醇转移酶也会导致突变的亨廷顿蛋白水平降低。提出的研究将促进我们对HD神经退行性变机制的理解，并可能导致新的治疗靶点的确定。由于蛋白质低聚物与几种神经退行性疾病的机制有关，因此拟议的研究也可以阐明这些疾病。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a progressive and ultimately fatal neurodegenerative disease that afflicts about 30000 people in the USA and has no effective treatment. HD is caused by a CAG expansion within the huntingtin gene. Pathological hallmarks of HD are neuronal accumulation of soluble and aggregated misfolded huntingtin protein and neuronal degeneration primarily involving striatum and neocortex. There is accumulating evidence that soluble oligomers of mutant huntingtin protein (mhtt) are important mediators of HD pathogenesis. Our long-term objective is to define the role of mhtt oligomers in HD and to determine if interventions that decrease oligomer levels are neuroprotective in HD mice and provide an effective target for treating human HD. We have preliminary data demonstrating that some oligomers of mutant huntingtin form via site-specific oxidation of cysteine residues. These findings have led us to hypothesize that oxidation-dependent mhtt oligomers are important mediators of HD. In this proposal we plan to address the role of these oligomeric species in the pathogenesis of HD. In Aim 1 we will determine how HD progression is modified by blocking or accelerating mutant huntingtin dimerization in mouse striatum. Our hypothesis is that dimerization of mutant huntingtin promotes HD progression. We will use a lentiviral system to generate mice expressing forms of mutant N171-82Q huntingtin that dimerize or are dimerization resistant and evaluate behavioral, biochemical and anatomic disease outcomes. In Aim 2 we will screen using a cell culture system for a thiol transferase enzyme(s) that promotes conversion of soluble oligomeric huntingtin to monomer. We hypothesize that a thiol transferase that promotes this conversion will also secondarily result in decreased mutant huntingtin levels. The proposed studies will advance our understanding of the mechanisms underlying neurodegeneration in HD and could lead to the identification of new therapeutic targets. Because protein oligomers have been implicated in mechanisms underlying several neurodegenerative disorders, the proposed research could also shed light on these diseases.