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

描述(申请人提供)：亨廷顿病(HD)是一种进行性和最终致命的神经退行性疾病，在美国约有30000人受到困扰，没有有效的治疗方法。先天性巨结肠症是由亨廷顿蛋白基因内的CAG扩张引起的。HD的病理特征是神经元堆积可溶的和聚集的误折叠亨廷顿蛋白，神经元变性，主要累及纹状体和新皮质。越来越多的证据表明，突变的亨廷顿蛋白(Huntingtin Protein，mHTT)的可溶性寡聚体是HD发病的重要介质。我们的长期目标是确定mHTT寡聚体在HD中的作用，并确定降低寡聚体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，突变的亨廷顿蛋白的一些寡聚体是通过半胱氨酸残基的定点氧化形成的。这些发现使我们假设氧化依赖的mHTT寡聚体是HD的重要介质。在这项建议中，我们计划解决这些寡聚物种在HD发病机制中的作用。在目标1中，我们将确定如何通过阻止或加速突变的亨廷顿蛋白在小鼠纹状体中的二聚化来改变HD进程。我们的假设是，突变的亨廷顿蛋白的二聚化促进了HD的进展。我们将使用慢病毒系统来产生表达二聚化或抵抗二聚化的突变型N171-82Q亨廷顿蛋白的小鼠，并评估行为、生化和解剖疾病的结果。在目标2中，我们将使用细胞培养系统筛选一种硫醇转移酶(S)，该酶能促进可溶性低聚亨廷顿蛋白转化为单体。我们假设，促进这种转化的硫醇转移酶也会继而导致突变的亨廷顿蛋白水平下降。拟议的研究将促进我们对HD神经变性机制的理解，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潜在机制有关，拟议中的研究也可能揭示这些疾病。

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.