Huntington's disease age-of-onset linked to polyglutamine aggregation nucleation
Huntington's disease age-of-onset linked to polyglutamine aggregation nucleation
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DOI：
10.1073/pnas.182276099
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发表时间：
2002-09-03
影响因子：
11.1
通讯作者：
Wetzel, R
中科院分区：
文献类型：
--
作者：
Chen, SM;Ferrone, FA;Wetzel, R
在亨廷顿氏病和相关的CAG重复扩增疾病中，在相应的疾病蛋白中含有36个重复的多聚谷氨酰胺[poly（Gln）]序列是良性的，而仅具有2-3个额外谷氨酰胺的序列与疾病风险相关。高于此阈值范围，较长的重复长度与较早的发病年龄相关。为了研究这些效应的生物物理基础，我们研究了一系列聚（Gln）肽的体外聚集动力学。我们发现，在37 degreesC的溶液中的聚（Gln）肽进行随机卷曲的β-折叠过渡与动力学叠加在其聚集动力学，这表明没有可溶性的，β-折叠丰富的中间体在聚集过程中。聚集体生长的时间过程的细节证实聚（Gln）聚集通过成核生长聚合发生。然而，令人惊讶的是，与蛋白质的有核生长聚合的传统模型相反，我们发现聚集核是单体。也就是说，聚（Gln）聚集的成核对应于不利的蛋白质折叠反应。使用动力学分析得出的参数，我们估计良性和病理性长度聚（Gln）之间的成核自由能差异小于1 kcal/mol。我们还使用的动力学参数来计算预测的聚集曲线非常低浓度的聚（谷氨酰胺），可能会获得在细胞中。预测的聚集滞后时间的重复长度依赖性差异与亨廷顿病的长度依赖性发病年龄差异在相同的范围内，这表明聚（Gln）聚集成核的生物物理学可能在确定疾病发作中发挥重要作用。
in Huntington's Disease and related expanded CAG repeat diseases, a polyglutamine [poly(Gin)] sequence containing 36 repeats in the corresponding disease protein is benign, whereas a sequence with only 2-3 additional glutamines is associated with disease risk. Above this threshold range, longer repeat lengths are associated with earlier ages-of-onset. To investigate the biophysical basis of these effects, we studied the in vitro aggregation kinetics of a,series of poly(Gin) peptides. We find that poly(Gin) peptides in solution at 37degreesC undergo a random coil to beta-sheet transition with kinetics superimposable on their aggregation kinetics, suggesting the absence of soluble, beta-sheet-rich intermediates in the aggregation process. Details of the time course of aggregate growth confirm that poly(Gin) aggregation occurs by nucleated growth polymerization. Surprisingly, however, and in contrast to conventional models of nucleated growth polymerization of proteins, we find that the aggregation nucleus is a monomer. That is, nucleation of poly(Gin) aggregation corresponds to an unfavorable protein folding reaction. Using parameters derived from the kinetic analysis, we estimate the difference in the free energy of nucleus formation between benign and pathological length poly(Gln)s to be less than 1 kcal/mol. We also use the kinetic parameters to calculate predicted aggregation curves for very low concentrations of poly(Gln) that might obtain in the cell. The repeat-length-dependent differences in predicted aggregation lag times are in the same range as the length-dependent age-of-onset differences in Huntington's disease, suggesting that the biophysics of poly(Gin) aggregation nucleation may play a major role in determining disease onset.