Amyloid-like features of polyglutamine aggregates and their assembly kinetics
Amyloid-like features of polyglutamine aggregates and their assembly kinetics
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DOI：
10.1021/bi011772q
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发表时间：
2002-06-11
期刊：
影响因子：
2.9
通讯作者：
Wetzel, R
中科院分区：
文献类型：
--
作者：
Chen, SM;Berthelier, V;Wetzel, R
某些蛋白质的多聚谷氨酰胺序列形成聚集体的这种依赖重复长度的趋势，可能是这些序列在诸如亨廷顿病等扩展的CAG重复疾病中具有细胞毒性的基础。我们在此报道了多种多聚谷氨酰胺（polyGln）聚集体的一些特征及其组装途径，它们与普遍认可的淀粉样纤维的定义特征有相似之处。多聚谷氨酰胺的聚集动力学表现出浓度和长度依赖性以及一个可通过接种而缩短的滞后期。多聚谷氨酰胺聚集体呈现出经典的富含β -折叠的圆二色性光谱，这与类淀粉样亚结构相符。这里所描述的所有体外聚集体的基本结构单元是一种宽度约为3纳米的细丝，类似于淀粉样纤维组装过程中的原纤维中间体。我们观察到这些丝状结构要么是孤立的细丝，要么是带状片层的组成部分，或者很少是在类淀粉样扭曲纤维中。这里所描述的所有多聚谷氨酰胺聚集体都能结合硫黄素T并使其荧光光谱发生位移。尽管所有测试的多聚谷氨酰胺聚集体都能结合刚果红染料，但只有相对较长的多聚谷氨酰胺肽的聚集体表现出刚果红双折射，而且这种双折射仅在这些聚集体的一小部分中被观察到。值得注意的是，一种对通用淀粉样纤维构象表位具有高选择性的单克隆抗体能够结合多聚谷氨酰胺聚集体。因此，多聚谷氨酰胺聚集体表现出淀粉样物质的大多数特征，但具有刚果红双折射的扭曲纤维结构在我们在此研究的多聚谷氨酰胺重复长度范围内并不是主要形式。我们还发现多聚谷氨酰胺肽表现出一种不寻常的依赖冷冻的聚集现象，这似乎是由肽和/或缓冲液成分的冷冻浓缩引起的。这具有基础和实际两方面的重要意义。多聚谷氨酰胺的聚集被揭示是一个高度特异性的过程，这与产物分子结构的高度有序性是一致的。这种有序结构，或者导致它的组装过程，可能是在亨廷顿病和其他扩展的CAG重复疾病中观察到的细胞特异性神经元变性的原因。
The repeat length-dependent tendency of the polyglutamine sequences of certain proteins to form aggregates may underlie the cytotoxicity of these sequences in expanded CAG repeat diseases such as Huntington's disease. We report here a number of features of various polyglutamine (polyGln) aggregates and their assembly pathways that bear a resemblance to generally recognized defining features of amyloid fibrils. PolyGln aggregation kinetics displays concentration and length dependence and a lag phase that can be abbreviated by seeding. PolyGln aggregates exhibit classical beta-sheet-rich circular dichroism spectra consistent with an amyloid-like substructure. The fundamental structural unit of all the in vitro aggregates described here is a filament about 3 nm in width, resembling the protofibrillar intermediates in amyloid fibril assembly. We observed these filamentous structures either as isolated threads, as components of ribbonlike sheets, or, rarely, in amyloid-like twisted fibrils. All of the polyGln aggregates described here bind thioflavin T and shift its fluorescence spectrum. Although all polyGln aggregates tested bind the dye Congo red, only aggregates of a relatively long polyGln peptide exhibit Congo red birefringence, and this birefringence is only observed in a small portion of these aggregates. Remarkably, a monoclonal antibody with high selectivity for a generic amyloid fibril conformational epitope is capable of binding polyGln aggregates. Thus, polyGln aggregates exhibit most of the characteristic features of amyloid, but the twisted fibril structure with Congo red birefringence is not the predominant form in the polyGln repeat length range studied here. We also find that polyGln peptides exhibit an unusual freezing-dependent aggregation that appears to be caused by the freeze concentration of peptide and/or buffer components. This is of both fundamental and practical significance. PolyGln aggregation is revealed to be a highly specific process consistent with a significant degree of order in the molecular structure of the product. This ordered structure, or the assembly process leading to it, may be responsible for the cell-specific neuronal degeneration observed in Huntington's and other expanded CAG repeat diseases.