The C. Eugene Bennett Department of Chemistry, West Virginia University, 217 Clark Hall, Morgantown, West Virginia 26506, United States.
Rockefeller Neurosciences Institutes, West Virginia University, 1 Medical Center Dr., P.O. Box 9303, Morgantown, West Virginia 26505, United States.
Biochemistry. 2022 Jul 19;61(14):1517-1530. doi: 10.1021/acs.biochem.2c00212. Epub 2022 Jun 27.
Expansion of a polyglutamine (polyQ) domain within the first exon of the huntingtin (htt) protein is the underlying cause of Huntington's disease, a genetic neurodegenerative disorder. PolyQ expansion triggers htt aggregation into oligomers, fibrils, and inclusions. The 17 N-terminal amino acids (Nt17) of htt-exon1, which directly precede the polyQ domain enhances polyQ fibrillization and functions as a lipid-binding domain. A variety of post-translational modifications occur within Nt17, including oxidation of two methionine residues. Here, the impact of oxidation within Nt17 on htt aggregation both in the presence and absence of lipid membranes was investigated. Treatment with hydrogen peroxide (HO) reduced fibril formation in a dose-dependent manner, resulting in shorter fibrils and an increased oligomer population. With excessive HO treatments, fibrils developed a unique morphological feature around their periphery. In the presence of total brain lipid vesicles, HO impacted fibrillization in a similar manner. That is, oligomerization was promoted at the expense of fibril elongation. The interaction of unoxidized and oxidized htt with supported lipid bilayers was directly observed using in situ atomic force microscopy. Without oxidation, granular htt aggregates developed on the bilayer surface. However, in the presence of HO, distinct plateau-like regions initially developed on the bilayer surface that gave way to rougher patches containing granular aggregates. Collectively, these observations suggest that oxidation of methionine residues within Nt17 plays a crucial role in both the aggregation of htt and its ability to interact with lipid surfaces.
亨廷顿病是一种遗传性神经退行性疾病，其根本病因是亨廷顿蛋白（htt）的第一个外显子中的聚谷氨酰胺（polyQ）结构域扩展。polyQ 扩展引发 htt 聚集形成寡聚体、原纤维和包含体。htt-exon1 中直接位于 polyQ 结构域之前的 17 个 N 端氨基酸（Nt17）增强了 polyQ 原纤维形成，并作为一个脂质结合结构域发挥作用。Nt17 中存在多种翻译后修饰，包括两个蛋氨酸残基的氧化。在此，研究了 Nt17 内氧化对 htt 在存在和不存在脂质膜时聚集的影响。过氧化氢（HO）处理以剂量依赖的方式降低了原纤维的形成，导致原纤维变短，寡聚体群体增加。用过量的 HO 处理后，原纤维在其周围发展出一种独特的形态特征。在存在全脑脂质囊泡的情况下，HO 以类似的方式影响原纤维的形成。也就是说，寡聚体的形成以原纤维伸长为代价得到促进。使用原位原子力显微镜直接观察了未氧化和氧化的 htt 与支持脂质双层的相互作用。没有氧化时，颗粒状 htt 聚集体在双层表面上发展。然而，在 HO 的存在下，最初在双层表面上形成明显的平坦区域，然后是含有颗粒状聚集体的更粗糙的斑块。总的来说，这些观察结果表明，Nt17 内蛋氨酸残基的氧化在 htt 的聚集及其与脂质表面相互作用的能力中都起着至关重要的作用。
