Knight Patrick D, Karamanos Theodoros K, Radford Sheena E, Ashcroft Alison E
Faculty of Biological Sciences, University of Leeds, Leeds, UK.
Eur J Mass Spectrom (Chichester). 2018 Feb;24(1):129-140. doi: 10.1177/1469066717729298. Epub 2017 Aug 29.
Amyloid diseases represent a growing social and economic burden in the developed world. Understanding the assembly pathway and the inhibition of amyloid formation is key to developing therapies to treat these diseases. The neurodegenerative condition Machado-Joseph disease is characterised by the self-aggregation of the protein ataxin-3. Ataxin-3 consists of a globular N-terminal Josephin domain, which can aggregate into curvilinear protofibrils, and an unstructured, dynamically disordered C-terminal domain containing three ubiquitin interacting motifs separated by a polyglutamine stretch. Upon expansion of the polyglutamine region above 50 residues, ataxin-3 undergoes a second stage of aggregation in which long, straight amyloid fibrils form. A peptide inhibitor of polyglutamine aggregation, known as polyQ binding peptide 1, has been shown previously to prevent the maturation of ataxin-3 fibrils. However, the mechanism of this inhibition remains unclear. Using nanoelectrospray ionisation-mass spectrometry, we demonstrate that polyQ binding peptide 1 binds to monomeric ataxin-3. By investigating the ability of polyQ binding peptide 1 to bind to truncated ataxin-3 constructs lacking one or more domains, we localise the site of this interaction to a 39-residue sequence immediately C-terminal to the Josephin domain. The results suggest a new mechanism for the inhibition of polyglutamine aggregation by polyQ binding peptide 1 in which binding to a region outside of the polyglutamine tract can prevent fibril formation, highlighting the importance of polyglutamine flanking regions in controlling aggregation and disease.
在发达国家，淀粉样疾病给社会和经济带来的负担日益加重。了解淀粉样蛋白的组装途径以及抑制其形成是开发治疗这些疾病疗法的关键。神经退行性疾病马查多-约瑟夫病的特征是ataxin-3蛋白的自我聚集。ataxin-3由一个球状的N端约瑟芬结构域和一个无结构、动态无序的C端结构域组成，前者可聚集成曲线状原纤维，后者包含三个由聚谷氨酰胺延伸段隔开的泛素相互作用基序。当聚谷氨酰胺区域扩展到50个以上残基时，ataxin-3会经历第二个聚集阶段，形成长的直淀粉样纤维。一种聚谷氨酰胺聚集的肽抑制剂，即聚Q结合肽1，此前已被证明可阻止ataxin-3纤维的成熟。然而，这种抑制作用的机制尚不清楚。我们使用纳米电喷雾电离质谱法证明，聚Q结合肽1与单体ataxin-3结合。通过研究聚Q结合肽1与缺失一个或多个结构域的截短ataxin-3构建体结合的能力，我们将这种相互作用的位点定位到约瑟芬结构域C端紧邻的一个39个残基的序列。这些结果提示了聚Q结合肽1抑制聚谷氨酰胺聚集的一种新机制，即与聚谷氨酰胺区域之外的一个区域结合可阻止纤维形成，突出了聚谷氨酰胺侧翼区域在控制聚集和疾病方面的重要性。
