Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA.
Int J Mol Sci. 2020 Jun 25;21(12):4542. doi: 10.3390/ijms21124542.
Alzheimer's disease is associated with the aggregation of the amyloid-β peptide (Aβ), resulting in the deposition of amyloid plaques in brain tissue. Recent scrutiny of the mechanisms by which Aβ aggregates induce neuronal dysfunction has highlighted the importance of the Aβ oligomers of this protein fragment. Because of the transient and heterogeneous nature of these oligomers, however, it has been challenging to investigate the detailed mechanisms by which these species exert cytotoxicity. To address this problem, we demonstrate here the use of rationally designed single-domain antibodies (DesAbs) to characterize the structure-toxicity relationship of Aβ oligomers. For this purpose, we use Zn-stabilized oligomers of the 40-residue form of Aβ (Aβ) as models of brain Aβ oligomers and two single-domain antibodies (DesAb and DesAb), designed to bind to epitopes at residues 18-24 and 34-40 of Aβ, respectively. We found that the DesAbs induce a change in structure of the Zn-stabilized Aβ oligomers, generating a simultaneous increase in their size and solvent-exposed hydrophobicity. We then observed that these increments in both the size and hydrophobicity of the oligomers neutralize each other in terms of their effects on cytotoxicity, as predicted by a recently proposed general structure-toxicity relationship, and observed experimentally. These results illustrate the use of the DesAbs as research tools to investigate the biophysical and cytotoxicity properties of Aβ oligomers.
阿尔茨海默病与淀粉样蛋白-β肽（Aβ）的聚集有关，导致脑组织中淀粉样斑块的沉积。最近对 Aβ 聚集诱导神经元功能障碍的机制的仔细研究强调了该蛋白质片段的 Aβ 低聚物的重要性。然而，由于这些低聚物的瞬态和异质性质，研究这些物质发挥细胞毒性的详细机制具有挑战性。为了解决这个问题，我们在这里展示了合理设计的单域抗体（DesAbs）用于表征 Aβ 低聚物的结构-毒性关系。为此，我们使用 Zn 稳定的 40 个残基形式的 Aβ（Aβ）的寡聚物作为脑 Aβ 寡聚物的模型，以及两种单域抗体（DesAb 和 DesAb），分别设计用于结合 Aβ 的残基 18-24 和 34-40 的表位。我们发现 DesAbs 诱导 Zn 稳定的 Aβ 寡聚物的结构发生变化，同时增加其大小和溶剂暴露的疏水性。然后，我们观察到这些寡聚物的大小和疏水性的增加在其对细胞毒性的影响方面相互中和，这与最近提出的一般结构-毒性关系的预测一致，并通过实验观察到。这些结果说明了 DesAbs 作为研究工具在研究 Aβ 低聚物的生物物理和细胞毒性特性方面的用途。
