Biomedical Sciences Graduate Program, University of Central Florida, Orlando, FL, USA.
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA.
FEBS J. 2017 May;284(9):1355-1369. doi: 10.1111/febs.14058. Epub 2017 Apr 10.
Amyloid β (Aβ) peptide plays a major role in Alzheimer's disease (AD) and occurs in multiple forms, including pyroglutamylated Aβ (AβpE). Identification and characterization of the most cytotoxic Aβ species is necessary for advancement in AD diagnostics and therapeutics. While in brain tissue multiple Aβ species act in combination, structure/toxicity studies and immunotherapy trials have been focused on individual forms of Aβ. As a result, the molecular composition and the structural features of "toxic Aβ oligomers" have remained unresolved. Here, we have used a novel approach, hydration from gas phase coupled with isotope-edited Fourier transform infrared (FTIR) spectroscopy, to identify the prefibrillar assemblies formed by Aβ and AβpE and to resolve the structures of both peptides in combination. The peptides form unusual β-sheet oligomers stabilized by intramolecular H-bonding as opposed to intermolecular H-bonding in the fibrils. Time-dependent morphological changes in peptide assemblies have been visualized by atomic force microscopy. Aβ/AβpE hetero-oligomers exert unsurpassed cytotoxic effect on PC12 cells as compared to oligomers of individual peptides or fibrils. These findings lead to a novel concept that Aβ/AβpE hetero-oligomers, not just Aβ or AβpE oligomers, constitute the main neurotoxic conformation. The hetero-oligomers thus present a new biomarker that may be targeted for development of more efficient diagnostic and immunotherapeutic strategies to combat AD.
淀粉样蛋白β（Aβ）肽在阿尔茨海默病（AD）中起主要作用，并且以多种形式存在，包括焦谷氨酸化的 Aβ（AβpE）。鉴定和描述最具细胞毒性的 Aβ 物种对于 AD 诊断和治疗的进展是必要的。虽然在脑组织中多种 Aβ 物种联合作用，但结构/毒性研究和免疫疗法试验一直集中在 Aβ 的个别形式上。结果，“毒性 Aβ 低聚物”的分子组成和结构特征仍未得到解决。在这里，我们使用了一种新方法，即气相水合作用与同位素编辑傅里叶变换红外（FTIR）光谱相结合，来鉴定 Aβ 和 AβpE 形成的原纤维前组装体，并解析这两种肽的结构。这些肽形成了不寻常的β-折叠寡聚物，这些寡聚物通过分子内氢键稳定，而不是在纤维中通过分子间氢键稳定。通过原子力显微镜观察到肽组装体的时间依赖性形态变化。与单个肽或纤维的寡聚物相比，Aβ/AβpE 杂寡聚物对 PC12 细胞表现出无与伦比的细胞毒性作用。这些发现导致了一个新的概念，即 Aβ/AβpE 杂寡聚物，而不仅仅是 Aβ 或 AβpE 寡聚物，构成了主要的神经毒性构象。因此，杂寡聚物提供了一个新的生物标志物，可用于开发更有效的诊断和免疫治疗策略来对抗 AD。
