Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96 Gothenburg, Sweden.
Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96 Gothenburg, Sweden.
Biochim Biophys Acta Biomembr. 2017 Oct;1859(10):1921-1929. doi: 10.1016/j.bbamem.2017.05.012. Epub 2017 May 28.
Alzheimer's disease is associated with the aggregation of amyloid-β (Aβ) peptides into oligomers and fibrils. We have explored how model lipid membranes modulate the rate and mechanisms of Aβ(1-42) self-assembly, in order to shed light on how this pathological reaction may occur in the lipid-rich environments that the peptide encounters in the brain. Using a combination of in vitro biophysical experiments and theoretical approaches, we show that zwitterionic DOPC lipid vesicles accelerate the Aβ(1-42) fibril growth rate by interacting specifically with the growing fibrils. We probe this interaction with help of a purpose-developed Förster resonance energy transfer assay that monitors the proximity between a fibril-specific dye and fluorescent lipids in the lipid vesicle membrane. To further rationalise these findings we use mathematical models to fit the aggregation kinetics of Aβ(1-42) and find that lipid vesicles alter specific mechanistic steps in the aggregation reaction; they augment monomer-dependent secondary nucleation at the surface of existing fibrils and facilitate monomer-independent catalytic processes consistent with fibril fragmentation. We further show that DOPC vesicles have no effect on primary nucleation. This finding is consistent with experiments showing that Aβ(1-42) monomers do not directly bind to the lipid bilayer. Taken together, our results show that plain lipid membranes with charge and composition that is representative of outer cell membranes can significantly augment autocatalytic steps in the self-assembly of Aβ(1-42) into fibrils. This new insight suggests that strategies to reduce fibril-lipid interactions in the brain may have therapeutic value.
阿尔茨海默病与淀粉样β（Aβ）肽聚集成低聚物和纤维有关。我们探索了模型脂质膜如何调节 Aβ（1-42）自组装的速率和机制，以便了解这种病理反应如何在肽在大脑中遇到的富含脂质的环境中发生。我们使用体外生物物理实验和理论方法的组合，表明带电荷的 DOPC 脂质囊泡通过与生长的纤维特异性相互作用来加速 Aβ（1-42）纤维生长速率。我们使用专门开发的Förster 共振能量转移测定法来探测这种相互作用，该测定法监测纤维特异性染料与脂质囊泡膜中荧光脂质之间的接近度。为了进一步合理化这些发现，我们使用数学模型拟合 Aβ（1-42）的聚集动力学，并发现脂质囊泡改变了聚集反应中的特定机制步骤；它们增加了单体依赖的现有纤维表面上的二次成核，并促进了单体独立的催化过程，与纤维碎片一致。我们进一步表明，DOPC 囊泡对初级成核没有影响。这一发现与实验一致，表明 Aβ（1-42）单体不会直接与脂质双层结合。总的来说，我们的结果表明，具有代表性的细胞膜外电荷和组成的普通脂质膜可以显著增加 Aβ（1-42）自组装成纤维的自动催化步骤。这一新的见解表明，减少大脑中纤维 - 脂质相互作用的策略可能具有治疗价值。
