Department of Chemistry, The Scripps Research Institute and The Skaggs Institute for Chemical Biology, La Jolla, California, USA.
Nat Chem Biol. 2011 Jul 31;7(9):602-9. doi: 10.1038/nchembio.624.
Amyloid-β amyloidogenesis is reported to occur via a nucleated polymerization mechanism. If this is true, the energetically unfavorable oligomeric nucleus should be very hard to detect. However, many laboratories have detected early nonfibrillar amyloid-β oligomers without observing amyloid fibrils, suggesting that a mechanistic revision may be needed. Here we introduce Cys-Cys-amyloid-β(1-40), which cannot bind to the latent fluorophore FlAsH as a monomer, but can bind FlAsH as an nonfibrillar oligomer or as a fibril, rendering the conjugates fluorescent. Through FlAsH monitoring of Cys-Cys-amyloid-β(1-40) aggregation, we found that amyloid-β(1-40) rapidly and efficiently forms spherical oligomers in vitro (85% yield) that are kinetically competent to slowly convert to amyloid fibrils by a nucleated conformational conversion mechanism. This methodology was used to show that plasmalogen ethanolamine vesicles eliminate the proteotoxicity-associated oligomerization phase of amyloid-β amyloidogenesis while allowing fibril formation, rationalizing how low concentrations of plasmalogen ethanolamine in the brain are epidemiologically linked to Alzheimer's disease.
淀粉样β蛋白的淀粉样生成被报道是通过成核聚合机制发生的。如果这是真的，那么能量上不利的寡聚核应该非常难以检测到。然而，许多实验室已经检测到了早期无纤维状的淀粉样β寡聚物，而没有观察到淀粉样纤维，这表明可能需要对机制进行修正。在这里，我们引入了 Cys-Cys-淀粉样β（1-40），它不能作为单体与潜伏荧光团 FlAsH 结合，但可以作为无纤维状寡聚物或纤维状结合 FlAsH，使缀合物具有荧光性。通过 FlAsH 监测 Cys-Cys-淀粉样β（1-40）的聚集，我们发现淀粉样β（1-40）在体外迅速有效地形成球形寡聚物（85%产率），这些寡聚物在动力学上有能力通过成核构象转化机制缓慢转化为淀粉样纤维。这种方法被用于表明鞘磷脂乙醇胺囊泡消除了淀粉样β淀粉样生成的与蛋白毒性相关的寡聚化阶段，同时允许纤维形成，这合理地解释了为什么大脑中低浓度的鞘磷脂乙醇胺与阿尔茨海默病在流行病学上有关。
