Lee Sungmun, Fernandez Erik J, Good Theresa A
Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
Protein Sci. 2007 Apr;16(4):723-32. doi: 10.1110/ps.062514807. Epub 2007 Feb 27.
beta-amyloid peptide (Abeta) is one of the main protein components of senile plaques associated with Alzheimer's disease (AD). Abeta readily aggregates to forms fibrils and other aggregated species that have been shown to be toxic in a number of studies. In particular, soluble oligomeric forms are closely related to neurotoxicity. However, the relationship between neurotoxicity and the size of Abeta aggregates or oligomers is still under investigation. In this article, we show that different Abeta incubation conditions in vitro can affect the rate of Abeta fibril formation, the conformation and stability of intermediates in the aggregation pathway, and toxicity of aggregated species formed. When gently agitated, Abeta aggregates faster than Abeta prepared under quiescent conditions, forming fibrils. The morphology of fibrils formed at the end of aggregation with or without agitation, as observed in electron micrographs, is somewhat different. Interestingly, intermediates or oligomers formed during Abeta aggregation differ greatly under agitated and quiescent conditions. Unfolding studies in guanidine hydrochloride indicate that fibrils formed under quiescent conditions are more stable to unfolding in detergent than aggregation associated oligomers or Abeta fibrils formed with agitation. In addition, Abeta fibrils formed under quiescent conditions were less toxic to differentiated SH-SY5Y cells than the Abeta aggregation associated oligomers or fibrils formed with agitation. These results highlight differences between Abeta aggregation intermediates formed under different conditions and provide insight into the structure and stability of toxic Abeta oligomers.
β-淀粉样肽（Aβ）是与阿尔茨海默病（AD）相关的老年斑的主要蛋白质成分之一。Aβ很容易聚集形成纤维以及其他聚集形式，多项研究表明这些聚集形式具有毒性。特别是，可溶性寡聚体形式与神经毒性密切相关。然而，神经毒性与Aβ聚集体或寡聚体大小之间的关系仍在研究中。在本文中，我们表明体外不同的Aβ孵育条件会影响Aβ纤维形成的速率、聚集途径中中间体的构象和稳定性以及所形成聚集形式的毒性。轻轻搅拌时，Aβ比在静态条件下制备的Aβ聚集得更快，形成纤维。在电子显微镜下观察，无论有无搅拌，聚集结束时形成的纤维形态都有所不同。有趣的是，Aβ聚集过程中形成的中间体或寡聚体在搅拌和静态条件下差异很大。在盐酸胍中的展开研究表明，在静态条件下形成的纤维在去污剂中比聚集相关的寡聚体或搅拌形成的Aβ纤维更稳定，不易展开。此外，在静态条件下形成的Aβ纤维对分化的SH-SY5Y细胞的毒性低于搅拌形成的Aβ聚集相关寡聚体或纤维。这些结果突出了在不同条件下形成的Aβ聚集中间体之间的差异，并为有毒Aβ寡聚体的结构和稳定性提供了见解。
