Department of Medicinal Chemistry, Center for Frontier Research in Medicinal Science, Kyoto Pharmaceutical University, Kyoto 607-8412, Japan.
Bioorg Med Chem. 2011 Jun 15;19(12):3787-92. doi: 10.1016/j.bmc.2011.04.056. Epub 2011 May 6.
The recently identified E22Δ-type amyloid β peptide (Aβ) mutants are reported to favor oligomerization over fibrillization and to exhibit more-potent synaptotoxicity than does wild-type (WT) Aβ. Aβ(E22Δ) mutants can thus be expected to serve as tools for clarifying the impact of Aβ oligomers in Alzheimer's disease (or Alzheimer's-type dementia). However, the biochemical and biophysical properties of Aβ(E22Δ) have not been conclusively determined. Here, we evaluated the self-assembly pathways of Aβ(E22Δ) mutants generated from water-soluble, non-aggregative O-acyl isopeptide precursors. Circular dichroism spectroscopy, Western blot analysis, and thioflavin-T fluorescence intensity and cellular toxicity assays suggest that the self-assembly pathways of Aβ(E22Δ) differed from those of Aβ(WT). Aβ1-40(E22Δ) underwent a rapid random coil→β-sheet conformational change in its monomeric or low-molecular-weight oligomeric states, whereas Aβ1-40(WT) self-assembled gradually without losing its propensity to form random coil structures. The Aβ1-42(E22Δ) monomer formed β-sheet-rich oligomers more rapidly than did Aβ1-42(WT). Additionally, the Aβ1-42(E22Δ) oligomers appear to differ from Aβ1-42(WT) oligomers in size, shape, or both. These results should provide new insights into the functions of Aβ(E22Δ) mutants.
最近发现的 E22Δ 型淀粉样 β 肽 (Aβ) 突变体倾向于寡聚化而不是纤维化，并且比野生型 (WT) Aβ 具有更强的突触毒性。因此，可以预期 Aβ(E22Δ) 突变体将作为阐明 Aβ 寡聚物在阿尔茨海默病 (或阿尔茨海默病型痴呆) 中的作用的工具。然而，Aβ(E22Δ) 的生化和生物物理特性尚未得到明确确定。在这里，我们评估了水溶性、非聚集 O-酰基异肽前体产生的 Aβ(E22Δ) 突变体的自组装途径。圆二色光谱、Western blot 分析、硫黄素 T 荧光强度和细胞毒性测定表明，Aβ(E22Δ) 的自组装途径不同于 Aβ(WT)。Aβ1-40(E22Δ) 在其单体或低分子量寡聚物状态下迅速经历无规卷曲→β-折叠构象变化，而 Aβ1-40(WT) 则逐渐自组装，而不会失去形成无规卷曲结构的倾向。Aβ1-42(E22Δ) 单体比 Aβ1-42(WT) 更快地形成富含β-折叠的寡聚物。此外，Aβ1-42(E22Δ) 寡聚物在大小、形状或两者上似乎与 Aβ1-42(WT) 寡聚物不同。这些结果应该为 Aβ(E22Δ) 突变体的功能提供新的见解。
