Irie Yumi, Murakami Kazuma, Hanaki Mizuho, Hanaki Yusuke, Suzuki Takashi, Monobe Yoko, Takai Tomoyo, Akagi Ken-Ichi, Kawase Taiji, Hirose Kenji, Irie Kazuhiro
Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University , Kyoto 606-8502, Japan.
National Institute of Biomedical Innovation, Health and Nutrition , Osaka 567-0085, Japan.
ACS Chem Neurosci. 2017 Apr 19;8(4):807-816. doi: 10.1021/acschemneuro.6b00390. Epub 2017 Jan 12.
The formation of soluble oligomers of amyloid β42 and 40 (Aβ42, Aβ40) is the initial event in the pathogenesis of Alzheimer's disease (AD). Based on previous systematic proline replacement and solid-state NMR, we proposed a toxic dimer structure of Aβ42, a highly aggregative alloform, with a turn at positions 22 and 23, and a hydrophobic core in the C-terminal region. However, in addition to Aβ42, Aβ40 dimers can also contribute to AD progression because of the more abundance of Aβ40 monomer in biological fluids. Here, we describe the synthesis and characterization of three dimer models of the toxic-conformation constrained E22P-Aβ40 using l,l-2,6-diaminopimeric acid (DAP) or l,l-2,8-diaminoazelaic acid (DAZ) linker at position 30, which is incorporated into the intermolecular parallel β-sheet region, and DAP at position 38 in the C-terminal hydrophobic core. E22P-A30DAP-Aβ40 dimer (1) and E22P-A30DAZ-Aβ40 dimer (2) existed mainly in oligomeric states even after 2 weeks incubation without forming fibrils, unlike the corresponding monomer. Their neurotoxicity toward SH-SY5Y neuroblastoma cells was very weak. In contrast, E22P-G38DAP-Aβ40 dimer (3) formed β-sheet-rich oligomeric aggregates, and exhibited more potent neurotoxicity than the corresponding monomer. Ion mobility-mass spectrometry suggested that high molecular-weight oligomers (12-24-mer) of 3 form, but not for 1 and 2 after 4 h incubation. These findings indicate that formation of the hydrophobic core at the C-terminus, rather than intermolecular parallel β-sheet, triggers the formation of toxic Aβ oligomers. Compound 3 may be a suitable model for studying the etiology of Alzheimer's disease.
淀粉样蛋白β42和40（Aβ42、Aβ40）可溶性寡聚体的形成是阿尔茨海默病（AD）发病机制中的初始事件。基于先前的系统性脯氨酸置换和固态核磁共振，我们提出了Aβ42（一种高度聚集的异构体）的有毒二聚体结构，其在22和23位有一个转角，在C端区域有一个疏水核心。然而，除了Aβ42，Aβ40二聚体也可能导致AD进展，因为生物体液中Aβ40单体更为丰富。在此，我们描述了三种有毒构象受限的E22P - Aβ40二聚体模型的合成与表征，这些模型在30位使用l，l - 2,6 - 二氨基庚二酸（DAP）或l，l - 2,8 - 二氨基壬二酸（DAZ）连接子，该连接子被纳入分子间平行β - 折叠区域，以及在C端疏水核心的38位使用DAP。E22P - A30DAP - Aβ40二聚体（1）和E22P - A30DAZ - Aβ40二聚体（2）即使在孵育2周后也主要以寡聚状态存在，未形成纤维，这与相应单体不同。它们对SH - SY5Y神经母细胞瘤细胞的神经毒性非常弱。相比之下，E22P - G38DAP - Aβ40二聚体（3）形成了富含β - 折叠的寡聚聚集体，并且比相应单体表现出更强的神经毒性。离子淌度 - 质谱表明，孵育4小时后，3形成高分子量寡聚体（12 - 24聚体），而1和2则未形成。这些发现表明，C端疏水核心的形成而非分子间平行β - 折叠触发了有毒Aβ寡聚体的形成。化合物3可能是研究阿尔茨海默病病因的合适模型。
