Elucidation of aggregation mechanism of Alzheimer's β-peptides and development of their aggregation inhibitors

阿尔茨海默病的神经病理学特征是淀粉样蛋白在辫状实质和皮质血管中的进行性沉积。这种沉积物主要由40和42聚体的β淀粉样肽（Aβ40、Aβ42）组成，具有神经毒性和聚集能力。家族性阿尔茨海默病中的脑淀粉样血管病（CAA）与这些Aβ肽编码区内的错义突变有关。为了阐明Aβ肽的聚集机制，我们合成了CAA中发现的Aβ40和Aβ42的所有变体，并以高纯度的形式在PC 12细胞中检测了它们的神经毒性和聚集能力，所有Aβ40 22和23位突变体都显示出比野生型Aβ40更强的神经毒性。Aβ42 22和23位突变体的神经毒性也有类似的趋势，其神经毒性是相应Aβ40突变体的50 ~ 200倍，表明这些Aβ42突变体主要参与CAA的发病。特别是，E 关于我们 22 Q-A β42（荷兰）和E22 K-A β42（意大利）广泛聚集，支持荷兰和意大利患者被诊断为遗传性脑出血伴淀粉样变性的临床证据。相比之下，A21 G（佛兰芒）突变除了Aβ突变体的理化性质外，还需要其他解释。FI-IR光谱表明聚集增加了Aβ肽的β折叠含量。然而，转角也是聚集的关键二级结构，因为22和23位的残基优选形成两个残基的β-转角显著增强聚集能力。只有E22 P-A β42广泛聚集，神经毒性比野生型Aβ42强，表明15 - 21和24 - 32位残基参与分子间β折叠的形成，22和23位转角的形成在Aβ肽的聚集和神经毒性中起关键作用。这些发现为设计新的Aβ肽聚集抑制剂奠定了基础。少

Alzheimer's disease is neuropathologically characterized by the progressive deposition of amyloid in the braid parenchyma and cortical blood vessels. This deposition mainly consists of 40-and 42-mer β-amyloid peptides (Aβ40, Aβ42) which show neurotoxicity and aggregative ability. Cerebral amyloid angiopathy (CAA) in familial Alzheimer's disease is related to missense mutations inside the coding region of these Aβpeptides. In order to clarify the aggregation mechanism of Aβpeptides, all of the variants of Aβ40 and Aβ42 found in CAA were synthesized in a highly pure form and examined for neurotoxicity in PC12 cells and aggregative ability.All of the Aβ40 mutants at positions 22 and 23 showed stronger neurotoxicity than wild-type Aβ40. Similar tendency was observed for Aβ42 mutants at positions 22 and 23 whose neurotoxicity was 50〜200 times stronger than that of the corresponding Aβ40 mutants, indicating that these Aβ42 mutants are mainly involved in the pathogenesis of CAA. Especially, E … More 22Q-Aβ42 (Dutch) and E22K-Aβ42 (Italian) aggregated extensively, supporting the clinical evidence that Dutch and Italian patients are diagnosed as hereditary cerebral hemorrhage with amyloidosis. In contrast, A21 G (Flemish) mutation needs alternative explanation with the exception of physicochemical properties of Aβmutants. The FI-IR spectra suggested that aggregation increases theβ-sheet contents of the Aβpeptides. However, turn was also a critical secondary structure for aggregation since residues at positions 22 and 23 that preferably form two-residue β-turn significantly enhanced the aggregative ability.To identify amino acid residues that are important for the β-sheet formation, a series of proline-substituted mutants of Aβ42 was synthesized and their aggregative ability and neurotoxicity were investigated. Only E22P-Aβ42 extensively aggregated with stronger neurotoxicity than wild-type Aβ42, suggesting that the residues at positions 15〜21 and 24〜32 are involved in the intermolecular β-sheet formation, and that turn formation at positions 22 and 23 plays a crucial role in the aggregation and neurotoxicity of Aβpeptides. These findings become a basis for designing new aggregation inhibitors of Aβpeptides. Less