Analysis of the secondary structure of β-amyloid (Aβ42) fibrils by systematic proline replacement
Analysis of the secondary structure of β-amyloid (Aβ42) fibrils by systematic proline replacement
复制标题
DOI：
10.1074/jbc.m406262200
复制
发表时间：
2004-12-10
影响因子：
4.8
通讯作者：
Shirasawa, T
中科院分区：
文献类型：
--
作者：
Morimoto, A;Irie, K;Shirasawa, T
阿尔茨海默病中的淀粉样原纤维主要由40-和42-mer β-淀粉样肽（A β 40和A β 42）组成，其表现出聚集能力和神经毒性。尽管Abeta肽的聚集体富含分子间β折叠，但聚集体中Abeta的精确二级结构仍不清楚。为了鉴定参与β折叠形成的氨基酸残基，合成了34个脯氨酸取代的Abeta 42突变体，并检测了它们对PC 12细胞的聚集能力和神经毒性。脯氨酸很少出现在β折叠中，而它们很容易作为Pro-X角容纳在β转角中。在15-32位的突变体中，只有E22 P-Abeta 42广泛聚集，具有比野生型Abeta 42更强的神经毒性，这表明15-21位和24-32位的残基参与β折叠，22位和23位的转角在Abeta 42的聚集和神经毒性中起关键作用。C-末端脯氨酸突变体（A42 P-、I41 P-和V40 P-Abeta 42）几乎不聚集，具有极弱的细胞毒性，而C-末端苏氨酸突变体（A42 T-和I41 T-Abeta 42）强烈聚集，具有显著的细胞毒性。这些结果表明，Abeta 42的C端两个残基的疏水性与其聚集能力和神经毒性无关，而是C端三个残基采用β折叠。这些结果充分证明了Abeta 42和Abeta 40之间的聚集能力和神经毒性存在很大差异。与此相反，脯氨酸突变体的N-末端13个残基显示出强大的聚集能力和神经毒性类似的野生型Abeta 42。Abeta 42 β折叠区的鉴定是设计新的Abeta肽聚集抑制剂的基础。
Amyloid fibrils in Alzheimer's disease mainly consist of 40- and 42-mer beta-amyloid peptides (Abeta40 and Abeta42) that exhibit aggregative ability and neurotoxicity. Although the aggregates of Abeta peptides are rich in intermolecular beta-sheet, the precise secondary structure of Abeta in the aggregates remains unclear. To identify the amino acid residues involved in the beta-sheet formation, 34 proline-substituted mutants of Abeta42 were synthesized and their aggregative ability and neurotoxicity on PC12 cells were examined. Prolines are rarely present in beta-sheet, whereas they are easily accommodated in beta-turn as a Pro-X corner. Among the mutants at positions 15-32, only E22P-Abeta42 extensively aggregated with stronger neurotoxicity than wild-type Abeta42, suggesting that the residues at positions 15-21 and 24-32 are involved in the beta-sheet and that the turn at positions 22 and 23 plays a crucial role in the aggregation and neurotoxicity of Abeta42. The C-terminal proline mutants (A42P-, I41P-, and V40P-Abeta42) hardly aggregated with extremely weak cytotoxicity, whereas the C-terminal threonine mutants (A42T- and I41T-Abeta42) aggregated potently with significant cytotoxicity. These results indicate that the hydrophobicity of the C-terminal two residues of Abeta42 is not related to its aggregative ability and neurotoxicity, rather the C-terminal three residues adopt the beta-sheet. These results demonstrate well the large difference in aggregative ability and neurotoxicity between Abeta42 and Abeta40. In contrast, the proline mutants at the N-terminal 13 residues showed potent aggregative ability and neurotoxicity similar to those of wild-type Abeta42. The identification of the beta-sheet region of Abeta42 is a basis for designing new aggregation inhibitors of Abeta peptides.