期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：35
页码：15595-15600
DOI：10.1073/pnas.1001740107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Soluble oligomeric aggregates of the amyloid-{beta} peptide (A{beta}) have been implicated in the pathogenesis of Alzheimer's disease (AD). Although the conformation adopted by A{beta} within these aggregates is not known, a {beta}-hairpin conformation is known to be accessible to monomeric A{beta}. Here we show that this {beta}-hairpin is a building block of toxic A{beta} oligomers by engineering a double-cysteine mutant (called A{beta}CC) in which the {beta}-hairpin is stabilized by an intramolecular disulfide bond. A{beta}40CC and A{beta}42CC both spontaneously form stable oligomeric species with distinct molecular weights and secondary-structure content, but both are unable to convert into amyloid fibrils. Biochemical and biophysical experiments and assays with conformation-specific antibodies used to detect A{beta} aggregates in vivo indicate that the wild-type oligomer structure is preserved and stabilized in A{beta}CC oligomers. Stable oligomers are expected to become highly toxic and, accordingly, we find that {beta}-sheet-containing A{beta}42CC oligomers or protofibrillar species formed by these oligomers are 50 times more potent inducers of neuronal apoptosis than amyloid fibrils or samples of monomeric wild-type A{beta}42, in which toxic aggregates are only transiently formed. The possibility of obtaining completely stable and physiologically relevant neurotoxic A{beta} oligomer preparations will facilitate studies of their structure and role in the pathogenesis of AD. For example, here we show how kinetic partitioning into different aggregation pathways can explain why A{beta}42 is more toxic than the shorter A{beta}40, and why certain inherited mutations are linked to protofibril formation and early-onset AD.
关键词：amyloid-β peptide ; protein aggregation ; protein structure ; protofibril ; β-hairpin conformation
