Role of Species-Specific Primary Structure Differences in A尾42 Assembly and Neurotoxicity

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• 作者：Robin Roychaudhuri ; Xueyun Zheng ; Aleksey Lomakin ; Panchanan Maiti ; Margaret M. Condron ; George B. Benedek ; Gal Bitan ; Michael T. Bowers ; David B. Teplow
• 刊名：ACS Chemical Neuroscience
• 出版年：2015
• 出版时间：December 16, 2015
• 年：2015
• 卷：6
• 期：12
• 页码：1941-1955
• 全文大小：776K
• ISSN：1948-7193

文摘

A variety of species express the amyloid 尾-protein (A尾 (the term 鈥淎尾鈥?refers both to A尾40 and A尾42, whereas 鈥淎尾40鈥?and 鈥淎尾42鈥?refer to each isoform specifically). Those species expressing A尾 with primary structure identical to that expressed in humans have been found to develop amyloid deposits and Alzheimer鈥檚 disease-like neuropathology. In contrast, the A尾 sequence in mice and rats contains three amino acid substitutions, Arg5Gly, His13Arg, and Tyr10Phe, which apparently prevent the development of AD-like neuropathology. Interestingly, the brush-tailed rat, Octodon degus, expresses A尾 containing only one of these substitutions, His13Arg, and does develop AD-like pathology. We investigate here the biophysical and biological properties of A尾 peptides from humans, mice (Mus musculus), and rats (Octodon degus). We find that each peptide displays statistical coil 鈫?尾-sheet secondary structure transitions, transitory formation of hydrophobic surfaces, oligomerization, formation of annuli, protofibrils, and fibrils, and an inverse correlation between rate of aggregation and aggregate size (faster aggregation produced smaller aggregates). The rank order of assembly rate was mouse > rat > A尾42. The rank order of neurotoxicity of assemblies formed by each peptide immediately after preparation was A尾42 > mouse 鈮?rat. These data do not support long-standing hypotheses that the primary factor controlling development of AD-like neuropathology in rodents is A尾 sequence. Instead, the data support a hypothesis that assembly quaternary structure and organismal responses to toxic peptide assemblies mediate neuropathogenetic effects. The implication of this hypothesis is that a valid understanding of disease causation within a given system (organism, tissue, etc.) requires the coevaluation of both biophysical and cell biological properties of that system.