Biochemical stages of amyloid-β peptide aggregation and accumulation in the human brain and their association with symptomatic and pathologically preclinical Alzheimer's disease
Biochemical stages of amyloid-β peptide aggregation and accumulation in the human brain and their association with symptomatic and pathologically preclinical Alzheimer's disease
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DOI：
10.1093/brain/awt362
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发表时间：
2014-03-01
期刊：
影响因子：
14.5
通讯作者：
Thal, Dietmar Rudolf
中科院分区：
文献类型：
--
作者：
Upadhaya, Ajeet Rijal;Kosterin, Irina;Thal, Dietmar Rudolf
阿尔茨海默氏病的特征是淀粉样β肽在大脑中沉积。据报道，N 端截短导致 A beta (N3pE) 的形成和丝氨酸 8 的磷酸化可改变淀粉样蛋白 - β 的聚集特性。生物化学上，可溶性、可分散性、膜相关性和不溶性、斑块相关性β-淀粉样蛋白聚集体已被区分。可溶性和可分散的β淀粉样蛋白聚集体均与细胞外液或细胞内液混合，但可分散的聚集体可以通过超速离心从溶液中的蛋白质中清除。为了阐明磷酸化淀粉样蛋白-β 和 Aβ(N3pE) 在可溶性、可分散性、膜相关性和斑块相关性淀粉样蛋白-β 聚集体中在阿尔茨海默病发病机制中的作用，我们研究了 21 例有症状的阿尔茨海默病患者、33 例病理性临床前阿尔茨海默病病例和 20 例对照病例的大脑。蛋白质印迹分析表明，在阿尔茨海默氏病最早的临床前阶段，可溶性、可分散性、膜相关性和斑块相关性淀粉样蛋白-β 聚集体并未表现出可检测量的 Aβ(N3pE) 和磷酸化淀粉样蛋白-β。该阶段被称为淀粉样蛋白-β聚集和积累的生化阶段1。在生化淀粉样蛋白-β 2 阶段中，还发现了 A beta(N3pE)，而磷酸化淀粉样蛋白-β 仅限于生化淀粉样蛋白-β 3 阶段，即淀粉样蛋白-β 聚集的最后阶段。在可分散、膜相关和斑块相关部分中观察到磷酸化淀粉样蛋白-β。我们样本中所有有症状的阿尔茨海默氏病病例均符合生化β-淀粉样蛋白第3阶段标准，即检测到磷酸化β-淀粉样蛋白。大多数（但不是全部）病理性临床前阿尔茨海默病病例的生化淀粉样蛋白 β 阶段为 1 或 2 期。免疫组织化学证实了淀粉样蛋白斑中淀粉样蛋白 β、A β (N3pE) 和磷酸化淀粉样蛋白 β 的分层发生。因此，在所有有症状的阿尔茨海默病病例中都可以看到含有磷酸化淀粉样蛋白的斑块，但仅在少数非痴呆对照受试者中可见。生化β-淀粉样蛋白阶段与β-淀粉样蛋白斑块沉积的扩张以及神经原纤维缠结病理学相关。综上所述，我们证明 A beta(N3pE) 和磷酸化淀粉样蛋白-β 不仅可以在斑块中检测到，而且可以在斑块外的可溶性和可分散的淀粉样蛋白-β 聚集体中检测到。它们以分层顺序出现，可以区分三个阶段。根据我们的研究结果，人们很容易推测β-淀粉样蛋白聚集和积累的这种分层生化序列与疾病进展有关，并且可能与β-淀粉样蛋白聚集体毒性的增加有关。
Alzheimer's disease is characterized by the deposition of amyloid-beta peptide in the brain. N-terminal truncation resulting in the formation of A beta(N3pE) and phosphorylation at serine 8 have been reported to modify aggregation properties of amyloid-beta. Biochemically, soluble, dispersible, membrane-associated, and insoluble, plaque-associated amyloid-beta aggregates have been distinguished. Soluble and dispersible amyloid-beta aggregates are both in mixture with the extracellular or intracellular fluid but dispersible aggregates can be cleared from proteins in solution by ultracentrifugation. To clarify the role of phosphorylated amyloid-beta and A beta(N3pE) in soluble, dispersible, membrane-associated, and plaque-associated amyloid-beta aggregates in the pathogenesis of Alzheimer's disease we studied brains from 21 cases with symptomatic Alzheimer's disease, 33 pathologically preclinical Alzheimer's disease cases, and 20 control cases. Western blot analysis showed that soluble, dispersible, membrane-associated and plaque-associated amyloid-beta aggregates in the earliest preclinical stage of Alzheimer's disease did not exhibit detectable amounts of A beta(N3pE) and phosphorylated amyloid-beta. This stage was referred to as biochemical stage 1 of amyloid-beta aggregation and accumulation. In biochemical amyloid-beta stage 2, A beta(N3pE) was additionally found whereas phosphorylated amyloid-beta was restricted to biochemical amyloid-beta stage 3, the last stage of amyloid-beta aggregation. Phosphorylated amyloid-beta was seen in the dispersible, membrane-associated, and plaque-associated fraction. All cases with symptomatic Alzheimer's disease in our sample fulfilled biochemical amyloid-beta stage 3 criteria, i.e. detection of phosphorylated amyloid-beta. Most, but not all, cases with pathologically preclinical Alzheimer's disease had biochemical amyloid-beta stages 1 or 2. Immunohistochemistry confirmed the hierarchical occurrence of amyloid-beta, A beta(N3pE), and phosphorylated amyloid-beta in amyloid plaques. Phosphorylated amyloid-beta containing plaques were, thereby, seen in all symptomatic cases with Alzheimer's disease but only in a few non-demented control subjects. The biochemical amyloid-beta stages correlated with the expansion of amyloid-beta plaque deposition and with that of neurofibrillary tangle pathology. Taken together, we demonstrate that A beta(N3pE) and phosphorylated amyloid-beta are not only detectable in plaques, but also in soluble and dispersible amyloid-beta aggregates outside of plaques. They occur in a hierarchical sequence that allows the distinction of three stages. In light of our findings, it is tempting to speculate that this hierarchical, biochemical sequence of amyloid-beta aggregation and accumulation is related to disease progression and may be relevant for an increasing toxicity of amyloid-beta aggregates.