Laboratory of Neuropathology, Institute of Pathology, Center for Clinical Research at the University of Ulm, Ulm, Germany.
Neurobiol Aging. 2012 Nov;33(11):2641-60. doi: 10.1016/j.neurobiolaging.2011.12.032. Epub 2012 Feb 2.
Soluble amyloid β-protein (Aβ) aggregates have been identified in the Alzheimer's disease (AD) brain. Dispersed Aβ aggregates in the brain parenchyma are different from soluble, membrane-associated and plaque-associated solid aggregates. They are in mixture with the extra- or intracellular fluid but can be separated from soluble proteins by ultracentrifugation. To clarify the role of dispersible Aβ aggregates for neurodegeneration we analyzed 2 different amyloid precursor protein (APP)-transgenic mouse models. APP23 mice overexpress human mutant APP with the Swedish mutation. APP51/16 mice express high levels of human wild type APP. Both mice develop Aβ-plaques. Dendritic degeneration, neuron loss, and loss of asymmetric synapses were seen in APP23 but not in APP51/16 mice. The soluble and dispersible fractions not separated from one another were received as supernatant after centrifugation of native forebrain homogenates at 14,000 × g. Subsequent ultracentrifugation separated the soluble, i.e., the supernatant, from the dispersible fraction, i.e., the resuspended pellet. The major biochemical difference between APP23 and APP51/16 mice was that APP23 mice exhibited higher levels of dispersible Aβ oligomers, protofibrils and fibrils precipitated with oligomer (A11) and protofibril/fibril (B10AP) specific antibodies than APP51/16 mice. These differences, rather than soluble Aβ and Aβ plaque pathology were associated with dendritic degeneration, neuron, and synapse loss in APP23 mice in comparison with APP51/16 mice. Immunoprecipitation of dispersible Aβ oligomers, protofibrils, and fibrils revealed that they were associated with APP C-terminal fragments (APP-CTFs). These results indicate that dispersible Aβ oligomers, protofibrils, and fibrils represent an important pool of Aβ aggregates in the brain that critically interact with membrane-associated APP C-terminal fragments. The concentration of dispersible Aβ aggregates, thereby, presumably determines its toxicity.
可溶性淀粉样β蛋白（Aβ）聚集体已在阿尔茨海默病（AD）脑中被发现。脑实质中分散的 Aβ聚集体与可溶性、膜相关和斑块相关的固体聚集体不同。它们与细胞外或细胞内液混合，但可以通过超速离心与可溶性蛋白分离。为了阐明可分散 Aβ聚集体对神经退行性变的作用，我们分析了 2 种不同的淀粉样前体蛋白（APP）转基因小鼠模型。APP23 小鼠过度表达具有瑞典突变的人突变 APP。APP51/16 小鼠表达高水平的人野生型 APP。两种小鼠均发展出 Aβ 斑块。在 APP23 小鼠中可见树突变性、神经元丢失和不对称突触丢失，但在 APP51/16 小鼠中未见。未分离的可溶性和可分散部分在 14,000×g 离心原生大脑匀浆后作为上清液接收。随后的超速离心将可溶性部分，即上清液，与可分散部分，即重新悬浮的沉淀分离。APP23 和 APP51/16 小鼠之间的主要生化差异在于 APP23 小鼠表现出更高水平的可分散 Aβ 寡聚体、原纤维和纤维，这些物质用寡聚体（A11）和原纤维/纤维（B10AP）特异性抗体沉淀。与 APP51/16 小鼠相比，这些差异而非可溶性 Aβ 和 Aβ 斑块病理学与 APP23 小鼠中的树突变性、神经元和突触丢失相关。可分散的 Aβ 寡聚体、原纤维和纤维的免疫沉淀表明它们与 APP C 端片段（APP-CTFs）相关。这些结果表明，可分散的 Aβ 寡聚体、原纤维和纤维代表脑中 Aβ 聚集体的一个重要池，与膜相关的 APP C 端片段密切相互作用。可分散 Aβ 聚集体的浓度，因此，可能决定其毒性。
