Jin Sha, Kedia Niraja, Illes-Toth Eva, Haralampiev Ivan, Prisner Simon, Herrmann Andreas, Wanker Erich E, Bieschke Jan
From the Proteomics and Molecular Mechanisms of Neurodegenerative Diseases, Max Delbrück Center for Molecular Medicine, 13125 Berlin-Buch, Germany, the Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63130.
the Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63130.
J Biol Chem. 2016 Sep 9;291(37):19590-606. doi: 10.1074/jbc.M115.691840. Epub 2016 Jul 25.
The accumulation of amyloid β peptide(1-42) (Aβ(1-42)) in extracellular plaques is one of the pathological hallmarks of Alzheimer disease (AD). Several studies have suggested that cellular reuptake of Aβ(1-42) may be a crucial step in its cytotoxicity, but the uptake mechanism is not yet understood. Aβ may be present in an aggregated form prior to cellular uptake. Alternatively, monomeric peptide may enter the endocytic pathway and conditions in the endocytic compartments may induce the aggregation process. Our study aims to answer the question whether aggregate formation is a prerequisite or a consequence of Aβ endocytosis. We visualized aggregate formation of fluorescently labeled Aβ(1-42) and tracked its internalization by human neuroblastoma cells and neurons. β-Sheet-rich Aβ(1-42) aggregates entered the cells at low nanomolar concentration of Aβ(1-42). In contrast, monomer uptake faced a concentration threshold and occurred only at concentrations and time scales that allowed Aβ(1-42) aggregates to form. By uncoupling membrane binding from internalization, we found that Aβ(1-42) monomers bound rapidly to the plasma membrane and formed aggregates there. These structures were subsequently taken up and accumulated in endocytic vesicles. This process correlated with metabolic inhibition. Our data therefore imply that the formation of β-sheet-rich aggregates is a prerequisite for Aβ(1-42) uptake and cytotoxicity.
淀粉样β肽（1-42）（Aβ（1-42））在细胞外斑块中的积累是阿尔茨海默病（AD）的病理特征之一。多项研究表明，细胞对Aβ（1-42）的再摄取可能是其细胞毒性的关键步骤，但摄取机制尚不清楚。Aβ在细胞摄取之前可能以聚集形式存在。或者，单体肽可能进入内吞途径，内吞区室中的条件可能诱导聚集过程。我们的研究旨在回答聚集形成是Aβ内吞作用的先决条件还是结果这一问题。我们观察了荧光标记的Aβ（1-42）的聚集形成，并追踪了其被人神经母细胞瘤细胞和神经元内化的过程。富含β-折叠的Aβ（1-42）聚集体在低纳摩尔浓度的Aβ（1-42）下进入细胞。相比之下，单体摄取存在浓度阈值，且仅在允许Aβ（1-42）聚集体形成的浓度和时间尺度下发生。通过将膜结合与内化解偶联，我们发现Aβ（1-42）单体迅速与质膜结合并在那里形成聚集体。这些结构随后被摄取并积聚在内吞小泡中。这一过程与代谢抑制相关。因此，我们的数据表明，富含β-折叠的聚集体的形成是Aβ（1-42）摄取和细胞毒性的先决条件。
