Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 60153, USA.
Integrative Cell Biology Program, Loyola University Chicago, Maywood, IL, 60153, USA.
Acta Neuropathol. 2017 Oct;134(4):629-653. doi: 10.1007/s00401-017-1722-x. Epub 2017 May 19.
Numerous pathological amyloid proteins spread from cell to cell during neurodegenerative disease, facilitating the propagation of cellular pathology and disease progression. Understanding the mechanism by which disease-associated amyloid protein assemblies enter target cells and induce cellular dysfunction is, therefore, key to understanding the progressive nature of such neurodegenerative diseases. In this study, we utilized an imaging-based assay to monitor the ability of disease-associated amyloid assemblies to rupture intracellular vesicles following endocytosis. We observe that the ability to induce vesicle rupture is a common feature of α-synuclein (α-syn) assemblies, as assemblies derived from WT or familial disease-associated mutant α-syn all exhibited the ability to induce vesicle rupture. Similarly, different conformational strains of WT α-syn assemblies, but not monomeric or oligomeric forms, efficiently induced vesicle rupture following endocytosis. The ability to induce vesicle rupture was not specific to α-syn, as amyloid assemblies of tau and huntingtin Exon1 with pathologic polyglutamine repeats also exhibited the ability to induce vesicle rupture. We also observe that vesicles ruptured by α-syn are positive for the autophagic marker LC3 and can accumulate and fuse into large, intracellular structures resembling Lewy bodies in vitro. Finally, we show that the same markers of vesicle rupture surround Lewy bodies in brain sections from PD patients. These data underscore the importance of this conserved endocytic vesicle rupture event as a damaging mechanism of cellular invasion by amyloid assemblies of multiple neurodegenerative disease-associated proteins, and suggest that proteinaceous inclusions such as Lewy bodies form as a consequence of continued fusion of autophagic vesicles in cells unable to degrade ruptured vesicles and their amyloid contents.
在神经退行性疾病中，许多病理性淀粉样蛋白从一个细胞扩散到另一个细胞，从而促进了细胞病理学的传播和疾病的进展。因此，了解与疾病相关的淀粉样蛋白组装体进入靶细胞并诱导细胞功能障碍的机制，是理解此类神经退行性疾病进行性特征的关键。在这项研究中，我们利用基于成像的测定法来监测与疾病相关的淀粉样蛋白组装体在细胞内小泡内化后破裂小泡的能力。我们观察到，诱导小泡破裂的能力是α-突触核蛋白（α-syn）组装体的共同特征，因为源自 WT 或家族性疾病相关突变α-syn 的组装体都具有诱导小泡破裂的能力。同样，WTα-syn 组装体的不同构象应变，但不是单体或寡聚形式，在内化后有效地诱导小泡破裂。诱导小泡破裂的能力不仅限于α-syn，因为具有病理多聚谷氨酰胺重复的tau 和 huntingtin Exon1 的淀粉样蛋白组装体也具有诱导小泡破裂的能力。我们还观察到，α-syn 破裂的小泡对自噬标记物 LC3 呈阳性，并可以在体外积累并融合成类似于路易体的大的细胞内结构。最后，我们表明，PD 患者脑切片中围绕路易体的同样的小泡破裂标志物。这些数据强调了这种保守的内吞小泡破裂事件作为多种神经退行性疾病相关蛋白的淀粉样蛋白组装体对细胞入侵的破坏性机制的重要性，并表明蛋白质包含物（如路易体）的形成是由于无法降解破裂的小泡及其淀粉样内容物的细胞中自噬小泡的持续融合所致。
