β2-microglobulin amyloid fibrils are nanoparticles that disrupt lysosomal membrane protein trafficking and inhibit protein degradation by lysosomes.
β2-microglobulin amyloid fibrils are nanoparticles that disrupt lysosomal membrane protein trafficking and inhibit protein degradation by lysosomes.
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DOI：
10.1074/jbc.m114.586222
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发表时间：
2014-12-26
期刊：
影响因子：
--
通讯作者：
Hewitt EW
中科院分区：
文献类型：
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作者：
Jakhria T;Hellewell AL;Porter MY;Jackson MP;Tipping KW;Xue WF;Radford SE;Hewitt EW
背景：淀粉样蛋白病的致病因素和病理机制还不清楚。结果如下：β2-微球蛋白淀粉样原纤维显示长度依赖性内化，改变溶酶体膜蛋白的运输，并抑制溶酶体对蛋白质的降解。结论：淀粉样原纤维充当纳米颗粒，破坏膜运输和蛋白质降解。意义：原纤维长度，通过决定进入细胞内室，可能有助于淀粉样疾病。淀粉样原纤维的片段化产生长度减少但分子结构不变的原纤维。所得纳米级原纤维颗粒比未破碎的原纤维更大程度地抑制四唑鎓染料3-（4，5-二甲基噻唑-2-基）-2，5-二苯基溴化四唑鎓（MTT）（一种常用于测量细胞活力的底物）的细胞还原。在这里，我们发现β2-微球蛋白（β 2 m）淀粉样纤维的内化依赖于纤维长度，破碎的纤维更有效地被细胞内化。相应地，抑制片段化β 2 m原纤维的内化拯救了细胞MTT减少。然而，用片段化的β 2 m原纤维孵育细胞不会导致细胞死亡。相反，片段化的β 2 m原纤维在溶酶体中积累，改变溶酶体膜蛋白的运输，并抑制溶酶体对模型蛋白底物的降解。这些发现表明，在淀粉样蛋白组装反应早期或通过较长原纤维的断裂形成的纳米级原纤维可以通过破坏溶酶体的蛋白质降解和内溶酶体途径中的运输在淀粉样蛋白疾病中发挥作用。
Background: The causative agents and pathological mechanisms of amyloid disease are poorly understood. Results: β2-Microglobulin amyloid fibrils display length-dependent internalization, alter trafficking of lysosomal membrane proteins, and inhibit the degradation of proteins by lysosomes. Conclusion: Amyloid fibrils act as nanoparticles that disrupt membrane trafficking and protein degradation. Significance: Fibril length, by determining access to intracellular compartments, may contribute to amyloid disease. Fragmentation of amyloid fibrils produces fibrils that are reduced in length but have an otherwise unchanged molecular architecture. The resultant nanoscale fibril particles inhibit the cellular reduction of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), a substrate commonly used to measure cell viability, to a greater extent than unfragmented fibrils. Here we show that the internalization of β2-microglobulin (β2m) amyloid fibrils is dependent on fibril length, with fragmented fibrils being more efficiently internalized by cells. Correspondingly, inhibiting the internalization of fragmented β2m fibrils rescued cellular MTT reduction. Incubation of cells with fragmented β2m fibrils did not, however, cause cell death. Instead, fragmented β2m fibrils accumulate in lysosomes, alter the trafficking of lysosomal membrane proteins, and inhibit the degradation of a model protein substrate by lysosomes. These findings suggest that nanoscale fibrils formed early during amyloid assembly reactions or by the fragmentation of longer fibrils could play a role in amyloid disease by disrupting protein degradation by lysosomes and trafficking in the endolysosomal pathway.