Amyloid seeds formed by cellular uptake, concentration, and aggregation of the amyloid-beta peptide
Amyloid seeds formed by cellular uptake, concentration, and aggregation of the amyloid-beta peptide
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DOI：
10.1073/pnas.0911281106
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发表时间：
2009-12-01
影响因子：
11.1
通讯作者：
Lee, Jin-Moo
中科院分区：
文献类型：
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作者：
Hu, Xiaoyan;Crick, Scott L.;Lee, Jin-Moo
阿尔茨海默病(AD)的神经病理特征之一是淀粉样斑块，主要由聚集的淀粉样β蛋白(Aβ)多肽组成。在体外，Aβ(1-42)是斑块中发现的Aβ的主要同种异型，在微摩尔浓度和酸性pH下自组装成纤维。在pH值为中性、Aβ浓度在纳摩尔范围内的大脑细胞外液中不存在这种情况。在这里，我们发现细胞外浓度低至1 nM的可溶性Aβ(Saβ)可被小鼠皮质神经元和神经母细胞瘤(SHSY5Y)细胞摄取，但不被人胚胎肾(HEK293)细胞摄取。摄取后，Aβ在LysoTracker阳性的酸性囊泡(可能是晚期的内体或溶酶体)中积累，其中有效浓度(>；2.5µM)比细胞外液中的浓度(25 NM)高两个数量级以上，通过激光扫描共聚焦显微镜的荧光强度来定量。此外，SHSY5Y细胞与1亩Aβ(1-42)孵育数天后，显示出细胞内高分子量(HMW；200 kDa)聚集体的时间依赖性增加，而在Aβ(1-40)存在的细胞中，这些聚集体是不存在的。这些Aβ(1-42)负载细胞的匀浆能够种植淀粉样原纤维生长。这些结果表明，某些细胞可以在较低的生理浓度下摄取细胞外的Aβ，然后浓缩到内体/溶酶体内。在高浓度下，囊泡Aβ聚集形成HMW物种，能够播种淀粉样原纤维的生长。我们推测，在AD发病过程中，这些聚集体的挤出可能导致细胞外淀粉样斑块的形成。
One of the neuropathological hallmarks of Alzheimer's disease (AD) is the amyloid plaque, primarily composed of aggregated amyloid-beta (A beta) peptide. In vitro, A beta(1-42), the major alloform of A beta found in plaques, self-assembles into fibrils at micromolar concentrations and acidic pH. Such conditions do not exist in the extracellular fluid of the brain where the pH is neutral and A beta concentrations are in the nanomolar range. Here, we show that extracellular soluble A beta (sA beta) at concentrations as low as 1 nM was taken up by murine cortical neurons and neuroblastoma (SHSY5Y) cells but not by human embryonic kidney (HEK293) cells. Following uptake, A beta accumulated in Lysotracker-positive acidic vesicles (likely late endosomes or lysosomes) where effective concentrations (>2.5 mu M) were greater than two orders of magnitude higher than that in the extracellular fluid (25 nM), as quantified by fluorescence intensity using laser scanning confocal microscopy. Furthermore, SHSY5Y cells incubated with 1 mu M A beta(1-42) for several days demonstrated a time-dependent increase in intracellular high molecular weight (HMW) (>200 kDa) aggregates, which were absent in cells grown in the presence of A beta(1-40). Homogenates from these A beta(1-42)-loaded cells were capable of seeding amyloid fibril growth. These results demonstrate that A beta can be taken up by certain cells at low physiologically relevant concentrations of extracellular A beta, and then concentrated into endosomes/lysosomes. At high concentrations, vesicular A beta aggregates to form HMW species which are capable of seeding amyloid fibril growth. We speculate that extrusion of these aggregates may seed extracellular amyloid plaque formation during AD pathogenesis.