Alternate aggregation pathways of the Alzheimer beta-amyloid peptide: Abeta association kinetics at endosomal pH.
Alternate aggregation pathways of the Alzheimer beta-amyloid peptide: Abeta association kinetics at endosomal pH.
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阿尔茨海默氏β-淀粉样肽的替代聚集途径：内体 pH 值下的 Abeta 关联动力学。
DOI：
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发表时间：
2003
影响因子：
5.6
通讯作者：
A. Chakrabartty
中科院分区：
文献类型：
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作者：
P. Gorman;C. Yip;P. Fraser;A. Chakrabartty
β-淀粉样肽（Abeta）纤维在神经元周围的沉积是阿尔茨海默病的不变特征，并且越来越多的证据表明纤维沉积物和/或前纤维中间体在所观察到的神经变性中起核心作用。A β生成的一个位点是内体，并且我们已经研究了在生理相关的时间范围内在内体pH下A β缔合的动力学。我们已经确定了三个不同的Abeta协会阶段，发生率相当于内体通过时间。在15秒内观察到大于200 nm的爆发相聚集体的快速形成。通过荧光共振能量转移检测到两个较慢的缔合相，并将其称为相1和相2聚集反应。在20 μ M Abeta，pH 6下，相1和相2聚集相的半衰期分别为3.15分钟和17.66分钟。原子力显微镜和动态光散射研究表明，突发相聚集体是大的和无定形的，而相1和2聚集体是球形的流体动力学半径约30 nm。在大爆发相聚集体与相1和相2球形颗粒之间存在明显的平衡，可能通过可溶性Abeta中间体介导。大爆发相聚集体形成迅速，然而，它们消失的平衡移向球形聚集体。这些聚集的物质不包含α-螺旋或β-结构，如通过圆二色性光谱测定的。然而，两周后观察到β-结构，这归因于样品的不溶性部分。两个月后，成熟的淀粉样纤维出现，球形聚集体明显减少。
The deposition of beta-amyloid peptide (Abeta) fibrils around neurons is an invariable feature of Alzheimer's disease and there is increasing evidence that fibrillar deposits and/or prefibrillar intermediates play a central role in the observed neurodegeneration. One site of Abeta generation is the endosomes, and we have investigated the kinetics of Abeta association at endosomal pH over physiologically relevant time frames. We have identified three distinct Abeta association phases that occur at rates comparable to endosomal transit times. Rapid formation of burst phase aggregates, larger than 200nm, was observed within 15 seconds. Two slower association phases were detected by fluorescence resonance energy transfer and termed phase 1 and phase 2 aggregation reactions. At 20 microM Abeta, pH 6, the half lives of the phase 1 and phase 2 aggregation phases were 3.15 minutes and 17.66 minutes, respectively. Atomic force microscopy and dynamic light scattering studies indicate that the burst phase aggregate is large and amorphous, while phase 1 and 2 aggregates are spherical with hydrodynamic radii around 30 nm. There is an apparent equilibrium, potentially mediated through a soluble Abeta intermediate, between the large burst phase aggregates and phase 1 and 2 spherical particles. The large burst phase aggregates form quickly, however, they disappear as the equilibrium shifts toward the spherical aggregates. These aggregated species do not contain alpha-helical or beta-structure as determined by circular dichroism spectroscopy. However, after two weeks beta-structure is observed and is attributable to the insoluble portion of the sample. After two months, mature amyloid fibrils appear and the spherical aggregates are significantly diminished.