The Alzheimer Disease Protective Mutation A2T Modulates Kinetic and Thermodynamic Properties of Amyloid-β (Aβ) Aggregation
The Alzheimer Disease Protective Mutation A2T Modulates Kinetic and Thermodynamic Properties of Amyloid-β (Aβ) Aggregation
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DOI：
10.1074/jbc.m114.599027
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发表时间：
2014-11-07
影响因子：
4.8
通讯作者：
De Strooper, Bart
中科院分区：
文献类型：
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作者：
Benilova, Iryna;Gallardo, Rodrigo;De Strooper, Bart
淀粉样前体蛋白（APP）的丙氨酸673位点的错义突变（该位点对应于淀粉样β（Aβ）序列中的第二个丙氨酸）对阿尔茨海默病的风险有重大影响；A2V是致病性的，而A2T是保护性的。假定淀粉样Aβ在神经退行性变中起关键作用，我们假设A2V和A2T突变都会导致Aβ特性发生明显变化，这可能至少部分解释了这些完全不同的表型。利用过表达人APP的原代神经元，我们观察到A2T突变体中Aβ的产生显著减少，而A2V突变体中Aβ的产生增加，这证实了来自非神经元细胞系的早期数据。更重要的是，硫黄素T荧光分析显示，这些突变虽然对Aβ42肽的聚集影响较小，但却极大地改变了Aβ40集合体的特性，A2V加速而A2T延迟Aβ肽的聚集。与动力学数据一致，Aβ A2T在平衡时的溶解度增加，在A2T突变体与野生型Aβ40的所有混合物中也观察到了这种效应。我们提出，除了APP的β - 分泌酶切割减少外，聚集倾向的降低可能是A2T替代所赋予的保护作用的一部分。因此，对这种突变的保护作用的解释比以前提出的要复杂得多。
Missense mutations in alanine 673 of the amyloid precursor protein (APP), which corresponds to the second alanine of the amyloid beta (A beta) sequence, have dramatic impact on the risk for Alzheimer disease; A2V is causative, and A2T is protective. Assuming a crucial role of amyloid-A beta in neurodegeneration, we hypothesized that both A2V and A2T mutations cause distinct changes in A beta properties that may at least partially explain these completely different phenotypes. Using human APP-overexpressing primary neurons, we observed significantly decreased A beta production in the A2T mutant along with an enhanced A beta generation in the A2V mutant confirming earlier data from non-neuronal cell lines. More importantly, thioflavin T fluorescence assays revealed that the mutations, while having little effect on A beta 42 peptide aggregation, dramatically change the properties of the A beta 40 pool with A2V accelerating and A2T delaying aggregation of the A beta peptides. In line with the kinetic data, A beta A2T demonstrated an increase in the solubility at equilibrium, an effect that was also observed in all mixtures of the A2T mutant with the wild type A beta 40. We propose that in addition to the reduced beta-secretase cleavage of APP, the impaired propensity to aggregate may be part of the protective effect conferred by A2T substitution. The interpretation of the protective effect of this mutation is thus much more complicated than proposed previously.