Amyloid beta-protein dimers rapidly form stable synaptotoxic protofibrils.
Amyloid beta-protein dimers rapidly form stable synaptotoxic protofibrils.
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DOI：
10.1523/jneurosci.3537-10.2010
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发表时间：
2010-10-27
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影响因子：
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通讯作者：
Walsh DM
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作者：
O'Nuallain B;Freir DB;Nicoll AJ;Risse E;Ferguson N;Herron CE;Collinge J;Walsh DM
淀粉样蛋白(Aβ-Protein，Aβ)的非纤维、水溶性低分子组装被认为在阿尔茨海默病(AD)中起着重要作用。人脑的水提物含有Aβ组件，它们在十二烷基硫酸钠-PAGE上迁移，并以二聚体(~8 kDa)的形式洗脱，可以阻止长时程增强和损害大鼠的记忆巩固。这些物种在阿尔茨海默病脑提取液中被特异和敏感地检测到，这表明十二烷基硫酸钠稳定的二聚体可能是与AD相关的突触毒素组装的基本构件。因此，了解A-β二聚体的结构和性质是非常有意义的。在缺乏足够的脑源性二聚体来促进生物物理分析的情况下，我们产生了旨在模拟自然物种的合成二聚体。为此，用含有半胱氨酸的β(1-40)代替丝氨酸26来产生二硫键交联二聚体(AβS26C)2。这种二聚体没有可检测到的二级结构，产生了与~8.6 kDa蛋白质一致的分析超速离心谱，并且对海马长时程增强没有影响。然而，(AβS26C)2比AβS26C或野生型单体更快地聚集并形成稳定的富含β-Sheet的硫代黄素T阳性的原纤丝状集合体。而野生型Aβ聚集形成典型的淀粉样纤维，而(AβS26C)2形成的原纤丝样结构在小鼠海马区持续时间较长，并有效地抑制LTP。这些数据支持这样一种观点，即Aβ二聚体可能通过与Aβ单体不同的过程稳定原纤维中间体的形成，并且较高分子量的前纤维集合体是Aβ毒性的直接媒介。
Non-fibrillar, water-soluble low-molecular weight assemblies of the amyloid β-protein (Aβ) are believed to play an important role in Alzheimer’s disease (AD). Aqueous extracts of human brain contain Aβ assemblies which migrate on SDS-PAGE and elute from size exclusion as dimers (~8 kDa) and can block long term potentiation and impair memory consolidation in the rat. Such species are detected specifically and sensitively in extracts of Alzheimer brain suggesting that SDS-stable dimers may be the basic building blocks of AD-associated synaptotoxic assemblies. Consequently, understanding the structure and properties of Aβ dimers is of great interest. In the absence of sufficient brain-derived dimer to facilitate biophysical analysis, we generated synthetic dimers designed to mimic the natural species. For this, Aβ(1-40) containing cysteine in place of serine 26 was used to produce disulphide cross-linked dimer, (AβS26C)2. Such dimers had no detectable secondary structure, produced an analytical ultracentrifugation (AUC) profile consistent for an ~8.6 kDa protein, and had no effect on hippocampal long term potentiation (LTP). However, (AβS26C)2 aggregated more rapidly than either AβS26C or wild type monomers and formed parastable β-sheet rich, thioflavin T positive, protofibril-like assemblies. Whereas wild type Aβ aggregated to form typical amyloid fibrils, the protofibril-like structures formed by (AβS26C)2 persisted for prolonged periods and potently inhibited LTP in mouse hippocampus. These data support the idea that Aβ dimers may stabilize the formation of fibril intermediates by a process distinct from that available to Aβ monomer and that higher molecular weight pre-fibrillar assemblies are the proximate mediators of Aβ toxicity.