Evans Christopher G, Wisén Susanne, Gestwicki Jason E
Department of Pathology and the Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
J Biol Chem. 2006 Nov 3;281(44):33182-91. doi: 10.1074/jbc.M606192200. Epub 2006 Sep 14.
Alzheimer disease is a neurological disorder that is characterized by the presence of fibrils and oligomers composed of the amyloid beta (Abeta) peptide. In models of Alzheimer disease, overexpression of molecular chaperones, specifically heat shock protein 70 (Hsp70), suppresses phenotypes related to Abeta aggregation. These observations led to the hypothesis that chaperones might interact with Abeta and block self-association. However, although biochemical evidence to support this model has been collected in other neurodegenerative systems, the interaction between chaperones and Abeta has not been similarly explored. Here, we examine the effects of Hsp70/40 and Hsp90 on Abeta aggregation in vitro. We found that recombinant Hsp70/40 and Hsp90 block Abeta self-assembly and that these chaperones are effective at substoichiometric concentrations (approximately 1:50). The anti-aggregation activity of Hsp70 can be inhibited by a nonhydrolyzable nucleotide analog and encouraged by pharmacological stimulation of its ATPase activity. Finally, we were interested in discerning what type of amyloid structures can be acted upon by these chaperones. To address this question, we added Hsp70/40 and Hsp90 to pre-formed oligomers and fibrils. Based on thioflavin T reactivity, the combination of Hsp70/40 and Hsp90 caused structural changes in oligomers but had little effect on fibrils. These results suggest that if these chaperones are present in the same cellular compartment in which Abeta is produced, Hsp70/40 and Hsp90 may suppress the early stages of self-assembly. Thus, these results are consistent with a model in which pharmacological activation of chaperones might have a favorable therapeutic effect on Alzheimer disease.
阿尔茨海默病是一种神经退行性疾病，其特征是存在由β-淀粉样蛋白（Aβ）肽组成的纤维和寡聚体。在阿尔茨海默病模型中，分子伴侣的过表达，特别是热休克蛋白70（Hsp70），可抑制与Aβ聚集相关的表型。这些观察结果导致了这样一种假设，即伴侣蛋白可能与Aβ相互作用并阻止其自我缔合。然而，尽管在其他神经退行性系统中已经收集到支持该模型的生化证据，但伴侣蛋白与Aβ之间的相互作用尚未得到类似的研究。在这里，我们研究了Hsp70/40和Hsp90对体外Aβ聚集的影响。我们发现重组Hsp70/40和Hsp90可阻止Aβ的自我组装，并且这些伴侣蛋白在亚化学计量浓度（约1:50）下有效。Hsp70的抗聚集活性可被不可水解的核苷酸类似物抑制，并通过对其ATPase活性的药理学刺激而增强。最后，我们感兴趣的是辨别这些伴侣蛋白可以作用于何种类型的淀粉样结构。为了解决这个问题，我们将Hsp70/40和Hsp90添加到预先形成的寡聚体和纤维中。基于硫黄素T反应性，Hsp70/40和Hsp90的组合导致寡聚体结构发生变化，但对纤维几乎没有影响。这些结果表明，如果这些伴侣蛋白存在于产生Aβ的同一细胞区室中，Hsp70/40和Hsp90可能会抑制自我组装的早期阶段。因此，这些结果与一种模型一致，即伴侣蛋白的药理学激活可能对阿尔茨海默病具有有利治疗作用。
