Structural properties of Aβ protofibrils stabilized by a small molecule
Structural properties of Aβ protofibrils stabilized by a small molecule
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DOI：
10.1073/pnas.0408582102
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发表时间：
2005-05-17
影响因子：
11.1
通讯作者：
Wetzel, R
中科院分区：
文献类型：
--
作者：
Williams, AD;Sega, M;Wetzel, R
亚稳态寡聚体和原纤维形式的淀粉样蛋白已经被认为是淀粉样蛋白形成中的通路组装中间体，并且是包括阿尔茨海默病在内的许多淀粉样疾病中的主要毒性物质。在这里，我们描述了一种化学生物学方法来分析A β原纤维的结构。文库筛选产生了几种刺激A β聚集的分子。这些化合物之一，氯化钙咪达唑鎓（CLC），快速有效地将A β（1-40）单体转化为原纤维簇。如通过电子显微镜所监测的，当在37 ° C下在PBS中孵育时，这些原纤维持续数天，仅在数周后缓慢转变为纤维状结构。与正常的原纤维一样，CLC-A β聚集体表现出低的硫磺素T反应。与A β原纤维一样，成簇的原纤维结合抗淀粉样蛋白Ab WO 1。CLC-A β聚集体表现出与从自发A β原纤维形成反应中分离的原纤维相同的对氢-氘交换的保护：在原纤维中，39个A β（1-40）骨架酰胺质子中约有12个被保护免于交换，相比之下，淀粉样蛋白原纤维中约有两倍的数量。扫描脯氨酸诱变分析表明，在这些原纤维组件中的A β分子表现出相同的灵活的N和C末端作为成熟的淀粉样蛋白原纤维。原纤维和原纤维之间A β构象的主要差异是原纤维中22-29片段中增加的结构定义。除了有助于结构分析，能够促进寡聚体和原纤维形成的化合物可能具有治疗潜力，如果它们以不能参与毒性途径的形式和/或位置螯合A β。
Metastable oligomeric and protofibrillar forms of amyloidogenic proteins have been implicated as on-pathway assembly intermediates in amyloid formation and as the major toxic species in a number of amyloid diseases including Alzheimer's disease. We describe here a chemical biology approach to structural analysis of A beta protofibrils. Library screening yielded several molecules that stimulate A beta aggregation. One of these compounds, calmidazolium chloride (CLC), rapidly and efficiently converts A beta(1-40) monomers into clusters of protofibrils. As monitored by electron microscopy, these protofibrils persist for days when incubated in PBS at 37 degrees C, with a slow transition to fibrillar structures apparent only after several weeks. Like normal protofibrils, the CLC-A beta aggregates exhibit a low thioflavin T response. Like A beta fibrils, the clustered protofibrils bind the anti-amyloid Ab WO1. The CLC-A beta aggregates exhibit the same protection from hydrogen-deuterium exchange as do protofibrils isolated from a spontaneous A beta fibril formation reaction: approximate to 12 of the 39 A beta(1-40) backbone amide protons are protected from exchange in the protofibril, compared with approximately twice that number in amyloid fibrils. Scanning proline mutagenesis analysis shows that the A beta molecule in these protofibrillar assemblies exhibits the same flexible N and C termini as do mature amyloid fibrils. The major difference in A beta conformation between fibrils and protofibrils is added structural definition in the 22-29 segment in the fibril. Besides aiding structural analysis, compounds capable of facilitating oligomer and protofibril formation might have therapeutic potential, if they act to sequester A beta in a form and/or location that cannot engage the toxic pathway.