Hatters Danny M, Zhong Ning, Rutenber Earl, Weisgraber Karl H
Gladstone Institute of Neurological Disease, 1650 Owens Street, San Francisco, CA 94158, USA.
J Mol Biol. 2006 Sep 1;361(5):932-44. doi: 10.1016/j.jmb.2006.06.080. Epub 2006 Aug 7.
The three isoforms of apolipoprotein (apo) E are strongly associated with different risks for Alzheimer's disease: apoE4>apoE3>apoE2. Here, we show at physiological salt concentrations and pH that native tetramers of apoE form soluble aggregates in vitro that bind the amyloid dyes thioflavin T and Congo red. However, unlike classic amyloid fibrils, the aggregates adopt an irregular protofilament-like morphology and are seemingly highly alpha-helical. The aggregates formed at substantially different rates (apoE4>apoE3>apoE2) and were significantly more toxic to cultured neuronal cells than the tetramer. Since the three isoforms have large differences in conformational stability that can influence aggregation and amyloid pathways, we tested the effects of mutations that increased or decreased stability. Decreasing the conformational stability of the amino-terminal domain of apoE increased aggregation rates and vice versa. Our findings provide a new perspective for an isoform-specific pathogenic role for apoE aggregation in which differences in the conformational stability of the amino-terminal domain mediate neurodegeneration.
载脂蛋白（apo）E的三种异构体与阿尔茨海默病的不同风险密切相关：apoE4>apoE3>apoE2。在此，我们发现在生理盐浓度和pH条件下，apoE的天然四聚体在体外形成可溶性聚集体，这些聚集体能结合淀粉样染料硫黄素T和刚果红。然而，与经典的淀粉样纤维不同，这些聚集体呈现出不规则的原纤维样形态，且似乎具有高度的α螺旋结构。这些聚集体以显著不同的速率形成（apoE4>apoE3>apoE2），并且对培养的神经元细胞的毒性明显高于四聚体。由于这三种异构体在构象稳定性上有很大差异，而构象稳定性会影响聚集和淀粉样蛋白生成途径，我们测试了增加或降低稳定性的突变的影响。降低apoE氨基末端结构域的构象稳定性会增加聚集速率，反之亦然。我们的研究结果为apoE聚集的异构体特异性致病作用提供了一个新视角，其中氨基末端结构域构象稳定性的差异介导了神经退行性变。
