Department of Chemistry, University of Massachusetts-Amherst, 374 Lederle Graduate Research Tower A, 710 North Pleasant Street, Amherst, Massachusetts 01003, United States.
Biochemistry. 2020 Mar 17;59(10):1093-1103. doi: 10.1021/acs.biochem.0c00043. Epub 2020 Mar 3.
Epigallocatechin-3-gallate (EGCG) is a catechin found in green tea that can inhibit the amyloid formation of a wide variety of proteins. EGCG's ability to prevent or redirect the amyloid formation of so many proteins may reflect a common mechanism of action, and thus, greater molecular-level insight into how it exerts its effect could have broad implications. Here, we investigate the molecular details of EGCG's inhibition of the protein β-2-microglobulin (β2m), which forms amyloids in patients undergoing long-term dialysis treatment. Using size-exclusion chromatography and a collection of mass spectrometry-based techniques, we find that EGCG prevents Cu(II)-induced β2m amyloid formation by diverting the normal progression of preamyloid oligomers toward the formation of spherical, redissolvable aggregates. EGCG exerts its effect by binding with a micromolar affinity ( ≈ 5 μM) to the β2m monomer on the edge of two β-sheets near the N-terminus. This interaction destabilizes the preamyloid dimer and prevents the formation of a tetramer species previously shown to be essential for Cu(II)-induced β2m amyloid formation. EGCG's binding at the edge of the β-sheets in β2m is consistent with a previous hypothesis that EGCG generally prevents amyloid formation by binding cross-β-sheet aggregation intermediates.
没食子酸表没食子儿茶素酯（EGCG）是绿茶中的一种儿茶素，可以抑制多种蛋白质的淀粉样形成。EGCG 能够预防或改变如此多的蛋白质的淀粉样形成，这可能反映了一种共同的作用机制，因此，更深入地了解其作用机制可能具有广泛的意义。在这里，我们研究了 EGCG 抑制蛋白质β-2-微球蛋白（β2m）形成淀粉样纤维的分子细节，β2m 在接受长期透析治疗的患者中会形成淀粉样纤维。我们使用分子筛层析和一系列基于质谱的技术，发现 EGCG 通过将正常的前淀粉样寡聚物的进展转向形成球形、可再溶解的聚集体，从而阻止 Cu(II)诱导的β2m 淀粉样形成。EGCG 通过与β2m 单体在 N 端附近的两个β-折叠边缘以微摩尔亲和力（≈5μM）结合来发挥作用。这种相互作用使前淀粉样二聚体不稳定，并阻止了先前显示对 Cu(II)诱导的β2m 淀粉样形成至关重要的四聚体的形成。EGCG 在β2m 的β-折叠边缘的结合与之前的一个假设一致，即 EGCG 通常通过结合跨β-折叠聚集中间体来防止淀粉样形成。
