Krotee Pascal, Rodriguez Jose A, Sawaya Michael R, Cascio Duilio, Reyes Francis E, Shi Dan, Hattne Johan, Nannenga Brent L, Oskarsson Marie E, Philipp Stephan, Griner Sarah, Jiang Lin, Glabe Charles G, Westermark Gunilla T, Gonen Tamir, Eisenberg David S
Department of Biological Chemistry, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States.
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, United States.
Elife. 2017 Jan 3;6:e19273. doi: 10.7554/eLife.19273.
hIAPP fibrils are associated with Type-II Diabetes, but the link of hIAPP structure to islet cell death remains elusive. Here we observe that hIAPP fibrils are cytotoxic to cultured pancreatic β-cells, leading us to determine the structure and cytotoxicity of protein segments composing the amyloid spine of hIAPP. Using the cryoEM method MicroED, we discover that one segment, 19-29 S20G, forms pairs of β-sheets mated by a dry interface that share structural features with and are similarly cytotoxic to full-length hIAPP fibrils. In contrast, a second segment, 15-25 WT, forms non-toxic labile β-sheets. These segments possess different structures and cytotoxic effects, however, both can seed full-length hIAPP, and cause hIAPP to take on the cytotoxic and structural features of that segment. These results suggest that protein segment structures represent polymorphs of their parent protein and that segment 19-29 S20G may serve as a model for the toxic spine of hIAPP.
人胰岛淀粉样多肽（hIAPP）纤维与2型糖尿病相关，但hIAPP结构与胰岛细胞死亡之间的联系仍不清楚。在这里，我们观察到hIAPP纤维对培养的胰腺β细胞具有细胞毒性，这促使我们确定构成hIAPP淀粉样蛋白主干的蛋白质片段的结构和细胞毒性。使用低温电子显微镜方法MicroED，我们发现一个片段，即19 - 29 S20G，形成了由干燥界面配对的β-折叠片层对，其与全长hIAPP纤维具有共同的结构特征且细胞毒性相似。相比之下，第二个片段，即15 - 25 WT，形成无毒的不稳定β-折叠片层。这些片段具有不同的结构和细胞毒性作用，然而，两者都可以引发全长hIAPP的形成，并使hIAPP呈现出该片段的细胞毒性和结构特征。这些结果表明，蛋白质片段结构代表其母体蛋白质的多晶型物，并且19 - 29 S20G片段可能作为hIAPP毒性主干的模型。
