Sir William Dunn School of Pathology, University of Oxford, OX1 3RE Oxford, United Kingdom.
Department of Bioengineering, Imperial College London, South Kensington Campus, SW7 2AZ London, United Kingdom.
Proc Natl Acad Sci U S A. 2020 Jun 2;117(22):12050-12061. doi: 10.1073/pnas.1916716117. Epub 2020 May 15.
Amyloidoses (misfolded polypeptide accumulation) are among the most debilitating diseases our aging societies face. Amyloidogenesis can be catalyzed by hydrophobic-hydrophilic interfaces (e.g., air-water interface in vitro [AWI]). We recently demonstrated hydrogelation of the amyloidogenic type II diabetes-associated islet amyloid polypeptide (IAPP), a hydrophobic-hydrophilic interface-dependent process with complex kinetics. We demonstrate that human IAPP undergoes AWI-catalyzed liquid-liquid phase separation (LLPS), which initiates hydrogelation and aggregation. Insulin modulates these processes but does not prevent them. Using nonamyloidogenic rat IAPP, we show that, whereas LLPS does not require the amyloidogenic sequence, hydrogelation and aggregation do. Interestingly, both insulin and rat sequence delayed IAPP LLPS, which may reflect physiology. By developing an experimental setup and analysis tools, we show that, within the whole system (beyond the droplet stage), macroscopic interconnected aggregate clusters form, grow, fuse, and evolve via internal rearrangement, leading to overall hydrogelation. As the AWI-adsorbed gelled layer matures, its microviscosity increases. LLPS-driven aggregation may be a common amyloid feature and integral to pathology.
淀粉样变性（错误折叠多肽的积累）是我们老龄化社会面临的最具破坏性的疾病之一。淀粉样形成可以被疏水性-亲水性界面（例如，体外的气-液界面（AWI））催化。我们最近证明了与 II 型糖尿病相关的胰岛淀粉样多肽（IAPP）的水凝胶化，这是一个依赖于疏水性-亲水性界面的复杂动力学过程。我们证明人 IAPP 经历了 AWI 催化的液-液相分离（LLPS），这引发了水凝胶化和聚集。胰岛素调节这些过程，但不能阻止它们。使用非淀粉样变性的大鼠 IAPP，我们表明，尽管 LLPS 不需要淀粉样变性序列，但水凝胶化和聚集需要。有趣的是，胰岛素和大鼠序列都延迟了 IAPP 的 LLPS，这可能反映了生理学。通过开发实验装置和分析工具，我们表明，在整个系统（超出液滴阶段）中，宏观相互连接的聚集体簇形成、生长、融合和通过内部重排进化，导致整体水凝胶化。随着 AWI 吸附的凝胶层成熟，其微粘度增加。LLPS 驱动的聚集可能是一种常见的淀粉样特征，是病理学的组成部分。
