Structural Identification of Individual Helical Amyloid Filaments by Integration of Cryo-Electron Microscopy-Derived Maps in Comparative Morphometric Atomic Force Microscopy Image Analysis

• DOI: 10.1016/j.jmb.2022.167466
• Publication Date: 2022-01-22T15:48:22Z
• Authors: Liisa Lutter; Youssra K. Al-Hilaly; Christopher J. Se...; Mick F. Tuite; Claude M. Wischik; Louise C. Serpell; Wei-Feng Xue
• Keywords: 0301 basic medicine; 570; Amyloid; Supplementary Information; Biophysics; cryo-electron microscopy; Amyloidogenic Proteins; R Medicine (General); Microscopy, Atomic Force; Protein Structure, Secondary; polymorphism; 03 medical and health sciences; SDG 3 - Good Health and Well-being; Alzheimer Disease; structural biology; Humans; QP506; Molecular Biology; BB/S003312/1; atomic force microscopy; Q; Cryoelectron Microscopy; amyloid; Amyloidosis; R1; 3. Good health; Engineering and Physical Sciences Research Council (EPSRC); EP/R513246/1; Biotechnology and Biological Sciences Research Council (BBSRC); Fast Track; QP517

ABSTRACTThe presence of amyloid fibrils is a hallmark of more than 50 human disorders, including neurodegenerative diseases and systemic amyloidoses. A key unresolved challenge in understanding the involvement of amyloid in disease is to explain the relationship between individual structural polymorphs of amyloid fibrils, in potentially mixed populations, and the specific pathologies with which they are associated. Although cryo-electron microscopy (cryo-EM) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy methods have been successfully employed in recent years to determine the structures of amyloid fibrils with high resolution detail, they rely on ensemble averaging of fibril structures in the entire sample or significant subpopulations. Here, we report a method for structural identification of individual fibril structures imaged by atomic force microscopy (AFM) by integration of high-resolution maps of amyloid fibrils determined by cryo-EM in comparative AFM image analysis. This approach was demonstrated using the hitherto structurally unresolved amyloid fibrils formed in vitro from a fragment of tau (297-391), termed ‘dGAE’. Our approach established unequivocally that dGAE amyloid fibrils bear no structural relationship to heparin-induced tau fibrils formed in vitro. Furthermore, our comparative analysis resulted in the prediction that dGAE fibrils are closely related structurally to the paired helical filaments (PHFs) isolated from Alzheimer’s disease (AD) brain tissue characterised by cryo-EM. These results show the utility of individual particle structural analysis using AFM, provide a workflow of how cryo-EM data can be incorporated into AFM image analysis and facilitate an integrated structural analysis of amyloid polymorphism.