Structural analysis of SAA-amyloid fibrils by cryo-EM and NMR

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AA amyloidosis presents, among all protein misfolding diseases, unique advantages for studying the structure, formation and propagation of pathogenic amyloids. There are highly relevant in vitro, cell culture and mouse model systems to reproduce crucial steps of amyloid fibril formation. Amyloid deposits are comparatively large-sized and amenable for biochemical analysis. Murine SAA1 is an extracellular protein and small enough to be well accessible for NMR. These features enable us to take an integrative structural biology approach in which we use cryo-electron microscopy (EM) and solid-state NMR spectroscopy to analyze the structure of the fibrils. These fibril structures are relevant for disease because they give rise to tissue damage and underlie the spreading of disease and protein misfolding inside the tissue. The two major techniques employed in this project, cryo-EM and solid-state NMR, are perfectly complementary. Cryo-EM can determine the overall electron density, symmetry and protofilament substructure and is amenable to body-derived fibrils. Solid-state NMR is an ideal tool to characterize dynamic regions within the aggregate. In this project we want to complementarily apply these techniques to study the structure of pathogenically relevant AA amyloid fibrils by examining bona fide fibrils from murine spleen, cell culture derived and in vitro formed fibrils.