Cryo-EM Observation of AA Amyloid Fibrils in Mouse Model of Systemic AApoAII Amyloidosis.

The co-deposition of amyloid fibrils from different precursor proteins is a topic of increasing relevance for protein misfolding diseases. Using cryo-electron microscopy (cryo-EM), we here determined the structures of two serum amyloid A (SAA) protein-derived amyloid fibril morphologies that were extracted from a mouse strain that is primarily known to be associated with apolipoprotein A-II-derived amyloid fibrils. The two fibril morphologies show the same protomer conformation as in previously reported ex vivo amyloid fibrils from SAA protein but a different relative arrangement of fibril protein stacks. These data establish that serum amyloid A-derived amyloid fibrils share the same fibril protein fold in different mouse strains and disease contexts.