Hammarstrom, P. | bioRxiv Science

bioRxiv2023

Divergent age-dependent conformational rearrangement within Aβ-amyloid deposits in APP23, APPPS1, and AppNL-F mice

Amyloid plaques composed of fibrils of misfolded A{beta} peptides are pathological hallmarks of Alzheimers disease (AD). A{beta} fibrils are polymorphic in their tertiary and quaternary molecular structures. This structural polymorphism may carry different pathologic potency and can putatively contribute to clinical phenotypes of AD. Therefore, mapping of structural polymorphism of A{beta} fibrils is valuable to understand disease mechanisms. Here, we investigated how A{beta} fibril morphology in situ differs in A{beta} plaque of different mouse models expressing familial mutations in the A{beta}PP gene. We used a combination of conformation-sensitive luminescent conjugated oligothiophene (LCO) ligands, A{beta}-specific antibodies, and different fluorescence microscopy techniques. LCO fluorescence mapping revealed that mouse models APP23, APPPS1, and AppNL-F have different fibril structures depending on A{beta}PP-processing genotype. Co-staining of A{beta}-specific antibodies showed that individual plaques from APP23 mice, expressing Swedish mutations (NL) have two distinct fibril polymorph regions of core and corona. The plaque core is predominantly composed of compact A{beta}40 fibrils and the corona region is dominated by diffusely packed A{beta}40 fibrils. On the other hand, the APP knock-in mouse AppNL-F, expressing Iberian mutation (F) along with Swedish mutation has tiny, cored plaques consisting mainly of compact A{beta}42 fibrils, vastly different from APP23 even at elevated age up to 21 months. Age dependent polymorph maturation of plaque cores observed for APP23 and APPPS1 mice >12 months, was minuscule in AppNL-F. These structural studies of amyloid plaques in situ can map disease-relevant fibril polymorph distributions to guide the design of diagnostic and therapeutic molecules. SignificanceAlzheimers disease (AD) is associated with the formation of deposits in the brain known as A{beta}-amyloid plaques. AD can emerge as a sporadic disease or due to familial mutations in genes encoding for A{beta} precursor and processing proteins. The A{beta}-amyloid found in plaques displays different structures in sporadic AD and in various types of familial AD. We hypothesize that understanding plaque morphology and development is crucial for understanding the initiation and progression of AD. We here compared amyloid structures in three of the most used mouse models of human A{beta}-plaque formation. Our findings suggest significant differences in plaque morphologies and structural maturation processes during aging. Our results emphasize that strain-like differences of A{beta}-amyloids develop as a function of A{beta} precursor protein-processing genetics and age.

neuroscience↗

bioRxiv2021

Amyloidogenesis of SARS-CoV-2 Spike Protein

SARS-CoV-2 infection is associated with a surprising number of morbidities. Uncanny similarities with amyloid-disease associated blood coagulation and fibrinolytic disturbances together with neurologic and cardiac problems led us to investigate the amyloidogenicity of the SARS-CoV-2 Spike protein (S-protein). Amyloid fibril assays of peptide library mixtures and theoretical predictions identified seven amyloidogenic sequences within the S-protein. All seven peptides in isolation formed aggregates during incubation at 37{degrees}C. Three 20-amino acid long synthetic Spike peptides (sequence 191-210, 599-618, 1165-1184) fulfilled three amyloid fibril criteria: nucleation dependent polymerization kinetics by ThT, Congo red positivity and ultrastructural fibrillar morphology. Full-length folded S-protein did not form amyloid fibrils, but amyloid-like fibrils with evident branching were formed during 24 hours of S-protein co-incubation with the protease neutrophil elastase (NE) in vitro. NE efficiently cleaved S-protein rendering exposure of amyloidogenic segments and accumulation of the peptide 193-202, part of the most amyloidogenic synthetic Spike peptide. NE is overexpressed at inflamed sites of viral infection and at vaccine injection sites. Our data propose a molecular mechanism for amyloidogenesis of SARS-CoV-2 S-protein in humans facilitated by endoproteolysis. The potential implications of S-protein amyloidogenesis in COVID-19 disease associated pathogenesis and consequences following S-protein based vaccines should be addressed in understanding the disease, long COVID-19, and vaccine side effects.

biochemistry↗