Project Summary/Abstract Recently, significant progress in understanding tauopathies and how tau aggregates lead to neurodegeneration has been made by the description of the atomic structures of tau filaments from human brain. We have established that the morphology of tau filaments comprising of all six tau isoforms (3R+4R tau) in diseases associated with extracellular amyloid deposition is identical, regardless of the amino acid sequence of the amyloid subunit. To gain further understanding on how different amyloids elicit a tau response comprising of 3R+4R tau with a common fold (AD fold), we characterized the structures of filaments of human extracellular amyloid-β (Aβ) in Alzheimer disease (AD) and Prion protein amyloid (APrP) in Prion diseases. In addition, we characterized the structures of α-synuclein filaments in Diffuse Lewy body disease, Parkinson disease and Multiple system atrophy, and TMEM106B filaments in several neurodegenerative diseases and aging. The studies proposed in this MPI application are a logical continuation of this groundbreaking work. These studies are in response to PAR-22-208 “Structural Biology of Alzheimer's Disease Related Dementias (ADRDs) Proteinopathies” (R01) The main goals of this application are to continue to characterize, from brain tissue, the structure of filaments at high atomic-level resolution for future use in PET ligand development and other related purposes, with special emphasis on mutations/genotypes and sporadic versus familial forms of disease, different ages of onset (e.g. early vs. late onset), and presence of co-pathologies. In addition, we propose to characterize fibrils derived from in vivo sources such as relevant animal models and biologically relevant in vitro systems, and to synthesize, identify, and characterize amyloid-specific ligands. In order to achieve our goals, our proposal has three specific aims. The first is to perform cryo-EM studies on a large cohort of EOAD individuals with different APOE genotypes and age at onset, and familial EOAD individuals with different clinical, genetic and neuropathologic features. In addition, we will determine for the first time the structure of filaments in individuals with Down syndrome, familial British and Danish dementia and the structure and identity of Biondi bodies. Second, we will generate a cryo-EM map and determine the corresponding atomic models of filaments extracted from the brain of murine models and generate high-resolution 3D images of the amyloid structures. Lastly, we will characterize by cryo-EM the structure of recombinant tau and synthetic peptides homologous to Aβ, ABri and ADan and compare our results with the peptides isolated from human and animal models. We will also synthesize, identify, and characterize amyloid-specific ligands.

Project Narrative Cryo-EM has enabled the characterization of protein structures of amyloid fibrils found in various AD/ADRD conditions, showing for the first time that different proteinopathies of the same underlying protein can have dramatically different fibril structures. The main goal of this application is to elucidate the structural basis of amyloid fibrils in hereditary and sporadic amyloidoses, Down syndrome, mouse models, and in vitro systems, and the development of structure-informed ligands that could be used for in vivo imaging.