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Quantitative proteomics of tau and Aβ amyloid in detergent insoluble fractions from Alzheimer’s disease brains

ABSTRACT: The two hallmarks of Alzheimer’s disease (AD) are A-amyloid- (A) plaques and neurofibrillary tangles marked by phosphorylated tau. There is compelling evidence that aggregating A drives tau accumulation, a process that involves synaptic degeneration leading to cognitive impairment. Conversely there is a growing realization that non-fibrillar (oligomeric) forms of Aβ mediate toxicity in AD. Using quantitative proteomics, we find that AD brain sarkosyl-insoluble pellets are greatly enriched with A at almost equimolar levels to N-terminal truncated microtubule binding region (MTBR) isoforms of tau with multiple post-translational modifications (PTMs). The extracted R3-R4 tau peptides are 100-fold higher compared to N-terminus intact tau peptides. Substantial proportions of site-specific phosphorylation at T181 (~ 22 %) and T217 (~ 16 %) along with other PTMs in the proline rich region (PRR) and MTBR indicate a regional susceptibility of PTMs in aggregated tau. Immuno-electron microscopy reveals that co-purified A and tau co-localize to globular non-filamentous aggregates.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Brain

SUBMITTER: Soumya Mukherjee

LAB HEAD: Colin Masters

PROVIDER: PXD032389 | Pride | 2022-06-04

REPOSITORIES: Pride

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			Action	DRS
	190121_Soumya_Mirauda_ML-1.raw	Raw
	190121_Soumya_Mirauda_ML-2.raw	Raw
	190121_Soumya_Mirauda_ML-3.raw	Raw
	190121_Soumya_Mirauda_ML-4.raw	Raw
	190121_Soumya_Mirauda_ML-5.raw	Raw

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Project description:In human neurodegenerative diseases associated with the intracellular aggregation of Tau protein, the ordered cores of Tau filaments adopt distinct folds. Here, we analyze Tau filaments isolated from the brain of individuals affected by Prion-Protein cerebral amyloid angiopathy (PrP-CAA) and Gerstmann-Sträussler-Scheinker (GSS) disease, two genetically determined Prion protein (PrP) amyloidoses characterized by the deposition of PrP amyloid (APrP) in the vessel walls and in the cerebral parenchyma, respectively. A nonsense and a missense mutation in the PRNP gene lead to a premature termination of translation at codon position 160 (Q160Ter) of PrP in PrP-CAA, or to the substitution of an amino acid at residue 198 (F198S) of PrP in GSS. These two diseases have different clinical and pathologic phenotypes; however, in both diseases, neuropathologic analyses have consistently shown the presence of numerous neurofibrillary tangles (NFTs) made of filamentous Tau aggregates in neurons. We report that Tau filaments in PrP-CAA and GSS are composed of 3-repeat and 4-repeat Tau isoforms, having a striking similarity to NFTs in Alzheimer disease (AD). In PrP-CAA, Tau filaments are made of both paired helical filaments (PHFs) and straight filaments (SFs), while in GSS only PHFs were found. Mass spectrometry analyses of Tau filaments extracted from PrP-CAA and GSS brains show the presence of post-translational modifications that are comparable to those seen in Tau aggregates from AD. Cryo-EM analysis reveals that the atomic models of the Tau filaments obtained from PrP-CAA and GSS are identical to those of the Tau filaments from AD, and are therefore distinct from those of Pick disease, chronic traumatic encephalopathy, and corticobasal degeneration. Our data support the hypothesis that in the presence of amyloid deposits and regardless of the primary amino acid sequence of the amyloid protein, similar molecular mechanisms are at play in the formation of identical Tau filaments.

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Quantitative proteomics of tau and Aβ amyloid in detergent insoluble fractions from Alzheimer’s disease brains

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