Browsing by Subject "Aspartic acid"

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    Does Data-Independent Acquisition Data Contain Hidden Gems? A Case Study Related to Alzheimer's Disease
    (American Chemical Society, 2022) Hubbard, Evan E.; Heil, Lilian R.; Merrihew, Gennifer E.; Chhatwal, Jasmeer P.; Farlow, Martin R.; McLean, Catriona A.; Ghetti, Bernardino; Newell, Kathy L.; Frosch, Matthew P.; Bateman, Randall J.; Larson, Eric B.; Keene, C. Dirk; Perrin, Richard J.; Montine, Thomas J.; MacCoss, Michael J.; Julian, Ryan R.; Pathology and Laboratory Medicine, School of Medicine
    One of the potential benefits of using data-independent acquisition (DIA) proteomics protocols is that information not originally targeted by the study may be present and discovered by subsequent analysis. Herein we reanalyzed DIA data originally recorded for global proteomic analysis to look for isomerized peptides, which occur as a result of spontaneous chemical modifications to long-lived proteins. Examination of a large set of human brain samples revealed a striking relationship between Alzheimer’s disease (AD) status and isomerization of aspartic acid in a peptide from tau. Relative to controls, a surprising increase in isomer abundance was found in both autosomal dominant and sporadic AD samples. To explore potential mechanisms that might account for these observations, quantitative analysis of proteins related to isomerization repair and autophagy was performed. Differences consistent with reduced autophagic flux in AD-related samples relative to controls were found for numerous proteins, including most notably p62, a recognized indicator of autophagic inhibition. These results suggest, but do not conclusively demonstrate, that lower autophagic flux may be strongly associated with loss of function in AD brains. This study illustrates that DIA data may contain unforeseen results of interest, and may be particularly useful for pilot studies investigating new research directions. In this case, a promising target for future investigations into the therapy and prevention of AD has been identified.
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    Increased Tau Phosphorylation and Tau Truncation, and Decreased Synaptophysin Levels in Mutant BRI2/Tau Transgenic Mice
    (Public Library of Science, 2013) Garringer, Holly J.; Murrell, Jill; Sammeta, Neeraja; Gnezda, Anita; Ghetti, Bernardino; Vidal, Ruben; Pathology and Laboratory Medicine, School of Medicine
    Familial Danish dementia (FDD) is an autosomal dominant neurodegenerative disease caused by a 10-nucleotide duplication-insertion in the BRI(2) gene. FDD is clinically characterized by loss of vision, hearing impairment, cerebellar ataxia and dementia. The main neuropathologic findings in FDD are the deposition of Danish amyloid (ADan) and the presence of neurofibrillary tangles (NFTs). Here we investigated tau accumulation and truncation in double transgenic (Tg-FDD-Tau) mice generated by crossing transgenic mice expressing human Danish mutant BRI(2) (Tg-FDD) with mice expressing human 4-repeat mutant Tau-P301S (Tg-Tau). Compared to Tg-Tau mice, we observed a significant enhancement of tau deposition in Tg-FDD-Tau mice. In addition, a significant increase in tau cleaved at aspartic acid (Asp) 421 was observed in Tg-FDD-Tau mice. Tg-FDD-Tau mice also showed a significant decrease in synaptophysin levels, occurring before widespread deposition of fibrillar ADan and tau can be observed. Thus, the presence of soluble ADan/mutant BRI(2) can lead to significant changes in tau metabolism and synaptic dysfunction. Our data provide new in vivo insights into the pathogenesis of FDD and the pathogenic pathway(s) by which amyloidogenic peptides, regardless of their primary amino acid sequence, can cause neurodegeneration.