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Updated: Jul 17, 2026

Biochemical Purification and Proteomic Characterization of Amyloid Fibril Cores from the Brain
Published on: April 28, 2022
The 20S proteasome isolated from Alzheimer's disease brain shows post-translational modifications but unchanged
Frank Gillardon1, Alexander Kloss, Matthias Berg
1Boehringer Ingelheim Pharma GmbH & Co, KG, CNS Research, Biberach an der Riss, Germany. frank.gillardon@bc.boehringer-ingelheim.com
Abstract:
Chronic neurodegenerative diseases are characterized by the accumulation of aggregated protein species, and functional impairment of the ubiquitin proteasome system has been hypothesized to contribute to neuronal cell loss. Decreased proteolytic activity of the 20S proteasome has been shown postmortem in crude brain lysates from Alzheimer's disease (AD) patients. In the present study, we demonstrate, however, that catalytic activity of the 20S proteasome increases during chromatographic purification from AD brains as compared with age-matched controls. By two-dimensional difference gel electrophoresis we detected pI shifts in several proteasome subunits in AD samples pointing to differential post-translational modifications. Moreover, we identified N-terminal acetylation and dephosphorylation of subunit alpha7 in AD by tandem mass spectrometry. Thus, reduced peptidase activity in AD brain extracts is not an intrinsic property of the 20S proteasome, but may be resulting from the presence of endogenous inhibitory proteins or substrates. Post-translational modifications of non-catalytic subunits in situ may contribute to the trend towards enhanced hydrolytic activity of the isolated 20S proteasome after removal of the endogenous inhibitors.
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