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The 20S proteasome isolated from Alzheimer’s disease brain shows post‐translational modifications but unchanged proteolytic activity
Author(s) -
Gillardon Frank,
Kloß Alexander,
Berg Matthias,
Neumann Manuela,
Mechtler Karl,
Hengerer Bastian,
Dahlmann Burkhardt
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2006.04438.x
Subject(s) - proteasome , proteolysis , protein subunit , dephosphorylation , ubiquitin , biochemistry , endogeny , alzheimer's disease , chemistry , acetylation , biology , enzyme , microbiology and biotechnology , disease , phosphatase , medicine , gene
Summary 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 α7 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.