Correlation Engine 2.0
Clear Search sequence regions

Sizes of these terms reflect their relevance to your search.

Production of amyloid β-protein (Aβ) is carried out by the membrane-embedded γ-secretase complex. Mutations in the transmembrane domain of amyloid β-protein precursor (APP) associated with early-onset familial Alzheimer's disease (FAD) can alter the ratio of aggregation-prone 42-residue (Aβ42) to 40-residue (Aβ40). However, APP substrate is proteolyzed processively by γ-secretase along two pathways: Aβ49→Aβ46→Aβ43→Aβ40 and Aβ48→Aβ45→Aβ42→Aβ38. Effects of FAD mutations on each proteolytic step are unknown, largely due to difficulties in detecting and quantifying longer peptides. To address this, we carried out systematic and quantitative analyses of all tri- and tetrapeptide coproducts from proteolysis of wild-type and 14 FAD-mutant APP substrates by purified γ-secretase. These small peptides, including FAD-mutant forms, were detected by tandem mass spectrometry and quantified by establishing concentration curves for each of 32 standards. APP intracellular domain (AICD) coproducts were quantified by immunoblot, and the ratio of AICD products corresponding to Aβ48 and Aβ49 was determined by mass spectrometry. Levels of individual peptides were determined by subtracting levels of peptide coproducts associated with degradation from those associated with production. This method was validated for Aβ40 and Aβ42 by specific ELISAs and production of equimolar levels of and AICD. Not all mutant substrates led to increased Aβ42/40. However, all 14 disease-causing mutations led to inefficient processing of longer forms of ≥ 45 residues. In addition, the effects of certain mutations provided insight into the mechanism of processive proteolysis: intermediate peptides apparently remain bound for subsequent trimming and are not released and reassociated. Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.


Sujan Devkota, Todd D Williams, Michael S Wolfe. Familial Alzheimer's disease mutations in amyloid protein precursor alter proteolysis by γ-secretase to increase amyloid β-peptides of ≥45 residues. The Journal of biological chemistry. 2021 Jan-Jun;296:100281

Expand section icon Mesh Tags

Expand section icon Substances

PMID: 33450230

View Full Text