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The Alzheimer's Disease γ-Secretase Generates Higher 42:40 Ratios for β-Amyloid Than for p3 Peptides


Siegel, Gabriele; Gerber, Hermeto; Koch, Philipp; Bruestle, Oliver; Fraering, Patrick C; Rajendran, Lawrence (2017). The Alzheimer's Disease γ-Secretase Generates Higher 42:40 Ratios for β-Amyloid Than for p3 Peptides. Cell Reports, 19(10):1967-1976.

Abstract

Alzheimer's disease is characterized by intracerebral deposition of β-amyloid (Aβ). While Aβ40 is the most abundant form, neurotoxicity is mainly mediated by Aβ42. Sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases gives rise to full-length Aβ (Aβ1-x) and N-terminally truncated Aβ' (Aβ11-x) whereas cleavage by α- and γ-secretases leads to the shorter p3 peptides (Aβ17-x). We uncovered significantly higher ratios of 42- versus 40-ending variants for Aβ and Aβ' than for p3 secreted by mouse neurons and human induced pluripotent stem cell (iPSC)-derived neurons or produced in a cell-free γ-secretase assay with recombinant APP-CTFs. The 42:40 ratio was highest for Aβ', followed by Aβ and then p3. Mass spectrometry analysis of APP intracellular domains revealed differential processing of APP-C83, APP-C89, and APP-C99 by γ-secretase already at the ε-cleavage stage. This mechanistic insight could aid in developing substrate-targeted modulators of APP-C99 processing to specifically lower the Aβ42:Aβ40 ratio without compromising γ-secretase function.

Abstract

Alzheimer's disease is characterized by intracerebral deposition of β-amyloid (Aβ). While Aβ40 is the most abundant form, neurotoxicity is mainly mediated by Aβ42. Sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases gives rise to full-length Aβ (Aβ1-x) and N-terminally truncated Aβ' (Aβ11-x) whereas cleavage by α- and γ-secretases leads to the shorter p3 peptides (Aβ17-x). We uncovered significantly higher ratios of 42- versus 40-ending variants for Aβ and Aβ' than for p3 secreted by mouse neurons and human induced pluripotent stem cell (iPSC)-derived neurons or produced in a cell-free γ-secretase assay with recombinant APP-CTFs. The 42:40 ratio was highest for Aβ', followed by Aβ and then p3. Mass spectrometry analysis of APP intracellular domains revealed differential processing of APP-C83, APP-C89, and APP-C99 by γ-secretase already at the ε-cleavage stage. This mechanistic insight could aid in developing substrate-targeted modulators of APP-C99 processing to specifically lower the Aβ42:Aβ40 ratio without compromising γ-secretase function.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute for Regenerative Medicine (IREM)
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:6 June 2017
Deposited On:01 Feb 2018 11:08
Last Modified:19 Feb 2018 10:37
Publisher:Cell Press (Elsevier)
ISSN:2211-1247
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1016/j.celrep.2017.05.034
PubMed ID:28591569

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