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Amyloid precursor protein mutation E682K at the alternative ?-secretase cleavage ?'-site increases A? generation.

ABSTRACT: BACE1 cleaves the amyloid precursor protein (APP) at the ?-cleavage site (Met(671) -Asp(672) ) to initiate the generation of amyloid peptide A?. BACE1 is also known to cleave APP at a much less well-characterized ?'-cleavage site (Tyr(681) -Glu(682) ). We describe here the identification of a novel APP mutation E682K located at this ?'-site in an early onset Alzheimer's disease (AD) case. Functional analysis revealed that this E682K mutation blocked the ?'-site and shifted cleavage of APP to the ?-site, causing increased A? production. This work demonstrates the functional importance of APP processing at the ?'-site and shows how disruption of the balance between ?- and ?'-site cleavage may enhance the amyloidogenic processing and consequentially risk for AD. Increasing exon- and exome-based sequencing efforts will identify many more putative pathogenic mutations without conclusive segregation-based evidence in a single family. Our study shows how functional analysis of such mutations allows to determine the potential pathogenic nature of these mutations. We propose to classify the E682K mutation as probable pathogenic awaiting further independent confirmation of its association with AD in other patients.

SUBMITTER: Zhou L

PROVIDER: S-EPMC3377078 | biostudies-other | 2011 May

REPOSITORIES: biostudies-other

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Amyloid precursor protein mutation E682K at the alternative β-secretase cleavage β'-site increases Aβ generation.

Zhou Lujia L Brouwers Nathalie N Benilova Iryna I Vandersteen Annelies A Mercken Marc M Van Laere Koen K Van Damme Philip P Demedts David D Van Leuven Fred F Sleegers Kristel K Broersen Kerensa K Van Broeckhoven Christine C Vandenberghe Rik R De Strooper Bart B

EMBO molecular medicine 20110415 5

BACE1 cleaves the amyloid precursor protein (APP) at the β-cleavage site (Met(671) -Asp(672) ) to initiate the generation of amyloid peptide Aβ. BACE1 is also known to cleave APP at a much less well-characterized β'-cleavage site (Tyr(681) -Glu(682) ). We describe here the identification of a novel APP mutation E682K located at this β'-site in an early onset Alzheimer's disease (AD) case. Functional analysis revealed that this E682K mutation blocked the β'-site and shifted cleavage of APP to the ...[more]

PMID: 21500352

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Project description:BackgroundThree amino acid differences between rodent and human APP affect medically important features, including β-secretase cleavage of APP and Aβ peptide aggregation (De Strooper et al., EMBO J 14:4932-38, 1995; Ueno et al., Biochemistry 53:7523-30, 2014; Bush, 2003, Trends Neurosci 26:207-14). Most rodent models for Alzheimer's disease (AD) are, therefore, based on the human APP sequence, expressed from artificial mini-genes randomly inserted in the rodent genome. While these models mimic rather well various biochemical aspects of the disease, such as Aβ-aggregation, they are also prone to overexpression artifacts and to complex phenotypical alterations, due to genes affected in or close to the insertion site(s) of the mini-genes (Sasaguri et al., EMBO J 36:2473-87, 2017; Goodwin et al., Genome Res 29:494-505, 2019). Knock-in strategies which introduce clinical mutants in a humanized endogenous rodent APP sequence (Saito et al., Nat Neurosci 17:661-3, 2014) represent useful improvements, but need to be compared with appropriate humanized wildtype (WT) mice.MethodsComputational modelling of the human β-CTF bound to BACE1 was used to study the differential processing of rodent and human APP. We humanized the three pivotal residues we identified G676R, F681Y and R684H (labeled according to the human APP770 isoform) in the mouse and rat genomes using a CRISPR-Cas9 approach. These new models, termed mouse and rat Apphu/hu, express APP from the endogenous promotor. We also introduced the early-onset familial Alzheimer's disease (FAD) mutation M139T into the endogenous Rat Psen1 gene.ResultsWe show that introducing these three amino acid substitutions into the rodent sequence lowers the affinity of the APP substrate for BACE1 cleavage. The effect on β-secretase processing was confirmed as both humanized rodent models produce three times more (human) Aβ compared to the original WT strain. These models represent suitable controls, or starting points, for studying the effect of transgenes or knock-in mutations on APP processing (Saito et al., Nat Neurosci 17:661-3, 2014). We introduced the early-onset familial Alzheimer's disease (FAD) mutation M139T into the endogenous Rat Psen1 gene and provide an initial characterization of Aβ processing in this novel rat AD model.ConclusionThe different humanized APP models (rat and mouse) expressing human Aβ and PSEN1 M139T are valuable controls to study APP processing in vivo allowing the use of a human Aβ ELISA which is more sensitive than the equivalent system for rodents. These animals will be made available to the research community.

Dataset Information

Amyloid precursor protein mutation E682K at the alternative ?-secretase cleavage ?'-site increases A? generation.

Publications

Amyloid precursor protein mutation E682K at the alternative β-secretase cleavage β'-site increases Aβ generation.

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