Specific mutations in the cholesterol-binding site of APP alter its processing and favor the production of shorter, less toxic Aβ peptides

Hanbouch, L. et al. (2022) Specific mutations in the cholesterol-binding site of APP alter its processing and favor the production of shorter, less toxic Aβ peptides. Molecular Neurobiology, 59(11), pp. 7056-7073. (doi: 10.1007/s12035-022-03025-9) (PMID:36076005) (PMCID:PMC9525381)

Abstract

Excess brain cholesterol is strongly implicated in the pathogenesis of Alzheimer’s disease (AD). Here we evaluated how the presence of a cholesterol-binding site (CBS) in the transmembrane and juxtamembrane regions of the amyloid precursor protein (APP) regulates its processing. We generated nine point mutations in the APP gene, changing the charge and/or hydrophobicity of the amino-acids which were previously shown as part of the CBS. Most mutations triggered a reduction of amyloid-β peptides Aβ40 and Aβ42 secretion from transiently transfected HEK293T cells. Only the mutations at position 28 of Aβ in the APP sequence resulted in a concomitant significant increase in the production of shorter Aβ peptides. Mass spectrometry (MS) confirmed the predominance of Aβx-33 and Aβx-34 with the APPK28A mutant. The enzymatic activity of α-, β-, and γ-secretases remained unchanged in cells expressing all mutants. Similarly, subcellular localization of the mutants in early endosomes did not differ from the APPWT protein. A transient increase of plasma membrane cholesterol enhanced the production of Aβ40 and Aβ42 by APPWT, an effect absent in APPK28A mutant. Finally, WT but not CBS mutant Aβ derived peptides bound to cholesterol-rich exosomes. Collectively, the present data revealed a major role of juxtamembrane amino acids of the APP CBS in modulating the production of toxic Aβ species. More generally, they underpin the role of cholesterol in the pathophysiology of AD.

• Item Type: Articles
• Keywords: Alzheimer’s disease, mutant, cholesterol, Aβ, amyloid precursor protein.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Millan, Dr Mark
• Authors: Hanbouch, L., Schaack, B., Kasri, A., Fontaine, G., Gkanatsiou, E., Brinkmalm, G., Camporesi, E., Portelius, E., Blennow, K., Mourier, G., Gilles, N., Millan, M. J., Marquer, C., Zetterberg, H., Boussicault, L., and Potier, M.-C.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Molecular Neurobiology
• Publisher: Springer
• ISSN: 0893-7648
• ISSN (Online): 1559-1182
• Published Online: 09 September 2022
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Molecular Neurobiology 59(11): 7056-7073
• Publisher Policy: Reproduced under a Creative Commons License
• Data DOI: 10.5281/zenodo.6274232