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Exclusively targeting beta-secretase to lipid rafts by GPI-anchor addition up-regulates beta-site processing of the amyloid precursor protein

Cordy, J.M., Hussain, I., Dingwall, C., Hooper, N.M. and Turner, A.J. (2003) Exclusively targeting beta-secretase to lipid rafts by GPI-anchor addition up-regulates beta-site processing of the amyloid precursor protein. Proceedings of the National Academy of Sciences, 100 (20). pp. 11735-11740. ISSN 0027-8424

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Abstract

β-Secretase (BACE, Asp-2) is a transmembrane aspartic proteinase responsible for cleaving the amyloid precursor protein (APP) to generate the soluble ectodomain sAPPβ and its C-terminal fragment CTFβ. CTFβ is subsequently cleaved by γ-secretase to produce the neurotoxic/synaptotoxic amyloid-β peptide (Aβ) that accumulates in Alzheimer's disease. Indirect evidence has suggested that amyloidogenic APP processing may preferentially occur in lipid rafts. Here, we show that relatively little wild-type BACE is found in rafts prepared from a human neuroblastoma cell line (SH-SY5Y) by using Triton X-100 as detergent. To investigate further the significance of lipid rafts in APP processing, a glycosylphosphatidylinositol (GPI) anchor has been added to BACE, replacing the transmembrane and C-terminal domains. The GPI anchor targets the enzyme exclusively to lipid raft domains. Expression of GPIBACE substantially up-regulates the secretion of both sAPPβ and amyloid-β peptide over levels observed from cells overexpressing wild-type BACE. This effect was reversed when the lipid rafts were disrupted by depleting cellular cholesterol levels. These results suggest that processing of APP to the amyloid-β peptide occurs predominantly in lipid rafts and that BACE is the rate-limiting enzyme in this process. The processing of the APP(695) isoform by GPI-BACE was up-regulated 20-fold compared with wild-type BACE, whereas only a 2-fold increase in the processing of APP(751/770)was seen, implying a differential compartmentation of the APP isoforms. Changes in the local membrane environment during aging may facilitate the cosegregation of APP and BACE leading to increased β-amyloid production.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 2003 by the National Academy of Sciences
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Biological Sciences (Leeds) > Institute of Molecular and Cellular Biology (Leeds)
Depositing User: Sherpa Assistant
Date Deposited: 13 Mar 2006
Last Modified: 07 Jun 2014 10:35
Published Version: http://www.pnas.org/cgi/content/full/100/20/11735
Status: Published
Refereed: Yes
Identification Number: 10.1073/pnas.1635130100
URI: http://eprints.whiterose.ac.uk/id/eprint/559

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