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The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells

INTRODUCTION: The A673T mutation in the amyloid precursor protein (APP) protects against Alzheimer’s disease by reducing β-amyloid protein (Aβ) production. This mutation reduced the release of the soluble APP fragment (sAPPβ), which is processed by β-secretase, suggesting a concomitant decrease in t...

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Autores principales: Kokawa, Asuka, Ishihara, Seiko, Fujiwara, Hitomi, Nobuhara, Mika, Iwata, Minori, Ihara, Yasuo, Funamoto, Satoru
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632685/
https://www.ncbi.nlm.nih.gov/pubmed/26531305
http://dx.doi.org/10.1186/s40478-015-0247-6
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author Kokawa, Asuka
Ishihara, Seiko
Fujiwara, Hitomi
Nobuhara, Mika
Iwata, Minori
Ihara, Yasuo
Funamoto, Satoru
author_facet Kokawa, Asuka
Ishihara, Seiko
Fujiwara, Hitomi
Nobuhara, Mika
Iwata, Minori
Ihara, Yasuo
Funamoto, Satoru
author_sort Kokawa, Asuka
collection PubMed
description INTRODUCTION: The A673T mutation in the amyloid precursor protein (APP) protects against Alzheimer’s disease by reducing β-amyloid protein (Aβ) production. This mutation reduced the release of the soluble APP fragment (sAPPβ), which is processed by β-secretase, suggesting a concomitant decrease in the β-carboxyl fragment of APP (C99), which is a direct substrate of γ-secretase for Aβ production. However, it remains controversial whether the level of C99 is significantly reduced in cells expressing APP that carry A673T as the cause of reduced Aβ production. Here, we investigated the effect of the A673T mutation in C99 on γ-cleavage in cells. RESULTS: We found that the level of C99 in cells expressing APP A673T was indistinctive of that observed in cells expressing wild-type APP, although the release of sAPPβ was significantly reduced in the APP A673T cells. In addition, our reconstituted β-secretase assay demonstrated no significant difference in β-cleavage on an APP fragment carrying the A673T mutation compared with the wild-type fragment. Importantly, cells expressing C99 containing the A673T mutation (C99 A2T; in accordance with the Aβ numbering) produced roughly half the level of Aβ compared with the wild-type C99, suggesting that the C99 A2T is an insufficient substrate of γ-secretase in cells. A cell-free γ-secretase assay revealed that Aβ production from the microsomal fraction of cells expressing C99 A2T was diminished. A sucrose gradient centrifugation analysis indicated that the levels of the C99 A2T that was codistributed with γ-secretase components in the raft fractions were reduced significantly. CONCLUSIONS: Our data indicate that the A673T mutation in APP alters the release of sAPPβ, but not the C99 level, and that the C99 A2T is an inefficient substrate for γ-secretase in cell-based assay. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40478-015-0247-6) contains supplementary material, which is available to authorized users.
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spelling pubmed-46326852015-11-05 The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells Kokawa, Asuka Ishihara, Seiko Fujiwara, Hitomi Nobuhara, Mika Iwata, Minori Ihara, Yasuo Funamoto, Satoru Acta Neuropathol Commun Research INTRODUCTION: The A673T mutation in the amyloid precursor protein (APP) protects against Alzheimer’s disease by reducing β-amyloid protein (Aβ) production. This mutation reduced the release of the soluble APP fragment (sAPPβ), which is processed by β-secretase, suggesting a concomitant decrease in the β-carboxyl fragment of APP (C99), which is a direct substrate of γ-secretase for Aβ production. However, it remains controversial whether the level of C99 is significantly reduced in cells expressing APP that carry A673T as the cause of reduced Aβ production. Here, we investigated the effect of the A673T mutation in C99 on γ-cleavage in cells. RESULTS: We found that the level of C99 in cells expressing APP A673T was indistinctive of that observed in cells expressing wild-type APP, although the release of sAPPβ was significantly reduced in the APP A673T cells. In addition, our reconstituted β-secretase assay demonstrated no significant difference in β-cleavage on an APP fragment carrying the A673T mutation compared with the wild-type fragment. Importantly, cells expressing C99 containing the A673T mutation (C99 A2T; in accordance with the Aβ numbering) produced roughly half the level of Aβ compared with the wild-type C99, suggesting that the C99 A2T is an insufficient substrate of γ-secretase in cells. A cell-free γ-secretase assay revealed that Aβ production from the microsomal fraction of cells expressing C99 A2T was diminished. A sucrose gradient centrifugation analysis indicated that the levels of the C99 A2T that was codistributed with γ-secretase components in the raft fractions were reduced significantly. CONCLUSIONS: Our data indicate that the A673T mutation in APP alters the release of sAPPβ, but not the C99 level, and that the C99 A2T is an inefficient substrate for γ-secretase in cell-based assay. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40478-015-0247-6) contains supplementary material, which is available to authorized users. BioMed Central 2015-11-04 /pmc/articles/PMC4632685/ /pubmed/26531305 http://dx.doi.org/10.1186/s40478-015-0247-6 Text en © Kokawa et al. 2015 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Kokawa, Asuka
Ishihara, Seiko
Fujiwara, Hitomi
Nobuhara, Mika
Iwata, Minori
Ihara, Yasuo
Funamoto, Satoru
The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title_full The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title_fullStr The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title_full_unstemmed The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title_short The A673T mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
title_sort a673t mutation in the amyloid precursor protein reduces the production of β-amyloid protein from its β-carboxyl terminal fragment in cells
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632685/
https://www.ncbi.nlm.nih.gov/pubmed/26531305
http://dx.doi.org/10.1186/s40478-015-0247-6
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