Mutant Presenilin 1 Increases the Expression and Activity of BACE1

Luca Giliberto,Roberta Borghi,Alessandra Piccini,Rosa Mangerini,Sandro Sorbi,Gabriella Cirmena,Anna Garuti,Bernardino Ghetti,Fabrizio Tagliavini,Mohamed R Mughal,Mark P Mattson,Xiongwei Zhu,Xinglong Wang,Michela Guglielmotto,Elena Tamagno,Massimo Tabaton

doi:10.1074/jbc.m805685200

Abstract

Mutations of the presenilin 1 (PS1) gene are the most common cause of early onset familial Alzheimer disease (FAD). PS1 mutations alter the activity of the gamma-secretase on the beta-amyloid precursor protein (APP), leading to selective overproduction of beta-amyloid (Abeta) 42 peptides, the species that forms oligomers that may exert toxic effects on neurons. Here we show that PS1 mutations, expressed both transiently and stably, in non-neuronal and neuronal cell lines increase the expression and the activity of the beta-secretase (BACE1), the rate-limiting step of Abeta production. Also, BACE1 expression and activity are elevated in brains of PS1 mutant knock-in mice compared with wild type littermates as well as in cerebral cortex of FAD cases bearing various PS1 mutations compared with in sporadic AD cases and controls. The up-regulation of BACE1 by PS1 mutations requires the gamma-secretase cleavage of APP and is proportional to the amount of secreted Abeta42. Abeta42, and not AICD (APP intracellular domain), is indeed the APP derivative that mediates the overexpression of BACE1. The effect of PS1 mutations on BACE1 may contribute to determine the wide clinical and pathological phenotype of early onset FAD.

Highlights

Mutations of the presenilin 1 (PS1) gene are the most common cause of early onset familial Alzheimer disease (FAD)
In the cerebral cortex of FAD cases with mutations of PS1, the relative percentage of the two N-terminal-truncated A␤ species is significantly increased in comparison to sporadic AD cases [7]
The known effect of PS1 mutations is the alteration of the ␥-secretase cleavage on amyloid precursor protein (APP), leading to the relative increased production of A␤42 species [3, 4]

Summary

Introduction

Mutations of the presenilin 1 (PS1) gene are the most common cause of early onset familial Alzheimer disease (FAD). 293 APPwt cells, indicating that the up-regulation of BACE1 determined by the PS1 mutations was not compensated by the presence of the wild type PS1; they showed an increase of BACE1 protein levels

Results

Conclusion