标题：Mechanism of the cleavage specificity of Alzheimer’s disease γ-secretase identified by phenylalanine-scanning mutagenesis of the transmembrane domain of the amyloid precursor protein
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：6
页码：3053-3058
DOI：10.1073/pnas.96.6.3053
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Proteolytic processing of the amyloid precursor protein by {beta}-secretase yields A4CT (C99), which is cleaved further by the as yet unknown {gamma}-secretase, yielding the {beta}-amyloid (A{beta}) peptide with 40 (A{beta}40) or 42 residues (A{beta}42). Because the position of {gamma}-secretase cleavage is crucial for the pathogenesis of Alzheimer's disease, we individually replaced all membrane-domain residues of A4CT outside the A{beta} domain with phenylalanine, stably transfected the constructs in COS7 cells, and determined the effect of these mutations on the cleavage specificity of {gamma}-secretase (A{beta}42/A{beta}40 ratio). Compared with wild-type A4CT, mutations at Val-44, Ile-47, and Val-50 led to decreased A{beta}42/A{beta}40 ratios, whereas mutations at Thr-43, Ile-45, Val-46, Leu-49, and Met-51 led to increased A{beta}42/A{beta}40 ratios. A massive effect was observed for I45F (34-fold increase) making this construct important for the generation of animal models for Alzheimer's disease. Unlike the other mutations, A4CT-V44F was processed mainly to A{beta}38, as determined by mass spectrometry. Our data provide a detailed model for the active site of {gamma}-secretase: {gamma}-secretase interacts with A4CT by binding to one side of the -helical transmembrane domain of A4CT. Mutations in the transmembrane domain of A4CT interfere with the interaction between {gamma}-secretase and A4CT and, thus, alter the cleavage specificity of {gamma}-secretase.
