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Dominant negative effect of the loss-of-function γ-secretase mutants on the wild-type enzyme through heterooligomerization

  1. Yigong Shia,b,c,d,2
  1. aBeijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, China;
  2. bTsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China;
  3. cCenter for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China;
  4. dInstitute of Biology, Westlake Institute for Advanced Study, Xihu District, Hangzhou 310064, Zhejiang Province, China
  1. Contributed by Yigong Shi, September 12, 2017 (sent for review August 2, 2017; reviewed by Yue-Ming Li, Jie Shen, and Gang Yu)

Significance

The vast majority of familial Alzheimer’s disease (AD) cases are linked to mutations in presenilin-1 (PS1) in an autosomal dominant manner. PS1 is the catalytic component of γ-secretase, which cleaves amyloid precursor protein into Aβ peptides. It remains unclear whether the causal role of PS1 mutations in AD development is effected through γ-secretase, and if yes, whether the dominant negative effect of PS1 mutant allele is effected through the proteolytic activity of γ-secretase. In this study, we provide compelling evidence to prove a dominant negative effect by the loss-of-function γ-secretase mutants on the production of Aβ42/40 by WT γ-secretase through hetero-oligomerization. These data, together with our prior knowledge on the function of γ-secretase, have important ramifications on the two key questions listed here.

Abstract

γ-secretase is an intramembrane protease complex consisting of nicastrin, presenilin-1/2, APH-1a/b, and Pen-2. Hydrolysis of the 99-residue transmembrane fragment of amyloid precursor protein (APP-C99) by γ-secretase produces β-amyloid (Aβ) peptides. Pathogenic mutations in PSEN1 and PSEN2, which encode the catalytic subunit presenilin-1/2 of γ-secretase, lead to familial Alzheimer’s disease in an autosomal dominant manner. However, the underlying mechanism of how the mutant PSEN gene may affect the function of the WT allele remains to be elucidated. Here we report that each of the loss-of-function γ-secretase variants that carries a PSEN1 mutation suppresses the protease activity of the WT γ-secretase on Aβ production. Each of these γ-secretase variants forms a stable oligomer with the WT γ-secretase in vitro in the presence of the detergent CHAPSO {3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate}, but not digitonin. Importantly, robust protease activity of γ-secretase is detectable in the presence of CHAPSO, but not digitonin. These experimental observations suggest a dominant negative effect of the γ-secretase, in which the protease activity of WT γ-secretase is suppressed by the loss-of-function γ-secretase variants through hetero-oligomerization. The relevance of this finding to the genesis of Alzheimer’s disease is critically evaluated.

Footnotes

  • ?1R.Z. and G. Yang contributed equally to this work.

  • ?2To whom correspondence may be addressed. Email: zhour13{at}mails.tsinghua.edu.cn, yanggh{at}mail.tsinghua.edu.cn, or shi-lab{at}tsinghua.edu.cn.
  • Author contributions: R.Z., G. Yang, and Y.S. designed research; R.Z. and G. Yang performed research; R.Z., G. Yang, and Y.S. analyzed data; and R.Z., G. Yang, and Y.S. wrote the paper.

  • Reviewers: Y.-M.L., Memorial Sloan-Kettering Cancer Center; J.S., Brigham and Women's Hospital, Harvard Medical School; and G. Yu, UT Southwestern Medical Center.

  • Conflict of interest statement: Y.S. and Y.-M.L. were co-authors on a 2015 paper.

  • See Commentary on page 12635.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1713605114/-/DCSupplemental.

This is an open access article distributed under the PNAS license.

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