Somatostatin binds to the human amyloid β peptide and favors the formation of distinct oligomers

Abstract

The amyloid β peptide (Aβ) is a key player in the etiology of Alzheimer disease (AD), yet a systematic investigation of its molecular interactions has not been reported. Here we identified by quantitative mass spectrometry proteins in human brain extract that bind to oligomeric Aβ1-42 (oAβ1-42) and/or monomeric Aβ1-42 (mAβ1-42) baits. Remarkably, the cyclic neuroendocrine peptide somatostatin-14 (SST14) was observed to be the most selectively enriched oAβ1-42 binder. The binding interface comprises a central tryptophan within SST14 and the N-terminus of Aβ1-42. The presence of SST14 inhibited Aβ aggregation and masked the ability of several antibodies to detect Aβ. Notably, Aβ1-42, but not Aβ1-40, formed in the presence of SST14 oligomeric assemblies of 50 to 60 kDa that were visualized by gel electrophoresis, nanoparticle tracking analysis and electron microscopy. These findings may be relevant for Aβ-directed diagnostics and may signify a role of SST14 in the etiology of AD.

Data availability

The following data sets were generated

Article and author information

Author details

  1. Hansen Wang

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    Competing interests
    Hansen Wang, Holds provisionary US patent on amyloid-beta binding polypeptides based on the results of this study (filing number 62/451,309)..
  2. Lisa D Muiznieks

    Molecular Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, Canada
    Competing interests
    No competing interests declared.
  3. Punam Ghosh

    Department of Medical Biophysics, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
  4. Declan Williams

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
  5. Michael Solarski

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
  6. Andrew Fang

    Department of Biochemistry, University of Alberta, Edmonton, Canada
    Competing interests
    No competing interests declared.
  7. Alejandro Ruiz-Riquelme

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6581-7132
  8. Régis Pomès

    Molecular Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, Canada
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-3068-9833
  9. Joel C Watts

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
  10. Avi Chakrabartty

    Department of Medical Biophysics, University of Toronto, Toronto, Canada
    Competing interests
    No competing interests declared.
  11. Holger Wille

    Department of Biochemistry, University of Alberta, Edmonton, Canada
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5102-8706
  12. Simon Sharpe

    Molecular Medicine Program, Research Institute, The Hospital for Sick Children, Toronto, Canada
    Competing interests
    No competing interests declared.
  13. Gerold Schmitt-Ulms

    Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Canada
    For correspondence
    g.schmittulms@utoronto.ca
    Competing interests
    Gerold Schmitt-Ulms, Holds provisionary US patent on amyloid-beta binding polypeptides based on the results of this study (filing number 62/451,309).
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6962-0919

Funding

Canadian Institutes of Health Research

  • Gerold Schmitt-Ulms

Ontario Centres for Excellence

  • Simon Sharpe
  • Gerold Schmitt-Ulms

Alberta Innovates Bio Solutions (201600028)

  • Holger Wille
  • Gerold Schmitt-Ulms

Heart and Stroke Foundation of Canada (G-15-0009148)

  • Simon Sharpe

Canada Foundation for Innovation

  • Gerold Schmitt-Ulms

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Randy Schekman, Howard Hughes Medical Institute, University of California, Berkeley, United States

Ethics

Animal experimentation: The work was performed in strict accordance with University of Toronto animal care and biosafety recommendations. All mice were handled according to procedures approved (AUP4183.3) by the animal care committee at University Health Network overseeing work at the Krembil Discovery Centre (Toronto). The handling of samples and reagents followed biosafety procedures approved (208-S06-2) by the University of Toronto Biosafety Program.

Version history

  1. Received: November 18, 2016
  2. Accepted: June 14, 2017
  3. Accepted Manuscript published: June 26, 2017 (version 1)
  4. Version of Record published: July 11, 2017 (version 2)

Copyright

© 2017, Wang et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 2,690
    views
  • 545
    downloads
  • 34
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Hansen Wang
  2. Lisa D Muiznieks
  3. Punam Ghosh
  4. Declan Williams
  5. Michael Solarski
  6. Andrew Fang
  7. Alejandro Ruiz-Riquelme
  8. Régis Pomès
  9. Joel C Watts
  10. Avi Chakrabartty
  11. Holger Wille
  12. Simon Sharpe
  13. Gerold Schmitt-Ulms
(2017)
Somatostatin binds to the human amyloid β peptide and favors the formation of distinct oligomers
eLife 6:e28401.
https://doi.org/10.7554/eLife.28401

Share this article

https://doi.org/10.7554/eLife.28401

Further reading

    1. Biochemistry and Chemical Biology
    2. Structural Biology and Molecular Biophysics
    Marian Brenner, Christoph Zink ... Antje Gohla
    Research Article

    Vitamin B6 deficiency has been linked to cognitive impairment in human brain disorders for decades. Still, the molecular mechanisms linking vitamin B6 to these pathologies remain poorly understood, and whether vitamin B6 supplementation improves cognition is unclear as well. Pyridoxal 5’-phosphate phosphatase (PDXP), an enzyme that controls levels of pyridoxal 5’-phosphate (PLP), the co-enzymatically active form of vitamin B6, may represent an alternative therapeutic entry point into vitamin B6-associated pathologies. However, pharmacological PDXP inhibitors to test this concept are lacking. We now identify a PDXP and age-dependent decline of PLP levels in the murine hippocampus that provides a rationale for the development of PDXP inhibitors. Using a combination of small-molecule screening, protein crystallography, and biolayer interferometry, we discover, visualize, and analyze 7,8-dihydroxyflavone (7,8-DHF) as a direct and potent PDXP inhibitor. 7,8-DHF binds and reversibly inhibits PDXP with low micromolar affinity and sub-micromolar potency. In mouse hippocampal neurons, 7,8-DHF increases PLP in a PDXP-dependent manner. These findings validate PDXP as a druggable target. Of note, 7,8-DHF is a well-studied molecule in brain disorder models, although its mechanism of action is actively debated. Our discovery of 7,8-DHF as a PDXP inhibitor offers novel mechanistic insights into the controversy surrounding 7,8-DHF-mediated effects in the brain.

    1. Biochemistry and Chemical Biology
    2. Stem Cells and Regenerative Medicine
    Parthasarathy Sampathkumar, Heekyung Jung ... Yang Li
    Research Article

    Molecules that facilitate targeted protein degradation (TPD) offer great promise as novel therapeutics. The human hepatic lectin asialoglycoprotein receptor (ASGR) is selectively expressed on hepatocytes. We have previously engineered an anti-ASGR1 antibody-mutant RSPO2 (RSPO2RA) fusion protein (called SWEETS) to drive tissue-specific degradation of ZNRF3/RNF43 E3 ubiquitin ligases, which achieved hepatocyte-specific enhanced Wnt signaling, proliferation, and restored liver function in mouse models, and an antibody–RSPO2RA fusion molecule is currently in human clinical trials. In the current study, we identified two new ASGR1- and ASGR1/2-specific antibodies, 8M24 and 8G8. High-resolution crystal structures of ASGR1:8M24 and ASGR2:8G8 complexes revealed that these antibodies bind to distinct epitopes on opposing sides of ASGR, away from the substrate-binding site. Both antibodies enhanced Wnt activity when assembled as SWEETS molecules with RSPO2RA through specific effects sequestering E3 ligases. In addition, 8M24-RSPO2RA and 8G8-RSPO2RA efficiently downregulate ASGR1 through TPD mechanisms. These results demonstrate the possibility of combining different therapeutic effects and degradation mechanisms in a single molecule.