Copper ion incorporation in α-synuclein amyloids

Gulshan Walke, Ranjeet Kumar, Pernilla Wittung-Stafshede

Research output: Contribution to journalArticlepeer-review

Abstract

Copper ion dys-homeostasis is linked to neurodegenerative diseases involving amyloid formation. Even if many amyloidogenic proteins can bind copper ions as monomers, little is known about copper interactions with the resulting amyloid fibers. Here, we investigate copper interactions with α-synuclein, the amyloid-forming protein in Parkinson's disease. Copper (Cu(II)) binds tightly to monomeric α-synuclein in vitro involving the N-terminal amine and the side chain of His50. Using purified protein and biophysical methods in vitro, we reveal that copper ions are readily incorporated into the formed amyloid fibers when present at the start of aggregation reactions, and the metal ions also bind if added to pre-formed amyloids. Efficient incorporation is observed for α-synuclein variants with perturbation of either one of the high-affinity monomer copper-binding residues (i.e., N-terminus or His50) whereas a variant with both N-terminal acetylation and His50 substituted with Ala does not incorporate any copper into the amyloids. Both the morphology of the resulting α-synuclein amyloids (amyloid fiber pitch, secondary structure, proteinase sensitivity) and the copper chemical properties (redox activity, chemical potential) are altered when copper is incorporated into amyloids. We speculate that copper chelation by α-synuclein amyloids contributes to the observed copper dys-homeostasis (e.g., reduced bioavailable levels) in Parkinson's disease patients. At the same time, amyloid-copper interactions may be protective to neuronal cells as they will shield aberrantly free copper ions from promotion of toxic reactive oxygen species.

Original languageEnglish
Article numbere4956
JournalProtein Science
Volume33
Issue number4
DOIs
StatePublished - Apr 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2024 The Authors. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.

Keywords

  • aggregation
  • alpha-synuclein
  • amyloid
  • copper
  • reactive oxygen species

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