title: Impact of methionine oxidation as an initial event on the pathway of human prion protein conversion.
abstract: Prion diseases comprise a group of fatal neurodegenerative disorders characterized by the autocatalytic conversion of the cellular prion protein PrP(C) into the infectious misfolded isoform PrP(Sc). Increasing evidence supports a specific role of oxidative stress in the onset of pathogenesis. Although the associated molecular mechanisms remain to be elucidated in detail, several studies currently suggest that methionine oxidation already detected in misfolded PrP(Sc) destabilizes the native PrP fold as an early event in the conversion pathway. To obtain more insights about the specific impact of surface-exposed methionine residues on the oxidative-induced conversion of human PrP we designed, produced, and comparatively investigated two new pseudosulfoxidation mutants of human PrP 121-231 that comprises the well-folded C-terminal domain. Applying circular dichroism spectroscopy and dynamic light scattering techniques we showed that pseudosulfoxidation of all surface exposed Met residues formed a monomeric molten globule-like species with striking similarities to misfolding intermediates recently reported by other groups. However, individual pseudosulfoxidation at the polymorphic M129 site did not significantly contribute to the structural destabilization. Further metal-induced oxidation of the partly unfolded pseudosulfoxidation mutant resulted in the formation of an oligomeric state that shares a comparable size and stability with PrP oligomers detected after the application of different other triggers for structural conversion, indicating a generic misfolding pathway of PrP. The obtained results highlight the specific importance of methionine oxidation at surface exposed residues for PrP misfolding, strongly supporting the hypothesis that increased oxidative stress could be one causative event for sporadic prion diseases and other neurodegenerative disorders.
authors.affiliation: Institute of Biochemistry and Molecular Biology; Department of Chemistry; University of Hamburg, c/o DESY; Hamburg, Germany.
authors.forename: Mohammed I Y
authors.initials: MI
authors.lastname: Elmallah
authors.affiliation: Institute for Molecular and Cellular Cognition; Center for Molecular Neurobiology (ZMNH); University Medical Center Eppendorf; Hamburg, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Borgmeyer
authors.affiliation: Institute of Biochemistry and Molecular Biology; Department of Chemistry; University of Hamburg, c/o DESY; Hamburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Betzel
authors.affiliation: Joint Laboratory for Structural Biology of Infection and Inflammation; Institute of Biochemistry and Molecular Biology; University of Hamburg; and Institute of Biochemistry; University of Lübeck, c/o DESY; Hamburg, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Redecke
mesh_terms: D006801:Humans; D008670:Metals / Q000378:metabolism; D008715:Methionine / Q000032:analysis / Q000378:metabolism*; D009154:Mutation; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017096:Prion Diseases / Q000235:genetics / Q000378:metabolism*; D011328:Prions / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary
chemical_list: D008670:Metals; D011328:Prions; D008715:Methionine
keywords: metal induced oxidation; methionine oxidation; oxidative stress; polymorphism; prion protein conversion