title: Changes in secondary structure of α-synuclein during oligomerization induced by reactive aldehydes.
abstract: The oxidative stress-related reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) have been shown to promote formation of α-synuclein oligomers in vitro. However, the changes in secondary structure of α-synuclein and the kinetics of the oligomerization process are not known and were the focus of this study. Size exclusion chromatography showed that after 1 h of incubation, HNE induced the formation of an oligomeric α-synuclein peak with a molecular weight of about ∼2000 kDa, which coincided with a decreasing ∼50 kDa monomeric peak. With prolonged incubation (up to 24 h) the oligomeric peak became the dominating molecular species. In contrast, in the presence of ONE, a ∼2000 oligomeric peak was exclusively observed after 15 min of incubation and this peak remained constant with prolonged incubation. Western blot analysis of HNE-induced α-synuclein oligomers showed the presence of monomers (15 kDa), SDS-resistant low molecular (30-160 kDa) and high molecular weight oligomers (≥260 kDa), indicating that the oligomers consisted of both covalent and non-covalent protein. In contrast, ONE-induced α-synuclein oligomers only migrated as covalent cross-linked high molecular-weight material (≥300 kDa). Both circular dichroism (CD) and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed that the formation of HNE- and ONE-induced oligomers coincided with a spectral change from random coil to β-sheet. However, ONE-induced α-synuclein oligomers exhibited a slightly higher degree of β-sheet. Taken together, our results indicate that both HNE and ONE induce a change from random coil to β-sheet structure that coincides with the formation of α-synuclein oligomers; albeit through different kinetic pathways depending on the degree of cross-linking.
authors.affiliation: Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Sweden.
authors.forename: Yixiao
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Christofer
authors.initials: C
authors.lastname: Lendel
authors.affiliation: Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Österlund
authors.affiliation: BioArctic Neuroscience, Stockholm, Sweden.
authors.forename: Alex
authors.initials: A
authors.lastname: Kasrayan
authors.affiliation: Department of Public Health and Caring Sciences, Rudbeck Laboratory, Uppsala University, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Lannfelt
authors.affiliation: Department of Public Health and Caring Sciences, Rudbeck Laboratory, Uppsala University, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Ingelsson
authors.affiliation: Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Nikolajeff
authors.affiliation: Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Karlsson
authors.affiliation: Department of Public Health and Caring Sciences, Rudbeck Laboratory, Uppsala University, Sweden. Electronic address: joakim.bergstrom@pubcare.uu.se.
authors.forename: Joakim
authors.initials: J
authors.lastname: Bergström
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D010084:Oxidation-Reduction; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D051844:alpha-Synuclein / Q000737:chemistry*
chemical_list: C403894:4-oxo-2-nonenal; D000447:Aldehydes; D011994:Recombinant Proteins; D051844:alpha-Synuclein; C027576:4-hydroxy-2-nonenal
keywords: 4-Hydroxy-2-nonenal; 4-Oxo-2-nonenal; Aggregation; Alpha-synuclein; Amyloid; Dementia with Lewy bodies; Oligomers; Oxidative stress; Parkinson's disease