期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 294, 期 14, 页码 5657-5665出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA118.001907
关键词
alpha-synuclein (-synuclein); dopamine; amyloid; mass spectrometry (MS); circular dichroism (CD); Fourier transform IR (FTIR); neurodegenerative disease; epigallocatechin-3-gallate; ion mobility (IM); methionine oxidation
资金
- Fondazione Regionale per la Ricerca Biomedica (FRRB-Regione Lombardia)
- University of MilanoBicocca (FAR -Fondo di Ateneo per la Ricerca)
- EU COST Action [BM1403]
alpha-Synuclein (AS) is an intrinsically disordered protein highly expressed in dopaminergic neurons. Its amyloid aggregates are the major component of Lewy bodies, a hallmark of Parkinson's disease (PD). AS is particularly exposed to oxidation of its methionine residues, both in vivo and in vitro. Oxidative stress has been implicated in PD and oxidized -synuclein has been shown to assemble into soluble, toxic oligomers, rather than amyloid fibrils. However, the structural effects of methionine oxidation are still poorly understood. In this work, oxidized AS was obtained by prolonged incubations with dopamine (DA) or epigallocatechin-3-gallate (EGCG), two inhibitors of AS aggregation, indicating that EGCG promotes the same final oxidation product as DA. The conformational transitions of the oxidized and non-oxidized protein were monitored by complementary biophysical techniques, including MS, ion mobility (IM), CD, and FTIR spectroscopy assays. Although the two variants displayed very similar structures under conditions that stabilize highly disordered or highly ordered states, differences emerged in the intermediate points of transitions induced by organic solvents, such as trifluoroethanol (TFE) and methanol (MeOH), indicating a lower propensity of the oxidized protein for forming either - or -type secondary structures. Furthermore, oxidized AS displayed restricted secondary-structure transitions in response to dehydration and slightly amplified tertiary-structure transitions induced by ligand binding. This difference in susceptibility to induced folding could explain the loss of fibrillation potential observed for oxidized AS. Finally, site-specific oxidation kinetics point out a minor delay in Met-127 modification, likely due to the effects of AS intrinsic structure.
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