TY - JOUR
T1 - Early events in copper-ion catalyzed oxidation of α-synuclein
AU - Tiwari, Manish Kumar
AU - Leinisch, Fabian
AU - Sahin, Cagla
AU - Møller, Ian Max
AU - Otzen, Daniel Erik
AU - Davies, Michael Jonathan
AU - Bjerrum, Morten Jannik
N1 - Copyright © 2018. Published by Elsevier Inc.
PY - 2018/6
Y1 - 2018/6
N2 - Previous studies on metal-ion catalyzed oxidation of α-synuclein oxidation have mostly used conditions that result in extensive modification precluding an understanding of the early events in this process. In this study, we have examined time-dependent oxidative events related to α-synuclein modification using six different molar ratios of Cu2+/H2O2/protein and Cu2+/H2O2/ascorbate/protein resulting in mild to moderate extents of oxidation. For a Cu2+/H2O2/protein molar ratio of 2.3:7.8:1 only low levels of carbonyls were detected (0.078 carbonyls per protein), whereas a molar ratio of 4.7:15.6:1 gave 0.22 carbonyls per α-synuclein within 15min. With the latter conditions, rapid conversion of 3 out of 4 methionines (Met) to methionine sulfoxide, and 2 out of 4 tyrosines (Tyr) were converted to products including inter- and intra-molecular dityrosine cross-links and protein oligomers, as determined by SDS-PAGE and Western blot analysis. Limited histidine (His) modification was observed. The rapid formation of dityrosine cross-links was confirmed by fluorescence and mass-spectrometry. These data indicate that Met and Tyr oxidation are early events in Cu2+/H2O2-mediated damage, with carbonyl formation being a minor process. With the Cu2+/H2O2/ascorbate system, rapid protein carbonyl formation was detected with the first 5min, but after this time point, little additional carbonyl formation was detected. With this system, lower levels of Met and Tyr oxidation were detected (2 Met and 1 Tyr modified with a Cu2+/H2O2/ascorbate/protein ratio of 2.3:7.8:7.8:1), but greater His oxidation. Only low levels of intra- dityrosine cross-links and no inter- dityrosine oligomers were detected under these conditions, suggesting that ascorbate limits Cu2+/H2O2-induced α-synuclein modification.
AB - Previous studies on metal-ion catalyzed oxidation of α-synuclein oxidation have mostly used conditions that result in extensive modification precluding an understanding of the early events in this process. In this study, we have examined time-dependent oxidative events related to α-synuclein modification using six different molar ratios of Cu2+/H2O2/protein and Cu2+/H2O2/ascorbate/protein resulting in mild to moderate extents of oxidation. For a Cu2+/H2O2/protein molar ratio of 2.3:7.8:1 only low levels of carbonyls were detected (0.078 carbonyls per protein), whereas a molar ratio of 4.7:15.6:1 gave 0.22 carbonyls per α-synuclein within 15min. With the latter conditions, rapid conversion of 3 out of 4 methionines (Met) to methionine sulfoxide, and 2 out of 4 tyrosines (Tyr) were converted to products including inter- and intra-molecular dityrosine cross-links and protein oligomers, as determined by SDS-PAGE and Western blot analysis. Limited histidine (His) modification was observed. The rapid formation of dityrosine cross-links was confirmed by fluorescence and mass-spectrometry. These data indicate that Met and Tyr oxidation are early events in Cu2+/H2O2-mediated damage, with carbonyl formation being a minor process. With the Cu2+/H2O2/ascorbate system, rapid protein carbonyl formation was detected with the first 5min, but after this time point, little additional carbonyl formation was detected. With this system, lower levels of Met and Tyr oxidation were detected (2 Met and 1 Tyr modified with a Cu2+/H2O2/ascorbate/protein ratio of 2.3:7.8:7.8:1), but greater His oxidation. Only low levels of intra- dityrosine cross-links and no inter- dityrosine oligomers were detected under these conditions, suggesting that ascorbate limits Cu2+/H2O2-induced α-synuclein modification.
U2 - 10.1016/j.freeradbiomed.2018.04.559
DO - 10.1016/j.freeradbiomed.2018.04.559
M3 - Journal article
C2 - 29689296
SN - 0891-5849
VL - 121
SP - 38
EP - 50
JO - Free Radical Biology & Medicine
JF - Free Radical Biology & Medicine
ER -