Early events in copper-ion catalyzed oxidation of α-synuclein

Manish Kumar Tiwari; Fabian Leinisch; Cagla Sahin; Ian Max Møller; Daniel Erik Otzen; Michael Jonathan Davies; Morten Jannik Bjerrum

doi:10.1016/j.freeradbiomed.2018.04.559

Early events in copper-ion catalyzed oxidation of α-synuclein

Manish Kumar Tiwari, Fabian Leinisch, Cagla Sahin, Ian Max Møller, Daniel Erik Otzen, Michael Jonathan Davies, Morten Jannik Bjerrum

16 Citations (Scopus)

Abstract

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.

Original language	English
Journal	Free Radical Biology & Medicine
Volume	121
Pages (from-to)	38-50
Number of pages	13
ISSN	0891-5849
DOIs	https://doi.org/10.1016/j.freeradbiomed.2018.04.559
Publication status	Published - Jun 2018

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@article{de99a38e4aeb425896382e52e0e0e6d8,

title = "Early events in copper-ion catalyzed oxidation of α-synuclein",

abstract = "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.",

author = "Tiwari, {Manish Kumar} and Fabian Leinisch and Cagla Sahin and M{\o}ller, {Ian Max} and Otzen, {Daniel Erik} and Davies, {Michael Jonathan} and Bjerrum, {Morten Jannik}",

note = "Copyright {\textcopyright} 2018. Published by Elsevier Inc.",

year = "2018",

month = jun,

doi = "10.1016/j.freeradbiomed.2018.04.559",

language = "English",

volume = "121",

pages = "38--50",

journal = "Free Radical Biology & Medicine",

issn = "0891-5849",

publisher = "Elsevier",

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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

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 -

Early events in copper-ion catalyzed oxidation of α-synuclein

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