title: Redox cycling of 1,2-naphthoquinone by thioredoxin1 through Cys32 and Cys35 causes inhibition of its catalytic activity and activation of ASK1/p38 signaling.
abstract: 1,2-Naphthoquinone (1,2-NQ) is an atmospheric chemical capable of (1) redox cycling with electron donors and (2) covalent modification of nucleophilic groups on proteins. In the present study, we investigated its interaction with the redox protein, thioredoxin1 (Trx1), which led to oxidative stress-dependent cell damage. In experiments with purified wild-type Trx1 and its double mutant (32S/35S Trx1), we found that incubation of Trx1 with 1,2-NQ resulted in a redox cycling reaction, generating superoxide and hydrogen peroxide involving Cys32 and Cys35 and an arylation reaction resulting in covalent modification of Lys85 together with a loss of Trx activity. A significant fraction of the lost Trx1 activity following interaction with 1,2-NQ was restored by dithiothreitol. Exposure of RAW264.7 cells to 1,2-NQ generated reactive oxygen species (ROS) and caused a decrease in Trx activity. Trx is a negative regulator of apoptosis signal-regulating kinase 1 (ASK1), and under the conditions of the experiment, 1,2-NQ activated ASK1 and p38, leading to PARP cleavage and apoptotic cell death that were blocked by pretreatment with polyethylene glycol-catalase. These results suggest that Trx1 readily undergoes oxidative modification by 1,2-NQ through the proximal thiols Cys32 and Cys35. It seems likely that ROS production concomitant with decline in cellular Trx activity plays a role in the activation of ASK1/p38 signaling to promote apoptotic cell death cause by 1,2-NQ exposure.
authors.affiliation: Environmental Medicine Section, Doctoral Program in Biomedical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shinkai
authors.forename: Noriko
authors.initials: N
authors.lastname: Iwamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Miura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Arthur K
authors.initials: AK
authors.lastname: Cho
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kumagai
mesh_terms: D000818:Animals; D055162:Biocatalysis; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism*; D051379:Mice; D009285:Naphthoquinones / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013879:Thioredoxins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D009285:Naphthoquinones; D017382:Reactive Oxygen Species; D013879:Thioredoxins; C040756:1,2-naphthoquinone; D048051:p38 Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse; D003545:Cysteine