title: Activation of Nrf2 by arsenite and monomethylarsonous acid is independent of Keap1-C151: enhanced Keap1-Cul3 interaction.
abstract: Drinking water contaminated with arsenic, a human carcinogen, is a worldwide health issue. An understanding of cellular signaling events in response to arsenic exposure and rational designing of strategies to reduce arsenic damages by modulating signaling events are important to fight against arsenic-induced diseases. Previously, we reported that activation of the Nrf2-mediated cellular defense pathway confers protection against toxic effects induced by sodium arsenite [As(III)] or monomethylarsonous acid [MMA(III)]. Paradoxically, arsenic has been reported to induce the Nrf2-dependent signaling pathway. Here, we report the unique mechanism of Nrf2 induction by arsenic. Similar to tert-butylhydroquinone (tBHQ) or sulforaphane (SF), arsenic induced the Nrf2-dependent response through enhancing Nrf2 protein levels by inhibiting Nrf2 ubiquitination and degradation. However, the detailed action of arsenic in Nrf2 induction is different from that of tBHQ or SF. Arsenic markedly enhanced the interaction between Keap1 and Cul3, subunits of the E3 ubiquitin ligase for Nrf2, which led to impaired dynamic assembly/disassembly of the E3 ubiquitin ligase and thus decreased its ligase activity. Furthermore, induction of Nrf2 by arsenic is independent of the previously identified C151 residue in Keap1 that is required for Nrf2 activation by tBHQ or SF. Distinct mechanisms of Nrf2 activation by seemingly harmful and beneficial reagents provide a molecular basis to design Nrf2-activating agents for therapeutic intervention.
authors.affiliation: Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Wang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Sun
authors.forename: Weimin
authors.initials: W
authors.lastname: Chen
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Li
authors.forename: Nicole F
authors.initials: NF
authors.lastname: Villeneuve
authors.forename: Donna D
authors.initials: DD
authors.lastname: Zhang
mesh_terms: D018053:Arsenites / Q000494:pharmacology*; D045744:Cell Line, Tumor; D044842:Cullin Proteins / Q000502:physiology*; D003545:Cysteine; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000502:physiology*; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009942:Organometallic Compounds / Q000494:pharmacology*; D044767:Ubiquitin-Protein Ligases / Q000502:physiology
chemical_list: D018053:Arsenites; C503645:CUL3 protein, human; D044842:Cullin Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D009942:Organometallic Compounds; C406082:monomethylarsonous acid; D044767:Ubiquitin-Protein Ligases; D003545:Cysteine; C015001:arsenite