title: Nitric oxide activation of Keap1/Nrf2 signaling in human colon carcinoma cells.
abstract: The transcription factor NF-E2-related nuclear factor 2 (Nrf2) regulates expression of genes that protect cells from oxidative damage. Here, we characterized nitric oxide (*NO)-induced Nrf2-Kelch-like ECH-associated protein 1 (Keap1) signaling and its role in counteracting *NO-induced apoptosis of human colon cancer HCT116 cells. Nrf2 was localized in the cytoplasm in control cells; *NO triggered its rapid nuclear accumulation, transcriptional activation, and up-regulation of HO-1, NQO1, and GCL, but not GST A4 and P1 subunits. Nrf2 accumulation in the nucleus was also associated with enhanced transcription and posttranscriptional modifications. (S)-nitrosation of Keap1 may contribute to nuclear accumulation of Nrf2 by facilitating its dissociation from Keap1, thus initiating *NO-mediated Nrf2-Keap1 signaling. *NO-mediated induction of ARE-dependent genes occurred well before apoptosis, as judged by caspase 3 activation. Collectively, these results show that the Nrf2-Keap1 signaling pathway mediates protective cellular responses to mitigate *NO-induced damage and may contribute to the relative resistance of HCT116 to *NO-induced cytotoxicity.
authors.affiliation: Department of Biological Engineering and Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Chun-Qi
authors.initials: CQ
authors.lastname: Li
authors.forename: Min Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Godoy
authors.forename: Apinya
authors.initials: A
authors.lastname: Thiantanawat
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Trudel
authors.forename: Gerald N
authors.initials: GN
authors.lastname: Wogan
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D003593:Cytoplasm / Q000378:metabolism; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D018613:Microscopy, Confocal; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000494:pharmacology*; D015538:Nitrosation; D021381:Protein Transport / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: 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; D009569:Nitric Oxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D053148:Caspase 3
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