title: ROS-generating oxidases Nox1 and Nox4 contribute to oncogenic Ras-induced premature senescence.
abstract: Activated oncogenes induce premature cellular senescence, a permanent state of proliferative arrest in primary rodent and human fibroblasts. Recent studies suggest that generation of reactive oxygen species (ROS) is involved in oncogenic Ras-induced premature senescence. However, the signaling mechanism controlling this oxidant-mediated irreversible growth arrest is not fully understood. Here, we show that through the Ras/MEK pathway, Ras oncogene up-regulated the expression of superoxide-generating oxidases, Nox1 in rat REF52 cells and Nox4 in primary human lung TIG-3 cells, leading to an increase in intracellular level of ROS. Ablation of Nox1 and Nox4 by small interfering RNAs (siRNAs) blocked the RasV12 senescent phenotype including β-galactosidase activity, growth arrest and accumulation of tumor suppressors such as p53 and p16Ink4a. This suggests that Nox-generated ROS transduce senescence signals by activating the p53 and p16Ink4a pathway. Furthermore, Nox1 and Nox4 siRNAs inhibited both Ras-induced DNA damage response and p38MAPK activation, whereas overexpression of Nox1 and Nox4 alone was able to induce senescence. The involvement of Nox1 in Ras-induced senescence was also confirmed with embryonic fibroblasts derived from Nox1 knockout mice. Together, these findings suggest that Nox1- and Nox4-generated ROS play an important role in Ras-induced premature senescence, which may involve DNA damage response and p38MAPK signaling pathways.
authors.affiliation: Department of Molecular Biology and Biochemistry, Shinshu University Graduate School of Medicine, Matsumoto, Nagano, 390-8621, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kodama
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kato
authors.forename: Shuichi
authors.initials: S
authors.lastname: Furuta
authors.forename: Shouta
authors.initials: S
authors.lastname: Ueno
authors.forename: Yugen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Kuniharu
authors.initials: K
authors.lastname: Matsuno
authors.forename: Chihiro
authors.initials: C
authors.lastname: Yabe-Nishimura
authors.forename: Eiji
authors.initials: E
authors.lastname: Tanaka
authors.forename: Tohru
authors.initials: T
authors.lastname: Kamata
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D016922:Cellular Senescence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004249:DNA Damage; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D006801:Humans; D051379:Mice; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000074624:NADPH Oxidase 1; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C000614711:NOX1 protein, mouse; C000614712:NOX1 protein, rat; C422943:Nox4 protein, mouse; D048051:p38 Mitogen-Activated Protein Kinases; D015689:Oncogene Protein p21(ras)