title: FOXO3-induced reactive oxygen species are regulated by BCL2L11 (Bim) and SESN3.
abstract: FOXO transcription factors induce apoptosis and regulate cellular production of reactive oxygen species (ROS). To identify the sequence of molecular events underlying FOXO3 (FKHRL1)-induced apoptosis, we studied the regulation and function of FOXO3 by expressing an ECFP-tagged FOXO3 or a 4OH-tamoxifen (4OHT)-inducible FOXO3-ERtm fusion protein in SH-EP and STA-NB15 neuronal cells. After knockdown of FOXO3 or expression of a dominant-negative FOXO3 mutant we observed that etoposide- and doxorubicin-induced elevation of cellular ROS depends on FOXO3 activation and induction of its transcriptional target BCL2L11 (Bim). Activation of FOXO3 on its own induced two sequential ROS waves as measured by reduced MitoTrackerRed in live cell microscopy. Induction of Bim by FOXO3 is essential for this phenomenon because Bim knockdown or ectopic expression of BCL2L1 (BclxL) prevented FOXO3-mediated overproduction of ROS and apoptosis. Tetracycline-controlled expression of Bim impaired mitochondrial respiration and caused ROS production, suggesting that FOXO3 induces uncoupling of mitochondrial respiration through Bim. FOXO3 also activated a ROS rescue pathway by inducing the peroxiredoxin SESN3 (Sestrin3), which is responsible for the biphasic ROS accumulation. Knockdown of SESN3 caused an increase of FOXO3-induced ROS and accelerated apoptosis. The combined data clearly demonstrate that FOXO3 activates overproduction of ROS as a consequence of Bim-dependent impairment of mitochondrial respiration in neuronal cells, which leads to apoptosis.
authors.affiliation: Tyrolean Cancer Research Institute, Innsbruck,  Austria.
authors.forename: Judith
authors.initials: J
authors.lastname: Hagenbuchner
authors.forename: Andrey
authors.initials: A
authors.lastname: Kuznetsov
authors.forename: Martin
authors.initials: M
authors.lastname: Hermann
authors.forename: Barbara
authors.initials: B
authors.lastname: Hausott
authors.forename: Petra
authors.initials: P
authors.lastname: Obexer
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ausserlechner
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D004317:Doxorubicin / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013752:Tetracycline / Q000494:pharmacology; D000084622:Sestrins
chemical_list: D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D004317:Doxorubicin; D005047:Etoposide; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D013752:Tetracycline; C000606775:BCL2L11 protein, human; C499517:FOXO3 protein, human; C485523:SESN3 protein, human; D000084622:Sestrins