Regulation of DEPP by the transcription factor FOXO3

FOXO transcription factors control cellular formation of reactive oxygen species (ROS), which critically contribute to cell survival and cell death in neuroblastoma. In this thesis we report that C10orf10, also named “decidual protein induced by progesterone” (DEPP), is a direct transcriptional target of FOXO3 and is regulated by three distinctive FOXO3 binding sites located on the DEPP promoter. As there is little known about the physiological function of DEPP we investigated whether DEPP expression affects essential cellular functions like proliferation, migration, apoptosis and autophagy, which are frequently deregulated in cancer cells. In neuroblastoma FOXO3-triggered apoptosis involves a biphasic ROS accumulation. The effect of DEPP expression on cellular ROS was measured by live cell fluorescence microscopy using the ROS-sensitive dye reduced MitoTracker Red CM-H2XROS. We found that DEPP knockdown in SH-EP/FOXO3-shDEPP and NB15/FOXO3-shDEPP cells inhibits ROS accumulation during FOXO3 activation and attenuates FOXO3-induced apoptosis, whereas its overexpression in SH-EP/tetDEPP and SH-EP/tetEYFP-DEPP cells raises cellular ROS levels and sensitizes to cell death. Furthermore, the elevated cellular ROS levels due to ectopic DEPP expression triggered the induction of autophagy. In neuronal cells cellular steady state ROS are mainly detoxified in peroxisomes by the enzyme CAT/catalase. As DEPP contains a peroxisomal-targeting-signal-type-2 (PTS2) sequence at its N-terminus that enables protein import into peroxisomes, we analyzed the effect of DEPP on peroxisomal function by measuring the catalase enzyme activity. Catalase activity was reduced by conditional DEPP overexpression and significantly increased in SH-EP/FOXO3-shDEPP knockdown cells. Consistent with the changes in catalase activity, ectopic DEPP expression increased H2O2-induced apoptosis, whereas SH-EP/FOXO3-shDEPP and NB15/FOXO3-shDEPP cells were much more resistant to H2O2 treatment. Furthermore we p
by Stefan Salcher
Enth. u.a. 2 Veröff. d. Verf. aus den Jahren 2014
Innsbruck, Med. Univ., Diss., 2014
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