Foxo3

SUMOylation and the oncogenic E17K mutation affect AKT1 subcellular distribution and impact on Nanog-binding dynamics to chromatin in embryonic stem cells

AKT/PKB is a kinase involved in the regulation of a plethora of cell processes. Particularly, in embryonic stem cells (ESCs), AKT is crucial for the maintenance of pluripotency. Although the activation of this kinase relies on its recruitment to the cellular membrane and subsequent phosphorylation, multiple other post-translational modifications (PTMs), including SUMOylation, fine-tune its activity and target specificity. Since this PTM can also modify the localization and availability of different proteins, in this work we explored if SUMOylation impacts on the subcellular compartmentalization and distribution of AKT1 in ESCs. We found that this PTM does not affect AKT1 membrane recruitment, but it modifies the AKT1 nucleus/cytoplasm distribution, increasing its nuclear presence. Additionally, within this compartment, we found that AKT1 SUMOylation also impacts on the chromatin-binding dynamics of NANOG, a central pluripotency transcription factor. Remarkably, the oncogenic E17K AKT1 mutant produces major changes in all these parameters increasing the binding of NANOG to its targets, also in a SUMOylation dependent manner. These findings demonstrate that SUMOylation modulates AKT1 subcellular distribution, thus adding an extra layer of regulation of its function, possibly by affecting the specificity and interaction with its downstream targets.

Antioxidant Responses Induced by Short-Term Activity–Estivation–Arousal Cycle in Pomacea canaliculata

Long-term estivation (45 days) in the apple snail Pomacea canaliculata induces an increase of non-enzymatic antioxidants, such as uric acid and reduced glutathione (GSH), which constitutes an alternative to the adaptive physiological strategy of preparation for oxidative stress (POS). Here, we studied markers of oxidative stress damage, uric acid levels, and non-enzymatic antioxidant capacity, enzymatic antioxidant defenses, such as superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), and transcription factors expression [forkhead box protein O (FOXO), hypoxia-inducible factor-1 alpha (HIF1α), and nuclear factor erythroid 2-related factor 2 (Nrf2)] in control active animals, 7-day estivating and aroused snails, in digestive gland, gill, and lung tissue samples. In the digestive gland, SOD and CAT activities significantly increased after estivation and decreased during arousal. Meanwhile, GST activity decreased significantly during the activity–estivation–arousal cycle. Gill CAT activity increased significantly at 7 days of estivation, and it decreased during arousal. In the lung, the CAT activity level increased significantly during the cycle. FOXO upregulation was observed in the studied tissues, decreasing its expression only in the gill of aroused animals during the cycle. HIF1α and Nrf2 transcription factors decreased their expression during estivation in the gill, while in the lung and the digestive gland, both transcription factors did not show significant changes. Our results showed that the short-term estivation induced oxidative stress in different tissues of P. canaliculata thereby increasing overall antioxidant enzymes activity and highlighting the role of FOXO regulation as a possible underlying mechanism of the POS strategy.

Time- and dose-dependent gene expression in sea urchin embryos exposed to UVB

The increase of UVB radiation reaching marine environment has harmful effects on living organisms. Paracentrotus lividus sea urchin embryos living in shallow water are exposed to radiations, providing a good model for studying the molecular mechanisms activated upon UV stress. Here, we report the modulated time- and dose-dependent expression of six genes, known to be involved in stress response, in embryos exposed at cleavage to 400 and 800 J/m(2) UVB, and collected at early (morula) and later (gastrula) stages. We analyzed their mRNA levels by QPCR and found that Pl-14-3-3 showed a dose-dependent induction, both early and late in development; Pl-c-jun was up-regulated proportionally to the UVB dose at early stages and only at 800 J/m(2) UVB at later stages; Pl-XPB-ERCC3, Pl-MT and Pl-NF-kB were highly up-regulated later in development at the high dose, with the exception of Pl-XPB-ERCC3 whose mRNA levels were high also at the lower dose; Pl-FOXO expression was not affected by UVB radiation. We believe that the identification of UVB-responsive genes in irradiated sea urchin embryos, reported for the first time in this study, will be helpful for the understanding of the involved molecular pathways. The correlation between the impaired morphogenesis, affecting endo-mesoderm differentiation, and gene modulations described herewith is also discussed.