SIRT1 Deficiency Downregulates PTEN/JNK/FOXO1 Pathway to Block Reactive Oxygen Species-Induced Apoptosis in Mouse Embryonic Stem Cells

Abstract

Silent mating type information regulation 2 homolog 1 (SIRT1) plays a critical role in reactive oxygen speciestriggered apoptosis in mouse embryonic stem (mES) cells. Here, we investigated a possible role for the PTEN=Akt=JNK pathway in the SIRT1-mediated apoptosis pathway in mES cells. Akt was activated by removal of anti-oxidant 2-mercaptoethanol in SIRT1À=À mES cells. Since PTEN is a negative regulator of Akt and its activity can be modulated by acetylation, we investigated if SIRT1 deacetylated PTEN to downregulate Akt to trigger apoptosis in anti-oxidant-free culture conditions. PTEN was hyperacetylated and excluded from the nucleus in SIRT1À=À mES cells, consistent with enhanced Akt activity. SIRT1 deficiency enhanced the acetylation=phos-phorylation level of FOXO1 and subsequently inhibited the nuclear localization of FOXO1. Cellular acetylation levels were enhanced by DNA-damaging agent, not by removal of anti-oxidant. c-Jun NH2-terminal kinase ( JNK) was activated by removal of anti-oxidant in SIRT1-dependent manner. Although p53 acetylation was stronger in SIRT1 À=À mES cells, DNA-damaging stress activated phosphorylation and enhanced cellular levels of p53 irrespective of SIRT1, whereas removal of anti-oxidant slightly activated p53 only with SIRT1. Expression levels of Bim and Puma were increased in anti-oxidant-free culture conditions in an SIRT1-dependent manner and treatment with JNK inhibitor blocked induction of Bim expression. DNA-damaging agent activated caspase3 regardless of SIRT1. Our data support an important role for SIRT1 in preparing the PTEN=JNK=FOXO1 pathway to respond to cellular reactive oxygen species.

Genistein accelerates refractory wound healing by suppressing superoxide and FoxO1/iNOS pathway in type 1 diabetes

“…FoxO1 has been shown to mediate an autofeedback loop regulating SIRT1 expression, and FoxO1 depletion by siRNA reduced SIRT1 expression at both the messenger RNA and protein levels in vascular smooth muscle cells and HEK293 cells [39]. In mouse embryonic stem cells, SIRT1 deficiency down-regulated the PTEN/JNK/FoxO1 pathway to block ROS-induced apoptosis [40]. Recently, SIRT1 was reported as a negative regulator of β-cell proliferation [41].…”

Protective effects and mechanisms of sirtuins in the nervous system

“…SIRT1 is reported to deacetylate PTEN at Lys402 and hinder the interaction of PTEN with its binding partners (Ikenoue et al ., 2008). Similarly in mouse embryonic stem cells, SIRT1 deficiency leads to increased levels of acetylated PTEN, which is associated with apoptosis in response to oxidative stress (Chae and Broxmeyer, 2011). However, it has not been determined whether SIRT1 can also deacetylate PTEN in neurons, and if this action will be neuroprotective.…”

Regulation of forkhead box O1 (FOXO1) by protein kinase B and glucocorticoids: different mechanisms of induction of beta cell death in vitro

“…Our study unfolds an important molecular mechanism which determines subcellular localisation of FOXO1. Nuclear activity of FOXO1 depends on additional modifications such as acetylation [38]. Further studies are needed to understand the regulation of nuclear FOXO1 activity.…”