Nutrient availability regulates SIRT1 through a forkhead-dependent pathway.
ABSTRACT Nutrient availability regulates life-span in a wide range of organisms. We demonstrate that in mammalian cells, acute nutrient withdrawal simultaneously augments expression of the SIRT1 deacetylase and activates the Forkhead transcription factor Foxo3a. Knockdown of Foxo3a expression inhibited the starvation-induced increase in SIRT1 expression. Stimulation of SIRT1 transcription by Foxo3a was mediated through two p53 binding sites present in the SIRT1 promoter, and a nutrient-sensitive physical interaction was observed between Foxo3a and p53. SIRT1 expression was not induced in starved p53-deficient mice. Thus, in mammalian cells, p53, Foxo3a, and SIRT1, three proteins separately implicated in aging, constitute a nutrient-sensing pathway.
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ABSTRACT: The cumulative effects of cellular senescence and cell loss over time in various tissues and organs are considered major contributing factors to the ageing process. In various organisms, caloric restriction (CR) slows ageing and increases lifespan, at least in part, by activating nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases of the sirtuin family. Here, we use an in vitro model of CR to study the effects of this dietary regime on replicative senescence, cellular lifespan and modulation of the SIRT1 signaling pathway in normal human diploid fibroblasts. We found that serum from calorie-restricted animals was able to delay senescence and significantly increase replicative lifespan in these cells, when compared to serum from ad libitum fed animals. These effects correlated with CR-mediated increases in SIRT1 and decreases in p53 expression levels. In addition, we show that manipulation of SIRT1 levels by either over-expression or siRNA-mediated knockdown resulted in delayed and accelerated cellular senescence, respectively. Our results demonstrate that CR can delay senescence and increase replicative lifespan of normal human diploid fibroblasts in vitro and suggest that SIRT1 plays an important role in these processes.Aging 03/2015; 7(3):152-66. · 4.89 Impact Factor
Canadian Journal of Diabetes 10/2012; 36(5):S52. DOI:10.1016/j.jcjd.2012.07.379 · 0.46 Impact Factor
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ABSTRACT: Reversible lysine acetylation is a highly regulated post-translational protein modification that is known to regulate several signaling pathways. However, little is known about the radiation-induced changes in the acetylome. In this study, we analyzed the acute post-translational acetylation changes in primary human cardiac microvascular endothelial cells 4 h after a gamma radiation dose of 2 Gy. The acetylated peptides were enriched using anti-acetyl conjugated agarose beads. A total of 54 proteins were found to be altered in their acetylation status, 23 of which were deacetylated and 31 acetylated. Pathway analyses showed three protein categories particularly affected by radiation-induced changes in the acetylation status: the proteins involved in the translation process, the proteins of stress response, and mitochondrial proteins. The activation of the canonical and non-canonical Wnt signaling pathways affecting actin cytoskeleton signaling and cell cycle progression was predicted. The protein expression levels of two nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, sirtuin 1 and sirtuin 3, were significantly but transiently upregulated 4 but not 24 h after irradiation. The status of the p53 protein, a target of sirtuin 1, was found to be rapidly stabilized by acetylation after radiation exposure. These findings indicate that post-translational modification of proteins by acetylation and deacetylation is essentially affecting the radiation response of the endothelium. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.Journal of Radiation Research 04/2015; DOI:10.1093/jrr/rrv014 · 1.69 Impact Factor