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SIRT1 negatively regulates the mammalian target of rapamycin.

Ghosh HS, McBurney M, Robbins PD - PLoS ONE (2010)

Bottom Line: We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions.The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner.These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT
The IGF/mTOR pathway, which is modulated by nutrients, growth factors, energy status and cellular stress regulates aging in various organisms. SIRT1 is a NAD+ dependent deacetylase that is known to regulate caloric restriction mediated longevity in model organisms, and has also been linked to the insulin/IGF signaling pathway. Here we investigated the potential regulation of mTOR signaling by SIRT1 in response to nutrients and cellular stress. We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions. The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner. Furthermore, we demonstrate that SIRT1 interacts with TSC2, a component of the mTOR inhibitory-complex upstream to mTORC1, and regulates mTOR signaling in a TSC2 dependent manner. These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.

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Resveratrol's effect on mTOR activity in TSC2 and SIRT1  cells.(A) Wild-type and TSC2  MEFs were either mock treated or treated with 10 mM nicotinamide or 50 µM resveratrol as indicated. (B) Wild-type and SIRT1  MEFs were mock-treated or treated with 25, 50 or 100 µM resveratrol as indicated. The ratio of band intensities between the SIRT1  and corresponding WT MEFs for each group was calculated after normalizing the phospho-protein signals with the total protein signals. The calculations were done using ImageJ software.
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pone-0009199-g004: Resveratrol's effect on mTOR activity in TSC2 and SIRT1 cells.(A) Wild-type and TSC2 MEFs were either mock treated or treated with 10 mM nicotinamide or 50 µM resveratrol as indicated. (B) Wild-type and SIRT1 MEFs were mock-treated or treated with 25, 50 or 100 µM resveratrol as indicated. The ratio of band intensities between the SIRT1 and corresponding WT MEFs for each group was calculated after normalizing the phospho-protein signals with the total protein signals. The calculations were done using ImageJ software.

Mentions: Since the above results suggested that SIRT1 acts upstream of mTORC1 to downregulate mTOR signaling similar to TSC2, we investigated if the SIRT1-mediated down-regulation of mTOR signaling was TSC2 dependent. We treated WT and TSC2 MEFs with the SIRT1 activator resveratrol (RES), and SIRT1 inhibitor nicotinamide (NAM). As expected, only the TSC2 MEFs showed an increased S6 phosphorylation. In contrast, NAM treatment induced S6 phosphorylation in WT MEFs (Figure 4A), suggesting a potential role for SIRT1 in TSC2-mediated inhibition of mTORC1 activity. Interestingly, the SIRT1 activator, RES, could not inhibit S6 phosphorylation in absence of TSC2, indicating that SIRT1 may be dependent on TSC2 for inhibiting mTORC1 activity. In addition, no further decrease in S6 phosphorylation in response to RES treatment was observed in WT cells, possibly due to the lower basal levels of S6 phosphorylation in WT cells which are both TSC2 and SIRT1 positive.


SIRT1 negatively regulates the mammalian target of rapamycin.

Ghosh HS, McBurney M, Robbins PD - PLoS ONE (2010)

Resveratrol's effect on mTOR activity in TSC2 and SIRT1  cells.(A) Wild-type and TSC2  MEFs were either mock treated or treated with 10 mM nicotinamide or 50 µM resveratrol as indicated. (B) Wild-type and SIRT1  MEFs were mock-treated or treated with 25, 50 or 100 µM resveratrol as indicated. The ratio of band intensities between the SIRT1  and corresponding WT MEFs for each group was calculated after normalizing the phospho-protein signals with the total protein signals. The calculations were done using ImageJ software.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821410&req=5

pone-0009199-g004: Resveratrol's effect on mTOR activity in TSC2 and SIRT1 cells.(A) Wild-type and TSC2 MEFs were either mock treated or treated with 10 mM nicotinamide or 50 µM resveratrol as indicated. (B) Wild-type and SIRT1 MEFs were mock-treated or treated with 25, 50 or 100 µM resveratrol as indicated. The ratio of band intensities between the SIRT1 and corresponding WT MEFs for each group was calculated after normalizing the phospho-protein signals with the total protein signals. The calculations were done using ImageJ software.
Mentions: Since the above results suggested that SIRT1 acts upstream of mTORC1 to downregulate mTOR signaling similar to TSC2, we investigated if the SIRT1-mediated down-regulation of mTOR signaling was TSC2 dependent. We treated WT and TSC2 MEFs with the SIRT1 activator resveratrol (RES), and SIRT1 inhibitor nicotinamide (NAM). As expected, only the TSC2 MEFs showed an increased S6 phosphorylation. In contrast, NAM treatment induced S6 phosphorylation in WT MEFs (Figure 4A), suggesting a potential role for SIRT1 in TSC2-mediated inhibition of mTORC1 activity. Interestingly, the SIRT1 activator, RES, could not inhibit S6 phosphorylation in absence of TSC2, indicating that SIRT1 may be dependent on TSC2 for inhibiting mTORC1 activity. In addition, no further decrease in S6 phosphorylation in response to RES treatment was observed in WT cells, possibly due to the lower basal levels of S6 phosphorylation in WT cells which are both TSC2 and SIRT1 positive.

Bottom Line: We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions.The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner.These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.

ABSTRACT
The IGF/mTOR pathway, which is modulated by nutrients, growth factors, energy status and cellular stress regulates aging in various organisms. SIRT1 is a NAD+ dependent deacetylase that is known to regulate caloric restriction mediated longevity in model organisms, and has also been linked to the insulin/IGF signaling pathway. Here we investigated the potential regulation of mTOR signaling by SIRT1 in response to nutrients and cellular stress. We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions. The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner. Furthermore, we demonstrate that SIRT1 interacts with TSC2, a component of the mTOR inhibitory-complex upstream to mTORC1, and regulates mTOR signaling in a TSC2 dependent manner. These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.

Show MeSH