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Control of Foxo1 gene expression by co-activator P300.

Wondisford AR, Xiong L, Chang E, Meng S, Meyers DJ, Li M, Cole PA, He L - J. Biol. Chem. (2013)

Bottom Line: In the fed state, elevated insulin phosphorylates FOXO1 via AKT, leading to its nuclear exclusion and degradation.Because cAMP-PKA regulates hepatic glucose production through cAMP-response element-binding protein co-activators, we depleted these co-activators using adenoviral shRNAs.In addition, inhibition of histone acetyltransferase activity of P300 significantly decreased hepatic Foxo1 mRNA and FOXO1 protein levels in fasted mice, as well as fasting blood glucose levels.

View Article: PubMed Central - PubMed

Affiliation: From the Division of Metabolism, Department of Pediatrics and.

ABSTRACT
FOXO1 is an important downstream mediator of the insulin signaling pathway. In the fed state, elevated insulin phosphorylates FOXO1 via AKT, leading to its nuclear exclusion and degradation. A reduction in nuclear FOXO1 levels then leads to suppression of hepatic glucose production. However, the mechanism leading to expression of Foxo1 gene in the fasted state is less clear. We found that Foxo1 mRNA and FOXO1 protein levels of Foxo1 were increased significantly in the liver of mice after 16 h of fasting. Furthermore, dibutyrl cAMP stimulated the expression of Foxo1 at both mRNA and protein level in hepatocytes. Because cAMP-PKA regulates hepatic glucose production through cAMP-response element-binding protein co-activators, we depleted these co-activators using adenoviral shRNAs. Interestingly, only depletion of co-activator P300 resulted in the decrease of Foxo1 mRNA and FOXO1 protein levels. In addition, inhibition of histone acetyltransferase activity of P300 significantly decreased hepatic Foxo1 mRNA and FOXO1 protein levels in fasted mice, as well as fasting blood glucose levels. By characterization of Foxo1 gene promoter, P300 regulates the Foxo1 gene expression through the binding to tandem cAMP-response element sites in the proximal promoter region of Foxo1 gene.

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Related in: MedlinePlus

Fasting induces Foxo1 gene expression.a, Foxo1 mRNA levels compared in the liver of mice sacrificed at fed or fasted (16 h) states (n = 5). Real-time qPCR was used to measure gene expression (normalized to 36B4 expression levels). Asterisk (*) signifies that groups with same treatment are significantly different (p < 0.05). Error bars, S.E. b, phosphorylation status of CREB, AKT and total AKT, CREB, and Foxo1 protein levels in the liver from fed and 16-h fasted mice are shown (n = 5). c, fasting led to the early induction of Foxo1 expression. The Foxo1 protein levels in the liver of mice sacrificed are shown at the indicated fasting time points. Each lane represents sample pooled from two mice.
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Figure 1: Fasting induces Foxo1 gene expression.a, Foxo1 mRNA levels compared in the liver of mice sacrificed at fed or fasted (16 h) states (n = 5). Real-time qPCR was used to measure gene expression (normalized to 36B4 expression levels). Asterisk (*) signifies that groups with same treatment are significantly different (p < 0.05). Error bars, S.E. b, phosphorylation status of CREB, AKT and total AKT, CREB, and Foxo1 protein levels in the liver from fed and 16-h fasted mice are shown (n = 5). c, fasting led to the early induction of Foxo1 expression. The Foxo1 protein levels in the liver of mice sacrificed are shown at the indicated fasting time points. Each lane represents sample pooled from two mice.

Mentions: Because phosphorylation of FOXO1 by activated AKT in the insulin signaling pathway results in FOXO1 nuclear exclusion and degradation in the fed state (12, 13), it is conceivable that fasting might increase FOXO1 levels due to its important role in stimulating gluconeogenesis and maintaining euglycemia (7–9). Indeed, hepatic Foxo1 mRNA levels increase approximately 3-fold in the liver of mice after 16 h of fasting (Fig. 1a). FOXO1 protein levels were also markedly increased in the fasted state, which was associated with an increase in phospho-CREB and a decrease in phospho-AKT (Fig. 1b). In a fasting time course experiment, FOXO1 protein levels increased as early as 2 h after the start of fasting and steadily increased in the fasting period (Fig. 1c).


Control of Foxo1 gene expression by co-activator P300.

Wondisford AR, Xiong L, Chang E, Meng S, Meyers DJ, Li M, Cole PA, He L - J. Biol. Chem. (2013)

Fasting induces Foxo1 gene expression.a, Foxo1 mRNA levels compared in the liver of mice sacrificed at fed or fasted (16 h) states (n = 5). Real-time qPCR was used to measure gene expression (normalized to 36B4 expression levels). Asterisk (*) signifies that groups with same treatment are significantly different (p < 0.05). Error bars, S.E. b, phosphorylation status of CREB, AKT and total AKT, CREB, and Foxo1 protein levels in the liver from fed and 16-h fasted mice are shown (n = 5). c, fasting led to the early induction of Foxo1 expression. The Foxo1 protein levels in the liver of mice sacrificed are shown at the indicated fasting time points. Each lane represents sample pooled from two mice.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3924295&req=5

Figure 1: Fasting induces Foxo1 gene expression.a, Foxo1 mRNA levels compared in the liver of mice sacrificed at fed or fasted (16 h) states (n = 5). Real-time qPCR was used to measure gene expression (normalized to 36B4 expression levels). Asterisk (*) signifies that groups with same treatment are significantly different (p < 0.05). Error bars, S.E. b, phosphorylation status of CREB, AKT and total AKT, CREB, and Foxo1 protein levels in the liver from fed and 16-h fasted mice are shown (n = 5). c, fasting led to the early induction of Foxo1 expression. The Foxo1 protein levels in the liver of mice sacrificed are shown at the indicated fasting time points. Each lane represents sample pooled from two mice.
Mentions: Because phosphorylation of FOXO1 by activated AKT in the insulin signaling pathway results in FOXO1 nuclear exclusion and degradation in the fed state (12, 13), it is conceivable that fasting might increase FOXO1 levels due to its important role in stimulating gluconeogenesis and maintaining euglycemia (7–9). Indeed, hepatic Foxo1 mRNA levels increase approximately 3-fold in the liver of mice after 16 h of fasting (Fig. 1a). FOXO1 protein levels were also markedly increased in the fasted state, which was associated with an increase in phospho-CREB and a decrease in phospho-AKT (Fig. 1b). In a fasting time course experiment, FOXO1 protein levels increased as early as 2 h after the start of fasting and steadily increased in the fasting period (Fig. 1c).

Bottom Line: In the fed state, elevated insulin phosphorylates FOXO1 via AKT, leading to its nuclear exclusion and degradation.Because cAMP-PKA regulates hepatic glucose production through cAMP-response element-binding protein co-activators, we depleted these co-activators using adenoviral shRNAs.In addition, inhibition of histone acetyltransferase activity of P300 significantly decreased hepatic Foxo1 mRNA and FOXO1 protein levels in fasted mice, as well as fasting blood glucose levels.

View Article: PubMed Central - PubMed

Affiliation: From the Division of Metabolism, Department of Pediatrics and.

ABSTRACT
FOXO1 is an important downstream mediator of the insulin signaling pathway. In the fed state, elevated insulin phosphorylates FOXO1 via AKT, leading to its nuclear exclusion and degradation. A reduction in nuclear FOXO1 levels then leads to suppression of hepatic glucose production. However, the mechanism leading to expression of Foxo1 gene in the fasted state is less clear. We found that Foxo1 mRNA and FOXO1 protein levels of Foxo1 were increased significantly in the liver of mice after 16 h of fasting. Furthermore, dibutyrl cAMP stimulated the expression of Foxo1 at both mRNA and protein level in hepatocytes. Because cAMP-PKA regulates hepatic glucose production through cAMP-response element-binding protein co-activators, we depleted these co-activators using adenoviral shRNAs. Interestingly, only depletion of co-activator P300 resulted in the decrease of Foxo1 mRNA and FOXO1 protein levels. In addition, inhibition of histone acetyltransferase activity of P300 significantly decreased hepatic Foxo1 mRNA and FOXO1 protein levels in fasted mice, as well as fasting blood glucose levels. By characterization of Foxo1 gene promoter, P300 regulates the Foxo1 gene expression through the binding to tandem cAMP-response element sites in the proximal promoter region of Foxo1 gene.

Show MeSH
Related in: MedlinePlus