Salt-inducible kinase 2 links transcriptional coactivator p300 phosphorylation to the prevention of ChREBP-dependent hepatic steatosis in mice
Julien Bricambert, Jonatan Miranda, Fadila Benhamed, Jean Girard, Catherine Postic, Renaud Dentin
Julien Bricambert, Jonatan Miranda, Fadila Benhamed, Jean Girard, Catherine Postic, Renaud Dentin
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Research Article Metabolism

Salt-inducible kinase 2 links transcriptional coactivator p300 phosphorylation to the prevention of ChREBP-dependent hepatic steatosis in mice

Abstract

Obesity and type 2 diabetes are associated with increased lipogenesis in the liver. This results in fat accumulation in hepatocytes, a condition known as hepatic steatosis, which is a form of nonalcoholic fatty liver disease (NAFLD), the most common cause of liver dysfunction in the United States. Carbohydrate-responsive element–binding protein (ChREBP), a transcriptional activator of glycolytic and lipogenic genes, has emerged as a major player in the development of hepatic steatosis in mice. However, the molecular mechanisms enhancing its transcriptional activity remain largely unknown. In this study, we have identified the histone acetyltransferase (HAT) coactivator p300 and serine/threonine kinase salt-inducible kinase 2 (SIK2) as key upstream regulators of ChREBP activity. In cultured mouse hepatocytes, we showed that glucose-activated p300 acetylated ChREBP on Lys672 and increased its transcriptional activity by enhancing its recruitment to its target gene promoters. SIK2 inhibited p300 HAT activity by direct phosphorylation on Ser89, which in turn decreased ChREBP-mediated lipogenesis in hepatocytes and mice overexpressing SIK2. Moreover, both liver-specific SIK2 knockdown and p300 overexpression resulted in hepatic steatosis, insulin resistance, and inflammation, phenotypes reversed by SIK2/p300 co-overexpression. Finally, in mouse models of type 2 diabetes and obesity, low SIK2 activity was associated with increased p300 HAT activity, ChREBP hyperacetylation, and hepatic steatosis. Our findings suggest that inhibition of hepatic p300 activity may be beneficial for treating hepatic steatosis in obesity and type 2 diabetes and identify SIK2 activators and specific p300 inhibitors as potential targets for pharmaceutical intervention.

Authors

Julien Bricambert, Jonatan Miranda, Fadila Benhamed, Jean Girard, Catherine Postic, Renaud Dentin

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Figure 4

Acetylation of ChREBP at Lys672 increases its binding to the DNA.

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Acetylation of ChREBP at Lys672 increases its binding to the DNA. (A) To...
(A) Top: Localization of ChREBP acetylation sites in its DNA-binding domain. Bottom: Effect of single point mutation of ChREBP acetylation sites on ChoRE-luc reporter activity in HepG2 cells overexpressing p300. (B) HepG2 cells transfected with p300 and with acetylation-deficient FLAG-ChREBP mutants. FLAG-ChREBP was immunoprecipitated, and acetylated ChREBP was detected by Western blot. (C) Acetylation levels of WT, DN, or K672R ChREBP by p300 in HepG2 cells. Mlk (Max-like protein X) is a ChREBP heteropartner required for ChREBP transcriptional activity in hepatocytes. (D) ChIP assay showing the effect of K672R mutation on ChREBP recruitment to the L-PK promoter following p300 overexpression in HepG2 cells. (E) Effect of K672R ChREBP mutant on L-PK expression in HepG2 cells overexpressing p300. (F) Acetylation levels of WT, DN, or K672R ChREBP in hepatocytes incubated with insulin and 5 or 25 mM glucose. (G) ChIP assay showing the effect of K672R mutation on ChREBP recruitment to the L-PK promoter in hepatocytes incubated with insulin and either 5 or 25 mM glucose. (H) Effect of K672R ChREBP mutant on LPK expression in hepatocytes incubated with insulin and either 5 or 25 mM glucose. (I) Effect of K672R ChREBP mutant on TG synthesis in hepatocytes incubated with insulin and either 5 or 25 mM glucose. In this figure, data are the average of 3 independent experiments (mean ± SEM; *P < 0.01).