O-GlcNAcylation Increases ChREBP Protein Content and Transcriptional Activity in the Liver
- Céline Guinez1,2,3,
- Gaëlle Filhoulaud1,2,3,
- Fadila Benhamed1,2,3,
- Solenne Marmier1,2,3,
- Céline Dubuquoy1,2,3,
- Renaud Dentin1,2,3,
- Marthe Moldes1,2,3,
- Anne-Françoise Burnol1,2,3,
- Xiaoyong Yang4,
- Tony Lefebvre5,
- Jean Girard1,2,3 and
- Catherine Postic1,2,3
- 1INSERM, U1016, Institut Cochin, Paris, France
- 2Centre National de la Recherche Scientifique, UMR 8104, Paris, France
- 3Department of Endocrinology, Metabolism and Cancer, Université Paris-Descartes, Paris, France
- 4Department of Comparative Medicine, Yale School of Medicine, New Haven, Connecticut
- 5Unit of Structural and Functional Glycobiology, UMR 8576, Centre National de la Recherche Scientifique, Université des Sciences et Technologies de Lille 1, Villeneuve d'Ascq, France
- Corresponding author: Catherine Postic, .
C.G. and G.F. contributed equally to this work.
OBJECTIVE Carbohydrate-responsive element–binding protein (ChREBP) is a key transcription factor that mediates the effects of glucose on glycolytic and lipogenic genes in the liver. We have previously reported that liver-specific inhibition of ChREBP prevents hepatic steatosis in ob/ob mice by specifically decreasing lipogenic rates in vivo. To better understand the regulation of ChREBP activity in the liver, we investigated the implication of O-linked β-N-acetylglucosamine (O-GlcNAc or O-GlcNAcylation), an important glucose-dependent posttranslational modification playing multiple roles in transcription, protein stabilization, nuclear localization, and signal transduction.
RESEARCH DESIGN AND METHODS O-GlcNAcylation is highly dynamic through the action of two enzymes: the O-GlcNAc transferase (OGT), which transfers the monosaccharide to serine/threonine residues on a target protein, and the O-GlcNAcase (OGA), which hydrolyses the sugar. To modulate ChREBPOG in vitro and in vivo, the OGT and OGA enzymes were overexpressed or inhibited via adenoviral approaches in mouse hepatocytes and in the liver of C57BL/6J or obese db/db mice.
RESULTS Our study shows that ChREBP interacts with OGT and is subjected to O-GlcNAcylation in liver cells. O-GlcNAcylation stabilizes the ChREBP protein and increases its transcriptional activity toward its target glycolytic (L-PK) and lipogenic genes (ACC, FAS, and SCD1) when combined with an active glucose flux in vivo. Indeed, OGT overexpression significantly increased ChREBPOG in liver nuclear extracts from fed C57BL/6J mice, leading in turn to enhanced lipogenic gene expression and to excessive hepatic T deposition. In the livers of hyperglycemic obese db/db mice, ChREBPOG levels were elevated compared with controls. Interestingly, reducing ChREBPOG levels via OGA overexpression decreased lipogenic protein content (ACC, FAS), prevented hepatic steatosis, and improved the lipidic profile of OGA-treated db/db mice.
CONCLUSIONS Taken together, our results reveal that O-GlcNAcylation represents an important novel regulation of ChREBP activity in the liver under both physiological and pathophysiological conditions.
- Received March 31, 2010.
- Accepted January 5, 2011.
- © 2011 by the American Diabetes Association.
Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.