O-GlcNAcylation of orphan nuclear receptor ERRγ promotes hepatic gluconeogenesis
Estrogen-related receptor γ (ERRγ) is a major positive regulator of hepatic gluconeogenesis. Its transcriptional activity is suppressed by phosphorylation signaled by insulin in the fed state, but whether post-translational modification (PTM) alters its gluconeogenic activity in the fasted state is not known. Metabolically active hepatocytes direct a small amount of glucose into the hexosamine biosynthetic pathway (HBP) leading to protein O-GlcNAcylation. Here we demonstrate that ERRγ is O-GlcNAcylated by O-GlcNAc transferase (OGT) in the fasted state. This stabilizes the protein by inhibiting proteasome mediated protein degradation, increasing ERRγ recruitment to gluconeogenic gene promoters. Mass spectrometry identifies two serine residues (S317, S319) present in the ERRγ ligand binding domain (LBD) that are O-GlcNAcylated. Mutation of these residues destabilizes ERRγ protein, and blocks the ability of ERRγ to induce gluconeogenesis in vivo. The impact of this pathway on gluconeogenesis in vivo was confirmed by the observation that decreasing the amount of O-GlcNAcylated ERRγ by overexpressing the deglycosylating enzyme O-GlcNAcase (OGA) decreases ERRγ dependent glucose production in fasted mice. We conclude that O-GlcNAcylation of ERRγ serves as a major signal to promote hepatic gluconeogenesis.
- Received November 4, 2015.
- Accepted June 14, 2016.
- © 2016 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.