A PGC-1α-O-GlcNAc Transferase Complex Regulates FoxO Transcription Factor Activity in Response to Glucose

Michael P Housley,Namrata D Udeshi,Joseph T Rodgers,Jeffrey Shabanowitz,Pere Puigserver,Donald F Hunt,Gerald W Hart

doi:10.1074/jbc.m808890200

Abstract

Metabolic and stress response gene regulation is crucial for the survival of an organism to a changing environment. Three key molecules that sense nutrients and broadly affect gene expression are the FoxO transcription factors, the transcriptional co-activator PGC-1alpha, and the dynamic post-translational modification, O-linked beta-N-acetylglucosamine (O-GlcNAc). Here we identify novel post-translational modifications of PGC-1alpha, including O-GlcNAc, and describe a novel mechanism for how PGC-1alpha co-activates transcription by FoxOs. In liver, in cultured cells, and in vitro with recombinant proteins, PGC-1alpha binds to O-GlcNAc transferase and targets the enzyme to FoxOs, resulting in their increased GlcNAcylation and increased transcriptional activity. Furthermore, glucose-enhanced activation of FoxO1 occurs via this PGC-1alpha-O-GlcNAc transferase-mediated GlcNAcylation. Therefore, one mechanism by which PGC-1alpha can serve as a co-activator of transcription is by targeting the O-GlcNAc transferase to increase GlcNAcylation of specific transcription factors important to nutrient/stress sensing and energy metabolism.

Highlights

Oxidative stress, in neuronal tissues [3]
Identification of Post-translational Modifications of PGC1␣—Using electron transfer dissociation (ETD) tandem mass spectrometry (MS/MS) and CAD-MS/MS, we identified multiple post-translational modifications of PGC-1␣ including O-GlcNAc, phosphorylation, acetylation, and monomethylation sites (Table 1 and supplemental Fig. S1)
Thr-294 (Thr-295 in human) is phosphorylated by glycogen synthase kinase-3␤ (GSK-3␤) [31].Methylation of PGC-1␣ has previously been shown to occur at Arg-665, Arg-667, and Arg-669 by protein arginine methyltransferase 1 (PRMT1) [32]. These studies did not detect in vitro methylation in the amino acid 306 –532 region, indicating that PRMT1 may not be the methyltransferase responsible for Arg-365 modification or that in vitro labeling at this site was inefficient relative to the acidic Glu region. 13 acetylation sites have been found throughout PGC-1␣ [4]

Summary

Introduction

Oxidative stress, in neuronal tissues [3]. PGC-1␣ regulates mitochondrial biosynthesis and respiration by stimulating the activity of a number of transcription factors including NRF-1/2, the peroxisome proliferator-activated receptors, the retinoid X receptors, and estrogen-related receptor ␣ [1]. A PGC-1␣-O-GlcNAc Transferase Complex Regulates FoxOs bolic-, stress response-, and longevity-related gene expression programs, responds to hyperglycemia through elevated GlcNAcylation in the liver. A functional interaction between OGT and PGC-1␣ increases GlcNAcylation of FoxO, resulting in enhanced transcriptional activation in response to glucose.

Results

Conclusion