Transcriptional regulation of O-GlcNAc homeostasis is disrupted in pancreatic cancer

Abstract

Many intracellular proteins are reversibly modified by -linked GlcNAc (-GlcNAc), a post-translational modification that dynamically regulates fundamental cellular processes in response to diverse environmental cues. Accumulating evidence indicates that both excess and deficiency of protein -GlcNAcylation can have deleterious effects on the cell, suggesting that maintenance of-GlcNAc homeostasis is essential for proper cellular function. However, the mechanisms through which -GlcNAc homeostasis is maintained in the physiologic state and altered in the disease state have not yet been investigated. Here, we demonstrate the existence of a homeostatic mechanism involving mutual regulation of the-GlcNAc-cycling enzymes -GlcNAc transferase (OGT) and-GlcNAcase (OGA) at the transcriptional level. Specifically, we found that OGA promotes transcription through cooperation with the histone acetyltransferase p300 and transcription factor CCAAT/enhancer-binding protein β (C/EBPβ). To examine the role of mutual regulation of OGT and OGA in the disease state, we analyzed gene expression data from human cancer data sets, which revealed that and expression levels are highly correlated in numerous human cancers, particularly in pancreatic adenocarcinoma. Using a -driven primary mouse pancreatic ductal adenocarcinoma (PDAC) cell line, we found that inhibition of extracellular signal-regulated kinase (ERK) signaling decreases OGA glycosidase activity and reduces OGT mRNA and protein levels, suggesting that ERK signaling may alter -GlcNAc homeostasis in PDAC by modulating OGA-mediated transcription. Our study elucidates a transcriptional mechanism that regulates cellular -GlcNAc homeostasis, which may lay a foundation for exploring-GlcNAc signaling as a therapeutic target for human disease.

Protein O-GlcNAcylation: emerging mechanisms and functions

“…5). Indeed, OGA has been shown to upregulate OGT gene expression through activation of the transcription factor CCAAT/enhancer-binding protein β (C/EBP-β) 93 . Conversely, pharmacological inhibition of OGA has been shown to increase MGEA5 gene expression, indicating that elevated cellular O -GlcNAcylation levels promote compensatory MGEA5 transcription, perhaps through enhanced O -GlcNAcylation of specific transcription factors and cofactors 94 .…”

O-GlcNAc as an Integrator of Signaling Pathways

“…Our recent work provides mechanistic insight into mutual regulation of OGT and OGA at the transcriptional level. Specifically, we found that OGA acts as a co-activator that directly promotes OGT transcription through cooperation with C/EBPβ and p300 histone acetyltransferase ( 70 ). Another recent work has suggested that there is a conserved OGT intronic splicing silencer that is necessary for OGT intron retention ( 71 ).…”

Hepatocyte nuclear factor 1 alpha (HNF1A) regulates transcription of O‐GlcNAc transferase in a negative feedback mechanism

“…Because O‐GlcNAcylation is of great importance for fundamental cell events, cells must maintain the homeostasis of the modification via the regulation of OGT/OGA or hexosamine biosynthesis pathway flux. A mutual regulation of OGT and OGA at the transcriptional level reportedly contributes to the hemostatic O‐GlcNAcylation in HepG2 cells . Besides the regulation of OGT protein via expression and degradation pathways, OGT is also regulated by E2F1 at the transcription level .…”