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Retinal Protein O-GlcNAcylation and the Ocular Renin-Angiotensin System: Signaling Cross-Roads in Diabetic Retinopathy

Author(s):

Sadie K. Dierschke and Michael D. Dennis*   Pages 1 - 18 ( 18 )

Abstract:


It is well established that diabetes and its associated hyperglycemia negatively impacts retinal function, yet we know little about the role played by augmented flux through the hexosamine biosynthetic pathway (HBP). This offshoot of the glycolytic pathway produces UDP-N-acetyl-glucosamine which serves as the substrate for post-translational Olinked modification of proteins in a process referred to as O-GlcNAcylation. HBP flux and subsequent protein OGlcNAcylation serve as a nutrient sensor, enabling cells to integrate metabolic information to appropriately modulate fundamental cellular processes including gene expression. Here we summarize the impact of diabetes on retinal physiology, highlighting recent studies that explore the role of O-GlcNAcylation-induced variation in mRNA translation in retinal dysfunction and the pathogenesis of diabetic retinopathy (DR). Augmented O-GlcNAcylation results in widespread variation in the selection of mRNAs for translation, in part, due to O-GlcNAcylation of the translational repressor 4E-BP1. Recent studies demonstrate that 4E-BP1 plays a critical role in regulating O-GlcNAcylation-induced changes in translation of the mRNAs encoding vascular endothelial growth factor (VEGF), a number of important mitochondrial proteins, and CD40, a key costimulatory molecule involved in diabetes-induced retinal inflammation. Remarkably, 4E-BP1/2 ablation delays the onset of diabetes-induced visual dysfunction in mice. Thus, pharmacological interventions to prevent the impact of O-GlcNAcylation on 4E-BP1 may represent promising therapeutics to address the development and progression of DR. In this regard, we discuss the potential interplay between retinal O-GlcNAcylation and the ocular renin-angiotensin system as a potential therapeutic target of future interventions.

Keywords:

Diabetes, retinopathy, O-GlcNAcylation, mRNA translation, renin-angiotensin system, oxidative stress, inflammation

Affiliation:

Department of Cellular and Molecular Physiology, Penn State College of Medicine;, Department of Ophthalmology, Penn State College of Medicine



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