Retinal O-linked N-acetylglucosamine protein modifications: implications for postnatal retinal vascularization and the pathogenesis of diabetic retinopathy.

Abstract

PURPOSE:

Hyperglycemia activates several metabolic pathways, including the hexosamine biosynthetic pathway. Uridine diphosphate N-acetylglucosamine (GlcNAc) is the product of the hexosamine biosynthetic pathway and the substrate for O-linked GlcNAc (O-GlcNAc) modification. This modification affects a wide range of proteins by altering their activity, cellular localization, and/or protein interactions. However, the role O-GlcNAcylation may play in normal postnatal retinal vascular development and in the ocular complications of diabetes, including diabetic retinopathy, requires further investigation.

METHODS:

The total levels of O-GlcNAc-modified proteins were evaluated by western blot analysis of lysates prepared from retinas obtained at different days during postnatal retinal vascularization and oxygen-induced ischemic retinopathy. Similar experiments were performed with retinal lysate prepared from diabetic Ins2(Akita/+) mice with different durations of diabetes and retinal vascular cells cultured under various glucose conditions. The localization of O-GlcNAc-modified proteins in the retinal vasculature was confirmed by immunofluorescence staining. The impact of altered O-GlcNAcylation on the migration of retinal vascular cells was determined using scratch wound and transwell migration assays.

RESULTS:

We detected an increase in protein O-GlcNAcylation during mouse postnatal retinal vascularization and aging, in part through the regulation of the enzymes that control this modification. The study of the diabetic Ins2(Akita/+) mouse retina showed an increase in the O-GlcNAc modification of retinal proteins. We also observed an increase in retinal O-GlcNAcylated protein levels during the neovascularization phase of oxygen-induced ischemic retinopathy. Our fluorescence microscopy data confirmed that the alterations in retinal O-GlcNAcylation are similarly represented in the retinal vasculature and in retinal pericytes and endothelial cells. Particularly, the migration of retinal pericytes, but not retinal endothelial cells, was attenuated by increased O-GlcNAc modification.

CONCLUSIONS:

The O-GlcNAc modification pattern changes during postnatal retinal vascular development and neovascularization, and its dysregulation under hyperglycemia and/or ischemia may contribute to the pathogenesis of the diabetic retinopathy and retinal neovascularization.

• Authors: Zafer Gurel, Kelsey M Sieg, Keegan D Shallow, Christine M Sorenson, Nader Sheibani
• Journal: Molecular vision (Mol Vis) Vol. 19 Pg. 1047-59 ( 2013) ISSN: 1090-0535 [Electronic] United States
• PMID: 23734074 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Eye Proteins
• Ins2 protein, mouse
• Insulin
• Glucose
• Acetylglucosamine

Topics

• Acetylglucosamine (metabolism)
• Aging (pathology)
• Animals
• Animals, Newborn
• Cell Movement (drug effects)
• Diabetic Retinopathy (metabolism, pathology, physiopathology)
• Eye Proteins (metabolism)
• Glucose (pharmacology)
• Glycosylation (drug effects)
• Insulin (genetics)
• Male
• Mice
• Mice, Inbred C57BL
• Neovascularization, Physiologic (drug effects)
• Pericytes (drug effects, metabolism, pathology)
• Protein Processing, Post-Translational (drug effects)
• Retina (growth & development, metabolism, pathology, physiopathology)
• Retinal Vessels (drug effects, growth & development, pathology, physiopathology)