The Translational Repressor 4E-BP1 Contributes to Diabetes-Induced Visual Dysfunction

Invest Ophthalmol Vis Sci. 2016 Mar;57(3):1327-37. doi: 10.1167/iovs.15-18719.

Abstract

Purpose: The translational repressor 4E-BP1 interacts with the mRNA cap-binding protein eIF4E and thereby promotes cap-independent translation of mRNAs encoding proteins that contribute to diabetic retinopathy. Interaction of 4E-BP1 with eIF4E is enhanced in the retina of diabetic rodents, at least in part, as a result of elevated 4E-BP1 protein expression. In the present study, we examined the role of 4E-BP1 in diabetes-induced visual dysfunction, as well as the mechanism whereby hyperglycemia promotes 4E-BP1 expression.

Methods: Nondiabetic and diabetic wild-type and 4E-BP1/2 knockout mice were evaluated for visual function using a virtual optomotor test (Optomotry). Retinas were harvested from nondiabetic and type 1 diabetic mice and analyzed for protein abundance and posttranslational modifications. Similar analyses were performed on cells in culture exposed to hyperglycemic conditions or an O-GlcNAcase inhibitor (Thiamet G [TMG]).

Results: Diabetes-induced visual dysfunction was delayed in mice deficient of 4E-BP1/2 as compared to controls. 4E-BP1 protein expression was enhanced by hyperglycemia in the retina of diabetic rodents and by hyperglycemic conditions in retinal cells in culture. A similar elevation in 4E-BP1 expression was observed with TMG. The rate of 4E-BP1 degradation was significantly prolonged by either hyperglycemic conditions or TMG. A PEST motif in the C-terminus of 4E-BP1 regulated polyubiquitination, turnover, and binding of an E3 ubiquitin ligase complex containing CUL3.

Conclusions: The findings support a model whereby elevated 4E-BP1 expression observed in the retina of diabetic rodents is the result of O-GlcNAcylation of 4E-BP1 within its PEST motif.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / biosynthesis
  • Carrier Proteins / genetics*
  • Cell Cycle Proteins
  • Cells, Cultured
  • Diabetes Mellitus, Experimental*
  • Diabetic Retinopathy / etiology
  • Diabetic Retinopathy / genetics
  • Diabetic Retinopathy / physiopathology*
  • Eukaryotic Initiation Factors
  • Gene Expression Regulation*
  • Immunoprecipitation
  • Male
  • Mice
  • Mice, Knockout
  • Peptide Initiation Factors / metabolism
  • Phosphoproteins / biosynthesis
  • Phosphoproteins / genetics*
  • Phosphorylation
  • RNA / genetics*
  • Repressor Proteins
  • Retina / metabolism
  • Retina / pathology
  • Retina / physiopathology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Visual Acuity*

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • Eif4ebp1 protein, mouse
  • Eukaryotic Initiation Factors
  • Peptide Initiation Factors
  • Phosphoproteins
  • Repressor Proteins
  • RNA