MicroRNA-31 targets FIH-1 to positively regulate corneal epithelial glycogen metabolism

FASEB J. 2012 Aug;26(8):3140-7. doi: 10.1096/fj.11-198515. Epub 2012 Apr 24.

Abstract

Corneal epithelium relies on abundant glycogen stores as its primary energy source. MicroRNA-31 (miR-31), a corneal epithelial-preferred miRNA, negatively regulates factor inhibiting hypoxia-inducible factor-1 (FIH-1). Since HIF-1α is involved in anaerobic energy production, we investigated the role that miR-31 and FIH-1 play in regulating corneal epithelial glycogen. We used antagomirs (antago) to reduce the level of miR-31 in primary human corneal epithelial keratinocytes (HCEKs), and a miR-31-resistant FIH-1 to increase FIH-1 levels. Antago-31 raised FIH-1 levels and significantly reduced glycogen stores in HCEKs compared to irrelevant-antago treatment. Similarly, HCEKs retrovirally transduced with a miR-31-resistant FIH-1 had markedly reduced glycogen levels compared with empty vector controls. In addition, we observed no change in a HIF-1α reporter or known genes downstream of HIF-1α indicating that the action of FIH-1 and miR-31 on glycogen is HIF-1α-independent. An enzyme-dead FIH-1 mutation failed to restore glycogen stores, indicating that FIH-1 negatively regulates glycogen in a hydroxylase-independent manner. FIH-1 overexpression in HCEKs decreased AKT signaling, activated GSK-3β, and inactivated glycogen synthase. Treatment of FIH-1-transduced HCEKs with either a myristolated Akt or a GSK-3β inhibitor restored glycogen stores, confirming the direct involvement of Akt/GSK-3β signaling. Silencing FIH-1 in HCEKs reversed the observed changes in Akt-signaling. Glycogen regulation in a HIF-1α-independent manner is a novel function for FIH-1 and provides new insight into how the corneal epithelium regulates its energy requirements.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cells, Cultured
  • Epithelium, Corneal / drug effects
  • Epithelium, Corneal / metabolism*
  • Female
  • Glycogen / metabolism*
  • Glycogen Synthase / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / metabolism
  • Glycogen Synthase Kinase 3 beta
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism*
  • Mice
  • MicroRNAs / physiology*
  • Mixed Function Oxygenases / antagonists & inhibitors*
  • Mixed Function Oxygenases / metabolism
  • Oligoribonucleotides / pharmacology
  • Proto-Oncogene Proteins c-akt / physiology
  • Repressor Proteins / antagonists & inhibitors*
  • Repressor Proteins / metabolism
  • Signal Transduction / drug effects

Substances

  • Hypoxia-Inducible Factor 1, alpha Subunit
  • MIRN31 microRNA, human
  • MicroRNAs
  • Oligoribonucleotides
  • Repressor Proteins
  • Glycogen
  • Mixed Function Oxygenases
  • HIF1AN protein, human
  • Glycogen Synthase
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, mouse
  • Proto-Oncogene Proteins c-akt
  • Glycogen Synthase Kinase 3