title: MicroRNA-31 targets FIH-1 to positively regulate corneal epithelial glycogen metabolism.
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.
authors.affiliation: Department of Dermatology, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Han
authors.initials: H
authors.lastname: Peng
authors.forename: Robert B
authors.initials: RB
authors.lastname: Hamanaka
authors.forename: Julia
authors.initials: J
authors.lastname: Katsnelson
authors.forename: Liang-Liang
authors.initials: LL
authors.lastname: Hao
authors.forename: Wending
authors.initials: W
authors.lastname: Yang
authors.forename: Navdeep S
authors.initials: NS
authors.lastname: Chandel
authors.forename: Robert M
authors.initials: RM
authors.lastname: Lavker
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000037:antagonists & inhibitors; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D035683:MicroRNAs / Q000502:physiology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009843:Oligoribonucleotides / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C534612:MIRN31 microRNA, human; D035683:MicroRNAs; D009843:Oligoribonucleotides; D012097:Repressor Proteins; D006003:Glycogen; D006899:Mixed Function Oxygenases; C439790:HIF1AN protein, human; D006006:Glycogen Synthase; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3