title: HIF-1α SUMOylation affects the stability and transcriptional activity of HIF-1α in human lens epithelial cells.
abstract: OBJECTIVE
  High blood glucose can induce oxidative damage and result in diabetic cataract. Oxidative stress induces various signal pathways including HIF-1α transcriptional signal to attenuate the damage of lenses. Whether HIF-1α SUMOylation can increase the activation of HIF-1α or if high glucose can affect the SUMOylation of HIF-1α in cultured human lens epithelial cells (HLECs) is still unknown, as well as the function of HIF-1α SUMOylation in oxidative damage induced by high glucose in HLECs. In the present study, we examined SUMO and SUMO E3 (Cbx4 and PIASy) expression induced by high glucose, and investigated SUMO or SUMO E3 overexpression that enhanced HIF-1α SUMOylation in HLECs.
  
  
  METHODS
  SRA01/04 cells, one kind of human lens epithelial cell line, were addressed in media with 5.5 mmol/l (normal control group), 25 mmol/l (high glucose1 group) and 50 mmol/l (high glucose2 group) final glucose respectively. Expression of SUMO1 ~ 4, Cbx4, PIASy, HIF-1α, GLUT1, and VEGFA were detected in the mRNA and protein levels by RT-PCR and Western blot analysis. Protein expression localization and co-localization were examined by immunofluorescence and co-immunofluorescence. The effects of SUMO overexpression, SUMO E3 overexpression, and Proteasome inhibitor MG132 respectively on the stability and transcriptional activity of HIF-1α were analyzed by immunoblot.
  
  
  RESULTS
  High glucose treatment induced SUMO1-4 expression and enhanced the expression of Cbx4 and PIASy. It also increased the expression of HIF-1α, GLUT1, and VEGFA. The co-localization of HIF-1α and SUMO was mainly in the nucleus induced by high glucose. Further studies showed that SUMO overexpression or SUMO E3 overexpression could enhance HIF-1α stability and transcriptional activity in HLECs. Proteasome inhibitor MG132 protected the stability and transcriptional activity of HIF-1α in the SRA01/04 cells.
  
  
  CONCLUSIONS
  HIF-1α SUMOylation affected the stability and transcriptional activity of HIF-1α in cultured human lens epithelial cells; SUMO overexpression or SUMO E3 overexpression enhanced the expression of HIF-1α, which is involved in inhibiting cell apoptosis and protecting lens opacification, and presumably plays a key role in protecting lenses from diabetic cataract.
authors: Department of Ophthalmology, the Fourth Affiliated Hospital of China Medical University; Key Laboratory of Lens Research of Liaoning Province, Eye Hospital of China Medical University, 11 Xinhua Road, Heping District, Shenyang, Liaoning Province, 110005, People's Republic of China.
authors: Xiao
authors: X
authors: Han
authors: Xin-Ling
authors: XL
authors: Wang
authors: Qin
authors: Q
authors: Li
authors: Xiao-Xuan
authors: XX
authors: Dong
authors: Jin-Song
authors: JS
authors: Zhang
authors: Qi-Chang
authors: QC
authors: Yan
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D007908:Lens, Crystalline / Q000166:cytology*; D008025:Ligases; D000075223:Poly-ADP-Ribose Binding Proteins; D063146:Polycomb-Group Proteins / Q000378:metabolism; D050828:Protein Inhibitors of Activated STAT / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D058207:Sumoylation; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C485891:PIAS4 protein, human; D000075223:Poly-ADP-Ribose Binding Proteins; D063146:Polycomb-Group Proteins; D050828:Protein Inhibitors of Activated STAT; D012333:RNA, Messenger; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C570427:CBX4 protein, human; D005947:Glucose