title: Cytoprotective effects of proteasome beta5 subunit overexpression in lens epithelial cells.
abstract: OBJECTIVE
  To determine whether the overexpression of the proteasome catalytic beta5 subunit (PSMB5) can induce the expression of the catalytic subunits beta1 and beta2, enhance proteasome activity, and exert a cytoprotective effect in lens epithelial cells.
  
  
  METHODS
  Cells from the human lens epithelial cell line SRA01/04 (LECs) were stably transfected either with a plasmid expressing the proteasome catalytic subunit beta5 or with an empty plasmid. beta-5-expressing LECs and controls were analyzed for the expression of beta1, beta2, beta5, and alpha6 proteasome subunits; chymotrypsin-like (CT-L) and peptidylglutamyl-peptide hydrolase (PGPH) catalytic activities; as well as for the accumulation of carbonylated proteins, rates of cell viability, and apoptosis after oxidative stress.
  
  
  RESULTS
  Stable expression of the beta5 proteasome subunit resulted in increased expression of the catalytic subunits beta1 and beta2, increased CT-L and PGPH proteasome activities, and increased resistance to accumulation of carbonylated proteins and cell death after oxidative stress.
  
  
  CONCLUSIONS
  The proteasome activity can be genetically "upregulated" in lens cells by overexpression of the beta5 catalytic subunit. The resulting increase in proteasome activity leads to a decrease in the accumulation of oxidized proteins and enhanced cell survival following oxidative stress.
authors.affiliation: Zhongshan Ophthalmic Center of Sun Yat-Sen University, State Key Laboratory of Ophthalmology, Guangzhou, China. yizhiliu_0001@yahoo.com
authors.forename: Yizhi
authors.initials: Y
authors.lastname: Liu
authors.forename: Xialin
authors.initials: X
authors.lastname: Liu
authors.forename: Tieying
authors.initials: T
authors.lastname: Zhang
authors.forename: Coralia
authors.initials: C
authors.lastname: Luna
authors.forename: Paloma B
authors.initials: PB
authors.lastname: Liton
authors.forename: Pedro
authors.initials: P
authors.lastname: Gonzalez
mesh_terms: D002460:Cell Line; D002470:Cell Survival; D002918:Chymotrypsin / Q000378:metabolism; D019610:Cytoprotection / Q000502:physiology*; D010450:Endopeptidases / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology; D005136:Eye Proteins / Q000378:metabolism; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D050050:Protein Carbonylation / Q000502:physiology
chemical_list: D005136:Eye Proteins; D010450:Endopeptidases; D002918:Chymotrypsin; C088874:PSMB5 protein, human; D046988:Proteasome Endopeptidase Complex; C114177:peptidylglutamylpeptide hydrolase