Lens epithelium-derived growth factor: Increased resistance to thermal andoxidative stresses

PURPOSE. TO investigate the role of lens epithelium- derived growth factor (LEDGF) in lens epithelial cells subjected to heat or oxidative stress and to determine the localization of LEDGF in lens epithelial cells at differen t temperatures. METHODS. Mouse lens epithelial cells overexpressing a fusion protein betwee n a green fluorescent protein (GFP) and LEDGF (GFP-LEDGF) were cultured for up to 7 days at various temperatures or for 24 hours in the presence of hy drogen peroxide. Translocation of GFP-LEDGF in the lens epithelial cells wa s monitored with a fluorescence microscope. Cell survival was determined wi th the trypan blue dye exclusion test. Expression of heat shock proteins (H sps) was studied with protein blot analyses using antibody probes. RESULTS. LEDGE was found in the cytosol of lens epithelial cells at 4 degre es C, 15 degrees C, and 28 degrees C, and in the nucleus and nucleolus at 3 7 degrees C. At 41 degrees C, it was apparent at higher levels in the cytos ol, nucleus, and nucleolus. Lens epithelial cells overexpressing LEDGF mani fested resistance to thermal and oxidative stress. Levels of Hsp 27, and al pha B-crystallin were elevated in these cells. Depriving lens epithelial ce lls of LEDGF with anti-LEDGF antibodies reduced nuclear localization of LED GF and induced cell death. CONCLUSIONS. The overexpression of LEDGF in lens epithelial cells conferred resistance to thermal and oxidative stress. The mechanism of this resistan ce appears to involve the increased expression of Hsp 27 and alpha B-crysta llin.