Effect of UV-A light on the chaperone-like properties of young and old lens alpha-crystallin

PURPOSE. To study the damaging effect of UV-A irradiation on the chaperone- like properties of alpha-crystallin and the subsequent recovery process of young and old bovine lenses. METHODS. Young and old bovine lenses were kept in organ culture. After 24 h ours of incubation they were irradiated with W-A at 365 nm, and optical qua lity measurements were performed during the experiments (192 hours), alpha- Crystallin and alpha A1-, alpha A2-, alpha B1-, and alpha B2-crysrallin sub units were analyzed, separated by gel filtration and cation exchange chroma tography, respectively, after different culture times. Protein patterns wer e obtained after two-dimensional (2-D) gel electrophoresis. Chaperone-like activin was determined on the basis of insulin B-chain and beta L-crystalli n aggregation assays. Aggregation of alpha-crystallin was analyzed, tryptop han fluorescence measurements were performed, and alpha-crystallin mRNA lev els were determined. RESULTS. The water-soluble alpha-crystallin obtained from old lenses compar ed with young lenses after UV irradiation had decreased chaperone activity, a higher molecular weight, and increased loss of tryptophan fluorescence. Moreover, alpha-crystallin mRNA virtually disappeared, whereas extra spots on the 2-D protein pattern appeared, possibly because of deamidation. CONCLUSIONS. alpha-Crystallin obtained from old lenses is more affected by irradiation than alpha-crystallin derived from young lenses. Moreover, it a ppeared that alpha B-crystallin from UV-treated old lenses compared with co ntrol lenses was less susceptible to UV-A than alpha A-crystallin. It may w ell be that alpha B-crystallin protects alpha A-crystallin in vivo.