UV-A-related alterations of young and adult lens water-insoluble alpha-crystallin, plasma membranous and cytoskeletal proteins

The damaging effects of UV-A irradiation on lens water insoluble alpha -cry stallin, plasma membranous and cytoskeletal proteins derived from bovine le nses were studied. Young and adult bovine lenses were kept viable for 2 mon ths in organ culture. After 24 h of incubation they were irradiated, and an alyses of the proteins by one-dimensional and two-dimensional gel electroph oresis followed by Western blotting were carried out at several time interv als. RNA isolation, PCR and Northern blotting were also performed. We ident ified age-related changes in water-insoluble alpha -crystallin, the major m embrane protein MP26 and the cytoskeletal proteins vimentin, phakinin and a ctin between control and UV-irradiated lenses. It appeared that adult lense s are more susceptible to UV light than young lenses, and protein modificat ion occurred more frequently in adult lenses. UV-A irradiation affects not only the cytoskeletal structure, as deduced by the abnormal arrangement of actin in the fiber cells, but also leads to degradation of actin mRNA. Furt hermore, analysis of the expression of hsp25 and hsp70 revealed some altera tion in the protein pattern of adult lenses. We suggest that degradation of the cytoskeletal proteins following irradiation is due to, at least in par t, the decreased protective ability of heat shock proteins upon aging.