Effect of UV-A light on the chaperone-like properties of young and old lens alpha-crystallin.
OBJECTIVE
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 hours of incubation they were irradiated with UV-A at 365 nm, and optical quality measurements were performed during the experiments (192 hours). alpha-Crystallin and alpha1-, alphaA2-, alphaB1-, and alphaB2-crystallin subunits were analyzed, separated by gel filtration and cation exchange chromatography, respectively, after different culture times. Protein patterns were obtained after two-dimensional (2-D) gel electrophoresis. Chaperone-like activity was determined on the basis of insulin B-chain and betaL-crystallin aggregation assays. Aggregation of alpha-crystallin was analyzed, tryptophan fluorescence measurements were performed, and alpha-crystallin mRNA levels were determined.


RESULTS
The water-soluble alpha-crystallin obtained from old lenses compared 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 appeared that alphaB-crystallin from UV-treated old lenses compared with control lenses was less susceptible to UV-A than alphaA-crystallin. It may well be that alphaB-crystallin protects alphaA-crystallin in vivo.
Weinreb
O
O
Department of Biochemistry, University of Nijmegen, The Netherlands.
van Boekel
M A
MA
Dovrat
A
A
Bloemendal
H
H
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D018833:Chaperonins / Q000378:metabolism*; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003459:Crystallins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003641:Deamination; D015180:Electrophoresis, Gel, Two-Dimensional; D007908:Lens, Crystalline / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D009924:Organ Culture Techniques; D012333:RNA, Messenger / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
D003459:Crystallins; D012333:RNA, Messenger; D018833:Chaperonins