[The molecular chaperone function of alpha-crystallin in age-related cataract]

To evaluate the molecular chaperone function of alpha-crystallin in age-related cataract.

alpha L-Crystallin of human clear and cataractous lenses in both the cortex and nucleus were separated by chromatography on Sephacryl S-300HR. The preventive effects of alpha L-crystallin on thermally induced aggregation of catalase were measured spectrophotometrically. The complex formation between a catalase and alpha L-crystallin during the aggregation experimental was detected by SDS-PAGE methods.

Human alpha L-crystallin specifically prevented catalase from thermal aggregation. Its preventive ability in cortex was greatly higher than that in nucleus of clear lenses. There was a remarkably decrease of preventive ability in cataractous lenses with statistical differences between the group under 65 years old and that over 65 years old, grade II and grade IV in over 65 years group, whereas alpha L-crystallin showed no statistical change in under 65 years group but its preventive ability was diminished in grade IV. SDS-PAGE showed that the 20 kDa bands had no significant decrease in water-soluble portion after heating 0.40 mim and 2 h, whereas the 65 kD bands were increased.

alpha-Crystallin can function as a molecular chaperone by preventing thermal aggregation of catalase. A decrease in chaperone function from cataractous lenses has been showed in age-dependent and opacification-dependent fashion, which may play an important role in formation of cataract.