Proteasome activity in human lens nuclei and correlation with age, gender and severity of cataract

Abstract

Purpose. The aim of this study was to measure proteasome activity in human lens nuclei resulting from cataract surgery and in different regions of donor lenses. Methods. The chymotrypsin-like, the trypsin-like and the peptidylglutamyl-peptide hydrolysing activities of the proteasome were studied using synthetic flourogenic substrates. Results. Proteasome activity did not show any correlation with age of the patients or with gender. Increased opacification of the lens nucleus, as estimated prior to surgery using a 4-grade scale, was significantly correlated with decreased activity of all peptidase activities in the insoluble fraction. In the donor lenses, all peptidase activities were highest in the epithelium and decreased rapidly towards the nucleus. Conclusions. The present study demonstrates that proteasome activity is preserved in the nucleus of lenses from elderly individuals, although a decrease can be seen with cataract formation. This finding may be of importance for elucidating the mechanism behind the formation of nuclear cataract.