Accumulation and abberrant modifications of crystallins in anterior polar cataracts

Crystallins are the major proteins found in the lens, and the localization of specific crystallins is well known. Overexpression and accumulation of a B-crystallin has been observed in response to stress conditions or in certain diseases, such as brain tumors and neurodegenerative diseases. The purpose of this study was to examine whether a-crystallins are modified during pathological myofibroblastic changes in lens epithelial cells. Lens epithelial cells attached to the anterior capsules of patients with nuclear or anterior polar cataracts were analyzed quantitatively for a-crystallin proteins and mRNAs using Western blot and RT-PCR analysis., respectively. The degree of modification of a-crystallins was determined by 2-dimensional gel electrophoresis followed by Western blotting. Higher molecular weight protein bands that were immunoreactive to anti- a A- and anti- a B-crystallin antibodies around 45 kDa accumulated more in the anterior polar cataract samples than in those with the nuclear type of cataracts. Also monomeric a B-crystallins accumulated more in lens epithelial cells of patients with anterior polar cataracts. By comparison, no significant changes were found in the levels of the mRNAs encoding a A- and a B-crystallins in the different types of cataracts. Both a A- and a B-crystallin proteins seemed to undergo more extensive modification in anterior polar cataracts. Conclusion. In addition to fibrotic changes, which accompany increased levels of extracellular matrix molecules, accumulation and abnormal modification of a-crystallins might be implicated in the pathogenic mechanism of this type of cataract.