Biomolecular Sciences Seminar Series

Dr. Kirsten Lampi, Oregon Health & Science University

Title: Protein Aggregation in the Eye Lens due to Cataract-associated Deamidation and Oxidation

Abstract: Crystallins are long-lived proteins found in high concentration in the eye lens. They accumulate numerous post-translational modifications during aging and are resistant to denaturation. Deamidation and oxidation of proteins are two of the most prevalent age-related modifications found in vivo. Deamidation at labile Asn and Gln residues in the human lens is associated with the highly prevalent age-related nuclear cataract. We have found that the cataract-associated deamidation at Asn (N) 14 and N76 in γS-crystallin was 3-11-fold greater in the insoluble fraction isolated in the nucleus of a highly brunescence human lens compared to an age-matched control. Deamidation at N14 and N76 led to increased protein dynamics and aggregation under oxidative conditions. During aging, the pool of lens glutathione diminishes in the center of the lens making sulfhydryls in crystallins more susceptible to oxidation. Using high resolution mass spectrometry, we identified a stepwise mechanism of disulfide crosslinking in γS-crystallin and the effect of deamidation on this pathway. These data provide a strong premise for our hypothesis that the cumulation of specific deamidations in lens crystallins facilitates non-native disulfide crosslinking between β/γ-crystallins initiating their aggregation. Such findings are crucial for establishing causality between the cumulation of post-translational modifications and cataract. And, while, deamidation may not be preventable, therapeutic intervention early with antioxidants targeted at specific sites may slow the onset of cataracts.

Host: Dr. Laxman Mainali