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YG Marrero, D Tang, MC Yappert, D Borchman; Influence of Age and Cataract on Alpha-Crystallin Interactions With Human Lens Lipids . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3557.
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Purpose: It has been hypothesized that alpha-crystallin binding to lens lipid membranes may contribute to the aggregation and reduced solubility of lens proteins with age and cataract formation. Lipid compositional and structural changes occur with age and cataract. In this study we determined the influence of these changes on the binding properties of alpha-crystallin to lipid membranes in vitro. Methods: Lipids were extracted from clear and mixed cataractous human lenses. Lipid composition and structure were measured using infrared spectroscopy. For the binding assay, bovine alpha-crystallin was used. Extracted lens lipids were extruded into large unilamellar vesicles. Alpha-crystallin - lipid binding was characterized by measuring the amount of free alpha-crystallin remaining in the supernatant after removing the bound alpha-crystallin and lipid by centrifugation. Results:It was evident from the intensity of the infrared carbonyl stretching band that the amount of fluid glycerol lipids decreased with age and cataract. Changes in the amide, trans-double bond and hydroxyl stretching bands indicated that lipid aldehydes and hydroxyls, both attributed to products of lipid oxidation, increase with age and cataract. Infrared spectra indicate that lipid hydrocarbon chain order increases with age and cataract. Alpha-crystallin - lipid binding studies showed that the Kd and binding capacity decreased with age. Binding properties obtained with cataractous lipids were similar to those observed for age-matched controls. Conclusion: Age-related changes in lipid composition and structure influence the binding properties of alpha-crystallin. Changes in lipid composition accompanying cataract had little affect on alpha-crystallin - lipid binding in vitro.
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