Age-dependent association of γ-crystallins with aged α-crystallins from old bovine lens

Purpose: Previous theoretical and experimental studies have predicted that the loss of weak protein interactions between alpha- and gamma-crystallins could result in a decrease in the transparent properties of the aging lens. Methods: alpha-Crystallins were prepared from the nucleus of old bovine lens, and gamma-crystallins were prepared from whole fetal bovine lens or from the nucleus of old bovine lens. The possible interactions of old alpha-crystallins with either old gamma-crystallins or fetal gamma-crystallins were quantitated at equilibrium using microequilibrium dialysis. The amount of each gamma-crystallin species in the "full" versus "empty" chambers was determined by reverse phase chromatography to obtain a binding ratio (full/empty). Results: A binding ratio greater than 1.00 is indicative of a alpha-crystallin/gamma-crystallin interaction. Within experimental error (+/- 2X standard deviation), there were no interactions between aged gamma-crystallins with aged alpha-crystallins while there were significant interactions between some of the fetal gamma-crystallins with aged a-crystallins. Conclusions: In the aged bovine lens, when transparency is known to decrease, there is no detectable interaction of gamma-crystallins with alpha-crystallins as measured by microequilibrium dialysis. The results are consistent with the hypothesis that short-range, weak, attractive interactions between alpha- and gamma-crystallins are necessary for maximum transparency of the lens.