Lens α-crystallin - lipid interactions

Document Type

Article

Publication Title

Investigative Ophthalmology and Visual Science

Abstract

Purpose. Lens a - crystallins compose 40% of the total crystallins and bind to pure lipid membranes. The role of cholesterol and phospholipid composition to the binding of a-crystallin was explored in this study. Methods. DPH and NBD-PE fluorescence probes were used to study the effects of a-crystallin binding on the head group and interior of membranes, a-crystallin binding was quantified by determining the a-crystallin concentration in pellets after centrifijgation, and by changes in probe fluorescence. Results. The binding capacity of a - crystallin was higher for sphingomyelin, than for dihydrosphingomyelin , the major human lens phospholipid. Cholesterol decreased the binding capacity and Kb of a - crystallin to disteroylphosphatidylchotine and sphingomyelin. With increased a - crystallin binding, the fluorescence intensity of the NBD-PE probe increased, a - crystallin - lipid binding was lower at higher (55° C) temperatures. Conclusions. Fluorescence data indicate that a - crystallin - lipid binding reduces the exposure of the lipid head group probe to water. A less polar environment about the probe could protect the lipids from soluble oxidants such as Hj02 and decrease membrane permeability to cations. Our data support the hypothesis that changes in membrane cholesterol and sphingomyelin content with age and region could influence a - crystallin membrane binding. The high dihydrosphingomyelin and cholesterol content of human lens membranes could moderate a - crystallin - membrane interactions in vivo.

Publication Date

12-1-1997

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