Abstract
Purpose :
α-Crystallin becomes increasingly membrane-bound with age and cataract formation. However, how the grade of cortical cataract (CC) and nuclear cataract (NC) influences α-crystallin binding to the cortical membrane (CM) and nuclear membrane (NM) is unclear. This study investigates the binding of α-crystallin to CM and NM derived from age-matched male and female human lenses with varying grades of CC and NC.
Methods :
Four pairs of human lenses from age-matched male and female donors of 68 and 73 years old were graded for CC and NC on a scale of 0 to 3 based on the opacity for CC and yellowness for NC. The CC for one additional male donor of 64 years was graded using the same criteria. The electron paramagnetic resonance spin-labeling method was used to investigate α-crystallin binding to CM and NM made from the total lipids (lipid plus cholesterol (Chol)) extracted from a single human lens. 4-palmitamido-TEMPO (4PT) spin-label was used to measure the percentage of membrane surface occupied (MSO) by α-crystallin and the physical properties (mobility, order, and hydrophobicity) of CM and NM on the membrane surface with α-crystallin binding.
Results :
Our study shows that MSO by α-crystallin in human CM and NM increases with an increase in the grade of CC and NC. The binding of α-crystallin resulted in a corresponding decrease in mobility on the membrane surface, indicating CM and NM become immobilized with α-crystallin binding. CM mobility decreased with an increased grade of CC for both male and female donors, whereas the male NM mobility showed no significant change, and female NM showed increased mobility with an increase in NC grade. α-Crystallin binding to CM and NM increased order and hydrophobicity on the membrane surface in both male and female donors, forming the hydrophobic barrier for the transport of polar and ionic molecules.
Conclusions :
The binding of α-crystallin to CM and NM increases with an increase in the grade of CC and NC, which might result from decreased Chol content in cataractous CM and NM. The physical properties of the CM and NM are altered with α-crystallin binding, which might play a significant role in modulating the integrity of CM and NM. These findings provide insight into the need for high Chol content in the lens membrane in inhibiting α-crystallin binding and maintaining lens transparency.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.