Binding of Alpha-Crystallin to Cortical and Nuclear Lens Lipid Membranes Derived from a Single Lens.

Abstract

Several studies reported that α-crystallin concentrations in the eye lens cytoplasm decrease with a corresponding increase in membrane-bound α-crystallin with age and cataracts. The influence of the lipid and cholesterol composition difference between cortical membrane (CM) and nuclear membrane (NM) on α-crystallin binding to membranes is still unclear. This study uses the electron paramagnetic resonance (EPR) spin-labeling method to investigate the α-crystallin binding to bovine CM and NM derived from the total lipids extracted from a single lens. Compared to CMs, NMs have a higher percentage of membrane surface occupied by α-crystallin and binding affinity, correlating with less mobility and more order below and on the surface of NMs. α-Crystallin binding to CM and NM decreases mobility with no significant change in order and hydrophobicity below and on the surface of membranes. Our results suggest that α-crystallin mainly binds on the surface of bovine CM and NM and such surface binding of α-crystallin to membranes in clear and young lenses may play a beneficial role in membrane stability. However, with decreased cholesterol content within the CM, which mimics the decreased cholesterol content in the cataractous lens membrane, α-crystallin binding increases the hydrophobicity below the membrane surface, indicating that α-crystallin binding forms a hydrophobic barrier for the passage of polar molecules, supporting the barrier hypothesis in developing cataracts.

• Authors: Raju Timsina, Samantha Wellisch, Dieter Haemmerle, Laxman Mainali
• Journal: International journal of molecular sciences (Int J Mol Sci) Vol. 23 Issue 19 (Sep 25 2022) ISSN: 1422-0067 [Electronic] Switzerland
• PMID: 36232595 (Publication Type: Journal Article)

Chemical References

• alpha-Crystallins
• Cholesterol

Topics

• Animals
• Cataract (metabolism)
• Cattle
• Cholesterol (metabolism)
• Lens, Crystalline (metabolism)
• Nuclear Envelope (metabolism)
• alpha-Crystallins