Bulletin of ANPA

Abstract submitted to ANPA Conference July 14–16, 2023

Volume 5, Number 1

Biological, Medical, Soft Matter and Chemical Physics

Abstract ID: ANPA2023-N00038

Abstract:

ANPA2023-N00038: A Study of β-and γ- Crystallin Interacting with Phospholipid Membrane Using Atomic Force Microscopy

Authors:

• Nawal khadka; Boise State University

• Preston Hazen; Boise State University

• Dieter Haemmerle; Boise State University

• Laxman Mainali; Boise State University

Highly concentrated lens proteins, mostly crystallins, are responsible for maintaining the structure and refractivity of the eye lens. With increasing age, these crystallins form soluble and insoluble high molecular weight aggregates, which associate with lens membrane leading to lens hardening and cataract formation. The mechanism of such an association is still unclear. In this study, we explore the interaction of native β- and γ- crystallin extracted and purified from the cortex of the bovine lens with cholesterol (Chol)/phosphatidylcholine (PC) membrane with varying Chol content using atomic force microscopy (AFM). We prepared a supported lipid membrane by incubating small unilamellar vesicles (SUVs) on top of a freshly cleaved mica surface. Incubating β-crystallin on a defect-free membrane introduced locally modified semi-transmembrane defects, whereas γ- crystallins formed transmembrane defects on the phospholipid membrane. Rather than developing in multiple locations, the β-crystallin-induced defects expand in the localized area, whereas no significant increase in the size of transmembrane defect induced by γ- crystallin, was observed with increased incubation time. Our result shows that Chol inhibits the formation of membrane defects when β- and γ- crystallin interact with the Chol/PC membrane, and the degree of inhibition depends upon Chol content in the membrane. At a Chol/PC mixing ratio of 1, no defects were observed in membrane with γ- crystallin, whereas the severity of defects on membrane was decreased with β- crystallin. In conclusion, β- crystallin forms semi-transmembrane defects whereas γ- crystallin forms transmembrane defects when interacting with phospholipid membrane, and Chol suppresses the formation of such defects in the membrane. These results indicate the significance of Chol in the eye lens membrane in protecting against cataracts and lens hardening.

To cite this abstract, use the following reference: https://anpaglobal.org/conference/2023/ANPA2023-N00038