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Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
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Interaction of βL- and γ-Crystallin with Phospholipid Membrane Using Atomic Force Microscopy
Nawal K Khadka1, Preston Hazen2, Dieter Haemmerle1
1Department of Physics, Boise State University, Boise, ID 83725, USA.
International Journal of Molecular Sciences
|November 14, 2023
Summary
Lens proteins beta- and gamma-crystallin interact with membranes, forming defects linked to cataract formation. Cholesterol inhibits these defects, potentially preventing cataracts by maintaining lens homeostasis.
Area of Science:
- Biochemistry
- Biophysics
- Ocular Science
Background:
- Lens proteins beta- and gamma-crystallin maintain eye lens structure and refractivity.
- Aging and cataract formation involve these proteins associating with the lens membrane, causing light scattering.
- The mechanism of crystallin-membrane association and its role in cataractogenesis is not fully understood.
Purpose of the Study:
- To investigate the interaction of beta- and gamma-crystallin with phospholipid membranes containing varying cholesterol concentrations.
- To elucidate the role of phospholipids and cholesterol in the association of crystallins with the lens membrane.
- To understand the structural changes induced by crystallin-membrane interactions and their potential link to cataract formation.
Main Methods:
- Preparation of small unilamellar vesicles (SUVs) composed of cholesterol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (Chol/POPC) with varied cholesterol content.
- Formation of supported lipid membranes on mica disks.
- Time-dependent association studies of bovine beta_L- and gamma-crystallin with membranes using atomic force microscopy (AFM) to obtain topographical images.
Main Results:
- Beta_L-crystallin formed semi-transmembrane defects, while gamma-crystallin formed transmembrane defects on phospholipid membranes.
- Defect size increased with incubation time for beta_L-crystallin, but not significantly for gamma-crystallin.
- Cholesterol inhibited defect formation, with higher cholesterol content leading to reduced or absent association and fewer defects. A Chol/POPC ratio of 1 prevented gamma-crystallin association and significantly reduced beta_L-crystallin induced defects.
Conclusions:
- The formation of semi-transmembrane and transmembrane defects by beta- and gamma-crystallin on phospholipid membranes may contribute to light scattering and cataract development.
- Cholesterol acts as a protective agent by suppressing the formation of these membrane defects.
- Cholesterol's inhibitory effect on crystallin-induced membrane defects suggests a role in maintaining lens membrane homeostasis and preventing cataract formation.
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