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Cellular localization and characterization of proteins that bind high density lipoprotein
B Hokland1, A J Mendez, J F Oram
1Department of Medicine, University of Washington, Seattle 98195.
Journal of Lipid Research
|September 1, 1992
Summary
Researchers identified key cell membrane proteins involved in high-density lipoprotein (HDL) binding. These HDL-binding proteins, particularly 110 and 130 kDa glycoproteins, are located on the cell surface, suggesting their role in cholesterol excretion.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Medicine
Background:
- High-density lipoprotein (HDL) facilitates reverse cholesterol transport by removing excess cholesterol from cells.
- A 110 kDa membrane protein has been proposed as a candidate HDL receptor.
- Understanding HDL-cell surface interactions is crucial for managing cholesterol homeostasis.
Purpose of the Study:
- To determine the cellular localization of HDL-binding proteins.
- To characterize the properties of these HDL-binding proteins.
- To identify potential HDL receptors on bovine aortic endothelial cells.
Main Methods:
- Ligand blot analysis to identify HDL-binding proteins.
- Cell fractionation using sucrose and Percoll gradients.
- Cross-linking studies and lectin affinity chromatography to assess protein exposure and glycosylation.
Main Results:
- Multiple HDL-binding proteins (105, 110, and 130 kDa) were identified in bovine aortic endothelial cells.
- These proteins co-fractionated with plasma membrane markers, indicating their plasma membrane localization.
- The 110 and 130 kDa proteins, identified as glycoproteins, were accessible to extracellular cross-linking, suggesting surface exposure.
Conclusions:
- The 110 and 130 kDa HDL-binding proteins are localized to the plasma membrane.
- These proteins, particularly the glycoproteins, are likely involved in the binding of HDL to the cell surface.
- This study provides evidence for specific HDL-binding proteins mediating cellular cholesterol efflux.