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Cholesterol regulates membrane binding and aggregation by annexin 2 at submicromolar Ca(2+) concentration
J Ayala-Sanmartin1, J P Henry, L A Pradel
1Unité de Biologie Cellulaire et Moléculaire de la Sécrétion, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France. ayala@ibpc.fr
Biochimica Et Biophysica Acta
|May 9, 2001
Summary
Cholesterol content in cell membranes influences annexin 2 binding. This protein
Area of Science:
- Cell Biology
- Membrane Biophysics
- Protein-Lipid Interactions
Background:
- Annexin 2, a calcium-regulated protein, is linked to exocytosis via phospholipid binding.
- Previous studies suggested calcium-dependent binding, but annexin 2 also binds to chromaffin granules without calcium.
Purpose of the Study:
- To investigate the role of membrane lipid composition, specifically cholesterol, in annexin 2 localization.
- To understand the Ca(2+)-independent binding of annexin 2 to membranes.
Main Methods:
- Utilized methyl-beta-cyclodextrin to deplete and restore cholesterol in chromaffin granule membranes.
- Tested annexin 2 binding to liposomes with varying lipid compositions (phosphatidylserine, cholesterol).
- Observed aggregation of liposomes by annexin 2 at low calcium concentrations.
Main Results:
- Cholesterol depletion by methyl-beta-cyclodextrin released bound annexin 2.
- Restoring cholesterol re-established Ca(2+)-independent annexin 2 binding.
- Annexin 2, particularly tetrameric form, binds to phosphatidylserine-containing liposomes, with binding enhanced by cholesterol.
- Tetrameric annexin 2 aggregated phosphatidylserine and cholesterol liposomes at low Ca(2+).
Conclusions:
- Membrane lipid composition, especially cholesterol, regulates annexin 2's subcellular location in resting cells.
- Annexin 2 may associate with membrane domains rich in phosphatidylserine and cholesterol.