Equilibrium-fluctuation-analysis of single liposome binding events reveals how cholesterol and Ca2+ modulate
Angelika Kunze1, Marta Bally, Fredrik Höök
1Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
Abstract:
Carbohydrate-carbohydrate interactions (CCIs) are of central importance for several biological processes. However, the ultra-weak nature of CCIs generates difficulties in studying this interaction, thus only little is known about CCIs. Here we present a highly sensitive equilibrium-fluctuation-analysis of single liposome binding events to supported lipid bilayers (SLBs) based on total internal reflection fluorescence (TIRF) microscopy that allows us to determine apparent kinetic rate constants of CCIs. The liposomes and SLBs both contained natural Le(x) glycosphingolipids (Galβ4(Fucα3)GlcNAcβ3Galβ4Glcβ1Cer), which were employed to mimic cell-cell contacts. The kinetic parameters of the self-interaction between Le(x)-containing liposomes and SLBs were measured and found to be modulated by bivalent cations. Even more interestingly, upon addition of cholesterol, the strength of the CCIs increases, suggesting that this interaction is strongly influenced by a cholesterol-dependent presentation and/or spatial organization of glycosphingolipids in cell membranes.
Related Concept Videos
Asymmetric Lipid Bilayer
Membrane Asymmetry Regulating Transporters
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...
Membrane Fluidity
Membrane Fluidity
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is a relatively...
Fluid Mosaic Model


