title: Equilibrium-fluctuation-analysis of single liposome binding events reveals how cholesterol and Ca2+ modulate glycosphingolipid trans-interactions.
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.
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
authors.forename: Angelika
authors.initials: A
authors.lastname: Kunze
authors.forename: Marta
authors.initials: M
authors.lastname: Bally
authors.forename: Fredrik
authors.initials: F
authors.lastname: Höök
authors.forename: Göran
authors.initials: G
authors.lastname: Larson
mesh_terms: D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000737:chemistry; D006028:Glycosphingolipids / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D006028:Glycosphingolipids; D008051:Lipid Bilayers; D008081:Liposomes; D002784:Cholesterol; D002118:Calcium