Agglutination and fusion of globoside GL-4 containing phospholipid vesicles mediated by lectins and calcium ion

Abstract

We have investigated the interaction of five N-acetylgalactosamine (GalNAc) specific lectins with the glycosphingolipid globoside GL-4, inserted into phospholipid vesicles composed of phosphatidyl-ethanolamine and phosphatidic acid, with respect to their ability to induce vesicle agglutination, fusion, and destabilization. The following lectins were used: soybean agglutinin (SBA); Sophora japonica agglutinin (SJA); Helix pomatia agglutinin (HPA); Ricinus communis agglutinin II (RCAII); and Codium fragile agglutinin (CFA). SBA and SJA caused rapid vesicle agglutination while HPA, CFA, and RCAII were ineffective. However, in the presence of RCAII, but not HPA and CFA, the addition of Ca2+ caused vesicle agglutination which was specifically inhibited by the haptenic sugar GalNAc, while ethylenediaminetetraacetic acid (EDTA) dissociated the vesicle complex. RCAII/Ca2+-induced vesicle agglutination was accomplished by binding of Ca2+ to RCAII after the lectin/receptor interaction. The rate of SBA-induced vesicle agglutination was increased in the presence of Ca2+, independent of the order of Ca2+ addition, and was not reversed by EDTA, indicating that the mechanism by which Ca2+ stimulated agglutination in this case was different from that observed in the presence of RCAII. In contrast to RCAII/Ca2+, SBA/Ca2+ induced of the vesicles, which occurred only when Ca2+ was added after lectin addition. Close approach of adjacent bilayers was accomplished by nonspecific interactions of SBA with the bilayer after lectin binding to the receptor as revealed by a limited extent of SBA-induced fusion and an enhanced membrane permeability upon lectin binding. The phenomena observed can be explained in terms of a Ca2+-modulated reorientation of the carbohydrate head group, causing it to adopt a more perpendicular orientation with respect to the plane of the bilayer.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane Fusion Induced by Small Molecules and Ions

“…Due to fusion, the inner contents of the vesicles get mixed together and the fluorescence of ANTS is quenched by DPX. The measurement of the decrease in fluorescence intensity gives the estimation of extent of content mixing [36, 38]. …”

Carbohydrate induced modulation of cell membrane VII. Binding of exogenous lectin increases osmofragility of erythrocytes

“…The non‐specific interactions of lipid domains with hydrophobic sites on legume lectins probably perturbs the membrane structure resulting in induction of leaks. Soybean agglutinin (SBA) mediated vesicle agglutination induces leakage of vesicle content followed by membrane fusion [19]. A massive disruption of the membrane permeability barrier is triggered when glycophorin incorporated in a bilayer consisting of unsaturated phosphatidyl ethanolamine (PE) is clustered upon addition of wheat germ agglutinin (WGA) which allows PEs to undergo the bilayer to non‐bilayer that is hexagonal H ″ phase transition [20].…”

Stimulation and inhibition of polymorphonuclear leukocytes phagocytosis by lipoamino acids isolated from Serratia marcescens

“…Phagocytic indices of ornithine lipid and serratamic acid were 205% and 143% of uncoated control bacteria respectively, while fusion indices of these compounds were not different from that of the control. This may be explained by the finding of Hoekstra et al, that the carbohydrate moiety of globoside (GL-4) liposomes anchored to the membrane by a hydrophobic group conferred inhibition of fusion in a model membrane system [25,26].…”