Membrane potential-dependent binding of polysialic acid to lipid monolayers and bilayers

Abstract

Abbreviations used:  diff -potassium diffusion potential,  S -surface potential; DP -degree of polymerization; ODA -octadecylamine; polySia -polysialic acid; OX-Voxonol V, TB -toluidine blue Abstract: Polysialic acids are linear polysaccharides composed of sialic acid monomers. These polyanionic chains are usually membrane-bound, and are expressed on the surfaces of neural, tumor and neuroinvasive bacterial cells. We used toluidine blue spectroscopy, the Langmuir monolayer technique and fluorescence spectroscopy to study the effects of membrane surface potential and transmembrane potential on the binding of polysialic acids to lipid bilayers and monolayers. Polysialic acid free in solution was added to the bathing solution to assess the metachromatic shift in the absorption spectra of toluidine blue, the temperature dependence of the fluorescence anisotropy of DPH in liposomes, the limiting molecular area in lipid monolayers, and the fluorescence spectroscopy of oxonol V in liposomes. Our results show that both a positive surface potential and a positive transmembrane potential inside the vesicles can facilitate the binding of polysialic acid chains to model lipid membranes. These observations suggest that these membrane potentials can also affect the polysialic acid-mediated interaction between cells.

Exosome‐associated polysialic acid modulates membrane potentials, membrane thermotropic properties, and raft‐dependent interactions between vesicles

“…These results are consistent with a reduction of negatively charged polySia chains at the outer exosomal surface after the Endo‐N treatment. The estimated change in the transmembrane potential value, based on OX‐V calibration curve for liposomes [39], is ca. −30 mV after 115 min of Endo‐N treatment.…”

“…We showed that the removal of polySia chains from the exosomal surface by Endo‐N makes membrane surface potential more positive, transmembrane potential more negative, and the activation energy for membrane anisotropy changes reduced. The modulation of membrane potentials by polySia chains can affect both function of membrane proteins embedded in the exosomal membranes and the interaction of exosomes with plasma membranes [39]. Next, we studied the differences between the abundance of polysialylated exosomes in FBS (fetal bovine serum) and in CBS (calf bovine serum).…”

“…Exosomes in PBS buffer were incubated for 1 h at 37 °C with a surface potential‐sensitive fluorescence probe ANS (5 µ m , (λ ex /λ em = 370/430 nm) [38], or with a transmembrane potential‐sensitive probe OX‐V (2 µ m , (λ ex /λ em = 610/639 nm) [39]. Exosome membrane fluorescence was measured using Cary Eclipse spectrofluorometer with cuvette holder maintained at 37 °C.…”

In vitro effects of prolonged exposure to quercetin and epigallocatechin gallate of the peripheral blood mononuclear cell membrane

“…Spector and Yorek believed that the best approach in the study of such alteration is to make functional observations with cultured cells and then explore the mechanism producing these effects with either a reconstituted system or isolated membranes modified by incubation with liposomes [60]. However, this approach needs not only a detailed analysis of the linkages between theoretical and experimental studies, but also different methods to evaluate cell membrane properties [61][62][63]. Ageing can also influence the cell membrane composition.…”

Interactions of bioactive molecules & nanomaterials with Langmuir monolayers as cell membrane models

“…Nowotarski et al [113] showed that the electrical profile of the membrane is also relevant More complex materials such as polysaccharide-protein complexes extracted from fungi or algae were made to interact with charged lipids to probe possible therapeutic actions [114,115]. Schmidt et al [114] showed that the very slightly surface active protein- Langmuir monolayers of cholesterol/DPPC = 0.9 [117] or as more complicated ternary and quaternary mixtures [118] with different compositions of its inner and outer leaflets.…”