Oligosaccharide Presentation Modulates the Molecular Recognition of Glycolipids by Galectins on Membrane Surfaces

Abstract

Galectins are a family of glycan binding proteins that stand out for the wide range of biological phenomena in which they are involved. Most galectin functions are associated with their glycan binding capacities, which are generally well characterized at the oligosaccharide level, but not at the glycoprotein or glycolipid level. Glycolipids form the part of cell membranes where they can act as galectin cellular receptors. In this scenario, glycan presentation as well as the membrane chemical and structural features are expected to have a strong impact in these molecular association processes. Herein, liposomes were used as membrane mimicking scaffolds for the presentation of glycosphingolipids (GSLs) and to investigate their interaction with Galectin-3 and the N-domain of Galectin-8 (Gal8N). The binding towards GM3 and GM1 and their non-silaylated GSLs was compared to the binding to the free glycans, devoid of lipid. The analysis was carried out using a combination of NMR methods, membrane perturbation studies, and molecular modeling. Our results showed a different tendency of the two galectins in their binding capacities towards the glycans, depending on whether they were free oligosaccharides or as part of GSL inserted into a lipid bilayer, highlighting the significance of GSL glycan presentation on membranes in lectin binding.

Spatial N-glycan rearrangement on α5β1integrin nucleates galectin-3 oligomers to determine endocytic fate

“…Second, simultaneous interaction with several spatially separated galactoses on protein N-glycans and/or GSLs is favored. Such relative orientation of glycan binding pockets towards the membrane surface has also been predicted by molecular dynamics simulations (Lete et al, 2022). In contrast, a tetramer model obtained by x- ray crystallography with N-terminally truncated versions of Gal3 assembled under non-natural conditions appears too compact to fit the EM density (Figure S4J), and orients the glycan binding pockets inwards, which is incompatible with simultaneous interaction with cargo and GSL glycans (Flores-Ibarra et al, 2018).…”

Enzymatic Glyco-Modification of Synthetic Membrane Systems

“…Another report, based on NMR and molecular modeling, supports our findings, highlighting the role of the presentation of the glycan in establishing the essential binding contacts. In liposomes, the Gal residue in LacCer was not permanently exposed to allow the interaction with galectins to take place efficiently [45]. Thus, LgtC binding to the membrane would be regulated by selecting the appropriate conformation of LacCer and the lipids surrounding LacCer.…”

Production and Characterization of a Bioemulsifier Derived from Microorganisms with Potential Application in the Food Industry

“…The glycolipids should be dissolved in deuterated chloroform before performing a series of 1D (1H and 13C) and 2D (such as HMQC, ROSY, COSY, and HMBC) NMR investigations. The NMR approach was used to conduct detailed investigations of glycolipid, which was recently published in the literature [76,77].…”