Selective Glycan Presentation in Liquid-Ordered or -Disordered Membrane Phases and its Effect on Lectin Binding

Glycan-protein interactions play a key role in various biological processes from fertilization to infections. Many of these interactions take place at the glycocalyx-a heavily glycosylated layer at the cell surface. Despite its significance, studying the glycocalyx remains challenging due to its complex, dynamic, and heterogeneous nature. This study introduces a glycocalyx model allowing for the first time to control spatial organization and heterogeneity of the glycan moieties. Glycan-mimetics with lipid-moieties that partition into either liquid-ordered (Lo, lipid rafts) or liquid-disordered (Ld) phases of giant unilamellar vesicles (GUVs), which serve as simplified cell membrane models mimicking lipid rafts, are developed. This phase-specific allocation allows controlled placement of glycan motifs in distinct membrane environments, creating heteromultivalent systems that replicate the natural glycocalyx's complexity. We show that phase localization of glycan mimetics significantly influences recruitment of protein receptors to the membrane. Glycan-conjugates in the ordered phase demonstrate enhanced lectin binding, supporting the idea that raft-like domains facilitate stronger receptor interactions. This study provides a platform for systematically investigating spatial and dynamic presentation of glycans in biological systems and presents the first experimental evidence that glycan accumulation in lipid rafts enhances receptor binding affinity, offering deeper insights into the glycocalyx's functional mechanisms.

Cholesterol, sphingolipids, and glycolipids: what do we know about their role in raft-like membranes?

Lipids rafts are considered to be functional nanoscale membrane domains enriched in cholesterol and sphingolipids, characteristic in particular of the external leaflet of cell membranes. Lipids, together with membrane-associated proteins, are therefore considered to form nanoscale units with potential specific functions. Although the understanding of the structure of rafts in living cells is quite limited, the possible functions of rafts are widely discussed in the literature, highlighting their importance in cellular functions. In this review, we discuss the understanding of rafts that has emerged based on recent atomistic and coarse-grained molecular dynamics simulation studies on the key lipid raft components, which include cholesterol, sphingolipids, glycolipids, and the proteins interacting with these classes of lipids. The simulation results are compared to experiments when possible.