Dynamics and recognition of glycosphingolipids in membranes: insights from different scales

Glycosphingolipids are the most complex molecules among mammalian lipids. They consist of a ceramide backbone and a glycan head, so their description combines the challenges of lipids and carbohydrates. The carbohydrate moiety (with high conformational flexibility) serves as a receptor for carbohydrate-binding proteins, e.g., lectins, including molecules of pathogenic origin. Glycosphingolipids exhibit inhomogeneous lateral diffusion, which supports the formation of nanoscale functional complexes during signal transduction. These complexes enriched with glycosphingolipids can also contain GPI-anchored proteins, transmembrane proteins, and phospholipids from both membrane leaflets via acyl chain interdigitation, thereby transmitting the signal from outside the cell to the cell interior. The formation process of such molecular complexes extends over a wide spatial and temporal range and still remains largely unexplored due to the resolution limits of existing observation techniques. In this review, we bring together insights into the dynamics of glycosphingolipids in membranes and their interactions with carbohydrate-binding proteins from high/super-resolution fluorescence microscopy and molecular modelling-illustrated with examples such as the gangliosides GM1 and GM3, and the globoside globotriaosylceramide (also known as Gb3, CD77, and P^k antigen)-to exemplify how the gap in spatial and temporal resolution between experimental and computational approaches is steadily narrowing. The selected case studies present investigations using both cells and membrane model systems, such as giant unilamellar vesicles and supported lipid bilayers, together with in silico lipid bilayers with the aim of reducing the environmental complexity to determine the key molecular determinants involved in functional complex formation, membrane bending, endocytosis, and signalling.