Role of Glycolipids in Lipid Rafts: A View through Atomistic Molecular Dynamics Simulations with Galactosylceramide

Even in small amounts, glycolipids are an integral part of lipid rafts and their cellular functions. Here we employ atomistic molecular dynamics simulations to consider galactosylceramide (GalCer), one of the common glycosphingolipids, and investigate its interactions with other raft components (cholesterol, POPC, sphingomyelin) as well as the role and the effects of GalCer on the physical properties of raft-like membranes. Our results for 5 mol % GalCer indicate that whereas the thickness of raft membranes is clearly increased by the addition of GalCer, the average area per lipid and lipid conformational order remain virtually unchanged. Notable changes are observed in lateral diffusion of the raft lipids. This is found to be associated with the interdigitation of GalCer. With cholesterol, GalCer is observed to interact specifically by shielding it from the water phase.