Influence of Ganglioside GM1 Concentration on Lipid Clustering and Membrane Properties and Curvature

Abstract

Gangliosides are a class of glycosphingolipids (GSLs) withamphiphilic character that are found at the outer leaflet of the cell membranes, where their ability to organize into special domainsmakes themvital cell membrane components. However, a molecular understanding of GSL-rich membranes in terms of their clustered organization, stability, and dynamics is still elusive. To gain molecular insight into the organization and dynamics of GSL-rich membranes, we performed all-atom molecular-dynamics simulations of bicomponent ganglioside GM1 in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers with varying concentrations ofGM1 (10%, 20%, and 30%).Overall, the simulations showvery good agreement with available experimental data, including x-ray electron density profiles along themembrane normal,NMRcarbohydrate proton-proton distances, and x-ray crystal structures. This validates the quality of our model systems for investigating GM1 clustering through an ordered-lipidcluster analysis. The increase inGM1 concentration induces tighter lipid packing, drivenmainly by inter-GM1 carbohydrate-carbohydrate interactions, leading to a greater preference for the positive curvature of GM1-containing membranes and larger cluster sizes of ordered-lipid clusters (with a composite of GM1 and POPC). These clusters tend to segregate and forma large percolated cluster at a 30% GM1 concentration at 293 K. At a higher temperature of 330 K, however, the segregation is not maintained.