Gangliosides as components of lipid membrane domains

Cell membrane components are organized as specialized domains involved in membrane-associated events such as cell signaling, cell adhesion and protein sorting. These membrane domains are enriched in sphingolipids and cholesterol, but display a low protein content. Theoretical considerations and experimental data suggest that some properties of gangliosides play an important role in the formation and stabilization of specific cell lipid membrane domains. Gangliosides are glycolipids with strong amphiphilic character and are particularly abundant in the plasma membranes, where they are inserted into the external leaflet with the hydrophobic ceramide moiety and with the oligosaccharide chain protruding into the extracellular medium. The geometry of the monomer inserted into the membrane, largely determined by the very large surface area occupied by the oligosaccharide chain, the ability of the ceramide amide linkage to form a network of hydrogen bonds at the water-lipid interface of cell membranes, the Delta(4) double bond of sphingosine proximal to the water-lipid interface, the capability of the oligosaccharide chain to interact with water, and the absence of double bonds into the double-tailed hydrophobic moiety, are the ganglioside features that will be discussed in this review, to show how gangliosides are responsible for the formation of cell lipid membrane domains characterized by strong positive curvature.