Sphingolipid organization in biomembranes: what physical studies of model membranes reveal

Recent cell biological studies suggest that sphingolipids and cholesterol may cluster in biomembranes to form raft-like microdomains. Such lipid domains are postulated to function as platforms involved in the lateral sorting of certain proteins during their trafficking within cells as well as during signal transduction events. Here, the physical interactions that occur between cholesterol and sphingolipids in model membrane systems are discussed within the context of microdomain formation. A model is presented in which the role of cholesterol is refined compared to earlier models.