Lipid rafts and insulin signaling.

Lipid rafts are domains within the plasma membrane that are enriched in cholesterol and lipids with saturated acyl chains. Specific proteins, including many signaling proteins, segregate into lipid rafts, and this process is important for certain signal transduction events in a variety of cell types. Within the past decade, data have emerged from many laboratories that implicate lipid rafts as critical for proper compartmentalization of insulin signaling in adipocytes. A subset of lipid rafts, caveolae, are coated with membrane proteins of the caveolin family. Direct interactions between resident raft proteins (caveolins and flotillin-1) and insulin-signaling molecules may organize these molecules in space and time to ensure faithful transduction of the insulin signal, at least with respect to the glucose-dependent actions of insulin in adipocytes. The in vivo relevance of this model remains to be determined.