Caveolae and Functional Domains of the Plasma Membrane.

Caveolae and rafts are two different domains of the plasma membrane. Caveolae are small invaginations and characterized by the presence of unique membrane proteins named caveolins. Caveolins bind cholesterol, form oligomers, interact with various signaling molecules, and induce caveolae formation. On the other hand, rafts are highly dynamic structure and do not take any characteristic shape; but both caveolae and rafts are enriched with sphingolipids and cholesterol and appear to contain many molecules in common. Some of the functions which have been ascribed to caveolae, such as signal transduction, may be mediated by both caveolae and rafts. Caveolins are thought to be involved in the intracellular cholesterol transport, and an increase or decrease of cholesterol content appears to affect caveolae and rafts. Mutation of caveolin genes or quantitational change of caveolae and caveolins has been reported to occur in several diseases. Further studies should elucidate the physiological roles as well as pathological changes of these functional domains in the plasma membrane.