Stomatin, flotillin-1, and flotillin-2 are major integral proteins of erythrocyte lipid rafts

Lipid rafts are sphingolipid- and cholesterol-rich membrane microdomains th at are insoluble in nonionic detergents, have a low buoyant density, and pr eferentially contain lipid-modified proteins, like glycosyl phosphatidylino sitol (GP1)-anchored proteins. The lipid rafts were isolated from human ery throcytes and major protein components were identified, Apart from the GPI- anchored proteins, the most abundant integral proteins were found to be the distantly related membrane proteins stomatin (band 7.2b), flotillin-1, and flotillin-2. Flotillins, already described as lipid raft components in neu rons and caveolae-associated proteins in A498 kidney cells, have not been r ecognized as red cell components yet. In addition, it was shown that the ma jor cytoskeletal proteins, spectrin, actin, band 4.1, and band 4.2, are par tly associated with the lipid rafts, Stomatin and the flotillins are presen t as independently organized high-order oligomers, suggesting that these co mplexes act as separate scaffolding components at the cytoplasmic face of e rythrocyte lipid rafts.