A PHOTO-REACTIVE DERIVATIVE OF GANGLIOSIDE GM1 SPECIFICALLY CROSS-LINKS VIP21-CAVEOLIN ON THE CELL-SURFACE

Previous studies have shown that sphingolipids mag be enriched in cave olae, plasmalemmal invaginations implicated in endocytosis and signal transduction. We synthesised a radio-labeled derivative of ganglioside GM1 bearing a photo-reactive cross-linker at the end of its acyl chai n, After insertion in the plasma membrane of cultured A431 or MDCK cel ls and photoactivation, the main protein cross-linked by the GM1 deriv ative was VIP21-caveolin, an essential structural component of caveola e, This result shows close proximity between GM1 molecules and VIP21-c aveolin in the caveolar membrane and strongly implicates sphingolipid segregation in the biogenesis of caveolae.