Long and unsaturated sphingomyelin determines selective

S.MATÉ; V. HERLAX; C. WOLF; L.BAKÁS

Bilbao

Congreso; 51 st International Conference on Bioscience of Lipids; 2010

Much of the evidence reported in cell or model systems suggest that cholesterol distribution in the cell embrane is heterogeneous and that it is concentrated in cholesterol and sphingomyelin-rich membrane domains called membrane rafts. Cholesterol depletion by cyclodextrins is a very used tool in rafts research and most of the literature assumed that if a cellular process is affected by cholesterol depletion, membrane rafts are involved. However, there are in the bibliography discrepancies about the question if cyclodextrins selectively remove cholesterol from rafts domains and it has been reported that the presence of sphingomyelin drastically reduced cholesterol extraction. In this study, we have utilized [4-14C]cholesterol labeled sheep erythrocytes, which are characterized for a very high SM content. We assayed cholesterol extraction by cyclodextrin treatment and the detergent-resistant membrane technique.  We detected and quantified cholesterol in different membrane domains. The results show that sheep erythrocytes membrane properties, determined by a very particular sphingomyelin content and chain composition, could explain a selective cholesterol extraction by cyclodextrin from domains of the membrane where this lipid is more concentrated.