Interaction of cholesterol with sphingomyelins: kinetics of cholesterol extraction by ciclodextrin from natural and model membranes

A.DAZA-MILLONE; V. HERLAX; M. ELENA VELA; L. BAKÁS; S.MATÉ

Congreso; XLII Reunión Anual de SAB; 2014

Preferential interaction between sphingomyelin (SM) and cholesterol (Chol) in both cell and model membranes has been proposed as central for the formation of Chol and SM-rich domains in membranes. However, Chol does not interact equally with different SMs; in fact, we have recently found that when an unsaturated sphingolipid, N-nervonoyl sphingomyelin (24:1Δ15), that is abundant in mammalian erythrocytes is included in the bilayers, no lateral phase separation is detected (1). The desorption kinetics of Chol from membranes can be used as a sensitive indicator of Chol/phospholipid interactions. In this concern, it was reported that lateral organization and SM content of the membrane affects Chol extraction. The aim of this work was to explore the degree of interaction between Chol and different SMs in model (SUVs) and natural membranes (erythrocytes), by measuring Chol efflux using cyclodextrin. We employed a Surface Plasmon Resonance approach, which allows monitoring the extraction process in real time, to address the question of kinetics of Chol extraction from membranes of different lateral organization. Finally, we studied the effects of Chol-depletion on the packing properties of erythrocytemembranes by determining the GP values of Laurdan by two photon microscopy