Homogeneous and Heterogeneous Bilayers of Ternary Lipid Compositions Containing Equimolar Ceramide and Cholesterol

• DOI: 10.1021/acs.langmuir.9b00324
• Publication Date: 2019-03-29T12:25:39Z
• Authors: Emilio J. Gonzále...; Ibai Artetxe; Aritz B. García-A...; Félix M. Goñi; Alicia Alonso
• Keywords: Diphenylhexatriene; Dipalmitoylphosphatidylcholine; Sphingolipid

Cell membranes have been proposed to be laterally inhomogeneous, particularly in the case of mammalian cells, due presence "domains" enriched sphingolipids and cholesterol (Chol). Among membrane sphingolipids, sphingomyelin (SM) cell plasma is known degraded ceramide (Cer) by acid sphingomyelinases under stress conditions. Since (Chol) abundant membrane, study ternary mixtures SM:Chol:Cer interesting from point view biophysics, it might physiologically relevant. In previous studies, we described homogeneous gel phase formed phospholipid:Chol:Cer at 54:23:23 mol ratios, where phospholipid was either SM or dipalmitoylphosphatidylcholine (DPPC). We now provide new data, based on trans-parinaric diphenylhexatriene fluorescence, supporting that includes all three components a single bilayer. The main question addressed this paper stability when bilayer composition changed, specifically proportion varied. To aim, prepared bilayers X:Y:Y which increased between 54 70 %. N-palmitoyl derivatives (pSM) Cer (pCer) used. observe for X = 60 %, clearly predominant. However, increases beyond i.e., 66:17:17 70:15:15 mixtures, lateral separation occurs micrometer scale. These data can interpreted terms pCer:Chol interaction, would predominate lower concentrations. putative complexes (or nanodomains) mix well with phospholipid. At higher concentrations pSM:pCer pSM:Chol interactions become more important, giving rise coexisting liquid-ordered phases respectively. Heterogeneity, separation, easily pSM than DPPC, indicating affinity over DPPC Chol Cer. observation heterogeneity, indicates Cer, related regulation through sphingolipid signaling pathway.