title: N-palmitoyl-sulfatide participates in lateral domain formation in complex lipid bilayers.
abstract: Sulfatides (galactosylceramidesulfates) are negatively charged glycosphingolipids that are important constituents of brain myelin membranes. These membranes are also highly enriched in galactosylceramide and cholesterol. It has been implicated that sulfatides, together with other sphingolipids, take part in lateral domain formation in biological membranes. This study was conducted to characterize the lateral phase behavior of N-palmitoyl-sulfatide in mixed bilayer membranes. Going from simple lipid mixtures with sulfatide as the only sphingolipid in a fluid matrix of POPC, to more complex membranes including other sphingolipids, we have examined 1) ordered domain formation with sulfatide, 2) sterol enrichment in such domains and 3) stabilization of the domains against temperature by the addition of calcium. Using two distinct phase selective fluorescent probes, trans-parinaric acid and cholestatrienol, together with a quencher in the fluid phase, we were able to distinguish between ordered domains in general and ordered domains enriched in sterol. We found that N-palmitoyl-sulfatide formed ordered domains when present as the only sphingolipid in a fluid phospholipid bilayer, but these domains did not contain sterol and their stability was unaffected by calcium. However, at low, physiologically relevant concentrations, sulfatide partitioned favorably into domains enriched in other sphingolipids and cholesterol. These domains were stabilized against temperature in the presence of divalent cations. We conclude that sulfatides are likely to affect the lateral organization of biomembranes.
authors.affiliation: Department of Biochemistry and Pharmacy, Abo Akademi University, 20520 Turku, Finland.
authors.forename: Y J E
authors.initials: YJ
authors.lastname: Björkqvist
authors.forename: S
authors.initials: S
authors.lastname: Nybond
authors.forename: T K M
authors.initials: TK
authors.lastname: Nyholm
authors.forename: J P
authors.initials: JP
authors.lastname: Slotte
authors.forename: B
authors.initials: B
authors.lastname: Ramstedt
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002645:Chickens; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D005699:Galactosylceramides / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry; D013261:Sterols / Q000737:chemistry; D013433:Sulfoglycosphingolipids / Q000737:chemistry*; D013696:Temperature
chemical_list: D005231:Fatty Acids, Unsaturated; D005699:Galactosylceramides; D008051:Lipid Bilayers; C529351:N-palmitoylsulfatide; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D013261:Sterols; D013433:Sulfoglycosphingolipids; C033171:palmitoylsphingomyelin; C013641:parinaric acid; D002118:Calcium; C028694:1-palmitoyl-2-oleoylphosphatidylcholine