title: Cholesterol's interactions with serine phospholipids - a comparison of N-palmitoyl ceramide phosphoserine with dipalmitoyl phosphatidylserine.
abstract: In this study we have prepared ceramide phosphoserine (CerPS) and examined its sterol-interacting properties. CerPS is a hydrogen-bonding sphingolipid, but its head group differs from that found in sphingomyelin (SM). Based on diphenylhexatriene steady-state anisotropy measurements, we observed that fully hydrated N-palmitoyl CerPS had a gel-to-liquid crystalline phase transition temperature of about 51°C in 50mM sodium phosphate buffer (pH 7.4). This was close to the T(m) measured for 1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS) bilayers (T(m) 50.5°C). Based on cholestatrienol (CTL) quenching experiments in liquid disordered ternary bilayers (containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphcholine; POPC), cholesterol/CTL formed sterol-enriched ordered domains with CerPS. These had similar thermostability as the sterol domains formed with N-palmitoyl SM. Cholesterol failed to form sterol-enriched ordered domains with DPPS under comparable conditions. Based on the equilibrium partitioning of CTL, we observed that the affinity of sterol for bilayers containing POPC/CerPS/cholesterol (6:3:1 by mol) was much higher than the affinity measured for control fluid POPC/cholesterol (9:1 by mol) bilayers, but slightly less than seen for comparable PSM-containing bilayers. We conclude that the phosphoserine head group was less efficient than the phosphocholine head group in stabilizing sterol/sphingolipid interaction. However, hydrogen bonding apparently can overcome some of the negative effects of the phosphoserine head group, since CerPS interacted more favorably with cholesterol compared to DPPS.
authors.affiliation: Biochemistry, Department of Biosciences, Åbo Akademi University, 20520 Turku, Finland.
authors.forename: Christian
authors.initials: C
authors.lastname: Sergelius
authors.forename: Shou
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Oskar
authors.initials: O
authors.lastname: Engberg
authors.forename: Shigeo
authors.initials: S
authors.lastname: Katsumura
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D016880:Anisotropy; D001703:Biophysics / Q000379:methods; D002518:Ceramides / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry*; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D010768:Phosphoserine / Q000737:chemistry*; D012694:Serine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
chemical_list: D002518:Ceramides; D005231:Fatty Acids, Unsaturated; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D013109:Sphingomyelins; C033171:palmitoylsphingomyelin; D010768:Phosphoserine; D012694:Serine; D006859:Hydrogen; D002784:Cholesterol; C013641:parinaric acid; C028694:1-palmitoyl-2-oleoylphosphatidylcholine