title: Cholesterol stimulates and ceramide inhibits Sticholysin II-induced pore formation in complex bilayer membranes.
abstract: The pore forming capacity of Sticholysin II (StnII; isolated from Stichodactyla helianthus) in bilayer membranes containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), palmitoylsphingomyelin (PSM) and either cholesterol or palmitoyl ceramide (PCer) has been examined. The aim of the study was to elucidate how the presence of differently ordered PSM domains affected StnII oligomerization and pore formation. Cholesterol is known to enhance pore formation by StnII, and our results confirmed this and provide kinetic information for the process. The effect of cholesterol on bilayer permeabilization kinetics was concentration-dependent. In the concentration regime used (2.5-10nmol cholesterol in POPC:PSM 80:20 by nmol), cholesterol also increased the acyl chain order in the fluid PSM domain and thus decreased bilayer fluidity, suggesting that fluidity per se was not responsible for cholesterol's effect. Addition of PCer (2.5-10nmol) to the POPC:PSM (80:20 by nmol) bilayers attenuated StnII-induced pore formation, again in a concentration-dependent fashion. This addition also led to the formation of a PCer-rich gel phase. Addition of cholesterol to PCer-containing membranes could partially reduce the inhibitory effect of PCer on StnII pore formation. We conclude that the physical state of PSM (as influenced by either cholesterol or PCer) affected StnII binding and pore formation under the conditions examined.
authors.affiliation: Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors.forename: Ida
authors.initials: I
authors.lastname: Alm
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-Del-Pozo
authors.affiliation: Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland. Electronic address: jpslotte@abo.fi.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002518:Ceramides / Q000494:pharmacology*; D002784:Cholesterol / Q000494:pharmacology*; D003064:Cnidarian Venoms / Q000494:pharmacology*; D005452:Fluoresceins / Q000378:metabolism; D005454:Fluorescence Polarization; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008560:Membrane Fluidity / Q000187:drug effects*; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D012615:Sea Anemones; D020349:Surface Plasmon Resonance
chemical_list: D002518:Ceramides; D003064:Cnidarian Venoms; D005452:Fluoresceins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; C404794:sticholysin II; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; C007740:fluorexon
keywords: Membrane order; Membrane permeabilization; Sphingolipid; Surface plasmon resonance