title: Regulation of Sticholysin II-Induced Pore Formation by Lipid Bilayer Composition, Phase State, and Interfacial Properties.
abstract: Sticholysin II (StnII) is a pore-forming toxin that uses sphingomyelin (SM) as the recognition molecule in targeting membranes. After StnII monomers bind to SM, several toxin monomers act in concert to oligomerize into a functional pore. The regulation of StnII binding to SM, and the subsequent pore-formation process, is not fully understood. In this study, we examined how the biophysical properties of bilayers, originating from variations in the SM structure, from the presence of sterol species, or from the presence of increasingly polyunsaturated glycerophospholipids, affected StnII-induced pore formation. StnII-induced pore formation, as determined from calcein permeabilization, was fastest in the pure unsaturated SM bilayers. In 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/saturated SM bilayers (4:1 molar ratio), pore formation became slower as the chain length of the saturated SMs increased from 14 up to 24 carbons. In the POPC/palmitoyl-SM (16:0-SM) 4:1 bilayers, SM could not support pore formation by StnII if dimyristoyl-PC was included at 1:1 stoichiometry with 16:0-SM, suggesting that free clusters of SM were required for toxin binding and/or pore formation. Cholesterol and other sterols facilitated StnII-induced pore formation markedly, but the efficiency did not appear to correlate with the sterol structure. Benzyl alcohol was more efficient than sterols in enhancing the pore-formation process, suggesting that the effect on pore formation originated from alcohol-induced alteration of the hydrogen-bonding network in the SM-containing bilayers. Finally, we observed that pore formation by StnII was enhanced in the PC/16:0-SM 4:1 bilayers, in which the PC was increasingly unsaturated. We conclude that the physical state of bilayer lipids greatly affected pore formation by StnII. Phase boundaries were not required for pore formation, although SM in a gel state attenuated pore formation.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , 28040 Madrid, Spain.|Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland.
authors.forename: Juan
authors.initials: J
authors.lastname: Palacios-Ortega
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , 28040 Madrid, Spain.|Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland.
authors.forename: Mia
authors.initials: M
authors.lastname: Åstrand
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland.
authors.forename: Md Abdullah
authors.initials: MA
authors.lastname: Al Sazzad
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , 28040 Madrid, Spain.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , 28040 Madrid, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-del-Pozo
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D019905:Benzyl Alcohol / Q000737:chemistry; D003064:Cnidarian Venoms / Q000737:chemistry*; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D065546:Drug Liberation; D005452:Fluoresceins / Q000737:chemistry; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D010539:Permeability; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry; D016062:Porosity; D011721:Pyrenes / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry; D013261:Sterols / Q000737:chemistry; D013696:Temperature; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: C468114:1-palmitoyl-2-arachidonyl-3-phosphorylcholine; D003064:Cnidarian Venoms; D005452:Fluoresceins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D011721:Pyrenes; D013109:Sphingomyelins; D013261:Sterols; D053835:Unilamellar Liposomes; C033171:palmitoylsphingomyelin; C404794:sticholysin II; C033173:N-stearoylsphingomyelin; C055402:1-palmitoyl-2-linoleoylphosphatidylcholine; D019905:Benzyl Alcohol; D004134:Dimyristoylphosphatidylcholine; C007740:fluorexon