title: Visualization of Lipid Membrane Reorganization Induced by a Pore-Forming Toxin Using High-Speed Atomic Force Microscopy.
abstract: We examined the effect of a sphingomyelin (SM)-binding pore-forming toxin (PFT), lysenin, on the dynamics of a phase-separated membrane of SM, where SM formed liquid-ordered (Lo) domains with cholesterol (Chol) within a phosphatidylcholine-rich liquid-disordered (Ld) phase. We visualized the lysenin-induced membrane reorganization using high-speed atomic force microscope (HS-AFM). Lysenin oligomerized on the SM-rich Lo domain and simultaneously its oligomers assembled into a hexagonal close-packed (hcp) structure. The phase boundary was stable during the assembling of lysenin on the SM-rich domain, indicating that lysenin did not affect the line tension between Lo and Ld phases. After the full coverage of the SM-rich domain by oligomers, their hcp assembly gradually expanded into the Ld phase and eventually covered the entire membrane. Our results suggest that pore formation, i.e., insertion of lysenin into the membrane in its oligomeric state, induced the exclusion of SM and Chol from the SM-rich domain, which was followed by further binding and oligomerization of lysenin.
authors.affiliation: Lipid Biology Laboratory, RIKEN , Wako, Saitama 351-0198, Japan.
authors.forename: Neval
authors.initials: N
authors.lastname: Yilmaz
authors.affiliation: Lipid Biology Laboratory, RIKEN , Wako, Saitama 351-0198, Japan.|INSERM U106-Université Lyon1 , 69621 Villeurbanne, France.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D002784:Cholesterol / Q000737:chemistry; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010713:Phosphatidylcholines / Q000737:chemistry; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry*; D055503:Protein Multimerization; D013109:Sphingomyelins / Q000737:chemistry; D014118:Toxins, Biological / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D052899:Pore Forming Cytotoxic Proteins; D013109:Sphingomyelins; D014118:Toxins, Biological; C107040:lysenin; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine
keywords: high-speed atomic force microscopy; lysenin; oligomer; phase mixing; sphingomyelin