title: The pore forming capacity of Sticholysin I in dipalmitoyl phosphatidyl vesicles is tuned by osmotic stress.
abstract: The osmotic condition modulates the properties of liposomes, particularly those related to their stability and response to external agents such as membrane-active proteins or peptides. In a previous work, we have demonstrated that an osmotic shock can increase, per se, water influx/efflux and the exit of the fluorophore calcein entrapped in the aqueous pool of dipalmitoylphosphatidylcholine (DPPC) and DPPC:sphingomyelin (SM) large unilamellar vesicles (LUVs), suggesting a loss of integrity of the liposome bilayer. In the present work, we have extended our study in order to assess how an osmotic imbalance prior to or synchronous with the addition of a recombinant variant of the pore-forming toxin sticholysin I (rSt I) modifies its pore forming capacity in DPPC and DPPC:SM (1:1) LUVs. Our results conclusively show the capacity of hypotonic gradients to improve the pore forming capacity of rSt I molecules, even in pure DPPC liposomes, rendering pore-formation less dependent on the presence of sphyngomyelin. In fact, non-active toxins in DPPC liposomes become active by a hypotonic imbalance in a similar way to those containing SM as a second component.
authors.affiliation: Department of Chemistry, Faculty of Chemistry and Biology, University of Santiago de Chile, USACH, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Ahumada
authors.affiliation: Center of Medical Chemistry, Faculty of Medicine, Clínica Alemana-Universidad del Desarrollo, Chile.
authors.forename: C
authors.initials: C
authors.lastname: Calderon
authors.affiliation: Department of Chemistry, Faculty of Chemistry and Biology, University of Santiago de Chile, USACH, Chile. Electronic address: Eduardo.Lissi@usach.cl.
authors.forename: E
authors.initials: E
authors.lastname: Lissi
authors.affiliation: Laboratory of Biomembranes, Faculty of Biology, University of La Habana, Cuba.
authors.forename: C
authors.initials: C
authors.lastname: Alvarez
authors.affiliation: Laboratory of Biomembranes, Faculty of Biology, University of La Habana, Cuba.
authors.forename: M E
authors.initials: ME
authors.lastname: Lanio
authors.affiliation: Laboratory of Biomembranes, Faculty of Biology, University of La Habana, Cuba.
authors.forename: F
authors.initials: F
authors.lastname: Pazos
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D009997:Osmotic Pressure; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D052899:Pore Forming Cytotoxic Proteins; C121348:stycholysin I; D015060:1,2-Dipalmitoylphosphatidylcholine
keywords: Liposomes; Osmotic shock; Permeability; Sticholysins