title: Coexistence of a two-states organization for a cell-penetrating peptide in lipid bilayer.
abstract: Primary amphipathic cell-penetrating peptides transport cargoes across cell membranes with high efficiency and low lytic activity. These primary amphipathic peptides were previously shown to form aggregates or supramolecular structures in mixed lipid-peptide monolayers, but their behavior in lipid bilayers remains to be characterized. Using atomic force microscopy, we have examined the interactions of P(alpha), a primary amphipathic cell-penetrating peptide which remains alpha-helical whatever the environment, with dipalmitoylphosphatidylcholine (DPPC) bilayers. Addition of P(alpha) at concentrations up to 5 mol % markedly modified the supported bilayers topography. Long and thin filaments lying flat at the membrane surface coexisted with deeply embedded peptides which induced a local thinning of the bilayer. On the other hand, addition of P(alpha) only exerted very limited effects on the corresponding liposome's bilayer physical state, as estimated from differential scanning calorimetry and diphenylhexatriene fluorescence anisotropy experiments. The use of a gel-fluid phase separated supported bilayers made of a dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine mixture confirmed both the existence of long filaments, which at low peptide concentration were preferentially localized in the fluid phase domains and the membrane disorganizing effects of 5 mol % P(alpha). The simultaneous two-states organization of P(alpha), at the membrane surface and deeply embedded in the bilayer, may be involved in the transmembrane carrier function of this primary amphipathic peptide.
authors.affiliation: Nanostructures et Complexes Membranaires, Centre de Biochimie Structurale, INSERM UMR 554, CNRS UMR 5048-Université Montpellier I, 34090 Montpellier Cedex, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Plénat
authors.forename: Sylvie
authors.initials: S
authors.lastname: Boichot
authors.forename: Patrice
authors.initials: P
authors.lastname: Dosset
authors.forename: Pierre-Emmanuel
authors.initials: PE
authors.lastname: Milhiet
authors.forename: Christian
authors.initials: C
authors.lastname: Le Grimellec
mesh_terms: D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008560:Membrane Fluidity; D008968:Molecular Conformation; D010455:Peptides / Q000032:analysis / Q000737:chemistry*; D044367:Phase Transition; D010743:Phospholipids / Q000032:analysis / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010455:Peptides; D010743:Phospholipids