Coexistence of a Two-states Organization for a Cell Penetrating Peptide in Lipid Bilayer
Thomas Plenat 1, Sylvie Boichot 1, Patrice Dosset 2, Pierre Emmanuel Milhiet 2 and Christian Le Grimellec 1*
1 INSERM U554
2 CNRS UMR 5048
* To whom correspondence should be addressed. E-mail: clg{at}cbs.cnrs.fr.
Submitted on February 23, 2005
Revised on March 28, 2005
Accepted on 18 July 2005
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Abstract |
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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(), a primary amphipathic cell penetrating peptide which remains -helical whatever the environment, with dipalmitoylphosphatidylcholine (DPPC) bilayers. Addition of P() 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 () only exerted very limited effects on the corresponding liposomes bilayer physical state, as estimated from differential scanning calorimetry and diphenylhexatriene fluorescence anisotropy experiments. The use of gel-fluid phase separated supported bilayers made of a dioleoylphosphatidylcholine/DPPC 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(). The simultaneous two-states organization of P(), at the membrane surface and deeply embedded in the bilayer, may be involved in the transmembrane carrier function of this primary amphiphatic peptide.
Key Words:
AFM, DOPC, DPH anisotropy, DPPC, DSC, supported bilayers
