ENHANCED EFFICIENCY OF A TARGETED FUSOGENIC PEPTIDE

Membrane targeting was investigated as a potential strategy to increas e the fusogenic activity of an isolated fusion peptide. This was achie ved by coupling the fusogenic carboxy-terminal part of the beta-amyloi d peptide (A beta, amino acids 29-40), involved in Alzheimer's disease , to a positively charged peptide (PIP2-binding peptide, PBP) interact ing specifically with a naturally occurring negatively charged phospho lipid, phosphatidylinositol 4,5-bisphosphate (PIP2). Peptide-induced v esicle fusion was spectroscopically evidenced by: (i) mixing of membra ne lipids, (ii) mixing of aqueous vesicular contents, and (iii) an irr eversible increase in vesicle size, at concentrations five to six time s lower than the AP(29-40) peptide. In contrast, at these concentratio ns the PBP-A beta(29-40) peptide did not display any significant activ ity on neutral vesicles, indicating that negatively charged phospholip ids included as targets in the membranes, are required to compensate f or the lower hydrophobicity of this peptide. When the alpha-helical st ructure of the chimeric peptide was induced by dissolving it in triflu oroethanol, an increase of the fusogenic potential of the peptide was observed, supporting the hypothesis that the alpha-helical conformatio n of the peptide is crucial to trigger the lipid-peptide interaction. The specificity of the interaction between PIP2 and the PBP moiety, wa s shown by the less efficient targeting of the chimeric peptide to mem branes charged with phosphatidylserine. These data thus demonstrate th at the specific properties of both the A beta(29-40) and the PBP pepti de are conserved in the chimeric peptide, and that a synergetic effect is reached through chemical linkage of these two fragments. (C) 1998 Elsevier Science B.V. All rights reserved.