Synthesis by chemoselective ligation and biological evaluation of novel cell-permeable PKC-zeta pseudosubstrate lipopeptides

The ability of lipopeptides to passively cross the cell membrane opens new opportunities for the intracellular delivery of bioactive peptides. However , the production of large series of cell permeable lipopeptides is not triv ial due to their generally low solubility. We have evaluated the possibilit y of associating the fatty acid to the functional cargo using generally app licable ligation chemistries. To this end, we have designed an amphiphilic shuttle in which arginine residues served to solubilize the lipid part in a queous media, during both the assembly of the lipopeptide and the cellular assays. Our model peptide, the pseudosubstrate sequence of protein kinase C -zeta (PKC-zeta), was associated to the pentapeptide Gly-Arg-Gly-Arg-Lys(Pa m)-NH2 through thiazolidine, thioether, disulfide, or hydrazone linkages. T he cytoplasm import of the resulting constructs was monitored through the q uantification of the apoptosis specifically induced by PKC-zeta inhibition. Our observations suggested the interest of this noninvasive cellular impor t method to modulate the activity of an intracytoplasmic pharmacological ta rget and showed the influence of a non-amide link created between the funct ional peptide and the lipidic vector: optimal results, in terms of both spe cific activity and low basal cytotoxicity, were obtained with the thiazolid ine ligation product.