Hydrophobic Transmembrane-Peptide Lipid Conjugations Enhance Membrane Binding and Functional Activity in T-Cells

Abstract

Application of different delivery methods for therapeutic peptides has gained much attention in recent years. In this paper we conjugated a transmembrane hydrophobic peptide (core peptide; CP) derived from the T-cell antigen receptor alpha-chain sequence with either one (LP1), two (LP2), or three (LP3) palmitic acids through a Tris linkage. The effect of these lipopeptides (LPs) were compared to CP's activity both in vitro and in model membrane binding experiments using surface plasmon resonance. The influence of charged amino acids, arginine and lysine, within the CP sequence was examined by synthesizing analogues where arginine and lysine were replaced by the neutral amino acid alanine and these analogues were subsequently Tris-lipid conjugated with either one (XP1), two (XP2), or three (XP3) palmitic acids through a Tris linkage. The results indicated that the amount of irreversible binding for LPs were all greater than that of the underivatized CP in model membranes. None of the LPs could be dissociated from the liposome membranes, even after prolonged washing. Binding results for the neutral conjugates showed that only the XP1 bound to model membranes. This binding was 20% as efficient compared to LP1. In biological assays it was found that LP1 and XP1 were toxic to cells. LP3 inhibited IL-2 production more effectively than CP. Control lipopeptides (XP2, XP3) did not inhibit IL-2 production. These results demonstrate that the number of lipids conjugated to peptide, and the charged amino acids of CP, are both essential factors for peptide function and activity that can be enhanced by lipidation.