Loosening of Lipid Packing by Cell‐Surface Recruitment of Amphiphilic Peptides by Coiled‐Coil Tethering

Structure-Uptake Relationship Study of DABCYL Derivatives Linked to Cyclic Cell-Penetrating Peptides for Live-Cell Delivery of Synthetic Proteins

Modifying cyclic cell-penetrating deca-arginine (cR10) peptides with 4-(4-dimethylaminophenylazo)benzoic acid (DABCYL) improves the uptake efficiency of synthetic ubiquitin (Ub) cargoes into living cells. To probe the role of the DABCYL moiety, we performed time-lapse microscopy and fluorescence lifetime imaging microscopy (FLIM) of fluorescent DABCYL-R10 to evaluate the impact on cell entry by the formation of nucleation zones. Furthermore, we performed a structure-uptake relationship study with 13 DABCYL derivatives coupled to CPP to examine their effect on the cell-uptake efficiency when conjugated to mono-Ub through disulfide linkages. Our results show that through structure variations of the DABCYL moiety alone we could reach, at nanomolar concentration, an additional threefold increase in the cytosolic delivery of Ub, which will enable studies on various intracellular processes related to Ub signaling.

Enhancing the activity of membrane remodeling epsin-peptide by trimerization

Modulating the structural dynamics of biomembranes by inducing bilayer curvature and lipid packing defects has been highlighted as a practical tool to modify membrane-dependent cellular processes. Previously, we have reported on an amphipathic helical peptide derived from the N-terminal segment (residues 1-18, EpN18) of epsin-1, which can promote membrane remodeling including lipid packing defects in cell membranes. However, a high concentration is required to exhibit a pronounced effect. In this study, we demonstrate a significant increase in the membrane-remodeling effect of EpN18 by constructing a branched EpN18 homotrimer. Both monomer and trimer could enhance cell internalization of octaarginine (R8), a cell-penetrating peptide. The EpN18 trimer, however, promoted the uptake of R8 at an 80-fold lower concentration than the monomer. Analysis of the generalized polarization of a polarity-sensitive dye (di-4-ANEPPDHQ) revealed a higher efficacy of trimeric EpN18 in loosening the lipid packing in the cell membrane. Circular dichroism measurements in the presence of lipid vesicles showed that the EpN18 trimer has a higher α-helix content compared with the monomer. The stronger ability of the EpN18 trimer to impede negative bilayer curvature is also corroborated by solid-state ³¹P NMR spectroscopy. Hence, trimerizing peptides can be considered a promising approach for an exponential enhancement of their membrane-remodeling performance.