Topology of octaarginines (R8) or IRQ ligand on liposomes affects the contribution of macropinocytosis- and caveolae-mediated cellular uptake

Abstract

It was recently reported that liposomes modified with octaarginine (R8) and its analogue peptide (IRQRRRR: IRQ) are taken into NIH3T3 cells by unique pathways, macropinocytosis and caveolae-mediated endocytosis, respectively. This study evaluated the topology of these peptides as it relates to the uptake routes of liposomes, where they are modified either directly on the surface, or on the edge of a polyethylene glycol (PEG) spacer. The uptake mechanism of peptide-modified liposomes and peptide-modified PEG-liposomes was investigated by confocal laser scanning microscopy. To determine the contribution of clathrin-mediated endocytosis, macropinocytosis and caveolar endocytosis to the uptake of liposomes, the uptake was evaluated in the presence of these specific inhibitors. The uptake pathway changed from macropinocytosis to clathrin-mediated endocytosis when R8 was modified on the edge of a PEG spacer, indicating that the flexible display of R8 impaired the induction of macropinocytosis. However, the contribution of caveolae-mediated endocytosis increased when IRQ was conjugated to the distal end of the PEG chain, suggesting that flexible surface display enhanced IRQ recognition by the specific molecules in the caveolae. The present results demonstrate that topology control of the ligand affects the contribution of the entry pathway, depending on the uptake mechanism.

Dual-ligand modification of PEGylated liposomes shows better cell selectivity and efficient gene delivery

“…A recent study reported that the cellular uptake pathway of R8 modified LP also depends on the position of R8 i.e. whether it is on the surface of the lipid membrane of LP or on the top of the PEG [43]. The RGD modified PEG-LP (RGD-PEG-LP) is taken up mainly by caveolae-mediated endocytosis, which is consistent with findings reported by other research groups [36,44].…”

In vivo study of doxorubicin-loaded cell-penetrating peptide-modified pH-sensitive liposomes: biocompatibility, bio-distribution, and pharmacodynamics in BALB/c nude mice bearing human breast tumors

“… 7 , 8 CPPs, 9 small molecular transporters with the capabilities of cell penetration, internalization, and endosomal escape, due to the presence of large number of positively charged arginine residues in acidic environment, have the potential to be useful in drug delivery system. 10 , 11 However, poor specificity for cells is one of the drawbacks of CPPs. 12 By utilizing the function of hydration shell of PEG and acid sensitivity of hydrazone bond, we synthesized a kind of CPPL 13 to improve the selectivity of these peptides for tumor targeting.…”