A novel system enhancing the endosomal escapes of peptides promotes Bak BH3 peptide inducing apoptosis in lung cancer A549 cells

Abstract

Therapeutic peptides have been proven useful for treating various diseases. However, it is difficult for therapeutic peptides to reach their target sites with an effective concentration due to inefficient intracellular delivery. Although Tat transduction peptide is a promising tool to deliver therapeutic peptides into cells, the entrapment within endosomes and the nuclear localization of Tat transduction peptide severely limited the biological effects of Tat-linked cargos. In this study, we designed a novel peptide delivering system, Tat-INF7-ubiquitin (TIU), which consisted of Tat transduction peptide, endosomal escape enhancer peptide INF7, and ubiquitin protein. We found that the TIU system was able to efficiently deliver the mCherry fluorescent proteins and the apoptosis-inducing Bak BH3 peptide into the cytosol. The Bak BH3 peptide transported into the cells by the TIU system increased the apoptotic rate to 46.15 ± 4.86% (p < 0.001) in A549 cells, while Tat-BH3 could result in only 20.45 ± 2.89%. These results demonstrated that the TIU system could enhance the effects of therapeutic peptides by facilitating the transmembrane delivery of peptides into the cells and the escape of target proteins from the endosome efficiently.

Principles in the design of ligand-targeted cancer therapeutics and imaging agents

“…peptides 156,157 , pore-forming and caged fusogenic or cationic lipids 156,[158][159][160] , and photothermally activated complexes 161 have all been investigated for use in promoting drug egress from endosomes 162 . However, in each of these cases, notable heterogeneity and bulk have been added to the intended drug product, rendering the path to regulatory approval more difficult.…”

Novel pH Selective, Highly Lytic Peptides Based on a Chimeric Influenza Hemagglutinin Peptide/Cell Penetrating Peptide Motif

“…We theorized that the selectivity of the peptide and its pH responsiveness was governed directly by the pKa of the protonatable groups in the peptide, with the mixture of protonatable sidechains in peptide 6 providing the best overall profile. Peptide 6 (INF7-Tat) [24,25] was the most potent of these analogs at pH 5.5, while also maintaining the 3-fold pH selectivity of the lead peptide, and this peptide also demonstrated far superior physical properties and solubility behavior versus the others, and as such became our lead peptide for further optimization. We also prepared the chimeric fusion peptides of HA2 and INF7 with Penetratin (Table 1, 10 – 11 ), but surprisingly both were devoid of lytic activity, again confirming the uniqueness of the combination of Tat and the HA2—like peptides.…”

Ligand-Targeted Drug Delivery

“…Unfortunately, for biologic drugs such as enzymes, antibodies, siRNAs, or plasmids, the endosomal escape problem is much more difficult, because there is no reliable method for enhancing their passive permeability across membranes. Obviously, for these molecules, new methods to promote endosomal egress must be invented to ensure LTD potency. − Second, the hydrophobicity of the therapeutic warhead may sometimes require reversible modification to prevent LTD aggregation and precipitation. In the case of steroid hormone delivery, the payload’s water solubility has been creatively increased by esterifying phosphate to a free hydroxyl on the steroid with the hope that the phosphate would be removed by phosphatase action following uptake of the drug into an endosome. − Alternatively, the hydrophilicity of the spacer and linker can be enhanced to avoid LTD aggregation, micelle formation, or nonspecific adsorption to off-target cells .…”