title: Early endosomal escape of a cyclic cell-penetrating peptide allows effective cytosolic cargo delivery.
abstract: Cyclic heptapeptide cyclo(FΦRRRRQ) (cFΦR4, where Φ is l-2-naphthylalanine) was recently found to be efficiently internalized by mammalian cells. In this study, its mechanism of internalization was investigated by perturbing various endocytic events through the introduction of pharmacologic agents and genetic mutations. The results show that cFΦR4 binds directly to membrane phospholipids, is internalized into human cancer cells through endocytosis, and escapes from early endosomes into the cytoplasm. Its cargo capacity was examined with a wide variety of molecules, including small-molecule dyes, linear and cyclic peptides of various charged states, and proteins. Depending on the nature of the cargos, they may be delivered by endocyclic (insertion of cargo into the cFΦR4 ring), exocyclic (attachment of cargo to the Gln side chain), or bicyclic approaches (fusion of cFΦR4 and cyclic cargo rings). The overall delivery efficiency (i.e., delivery of cargo into the cytoplasm and nucleus) of cFΦR4 was 4-12-fold higher than those of nonaarginine, HIV Tat-derived peptide, or penetratin. The higher delivery efficiency, coupled with superior serum stability, minimal toxicity, and synthetic accessibility, renders cFΦR4 a useful transporter for intracellular cargo delivery and a suitable system for investigating the mechanism of endosomal escape.
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: Ziqing
authors.initials: Z
authors.lastname: Qian
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: LaRochelle
authors.forename: Bisheng
authors.initials: B
authors.lastname: Jiang
authors.forename: Wenlong
authors.initials: W
authors.lastname: Lian
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Hard
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Selner
authors.forename: Rinrada
authors.initials: R
authors.lastname: Luechapanichkul
authors.forename: Amy M
authors.initials: AM
authors.lastname: Barrios
authors.forename: Dehua
authors.initials: D
authors.lastname: Pei
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D057846:Cell-Penetrating Peptides / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D016503:Drug Delivery Systems / Q000379:methods; D011992:Endosomes / Q000378:metabolism*; D015696:Gene Products, tat / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D015696:Gene Products, tat; D009842:Oligopeptides; D010456:Peptides, Cyclic; C000591717:cyclo(phenylalanyl-2-naphthyalanyl-arginyl-arginyl-arginyl-arginyl-glutaminyl); C491427:nonaarginine; C414409:penetratin