title: Human-derived fusogenic peptides for the intracellular delivery of proteins.
abstract: The cytosolic delivery of therapeutic proteins (e.g., antibodies or enzymes) by cell-penetrating peptides (CPPs), such as a human immunodeficiency virus-derived TAT peptide, is facilitated by fusogenic peptides (FPs). For instance, we recently demonstrated that an FP, B18, which is derived from a sea urchin gamete fusion protein, promotes endosomal escape of an enhanced green fluorescent protein (eGFP)-TAT fusion protein directly conjugated to it. However, the potential clinical use of FPs raises concerns because all conventional FPs are non-human-derived. To solve this problem, we have attempted to identify novel human-derived FPs from two human proteins, including a human sperm protein, IZUMO1, which is involved in gamete recognition and fusion, and a human endogenous retroviral envelope protein, Syncytin1, which is involved in placental morphogenesis. Partial peptides from the core domains of the abovementioned proteins were chosen as candidates to generate human-derived FPs. We prepared fusion proteins of these peptides with eGFP and TAT in Escherichia coli and observed the localization of these fusion proteins in HeLa cells using confocal microscopy. Our results suggested that a 19-residues peptide of Syncytin1 (positions 322-340), named S19, possessed strong intracellular uptake activities with no detectable cytotoxicity. In addition, we estimated the number of molecules that escaped from endosomes using a nuclear localization signal, suggesting that the S19 peptide stimulated the intracellular delivery of TAT-fused eGFP by ~90-fold. Furthermore, we confirmed that S19 promoted the intracellular delivery of eGFP to various human cell lines, including HeLa, A431, HepG2, and SK-N-SH. In addition, we demonstrated that not only eGFP but also SNAP-tag and β-galactosidase were delivered efficiently and retained their activities.
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Sudo
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Niikura
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Kouta
authors.initials: K
authors.lastname: Iwaki
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Shunshi
authors.initials: S
authors.lastname: Kohyama
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Fujiwara
authors.affiliation: Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522, Japan. Electronic address: doi@bio.keio.ac.jp.
authors.forename: Nobuhide
authors.initials: N
authors.lastname: Doi
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D015686:Gene Products, env / Q000737:chemistry*; D015696:Gene Products, tat / Q000008:administration & dosage* / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000008:administration & dosage* / Q000235:genetics; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D010455:Peptides / Q000008:administration & dosage*; D011257:Pregnancy Proteins / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage / Q000737:chemistry
chemical_list: D015686:Gene Products, env; D015696:Gene Products, tat; C498176:IZUMO1 protein, human; D007136:Immunoglobulins; D008565:Membrane Proteins; D010455:Peptides; D011257:Pregnancy Proteins; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; C405335:syncytin; D049452:Green Fluorescent Proteins
keywords: Cell-penetrating peptides; Endocytosis; IZUMO1; Syncytin1