title: Fibroblast growth factor-12 (FGF12) translocation into intestinal epithelial cells is dependent on a novel cell-penetrating peptide domain: involvement of internalization in the in vivo role of exogenous FGF12.
abstract: The extracellular effect of fibroblast growth factor-12 (FGF12) remains unknown because FGF12 cannot activate any fibroblast growth factor receptors (FGFRs), and FGF12 is not currently thought to be released from cells. We reported previously that FGF12 plays an intracellular role in the inhibition of radiation-induced apoptosis. In this study, we demonstrated that recombinant FGF12 was able to be internalized into the cytoplasm of a rat intestinal epithelial cell line, IEC6, and this process was dependent on two novel cell-penetrating peptide (CPP) domains (CPP-M and CPP-C). In particular, CPP-C, composed of ∼10 amino acids, was identified as a specific domain of FGF12 and its subfamily in the C-terminal region (residues 140-149), although CPP-M was a common domain in the internal region of the FGF family. The absence of CPP-C from FGF12 or a mutation (E142L) in the CPP-C domain drastically reduced the internalization of FGF12 into cells. Therefore, CPP-C played an essential role in the internalization of FGF12. In addition, CPP-C was able to deliver other polypeptides into cells as a CPP because an FGF1/CPP-C chimeric protein was internalized into IEC6 cells more efficiently than wild-type FGF1. Finally, intraperitoneally added FGF12 inhibited radiation-induced apoptosis in the intestinal epithelial cells of BALB/c mice, and deletion of the CPP-C domain decreased the inhibition of the apoptosis. These findings suggest that exogenous FGF12 can play a role in tissues by translocating into cells through the plasma membrane, and the availability of this novel CPP provides a new tool for the intracellular delivery of bioactive molecules.
authors.affiliation: Department of Radiation Emergency Medicine, National Institute of Radiological Sciences, Inage-ku, Chiba 263-8555, Japan. f_naka@nirs.go.jp
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Nakayama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yasuda
authors.forename: Sachiko
authors.initials: S
authors.lastname: Umeda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Asada
authors.forename: Toru
authors.initials: T
authors.lastname: Imamura
authors.forename: Viktor
authors.initials: V
authors.lastname: Meineke
authors.forename: Makoto
authors.initials: M
authors.lastname: Akashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D057846:Cell-Penetrating Peptides / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats
chemical_list: D057846:Cell-Penetrating Peptides; C486356:FGF12 protein, human; D005346:Fibroblast Growth Factors