title: H(+)/peptide transporter (PEPT2) is expressed in human epidermal keratinocytes and is involved in skin oligopeptide transport.
abstract: Peptide transporter 2 (PEPT2) is a member of the proton-coupled oligopeptide transporter family, which mediates the cellular uptake of oligopeptides and peptide-like drugs. Although PEPT2 is expressed in many tissues, its expression in epidermal keratinocytes remains unclear. We investigated PEPT2 expression profile and functional activity in keratinocytes. We confirmed PEPT2 mRNA expression in three keratinocyte lines (normal human epidermal keratinocytes (NHEKs), immortalized keratinocytes, and malignant keratinocytes) by reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. In contrast to PEPT1, PEPT2 expression in the three keratinocytes was similar or higher than that in HepG2 cells, used as PEPT2-positive cells. Immunolocalization analysis using human skin showed epidermal PEPT2 localization. We studied keratinocyte transport function by measuring the oligopeptide content using liquid chromatography/tandem mass spectrometry. Glycylsarcosine uptake in NHEKs was pH-dependent, suggesting that keratinocytes could absorb small peptides in the presence of an inward H(+) gradient. We also performed a skin-permeability test of several oligopeptides using skin substitute, suggesting that di- and tripeptides pass actively through the epidermis. In conclusion, PEPT2 is expressed in keratinocytes and involved in skin oligopeptide uptake.
authors.affiliation: DHC Corporation Laboratories, Division 2, 2-42 Hamada, Mihama-ku, Chiba 261-0025, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Kudo
authors.affiliation: DHC Corporation Laboratories, Division 2, 2-42 Hamada, Mihama-ku, Chiba 261-0025, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Katayoshi
authors.affiliation: DHC Corporation Laboratories, Division 2, 2-42 Hamada, Mihama-ku, Chiba 261-0025, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Kobayashi-Nakamura
authors.affiliation: Department of Biological Chemistry, Division of Applied Life Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Japan.
authors.forename: Mitsugu
authors.initials: M
authors.lastname: Akagawa
authors.affiliation: DHC Corporation Laboratories, Division 2, 2-42 Hamada, Mihama-ku, Chiba 261-0025, Japan. Electronic address: knaito@dhc.co.jp.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Tsuji-Naito
mesh_terms: D000328:Adult; D001692:Biological Transport; D002478:Cells, Cultured; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009842:Oligopeptides / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D027981:Symporters / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D012333:RNA, Messenger; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2
keywords: Collagen-derived peptide; Glycylsarcosine (GlySar); Keratinocytes; Oligopeptide transporter (PEPT1 and PEPT2); Skin; Solute carrier 15 (SLC15)