title: Functional Expression of PEPT2 in the Human Distal Lung Epithelial Cell Line NCl-H441.
abstract: OBJECTIVE
  The peptide transporter PEPT2 is expressed in alveolar type II epithelial cells. So far, however, no appropriate alveolar epithelial cell line for studying PEPT2 function has been known. In this study, we examined the functional expression of PEPT2 in the human distal lung epithelial cell line NCl-H441 (H441).
  
  
  METHODS
  Expression of PEPT2 mRNA and protein was examined in H441 cells. Transport function of PEPT2 was studied using glycylsarcosine (Gly-Sar) as a substrate.
  
  
  RESULTS
  Lamellar bodies were well developed in H441 cells and mRNA expression of type II cell markers and PEPT2 increased during time in culture. PEPT2 protein expression was confirmed in H441 cells, but not in A549 cells, by immunostaining and Western blotting. The uptake of Gly-Sar in H441 cells was inhibited by cefadroxil, and the cefadroxil-sensitive uptake was pH-dependent and peaked at pH 6.5. Gly-Sar uptake in H441 cells showed saturation kinetics with a Km value of 112.5 μM. In addition, apical-to-basal, but not basal-to-apical, transport of cephalexin across H441 cell monolayers was sensitive to cefadroxil.
  
  
  CONCLUSIONS
  PEPT2 is functionally expressed in H441 cells, making the cell line a good in vitro model to study PEPT2 function and its regulation in human distal lung.
authors.affiliation: Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8553, Japan. takanom@hiroshima-u.ac.jp.
authors.forename: Mikihisa
authors.initials: M
authors.lastname: Takano
authors.affiliation: Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8553, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Sugimoto
authors.affiliation: School of Pharmacy and Pharmaceutical Sciences and Trinity Biomedical Sciences Institute, Trinity College Dublin, Panoz Institute, Dublin 2, Ireland.
authors.forename: Carsten
authors.initials: C
authors.lastname: Ehrhardt
authors.affiliation: Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8553, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Yumoto
mesh_terms: D002460:Cell Line; D004151:Dipeptides / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008168:Lung / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D027981:Symporters / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004151:Dipeptides; D012333:RNA, Messenger; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; C004194:glycylsarcosine
keywords: Gly-Sar uptake; alveolar epithelial cells; proton-coupled oligopeptide transporter; pulmonary drug disposition; transcellular transport