title: Stable transfection of MDCK cells with epitope-tagged human PepT1.
abstract: OBJECTIVE
  Establish and characterize a MDCK cell line that stably expressed PepT1.
  
  
  METHODS
  MDCK cells stably transfected with N-terminal HA-tagged hPepT1 were examined by immunostaining using antibodies to HA and hPepT1. HA-hPepT1 expression was verified by immunoprecipitation and Western blotting from cell lysates. The function of the expressed HA-hPepT1 was evaluated by glycyl-sarcosine uptake. The half-life of PepT1 on the cell surface was measured by biotinylation and chase-labeling of the cells, followed by immunoprecipitation with the anti-PepT1 antibody and blotting with HRP-streptavidin.
  
  
  RESULTS
  Immunolabeling with antibodies to HA and PepT1 showed fluorescence colocalization. Immunoprecipitation with the anti-HA antibody and Western blotting with the anti-PepT1 antibody showed a broad 90-105 kDa band, and vice versa when the antibodies were utilized in the reverse order. Glycyl-sarcosine uptake was increased in the stably transfected cells by 2-5 fold over untransfected control cells. The Km value of 375 microM accurately reflected the characteristic low affinity of PepT1. Finally, the half-life of the surface biotinylated HA-hPepT1 was measured to be 22 hrs.
  
  
  CONCLUSIONS
  A MDCK cell line stably expressed intact and functional HA-tagged hPepT1 on its cell surface. This cell line represents an alternative to the use of Caco-2 cells to evaluate PepT1 function.
authors.affiliation: Department of Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121, USA.
authors.forename: Chun
authors.initials: C
authors.lastname: Chu
authors.forename: Curtis T
authors.initials: CT
authors.lastname: Okamoto
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Hamm-Alvarez
authors.forename: Vincent H L
authors.initials: VH
authors.lastname: Lee
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004285:Dogs; D000939:Epitopes / Q000235:genetics*; D006207:Half-Life; D006389:Hemagglutinins, Viral / Q000235:genetics; D006801:Humans; D047468:Immunoprecipitation; D000074011:Peptide Transporter 1; D011956:Receptors, Cell Surface / Q000378:metabolism; D027981:Symporters / Q000235:genetics*; D014162:Transfection
chemical_list: D000939:Epitopes; D006389:Hemagglutinins, Viral; D000074011:Peptide Transporter 1; D011956:Receptors, Cell Surface; D027981:Symporters