Claudin-1 contributes to the epithelial barrier function in MDCK cells.
Tight junctions (TJs) create a paracellular permeability barrier and also act as a fence preventing intermixing of proteins and lipids between the apical and basolateral plasma membranes. Recently, claudin-1 has been identified as an integral membrane protein localizing at TJs, and introduced claudin-1 can form TJ-like networks in fibroblasts. To investigate the function of claudin-1, MDCK cells were transfected with a mammalian expression vector containing myc-tagged mouse claudin-1, and four stable clones were obtained. The myc-tagged claudin-1 precisely colocalized with both occludin and ZO-1 at cell-cell contact sites, indicating that exogenous claudin-1 was properly targeted to the TJs. Immunoblot analysis revealed that overexpression of claudin-1 increased expression of ZO-1 but not of occludin or ZO-2. The barrier functions of these cells were evaluated by transepithelial electrical resistance (TER) and paracellular flux. Claudin-1-expressing cells exhibited about four times higher TER than wild-type MDCK cells. Consistent with the increase of TER, the cells overexpressing claudin-1 showed reduced paracellular flux, estimated at 4 and 40 kD FITC-dextrans. These results suggest that claudin-1 is involved in the barrier function at TJs.
Inai
T
T
Department of Developmental Molecular Anatomy, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan. inai@ana2.med.kyushu-u.ac.jp
Kobayashi
J
J
Shibata
Y
Y
D000818:Animals; D001692:Biological Transport; D002450:Cell Communication / Q000502:physiology; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000502:physiology; D062445:Claudin-1; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D019108:Tight Junctions / Q000502:physiology
D062445:Claudin-1; C568113:Cldn1 protein, mouse; D008565:Membrane Proteins