Claudin-1 contributes to the epithelial barrier function in MDCK cells

• Published in: European journal of cell biology Vol. 78; no. 12; pp. 849 - 855
• Main Authors: Inai, Tetsuichiro, Kobayashi, Junichi, Shibata, Yosaburo
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.12.1999
• Subjects: Animals; Biological Transport; Cell Communication - physiology; Cell Line; Cell Membrane Permeability - physiology; Claudin-1; Dogs; epithelial barrier; Epithelial Cells - physiology; Epithelial Cells - ultrastructure; Membrane Proteins - physiology; Mice; occludin; tight junction; Tight Junctions - physiology; ZO-1; occludin; ZO-1; epithelial barrier; Claudin-1; tight junction
• ISSN: 0171-9335; 1618-1298
• DOI: 10.1016/S0171-9335(99)80086-7

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, MOCK 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 MOCK cells. Consistent with the increase of TER, the cells overexpressing claudin-1 showed reduced paracellular flux, estimated at 4 and 40 kO FITC-dextrans. The.se results suggest that claudin-1 is involved in the barrier function at TJs.