Functional dissociation of paracellular permeability and transepithelial electrical resistance and disruption of the apical-basolateral intramembrane diffusion barrier by expression of a mutant tight junction membrane protein.

• DOI: 10.1083/jcb.134.4.1031
• Publication Date: 2004-05-15T01:23:47Z
• Authors: M S Balda; J A Whitney; C Flores; S González; M Cereijido; K Matter
• Keywords: Occludin; Paracellular transport; Claudin; Septate junctions; Immunoelectron microscopy; Transport protein; Epithelial polarity

Tight junctions, the most apical of intercellular junctions that connect individual cells in a epithelial sheet, are thought to form seal restricts paracellular and intramembrane diffusion. To analyze functioning tight we generated stable MDCK strain 2 cell lines expressing either full-length or COOH-terminally truncated chicken occludin, only known transmembrane component junctions. Confocal immunofluorescence immunoelectron microscopy demonstrated mutant occludin was incorporated into but, contrast exhibited discontinuous junctional staining pattern also disrupted continuous ring formed by endogenous occludin. This rearrangement not paralleled apparent changes morphology as seen thin section electron nor discontinuities strands observed freeze-fracture. Nevertheless, expression both wild-type induced increased transepithelial electrical resistance (TER). In TER, particularly led severalfold increase flux small molecular weight tracers. Since selectivity for size different types cations unchanged, appears have activated an existing mechanism allows selective presence electrically sealed Occludin is involved formation apical/basolateral diffusion barrier, since found render incapable maintaining fluorescent lipid specifically labeled surface domain.