title: Truncation mutants of the tight junction protein ZO-1 disrupt corneal epithelial cell morphology.
abstract: The tight junction is the most apical intercellular junction of epithelial cells and regulates transepithelial permeability through the paracellular pathway. To examine possible functions for the tight junction-associated protein ZO-1, C-terminally truncated mutants and a deletion mutant of ZO-1 were epitope tagged and stably expressed in corneal epithelial cell lines. Only full-length ZO-1 and one N-terminal truncation mutant targeted to cell borders; other mutants showed variable cytoplasmic distributions. None of the mutants initially disrupted the localization of endogenous ZO-1. However, long-term stable expression of two of the N-terminal mutants resulted in a dramatic change in cell shape and patterns of gene expression. An elongated fibroblast-like shape replaced characteristic epithelial cobblestone morphology. In addition, vimentin and smooth muscle actin expression were up-regulated, although variable cytokeratin expression remained, suggesting a partial transformation to a mesenchymal cell type. Concomitant with the morphological change, the expression of the integral membrane tight junction protein occludin was significantly down-regulated. The localizations of endogenous ZO-1 and another family member, ZO-2, were disrupted. These findings suggest that ZO-1 may participate in regulation of cellular differentiation.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: S W
authors.initials: SW
authors.lastname: Ryeom
authors.forename: D
authors.initials: D
authors.lastname: Paul
authors.forename: D A
authors.initials: DA
authors.lastname: Goodenough
mesh_terms: D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D019573:Epithelium, Corneal / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D000939:Epitopes / Q000235:genetics; D006801:Humans; D007365:Intercellular Junctions; D008565:Membrane Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology; D008969:Molecular Sequence Data; D009154:Mutation; D062793:Occludin; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D011233:Precipitin Tests; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein
chemical_list: D000939:Epitopes; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010446:Peptide Fragments; D010750:Phosphoproteins; D011994:Recombinant Proteins; C569042:TJP1 protein, human; C569046:TJP2 protein, human; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein