title: Cdc42 GEF Tuba regulates the junctional configuration of simple epithelial cells.
abstract: Epithelial cells are typically arranged in a honeycomb-like pattern, minimizing their cell-cell contact areas, which suggests that some tension operates for shaping of the cell boundaries. However, the molecular mechanisms that generate such tension remain unknown. We found that Tuba, which is a Cdc42-specific GEF, was concentrated at the apical-most region of cell junctions in simple epithelia via its interaction with ZO-1. RNAi-mediated depletion of Tuba altered the geometrical configuration of cell junctions, resulting in a curved and slack appearance. At the subcellular level, Tuba inactivation modified the assembly pattern of junctional F-actin and E-cadherin. Tuba RNAi also retarded cell junction formation in calcium-switch experiments. Suppression of Cdc42 activity or depletion of N-WASP, which is an effector of Cdc42, mimicked the effects of Tuba depletion. Conversely, overexpression of dominant-active Cdc42 or N-WASP enhanced the junction formation of Tuba-depleted cells. These results suggest that Tuba controls the shaping of cell junctions through the local activation of Cdc42 and its effectors.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Yoshida-Honmachi, Kyoto 606-8501, Japan.
authors.forename: Tetsuhisa
authors.initials: T
authors.lastname: Otani
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ichii
authors.forename: Shinya
authors.initials: S
authors.lastname: Aono
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Takeichi
mesh_terms: D000199:Actins / Q000378:metabolism; D018938:Caco-2 Cells; D015820:Cadherins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure*; D020662:Guanine Nucleotide Exchange Factors / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D020764:cdc42 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: D000199:Actins; D015820:Cadherins; D003598:Cytoskeletal Proteins; C482331:DNMBP protein, human; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; C495771:WASL protein, human; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D062826:Zonula Occludens-1 Protein; D020764:cdc42 GTP-Binding Protein