title: Involvement of ASIP/PAR-3 in the promotion of epithelial tight junction formation.
abstract: The mammalian protein ASIP/PAR-3 interacts with atypical protein kinase C isotypes (aPKC) and shows overall sequence similarity to the invertebrate proteins C. elegans PAR-3 and Drosophila Bazooka, which are crucial for the establishment of polarity in various cells. The physical interaction between ASIP/PAR-3 and aPKC is also conserved in C. elegans PAR-3 and PKC-3 and in Drosophila Bazooka and DaPKC. In mammals, ASIP/PAR-3 colocalizes with aPKC and concentrates at the tight junctions of epithelial cells, but the biological meaning of ASIP/PAR-3 in tight junctions remains to be clarified. In the present study, we show that ASIP/PAR-3 staining distributes to the subapical domain of epithelial cell-cell junctions, including epithelial cells with less-developed tight junctions, in clear contrast with ZO-1, another tight-junction-associated protein, the staining of which is stronger in cells with well-developed tight junctions. Consistently, immunogold electron microscopy revealed that ASIP/PAR-3 concentrates at the apical edge of tight junctions, whereas ZO-1 distributes alongside tight junctions. To clarify the meaning of this characteristic localization of ASIP, we analyzed the effects of overexpressed ASIP/PAR-3 on tight junction formation in cultured epithelial MDCK cells. The induced overexpression of ASIP/PAR-3, but not its deletion mutant lacking the aPKC-binding sequence, promotes cell-cell contact-induced tight junction formation in MDCK cells when evaluated on the basis of transepithelial electrical resistance and occludin insolubilization. The significance of the aPKC-binding sequence in tight junction formation is also supported by the finding that the conserved PKC-phosphorylation site within this sequence, ASIP-Ser827, is phosphorylated at the most apical tip of cell-cell contacts during the initial phase of tight junction formation in MDCK cells. Together, our present data suggest that ASIP/PAR-3 regulates epithelial tight junction formation positively through interaction with aPKC.
authors.affiliation: Department of Molecular Biology, Yokohama City University School of Medicine, Kanazawa-ku, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Hirose
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Izumi
authors.forename: Yoji
authors.initials: Y
authors.lastname: Nagashima
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tamai-Nagai
authors.forename: Hidetake
authors.initials: H
authors.lastname: Kurihara
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Sakai
authors.forename: Yukari
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamanaka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Keiko
authors.initials: K
authors.lastname: Mizuno
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ohno
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002118:Calcium / Q000172:deficiency; D020013:Calcium Signaling / Q000502:physiology; D002352:Carrier Proteins; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules; D002451:Cell Compartmentation / Q000502:physiology; D018797:Cell Cycle Proteins; D016764:Cell Polarity / Q000502:physiology; D002478:Cells, Cultured; D017097:Electric Impedance; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D009154:Mutation / Q000502:physiology; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D018179:Receptors, Thrombin / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000235:genetics / Q000378:metabolism; D012995:Solubility / Q000187:drug effects; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure; D062826:Zonula Occludens-1 Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D015801:Helminth Proteins; D008565:Membrane Proteins; D062793:Occludin; C568986:Ocln protein, mouse; C568987:Ocln protein, rat; C115084:Pard3 protein, mouse; D010750:Phosphoproteins; D018179:Receptors, Thrombin; C569043:Tjp1 protein, mouse; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; C105295:protease-activated receptor 3; D012694:Serine; C115015:PKC-3 protein; D011493:Protein Kinase C; D002118:Calcium