title: Localization of membrane-associated guanylate kinase (MAGI)-1/BAI-associated protein (BAP) 1 at tight junctions of epithelial cells.
abstract: Membrane-associated guanylate kinase (MAGI)-1/BAI-associated protein (BAP) 1 and Synapse-associated protein (SAP) 97/human Discs-large tumor suppressor gene (hDLG) are ubiquitous isoforms of synaptic scaffolding molecule (S-SCAM) and Postsynaptic density (PSD)-95/SAP90, both of which are implicated in the structures of synapses, respectively. SAP97/hDLG is localized at epithelial junctions and may function as a scaffolding protein, but the subcellular localization or the function of MAGI-1/BAP1 has not been clarified. In intestinal epithelial cells, MAGI-1/BAP1 was localized at tight junctions, whereas SAP97/hDLG was localized diffusely at cell - cell junctions. In Madine Darby canine kidney (MDCK) cells, MAGI-1/BAP1 was colocalized with ZO-1, whereas SAP97/hDLG was colocalized with E-cadherin. In MDCK cells, dominant active and negative mutants of Rac1 small G protein changed the amounts of SAP97/hDLG at cell - cell junctions, but not that of MAGI-1/BAP1. When MDCK cells were switched to a low Ca2+ medium, E-cadherin disappeared from the plasma membrane, and cells were dissociated. The phorbol 12-myristate 13-acetate-treatment after the low Ca2+ switch induced a tight junction-like structure. MAGI-1/BAP1 was recruited with ZO-1 to this structure, but SAP97/hDLG or E-cadherin was not. These findings suggest that MAGI-1/BAP1 is a component of tight junctions of epithelial cells, and that its role is different from that of SAP97/hDLG.
authors.affiliation: Takai Biotimer Project, ERATO, Japan Science and Technology Corporation, c/o JCR Pharmaceuticals Co. Ltd., Kobe 651-2241, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Ide
authors.forename: Y
authors.initials: Y
authors.lastname: Hata
authors.forename: H
authors.initials: H
authors.lastname: Nishioka
authors.forename: K
authors.initials: K
authors.lastname: Hirao
authors.forename: I
authors.initials: I
authors.lastname: Yao
authors.forename: M
authors.initials: M
authors.lastname: Deguchi
authors.forename: A
authors.initials: A
authors.lastname: Mizoguchi
authors.forename: H
authors.initials: H
authors.lastname: Nishimori
authors.forename: T
authors.initials: T
authors.lastname: Tokino
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020533:Angiogenesis Inhibitors / Q000032:analysis; D000818:Animals; D000911:Antibodies, Monoclonal; D019556:COS Cells; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D051528:Guanylate Kinases; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D007421:Intestine, Small; D007668:Kidney; D008565:Membrane Proteins / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D009703:Nucleoside-Phosphate Kinase / Q000032:analysis / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection; D062826:Zonula Occludens-1 Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D008565:Membrane Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; C569042:TJP1 protein, human; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; C113338:MAGI1 protein, human; D013755:Tetradecanoylphorbol Acetate