title: Tight junction protein MAGI-1 is up-regulated by transfection with connexin 32 in an immortalized mouse hepatic cell line: cDNA microarray analysis.
abstract: Gap junctions are considered to play a crucial role in differentiation of epithelial cells, including hepatocytes. Recently, we found that Cx32 but not Cx26 was closely related to tight junctional proteins in primary cultured rat hepatocytes (Kojima et al., Exp Cell Res 263:193-201, 2001) and that Cx32 formation and/or Cx32-mediated intercellular communication could induce expression and function of tight junctions in a mouse hepatic cell line (Kojima et al., Exp Cell Res 276:40-51, 2002). In this study, to investigate the mechanisms of induction of tight junctions by transfection with Cx32, we performed cDNA microarray analysis of Cx32 transfectants, compared with parental cells derived from Cx32-deficient hepatocytes. In cDNA microarray analysis, a 2.5-fold increase in expression of membrane-associated guanylate kinase with inverted orientation-1 (MAGI-1), which is known to be localized at adherens and tight junction regions, was observed. High expression of MAGI-1 in Cx32 transfectants was confirmed by Western blotting and RT-PCR. MAGI-1 was colocalized with occludin, claudin-2, ZO-1, and F-actin, but not with E-cadherin in the apical-most regions at cell borders of Cx32 transfectants, similar to junctional adhesion molecule-1 (JAM-1), which may play a crucial role in formation and assembly of tight junctions. Treatment with the gap junction blocker 18beta-glycyrrhetinic acid did not affect expression of MAGI-1 and JAM-1 in Cx32 transfectants. These results suggest that Cx32 expression is in part related to induction of tight junctions through modulation of MAGI-1 expression in an immortalized mouse hepatic cell line.
authors.affiliation: Department of Pathology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Murata
authors.forename: Takashi
authors.initials: T
authors.lastname: Kojima
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Go
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Takano
authors.forename: Hideki
authors.initials: H
authors.lastname: Chiba
authors.forename: Takashi
authors.initials: T
authors.lastname: Tokino
authors.forename: Norimasa
authors.initials: N
authors.lastname: Sawada
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002461:Cell Line, Transformed; D017630:Connexins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018076:DNA, Complementary; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D022781:Hepatocytes / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D018992:Myelin-Associated Glycoprotein; D062793:Occludin; D020411:Oligonucleotide Array Sequence Analysis; D010750:Phosphoproteins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012235:Rhodamines; D019108:Tight Junctions / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation; D062826:Zonula Occludens-1 Protein; D000097002:Gap Junction beta-1 Protein
chemical_list: D000199:Actins; D015815:Cell Adhesion Molecules; D017630:Connexins; D018076:DNA, Complementary; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D018992:Myelin-Associated Glycoprotein; D062793:Occludin; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D012235:Rhodamines; D062826:Zonula Occludens-1 Protein; D000097002:Gap Junction beta-1 Protein; C498686:F11r protein, mouse; C104739:Mag protein, mouse; C568986:Ocln protein, mouse; C568987:Ocln protein, rat; C569043:Tjp1 protein, mouse; C569044:Tjp1 protein, rat