title: Knockdown of tight junction protein claudin-2 prevents bile canalicular formation in WIF-B9 cells.
abstract: The polarization of hepatocytes involves formation of functionally distinct sinusoidal (basolateral) and bile canalicular (apical) plasma membrane domains that are separated by tight junctions. Although various molecular mechanisms and signaling cascades including polarity complex proteins may contribute to bile canalicular formation in hepatocytes, the role of tight junction proteins in bile canalicular formation remains unclear. To investigate the role of the integral tight junction protein claudin-2 in bile canalicular formation, we depleted claudin-2 expression by siRNA in the polarized hepatic cell line WIF-B9 after treatment with or without phenobarbital. When WIF-B9 cells were treated with phenobarbital, claudin-2 expression and tight junction strands were markedly increased together with induction of canalicular formation with a biliary secretion function. Knockdown of claudin-2 prevented bile canalicular formation after treatment with or without phenobarbital. Furthermore, knockdown of claudin-2 caused a change from a hepatic polarized phenotype to a simple polarized phenotype, together with upregulation of pLKB1, pMAPK, pAkt and pp38 MAPK, but not pMLC, PTEN or cdc42, and an increase of intracellular vacuoles, which were present before bile canalicular formation. These results suggest that claudin-2 may affect not only the bile canalicular seal but also bile canalicular formation.
authors.affiliation: Departments of Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Son
authors.forename: Takashi
authors.initials: T
authors.lastname: Kojima
authors.forename: Catherine
authors.initials: C
authors.lastname: Decaens
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ito
authors.forename: Masafumi
authors.initials: M
authors.lastname: Imamura
authors.forename: Masaki
authors.initials: M
authors.lastname: Murata
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Hideki
authors.initials: H
authors.lastname: Chiba
authors.forename: Koichi
authors.initials: K
authors.lastname: Hirata
authors.forename: Norimasa
authors.initials: N
authors.lastname: Sawada
mesh_terms: D000818:Animals; D001648:Bile Canaliculi / Q000254:growth & development*; D002460:Cell Line; D006801:Humans; D006822:Hybrid Cells; D008099:Liver / Q000166:cytology; D008565:Membrane Proteins / Q000172:deficiency / Q000502:physiology*; D010641:Phenotype; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D015854:Up-Regulation / Q000235:genetics; D062827:Zonula Occludens-2 Protein
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; C569046:TJP2 protein, human; D062827:Zonula Occludens-2 Protein