Knockdown of tight junction protein claudin-2 prevents bile canalicular formation in WIF-B9 cells.
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.
Son
Seiichi
S
Departments of Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Kojima
Takashi
T
Decaens
Catherine
C
Yamaguchi
Hiroshi
H
Ito
Tatsuya
T
Imamura
Masafumi
M
Murata
Masaki
M
Tanaka
Satoshi
S
Chiba
Hideki
H
Hirata
Koichi
K
Sawada
Norimasa
N
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
D008565:Membrane Proteins; D034741:RNA, Small Interfering; C569046:TJP2 protein, human; D062827:Zonula Occludens-2 Protein