Role of epimorphin in bile duct formation of rat liver epithelial stem-like cells: Involvement of small G protein RhoA and C/EBPβ

Stem Cell and Regenerative Medicine Lab, Beijing Institute of Transfusion Medicine, Beijing, China.
Journal of Cellular Physiology (Impact Factor: 3.84). 11/2011; 226(11):2807-16. DOI: 10.1002/jcp.22625
Source: PubMed


Epimorphin/syntaxin 2 is a high conserved and very abundant protein involved in epithelial morphogenesis in various organs. We have shown recently that epimorphin (EPM), a protein exclusively expressed on the surface of hepatic stellate cells and myofibroblasts of the liver, induces bile duct formation of hepatic stem-like cells (WB-F344 cells) in a putative biophysical way. Therefore, the aim of this study was to present some of the molecular mechanisms by which EPM mediates bile duct formation. We established a biliary differentiation model by co-culture of EPM-overexpressed mesenchymal cells (PT67(EPM)) with WB-F344 cells. Here, we showed that EPM could promote WB-F344 cells differentiation into bile duct-like structures. Biliary differentiation markers were also elevated by EPM including Yp, Cx43, aquaporin-1, CK19, and gamma glutamyl transpeptidase (GGT). Moreover, the signaling pathway of EPM was analyzed by focal adhesion kinase (FAK), extracellular regulated kinase 1/2 (ERK1/2), and RhoA Western blot. Also, a dominant negative (DN) RhoA-WB-F344 cell line (WB(RhoA-DN)) was constructed. We found that the levels of phosphorylation (p) of FAK and ERK1/2 were up-regulated by EPM. Most importantly, we also showed that RhoA is necessary for EPM-induced activation of FAK and ERK1/2 and bile duct formation. In addition, a dual luciferase-reporter assay and CHIP assay was performed to reveal that EPM regulates GGT IV and GGT V expression differentially, possibly mediated by C/EBPβ. Taken together, these data demonstrated that EPM regulates bile duct formation of WB-F344 cells through effects on RhoA and C/EBPβ, implicating a dual aspect of this morphoregulator in bile duct epithelial morphogenesis.

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    • "In the adult liver, EPIM is expressed in the connective tissue surrounding blood vessels, along the sinusoidal lining where HSCs reside [18], [19] and in mesenchyme surrounding the bile duct where it is thought to play a role in duct formation [15], [20]. In vivo, there is a reduction in EPIM expression following liver injury and HSC activation [21]. "
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