Research Paper Volume 16, Issue 7 pp 6588—6612

TGF-β downstream of Smad3 and MAPK signaling antagonistically regulate the viability and partial epithelial–mesenchymal transition of liver progenitor cells

Yi-Min Sun1,2, , Yu Wu1, , Gan-Xun Li1, , Hui-Fang Liang1, , Tu-Ying Yong3, , Zifu Li3, , Bixiang Zhang1, , Xiao-Ping Chen1, , Guan-Nan Jin1,4, , Ze-Yang Ding1, ,

  • 1 Hepatic Surgery Center, Hubei Province for The Clinical Medicine Research Center of Hepatic Surgery and Hubei Key Laboratory of Hepatic-Biliary-Pancreatic Diseases, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
  • 2 Present address: Department of Gastrointestinal Surgery, Affiliated First Hospital, Yangtze University, Jingzhou, Hubei 434000, China
  • 3 National Engineering Research Center for Nanomedicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430071, China
  • 4 Present address: Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China

Received: May 12, 2023       Accepted: March 18, 2024       Published: April 5, 2024
How to Cite

Copyright: © 2024 Sun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Background: Liver progenitor cells (LPCs) are a subpopulation of cells that contribute to liver regeneration, fibrosis and liver cancer initiation under different circumstances.

Results: By performing adenoviral-mediated transfection, CCK-8 analyses, F-actin staining, transwell analyses, luciferase reporter analyses and Western blotting, we observed that TGF-β promoted cytostasis and partial epithelial–mesenchymal transition (EMT) in LPCs. In addition, we confirmed that TGF-β activated the Smad and MAPK pathways, including the Erk, JNK and p38 MAPK signaling pathways, and revealed that TGFβ-Smad signaling induced growth inhibition and partial EMT, whereas TGFβ-MAPK signaling had the opposite effects on LPCs. We further found that the activity of Smad and MAPK signaling downstream of TGF-β was mutually restricted in LPCs. Mechanistically, we found that TGF-β activated Smad signaling through serine phosphorylation of both the C-terminal and linker regions of Smad2 and 3 in LPCs. Additionally, TGFβ-MAPK signaling inhibited the phosphorylation of Smad3 but not Smad2 at the C-terminus, and it reinforced the linker phosphorylation of Smad3 at T179 and S213. We then found that overexpression of mutated Smad3 at linker phosphorylation sites intensifies TGF-β-induced cytostasis and EMT, mimicking the effects of MAPK inhibition in LPCs, whereas mutation of Smad3 at the C-terminus caused LPCs to blunt TGF-β-induced cytostasis and partial EMT.

Conclusion: These results suggested that TGF-β downstream of Smad3 and MAPK signaling were mutually antagonistic in regulating the viability and partial EMT of LPCs. This antagonism may help LPCs overcome the cytostatic effect of TGF-β under fibrotic conditions and maintain partial EMT and progenitor phenotypes.


LPCs: liver progenitor cells; ECM: extracellular matrix; EMT: epithelial–mesenchymal transition; TGF-β: transforming growth factor-β; MAPK: mitogen-activated protein kinase; SBE: Smad3 binding elements; GSK3β: glycogen synthetase kinase 3β; CDKs: cyclin-dependent kinases; HBx: HBV antigen X; pSmad3C: C-terminal phosphorylated Smad3; pSmad3L: linker phosphorylated Smad3.