Interactions between β-catenin and transforming growth factor-β signaling pathways mediate epithelial-mesenchymal transition and are dependent on the transcriptional co-activator cAMP-response element-binding protein (CREB)-binding protein (CBP).

Abstract

Interactions between transforming growth factor-β (TGF-β) and Wnt are crucial to many biological processes, although specific targets, rationale for divergent outcomes (differentiation versus block of epithelial proliferation versus epithelial-mesenchymal transition (EMT)) and precise mechanisms in many cases remain unknown. We investigated β-catenin-dependent and transforming growth factor-β1 (TGF-β1) interactions in pulmonary alveolar epithelial cells (AEC) in the context of EMT and pulmonary fibrosis. We previously demonstrated that ICG-001, a small molecule specific inhibitor of the β-catenin/CBP (but not β-catenin/p300) interaction, ameliorates and reverses pulmonary fibrosis and inhibits TGF-β1-mediated α-smooth muscle actin (α-SMA) and collagen induction in AEC. We now demonstrate that TGF-β1 induces LEF/TCF TOPFLASH reporter activation and nuclear β-catenin accumulation, while LiCl augments TGF-β-induced α-SMA expression, further confirming co-operation between β-catenin- and TGF-β-dependent signaling pathways. Inhibition and knockdown of Smad3, knockdown of β-catenin and overexpression of ICAT abrogated effects of TGF-β1 on α-SMA transcription/expression, indicating a requirement for β-catenin in these Smad3-dependent effects. Following TGF-β treatment, co-immunoprecipitation demonstrated direct interaction between endogenous Smad3 and β-catenin, while chromatin immunoprecipitation (ChIP)-re-ChIP identified spatial and temporal regulation of α-SMA via complex formation among Smad3, β-catenin, and CBP. ICG-001 inhibited α-SMA expression/transcription in response to TGF-β as well as α-SMA promoter occupancy by β-catenin and CBP, demonstrating a previously unknown requisite TGF-β1/β-catenin/CBP-mediated pro-EMT signaling pathway. Clinical relevance was shown by β-catenin/Smad3 co-localization and CBP expression in AEC of IPF patients. These findings suggest a new therapeutic approach to pulmonary fibrosis by specifically uncoupling CBP/catenin-dependent signaling downstream of TGF-β.

• Authors: Beiyun Zhou, Yixin Liu, Michael Kahn, David K Ann, Arum Han, Hongjun Wang, Cu Nguyen, Per Flodby, Qian Zhong, Manda S Krishnaveni, Janice M Liebler, Parviz Minoo, Edward D Crandall, Zea Borok
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 10 Pg. 7026-38 (Mar 02 2012) ISSN: 1083-351X [Electronic] United States
• PMID: 22241478 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Actins
• Bridged Bicyclo Compounds, Heterocyclic
• ICG 001
• Pyrimidinones
• SMAD3 protein, human
• Smad3 Protein
• Transforming Growth Factor beta1
• beta Catenin
• CREB-Binding Protein
• CREBBP protein, human

Topics

• Actins (biosynthesis)
• Bridged Bicyclo Compounds, Heterocyclic (pharmacology)
• CREB-Binding Protein
• Cell Line
• Cell Proliferation (drug effects)
• Epithelial Cells (metabolism, pathology)
• Epithelial-Mesenchymal Transition
• Gene Expression Regulation (drug effects, genetics)
• Humans
• Pulmonary Fibrosis (genetics, metabolism)
• Pyrimidinones (pharmacology)
• Signal Transduction
• Smad3 Protein (genetics, metabolism)
• Transforming Growth Factor beta1 (genetics, metabolism)
• beta Catenin (genetics, metabolism)