title: 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.affiliation: Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Beiyun
authors.initials: B
authors.lastname: Zhou
authors.forename: Yixin
authors.initials: Y
authors.lastname: Liu
authors.forename: Michael
authors.initials: M
authors.lastname: Kahn
authors.forename: David K
authors.initials: DK
authors.lastname: Ann
authors.forename: Arum
authors.initials: A
authors.lastname: Han
authors.forename: Hongjun
authors.initials: H
authors.lastname: Wang
authors.forename: Cu
authors.initials: C
authors.lastname: Nguyen
authors.forename: Per
authors.initials: P
authors.lastname: Flodby
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhong
authors.forename: Manda S
authors.initials: MS
authors.lastname: Krishnaveni
authors.forename: Janice M
authors.initials: JM
authors.lastname: Liebler
authors.forename: Parviz
authors.initials: P
authors.lastname: Minoo
authors.forename: Edward D
authors.initials: ED
authors.lastname: Crandall
authors.forename: Zea
authors.initials: Z
authors.lastname: Borok
mesh_terms: D000199:Actins / Q000096:biosynthesis; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D050882:CREB-Binding Protein; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000378:metabolism*; D011744:Pyrimidinones / Q000494:pharmacology; D015398:Signal Transduction; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; C492448:ICG 001; D011744:Pyrimidinones; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D051176:beta Catenin; D050882:CREB-Binding Protein; C494363:CREBBP protein, human