Epithelial-mesenchymal transition and nuclear β-catenin induced by conditional intestinal disruption of Cdh1 with Apc is E-cadherin EC1 domain dependent
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Julia Matheson1,*, Claudia Bühnemann1,*, Emma J. Carter1, David Barnes1, Hans-Jürgen Hoppe1, Jennifer Hughes1, Stephen Cobbold1, James Harper1, Hans Morreau2, Mirvat Surakhy1, A. Bassim Hassan1
1Tumour Growth Group, Oxford Molecular Pathology Institute, Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, United Kingdom
2Department of Pathology, Leiden University Medical Centre, Leiden, The Netherlands
A. Bassim Hassan, email: firstname.lastname@example.org
Keywords: E-cadherin, Apc, intestine, β-catenin, adhesion complex
Received: October 07, 2015 Accepted: August 08, 2016 Published: August 23, 2016
Two important protein-protein interactions establish E-cadherin (Cdh1) in the adhesion complex; homophilic binding via the extra-cellular (EC1) domain and cytoplasmic tail binding to β-catenin. Here, we evaluate whether E-cadherin binding can inhibit β-catenin when there is loss of Adenomatous polyposis coli (APC) from the β-catenin destruction complex. Combined conditional loss of Cdh1 and Apc were generated in the intestine, intestinal adenoma and adenoma organoids. Combined intestinal disruption (Cdh1fl/flApcfl/flVil-CreERT2) resulted in lethality, breakdown of the intestinal barrier, increased Wnt target gene expression and increased nuclear β-catenin localization, suggesting that E-cadherin inhibits β-catenin. Combination with an intestinal stem cell Cre (Lgr5CreERT2) resulted in ApcΔ/Δ recombination and adenoma, but intact Cdh1fl/fl alleles. Cultured ApcΔ/ΔCdh1fl/fl adenoma cells infected with adenovirus-Cre induced Cdh1fl/fl recombination (Cdh1Δ/Δ), disruption of organoid morphology, nuclear β-catenin localization, and cells with an epithelial-mesenchymal phenotype. Complementation with adenovirus expressing wild-type Cdh1 (Cdh1-WT) rescued adhesion and β-catenin membrane localization, yet an EC1 specific double mutant defective in homophilic adhesion (Cdh1-MutW2A, S78W) did not. These data suggest that E-cadherin inhibits β-catenin in the context of disruption of the APC-destruction complex, and that this function is also EC1 domain dependent. Both binding functions of E-cadherin may be required for its tumour suppressor activity.
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