Affiliation:
1. Department of Molecular Biology, AG Regulation of Gene Expression, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany
2. Helmholtz Zentrum München, Institute of Molecular Immunology, D-81377 Munich, Germany
Abstract
Epithelial junctions are dynamically and functionally linked to the actin cytoskeleton, and their disassembly is a key event during physiological and pathological processes. We recently showed that epithelial disintegration facilitates transcriptional activation via Rac, G-actin, MAL (also known as MRTF) and serum response factor (SRF). Here, we investigate which specific component of the epithelial junction is essential for this MAL-SRF-mediated transcription. The Ca2+-dependent dissociation of polarised epithelial cells depleted of ZO proteins – which form adherens junctions (AJs) but completely lack tight junctions (TJs) – fully activated SRF. By contrast, AGS gastric adenocarcinoma epithelial cells, which form TJs but are deficient in E-cadherin, and therefore also in AJs, failed to activate SRF. The introduction of wild-type E-cadherin in AGS cells restored AJ formation and MAL-SRF inducibility. To gain further insight into the membrane-proximal signalling, AGS cells were stably transfected with E-cadherin–α-catenin fusions. Despite restored formation of cell-cell contacts containing the nectin-afadin complex and p120-catenin, these cells did not activate SRF upon junction dissociation, suggesting that signal transmission depends on the C-terminal tail of E-cadherin. We conclude that the dissociation of intercellular E-cadherin interactions from AJs, and signals originating from the C-terminal region covering the β-catenin-binding site of E-cadherin, are essential for transcriptional activation via Rac, MAL and SRF, whereas TJs are not involved.
Publisher
The Company of Biologists
Cited by
20 articles.
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