title: Cell contact-dependent regulation of epithelial-myofibroblast transition via the rho-rho kinase-phospho-myosin pathway.
abstract: Epithelial-mesenchymal-myofibroblast transition (EMT), a key feature in organ fibrosis, is regulated by the state of intercellular contacts. Our recent studies have shown that an initial injury of cell-cell junctions is a prerequisite for transforming growth factor-beta1 (TGF-beta1)-induced transdifferentiation of kidney tubular cells into alpha-smooth muscle actin (SMA)-expressing myofibroblasts. Here we analyzed the underlying contact-dependent mechanisms. Ca(2+) removal-induced disruption of intercellular junctions provoked Rho/Rho kinase (ROK)-mediated myosin light chain (MLC) phosphorylation and Rho/ROK-dependent SMA promoter activation. Importantly, myosin-based contractility itself played a causal role, because the myosin ATPase inhibitor blebbistatin or a nonphosphorylatable, dominant negative MLC (DN-MLC) abolished the contact disruption-triggered SMA promoter activation, eliminated the synergy between contact injury and TGF-beta1, and suppressed SMA expression. To explore the responsible mechanisms, we investigated the localization of the main SMA-inducing transcription factors, serum response factor (SRF), and its coactivator myocardin-related transcription factor (MRTF). Contact injury enhanced nuclear accumulation of SRF and MRTF. These processes were inhibited by DN-Rho or DN-MLC. TGF-beta1 strongly facilitated nuclear accumulation of MRTF in cells with reduced contacts but not in intact epithelia. DN-myocardin abrogated the Ca(2+)-removal- +/- TGF-beta1-induced promoter activation. These studies define a new mechanism whereby cell contacts regulate epithelial-myofibroblast transition via Rho-ROK-phospho-MLC-dependent nuclear accumulation of MRTF.
authors.affiliation: St. Michael's Hospital Research Institute, Toronto, ON, Canada M5B 1W8.
authors.forename: Lingzhi
authors.initials: L
authors.lastname: Fan
authors.forename: Attila
authors.initials: A
authors.lastname: Sebe
authors.forename: Zalán
authors.initials: Z
authors.lastname: Péterfi
authors.forename: András
authors.initials: A
authors.lastname: Masszi
authors.forename: Ana C P
authors.initials: AC
authors.lastname: Thirone
authors.forename: Ori D
authors.initials: OD
authors.lastname: Rotstein
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Nakano
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McCulloch
authors.forename: Katalin
authors.initials: K
authors.lastname: Szászi
authors.forename: István
authors.initials: I
authors.lastname: Mucsi
authors.forename: András
authors.initials: A
authors.lastname: Kapus
mesh_terms: D000199:Actins / Q000235:genetics; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology*; D005347:Fibroblasts / Q000166:cytology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007684:Kidney Tubules / Q000166:cytology; D009130:Muscle, Smooth / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport; D026362:Serum Response Factor / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; C511173:Mrtfa protein, mouse; D010750:Phosphoproteins; D020033:Protein Isoforms; D026362:Serum Response Factor; D015534:Trans-Activators; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009218:Myosins; D020741:rho GTP-Binding Proteins; D002118:Calcium