Central role for Rho in TGF-β1-induced α-smooth muscle actin expression during epithelial-mesenchymal transition

András Masszi, Caterina Di Ciano, Gábor Sirokmány, William T. Arthur, Ori D. Rotstein, Jiaxu Wang, Christopher A.G. McCulloch, László Rosivall, István Mucsi, András Kapus

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Abstract

New research suggests that, during tubulointerstitial fibrosis, α-smooth muscle actin (SMA)-expressing mesenchymal cells might derive from the tubular epithelium via epithelial-mesenchymal transition (EMT). Although transforming growth factor-β1 (TGF-β1) plays a key role in EMT, the underlying cellular mechanisms are not well understood. Here we characterized TGF-β1-induced EMT in LLC-PK1 cells and examined the role of the small GTPase Rho and its effector, Rho kinase, (ROK) in the ensuing cytoskeletal remodeling and SMA expression. TGF-β1 treatment caused delocalization and downregulation of cell contact proteins (ZO-1, E-cadherin, β-catenin), cytoskeleton reorganization (stress fiber assembly, myosin light chain phosphorylation), and robust SMA synthesis. TGF-β1 induced a biphasic Rho activation. Stress fiber assembly was prevented by the Rho-inhibiting C3 transferase and by dominant negative (DN) ROK. The SMA promoter was activated strongly by constitutively active Rho but not ROK. Accordingly, TGF-β1-induced SMA promoter activation was potently abrogated by two Rho-inhibiting constructs, C3 transferase and p190RhoGAP, but not by DN-ROK. Truncation analysis showed that the first CC(A/T)richGG (CArG B) serum response factor-binding cis element is essential for the Rho responsiveness of the SMA promoter. Thus Rho plays a dual role in TGF-β1-induced EMT of renal epithelial cells. It is indispensable both for cytoskeleton remodeling and for the activation of the SMA promoter. The cytoskeletal effects are mediated via the Rho/ROK pathway, whereas the transcriptional effects are partially ROK independent.

Original languageEnglish
Pages (from-to)F911-F924
JournalAmerican Journal of Physiology - Renal Physiology
Volume284
Issue number5 53-5
Publication statusPublished - May 1 2003

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Keywords

  • Epithelial-mesenchymal transdifferentiation
  • Kidney proximal tubule cells
  • Rho kinase
  • Transforming growth factor-β

ASJC Scopus subject areas

  • Physiology
  • Urology

Cite this

Masszi, A., Di Ciano, C., Sirokmány, G., Arthur, W. T., Rotstein, O. D., Wang, J., McCulloch, C. A. G., Rosivall, L., Mucsi, I., & Kapus, A. (2003). Central role for Rho in TGF-β1-induced α-smooth muscle actin expression during epithelial-mesenchymal transition. American Journal of Physiology - Renal Physiology, 284(5 53-5), F911-F924.