TGFβ and BMP-2 regulate epicardial cell invasion via TGFβR3 activation of the Par6/Smurf1/RhoA pathway

Cell Signal. 2012 Feb;24(2):539-548. doi: 10.1016/j.cellsig.2011.10.006. Epub 2011 Oct 14.


Coronary vessel development requires transfer of mesothelial cells to the heart surface to form the epicardium where some cells subsequently undergo epithelial-mesenchymal transformation (EMT) and invade the subepicardial matrix. Tgfbr3(-/-) mice die due to failed coronary vessel formation associated with decreased epicardial cell invasion but the mediators downstream of TGFβR3 are not well described. TGFβR3-dependent endocardial EMT stimulated by either TGFβ2 or BMP-2 requires activation of the Par6/Smurf1/RhoA 1pathway where Activin Receptor Like Kinase (ALK5) signals Par6 to act downstream of TGFβ to recruit Smurf1 to target RhoA for degradation to regulate apical-basal polarity and tight junction dissolution. Here we asked if this pathway was operant in epicardial cells and if TGFβR3 was required to access this pathway. Targeting of ALK5 in Tgfbr3(+/+) cells inhibited loss of epithelial character and invasion. Overexpression of wild-type (wt) Par6, but not dominant negative (dn) Par6, induced EMT and invasion while targeting Par6 by siRNA inhibited EMT and invasion. Overexpression of Smurf1 and dnRhoA induced loss of epithelial character and invasion. Targeting of Smurf1 by siRNA or overexpression of constitutively active (ca) RhoA inhibited EMT and invasion. In Tgfbr3(-/-) epicardial cells which have a decreased ability to invade collagen gels in response to TGFβ2, overexpression of wtPar6, Smurf1, or dnRhoA had a diminished ability to induce invasion. Overexpression of TGFβR3 in Tgfbr3(-/-) cells, followed by siRNA targeting of Par6 or Smurf1, diminished the ability of TGFβR3 to rescue invasion demonstrating that the Par6/Smurf1/RhoA pathway is activated downstream of TGFβR3 in epicardial cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing / antagonists & inhibitors
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adenoviridae
  • Animals
  • Bone Morphogenetic Protein 2 / pharmacology
  • Cell Communication
  • Cell Differentiation
  • Cell Line
  • Cell Movement / drug effects
  • Coronary Vessels / cytology
  • Coronary Vessels / drug effects
  • Coronary Vessels / metabolism*
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Epithelial-Mesenchymal Transition / drug effects
  • Gene Expression / drug effects
  • Mice
  • Mice, Knockout
  • Pericardium / cytology
  • Pericardium / drug effects
  • Pericardium / metabolism*
  • Proteoglycans / deficiency
  • Proteoglycans / genetics*
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Receptors, Transforming Growth Factor beta / deficiency
  • Receptors, Transforming Growth Factor beta / genetics*
  • Signal Transduction* / drug effects
  • Transfection
  • Transforming Growth Factor beta2 / pharmacology
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Bone Morphogenetic Protein 2
  • Par6 protein, mouse
  • Proteoglycans
  • RNA, Small Interfering
  • Receptors, Transforming Growth Factor beta
  • Tgfb2 protein, mouse
  • Transforming Growth Factor beta2
  • betaglycan
  • Smurf1 protein, mouse
  • Ubiquitin-Protein Ligases
  • rhoA GTP-Binding Protein