title: Nuclear translocation of myocardin-related transcription factor-A during transforming growth factor beta-induced epithelial to mesenchymal transition of lens epithelial cells.
abstract: OBJECTIVE
  Transforming growth factor beta (TGFβ) is a known inducer of epithelial to mesenchymal transition (EMT), and studies in other systems have shown that nuclear localization of the myocardin-related transcription factor (MRTF) is downstream of TGFβ. In the following study, we investigated whether nuclear translocation of MRTF-A or MRTF-B is involved in TGFβ-induced EMT of lens epithelial cells (LECs). We further investigated the relationship between matrix metalloproteinase-2 and -9 (MMP-2/9) and MRTF in the EMT of LECs.
  
  
  METHODS
  Rat lens explant cultures were used as the model system. Explants were treated with TGFβ, an MMP-2/9 inhibitor, or actin binding drugs and immunostained for alpha smooth muscle actin (αSMA), MRTF-A, and MRTF-B. Cytoplasmic and nuclear intensities of cells were measured using ImageJ. Production of αSMA was measured using western blot analysis and ImageJ.
  
  
  RESULTS
  Untreated explant cells exhibited little αSMA expression, and MRTF-A and B were found to reside primarily in the cytosol. However, when stimulated with TGFβ, a significantly greater number of cells exhibited nuclear expression of MRTF-A, accompanied by an increase in αSMA expression. However, MRTF-B remained in the cytoplasm following TGFβ treatment. Cotreatment with an MMP-2/9 inhibitor and TGFβ resulted in reduced MRTF-A nuclear localization and αSMA expression compared to cells treated with TGFβ alone.
  
  
  CONCLUSIONS
  Our results are the first to demonstrate the expression of MRTF-A in LECs and that its nuclear translocation can be stimulated by TGFβ. Our data further suggest that MMP-2 and -9 are involved in the translocation of MRTF-A in LECs during TGFβ-induced EMT.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University Health Science Centre, Rm 1R10, 1200 Main St. West. Hamilton, ON, L8N 3Z5, Canada.
authors.forename: Madhuja
authors.initials: M
authors.lastname: Gupta
authors.forename: Anna
authors.initials: A
authors.lastname: Korol
authors.forename: Judith A
authors.initials: JA
authors.lastname: West-Mays
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014157:Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D000199:Actins; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D061965:Matrix Metalloproteinase Inhibitors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C557977:myocardin-related transcription factor-A, rat; C569168:myocardin-related transcription factor-B, rat; C498862:Acta2 protein, rat