title: Effects of TGF-β2 on cadherins and β-catenin in human trabecular meshwork cells.
abstract: OBJECTIVE
  The effects of TGF-β2 on cadherin-mediated cell-cell adhesion in human trabecular meshwork (HTM) cells were characterized, since TGF-β-induced changes in the cytoskeleton, cell-cell, and cell-matrix interactions of HTM cells are suggested to have a significant role in primary open angle glaucoma.
  
  
  METHODS
  The HTM cells were derived from donor cornea rings and treated with TGF-β2 or vehicle, and protein expression was studied by Western Blot, while protein localization was studied by fractionation of lysates and by confocal immunofluorescence microscopy. Cell-cell adhesion was assessed functionally in dissociation experiments and N-cadherin-mediated cell contact formation in cell spreading experiments on cadherin-coated substrates. A rho-associated protein kinase (ROCK) inhibitor was used to evaluate the contribution of cytoskeletal tension to TGF-β2-induced changes in protein expression and localization.
  
  
  RESULTS
  TGF-β2 activated Smad-2/3, serine-threonine kinase (AKT), and extracellular signal-regulated kinase (ERK) signaling, and enhanced expression of β-catenin as well as N- and OB-cadherin. The nuclear fraction of β-catenin was not enhanced by TGF-β2. Immunofluorescence microscopy revealed an increased localization of N-cadherin and β-catenin to cell-cell adhesions, and an increase in F-actin. The TGF-β2 increased cell-cell adhesion strength and enhanced N-cadherin-mediated cell contact formation. This effect was blocked by inhibition of mitogen-activated protein kinase kinase (MEK) or AKT. Cytoskeletal relaxation by a ROCK inhibitor did not prevent a TGF-β2-induced increase in cadherin and β-catenin expression.
  
  
  CONCLUSIONS
  The cytokine TGF-β2 enhances cadherin-mediated cell-cell adhesion and β-catenin expression in HTM cells. Increased cell-cell adhesion may contribute to biomechanical alterations in glaucomatous trabecular meshwork (TM), and changes in β-catenin levels and its possible sequestration to cell adhesion sites may affect Wnt signaling. Thus, the crosstalk of TGF-β2 and Wnt signaling in TM may deserve further investigation.
authors.affiliation: Department of Ophthalmology, Freiburg University Medical Center, Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wecker
authors.forename: Hong
authors.initials: H
authors.lastname: Han
authors.forename: Juliane
authors.initials: J
authors.lastname: Börner
authors.forename: Franz
authors.initials: F
authors.lastname: Grehn
authors.forename: Günther
authors.initials: G
authors.lastname: Schlunck
mesh_terms: D015153:Blotting, Western; D015820:Cadherins / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D002449:Cell Aggregation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics*; D005786:Gene Expression Regulation; D005902:Glaucoma, Open-Angle / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014129:Trabecular Meshwork / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D053781:Transforming Growth Factor beta2 / Q000494:pharmacology*; D051176:beta Catenin / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*
chemical_list: D015820:Cadherins; D053781:Transforming Growth Factor beta2; D051176:beta Catenin; D004247:DNA
keywords: TGF-beta; glaucoma; trabecular meshwork