title: Dlg-1 Interacts With and Regulates the Activities of Fibroblast Growth Factor Receptors and EphA2 in the Mouse Lens.
abstract: OBJECTIVE
  We previously showed that Discs large-1 (Dlg-1) regulates lens fiber cell structure and the fibroblast growth factor receptor (Fgfr) signaling pathway, a pathway required for fiber cell differentiation. Herein, we investigated the mechanism through which Dlg-1 regulates Fgfr signaling.
  
  
  METHODS
  Immunofluorescence was used to measure levels of Fgfr1, Fgfr2, and activated Fgfr signaling intermediates, pErk and pAkt, in control and Dlg-1-deficient lenses that were haplodeficient for Fgfr1 or Fgfr2. Immunoblotting was used to measure levels of N-cadherin, EphA2, β-catenin, and tyrosine-phosphorylated EphA2, Fgfr1, Fgfr2, and Fgfr3 in cytoskeletal-associated and cytosolic fractions of control and Dlg-1-deficient lenses. Complex formation between Dlg-1, N-cadherin, β-catenin, Fgfr1, Fgfr2, Fgfr3, and EphA2 was assessed by coimmunoprecipitation.
  
  
  RESULTS
  Lenses deficient for Dlg-1 and haplodeficient for Fgfr1 or Fgfr2 showed increased levels of Fgfr2 or Fgfr1, respectively. Levels of pErk and pAkt correlated with the level of Fgfr2. N-cadherin was reduced in the cytoskeletal-associated fraction and increased in the cytosolic fraction of Dlg-1-deficient lenses. Dlg-1 complexed with β-catenin, EphA2, Fgfr1, Fgfr2, and Fgfr3. EphA2 complexed with N-cadherin, β-catenin, Fgfr1, Fgfr2, and Fgfr3. Levels of these interactions were altered in Dlg-1-deficient lenses. Loss of Dlg-1 led to changes in Fgfr1, Fgfr2, Fgfr3, and EphA2 levels and to greater changes in the levels of their activation.
  
  
  CONCLUSIONS
  Dlg-1 complexes with and regulates the activities of EphA2, Fgfr1, Fgfr2, and Fgfr3. As EphA2 contains a Psd95/Dlg/ZO-1 (PDZ) binding motif, whereas Fgfrs do not, we propose that the PDZ protein, Dlg-1, modulates Fgfr signaling through regulation of EphA2.
authors.forename: SungKyoung
authors.initials: S
authors.lastname: Lee
authors.forename: Shalini
authors.initials: S
authors.lastname: Shatadal
authors.forename: Anne E
authors.initials: AE
authors.lastname: Griep
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation; D005786:Gene Expression Regulation; D047468:Immunoprecipitation; D007908:Lens, Crystalline / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics*; D036104:Receptor, EphA2 / Q000096:biosynthesis / Q000235:genetics*; D017468:Receptors, Fibroblast Growth Factor / Q000096:biosynthesis / Q000235:genetics*; D000074407:SAP90-PSD95 Associated Proteins; D015398:Signal Transduction
chemical_list: D009419:Nerve Tissue Proteins; D017468:Receptors, Fibroblast Growth Factor; D000074407:SAP90-PSD95 Associated Proteins; D012313:RNA; D036104:Receptor, EphA2