title: Rewiring integrin-mediated signaling and cellular response with the peripheral myelin protein 22 and epithelial membrane protein 2 components of the tetraspan web.
abstract: OBJECTIVE
  Integrin-mediated collagen gel contraction by ARPE-19 is an in vitro model for proliferative vitreoretinopathy (PVR), an aberrant wound healing response after retinal detachment or ocular trauma. Expression of the tetraspan protein epithelial membrane protein 2 (EMP2) controls gel contraction through FAK activation. Peripheral myelin protein 22 (PMP22), another member of the tetraspan web, is closely related to EMP2. The purpose of this study was to determine whether PMP22 also controls the contractile phase associated with PVR.
  
  
  METHODS
  Integrin expression, adhesion, and protein expression were assessed, respectively, through flow cytometry, binding to collagen types I and IV, and Western blot analysis. Collagen gel contraction was assessed using an in vitro assay.
  
  
  RESULTS
  Overexpression of PMP22 in ARPE-19 cells (ARPE-19/PMP22) resulted in increased collagen adhesion. Gel contraction, however, was reduced by greater than 50% in ARPE-19/PMP22 cells (P < 0.001). In contrast to the FAK activation observed by increasing EMP2 expression, PMP22 overexpression led to increased AKT activation. The decrease in gel contraction by the ARPE-19/PMP22 cells was partially reversed through either PMP22 siRNA or by blockade of AKT.
  
  
  CONCLUSIONS
  Relative expression of EMP2 or PMP22 within the tetraspan web drives a cellular response toward a FAK- or AKT-dependent pathway, respectively. EMP2 and PMP22 differentially regulate collagen gel contraction in the ARPE-19 cell line. The implication of this finding adds a new dimension to the concept of the tetraspan web, in which the abundance of individual tetraspan family members differentially regulates signal transduction and the downstream cellular response.
authors.affiliation: Department of Ophthalmology, University of California at Los Angeles, Los Angeles, California, USA.
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Morales
authors.forename: David
authors.initials: D
authors.lastname: Telander
authors.forename: Lucia
authors.initials: L
authors.lastname: Notterpek
authors.forename: Madhuri
authors.initials: M
authors.lastname: Wadehra
authors.forename: Jonathan
authors.initials: J
authors.lastname: Braun
authors.forename: Lynn K
authors.initials: LK
authors.lastname: Gordon
mesh_terms: D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002448:Cell Adhesion; D002460:Cell Line; D024042:Collagen Type I / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism; D005434:Flow Cytometry; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008954:Models, Biological; D009185:Myelin Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D018630:Vitreoretinopathy, Proliferative / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D024042:Collagen Type I; D024141:Collagen Type IV; C486403:EMP2 protein, human; D016023:Integrins; D008562:Membrane Glycoproteins; D009185:Myelin Proteins; C073687:PMP22 protein, human; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D051057:Proto-Oncogene Proteins c-akt