title: The integrin alpha5beta1 regulates alphavbeta3-mediated extracellular signal-regulated kinase activation.
abstract: BACKGROUND
  Integrin-mediated cell migration is essential for wound repair. Previous studies have shown that the interaction between integrins and the extracellular matrix (ECM) can initiate intracellular signaling pathways to regulate cell movement. Both the focal adhesion kinase (FAK) and the extracellular signal-regulated kinase/activated mitogen-activated protein kinase (ERK/MAPK) signaling pathways are required for efficient cell migration. Our previous work has shown that co-expression of the integrin alpha5beta1 inhibits alphavbeta3-mediated cell migration. We hypothesized that alpha5beta1 may regulate cell migration by modulating these alphavbeta3-mediated intracellular signaling events.
  
  
  METHODS
  CHO B3 (alphavbeta3+) and B3C5 (alphavbeta3+/alpha5beta1+) cells were monitored by flow cytometry to determine integrin expression. Cells were allowed to migrate on fibrinogen (FBG)-coated transwells, with or without PD98059, an inhibitor of the ERK activator, mitogen-activated protein kinase kinase (MEK). Fixation, staining, and cell counting were used to quantify cell migration. Cells adherent to FBG were lysed and analyzed for FAK and ERK/MAPK activation by immunoblotting followed by image analysis densitometry. All experiments were repeated in triplicate.
  
  
  RESULTS
  Treatment with PD98059 significantly decreased alphavbeta3-mediated cell migration on FBG (P = 0.0001) to a level comparable to untreated B3C5 cells. Following adhesion to FBG, B3 cells demonstrated a marked increase in ERK/MAPK activation compared to B3C5 cells. However, no significant difference was detected in FAK activation.
  
  
  CONCLUSIONS
  Signaling through the ERK/MAPK pathway is required for efficient alphavbeta3-mediated migration on FBG. Inhibition of alphavbeta3-mediated migration by the integrin alpha5beta1 correlates with altered intensity and duration of ERK/MAPK activation, but not FAK activation, in response to adhesion. This suggests a mechanism for the regulatory effect of alpha5beta1 on alphavbeta3-mediated cell migration.
authors.affiliation: Department of Surgery, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ 08903, USA.
authors.forename: Daphne P
authors.initials: DP
authors.lastname: Ly
authors.forename: Siobhan A
authors.initials: SA
authors.lastname: Corbett
mesh_terms: D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D006224:Cricetinae; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005340:Fibrinogen; D051416:Focal Adhesion Protein-Tyrosine Kinases; D039081:Integrin alpha5beta1 / Q000235:genetics / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D014162:Transfection
chemical_list: D039081:Integrin alpha5beta1; D039302:Integrin alphaVbeta3; D005340:Fibrinogen; D011505:Protein-Tyrosine Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases