title: Focal adhesion remodeling is crucial for glucose-stimulated insulin secretion and involves activation of focal adhesion kinase and paxillin.
abstract: OBJECTIVE
  Actin cytoskeleton remodeling is known to be involved in glucose-stimulated insulin secretion (GSIS). We have observed glucose-stimulated changes at the β-cell basal membrane similar to focal adhesion remodeling in cell migration. This led us to study the role of two key focal adhesion proteins, focal adhesion kinase (FAK) and paxillin, in GSIS.
  
  
  METHODS
  All studies were performed using rat primary β-cells or isolated islets. Protein phosphorylation and subcellular localization were determined by Western blotting and confocal immunofluorescence, respectively. Insulin was measured by radioimmunoassay. Both siRNA and pharmacological approaches were used to assess the role of FAK and paxillin in glucose-stimulated focal adhesion remodeling and insulin secretion.
  
  
  RESULTS
  Glucose stimulation of β-cells in monolayer significantly increased phosphorylation of FAK and paxillin as well as cell surface area. This coincided with the appearance at the basal membrane of numerous shorter actin filopodial extensions, containing not only phosphorylated paxillin, FAK, and extracellular signal-related kinase 1/2 but also two SNARE proteins, synaptosomal-associated protein 25 and syntaxin 1, indicating involvement in exocytosis. SR7037 completely inhibited this sequence of events, indicating the requirement of increased cytosolic Ca²(+). Furthermore, knockdown of paxillin significantly decreased GSIS, as did inhibition of glucose-induced FAK phosphorylation by compound Y15. Key findings were confirmed in β-cells within the natural setting of islets.
  
  
  CONCLUSIONS
  Glucose-stimulated remodeling of focal adhesions and phosphorylation of FAK and paxillin are involved in full development of GSIS, indicating a previously unknown role for focal adhesion remodeling in pancreatic β-cell function.
authors.affiliation: Department of Genetic Medicine and Development, University Medical Center, University of Geneva, Geneva, Switzerland. dieter.rondas@unige.ch
authors.forename: Dieter
authors.initials: D
authors.lastname: Rondas
authors.forename: Alejandra
authors.initials: A
authors.lastname: Tomas
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005419:Flavonoids / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D018613:Microscopy, Confocal; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051419:Paxillin / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D034622:RNA Interference; D051381:Rats
chemical_list: D005419:Flavonoids; D007328:Insulin; D051419:Paxillin; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D005947:Glucose; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one