title: Novel mechanistic link between focal adhesion remodeling and glucose-stimulated insulin secretion.
abstract: Actin cytoskeleton remodeling is well known to be positively involved in glucose-stimulated pancreatic β cell insulin secretion. We have observed glucose-stimulated focal adhesion remodeling at the β cell surface and have shown this to be crucial for glucose-stimulated insulin secretion. However, the mechanistic link between such remodeling and the insulin secretory machinery remained unknown and was the major aim of this study. MIN6B1 cells, a previously validated model of primary β cell function, were used for all experiments. Total internal reflection fluorescence microscopy revealed the glucose-responsive co-localization of focal adhesion kinase (FAK) and paxillin with integrin β1 at the basal cell surface after short term stimulation. In addition, blockade of the interaction between β1 integrins and the extracellular matrix with an anti-β1 integrin antibody (Ha2/5) inhibited short term glucose-induced phosphorylation of FAK (Tyr-397), paxillin (Tyr-118), and ERK1/2 (Thr-202/Tyr-204). Pharmacological inhibition of FAK activity blocked glucose-induced actin cytoskeleton remodeling and glucose-induced disruption of the F-actin/SNAP-25 association at the plasma membrane as well as the distribution of insulin granules to regions in close proximity to the plasma membrane. Furthermore, FAK inhibition also completely blocked short term glucose-induced activation of the Akt/AS160 signaling pathway. In conclusion, these results indicate 1) that glucose-induced activation of FAK, paxillin, and ERK1/2 is mediated by β1 integrin intracellular signaling, 2) a mechanism whereby FAK mediates glucose-induced actin cytoskeleton remodeling, hence allowing docking and fusion of insulin granules to the plasma membrane, and 3) a possible functional role for the Akt/AS160 signaling pathway in the FAK-mediated regulation of glucose-stimulated insulin secretion.
authors.affiliation: Department of Genetic Medicine and Development, University of Geneva, CH-1211 Geneva 4, 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: Martinho
authors.initials: M
authors.lastname: Soto-Ribeiro
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wehrle-Haller
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism; D022001:Focal Adhesions / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D051419:Paxillin / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013549:Sweetening Agents / Q000494:pharmacology*; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D020690:GTPase-Activating Proteins; D007328:Insulin; D019012:Integrin beta1; D051419:Paxillin; C496063:Pxn protein, rat; C494210:Snap25 protein, rat; D013549:Sweetening Agents; D050825:Synaptosomal-Associated Protein 25; C533101:TBC1D4 protein, rat; D051417:Focal Adhesion Kinase 1; C496052:Ptk2 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D048052:Mitogen-Activated Protein Kinase 3; D005947:Glucose