title: GLP-1 mediates antiapoptotic effect by phosphorylating Bad through a beta-arrestin 1-mediated ERK1/2 activation in pancreatic beta-cells.
abstract: Strategies based on activating GLP-1 receptor (GLP-1R) are intensively developed for the treatment of type 2 diabetes. The exhaustive knowledge of the signaling pathways linked to activated GLP-1R within the beta-cells is of major importance. In beta-cells, GLP-1 activates the ERK1/2 cascade by diverse pathways dependent on either Galpha(s)/cAMP/cAMP-dependent protein kinase (PKA) or beta-arrestin 1, a scaffold protein. Using pharmacological inhibitors, beta-arrestin 1 small interfering RNA, and islets isolated from beta-arrestin 1 knock-out mice, we demonstrate that GLP-1 stimulates ERK1/2 by two temporally distinct pathways. The PKA-dependent pathway mediates rapid and transient ERK1/2 phosphorylation that leads to nuclear translocation of the activated kinases. In contrast, the beta-arrestin 1-dependent pathway produces a late ERK1/2 activity that is restricted to the beta-cell cytoplasm. We further observe that GLP-1 phosphorylates the cytoplasmic proapoptotic protein Bad at Ser-112 but not at Ser-155. We find that the beta-arrestin 1-dependent ERK1/2 activation engaged by GLP-1 mediates the Ser-112 phosphorylation of Bad, through p90RSK activation, allowing the association of Bad with the scaffold protein 14-3-3, leading to its inactivation. beta-Arrestin 1 is further found to mediate the antiapoptotic effect of GLP-1 in beta-cells through the ERK1/2-p90RSK-phosphorylation of Bad. This new regulatory mechanism engaged by activated GLP-1R involving a beta-arrestin 1-dependent spatiotemporal regulation of the ERK1/2-p90RSK activity is now suspected to participate in the protection of beta-cells against apoptosis. Such signaling mechanism may serve as a prototype to generate new therapeutic GLP-1R ligands.
authors.affiliation: INSERM, U661, Equipe Avenir, CNRS, UMR5203, Institut de Génomique Fonctionnelle, Université Montpellier I and II, 34094 Montpellier Cedex 5, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Quoyer
authors.forename: Christine
authors.initials: C
authors.lastname: Longuet
authors.forename: Christophe
authors.initials: C
authors.lastname: Broca
authors.forename: Nathalie
authors.initials: N
authors.lastname: Linck
authors.forename: Safia
authors.initials: S
authors.lastname: Costes
authors.forename: Elodie
authors.initials: E
authors.lastname: Varin
authors.forename: Joël
authors.initials: J
authors.lastname: Bockaert
authors.forename: Gyslaine
authors.initials: G
authors.lastname: Bertrand
authors.forename: Stéphane
authors.initials: S
authors.lastname: Dalle
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D019390:Arrestins / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D012694:Serine; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D051025:bcl-Associated Death Protein / Q000737:chemistry / Q000378:metabolism*; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
chemical_list: D048948:14-3-3 Proteins; C000605255:Arrb1 protein, mouse; D019390:Arrestins; D051025:bcl-Associated Death Protein; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D012694:Serine; D052216:Glucagon-Like Peptide 1; D000242:Cyclic AMP; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3