title: beta-Arrestin 1 is required for PAC1 receptor-mediated potentiation of long-lasting ERK1/2 activation by glucose in pancreatic beta-cells.
abstract: In pancreatic beta-cells, the pituitary adenylate cyclase-activating polypeptide (PACAP) exerts a potent insulin secretory effect via PAC(1) and VPAC receptors (Rs) through the Galpha(s)/cAMP/protein kinase A pathway. Here, we investigated the mechanisms linking PAC(1)R to ERK1/2 activation in INS-1E beta-cells and pancreatic islets. PACAP caused a transient (5 min) increase in ERK1/2 phosphorylation via PAC(1)Rs and promoted nuclear translocation of a fraction of cytosolic p-ERK1/2. Both protein kinase A- and Src-dependent pathways mediated this transient ERK1/2 activation. Moreover, PACAP potentiated glucose-induced long-lasting ERK1/2 activation. Blocking Ca(2+) influx abolished glucose-induced ERK1/2 activation and PACAP potentiating effect. Glucose stimulation during KCl depolarization showed that, in addition to the triggering signal (rise in cytosolic [Ca(2+)]), the amplifying pathway was also involved in glucose-induced sustained ERK1/2 activation and was required for PACAP potentiation. The finding that at 30 min glucose-induced p-ERK1/2 was detected in both cytosol and nucleus while the potentiating effect of PACAP was only observed in the cytosol, suggested the involvement of the scaffold protein beta-arrestin. Indeed, beta-arrestin 1 (beta-arr1) depletion (in beta-arr1 knockout mouse islets or in INS-1E cells by siRNA) completely abolished PACAP potentiation of long-lasting ERK1/2 activation by glucose. Finally, PACAP potentiated glucose-induced CREB transcriptional activity and IRS-2 mRNA expression mainly via the ERK1/2 signaling pathway, and likewise, beta-arr1 depletion reduced the PACAP potentiating effect on IRS-2 expression. These results establish for the first time that PACAP potentiates glucose-induced long-lasting ERK1/2 activation via a beta-arr1-dependent pathway and thus provide new insights concerning the mechanisms of PACAP and glucose actions in pancreatic beta-cells.
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS, Unité Mixte de Recherche 5203, INSERM, U661, Université Montpellier I, and Université Montpellier II, 34094 Montpellier Cedex 5, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Broca
authors.forename: Julie
authors.initials: J
authors.lastname: Quoyer
authors.forename: Safia
authors.initials: S
authors.lastname: Costes
authors.forename: Nathalie
authors.initials: N
authors.lastname: Linck
authors.forename: Annie
authors.initials: A
authors.lastname: Varrault
authors.forename: Pierre-Marie
authors.initials: PM
authors.lastname: Deffayet
authors.forename: Joël
authors.initials: J
authors.lastname: Bockaert
authors.forename: Stéphane
authors.initials: S
authors.lastname: Dalle
authors.forename: Gyslaine
authors.initials: G
authors.lastname: Bertrand
mesh_terms: D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins / Q000096:biosynthesis / Q000235:genetics; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / Q000235:genetics / Q000378:metabolism*; D013549:Sweetening Agents / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
chemical_list: C495402:Adcyap1 protein, mouse; C495504:Adcyap1r1 protein, mouse; C000605255:Arrb1 protein, mouse; D019390:Arrestins; C492004:Creb1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D055504:Insulin Receptor Substrate Proteins; C526298:Irs2 protein, mouse; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D013549:Sweetening Agents; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D005947:Glucose; D002118:Calcium