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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Arrestins / genetics
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Arrestins / metabolism*
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Calcium / metabolism
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Calcium Signaling / drug effects
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Calcium Signaling / physiology
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Cell Line
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Cell Nucleus / genetics
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Cell Nucleus / metabolism
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Cyclic AMP Response Element-Binding Protein / genetics
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Cyclic AMP Response Element-Binding Protein / metabolism
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Cytosol / metabolism
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Enzyme Activation / drug effects
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Enzyme Activation / physiology
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / physiology
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Glucose / metabolism
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Glucose / pharmacology*
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Insulin Receptor Substrate Proteins / biosynthesis
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Insulin Receptor Substrate Proteins / genetics
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Insulin-Secreting Cells / cytology
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Insulin-Secreting Cells / metabolism*
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MAP Kinase Signaling System / drug effects
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MAP Kinase Signaling System / physiology
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Male
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Mice
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Mice, Knockout
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Mitogen-Activated Protein Kinase 1 / genetics
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3 / genetics
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Mitogen-Activated Protein Kinase 3 / metabolism*
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Phosphorylation / drug effects
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Phosphorylation / physiology
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Pituitary Adenylate Cyclase-Activating Polypeptide / genetics
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Pituitary Adenylate Cyclase-Activating Polypeptide / metabolism
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RNA, Messenger / biosynthesis
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RNA, Messenger / genetics
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / genetics
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / metabolism*
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Sweetening Agents / metabolism
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Sweetening Agents / pharmacology*
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Time Factors
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beta-Arrestin 1
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beta-Arrestins
Substances
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Adcyap1 protein, mouse
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Adcyap1r1 protein, mouse
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Arrb1 protein, mouse
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Arrestins
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Creb1 protein, mouse
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Cyclic AMP Response Element-Binding Protein
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Insulin Receptor Substrate Proteins
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Irs2 protein, mouse
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Pituitary Adenylate Cyclase-Activating Polypeptide
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RNA, Messenger
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
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Sweetening Agents
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beta-Arrestin 1
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beta-Arrestins
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Glucose
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Calcium