title: Cav1.2 and Cav1.3 are differentially coupled to glucagon-like peptide-1 potentiation of glucose-stimulated insulin secretion in the pancreatic beta-cell line INS-1.
abstract: The incretin peptides, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), potentiate glucose-stimulated insulin secretion (GSIS) and beta-cell proliferation and differentiation. Ca(2+) influx via voltage-gated L-type Ca(2+) channels is required for GLP-1 and GIP potentiation of GSIS. We investigated the role of the L-type Ca(2+) channels Ca(v)1.2 and Ca(v)1.3 in mediating GLP-1- and GIP-stimulated events in INS-1 cells and INS-1 cell lines expressing dihydropyridine-insensitive (DHPi) mutants of either Ca(v)1.2 or Ca(v)1.3. Ca(v)1.3/DHPi channels supported full potentiation of GSIS by GLP-1 (50 nM) compared with untransfected INS-1 cells. However, GLP-1-potentiated GSIS mediated by Ca(v)1.2/DHPi channels was markedly reduced compared with untransfected INS-1 cells. In contrast, GIP (10 nM) potentiation of GSIS mediated by both Ca(v)1.2/DHPi and Ca(v)1.3/DHPi channels was similar to that observed in untransfected INS-1 cells. Disruption of intracellular Ca(2+) release with thapsigargin, ryanodine, or 2-aminoethyldiphenylborate and inhibition of protein kinase A (PKA) or protein kinase C (PKC) significantly reduced GLP-1 potentiation of GSIS by Ca(v)1.3/DHPi channels and by endogenous L-type channels in INS-1 cells, but not by Ca(v)1.2/DHPi channels. Inhibition of glucose-stimulated phospholipase C activity with 1-(6-((17b-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122) did not inhibit potentiation of GSIS by GLP-1 in INS-1 cells. In contrast, wortmannin, an inhibitor of phosphatidylinositol 3-kinase, and 2'-amino-3'-methoxyflavone (PD98059), an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase, both markedly inhibited GLP-1 potentiation of GSIS by endogenous channels in INS-1 cells and Ca(v)1.3/DHPi channels, but not by Ca(v)1.2/DHPi channels. Thus, Ca(v)1.3 is preferentially coupled to GLP-1 potentiation of GSIS in INS-1 cells via a mechanism that requires intact intracellular Ca(2+) stores, PKA and PKC activity, and activation of ERK1/2.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Sarah Melissa P
authors.initials: SM
authors.lastname: Jacobo
authors.forename: Marcy L
authors.initials: ML
authors.lastname: Guerra
authors.forename: Gregory H
authors.initials: GH
authors.lastname: Hockerman
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000235:genetics; D020747:Calcium Channels, T-Type / Q000187:drug effects* / Q000235:genetics; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004095:Dihydropyridines / Q000494:pharmacology; D005749:Gastric Inhibitory Polypeptide / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D007202:Indicators and Reagents; D007328:Insulin / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism / Q000502:physiology; D010957:Plasmids / Q000235:genetics; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013268:Stimulation, Chemical
chemical_list: C500994:Cacna1g protein, rat; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D004095:Dihydropyridines; D007202:Indicators and Reagents; D007328:Insulin; C419385:L-type calcium channel alpha(1C); D019269:Phosphatidylinositol 4,5-Diphosphate; D005749:Gastric Inhibitory Polypeptide; D011189:Potassium Chloride; D052216:Glucagon-Like Peptide 1; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D005947:Glucose