Cav1.2 and Cav1.3 Are Differentially Coupled to Glucagon-Like Peptide-1 Potentiation of Glucose-Stimulated Insulin Secretion in the Pancreatic β-Cell Line INS-1

• Published in: The Journal of pharmacology and experimental therapeutics 2009-11, Vol.331 (2), p.724-732
• Main Authors: Jacobo, Sarah Melissa P., Guerra, Marcy L., Hockerman, Gregory H.
• Format: Article
• Language: English
• Subjects: Animals; Calcium Channel Blockers - pharmacology; Calcium Channels, L-Type - drug effects; Calcium Channels, L-Type - genetics; Calcium Channels, T-Type - drug effects; Calcium Channels, T-Type - genetics; Cell Line; Cyclic AMP-Dependent Protein Kinases - metabolism; Dihydropyridines - pharmacology; Endocrine and Diabetes; Gastric Inhibitory Polypeptide - pharmacology; Glucagon-Like Peptide 1 - pharmacology; Glucose - pharmacology; Indicators and Reagents; Insulin - metabolism; Insulin-Secreting Cells - drug effects; Insulin-Secreting Cells - metabolism; Mutation; Phosphatidylinositol 4,5-Diphosphate - metabolism; Phosphatidylinositol 4,5-Diphosphate - physiology; Plasmids - genetics; Potassium Chloride - pharmacology; Protein Kinase C - metabolism; Rats; Signal Transduction - drug effects; Stimulation, Chemical
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.109.158519

The incretin peptides, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), potentiate glucose-stimulated insulin secretion (GSIS) and β-cell proliferation and differentiation. Ca2+ influx via voltage-gated L-type Ca2+ channels is required for GLP-1 and GIP potentiation of GSIS. We investigated the role of the L-type Ca2+ channels Cav1.2 and Cav1.3 in mediating GLP-1- and GIP-stimulated events in INS-1 cells and INS-1 cell lines expressing dihydropyridine-insensitive (DHPi) mutants of either Cav1.2 or Cav1.3. Cav1.3/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 Cav1.2/DHPi channels was markedly reduced compared with untransfected INS-1 cells. In contrast, GIP (10 nM) potentiation of GSIS mediated by both Cav1.2/DHPi and Cav1.3/DHPi channels was similar to that observed in untransfected INS-1 cells. Disruption of intracellular Ca2+ 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 Cav1.3/DHPi channels and by endogenous L-type channels in INS-1 cells, but not by Cav1.2/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 Cav1.3/DHPi channels, but not by Cav1.2/DHPi channels. Thus, Cav1.3 is preferentially coupled to GLP-1 potentiation of GSIS in INS-1 cells via a mechanism that requires intact intracellular Ca2+ stores, PKA and PKC activity, and activation of ERK1/2.