title: Glucagon-like peptide-1 mobilizes intracellular Ca2+ and stimulates mitochondrial ATP synthesis in pancreatic MIN6 beta-cells.
abstract: Glucagon-like peptide-1 (GLP-1) is a potent regulator of glucose-stimulated insulin secretion whose mechanisms of action are only partly understood. In the present paper, we show that at low (3 mM) glucose concentrations, GLP-1 increases the free intramitochondrial concentrations of both Ca(2+) ([Ca(2+)](m)), and ATP ([ATP](m)) in clonal MIN6 beta-cells. Suggesting that cAMP-mediated release of Ca(2+) from intracellular stores is responsible for these effects, increases in [ATP](m) that were induced by GLP-1 were completely blocked by the Rp isomer of adenosine-3',5'-cyclic monophosphothioate (Rp-cAMPS), or by chelation of intracellular Ca(2+). Furthermore, inhibition of Ins(1,4,5) P (3) (IP(3)) receptors with xestospongin C, or application of ryanodine, partially inhibited GLP-1-induced [ATP](m) increases, and the simultaneous blockade of both IP(3) and ryanodine receptors (RyR) completely eliminated the rise in [ATP](m). GLP-1 appeared to prompt Ca(2+)-induced Ca(2+) release through IP(3) receptors via a protein kinase A (PKA)-mediated phosphorylation event, since ryanodine-insensitive [ATP](m) increases were abrogated with the PKA inhibitor, H89. In contrast, the effects of GLP-1 on RyR-mediated [ATP](m) increases were apparently mediated by the cAMP-regulated guanine nucleotide exchange factor cAMP-GEFII, since xestospongin C-insensitive [ATP](m) increases were blocked by a dominant-negative form of cAMP-GEFII (G114E,G422D). Taken together, these results demonstrate that GLP-1 potentiates glucose-stimulated insulin release in part via the mobilization of intracellular Ca(2+), and the stimulation of mitochondrial ATP synthesis.
authors.affiliation: Henry Wellcome Laboratories for Integrated Cell Signalling, Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuboi
authors.forename: Gabriela
authors.initials: G
authors.lastname: da Silva Xavier
authors.forename: George G
authors.initials: GG
authors.lastname: Holz
authors.forename: Laurence S
authors.initials: LS
authors.lastname: Jouaville
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Thomas
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rutter
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002614:Chelating Agents / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D047028:Macrocyclic Compounds; D008928:Mitochondria / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D011498:Protein Precursors / Q000494:pharmacology*; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D007328:Insulin; D047028:Macrocyclic Compounds; D010080:Oxazoles; D010446:Peptide Fragments; D011498:Protein Precursors; D019837:Ryanodine Receptor Calcium Release Channel; D013873:Thionucleotides; C108644:xestospongin A; D012433:Ryanodine; D005576:Colforsin; C016957:adenosine-3',5'-cyclic phosphorothioate; D004533:Egtazic Acid; D052216:Glucagon-Like Peptide 1; D000255:Adenosine Triphosphate; D002217:Carbachol; D005934:Glucagon; D000242:Cyclic AMP; D005947:Glucose; D003981:Diazoxide; D002118:Calcium