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Using the MIN6 B-cell line, we investigated the hypothesis that miniglucagon, the C-terminal () fragment processed from glucagon and present in pancreatic A cells, modulates insulin release, and we analyzed its cellular mode of action. We show that, at concentrations ranging from 0.01 to 1000 pM, miniglucagon dose-dependently (ID50 = 1 pM) inhibited by 80-100% the insulin release triggered by glucose, glucagon, glucagon-like peptide-1-(7-36) amide (tGLP-1), or glibenclamide, but not that induced by carbachol. Miniglucagon had no significant effects on cellular cAMP levels. The increase in 45Ca2+ uptake induced by depolarizing agents (glucose or extracellular K+), by glucagon, or by the Ca2+channel agonist Bay K-8644 was blocked by miniglucagon at the doses active on insulin release. Electrophysiological experiments indicated that miniglucagon induces membrane hyperpolarization, probably by opening potassium channels, which terminated glucose-induced electrical activity. Pretreatment with pertussis toxin abolished the effects of miniglucagon on insulin release. It is concluded that miniglucagon is a highly potent and efficient inhibitor of insulin release by closing, via hyperpolarization, voltage-dependent Ca2+ channels linked to a pathway involving a pertussis toxin-sensitive G protein.


Journal article


J Biol Chem

Publication Date





10869 - 10876


Calcium, Calcium Channels, Cell Line, Cholinergic Agonists, Cyclic AMP, Glucagon, Glucagon-Like Peptide 1, Glucagon-Like Peptides, Glucose, Insulin, Insulin Antagonists, Ion Transport, Islets of Langerhans, Membrane Potentials, Peptide Fragments, Peptides, Pertussis Toxin, Virulence Factors, Bordetella