title: ATP sensitivity of the ATP-sensitive K+ channel in intact and permeabilized pancreatic beta-cells.
abstract: ATP-sensitive K(+) channels (K(ATP) channels) couple cell metabolism to electrical activity and thereby to physiological processes such as hormone secretion, muscle contraction, and neuronal activity. However, the mechanism by which metabolism regulates K(ATP) channel activity, and the channel sensitivity to inhibition by ATP in its native environment, remain controversial. Here, we used alpha-toxin to permeabilize single pancreatic beta-cells and measure K(ATP) channel ATP sensitivity. We show that the channel ATP sensitivity is approximately sevenfold lower in the permeabilized cell than in the inside-out patch and that this is caused by interaction of Mg-nucleotides with the nucleotide-binding domains of the SUR1 subunit of the channel. The ATP sensitivity observed in permeabilized cells accounts quantitatively for K(ATP) channel activity in intact cells. Thus, our results show that the principal metabolic regulators of K(ATP) channel activity are MgATP and MgADP.
authors.affiliation: University Laboratory of Physiology, Oxford University, Oxford, OX1 3PT, UK.
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Tarasov
authors.forename: Christophe A J
authors.initials: CA
authors.lastname: Girard
authors.forename: Frances M
authors.initials: FM
authors.lastname: Ashcroft
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000187:drug effects / Q000502:physiology; D000214:Acyl Coenzyme A / Q000502:physiology; D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006460:Hemolysin Proteins; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011955:Receptors, Drug / Q000187:drug effects / Q000502:physiology; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel
chemical_list: D018528:ATP-Binding Cassette Transporters; D000214:Acyl Coenzyme A; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D001427:Bacterial Toxins; D005947:Glucose; D006460:Hemolysin Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577508:Abcc8 protein, mouse; C021091:staphylococcal alpha-toxin