title: ATP modulates interaction of syntaxin-1A with sulfonylurea receptor 1 to regulate pancreatic beta-cell KATP channels.
abstract: ATP-sensitive potassium (K(ATP)) channels are regulated by a variety of cytosolic factors (adenine nucleotides, Mg(2+), phospholipids, and pH). We previously reported that K(ATP) channels are also regulated by endogenous membrane-bound SNARE protein syntaxin-1A (Syn-1A), which binds both nucleotide-binding folds of sulfonylurea receptor (SUR)1 and 2A, causing inhibition of K(ATP) channel activity in pancreatic islet β-cells and cardiac myocytes, respectively. In this study, we show that ATP dose-dependently inhibits Syn-1A binding to SUR1 at physiological concentrations, with the addition of Mg(2+) causing a decrease in the ATP-induced inhibitory effect. This ATP disruption of Syn-1A binding to SUR1 was confirmed by FRET analysis in living HEK293 cells. Electrophysiological studies in pancreatic β-cells demonstrated that reduced ATP concentrations increased K(ATP) channel sensitivity to Syn-1A inhibition. Depletion of endogenous Syn-1A in insulinoma cells by botulinum neurotoxin C1 proteolysis followed by rescue with exogenous Syn-1A showed that Syn-1A modulates K(ATP) channel sensitivity to ATP. Thus, our data indicate that although both ATP and Syn-1A independently inhibit β-cell K(ATP) channel gating, they could also influence the sensitivity of K(ATP) channels to each other. These findings provide new insight into an alternate mechanism by which ATP regulates pancreatic β-cell K(ATP) channel activity, not only by its direct actions on Kir6.2 pore subunit, but also via ATP modulation of Syn-1A binding to SUR1.
authors.affiliation: Department of Medicine, University of Toronto and University Health Network, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Youhou
authors.initials: Y
authors.lastname: Kang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Liang
authors.forename: Yuk-Man
authors.initials: YM
authors.lastname: Leung
authors.forename: Betty
authors.initials: B
authors.lastname: Ng
authors.forename: Huanli
authors.initials: H
authors.lastname: Xie
authors.forename: Nathan
authors.initials: N
authors.lastname: Chang
authors.forename: Joseph
authors.initials: J
authors.lastname: Chan
authors.forename: Show-Ling
authors.initials: SL
authors.lastname: Shyng
authors.forename: Robert G
authors.initials: RG
authors.lastname: Tsushima
authors.forename: Herbert Y
authors.initials: HY
authors.lastname: Gaisano
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology; D051379:Mice; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism*; D064233:Sulfonylurea Receptors; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: C577507:ABCC8 protein, human; D018528:ATP-Binding Cassette Transporters; C577508:Abcc8 protein, mouse; C577509:Abcc8 protein, rat; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; C494212:STX1A protein, human; C494214:Stx1a protein, mouse; C494213:Stx1a protein, rat; D064233:Sulfonylurea Receptors; D050827:Syntaxin 1; D000255:Adenosine Triphosphate