title: A role of the sulfonylurea receptor 1 in endocytic trafficking of ATP-sensitive potassium channels.
abstract: The ATP-sensitive potassium (K(ATP) ) channel consisting of sulfonylurea receptor 1 (SUR1) and inward-rectifier potassium channel 6.2 (Kir6.2) has a well-established role in insulin secretion. Mutations in either subunit can lead to disease due to aberrant channel gating, altered channel density at the cell surface or a combination of both. Endocytic trafficking of channels at the plasma membrane is one way to influence surface channel numbers. It has been previously reported that channel endocytosis is dependent on a tyrosine-based motif in Kir6.2, while SUR1 alone is unable to internalize. In this study, we followed endocytic trafficking of surface channels in real time by live-cell imaging of channel subunits tagged with an extracellular minimal α-bungarotoxin-binding peptide labeled with a fluorescent dye. We show that SUR1 undergoes endocytosis independent of Kir6.2. Moreover, mutations in the putative endocytosis motif of Kir6.2, Y330C, Y330A and F333I are unable to prevent channel endocytosis. These findings challenge the notion that Kir6.2 bears the sole endocytic signal for K(ATP) channels and support a role of SUR1 in this trafficking process.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239, USA. cathrin.bruederle@gmail.com
authors.forename: Cathrin E
authors.initials: CE
authors.lastname: Bruederle
authors.forename: Joel
authors.initials: J
authors.lastname: Gay
authors.forename: Show-Ling
authors.initials: SL
authors.lastname: Shyng
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000378:metabolism; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D009154:Mutation; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism*; D064233:Sulfonylurea Receptors; D014168:Transferrin / Q000378:metabolism; D000099161:Kcnj11 Channel
chemical_list: D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate; D002038:Bungarotoxins; D002966:Clathrin; D034281:Dynamins; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D014168:Transferrin; D000099161:Kcnj11 Channel