title: Identification of molecular regions responsible for the membrane trafficking of Kir6.2.
abstract: The subunits of the pancreatic ATP-sensitive potassium channel Kir6.2 and the sulphonylurea receptor (SUR1) contain endoplasmic reticulum (ER) retention signals (RKR), which prevent their plasma membrane expression when expressed individually. When co-expressed, however, these signals are masked and the complex traffics to the plasma membrane. To investigate this further, we have expressed epitope-tagged chimaeras between Kir6.2 and Kir2.1 (which traffics to the membrane independently of SUR1) in Xenopus oocytes alone and together with SUR1. By staining sections of the oocytes, we show that, in addition to the ER retention signal present in the distal C-terminus, the M2 transmembrane and the proximal C-terminal regions also contribute to the inability of Kir6.2 to traffic to the membrane in the absence of SUR1. Furthermore, by staining the whole oocytes for the hexa-histidine tag attached to the N-terminus of SUR1, we provide direct experimental evidence that the N-terminus of SUR1 is extracellular.
authors.affiliation: School of Biomedical Sciences, University of Leeds, UK.
authors.forename: E
authors.initials: E
authors.lastname: Hough
authors.forename: D J
authors.initials: DJ
authors.lastname: Beech
authors.forename: A
authors.initials: A
authors.lastname: Sivaprasadarao
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000235:genetics; D019556:COS Cells; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D004594:Electrophysiology; D000939:Epitopes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D005905:Glyburide / Q000378:metabolism / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D009865:Oocytes / Q000502:physiology; D010179:Pancreas / Q000737:chemistry / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014316:Tritium; D014981:Xenopus
chemical_list: D000939:Epitopes; D007004:Hypoglycemic Agents; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D014316:Tritium; D005905:Glyburide