title: Scavenging of 14-3-3 proteins reveals their involvement in the cell-surface transport of ATP-sensitive K+ channels.
abstract: Arginine (Arg)-based endoplasmic reticulum (ER)-localization signals are involved in the quality control of different heteromultimeric membrane protein complexes. ATP-sensitive potassium (KATP) channels are unique because each subunit in the heterooctamer contains an Arg-based ER-localization signal. We have dissected the inactivation events that override the ER-localization activity of the eight peptide-sorting motifs. Employing a 14-3-3-scavenger construct to lower the availability of 14-3-3 proteins, we found that 14-3-3 proteins promote the cell-surface expression of heterologously expressed and native KATP channels. 14-3-3 proteins were detected in physical association with KATP channels in a pancreatic beta-cell line. Our results suggest that the Arg-based signal present in Kir6.2 is sterically masked by the SUR1 subunit. By contrast, 14-3-3 proteins functionally antagonized the Arg-based signal present in SUR1. The last ten amino acids were required for efficient 14-3-3 recruitment to multimeric forms of the Kir6.2 C-terminus. Channels containing a pore-forming subunit lacking these residues reached the cell surface inefficiently but were functionally indistinguishable from channels formed by the full-length subunits. In conclusion, 14-3-3 proteins promote the cell-surface transport of correctly assembled complexes but do not regulate the activity of KATP channels at the cell surface.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Heusser
authors.forename: Hebao
authors.initials: H
authors.lastname: Yuan
authors.forename: Ioana
authors.initials: I
authors.lastname: Neagoe
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Tarasov
authors.forename: Frances M
authors.initials: FM
authors.lastname: Ashcroft
authors.forename: Blanche
authors.initials: B
authors.lastname: Schwappach
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000378:metabolism; D015153:Blotting, Western; D019556:COS Cells; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D005260:Female; D015870:Gene Expression / Q000235:genetics; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014981:Xenopus; D000099161:Kcnj11 Channel
chemical_list: D048948:14-3-3 Proteins; D000255:Adenosine Triphosphate; D001120:Arginine; D008565:Membrane Proteins; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D000099161:Kcnj11 Channel