title: Signal-dependent export of GABA transporter 1 from the ER-Golgi intermediate compartment is specified by a C-terminal motif.
abstract: The C-terminus of GABA transporter 1 (GAT1, SLC6A1) is required for trafficking of the protein through the secretory pathway to reach its final destination, i.e. the rim of the synaptic specialization. We identified a motif of three hydrophobic residues (569VMI571) that was required for export of GAT1 from the ER-Golgi intermediate compartment (ERGIC). This conclusion was based on the following observations: (i) GAT1-SSS, the mutant in which 569VMI571 was replaced by serine residues, was exported from the ER in a COPII-dependent manner but accumulated in punctate structures and failed to reach the Golgi; (ii) under appropriate conditions (imposing a block at 15 degrees C, disruption of COPI), these structures also contained ERGIC53; (iii) the punctae were part of a dynamic compartment, because it was accessible to a second anterograde cargo [the temperature-sensitive variant of vesicular stomatitis virus G protein (VSV-G)] and because GAT1-SSS could be retrieved from the punctate structures by addition of a KKxx-based retrieval motif, which supported retrograde transport to the ER. To the best of our knowledge, the VMI-motif of GAT1 provides the first example of a cargo-based motif that specifies export from the ERGIC.
authors.affiliation: Institute of Pharmacology, Center of Biomolecular Medicine and Pharmacology, Medical University of Vienna, Waehringer Str. 13a, 1090 Vienna, Austria.
authors.forename: Hesso
authors.initials: H
authors.lastname: Farhan
authors.forename: Veronika
authors.initials: V
authors.lastname: Reiterer
authors.forename: Alexander
authors.initials: A
authors.lastname: Kriz
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Hauri
authors.forename: Margit
authors.initials: M
authors.lastname: Pavelka
authors.forename: Harald H
authors.initials: HH
authors.lastname: Sitte
authors.forename: Michael
authors.initials: M
authors.lastname: Freissmuth
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002478:Cells, Cultured; D004151:Dipeptides / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D050485:GABA Plasma Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008969:Molecular Sequence Data; D009474:Neurons / Q000737:chemistry; D021381:Protein Transport; D051381:Rats; D012694:Serine / Q000235:genetics; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D015415:Biomarkers; D004151:Dipeptides; D050485:GABA Plasma Membrane Transport Proteins; D033921:Vesicular Transport Proteins; D012694:Serine; C024575:lysyllysine