title: The ER v-SNAREs are required for GPI-anchored protein sorting from other secretory proteins upon exit from the ER.
abstract: Glycosylphosphatidylinositol (GPI)-anchored proteins exit the ER in distinct vesicles from other secretory proteins, and this sorting event requires the Rab GTPase Ypt1p, tethering factors Uso1p, and the conserved oligomeric Golgi complex. Here we show that proper sorting depended on the vSNAREs, Bos1p, Bet1p, and Sec22p. However, the t-SNARE Sed5p was not required for protein sorting upon ER exit. Moreover, the sorting defect observed in vitro with bos1-1 extracts was also observed in vivo and was visualized by EM. Finally, transport and maturation of the GPI-anchored protein Gas1p was specifically affected in a bos1-1 mutant at semirestrictive temperature. Therefore, we propose that v-SNAREs are part of the cargo protein sorting machinery upon exit from the ER and that a correct sorting process is necessary for proper maturation of GPI-anchored proteins.
authors.affiliation: Biozentrum of the University of Basel, Basel, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Morsomme
authors.forename: Cristina
authors.initials: C
authors.lastname: Prescianotto-Baschong
authors.forename: Howard
authors.initials: H
authors.lastname: Riezman
mesh_terms: D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D005057:Eukaryotic Cells / Q000378:metabolism* / Q000648:ultrastructure; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D009154:Mutation / Q000235:genetics; D021381:Protein Transport / Q000235:genetics*; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface / Q000378:metabolism; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D022161:Transport Vesicles / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D033921:Vesicular Transport Proteins
chemical_list: C107845:BET1 protein, S cerevisiae; C068037:BOS1 protein, S cerevisiae; C066709:GAS1 protein, S cerevisiae; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C106909:Sec22 protein, S cerevisiae; D033921:Vesicular Transport Proteins