The Rab GTPase Ypt1p and tethering factors couple protein sorting at the ER to vesicle targeting to the Golgi apparatus.
GPI-anchored proteins exit the ER in distinct vesicles from other secretory proteins, and this sorting event can be reproduced in vitro. When extracts from a uso1 mutant were used, the sorting of GPI-anchored proteins from other secretory proteins was defective. Complementation with purified Uso1p restored sorting. The Rab GTPase Ypt1p and the tethering factors Sec34p and Sec35p, but not Bet3p, a member of the TRAPP complex, were also required for protein sorting upon ER exit. Therefore, the Ypt1p tethering complex couples protein sorting in the ER to vesicle targeting to the Golgi apparatus. Sorting of GPI-anchored proteins from other secretory proteins was also observed in vivo. The sorting defect observed in vitro with uso1 and ypt1 mutants was reproduced in vivo.
Morsomme
Pierre
P
Biozentrum of the University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Riezman
Howard
H
D033942:Adaptor Proteins, Vesicular Transport; D026905:Amino Acid Transport Systems; D002352:Carrier Proteins / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
D033942:Adaptor Proteins, Vesicular Transport; D026905:Amino Acid Transport Systems; C112749:COG2 protein, S cerevisiae; C401396:COG3 protein, S cerevisiae; D002352:Carrier Proteins; D005656:Fungal Proteins; C491145:GAP1 protein, S cerevisiae; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C086888:USO1 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D020703:ras GTPase-Activating Proteins; C406327:transport protein particle, TRAPP; C060755:YPT1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins