title: Inhibiting endoplasmic reticulum (ER)-associated degradation of misfolded Yor1p does not permit ER export despite the presence of a diacidic sorting signal.
abstract: Capture of newly synthesized proteins into endoplasmic reticulum (ER)-derived coat protomer type II (COPII) vesicles represents a critical juncture in the quality control of protein biogenesis within the secretory pathway. The yeast ATP-binding cassette transporter Yor1p is a pleiotropic drug pump that shows homology to the human cystic fibrosis transmembrane conductance regulator (CFTR). Deletion of a phenylalanine residue in Yor1p, equivalent to the major disease-causing mutation in CFTR, causes ER retention and degradation via ER-associated degradation. We have examined the relationship between protein folding, ERAD and forward transport during Yor1p biogenesis. Uptake of Yor1p into COPII vesicles is mediated by an N-terminal diacidic signal that likely interacts with the "B-site" cargo-recognition domain on the COPII subunit, Sec24p. Yor1p-DeltaF is subjected to complex ER quality control involving multiple cytoplasmic chaperones and degradative pathways. Stabilization of Yor1p-DeltaF by inhibiting its degradation does not permit access of Yor1p-DeltaF to COPII vesicles. We propose that the ER quality control checkpoint engages misfolded Yor1p even after it has been stabilized by inhibition of the degradative pathway.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY 10027-6902, USA.
authors.forename: Silvere
authors.initials: S
authors.lastname: Pagant
authors.forename: Leslie
authors.initials: L
authors.lastname: Kung
authors.forename: Mariana
authors.initials: M
authors.lastname: Dorrington
authors.forename: Marcus C S
authors.initials: MC
authors.lastname: Lee
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Miller
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism*; D020816:Amino Acid Motifs; D022181:COP-Coated Vesicles / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D050505:Mutant Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C097077:YOR1 protein, S cerevisiae; C077072:UBC7 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes