title: Distinct ubiquitin-ligase complexes define convergent pathways for the degradation of ER proteins.
abstract: Many misfolded endoplasmic reticulum (ER) proteins are eliminated by ERAD, a process in which substrates are polyubiquitylated and moved into the cytosol for proteasomal degradation. We have identified in S. cerevisiae distinct ubiquitin-ligase complexes that define different ERAD pathways. Proteins with misfolded ER-luminal domains use the ERAD-L pathway, in which the Hrd1p/Hrd3p ligase forms a near stoichiometric membrane core complex by binding to Der1p via the linker protein Usa1p. This core complex associates through Hrd3p with Yos9p, a substrate recognition protein in the ER lumen. Substrates with misfolded intramembrane domains define a pathway (ERAD-M) that differs from ERAD-L by being independent of Usa1p and Der1p. Membrane proteins with misfolded cytosolic domains use the ERAD-C pathway and are directly targeted to the Doa10p ubiquitin ligase. All three pathways converge at the Cdc48p ATPase complex. These results lead to a unifying concept for ERAD that may also apply to mammalian cells.
authors.affiliation: Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Pedro
authors.initials: P
authors.lastname: Carvalho
authors.forename: Veit
authors.initials: V
authors.lastname: Goder
authors.forename: Tom A
authors.initials: TA
authors.lastname: Rapoport
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000074405:Valosin Containing Protein
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C098515:DER1 protein, S cerevisiae; C120810:EXO84 protein, S cerevisiae; D005656:Fungal Proteins; C104622:HRD3 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C495027:Yos9 protein, S cerevisiae; C104621:HRD1 protein, S cerevisiae; C091362:SSM4 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein; D008025:Ligases