title: Sequential quality-control checkpoints triage misfolded cystic fibrosis transmembrane conductance regulator.
abstract: Cystic fibrosis arises from the misfolding and premature degradation of CFTR Delta F508, a Cl- ion channel with a single amino acid deletion. Yet, the quality-control machinery that selects CFTR Delta F508 for degradation and the mechanism for its misfolding are not well defined. We identified an ER membrane-associated ubiquitin ligase complex containing the E3 RMA1, the E2 Ubc6e, and Derlin-1 that cooperates with the cytosolic Hsc70/CHIP E3 complex to triage CFTR and CFTR Delta F508. Derlin-1 serves to retain CFTR in the ER membrane and interacts with RMA1 and Ubc6e to promote CFTR's proteasomal degradation. RMA1 is capable of recognizing folding defects in CFTR Delta F508 coincident with translation, whereas the CHIP E3 appears to act posttranslationally. A folding defect in CFTR Delta F508 detected by RMA1 involves the inability of CFTR's second membrane-spanning domain to productively interact with amino-terminal domains. Thus, the RMA1 and CHIP E3 ubiquitin ligases act sequentially in ER membrane and cytosol to monitor the folding status of CFTR and CFTR Delta F508.
authors.affiliation: Department of Cell and Developmental Biology, UNC-Chapel Hill School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Younger
authors.forename: Liling
authors.initials: L
authors.lastname: Chen
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Ren
authors.forename: Meredith F N
authors.initials: MF
authors.lastname: Rosser
authors.forename: Emma L
authors.initials: EL
authors.lastname: Turnbull
authors.forename: Chun-Yang
authors.initials: CY
authors.lastname: Fan
authors.forename: Cam
authors.initials: C
authors.lastname: Patterson
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Cyr
mesh_terms: D002460:Cell Line; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D017510:Protein Folding; D011499:Protein Processing, Post-Translational / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: C487709:DERL1 protein, human; D004268:DNA-Binding Proteins; D050883:HSC70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C082461:UBC6 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; C111501:RNF5 protein, human; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases