title: The tissue-specific Rep8/UBXD6 tethers p97 to the endoplasmic reticulum membrane for degradation of misfolded proteins.
abstract: The protein known as p97 or VCP in mammals and Cdc48 in yeast is a versatile ATPase complex involved in several biological functions including membrane fusion, protein folding, and activation of membrane-bound transcription factors. In addition, p97 plays a central role in degradation of misfolded secretory proteins via the ER-associated degradation pathway. This functional diversity of p97 depends on its association with various cofactors, and to further our understanding of p97 function it is important that these cofactors are identified and analyzed. Here, we isolate and characterize the human protein named Rep8 or Ubxd6 as a new cofactor of p97. Mouse Rep8 is highly tissue-specific and abundant in gonads. In testes, Rep8 is expressed in post-meiotic round spermatids, whereas in ovaries Rep8 is expressed in granulosa cells. Rep8 associates directly with p97 via its UBX domain. We show that Rep8 is a transmembrane protein that localizes to the ER membrane with its UBX domain facing the cytoplasm. Knock-down of Rep8 expression in human cells leads to a decreased association of p97 with the ER membrane and concomitantly a retarded degradation of misfolded ER-derived proteasome substrates. Thus, Rep8 tethers p97 to the ER membrane for efficient ER-associated degradation.
authors.affiliation: Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Louise
authors.initials: L
authors.lastname: Madsen
authors.forename: Franziska
authors.initials: F
authors.lastname: Kriegenburg
authors.forename: Andrea
authors.initials: A
authors.lastname: Vala
authors.forename: Diana
authors.initials: D
authors.lastname: Best
authors.forename: Søren
authors.initials: S
authors.lastname: Prag
authors.forename: Kay
authors.initials: K
authors.lastname: Hofmann
authors.forename: Michael
authors.initials: M
authors.lastname: Seeger
authors.forename: Ian R
authors.initials: IR
authors.lastname: Adams
authors.forename: Rasmus
authors.initials: R
authors.lastname: Hartmann-Petersen
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D060746:Endoplasmic Reticulum-Associated Degradation; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D008545:Melanoma / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D000074405:Valosin Containing Protein
chemical_list: D018797:Cell Cycle Proteins; D011506:Proteins; D012333:RNA, Messenger; C104829:UBXN8 protein, human; D025801:Ubiquitin; C482345:SYVN1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein; C000614179:Vcp protein, mouse