title: Role of p97 AAA-ATPase in the retrotranslocation of the cholera toxin A1 chain, a non-ubiquitinated substrate.
abstract: The enzymatic A1 chain of cholera toxin retrotranslocates across the endoplasmic reticulum membrane into the cytosol, where it induces toxicity. Almost all other retrotranslocation substrates are modified by the attachment of polyubiquitin chains and moved into the cytosol by the ubiquitin-interacting p97 ATPase complex. The cholera toxin A1 chain, however, can induce toxicity in the absence of ubiquitination, and the motive force that drives retrotranslocation is not known. Here, we use adenovirus expressing dominant-negative mutants of p97 to test whether p97 is required for toxin action. We find that cholera toxin still functions with only a small decrease in potency in cells that cannot retrotranslocate other substrates at all. These results suggest that p97 does not provide the primary driving force for extracting the A1 chain from the endoplasmic reticulum, a finding that is consistent with a requirement for polyubiquitination in p97 function.
authors.affiliation: GI Cell Biology, Children's Hospital Boston, the Harvard Digestive Diseases Center, Harvard Medical School, Massachusetts 02115, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Kothe
authors.forename: Yihong
authors.initials: Y
authors.lastname: Ye
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Wagner
authors.forename: Heidi E
authors.initials: HE
authors.lastname: De Luca
authors.forename: Eli
authors.initials: E
authors.lastname: Kern
authors.forename: Tom A
authors.initials: TA
authors.lastname: Rapoport
authors.forename: Wayne I
authors.initials: WI
authors.lastname: Lencer
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000502:physiology*; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001254:Astrocytoma / Q000378:metabolism; D019556:COS Cells; D045744:Cell Line, Tumor; D002772:Cholera Toxin / Q000737:chemistry* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005799:Genes, Dominant; D005805:Genes, MHC Class I / Q000235:genetics; D006801:Humans; D047468:Immunoprecipitation; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000502:physiology*; D011485:Protein Binding; D017510:Protein Folding; D021381:Protein Transport; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D025801:Ubiquitin; D002772:Cholera Toxin; D000242:Cyclic AMP; D000251:Adenosine Triphosphatases; C404942:p97 ATPase