title: A novel ER J-protein DNAJB12 accelerates ER-associated degradation of membrane proteins including CFTR.
abstract: Cytosolic Hsc70/Hsp70 are known to contribute to the endoplasmic reticulum (ER)-associated degradation of membrane proteins. However, at least in mammalian cells, its partner ER-localized J-protein for this cellular event has not been identified. Here we propose that this missing protein is DNAJB12. Protease protection assay and immunofluorescence study revealed that DNAJB12 is an ER-localized single membrane-spanning protein carrying a J-domain facing the cytosol. Using co-immunoprecipitation assay, we found that DNAJB12 is able to bind Hsc70 and thus can recruit Hsc70 to the ER membrane. Remarkably, cellular overexpression of DNAJB12 accelerated the degradation of misfolded membrane proteins including cystic fibrosis transmembrane conductance regulator (CFTR), but not a misfolded luminal protein. The DNAJB12-dependent degradation of CFTR was compromised by a proteasome inhibitor, lactacystin, suggesting that this process requires the ubiquitin-proteasome system. Conversely, knockdown of DNAJB12 expression attenuated the degradation of CFTR. Thus, DNAJB12 is a novel mammalian ER-localized J-protein that plays a vital role in the quality control of membrane proteins.
authors.affiliation: Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors.forename: Yo-hei
authors.initials: YH
authors.lastname: Yamamoto
authors.forename: Taiji
authors.initials: T
authors.lastname: Kimura
authors.forename: Shuku
authors.initials: S
authors.lastname: Momohara
authors.forename: Masato
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Tokio
authors.initials: T
authors.lastname: Tani
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kimata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kadokura
authors.forename: Kenji
authors.initials: K
authors.lastname: Kohno
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology*; D057809:HEK293 Cells; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D054730:Protein Interaction Domains and Motifs
chemical_list: C505032:CFTR protein, human; C494649:DNAJB12 protein, human; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator