title: ERp46 binds to AdipoR1, but not AdipoR2, and modulates adiponectin signalling.
abstract: The pleiotropic effects of the insulin-sensitizing adipokine adiponectin are mediated, at least in part, by two seven-transmembrane domain receptors AdipoR1 and AdipoR2. Recent reports indicate a role for AdipoR-binding proteins, namely APPL1, RACK1 and CK2beta, in proximal signal transduction events. Here we demonstrate that endoplasmic reticulum protein 46 (ERp46) interacts specifically with AdipoR1 and provide evidence that ERp46 modulates adiponectin signalling. Co-immunoprecipitation followed by mass spectrometry identified ERp46 as an AdipoR1-, but not AdipoR2-, interacting protein. Analysis of truncated constructs and GST-fusion proteins revealed the interaction was mediated by the cytoplasmic, N-terminal residues (1-70) of AdipoR1. Indirect immunofluorescence microscopy and subcellular fractionation studies demonstrated that ERp46 was present in the ER and the plasma membrane (PM). Transient knockdown of ERp46 increased the levels of AdipoR1, and AdipoR2, at the PM and this correlated with increased adiponectin-stimulated phosphorylation of AMPK. In contrast, adiponectin-stimulated phosphorylation of p38MAPK was reduced following ERp46 knockdown. Collectively these results establish ERp46 as the first AdipoR1-specific interacting protein and suggest a role for ERp46 in adiponectin receptor biology and adiponectin signalling.
authors.affiliation: Diamantina Institute for Cancer, Immunology and Metabolic Medicine, University of Queensland, Princess Alexandra Hospital, Brisbane, QLD 4102, Australia.
authors.forename: Hayley K
authors.initials: HK
authors.lastname: Charlton
authors.forename: Julie
authors.initials: J
authors.lastname: Webster
authors.forename: Sarah
authors.initials: S
authors.lastname: Kruger
authors.forename: Fiona
authors.initials: F
authors.lastname: Simpson
authors.forename: Ayanthi A
authors.initials: AA
authors.lastname: Richards
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Whitehead
mesh_terms: D052242:Adiponectin / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism*; D025941:Protein Interaction Mapping; D054419:Receptors, Adiponectin / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D052242:Adiponectin; D054419:Receptors, Adiponectin; D019704:Protein Disulfide-Isomerases; C480743:TXNDC5 protein, human