title: Prohibitin: A Novel Molecular Player in KDEL Receptor Signalling.
abstract: The KDEL receptor (KDELR) is a seven-transmembrane-domain protein involved in retrograde transport of protein chaperones from the Golgi complex to the endoplasmic reticulum. Our recent findings have shown that the Golgi-localised KDELR acts as a functional G-protein-coupled receptor by binding to and activating Gs and Gq. These G proteins induce activation of PKA and Src and regulate retrograde and anterograde Golgi trafficking. Here we used an integrated coimmunoprecipitation and mass spectrometry approach to identify prohibitin-1 (PHB) as a KDELR interactor. PHB is a multifunctional protein that is involved in signal transduction, cell-cycle control, and stabilisation of mitochondrial proteins. We provide evidence that depletion of PHB induces intense membrane-trafficking activity at the ER-Golgi interface, as revealed by formation of GM130-positive Golgi tubules, and recruitment of p115, β-COP, and GBF1 to the Golgi complex. There is also massive recruitment of SEC31 to endoplasmic-reticulum exit sites. Furthermore, absence of PHB decreases the levels of the Golgi-localised KDELR, thus preventing KDELR-dependent activation of Golgi-Src and inhibiting Golgi-to-plasma-membrane transport of VSVG. We propose a model whereby in analogy to previous findings (e.g., the RAS-RAF signalling pathway), PHB can act as a signalling scaffold protein to assist in KDELR-dependent Src activation.
authors.affiliation: Department of Cellular and Translational Pharmacology, Fondazione Mario Negri Sud, 66030 Santa Maria Imbaro, Italy ; Department of Cell Biology & Signalling, The FIRC Institute of Molecular Oncology (IFOM), 20139 Milan, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Giannotta
authors.affiliation: Department of Cellular and Translational Pharmacology, Fondazione Mario Negri Sud, 66030 Santa Maria Imbaro, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Fragassi
authors.affiliation: Proteomic Core Facility, Fondazione Mario Negri Sud, 66030 Santa Maria Imbaro, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Tamburro
authors.affiliation: Department of Cellular and Translational Pharmacology, Fondazione Mario Negri Sud, 66030 Santa Maria Imbaro, Italy.
authors.forename: Capone
authors.initials: C
authors.lastname: Vanessa
authors.affiliation: Institute of Protein Biochemistry, National Research Council and Telethon Institute of Genetics and Medicine, 80131 Naples, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Luini
authors.affiliation: Department of Cellular and Translational Pharmacology, Fondazione Mario Negri Sud, 66030 Santa Maria Imbaro, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Sallese
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D000091402:Prohibitins; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics*; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases / Q000235:genetics*
chemical_list: C064459:KDEL receptor; C000717328:PHB protein, human; D000091402:Prohibitins; D018000:Receptors, Peptide; D012097:Repressor Proteins; D019061:src-Family Kinases