title: Nucleophosmin and nucleolin regulate K-Ras plasma membrane interactions and MAPK signal transduction.
abstract: The spatial organization of Ras proteins into nanoclusters on the inner leaflet of the plasma membrane is essential for high fidelity signaling through the MAPK pathway. Here we identify two selective regulators of K-Ras nanoclustering from a proteomic screen for K-Ras interacting proteins. Nucleophosmin (NPM) and nucleolin are predominantly localized to the nucleolus but also have extranuclear functions. We show that a subset of NPM and nucleolin localizes to the inner leaflet of plasma membrane and forms specific complexes with K-Ras but not other Ras isoforms. Active GTP-loaded and inactive GDP-loaded K-Ras both interact with NPM, although NPM-K-Ras binding is increased by growth factor receptor activation. NPM and nucleolin both stabilize K-Ras levels on the plasma membrane, but NPM concurrently increases the clustered fraction of GTP-K-Ras. The increase in nanoclustered GTP-K-Ras in turn enhances signal gain in the MAPK pathway. In summary these results reveal novel extranucleolar functions for NPM and nucleolin as regulators of K-Ras nanocluster formation and activation of the MAPK pathway. The study also identifies a new class of K-Ras nanocluster regulator that operates independently of the structural scaffold galectin-3.
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Kerry L
authors: KL
authors: Inder
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Chiyan
authors: C
authors: Lau
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia; Diamantina Institute for Cancer, Immunology and Metabolic Medicine, Princess Alexandra Hospital, University of Queensland, Brisbane 4102, Australia.
authors: Dorothy
authors: D
authors: Loo
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Natasha
authors: N
authors: Chaudhary
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Andrew
authors: A
authors: Goodall
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Sally
authors: S
authors: Martin
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia.
authors: Alun
authors: A
authors: Jones
authors: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas 77030.
authors: Dharini
authors: D
authors: van der Hoeven
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia; Centre for Microscopy and Microanalysis, University of Queensland, Brisbane 4072, Australia.
authors: Robert G
authors: RG
authors: Parton
authors: Institute for Molecular Bioscience, University of Queensland, Brisbane 4072, Australia; Diamantina Institute for Cancer, Immunology and Metabolic Medicine, Princess Alexandra Hospital, University of Queensland, Brisbane 4102, Australia. Electronic address: m.hill2@uq.edu.au.
authors: Michelle M
authors: MM
authors: Hill
authors: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas 77030. Electronic address: john.f.hancock@uth.tmc.edu.
authors: John F
authors: JF
authors: Hancock
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D006224:Cricetinae; D003412:Cricetulus; D011905:Genes, ras; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*; D000097796:Nucleolin
chemical_list: D020928:Mitogen-Activated Protein Kinases; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D018631:ras Proteins; D000097796:Nucleolin; C000716967:NPM1 protein, human