title: The cell surface expressed nucleolin is a glycoprotein that triggers calcium entry into mammalian cells.
abstract: Nucleolin is an ubiquitous nucleolar phosphoprotein involved in fundamental aspects of transcription regulation, cell proliferation and growth. It has also been described as a shuttling molecule between nucleus, cytosol and the cell surface. Several studies have demonstrated that surface nucleolin serves as a receptor for various extracellular ligands implicated in cell proliferation, differentiation, adhesion, mitogenesis and angiogenesis. Previously, we reported that nucleolin in the extranuclear cell compartment is a glycoprotein containing N- and O-glycans. In the present study, we show that glycosylation is an essential requirement for surface nucleolin expression, since it is prevented when cells are cultured in the presence of tunicamycin, an inhibitor of N-glycosylation. Accordingly, surface but not nuclear nucleolin is radioactively labeled upon metabolic labeling of cells with [(3)H]glucosamine. Besides its well-demonstrated role in the internalization of specific ligands, here we show that ligand binding to surface nucleolin could also induce Ca(2+) entry into cells. Indeed, by flow cytometry, microscopy and patch-clamp experiments, we show that the HB-19 pseudopeptide, which binds specifically surface nucleolin, triggers rapid and intense membrane Ca(2+) fluxes in various types of cells. The use of several drugs then indicated that Store-Operated Ca(2+) Entry (SOCE)-like channels are involved in the generation of these fluxes. Taken together, our findings suggest that binding of an extracellular ligand to surface nucleolin could be involved in the activation of signaling pathways by promoting Ca(2+) entry into cells.
authors.affiliation: Unité de Glycobiologie Structurale et Fonctionnelle, Unité Mixte de Recherche no 8576 du Centre National de la Recherche Scientifique, France.
authors.forename: Marie-Estelle
authors.initials: ME
authors.lastname: Losfeld
authors.forename: Diala El
authors.initials: DE
authors.lastname: Khoury
authors.forename: Pascal
authors.initials: P
authors.lastname: Mariot
authors.forename: Mathieu
authors.initials: M
authors.lastname: Carpentier
authors.forename: Bernard
authors.initials: B
authors.lastname: Krust
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Briand
authors.forename: Joël
authors.initials: J
authors.lastname: Mazurier
authors.forename: Ara G
authors.initials: AG
authors.lastname: Hovanessian
authors.forename: Dominique
authors.initials: D
authors.lastname: Legrand
mesh_terms: D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D017252:CD3 Complex / Q000276:immunology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D005944:Glucosamine / Q000378:metabolism; D006023:Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D014415:Tunicamycin / Q000494:pharmacology; D000097796:Nucleolin
chemical_list: D000906:Antibodies; D017252:CD3 Complex; D002118:Calcium; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004533:Egtazic Acid; D005944:Glucosamine; D006023:Glycoproteins; D010455:Peptides; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D014415:Tunicamycin; D000097796:Nucleolin; C121944:HB-19 peptide