title: Inhibition of receptor-dependent urokinase signaling by specific Ser to Glu substitutions.
abstract: We have previously reported that phosphorylation of human urokinase on Ser138/303 abolishes its catalytic-independent motogen and proadhesive abilities, whereas receptor binding is not affected. Here we show that substitution of the two relevant serines with glutamic acid residues impairs the ability of urokinase to mobilize a variety of human and mouse cell lines as well as human primary T lymphocytes. Accordingly, urokinase receptor-dependent signaling, leading to cytoskeletal rearrangements and paxillin re-distribution, does not occur in MCF-7 breast carcinoma cells exposed to 'phosphorylation-like' urokinase. Unlike the wild-type form, di-substituted urokinase is unable to induce the physical association of urokinase receptor with alphavbeta5 vitronectin receptor, which is required for MCF-7 urokinase-dependent cell migration. Finally, the di-substituted variant fails to activate p55fgr, a member of the Src tyrosine kinase family, which mediates cell migration and adhesion of U937 myelomonocytic cells. In conclusion, the finding that specific amino acid substitutions strongly interfere with the ability of urokinase to stimulate cell migration, and the associated intracellular events uncover a novel way to regulate urokinase receptor-dependent signaling.
authors.affiliation: Department of Experimental Oncology, National Cancer Institute, Naples, Italy.
authors.forename: Maria Vincenza
authors.initials: MV
authors.lastname: Carriero
authors.forename: Paola
authors.initials: P
authors.lastname: Franco
authors.forename: Lucia
authors.initials: L
authors.lastname: Gargiulo
authors.forename: Immacolata
authors.initials: I
authors.lastname: Vocca
authors.forename: Letizia
authors.initials: L
authors.lastname: Cito
authors.forename: Laura
authors.initials: L
authors.lastname: Fontana
authors.forename: Ciro
authors.initials: C
authors.lastname: Iaccarino
authors.forename: Giovanna
authors.initials: G
authors.lastname: Del Pozzo
authors.forename: John
authors.initials: J
authors.lastname: Guardiola
authors.forename: Maria Patrizia
authors.initials: MP
authors.lastname: Stoppelli
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D018698:Glutamic Acid; D006801:Humans; D051379:Mice; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D055293:Receptors, Urokinase Plasminogen Activator; D019030:Receptors, Vitronectin / Q000378:metabolism; D012694:Serine; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019061:src-Family Kinases
chemical_list: D003598:Cytoskeletal Proteins; D009856:Oncogene Proteins, Viral; C524898:PLAUR protein, human; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; C524899:Plaur protein, mouse; D011518:Proto-Oncogene Proteins; C496062:Pxn protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D019030:Receptors, Vitronectin; D018698:Glutamic Acid; D012694:Serine; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases; D014568:Urokinase-Type Plasminogen Activator