title: Phagocyte spreading and phagocytosis in the compound ascidian Botryllus schlosseri: evidence for an integrin-like, RGD-dependent recognition mechanism.
abstract: The involvement of integrins in phagocyte spreading and phagocytosis was investigated in the compound ascidian Botryllus schlosseri. The number of spreading cells was significantly reduced when adhesion occurred in the presence of the tetrapeptide Arg--Gly--Asp--Ser (RGDS), but not of Arg--Gly--Glu--Ser (RGES) indicating the involvement of RGD-mediated adhesion mechanisms in phagocyte spreading. The significant decrease of the fraction of spreading cells in the presence of Botryllus blood plasma suggests the presence of RGD-containing molecules in the blood of our species. The increase in the same index when blood plasma-coated slides as well as fibrinogen- and fibronectin-coated coverslips were used, fits with the above hypothesis. Adhesion in the presence of RGDS leads to a consistent alteration of the actin cytoskeleton, in agreement with the known role of integrin adhesion in microfilament organization. Phagocytosis was greatly reduced by RGDS in the incubation medium, but not by RGES, and was significantly increased by coating yeast cells with fibronectin or blood plasma. Both spreading and phagocytic capability were severely inhibited by wortmannin, suggesting the importance of phosphatidylinositol-3-kinase in integrin-mediated signal transduction in ascidians.
authors.affiliation: Department of Biology, University of Padova, Via U. Bassi 58/B, 35131, Padova, Italy. ballarin@civ.bio.unipd.it
authors.forename: Loriano
authors.initials: L
authors.lastname: Ballarin
authors.forename: Massimo
authors.initials: M
authors.lastname: Scanferla
authors.forename: Francesca
authors.initials: F
authors.lastname: Cima
authors.forename: Armando
authors.initials: A
authors.lastname: Sabbadin
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002448:Cell Adhesion / Q000276:immunology; D003470:Culture Media; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006434:Hemocytes / Q000166:cytology / Q000276:immunology; D016023:Integrins / Q000737:chemistry / Q000276:immunology; D009842:Oligopeptides / Q000276:immunology; D010586:Phagocytes / Q000166:cytology / Q000276:immunology*; D010587:Phagocytosis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012441:Saccharomyces cerevisiae / Q000276:immunology; D015398:Signal Transduction; D014561:Urochordata / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D003470:Culture Media; D004791:Enzyme Inhibitors; D016023:Integrins; D009842:Oligopeptides; D000081082:Phosphoinositide-3 Kinase Inhibitors; C059453:RGES peptide; C046617:arginyl-glycyl-aspartyl-serine; D000077191:Wortmannin