title: Anti-CD20 therapeutic antibody rituximab modifies the functional organization of rafts/microdomains of B lymphoma cells.
abstract: Incubation of Burkitt lymphoma-derived Raji cells at physiological temperature with submicromolar concentrations of humanized anti-CD20 antibody rituximab (RTX) redistributes CD20 to liquid-ordered, plasma membrane rafts. This accumulation of the CD20 tetraspan protein in rafts does not change the existing lipid and phosphoprotein composition but makes sphingolipids and the Src regulator Cbp/PAG (Csk-binding protein/phosphoprotein associated with glycosphingolipid-enriched microdomain) transmembrane phosphoprotein more resistant to n-octyl-beta-pyranoside, a detergent that dissociates sphingolipid clusters. On the contrary, sphingolipids and Cbp/PAG are not protected by the presence of CD20 against the disruptive effects of methyl-beta-cyclodextrin, a cyclic carbohydrate that removes membrane cholesterol. After accumulation of CD20, the activity of the raft-associated Lyn kinase is down-regulated without apparent alteration of its relationship to substrates. Moreover, in rafts of lymphoblastoid cells that express lower amounts of Cbp/PAG, RTX redistributes CD20 to rafts but does not modulate the raft-associated protein tyrosine kinase activity, suggesting that the presence of Cbp/PAG protein in rafts is necessary for RTX to exert its transmembrane "signaling effects." Lastly, redistribution of CD20 in rafts renders the glycosylphosphatidyl inositol (GPI)-linked CD55 C'-defense protein hypersensitive to glycosylphosphatidyl inositol-specific phospholipases. By redistributing CD20 to rafts, RTX modifies their stability and organization and modulates the associated signaling pathways and C' defense capacity.
authors.affiliation: Department of Pathology, Faculty of Medicine, Centre médical universitaire, 1211 Geneva 4, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Semac
authors.forename: Carmen
authors.initials: C
authors.lastname: Palomba
authors.forename: Karina
authors.initials: K
authors.lastname: Kulangara
authors.forename: Natacha
authors.initials: N
authors.lastname: Klages
authors.forename: Gerhild
authors.initials: G
authors.lastname: van Echten-Deckert
authors.forename: Bettina
authors.initials: B
authors.lastname: Borisch
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Hoessli
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018958:CD55 Antigens / Q000378:metabolism; D003505:Cyclodextrins / Q000737:chemistry; D005960:Glucosides / Q000737:chemistry; D006801:Humans; D016393:Lymphoma, B-Cell / Q000188:drug therapy / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D000069283:Rituximab; D010738:Type C Phospholipases / Q000378:metabolism; D047392:beta-Cyclodextrins; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D018958:CD55 Antigens; D003505:Cyclodextrins; D005960:Glucosides; D008563:Membrane Lipids; D008565:Membrane Proteins; D010750:Phosphoproteins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C018619:octyl-beta-D-glucoside; D000069283:Rituximab; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D010738:Type C Phospholipases; D010739:Phospholipase D