title: Cytoskeleton-mediated death receptor and ligand concentration in lipid rafts forms apoptosis-promoting clusters in cancer chemotherapy.
abstract: While investigating the mechanism of action of the novel antitumor drug Aplidin, we have discovered a potent and novel cell-killing mechanism that involves the formation of Fas/CD95-driven scaffolds in membrane raft clusters housing death receptors and apoptosis-related molecules. Fas, tumor necrosis factor-receptor 1, and tumor necrosis factor-related apoptosis-inducing ligand receptor 2/death receptor 5 were clustered into lipid rafts in leukemic Jurkat cells following Aplidin treatment, the presence of Fas being essential for apoptosis. Preformed membrane-bound Fas ligand (FasL) as well as downstream signaling molecules, including Fas-associated death domain-containing protein, procaspase-8, procaspase-10, c-Jun amino-terminal kinase, and Bid, were also translocated into lipid rafts, connecting death receptor extrinsic and mitochondrial intrinsic apoptotic pathways. Blocking Fas/FasL interaction partially inhibited Aplidin-induced apoptosis. Aplidin was rapidly incorporated into membrane rafts, and drug uptake was inhibited by lipid raft disruption. Actin-linking proteins ezrin, moesin, RhoA, and RhoGDI were conveyed into Fas-enriched rafts in drug-treated leukemic cells. Disruption of lipid rafts and interference with actin cytoskeleton prevented Fas clustering and apoptosis. Thus, Aplidin-induced apoptosis involves Fas activation in both a FasL-independent way and, following Fas/FasL interaction, an autocrine way through the concentration of Fas, membrane-bound FasL, and signaling molecules in membrane rafts. These data indicate a major role of actin cytoskeleton in the formation of Fas caps and highlight the crucial role of the clusters of apoptotic signaling molecule-enriched rafts in apoptosis, acting as concentrators of death receptors and downstream signaling molecules and as the linchpin from which a potent death signal is launched.
authors.affiliation: Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas-Universidad de Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Gajate
authors.forename: Faustino
authors.initials: F
authors.lastname: Mollinedo
mesh_terms: D000199:Actins / Q000502:physiology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D003599:Cytoskeleton / Q000502:physiology*; D047630:Depsipeptides / Q000494:pharmacology; D053222:Fas Ligand Protein; D006801:Humans; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D010456:Peptides, Cyclic; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D019014:fas Receptor / Q000502:physiology
chemical_list: D000199:Actins; D000970:Antineoplastic Agents; D047630:Depsipeptides; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D010456:Peptides, Cyclic; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; C505639:TNFRSF10B protein, human; D019014:fas Receptor; C098980:plitidepsin