title: p56Lck tyrosine kinase enhances the assembly of death-inducing signaling complex during Fas-mediated apoptosis.
abstract: Although the death-inducing signaling complex (DISC) is rapidly assembled, several lines of evidence suggest that formation of this complex is not the first consequence of cell surface CD95 (Fas) stimulation but rather a later step in this process. Activation of Fas triggers a cascade of signaling events that culminate in cellular apoptosis. Tyrosine kinases are critical effectors in T cell activation. However, their functional involvement in death receptor-mediated apoptosis is unknown. Here, we used p56(Lck)-deficient cells to show that CD95-induced cell death is highly dependent on p56(Lck) activity and its localization within plasma membrane. We found that p56(Lck) acts upstream of the mitochondria; in the absence of p56(Lck), Bid cleavage and the release of cytochrome c were severely impaired. Moreover, p56(Lck)-deficient cells or cells expressing an inactive form of p56(Lck) displayed defective formation of the DISC post CD95 stimulation. In vivo reconstitution of thymocytes from p56(lck)-deficient mice, which are resistant to apoptosis, with p56(Lck) restored Fas-mediated cell death. Our results support a novel model whereby sensitivity to apoptosis is regulated through quantitative changes in the stoichiometry of DISC components triggered by p56(Lck) activation and localization.
authors.affiliation: Laboratoire d'Immunologie, Centre de Recherche CHUM Saint-Luc, Montréal H2X 1P1, Canada.
authors.forename: Ehssan
authors.initials: E
authors.lastname: Sharif-Askari
authors.forename: Denis
authors.initials: D
authors.lastname: Gaucher
authors.forename: Rabih
authors.initials: R
authors.lastname: Halwani
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ma
authors.forename: Kevin
authors.initials: K
authors.lastname: Jao
authors.forename: Ali
authors.initials: A
authors.lastname: Abdallah
authors.forename: Elias K
authors.initials: EK
authors.lastname: Haddad
authors.forename: Rafick-Pierre
authors.initials: RP
authors.lastname: Sékaly
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology / Q000235:genetics; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000502:physiology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000201:enzymology*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C494815:Bid protein, mouse; D053418:Death Domain Receptor Signaling Adaptor Proteins; D019014:fas Receptor; D045304:Cytochromes c; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)