title: Zeta-associated protein of 70 kDa (ZAP-70), but not Syk, tyrosine kinase can mediate apoptosis of T cells through the Fas/Fas ligand, caspase-8 and caspase-3 pathways.
abstract: The TCR zeta-chain-associated protein of 70 kDA (ZAP-70) and Syk tyrosine kinases play critical roles in regulating TCR-mediated signal transduction. They not only share some overlapped functions but also may play unique roles in regulating the function and development of T cells. However, it is not known whether they have different effects on the activation and activation-induced cell death of T cells. To address this question, we generated cDNAs encoding chimeric molecules that a tailless TCR zeta-chain was directly linked to truncated ZAP-70 (Z/ZAP) or Syk (Z/Syk) molecules lacking the two Src homology 2 domains. Transfection of these molecules into zeta-chain-deficient cells restored their TCR expression. In addition, Z/ZAP and Z/Syk transfectants but not control cells demonstrated kinase activities in phosphorylating an exogenous substrate specific for ZAP-70 and Syk kinases. Z/ZAP transfectants activated through TCRs underwent a faster time course of apoptosis and had a greater percentage of apoptotic cells than that of Z/Syk and control cells. Activated Z/ZAP transfectants increased Fas and Fas ligand (FasL) expression 3- and 40-fold, respectively. Blocking of the Fas/FasL interaction could inhibit the apoptosis of Z/ZAP transfectants. In contrast, although activated Z/Syk transfectants could increase FasL expression, their Fas expression actually decreased and the percentage of apoptotic cells did not increase. Further studies of the mechanisms revealed that activation of Z/ZAP but not Z/Syk transfectants resulted in rapid activation of caspase-3 and caspase-8 that could also be inhibited by blocking Fas/FasL interaction. These results demonstrated that ZAP-70 and Syk play distinct roles in T cell activation and activation-induced cell death.
authors.affiliation: Division of Immunology, Beckman Research Institute, City of Hope, Duarte, CA 91010, USA.
authors.forename: Lingwen
authors.initials: L
authors.lastname: Zhong
authors.forename: Chun-Hua
authors.initials: CH
authors.lastname: Wu
authors.forename: Wen-Hui
authors.initials: WH
authors.lastname: Lee
authors.forename: Chih-Pin
authors.initials: CP
authors.lastname: Liu
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D053148:Caspase 3; D053181:Caspase 8; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D016923:Cell Death / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D004792:Enzyme Precursors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053222:Fas Ligand Protein; D007376:Interleukin-2 / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type; D008024:Ligands; D008213:Lymphocyte Activation / Q000235:genetics; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D000072377:Syk Kinase; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D014162:Transfection; D051746:ZAP-70 Protein-Tyrosine Kinase; D019014:fas Receptor / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D053148:Caspase 3; D053181:Caspase 8; D061945:Caspase Inhibitors; D020169:Caspases; D004792:Enzyme Precursors; D053222:Fas Ligand Protein; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type; D008024:Ligands; D008562:Membrane Glycoproteins; D011505:Protein-Tyrosine Kinases; D011993:Recombinant Fusion Proteins; D000072377:Syk Kinase; D051746:ZAP-70 Protein-Tyrosine Kinase; D019014:fas Receptor; D000099192:CD69 Antigens; C505658:Fasl protein, mouse; C000606897:Syk protein, mouse; C497262:Zap70 protein, mouse; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse