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.
Publication types
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Comparative Study
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Antigens, CD / biosynthesis
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Antigens, Differentiation, T-Lymphocyte / biosynthesis
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Apoptosis / genetics
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Apoptosis / immunology*
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Caspase 3
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Caspase 8
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Caspase Inhibitors
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Caspases / physiology*
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Cell Death / genetics
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Cell Death / immunology
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Cell Line, Tumor
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Enzyme Activation / genetics
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Enzyme Activation / immunology
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Enzyme Precursors / biosynthesis
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Enzyme Precursors / genetics
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Enzyme Precursors / metabolism
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Enzyme Precursors / physiology*
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Fas Ligand Protein
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Interleukin-2 / biosynthesis
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Intracellular Signaling Peptides and Proteins
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Lectins, C-Type
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Ligands
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Lymphocyte Activation / genetics
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Membrane Glycoproteins / antagonists & inhibitors
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Membrane Glycoproteins / biosynthesis
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Membrane Glycoproteins / physiology*
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Mice
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Phosphorylation
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Protein-Tyrosine Kinases / biosynthesis
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism
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Protein-Tyrosine Kinases / physiology*
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Recombinant Fusion Proteins / biosynthesis
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Signal Transduction / genetics
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Signal Transduction / immunology*
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Syk Kinase
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T-Lymphocytes / cytology
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T-Lymphocytes / enzymology*
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T-Lymphocytes / immunology
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Transfection
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ZAP-70 Protein-Tyrosine Kinase
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fas Receptor / biosynthesis
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fas Receptor / metabolism
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fas Receptor / physiology*
Substances
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Antigens, CD
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Antigens, Differentiation, T-Lymphocyte
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CD69 antigen
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Caspase Inhibitors
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Enzyme Precursors
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Fas Ligand Protein
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Fasl protein, mouse
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Interleukin-2
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Intracellular Signaling Peptides and Proteins
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Lectins, C-Type
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Ligands
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Membrane Glycoproteins
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Recombinant Fusion Proteins
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fas Receptor
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Protein-Tyrosine Kinases
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Syk Kinase
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Syk protein, mouse
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ZAP-70 Protein-Tyrosine Kinase
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Zap70 protein, mouse
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Casp3 protein, mouse
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Casp8 protein, mouse
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Caspase 3
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Caspase 8
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Caspases