Abstract
We established Jurkat transfectants that overexpress Pyk2 or its mutants, K457A (lysine 457 was mutated to alanine), Pyk2-Y402F (tyrosine 402 to phenylalanine), and Pyk2-Y881F to investigate the role of Pyk2 in T cell activation. Pyk2 as well as kinase-inactive Pyk2-K457A, was phosphorylated at tyrosine residues 402, 580, and 881 upon T cell antigen receptor cross-linking, indicating that these residues are phosphorylated by other tyrosine kinase(s). However, no tyrosine phosphorylation of Pyk2-Y402F was detected while more than 60% of the tyrosine phosphorylation was observed in Pyk2-Y881F. Pyk2-Y402F inhibited the activation of endogenous Pyk2. The degree of activation of both c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase but not extracellular signal-regulated protein kinase after concurrent ligation of T cell antigen receptor and CD28 was reduced by more than 50% in the clones expressing Pyk2-Y402F. Consistent with this inhibition, IL-2 production was significantly diminished in the Pyk2-Y402F-expressing clones. Furthermore, we found that Pyk2, when overexpressed, associates with Zap70 and Vav. Taken together, these findings suggest that Pyk2 is involved in the activation of T cells through its tyrosine 402.
MeSH terms
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CD28 Antigens / metabolism
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Cell Cycle Proteins*
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Enzyme Activation
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Focal Adhesion Kinase 2
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Glutathione Transferase / metabolism
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Humans
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Interleukin-2 / biosynthesis*
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JNK Mitogen-Activated Protein Kinases*
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Jurkat Cells
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Lymphocyte Activation*
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Mitogen-Activated Protein Kinases / metabolism
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Mutation
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Phosphorylation
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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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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-vav
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Receptors, Antigen, T-Cell / metabolism
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Recombinant Fusion Proteins / metabolism
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T-Lymphocytes / metabolism*
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Transfection
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Tyrosine / metabolism*
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ZAP-70 Protein-Tyrosine Kinase
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p38 Mitogen-Activated Protein Kinases
Substances
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CD28 Antigens
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Cell Cycle Proteins
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Interleukin-2
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-vav
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Receptors, Antigen, T-Cell
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Recombinant Fusion Proteins
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VAV1 protein, human
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Tyrosine
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Glutathione Transferase
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Protein-Tyrosine Kinases
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Focal Adhesion Kinase 2
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ZAP-70 Protein-Tyrosine Kinase
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ZAP70 protein, human
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase Kinases