Abstract
The Tpl-2 kinase activates the nuclear factor of activated T cells (NFAT) and induces IL-2 expression in T-cell lines. Here we show that the activation of the IL-2 promoter by Tpl-2 is inhibited by mutant signaling molecules that inhibit the mitogen-activated protein kinase (MAPK) or the calcineurin/NFAT pathways and is promoted by combinations of signaling molecules that activate these pathways. We, therefore, conclude that signals generated by the convergence of the MAPK and the calcineurin/NFAT pathway are necessary and sufficient for the activation of the IL-2 promoter by Tpl-2. The activation of both the IL-2 promoter and an NFAT-driven minimal promoter were shown to depend on signals transduced by Raf1. However, it was only the IL-2 promoter whose activation by Tpl-2 was fully blocked by the dominant negative mutant MEK1S218/222A and the MEK1/MEK2 inhibitor PD098059. Since the activation of NFAT is MAPK-dependent these findings suggested that the activation of MAPK by Tpl-2 is either independent or only partially dependent on MEK1 and MEK2. In addition, they suggested that the activation of the IL-2 promoter is under the control of not only NFAT but also a second factor whose activation is MEK-dependent. Experiments in COS-1 and EL-4 cells confirmed both hypotheses and revealed that the second factor activated by Tpl-2 is NF-kappaB. While the activation of the IL-2 promoter and an NFAT-driven minimal promoter by Tpl-2 was fully blocked by the dominant negative mutant NFAT delta418, it was only partially blocked by the calcineurin inhibitor cyclosporin A suggesting that the Tpl-2-mediated NFAT activation is under the control of a combination of calcineurin-dependent and independent pathways. Both pathways were fully blocked by Bcl-2 or Bcl-X(L).
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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COS Cells
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Calcineurin / physiology*
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism
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Calcium-Calmodulin-Dependent Protein Kinases / physiology
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Cyclosporine / pharmacology
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DNA-Binding Proteins / metabolism*
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Enzyme Inhibitors / pharmacology
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Flavonoids / pharmacology
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Gene Expression Regulation / physiology*
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Humans
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Immunosuppressive Agents / pharmacology
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Interleukin-2 / biosynthesis*
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Interleukin-2 / genetics
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Jurkat Cells
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Lymphoma, T-Cell / pathology
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MAP Kinase Kinase 1
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MAP Kinase Kinase 2
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MAP Kinase Kinase Kinases*
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Mice
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinase Kinases*
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Mitogen-Activated Protein Kinases*
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NF-kappa B / metabolism*
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NFATC Transcription Factors
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Neoplasm Proteins / physiology
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Nuclear Proteins*
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Promoter Regions, Genetic
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / physiology*
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Protein-Tyrosine Kinases / physiology
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Proto-Oncogene Proteins / antagonists & inhibitors
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-bcl-2 / physiology
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Proto-Oncogene Proteins c-raf / physiology
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Signal Transduction / physiology*
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T-Lymphocytes / metabolism*
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Transcription Factors / metabolism*
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Transcription, Genetic*
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Tumor Cells, Cultured
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bcl-X Protein
Substances
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BCL2L1 protein, human
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Bcl2l1 protein, mouse
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DNA-Binding Proteins
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Enzyme Inhibitors
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Flavonoids
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Immunosuppressive Agents
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Interleukin-2
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NF-kappa B
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NFATC Transcription Factors
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Neoplasm Proteins
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Nuclear Proteins
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Transcription Factors
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bcl-X Protein
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Cyclosporine
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MAP2K2 protein, human
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-raf
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Calcium-Calmodulin-Dependent Protein Kinases
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinases
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MAP3K8 protein, human
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Map3k8 protein, mouse
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MAP Kinase Kinase 1
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MAP Kinase Kinase 2
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MAP2K1 protein, human
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Map2k1 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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Calcineurin
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one