Docking protein Gab2 is phosphorylated by ZAP-70 and negatively regulates T cell receptor signaling by recruitment of inhibitory molecules.
To maintain various T cell responses and immune equilibrium, activation signals triggered by T cell antigen receptor (TCR) must be regulated by inhibitory signals. Gab2, an adaptor protein of the insulin receptor substrate-1 family, has been shown to be involved in the downstream signaling from cytokine receptors. We investigated the ... functional role of Gab2 in TCR-mediated signal transduction. Gab2 was phosphorylated by ZAP-70 and co-precipitated with phosphoproteins, such as ZAP-70, LAT, and CD3zeta, upon TCR stimulation. Overexpression of Gab2 in Jurkat cells or antigen-specific T cell hybridomas resulted in the inhibition of NF-AT activation, interleukin-2 production, and tyrosine phosphorylation. The structure-function relationship of Gab2 was analyzed by mutants of Gab2. The Gab2 mutants lacking SHP-2-binding sites mostly abrogated the inhibitory activity of Gab2, but its inhibitory function was restored by fusing to active SHP-2 as a chimeric protein. A mutant with defective phosphatidylinositol 3-kinase binding capacity also impaired the inhibitory activity, and the pleckstrin homology domain-deletion mutant revealed a crucial function of the pleckstrin homology domain for localization to the plasma membrane. These results suggest that Gab2 is a substrate of ZAP-70 and functions as a switch molecule toward inhibition of TCR signal transduction by mediating the recruitment of inhibitory molecules to the TCR signaling complex.
Mesh Terms:
1-Phosphatidylinositol 3-Kinase, Adaptor Proteins, Signal Transducing, Animals, Antigens, CD, Antigens, CD3, Antigens, Differentiation, T-Lymphocyte, Binding Sites, Blotting, Western, Carrier Proteins, Cell Line, Cytokines, DNA, Dose-Response Relationship, Drug, Flow Cytometry, Humans, Hybridomas, Interleukin-2, Intracellular Signaling Peptides and Proteins, Jurkat Cells, Luciferases, Lymphocyte Activation, Membrane Proteins, Mice, Mutation, Phosphoproteins, Phosphorylation, Precipitin Tests, Protein Binding, Protein Structure, Tertiary, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, Receptors, Antigen, T-Cell, SH2 Domain-Containing Protein Tyrosine Phosphatases, Signal Transduction, Structure-Activity Relationship, Transfection, Tyrosine, ZAP-70 Protein-Tyrosine Kinase, src Homology Domains
1-Phosphatidylinositol 3-Kinase, Adaptor Proteins, Signal Transducing, Animals, Antigens, CD, Antigens, CD3, Antigens, Differentiation, T-Lymphocyte, Binding Sites, Blotting, Western, Carrier Proteins, Cell Line, Cytokines, DNA, Dose-Response Relationship, Drug, Flow Cytometry, Humans, Hybridomas, Interleukin-2, Intracellular Signaling Peptides and Proteins, Jurkat Cells, Luciferases, Lymphocyte Activation, Membrane Proteins, Mice, Mutation, Phosphoproteins, Phosphorylation, Precipitin Tests, Protein Binding, Protein Structure, Tertiary, Protein Tyrosine Phosphatase, Non-Receptor Type 11, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, Receptors, Antigen, T-Cell, SH2 Domain-Containing Protein Tyrosine Phosphatases, Signal Transduction, Structure-Activity Relationship, Transfection, Tyrosine, ZAP-70 Protein-Tyrosine Kinase, src Homology Domains
J. Biol. Chem.
Date: Nov. 30, 2001
PubMed ID: 11572860
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