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.
Yamasaki
S
S
Molecular Genetics, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan.
Nishida
K
K
Hibi
M
M
Sakuma
M
M
Shiina
R
R
Takeuchi
A
A
Ohnishi
H
H
Hirano
T
T
Saito
T
T
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D001665:Binding Sites; D015153:Blotting, Western; D017252:CD3 Complex / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D006825:Hybridomas / Q000378:metabolism; D007376:Interleukin-2 / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D037181:Lectins, C-Type; D008156:Luciferases / Q000378:metabolism; D008213:Lymphocyte Activation; D008565:Membrane Proteins; D051379:Mice; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase; D018909:src Homology Domains; D000099192:CD69 Antigens
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D002352:Carrier Proteins; D016207:Cytokines; D004247:DNA; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type; D008156:Luciferases; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D011505:Protein-Tyrosine Kinases; D011948:Receptors, Antigen, T-Cell; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D014443:Tyrosine; D051746:ZAP-70 Protein-Tyrosine Kinase; D000099192:CD69 Antigens; C121704:CD3 antigen, zeta chain; C490895:GAB2 protein, human; C490894:Gab2 protein, mouse; C110810:LAT protein, human; C491734:Lat protein, mouse; C497261:ZAP70 protein, human; C497262:Zap70 protein, mouse; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse