Gads/Grb2-mediated association with LAT is critical for the inhibitory function of Gab2 in T cells.
A docking protein, Gab2, is recruited to the vicinity of the TCR complex and inhibits downstream signaling by interaction with negative regulators. However, the molecular mechanisms of this recruitment remain unclear. We have found that Gab2 associates with LAT upon TCR stimulation and that LAT is essential for Gab2 phosphorylation. By analysis of several Gab2 mutants, the c-Met binding domain (MBD) of Gab2 was found to be both necessary and sufficient for stimulation-induced LAT binding. Within the MBD domain, a novel Grb2 SH3 binding motif, PXXXR, is critical for constitutive association with Gads/Grb2. Through this association, Gab2 is recruited to the lipid raft after TCR ligation and exerts inhibitory function. The in vivo significance of this association is illustrated by the fact that T-cell responses are impaired in transgenic mice expressing wild-type Gab2 but not in mice expressing mutant Gab2 lacking the motif. Furthermore, T cells from Gab2-deficient mice showed enhanced proliferative responses upon TCR stimulation. These results indicate that Gads/Grb2-mediated LAT association is critical for the inhibitory function of Gab2, implying that Gab2 induced in stimulated T cells may exert an efficient negative feedback loop by recruiting inhibitory molecules to the lipid raft and competing with SLP-76 through Gads binding.
Yamasaki
Sho
S
Department of Molecular Genetics, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba 260-8670, Japan.
Nishida
Keigo
K
Sakuma
Machie
M
Berry
Donna
D
McGlade
C Jane
CJ
Hirano
Toshio
T
Saito
Takashi
T
D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D051380:GRB2 Adaptor Protein; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000502:physiology; D046911:Macromolecular Substances; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C490895:GAB2 protein, human; C409587:GRAP2 protein, human; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C490894:Gab2 protein, mouse; C495949:Grb2 protein, mouse; C110810:LAT protein, human; C491734:Lat protein, mouse; D046911:Macromolecular Substances; D008565:Membrane Proteins; C498726:Mona protein, mouse; D010750:Phosphoproteins; D011506:Proteins; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins