TCR/CD3-Induced activation and binding of Emt/Itk to linker of activated T cell complexes: requirement for the Src homology 2 domain.
Expressed in mast and T cells/inducible T cell tyrosine kinase (Emt/Itk), a Tec family protein tyrosine kinase, is critical for the development and activation of T lymphocytes. The mechanism through which Emt/Itk mediates its effector functions is poorly understood. In this study, we show that the Emt/Itk Src homology 2 (SH2) domain is critical for the transphosphorylation and activation of Emt/Itk catalytic activity that is mediated by TCR/CD3 engagement. Furthermore, we find that the Emt/Itk SH2 domain is essential for the formation of TCR/CD3-inducible Emt/Itk-LAT complexes, whereas the SH3 domain and catalytic activity are not required. The Emt/Itk-linker of activated T cells (LAT) complexes are biologically important because Jurkat T cells with deficient LAT expression (JCaM2) fail to increase Emt/Itk tyrosine phosphorylation upon TCR/CD3 stimulation. Confocal microscopy reveals that in activated cells, LAT complexes colocalize with TCR/CD3. The present data suggest that upon TCR/CD3 engagement, the Emt/Itk SH2 domain mediates the formation of a molecular complex containing Emt/Itk, LAT, and TCR/CD3; this complex is essential for Emt/Itk activation and function.
Ching
K A
KA
Department of Biology and Molecular Biology Institute, San Diego State University, CA 92182, USA.
Grasis
J A
JA
Tailor
P
P
Kawakami
Y
Y
Kawakami
T
T
Tsoukas
C D
CD
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001704:Biopolymers / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology; D005822:Genetic Vectors / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006801:Humans; D019169:Jurkat Cells; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D010750:Phosphoproteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D014162:Transfection; D018909:src Homology Domains / Q000276:immunology* / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D001704:Biopolymers; D002352:Carrier Proteins; C110810:LAT protein, human; C491734:Lat protein, mouse; D008164:Luminescent Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D049452:Green Fluorescent Proteins; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase