Identification of the minimal tyrosine residues required for linker for activation of T cell function.
The linker for activation of T cells (LAT) is essential for signaling through the T cell receptor (TCR). Following TCR stimulation, LAT becomes tyrosine-phosphorylated, creating docking sites for other signaling proteins such as phospholipase C-gamma(1) (PLC-gamma(1)), Grb2, and Gads. In this study, we have attempted to identify the critical tyrosine residues in LAT that mediate TCR activation-induced mobilization of intracellular Ca(2+) and activation of the MAP kinase Erk2. By using the LAT-deficient Jurkat derivative, J.CaM2, stable cell lines were established expressing various tyrosine mutants of LAT. We show that three specific tyrosine residues (Tyr(132), Tyr(171), and Tyr(191)) are necessary and sufficient to achieve a Ca(2+) flux following TCR stimulation. These tyrosine residues function by reconstituting PLC-gamma(1) phosphorylation and recruitment to LAT. However, these same tyrosines can only partially reconstitute Erk activation. Full reconstitution of Erk requires two additional tyrosine residues (Tyr(110) and Tyr(226)), both of which have the Grb2-binding motif YXN. This reconstitution of Erk activation requires that the critical tyrosine residues be on the same molecule of LAT, suggesting that a single LAT molecule nucleates multiple protein-protein interactions required for optimal signal transduction.
Lin
J
J
Department of Medicine, Biomedical Sciences Graduate Program, Howard Hughes Medical Institute, University of California, San Francisco, California 94143-0795, USA.
Weiss
A
A
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D008156:Luciferases / Q000032:analysis / Q000235:genetics; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D021122:Protein Subunits; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C110810:LAT protein, human; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D021122:Protein Subunits; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D014443:Tyrosine; D008156:Luciferases; D019950:Mitogen-Activated Protein Kinase 1; D002118:Calcium