Abstract
CD45 plays a critical role in T-cell receptor (TCR)-mediated signaling. In a yeast two-hybrid screen, SKAP55, the Src kinase-associated phosphoprotein of unknown function, was found as a substrate which associated with CD45 in vivo. Mutational analysis demonstrated the pivotal role of Tyr-232 in SKAP55 in the association with CD45. In Jurkat cells, anti-CD3 antibody stimulation promoted SKAP55 tyrosine phosphorylation and translocation from the cytoplasm to the membrane. Overexpression of SKAP55 in these cells induced transcriptional activation of the IL-2 promoter, while mutant SKAP55-Y232F totally suppressed the promoter activity. Furthermore, overexpression of SKAP55-Y232F also caused the tyrosine hyperphosphorylation of Fyn with a decreased kinase activity. Thus, SKAP55 is an essential adapter to couple CD45 with the Src family kinases for dephosphorylation and, thus, positively regulates TCR signaling.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antibodies / pharmacology
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Binding Sites
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Biological Transport, Active
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CD3 Complex / metabolism
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Cell Membrane / metabolism
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Cytoplasm / metabolism
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Humans
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Interleukin-2 / genetics
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Jurkat Cells
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Leukocyte Common Antigens / chemistry
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Leukocyte Common Antigens / genetics
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Leukocyte Common Antigens / metabolism*
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Mutagenesis, Site-Directed
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Phosphoproteins / chemistry
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Phosphoproteins / genetics
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Phosphoproteins / metabolism*
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Phosphorylation
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Promoter Regions, Genetic
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Protein Structure, Tertiary
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-fyn
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Receptors, Antigen, T-Cell / genetics
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Receptors, Antigen, T-Cell / metabolism*
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Signal Transduction
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Substrate Specificity
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T-Lymphocytes / immunology
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T-Lymphocytes / metabolism
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Transcription, Genetic
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Two-Hybrid System Techniques
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Tyrosine / metabolism
Substances
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Antibodies
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CD3 Complex
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Interleukin-2
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Phosphoproteins
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Proto-Oncogene Proteins
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Receptors, Antigen, T-Cell
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Recombinant Proteins
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SKAP1 protein, human
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Tyrosine
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FYN protein, human
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Proto-Oncogene Proteins c-fyn
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Leukocyte Common Antigens