Molecular cloning of SLP-76, a 76-kDa tyrosine phosphoprotein associated with Grb2 in T cells.
The activation of protein tyrosine kinases is a critical event in T cell antigen receptor (TCR)-mediated signaling. One substrate of the TCR-activated protein tyrosine kinase pathway is a 76-kDa protein (pp76) that associates with the adaptor protein Grb2. In this report we describe the purification of pp76 and the molecular ... cloning of its cDNA, which encodes a novel 533-amino acid protein with a single carboxyl-terminal Src homology 2 (SH2) domain. Although no recognizable motifs related to tyrosine, serine/threonine, or lipid kinase domains are present in the predicted amino acid sequence, it contains several potential motifs recognized by SH2 and SH3 domains. A cDNA encoding the murine homologue of pp76 was also isolated and predicts a protein with 84% amino acid identity to human pp76. Northern analysis demonstrates that pp76 mRNA is expressed solely in peripheral blood leukocytes, thymus, and spleen; and in human T cell, B cell and monocytic cell lines. In vitro translation of pp76 cDNA gives rise to a single product of 76 kDa that associates with a GST/Grb2 fusion protein, demonstrating a direct association between these two molecules. Additionally, a GST fusion protein consisting of the predicted SH2 domain of pp76 precipitates two tyrosine phosphoproteins from Jurkat cell lysates, and antiserum directed against phospholipase C-gamma 1 coprecipitates a tyrosine phosphoprotein with an electrophoretic mobility identical to that of pp76. These results demonstrate that this novel protein, which we term SLP-76 (SH2 domain-containing Leukocyte Protein of 76 kDa), is likely to play an important role in TCR-mediated intracellular signal transduction.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, B-Lymphocytes, Base Sequence, Cell Line, Cloning, Molecular, ErbB Receptors, GRB2 Adaptor Protein, Gene Expression, HeLa Cells, Humans, Leukocytes, Mice, Molecular Sequence Data, Molecular Weight, Oligodeoxyribonucleotides, Organ Specificity, Phosphoproteins, Protein-Tyrosine Kinases, Proteins, RNA, Messenger, Sequence Homology, Amino Acid, Spleen, T-Lymphocytes, Thymus Gland, Tumor Cells, Cultured, Tyrosine
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, B-Lymphocytes, Base Sequence, Cell Line, Cloning, Molecular, ErbB Receptors, GRB2 Adaptor Protein, Gene Expression, HeLa Cells, Humans, Leukocytes, Mice, Molecular Sequence Data, Molecular Weight, Oligodeoxyribonucleotides, Organ Specificity, Phosphoproteins, Protein-Tyrosine Kinases, Proteins, RNA, Messenger, Sequence Homology, Amino Acid, Spleen, T-Lymphocytes, Thymus Gland, Tumor Cells, Cultured, Tyrosine
J. Biol. Chem.
Date: Mar. 31, 1995
PubMed ID: 7706237
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