Distinct tyrosine phosphorylation sites in ZAP-70 mediate activation and negative regulation of antigen receptor function.
Biochemical and genetic evidence has implicated two families of protein tyrosine kinases (PTKs), the Src- and Syk-PTKs, in T- and B-cell antigen receptor signaling. ZAP-70 is a member of the Syk-PTKs that associates with the T-cell antigen receptor and undergoes tyrosine phosphorylation following receptor activation. Three tyrosine residues, Tyr-292, -492, and -493, have been identified as sites of phosphorylation following T-cell antigen receptor engagement. Utilizing ZAP-70- and Syk-deficient lymphocytes (Syk-DT40 cells), we provide biochemical and functional evidence that heterologous trans-phosphorylation of Tyr-493 by a Src-PTK is required for antigen receptor-mediated activation of both the calcium and ras pathways. In contrast, cells expressing mutations at Tyr-292 or -492 demonstrate hyperactive T- and B-cell antigen receptor phenotypes. Thus, phosphorylation of ZAP-70 mediates both activation and inactivation of antigen receptor signaling.
Kong
G
G
Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Dalton
M
M
Bubeck Wardenburg
J
J
Straus
D
D
Kurosaki
T
T
Chan
A C
AC
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology; D004792:Enzyme Precursors / Q000172:deficiency / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000473:pathology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000502:physiology; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry*; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D000072377:Syk Kinase; D014407:Tumor Cells, Cultured; D051746:ZAP-70 Protein-Tyrosine Kinase
D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D011948:Receptors, Antigen, T-Cell; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D002118:Calcium