Phosphorylation of Tyr342 in the linker region of Syk is critical for Fc epsilon RI signaling in mast cells.
The linker region of Syk and ZAP70 tyrosine kinases plays an important role in regulating their function. There are three conserved tyrosines in this linker region; Tyr317 of Syk and its equivalent residue in ZAP70 were previously shown to negatively regulate the function of Syk and ZAP70. Here we studied the roles of the other two tyrosines, Tyr342 and Tyr346 of Syk, in Fc epsilon RI-mediated signaling. Antigen stimulation resulted in Tyr342 phosphorylation in mast cells. Syk with Y342F mutation failed to reconstitute Fc epsilon RI-initiated histamine release. In the Syk Y342F-expressing cells there was dramatically impaired receptor-induced phosphorylation of multiple signaling molecules, including LAT, SLP-76, phospholipase C-gamma2, but not Vav. Compared to wild-type Syk, Y342F Syk had decreased binding to phosphorylated immunoreceptor tyrosine-based activation motifs and reduced kinase activity. Surprisingly, mutation of Tyr346 had much less effect on Fc epsilon RI-dependent mast cell degranulation. An anti-Syk-phospho-346 tyrosine antibody indicated that antigen stimulation induced only a very minor increase in the phosphorylation of this tyrosine. Therefore, Tyr342, but not Tyr346, is critical for regulating Syk in mast cells and the function of these tyrosines in immune receptor signaling appears to be different from what has been previously reported for the equivalent residues of ZAP70.
Zhang
Juan
J
Receptors and Signal Transduction Section, Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA. lzhang@didr.nidcr.nih.gov
Berenstein
Elsa
E
Siraganian
Reuben P
RP
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D000001:Calcimycin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D018797:Cell Cycle Proteins; D015550:Cell Degranulation; D002460:Cell Line; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D008407:Mast Cells / Q000166:cytology / Q000201:enzymology* / Q000276:immunology / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D051381:Rats; D017455:Receptors, IgE / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000072377:Syk Kinase; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D000906:Antibodies; D018797:Cell Cycle Proteins; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores; D007527:Isoenzymes; D010455:Peptides; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D017455:Receptors, IgE; C496618:VAV1 protein, human; C496620:Vav1 protein, rat; D007073:Immunoglobulin E; D000001:Calcimycin; D014443:Tyrosine; C089212:protein kinase D; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606898:Syk protein, rat; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D020830:rac1 GTP-Binding Protein; D002118:Calcium