Abstract
Upon B-cell antigen receptor (BCR) activation, the protein tyrosine kinase Syk phosphorylates the adaptor protein SH2 domain-containing leukocyte protein of 65 kDa (SLP-65), thus coupling the BCR to diverse signalling pathways. Here, we report that SLP-65 is not only a downstream target and substrate of Syk but also a direct binding-partner and activator of this kinase. This positive feedback is mediated by the binding of the SH2 domain of SLP-65 to an autophosphorylated tyrosine of Syk. The mutant B cells that cannot form the Syk/SLP-65 complex are defective in BCR-induced extracellular signal-regulated kinase, nuclear factor kappa B and nuclear factor of activated T cells, but not Akt activation, and are blocked in B-cell development. Furthermore, we show that formation of the Syk/SLP-65 complex is required for sustained Ca(2+) responses in activated B cells. We suggest that after activation and internalization of the BCR, Syk remains active as part of a membrane-bound Syk/SLP-65 complex controlling sustained signalling and calcium influx.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism
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Animals
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Calcium / metabolism
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Calcium Signaling / genetics
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Calcium Signaling / physiology*
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Cell Differentiation
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Cell Line
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Extracellular Signal-Regulated MAP Kinases / genetics
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Extracellular Signal-Regulated MAP Kinases / metabolism
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Flow Cytometry
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Luciferases / genetics
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Luciferases / metabolism
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Mice
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Mice, Knockout
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Models, Biological
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Mutation
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NF-kappa B / genetics
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NF-kappa B / metabolism
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Phosphorylation
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Protein Binding
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism
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Receptors, Antigen, B-Cell / genetics
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Receptors, Antigen, B-Cell / metabolism*
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Syk Kinase
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Transfection
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Tyrosine / genetics
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Tyrosine / metabolism
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src Homology Domains / genetics
Substances
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Adaptor Proteins, Signal Transducing
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Intracellular Signaling Peptides and Proteins
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NF-kappa B
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Receptors, Antigen, B-Cell
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Recombinant Fusion Proteins
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Green Fluorescent Proteins
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Tyrosine
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Luciferases
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Protein-Tyrosine Kinases
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Syk Kinase
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Syk protein, mouse
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Proto-Oncogene Proteins c-akt
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Extracellular Signal-Regulated MAP Kinases
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Calcium