Abstract
The Syk protein-tyrosine kinase is phosphorylated on multiple tyrosines after the aggregation of the B cell antigen receptor. However, metabolic labeling experiments indicate that Syk is inducibly phosphorylated to an even greater extent on serine after receptor ligation. A combination of phosphopeptide mapping and mass spectrometric analyses indicates that serine 291 is a major site of phosphorylation. Serine 291 lies within a 23-amino acid insert located within the linker B region that distinguishes Syk from SykB and Zap-70. The phosphorylation of serine-291 by protein kinase C enhances the ability of Syk to couple the antigen receptor to the activation of the transcription factors NFAT and Elk-1. Protein interaction studies indicate a role for the phosphorylated linker insert in promoting an interaction between Syk and the chaperone protein, prohibitin.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Humans
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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NFATC Transcription Factors / genetics
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NFATC Transcription Factors / metabolism
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Peptide Mapping / methods
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Phosphorylation / physiology
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Receptors, Antigen, B-Cell / genetics
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Receptors, Antigen, B-Cell / metabolism
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Serine / genetics
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Serine / metabolism*
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Syk Kinase
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U937 Cells
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ZAP-70 Protein-Tyrosine Kinase / genetics
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ZAP-70 Protein-Tyrosine Kinase / metabolism
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ets-Domain Protein Elk-1 / genetics
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ets-Domain Protein Elk-1 / metabolism
Substances
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ELK1 protein, human
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Intracellular Signaling Peptides and Proteins
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NFATC Transcription Factors
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Receptors, Antigen, B-Cell
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ets-Domain Protein Elk-1
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Serine
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Protein-Tyrosine Kinases
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SYK protein, human
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Syk Kinase
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ZAP-70 Protein-Tyrosine Kinase
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ZAP70 protein, human