Differential Intrinsic Enzymatic Activity of Syk and Zap-70 Protein-tyrosine Kinases

Differential intrinsic enzymatic activity of Syk and Zap-70 protein-tyrosine kinases.

Syk and Zap-70 are related protein-tyrosine kinases implicated in antigen and Fc receptor signaling. While Zap-70 is restricted to T-cells and natural killer cells, Syk accumulates in B-cells, mast cells, platelets, and immature T-cells. In addition, we found that an isoform of Syk (SykB), which carries a 23-amino acid deletion in the "linker" region, is prominently expressed in bone marrow. To...

Differential Activation of the Tyrosine Kinases ZAP-70 and Syk After FcgRI Stimulation

Engagement of the high-affinity IgG Fc receptor (FcgRI) actiSyk nor MAP kinase activation was affected by the presence of ZAP-70. Although transduced ZAP-70 had in vitro kinase vates a signal transduction pathway involving tyrosine phosphorylation of associated kinases. We compared the activity and associated with FceRIg after receptor aggregation, it was not tyrosine phosphorylated. In contras...

Ubiquitination and degradation of Syk and ZAP-70 protein tyrosine kinases in human NK cells upon CD16 engagement.

Syk and ZAP-70 nonreceptor protein tyrosine kinases (PTKs) are essential elements in several cascades coupling immune receptors to intracellular responses. The critical role of these kinases in promoting the propagation of intracellular signaling requires a tight regulation of their activity, thus the existence of a negative feedback loop regulating their expression can be hypothesized. Herein,...

Analysis of the interaction of ZAP-70 and syk protein-tyrosine kinases with the T-cell antigen receptor by plasmon resonance.

Tyrosine phosphorylation of a 17-amino acid immunoreceptor tyrosine-based activation motif (ITAM), conserved in each of the signaling subunits of the T-cell antigen receptor (TCR), mediates the recruitment of ZAP-70 and syk protein-tyrosine kinases (PTKs) to the activated receptor. The interaction between the two tandemly arranged Src-homology 2 (SH2) domains of this family of PTKs and each of ...

Differential Requirements for ZAP-70 in TCR