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Direct T cell activation by chimeric single chain Fv-Syk promotes Syk-Cbl association and Cbl phosphorylation
C J Fitzer-Attas1, D G Schindler, T Waks
1Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel.
The Journal of Biological Chemistry
|March 28, 1997
Summary
This study identifies Cbl as a primary substrate for Syk, a key protein in T cell activation. Efficient phospholipase C-gamma (PLC-gamma) phosphorylation requires multiple tyrosine kinases.
Area of Science:
- Immunology
- Cell Signaling
- Molecular Biology
Background:
- Protein tyrosine kinase Syk is crucial for immune recognition receptor signaling and T cell activation.
- Understanding downstream signaling elements of Syk is essential for elucidating T cell activation pathways.
Purpose of the Study:
- To identify signaling molecules directly downstream of Syk in T cell activation.
- To investigate the role of Syk in Cbl and phospholipase C-gamma (PLC-gamma) phosphorylation.
- To circumvent T cell receptor (TCR)/CD3 activation of Src family kinases.
Main Methods:
- Constructed a chimeric Syk signaling molecule (scFv-Syk) for direct antigen engagement.
- Utilized a murine T cell hybridoma model.
- Analyzed protein-protein interactions and tyrosine phosphorylation events.
Main Results:
- Direct aggregation of scFv-Syk with antigen induced interleukin-2 production and target cell lysis.
- scFv-Syk aggregation increased association with Cbl and promoted Cbl tyrosine phosphorylation.
- Antigen-driven PLC-gamma phosphorylation was uncoupled from Cbl phosphorylation in scFv-Syk-transfected cells.
Conclusions:
- Syk can initiate T cell signaling and directly activate downstream machinery.
- Cbl is a primary tyrosine kinase substrate in the Syk-mediated signaling pathway.
- Efficient PLC-gamma phosphorylation may necessitate the combined action of multiple tyrosine kinase families.