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Grb10/GrbIR as an in vivo substrate of Tec tyrosine kinase
1Department of Molecular Biology, Jichi Medical School, Tochigi, Japan. hmano@jichi.ac.jp
Background:
Tec is a member of the recently emerging subfamily among nonreceptor protein-tyrosine kinases (PTKs). Although many members of this family have been shown to be involved in a wide range of cytokine-mediated signalling systems, the molecular mechanism by which they exert in vivo effects remains obscure. To gain insights into the downstream pathways of Tec, we here looked for Tec-interacting proteins (TIPs) by using the yeast two-hybrid screening.
Results:
One of TIPs turned out to be Grb10/GrbIR, which carries one pleckstrin homology domain and one Src homology 2 domain. Grb10/GrbIR was known to bind receptor PTKs in a ligand-dependent fashion, but not to be phosphorylated on tyrosine residues. In a transient expression system in human kidney 293 cells, however, Grb10/GrbIR becomes profoundly tyrosine-phosphorylated by Tec, but not by Syk, Jak2 or insulin receptor. We also reveal that expression of Grb10/GrbIR suppresses the cytokine-driven and Tec-driven activation of the c-fos promoter.
Conclusion:
Our results indicate a novel role of Grb10/GrbIR as an effector molecule to a subset of nonreceptor PTKs.
Insights
Tec-interacting protein Grb10/GrbIR is tyrosine-phosphorylated by Tec, a nonreceptor protein-tyrosine kinase (PTK). This interaction suppresses cytokine-driven and Tec-driven c-fos promoter activation, revealing Grb10/GrbIR
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Biochemistry
Background:
- Tec is a nonreceptor protein-tyrosine kinase (PTK) involved in cytokine signaling.
- The precise in vivo mechanisms of Tec signaling remain unclear.
- Investigating Tec-interacting proteins (TIPs) can elucidate downstream pathways.
Purpose of the Study:
- To identify proteins that interact with Tec (TIPs).
- To understand the functional role of Tec-interacting proteins in cellular signaling.
Main Methods:
- Yeast two-hybrid screening to identify TIPs.
- Transient expression in human kidney 293 cells.
- Analysis of tyrosine phosphorylation and promoter activation.
Main Results:
- Grb10/GrbIR was identified as a Tec-interacting protein (TIP).
- Tec, but not other kinases, induced tyrosine phosphorylation of Grb10/GrbIR.
- Grb10/GrbIR expression suppressed cytokine- and Tec-driven c-fos promoter activation.
Conclusions:
- Grb10/GrbIR acts as an effector molecule for a subset of nonreceptor PTKs, including Tec.
- This study reveals a novel signaling role for Grb10/GrbIR in Tec-mediated pathways.