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Tec protein-tyrosine kinase is an effector molecule of Lyn protein-tyrosine kinase
H Mano1, Y Yamashita, A Miyazato
1Department of Molecular Biology, Jichi Medical School, Tochigi-ken, Japan.
Abstract:
The Tec family is a recently emerging subfamily among nonreceptor type protein-tyrosine kinases (PTKs) consisting of Tec, Txk, Btk, Bmx, and Itk/Tsk/Emt. They have a long amino-terminal unique region containing a pleckstrin homology domain and a Tec-homology domain. We could previously show that, through the Tec-homology domain, Tec is bound to Lyn kinase both in vitro and in vivo. Because Tec is coexpressed with Lyn in many hematopoietic cell types, it has been intriguing to investigate the biological role of the Tec-Lyn association. Here we demonstrate that Lyn can phosphorylate tyrosine residues of the Tec protein, and thereby activate Tec in 3T3 fibroblasts. However, coexpression of Tec has little effect on the phospho-tyrosine-contents of Lyn. By using the in vitro kinase assay and the yeast system, we could prove that the Tec protein is a direct substrate of the Lyn kinase both in vitro and in vivo. From this evidence we conclude that Tec acts downstream of Lyn in intracellular signaling pathways. This is a novel case where one PTK is phosphorylated and regulated by another.
Insights
Lyn kinase phosphorylates and activates Tec protein, revealing a novel regulatory pathway in intracellular signaling. This study demonstrates Tec acts downstream of Lyn, highlighting a new mechanism of protein-tyrosine kinase regulation.
Area of Science:
- Biochemistry
- Cell Signaling
- Molecular Biology
Background:
- The Tec family is a subfamily of nonreceptor protein-tyrosine kinases (PTKs).
- Tec and Lyn kinases are coexpressed in many hematopoietic cell types.
- Previous research established an in vitro and in vivo association between Tec and Lyn kinases via the Tec-homology domain.
Purpose of the Study:
- To investigate the biological role of the Tec-Lyn kinase association.
- To determine if Lyn kinase regulates Tec protein activity.
- To elucidate the signaling pathway involving Tec and Lyn kinases.
Main Methods:
- In vitro kinase assays.
- Yeast two-hybrid system for protein interaction studies.
- Coexpression of Tec and Lyn in 3T3 fibroblasts to analyze phosphorylation and activation states.
Main Results:
- Lyn kinase directly phosphorylates tyrosine residues on Tec protein, leading to Tec activation in fibroblasts.
- Tec protein is a direct substrate of Lyn kinase, confirmed by in vitro and yeast system assays.
- Tec coexpression has minimal impact on Lyn kinase's phospho-tyrosine content, suggesting unidirectional regulation.
Conclusions:
- Tec protein functions downstream of Lyn kinase in intracellular signaling pathways.
- This study presents a novel instance of one protein-tyrosine kinase (PTK) being phosphorylated and regulated by another PTK.
- The findings elucidate a new regulatory mechanism within the Tec kinase family and their interaction with Src family kinases like Lyn.