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Son of sevenless binds to the SH3 domain of src-type tyrosine kinase
1Signal Transduction Laboratory, Mogam Biotechnology Research Institute, Younginsi, Korea.
Abstract:
To identify molecules which bind to the SH3 domains of p56lck, we screened a mouse T-cell lymphoma cDNA library using the yeast two-hybrid system. As a result, we obtained several positive clones including the Son of Sevenless gene which encodes a mammalian homolog of Drosophila Ras GDP/GTP exchange factor. In a subsequent analysis with the yeast two-hybrid system, Sos associated only with the constitutively active form of p56lck (F505) but not with wild type p56lck (Y505), indicating the requirement for an active conformation of p56lck for binding to Sos. Subsequently, we have demonstrated in vitro that the SH3 domain of p56lck as well as the proline-rich sequences of Sos are responsible for this association. In addition, the proline-rich domain of Sos also bound to the SH3 domains of other src-type tyrosine kinases, src and fyn, but not to that of PLC-gamma. More importantly, the p56lck SH3-Sos interaction was enhanced by serum stimulation, suggesting the possibility that the direct interaction between p56lck SH3 and Sos may contribute to the regulation of the Ras pathway.
Insights
Researchers identified the Son of Sevenless (Sos) gene binding to the p56lck SH3 domain in T-cells. This interaction, crucial for Ras pathway regulation, requires an active p56lck conformation and is enhanced by serum stimulation.
Area of Science:
- Molecular Biology
- Cell Signaling
- Immunology
Background:
- The p56lck tyrosine kinase plays a critical role in T-cell receptor signaling.
- SH3 domains are known to mediate protein-protein interactions in signaling pathways.
- The Son of Sevenless (Sos) protein is a guanine nucleotide exchange factor for Ras.
Purpose of the Study:
- To identify proteins that bind to the SH3 domains of p56lck.
- To elucidate the molecular mechanism of p56lck and Sos interaction.
- To investigate the role of this interaction in regulating the Ras pathway.
Main Methods:
- Yeast two-hybrid screening of a mouse T-cell lymphoma cDNA library.
- In vitro binding assays using purified proteins.
- Analysis of protein interactions under different cellular conditions (e.g., serum stimulation).
Main Results:
- The Son of Sevenless (Sos) gene was identified as a binding partner for p56lck.
- Sos binding to p56lck requires a constitutively active conformation of p56lck.
- The SH3 domain of p56lck and proline-rich sequences of Sos mediate the interaction.
- This interaction is enhanced by serum stimulation and also occurs with other src-type kinases like Src and Fyn.
Conclusions:
- The direct interaction between p56lck SH3 and Sos is a key event in T-cell signaling.
- This interaction likely contributes to the regulation of the Ras pathway.
- The findings provide insights into the molecular basis of T-cell activation and signal transduction.