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The v-Src SH3 domain binds phosphatidylinositol 3'-kinase
X Liu1, L E Marengere, C A Koch
1Division of Molecular and Developmental Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
Molecular and Cellular Biology
|September 1, 1993
Summary
The v-Src tyrosine kinase interacts with phosphatidylinositol 3-kinase (PI 3-kinase) through its SH3 domain. This interaction involves direct binding to the p85 subunit of PI 3-kinase, influencing cellular transformation.
Area of Science:
- Cellular Biology
- Molecular Oncology
- Signal Transduction
Background:
- v-Src tyrosine kinase activation in fibroblasts leads to elevated polyphosphoinositides.
- This elevation is linked to phosphatidylinositol 3-kinase (PI 3-kinase) activation.
- PI 3-kinase activity is increased in v-Src-transformed cells and associates with v-Src.
Purpose of the Study:
- To identify the specific regions of v-Src responsible for interacting with PI 3-kinase.
- To elucidate the molecular mechanism of v-Src and PI 3-kinase interaction.
Main Methods:
- Expression of v-Src SH2 and SH3 domains in bacteria.
- In vitro binding assays using bacterial domain expression products and fibroblast lysates.
- Site-directed mutagenesis of conserved residues within the v-Src SH3 domain.
Main Results:
- The v-Src SH3 domain, not the SH2 domain, directly binds PI 3-kinase in vitro.
- Mutations in conserved SH3 residues abolish PI 3-kinase binding.
- The v-Src SH3 domain binds to the N-terminal region of the p85 alpha subunit of PI 3-kinase.
Conclusions:
- The v-Src SH3 domain mediates the interaction with PI 3-kinase.
- Direct binding of the v-Src SH3 domain to p85 is crucial for this interaction.
- This interaction likely plays a role in v-Src-mediated cellular transformation.