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The type 2 vascular endothelial growth factor receptor recruits insulin receptor substrate-1 in its signalling
Duraisamy Senthil1, Goutam Ghosh Choudhury, Basant K Bhandari
1Department of Medicine, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
Abstract:
Vascular endothelial growth factor (VEGF) isoforms exert their biological effects through receptors that possess intrinsic tyrosine kinase activity. Whether VEGF binding to its receptors recruits insulin receptor substrate (IRS) family of docking proteins to the receptor is not known. Following incubation of mouse kidney proximal tubular epithelial cells with VEGF, we observed an increase in tyrosine phosphorylation of several proteins, including one of approximately 200 kDa, suggesting possible regulation of phosphorylation of IRS proteins. VEGF augmented tyrosine phosphorylation of IRS-1 in kidney epithelial cells and rat heart endothelial cells in a time-dependent manner. In the epithelial cells, association of IRS-1 with type 2 VEGF receptor was promoted by VEGF. VEGF also increased association of IRS-1 with the p85 regulatory subunit of phosphoinositide 3-kinase (PI 3-kinase), and PI 3-kinase activity in IRS-1 immunoprecipitates was increased in VEGF-treated cells. Incubation of epithelial cells with antisense IRS-1 oligonucleotide, but not sense oligonucleotide, reduced expression of the protein and VEGF-induced PI 3-kinase activity in IRS-1 immunoprecipitates. Additionally, VEGF-induced protein synthesis was also impaired by antisense but not sense IRS-1 oligonucleotide. These data provide the first evidence that binding of VEGF to its type 2 receptor promotes association of IRS-1 with the receptor complex. This association may account for some of the increase in VEGF-induced PI 3-kinase activity, and the increase in de novo protein synthesis seen in renal epithelial cells.
Insights
Vascular Endothelial Growth Factor (VEGF) binding to its type 2 receptor promotes insulin receptor substrate-1 (IRS-1) association, enhancing phosphoinositide 3-kinase activity and protein synthesis in kidney cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Vascular Endothelial Growth Factor (VEGF) mediates biological effects via tyrosine kinase receptors.
- The interaction between VEGF receptors and insulin receptor substrate (IRS) proteins is not fully understood.
Purpose of the Study:
- To investigate whether VEGF binding to its receptors recruits IRS proteins.
- To elucidate the role of IRS-1 in VEGF-induced signaling pathways.
Main Methods:
- Incubation of mouse kidney proximal tubular epithelial cells and rat heart endothelial cells with VEGF.
- Analysis of protein tyrosine phosphorylation and protein-protein interactions using immunoprecipitation.
- Assessment of phosphoinositide 3-kinase (PI 3-kinase) activity.
- Use of antisense and sense oligonucleotides to modulate IRS-1 expression.
Main Results:
- VEGF increased tyrosine phosphorylation of IRS-1 in kidney epithelial and heart endothelial cells.
- VEGF promoted the association of IRS-1 with the type 2 VEGF receptor and the p85 regulatory subunit of PI 3-kinase.
- VEGF-induced PI 3-kinase activity and protein synthesis were dependent on IRS-1 expression.
Conclusions:
- VEGF binding to its type 2 receptor facilitates IRS-1 recruitment to the receptor complex.
- This interaction contributes to increased VEGF-induced PI 3-kinase activity and de novo protein synthesis in renal epithelial cells.