Phosphorylation of the PDGF receptor beta subunit creates a tight binding site for phosphatidylinositol 3 kinase.

Abstract

The beta subunit of the platelet derived growth factor receptor (PDGFR) coprecipitates with a phosphatidyl‐inositol 3 kinase activity (PI3K) following stimulation of cells by PDGF. Mutagenesis of a tyrosine (Y) phosphorylation site, Y751, in the PDGFR, greatly reduces PI3K, consistent with the possibility that phosphorylation of Y751 signals association of PI3K. To test this we have reconstituted the binding of the PDGFR beta subunit and PI3K in vitro. Binding is rapid, saturable and requires phosphorylation of the PDGFR at Y751, but does not require PDGF‐dependent phosphorylation of PI3K. To test which portions of the PDGFR are important for binding, we used an antibody to a small region of the receptor that includes Y751. This antibody blocked in vitro binding of PI3K to the receptor, while an antiserum to the C‐terminus of the receptor had no effect on binding of PI3K. In addition, we found that PDGF stimulation of a cell results in the association of essentially all the PI3K activity with cellular PDGFRs. These data suggest that PI3K is a specific ligand for PDGF receptors that are phosphorylated at Y751.

Platelet-derived Growth Factor Stimulation of Monocyte Chemoattractant Protein-1 Gene Expression Is Mediated by Transient Activation of the Phosphoinositide 3-Kinase Signal Transduction Pathway

“…Within the human PDGF ␤-receptor subunit, tyrosines 740 and 751 serve, in the phosphorylated state, as binding sites for the p85 adapter subunit of PI 3-kinase (38). As shown by immunoblot analysis with phosphorylation state-specific antibodies (29), neither wortmannin nor LY294002 interfered with phosphorylation of the p85 recognition sites (Fig.…”

Expression and differential signaling of heregulins in pancreatic cancer cells

“…66 Briefly, immunoprecipitated PY-20 from approximately 5 3 10 5 cells was incubated with phosphatidylinositol in the presence of [ 32 P]-g-adenosine triphosphate (ATP). The reactions were terminated, and the phospholipids were extracted and resolved by thin-layer chromatography.…”

LL5β Is a Phosphatidylinositol (3,4,5)-Trisphosphate Sensor That Can Bind the Cytoskeletal Adaptor, γ-Filamin

“…A number of receptor tyrosine kinases (relevant here, the PDGF ␤-receptor) are capable of binding type IA PI3Ks at specific tyrosine residues that become phosphorylated following ligand binding (4). Mutation of these tyrosines to phenylalanine blocks type IA PI3K binding and activation but does not affect association of other effectors (1,5). Stable, clonal cell lines have been created overexpressing wild-type PDGF-␤ receptors or (Y740F/Y751F) PDGF-␤ receptors (6) that have allowed the impact of selectivity blocking type IA PI3K activation to be assessed in vivo (7).…”