Interaction of the p85 subunit of PI 3-kinase and its N-terminal SH2 domain with a PDGF receptor phosphorylation site: structural features and analysis of conformational changes.

Abstract

Circular dichroism and fluorescence spectroscopy were used to investigate the structure of the p85 alpha subunit of the PI 3‐kinase, a closely related p85 beta protein, and a recombinant SH2 domain‐containing fragment of p85 alpha. Significant spectral changes, indicative of a conformational change, were observed on formation of a complex with a 17 residue peptide containing a phosphorylated tyrosine residue. The sequence of this peptide is identical to the sequence surrounding Tyr751 in the kinase‐insert region of the platelet‐derived growth factor beta‐receptor (beta PDGFR). The rotational correlation times measured by fluorescence anisotropy decay indicated that phosphopeptide binding changed the shape of the SH2 domain‐containing fragment. The CD and fluorescence spectroscopy data support the secondary structure prediction based on sequence analysis and provide evidence for flexible linker regions between the various domains of the p85 proteins. The significance of these results for SH2 domain‐containing proteins is discussed.

Activation of the EBV/C3d Receptor (CR2, CD21) on Human B Lymphocyte Surface Triggers Tyrosine Phosphorylation of the 95-kDa Nucleolin and Its Interaction with Phosphatidylinositol 3 Kinase

“…Furthermore, our previous demonstration that CR2 activation led to activation of PI 3 kinase activity (39) and the herein identification of the p95 nucleolin suggest that interaction of tyrosine phosphorylated nucleolin with SH2 domains of the p85 subunit of PI 3 kinase more likely implies a similar mechanism to that already described by others (48) in activation of PI 3 kinase activity: i.e., Ptyr-containing protein by interacting with SH2 domain of p85 induces a conformational change in this regulatory subunit that activates the p110 catalytic subunit (48). One well-identified target of PI 3 kinase activation is the protein kinase Akt that plays a major role in protecting cells from apoptosis and in promoting cell proliferation (49,50).…”

Phosphorylation profiles of protein kinases in alveolar and embryonal rhabdomyosarcoma

“…We have also been able to obtain phosphorylation profiles of these selected tyrosine kinases and serine/threonine kinases in the mTOR and PKC pathways from rhabdomyosarcoma patient tissues. These protein kinases have been shown to contribute to cell proliferation and cell survival [31][32][33][34][35][36][37][38][39][40][41][42] and most of them are likely to play crucial roles in tumor development and progression of rhabdomyosarcomas. Therefore, selective small molecular inhibitors that block these activated protein kinases may be useful therapeutic reagents.…”

Interaction of Wild Type and Dominant-Negative p55PIK Regulatory Subunit of Phosphatidylinositol 3-Kinase with Insulin-Like Growth Factor-1 Signaling Proteins

“…This suggests that binding of p85 SH2 domains to phosphotyrosine-containing sequences leads to conformational changes in the protein. These structural modifications would be transmitted to p110 through its association with the IS domain of p85, resulting in p110 activation (10,11).…”