Structural and biochemical evaluation of the interaction of the phosphatidylinositol 3-kinase p85 alpha src homology 2 domains with phosphoinositidesand inositol polyphosphates

Citation
P. Lo Surdo et al., Structural and biochemical evaluation of the interaction of the phosphatidylinositol 3-kinase p85 alpha src homology 2 domains with phosphoinositidesand inositol polyphosphates, J BIOL CHEM, 274(22), 1999, pp. 15678-15685
Citations number
49
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
00219258 → ACNP
Volume
274
Issue
22
Year of publication
1999
Pages
15678 - 15685
Database
ISI
SICI code
0021-9258(19990528)274:22<15678:SABEOT>2.0.ZU;2-2
Abstract
Src homology 2 (SH2) domains exist in many intracellular proteins and have well characterized roles in signal transduction. SH2 domains bind to phosph otyrosine (Tyr(P))-containing proteins. Although tyrosine phosphorylation i s essential for protein-SHE domain interactions, the binding specificity al so derives from sequences C-terminal to the Tyr(P) residue. The high affini ty and specificity of this interaction is critical for precluding aberrant cross-talk between signaling pathways. The p85 alpha subunit of phosphoinos itide S-kinase (PI 3-kinase) contains two SH2 domains, and it has been prop osed that in competition with Tyr(P) binding they may also mediate membrane attachment via interactions with phosphoinositide products of PI 3-kinase. We used nuclear magnetic resonance spectroscopy and biosensor experiments to investigate interactions between the p85 alpha SH2 domains and phosphoin ositides or inositol polyphosphates. We reported previously a similar appro ach when demonstrating that some pleckstrin homology domains show binding s pecificity for distinct phosphoinositides (Salim, K., Bottomley, M. J., Que rfurth, E., Zvelebil, M. J., Gout, I., Scaife, R., Margolis, R. L., Gigg, R ., Smith, C. I., Driscoll, P. C., Waterfield, M. D., and Panayotou, G. (199 6) EMBO J. 15, 6241-6250). However, neither SH2 domain exhibited binding sp ecificity for phosphoinositides in phospholipid bilayers. We show that the p85 alpha SH2 domain Tyr(P) binding pockets indiscriminately accommodate ph osphoinositides and inositol polyphosphates. Binding of the SH2 domains to Tyr(P) peptides was only poorly competed for by phosphoinositides or inosit ol polyphosphates. We conclude that these ligands do not bind p85 alpha SH2 domains with high affinity or specificity. Moreover, we observed that alth ough wortmannin blocks PI S-kinase activity in vivo, it does not affect the ability of tyrosine-phosphorylated proteins to bind to p85 alpha. Conseque ntly phosphoinositide prodcts of PI 3 kinase are unlikely to regulate signa ling through p85 alpha SH2 domains.