Dynamics of the Phosphoinositide 3-Kinase p110δ Interaction with p85α and Membranes Reveals Aspects of Regulation Distinct from p110α

• Published in: Structure (London) Vol. 19; no. 8; pp. 1127 - 1137
• Main Authors: Burke, John E., Vadas, Oscar, Berndt, Alex, Finegan, Tara, Perisic, Olga, Williams, Roger L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 10-08-2011; Cell Press
• Subjects: Amino Acid Substitution; Animals; Class I Phosphatidylinositol 3-Kinases; Class Ia Phosphatidylinositol 3-Kinase - chemistry; Class Ia Phosphatidylinositol 3-Kinase - genetics; Deuterium Exchange Measurement; Humans; Liposomes - chemistry; Membrane Lipids - chemistry; Mice; Models, Molecular; Mutagenesis, Site-Directed; Peptide Fragments; Phosphatidylinositol 3-Kinases - chemistry; Protein Binding; Protein Interaction Domains and Motifs; Protein Structure, Secondary; Receptors, Platelet-Derived Growth Factor - chemistry; Surface Properties
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2011.06.003

Phosphoinositide 3-kinase δ is upregulated in lymphocytic leukemias. Because the p85-regulatory subunit binds to any class IA subunit, it was assumed there is a single universal p85-mediated regulatory mechanism; however, we find isozyme-specific inhibition by p85α. Using deuterium exchange mass spectrometry (DXMS), we mapped regulatory interactions of p110δ with p85α. Both nSH2 and cSH2 domains of p85α contribute to full inhibition of p110δ, the nSH2 by contacting the helical domain and the cSH2 via the C terminus of p110δ. The cSH2 inhibits p110β and p110δ, but not p110α, implying that p110α is uniquely poised for oncogenic mutations. Binding RTK phosphopeptides disengages the SH2 domains, resulting in exposure of the catalytic subunit. We find that phosphopeptides greatly increase the affinity of the heterodimer for PIP2-containing membranes measured by FRET. DXMS identified regions decreasing exposure at membranes and also regions gaining exposure, indicating loosening of interactions within the heterodimer at membranes.
► Both nSH2 and cSH2 of p85α inhibit p110δ, and pY peptides or mutations activate ► DXMS mapped dynamic changes in free p110δ and p110δ/p85 with and without pY peptides ► pY peptide increases p110δ/p85 affinity for lipids; interactions were mapped by DXMS ► cSH2 point mutation in p85α activates p110δ and p110β, but not p110α