Molecular determinants of PI3K?-mediated activation downstream of G-protein-coupled receptors (GPCRs).

ABSTRACT: Phosphoinositide 3-kinase gamma (PI3K?) has profound roles downstream of G-protein-coupled receptors in inflammation, cardiac function, and tumor progression. To gain insight into how the enzyme's activity is shaped by association with its p101 adaptor subunit, lipid membranes, and G?? heterodimers, we mapped these regulatory interactions using hydrogen-deuterium exchange mass spectrometry. We identify residues in both the p110? and p101 subunits that contribute critical interactions with G?? heterodimers, leading to PI3K? activation. Mutating G??-interaction sites of either p110? or p101 ablates G-protein-coupled receptor-mediated signaling to p110?/p101 in cells and severely affects chemotaxis and cell transformation induced by PI3K? overexpression. Hydrogen-deuterium exchange mass spectrometry shows that association with the p101 regulatory subunit causes substantial protection of the RBD-C2 linker as well as the helical domain of p110?. Lipid interaction massively exposes that same helical site, which is then stabilized by G??. Membrane-elicited conformational change of the helical domain could help prepare the enzyme for G?? binding. Our studies and others identify the helical domain of the class I PI3Ks as a hub for diverse regulatory interactions that include the p101, p87 (also known as p84), and p85 adaptor subunits; Rab5 and G?? heterodimers; and the ?-adrenergic receptor kinase.

SUBMITTER: Vadas O 

PROVIDER: S-EPMC3839701 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature