title: Assigning functional domains within the p101 regulatory subunit of phosphoinositide 3-kinase gamma.
abstract: Phosphoinositide 3-Kinase (PI3K) gamma is a lipid kinase that is regulated by G-protein-coupled receptors. It plays a crucial role in inflammatory and allergic processes. Activation of PI3Kgamma is primarily mediated by Gbetagamma subunits. The regulatory p101 subunit of PI3Kgamma binds to Gbetagamma and, thereby, recruits the catalytic p110gamma subunit to the plasma membrane. Despite its crucial role in the activation of PI3Kgamma, the structural organization of p101 is still largely elusive. Employing fluorescence resonance energy transfer measurements, coimmunoprecipitation and colocalization studies with p101 deletion mutants, we show here that distinct regions within the p101 primary structure are responsible for interaction with p110gamma and Gbetagamma. The p110gamma binding site is confined to the N terminus, whereas binding to Gbetagamma is mediated by a C-terminal domain of p101. These domains appear to be highly conserved among various species ranging from Xenopus to men. In addition to establishing a domain structure for p101, our results point to the existence of a previously unknown, p101-related regulatory subunit for PI3Kgamma.
authors.affiliation: Institut für Pharmakologie, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Thielallee 67-73, 14195 Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Voigt
authors.forename: Carsten
authors.initials: C
authors.lastname: Brock
authors.forename: Bernd
authors.initials: B
authors.lastname: Nürnberg
authors.forename: Michael
authors.initials: M
authors.lastname: Schaefer
mesh_terms: D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D058544:Class Ib Phosphatidylinositol 3-Kinase; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D017353:Gene Deletion; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007527:Isoenzymes / Q000737:chemistry* / Q000502:physiology*; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546760:PIK3CG protein, human; C546764:Pik3cg protein, mouse