title: Identification and characterization of the autophosphorylation sites of phosphoinositide 3-kinase isoforms beta and gamma.
abstract: Class I phosphoinositide 3-kinases (PI3Ks) are bifunctional enzymes possessing lipid kinase activity and the capacity to phosphorylate their catalytic and/or regulatory subunits. In this study, in vitro autophosphorylation of the G protein-sensitive p85-coupled class I(A) PI3K beta and p101-coupled class I(B) PI3K gamma was examined. Autophosphorylation sites of both PI3K isoforms were mapped to C-terminal serine residues of the catalytic p110 subunit (i.e. serine 1070 of p110 beta and serine 1101 of p110 gamma). Like other class I(A) PI3K isoforms, autophosphorylation of p110 beta resulted in down-regulated PI3K beta lipid kinase activity. However, no inhibitory effect of p110 gamma autophosphorylation on PI3K gamma lipid kinase activity was observed. Moreover, PI3K beta and PI3K gamma differed in the regulation of their autophosphorylation. Whereas p110 beta autophosphorylation was stimulated neither by G beta gamma complexes nor by a phosphotyrosyl peptide derived from the platelet-derived growth factor receptor, autophosphorylation of p110 gamma was significantly enhanced by G beta gamma in a time- and concentration-dependent manner. In summary, we show that autophosphorylation of both PI3K beta and PI3K gamma occurs in a C-terminal region of the catalytic p110 subunit but differs in its regulation and possible functional consequences, suggesting distinct roles of autophosphorylation of PI3K beta and PI3K gamma.
authors.affiliation: Institut für Biochemie und Molekularbiologie II, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Czupalla
authors.forename: Miran
authors.initials: M
authors.lastname: Culo
authors.forename: Eva-Christina
authors.initials: EC
authors.lastname: Müller
authors.forename: Carsten
authors.initials: C
authors.lastname: Brock
authors.forename: H Peter
authors.initials: HP
authors.lastname: Reusch
authors.forename: Karsten
authors.initials: K
authors.lastname: Spicher
authors.forename: Eberhard
authors.initials: E
authors.lastname: Krause
authors.forename: Bernd
authors.initials: B
authors.lastname: Nürnberg
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002384:Catalysis; D002460:Cell Line; D017931:DNA Primers; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D011994:Recombinant Proteins; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases