RESUMO
Protein kinase B (PKB) is activated in response to phosphoinositide 3-kinases and their lipid products phosphatidylinositol 3,4, 5-trisphosphate [PtdIns(3,4,5)P3] and PtdIns(3,4)P2 in the signaling pathways used by a wide variety of growth factors, antigens, and inflammatory stimuli. PKB is a direct target of these lipids, but this regulation is complex. The lipids can bind to the pleckstrin homologous domain of PKB, causing its translocation to the membrane, and also enable upstream, Thr308-directed kinases to phosphorylate and activate PKB. Four isoforms of these PKB kinases were purified from sheep brain. They bound PtdIns(3,4,5)P3 and associated with lipid vesicles containing it. These kinases contain an NH2-terminal catalytic domain and a COOH-terminal pleckstrin homologous domain, and their heterologous expression augments receptor activation of PKB, which suggests they are the primary signal transducers that enable PtdIns(3,4,5)P3 or PtdIns- (3,4)P2 to activate PKB and hence to control signaling pathways regulating cell survival, glucose uptake, and glycogen metabolism.
Assuntos
Fosfatos de Fosfatidilinositol/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Transdução de Sinais , Proteínas Quinases Dependentes de 3-Fosfoinositídeo , Processamento Alternativo , Sequência de Aminoácidos , Animais , Linhagem Celular , Membrana Celular/enzimologia , Clonagem Molecular , DNA Complementar , Drosophila , Proteínas de Drosophila , Ativação Enzimática , Humanos , Lipossomos/metabolismo , Dados de Sequência Molecular , Fases de Leitura Aberta , Fosforilação , Fator de Crescimento Derivado de Plaquetas/farmacologia , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/isolamento & purificação , Proteínas Proto-Oncogênicas c-akt , Ratos , Proteínas Recombinantes/metabolismo , OvinosRESUMO
The solid phase synthesis of oligoribonucleotides using the H-phosphonate approach and the 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl (Ctmp) and dimethoxytrityl (DMTr) groups, respectively, for the protection of the 2'- and 5'-hydroxy functions is described. The use of a new reagent, tris-(1,1,1,3,3,3-hexafluoro-2-propyl) phosphite for the preparation of nucleoside H-phosphonate units is also discussed in detail.