Phosphatidylinositol 3-kinase activation is required for insulin stimulation of pp70 S6 kinase, DNA synthesis, and glucose transporter translocation.
Phosphatidylinositol 3-kinase (PI 3-kinase) is stimulated by insulin and a variety of growth factors, but its exact role in signal transduction remains unclear. We have used a novel, highly specific inhibitor of PT 3-kinase to dissect the role of this enzyme in insulin action. Treatment of intact 3T3-L1 adipocytes with LY294002 produced a dose-dependent inhibition of insulin-stimulated PI 3-kinase (50% inhibitory concentration, 6 microM) with > 95% reduction in the levels of phosphatidylinositol-3,4,5-trisphosphate without changes in the levels of phosphatidylinositol-4-monophosphate or its derivatives. In parallel, there was a complete inhibition of insulin-stimulated phosphorylation and activation of pp70 S6 kinase. Inhibition of PI 3-kinase also effectively blocked insulin- and serum-stimulated DNA synthesis and insulin-stimulated glucose uptake by inhibiting translocation of GLUT 4 glucose transporters to the plasma membrane. By contrast, LY294002 had no effect on insulin stimulation of mitogen-activated protein kinase or pp90 S6 kinase. Thus, activation of PI 3-kinase plays a critical role in mammalian cells and is required for activation of pp70 S6 kinase and DNA synthesis and certain forms of intracellular vesicular trafficking but not mitogen-activated protein kinase or pp90 S6 kinase activation. These data suggest that PI 3-kinase is not only an important component but also a point of divergence in the insulin signaling network.
Cheatham
B
B
Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02215.
Vlahos
C J
CJ
Cheatham
L
L
Wang
L
L
Blenis
J
J
Kahn
C R
CR
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D008954:Models, Biological; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction / Q000187:drug effects
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002867:Chromones; D004247:DNA; D003847:Deoxyglucose; D004791:Enzyme Inhibitors; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one