title: PI3 kinase directly phosphorylates Akt1/2 at Ser473/474 in the insulin signal transduction pathway.
abstract: Insulin stimulated translocation of the glucose transporter GLUT4 from the cytosol to the plasma membrane in a concentration (1  nM-1  μM)-dependent manner and increased glucose uptake in 3T3-L1 adipocytes. Insulin-induced GLUT4 translocation to the cell surface was prevented by the phosphoinositide 3 kinase (PI3K) inhibitor wortmannin, the 3-phosphoinositide-dependent protein kinase 1 (PDK1) inhibitor BX912 or the Akt1/2 inhibitor MK2206, and by knocking-down PI3K, PDK1 or Akt1/2. Insulin increased phosphorylation of Akt1/2 at Thr308/309 and Ser473/474, to activate Akt1/2, in the adipocytes. Insulin-induced phosphorylation of Akt1/2 was suppressed by wortmannin and knocking-down PI3K, while no significant inhibition of the phosphorylation was obtained with BX912 or knocking-down PDK1. In the cell-free Akt assay, PI3K phosphorylated Akt1 both at Thr308 and Ser473 and Akt2 at Ser474 alone. In contrast, PDK1 phosphorylates Akt1 at Thr308 and Akt2 at Thr309. The results of this study indicate that PI3K activates Akt1, independently of PDK1, and Akt2 by cooperating with PDK1 in the insulin signal transduction pathway linked to GLUT4 translocation.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: T
authors.initials: T
authors.lastname: Kanno
authors.forename: T
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D034622:RNA Interference; D012694:Serine / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D005947:Glucose; D051275:Glucose Transporter Type 4; D006575:Heterocyclic Compounds, 3-Ring; D007004:Hypoglycemic Agents; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D012694:Serine; D013912:Threonine; D000077191:Wortmannin; C548887:MK 2206; C000631433:Pdk1 protein, mouse; C495693:Slc2a4 protein, mouse; C514862:Akt1 protein, mouse; C494922:Akt2 protein, mouse
keywords: GLUT4; adipocyte; cell biology; insulin signaling