title: Insulin-mediated targeting of phosphatidylinositol 3-kinase to GLUT4-containing vesicles.
abstract: Phosphatidylinositol (PI) 3-kinase is hypothesized to be a signaling element in the acute redistribution of intracellular GLUT4 glucose transporters to the plasma membrane in response to insulin. However, some receptors activate PI 3-kinase without causing GLUT4 translocation, suggesting specific cellular localization may be critical to this PI 3-kinase function. Consistent with this idea, complexes containing PI 3-kinase bound to insulin receptor substrate 1 (IRS-1) in 3T3-L1 adipocytes are associated with intracellular membranes (Heller-Harrison, R., Morin, M. and Czech, M. (1995) J. Biol. Chem. 270, 24442-24450). We report here that in response to insulin, activated complexes of IRS-1.PI 3-kinase can be immunoprecipitated with anti-IRS-1 antibody from detergent extracts of immunoadsorbed GLUT4-containing vesicles prepared from 3T3-L1 adipocytes. The targeting of PI 3-kinase to rat adipocyte GLUT4-containing vesicles using vesicles prepared by sucrose velocity gradient ultracentrifugation was also demonstrated. Insulin treatment caused a 2.3-fold increase in immunoreactive p85 protein in these GLUT4-containing vesicles while anti-p85 immunoprecipitates of PI 3-kinase activity in GLUT4-containing vesicle extracts increased to a similar extent. HPLC analysis of the GLUT4 vesicle-associated PI 3-kinase activity showed insulin-mediated increases in PI 3-P, PI 3,4-P2, and PI 3,4,5-P3 when PI, PI 4-P, and PI 4,5-P2 were used as substrates. Our data demonstrate that insulin directs the association of PI 3-kinase with GLUT4-containing vesicles in 3T3-L1 and rat adipocytes, consistent with the hypothesis that PI 3-kinase is involved in the insulin-regulated movement of GLUT4 to the plasma membrane.
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester, Massachusetts 01605, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Heller-Harrison
authors.forename: M
authors.initials: M
authors.lastname: Morin
authors.forename: A
authors.initials: A
authors.lastname: Guilherme
authors.forename: M P
authors.initials: MP
authors.lastname: Czech
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects; D004789:Enzyme Activation; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D015388:Organelles / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000502:physiology; D015398:Signal Transduction
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C526296:Irs1 protein, rat; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011972:Receptor, Insulin