title: Effect of the activation of phosphatidylinositol 3-kinase by a thiophosphotyrosine peptide on glucose transport in 3T3-L1 adipocytes.
abstract: Insulin causes the activation of phosphatidylinositol 3-kinase (PI 3-kinase) through complexation of tyrosine-phosphorylated YMXM motifs on insulin receptor substrate 1 with the Src homology 2 domains of PI 3-kinase. Previous studies with inhibitors have indicated that activation of PI 3-kinase is necessary for the stimulation of glucose transport in adipocytes. Here, we investigate whether this activation is sufficient for this effect. Short peptides containing two tyrosine-phosphorylated or thiophosphorylated YMXM motifs potently activated PI 3-kinase in the cytosol from 3T3-L1 adipocytes. Introduction of the phosphatase-resistant thiophosphorylated peptide into 3T3-L1 adipocytes through permeabilization with Staphylococcus aureus alpha-toxin stimulated PI 3-kinase as strongly as insulin. However, under the same conditions the peptide increased glucose transport into the permeabilized cells only 20% as well as insulin. Determination of the distribution of the glucose transporter isotype GLUT4 by confocal immunofluorescence showed that GLUT4 translocation to the plasma membrane can account for the effect of the peptide. These results suggest that one or more other insulin-triggered signaling pathways, besides the PI 3-kinase one, participate in the stimulation of glucose transport.
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Herbst
authors.forename: G C
authors.initials: GC
authors.lastname: Andrews
authors.forename: L G
authors.initials: LG
authors.lastname: Contillo
authors.forename: D H
authors.initials: DH
authors.lastname: Singleton
authors.forename: P E
authors.initials: PE
authors.lastname: Genereux
authors.forename: E M
authors.initials: EM
authors.lastname: Gibbs
authors.forename: G E
authors.initials: GE
authors.lastname: Lienhard
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation; D002454:Cell Differentiation; D002463:Cell Membrane Permeability; D003600:Cytosol / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D051379:Mice; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000302:isolation & purification; D009124:Muscle Proteins; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011485:Protein Binding; D018909:src Homology Domains
chemical_list: D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009842:Oligopeptides; C495693:Slc2a4 protein, mouse; C096390:tyrosyl-norleucyl-prolyl-norleucyl-seryl-glycyl-seryl-tyrosyl-norleucyl-prolyl-norleucyl-serine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D005947:Glucose