Identification of wortmannin-sensitive targets in 3T3-L1 adipocytes. Dissociation of insulin-stimulated glucose uptake and GLUT4 translocation

Sharon F. Hausdorff, Diane C. Fingar, Kazuko Morioka, Luis A. Garza, Eileen L. Whiteman, Scott A. Summers, Morris J. Birnbaum

Research output: Contribution to journalArticle

Abstract

The current studies investigated the contribution of phosphatidylinositol 3-kinase (PI3-kinase) isoforms to insulin-stimulated glucose uptake and glucose transporter 4 (GLUT4) translocation. Experiments involving the microinjection of antibodies specific for the p110 catalytic subunit of class I PI3-kinases demonstrated an absolute requirement for this form of the enzyme in GLUT4 translocation. This finding was confirmed by the demonstration that the PI3-kinase antagonist wortmannin inhibits GLUT4 and insulin-responsive aminopeptidase translocation with a dose response identical to that required to inhibit another class I PI3-kinase-dependent event, activation of pp70 S6-kinase. Interestingly, wortmannin inhibited insulin-stimulated glucose uptake at much lower doses, suggesting the existence of a second, higher affinity target of the drug. Subsequent removal of wortmannin from the media shifted this dose-response curve to one resembling that for GLUT4 translocation and pp70 S6-kinase. This is consistent with the lower affinity target being p110, which is irreversibly inhibited by wortmannin. Wortmannin did not reduce glucose uptake in cells stably expressing Myr-Akt, which constitutively induced GLUT4 translocation to the plasma membrane; this demonstrates that wortmannin does not inhibit the transporters directly. In addition to elucidating a second wortmannin- sensitive pathway in 3T3-L1 adipocytes, these studies suggest that the presence of GLUT4 on the plasma membrane is not sufficient for activation of glucose uptake.

Original languageEnglish (US)
Pages (from-to)24677-24684
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number35
DOIs
StatePublished - Aug 27 1999
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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