TY - JOUR
T1 - Identification of wortmannin-sensitive targets in 3T3-L1 adipocytes. Dissociation of insulin-stimulated glucose uptake and GLUT4 translocation
AU - Hausdorff, Sharon F.
AU - Fingar, Diane C.
AU - Morioka, Kazuko
AU - Garza, Luis A.
AU - Whiteman, Eileen L.
AU - Summers, Scott A.
AU - Birnbaum, Morris J.
PY - 1999/8/27
Y1 - 1999/8/27
N2 - 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.
AB - 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.
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U2 - 10.1074/jbc.274.35.24677
DO - 10.1074/jbc.274.35.24677
M3 - Article
C2 - 10455135
AN - SCOPUS:0033609911
SN - 0021-9258
VL - 274
SP - 24677
EP - 24684
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 35
ER -