Tyrosine kinase-deficient mutant human insulin receptors (Met1153--&gt;Ile) overexpressed in transfected rat adipose cells fail to mediate translocation of epitope-tagged GLUT4.

Quon, Michael J.; Guerre-Millo, Michéle; Zarnowski, Mary Jane; Butte, Atul J.; Em, Manevich; Cushman, Samuel W.; Taylor, Simeon I.

doi:10.1073/pnas.91.12.5587

Cited by 93 publications

(111 citation statements)

References 27 publications

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“…Expression of GLUT4-HA was ϳ5% of the adipocytes subjected to electroporation. This system allowed us to overcome the potential difficulty of studying such a small population of cells using GLUT4-HA as a reporter gene (16). Therefore, we could study transiently transfected cells exclusively without interference from nontransfected cells.…”

Section: Discussionmentioning

confidence: 99%

Troglitazone Not Only Increases GLUT4 but Also Induces Its Translocation in Rat Adipocytes

et al. 2001

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Thiazolidinediones, insulin-sensitizing agents, have been reported to increase glucose uptake along with the expression of glucose transporters in adipocytes and cardiomyocytes. Recently, we have further suggested that the translocation of GLUT4 is stimulated by thiazolidinediones in L6 myocytes. However, the direct effects of thiazolidinediones on translocation of glucose transporters have not yet been determined. In this study, using hemagglutinin epitope-tagged GLUT4 (GLUT4-HA), we provide direct evidence of the effect of troglitazone on the translocation of GLUT4 in rat epididymal adipocytes. Primary cultures of rat adipocytes were transiently transfected with GLUT4-HA and overexpressed eightfold compared with endogenous GLUT4 in transfected cells. A total of 24 h of treatment with troglitazone (10 ؊4 mol/l) increased the cell surface level of GLUT4-HA by 1.5 ؎ 0.03-fold (P < 0.01) without changing the total amount of GLUT4-HA, whereas it increased the protein level of endogenous GLUT4 (1.4-fold) without changing that of GLUT1. Thus, the direct effect on the translocation can be detected apart from the increase in endogenous GLUT4 content using GLUT4-HA. Troglitazone not only increased the translocation of GLUT4-HA on the cell surface in the basal state but also caused a leftward shift in the doseresponse relations between GLUT4-HA translocation and insulin concentration in the medium (ED 50 : from ϳ0.1 to 0.03 nmol/l). These effects may partly contribute to the antidiabetic activity of troglitazone in patients with obesity and type 2 diabetes.

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Section: Discussionmentioning

confidence: 99%

Troglitazone Not Only Increases GLUT4 but Also Induces Its Translocation in Rat Adipocytes

et al. 2001

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“…Both IRS-1 and the recently discovered IRS-2 play a major role in insulin-mediated metabolic signaling and glucose transport (Rice and Garner, 1994;Quon et al, 1994). Many of the e ects of insulin are thought to be mediated by the interaction of IRS-1 and IRS-2 (Sun et al, 1991) with SH2-containing enzymes and adaptor molecules .…”

Section: Introductionmentioning

confidence: 99%

Allelic deletion at 11q23.3-q25 is an early event in cervical neoplasia

et al. 1998

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We have studied the involvement of murine c-Crk, an SH2/SH3 containing adaptor protein, in signaling pathways stimulated by di erent receptor tyrosine kinases. We show here that c-Crk is associated with components of insulin-and PDGF-dependent signaling pathways. Insulin treatment of murine myoblast cells induces the formation of stable complex of endogenous cCrk with insulin receptor substrate-1 (IRS-1) mediated via the SH2 domain of Crk. The ligand dependent physical association of c-Crk with IRS-1 is direct. However IRS-1 is also co-precipitated with c-Crk from quiescent L6 cells. The association of IRS-1 with c-Crk in quiescent cells is probably not direct since Far Western blot analysis did not reveal the binding of neither SH2 domain nor amino-terminal SH3 domain of c-Crk to IRS-1 from unstimulated cells. We also show that PDGF treatment of murine myoblast cells induces association of c-Crk with the PDGF receptor and tyrosine phosphorylation of c-Crk. Overexpression of cCrk enhanced insulin-but not PDGF-induced activation of MAP kinases when compared to parental cell lines. Thus, the formation of the direct IRS-1/Crk complex appears to be crucial for Crk-mediated insulin-induced activation of MAP kinase, whereas Crk is probably involved in other PDGF-induced responses. These data provide support to the hypothesis that insulin and PDGF employ di erent mechanisms for activation of MAP kinase cascade.

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“…The requirement for an active receptor tyrosine kinase as a prerequisite for GLUT4 translocation has also recently been demonstrated in a rat adipocyte transfection system. Overexpression of human insulin receptors raises basal levels of GLUT4 expression but receptors with a Met1153-Ile mutation (lacking tyrosine kinase activity) fail to mediate this enhanced basal translocation [14].…”

Section: Insulin Receptor Mutants Altering Glucose Transportmentioning

confidence: 99%