Insulin stimulation of GLUT-4 translocation: a model for regulated recycling

To study molecular mechanisms for glucosamine-induced insulin resistance, we induced complete and reversible insulin resistance in 3T3-L1 adipocytes with glucosamine in a dose- and time-dependent manner (maximal effects at 50 mM glucosamine after 6 h). In these cells, glucosamine impaired insulin-stimulated GLUT-4 translocation. Glucosamine (6 h) did not affect insulin-stimulated tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 and -2 and weakly, if at all, impaired insulin stimulation of phosphatidylinositol 3-kinase. Glucosamine, however, severely impaired insulin stimulation of Akt. Inhibition of insulin-stimulated glucose transport was correlated with that of Akt activity. In these cells, glucosamine also inhibited insulin stimulation of p70 S6 kinase. Glucosamine did not alter basal glucose transport and insulin stimulation of GLUT-1 translocation and mitogen-activated protein kinase. In summary, glucosamine induced complete and reversible insulin resistance in 3T3-L1 adipocytes. This insulin resistance was accompanied by impaired insulin stimulation of GLUT-4 translocation and Akt activity, without significant impairment of upstream molecules in insulin-signaling pathway.

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Lipid raft microdomain compartmentalization of TC10 is required for insulin signaling and GLUT4 translocation

The Journal of Cell Biology ◽

10.1083/jcb.200102078 ◽

2001 ◽

Vol 154 (4) ◽

pp. 829-840 ◽

Cited By ~ 118

Author(s):

Robert T. Watson ◽

Satoshi Shigematsu ◽

Shian-Huey Chiang ◽

Silvia Mora ◽

Makoto Kanzaki ◽

...

Keyword(s):

Lipid Raft ◽

Membrane Trafficking ◽

Glucose Transporter ◽

Spatial Separation ◽

Glut4 Translocation ◽

Insulin Stimulation ◽

Glut 4 Translocation ◽

Raft Domains ◽

Lipid Raft Microdomains ◽

Stimulation Of

Recent studies indicate that insulin stimulation of glucose transporter (GLUT)4 translocation requires at least two distinct insulin receptor–mediated signals: one leading to the activation of phosphatidylinositol 3 (PI-3) kinase and the other to the activation of the small GTP binding protein TC10. We now demonstrate that TC10 is processed through the secretory membrane trafficking system and localizes to caveolin-enriched lipid raft microdomains. Although insulin activated the wild-type TC10 protein and a TC10/H-Ras chimera that were targeted to lipid raft microdomains, it was unable to activate a TC10/K-Ras chimera that was directed to the nonlipid raft domains. Similarly, only the lipid raft–localized TC10/ H-Ras chimera inhibited GLUT4 translocation, whereas the TC10/K-Ras chimera showed no significant inhibitory activity. Furthermore, disruption of lipid raft microdomains by expression of a dominant-interfering caveolin 3 mutant (Cav3/DGV) inhibited the insulin stimulation of GLUT4 translocation and TC10 lipid raft localization and activation without affecting PI-3 kinase signaling. These data demonstrate that the insulin stimulation of GLUT4 translocation in adipocytes requires the spatial separation and distinct compartmentalization of the PI-3 kinase and TC10 signaling pathways.

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Translocation of the brain-type glucose transporter largely accounts for insulin stimulation of glucose transport in BC3H-1 myocytes

Biochemical Journal ◽

10.1042/bj2690597 ◽

1990 ◽

Vol 269 (3) ◽

pp. 597-601 ◽

Cited By ~ 31

Author(s):

D M Calderhead ◽

K Kitagawa ◽

G E Lienhard ◽

G W Gould

Keyword(s):

Glucose Transport ◽

Glucose Transporter ◽

Fold Increase ◽

The Other ◽

Insulin Stimulation ◽

Glut 1 ◽

Glut 4 ◽

Rat Soleus Muscle ◽

The Brain ◽

Stimulation Of

Insulin-stimulated glucose transport was examined in BC3H-1 myocytes. Insulin treatment lead to a 2.7 +/- 0.3-fold increase in the rate of deoxyglucose transport and, under the same conditions, a 2.1 +/- 0.1-fold increase in the amount of the brain-type glucose transporter (GLUT 1) at the cell surface. It has been shown that some insulin-responsive tissues express a second, immunologically distinct, transporter, namely GLUT 4. We report here that BC3H-1 myocytes and C2 and G8 myotubes express only GLUT 1; in contrast, rat soleus muscle and heart express 3-4 times higher levels of GLUT 4 than GLUT 1. Thus translocation of GLUT 1 can account for most, if not all, of the insulin stimulation of glucose transport in BC3H-1 myocytes. On the other, hand, neither BC3H-1 myocytes nor the other muscle-cell lines are adequate as models for the study of insulin regulation of glucose transport in muscle tissue.

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Mechanisms underlying impaired GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.279.6.e1311 ◽

2000 ◽

Vol 279 (6) ◽

pp. E1311-E1318 ◽

Cited By ~ 61

Author(s):

Kentaro Kawanaka ◽

Lorraine A. Nolte ◽

Dong-Ho Han ◽

Polly A. Hansen ◽

John O. Holloszy

Keyword(s):

Glucose Transport ◽

Kinase Activity ◽

Amp Kinase ◽

Glut 4 ◽

Glut 4 Translocation ◽

Insulin Responsiveness ◽

Muscle Glucose Transport ◽

Pkb Phosphorylation ◽

Fasted Rats ◽

Stimulation Of

Exercise training induces an increase in GLUT-4 in muscle. We previously found that feeding rats a high-carbohydrate diet after exercise, with muscle glycogen supercompensation, results in a decrease in insulin responsiveness so severe that it masks the effect of a training-induced twofold increase in GLUT-4 on insulin-stimulated muscle glucose transport. One purpose of this study was to determine whether insulin signaling is impaired. Maximally insulin-stimulated phosphatidylinositol (PI) 3-kinase activity was not significantly reduced, whereas protein kinase B (PKB) phosphorylation was ∼50% lower ( P < 0.01) in muscles of chow-fed, than in those of fasted, exercise-trained rats. Our second purpose was to determine whether contraction-stimulated glucose transport is also impaired. The stimulation of glucose transport and the increase in cell surface GLUT-4 induced by contractions were both decreased by ∼65% in glycogen-supercompensated muscles of trained rats. The contraction-stimulated increase in AMP kinase activity, which has been implicated in the activation of glucose transport by contractions, was ∼80% lower in the muscles of the fed compared with the fasted rats 18 h after exercise. These results show that both the insulin- and contraction-stimulated pathways for muscle glucose transport activation are impaired in glycogen-supercompensated muscles and provide insight regarding possible mechanisms.

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