Actin filaments participate in the relocalization of phosphatidylinositol 3-kinase to glucose transporter containing compartments and in the stimulation of glucose uptake in 3T3-L1 adipocytes

Cells require growth factors to support glucose metabolism for survival and growth. It is unclear, however, how noninsulin growth factors may regulate glucose uptake and glucose transporters. We show that the hematopoietic growth factor interleukin (IL)3, maintained the glucose transporter Glut1 on the cell surface and promoted Rab11a-dependent recycling of intracellular Glut1. IL3 required phosphatidylinositol-3 kinase activity to regulate Glut1 trafficking, and activated Akt was sufficient to maintain glucose uptake and surface Glut1 in the absence of IL3. To determine how Akt may regulate Glut1, we analyzed the role of Akt activation of mammalian target of rapamycin (mTOR)/regulatory associated protein of mTOR (RAPTOR) and inhibition of glycogen synthase kinase (GSK)3. Although Akt did not require mTOR/RAPTOR to maintain surface Glut1 levels, inhibition of mTOR/RAPTOR by rapamycin greatly diminished glucose uptake, suggesting Akt-stimulated mTOR/RAPTOR may promote Glut1 transporter activity. In contrast, inhibition of GSK3 did not affect Glut1 internalization but nevertheless maintained surface Glut1 levels in IL3-deprived cells, possibly via enhanced recycling of internalized Glut1. In addition, Akt attenuated Glut1 internalization through a GSK3-independent mechanism. These data demonstrate that intracellular trafficking of Glut1 is a regulated component of growth factor-stimulated glucose uptake and that Akt can promote Glut1 activity and recycling as well as prevent Glut1 internalization.

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TC10α Is Required for Insulin-Stimulated Glucose Uptake in Adipocytes

Endocrinology ◽

10.1210/en.2006-1167 ◽

2007 ◽

Vol 148 (1) ◽

pp. 27-33 ◽

Cited By ~ 64

Author(s):

Louise Chang ◽

Shian-Huey Chiang ◽

Alan R. Saltiel

Keyword(s):

Plasma Membrane ◽

Growth Factor ◽

Glucose Uptake ◽

Glucose Transporter ◽

Platelet Derived Growth Factor ◽

Phosphatidylinositol 3 Kinase ◽

Independent Manner ◽

Rho Family ◽

Glucose Transporter Glut4 ◽

Stimulation Of

Previous studies have suggested that activation of the Rho family member GTPase TC10 is necessary but not sufficient for the stimulation of glucose transport by insulin. We show here that endogenous TC10α is rapidly activated in response to insulin in 3T3L1 adipocytes in a phosphatidylinositol 3-kinase-independent manner, whereas platelet-derived growth factor was without effect. Knockdown of TC10α but not TC10β by RNA interference inhibited insulin-stimulated glucose uptake as well as the translocation of the insulin-sensitive glucose transporter GLUT4 from intracellular sites to the plasma membrane. In contrast, loss of TC10α had no effect on the stimulation of Akt by insulin. Additionally, knockdown of TC10α inhibited insulin-stimulated translocation of its effector CIP4. These data indicate that TC10α is specifically required for insulin-stimulated glucose uptake in adipocytes.

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Activation of Mitogen-activated Protein Kinase and Phosphatidylinositol 3′-Kinase Is Not Sufficient for the Hormonal Stimulation of Glucose Uptake, Lipogenesis, or Glycogen Synthesis in 3T3-L1 Adipocytes

Journal of Biological Chemistry ◽

10.1074/jbc.270.7.3442 ◽

1995 ◽

Vol 270 (7) ◽

pp. 3442-3446 ◽

Cited By ~ 102

Author(s):

Russell J. Wiese ◽

Cynthia Corley Mastick ◽

Dan F. Lazar ◽

Alan R. Saltiel

Keyword(s):

Protein Kinase ◽

Glucose Uptake ◽

Glycogen Synthesis ◽

Mitogen Activated Protein Kinase ◽

Phosphatidylinositol 3 Kinase ◽

Hormonal Stimulation ◽

Mitogen Activated Protein ◽

Stimulation Of ◽

Phosphatidylinositol 3

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Insulin and Leptin Induce Glut4 Plasma Membrane Translocation and Glucose Uptake in a Human Neuronal Cell Line by a Phosphatidylinositol 3-Kinase- Dependent Mechanism

Endocrinology ◽

10.1210/en.2005-1464 ◽

2006 ◽

Vol 147 (5) ◽

pp. 2550-2556 ◽

Cited By ~ 87

Author(s):

Yacir Benomar ◽

Nadia Naour ◽

Alain Aubourg ◽

Virginie Bailleux ◽

Arieh Gertler ◽

...

Keyword(s):

Glucose Uptake ◽

Neuronal Cells ◽

Neuronal Cell ◽

Glut4 Translocation ◽

Phosphatidylinositol 3 Kinase ◽

Human Neuronal Cell ◽

The Impact ◽

Dependent Mechanism ◽

Stimulation Of ◽

Phosphatidylinositol 3

The insulin-sensitive glucose transporter Glut4 is expressed in brain areas that regulate energy homeostasis and body adiposity. In contrast with peripheral tissues, however, the impact of insulin on Glut4 plasma membrane (PM) translocation in neurons is not known. In this study, we examined the role of two anorexic hormones (leptin and insulin) on Glut4 translocation in a human neuronal cell line that express endogenous insulin and leptin receptors. We show that insulin and leptin both induce Glut4 translocation to the PM of neuronal cells and activate glucose uptake. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, totally abolished insulin- and leptin-dependent Glut4 translocation and stimulation of glucose uptake. Thus, Glut4 translocation is a phosphatidylinositol 3-kinase-dependent mechanism in neuronal cells. Next, we investigated the impact of chronic insulin and leptin treatments on Glut4 expression and translocation. Chronic exposure of neuronal cells to insulin or leptin down-regulates Glut4 proteins and mRNA levels and abolishes the acute stimulation of glucose uptake in response to acute insulin or leptin. In addition, chronic treatment with either insulin or leptin impaired Glut4 translocation. A cross-desensitization between insulin and leptin was apparent, where exposure to insulin affects leptin-dependent Glut4 translocation and vice versa. This cross-desensitization could be attributed to the increase in suppressor of cytokine signaling-3 expression, which was demonstrated in response to each hormone. These results provide evidence to suggest that Glut4 translocation to neuronal PM is regulated by both insulin and leptin signaling pathways. These pathways might contribute to an in vivo glucoregulatory reflex involving a neuronal network and to the anorectic effect of insulin and leptin.

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Actin filaments participate in the relocalization of phosphatidylinositol3-kinase to glucose transporter-containing compartments and in the stimulation of glucose uptake in 3T3-L1 adipocytes

Biochemical Journal ◽

10.1042/bj3310917 ◽

1998 ◽

Vol 331 (3) ◽

pp. 917-928 ◽

Cited By ~ 115

Author(s):

Qinghua WANG ◽

Philip J. BILAN ◽

Theodoros TSAKIRIDIS ◽

Aleksander HINEK ◽

Amira KLIP

Keyword(s):

Plasma Membrane ◽

Glucose Uptake ◽

Actin Filament ◽

Actin Filaments ◽

Glucose Transporter ◽

Kinase Activity ◽

Glucose Transporters ◽

Cytochalasin D ◽

Insulin Dependent ◽

Stimulation Of

Insulin stimulates the rate of glucose uptake into muscle and adipose cells by translocation of glucose transporters from an intracellular storage pool to the plasma membrane. This event requires the prior activation of phosphatidylinositol 3-kinase (PI 3-kinase). Here we report that insulin causes an increase in wortmannin-sensitive PI 3-kinase activity and a gain in the enzyme's regulatory and catalytic subunits p85α and p110β (but not p110α) in the intracellular compartments containing glucose transporters. The hormone also caused a marked reorganization of actin filaments, which was prevented by cytochalasin D. Cytochalasin D also decreased significantly the insulin-dependent association of PI 3-kinase activity and the levels of insulin receptor substrate (IRS)-1, p85α and p110β with immunopurified GLUT4-containing compartments. In contrast, the drug did not alter the insulin-induced tyrosine phosphorylation of IRS-1, the association of PI 3-kinase with IRS-1, or the stimulation of PI 3-kinase by insulin in anti-(IRS-1) or anti-p85 immunoprecipitates from whole cell lysates. Cytochalasin D, and the chemically unrelated latrunculin B, which also inhibits actin filament reassembly, prevented the insulin stimulation of glucose transport by approx. 50%. Cytochalasin D decreased by about one-half the insulin-dependent translocation to the plasma membrane of the GLUT1 and GLUT4 glucose transporters. The results suggest that the existence of intact actin filament is correlated with the full recruitment of glucose transporters by insulin. The underlying function of the actin filaments might be to facilitate the insulin-mediated association of the p85–p110 PI 3-kinase with glucose-transporter-containing compartments.

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