Turning Signals On and Off: GLUT4 Traffic in the Insulin-Signaling Highway

Physiology ◽  
2005 ◽  
Vol 20 (4) ◽  
pp. 271-284 ◽  
Author(s):  
Farah S. L. Thong ◽  
Chandrasagar B. Dugani ◽  
Amira Klip
Keyword(s):  
Skeletal Muscle ◽  
Insulin Signaling ◽  
Glucose Transporter ◽  
Round Trip ◽  
Insulin Stimulation ◽  
Adipose Tissues ◽  
Intracellular Compartments ◽  
Glucose Transporter Glut4 ◽  
Molecular Signals ◽  
Stimulation Of

Insulin stimulation of glucose uptake into skeletal muscle and adipose tissues is achieved by accelerating glucose transporter GLUT4 exocytosis from intracellular compartments to the plasma membrane and minimally reducing its endocytosis. The round trip of GLUT4 is intricately regulated by diverse signaling molecules impinging on specific compartments. Here we highlight the key molecular signals that are turned on and off by insulin to accomplish this task.

scholarly journals Insulin Stimulation of GLUT4 Exocytosis, but Not Its Inhibition of Endocytosis, Is Dependent on RabGAP AS160

2004 ◽  
Vol 15 (10) ◽  
pp. 4406-4415 ◽  
Author(s):  
Anja Zeigerer ◽  
Mary Kate McBrayer ◽  
Timothy E. McGraw
Keyword(s):  
Plasma Membrane ◽  
Blood Glucose ◽  
Insulin Signaling ◽  
Glucose Transporter ◽  
Whole Body ◽  
Insulin Stimulation ◽  
Molecular Events ◽  
Intracellular Compartments ◽  
Blood Glucose Homeostasis ◽  
Stimulation Of

Insulin maintains whole body blood glucose homeostasis, in part, by regulating the amount of the GLUT4 glucose transporter on the cell surface of fat and muscle cells. Insulin induces the redistribution of GLUT4 from intracellular compartments to the plasma membrane, by stimulating a large increase in exocytosis and a smaller inhibition of endocytosis. A considerable amount is known about the molecular events of insulin signaling and the complex itinerary of GLUT4 trafficking, but less is known about how insulin signaling is transmitted to GLUT4 trafficking. Here, we show that the AS160 RabGAP, a substrate of Akt, is required for insulin stimulation of GLUT4 exocytosis. A dominant-inhibitory mutant of AS160 blocks insulin stimulation of exocytosis at a step before the fusion of GLUT4-containing vesicles with the plasma membrane. This mutant, however, does not block insulin-induced inhibition of GLUT4 endocytosis. These data support a model in which insulin signaling to the exocytosis machinery (AS160 dependent) is distinct from its signaling to the internalization machinery (AS160 independent).

scholarly journals Signalling components involved in contraction-inducible substrate uptake into cardiac myocytes

2004 ◽  
Vol 63 (2) ◽  
pp. 251-258 ◽  
Author(s):  
Joost J. F. P. Luiken ◽  
Susan L. M. Coort ◽  
Debby P. Y. Koonen ◽  
Arend Bonen ◽  
Jan F. C. Glatz
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Cardiac Myocytes ◽  
Glucose Transporter ◽  
Contractile Activity ◽  
Mechanical Activity ◽  
Substrate Uptake ◽  
Extracellular Signal ◽  
Intracellular Compartments ◽  
Glucose Transporter Glut4

Glucose and long-chain fatty acids (LCFA) are two major substrates used by heart and skeletal muscle to support contractile activity. In quiescent cardiac myocytes a substantial portion of the glucose transporter GLUT4 and the putative LCFA transporter fatty acid translocase (FAT)/CD36 are stored in intracellular compartments. Induction of cellular contraction by electrical stimulation results in enhanced uptake of both glucose and LCFA through translocation of GLUT4 and FAT/CD36 respectively to the sarcolemma. The involvement of protein kinase A, AMP-activated protein kinase (AMPK), protein kinase C (PKC) isoforms and the extracellular signal-regulated kinases was evaluated in cardiac myocytes as candidate signalling enzymes involved in recruiting these transporters in response to contraction. The collected evidence excluded the involvement of PKA and implicated an important role for AMPK and for one (or more) PKC isoform(s) in contraction-induced translocation of both GLUT4 and FAT/CD36. The unravelling of further components along this contraction pathway can provide valuable information on the coordinated regulation of the uptake of glucose and of LCFA by an increase in mechanical activity of heart and skeletal muscle.

scholarly journals Substrate specificity and effect on GLUT4 translocation of the Rab GTPase-activating protein Tbc1d1

2007 ◽  
Vol 403 (2) ◽  
pp. 353-358 ◽  
Author(s):  
William G. Roach ◽  
Jose A. Chavez ◽  
Cristinel P. Mîinea ◽  
Gustav E. Lienhard
Keyword(s):  
Plasma Membrane ◽  
Glucose Transporter ◽  
Insulin Treatment ◽  
Ectopic Expression ◽  
Rab Gtpase ◽  
Glut4 Translocation ◽  
Gtpase Activating Protein ◽  
Insulin Stimulation ◽  
Glucose Transporter Glut4 ◽  
Stimulation Of

Insulin stimulation of the trafficking of the glucose transporter GLUT4 to the plasma membrane is controlled in part by the phosphorylation of the Rab GAP (GTPase-activating protein) AS160 (also known as Tbc1d4). Considerable evidence indicates that the phosphorylation of this protein by Akt (protein kinase B) leads to suppression of its GAP activity and results in the elevation of the GTP form of a critical Rab. The present study examines a similar Rab GAP, Tbc1d1, about which very little is known. We found that the Rab specificity of the Tbc1d1 GAP domain is identical with that of AS160. Ectopic expression of Tbc1d1 in 3T3-L1 adipocytes blocked insulin-stimulated GLUT4 translocation to the plasma membrane, whereas a point mutant with an inactive GAP domain had no effect. Insulin treatment led to the phosphorylation of Tbc1d1 on an Akt site that is conserved between Tbc1d1 and AS160. These results show that Tbc1d1 regulates GLUT4 translocation through its GAP activity, and is a likely Akt substrate. An allele of Tbc1d1 in which Arg125 is replaced by tryptophan has very recently been implicated in susceptibility to obesity by genetic analysis. We found that this form of Tbc1d1 also inhibited GLUT4 translocation and that this effect also required a functional GAP domain.

scholarly journals Insulin Increases Cell Surface GLUT4 Levels by Dose Dependently Discharging GLUT4 into a Cell Surface Recycling Pathway

2004 ◽  
Vol 24 (14) ◽  
pp. 6456-6466 ◽  
Author(s):  
Roland Govers ◽  
Adelle C. F. Coster ◽  
David E. James
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Glucose Transporter ◽  
Insulin Dose ◽  
Cell Types ◽  
Insulin Stimulation ◽  
Intracellular Compartments ◽  
A Cell ◽  
Recycling Pathway ◽  
Glucose Transporter Glut4

ABSTRACT The insulin-responsive glucose transporter GLUT4 plays an essential role in glucose homeostasis. A novel assay was used to study GLUT4 trafficking in 3T3-L1 fibroblasts/preadipocytes and adipocytes. Whereas insulin stimulated GLUT4 translocation to the plasma membrane in both cell types, in nonstimulated fibroblasts GLUT4 readily cycled between endosomes and the plasma membrane, while this was not the case in adipocytes. This efficient retention in basal adipocytes was mediated in part by a C-terminal targeting motif in GLUT4. Insulin caused a sevenfold increase in the amount of GLUT4 molecules present in a trafficking cycle that included the plasma membrane. Strikingly, the magnitude of this increase correlated with the insulin dose, indicating that the insulin-induced appearance of GLUT4 at the plasma membrane cannot be explained solely by a kinetic change in the recycling of a fixed intracellular GLUT4 pool. These data are consistent with a model in which GLUT4 is present in a storage compartment, from where it is released in a graded or quantal manner upon insulin stimulation and in which released GLUT4 continuously cycles between intracellular compartments and the cell surface independently of the nonreleased pool.

Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes

2006 ◽  
Vol 291 (4) ◽  
pp. E817-E828 ◽  
Author(s):  
Taku Nedachi ◽  
Makoto Kanzaki
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
C2c12 Myotubes ◽  
Glut4 Translocation ◽  
Insulin Stimulation ◽  
Extracellular Glucose ◽  
Insulin Dependent ◽  
Stimulation Of

It is well established that insulin stimulation of glucose uptake in skeletal muscle cells is mediated through translocation of GLUT4 from intracellular storage sites to the cell surface. However, the established skeletal muscle cell lines, with the exception of L6 myocytes, reportedly show minimal insulin-dependent glucose uptake and GLUT4 translocation. Using C2C12 myocytes expressing exofacial-Myc-GLUT4-enhanced cyan fluorescent protein, we herein show that differentiated C2C12 myotubes are equipped with basic GLUT4 translocation machinery that can be activated by insulin stimulation (∼3-fold increase as assessed by anti-Myc antibody uptake and immunostaining assay). However, this insulin stimulation of GLUT4 translocation was difficult to demonstrate with a conventional 2-deoxyglucose uptake assay because of markedly elevated basal glucose uptake via other glucose transporter(s). Intriguingly, the basal glucose transport activity in C2C12 myotubes appeared to be acutely suppressed within 5 min by preincubation with a pathophysiologically high level of extracellular glucose (25 mM). In contrast, this activity was augmented by acute glucose deprivation via an unidentified mechanism that is independent of GLUT4 translocation but is dependent on phosphatidylinositol 3-kinase activity. Taken together, these findings indicate that regulation of the facilitative glucose transport system in differentiated C2C12 myotubes can be achieved through surprisingly acute glucose-dependent modulation of the activity of glucose transporter(s), which apparently contributes to obscuring the insulin augmentation of glucose uptake elicited by GLUT4 translocation. We herein also describe several methods of monitoring insulin-dependent glucose uptake in C2C12 myotubes and propose this cell line to be a useful model for analyzing GLUT4 translocation in skeletal muscle.

TNF-α impairs insulin signaling and insulin stimulation of glucose uptake in C2C12muscle cells

1999 ◽  
Vol 276 (5) ◽  
pp. E849-E855 ◽  
Author(s):  
Luis F. del Aguila ◽  
Kevin P. Claffey ◽  
John P. Kirwan
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Tyrosine Phosphorylation ◽  
Insulin Signaling ◽  
Insulin Stimulation ◽  
Kinase Activation ◽  
Tnf Α ◽  
Impaired Insulin ◽  
Stimulation Of

Physiological stressors such as sepsis and tissue damage initiate an acute immune response and cause transient systemic insulin resistance. This study was conducted to determine whether tumor necrosis factor-α (TNF-α), a cytokine produced by immune cells during skeletal muscle damage, decreases insulin responsiveness at the cellular level. To examine the molecular mechanisms associated with TNF-α and insulin action, we measured insulin receptor substrate (IRS)-1- and IRS-2-mediated phosphatidylinositol 3-kinase (PI 3-kinase) activation, IRS-1-PI 3-kinase binding, IRS-1 tyrosine phosphorylation, and the phosphorylation of two mitogen-activated protein kinases (MAPK, known as p42MAPK and p44MAPK) in cultured C2C12myotubes. Furthermore, we determined the effects of TNF-α on insulin-stimulated 2-deoxyglucose (2-DG) uptake. We observed that TNF-α impaired insulin stimulation of IRS-1- and IRS-2-mediated PI 3-kinase activation by 54 and 55% ( P< 0.05), respectively. In addition, TNF-α decreased insulin-stimulated IRS-1 tyrosine phosphorylation by 40% ( P < 0.05). Furthermore, TNF-α repressed insulin-induced p42MAPKand p44MAPK tyrosine phosphorylation by 81% ( P < 0.01). TNF-α impairment of insulin signaling activation was accompanied by a decrease ( P < 0.05) in 2-DG uptake in the muscle cells (60 ± 4 vs. 44 ± 6 pmol ⋅ min−1 ⋅ mg−1). These data suggest that increases in TNF-α may cause insulin resistance in skeletal muscle by inhibiting IRS-1- and IRS-2-mediated PI 3-kinase activation as well as p42MAPK and p44MAPK tyrosine phosphorylation, leading to impaired insulin-stimulated glucose uptake.

scholarly journals Reduction of Insulin-Stimulated Glucose Uptake in L6 Myotubes by the Protein Kinase Inhibitor SB203580 Is Independent of p38MAPK Activity

Endocrinology ◽  
2005 ◽  
Vol 146 (9) ◽  
pp. 3773-3781 ◽  
Author(s):  
C. N. Antonescu ◽  
C. Huang ◽  
W. Niu ◽  
Z. Liu ◽  
P. A. Eyers ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Kinase Inhibitor ◽  
Dominant Negative ◽  
Small Interfering Rnas ◽  
Insulin Stimulation ◽  
L6 Myotubes ◽  
Low Levels ◽  
Glucose Transporter Glut4

Abstract Insulin increases glucose uptake through translocation of the glucose transporter GLUT4 to the plasma membrane. We previously showed that insulin activates p38MAPK, and inhibitors of p38MAPKα and p38MAPKβ (e.g. SB203580) reduce insulin-stimulated glucose uptake without affecting GLUT4 translocation. This observation suggested that insulin may increase GLUT4 activity via p38α and/or p38β. Here we further explore the possible participation of p38MAPK through a combination of molecular strategies. SB203580 reduced insulin stimulation of glucose uptake in L6 myotubes overexpressing an SB203580-resistant p38α (drug-resistant p38α) but barely affected phosphorylation of the p38 substrate MAPK-activated protein kinase-2. Expression of dominant-negative p38α or p38β reduced p38MAPK phosphorylation by 70% but had no effect on insulin-stimulated glucose uptake. Gene silencing via isoform-specific small interfering RNAs reduced expression of p38α or p38β by 60–70% without diminishing insulin-stimulated glucose uptake. SB203580 reduced photoaffinity labeling of GLUT4 by bio-LC-ATB-BMPA only in the insulin-stimulated state. Unless low levels of p38MAPK suffice to regulate glucose uptake, these results suggest that the inhibition of insulin-stimulated glucose transport by SB203580 is likely not mediated by p38MAPK. Instead, changes experienced by insulin-stimulated GLUT4 make it susceptible to inhibition by SB203580.

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

2001 ◽  
Vol 154 (4) ◽  
pp. 829-840 ◽  
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.

scholarly journals SEC16A is a RAB10 effector required for insulin-stimulated GLUT4 trafficking in adipocytes

2016 ◽  
Vol 214 (1) ◽  
pp. 61-76 ◽  
Author(s):  
Joanne Bruno ◽  
Alexandria Brumfield ◽  
Natasha Chaudhary ◽  
David Iaea ◽  
Timothy E. McGraw
Keyword(s):  
Glucose Transporter ◽  
Whole Body ◽  
Site Formation ◽  
Coated Vesicle ◽  
Coat Proteins ◽  
Insulin Stimulation ◽  
Exit Site ◽  
Recycling Endosome ◽  
Transport Vesicles ◽  
Intracellular Compartments

RAB10 is a regulator of insulin-stimulated translocation of the GLUT4 glucose transporter to the plasma membrane (PM) of adipocytes, which is essential for whole-body glucose homeostasis. We establish SEC16A as a novel RAB10 effector in this process. Colocalization of SEC16A with RAB10 is augmented by insulin stimulation, and SEC16A knockdown attenuates insulin-induced GLUT4 translocation, phenocopying RAB10 knockdown. We show that SEC16A and RAB10 promote insulin-stimulated mobilization of GLUT4 from a perinuclear recycling endosome/TGN compartment. We propose RAB10–SEC16A functions to accelerate formation of the vesicles that ferry GLUT4 to the PM during insulin stimulation. Because GLUT4 continually cycles between the PM and intracellular compartments, the maintenance of elevated cell-surface GLUT4 in the presence of insulin requires accelerated biogenesis of the specialized GLUT4 transport vesicles. The function of SEC16A in GLUT4 trafficking is independent of its previously characterized activity in ER exit site formation and therefore independent of canonical COPII-coated vesicle function. However, our data support a role for SEC23A, but not the other COPII components SEC13, SEC23B, and SEC31, in the insulin stimulation of GLUT4 trafficking, suggesting that vesicles derived from subcomplexes of COPII coat proteins have a role in the specialized trafficking of GLUT4.

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