scholarly journals A Role for Protein Kinase Bβ/Akt2 in Insulin-Stimulated GLUT4 Translocation in Adipocytes

1999 ◽  
Vol 19 (11) ◽  
pp. 7771-7781 ◽  
Author(s):  
Michelle M. Hill ◽  
Sharon F. Clark ◽  
David F. Tucker ◽  
Morris J. Birnbaum ◽  
David E. James ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Growth Factor ◽  
Protein Kinase ◽  
Glucose Transporter ◽  
Glut4 Translocation ◽  
Glucose Transporter 4 ◽  
Significant Extent ◽  
Downstream Target ◽  
Substrate Peptide ◽  
Pkb Phosphorylation

ABSTRACT Insulin stimulates glucose uptake into muscle and fat cells by promoting the translocation of glucose transporter 4 (GLUT4) to the cell surface. Phosphatidylinositide 3-kinase (PI3K) has been implicated in this process. However, the involvement of protein kinase B (PKB)/Akt, a downstream target of PI3K in regulation of GLUT4 translocation, has been controversial. Here we report that microinjection of a PKB substrate peptide or an antibody to PKB inhibited insulin-stimulated GLUT4 translocation to the plasma membrane by 66 or 56%, respectively. We further examined the activation of PKB isoforms following treatment of cells with insulin or platelet-derived growth factor (PDGF) and found that PKBβ is preferentially expressed in both rat and 3T3-L1 adipocytes, whereas PKBα expression is down-regulated in 3T3-L1 adipocytes. A switch in growth factor response was also observed when 3T3-L1 fibroblasts were differentiated into adipocytes. While PDGF was more efficacious than insulin in stimulating PKB phosphorylation in fibroblasts, PDGF did not stimulate PKBβ phosphorylation to any significant extent in adipocytes, as assessed by several methods. Moreover, insulin, but not PDGF, stimulated the translocation of PKBβ to the plasma membrane and high-density microsome fractions of 3T3-L1 adipocytes. These results support a role for PKBβ in insulin-stimulated glucose transport in adipocytes.

scholarly journals Akt2 phosphorylates Synip to regulate docking and fusion of GLUT4-containing vesicles

2005 ◽  
Vol 168 (6) ◽  
pp. 921-928 ◽  
Author(s):  
Eijiro Yamada ◽  
Shuichi Okada ◽  
Tsugumichi Saito ◽  
Kihachi Ohshima ◽  
Minoru Sato ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Membrane Fusion ◽  
Glucose Transporter ◽  
Protein Kinase B ◽  
Specific Substrate ◽  
Glucose Transporter 4 ◽  
Wild Type ◽  
Phosphorylation Motif

We have identified an unusual potential dual Akt/protein kinase B consensus phosphorylation motif in the protein Synip (RxKxRS97xS99). Surprisingly, serine 97 is not appreciably phosphorylated, whereas serine 99 is only a specific substrate for Akt2 but not Akt1 or Akt3. Although wild-type Synip (WT-Synip) undergoes an insulin-stimulated dissociation from Syntaxin4, the Synip serine 99 to phenylalanine mutant (S99F-Synip) is resistant to Akt2 phosphorylation and fails to display insulin-stimulated Syntaxin4 dissociation. Furthermore, overexpression of WT-Synip in 3T3L1 adipocytes had no effect on insulin-stimulated recruitment of glucose transporter 4 (GLUT4) to the plasma membrane, whereas overexpression of S99F-Synip functioned in a dominant-interfering manner by preventing insulin-stimulated GLUT4 recruitment and plasma membrane fusion. These data demonstrate that insulin activation of Akt2 specifically regulates the docking/fusion step of GLUT4-containing vesicles at the plasma membrane through the regulation of Synip phosphorylation and Synip–Syntaxin4 interaction.

scholarly journals Inhibition of insulin-stimulated phosphorylation of the intracellular domain of phospholemman decreases insulin-dependent GLUT4 translocation in streptolysin-O-permeabilized adipocytes

1999 ◽  
Vol 343 (1) ◽  
pp. 151-157 ◽  
Author(s):  
Otto WALAAS ◽  
Robert S. HORN ◽  
S. Ivar WALAAS
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Glucose Transporter ◽  
Insulin Signalling ◽  
Glut4 Translocation ◽  
Intracellular Domain ◽  
Kinase C ◽  
Streptolysin O

A variety of studies indicate that protein kinase C might be involved in the insulin signalling cascade leading to translocation of the insulin-regulated glucose transporter GLUT4 from intracellular pools to the plasma membrane. Phospholemman is a plasma-membrane protein kinase C substrate whose phosphorylation is increased by insulin in intact muscle [Walaas, Czernik, Olstad, Sletten and Walaas (1994) Biochem. J. 304, 635-640]. The present study examined whether the inhibition of phospholemman phosphorylation modulates the effects of insulin on GLUT4 translocation. For this purpose, a synthetic peptide derived from the intracellular domain of phospholemman with the phosphorylatable serine residues replaced with alanine residues was prepared. This peptide was found to decrease the protein kinase C-catalysed phosphorylation of a synthetic phospholemman peptide in vitro. When introduced into streptolysin-O-permeabilized adipocytes, the peptide decreased the effects of insulin on both the phosphorylation of phospholemman and the recruitment of GLUT4 to the plasma membrane. Similarly, the internalization of phospholemman antibodies, which also decreased the protein kinase C-mediated phosphorylation of the synthetic phospholemman peptide in vitro, decreased the effect of insulin on GLUT4 translocation in the adipocytes. The results suggest that phosphorylation of the intracellular domain of phospholemman might be involved in modulating the insulin-induced translocation of GLUT4 to the plasma membrane.

scholarly journals Activation of Protein Kinase Cζ Induces Serine Phosphorylation of VAMP2 in the GLUT4 Compartment and Increases Glucose Transport in Skeletal Muscle

2001 ◽  
Vol 21 (22) ◽  
pp. 7852-7861 ◽  
Author(s):  
Liora Braiman ◽  
Addy Alt ◽  
Toshio Kuroki ◽  
Motoi Ohba ◽  
Asia Bak ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Protein Kinase ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
Primary Cultures ◽  
Dominant Negative ◽  
Serine Phosphorylation ◽  
Glut4 Translocation

ABSTRACT Insulin stimulates glucose uptake into skeletal muscle tissue mainly through the translocation of glucose transporter 4 (GLUT4) to the plasma membrane. The precise mechanism involved in this process is presently unknown. In the cascade of events leading to insulin-induced glucose transport, insulin activates specific protein kinase C (PKC) isoforms. In this study we investigated the roles of PKCζ in insulin-stimulated glucose uptake and GLUT4 translocation in primary cultures of rat skeletal muscle. We found that insulin initially caused PKCζ to associate specifically with the GLUT4 compartments and that PKCζ together with the GLUT4 compartments were then translocated to the plasma membrane as a complex. PKCζ and GLUT4 recycled independently of one another. To further establish the importance of PKCζ in glucose transport, we used adenovirus constructs containing wild-type or kinase-inactive, dominant-negative PKCζ (DNPKCζ) cDNA to overexpress this isoform in skeletal muscle myotube cultures. We found that overexpression of PKCζ was associated with a marked increase in the activity of this isoform. The overexpressed, active PKCζ coprecipitated with the GLUT4 compartments. Moreover, overexpression of PKCζ caused GLUT4 translocation to the plasma membrane and increased glucose uptake in the absence of insulin. Finally, either insulin or overexpression of PKCζ induced serine phosphorylation of the GLUT4-compartment-associated vesicle-associated membrane protein 2. Furthermore, DNPKCζ disrupted the GLUT4 compartment integrity and abrogated insulin-induced GLUT4 translocation and glucose uptake. These results demonstrate that PKCζ regulates insulin-stimulated GLUT4 translocation and glucose transport through the unique colocalization of this isoform with the GLUT4 compartments.

scholarly journals Role of Insulin-dependent Cortical Fodrin/Spectrin Remodeling in Glucose Transporter 4 Translocation in Rat Adipocytes

2006 ◽  
Vol 17 (10) ◽  
pp. 4249-4256 ◽  
Author(s):  
Libin Liu ◽  
Mark P. Jedrychowski ◽  
Steven P. Gygi ◽  
Paul F. Pilch
Keyword(s):  
Plasma Membrane ◽  
Glucose Transporter ◽  
Cytochalasin D ◽  
Resting Cells ◽  
Glut4 Translocation ◽  
Glucose Transporter 4 ◽  
Rat Adipocytes ◽  
Protein Receptor ◽  
Latrunculin A ◽  
Syntaxin 4

Fodrin or nonerythroid spectrin is an abundant component of the cortical cytoskeletal network in rat adipocytes. Fodrin has a highly punctate distribution in resting cells, and insulin causes a dramatic remodeling of fodrin to a more diffuse pattern. Insulin-mediated remodeling of actin occurs to a lesser extent than does that of fodrin. We show that fodrin interacts with the t-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) syntaxin 4, and this interaction is increased by insulin stimulation and decreased by prior latrunculin A treatment. Latrunculin A disrupts all actin filaments, inhibits glucose transporter 4 (GLUT4) translocation, and causes fodrin to partially redistribute from the plasma membrane to the cytosol. In contrast, cytochalasin D disrupts only the short actin filament signal, and cytochalasin D neither inhibits GLUT4 translocation nor fodrin redistribution in adipocytes. Together, our data suggest that insulin induces remodeling of the fodrin–actin network, which is required for the fusion of GLUT4 storage vesicles with the plasma membrane by permitting their access to the t-SNARE syntaxin 4.

scholarly journals Antidiabetic and Antihyperlipidemic Effects ofClitocybe nudaon Glucose Transporter 4 and AMP-Activated Protein Kinase Phosphorylation in High-Fat-Fed Mice

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Mei-Hsing Chen ◽  
Cheng-Hsiu Lin ◽  
Chun-Ching Shih
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Glucose Transporter ◽  
Body Weight Gain ◽  
Glucose Production ◽  
Hypolipidemic Effect ◽  
Glucose Transporter 4 ◽  
High Fat ◽  
Hepatic Expression ◽  
Amp Activated Protein Kinase

The objective of this study was to evaluate the antihyperlipidemic and antihyperglycemic effects and mechanism of the extract ofClitocybe nuda(CNE), in high-fat- (HF-) fed mice. C57BL/6J was randomly divided into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed with a HF diet for 8 weeks. Then, the HF group was subdivided into five groups and was given orally CNE (including C1: 0.2, C2: 0.5, and C3: 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks. CNE effectively prevented HF-diet-induced increases in the levels of blood glucose, triglyceride, insulin (P<0.001,P<0.01,P<0.05, resp.) and attenuated insulin resistance. By treatment with CNE, body weight gain, weights of white adipose tissue (WAT) and hepatic triacylglycerol content were reduced; moreover, adipocytes in the visceral depots showed a reduction in size. By treatment with CNE, the protein contents of glucose transporter 4 (GLUT4) were significantly increased in C3-treated group in the skeletal muscle. Furthermore, CNE reduces the hepatic expression of glucose-6-phosphatase (G6Pase) and glucose production. CNE significantly increases protein contents of phospho-AMP-activated protein kinase (AMPK) in the skeletal muscle and adipose and liver tissues. Therefore, it is possible that the activation of AMPK by CNE leads to diminished gluconeogenesis in the liver and enhanced glucose uptake in skeletal muscle. It is shown that CNE exhibits hypolipidemic effect in HF-fed mice by increasing ATGL expression, which is known to help triglyceride to hydrolyze. Moreover, antidiabetic properties of CNE occurred as a result of decreased hepatic glucose production via G6Pase downregulation and improved insulin sensitization. Thus, amelioration of diabetic and dyslipidemic states by CNE in HF-fed mice occurred by regulation of GLUT4, G6Pase, ATGL, and AMPK phosphorylation.

α-amyrin induce GLUT4 translocation mediated by AMPK and PPARδ/γ in C2C12 myoblasts

2021 ◽  
Author(s):  
Abraham Giacoman-Martínez ◽  
Francisco Javier Alarcón-Aguilar ◽  
Alejandro Zamilpa-Alvarez ◽  
Fengyang Huang ◽  
Rodrigo Romero ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Glucose Transporter ◽  
Metabolic Diseases ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Peroxisome Proliferator ◽  
Glut4 Translocation ◽  
Pentacyclic Triterpene ◽  
C2c12 Myoblasts

α-amyrin, a natural pentacyclic triterpene, have anti-hyperglycemic effect in mice and dual PPARδ/γ action in 3T3-L1 adipocytes, and potential in the control of type 2 diabetes (T2D). About 80% of glucose uptake occurs in skeletal muscle cells, playing a significant role in IR and T2D. Peroxisome-proliferator activated receptors (PPARs), in particular PPARδ and PPARγ, are involved in the regulation of lipids and carbohydrates and, along adenosine-monophosphate (AMP)-activated protein kinase (AMPK) and protein kinase B (Akt/PKB), are implicated in translocation of glucose transporter 4 (GLUT4). However, it is still unknown whether α-amyrin can affect these pathways in skeletal muscle cells. The work's objective was to determine the action of α-amyrin in PPARδ, PPARγ, AMPK, and Akt/PKB in C2C12 myoblasts. The expression of PPARδ, PPARγ, FATP, and GLUT4 was quantified using RT-qPCR and Western blot. α-amyrin increased these markers along with p-AMPK but not p-Akt/PKB. Molecular docking showed that α-amyrin acts as an AMPK-allosteric activator, and may be related to GLUT4 translocation, evidenced by confocal microscopy. These data support that α-amyrin could have an insulin-mimetic action in C2C12 myoblasts and should be considered as a bioactive molecule for new multitarget drugs with utility in T2D and other metabolic diseases.

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