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AKT1 INS (1 - 50 of 56)
PMID: 10078574
Hyperglycemia inhibits insulin activation of Akt/protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle.
... inhibits insulin activation of Akt/protein kinase B but ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10078574

Hyperglycemia inhibits insulin activation of Akt/protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle.
Source

Diabetes (March 1999)

Abstract

Hyperglycemia inhibits insulin activation of Akt/protein kinase B but not phosphatidylinositol 3-kinase in rat skeletal muscle. Sustained hyperglycemia impairs insulin-stimulated glucose utilization in the skeletal muscle of both humans and experimental animals -- a phenomenon referred to clinically as glucose toxicity. To study how this occurs, a model was developed in which hyperglycemia produces insulin resistance in vitro. Rat extensor digitorum longus muscles were preincubated for 4 h in Krebs-Henseleit solution containing glucose or glucose + insulin at various concentrations, after which insulin action was studied. Preincubation with 25 mmol/l glucose + insulin (10 mU/ml) led to a 70% decrease in the ability of insulin (10 mU/ml) to stimulate glucose incorporation into glycogen and a 30% decrease in 2-deoxyglucose (2-DG) uptake, compared with muscles incubated with 0 mmol/l glucose. Glucose incorporation into lipid and its oxidation to CO2 were marginally diminished, if at all. The alterations of glycogen synthesis and 2-DG uptake were first evident after 1 h and were maximal after 2 h of preincubation; they were not observed in muscles preincubated with 25 mmol/l glucose + insulin for 5 min. Preincubation for 4 h with 25 mmol/l glucose in the absence of insulin produced a similar although somewhat smaller decrease in insulin-stimulated glycogen synthesis; however, it did not alter 2-DG uptake, glucose oxidation to CO2, or incorporation into lipids. Studies of insulin signaling in the latter muscles revealed that activation of Akt/protein kinase B (PKB) was diminished by 60%, compared with that of muscles preincubated in a glucose-free medium; whereas activation of phosphatidylinositol (PI) 3-kinase, an upstream regulator of Akt/PKB in the insulin-signaling cascade, and of mitogen-activated protein (MAP) kinase, a parallel signal, was unaffected. Immunoblots demonstrated that this was not due to a change in Akt/PKB abundance. The results indicate that hyperglycemia-induced insulin resistance can be studied in rat skeletal muscle in vitro. They suggest that impairment of insulin action in these muscles is related to inhibition of Akt/PKB by events that do not affect PI 3-kinase.

PMID: 10187855
Oxidative stress disrupts insulin-induced cellular redistribution of insulin receptor substrate-1 and phosphatidylinositol 3-kinase in 3T3-L1 adipocytes. A putative cellular mechanism for impaired protein kinase B activation and GLUT4 translocation.
... in insulin stimulated ... impaired activation of PKBalpha and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10187855

Oxidative stress disrupts insulin-induced cellular redistribution of insulin receptor substrate-1 and phosphatidylinositol 3-kinase in 3T3-L1 adipocytes. A putative cellular mechanism for impaired protein kinase B activation and GLUT4 translocation.
Source

The Journal of biological chemistry (4/9/1999)

Abstract

Oxidative stress disrupts insulin-induced cellular redistribution of insulin receptor substrate-1 and phosphatidylinositol 3-kinase in 3T3-L1 adipocytes. A putative cellular mechanism for impaired protein kinase B activation and GLUT4 translocation. In a recent study we have demonstrated that 3T3-L1 adipocytes exposed to low micromolar H2O2 concentrations display impaired insulin stimulated GLUT4 translocation from internal membrane pools to the plasma membrane (Rudich, A., Tirosh, A., Potashnik, R., Hemi, R., Kannety, H., and Bashan, N. (1998) Diabetes 47, 1562-1569). In this study we further characterize the cellular mechanisms responsible for this observation. Two-hour exposure to approximately 25 microM H2O2 (generated by adding glucose oxidase to the medium) resulted in disruption of the normal insulin stimulated insulin receptor substrate (IRS) -1 and phosphatidylinositol (PI) 3-kinase cellular redistribution between the cytosol and an internal membrane pool (low density microsomal fraction (LDM)). This was associated with reduced insulin-stimulated IRS-1 and p85-associated PI 3-kinase activities in the LDM (84 and 96% inhibition, respectively). The effect of this finding on the downstream insulin signal was demonstrated by a 90% reduction in insulin stimulated protein kinase B (PKB) serine 473 phosphorylation and impaired activation of PKBalpha and PKBgamma. Both control and oxidized cells exposed to heat shock displayed a wortmannin insensitive PKB serine phosphorylation and activity. These data suggest that activation of PKB and GLUT4 translocation are insulin signaling events dependent upon a normal insulin induced cellular compartmentalization of PI 3-kinase and IRS-1, which is oxidative stress-sensitive. These findings represent a novel cellular mechanism for the induction of insulin resistance in response to changes in the extracellular environment.

PMID: 10444426
In vivo regulation of protein-serine kinases by insulin in skeletal muscle of fructose-hypertensive rats.
... insulin stimulation ... was enhanced, ... both PKB and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10444426

In vivo regulation of protein-serine kinases by insulin in skeletal muscle of fructose-hypertensive rats.
Source

The American journal of physiology (August 1999)

Abstract

In vivo regulation of protein-serine kinases by insulin in skeletal muscle of fructose-hypertensive rats. The effects of tail-vein insulin injection (2 U/kg) on the regulation of protein-serine kinases in hindlimb skeletal muscle were investigated in hyperinsulinemic hypertensive fructose-fed (FF) animals that had been fasted overnight. Basal protein kinase B (PKB) activity was elevated about twofold in FF rats and was not further stimulated by insulin. Phosphatidylinositol 3-kinase (PI3K), which lies upstream of PKB, was increased approximately 3.5-fold within 2-5 min by insulin in control rats. Basal and insulin-activated PI3K activities were further enhanced up to 2-fold and 1.3-fold, respectively, in FF rats. The 70-kDa S6 kinase (S6K) was stimulated about twofold by insulin in control rats. Both basal and insulin-stimulated S6K activity was further enhanced up to 1.5-fold and 3.5-fold, respectively, in FF rats. In control rats, insulin caused a 40-50% reduction of the phosphotransferase activity of the beta-isoform of glycogen synthase kinase 3 (GSK-3beta), which is a PKB target in vitro. Basal GSK-3beta activity was decreased by approximately 40% in FF rats and remained unchanged after insulin treatment. In summary, 1) the PI3K -- > PKB -- > S6K pathway was upregulated under basal conditions, and 2) insulin stimulation of PI3K and S6K activities was enhanced, but both PKB and GSK-3 were refractory to the effects of insulin in FF rats.

PMID: 10781824
Okadaic acid inhibits insulin-induced glucose transport in fetal brown adipocytes in an Akt-independent and protein kinase C zeta-dependent manner.
... activation of Akt/PKB or ... by insulin remained ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10781824

Okadaic acid inhibits insulin-induced glucose transport in fetal brown adipocytes in an Akt-independent and protein kinase C zeta-dependent manner.
Source

FEBS letters (4/21/2000)

Abstract

Okadaic acid inhibits insulin-induced glucose transport in fetal brown adipocytes in an Akt-independent and protein kinase C zeta-dependent manner. In the present study we have investigated the effect of increased serine/threonine phosphorylation of insulin receptor substrates-1 and -2 (IRS-1 and IRS-2) by okadaic acid pretreatment on brown adipocyte insulin signalling leading to glucose transport, an important metabolic effect of insulin in brown adipose tissue. Okadaic acid pretreatment before insulin stimulation decreased IRS-1 and IRS-2 tyrosine phosphorylation in parallel to a decrease in their sodium dodecyl sulfate-polyacrylamide gel electrophoresis mobility. IRS-1/IRS-2-associated p85alpha and phosphatidylinositol (PI) 3-kinase enzymatic activity were partly reduced in brown adipocytes pretreated with okadaic acid upon stimulation with insulin. Furthermore, insulin-induced glucose uptake was totally abolished by the inhibitor in parallel with a total inhibition of insulin-induced protein kinase C (PKC) zeta activity. However, activation of Akt/PKB or p70 S6 kinase (p70 (s6k)) by insulin remained unaltered. Our results suggest that downstream of PI 3-kinase, insulin signalling diverges into at least two independent pathways through Akt/PKB and PKC zeta, the PKC zeta pathway contributing to glucose transport induced by insulin in fetal brown adipocytes.

PMID: 10842657
Insulin signaling and action in fat cells: associations with insulin resistance and type 2 diabetes.
Downstream activation and ... of PKB/Akt by insulin were ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10842657

Insulin signaling and action in fat cells: associations with insulin resistance and type 2 diabetes.
Source

Annals of the New York Academy of Sciences (11/18/1999)

Abstract

Insulin signaling and action in fat cells: associations with insulin resistance and type 2 diabetes. Adipose tissue only accounts for a relatively small proportion (< 10%) of the peripheral glucose utilization in response to insulin. However, the fat cells may still play an important role in insulin resistance and Syndrome X through, for instance, its endocrine functions (production of leptin, TNF alpha, PAI-1, etc.) and involvement in lipid metabolism (FFA release and hydrolysis of triglycerides). The fat cells are also highly sensitive to insulin and may thus be used to elucidate molecular mechanisms for insulin resistance in man. Examinations of the intracellular signaling mechanisms for insulin in fat cells from individuals with Type 2 diabetes revealed markedly lower insulin-stimulated PI3-kinase activity. This was due to a pronounced reduction in the cellular expression of the docking protein, IRS 1, whereas expression of IRS 2 was normal. However, IRS 2-associated PI3-kinase activity was only approximately one-third of that found to be associated with IRS 1 in normal cells. Downstream activation and serine phosphorylation of PKB/Akt by insulin were also markedly reduced in Type 2 diabetes. Furthermore, the dose-response curve for this effect of insulin was similar to that for glucose transport in both normal and Type 2 diabetic cells. Thus, these data show that both PI3-kinase and PKB activation by insulin are markedly reduced in Type 2 diabetes. We also examined whether an attenuated activation of PI3-kinase by insulin can be seen in non-diabetic insulin-resistant states. Approximately 30% of healthy subjects with at least two first-degree relatives with Type 2 diabetes exhibited perturbations in IRS-1 expression and signaling. These individuals were characterized by insulin resistance as well as other markers of Syndrome X. Thus, impaired IRS-1 expression and downstream signaling events in fat cells in response to insulin are associated with insulin resistance and Syndrome X.

PMID: 10842662
Signaling pathways mediating insulin-stimulated glucose transport.
... both insulin's activation of Akt/PKB as ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10842662

Signaling pathways mediating insulin-stimulated glucose transport.
Source

Annals of the New York Academy of Sciences (11/18/1999)

Abstract

Signaling pathways mediating insulin-stimulated glucose transport. A major action of insulin is to accelerate the rate of uptake of sugar into muscle and adipose cells following a meal. The biochemical mechanism by which this is accomplished has been a subject of intense experimentation, although elucidation of the pathways has remained elusive. In recent years, numerous signaling molecules and cascades modulated by insulin have been identified, although few have been definitively established as important to the metabolic actions of the hormone. An exception to this is the lipid kinase phosphatidylinositide 3'-kinase, which, under many conditions, appears absolutely required for insulin to stimulate hexose uptake into adipocytes. Akt/PKB, a serine/threonine protein kinase activated by insulin in a phosphatidylinositide 3'-kinase-dependent manner, has been implicated as a critical mediator of insulin's actions on metabolism and cell survival. Nonetheless, Akt/PKB's role in many insulin effects, particularly accelerated glucose transport, remains controversial. Interestingly, soluble analogues of ceramide antagonize both insulin's activation of Akt/PKB as well as its stimulation of glucose transport, consistent with a causal relationship between the two.

PMID: 10866052
Insulin signaling and action in cultured skeletal muscle cells from lean healthy humans with high and low insulin sensitivity.
... insulin activation of protein kinase B (PKB) was ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10866052

Insulin signaling and action in cultured skeletal muscle cells from lean healthy humans with high and low insulin sensitivity.
Source

Diabetes (June 2000)

Abstract

Insulin signaling and action in cultured skeletal muscle cells from lean healthy humans with high and low insulin sensitivity. The aim of these studies was to investigate whether insulin resistance is primary to skeletal muscle. Myoblasts were isolated from muscle biopsies of 8 lean insulin-resistant and 8 carefully matched insulin-sensitive subjects (metabolic clearance rates as determined by euglycemic-hyperinsulinemic clamp: 5.8 +/- 0.5 vs. 12.3 +/- 1.7 ml x kg (-1) x min (-1), respectively; P < or = 0.05) and differentiated to myotubes. In these cells, insulin stimulation of glucose uptake, glycogen synthesis, insulin receptor (IR) kinase activity, and insulin receptor substrate 1-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity were measured. Furthermore, insulin activation of protein kinase B (PKB) was compared with immunoblotting of serine residues at position 473. Basal glucose uptake (1.05 +/- 0.07 vs. 0.95 +/- 0.07 relative units, respectively; P = 0.49) and basal glycogen synthesis (1.02 +/- 0.11 vs. 0.98 +/- 0.11 relative units, respectively; P = 0.89) were not different in myotubes from insulin-resistant and insulin-sensitive subjects. Maximal insulin responsiveness of glucose uptake (1.35 +/- 0.03-fold vs. 1.41 +/- 0.05-fold over basal for insulin-resistant and insulin-sensitive subjects, respectively; P = 0.43) and glycogen synthesis (2.00 +/- 0.13-fold vs. 2.10 +/- 0.16-fold over basal for insulin-resistant and insulin-sensitive subjects, respectively; P = 0.66) were also not different. Insulin stimulation (1 nmol/l) of IR kinase and PI 3-kinase were maximal within 5 min (approximately 8- and 5-fold over basal, respectively), and insulin activation of PKB was maximal within 15 min (approximately 3.5-fold over basal). These time kinetics were not significantly different between groups. In summary, our data show that insulin action and signaling in cultured skeletal muscle cells from normoglycemic lean insulin-resistant subjects is not different from that in cells from insulin-sensitive subjects. This suggests an important role of environmental factors in the development of insulin resistance in skeletal muscle.

... and insulin activation of PKB was ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10866052

Insulin signaling and action in cultured skeletal muscle cells from lean healthy humans with high and low insulin sensitivity.
Source

Diabetes (June 2000)

Abstract

Insulin signaling and action in cultured skeletal muscle cells from lean healthy humans with high and low insulin sensitivity. The aim of these studies was to investigate whether insulin resistance is primary to skeletal muscle. Myoblasts were isolated from muscle biopsies of 8 lean insulin-resistant and 8 carefully matched insulin-sensitive subjects (metabolic clearance rates as determined by euglycemic-hyperinsulinemic clamp: 5.8 +/- 0.5 vs. 12.3 +/- 1.7 ml x kg (-1) x min (-1), respectively; P < or = 0.05) and differentiated to myotubes. In these cells, insulin stimulation of glucose uptake, glycogen synthesis, insulin receptor (IR) kinase activity, and insulin receptor substrate 1-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity were measured. Furthermore, insulin activation of protein kinase B (PKB) was compared with immunoblotting of serine residues at position 473. Basal glucose uptake (1.05 +/- 0.07 vs. 0.95 +/- 0.07 relative units, respectively; P = 0.49) and basal glycogen synthesis (1.02 +/- 0.11 vs. 0.98 +/- 0.11 relative units, respectively; P = 0.89) were not different in myotubes from insulin-resistant and insulin-sensitive subjects. Maximal insulin responsiveness of glucose uptake (1.35 +/- 0.03-fold vs. 1.41 +/- 0.05-fold over basal for insulin-resistant and insulin-sensitive subjects, respectively; P = 0.43) and glycogen synthesis (2.00 +/- 0.13-fold vs. 2.10 +/- 0.16-fold over basal for insulin-resistant and insulin-sensitive subjects, respectively; P = 0.66) were also not different. Insulin stimulation (1 nmol/l) of IR kinase and PI 3-kinase were maximal within 5 min (approximately 8- and 5-fold over basal, respectively), and insulin activation of PKB was maximal within 15 min (approximately 3.5-fold over basal). These time kinetics were not significantly different between groups. In summary, our data show that insulin action and signaling in cultured skeletal muscle cells from normoglycemic lean insulin-resistant subjects is not different from that in cells from insulin-sensitive subjects. This suggests an important role of environmental factors in the development of insulin resistance in skeletal muscle.

PMID: 11054117
Peroxovanadate induces tyrosine phosphorylation of phosphoinositide-dependent protein kinase-1 potential involvement of src kinase.
Activation of PKB by insulin is ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11054117

Peroxovanadate induces tyrosine phosphorylation of phosphoinositide-dependent protein kinase-1 potential involvement of src kinase.
Source

European journal of biochemistry / FEBS (November 2000)

Abstract

Peroxovanadate induces tyrosine phosphorylation of phosphoinositide-dependent protein kinase-1 potential involvement of src kinase. Phosphoinositide-dependent protein kinase-1 (PDK1) is a recently identified kinase that phosphorylates and activates protein kinase B (PKB). Activation of PKB by insulin is linked to its translocation from the cytosol to the plasma membrane. However, no data are available yet concerning the localization of PDK1 in insulin-sensitive tissue. Using isolated adipocytes, we studied the effect of insulin and of an insulin-mimicking agent peroxovanadate on the subcellular localization of PDK1. In unstimulated adipocytes, overexpressed PDK1 was mostly cytosolic with a low amount associated to membranes. Peroxovanadate stimulation induced the redistribution of PDK1 to the membranes while insulin was without effect. This peroxovanadate effect was dependent on phosphatidylinositol 3,4,5 triphosphate [PtdIns (3,4,5) P3] production as inhibition of PtdIns 3-kinase by wortmannin or deletion of the PH domain of PDK1 prevented the peroxovanadate-induced translocation of PDK1. Further, peroxovanadate-treatment induced a tyrosine phosphorylation of PDK1 which was wortmannin insensitive and did not require the PH domain of PDK1. An inhibitor of Src kinase (PP2) decreased the peroxovanadate-induced PDK1 tyrosine phosphorylation and overexpression of v-Src stimulated this phosphorylation. Mutation of tyrosine 373 of PDK1 abolished the v-Src induced PDK1 tyrosine phosphorylation and partially reduced the effect of peroxovanadate. Our findings suggest that PDK1 could be a substrate for tyrosine kinases and identify Src kinase as one of the tyrosine kinases able to phosphorylate PDK1.

PMID: 11101193
Effect of vanadate and insulin on glucose transport in isolated adult rat cardiomyocytes.
... that insulin stimulation ... is due to ... of protein kinase B, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11101193

Effect of vanadate and insulin on glucose transport in isolated adult rat cardiomyocytes.
Source

Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy (October 2000)

Abstract

Effect of vanadate and insulin on glucose transport in isolated adult rat cardiomyocytes. It is now widely accepted that insulin stimulation of glucose uptake by muscle cells is due to the activation of protein kinase B, leading to the recruitment of glucose transporter proteins from an intracellular compartment to the plasma membrane. Vanadate is a protein tyrosine phosphatase (PTP) inhibitor and a known insulin mimetic agent. Vanadate causes an increase of glucose transport in various tissues, but the mechanism of stimulation is not clearly understood. Hence in the present study, we have compared the mechanism of 2-deoxy-D-glucose transport induced by vanadate and insulin in isolated rat cardiomyocytes. Vanadate stimulated deoxyglucose transport in a time- and concentration-dependent manner. Insulin (100 nM) and vanadate (5 mM) stimulated 2-deoxy-D-glucose transport on an average by 3- and 2-fold respectively over basal values. The stimulation of glucose transport was accompanied by an activation of protein kinase B (PKB). This study also revealed that the activation of PKB and stimulation of 2-deoxyglucose uptake by vanadate and insulin are inhibited by treatment with wortmannin, a specific inhibitor of phoshatidylinositol 3-kinase (PI 3-kinase). Hence, we conclude that both insulin and vanadate follow the same signalling pathway downstream of PI 3-kinase to stimulate 2-deoxy-D-glucose transport.

PMID: 11481324
Insulin receptor substrate-2 phosphorylation is necessary for protein kinase C zeta activation by insulin in L6hIR cells.
... to Akt/PKB inhibition.... insulin induced protein ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11481324

Insulin receptor substrate-2 phosphorylation is necessary for protein kinase C zeta activation by insulin in L6hIR cells.
Source

The Journal of biological chemistry (10/5/2001)

Abstract

Insulin receptor substrate-2 phosphorylation is necessary for protein kinase C zeta activation by insulin in L6hIR cells. We have investigated glycogen synthase (GS) activation in L6hIR cells expressing a peptide corresponding to the kinase regulatory loop binding domain of insulin receptor substrate-2 (IRS-2) (KRLB). In several clones of these cells (B2, F4), insulin-dependent binding of the KRLB to insulin receptors was accompanied by a block of IRS-2, but not IRS-1, phosphorylation, and insulin receptor binding. GS activation by insulin was also inhibited by > 70% in these cells (p < 0.001). The impairment of GS activation was paralleled by a similarly sized inhibition of glycogen synthase kinase 3 alpha (GSK3 alpha) and GSK3 beta inactivation by insulin with no change in protein phosphatase 1 activity. PDK1 (a phosphatidylinositol trisphosphate-dependent kinase) and Akt/protein kinase B (PKB) activation by insulin showed no difference in B2, F4, and in control L6hIR cells. At variance, insulin did not activate PKC zeta in B2 and F4 cells. In L6hIR, inhibition of PKC zeta activity by either a PKC zeta antisense or a dominant negative mutant also reduced by 75% insulin inactivation of GSK3 alpha and -beta (p < 0.001) and insulin stimulation of GS (p < 0.002), similar to Akt/PKB inhibition. In L6hIR, insulin induced protein kinase C zeta (PKC zeta) co-precipitation with GSK3 alpha and beta. PKC zeta also phosphorylated GSK3 alpha and -beta. Alone, these events did not significantly affect GSK3 alpha and -beta activities. Inhibition of PKC zeta activity, however, reduced Akt/PKB phosphorylation of the key serine sites on GSK3 alpha and -beta by > 80% (p < 0.001) and prevented full GSK3 inactivation by insulin. Thus, IRS-2, not IRS-1, signals insulin activation of GS in the L6hIR skeletal muscle cells. In these cells, insulin inhibition of GSK3 alpha and -beta requires dual phosphorylation by both Akt/PKB and PKC zeta.

PMID: 11701440
Normal Akt/PKB with reduced PI3K activation in insulin-resistant mice.
... normal activation of protein kinase B ... by insulin is ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11701440

Normal Akt/PKB with reduced PI3K activation in insulin-resistant mice.
Source

American journal of physiology. Endocrinology and metabolism (December 2001)

Abstract

Normal Akt/PKB with reduced PI3K activation in insulin-resistant mice. Insulin stimulates muscle and adipose tissue to absorb glucose through a signaling cascade that is incompletely understood. Insulin resistance, the inability of insulin to appropriately stimulate glucose uptake, is a hallmark of type 2 diabetes mellitus. The development of experimental systems that model human insulin resistance is important in elucidating the defects responsible for the development of type 2 diabetes. When two strains of mice, BTBR and C57BL/6J (B6), are crossed, the resultant male offspring (BtB6) demonstrate insulin resistance in muscle tissue. Here, we report an insulin resistance phenotype in adipose tissue from lean, nondiabetic BtB6 mice similar to that observed in human muscle. Adipocytes isolated from insulin-resistant male mice display 65% less insulin-stimulated glucose uptake compared with insulin-sensitive female mice. Similarly, adipocytes from insulin-resistant mice have diminished insulin-stimulated IRS-1 phosphorylation and phosphatidylinositol 3-kinase (PI3K) activation. However, normal activation of protein kinase B (Akt/PKB) by insulin is observed. Thus BtB6 mice demonstrate the dissociation of insulin-stimulated PI3K activity and Akt/PKB activation and represent a useful model to investigate the causes of insulin resistance in humans.

PMID: 11855663
Insulin in combination with vanadate stimulates glucose transport in isolated cardiomyocytes from obese Zucker rats.
... activation of PKB by ... plus insulin was ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11855663

Insulin in combination with vanadate stimulates glucose transport in isolated cardiomyocytes from obese Zucker rats.
Source

Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy (September 2001)

Abstract

Insulin in combination with vanadate stimulates glucose transport in isolated cardiomyocytes from obese Zucker rats. Insulin stimulates glucose uptake in muscle cells via activation of protein kinase B (PKB). The protein tyrosine phosphatase (PTP) inhibitor vanadate, is a known insulin mimetic agent but the mechanism whereby vanadate exerts its effect is not clearly understood. Vanadate also has beneficial effects in the diabetic myocardium. The aim of this study was to correlate insulin stimulation of glucose uptake and PKB activation with that induced by vanadate in adult ventricular myocytes from lean and obese Zucker fa/fa rats. In lean Zucker rats, 100 nM insulin and 5 mM vanadate stimulated myocardial 2-deoxy-D- [3] glucose (2-DG) uptake from 27.17 +/- 1.72 to 96.52 +/- 10.87 and 43.86 +/- 4.02 pmole/mg protein p/30 min respectively while a combination of insulin and vanadate could not improve the maximal response of insulin. In obese Zucker hearts, basal as well as insulin and vanadate stimulated glucose uptake were severely impaired (15.49 +/- 1.44 vs 25.51 +/- 3.11 and 20.11 +/- 1.68 pmole/mg protein/30 min respectively). A combination of insulin and vanadate, resulted in a response significantly improved from the maximal response of insulin. This stimulation of 2-DG uptake was, in all instances, blocked by the PI 3-kinase inhibitors wortmannin and LY 294002. Insulin could not activate PKB, as measured by the Ser473 phosphorylated form of the enzyme, in the obese Zucker rats to the same extent as in lean controls. Similar to glucose uptake, activation of PKB by vanadate plus insulin was significantly more than that accomplished by insulin alone in obese rats. Both insulin and vanadate activation of PKB was prevented by wortmannin and LY 294002. Thus, the present study demonstrates that: (i) in cardiomyocytes from lean and obese Zucker rats, both insulin and vanadate stimulate glucose uptake and PKB activation through a PI 3-kinase sensitive pathway. (ii) In obese Zucker rats, neither insulin nor vanadate could induce glucose uptake or activation of PKB to the same extent as in lean controls. (iii) A combination of insulin with vanadate may be beneficial to increase glucose uptake in diabetic hearts, as this gives a better response than insulin alone.

... neither insulin nor ... could induce glucose ... of PKB to ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11855663

Insulin in combination with vanadate stimulates glucose transport in isolated cardiomyocytes from obese Zucker rats.
Source

Cardiovascular drugs and therapy / sponsored by the International Society of Cardiovascular Pharmacotherapy (September 2001)

Abstract

Insulin in combination with vanadate stimulates glucose transport in isolated cardiomyocytes from obese Zucker rats. Insulin stimulates glucose uptake in muscle cells via activation of protein kinase B (PKB). The protein tyrosine phosphatase (PTP) inhibitor vanadate, is a known insulin mimetic agent but the mechanism whereby vanadate exerts its effect is not clearly understood. Vanadate also has beneficial effects in the diabetic myocardium. The aim of this study was to correlate insulin stimulation of glucose uptake and PKB activation with that induced by vanadate in adult ventricular myocytes from lean and obese Zucker fa/fa rats. In lean Zucker rats, 100 nM insulin and 5 mM vanadate stimulated myocardial 2-deoxy-D- [3] glucose (2-DG) uptake from 27.17 +/- 1.72 to 96.52 +/- 10.87 and 43.86 +/- 4.02 pmole/mg protein p/30 min respectively while a combination of insulin and vanadate could not improve the maximal response of insulin. In obese Zucker hearts, basal as well as insulin and vanadate stimulated glucose uptake were severely impaired (15.49 +/- 1.44 vs 25.51 +/- 3.11 and 20.11 +/- 1.68 pmole/mg protein/30 min respectively). A combination of insulin and vanadate, resulted in a response significantly improved from the maximal response of insulin. This stimulation of 2-DG uptake was, in all instances, blocked by the PI 3-kinase inhibitors wortmannin and LY 294002. Insulin could not activate PKB, as measured by the Ser473 phosphorylated form of the enzyme, in the obese Zucker rats to the same extent as in lean controls. Similar to glucose uptake, activation of PKB by vanadate plus insulin was significantly more than that accomplished by insulin alone in obese rats. Both insulin and vanadate activation of PKB was prevented by wortmannin and LY 294002. Thus, the present study demonstrates that: (i) in cardiomyocytes from lean and obese Zucker rats, both insulin and vanadate stimulate glucose uptake and PKB activation through a PI 3-kinase sensitive pathway. (ii) In obese Zucker rats, neither insulin nor vanadate could induce glucose uptake or activation of PKB to the same extent as in lean controls. (iii) A combination of insulin with vanadate may be beneficial to increase glucose uptake in diabetic hearts, as this gives a better response than insulin alone.

PMID: 12112022
Different cellular localization, translocation, and insulin-induced phosphorylation of PKBalpha in HepG2 cells and hepatocytes.
Insulin induced the ... phosphorylated PKBalpha from ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12112022

Different cellular localization, translocation, and insulin-induced phosphorylation of PKBalpha in HepG2 cells and hepatocytes.
Source

Journal of cellular biochemistry (2002)

Abstract

Different cellular localization, translocation, and insulin-induced phosphorylation of PKBalpha in HepG2 cells and hepatocytes. Protein kinase B (PKB), a serine/threonine protein kinase, prevents apoptosis and promotes cellular transformation. PKB activity is stimulated by insulin. In this report, we examined the relative amounts of expression, location, and translocation upon insulin stimulation of PKBalpha in normal primary hepatocytes and carcinoma cells, HepG2 cells. Non-phosphorylated PKBalpha was present in both types of unstimulated cells. The phosphorylated form of the enzyme was present in the nucleus of unstimulated HepG2 cells but not in normal hepatocytes. In the cytoplasm, PKBalpha was found in greater abundance in the hepatocytes as compared in HepG2 cells. Insulin induced the translocation of phosphorylated PKBalpha from the nucleus to the nuclear membrane in HepG2 cells. In contrast, insulin caused translocation and phosphorylation of PKBalpha from the cytosol to the plasma membrane in normal hepatocytes. In addition, there is a higher expression of PKBalpha in the HepG2 cells as compared to normal primary hepatocytes. These findings provide an important distinction between hepatocellular HepG2 cells and normal liver cells and suggest that the presence of constitutively active nuclear PKB in the transformed cells might be an important contributor in cell transformation and immortality of hepatoma cells.

PMID: 12392881
Insulin and ischemia stimulate glycolysis by acting on the same targets through different and opposing signaling pathways.
... that PKB is not required for ... by insulin and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12392881

Insulin and ischemia stimulate glycolysis by acting on the same targets through different and opposing signaling pathways.
Source

Journal of molecular and cellular cardiology (September 2002)

Abstract

Insulin and ischemia stimulate glycolysis by acting on the same targets through different and opposing signaling pathways. The stimulation of heart glycolysis by insulin and ischemia involves the recruitment of the glucose transporter GLUT4 to the plasma membrane and the activation of 6-phosphofructo-2-kinase (PFK-2), which in turn increases the concentration of fructose 2,6-bisphosphate, a well-known stimulator of glycolysis. This review focuses on the mechanisms responsible for PFK-2 activation by insulin and ischemia in heart. Heart PFK-2 is phosphorylated by various protein kinases, including protein kinase B (PKB), thought to mediate most, if not all, short-term effects of insulin, and the AMP-activated protein kinase (AMPK), known to be activated under anaerobic conditions. We found that PKB is not required for PFK-2 activation by insulin and we partially purified an insulin-sensitive PFK-2 kinase, that differs from PKB and from other insulin-stimulated protein kinases. We also demonstrated that AMPK mediates PFK-2 activation by ischemia. Finally, our study of the interaction between the signaling pathways of insulin and ischemia revealed opposite effects on signaling. Intracellular acidosis induced by ischemia inhibited insulin signaling, whereas insulin pretreatment antagonized AMPK activation by ischemia.

PMID: 12502490
Dietary cod protein restores insulin-induced activation of phosphatidylinositol 3-kinase/Akt and GLUT4 translocation to the T-tubules in skeletal muscle of high-fat-fed obese rats.
The activation of ... kinase Akt/PKB by insulin, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12502490

Dietary cod protein restores insulin-induced activation of phosphatidylinositol 3-kinase/Akt and GLUT4 translocation to the T-tubules in skeletal muscle of high-fat-fed obese rats.
Source

Diabetes (January 2003)

Abstract

Dietary cod protein restores insulin-induced activation of phosphatidylinositol 3-kinase/Akt and GLUT4 translocation to the T-tubules in skeletal muscle of high-fat-fed obese rats. Diet-induced obesity is known to cause peripheral insulin resistance in rodents. We have recently found that feeding cod protein to high-fat-fed rats prevents the development of insulin resistance in skeletal muscle. In the present study, we have further explored the cellular mechanisms behind this beneficial effect of cod protein on skeletal muscle insulin sensitivity. Rats were fed a standard chow diet or a high-fat diet in which the protein source was either casein, soy, or cod proteins for 4 weeks. Whole-body and muscle glucose disposal were reduced by approximately 50% in rats fed high-fat diets with casein or soy proteins, but these impairments were not observed in animals fed cod protein. Insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrate (IRS) proteins were similar in muscle of chow- and high-fat-fed rats regardless of the dietary protein source. However, IRS-1-associated phosphatidylinositol (PI) 3-kinase activity was severely impaired (-60%) in muscle of high-fat-fed rats consuming casein or soy protein. In marked contrast, feeding rats with cod protein completely prevented the deleterious effect of fat feeding on insulin-stimulated PI 3-kinase activity. The activation of the downstream kinase Akt/PKB by insulin, assessed by in vitro kinase assay and phosphorylation of GSK-3beta, were also impaired in muscle of high-fat-fed rats consuming casein or soy protein, but these defects were also fully prevented by dietary cod protein. However, no effect of cod protein was observed on atypical protein kinase C activity. Normalization of PI 3-kinase/Akt activation by insulin in rats fed high-fat diets with cod protein was associated with improved translocation of GLUT4 to the T-tubules but not to the plasma membrane. Taken together, these results show that dietary cod protein is a natural insulin-sensitizing agent that appears to prevent obesity-linked muscle insulin resistance by normalizing insulin activation of the PI 3-kinase/Akt pathway and by selectively improving GLUT4 translocation to the T-tubules.

PMID: 12514263
Glucose-6-phosphatase activity is not suppressed but the mRNA level is increased by a sucrose-enriched meal in rats.
Insulin receptor substrate (IRS) phosphorylation ... and activation of protein kinase B (PKB) were ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12514263

Glucose-6-phosphatase activity is not suppressed but the mRNA level is increased by a sucrose-enriched meal in rats.
Source

The Journal of nutrition (January 2003)

Abstract

Glucose-6-phosphatase activity is not suppressed but the mRNA level is increased by a sucrose-enriched meal in rats. The expression of glucose-6-phosphatase (G6Pase) mRNA is repressed by insulin and stimulated by cAMP and dexamethasone, with the insulin effect dominant. Both lipids and glucose increase the expression of G6Pase mRNA under conditions in which insulin is either absent or at basal levels. The aim of the present study was to investigate dietary nutrient regulation of G6Pase mRNA and protein under postprandial conditions. Male rats (n = 6-8/group) were deprived of food for 48 h and then either remained food deprived (FD) or were refed diets containing 68% cornstarch and 12% corn oil (ST;% energy), 68% sucrose and 12% corn oil (SU) or 35% cornstarch and 45% corn oil (HF) for 3 h. Rats were anesthetized, blood was drawn from the portal vein, and the liver was removed and immediately processed for subsequent analyses. Energy intake over the 3-h refeeding period did not differ among groups (209 +/- 25 kJ). Portal vein glucose and insulin were 5.0 +/- 0.2 mmol/L and 90 +/- 18 pmol/L, respectively, in FD rats and were not significantly different among the refed groups (14.5 +/- 1.2 mmol/L and 1302 +/- 154 pmol/L, respectively). Compared with the FD rats, G6Pase mRNA was approximately 50% lower in ST and HF groups, whereas it was approximately 1.6 fold higher in SU-refed rats (P < 0.05). G6Pase activity in whole liver homogenates was lower in ST and HF rats than in FD and SU rats. Insulin receptor substrate (IRS) phosphorylation, IRS-association with phosphatidylinositol 3 (PI3)-kinase and activation of protein kinase B (PKB) were not significantly different among the refed groups. However, glycogen synthase kinase-3alpha phosphorylation was lower and cAMP response element binding protein (CREB) phosphorylation was higher in SU rats than in ST and HF refed groups. Thus, the postprandial environment after ingestion of sucrose appears to overcome the dominant effects of insulin on G6Pase mRNA, perhaps via cellular changes that reduce phosphorylation of, and therefore activate, glycogen synthase kinase-3alpha.

PMID: 12531425
Mechanism of inhibition of insulin-stimulated glucose transport by 4-bromocrotonic acid in 3T3-L1 adipocytes.
... found insulin activation of protein kinase B (PKB) and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12531425

Mechanism of inhibition of insulin-stimulated glucose transport by 4-bromocrotonic acid in 3T3-L1 adipocytes.
Source

Cellular signalling (March 2003)

Abstract

Mechanism of inhibition of insulin-stimulated glucose transport by 4-bromocrotonic acid in 3T3-L1 adipocytes. We have demonstrated previously that 4-bromocrotonic acid (Br-C4) inhibited insulin-stimulated glucose transport by interfering with GLUT4 translocation. In the present study, we further examined the underlying mechanism involved. Since insulin-induced insulin receptor substrate-1-associated phosphatidylinositol (PI) 3-kinase activity was not altered by Br-C4, we determined and found insulin activation of protein kinase B (PKB) and protein kinase Clambda (PKClambda) were both inhibited. However, time-course studies showed that only the inhibition of PKB activation correlated with the inhibition of insulin-stimulated glucose transport. In concert, insulin-stimulated Ser (473/474) phosphorylation on PKB (alpha/beta) were similarly decreased by Br-C4. The finding that okadaic acid-stimulated glucose transport and PKClambda activity were both inhibited by Br-C4 suggested that the effect of Br-C4 on Ser (473/474) phosphorylation was not mediated by protein phosphatase 2A. Moreover, whereas Br-C4 nearly abolished insulin-stimulated integrin-linked kinase (ILK) activity, it only inhibited insulin-stimulated PKB activity by 20%, implying that ILK was not the major kinase for Ser (473/474) phosphorylation. Taken together, these results support the notion that PKB is involved in insulin-stimulated glucose transport. In addition, Br-C4 seems to inhibit insulin-stimulated glucose transport via inhibiting insulin activation of PKB, probably by interfering with insulin activation of an upstream kinase responsible for the phosphorylation of Ser (473/474) residue.

... inhibiting insulin activation of PKB, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12531425

Mechanism of inhibition of insulin-stimulated glucose transport by 4-bromocrotonic acid in 3T3-L1 adipocytes.
Source

Cellular signalling (March 2003)

Abstract

Mechanism of inhibition of insulin-stimulated glucose transport by 4-bromocrotonic acid in 3T3-L1 adipocytes. We have demonstrated previously that 4-bromocrotonic acid (Br-C4) inhibited insulin-stimulated glucose transport by interfering with GLUT4 translocation. In the present study, we further examined the underlying mechanism involved. Since insulin-induced insulin receptor substrate-1-associated phosphatidylinositol (PI) 3-kinase activity was not altered by Br-C4, we determined and found insulin activation of protein kinase B (PKB) and protein kinase Clambda (PKClambda) were both inhibited. However, time-course studies showed that only the inhibition of PKB activation correlated with the inhibition of insulin-stimulated glucose transport. In concert, insulin-stimulated Ser (473/474) phosphorylation on PKB (alpha/beta) were similarly decreased by Br-C4. The finding that okadaic acid-stimulated glucose transport and PKClambda activity were both inhibited by Br-C4 suggested that the effect of Br-C4 on Ser (473/474) phosphorylation was not mediated by protein phosphatase 2A. Moreover, whereas Br-C4 nearly abolished insulin-stimulated integrin-linked kinase (ILK) activity, it only inhibited insulin-stimulated PKB activity by 20%, implying that ILK was not the major kinase for Ser (473/474) phosphorylation. Taken together, these results support the notion that PKB is involved in insulin-stimulated glucose transport. In addition, Br-C4 seems to inhibit insulin-stimulated glucose transport via inhibiting insulin activation of PKB, probably by interfering with insulin activation of an upstream kinase responsible for the phosphorylation of Ser (473/474) residue.

PMID: 12923231
CD36 deficiency increases insulin sensitivity in muscle, but induces insulin resistance in the liver in mice.
... hepatic activation of protein kinase B by insulin, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12923231

CD36 deficiency increases insulin sensitivity in muscle, but induces insulin resistance in the liver in mice.
Source

Journal of lipid research (December 2003)

Abstract

CD36 deficiency increases insulin sensitivity in muscle, but induces insulin resistance in the liver in mice. CD36 (fatty acid translocase) is involved in high-affinity peripheral fatty acid uptake. Mice lacking CD36 exhibit increased plasma free fatty acid and triglyceride (TG) levels and decreased glucose levels. Studies in spontaneous hypertensive rats lacking functional CD36 link CD36 to the insulin-resistance syndrome. To clarify the relationship between CD36 and insulin sensitivity in more detail, we determined insulin-mediated whole-body and tissue-specific glucose uptake in CD36-deficient (CD36-/-) mice. Insulin-mediated whole-body and tissue-specific glucose uptake was measured by d- [3H] glucose and 2-deoxy-d- [1-3H] glucose during hyperinsulinemic clamp in CD36-/- and wild-type control littermates (CD36+/+) mice. Whole-body and muscle-specific insulin-mediated glucose uptake was significantly higher in CD36-/- compared with CD36+/+ mice. In contrast, insulin completely failed to suppress endogenous glucose production in CD36-/- mice compared with a 40% reduction in CD36+/+ mice. This insulin-resistant state of the liver was associated with increased hepatic TG content in CD36-/- mice compared with CD36+/+ mice (110.9 +/- 12.0 and 68.9 +/- 13.6 microg TG/mg protein, respectively). Moreover, hepatic activation of protein kinase B by insulin, measured by Western blot, was reduced by 54%. Our results show a dissociation between increased muscle and decreased liver insulin sensitivity in CD36-/- mice.

PMID: 14500580
Insulin inhibition of transcription stimulated by the forkhead protein Foxo1 is not solely due to nuclear exclusion.
... by activation of protein kinase B (PKB)/Akt by insulin and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 14500580

Insulin inhibition of transcription stimulated by the forkhead protein Foxo1 is not solely due to nuclear exclusion.
Source

Endocrinology (December 2003)

Abstract

Insulin inhibition of transcription stimulated by the forkhead protein Foxo1 is not solely due to nuclear exclusion. The FOXO family of forkhead transcription factors stimulates the transcription of target genes involved in many fundamental cell processes, including cell survival, cell cycle progression, DNA repair, and insulin sensitivity. The activity of FOXO proteins is principally regulated by activation of protein kinase B (PKB)/Akt by insulin and other cytokines. PKB/Akt phosphorylates three consensus sites in FOXO proteins, leading to their export from the nucleus and the inhibition of FOXO-stimulated transcription. It has been widely accepted that the decreased transcription results from reduced abundance of FOXO proteins in the nucleus. In the present study we mutated Leu375 to alanine in the nuclear export signal of Foxo1 (mouse FOXO1), so that it would remain in the nucleus of H4IIE rat hepatoma cells after insulin treatment, and determined whether insulin could still inhibit transcription stimulated by the Foxo1 mutant. Despite the retention of the Foxo1 mutant in the nucleus, insulin inhibited L375A-Foxo1-stimulated transcription to the same extent as transcription stimulated by wild-type Foxo1. Similar results were obtained using reporter plasmids containing the rat IGF-binding protein-1 promoter or a minimal promoter with three copies of the insulin response element to which FOXO proteins bind. We conclude that insulin can inhibit Foxo1-stimulated transcription even when nuclear export of Foxo1 is prevented, indicating that insulin inhibition can occur by direct mechanisms that do not depend on altering the subcellular distribution of the transcription factor.

PMID: 14505487
Analysis of the role of protein kinase B (cAKT) in insulin-dependent induction of glucokinase and sterol regulatory element-binding protein 1 (SREBP1) mRNAs in hepatocytes.
Activation of PKB by insulin was ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 14505487

Analysis of the role of protein kinase B (cAKT) in insulin-dependent induction of glucokinase and sterol regulatory element-binding protein 1 (SREBP1) mRNAs in hepatocytes.
Source

The Biochemical journal (12/15/2003)

Abstract

Analysis of the role of protein kinase B (cAKT) in insulin-dependent induction of glucokinase and sterol regulatory element-binding protein 1 (SREBP1) mRNAs in hepatocytes. Previous work showed that acute stimulation of a conditionally active protein kinase B (PKB or cAKT) was sufficient to elicit insulin-like induction of GCK (glucokinase) and SREBP1 (sterol regulatory element-binding protein 1) in hepatocytes [Iynedjian, Roth, Fleischmann and Gjinovci (2000) Biochem. J. 351, 621-627; Fleischmann and Iynedjian (2000) Biochem. J. 349, 13-17]. The objective of the present study was to determine whether activation of PKB during insulin stimulation of hepatocytes was a necessary condition for the induction of the two genes. Activation of PKB by insulin was inhibited by pretreatment of the hepatocytes with C2 ceramide. This resulted in the inhibition of insulin-dependent increases in GCK and SREBP1 mRNAs. A triple mutant of PKB failed to interfere with insulin activation of PKB in hepatocytes even at high overexpression levels achieved after adenovirus transduction. A PKB-CaaX fusion protein, which can act as a dominant-negative inhibitor of PKB activation in other cells, was shown to be constitutively activated in hepatocytes and to trigger insulin-like induction of GCK and SREBP1. In addition, constitutive PKB-CaaX activity caused refractoriness of the hepatocytes to insulin signalling at an upstream step resulting in the inhibition of both extracellular-signal-regulated kinase 1/2 and endogenous PKB activation. The stimulation of gene expression by constitutively active PKB-CaaX and inhibition of the insulin effect by ceramide are compatible with a role for PKB in the insulin-dependent induction of GCK and SREBP1.

... with insulin activation of PKB in ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 14505487

Analysis of the role of protein kinase B (cAKT) in insulin-dependent induction of glucokinase and sterol regulatory element-binding protein 1 (SREBP1) mRNAs in hepatocytes.
Source

The Biochemical journal (12/15/2003)

Abstract

Analysis of the role of protein kinase B (cAKT) in insulin-dependent induction of glucokinase and sterol regulatory element-binding protein 1 (SREBP1) mRNAs in hepatocytes. Previous work showed that acute stimulation of a conditionally active protein kinase B (PKB or cAKT) was sufficient to elicit insulin-like induction of GCK (glucokinase) and SREBP1 (sterol regulatory element-binding protein 1) in hepatocytes [Iynedjian, Roth, Fleischmann and Gjinovci (2000) Biochem. J. 351, 621-627; Fleischmann and Iynedjian (2000) Biochem. J. 349, 13-17]. The objective of the present study was to determine whether activation of PKB during insulin stimulation of hepatocytes was a necessary condition for the induction of the two genes. Activation of PKB by insulin was inhibited by pretreatment of the hepatocytes with C2 ceramide. This resulted in the inhibition of insulin-dependent increases in GCK and SREBP1 mRNAs. A triple mutant of PKB failed to interfere with insulin activation of PKB in hepatocytes even at high overexpression levels achieved after adenovirus transduction. A PKB-CaaX fusion protein, which can act as a dominant-negative inhibitor of PKB activation in other cells, was shown to be constitutively activated in hepatocytes and to trigger insulin-like induction of GCK and SREBP1. In addition, constitutive PKB-CaaX activity caused refractoriness of the hepatocytes to insulin signalling at an upstream step resulting in the inhibition of both extracellular-signal-regulated kinase 1/2 and endogenous PKB activation. The stimulation of gene expression by constitutively active PKB-CaaX and inhibition of the insulin effect by ceramide are compatible with a role for PKB in the insulin-dependent induction of GCK and SREBP1.

PMID: 14711831
Protein kinase C-zeta and protein kinase B regulate distinct steps of insulin endocytosis and intracellular sorting.
... wild-type protein kinase B (PKB)-alpha or... increase of intact insulin release ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 14711831

Protein kinase C-zeta and protein kinase B regulate distinct steps of insulin endocytosis and intracellular sorting.
Source

The Journal of biological chemistry (3/19/2004)

Abstract

Protein kinase C-zeta and protein kinase B regulate distinct steps of insulin endocytosis and intracellular sorting. We have investigated the molecular mechanisms regulating insulin internalization and intracellular sorting. Insulin internalization was decreased by 50% upon incubation of the cells with the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002. PI3K inhibition also reduced insulin degradation and intact insulin release by 50 and 75%, respectively. Insulin internalization was reduced by antisense inhibition of protein kinase C-zeta (PKCzeta) expression and by overexpression of a dominant negative PKCzeta mutant (DN-PKCzeta). Conversely, overexpression of PKCzeta increased insulin internalization as a function of the PKCzeta levels achieved in the cells. Expression of wild-type protein kinase B (PKB)-alpha or of a constitutively active form (myr-PKB) did not significantly alter insulin internalization and degradation but produced a 100% increase of intact insulin release. Inhibition of PKB by a dominant negative mutant (DN-PKB) or by the pharmacological inhibitor ML-9 reduced intact insulin release by 75% with no effect on internalization and degradation. In addition, overexpression of Rab5 completely rescued the effect of PKCzeta inhibition on insulin internalization but not that of PKB inhibition on intact insulin recycling. Indeed, PKCzeta bound to and activated Rab5. Thus, PI3K controls different steps within the insulin endocytic itinerary. PKCzeta appears to mediate the PI3K effect on insulin internalization in a Rab5-dependent manner, whereas PKB directs intracellular sorting toward intact insulin release.

... of PKB by ... ML-9 reduced intact insulin release ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 14711831

Protein kinase C-zeta and protein kinase B regulate distinct steps of insulin endocytosis and intracellular sorting.
Source

The Journal of biological chemistry (3/19/2004)

Abstract

Protein kinase C-zeta and protein kinase B regulate distinct steps of insulin endocytosis and intracellular sorting. We have investigated the molecular mechanisms regulating insulin internalization and intracellular sorting. Insulin internalization was decreased by 50% upon incubation of the cells with the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002. PI3K inhibition also reduced insulin degradation and intact insulin release by 50 and 75%, respectively. Insulin internalization was reduced by antisense inhibition of protein kinase C-zeta (PKCzeta) expression and by overexpression of a dominant negative PKCzeta mutant (DN-PKCzeta). Conversely, overexpression of PKCzeta increased insulin internalization as a function of the PKCzeta levels achieved in the cells. Expression of wild-type protein kinase B (PKB) -alpha or of a constitutively active form (myr-PKB) did not significantly alter insulin internalization and degradation but produced a 100% increase of intact insulin release. Inhibition of PKB by a dominant negative mutant (DN-PKB) or by the pharmacological inhibitor ML-9 reduced intact insulin release by 75% with no effect on internalization and degradation. In addition, overexpression of Rab5 completely rescued the effect of PKCzeta inhibition on insulin internalization but not that of PKB inhibition on intact insulin recycling. Indeed, PKCzeta bound to and activated Rab5. Thus, PI3K controls different steps within the insulin endocytic itinerary. PKCzeta appears to mediate the PI3K effect on insulin internalization in a Rab5-dependent manner, whereas PKB directs intracellular sorting toward intact insulin release.

PMID: 15138635
Ang II attenuates IGF-1-stimulated Na+, K(+)-ATPase activity via PI3K/Akt pathway in vascular smooth muscle cells.
... the role of ... serine/threonine protein kinase B ... between insulin-like growth factor-1 (IGF-1) and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15138635

Ang II attenuates IGF-1-stimulated Na+, K(+)-ATPase activity via PI3K/Akt pathway in vascular smooth muscle cells.
Source

International journal of molecular medicine (June 2004)

Abstract

Ang II attenuates IGF-1-stimulated Na+, K (+) -ATPase activity via PI3K/Akt pathway in vascular smooth muscle cells. We have investigated the role of phosphatidylinositol 3-kinase (PI3K) and serine/threonine protein kinase B (Akt) in mediating vascular smooth muscle cells (VSMC) sodium pump (Na+, K (+) -ATPase) regulatory interactions between insulin-like growth factor-1 (IGF-1) and angiotensin II (Ang II). Treatment with IGF-1 (100 nM) for 30 min or Ang II (100 nM) for 10 min increased sodium pump activity. Pretreatment with Ang II for 10 min, abolished IGF-1 increased sodium pump activity. Given separately for 6 h, Ang II and IGF-1 stimulated alpha1 mRNA accumulation. Phosphorylation on Ser473 of Akt was increased after treatment with both IGF-1 and Ang II. Pretreatment with 100 nM of PI3K inhibitor Wortmannin (WT) for 30 min decreased: IGF-1 and Ang II-stimulated pump activity, phosphorylation of Akt and PI3K protein expression. Pretreatment with Ang II attenuated IGF-1-stimulated sodium pump activity, phosphorylation of Akt and PI3K protein expression. IGF-1 increased the association between IRS-1 and p85, and Ang II as well as PI3K inhibition decreased this IGF-1 effect. These results suggest that Ang II, which increases pump activity alone, reduces the IGF-1 stimulation of sodium pump activity by attenuating PI3K/Akt signaling. These results implicate PI3K/Akt pathways in Ang II/IGF-1 regulation of the sodium pump in VSMC.

PMID: 15256535
Tissue-specific differences in activation of atypical protein kinase C and protein kinase B in muscle, liver, and adipocytes of insulin receptor substrate-1 knockout mice.
... examined insulin activation of ... and PKB in ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15256535

Tissue-specific differences in activation of atypical protein kinase C and protein kinase B in muscle, liver, and adipocytes of insulin receptor substrate-1 knockout mice.
Source

Molecular endocrinology (Baltimore, Md.; October 2004)

Abstract

Tissue-specific differences in activation of atypical protein kinase C and protein kinase B in muscle, liver, and adipocytes of insulin receptor substrate-1 knockout mice. Insulin receptor substrates (IRSs) 1 and 2 are postulated to control the activation of phosphatidylinositol 3-kinase (PI3K) -dependent signaling factors, namely, atypical protein kinase C (aPKC) and protein kinase B (PKB) /Akt, which mediate metabolic effects of insulin. However, it is uncertain whether aPKC and PKB are activated together or differentially in response to IRS-1 and IRS-2 activation in insulin-sensitive tissues. Presently, we examined insulin activation of aPKC and PKB in vastus lateralis muscle, adipocytes, and liver in wild-type and IRS-1 knockout mice, and observed striking tissue-specific differences. In muscle of IRS-1 knockout mice, the activation of both aPKC and PKB was markedly diminished. In marked contrast, only aPKC activation was diminished in adipocytes, and only PKB activation was diminished in liver. These results suggest that IRS-1 is required for: 1) activation of both aPKC and PKB in muscle; 2) aPKC, but not PKB, activation in adipocytes; and 3) PKB, but not aPKC, activation in liver. Presumably, IRS-2 or other PI3K activators account for the normal activation of aPKC in liver and PKB in adipocytes of IRS-1 knockout mice. These complexities in aPKC and PKB activation may be relevant to metabolic abnormalities seen in tissues in which IRS-1 or IRS-2 is specifically or predominantly down-regulated.

PMID: 15469416
Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes.
... of PKB-mediated insulin signalling ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15469416

Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes.
Source

The Biochemical journal (2/15/2005)

Abstract

Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes. The protein TRB3 (tribbles 3), also called NIPK (neuronal cell death-inducible protein kinase), was recently identified as a protein-protein interaction partner and an inhibitor of PKB (protein kinase B). To explore the hypothesis that TRB3/NIPK might act as a negative regulator of insulin signalling in the liver, this protein was overexpressed by adenoviral transduction of primary cultures of rat hepatocytes, and various aspects of insulin action were investigated. The insulin-induced phosphorylation of Ser-473 and Thr-308 of PKB was found to be undiminished in transduced hepatocytes with a molar excess of TRB3/NIPK over PKB of more than 25-fold. Consistent with unimpaired insulin activation of PKB, the stimulation of Ser-21 and Ser-9 phosphorylation of glycogen synthase kinase 3-alpha and -beta, and the apparent phosphorylation level of 4E-BP1 (eukaryotic initiation factor 4-binding protein 1), were similar in transduced and control hepatocytes. The induction by insulin of the mRNAs encoding glucokinase and SREBF1 (sterol-regulatory-element-binding factor 1) were also normal in TRB3/NIPK hepatocytes. In contrast, the insulin-dependent induction of these two genes, as well as the activation of PKB, were shown to be suppressed in hepatocytes treated with the lipid ether compound PIA6 (phosphatidylinositol ether lipid analogue 6), a recently discovered specific inhibitor of PKB. Since TRB3/NIPK was reported to be increased in the liver of fasting mice, the effects of glucagon, glucocorticoids and insulin on the level of endogenous TRB3/NIPK mRNA in primary hepatocytes were investigated. No significant change in mRNA level occurred under any of the hormonal treatments. The present study does not support the hypothesis that the physiological role of TRB3/NIPK might be to put a brake on insulin signalling in hepatocytes.

... unimpaired insulin activation of PKB, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15469416

Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes.
Source

The Biochemical journal (2/15/2005)

Abstract

Lack of evidence for a role of TRB3/NIPK as an inhibitor of PKB-mediated insulin signalling in primary hepatocytes. The protein TRB3 (tribbles 3), also called NIPK (neuronal cell death-inducible protein kinase), was recently identified as a protein-protein interaction partner and an inhibitor of PKB (protein kinase B). To explore the hypothesis that TRB3/NIPK might act as a negative regulator of insulin signalling in the liver, this protein was overexpressed by adenoviral transduction of primary cultures of rat hepatocytes, and various aspects of insulin action were investigated. The insulin-induced phosphorylation of Ser-473 and Thr-308 of PKB was found to be undiminished in transduced hepatocytes with a molar excess of TRB3/NIPK over PKB of more than 25-fold. Consistent with unimpaired insulin activation of PKB, the stimulation of Ser-21 and Ser-9 phosphorylation of glycogen synthase kinase 3-alpha and -beta, and the apparent phosphorylation level of 4E-BP1 (eukaryotic initiation factor 4-binding protein 1), were similar in transduced and control hepatocytes. The induction by insulin of the mRNAs encoding glucokinase and SREBF1 (sterol-regulatory-element-binding factor 1) were also normal in TRB3/NIPK hepatocytes. In contrast, the insulin-dependent induction of these two genes, as well as the activation of PKB, were shown to be suppressed in hepatocytes treated with the lipid ether compound PIA6 (phosphatidylinositol ether lipid analogue 6), a recently discovered specific inhibitor of PKB. Since TRB3/NIPK was reported to be increased in the liver of fasting mice, the effects of glucagon, glucocorticoids and insulin on the level of endogenous TRB3/NIPK mRNA in primary hepatocytes were investigated. No significant change in mRNA level occurred under any of the hormonal treatments. The present study does not support the hypothesis that the physiological role of TRB3/NIPK might be to put a brake on insulin signalling in hepatocytes.

PMID: 15479767
Amino acids and leucine allow insulin activation of the PKB/mTOR pathway in normal adipocytes treated with wortmannin and in adipocytes from db/db mice.
... improve insulin activation of PKB in ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15479767

Amino acids and leucine allow insulin activation of the PKB/mTOR pathway in normal adipocytes treated with wortmannin and in adipocytes from db/db mice.
Source

FASEB journal : official publication of the Federation of American Societies for Experimental Biology (December 2004)

Abstract

Amino acids and leucine allow insulin activation of the PKB/mTOR pathway in normal adipocytes treated with wortmannin and in adipocytes from db/db mice. Amino acids are nutrients responsible for mammalian target of rapamycin (mTOR) regulation in mammalian cells. The mTOR protein is mainly known for its role in regulating cell growth, notably via protein synthesis. In addition to amino acids, mTOR is regulated by insulin via a phosphatidylinositol 3-kinase (PI 3-kinase) -dependent pathway. mTOR mediates crosstalk between amino acids and insulin signaling. We show that in freshly isolated rat adipocytes, insulin stimulates the phosphorylation of mTOR on serine 2448, a protein kinase B (PKB) consensus phosphorylation site. This site is also phosphorylated by amino acids, which in contrast to insulin do not activate PKB. Moreover, insulin and amino acids have an additive effect on mTOR phosphorylation, indicating that they act via two independent pathways. Importantly, amino acids, notably leucine, permit insulin to stimulate PKB when PI 3-kinase is inhibited. They also rescue glucose transport and the mTOR pathway. Further, leucine alone can improve insulin activation of PKB in db/db mice. Our results define the importance of amino acids in insulin signaling and reveal leucine as a key amino acid in disease situations associated with insulin-resistance in adipocytes.

PMID: 15684405
Activation of SOCS-3 by resistin.
... including insulin receptor (IR) phosphorylation ... and activation of protein kinase B/Akt.   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15684405

Activation of SOCS-3 by resistin.
Source

Molecular and cellular biology (February 2005)

Abstract

Activation of SOCS-3 by resistin. Resistin is an adipocyte hormone that modulates glucose homeostasis. Here we show that in 3T3-L1 adipocytes, resistin attenuates multiple effects of insulin, including insulin receptor (IR) phosphorylation, IR substrate 1 (IRS-1) phosphorylation, phosphatidylinositol-3-kinase (PI3K) activation, phosphatidylinositol triphosphate production, and activation of protein kinase B/Akt. Remarkably, resistin treatment markedly induces the gene expression of suppressor of cytokine signaling 3 (SOCS-3), a known inhibitor of insulin signaling. The 50% effective dose for resistin induction of SOCS-3 is approximately 20 ng/ml, close to levels of resistin in serum. Association of SOCS-3 protein with the IR is also increased by resistin. Inhibition of SOCS function prevented resistin from antagonizing insulin action in adipocytes. SOCS-3 induction is the first cellular effect of resistin that is independent of insulin and is a likely mediator of resistin's inhibitory effect on insulin signaling in adipocytes.

PMID: 15755733
Insulin stimulates postsynaptic density-95 protein translation via the phosphoinositide 3-kinase-Akt-mammalian target of rapamycin signaling pathway.
... insulin rapidly induced the... protein kinase B ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15755733

Insulin stimulates postsynaptic density-95 protein translation via the phosphoinositide 3-kinase-Akt-mammalian target of rapamycin signaling pathway.
Source

The Journal of biological chemistry (5/6/2005)

Abstract

Insulin stimulates postsynaptic density-95 protein translation via the phosphoinositide 3-kinase-Akt-mammalian target of rapamycin signaling pathway. Insulin receptors are highly enriched at neuronal synapses, but whose function remains unclear. Here we present evidence that brief incubations of rat hippocampal slices with insulin resulted in an increased protein expression of dendritic scaffolding protein postsynaptic density-95 (PSD-95) in area CA1. This insulin-induced increase in the PSD-95 protein expression was inhibited by the tyrosine kinase inhibitor, AG1024, phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin, translational inhibitors, anisomycin and rapamycin, but not by LY303511 (an inactive analogue of LY294002), and transcriptional inhibitor, actinomycin D, suggesting that insulin regulates the translation of PSD-95 by activating the receptor tyrosine kinase-PI3K-mammalian target of rapamycin (mTOR) signaling pathway. A similar insulin-induced increase in the PSD-95 protein expression was detected after stimulation of the synaptic fractions isolated from the hippocampal neurons. Furthermore, insulin treatment did not affect the PSD-95 mRNA levels. In agreement, insulin rapidly induced the phosphorylation of 3-phosphoinositide-dependent protein kinase-1 (PDK1), protein kinase B (Akt), and mTOR, effects that were prevented by the AG1024 and LY294002. We also show that insulin stimulated the phosphorylation of 4E-binding protein 1 (4E-BP1) and p70S6 kinase (p70S6K) in a mTOR-dependent manner. Finally, we demonstrate the constitutive expression of PSD-95 mRNA in the synaptic fractions isolated from hippocampal neurons. Taken together, these findings suggest that activation of the PI3K-Akt-mTOR signaling pathway is essential for the insulin-induced up-regulation of local PSD-95 protein synthesis in neuronal dendrites and indicate a new molecular mechanism that may contribute to the modulation of synaptic function by insulin in hippocampal area CA1.

PMID: 15780083
Insulin-like growth factors inhibit podocyte apoptosis through the PI3 kinase pathway.
... the insulin receptor substrate (IRS)-1-p85 complex ... and activation of ... AKT/PKB) ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 15780083

Insulin-like growth factors inhibit podocyte apoptosis through the PI3 kinase pathway.
Source

Kidney international (April 2005)

Abstract

Insulin-like growth factors inhibit podocyte apoptosis through the PI3 kinase pathway. [BACKGROUND] Abnormal podocyte development and progressive podocyte injury have been implicated in a number of human kidney diseases. Factors necessary for regulating development and maintenance of this cell type are only beginning to emerge. [METHODS] To study the role of the insulin-like growth factor (IGF) system in regulating podocyte survival, we induced human fetal podocytes to undergo apoptosis. We demonstrated a significant increase in apoptosis when these cells were incubated in the presence of etoposide, as measured by DNA fragmentation and nuclear membrane condensation and blebbing. [RESULTS] Podocyte apoptosis was reduced to control levels when the cells were coincubated in the presence of IGF-1. We showed that the protective effect of IGFs in this cell type was mediated through the activation of the phosphatidylinositol 3'-kinase (PI3K) pathway. IGF-1 stimulation resulted in the formation of the insulin receptor substrate (IRS)-1-p85 complex, an increase in PI3 kinase activity, and activation of protein kinase B (AKT/PKB) and the bcl-2 family member bad. Incubation of the podocytes with inhibitors of the PI3 kinase pathway resulted in a loss of this IGF-1 protective effect. [CONCLUSION] These data demonstrate an important role for the IGF system in fetal podocyte survival in vitro, and suggest potential mediators to slow or alleviate the loss or damage of the podocyte in progressive renal disease.

PMID: 17170229
Angiotensin II does not stimulate proliferation of rat thyroid PC Cl3 cell line.
Insulin had... induced the ... of PKB, ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 17170229

Angiotensin II does not stimulate proliferation of rat thyroid PC Cl3 cell line.
Source

The Journal of endocrinology (December 2006)

Abstract

Angiotensin II does not stimulate proliferation of rat thyroid PC Cl3 cell line. In PC Cl3 cells, a rat thyroid cell line, angiotensin (Ang II) activates the atypical protein kinase C-zeta (PKC-zeta) and the extracellular signal-regulated kinase (ERK) pathways. We here studied the Ang II effects on PC Cl3 cell proliferation. It was found that Ang II: (1) induced the phosphorylation of protein kinase B (PKB), (2) induced the growth-related early gene c-fos expression, (3) enhanced the cyclin E and p27 (kip) expression, (4) had no effects on Cdk2, and (5) did not affect the transition from G0/G1 to S phase. Inhibition of phosphoinositide-3kinase by LY294002 further increased the effect of Ang II on p27 (kip) induction, whilst PKCs inhibition by GF109203X decreased such effect. The role of PKC-zeta was recognized by the use of a synthetic myristoylated peptide with sequences based on the endogenous PKC-zeta pseudosubstrate and by PKC-zeta downregulation using the small interfering RNA (siRNA). Insulin had a replicating effect on PC Cl3 cells, induced the phosphorylation of PKB, decreased p27 (kip) expression and had no effect on the PKC-zeta cytosol-to-membrane translocation. PC Cl3 cell proliferation was induced more potently by simultaneous stimulation with insulin and Ang II than by stimulation with insulin alone, and the effect on p27 (kip) expression was similar to that obtained with insulin only. These observations demonstrate that in PC Cl3 cells Ang II causes a block in G1 phase, although both ERK and PKB pathways are activated, and this effect may be due to the upregulation of p27 (kip) and PKC-zeta operativity.

PMID: 17520061
Molecular mechanisms of the diabetogenic effects of arsenic: inhibition of insulin signaling by arsenite and methylarsonous acid.
... inhibit insulin-stimulated glucose uptake (ISGU) in ... of protein kinase B ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 17520061

Molecular mechanisms of the diabetogenic effects of arsenic: inhibition of insulin signaling by arsenite and methylarsonous acid.
Source

Environmental health perspectives (May 2007)

Abstract

Molecular mechanisms of the diabetogenic effects of arsenic: inhibition of insulin signaling by arsenite and methylarsonous acid. [BACKGROUND] Increased prevalences of diabetes mellitus have been reported among individuals chronically exposed to inorganic arsenic (iAs). However, the mechanisms underlying the diabetogenic effects of iAs have not been characterized. We have previously shown that trivalent metabolites of iAs, arsenite (iAs (III)) and methylarsonous acid (MAs (III)) inhibit insulin-stimulated glucose uptake (ISGU) in 3T3-L1 adipocytes by suppressing the insulin-dependent phosphorylation of protein kinase B (PKB/Akt). [OBJECTIVES] Our goal was to identify the molecular mechanisms responsible for the suppression of PKB/Akt phosphorylation by iAs (III) and MAs (III). [METHODS] The effects of iAs (III) and MAs (III) on components of the insulin-activated signal transduction pathway that regulate PKB/Akt phosphorylation were examined in 3T3-L1 adipocytes. [RESULTS] Subtoxic concentrations of iAs (III) or MAs (III) had little or no effect on the activity of phosphatidylinositol 3-kinase (PI-3K), which synthesizes phosphatidylinositol-3,4,5-triphosphate (PIP (3)), or on phosphorylation of PTEN (phosphatase and tensin homolog deleted on chromosome ten), a PIP (3) phosphatase. Neither iAs (III) nor MAs (III) interfered with the phosphorylation of 3-phosphoinositide-dependent kinase-1 (PDK-1) located downstream from PI-3K. However, PDK-1 activity was inhibited by both iAs (III) and MAs (III). Consistent with these findings, PDK-1-catalyzed phosphorylation of PKB/Akt (Thr308) and PKB/Akt activity were suppressed in exposed cells. In addition, PKB/Akt (Ser473) phosphorylation, which is catalyzed by a putative PDK-2, was also suppressed. Notably, expression of constitutively active PKB/Akt restored the normal ISGU pattern in adipocytes treated with either iAs (III) or MAs (III). [CONCLUSIONS] These results suggest that inhibition of the PDK-1/PKB/Akt-mediated transduction step is the key mechanism for the inhibition of ISGU in adipocytes exposed to iAs (III) or MAs (III), and possibly for impaired glucose tolerance associated with human exposures to iAs.

PMID: 17572871
Insulin-induced GLUT4 translocation to the plasma membrane is blunted in large compared with small primary fat cells isolated from the same individual.
Activation of ... and Akt1 ... by insulin was ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 17572871

Insulin-induced GLUT4 translocation to the plasma membrane is blunted in large compared with small primary fat cells isolated from the same individual.
Source

Diabetologia (August 2007)

Abstract

Insulin-induced GLUT4 translocation to the plasma membrane is blunted in large compared with small primary fat cells isolated from the same individual. [AIMS/HYPOTHESIS] Several studies have suggested that large fat cells are less responsive to insulin than small fat cells. However, in these studies, large fat cells from obese individuals were compared with smaller fat cells from leaner participants, in effect making it impossible to draw conclusions about whether there is a causal relationship between fat cell size and insulin sensitivity. We hypothesised that small fat cells might be more insulin-responsive than large adipocytes when obtained from the same individual. [MATERIALS AND METHODS] We developed a method of sorting isolated primary human fat cells by using nylon filters of two different pore sizes. The cells were stained to visualise DNA, which allowed discrimination from artefacts such as lipid droplets. The sorted cells were left to recover overnight, since we had previously demonstrated that this is necessary for correct assessment of insulin response. [RESULTS] We found similar amounts of the insulin receptor (IR), IRS-1 and GLUT4 when we compared small and large adipocytes from the same volunteer by immunoblotting experiments using the same total cell volume from both cell populations. Activation of IR, IRS-1 and Akt1 (also known as protein kinase B) by insulin was similar in the two cell populations. However, immunofluorescence confocal microscopy of plasma membrane sheets did not reveal any increase in the amount of GLUT4 in the plasma membrane following insulin stimulation in the large fat cells, whereas we saw a twofold increase in the amount of GLUT4 in the small fat cells. [CONCLUSIONS/INTERPRETATION] Our results support a causal relationship between the accumulation of large fat cells in obese individuals and reduced insulin responsiveness.

PMID: 18534131
Musclin inhibits insulin activation of Akt/protein kinase B in rat skeletal muscle.
... inhibits insulin activation of Akt/protein kinase B in ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 18534131

Musclin inhibits insulin activation of Akt/protein kinase B in rat skeletal muscle.
Source

The Journal of international medical research (0)

Abstract

Musclin inhibits insulin activation of Akt/protein kinase B in rat skeletal muscle. Musclin is a muscle-derived secretory peptide that induces insulin resistance in vitro. We studied the effect of musclin (0.5 microg/ml) on insulin-stimulated glucose uptake in rat skeletal muscles and also the effect of rosiglitazone (0.4 microg/ml). Preincubation of muscles with musclin resulted in decreased insulin-stimulated glucose uptake. Musclin also reduced expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and liver X receptor alpha (LXRalpha) mRNAs, although expression of glucose transporter 4 mRNA was unaltered. Rosiglitazone attenuated the effects of musclin on glucose uptake and PPARgamma and LXRalpha mRNA expression. Western blotting demonstrated that activation of protein kinase B (Akt/PKB) in the insulin-signalling cascade was decreased by musclin but corrected by rosiglitazone. These findings suggest that musclin-induced impairment of insulin-stimulated glucose uptake in skeletal muscle is related to Akt/PKB inhibition and might be modulated by PPARgamma/LXRalpha.

PMID: 18679014
The role of PI3/Akt pathway in the protective effect of insulin against corticosterone cell death induction in hippocampal cell culture.
... that insulin induced the ... of protein kinase B ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 18679014

The role of PI3/Akt pathway in the protective effect of insulin against corticosterone cell death induction in hippocampal cell culture.
Source

Neuroendocrinology (2008)

Abstract

The role of PI3/Akt pathway in the protective effect of insulin against corticosterone cell death induction in hippocampal cell culture. Corticosterone induces neuroanatomical and neurochemical changes in the hippocampus that are associated with cognitive impairments. In the present study corticosterone induced cell death in primary hippocampal neurons cultured in Neurobasal + B27 medium. Insulin prevents neuronal cell death induced in a concentration dependent manner. The neuroprotective effect of insulin was reversed by LY294002, a phosphatidylinositol 3'-kinase (PI3 kinase) inhibitor, whereas the mitogen-activated protein kinase (MAPK) inhibitor PD98059, an upstream blocker of MAPK had no effect. Western blot analyses showed that insulin induced the activation of protein kinase B (Akt). These results suggest that insulin can prevent neuronal cell death induced by corticosterone in hippocampal neurons by modulating the activity of the PI3 kinase/Akt pathway.

PMID: 19281842
Hydrogen peroxide impairs insulin-stimulated assembly of mTORC1.
Insulin signaling ... is dependent upon ... of Akt/PKB and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 19281842

Hydrogen peroxide impairs insulin-stimulated assembly of mTORC1.
Source

Free radical biology & medicine (6/1/2009)

Abstract

Hydrogen peroxide impairs insulin-stimulated assembly of mTORC1. Oxidants are well recognized for their capacity to reduce the phosphorylation of the mammalian target of rapamycin (mTOR) substrates, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) and p70 S6 kinase 1 (S6K1), thereby hindering mRNA translation at the level of initiation. mTOR functions to regulate mRNA translation by forming the signaling complex mTORC1 (mTOR, raptor, GbetaL). Insulin signaling to mTORC1 is dependent upon phosphorylation of Akt/PKB and the inhibition of the tuberous sclerosis complex (TSC1/2), thereby enhancing the phosphorylation of 4E-BP1 and S6K1. In this study we report the effect of H (2) O (2) on insulin-stimulated mTORC1 activity and assembly using A549 and bovine aortic smooth muscle cells. We show that insulin stimulated the phosphorylation of TSC2 leading to a reduction in raptor-mTOR binding and in the quantity of proline-rich Akt substrate 40 (PRAS40) precipitating with mTOR. Insulin also increased 4E-BP1 coprecipitating with mTOR and the phosphorylation of the mTORC1 substrates 4E-BP1 and S6K1. H (2) O (2), on the other hand, opposed the effects of insulin by increasing raptor-mTOR binding and the ratio of PRAS40/raptor derived from the mTOR immunoprecipitates in both cell types. These effects occurred in conjunction with a reduction in 4E-BP1 phosphorylation and the 4E-BP1/raptor ratio. siRNA-mediated knockdown of PRAS40 in A549 cells partially reversed the effect of H (2) O (2) on 4E-BP1 phosphorylation but not on S6K1. These findings are consistent with PRAS40 functioning as a negative regulator of insulin-stimulated mTORC1 activity during oxidant stress.

PMID: 19502418
Involvement of Per-Arnt-Sim Kinase and extracellular-regulated kinases-1/2 in palmitate inhibition of insulin gene expression in pancreatic beta-cells.
... the role of... protein kinase B (PKB), ... of insulin gene ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 19502418

Involvement of Per-Arnt-Sim Kinase and extracellular-regulated kinases-1/2 in palmitate inhibition of insulin gene expression in pancreatic beta-cells.
Source

Diabetes (September 2009)

Abstract

Involvement of Per-Arnt-Sim Kinase and extracellular-regulated kinases-1/2 in palmitate inhibition of insulin gene expression in pancreatic beta-cells. [OBJECTIVE] Prolonged exposure of pancreatic beta-cells to simultaneously elevated levels of fatty acids and glucose (glucolipotoxicity) impairs insulin gene transcription. However, the intracellular signaling pathways mediating these effects are mostly unknown. This study aimed to ascertain the role of extracellular-regulated kinases (ERKs) 1/2, protein kinase B (PKB), and Per-Arnt-Sim kinase (PASK) in palmitate inhibition of insulin gene expression in pancreatic beta-cells. [RESEARCH DESIGN AND METHODS] MIN6 cells and isolated rat islets were cultured in the presence of elevated glucose, with or without palmitate or ceramide. ERK1/2 phosphorylation, PKB phosphorylation, and PASK expression were examined by immunoblotting and real-time PCR. The role of these kinases in insulin gene expression was assessed using pharmacological and molecular approaches. [RESULTS] Exposure of MIN6 cells and islets to elevated glucose induced ERK1/2 and PKB phosphorylation, which was further enhanced by palmitate. Inhibition of ERK1/2, but not of PKB, partially prevented the inhibition of insulin gene expression in the presence of palmitate or ceramide. Glucose-induced expression of PASK mRNA and protein levels was reduced in the presence of palmitate. Overexpression of wild-type PASK increased insulin and pancreatic duodenal homeobox-1 gene expression in MIN6 cells and rat islets incubated with glucose and palmitate, whereas overexpression of a kinase-dead PASK mutant in rat islets decreased expression of insulin and pancreatic duodenal homeobox-1 and increased C/EBPbeta expression. [CONCLUSIONS] Both the PASK and ERK1/2 signaling pathways mediate palmitate inhibition of insulin gene expression. These findings identify PASK as a novel mediator of glucolipotoxicity on the insulin gene in pancreatic beta-cells.

PMID: 21933986
FoxO feedback control of basal IRS-2 expression in pancreatic ß-cells is distinct from that in hepatocytes.
... by insulin/IGF-I ... constitutive activation of protein kinase B (PKB) significantly ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 21933986

FoxO feedback control of basal IRS-2 expression in pancreatic ß-cells is distinct from that in hepatocytes.
Source

Diabetes (November 2011)

Abstract

FoxO feedback control of basal IRS-2 expression in pancreatic ß-cells is distinct from that in hepatocytes. [OBJECTIVE] Appropriate regulation of insulin receptor substrate 2 (IRS-2) expression in pancreatic ß-cells is essential to adequately compensate for insulin resistance. In liver, basal IRS-2 expression is controlled via a temporal negative feedback of sterol regulatory element-binding protein 1 (SREBP-1) to antagonize transcription factors forkhead box class O (FoxO) 1/FoxO3a at an insulin response element (IRE) on the IRS-2 promoter. The purpose of the study was to examine if a similar mechanism controlled IRS-2 expression in ß-cells. [RESEARCH DESIGN AND METHODS] IRS-2 mRNA and protein expression, as well as IRS-2 gene promoter activity, were examined in isolated rat islets. Specific transcription factor association with the IRE on the IRS-2 promoter was examined by chromatin immunoprecipitation (ChIP) assay, and their nuclear translocation was examined by immunofluorescence. A direct in vivo effect of insulin on control of IRS-2 expression in liver and pancreatic islets was also investigated. [RESULTS] In IRS-2 promoter-reporter assays conducted in isolated islets, removal of the IRE decreased basal IRS-2 promoter activity in ß-cells up to 80%. Activation of IRS signaling in isolated rat islets by insulin/IGF-I (used as an experimental in vitro tool) or downstream constitutive activation of protein kinase B (PKB) significantly decreased IRS-2 expression. In contrast, inhibition of phosphatidylinositol 3-kinase (PI3K) or PKB significantly increased IRS-2 levels in ß-cells. ChIP assays indicated that transcription factors FoxO1 and FoxO3a associated with the IRE on the IRS-2 promoter in ß-cells in a PI3K/PKB-dependent manner, whereas others, such as SREBP-1, the transcription factor binding to immunoglobulin heavy chain enhancer 3', and the aryl hydrocarbon receptor nuclear translocator (ARNT), did not. However, only FoxO3a, not FoxO1, was capable of driving IRS-2 promoter activity via the IRE in ß-cells. In vivo studies showed insulin was able to suppress IRS-2 expression via activation of SREBP-1 in the liver, but this mechanism was not apparent in pancreatic islets from the same animal. [CONCLUSIONS] The molecular mechanism for feedback control of IRS signaling to decrease IRS-2 expression in liver and ß-cells is quite distinct, with a predominant role played by FoxO3a in ß-cells.

PMID: 22293506
Effects of ritonavir-boosted darunavir, atazanavir and lopinavir on adipose functions and insulin sensitivity in murine and human adipocytes.
... on insulin activation of protein kinase B ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 22293506

Effects of ritonavir-boosted darunavir, atazanavir and lopinavir on adipose functions and insulin sensitivity in murine and human adipocytes.
Source

Antiviral therapy (2012)

Abstract

Effects of ritonavir-boosted darunavir, atazanavir and lopinavir on adipose functions and insulin sensitivity in murine and human adipocytes. [BACKGROUND] Ritonavir-boosted protease inhibitors (PIs) could adversely affect metabolism and adipose tissue to different extents, depending on the molecule. Using drugs with minimal adverse metabolic effects is an important consideration in at-risk HIV-infected patients. In vitro adipocyte models can be useful for comparing the effects of different PIs. [METHODS] We compared the effects of darunavir, darunavir/ritonavir, atazanavir/ritonavir and lopinavir/ritonavir in murine and human adipocytes on differentiation, mitochondrial function, reactive oxygen species (ROS) production and insulin sensitivity. [RESULTS] In human and murine adipocytes, differentiation evaluated by lipid content and protein expression of adipogenic markers, mitochondrial function evaluated by aggregation of the cationic dye JC-1 and by 3- [4,5-dimethylthiazol-2-yl] -2,5 diphenyltetrazolium bromide lysis, and mitochondrial mass evaluated by MitoTracker fluorescence and the expression of mitochondrial proteins were unaffected by darunavir, mildly affected by darunavir/ritonavir and further altered by atazanavir/ritonavir and lopinavir/ritonavir. ROS production was unaltered by darunavir and darunavir/ritonavir but was increased by lopinavir/ritonavir and atazanavir/ritonavir. Regarding insulin sensitivity, darunavir and darunavir/ritonavir had no significant effect on insulin activation of protein kinase B (Akt/PKB) and MAP kinase and of glucose transport, whereas lopinavir/ritonavir and atazanavir/ritonavir partly impaired the effect of insulin. The effect of atazanavir/ritonavir was generally milder than that of lopinavir/ritonavir. [CONCLUSIONS] The various PIs differentially modified adipocyte functions. Darunavir alone did not affect adipocyte functions and only modestly altered differentiation and mitochondrial function when associated with ritonavir. Lopinavir/ritonavir adversely affected differentiation and lipid content, mitochondrial function, ROS production and insulin sensitivity, and the effect of atazanavir/ritonavir was intermediate. Thus, in vitro, darunavir/ritonavir presented a safer metabolic profile on adipocytes than atazanavir/ritonavir and lopinavir/ritonavir.

PMID: 22811470
Insulin detemir enhances proglucagon gene expression in the intestinal L cells via stimulating ß-catenin and CREB activities.
... that d-INS induced rapid ... of protein kinase B ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 22811470

Insulin detemir enhances proglucagon gene expression in the intestinal L cells via stimulating ß-catenin and CREB activities.
Source

American journal of physiology. Endocrinology and metabolism (9/15/2012)

Abstract

Insulin detemir enhances proglucagon gene expression in the intestinal L cells via stimulating ß-catenin and CREB activities. Insulin therapy using insulin detemir (d-INS) has demonstrated weight-sparing effects compared with other insulin formulations. Mechanisms underlying these effects, however, remain largely unknown. Here we postulate that the intestinal tissues' selective preference allows d-INS to exert enhanced action on proglucagon (Gcg) expression and the production of glucagon-like peptide (GLP) -1, an incretin hormone possessing both glycemia-lowering and weight loss effects. To test this hypothesis, we used obese type 2 diabetic db/db mice and conducted a 14-day intervention with daily injection of a therapeutic dose of d-INS or human insulin (h-INS) in these mice. The body weight of the mice after 14-day daily injection of d-INS (5 IU/kg) was decreased significantly compared with those injected with the same dose of h-INS or saline. The weight-sparing effect of d-INS was associated with significantly elevated circulating levels of total GLP-1 and reduced food intake. Histochemistry analysis demonstrated that d-INS induced rapid phosphorylation of protein kinase B (Akt) in the gut L cells of normal mice. Western blotting showed that d-INS stimulated Akt activation in a more rapid and enhanced fashion in the mouse distal ileum compared with those by h-INS. In vitro investigation in primary fetal rat intestinal cell (FRIC) cultures showed that d-INS increased Gcg mRNA expression as determined by Northern blotting and real-time RT-PCR. Consistent with these in vivo investigations, d-INS significantly increased GLP-1 secretion in FRIC cultures. Consistently, d-INS was also shown to induce rapid phosphorylation of Akt in the clonal gut cell line GLUTag. Furthermore, d-INS increased ß-catenin phosphorylation, its nuclear translocation, and enhanced cAMP response element-binding protein (CREB) phosphorylation in a phosphatidylinositol 3-kinase and/or mitogen-activated protein kinase kinase/extracellular signal-regulated kinase-sensitive manner. We suggest that the weight-sparing benefit of d-INS in mice is related to its intestinal tissues preference that leads to profound stimulation of Gcg expression and enhanced GLP-1 secretion in intestinal L cells, potentially involving the activation of insulin/ß-catenin/CREB signaling pathways.

PMID: 8645147
Specific binding of the Akt-1 protein kinase to phosphatidylinositol 3,4,5-trisphosphate without subsequent activation.
... the activation of Akt-1 by ... and insulin.   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8645147

Specific binding of the Akt-1 protein kinase to phosphatidylinositol 3,4,5-trisphosphate without subsequent activation.
Source

The Biochemical journal (5/1/1996)

Abstract

Specific binding of the Akt-1 protein kinase to phosphatidylinositol 3,4,5-trisphosphate without subsequent activation. Recent evidence has suggested that activation of phosphoinositide 3-kinase (PI 3-kinase) is required for the activation of Akt-1 by growth factors and insulin. Here we demonstrate by two independent methods that Akt-1 from L6 myotubes binds to PtdIns (3,4,5) P3, PtdIns (3,4) P2 and PtdIns (4,5) P2 when presented against a background of phosphatidylserine (PtdSer) or a 1: 1 mixture of PtdSer and phosphatidylcholine (PtdCho). No binding was observed with the lipids PtdIns (3,5) P2, PtdIns4P and PtdIns3P or background lipids. Activated, hyperphosphorylated forms of Akt-1 from insulin-stimulated L6 myotubes bound to PtdIns (3,4,5) P3 in a similar manner as inactive Akt-1. Quantitative analysis using surface plasmon resonance showed that the equilibrium association constant for the binding of Akt-1 to PtdIns (3,4,5) P3 was submicromolar and that PtdIns (3,4) P2 and PtdIns (4,5) P2 bound to Akt-1 with 3- and 6-fold lower affinities respectively. Interaction of Akt-1 with PtdIns (3,4,5) P3 did not activate the protein kinase activity, either before or after incubation with MgATP. A model is presented in which PtdIns (3,4,5) P3 may prime Akt-1 for activation by another protein kinase, perhaps by recruiting it to the plasma membrane.

PMID: 8978681
Mechanism of activation of protein kinase B by insulin and IGF-1.
... of activation of protein kinase B by insulin and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8978681

Mechanism of activation of protein kinase B by insulin and IGF-1.
Source

The EMBO journal (12/2/1996)

Abstract

Mechanism of activation of protein kinase B by insulin and IGF-1. Insulin activated endogenous protein kinase B alpha (also known as RAC/Akt kinase) activity 12-fold in L6 myotubes, while after transfection into 293 cells PKBalpha was activated 20- and 50-fold in response to insulin and IGF-1 respectively. In both cells, the activation of PKBalpha was accompanied by its phosphorylation at Thr308 and Ser473 and, like activation, phosphorylation of both of these residues was prevented by the phosphatidylinositol 3-kinase inhibitor wortmannin. Thr308 and/or Ser473 were mutated to Ala or Asp and activities of mutant PKBalpha molecules were analysed after transfection into 293 cells. The activity of wild-type and mutant PKBalpha was also measured in vitro after stoichiometric phosphorylation of Ser473 by MAPKAP kinase-2. These experiments demonstrated that activation of PKBalpha by insulin or insulin-like growth factor-1 (IGF-1) results from phosphorylation of both Thr308 and Ser473, that phosphorylation of both residues is critical to generate a high level of PKBalpha activity and that the phosphorylation of Thr308 in vivo is not dependent on phosphorylation of Ser473 or vice versa. We propose a model whereby PKBalpha becomes phosphorylated and activated in insulin/IGF-1-stimulated cells by an upstream kinase (s).

... that activation of PKBalpha by insulin or ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8978681

Mechanism of activation of protein kinase B by insulin and IGF-1.
Source

The EMBO journal (12/2/1996)

Abstract

Mechanism of activation of protein kinase B by insulin and IGF-1. Insulin activated endogenous protein kinase B alpha (also known as RAC/Akt kinase) activity 12-fold in L6 myotubes, while after transfection into 293 cells PKBalpha was activated 20- and 50-fold in response to insulin and IGF-1 respectively. In both cells, the activation of PKBalpha was accompanied by its phosphorylation at Thr308 and Ser473 and, like activation, phosphorylation of both of these residues was prevented by the phosphatidylinositol 3-kinase inhibitor wortmannin. Thr308 and/or Ser473 were mutated to Ala or Asp and activities of mutant PKBalpha molecules were analysed after transfection into 293 cells. The activity of wild-type and mutant PKBalpha was also measured in vitro after stoichiometric phosphorylation of Ser473 by MAPKAP kinase-2. These experiments demonstrated that activation of PKBalpha by insulin or insulin-like growth factor-1 (IGF-1) results from phosphorylation of both Thr308 and Ser473, that phosphorylation of both residues is critical to generate a high level of PKBalpha activity and that the phosphorylation of Thr308 in vivo is not dependent on phosphorylation of Ser473 or vice versa. We propose a model whereby PKBalpha becomes phosphorylated and activated in insulin/IGF-1-stimulated cells by an upstream kinase (s).

PMID: 9094314
Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha.
... that insulin or ... 1 induce the ... of PKB at ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 9094314

Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha.
Source

Current biology : CB (4/1/1997)

Abstract

Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha. BACKGROUND: Protein kinase B (PKB), also known as c-Akt, is activated rapidly when mammalian cells are stimulated with insulin and growth factors, and much of the current interest in this enzyme stems from the observation that it lies ` downstream' of phosphoinositide 3-kinase on intracellular signalling pathways. We recently showed that insulin or insulin-like growth factor 1 induce the phosphorylation of PKB at two residues, Thr308 and Ser473. The phosphorylation of both residues is required for maximal activation of PKB. The kinases that phosphorylate PKB are, however, unknown. RESULTS: We have purified 500 000-fold from rabbit skeletal muscle extracts a protein kinase which phosphorylates PKBalpha at Thr308 and increases its activity over 30-fold. We tested the kinase in the presence of several inositol phospholipids and found that only low micromolar concentrations of the D enantiomers of either phosphatidylinositol 3,4,5-triphosphate (PtdIns (3,4,5) P3) or PtdIns (3,4) P2 were effective in potently activating the kinase, which has been named PtdIns (3,4,5) P3-dependent protein kinase-1 (PDK1). None of the inositol phospholipids tested activated or inhibited PKBalpha or induced its phosphorylation under the conditions used. PDK1 activity was not affected by wortmannin, indicating that it is not likely to be a member of the phosphoinositide 3-kinase family. CONLCUSIONS: PDK1 is likely to be one of the protein kinases that mediate the activation of PKB by insulin and growth factors. PDK1 may, therefore, play a key role in mediating many of the actions of the second messenger (s) PtdIns (3,4, 5) P3 and/or PtdIns (3,4) P2.

... the activation of PKB by insulin and ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 9094314

Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha.
Source

Current biology : CB (4/1/1997)

Abstract

Characterization of a 3-phosphoinositide-dependent protein kinase which phosphorylates and activates protein kinase Balpha. BACKGROUND: Protein kinase B (PKB), also known as c-Akt, is activated rapidly when mammalian cells are stimulated with insulin and growth factors, and much of the current interest in this enzyme stems from the observation that it lies ` downstream' of phosphoinositide 3-kinase on intracellular signalling pathways. We recently showed that insulin or insulin-like growth factor 1 induce the phosphorylation of PKB at two residues, Thr308 and Ser473. The phosphorylation of both residues is required for maximal activation of PKB. The kinases that phosphorylate PKB are, however, unknown. RESULTS: We have purified 500 000-fold from rabbit skeletal muscle extracts a protein kinase which phosphorylates PKBalpha at Thr308 and increases its activity over 30-fold. We tested the kinase in the presence of several inositol phospholipids and found that only low micromolar concentrations of the D enantiomers of either phosphatidylinositol 3,4,5-triphosphate (PtdIns (3,4,5) P3) or PtdIns (3,4) P2 were effective in potently activating the kinase, which has been named PtdIns (3,4,5) P3-dependent protein kinase-1 (PDK1). None of the inositol phospholipids tested activated or inhibited PKBalpha or induced its phosphorylation under the conditions used. PDK1 activity was not affected by wortmannin, indicating that it is not likely to be a member of the phosphoinositide 3-kinase family. CONLCUSIONS: PDK1 is likely to be one of the protein kinases that mediate the activation of PKB by insulin and growth factors. PDK1 may, therefore, play a key role in mediating many of the actions of the second messenger (s) PtdIns (3,4, 5) P3 and/or PtdIns (3,4) P2.

PMID: 9449962
Cross-talk between phospholipase C and phosphoinositide 3-kinase signalling pathways.
The activation of PKB by insulin appears ...   (details)

AKT1 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 9449962

Cross-talk between phospholipase C and phosphoinositide 3-kinase signalling pathways.
Source

Biochemical Society transactions (November 1997)

Abstract

Cross-talk between phospholipase C and phosphoinositide 3-kinase signalling pathways. 1321N1 astrocytoma cells have proved a valuable model system in which to study interactions between two major PtdIns (4,5) P2-utilizing signaling pathways, since they possess receptor populations which elicit independent activation of PI 3-kinase and a G-protein-dependent PLC respectively. Activation of PLC down-regulates PI 3-kinase by at least two mechanisms involving inhibition of IRS-1-associated PI 3-kinase and acute activation of a PtdIns (3,4,5) P3 5-phosphatase. PKB, which is an important early PI 3-kinase-dependent component of insulin signalling pathways, is also down-regulated by PLC-coupled agonists. The activation of PKB by insulin appears to involve a novel PtdIns (3,4,5) P3-dependent protein kinase, which we have named PDK1. The molecular mechanisms underlying PtdIns (3,4,5) P3-stimulated phosphorylation and activation of PKB by PDK1 are currently under investigation.