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ANXA6 INS (1 - 14 of 14)
PMID: 10100627
Role of ERK1/ERK2 and p70S6K pathway in insulin signalling of protein synthesis.
Role of ... and p70S6K pathway in insulin signalling ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 10100627

Role of ERK1/ERK2 and p70S6K pathway in insulin signalling of protein synthesis.
Source

FEBS letters (3/5/1999)

Abstract

Role of ERK1/ERK2 and p70S6K pathway in insulin signalling of protein synthesis. The signalling pathways by which insulin triggers protein synthesis were studied using an antisense strategy to deplete ERK1/ERK2 and rapamycin to inhibit the p70S6K pathway. The results indicated that ERK1/ERK2 principally regulated the amount of the protein synthesis machinery available in the cell while the p70S6K pathway contributed to modulating its activation in response to insulin. ERK1/ERK2 also mediated in a small proportion of insulin-stimulated protein synthesis which included the induction of c-fos protein. When c-fos induction was blocked the majority of insulin-stimulated protein synthesis still occurred and thus did not require transcriptional regulation of c-fos or its targets.

PMID: 11404220
Zinc stimulates the activity of the insulin- and nutrient-regulated protein kinase mTOR.
... and insulin activations of p70 ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 11404220

Zinc stimulates the activity of the insulin- and nutrient-regulated protein kinase mTOR.
Source

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

Abstract

Zinc stimulates the activity of the insulin- and nutrient-regulated protein kinase mTOR. Recent studies indicate that zinc activates p70 S6 kinase (p70 (S6k)) by a mechanism involving phosphatidylinositol 3-kinase (PI 3-kinase) and Akt (protein kinase B). Here it is shown that phenanthroline, a zinc and heavy metal chelator, inhibited both amino acid- and insulin-stimulated phosphorylation of p70 (S6k). Both amino acid and insulin activations of p70 (S6k) involve a rapamycin-sensitive step that involves the mammalian target of rapamycin (mTOR, also known as FRAP and RAFT). However, in contrast to insulin, amino acids activate p70 (S6k) by an unknown PI 3-kinase- and Akt-independent mechanism. Thus the effects of chelator on amino acid activation of p70 (S6k) were surprising. For this reason, we tested the hypothesis that zinc directly regulates mTOR activity, independently of PI 3-kinase activation. In support of this, basal and amino acid stimulation of p70 (S6k) phosphorylation was increased by zinc addition to the incubation media. Furthermore, the protein kinase activities of mTOR immunoprecipitated from rat brain lysates were stimulated two- to fivefold by 10-300 microM Zn2+ in the presence of an excess of either Mn2+ or Mg2+, whereas incubation with 1,10-phenanthroline had no effect. These findings indicate that Zn2+ regulates, but is not absolutely required for, mTOR protein kinase activity. Zinc also stimulated a recombinant human form of mTOR. The stimulatory effects of Zn2+ were maximal at approximately 100 microM but decreased and became inhibitory at higher physiologically irrelevant concentrations. Micromolar concentrations of other divalent cations, Ca2+, Fe2+, and Mn2+, had no effect on the protein kinase activity of mTOR in the presence of excess Mg2+. Our results and the results of others suggest that zinc acts at multiple steps in amino acid- and insulin cell-signaling pathways, including mTOR, and that the additive effects of Zn2+ on these steps may thereby promote insulin and nutritional signaling.

PMID: 12014987
The Src-family tyrosine kinase inhibitor PP1 interferes with the activation of ribosomal protein S6 kinases.
... the activation of ... p70S6K1 and ... by insulin, ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 12014987

The Src-family tyrosine kinase inhibitor PP1 interferes with the activation of ribosomal protein S6 kinases.
Source

The Biochemical journal (8/15/2002)

Abstract

The Src-family tyrosine kinase inhibitor PP1 interferes with the activation of ribosomal protein S6 kinases. Considerable biochemical and pharmacological evidence suggests that the activation of ribosomal protein S6 kinases (S6Ks) by activated receptor tyrosine kinases involves multiple co-ordinated input signals. However, the identities of many of these inputs remain poorly described, and their precise involvement in S6K activation has been the subject of great investigative effort. In the present study, we have shown that 4-amino-5- (4-methylphenyl) -7- (t-butyl) pyrazolo [3,4-d] pyrimidine (PP1), a selective inhibitor of the Src family of non-receptor tyrosine kinases, interferes with the activation of 70 and 85 kDa S6K gene products (p70S6K1 and p85S6K1) by insulin, insulin-like growth factor 1, sodium orthovanadate and activated alleles of phosphoinositide 3-kinase and H-Ras. PP1 also impedes the activation of AKT/protein kinase B and the extracellular signal-regulated protein kinases 1 and 2 by these various stimuli. Insulin-like growth factor 1 was observed to induce a sustained increase in c-Src autophosphorylation as revealed using anti-phospho-Y416 antisera, but this effect was absent from the cells treated with PP1. To conclude, an activated allele of p70S6K1 is compared with the wild-type allele, resistant to inhibition by PP1 when co-expressed with phosphoinositide-dependent kinase 1 (PDK1), suggesting that PP1 affects p70S6K1 via a PDK1-independent pathway. Thus activation of Src may supply a necessary signal for the activation of p70S6K1 and possibly other S6Ks.

PMID: 16272686
Insulin signaling in adipocytes differentiated from mouse stromal MC3T3-G2/PA6 cells.
... insulin induced the ... ribosomal p70 S6 protein kinase (p70 S6K) at ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 16272686

Insulin signaling in adipocytes differentiated from mouse stromal MC3T3-G2/PA6 cells.
Source

Biological & pharmaceutical bulletin (November 2005)

Abstract

Insulin signaling in adipocytes differentiated from mouse stromal MC3T3-G2/PA6 cells. The stromal MC3T3-G2/PA6 (PA6) cells from mouse clavaria did not require insulin for differentiation into mature adipose cells, although insulin is well known to play a key role in adipocyte differentiation. Large lipid droplets were observed in the cytoplasm of PA6 cells, and mRNA expression of the adipose specific proteins (aP2, PPARgamma, C/EBPalpha, FAS, GLUT4, leptin, and adiponectin) as differentiation markers appeared or increased clearly in the cells at 8 d after stimulation without insulin. In addition, the glycerol released from the cells (lipolysis) was increased in a concentration-dependent manner by isoproterenol. However, the isoproterenol-induced lipolysis in the cells was not influenced by treatment with insulin, although that was observed in extramedullary adipocytes, 3T3-L1 cells. On the other hand, the 2-deoxy-D- [1-3H] glucose uptake in differentiated PA6 cells also increased by insulin, as shown in other adipose cells. In the cells, insulin induced the phosphorylation of extracellular signal-regulated kinases (Erks), Akt at Ser 473 and ribosomal p70 S6 protein kinase (p70 S6K) at Thr 389, and the insulin-induced 2-deoxy-D- [1-3H] glucose uptake was inhibited by pre-treatment with wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), or ML-9, an Akt inhibitor. These results suggest that the insulin signal for adipogenesis (lipogenesis) and lipolysis in bone marrow stroma PA6 cells differs from extramedullary adipocytes, such as 3T3-L1 cells.

PMID: 16293713
Identification of the insulin signaling cascade in the regulation of alpha-class glutathione S-transferase expression in primary cultured rat hepatocytes.
... that PI3K/Akt/p70S6K signaling ... low insulin levels ... potentially increase the ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 16293713

Identification of the insulin signaling cascade in the regulation of alpha-class glutathione S-transferase expression in primary cultured rat hepatocytes.
Source

The Journal of pharmacology and experimental therapeutics (March 2006)

Abstract

Identification of the insulin signaling cascade in the regulation of alpha-class glutathione S-transferase expression in primary cultured rat hepatocytes. We reported previously that insulin elevated alpha-class glutathione S-transferase (GSTs) protein levels in primary cultured rat hepatocytes (Kim et al., 2003b). In contrast, glucagon down-regulated alpha- and pi-class GST expression, and mechanistic research implicated cAMP and protein kinase A in this process (Kim et al., 2003b). The present study examines the signaling pathways involved in the regulation of alpha-class GST in response to insulin in primary cultured rat hepatocytes. Protein levels of GSTA1/2 and GSTA3/5 and activity of GST toward 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD) were increased in an insulin concentration-dependent manner. Treatment of cells with the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002 [2- (4-morpholinyl) -8-phenyl-4H-1-benzopyran-4-one] or rapamycin, an inhibitor of mammalian target of rapamycin and ribosomal p70 S6 kinase (p70S6K) phosphorylation, or with an adenovirus containing green fluorescent protein and a dominant-negative and kinase-dead Akt, effectively inhibited the insulin-mediated increase in alpha-class GST expression and GST activity toward NBD. In contrast, PD98059 (2'-amino-3'-methoxyflavone), an inhibitor of mitogen-activated protein kinase kinase, SP600125 (1,9-pyrazoloanthrone), an inhibitor of c-Jun N-terminal kinase, SB203580 [4- (4-fluorophenyl) -2- (4-methylsulfinylphenyl) -5- (4-pyridyl) 1H-imadazole], an inhibitor of p38 mitogen-activated protein kinase, or bisindolylmaleimide, a broad spectrum inhibitor of protein kinase C, did not inhibit the insulin-mediated increase in alpha-class GST protein levels in hepatocytes. These results show that PI3K/Akt/p70S6K signaling is active in the insulin-mediated up-regulation of the antioxidant defense system and that low insulin levels, as encountered in diabetes, potentially increase the susceptibility of hepatocytes to xenobiotic-mediated and/or oxidative stress-mediated damage.

PMID: 16774940
Reactive oxygen species regulate insulin-induced VEGF and HIF-1alpha expression through the activation of p70S6K1 in human prostate cancer cells.
... that insulin induced H2O2 ... and p70S6K1 activation ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 16774940

Reactive oxygen species regulate insulin-induced VEGF and HIF-1alpha expression through the activation of p70S6K1 in human prostate cancer cells.
Source

Carcinogenesis (January 2007)

Abstract

Reactive oxygen species regulate insulin-induced VEGF and HIF-1alpha expression through the activation of p70S6K1 in human prostate cancer cells. Vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1 (HIF-1) are important regulators of angiogenesis. HIF-1 is composed of HIF-1alpha and HIF-1beta subunits, and regulates VEGF expression at transcriptional level. In this study, we demonstrated that insulin induced H2O2 production and p70S6K1 activation in PC-3 prostate cancer cells. The inhibition of H2O2 production by catalase abolished insulin-induced p70S6K1 activation. H2O2 production is also required for insulin-induced VEGF and HIF-1alpha expression in the cells. Over-expression of p70S6K1 or HIF-1alpha reversed catalase- and rapamycin-inhibited VEGF transcriptional activation. These results suggest that insulin induced HIF-1alpha and VEGF expression through H2O2 production and p70S6K1 activation in prostate cancer cells. In addition, we found that inhibition of p70S6K1 by rapamycin decreased prostate tumor angiogenesis, suggesting that p70S6K1 plays an important role in tumor angiogenesis. These results provide some useful information for prostate cancer therapy in the future.

PMID: 16984645
EGF-induced activation of Akt results in mTOR-dependent p70S6 kinase phosphorylation and inhibition of HC11 cell lactogenic differentiation.
The activation of p70S6K by insulin or ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 16984645

EGF-induced activation of Akt results in mTOR-dependent p70S6 kinase phosphorylation and inhibition of HC11 cell lactogenic differentiation.
Source

BMC cell biology (2006)

Abstract

EGF-induced activation of Akt results in mTOR-dependent p70S6 kinase phosphorylation and inhibition of HC11 cell lactogenic differentiation. [BACKGROUND] HC11 mouse mammary epithelial cells differentiate in response to lactogenic hormone resulting in expression of milk proteins including beta-casein. Previous studies have shown that epidermal growth factor (EGF) blocks differentiation not only through activation of the Ras/Mek/Erk pathway but also implicated phosphatidylinositol-3-kinase (PI-3-kinase) signaling. The current study analyzes the mechanism of the PI-3-kinase pathway in an EGF-induced block of HC11 lactogenic differentiation. [RESULTS] HC11 and HC11-luci cells, which contain luciferase gene under the control of a beta-casein promotor, were treated with specific chemical inhibitors of signal transduction pathways or transiently infected/transfected with vectors encoding dominant negative-Akt (DN-Akt) or conditionally active-Akt (CA-Akt). The expression of CA-Akt inhibited lactogenic differentiation of HC11 cells, and the infection with DN-Akt adenovirus enhanced beta-casein transcription and rescued beta-casein promotor-regulated luciferase activity in the presence of EGF. Treatment of cells with Rapamycin, an inhibitor of mTOR, blocked the effects of EGF on beta-casein promotor driven luciferase activity as effectively as PI-3-kinase inhibitors. While expression of CA-Akt caused a constitutive activation of p70S6 kinase (p70S6K) in HC11 cells, the inhibition of either PI-3-kinase or mTOR abolished the activation of p70S6K by EGF. The activation of p70S6K by insulin or EGF resulted in the phosphorylation of ribosomal protein S6 (RPS6), elongation initiation factor 4E (elF4E) and 4E binding protein1 (4E-BP1). But lower levels of PI-3-K and mTOR inhibitors were required to block insulin-induced phosphorylation of RPS6 than EGF-induced phosphorylation, and insulin-induced phosphorylation of elF4E and 4E-BP1 was not completely mTOR dependent suggesting some diversity of signaling for EGF and insulin. In HC11 cells undergoing lactogenic differentiation the phosphorylation of p70S6K completely diminished by 12 hours, and this was partly attributable to dexamethasone, a component of lactogenic hormone mix. However, p70S6K phosphorylation persisted in the presence of lactogenic hormone and EGF, but the activation could be blocked by a PI-3-kinase inhibitor. [CONCLUSION] PI-3-kinase signaling contributes to the EGF block of lactogenic differentiation via Akt and p70S6K. The EGF-induced activation of PI-3-kinase-Akt-mTOR regulates phosphorylation of molecules including ribosomal protein S6, eIF4E and 4E-BP1 that influence translational control in HC11 cells undergoing lactogenic differentiation.

PMID: 1782669
A cell cycle ts mutant, tsJT16, is defective in p70 synthesis through protein kinase C-dependent and -independent pathways.
... and insulin did not induce p70.   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 1782669

A cell cycle ts mutant, tsJT16, is defective in p70 synthesis through protein kinase C-dependent and -independent pathways.
Source

Cell structure and function (August 1991)

Abstract

A cell cycle ts mutant, tsJT16, is defective in p70 synthesis through protein kinase C-dependent and -independent pathways. tsJT16 is a G0/G1 ts mutant from the Fischer rat fibroblast line. It has a ts defect in a function operating early after growth stimulation with fetal bovine serum (FBS). A primarily induced gene product, p70, was not synthesized at 40 degrees C after stimulation with serum, while c-fos and c-myc mRNAs accumulated under the same condition. This paper reports that p70 was synthesized following stimulation of G0-arrested cells with platelet-derived growth factor, epidermal growth factor (EGF), and 12-0-tetradecanoylphorbol-13-acetate (TPA) at 34 degrees C, but not at 40 degrees C. However, it was synthesized at both temperatures after addition of A23187. In protein kinase C-deprived cells, peptide growth factors and A23187 induced p70 at 34 degrees C, whereas TPA did not. Fibroblast growth factor and insulin did not induce p70. Induction of c-fos and c-myc occurred at both temperatures after the stimulation with FBS, TPA or A23187. These results indicated that the defect in tsJT16 to induce p70 is likely to be located at the common downstream of protein kinase C-dependent and -independent pathways, but is independent from the pathway of calcium mobilization.

PMID: 20936651
Comparison of intracellular signalling by insulin and the hypermitogenic AspB10 analogue in MCF-7 breast adenocarcinoma cells.
... insulin induced phosphorylation... p70S6K, ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 20936651

Comparison of intracellular signalling by insulin and the hypermitogenic AspB10 analogue in MCF-7 breast adenocarcinoma cells.
Source

Journal of applied toxicology : JAT (May 2011)

Abstract

Comparison of intracellular signalling by insulin and the hypermitogenic AspB10 analogue in MCF-7 breast adenocarcinoma cells. We compared mitogenicity and intracellular signalling by human insulin and the AspB10 (X-10) human insulin analogue in MCF-7 human mammary adenocarcinoma cells. By flow analysis of phosphorylated histone H3 or cell cycle distributions, insulin and X-10 were mitogenic at physiologically relevant concentrations (2 nm to 74 pm range), with X-10 being approximately 3-fold more mitogenic than insulin. By western blotting with phospho-specific antibodies, insulin induced phosphorylation of IRS-1, Akt, p70S6K, S6 ribosomal protein, 4E-BP1, FoxO3a, FoxO1, p44/42 MAPK and the EGFR. Blocking with wortmannin, rapamycin and U0126 showed that these signalling events conformed to the canonical PI3K pathway. IRS-1 (Ser302) phosphorylation was abolished by wortmannin and rapamycin, suggesting a feedback from the PI3K pathway on insulin signalling. Compared with equimolar insulin, X-10 caused up to 2-fold higher phosphorylation of all proteins examined in this study. The phosphorylation sites that responded most strongly to insulin were not generally the same as those responding most strongly to X-10. In the PI3K pathway, the most X-10-sensitive protein localized to the translation-regulating arm (p70S6K), with FoxO3a and FoxO1 transcription factors showing a more comparable response to insulin and X-10. Using flow analysis, we confirmed the correlation between insulin-triggered translational activation in G0/G1 (S6 phosphorylation) and S-phase entry by MCF-7 cells. In summary, our findings implicate asymmetrical PI3K pathway activation and specifically stimulation of protein translation in the hypermitogenic effect of insulin analogues such as X-10. It remains to be shown whether these findings are relevant to other human mammary cancer cell types.

PMID: 8063749
Activation of ribosomal protein S6 kinases does not increase glycogen synthesis or glucose transport in rat adipocytes.
... blocked activation of p70S6K by insulin, ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8063749

Activation of ribosomal protein S6 kinases does not increase glycogen synthesis or glucose transport in rat adipocytes.
Source

The Journal of biological chemistry (8/19/1994)

Abstract

Activation of ribosomal protein S6 kinases does not increase glycogen synthesis or glucose transport in rat adipocytes. Rat adipocytes were incubated with insulin or epidermal growth factor (EGF) before the mitogen-activated protein (MAP) kinases, ERK-1 and ERK-2, and the ribosomal protein S6 kinases, Rsk-2 and p70S6K, were resolved by ion exchange chromatography and identified by immunoblotting. EGF was more effective than insulin in increasing the activity of two kinases that reacted with Rsk-2 antibody (2- and 2.5-fold with EGF versus 1.6- and 1.2-fold with insulin). EGF was also more effective than insulin in increasing the activity of ERK-1 (5-fold versus 2-fold) and ERK-2 (2.5-fold versus 1.5 fold). The activity of p70S6K was increased by approximately the same extent by EGF and insulin (1.7-fold versus 2-fold). Rapamycin blocked activation of p70S6K by insulin, but it did not attenuate the effect (2-fold) of insulin on increasing the glycogen synthase activity ratio (+/-glucose-6-P). Insulin increased glucose incorporation into glycogen and 2-deoxyglucose uptake by approximately 5-fold, whereas EGF and phorbol 12-myristate were without effect. Thus, activation of MAP kinases and ribosomal protein S6 kinases appears insufficient to activate glycogen synthase or glucose transport, the two key components in the stimulation of glycogen synthesis by insulin.

PMID: 8524413
Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B.
... the activation of ... and p70S6k by insulin in ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8524413

Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B.
Source

Nature (0)

Abstract

Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B. Glycogen synthase kinase-3 (GSK3) is implicated in the regulation of several physiological processes, including the control of glycogen and protein synthesis by insulin, modulation of the transcription factors AP-1 and CREB, the specification of cell fate in Drosophila and dorsoventral patterning in Xenopus embryos. GSK3 is inhibited by serine phosphorylation in response to insulin or growth factors and in vitro by either MAP kinase-activated protein (MAPKAP) kinase-1 (also known as p90rsk) or p70 ribosomal S6 kinase (p70S6k). Here we show, however, that agents which prevent the activation of both MAPKAP kinase-1 and p70S6k by insulin in vivo do not block the phosphorylation and inhibition of GSK3. Another insulin-stimulated protein kinase inactivates GSK3 under these conditions, and we demonstrate that it is the product of the proto-oncogene protein kinase B (PKB, also known as Akt/RAC). Like the inhibition of GSK3 (refs 10, 14), the activation of PKB is prevented by inhibitors of phosphatidylinositol (PI) 3-kinase.

PMID: 8633019
4E-BP1 phosphorylation is mediated by the FRAP-p70s6k pathway and is independent of mitogen-activated protein kinase.
... insulin,... induces 4E-BP1 ... and p70s6k activation ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 8633019

4E-BP1 phosphorylation is mediated by the FRAP-p70s6k pathway and is independent of mitogen-activated protein kinase.
Source

Proceedings of the National Academy of Sciences of the United States of America (4/30/1996)

Abstract

4E-BP1 phosphorylation is mediated by the FRAP-p70s6k pathway and is independent of mitogen-activated protein kinase. It has previously been argued that the repressor of protein synthesis initiation factor 4E, 4E-BP1, is a direct in vivo target of p42mapk. However, the immunosuppressant rapamycin blocks serum-induced 4E-BP1 phosphorylation and, in parallel, p70s6k activation, with no apparent effect on p42mapk activation. Consistent with this finding, the kinetics of serum-induced 4E-BP1 phosphorylation closely follow those of p70s6k activation rather than those of p42mapk. More striking, insulin, which does not induce p42mapk activation in human 293 cells or Swiss mouse 3T3 cells, induces 4E-BP1 phosphorylation and p70s6k activation in both cell types. Anisomycin, which, like insulin, does not activate p42mapk, promotes a small parallel increase in 4E-BP1 phosphorylation and p70s6k activation. The insulin effect on 4E-BP1 phosphorylation and p70s6k activation in both cell types is blocked by SQ20006, wortmannin, and rapamycin. These three inhibitors have no effect on p42mapk activation induced by phorbol 12-tetradecanoate 13-acetate, though wortmannin partially suppresses both the p70s6k response and the 4E-BP1 response. Finally, in porcine aortic endothelial cells stably transfected with either the wild-type platelet-derived growth factor receptor or a mutant receptor bearing the double point mutation 740F/751F, p42mapk activation in response to platelet-derived growth factor is unimpaired, but increased 4E-BP1 phosphorylation is ablated, as previously reported for p70s6k. The data presented here demonstrate that 4E-BP1 phosphorylation is mediated by the FRAP-p70s6k pathway and is independent of mitogen-activated protein kinase.

PMID: 9632736
Regulation of the p70 S6 kinase by phosphorylation in vivo. Analysis using site-specific anti-phosphopeptide antibodies.
Activation of p70 by insulin was ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 9632736

Regulation of the p70 S6 kinase by phosphorylation in vivo. Analysis using site-specific anti-phosphopeptide antibodies.
Source

The Journal of biological chemistry (6/26/1998)

Abstract

Regulation of the p70 S6 kinase by phosphorylation in vivo. Analysis using site-specific anti-phosphopeptide antibodies. The p70 S6 kinase is activated by diverse stimuli through a multisite phosphorylation directed at three separate domains as follows: a cluster of (Ser/Thr) Pro sites in an autoinhibitory segment in the noncatalytic carboxyl-terminal tail; Thr-252 in the activation loop of the catalytic domain; and Ser-394 and Thr-412 in a segment immediately carboxyl-terminal to the catalytic domain. Phosphorylation of Thr-252 in vitro by the enzyme phosphatidylinositol 3-phosphate-dependent kinase-1 or mutation of Thr-412 -- > Glu has each been shown previously to engender some activation of the p70 S6 kinase, whereas both modifications together produce 20-30-fold more activity than either alone. We employed phospho-specific anti-peptide antibodies to examine the relative phosphorylation at several of these sites in wild type and various p70 mutants, in serum-deprived cells, and in response to activators and inhibitors of p70 S6 kinase activity. Substantial phosphorylation of p70 Thr-252 and Ser-434 was present in serum-deprived cells, whereas Thr-412 and Thr-444/Ser-447 were essentially devoid of phospho-specific immunoreactivity. Activation of p70 by insulin was accompanied by a coordinate increase in phosphorylation at all sites examined, together with a slowing in mobility on SDS-PAGE of a portion of p70 polypeptides. Upon addition of rapamycin or wortmannin to insulin-treated cells, the decrease in activity of p70 was closely correlated with the disappearance of anti-Thr-412 (P) immunoreactivity and the most slowly migrating p70 polypeptides, whereas considerable phosphorylation at Ser-434 and Thr-252 persisted after the disappearance of 40 S kinase activity. The central role of Thr-412 phosphorylation in the regulation of kinase activity was further demonstrated by the close correlation of the effects of various deletions and point mutations on p70 activity and Thr-412 phosphorylation. In conclusion, although p70 activity depends on a disinhibition from the carboxyl-terminal tail and the simultaneous phosphorylation at both Thr-252 and Thr-412, p70 activity in vivo is most closely related to the state of phosphorylation at Thr-412.

PMID: 9737973
Platelet-derived growth factor inhibits insulin stimulation of insulin receptor substrate-1-associated phosphatidylinositol 3-kinase in 3T3-L1 adipocytes without affecting glucose transport.
... insulin activation of ... and p70 ...   (details)

ANXA6 INS

Type:  positive regulation
Is this interaction correct?
Yes
No

Comments

PMID: 9737973

Platelet-derived growth factor inhibits insulin stimulation of insulin receptor substrate-1-associated phosphatidylinositol 3-kinase in 3T3-L1 adipocytes without affecting glucose transport.
Source

The Journal of biological chemistry (9/25/1998)

Abstract

Platelet-derived growth factor inhibits insulin stimulation of insulin receptor substrate-1-associated phosphatidylinositol 3-kinase in 3T3-L1 adipocytes without affecting glucose transport. Phosphatidylinositol 3-kinase (PI3K) activation is necessary for insulin-responsive glucose transporter (GLUT4) translocation and glucose transport. Insulin and platelet-derived growth factor (PDGF) stimulate PI3K activity in 3T3-L1 adipocytes, but only insulin is capable of stimulating GLUT4 translocation and glucose transport. We found that PDGF causes serine/threonine phosphorylation of insulin receptor substrate 1 (IRS-1) in 3T3-L1 cells, measured by altered mobility on SDS-polyacrylamide gel, and this leads to a decrease in insulin-stimulated tyrosine phosphorylation of IRS-1. The PI3K inhibitors wortmannin and LY294002 inhibit the PDGF-induced phosphorylation of IRS-1, whereas the MEK inhibitor PD98059 was without a major effect. PDGF pretreatment for 60-90 min led to a marked 80-90% reduction in insulin stimulatable phosphotyrosine and IRS-1-associated PI3K activity. We examined the functional consequences of this decrease in IRS-1-associated PI3K activity. Interestingly, insulin stimulation of GLUT4 translocation and glucose transport was unaffected by 60-90 min of PDGF preincubation. Furthermore, insulin activation of Akt and p70 (s6kinase), kinases downstream of PI3K, was unaffected by PDGF pretreatment. Wortmannin was capable of blocking these insulin actions following PDGF pretreatment, suggesting that PI3K was still necessary for these effects. In conclusion, 1) PDGF causes serine/threonine phosphorylation of IRS-1, and PI3K, or a kinase downstream of PI3K, mediates this phosphorylation. 2) This PDGF-induced phosphorylation of IRS-1 leads to a significant decrease in insulin-stimulated PI3K activity. 3) PDGF has no effect on insulin stimulation of Akt, p70 (s6kinase), GLUT4 translocation, or glucose transport. 4) This suggests the existence of an IRS-1-independent pathway leading to the activation of PI3K, Akt, and p70 (s6kinase); GLUT4 translocation; and glucose transport.