scholarly journals The inhibition of glycogen synthase kinase-3 by insulin or insulin-like growth factor 1 in the rat skeletal muscle cell line L6 is blocked by wortmannin, but not by rapamycin: evidence that wortmannin blocks activation of the mitogen-activated protein kinase pathway in L6 cells between Ras and Raf

1994 ◽  
Vol 303 (1) ◽  
pp. 21-26 ◽  
Author(s):  
D A E Cross ◽  
D R Alessi ◽  
J R Vandenheede ◽  
H E McDowell ◽  
H S Hundal ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Map Kinase ◽  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase 3 ◽  
Rat Skeletal Muscle ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Skeletal Muscle Cell Line ◽  
Stimulation Of

Glycogen synthase kinase-3 (GSK3) is inactivated in vitro by p70 S6 kinase or MAP kinase-activated protein kinase-1 beta (MAPKAP kinase-1 beta; also known as Rsk-2). Here we show that GSK3 isoforms are inhibited by 40% within minutes after stimulation of the rat skeletal-muscle cell line L6 with insulin-like growth factor-1 (IGF-1) or insulin. GSK3 was similarly inhibited in rabbit skeletal muscle after an intravenous injection of insulin. Inhibition resulted from increased phosphorylation of GSK3, probably at a serine/threonine residue(s), because it was reversed by incubation with protein phosphatase-2A. Rapamycin blocked the activation of p70 S6 kinase by IGF-1 in L6 cells, but had no effect on the inhibition of GSK3 or the activation of MAPKAP kinase-1 beta. In contrast, wortmannin, a potent inhibitor of PtdIns 3-kinase, prevented the inactivation of GSK3 and the activation of MAPKAP kinase-1 beta and p70 S6 kinase by IGF-1 or insulin. Wortmannin also blocked the activation of p74raf-1. MAP kinase kinase and p42 MAP kinase, but not the formation of GTP-Ras by IGF-1. The results suggest that the stimulation of glycogen synthase by insulin/IGF-1 in skeletal muscle involves the MAP-KAP kinase-1-catalysed inhibition of GSK3, as well as the previously described activation of the glycogen-associated form of protein phosphatase-1.

Differential regulation of MAP kinase, p70S6K, and Akt by contraction and insulin in rat skeletal muscle

1999 ◽  
Vol 276 (5) ◽  
pp. E870-E878 ◽  
Author(s):  
Daniel J. Sherwood ◽  
Scott D. Dufresne ◽  
Jeffrey F. Markuns ◽  
Bentley Cheatham ◽  
David E. Moller ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Map Kinase ◽  
Contractile Activity ◽  
Kinase Signaling ◽  
Rat Skeletal Muscle ◽  
S6 Kinase ◽  
Map Kinase Signaling ◽  
Map Kinase Pathway ◽  
Kinase Pathway ◽  
Stimulation Of

To study the effects of contractile activity on mitogen-activated protein kinase (MAP kinase), p70 S6 kinase (p70S6K), and Akt kinase signaling in rat skeletal muscle, hindlimb muscles were contracted by electrical stimulation of the sciatic nerve for periods of 15 s to 60 min. Contraction resulted in a rapid and transient activation of Raf-1 and MAP kinase kinase 1, a rapid and more sustained activation of MAP kinase and the 90-kDa ribosomal S6 kinase 2, and a dramatic increase in c- fos mRNA expression. Contraction also resulted in an apparent increase in the association of Raf-1 with p21Ras, although stimulation of MAP kinase signaling occurred independent of Shc, IRS1, and IRS2 tyrosine phosphorylation or the formation of Shc/Grb2 or IRS1/Grb2 complexes. Insulin was considerably less effective than contraction in stimulating the MAP kinase pathway. However, insulin, but not contraction, increased p70S6K and Akt activities in the muscle. These results demonstrate that contraction-induced activation of the MAP kinase pathway is independent of proximal steps in insulin and/or growth factor-mediated signaling, and that contraction and insulin have discordant effects with respect to the activation of the MAP kinase pathway vs. p70S6K and Akt. Of the numerous stimulators of MAP kinase in skeletal muscle, contractile activity emerges as a potent and physiologically relevant activator of MAP kinase signaling, and thus activation of this pathway is likely to be an important molecular mechanism by which skeletal muscle cells transduce mechanical and/or biochemical signals into downstream biological responses.

scholarly journals Wortmannin inhibits the effects of insulin and serum on the activities of glycogen synthase kinase-3 and mitogen-activated protein kinase

1994 ◽  
Vol 303 (1) ◽  
pp. 15-20 ◽  
Author(s):  
G I Welsh ◽  
E J Foulstone ◽  
S W Young ◽  
J M Tavaré ◽  
C G Proud
Keyword(s):  
Map Kinase ◽  
Phorbol Ester ◽  
Glycogen Synthase ◽  
Chinese Hamster Ovary Cells ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Parental Cell Line ◽  
S6 Kinase ◽  
Mitogen Activated Protein ◽  
Kinase Pathway

We have previously shown that insulin causes inactivation of glycogen synthase kinase-3 (GSK-3) in Chinese hamster ovary cells over-expressing the human insulin receptor (CHO.T cells). We now show that serum and phorbol ester also cause rapid inactivation of GSK-3, both in CHO.T cells and in the nontransfected parental cell line, CHO.K1 cells. Rapamycin was without effect on the inactivation of GSK-3 by insulin, serum or phorbol ester, indicating that the p70 S6 kinase pathway is not involved. In contrast, wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, blocked the effects of both insulin and serum on GSK-3 activity, and also substantially reduced the activation of both p90 S6 kinase (by insulin) and mitogen-activated protein (MAP) kinase (by insulin and serum). These findings imply (i) that GSK-3 activity is regulated by a cascade involving MAP kinase and p90 S6 kinase and (ii) that wortmannin affects an early step in the MAP kinase pathway. One can infer from this that GSK-3 may be an important regulatory enzyme for the control of several biosynthetic pathways, key enzymes in which are regulated by GSK-3-mediated phosphorylation. Wortmannin had a smaller effect on the activation of MAP kinase by phorbol ester, indicating that phorbol esters may stimulate MAP kinase by a different or additional mechanism to that employed by insulin or serum. Wortmannin had very little effect on the inactivation of GSK-3 by phorbol ester: possible reasons for this are discussed.

scholarly journals Increase in Subcellular GSK-3 Clusters in Insulin- and Adrenaline-treated Differentiated Rat Skeletal Muscle Fibres

2020 ◽  
Author(s):  
Katja Fink ◽  
Mateja Lobe Prebil ◽  
Nina Vardjan ◽  
Jorgen Jensen ◽  
Robert Zorec ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Metabolic Regulation ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase 3 ◽  
Muscle Fibres ◽  
Optical Section ◽  
Rat Skeletal Muscle ◽  
Average Size ◽  
Skeletal Muscle Fibres

Glycogen synthase kinase 3 (GSK-3) plays an important role in metabolic regulation in skeletal muscles, and both insulin and adrenaline stimulate   GKS-3 phosphorylation. The aim of the present study was to study the effect of insulin and adrenaline on GSK-3 localisation in skeletal muscles.We characterized subcellular localization of (GSK-3) signal protein in fully differentiated muscle fibre by immunofluorescence and confocal microscopy. We stimulated muscle fibres with insulin and/or adrenaline. Images were analysed by segmentation of single central optical section of the muscle.We found GSK-3 to be localised in clusters. The number of GSK-3 clusters and their average size were increased after stimulation with insulin and/or adrenaline. Average GSK-3 particle size is linearly related to their quantity.We conclude that subcellular GSK-3 in isolated skeletal muscle fibres is localized in clusters and clustering increased after stimulation with insulin and/or adrenaline.

scholarly journals The mechanism by which epidermal growth factor inhibits glycogen synthase kinase 3 in A431 cells

1994 ◽  
Vol 303 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Y Saito ◽  
J R Vandenheede ◽  
P Cohen
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
A431 Cells ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Epidermal Growth

Glycogen synthase kinase 3 (GSK3) was inhibited by 50% within 5 min when A431 cells were stimulated with epidermal growth factor (EGF). The inhibition was unaffected by rapamycin at concentrations which blocked the activation of p70 S6 kinase, and reversed by incubation with protein phosphatase-1. EGF stimulation of A431 cells inhibited GSK3 alpha and GSK3 beta to a similar extent, and inhibition was accompanied by phosphorylation of the tryptic peptides containing the serine residues phosphorylated in vitro by p70 S6 kinase or MAP kinase-activated protein (MAPKAP) kinase-1 beta (also termed Rsk-2). These results demonstrate that EGF inhibits GSK3 by inducing phosphorylation of a serine residue and that GSK3 is not phosphorylated in vivo by either p70 S6 kinase or protein kinase C.

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

1999 ◽  
Vol 277 (2) ◽  
pp. E299-E307 ◽  
Author(s):  
Sanjay Bhanot ◽  
Baljinder S. Salh ◽  
Subodh Verma ◽  
John H. McNeill ◽  
Steven L. Pelech
Keyword(s):  
Skeletal Muscle ◽  
Glycogen Synthase ◽  
Insulin Injection ◽  
Glycogen Synthase Kinase 3 ◽  
Phosphatidylinositol 3 Kinase ◽  
S6 Kinase ◽  
Serine Kinases ◽  
Gsk 3Β

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 ∼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 β-isoform of glycogen synthase kinase 3 (GSK-3β), which is a PKB target in vitro. Basal GSK-3β activity was decreased by ∼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.

scholarly journals Cytosolic Protein Tyrosine Phosphatase-ε Is a Negative Regulator of Insulin Signaling in Skeletal Muscle

Endocrinology ◽  
2007 ◽  
Vol 149 (2) ◽  
pp. 605-614 ◽  
Author(s):  
Shlomit Aga-Mizrachi ◽  
Tamar Brutman-Barazani ◽  
Avraham I. Jacob ◽  
Asia Bak ◽  
Ari Elson ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Rna Silencing ◽  
Glycogen Synthase ◽  
Protein Kinase B ◽  
Negative Regulator ◽  
Glycogen Synthase Kinase 3 ◽  
Wild Type ◽  
Stimulation Of

Whereas positive regulatory events triggered by insulin binding to insulin receptor (IR) have been well documented, the mechanism by which the activated IR is returned to the basal status is not completely understood. Recently studies focused on the involvement of protein tyrosine phosphatases (PTPs) and how they might influence IR signaling. In this study, we examined the possibility that cytosolic PTPε (cytPTPε) is involved in IR signaling. Studies were performed on L6 skeletal muscle cells. cytPTPε was overexpressed by using pBABE retroviral expression vectors. In addition, we inhibited cytPTPε by RNA silencing. We found that insulin induced rapid association of cytPTPε with IR. Interestingly, this association appeared to occur in the plasma membrane and on stimulation with insulin the two proteins internalized together. Moreover, it appeared that almost all internalized IR was associated with cytPTPε. We found that knockdown of cytPTPε by RNA silencing increased insulin-induced tyrosine phosphorylation of IR and IR substrate (IRS)-1 as well as phosphorylation of protein kinase B and glycogen synthase kinase-3 and insulin-induced stimulation of glucose uptake. Moreover, overexpression of wild-type cytPTPε reduced insulin-induced tyrosine phosphorylation of IR, IRS-1, and phosphorylation of protein kinase B and glycogen synthase kinase-3 and insulin-induced stimulation of glucose uptake. Finally, insulin-induced tyrosine phosphorylation of IR and IRS-1 was greater in skeletal muscle from mice lacking the cytPTPε gene than that from wild-type control animals. We conclude that cytPTPε serves as another major candidate negative regulator of IR signaling in skeletal muscle.

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