Insulin stimulates protein synthesis in skeletal muscle by enhancing the association of eIF-4E and eIF-4G

1997 ◽  
Vol 272 (2) ◽  
pp. C754-C759 ◽  
Author(s):  
S. R. Kimball ◽  
C. V. Jurasinski ◽  
J. C. Lawrence ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Gastrocnemius Muscle ◽  
Binding Protein ◽  
Fold Increase ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Phosphorylated Form ◽  
Stimulation Of

Insulin stimulated protein synthesis in gastrocnemius muscle of perfused rat hindlimb preparations by approximately twofold. The stimulation of protein synthesis was associated with a 12-fold increase in the amount of eukaryotic initiation factor eIF-4G bound to the mRNA cap-binding protein eIF-4E. In part, the increased binding of eIF-4G to eIF-4E was a result of release of eIF-4E bound to the translational regulator, PHAS-I, through a mechanism involving enhanced phosphorylation of PHAS-I. However, the insulin-induced association of eIF-4E and eIF-4G was not due to increased net phosphorylation of eIF-4E because insulin decreased the amount present in the phosphorylated form from 86 to 59% of total eIF-4E. Overall, the results suggest that insulin stimulates protein synthesis in gastrocnemius muscle through a mechanism involving increased binding of eIF-4G to eIF-4E, which is in part due to phosphorylation of PHAS-I, resulting in a release of eIF-4E from the inactive PHAS-I x eIF-4E complex.

scholarly journals Effect of sepsis on eIE4E availability in skeletal muscle

2000 ◽  
Vol 279 (5) ◽  
pp. E1178-E1184 ◽  
Author(s):  
Thomas C. Vary ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Translation Initiation ◽  
Binding Protein ◽  
Abscess Formation ◽  
Sterile Inflammation ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Sterile Abscess ◽  
Inhibition Of Protein Synthesis

Chronic septic abscess formation causes an inhibition of protein synthesis in gastrocnemius that is not observed in rats with a sterile abscess. The inhibition is associated with an impaired translation initiation. The present study was designed to investigate the effects of sepsis on phosphorylation and availability of eukaryotic initiation factor (eIF)4E in gastrocnemius 5 days after induction of a sterile or septic abscess. Neither sepsis nor sterile inflammation altered the extent of eIF4E phosphorylation. Moreover, no changes in the amount of the binding protein 4E-BP1 associated with eIF4E or in the phosphorylation of 4E-BP1 were observed during sepsis or sterile inflammation. In contrast, sepsis and sterile inflammation caused a reduction in the relative amount of eIF4G bound to eIF4E compared with controls. The diminished amount of eIF4G bound to eIF4E was not the result of a reduced abundance of eIF4E. Sepsis, but not sterile inflammation, caused an increase in the cellular abundance of eIF4E. The results provide evidence that alterations in the eIF4E system are probably not rate controlling for the synthesis of total, mixed proteins in gastrocnemius during sepsis. Instead, on the basis of our previous studies, changes in eIF2B appear to be responsible for limiting protein synthesis in skeletal muscle during sepsis.

Regulation of eukaryotic initiation factor-2B activity in muscle of diabetic rats

1993 ◽  
Vol 264 (1) ◽  
pp. E101-E108 ◽  
Author(s):  
A. M. Karinch ◽  
S. R. Kimball ◽  
T. C. Vary ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Casein Kinase Ii ◽  
Diabetic Rats ◽  
Casein Kinase ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Fast Twitch

Peptide-chain initiation is inhibited in fast-twitch skeletal muscle, but not heart, of diabetic rats. We have investigated mechanisms that might maintain eukaryotic initiation factor (eIF)-2B activity, preventing loss of efficiency of protein synthesis in heart of diabetic rats but not in fast-twitch skeletal muscle. There was no change in the amount or phosphorylation state of eIF-2 in skeletal or cardiac muscle during diabetes. In contrast, eIF-2B activity was decreased in fast-twitch but not slow-twitch muscle from diabetic animals. NADP+ inhibited partially purified eIF-2B in vitro, but addition of equimolar NADPH reversed the inhibition. The NADPH-to-NADP+ ratio was unchanged in fast-twitch muscle after induction of diabetes but was increased in heart of diabetic rats, suggesting that NADPH also prevents inhibition of eIF-2B in vivo. The activity of casein kinase II, which can phosphorylate and activate eIF-2B in vitro, was significantly lower in extracts of fast-twitch, but not cardiac muscle, of diabetic rats compared with controls. The results presented here demonstrate that changes in eIF-2 alpha phosphorylation are not responsible for the effect of diabetes on eIF-2B activity in fast-twitch skeletal muscle. Modulation of casein kinase II activity may be a factor in the regulation of protein synthesis in muscle during acute diabetes. The activity of eIF-2B in heart might be maintained by the increased NADPH/NADP+.

Mammalian target of rapamycin pathway is up-regulated by both acute endurance exercise and chronic muscle contraction in rat skeletal muscle

2013 ◽  
Vol 38 (8) ◽  
pp. 862-869 ◽  
Author(s):  
Brittany A. Edgett ◽  
Melanie L. Fortner ◽  
Arend Bonen ◽  
Brendon J. Gurd
Keyword(s):  
Skeletal Muscle ◽  
Endurance Exercise ◽  
Gastrocnemius Muscle ◽  
Contractile Activity ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Pathway ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Sprague Dawley ◽  
Sprague Dawley Rats

This study examined changes in the expression of translation initiation regulatory proteins and mRNA following both an acute bout of endurance exercise and chronic muscle contractile activity. Female Sprague Dawley rats ran for 2 h at 15 m·min−1 followed by an increase in speed of 5 m·min−1 every 5 min until volitional fatigue. The red gastrocnemius muscle was harvested from nonexercised animals (control; n = 6) and from animals that exercised either immediately after exercise (n = 6) or following 3 h of recovery from exercise (n = 6). Compared with control, ribosomal protein S6 (rpS6) mRNA was elevated (p < 0.05) at both 0 h (+32%) and 3 h (+47%). Both a catalytic subunit of eukaryotic initiation factor 2B (eIF2Bε) (+127%) and mammalian target of rapamycin (mTOR) mRNA (+44%) were increased at 3 h, compared with control. Phosphorylation of mTOR (+40%) and S6 kinase 1 (S6K1) (+266%) were increased immediately after exercise (p < 0.05). Female Sprague Dawley rats also underwent chronic stimulation of the peroneal nerve continuously for 7 days. The red gastrocnemius muscle was removed 24 h after cessation of the stimulation. Chronic muscle stimulation increased (p < 0.05) mTOR protein (+74%), rpS6 (+31%), and eukaryotic initiation factor 2α (+44%, p = 0.069), and this was accompanied by an increase in cytochrome c (+31%). Increased resting phosphorylation was observed for rpS6 (+51%) (p < 0.05) but not for mTOR or eukaryotic initiation factor 4E binding protein 1. These experiments demonstrate that both acute and chronic contractile activity up-regulate the mTOR pathway and mitochondrial content in murine skeletal muscle. This up-regulation of the mTOR pathway may increase translation efficiency and may also represent an important control point in exercise-mediated mitochondrial biogenesis.

Angiotensin II inhibits insulin-stimulated phosphorylation of eukaryotic initiation factor 4E-binding protein-1 in proximal tubular epithelial cells

2001 ◽  
Vol 360 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Duraisamy SENTHIL ◽  
Jennifer L. FAULKNER ◽  
Goutam GHOSH CHOUDHURY ◽  
Hanna E. ABBOUD ◽  
Balakuntalam S. KASINATH
Keyword(s):  
Protein Synthesis ◽  
Angiotensin Ii ◽  
Insulin Signalling ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Tubular Epithelial Cells ◽  
Eukaryotic Initiation Factor 4E ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular ◽  
Stimulation Of

Interaction between angiotensin II, which binds a G-protein-coupled receptor, and insulin, a ligand for receptor tyrosine kinase, was examined in renal proximal tubular epithelial cells. Augmented protein translation by insulin involves activation of eukaryotic initiation factor 4E (eIF4E) which follows the release of the factor from a heterodimeric complex by phosphorylation of its binding protein, 4E-BP1. Angiotensin II (1nM) or insulin (1nM) individually stimulated 4E-BP1 phosphorylation. However, pre-incubation with angiotensin II abrogated insulin-induced phosphorylation of 4E-BP1, resulting in persistent binding to eIF4E. Although angiotensin II and insulin individually activated phosphoinositide 3-kinase and extracellular signal-regulated kinase (ERK)-1/−2-type mitogen-activated protein (MAP) kinase, pre-incubation with angiotensin II abolished insulin-induced stimulation of these kinases, suggesting more proximal events in insulin signalling may be intercepted. Pretreatment with angiotensin II markedly inhibited insulin-stimulated tyrosine phosphorylation of insulin-receptor β-chain and insulin-receptor substrate 1. Losartan prevented angiotensin II inhibition of insulin-induced ERK-1/−2-type MAP kinase activation and 4E-BP1 phosphorylation, suggesting mediation of the effect of angiotensin II by its type 1 receptor. Insulin-stimulated de novo protein synthesis was also abolished by pre-incubation with angiotensin II. These data show that angiotensin II inhibits 4E-BP1 phosphorylation and stimulation of protein synthesis induced by insulin by interfering with proximal events in insulin signalling. Our data provide a mechanistic basis for insulin insensitivity induced by angiotensin II.

Role of eIF4E in stimulation of protein synthesis by IGF-I in perfused rat skeletal muscle

2000 ◽  
Vol 278 (1) ◽  
pp. E58-E64 ◽  
Author(s):  
Thomas C. Vary ◽  
Leonard S. Jefferson ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Initiation Factor ◽  
Translational Efficiency ◽  
Rat Skeletal Muscle ◽  
Phosphorylation State ◽  
Factor I ◽  
Igf I ◽  
Stimulation Of

Insulin-like growth factor I (IGF-I) promotes anabolism by stimulating protein synthesis in skeletal muscle. In the present study, we have examined mechanisms by which IGF-I stimulates protein synthesis in skeletal muscle with a perfused rat hindlimb preparation. IGF-I (10 nM) stimulated protein synthesis over 2.7-fold. Total RNA content was unaffected, but translational efficiency was increased by IGF-I. We next examined the effect of IGF-I on eukaryotic initiation factor (eIF) 4E as a mechanism regulating translation initiation. IGF-I did not alter either the amount of eIF4E associated with the eIF4E binding protein 4E-BP1 or the phosphorylation state of 4E-BP1. Likewise, the phosphorylation state of eIF4E was unaltered by IGF-I. In contrast, the amount of eIF4E bound to eIF4G was increased threefold by IGF-I. We conclude that IGF-I regulates protein synthesis in skeletal muscle by enhancing formation of the active eIF4E ⋅ eIF4G complex.

Phosphorylation of eukaryotic initiation factor eIF2Bε in skeletal muscle during sepsis

2002 ◽  
Vol 283 (5) ◽  
pp. E1032-E1039 ◽  
Author(s):  
Thomas C. Vary ◽  
Gina Deiter ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Glycogen Synthase ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Sterile Inflammation ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Skeletal Muscle Protein

We reported that the inhibition of protein synthesis in skeletal muscle during sepsis correlated with reduced eukaryotic initiation factor eIF2B activity. The present studies define changes in eIF2Bε phosphorylation in gastrocnemius of septic animals. eIF2B kinase activity was significantly elevated 175% by sepsis compared with sterile inflammation, whereas eIF2B phosphatase activity was unaffected. Phosphorylation of eIF2Bε-Ser535 was significantly augmented over 2-fold and 2.5-fold after 3 and 5 days and returned to control values after 10 days of sepsis. Phosphorylation of glycogen synthase kinase-3 (GSK-3), a potential upstream kinase responsible for the elevated phosphorylation of eIF2Bε, was significantly reduced over 36 and 41% after 3 and 5 days and returned to control values after 10 days of sepsis. The phosphorylation of PKB, a kinase thought to directly phosphorylate and inactivate GSK-3, was significantly reduced ∼50% on day 3, but not on days 5 or 10, postinfection compared with controls. Treatment of septic rats with TNF-binding protein prevented the sepsis-induced changes in eIF2Bε and GSK-3 phosphorylation, implicating TNF in mediating the effects of sepsis. Thus increased phosphorylation of eIF2Bε via activation of GSK-3 is an important mechanism to account for the inhibition of skeletal muscle protein synthesis during sepsis. Furthermore, the study presents the first demonstration of changes in eIF2Bε phosphorylation in vivo.

scholarly journals Nitric oxide mediates NMDA-induced persistent inhibition of protein synthesis through dephosphorylation of eukaryotic initiation factor 4E-binding protein 1 and eukaryotic initiation factor 4G proteolysis

2008 ◽  
Vol 411 (3) ◽  
pp. 667-677 ◽  
Author(s):  
Valérie Petegnief ◽  
Míriam Font-Nieves ◽  
M. Elena Martín ◽  
Matilde Salinas ◽  
Anna M. Planas
Keyword(s):  
Nitric Oxide ◽  
Protein Synthesis ◽  
Molecular Mechanisms ◽  
Binding Protein ◽  
Initiation Factor ◽  
Protein Synthesis Inhibition ◽  
Eukaryotic Initiation Factor ◽  
Translation Inhibition ◽  
Synthesis Inhibition ◽  
Nos Inhibitors

Cerebral ischaemia causes long-lasting protein synthesis inhibition that is believed to contribute to brain damage. Energy depletion promotes translation inhibition during ischaemia, and the phosphorylation of eIF (eukaryotic initiation factor) 2α is involved in the translation inhibition induced by early ischaemia/reperfusion. However, the molecular mechanisms underlying prolonged translation down-regulation remain elusive. NMDA (N-methyl-D-aspartate) excitotoxicity is also involved in ischaemic damage, as exposure to NMDA impairs translation and promotes the synthesis of NO (nitric oxide), which can also inhibit translation. In the present study, we investigated whether NO was involved in NMDA-induced protein synthesis inhibition in neurons and studied the underlying molecular mechanisms. NMDA and the NO donor DEA/NO (diethylamine–nitric oxide sodium complex) both inhibited protein synthesis and this effect persisted after a 30 min exposure. Treatments with NMDA or NO promoted calpain-dependent eIF4G cleavage and 4E-BP1 (eIF4E-binding protein 1) dephosphorylation and also abolished the formation of eIF4E–eIF4G complexes; however, they did not induce eIF2α phosphorylation. Although NOS (NO synthase) inhibitors did not prevent protein synthesis inhibition during 30 min of NMDA exposure, they did abrogate the persistent inhibition of translation observed after NMDA removal. NOS inhibitors also prevented NMDA-induced eIF4G degradation, 4E-BP1 dephosphorylation, decreased eIF4E–eIF4G-binding and cell death. Although the calpain inhibitor calpeptin blocked NMDA-induced eIF4G degradation, it did not prevent 4E-BP1 dephosphorylation, which precludes eIF4E availability, and thus translation inhibition was maintained. The present study suggests that eIF4G integrity and hyperphosphorylated 4E-BP1 are needed to ensure appropriate translation in neurons. In conclusion, our data show that NO mediates NMDA-induced persistent translation inhibition and suggest that deficient eIF4F activity contributes to this process.

scholarly journals The distribution of eukaryotic initiation factor 4E after bouts of resistance exercise is altered by shortening of recovery periods

2020 ◽  
Vol 70 (1) ◽  
Author(s):  
Junya Takegaki ◽  
Riki Ogasawara ◽  
Karina Kouzaki ◽  
Satoshi Fujita ◽  
Koichi Nakazato ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Resistance Exercise ◽  
Translation Initiation ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Related Factors ◽  
Eukaryotic Initiation Factor 4E

Abstract Insufficient duration of recovery between resistance exercise bouts reduces the effects of exercise training, but the influence on muscle anabolic responses is not fully understood. Here, we investigated the changes in the distribution of eukaryotic initiation factor (eIF) 4E, a key regulator of translation initiation, and related factors in mouse skeletal muscle after three successive bouts of resistance exercise with three durations of recovery periods (72 h: conventional, 24 h: shorter, and 8 h: excessively shorter). Bouts of resistance exercise dissociated eIF4E from eIF4E binding protein 1, with the magnitude increasing with shorter recovery. Whereas bouts of resistance exercise with 72 h recovery increased the association of eIF4E and eIF4G, those with shorter recovery did not. Similar results were observed in muscle protein synthesis. These results suggest that insufficient recovery inhibited the association of eIF4E and eIF4G, which might cause attenuation of protein synthesis activation after bouts of resistance exercise.

Signaling pathways initiated by β-hydroxy-β-methylbutyrate to attenuate the depression of protein synthesis in skeletal muscle in response to cachectic stimuli

2007 ◽  
Vol 293 (4) ◽  
pp. E923-E931 ◽  
Author(s):  
Helen L. Eley ◽  
Steven T. Russell ◽  
Jeffrey H. Baxter ◽  
Pradip Mukerji ◽  
Michael J. Tisdale
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Mammalian Target Of Rapamycin ◽  
Elongation Factor ◽  
Initiation Factor ◽  
Α Subunit ◽  
Initiation Factor 2 ◽  
Dependent Protein ◽  
Ribosomal S6 Kinase ◽  
Stimulation Of

To investigate the mechanism by which β-hydroxy-β-methylbutyrate (HMB) attenuates the depression of protein synthesis in the skeletal muscle of cachectic mice, a study has been carried out in murine myotubes in the presence of proteolysis-inducing factor (PIF). PIF inhibited protein synthesis by 50% within 4 h, and this was effectively attenuated by HMB (25–50 μM). HMB (50 μM) alone stimulated protein synthesis, and this was attenuated by rapamycin (27 nM), an inhibitor of mammalian target of rapamycin (mTOR). Further evidence for an involvement of this pathway was shown by an increased phosphorylation of mTOR, the 70-kDa ribosomal S6 kinase (p70S6k), and initiation factor 4E-binding protein (4E-BP1) and an increased association of eukaryotic initiation factor 2 (eIF4E) with eIF4G. PIF alone induced a transient (1–2 h) stimulation of phosphorylation of mTOR and p70S6k. However, in the presence of HMB, phosphorylation of mTOR, p70S6k, and 4E-BP1 was increased, and inactive 4E-BP1-eIF4E complex was reduced, whereas the active eIF4G·eIF4E complex was increased, suggesting continual stimulation of protein synthesis. HMB alone reduced phosphorylation of elongation factor 2, but this effect was not seen in the presence of PIF. PIF induced autophosphorylation of the double-strand RNA-dependent protein kinase (PKR), leading to phosphorylation of eIF2 on the α-subunit, which would inhibit protein synthesis. However, in the presence of HMB, phosphorylation of PKR and eIF2α was attenuated, and this was also observed in skeletal muscle of cachectic mice administered HMB (0.25 g/kg). These results suggest that HMB attenuates the depression of protein synthesis by PIF in myotubes through multiple mechanisms.

Feeding stimulates protein synthesis in muscle and liver of neonatal pigs through an mTOR-dependent process

2000 ◽  
Vol 279 (5) ◽  
pp. E1080-E1087 ◽  
Author(s):  
Scot R. Kimball ◽  
Leonard S. Jefferson ◽  
Hahn V. Nguyen ◽  
Agus Suryawan ◽  
Jill A. Bush ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Complex Formation ◽  
Mammalian Target Of Rapamycin ◽  
Specific Inhibitor ◽  
Initiation Factor ◽  
Ribosomal Protein S6 ◽  
Eif4f Complex ◽  
Dependent Process ◽  
Stimulation Of

Protein synthesis is repressed in both skeletal muscle and liver after a short-term fast and is rapidly stimulated in response to feeding. Previous studies in rats and pigs have shown that the feeding-induced stimulation of protein synthesis is associated with activation of the 70-kDa ribosomal protein S6 kinase (S6K1) as well as enhanced binding of eukaryotic initiation factor eIF4E to eIF4G to form the active eIF4F complex. In cells in culture, hormones and nutrients regulate both of these events through a protein kinase termed the mammalian target of rapamycin (mTOR). In the present study, the involvement of mTOR in the feeding-induced stimulation of protein synthesis in skeletal muscle and liver was examined. Pigs at 7 days of age were fasted for 18 h, and then one-half of the animals were fed. In addition, one-half of the animals in each group were administered rapamycin (0.75 mg/kg) 2 h before feeding. The results reveal that treating 18-h fasted pigs with rapamycin, a specific inhibitor of mTOR, before feeding prevented the activation of S6K1 and the changes in eIF4F complex formation observed in skeletal muscle and liver after feeding. Rapamycin also ablated the feeding-induced stimulation of protein synthesis in liver. In contrast, in skeletal muscle, rapamycin attenuated, but did not prevent, the stimulation of protein synthesis in response to feeding. The results suggest that feeding stimulates hepatic protein synthesis through an mTOR-dependent process involving enhanced eIF4F complex formation and activation of S6K1. However, in skeletal muscle, these two processes may account for only part of the stimulation of protein synthesis, and thus additional steps may be involved in the response.

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