Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.31 (AMP-activated protein kinase)
 13,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein synthesis, in particular peptide-chain elongation, consumes cellular energy. Anoxia activates AMP-activated protein kinase (AMPK, see ), resulting in the inhibition of biosynthetic pathways to conserve ATP. In anoxic rat hepatocytes or in hepatocytes treated with 5-aminoimidazole-4-carboxamide (AICA) riboside, AMPK was activated and protein synthesis was inhibited. The inhibition of protein synthesis could not be explained by changes in the phosphorylation states of initiation factor 4E binding protein-1 (4E-BP1) or eukaryotic initiation factor 2alpha (eIF2alpha). However, the phosphorylation state of eukaryotic elongation factor 2 (eEF2) was increased in anoxic and AICA riboside-treated hepatocytes and in AICA riboside-treated CHO-K1 cells, and eEF2 phosphorylation is known to inhibit its activity. Incubation of CHO-K1 cells with increasing concentrations of 2-deoxyglucose suggested that the mammalian target of the rapamycin (mTOR) signaling pathway did not play a major role in controlling the level of eEF2 phosphorylation in response to mild ATP depletion. In HEK293 cells, transfection of a dominant-negative AMPK construct abolished the oligomycin-induced inhibition of protein synthesis and eEF2 phosphorylation. Lastly, eEF2 kinase, the kinase that phosphorylates eEF2, was activated in anoxic or AICA riboside-treated hepatocytes. Therefore, the activation of eEF2 kinase by AMPK, resulting in the phosphorylation and inactivation of eEF2, provides a novel mechanism for the inhibition of protein synthesis.
 ...
PMID:Activation of AMP-activated protein kinase leads to the phosphorylation of elongation factor 2 and an inhibition of protein synthesis. 1219 24

Protein synthesis, in particular peptide chain elongation, is an energy-consuming biosynthetic process. AMP-activated protein kinase (AMPK) is a key regulatory enzyme involved in cellular energy homeostasis. Therefore, we tested the hypothesis that, as in liver, it could mediate the inhibition of protein synthesis by oxygen deprivation in heart by modulating the phosphorylation of eukaryotic elongation factor-2 (eEF2), which becomes inactive in its phosphorylated form. In anoxic cardiomyocytes, AMPK activation was associated with an inhibition of protein synthesis and an increase in phosphorylation of eEF2. Rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), did not mimic the effect of oxygen deprivation to inhibit protein synthesis in cardiomyocytes or lead to eEF2 phosphorylation in perfused hearts, suggesting that AMPK activation did not inhibit mTOR/p70 ribosomal protein S6 kinase (p70S6K) signaling. Human recombinant eEF2 kinase (eEF2K) was phosphorylated by AMPK in a time- and AMP-dependent fashion, and phosphorylation led to eEF2K activation, similar to that observed in extracts from ischemic hearts. In contrast, increasing the workload resulted in a dephosphorylation of eEF2, which was rapamycin-insensitive, thus excluding a role for mTOR in this effect. eEF2K activity was unchanged by increasing the workload, suggesting that the decrease in eEF2 phosphorylation could result from the activation of an eEF2 phosphatase.
 ...
PMID:Myocardial ischemia and increased heart work modulate the phosphorylation state of eukaryotic elongation factor-2. 1292 Jan 34

Protein synthesis consumes a high proportion of the metabolic energy of mammalian cells, and most of this is used by peptide chain elongation. An important regulator of energy supply and demand in eukaryotic cells is the AMP-activated protein kinase (AMPK). The rate of peptide chain elongation can be modulated through the phosphorylation of eukaryotic elongation factor (eEF) 2, which inhibits its activity and is catalyzed by a specific calcium/calmodulin-dependent protein kinase termed eEF2 kinase. Here we show that AMPK directly phosphorylates eEF2 kinase, and we identify the major site of phosphorylation as Ser-398 in a regulatory domain of eEF2 kinase. AMPK also phosphorylates two other sites (Ser-78 and Ser-366) in eEF2 kinase in vitro. We develop appropriate phosphospecific antisera and show that phosphorylation of Ser-398 in eEF2 kinase is enhanced in intact cells under a range of conditions that activate AMPK and increase the phosphorylation of eEF2. Ser-78 and Ser-366 do not appear to be phosphorylated by AMPK within cells. Although cardiomyocytes appear to contain a distinct isoform of eEF2 kinase, it also contains a site corresponding to Ser-398 that is phosphorylated by AMPK in vitro. Stimuli that activate AMPK and increase eEF2 phosphorylation within cells increase the activity of eEF2 kinase. Thus, AMPK and eEF2 kinase may provide a key link between cellular energy status and the inhibition of protein synthesis, a major consumer of metabolic energy.
 ...
PMID:Stimulation of the AMP-activated protein kinase leads to activation of eukaryotic elongation factor 2 kinase and to its phosphorylation at a novel site, serine 398. 1470 57

A necessary mediator of cardiac myocyte enlargement is protein synthesis, which is controlled at the levels of both translation initiation and elongation. Eukaryotic elongation factor-2 (eEF2) mediates the translocation step of peptide-chain elongation and is inhibited through phosphorylation by eEF2 kinase. In addition, p70S6 kinase can regulate protein synthesis by phosphorylating eEF2 kinase or via phosphorylation of ribosomal protein S6. We have recently shown that eEF2 kinase is also controlled by phosphorylation by AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Moreover, the mammalian target of rapamycin has also been shown to be inhibited, indirectly, by AMPK, thus leading to the inhibition of p70S6 kinase. Although AMPK activation has been shown to modulate protein synthesis, it is unknown whether AMPK could also be a regulator of cardiac hypertrophic growth. Therefore, we investigated the role of AMPK activation in regulating protein synthesis during both phenylephrine- and Akt-induced cardiac hypertrophy. Metformin and 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside were used to activate AMPK in neonatal rat cardiac myocytes. Activation of AMPK significantly decreased protein synthesis induced by phenylephrine treatment or by expression of constitutively active Akt. Activation of AMPK also resulted in decreased p70S6 kinase phosphorylation and increased phosphorylation of eEF2, suggesting that inhibition of protein synthesis involves the eEF2 kinase/eEF2 axis and/or the p70S6 kinase pathway. Together, our data suggest that the inhibition of protein synthesis by pharmacological activation of AMPK may be a key regulatory mechanism by which hypertrophic growth can be controlled.
 ...
PMID:Activation of AMP-activated protein kinase inhibits protein synthesis associated with hypertrophy in the cardiac myocyte. 1515 10

Protein synthesis in skeletal muscle is known to decrease during contractions but the underlying regulatory mechanisms are unknown. Here, the effect of exercise on skeletal muscle eukaryotic elongation factor 2 (eEF2) phosphorylation, a key component in protein translation machinery, was examined. Eight healthy men exercised on a cycle ergometer at a workload eliciting approximately 67% peak pulmonary oxygen consumption (VO2 peak) with skeletal muscle biopsies taken from the vastus lateralis muscle at rest as well as after 1, 10, 30, 60 and 90 min of exercise. In response to exercise, there was a rapid (i.e. < 1 min) 5- to 7-fold increase in eEF2 phosphorylation at Thr56 that was sustained for 90 min of continuous exercise. The in vitro activity of skeletal muscle eEF2 kinase was not altered by exercise indicating that the increased activity of eEF2 kinase to eEF2 is not mediated by covalent mechanisms. In support of this, the increase in AMPK activity was temporally unrelated to eEF2 phosphorylation. However, skeletal muscle eEF2 kinase was potently activated by Ca(2)(+)-calmodulin in vitro, suggesting that the higher eEF2 phosphorylation in working skeletal muscle is mediated by allosteric activation of eEF2 kinase by Ca(2)(+) signalling via calmodulin. Given that eEF2 phosphorylation inhibits eEF2 activity and mRNA translation, these findings suggest that the inhibition of protein synthesis in contracting skeletal muscle is due to the Ca(2)(+)-induced stimulation of eEF2 kinase.
 ...
PMID:Exercise rapidly increases eukaryotic elongation factor 2 phosphorylation in skeletal muscle of men. 1621 Mar 46

Oxygen deprivation leads to the accumulation of misfolded proteins in the endoplasmic reticulum (ER), causing ER stress. Under conditions of ER stress, inhibition of protein synthesis and up-regulation of ER chaperone expression reduce the misfolded proteins in the ER. AMP-activated protein kinase (AMPK) is a key regulatory enzyme involved in energy homeostasis during hypoxia. It has been shown that AMPK activation is associated with inhibition of protein synthesis via phosphorylation of elongation factor 2 (eEF2) in cardiomyocytes. We therefore examined whether AMPK attenuates hypoxia-induced ER stress in neonatal rat cardiomyocytes. We found that hypoxia induced ER stress, as assessed by the expression of CHOP and BiP and cleavage of caspase 12. Knockdown of CHOP or caspase 12 through small interfering RNA (siRNA) resulted in decreased expression of cleaved poly(ADP-ribose) polymerase following exposure to hypoxia. We also found that hypoxia-induced CHOP expression and cleavage of caspase 12 were significantly inhibited by pretreatment with 5-aminoimidazole-4-carboxyamide-1-beta-D-ribofuranoside (AICAR), a pharmacological activator of AMPK. In parallel, adenovirus expressing dominant-negative AMPK significantly attenuated the cardioprotective effects of AICAR. Knockdown of eEF2 phosphorylation using eEF2 kinase siRNA abolished these cardioprotective effects of AICAR. Taken together, these findings demonstrate that activation of AMPK contributes to protection of the heart against hypoxic injury through attenuation of ER stress and that attenuation of protein synthesis via eEF2 inactivation may be the mechanism of cardioprotection by AMPK.
 ...
PMID:AMP-activated protein kinase protects cardiomyocytes against hypoxic injury through attenuation of endoplasmic reticulum stress. 1622 5

Tuberous sclerosis is an autosomal-dominant disorder caused by the mutation of one of the two tumor suppressor genes: TSC1 or TSC2, encoding protein products, hamartin, and tuberin, respectively. Both proteins form intracellular complexes exerting inhibitory activity on mammalian target of rapamycin (mTOR) kinase. It has been demonstrated that signal transduction from tuberin to mTOR is mediated by a G protein, Ras homologue enriched in brain (Rheb). In normal cells, tuberin having GTPase-activating protein properties toward Rheb controls signals of nutrient depletion, hypoxia, or stress, not allowing activation of mTOR and subsequent protein translation and cell proliferation. However, when environmental conditions change, tuberin is phosphorylated and it forms a complex with hamartin is degraded, and downstream targets of mTOR, S6K, and eEF2K, can be activated. In this review, we summarize very recent information contributing to our knowledge of TSC2 regulation by four cellular signaling pathways: PI3K/Akt, Ras/MAPK, LKB1/AMPK, and REDD1.
 ...
PMID:Positive and negative regulation of TSC2 activity and its effects on downstream effectors of the mTOR pathway. 1639 86

Ethanol decreases protein synthesis in cells, although the underlying regulatory mechanisms of this process are not fully established. In the present study incubation of C2C12 myocytes with 100 mm EtOH decreased protein synthesis while markedly increasing the phosphorylation of eukaryotic elongation factor 2 (eEF2), a key component of the translation machinery. Both mTOR and MEK pathways were found to play a role in regulating the effect of EtOH on eEF2 phosphorylation. Rapamycin, an inhibitor of mammalian target of rapamycin, and the MEK inhibitor PD98059 blocked the EtOH-induced phosphorylation of eEF2, whereas the p38 MAPK inhibitor SB202190 had no effect. Unexpectedly, EtOH decreased the phosphorylation and activity of the eEF2 upstream regulator eEF2 kinase. Likewise, treatment of cells with the inhibitor rottlerin did not block the stimulatory effect of EtOH on eEF2, suggesting that eEF2 kinase (eEF2K) does not play a role in regulating eEF2. In contrast, increased eEF2 phosphorylation was correlated with an increase in AMP-activated protein kinase (AMPK) phosphorylation and activity. Compound C, an inhibitor of AMPK, suppressed the effects of EtOH on eEF2 phosphorylation but had no effect on eEF2K, indicating that AMPK regulates eEF2 independent of eEF2K. Finally, EtOH decreased protein phosphatase 2A activity when either eEF2 or AMPK was used as the substrate. Thus, this later action may partially account for the increased phosphorylation of eEF2 in response to EtOH and the observed sensitivity of AMPK to rapamycin and PD98059 treatments. Collectively, the induction of eEF2 phosphorylation by EtOH is controlled by an increase in AMPK and a decrease in protein phosphatase 2A activity.
 ...
PMID:Alcohol regulates eukaryotic elongation factor 2 phosphorylation via an AMP-activated protein kinase-dependent mechanism in C2C12 skeletal myocytes. 1716 44

HIV anti-retroviral drugs decrease protein synthesis, although the underlying regulatory mechanisms of this process are not fully established. Therefore, we investigated the effects of the HIV protease inhibitor lopinavir (LPV) on protein metabolism. We also characterized the mechanisms that mediate the effects of this drug on elongation factor-2 (eEF2), a key component of the translational machinery. Treatment of C2C12 myocytes with LPV produced a dose-dependent inhibitory effect on protein synthesis. This effect was observed at 15 min and was maintained for at least 4 h. Mechanistically, LPV increased the phosphorylation of eEF2 and thereby decreased the activity of this protein. Increased phosphorylation of eEF2 was associated with increased activity of its upstream regulators AMP-activated protein kinase (AMPK) and eEF2 kinase (eEF2K). Both AMPK and eEF2K directly phosphorylated eEF2 in an in vitro kinase assay suggesting two distinct paths lead to eEF2 phosphorylation. To verify this connection, myocytes were treated with the AMPK inhibitor compound C. Compound C blocked eEF2K and eEF2 phosphorylation, demonstrating that LPV affects eEF2 activity via an AMPK-eEF2K dependent pathway. In contrast, incubation of myocytes with rottlerin suppressed eEF2K, but not eEF2 phosphorylation, suggesting that eEF2 can be regulated independent of eEF2K. Finally, LPV did not affect PP2A activity when either eEF2 or peptide was used as the substrate. Collectively, these results indicate that LPV decreases protein synthesis, at least in part, via inhibition of eEF2. This appears regulated by AMPK which can act directly on eEF2 or indirectly via the action of eEF2K.
 ...
PMID:Lopinavir impairs protein synthesis and induces eEF2 phosphorylation via the activation of AMP-activated protein kinase. 1871 74

Skeletal muscle protein synthesis rate decreases during contractions but the underlying regulatory mechanisms are poorly understood. It was hypothesized that there would be a coordinated regulation of eukaryotic elongation factor 2 (eEF2) and eukaryotic initiation factor 4E-binding protein 1 (4EBP1) phosphorylation by signalling cascades downstream of rises in intracellular [Ca(2+)] and decreased energy charge via AMP-activated protein kinase (AMPK) in contracting skeletal muscle. When fast-twitch skeletal muscles were contracted ex vivo using different protocols, the suppression of protein synthesis correlated more closely with changes in eEF2 than 4EBP1 phosphorylation. Using a combination of Ca(2+) release agents and ATPase inhibitors it was shown that the 60-70% suppression of fast-twitch skeletal muscle protein synthesis during contraction was equally distributed between Ca(2+) and energy turnover-related mechanisms. Furthermore, eEF2 kinase (eEF2K) inhibition completely blunted increases in eEF2 phosphorylation and partially blunted (i.e. 30-40%) the suppression of protein synthesis during contractions. The 3- to 5-fold increase in skeletal muscle eEF2 phosphorylation during contractions in situ was rapid and sustained and restricted to working muscle. The increase in eEF2 phosphorylation and eEF2K activation were downstream of Ca(2+)-calmodulin (CaM) but not other putative activating factors such as a fall in intracellular pH or phosphorylation by protein kinases. Furthermore, blunted protein synthesis and 4EBP1 dephosphorylation were unrelated to AMPK activity during contractions, which was exemplified by normal blunting of protein synthesis during contractions in muscles overexpressing kinase-dead AMPK. In summary, in fast-twitch skeletal muscle, the inhibition of eEF2 activity by phosphorylation downstream of Ca(2+)-CaM-eEF2K signalling partially contributes to the suppression of protein synthesis during exercise/contractions.
 ...
PMID:A Ca(2+)-calmodulin-eEF2K-eEF2 signalling cascade, but not AMPK, contributes to the suppression of skeletal muscle protein synthesis during contractions. 1933 5


1 2 3 Next >>