scholarly journals Oxytocin-Induced Activation of Eukaryotic Elongation Factor 2 in Myometrial Cells Is Mediated by Protein Kinase C

Endocrinology ◽  
2007 ◽  
Vol 149 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Dominic Devost ◽  
Marie-Eve Carrier ◽  
Hans H. Zingg
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Wide Spectrum ◽  
Elongation Factor ◽  
Direct Stimulation ◽  
Trophic Effect ◽  
Kinase C ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor

The nonapeptide oxytocin (OT) mediates a wide spectrum of biological action, many of them related to reproduction. Recently, we have shown that OT exerts a trophic effect on uterine smooth muscle cells and induces dephosphorylation, and thus activation, of the translation elongation factor eukaryotic elongation factor 2 (eEF2). The present study was designed to elucidate the mechanisms underlying this novel action of OT in the well-characterized human myometrial cell line hTERT-C3. Pathways known to induce eEF2 dephosphorylation are mammalian target of rapamycin (mTOR), and the MAPKs ERK1/2 and p38. Using a panel of chemical inhibitors of specific signaling pathways, we determined that none of these pathways played a role in OT-mediated eEF2 dephosphorylation. Because the OT receptor is a G protein-coupled receptor linked to Gαq, we tested the possibility that this OT action was mediated via protein kinase C (PKC). PKC activity was blocked by application of the general PKC chemical inhibitor Go6983 or by incubation with the cell-permeable PKC inhibitor peptide myr-psi PKC. With either approach, the effect of OT on eEF2 dephosphorylation was suppressed, indicating that the PKC pathway is essential for this OT action. Consistent with this idea, we also found that direct stimulation of PKC with the phorbol ester phorbol 12-myristate 13-acetate induced eEF2 dephosphorylation. Moreover, we observed that the stimulatory effect of OT on [35S]methionine incorporation into nascent proteins was blocked by PKC inhibition. Overall, these results define a novel hormonal signaling pathway that leads to eEF2 dephosphorylation and activation of protein synthesis.

scholarly journals Insights into the regulation of eukaryotic elongation factor 2 kinase and the interplay between its domains

2012 ◽  
Vol 442 (1) ◽  
pp. 105-118 ◽  
Author(s):  
Craig R. Pigott ◽  
Halina Mikolajek ◽  
Claire E. Moore ◽  
Stephen J. Finn ◽  
Curtis W. Phippen ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Catalytic Domain ◽  
Functional Organization ◽  
Elongation Factor ◽  
Kinase Domain ◽  
Conserved Residues ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Kinase Catalytic Domain ◽  
Eukaryotic Elongation Factor

eEF2K (eukaryotic elongation factor 2 kinase) is a Ca2+/CaM (calmodulin)-dependent protein kinase which regulates the translation elongation machinery. eEF2K belongs to the small group of so-called ‘α-kinases’ which are distinct from the main eukaryotic protein kinase superfamily. In addition to the α-kinase catalytic domain, other domains have been identified in eEF2K: a CaM-binding region, N-terminal to the kinase domain; a C-terminal region containing several predicted α-helices (resembling SEL1 domains); and a probably rather unstructured ‘linker’ region connecting them. In the present paper, we demonstrate: (i) that several highly conserved residues, implicated in binding ATP or metal ions, are critical for eEF2K activity; (ii) that Ca2+/CaM enhance the ability of eEF2K to bind to ATP, providing the first insight into the allosteric control of eEF2K; (iii) that the CaM-binding/α-kinase domain of eEF2K itself possesses autokinase activity, but is unable to phosphorylate substrates in trans; (iv) that phosphorylation of these substrates requires the SEL1-like domains of eEF2K; and (v) that highly conserved residues in the C-terminal tip of eEF2K are essential for the phosphorylation of eEF2, but not a peptide substrate. On the basis of these findings, we propose a model for the functional organization and control of eEF2K.

scholarly journals Insights Into the Pathologic Roles and Regulation of Eukaryotic Elongation Factor-2 Kinase

2021 ◽  
Vol 8 ◽  
Author(s):  
Darby J. Ballard ◽  
Hao-Yun Peng ◽  
Jugal Kishore Das ◽  
Anil Kumar ◽  
Liqing Wang ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Elongation Factor ◽  
Protein Translation ◽  
Negative Regulator ◽  
Translation Elongation ◽  
Elongation Factor 2 ◽  
Global Rate ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor

Eukaryotic Elongation Factor-2 Kinase (eEF2K) acts as a negative regulator of protein synthesis, translation, and cell growth. As a structurally unique member of the alpha-kinase family, eEF2K is essential to cell survival under stressful conditions, as it contributes to both cell viability and proliferation. Known as the modulator of the global rate of protein translation, eEF2K inhibits eEF2 (eukaryotic Elongation Factor 2) and decreases translation elongation when active. eEF2K is regulated by various mechanisms, including phosphorylation through residues and autophosphorylation. Specifically, this protein kinase is downregulated through the phosphorylation of multiple sites via mTOR signaling and upregulated via the AMPK pathway. eEF2K plays important roles in numerous biological systems, including neurology, cardiology, myology, and immunology. This review provides further insights into the current roles of eEF2K and its potential to be explored as a therapeutic target for drug development.

Abstract 204: Protective Roles of Eukaryotic Elongation Factor 2 Kinase on Rat Cardiomyoblast Death Under Glucose-deprived Condition

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Satoshi Kameshima ◽  
Muneyoshi Okada ◽  
Hideyuki Yamawaki
Keyword(s):  
Cell Death ◽  
Protein Kinase ◽  
Caspase 3 ◽  
Elongation Factor ◽  
H9c2 Cell ◽  
H9c2 Cells ◽  
Nuclear Condensation ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K; also known as calmodulin-dependent protein kinase III) has both active and inactive phosphorylation sites. An intracellular energy sensor, AMP-activated protein kinase (AMPK) was reported to activate eEF2K via increasing dephosphorylation at Ser366 (inactive site). Activated eEF2K phosphorylates and inactivates a specific substrate, eEF2, which results in the inhibition of protein translation consuming high energy. Glucose depletion (GD) is one of the primary causes for cardiomyocyte death in the developed cardiac hypertrophy. We have recently found that the expression and dephosphorylation of eEF2K (Ser366) and eEF2 phosphorylation were significantly increased in left ventricle of several cardiac hypertrophy models. However, it is almost unknown whether eEF2K/eEF2 signals affect GD-induced cardiomyocyte death. The aim of this study was to explore it. GD was induced by incubating H9c2 cells in a glucose-free medium. H9c2 cell viability, apoptotic-like nuclear condensation or protein expression was examined using a cell counting assay, DAPI staining or Western blotting, respectively. GD induced H9c2 cell death (p<0.01, n=6) and caspase-3 fragmentation (p<0.05, n=10-12). In addition, GD significantly increased phosphorylation of AMPK (p<0.05, n=6-8) and eEF2 (p<0.01, n=4-8) as well as eEF2K dephosphorylation at Ser366 (p<0.01, n=4-8). eEF2K gene knockdown (eEF2K KD) by siRNA transfection significantly increased GD-induced H9c2 cell death (p<0.05, n=7) and caspase-3 fragmentation (p<0.01, n=9). Moreover, eEF2K KD significantly facilitated GD-induced increase of nuclear condensation (44.0±3.3%, eEF2K siRNA vs. 30.9±2.4%, control siRNA p<0.01, n=5). AMPK KD did not affect GD-induced H9c2 cell death and eEF2K dephosphorylation. In conclusion, we for the first time revealed in H9c2 cells that activated eEF2K might play protective roles in GD-induced apoptosis via the inhibition of caspase-3 fragmentation, whereas AMPK activation is not directly related to the regulation of eEF2K/eEF2 signals in GD condition. The present results suggest eEF2K as a novel pharmacotherapeutic target for cardiac dysfunction.

scholarly journals Stress-induced regulation of eukaryotic elongation factor 2 kinase by SB 203580-sensitive and −insensitive pathways

2002 ◽  
Vol 367 (2) ◽  
pp. 525-532 ◽  
Author(s):  
Axel KNEBEL ◽  
Claire E. HAYDON ◽  
Nick MORRICE ◽  
Philip COHEN
Keyword(s):  
Protein Kinase ◽  
Elongation Factor ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor ◽  
Tnf Α ◽  
High Concentrations ◽  
Eef2 Kinase ◽  
Sb 203580

Eukaryotic elongation factor 2 (eEF2) kinase, the enzyme that inactivates eEF2, is controlled by phosphorylation. Previous work showed that stress-activated protein kinase 4 (SAPK4, also called p38Δ) inhibits eEF2 kinase in vitro by phosphorylating Ser-359, while ribosomal protein S6 kinases inhibit eEF2 kinase by phosphorylating Ser-366 [Knebel, Morrice and Cohen (2001) EMBO J. 20, 4360—4369; Wang, Li, Williams, Terada, Alessi and Proud (2001) EMBO J. 20, 4370—4379]. In the present study we have examined the effects of the protein synthesis inhibitor anisomycin and tumour necrosis factor-α (TNF-α) on the phosphorylation of eEF2 kinase. We demonstrate that Ser-359, Ser-366 and two novel sites (Ser-377 and Ser-396) are all phosphorylated in human epithelial KB cells, but only the phosphorylation of Ser-359 and Ser-377 increases in response to these agonists and correlates with the dephosphorylation (activation) of eEF2. Ser-377 is probably a substrate of MAPKAP-K2/K3 (mitogen-activated protein kinase-activated protein kinase 2/kinase 3) in cells, because eEF2 kinase is phosphorylated efficiently by these protein kinases in vitro and phosphorylation of this site, induced by TNF-α and low (but not high) concentrations of anisomycin, is prevented by SB 203580, which inhibits SAPK2a/p38, their ‘upstream’ activator. The phosphorylation of Ser-359 induced by high concentrations of anisomycin is probably catalysed by SAPK4/p38Δ in cells, because no other stress-activated, proline-directed protein kinase tested phosphorylates this site in vitro and phosphorylation is insensitive to SB 203580. Interestingly, the phosphorylation of Ser-359 induced by TNF-α or low concentrations of anisomycin is suppressed by SB 203580, indicating that phosphorylation is also mediated by a novel pathway. Since the phosphorylation of Ser-377 does not inhibit eEF2 kinase in vitro, our results suggest that anisomycin or TNF-α inhibit eEF2 kinase via the phosphorylation of Ser-359.

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