scholarly journals Phosphorylation of elongation factor 2 during Ca2+-mediated secretion from rat parotid acini

1992 ◽  
Vol 282 (3) ◽  
pp. 877-882 ◽  
Author(s):  
M T Hincke ◽  
A C Nairn
Keyword(s):  
Protein Synthesis ◽  
Phorbol Esters ◽  
Elongation Factor ◽  
Ionophore A23187 ◽  
Inhibit Protein Synthesis ◽  
Parotid Acinar Cells ◽  
Kinase C ◽  
Elongation Factor 2 ◽  
Parotid Cells ◽  
Rat Parotid

In this paper we report the rapid phosphorylation of a cytosolic 100 kDa protein during stimulation of secretion from dispersed aggregates of parotid acinar cells with Ca(2+)-mobilizing secretagogues (carbachol, Substance P, ATP and the Ca2+ ionophore A23187). Phosphorylation was inhibited by removal of extracellular Ca2+ but was not observed during stimulation with phorbol esters, suggesting that this protein is not a substrate for protein kinase C. Two-dimensional PAGE and immunoprecipitation with a specific antiserum indicated that this protein is elongation factor 2, whose Ca2+ calmodulin-dependent phosphorylation has been shown to inhibit protein synthesis [Nairn & Palfrey (1987) J. Biol. Chem. 262, 17299-17303]. These results suggest that phosphorylation of elongation factor 2 is the molecular mechanism for the inhibition of protein synthesis which has been previously observed in rat parotid cells during stimulation with Ca(2+)-mobilizing secretagogues.

Regulation and roles of elongation factor 2 kinase

2015 ◽  
Vol 43 (3) ◽  
pp. 328-332 ◽  
Author(s):  
Christopher G. Proud
Keyword(s):  
Protein Synthesis ◽  
Elongation Factor ◽  
Mrna Translation ◽  
Inhibit Protein Synthesis ◽  
Potential Therapeutic Target ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor ◽  
Nutrient Consumption ◽  
Almost All

Eukaryotic elongation factor 2 kinase (eEF2K) belongs to the small family of atypical protein kinases termed α-kinases, and is the only calcium/calmodulin (Ca/CaM)-dependent member of that group. It phosphorylates and inactivates eEF2, to slow down the rate of elongation, the stage in mRNA translation that consumes almost all the energy and amino acids consumed by protein synthesis. In addition to activation by Ca/CaM, eEF2K is also regulated by an array of other regulatory inputs, which include inhibition by the nutrient- and growth-factor activated signalling pathways. Recent evidence shows that eEF2K plays an important role in learning and memory, processes that require the synthesis of new proteins and involve Ca-mediated signalling. eEF2K is activated under conditions of nutrient and energy depletion. In cancer cells, or certain tumours, eEF2K exerts cytoprotective effects, which probably reflect its ability to inhibit protein synthesis, and nutrient consumption, under starvation conditions. eEF2K is being evaluated as a potential therapeutic target in cancer.

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.

scholarly journals Properties of receptor-controlled inositol trisphosphate formation in parotid acinar cells

1985 ◽  
Vol 225 (1) ◽  
pp. 263-266 ◽  
Author(s):  
D L Aub ◽  
J W Putney
Keyword(s):  
Inositol Phosphates ◽  
Inositol Trisphosphate ◽  
Calcium Ionophore ◽  
Acinar Cells ◽  
Receptor Occupancy ◽  
Parotid Acinar Cells ◽  
Parotid Cells ◽  
Rat Parotid ◽  
K Release ◽  
Substance P Receptors

Activation of muscarinic receptors in rat parotid cells results in breakdown of polyphosphoinositides liberating inositol phosphates, including inositol trisphosphate. Formation of inositol trisphosphate appears independent of agonist-induced Ca2+ mobilization, since neither formation nor degradation of inositol trisphosphate are appreciably altered in low-calcium media, and elevation of cytosolic Ca2+ with a calcium ionophore does not cause an increase in cellular inositol trisphosphate. Further, activation of substance P receptors and alpha 1-adrenoreceptors, but not beta-adrenoreceptors, increases inositol trisphosphate formation. The dose-response curve for methacholine activation of inositol trisphosphate formation more closely approximates the curve for receptor occupancy than for Ca2+-activated K+ release. These results are all consistent with the suggestion that inositol trisphosphate could function as a second messenger linking receptor occupation to cellular Ca2+ mobilization.

cAMP-dependent activation of protein synthesis correlates with dephosphorylation of elongation factor 2

FEBS Letters ◽  
1988 ◽  
Vol 228 (2) ◽  
pp. 327-331 ◽  
Author(s):  
A.S. Sitikov ◽  
P.N. Simonenko ◽  
E.A. Shestakova ◽  
A.G. Ryazanov ◽  
L.P. Ovchinnikov
Keyword(s):  
Protein Synthesis ◽  
Elongation Factor ◽  
Elongation Factor 2

scholarly journals Translation elongation factor 2 depletion by siRNA in mouse liver leads to mTOR-independent translational upregulation of ribosomal protein genes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maxim V. Gerashchenko ◽  
Mikhail V. Nesterchuk ◽  
Elena M. Smekalova ◽  
Joao A. Paulo ◽  
Piotr S. Kowalski ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mammalian Cells ◽  
Ribosomal Proteins ◽  
Mouse Liver ◽  
Negative Impact ◽  
Elongation Factor ◽  
Ribosome Profiling ◽  
Translation Elongation Factor ◽  
Translation Elongation ◽  
Elongation Factor 2

Abstract Due to breakthroughs in RNAi and genome editing methods in the past decade, it is now easier than ever to study fine details of protein synthesis in animal models. However, most of our understanding of translation comes from unicellular organisms and cultured mammalian cells. In this study, we demonstrate the feasibility of perturbing protein synthesis in a mouse liver by targeting translation elongation factor 2 (eEF2) with RNAi. We were able to achieve over 90% knockdown efficacy and maintain it for 2 weeks effectively slowing down the rate of translation elongation. As the total protein yield declined, both proteomics and ribosome profiling assays showed robust translational upregulation of ribosomal proteins relative to other proteins. Although all these genes bear the TOP regulatory motif, the branch of the mTOR pathway responsible for translation regulation was not activated. Paradoxically, coordinated translational upregulation of ribosomal proteins only occurred in the liver but not in murine cell culture. Thus, the upregulation of ribosomal transcripts likely occurred via passive mTOR-independent mechanisms. Impaired elongation sequesters ribosomes on mRNA and creates a shortage of free ribosomes. This leads to preferential translation of transcripts with high initiation rates such as ribosomal proteins. Furthermore, severe eEF2 shortage reduces the negative impact of positively charged amino acids frequent in ribosomal proteins on ribosome progression.

Angiotensin II regulates phosphorylation of translation elongation factor-2 in cardiac myocytes

2001 ◽  
Vol 281 (1) ◽  
pp. H161-H167 ◽  
Author(s):  
Allen D. Everett ◽  
Tamara D. Stoops ◽  
Angus C. Nairn ◽  
David Brautigan
Keyword(s):  
Protein Synthesis ◽  
Angiotensin Ii ◽  
Cardiac Myocytes ◽  
Elongation Factor ◽  
Protein Translation ◽  
Mitogen Activated Protein Kinase ◽  
Ang Ii ◽  
Elongation Factor 2 ◽  
Mitogen Activated Protein ◽  
20 Nm

Increased protein synthesis is the cardinal feature of cardiac hypertrophy. We have studied angiotensin II (ANG II)-dependent regulation of eukaryotic elongation factor-2 (eEF-2), an essential component of protein translation required for polypeptide elongation, in rat neonatal cardiac myocytes. eEF2 is fully active in its dephosphorylated state and is inhibited following phosphorylation by eEF2 kinase. ANG II treatment (10−10–10−7 M) for 30 min produced an AT1 receptor-specific and concentration- and time-dependent reduction in the phosphorylation of eEF-2. Protein phosphatase 2A (PP2A) inhibitors okadaic acid and fostriecin, but not the PP2B inhibitor FK506, attenuated ANG II-dependent dephosphorylation of eEF-2. ANG II activated mitogen-activated protein kinase, (MAPK) within 10 min of treatment, and blockade of MAPK activation with PD-98059 (1–20 nM) inhibited eEF-2 dephosphorylation. The effect of ANG II on eEF-2 dephosphorylation was also blocked by LY-29004 (1–20 nM), suggesting a role for phosphoinositide 3-kinase, but the mammalian target rapamycin inhibitor rapamycin (10–100 nM) had no effect. Together these results suggest that the ANG II-dependent increase in protein synthesis includes activation of eEF-2 via dephosphorylation by PP2A by a process that involves both PI3K and MAPK.

Phorbol esters stimulate somatostatin release from cultured cells

1986 ◽  
Vol 250 (5) ◽  
pp. G686-G690 ◽  
Author(s):  
K. Sugano ◽  
J. Park ◽  
A. Soll ◽  
T. Yamada
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Cultured Cells ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Ionophore A23187 ◽  
Muscarinic Agonists ◽  
Kinase C ◽  
Somatostatin Cells

Recent studies suggest that 12-O-tetradecanoylphorbol 13-acetate (TPA), one of a family of phorbol esters that are known tumor promoters, can activate intracellular Ca2+, phospholipid-dependent protein kinase (protein kinase C) directly. To examine the possible involvement of protein kinase C-mediated mechanisms in regulating gastric somatostatin release, we studied the effects of TPA on isolated enriched canine gastric somatostatin cells in short-term culture. TPA markedly stimulated somatostatin release such that nearly 10% of total cellular content of somatostatin was released into media within 2 h of incubation. Among the phorbol compounds tested, TPA was the most potent, with half-maximum effective dose (ED50) obtained at a dose of 5 X 10(-9) M. Phorbol 12,13-dibutyrate (PDBu) also stimulated somatostatin release but with only 5% of the potency of TPA, whereas phorbol compounds with no biological activity in other systems failed to stimulate somatostatin release. In the absence of extracellular Ca2+, the effects of TPA were significantly attenuated. In contrast, stimulation of somatostatin release by forskolin (10(-4) M) was not affected by Ca2+ deprivation but was potentiated by TPA. No such potentiation was observed when TPA was combined with the Ca2+ ionophore A23187. Carbamylcholine (10(-5) M), which inhibits the stimulatory actions of beta-adrenergic agonists or dibutyryl cyclic adenosine monophosphate on somatostatin cells, also inhibited TPA-induced somatostatin release. These data suggest the presence of dual stimulatory mechanisms for gut somatostatin release, both of which are susceptible to inhibition by muscarinic agonists.

Eukaryotic elongation factor-2 (eEF-2) activity in bovine mammary tissue in relation to milk protein synthesis

2002 ◽  
Vol 69 (2) ◽  
pp. 205-212 ◽  
Author(s):  
CLAUS T. CHRISTOPHERSEN ◽  
JAKOB KARLSEN ◽  
METTE O. NIELSEN ◽  
BENT RIIS
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Diphtheria Toxin ◽  
Milk Protein ◽  
Elongation Factor ◽  
Mammary Tissue ◽  
Limiting Factor ◽  
Elongation Factor 2 ◽  
High Level

The amount of protein synthesis translational elongation factor 2 (eEF-2) was estimated employing diphtheria toxin-dependent ADP-ribosylation in samples prepared from small amounts of tissue from mammary gland, skeletal muscle and liver from lactating dairy cows. A very high level of ADP-ribosylatable eEF-2 was found in mammary gland, amounting to 20-times the level found in liver and 50-times the level found in skeletal muscle. This obviously reflects the high protein synthesis activity in mammary tissue. To our knowledge, similar high activities have previously been reported only for cancer cells. A close linear relationship was found between the amount of diphtheria-toxin catalysed ADP-ribosylated eEF-2 and protein and casein output in milk from cows in late lactation. This strongly suggests that eEF-2 may be a limiting factor in milk protein synthesis.

scholarly journals Protein kinase C-dependent and -independent mechanisms regulating the parotid substance P receptor as revealed by differential effects of protein kinase C inhibitors

1988 ◽  
Vol 256 (2) ◽  
pp. 677-680 ◽  
Author(s):  
H Sugiya ◽  
J W Putney
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Substance P ◽  
Time Course ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Substance P Receptor ◽  
Rat Parotid

Substance P-induced inositol trisphosphate (InsP3) formation was inhibited by 1 microM-4 beta-phorbol 12,13-dibutyrate (PDBu) in rat parotid acinar cells. The inhibitory effect of PDBu was reversed by the protein kinase C inhibitors H-7 or K252a. Substance P also elicits a persistent desensitization of subsequent substance P-stimulated InsP3 formation. However, this desensitization was not inhibited by H-7. In addition, H-7 had no effect on the time course of substance P-induced InsP3 formation. These results suggest that, although activation of protein kinase C by phorbol esters can inhibit the substance P receptor-linked phospholipase C pathway, this mechanism apparently plays little, if any, role in regulating this system after activation by substance P.

Sign in / Sign up

Export Citation Format

Share Document