Role of elongation factor 2 in regulating peptide-chain elongation in the heart

1994 ◽  
Vol 266 (4) ◽  
pp. E628-E634 ◽  
Author(s):  
T. C. Vary ◽  
A. Nairn ◽  
C. J. Lynch
Keyword(s):  
Protein Synthesis ◽  
Elongation Factor ◽  
Diabetic Rats ◽  
Peptide Chain ◽  
Chain Elongation ◽  
Translational Efficiency ◽  
Ribosomal Subunits ◽  
Elongation Factor 2 ◽  
Cardiac Muscles

Cardiac muscles of experimentally induced diabetic rats show a progressive decrease in the rate of protein synthesis. The decline in protein synthesis is associated with decreases in both the number and efficiency of cardiac ribosomes. In hearts from 48 h diabetic rats, the decrease in protein synthesis was accounted for solely by a 28% reduction in the ribosome content. In contrast, the inhibition of protein synthesis in hearts from 72 h diabetic rats resulted from a reduction in both the ribosome content (28%) and the translational efficiency (30%). The decreased translational efficiency was not associated with an increase of RNA in ribosomal subunits, indicating the defect resulted from an inhibition of peptide-chain elongation/termination. Diabetes of 72 h duration resulted in a 37% inhibition in the rate of peptide-chain elongation. The decreased rate of peptide-chain elongation was associated with a 66% reduction in the amount of elongation factor 2 (EF-2). Treatment of diabetic rats with insulin for 3 days was sufficient to reverse the effects of 72 h diabetes on protein synthesis, RNA content, and translational efficiency. Also, insulin therapy increased the EF-2 content of diabetic rats to control values. These studies suggest that decreased EF-2 content is a molecular mechanism for the impaired rates of peptide-chain elongation in diabetes.

Regulation of hepatic protein synthesis in chronic inflammation and sepsis

1992 ◽  
Vol 262 (2) ◽  
pp. C445-C452 ◽  
Author(s):  
T. C. Vary ◽  
S. R. Kimball
Keyword(s):  
Protein Synthesis ◽  
Sterile Inflammation ◽  
Chain Elongation ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Translational Efficiency ◽  
Liver Protein ◽  
Ribosomal Subunits ◽  
Hepatic Protein Synthesis

The regulation of protein synthesis was determined in livers from control, sterile inflammatory, and septic animals. Total liver protein was increased in both sterile inflammation and sepsis. The rate of protein synthesis in vivo was measured by the incorporation of [3H]phenylalanine into liver proteins in a chronic (5 day) intra-abdominal abscess model. Both sterile inflammation and sepsis increased total hepatic protein synthesis approximately twofold. Perfused liver studies demonstrated that the increased protein synthesis rate in vivo resulted from a stimulation in the synthesis of both secreted and nonsecreted proteins. The total hepatic RNA content was increased 40% only in sterile inflammation, whereas the translational efficiency was increased twofold only in sepsis. The increase in translational efficiency was accompanied by decreases in the amount of free 40S and 60S ribosomal subunits in sepsis. Rates of peptide-chain elongation in vivo were increased 40% in both sterile inflammation and sepsis. These results demonstrate that sepsis induces changes in the regulation of hepatic protein synthesis that are independent of the general inflammatory response. In sterile inflammation, the increase in protein synthesis occurs by a combination of increased capacity and translational efficiency, while in sepsis, the mechanism responsible for accelerated protein synthesis is an increased translational efficiency.

scholarly journals Inhibition by ricin of protein synthesis in vitro. Inhibition of the binding of elongation factor 2 and of adenosine diphosphate-ribosylated elongation factor 2 to ribosomes

1975 ◽  
Vol 146 (1) ◽  
pp. 127-131 ◽  
Author(s):  
L Montanaro ◽  
S Sperti ◽  
A Mattioli ◽  
G Testoni ◽  
F Stirpe
Keyword(s):  
Protein Synthesis ◽  
Binding Sites ◽  
Polypeptide Chain ◽  
Elongation Factor ◽  
Adenosine Diphosphate ◽  
Chain Elongation ◽  
Elongation Factor 2 ◽  
In Vitro Inhibition ◽  
Liver Ribosomes

The binding of EF2 (elongation factor 2) and of ADP-ribosyl-EF 2 to rat liver ribosomes is inhibited by ricin. This result suggests that the native enzyme and its ADP-ribose derivative have the same or closely related binding sites on the ribosome. The inhibition by ricin of the binding of EF 2 to ribosomes is consistent with the previous observation that ricin affects EF 2-catalysed translocation during polypeptide chain elongation.

scholarly journals Inhibition of protein synthesis in vitro by crotins and ricin. Effect on the steps of peptide chain elongation

1976 ◽  
Vol 156 (1) ◽  
pp. 7-13 ◽  
Author(s):  
S Sperti ◽  
L Montanaro ◽  
A Mattioli ◽  
G Testoni ◽  
F Stirpe
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Elongation Factor ◽  
Artemia Salina ◽  
Chain Elongation ◽  
Gtp Hydrolysis ◽  
Elongation Factor 2 ◽  
The Individual ◽  
Liver Ribosomes

The effects of crotin I and crotin II on the partial reactions of polypeptide chain elongation were investigated and compared with the known effects of ricin. Crotin II was a more powerful inhibitor than crotin I, but no qualitative differences between the two crotins were found. Rat liver ribosomes, preincubated with crotins and washed through sucrose gradients, remained inactive in protein synthesis. Among the individual steps of elongation, the peptidyltransferase reaction was unaffected by crotins, but some of the reactions that involve the interaction of elongation factors 1 and 2 with ribosomes were modified. A strong inhibition of the binding of elongation factor 2 to ribosomes and a stimulation of the elongation factor2-dependent GTP hydrolysis were observed; this indicates the formation of a very unstable elongation factor 2-GDP-ribosome complex, which, however, allows a single round of translocation to take place in the presence ofelongation factor 2 and added GTP. The elongation factor 1-dependent GTP hydrolysis was inhibited by crotins, whereas the enzymic binding of aminoacyl-tRNA, to both rat liver and Artemia salina ribosomes, was scarcely affected. In a protein-synthesizing system the inhibition by crotins and by ricin leads to a block of the nascent peptides on the ribosomal aminoacyl-tRNA site, an effect consistent with inhibition at the level of translocation. The mechanism of action of crotins appears to be very similar to that of ricin.

Sepsis-induced changes in protein synthesis: differential effects on fast- and slow-twitch muscles

1992 ◽  
Vol 262 (6) ◽  
pp. C1513-C1519 ◽  
Author(s):  
T. C. Vary ◽  
S. R. Kimball
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Peptide Chain ◽  
Chain Elongation ◽  
Translational Efficiency ◽  
Fiber Types ◽  
Chain Initiation ◽  
Inhibition Of Protein Synthesis ◽  
Slow Twitch ◽  
Fast Twitch

Sepsis is associated with severe muscle wasting. Mechanisms responsible for sepsis-induced alterations in muscle protein metabolism were investigated in vivo and compared with changes induced by nonseptic inflammation. The rate of protein synthesis in mixed hindlimb muscles was not altered in inflammation but was inhibited 50% in sepsis. This inhibition did not result from a decreased RNA content. Instead, the translational efficiency was significantly reduced by 50% in skeletal muscle of septic animals compared with control. The effect of sepsis to lower the rate of protein synthesis was further examined using individual muscles containing different fiber types. Both the protein concentration and protein synthetic rate in fast-twitch muscles were reduced by sepsis, whereas neither of these parameters was affected in slow-twitch muscles or heart. The decreased translational efficiency did not result from a change in the rate of peptide-chain elongation. Instead, the sepsis-induced inhibition of protein synthesis resulted from a restraint in peptide-chain initiation because sepsis caused a 1.6-fold increase in free ribosomal subunits. Overall, sepsis, but not inflammation, caused an inhibition of protein synthesis primarily in muscles composed of fast-twitch fibers. The mechanism involved in the reduced rates of protein synthesis in muscles resulted from an inhibition of peptide-chain initiation, with no change in peptide-chain elongation.

Regulation of peptide-chain initiation in muscle during sepsis by interleukin-1 receptor antagonist

1996 ◽  
Vol 271 (3) ◽  
pp. E513-E520 ◽  
Author(s):  
T. C. Vary ◽  
L. Voisin ◽  
R. N. Cooney
Keyword(s):  
Protein Synthesis ◽  
Receptor Antagonist ◽  
Interleukin 1 ◽  
Peptide Chain ◽  
Initiation Factor ◽  
Translational Efficiency ◽  
Ribosomal Subunits ◽  
Chain Initiation ◽  
Interleukin 1 Receptor Antagonist ◽  
Inhibition Of Protein Synthesis

The mechanism by which interleukin-1 (IL-1) regulates protein synthesis in skeletal muscle during hypermetabolic sepsis in rats was investigated. Treatment of septic rats with a specific interleukin-1 receptor antagonist (IL-1ra) prevented the sepsis-induced inhibition of protein synthesis and translational efficiency in gastrocnemius. Analysis of ribosomal subunits revealed that the increase in free 40S and 60S ribosomal subunits observed in septic rats was prevented by infusion of IL-1ra, indicating peptide-chain initiation was maintained at control values. The failure of sepsis to inhibit peptide-chain initiation after infusion of IL-1ra correlated with a maintenance of the epsilon-subunit of eukaryotic initiation factor (eIF) 2B (eIF-2B epsilon) protein at control values. The alterations in the eIF-2B epsilon protein content in gastrocnemius of septic rats treated with or without IL-1ra were associated with corresponding changes in the abundance of eIF 2B epsilon mRNA. The results provide evidence that infusion of IL-1ra attenuates the sepsis-induced inhibition of protein synthesis by preventing the inhibition of peptide-chain initiation and downregulation of eIF-2B expression during sepsis.

scholarly journals Translational Roles of Elongation Factor 2 Protein Lysine Methylation

2014 ◽  
Vol 289 (44) ◽  
pp. 30511-30524 ◽  
Author(s):  
Maria C. Dzialo ◽  
Kyle J. Travaglini ◽  
Sean Shen ◽  
Kevin Roy ◽  
Guillaume F. Chanfreau ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Synthesis ◽  
Elongation Factor ◽  
Amino Acid Sequences ◽  
Fine Tuning ◽  
Lysine Methylation ◽  
Translational Machinery ◽  
Elongation Factor 2 ◽  
Translational Apparatus

Methylation of various components of the translational machinery has been shown to globally affect protein synthesis. Little is currently known about the role of lysine methylation on elongation factors. Here we show that in Saccharomyces cerevisiae, the product of the EFM3/YJR129C gene is responsible for the trimethylation of lysine 509 on elongation factor 2. Deletion of EFM3 or of the previously described EFM2 increases sensitivity to antibiotics that target translation and decreases translational fidelity. Furthermore, the amino acid sequences of Efm3 and Efm2, as well as their respective methylation sites on EF2, are conserved in other eukaryotes. These results suggest the importance of lysine methylation modification of EF2 in fine tuning the translational apparatus.

scholarly journals Effects of antibody to 5 S-RNA-binding protein on protein synthesis in Artemia salina ribosomes

1989 ◽  
Vol 259 (1) ◽  
pp. 277-281 ◽  
Author(s):  
N Kenmochi ◽  
Y Takahashi ◽  
N L Sato
Keyword(s):  
Protein Synthesis ◽  
Rna Binding ◽  
Rna Binding Protein ◽  
Elongation Factor ◽  
Artemia Salina ◽  
Globin Mrna ◽  
Ribosomal Subunits ◽  
Elongation Factor 2 ◽  
Subunit Interface

The effects of an affinity-purified polyclonal antibody to Artemia salina ribosomal protein L5 on protein synthesis in vitro were examined. The antibody interacted with 60 S subunits more strongly than with 80 S ribosomes, and inhibited reassociation of ribosomal subunits to some extent at 5 mM-Mg2+ but not at 10 mM. Polyphenylalanine synthesis in vitro at 10 mM-Mg2+ was significantly inhibited, especially when the antibody was first preincubated with 60 S subunits prior to the assay. The incorporation of amino acid directed by globin mRNA was inhibited only when the preincubation with 60 S subunits was carried out. On the other hand, no effect was detected on elongation factor 2- and 60 S subunit-dependent uncoupled GTPase activity. These results suggest that L5 is probably located at or near the subunit interface and may play an important role in protein synthesis.

scholarly journals Regulation of protein-synthesis elongation-factor-2 kinase by cAMP in adipocytes

1998 ◽  
Vol 336 (3) ◽  
pp. 525-529 ◽  
Author(s):  
Tricia A. DIGGLE ◽  
Nicholas T. REDPATH ◽  
Kate J. HEESOM ◽  
Richard M. DENTON
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Polypeptide Chain ◽  
Elongation Factor ◽  
Chain Elongation ◽  
Translation Elongation Factor ◽  
Translation Elongation ◽  
Eukaryotic Translation ◽  
Elongation Factor 2 ◽  
Fold Activation

Treatment of primary rat epididymal adipocytes or 3T3-L1 adipocytes with various agents which increase cAMP led to the phosphorylation of eukaryotic translation elongation factor-2 (eEF-2). The increase in eEF-2 phosphorylation was a consequence of the activation of eEF-2 kinase (eEF-2K), which is a Ca2+/calmodulin-dependent kinase. eEF-2K was shown to be essentially inactive at less than 0.1 µM free Ca2+ when measured in cell-free extracts. Treatment of adipocytes with isoproterenol induced Ca2+-independent eEF-2K activity, and an 8–10-fold activation of eEF-2K was observed at Ca2+ concentrations of less than 0.1 µM. Increased cAMP in 3T3-L1 adipocytes led to the inhibition of total protein synthesis and decreased the rate of polypeptide-chain elongation. We also show that the phosphorylation of eEF-2 and the activity of eEF-2K are insulin-regulated in adipocytes. These results demonstrate a novel mechanism for the control of protein synthesis by hormones which act by increasing cytoplasmic cAMP.

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