Elongation factor 2 as the target of the reaction product between sodium selenite and glutathione (GSSeSG) in the inhibiting of amino acid incorporation in vitro

Vernie, L.N.; Bont, W.S.; Ginjaar, H.B.; Emmelot, P.

doi:10.1016/0005-2787(75)90167-7

Cited by 25 publications

(9 citation statements)

References 10 publications

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“…The lack of effect in intact HeLa cells was verified by 32P-labeling analysis. Polysome analysis showed that ribosomes remained in polysomes in selenite-treated cells in which protein synthesis was inhibited by >90%, indicating that the primary block was at the level of elongation, as previously reported by Vernie et al (29). The differing results may be due to selenite having different effects on intact cells versus cell lysate systems.…”

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confidence: 77%

Initiation factor protein modifications and inhibition of protein synthesis.

Duncan¹

1987

Mol. Cell. Biol.

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The protein covalent modification state of eucaryotic initiation factors eIF-2 and eIF-4B in HeLa cells was examined after they were exposed to a variety of conditions or treatments that regulate protein synthesis. A few factors (e.g., variant pH and sodium fluoride) altered the phosphorylation state of the initiation factor proteins, but the majority (hypertonic medium, ethanol, dimethyl sulfoxide, sodium selenite, sodium azide, and colchicine) had no effect on either protein. While initiation factor phosphorylation may regulate protein synthesis in response to many physiological situations, other pathways can regulate protein synthesis under nonphysiological circumstances.The rate of protein synthesis in mammalian cells can be regulated by a variety of physiological (4,8,12,15) and nonphysiological (28) treatments. Inhibition principally occurs at the initiation phase (16,22), wherein Met-tRNA, ribosomal subunits, and mRNA associate to form the translationally active ribosome. Each of the initiation steps requires or is promoted by one or more protein cofactors, called eucaryotic initiation factors, which transiently associate with the translational machinery during the initiation process (20,22).These protein factors are, a priori, likely candidates to serve as regulatory molecules. Substantial evidence indicates that phosphorylation of 20 to 30% of the eIF-2a molecules leads to a protein synthesis inhibition of greater than 75% in rabbit reticulocytes (11, 16) and probably in other eucaryotic cells as well (6,8,27). We and others have shown that covalent modification or cleavage of initiation factor proteins correlates with an inhibition of protein synthesis in a variety of instances including hemin deprivation (11), nutrient deprivation (8), heat shock (3, 6, 9), and poliovirus infection (10). Although it now seems clear that initiation factors play a role in translational control in some situations, it remains to be determined how frequently modulations of initiation rate are mediated by eIF-2a phosphorylation and how many of the factors can serve as controlling elements.Using rapid, sensitive qualitative and quantitative techniques for examining covalent modification of the initiation factor proteins (5), we have shown that eIF-2a, eIF-2p, eIF-4B, and eIF-4Fp28 (CBP-I) are covalently altered when translation is inhibited in HeLa cells by either heat shock (6, 8a) or serum depletion (8). Both treatments induced parallel initiation factor changes, suggesting the existence of a common response pathway that could be linked to many dissimilar stimuli. We initiated the present study to extend our survey of initiation factor status during translational inhibitions.The initiation process is inhibited by increasing the tonicity of the growth medium (24). Excess NaCl (125 mM) inhibits by >95% the incorporation of amino acids into protein by HeLa cells (data not shown). In these and subsequent experiments, cytoplasmic lysates prepared from inhibited cells were analyzed by isoelectric focusing/sodium * Corresponding ...

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supporting

confidence: 77%

Initiation factor protein modifications and inhibition of protein synthesis.

Duncan¹

1987

Mol. Cell. Biol.

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“…Frenkel et al [65] have demonstrated that DNA polymerase a was inhibited by 1 pAf selenotrisulfide. This demonstration fits nicely with the observa tions of selenotrisulfide inhibition of protein synthesis [48,69] and cell growth [70], The data on the possible effects of selenotrisulfides on cell metabolism certainly warrant further investigation. Although there are se rious caveats to some of the other experi ments (see disussion on page 4), these path ways represent feasible mechanisms of sele nium action.…”

Section: Possible Mechanisms Of Selenium Actionsupporting

confidence: 59%

“…For in stance, selenium has been reported to inhibit calmodulin/Ca++-dependent protein kinases [45]; however, the apparent K, of the reac- In addition to concentration and form of selenite, the assay systems for evaluation of a selenium effect need to be carefully consid ered. Duncan and Hershey [46] demon strated convincingly that sodium selenite did not increase phosphorylation of eukaryotic initiation factor (eIF-2a) in intact HeLa cells, which was contrary to results obtained in a reticulocyte lysate system [47], The pri mary block in protein synthesis was on elon gation factor as suggested previously [48]. This experiment stresses the importance of evaluating selenium under physiological conditions in contrast to nonphysiological conditions.…”

Section: Possible Mechanisms Of Selenium Actioncontrasting

confidence: 50%

“…However, in one experiment, inhibition of cell growth was accompanied by inhibition of protein syn thesis under conditions where DNA and RNA synthesis was not altered [63,64]. The inhibition of protein synthesis was corre lated with inhibition of elongation factor 2 [48,64] but not eukaryotic initiation factor 2 [46].…”

Section: Possible Mechanisms Of Selenium Actionmentioning

confidence: 97%

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Current Ideas on Selenium as a Chemopreventive Agent

Medina

Morrison

1988

Path Immunopathol Res

102

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“…13) However, the intracellular selenite reduction system is still unknown. Thus far, the stepwise reduction of selenite by glutathione (GSH) 14) or thioredoxin reductase (TrxR) 15) has been suggested to be involved in intracellular selenite reduction. However, Talbot et al demonstrated that TrxR knockdown does not affect the incorporation of selenium into selenoproteins in lung adenocarcinoma cells.…”

mentioning

confidence: 99%

Glutathione contributes to the efflux of selenium from hepatoma cells

Imai

Kurihara

Esaki

et al. 2014

Bioscience, Biotechnology, and Biochemistry

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Selenite is a selenium source for selenoprotein biosynthesis in mammalian cells. Although previous studies have suggested the involvement of glutathione (GSH) and/or thioredoxin reductase in selenite metabolism, intracellular selenite metabolism remains largely unknown. Here, we report that GSH depletion did not affect the amount of selenoprotein in Hepa 1-6 cells, suggesting that GSH does not play a central role in the reduction of selenite in selenoprotein biosynthesis. On the other hand, we found that GSH is involved in the efflux of low-molecular-weight selenium compounds from cells, presumably via the formation of selenodiglutathione. Moreover, selenite inhibited the efflux of a fluorescent bimane-GS conjugate that is mediated by ATP-dependent multidrug-resistant proteins, implying the existence of an active transporter for selenodiglutathione. This is the first report demonstrating that GSH plays a role in selenium excretion from cells by forming a GSH-conjugate, which may contribute to the distribution, detoxification, and homeostasis of selenium in the body.

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Elongation factor 2 as the target of the reaction product between sodium selenite and glutathione (GSSeSG) in the inhibiting of amino acid incorporation in vitro

Cited by 25 publications

References 10 publications

Initiation factor protein modifications and inhibition of protein synthesis.

Initiation factor protein modifications and inhibition of protein synthesis.

Current Ideas on Selenium as a Chemopreventive Agent

Glutathione contributes to the efflux of selenium from hepatoma cells

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