scholarly journals Inhibition of protein synthesis and early protein processing by thapsigargin in cultured cells

1993 ◽  
Vol 289 (1) ◽  
pp. 71-79 ◽  
Author(s):  
W L Wong ◽  
M A Brostrom ◽  
G Kuznetsov ◽  
D Gmitter-Yellen ◽  
C O Brostrom
Keyword(s):  
Protein Synthesis ◽  
Mammalian Cells ◽  
Cultured Cells ◽  
Extracellular Fluid ◽  
Mrna Translation ◽  
Protein Processing ◽  
Pituitary Cells ◽  
Translational Initiation ◽  
Early Protein ◽  
Inhibition Of Protein Synthesis

Thapsigargin, a tumour-promoting sesquiterpene lactone, selectively inhibits the Ca(2+)-ATPase responsible for Ca2+ accumulation by the endoplasmic reticulum (ER). Mobilization of ER-sequestered Ca2+ to the cytosol and to the extracellular fluid subsequently ensues, with concomitant alteration of cellular functions. Thapsigargin was found to serve as a rapid, potent and efficacious inhibitor of amino acid incorporation in cultured mammalian cells. At concentrations mobilizing cell-associated Ca2+ to the extracellular fluid, thapsigargin provoked extensive inhibition of protein synthesis within 10 min. The inhibition in GH3 pituitary cells involved the synthesis of almost all polypeptides, was not associated with increased cytosolic free Ca2+ concentration ([Ca2+]i), and was not reversed at high extracellular Ca2+. The transient rise in [Ca2+]i triggered by ionomycin was diminished by thapsigargin. Polysomes failed to accumulate in the presence of the drug, indicative of impaired translational initiation. With longer (1-3 h) exposures to thapsigargin, recovery of translational activity was observed accompanied by increased synthesis of the ER protein glucose-regulated stress protein 78 or immunoglobulin heavy-chain binding protein (‘GRP78/BiP’) and its mRNA. Such inductions were comparable with those observed previously with Ca2+ ionophores which mobilize the cation from all intracellular sequestered sites. Actin mRNA concentrations declined significantly during such treatments. In HepG2 cells processing and secretion of the glycoprotein alpha 1-antitrypsin were rapidly suppressed by thapsigargin. Ca2+ sequestered specifically by the ER is concluded to be essential for optimal protein synthesis and processing. These rapid effects of thapsigargin on mRNA translation, protein processing and gene expression should be considered when evaluating potential mechanisms by which this tumour promoter influences cellular events.

scholarly journals Bacterial Ribonuclease MazF-Mediated Apoptosis as Potential Cancer Therapy

2021 ◽  
Author(s):  
Maryam Saffarian Abbas Zadeh ◽  
Rebecca Anne MacPherson ◽  
Guohui Huang ◽  
Hui Ding ◽  
Rhonda Reigers Powell ◽  
...  
Keyword(s):  
Cell Death ◽  
Protein Synthesis ◽  
Cell Lines ◽  
Mrna Translation ◽  
Protein Translation ◽  
Programmed Death ◽  
Inhibition Of Protein Synthesis ◽  
Cancer Agent ◽  
Cell Suicide ◽  
The Impact

Abstract Programmed cell death is a dynamic and critical mechanism of cell suicide in eukaryotes and prokaryotes. MazF is a ribonuclease protein involved in bacterial intracellular programmed death. This protein cleaves mRNAs at ACA sequences, leading to inhibition of protein synthesis and triggering cell death. Given that cancer is heterogenic and has varied susceptibility to treatment, we examined the impact of MazF proteins on the growth and viability of three cancer cell lines: MCF7, HT29, and AGS. These cell lines were transfected with ACA-less mazF mRNAs and evaluated for MazF-mediated cell death. The data illustrated that efficient MazF translation leads to a significant reduction in cell viability and is modulated by structural elements of ACA-less mazF mRNAs. In the presence of MazF, the levels of activated caspase-3 and -7 were significantly elevated in transfected cells, confirming the occurrence of apoptosis. We also quantified mRNA translation on a single-cell basis in MCF7 and AGS cell lines to examine MazF-mediated inhibition of protein synthesis. MazF expression significant decreases the levels of protein translation in the examined cell lines. This is the first report of MazF as a potential anti-cancer agent via induction of apoptosis in MCF7, AGS, and HT-29 cell lines.

scholarly journals DNA replication in mammalian cells. Altered patterns of initiation during inhibition of protein synthesis.

1975 ◽  
Vol 67 (3) ◽  
pp. 761-773 ◽  
Author(s):  
R Hand
Keyword(s):  
Protein Synthesis ◽  
Dna Replication ◽  
Antibiotic Treatment ◽  
Mammalian Cells ◽  
Specific Activity ◽  
High Specific Activity ◽  
Normal Pattern ◽  
Inhibition Of Protein Synthesis ◽  
Initiation Of Dna Replication ◽  
Cellular Dna

The effects of inhibition of protein synthesis by the antibiotics cycloheximide and puromycin on the initiation of DNA replication in mouse L cells were studied. Cellular DNA was pulse labeled with [3H]thymidine of high, then of low specific activity and prepared for fiber autoradiography. Autoradiograms containing multiple (up to four) replication units were analyzed. In control cells, the proportion of replication units that initiated during a 10-min, high specific activity pulse was approximately equal to the proportion initiating immediately before the pulse. The addition of cycloheximide or puromycin at the start of the pulse inhibited the frequency of initiation in that there was a decrease by up to one-third of units initiating during the pulse relative to controls. Replication direction was also altered. Addition of the antibiotics 2 h before the pulse reduced the proportion of bidirectional units observed from 0.98 to 0.70. Antibiotic treatment for 2 h also decreased initiation synchrony in that the proportion of multiunit autoradiograms on which neighboring units showed similar replication patterns (indicating temporally coordinated initiation) was reduced by one-half. These observations indicate that inhibition of protein synthesis alters the normal pattern of DNA initiation.

scholarly journals mTORC1 signalling and eIF4E/4E-BP1 translation initiation factor stoichiometry influence recombinant protein productivity from GS-CHOK1 cells

2016 ◽  
Vol 473 (24) ◽  
pp. 4651-4664 ◽  
Author(s):  
Lyne Jossé ◽  
Jianling Xie ◽  
Christopher G. Proud ◽  
C. Mark Smales
Keyword(s):  
Protein Synthesis ◽  
Cell Growth ◽  
Recombinant Protein ◽  
Cell Lines ◽  
Translation Initiation ◽  
Mammalian Cells ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cho Cell

Many protein-based biotherapeutics are produced in cultured Chinese hamster ovary (CHO) cell lines. Recent reports have demonstrated that translation of recombinant mRNAs and global control of the translation machinery via mammalian target of rapamycin (mTOR) signalling are important determinants of the amount and quality of recombinant protein such cells can produce. mTOR complex 1 (mTORC1) is a master regulator of cell growth/division, ribosome biogenesis and protein synthesis, but the relationship between mTORC1 signalling, cell growth and proliferation and recombinant protein yields from mammalian cells, and whether this master regulating signalling pathway can be manipulated to enhance cell biomass and recombinant protein production (rPP) are not well explored. We have investigated mTORC1 signalling and activity throughout batch culture of a panel of sister recombinant glutamine synthetase-CHO cell lines expressing different amounts of a model monoclonal IgG4, to evaluate the links between mTORC1 signalling and cell proliferation, autophagy, recombinant protein expression, global protein synthesis and mRNA translation initiation. We find that the expression of the mTORC1 substrate 4E-binding protein 1 (4E-BP1) fluctuates throughout the course of cell culture and, as expected, that the 4E-BP1 phosphorylation profiles change across the culture. Importantly, we find that the eIF4E/4E-BP1 stoichiometry positively correlates with cell productivity. Furthermore, eIF4E amounts appear to be co-regulated with 4E-BP1 amounts. This may reflect a sensing of either change at the mRNA level as opposed to the protein level or the fact that the phosphorylation status, as well as the amount of 4E-BP1 present, is important in the co-regulation of eIF4E and 4E-BP1.

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