Rapamycin-insensitive mTORC1 activity controls eIF4E:4E-BP1 binding

Livingstone, Mark; Bidinosti, Michael

doi:10.12688/f1000research.1-4.v1

Cited by 34 publications

(30 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They also noted prolonged dephosphorylation of 4E‐BP1 and a diminished polysome profile in response to rapamycin treatment. This is in contrast to our findings (and those of others [33, 35, 43, 44]) where dephosphorylation of 4E‐BP1 and translation are relatively rapamycin‐resistant events. As Courtes et al suggest, this may be due to the differences in cell type and highlights that further studies are required to define the details of molecular and biological response for other recombinant CHO cell lines (differing in terms of lineage, selection system, product and growth/productivity profile).…”

Section: Discussionsupporting

(Expert classified)

Chemical manipulation of the mTORC1 pathway in industrially relevant CHOK1 cells enhances production of therapeutic proteins

Dadehbeigi

Dickson

2015

Biotechnology Journal

View full text Add to dashboard Cite

The mammalian target of rapamycin complex 1 (mTORC1) is known as a central coordinator of protein synthesis and cell growth in response to the cellular environment. In this work, chemical manipulation of mTORC1 pathway was employed to enhance mAb production as well as increase understanding of intracellular pathways in GS-CHOK1 cells. Using the phosphorylation status of mTORC1 downstream targets, S6K1 and 4E-BP1, as read-outs of mTORC1 activity, we investigated the contribution of each target protein to growth and/or productivity. Inoculation of cultures in the presence of rapamycin, a specific inhibitor of mTORC1, increased viability and final titer. The initial increase in specific productivity and inhibition of growth by rapamycin correlated with diminished phospho-S6K1. However, inhibition was transient and cells recovered by unknown mechanisms. In contrast, phosphorylation of 4E-BP1 was preserved in response to rapamycin. Finally, we examined the activity of mTORC1 after addition of a custom-designed feed. Feeding led to substantial increase in growth and productivity and the phosphorylation of both targets was elevated. Though many details of mTORC1 signaling in CHO cells remain to be clarified, we have provided evidence that environmental manipulation of the mTORC1 pathway correlates with changes in cell growth and recombinant protein production.

show abstract

Section: Discussionsupporting

(Expert classified)

Chemical manipulation of the mTORC1 pathway in industrially relevant CHOK1 cells enhances production of therapeutic proteins

Dadehbeigi

Dickson

2015

Biotechnology Journal

View full text Add to dashboard Cite

show abstract

“…Rapamycin, although effective in inhibiting the S6 kinase arm of the mTORC1 signaling pathway, is relatively ineffective in its ability to induce 5= cap binding through steric hindrance of 4E-BP1 phosphorylation (7,26). One explanation for the discordant effects of rapamycin on fetal translation is a difference in the effect of the drug on 4E-BP1.…”

Section: R29 Regulation Of Hepatic Translation By Mtormentioning

confidence: 99%

Profiling of the fetal and adult rat liver transcriptome and translatome reveals discordant regulation by the mechanistic target of rapamycin (mTOR)

Boylan

Sanders

Neretti

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

of the fetal and adult rat liver transcriptome and translatome reveals discordant regulation by the mechanistic target of rapamycin (mTOR). Am J Physiol Regul Integr Comp Physiol 309: R22-R35, 2015. First published April 29, 2015 doi:10.1152/ajpregu.00114.2015.-The mechanistic target of rapamycin (mTOR) integrates growth factor signaling, nutrient abundance, cell growth, and proliferation. On the basis of our interest in somatic growth in the late gestation fetus, we characterized the role of mTOR in the regulation of hepatic gene expression and translation initiation in fetal and adult rats. Our strategy was to manipulate mTOR signaling in vivo and then characterize the transcriptome and translating mRNA in liver tissue. In adult rats, we used the nonproliferative growth model of refeeding after a period of fasting and the proliferative model of liver regeneration following partial hepatectomy. We also studied livers from preterm fetal rats (embryonic day 19) in which fetal hepatocytes are asynchronously proliferating. All three models employed rapamycin to inhibit mTOR signaling. Analysis of the transcriptome in fasted-refed animals showed rapamycin-mediated induction of genes associated with oxidative phosphorylation. Genes associated with RNA processing were downregulated. In liver regeneration, rapamycin induced genes associated with lysosomal metabolism, steroid metabolism, and the acute phase response. In fetal animals, rapamycin inhibited expression of genes in several functional categories that were unrelated to effects in the adult animals. Translation control showed marked fetal-adult differences. In both adult models, rapamycin inhibited the translation of genes with complex 5= untranslated regions, including those encoding ribosomal proteins. Fetal translation was resistant to the effects of rapamycin. We conclude that the mTOR pathway in liver serves distinct physiological roles in the adult and fetus, with the latter representing a condition of rapamycin resistance.

show abstract

“…Rapamycin has been reported to partially inhibit mTORC1 signaling as it ineffectively inhibits 4E-BP1 phosphorylation 44 . Indeed, siRNA knockdown of S6RP or 5 nM rapamycin effectively suppressed S6RP phosphorylation but upregulated 4E-BP1 phosphorylation (Fig.…”

Section: Resultsmentioning

confidence: 99%

Co-inhibition of mTORC1, HDAC and ESR1α retards the growth of triple-negative breast cancer and suppresses cancer stem cells

et al. 2018

View full text Add to dashboard Cite

Triple-negative breast cancer (TNBC) is the most refractory subtype of breast cancer. It causes the majority of breast cancer-related deaths, which has been largely associated with the plasticity of tumor cells and persistence of cancer stem cells (CSCs). Conventional chemotherapeutics enrich CSCs and lead to drug resistance and disease relapse. Development of a strategy capable of inhibiting both bulk and CSC populations is an unmet medical need. Inhibitors against estrogen receptor 1, HDACs, or mTOR have been studied in the treatment of TNBC; however, the results are inconsistent. In this work, we found that patient TNBC samples expressed high levels of mTORC1 and HDAC genes in comparison to luminal breast cancer samples. Furthermore, co-inhibition of mTORC1 and HDAC with rapamycin and valproic acid, but neither alone, reproducibly promoted ESR1 expression in TNBC cells. In combination with tamoxifen (inhibiting ESR1), both S6RP phosphorylation and rapamycin-induced 4E-BP1 upregulation in TNBC bulk cells was inhibited. We further showed that fractionated CSCs expressed higher levels of mTORC1 and HDAC than non-CSCs. As a result, co-inhibition of mTORC1, HDAC, and ESR1 was capable of reducing both bulk and CSC subpopulations as well as the conversion of fractionated non-CSC to CSCs in TNBC cells. These observations were partially recapitulated with the cultured tumor fragments from TNBC patients. Furthermore, co-administration of rapamycin, valproic acid, and tamoxifen retarded tumor growth and reduced CD44high/+/CD24low/− CSCs in a human TNBC xenograft model and hampered tumorigenesis after secondary transplantation. Since the drugs tested are commonly used in clinic, this study provides a new therapeutic strategy and a strong rationale for clinical evaluation of these combinations for the treatment of patients with TNBC.

show abstract

Rapamycin-insensitive mTORC1 activity controls eIF4E:4E-BP1 binding

Cited by 34 publications

References 38 publications

Chemical manipulation of the mTORC1 pathway in industrially relevant CHOK1 cells enhances production of therapeutic proteins

Chemical manipulation of the mTORC1 pathway in industrially relevant CHOK1 cells enhances production of therapeutic proteins

Profiling of the fetal and adult rat liver transcriptome and translatome reveals discordant regulation by the mechanistic target of rapamycin (mTOR)

Co-inhibition of mTORC1, HDAC and ESR1α retards the growth of triple-negative breast cancer and suppresses cancer stem cells

Contact Info

Product

Resources

About