scholarly journals Mifepristone increases mRNA translation rate, triggers the unfolded protein response, increases autophagic flux, and kills ovarian cancer cells in combination with proteasome or lysosome inhibitors

2016 ◽  
Vol 10 (7) ◽  
pp. 1099-1117 ◽  
Author(s):  
Lei Zhang ◽  
Maria B. Hapon ◽  
Alicia A. Goyeneche ◽  
Rekha Srinivasan ◽  
Carlos D. Gamarra-Luques ◽  
...  
Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1067
Author(s):  
Domenico Conza ◽  
Paola Mirra ◽  
Gaetano Calì ◽  
Luigi Insabato ◽  
Francesca Fiory ◽  
...  

Multiple lines of evidence suggest that metformin, an antidiabetic drug, exerts anti-tumorigenic effects in different types of cancer. Metformin has been reported to affect cancer cells’ metabolism and proliferation mainly through the activation of AMP-activated protein kinase (AMPK). Here, we show that metformin inhibits, indeed, endometrial cancer cells’ growth and induces apoptosis. More importantly, we report that metformin affects two important pro-survival pathways, such as the Unfolded Protein Response (UPR), following endoplasmic reticulum stress, and the WNT/β-catenin pathway. GRP78, a key protein in the pro-survival arm of the UPR, was indeed downregulated, while GADD153/CHOP, a transcription factor that mediates the pro-apoptotic response of the UPR, was upregulated at both the mRNA and protein level. Furthermore, metformin dramatically inhibited β-catenin mRNA and protein expression. This was paralleled by a reduction in β-catenin transcriptional activity, since metformin inhibited the activity of a TCF/LEF-luciferase promoter. Intriguingly, compound C, a well-known inhibitor of AMPK, was unable to prevent all these effects, suggesting that metformin might inhibit endometrial cancer cells’ growth and survival through the modulation of specific branches of the UPR and the inhibition of the Wnt/β-catenin pathway in an AMPK-independent manner. Our findings may provide new insights on the mechanisms of action of metformin and refine the use of this drug in the treatment of endometrial cancer.


2021 ◽  
Author(s):  
Christopher J Fields ◽  
Lu Li ◽  
Nicholas M Hiers ◽  
Tianqi Li ◽  
Peike Sheng ◽  
...  

MicroRNAs (miRNA) are short non-coding RNAs widely implicated in gene regulation. Most metazoan miRNAs utilize the RNase III enzymes Drosha and Dicer for biogenesis. One notable exception is the RNA polymerase II transcription start sites (TSS) miRNAs whose biogenesis does not require Drosha. The functional importance of the TSS-miRNA biogenesis is uncertain. To better understand the function of TSS-miRNAs, we applied a modified Crosslinking, Ligation, and Sequencing of Hybrids on Argonaute (AGO-qCLASH) to identify the targets for TSS-miRNAs in HCT116 colorectal cancer cells with or without DROSHA knockout. We observed that miR-320a hybrids dominate in TSS-miRNA hybrids identified by AGO-qCLASH. Targets for miR-320a are enriched in the eIF2 signaling pathway, a downstream component of the unfolded protein response. Consistently, in miR-320a mimic- and antagomir- transfected cells, differentially expressed genes are enriched in eIF2 signaling. Within the AGO-qCLASH data, we identified the endoplasmic reticulum (ER) chaperone Calnexin as a direct miR-320a target, thus connecting miR-320a to the unfolded protein response. During ER stress, but not amino acid deprivation, miR-320a up-regulates ATF4, a critical transcription factor for resolving ER stress. Our study investigates the targetome of the TSS-miRNAs in colorectal cancer cells and establishes miR-320a as a regulator of unfolded protein response.


2016 ◽  
Vol 36 (13) ◽  
pp. 1868-1880 ◽  
Author(s):  
David W. Reid ◽  
Angeline S. L. Tay ◽  
Jeyapriya R. Sundaram ◽  
Irene C. J. Lee ◽  
Qiang Chen ◽  
...  

Phosphorylation of eukaryotic initiation factor 2α (eIF2α) controls transcriptome-wide changes in mRNA translation in stressed cells. While phosphorylated eIF2α (P-eIF2α) attenuates global protein synthesis, mRNAs encoding stress proteins are more efficiently translated. Two eIF2α phosphatases, containing GADD34 and CReP, catalyze P-eIF2α dephosphorylation. The current view of GADD34, whose transcription is stress induced, is that it functions in a feedback loop to resolve cell stress. In contrast, CReP, which is constitutively expressed, controls basal P-eIF2α levels in unstressed cells. Our studies show that GADD34 drives substantial changes in mRNA translation in unstressed cells, particularly targeting the secretome. Following activation of the unfolded protein response (UPR), rapid translation ofGADD34mRNA occurs and GADD34 is essential for UPR progression. In the absence of GADD34, eIF2α phosphorylation is persistently enhanced and the UPR translational program is significantly attenuated. This “stalled” UPR is relieved by the subsequent activation of compensatory mechanisms that include AKT-mediated suppression of PKR-like kinase (PERK) and increased expression ofCRePmRNA, partially restoring protein synthesis. Our studies highlight the coordinate regulation of UPR by the GADD34- and CReP-containing eIF2α phosphatases to control cell viability.


2015 ◽  
Vol 6 (11) ◽  
pp. 1122-1127 ◽  
Author(s):  
Alpa Sidhu ◽  
Justin R. Miller ◽  
Ashootosh Tripathi ◽  
Danielle M. Garshott ◽  
Amy L. Brownell ◽  
...  

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