scholarly journals Gambogenic Acid Induces Endoplasmic Reticulum Stress in Colorectal Cancer via the Aurora A Pathway

2021 ◽  
Vol 9 ◽  
Author(s):  
Cheng Liu ◽  
Jiaxin Xu ◽  
Chenxu Guo ◽  
Xugang Chen ◽  
Chunmei Qian ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Aurora A ◽  
Eukaryotic Translation ◽  
Induced Apoptosis

Colorectal cancer (CRC) is one of the most common malignancies in the world and has a poor prognosis. In the present research, gambogenic acid (GNA), isolated from the traditional Chinese medicine gamboge, markedly induced apoptosis and inhibited the proliferation of CRC in vitro and in vivo. Furthermore, GNA triggered endoplasmic reticulum (ER) stress, which subsequently activated inositol-requiring enzyme (IRE) 1α and the eukaryotic translation initiation factor (eIF) 2α pathway. Pretreatment with salubrinal (an eIF2α inhibitor) rescued GNA-induced cell death. Furthermore, GNA downregulated the expression of Aurora A. The Aurora A inhibitor alisertib decreased ER stress. In human colorectal adenocarcinoma tissue, Aurora A was upregulated compared to normal colorectal epithelial nuclei. Furthermore, GNA ameliorated mouse colitis-associated cancer models. Our findings demonstrated that GNA significantly inhibited the proliferation of CRC through activation of ER stress by regulating Aurora A, which indicates the potential of GNA for preventing the progression of CRC.

scholarly journals The circular RNA circ-ERBIN promotes growth and metastasis of colorectal cancer by miR-125a-5p and miR-138-5p/4EBP-1 mediated cap-independent HIF-1α translation

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Liang-Yan Chen ◽  
Lian Wang ◽  
Yue-Xiang Ren ◽  
Zheng Pang ◽  
Yao Liu ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Protein Translation ◽  
Circular Rna ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Luciferase Reporter ◽  
Western Blots ◽  
Eukaryotic Translation

Abstract Background Circular RNA (circRNAs) and hypoxia have been found to play the key roles in the pathogenesis and progression of cancer including colorectal cancer (CRC). However, the expressions and functions of the specific circRNAs in regulating hypoxia-involved CRC metastasis, and the circRNAs that are relevant to regulate HIF-1α levels in CRC remain elusive. Methods qRT-PCR was used to detect the expression of circRNAs and mRNA in CRC cells and tissues. Fluorescence in situ hybridization (FISH) was used to analyze the location of circ-ERBIN. Function-based experiments were performed using circ-ERBIN overexpression and knockdown cell lines in vitro and in vivo, including CCK8, colony formation, EdU assay, transwell, tumor growth and metastasis models. Mechanistically, luciferase reporter assay, western blots and immunohistochemical stainings were performed. Results Circ-Erbin was highly expressed in the CRC cells and Circ-Erbin overexpression facilitated the proliferation, migration and metastasis of CRC in vitro and in vivo. Notably, circ-Erbin overexpression significantly promoted angiogenesis by increasing the expression of hypoxia induced factor (HIF-1α) in CRC. Mechanistically, circ-Erbin accelerated a cap-independent protein translation of HIF-1α in CRC cells as the sponges of miR-125a-5p and miR-138-5p, which synergistically targeted eukaryotic translation initiation factor 4E binding protein 1(4EBP-1). Conclusions Our findings uncover a key mechanism for circ-Erbin mediated HIF-1α activation by miR-125a-5p-5p/miR-138-5p/4EBP-1 axis and circ-ERBIN is a potential target for CRC treatment.

scholarly journals Cereulide Exposure Caused Cytopathogenic Damages of Liver and Kidney in Mice

2021 ◽  
Vol 22 (17) ◽  
pp. 9148
Author(s):  
Danyang Li ◽  
Ruqin Lin ◽  
Yangyang Xu ◽  
Qingmei Chen ◽  
Fengru Deng ◽  
...  
Keyword(s):  
Er Stress ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Inflammatory Factors ◽  
Eukaryotic Translation ◽  
Toxicological Effects ◽  
Liver And Kidney ◽  
Toxicological Mechanism

Cereulide is one of the main food-borne toxins for vomiting synthesized by Bacillus cereus, and it widely contaminates meat, eggs, milk, and starchy foods. However, the toxicological effects and mechanisms of the long-time exposure of cereulide in vivo remain unknown. In this study, oral administration of 50 and 200 μg/kg body weight cereulide in the mice for 28 days caused oxidative stress in liver and kidney tissues and induce abnormal expression of inflammatory factors. In pathogenesis, cereulide exposure activated endoplasmic reticulum stress (ER stress) via the pathways of inositol-requiring enzyme 1α (IRE1α)/Xbox binding protein (XBP1) and PRKR-like ER kinase (PERK)/eukaryotic translation initiation factor 2α (eIF2α), and consequently led to the apoptosis and tissue damages in mouse liver and kidney. In vitro, we confirmed that the accumulation of reactive oxygen species (ROS) caused by cereulide is the main factor leading to ER stress in HepaRG and HEK293T cells. Supplementation of sodium butyrate (NaB) inhibited the activations of IRE1α/XBP1 and PERK/eIF2α pathways caused by cereulide exposure in mice, and reduced the cell apoptosis in liver and kidney. In conclusion, this study provides a new insight in understanding the toxicological mechanism and prevention of cereulide exposure.

scholarly journals Dehydrodiisoeugenol inhibits colorectal cancer growth by endoplasmic reticulum stress-induced autophagic pathways

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Changhong Li ◽  
Kui Zhang ◽  
Guangzhao Pan ◽  
Haoyan Ji ◽  
Chongyang Li ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Endoplasmic Reticulum ◽  
Cell Growth ◽  
Er Stress ◽  
Cancer Cells ◽  
Tumor Xenograft ◽  
Anticancer Activities ◽  
Colorectal Cancer Cells

Abstract Background Dehydrodiisoeugenol (DEH), a novel lignan component extracted from nutmeg, which is the seed of Myristica fragrans Houtt, displays noticeable anti-inflammatory and anti-allergic effects in digestive system diseases. However, the mechanism of its anticancer activity in gastrointestinal cancer remains to be investigated. Methods In this study, the anticancer effect of DEH on human colorectal cancer and its underlying mechanism were evaluated. Assays including MTT, EdU, Plate clone formation, Soft agar, Flow cytometry, Electron microscopy, Immunofluorescence and Western blotting were used in vitro. The CDX and PDX tumor xenograft models were used in vivo. Results Our findings indicated that treatment with DEH arrested the cell cycle of colorectal cancer cells at the G1/S phase, leading to significant inhibition in cell growth. Moreover, DEH induced strong cellular autophagy, which could be inhibited through autophagic inhibitors, with a rction in the DEH-induced inhibition of cell growth in colorectal cancer cells. Further analysis indicated that DEH also induced endoplasmic reticulum (ER) stress and subsequently stimulated autophagy through the activation of PERK/eIF2α and IRE1α/XBP-1 s/CHOP pathways. Knockdown of PERK or IRE1α significantly decreased DEH-induced autophagy and retrieved cell viability in cells treated with DEH. Furthermore, DEH also exhibited significant anticancer activities in the CDX- and PDX-models. Conclusions Collectively, our studies strongly suggest that DEH might be a potential anticancer agent against colorectal cancer by activating ER stress-induced inhibition of autophagy.

scholarly journals Binding of eukaryotic translation initiation factor 4E (eIF4E) to eIF4G represses translation of uncapped mRNA.

1997 ◽  
Vol 17 (12) ◽  
pp. 6876-6886 ◽  
Author(s):  
S Z Tarun ◽  
A B Sachs
Keyword(s):  
Translation Initiation ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Stimulation Of

mRNA translation in crude extracts from the yeast Saccharomyces cerevisiae is stimulated by the cap structure and the poly(A) tail through the binding of the cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) and the poly(A) tail-binding protein Pab1p. These proteins also bind to the translation initiation factor eIF4G and thereby link the mRNA to the general translational apparatus. In contrast, uncapped, poly(A)-deficient mRNA is translated poorly in yeast extracts, in part because of the absence of eIF4E and Pab1p binding sites on the mRNA. Here, we report that uncapped-mRNA translation is also repressed in yeast extracts due to the binding of eIF4E to eIF4G. Specifically, we find that mutations which weaken the eIF4E binding site on the yeast eIF4G proteins Tif4631p and Tif4632p lead to temperature-sensitive growth in vivo and the stimulation of uncapped-mRNA translation in vitro. A mutation in eIF4E which disturbs its ability to interact with eIF4G also leads to a stimulation of uncapped-mRNA translation in vitro. Finally, overexpression of eIF4E in vivo or the addition of excess eIF4E in vitro reverses these effects of the mutations. These data support the hypothesis that the eIF4G protein can efficiently stimulate translation of exogenous uncapped mRNA in extracts but is prevented from doing so as a result of its association with eIF4E. They also suggest that some mRNAs may be translationally regulated in vivo in response to the amount of free eIF4G in the cell.

scholarly journals Coupled Release of Eukaryotic Translation Initiation Factors 5B and 1A from 80S Ribosomes following Subunit Joining

2007 ◽  
Vol 27 (6) ◽  
pp. 2384-2397 ◽  
Author(s):  
Jeanne M. Fringer ◽  
Michael G. Acker ◽  
Christie A. Fekete ◽  
Jon R. Lorsch ◽  
Thomas E. Dever
Keyword(s):  
Translation Initiation ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Cell Extracts ◽  
Eukaryotic Translation Initiation ◽  
Subunit Joining

ABSTRACT The translation initiation GTPase eukaryotic translation initiation factor 5B (eIF5B) binds to the factor eIF1A and catalyzes ribosomal subunit joining in vitro. We show that rapid depletion of eIF5B in Saccharomyces cerevisiae results in the accumulation of eIF1A and mRNA on 40S subunits in vivo, consistent with a defect in subunit joining. Substituting Ala for the last five residues in eIF1A (eIF1A-5A) impairs eIF5B binding to eIF1A in cell extracts and to 40S complexes in vivo. Consistently, overexpression of eIF5B suppresses the growth and translation initiation defects in yeast expressing eIF1A-5A, indicating that eIF1A helps recruit eIF5B to the 40S subunit prior to subunit joining. The GTPase-deficient eIF5B-T439A mutant accumulated on 80S complexes in vivo and was retained along with eIF1A on 80S complexes formed in vitro. Likewise, eIF5B and eIF1A remained associated with 80S complexes formed in the presence of nonhydrolyzable GDPNP, whereas these factors were released from the 80S complexes in assays containing GTP. We propose that eIF1A facilitates the binding of eIF5B to the 40S subunit to promote subunit joining. Following 80S complex formation, GTP hydrolysis by eIF5B enables the release of both eIF5B and eIF1A, and the ribosome enters the elongation phase of protein synthesis.

scholarly journals Homocysteine induces melanocytes apoptosis via PERK–eIF2α–CHOP pathway in vitiligo

2020 ◽  
Vol 134 (10) ◽  
pp. 1127-1141 ◽  
Author(s):  
Jiaxi Chen ◽  
Tongtian Zhuang ◽  
Jianru Chen ◽  
Yangzi Tian ◽  
Xiuli Yi ◽  
...  
Keyword(s):  
Folic Acid ◽  
Stress Protein ◽  
Folic Acid Supplementation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Homologous Protein ◽  
Apoptotic Effect ◽  
Induced Apoptosis

Abstract Vitiligo is a depigmentation disorder that develops as a result of the progressive disappearance of epidermal melanocytes. The elevated level of amino acid metabolite homocysteine (Hcy) has been identified as circulating marker of oxidative stress and known as a risk factor for vitiligo. However, the mechanism underlying Hcy-regulated melanocytic destruction is currently unknown. The present study aims to elucidate the effect of Hcy on melanocytic destruction and its involvement in the pathogenesis of vitiligo. Our results showed that Hcy level was significantly elevated in the serum of progressive vitiligo patients. Notably, Hcy induced cell apoptosis in melanocytes via activating reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress protein kinase RNA-like ER kinase (PERK)–eukaryotic translation initiation factor 2α (eIF2α)–C/EBP homologous protein (CHOP) pathway. More importantly, folic acid, functioning in the transformation of Hcy, could lower the intracellular Hcy level and further reverse the apoptotic effect of Hcy on melanocytes. Additionally, Hcy disrupted melanogenesis whereas folic acid supplementation could reverse the melanogenesis defect induced by Hcy in melanocytes. Taken together, Hcy is highly increased in vitiligo patients at progressive stage, and our in vitro studies revealed that folic acid could protect melanocytes from Hcy-induced apoptosis and melanin synthesis inhibition, indicating folic acid as a potential benefit agent for patients with progressive vitiligo.

scholarly journals APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress

2018 ◽  
Vol 38 (4) ◽  
Author(s):  
Hongxiu Wen ◽  
Vinod Kumar ◽  
Xiqian Lan ◽  
Seyedeh Shadafarin Marashi Shoshtari ◽  
Judith M. Eng ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Kidney Diseases ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Wild Type ◽  
Eukaryotic Translation ◽  
Risk Variants ◽  
Eukaryotic Translation Initiation ◽  
Underlying Mechanisms

Two coding sequence variants (G1 and G2) of Apolipoprotein L1 (APOL1) gene have been implicated as a higher risk factor for chronic kidney diseases (CKD) in African Americans when compared with European Americans. Previous studies have suggested that the APOL1 G1 and G2 variant proteins are more toxic to kidney cells than the wild-type APOL1 G0, but the underlying mechanisms are poorly understood. To determine whether endoplasmic reticulum (ER) stress contributes to podocyte toxicity, we generated human podocytes (HPs) that stably overexpressed APOL1 G0, G1, or G2 (Vec/HPs, G0/HPs, G1/HPs, and G2/HPs). Propidium iodide staining showed that HP overexpressing the APOL1 G1 or G2 variant exhibited a higher rate of necrosis when compared with those overexpressing the wild-type G0 counterpart. Consistently, the expression levels of nephrin and podocin proteins were significantly decreased in the G1- or G2-overexpressing cells despite the maintenance of their mRNA expressions levels. In contrast, the expression of the 78-kDa glucose-regulated protein ((GRP78), also known as the binding Ig protein, BiP) and the phosphorylation of the eukaryotic translation initiation factor 1 (eIF1) were significantly elevated in the G1/HPs and G2/HPs, suggesting a possible occurrence of ER stress in these cells. Furthermore, ER stress inhibitors not only restored nephrin protein expression, but also provided protection against necrosis in G1/HPs and G2/HPs, suggesting that APOL1 risk variants cause podocyte injury partly through enhancing ER stress.

scholarly journals Cytoplasmic eIF6 promotes OSCC malignant behavior through AKT pathway

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Zechen Zhao ◽  
Weiming Chu ◽  
Yang Zheng ◽  
Chao Wang ◽  
Yuemei Yang ◽  
...  
Keyword(s):  
Western Blot ◽  
Direct Interaction ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Migration And Invasion ◽  
Eukaryotic Translation ◽  
Mesenchymal Transformation

Abstract Background Eukaryotic translation initiation factor 6 (eIF6), also known as integrin β4 binding protein, is involved in ribosome formation and mRNA translation, acting as an anti-association factor. It is also essential for the growth and reproduction of cells, including tumor cells. Yet, its role in oral squamous cell carcinoma (OSCC) remains unclear. Methods The expression characteristics of eIF6 in 233 samples were comprehensively analyzed by immunohistochemical staining (IHC). Effects of eIF6 over-expression and knockdown on cell proliferation, migration and invasion were determined by CCK-8, wound healing and Transwell assays. Western blot, immunofluorescence (IF) and co-immunoprecipitation (co-IP) were performed for mechanical verification. Results We found that cytoplasmic eIF6 was abnormally highly expressed in OSCC tissues, and its expression was associated with tumor size and the clinical grade. Amplification of eIF6 promoted the growth, migration and invasion capabilities of OSCC cell lines in vitro and tumor growth in vivo. Through Western blot analysis, we further discovered that eIF6 significantly promotes epithelial-mesenchymal transformation (EMT) in OSCC cells, while depletion of eIF6 can reverse this process. Mechanistically, eIF6 promoted tumor progression by activating the AKT signaling pathway. By performing co-immunoprecipitation, we discovered a direct interaction between endogenous eIF6 and AKT protein in the cytoplasm. Conclusion These results demonstrated that eIF6 could be a new therapeutic target in OSCC, thus providing a new basis for the prognosis of OSCC patients in the future.

scholarly journals Generation of Multiple Isoforms of Eukaryotic Translation Initiation Factor 4GI by Use of Alternate Translation Initiation Codons

2002 ◽  
Vol 22 (13) ◽  
pp. 4499-4511 ◽  
Author(s):  
Marshall P. Byrd ◽  
Miguel Zamora ◽  
Richard E. Lloyd
Keyword(s):  
Translation Initiation ◽  
Cdna Clone ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Ires Element

ABSTRACT Eukaryotic translation initiation factor 4GI (eIF4GI) is an essential protein that is the target for translational regulation in many cellular processes and viral systems. It has been shown to function in both cap-dependent and cap-independent translation initiation by recruiting the 40S ribosomal subunit to the mRNA cap structure or internal ribosome entry site (IRES) element, respectively. Interestingly eIF4GI mRNA itself has been reported to contain an IRES element in its 5′ end that facilitates eIF4GI protein synthesis via a cap-independent mechanism. In HeLa cells, eIF4GI exists as several isoforms that differ in their migration in sodium dodecyl sulfate (SDS) gels; however, the nature of these isoforms was unclear. Here, we report a new cDNA clone for eIF4GI that extends the 5′ sequence 340 nucleotides beyond the previously published sequence. The new extended sequence of eIF4GI is located on chromosome 3, within two additional exons immediately upstream of the previously published eIF4GI sequence. When mRNA transcribed from this cDNA clone was translated in vitro, five eIF4GI polypeptides were generated that comigrated in SDS-polyacrylamide gels with the five isoforms of native eIF4GI. Furthermore, translation of eIF4GI-enhanced green fluorescent protein fusion constructs in vitro or in vivo generated five isoforms of fusion polypeptides, suggesting that multiple isoforms of eIF4GI are generated by alternative translation initiation in vitro and in vivo. Mutation of two of the five in-frame AUG residues in the eIF4GI cDNA sequence resulted in loss of corresponding polypeptides after translation in vitro, confirming alternate use of AUGs as the source of the multiple polypeptides. The 5′ untranslated region of eIF4GI mRNA also contains an out-of-frame open reading frame (ORF) that may down-regulate expression of eIF4GI. Further, data are presented to suggest that a proposed IRES embedded in the eIF4GI ORF is able to catalyze synthesis of multiple eIF4GI isoforms as well. Our data suggest that expression of the eIF4GI isoforms is partly controlled by a complex translation strategy involving both cap-dependent and cap-independent mechanisms.

scholarly journals Eukaryotic Translation Initiation Factor 4G Is Targeted for Proteolytic Cleavage by Caspase 3 during Inhibition of Translation in Apoptotic Cells

1998 ◽  
Vol 18 (12) ◽  
pp. 7565-7574 ◽  
Author(s):  
Wilfred E. Marissen ◽  
Richard E. Lloyd
Keyword(s):  
Translation Initiation ◽  
Caspase 3 ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Apoptotic Cells ◽  
Eukaryotic Translation ◽  
Cell Lysates ◽  
Cellular Translation

ABSTRACT Although much is known about the multiple mechanisms which induce apoptosis, comparatively little is understood concerning the execution phase of apoptosis and the mechanism(s) of cell killing. Several reports have demonstrated that cellular translation is shut off during apoptosis; however, details of the mechanism of translation inhibition are lacking. Translation initiation factor 4G (eIF4G) is a crucial protein required for binding cellular mRNA to ribosomes and is known to be cleaved as the central part of the mechanism of host translation shutoff exerted by several animal viruses. Treatment of HeLa cells with the apoptosis inducers cisplatin and etoposide resulted in cleavage of eIF4G, and the extent of its cleavage correlated with the onset and extent of observed inhibition of cellular translation. The eIF4G-specific cleavage activity could be measured in cell lysates in vitro and was inhibited by the caspase inhibitor Ac-DEVD-CHO at nanomolar concentrations. A combination of in vivo and in vitro inhibitor studies suggest the involvement of one or more caspases in the activation and execution of eIF4G cleavage. Furthermore recombinant human caspase 3 was expressed in bacteria, and when incubated with HeLa cell lysates, was shown to produce the same eIF4G cleavage products as those observed in apoptotic cells. In addition, purified caspase 3 caused cleavage of purified eIF4G, demonstrating that eIF4G could serve as a substrate for caspase 3. Taken together, these data suggest that cellular translation is specifically inhibited during apoptosis by a mechanism involving cleavage of eIF4G, an event dependent on caspase activity.

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