Endoplasmic reticulum stress stimulates p53 expression through NF-κB activation

Tumour suppressor protein sMEK1 links to IRE1 signalling pathway to modulate its activity during ER stress

The Endoplasmic Reticulum is a pervasive, dynamic cellular organelle that performs a wide range of functions in the eukaryotic cell, including protein folding and maturation. Upon stress, ER activates an adaptive cellular pathway, namely Unfolded Protein Response, that transduces information from ER to nucleus, restoring homeostasis in the ER milieu. UPR consists of three membrane-tethered sensors; IRE1, PERK and ATF6. Among all the UPR sensors, the IRE1 branch acts as a central pathway that orchestrates several pathways to determine cell fate. However, the detailed knowledge underlying the whole process is not understood yet. Previously, we determined the sMEK1 as one of the interacting partners of IRE1. sMEK1 is a protein phosphatase, which has been indicated in a number of critical cellular functions like apoptosis, cell proliferation, and tumour suppression. In this study, we evaluated the role of sMEK1 on the IRE1 signalling pathway. Our data indicate that sMEK1 can inhibit IRE1 phosphorylation under ER stress. This inhibitory effect of sMEK1 could be reflected in its downstream effectors, Xbp1 and RIDD, which are downregulated in the presence of sMEK1. We also found that the repressing effect of sMEK1 was specific to the IRE1 signalling pathway and could be preserved even under prolonged ER stress. Our findings also indicate that sMEK1 can inhibit IRE1 and its downstream molecules under ER stress irrespective of other UPR sensors. These results help to draw the mechanistic details giving insights into different molecular connections of UPR with other pathways.

p53-Mediated Mitochondrial Translocation of EI24 Triggered by ER Stress Plays an Important Role in Arsenic-Induced Liver Damage via Activating Mitochondrial Apoptotic Pathway

Chronic arsenic poisoning is a public health problem worldwide. In addition to skin lesions, the detrimental effect of arsenic poisoning on liver damage is one of the major issues. Our previous studies demonstrated that endoplasmic reticulum (ER) stress and p53 were associated with arsenic-induced liver damage. Literature has shown that EI24 is involved in hepatocyte hypertrophy; however, the underlying role and mechanism in arsenic-induced liver damage have not been fully elucidated. In this study, we explored the role of ER stress, p53, and EI24 as well as the regulatory relationship in arsenic poisoning populations and L-02 cells treated with distinct concentration NaAsO2 (2.5, 5, 10, and 20 μM). Results showed that as with arsenic dose increment, expression levels of ER stress key proteins GRP78, ATF4, and CHOP were significantly enhanced. Additionally, p53 expression in nucleus, p53 phosphorylation at Ser15 and Ser1392, and p53 acetylation at lys382 were significantly increased in NaAsO2-treated L-02 cells. ER stress inhibitor 4-phenylbutyric acid (4-PBA) decreased the expression of p53 phosphorylation at Ser 392, p53 acetylation at lys382, and p53 expression in nucleus. Additionally, in 5 μM NaAsO2 condition, p53 inhibitor pifithrin-α (PFT-α) aggravated 5 μM NaAsO2-induced GRP78, ATF4, and CHOP expressions, cell apoptosis, and protein-SH consumption. But in 20 μM NaAsO2 condition, PFT-α attenuated NaAsO2-induced cell apoptosis. Further results showed that 20 μM NaAsO2 facilitated translocation of EI24 from ER to mitochondrion and interaction with VDAC2, leading to activate mitochondrial apoptotic pathway, but not observed in the 5-μM NaAsO2 group. Moreover, PFT-α and 4-PBA inhibited 20 μM NaAsO2-induced EI24 expression in mitochondrion. Collectively, our results indicated that arsenic induced p53 activation via ER stress, under relatively low NaAsO2 concentration, NaAsO2-triggered p53 activation protected cells from apoptosis by alleviating ER stress. Another finding was that under relatively high NaAsO2 concentration, NaAsO2-activated p53 facilitated EI24 mitochondrial translocation and caused mitochondrial permeability increase, which represented a switch of p53 from a benefit role to pro-apoptosis function in NaAsO2-treated cells. The study contributed to in-depth understanding the mechanism of arsenic-induced liver damage and providing potential clues for following study.

Trappc1 intrinsically prevents ferroptosis of naive T cells to avoid spontaneous autoinflammatory disease in mice

T lymphocytes are pivotal in adaptive immunity. The role of the trafficking protein particle complex (TRAPPC) in regulating T-cell development and homeostasis is unknown. Using CD4cre -Trappc1flox/flox (Trappc1 cKO) mice, we found that Trappc1 deficiency in T cells significantly decreased cell number of naive T cells in the periphery, whereas thymic T-cell development in Trappc1 cKO mice was identical as WT mice. In the culture assays and mouse models with adoptive transfer of the sorted WT (CD45.1+ CD45.2+ ) and Trappc1 cKO naive T cells (CD45.2+ ) to CD45.1+ syngeneic mice, Trappc1-deficient naive T cells showed significantly reduced survival ability compared with WT cells. RNA-seq and molecular studies showed that Trappc1 deficiency in naive T cells reduced protein transport from the endoplasmic reticulum to the Golgi apparatus, enhanced unfolded protein responses, increased P53 transcription, intracellular Ca2+ , Atf4-CHOP, oxidative phosphorylation, and lipid peroxide accumulation, and subsequently led to ferroptosis. Trappc1 deficiency in naive T cells increased ferroptosis-related damage-associated molecular pattern molecules like high mobility group box 1 or lipid oxidation products like prostaglandin E2, leukotriene B4, leukotriene C4, and leukotriene D4. Functionally, the culture supernatant of Trappc1 cKO naive T cells significantly promoted neutrophils to express inflammatory cytokines like TNFα and IL-6, which was rescued by lipid peroxidation inhibitor Acetylcysteine. Importantly, Trappc1 cKO mice spontaneously developed severe autoinflammatory disease 4 weeks after birth. Thus, intrinsic expression of Trappc1 in naive T cells plays an integral role in maintaining T-cell homeostasis to avoid proinflammatory naive T-cell death-caused autoinflammatory syndrome in mice. This study highlights the importance of the TRAPPC in T-cell biology.

The impact of TP53 activation and apoptosis in primary hereditary microcephaly

Autosomal recessive primary microcephaly (MCPH) is a constellation of disorders that share significant brain size reduction and mild to moderate intellectual disability, which may be accompanied by a large variety of more invalidating clinical signs. Extensive neural progenitor cells (NPC) proliferation and differentiation are essential to determine brain final size. Accordingly, the 30 MCPH loci mapped so far (MCPH1-MCPH30) encode for proteins involved in microtubule and spindle organization, centriole biogenesis, nuclear envelope, DNA replication and repair, underscoring that a wide variety of cellular processes is required for sustaining NPC expansion during development. Current models propose that altered balance between symmetric and asymmetric division, as well as premature differentiation, are the main mechanisms leading to MCPH. Although studies of cellular alterations in microcephaly models have constantly shown the co-existence of high DNA damage and apoptosis levels, these mechanisms are less considered as primary factors. In this review we highlight how the molecular and cellular events produced by mutation of the majority of MCPH genes may converge on apoptotic death of NPCs and neurons, via TP53 activation. We propose that these mechanisms should be more carefully considered in the alterations of the sophisticated equilibrium between proliferation, differentiation and death produced by MCPH gene mutations. In consideration of the potential druggability of cell apoptotic pathways, a better understanding of their role in MCPH may significantly facilitate the development of translational approaches.

P53 in endothelial function and unfolded protein response regulation

Vascular barrier dysfunction due to endothelial hyperpermeability has been associated with the pathophysiology of sepsis and severe lung injury, which may inflict acute respiratory distress syndrome (ARDS). Our group is focused on the mechanisms operating towards the regulation of endothelial permeability, to contribute in the development of efficient and targeted countermeasures against ARDS. Unfortunately, the number of ARDS-related deaths in the intensive care units has dramatically increased during the COVID-19 era. The findings described herein inform the corresponding scientific and medical community on the relation of P53 and stress responses in barrier function.

Role of lncRNA LIPE-AS1 in adipogenesis

Recent studies have identified long non-coding RNAs (lncRNAs) as potential regulators of adipogenesis. In this study, we have characterized a lncRNA, LIPE-AS1, that spans genes CEACAM1 to LIPE in man with conservation of genomic organization and tissue expression between mouse and man. Tissue-specific expression of isoforms of the murine lncRNA were found in liver and adipose tissue, one of which, designated mLas-V3, overlapped the Lipe gene encoding hormone-sensitive lipase in both mouse and man suggesting that it may have a functional role in adipose tissue. Knock down of expression of mLas-V3 using anti-sense oligos (ASOs) led to a significant decrease in the differentiation of the OP9 pre-adipocyte cell line through the down regulation of the major adipogenic transcription factors Pparg and Cebpa. Knock down of mLas-V3 induced apoptosis during the differentiation of OP9 cells as shown by expression of active caspase-3, a change in the localization of LIP/LAP isoforms of C/EBPβ, and expression of the cellular stress induced factors CHOP, p53, PUMA, and NOXA. We conclude that mLas-V3 may play a role in protecting against stress associated with adipogenesis, and its absence leads to apoptosis.

Human Estrogen Receptor Alpha Antagonists, Part 3: 3-D Pharmacophore and 3-D QSAR Guided Brefeldin A Hit-to-Lead Optimization toward New Breast Cancer Suppressants

The estrogen receptor α (ERα) is an important biological target mediating 17β-estradiol driven breast cancer (BC) development. Aiming to develop innovative drugs against BC, either wild-type or mutated ligand-ERα complexes were used as source data to build structure-based 3-D pharmacophore and 3-D QSAR models, afterward used as tools for the virtual screening of National Cancer Institute datasets and hit-to-lead optimization. The procedure identified Brefeldin A (BFA) as hit, then structurally optimized toward twelve new derivatives whose anticancer activity was confirmed both in vitro and in vivo. Compounds as SERMs showed picomolar to low nanomolar potencies against ERα and were then investigated as antiproliferative agents against BC cell lines, as stimulators of p53 expression, as well as BC cell cycle arrest agents. Most active leads were finally profiled upon administration to female Wistar rats with pre-induced BC, after which 3DPQ-12, 3DPQ-3, 3DPQ-9, 3DPQ-4, 3DPQ-2, and 3DPQ-1 represent potential candidates for BC therapy.

On the origin of metastases: Induction of pro-metastatic states after impending cell death via ER stress, reprogramming, and a cytokine storm

How metastatic cells arise is unclear. Here, we search for the induction of recently characterized pro-metastatic states as a surrogate for the origin of metastasis. Since cell-death-inducing therapies can paradoxically promote metastasis, we ask if such treatments induce pro-metastatic states in human colon cancer cells. We find that post-near-death cells acquire pro-metastatic states (PAMEs) and form distant metastases in vivo. These PAME ("let's go" in Greek) cells exhibit a multifactorial cytokine storm as well as signs of enhanced endoplasmic reticulum (ER) stress and nuclear reprogramming, requiring CXCL8, INSL4, IL32, PERK-CHOP, and NANOG. PAMEs induce neighboring tumor cells to become PAME-induced migratory cells (PIMs): highly migratory cells that re-enact the storm and enhance PAME migration. Metastases are thus proposed to originate from the induction of pro-metastatic states through intrinsic and extrinsic cues in a pro-metastatic tumoral ecosystem, driven by an impending cell-death experience involving ER stress modulation, metastatic reprogramming, and paracrine recruitment via a cytokine storm.

Zinc Supplementation Enhances the Pro-Death Function of UPR in Lymphoma Cells Exposed to Radiation

Simple Summary

It is of fundamental importance to find strategies able to reduce the minimum doses of anticancer treatments, such as radiations, and concomitantly maintain efficient killing of cancer cells. The interconnection between ER stress and DNA repair may represent a promising approach to obtaining this goal. Here we found that pretreatment of lymphoma cells with Zinc chloride rendered these cells more sensitive to 2 Gy radiation. The exacerbation of ER stress and the activation pro-death function of UPR were among the underlying mechanisms leading to higher cytotoxicity of Zinc/radiation combination treatment. This evidence encourages the use of Zinc to reduce the doses of radiation in the treatment of lymphoma cells, allowing a high cytotoxicity to be obtained while minimizing the side effects.

Abstract

We have previously shown that Zinc supplementation triggered ER stress/UPR in cancer cells undergoing treatment by genotoxic agents, reactivated wtp53 in cancer cells harboring mutant p53 (mutp53) and potentiated the activity of wtp53 in those carrying wtp53. In this study, we used Zinc chloride alone or in combination with 2 Gy radiation to treat Primary Effusion Lymphoma (PEL) cells, an aggressive B-cell lymphoma associated with KSHV that harbors wt or partially functioning p53. We found that Zinc triggered a mild ER stress/UPR in these lymphoma cells and activated ERK1/2, molecule known to sustain cell survival in the course of UPR activation. In combination with radiations, Zinc triggered a stronger p53 activation that counteracted its mediated ERK1/2 phosphorylation, further upregulating the UPR molecule CHOP and promoting cell death. These data suggest that Zinc supplementation could be a promising strategy to reduce the doses of radiation and possibly of other DNA-damaging agents to obtain an efficient capacity to induce lymphoma cell death.

Expression of Human Mutant Preproinsulins Induced Unfolded Protein Response, Gadd45 Expression, JAK-STAT Activation, and Growth Inhibition in Drosophila

Mutations in the insulin gene (INS) are frequently associated with human permanent neonatal diabetes mellitus. However, the mechanisms underlying the onset of this genetic disease is not sufficiently decoded. We induced expression of two types of human mutant INSs in Drosophila using its ectopic expression system and investigated the resultant responses in development. Expression of the wild-type preproinsulin in the insulin-producing cells (IPCs) throughout the larval stage led to a stimulation of the overall and wing growth. However, ectopic expression of human mutant preproinsulins, hINSC96Y and hINSLB15YB16delinsH, neither of which secreted from the β-cells, could not stimulate the Drosophila growth. Furthermore, neither of the mutant polypeptides induced caspase activation leading to apoptosis. Instead, they induced expression of several markers indicating the activation of unfolded protein response, such as ER stress-dependent Xbp1 mRNA splicing and ER chaperone induction. We newly found that the mutant polypeptides induced the expression of Growth arrest and DNA-damage-inducible 45 (Gadd45) in imaginal disc cells. ER stress induced by hINSC96Y also activated the JAK-STAT signaling, involved in inflammatory responses. Collectively, we speculate that the diabetes-like growth defects appeared as a consequence of the human mutant preproinsulin expression was involved in dysfunction of the IPCs, rather than apoptosis.

The Leloir Cycle in Glioblastoma: Galactose Scavenging and Metabolic Remodeling

BACKGROUND

Glioblastoma (GBM) can use metabolic fuels other than glucose (Glc). The ability of GBM to use galactose (Gal) as a fuel via the Leloir pathway is investigated.

METHODS

Gene transcript data were accessed to determine the association between expression of genes of the Leloir pathway and patient outcomes. Growth studies were performed on five primary patient-derived GBM cultures using Glc-free media supplemented with Gal. The role of Glut3/Glut14 in sugar import was investigated using antibody inhibition of hexose transport. A specific inhibitor of GALK1 (Cpd36) was used to inhibit Gal catabolism. Gal metabolism was examined using proton, carbon and phosphorous NMR spectroscopy, with ¹³C-labeled Glc and Gal as tracers.

RESULTS

Data analysis from published databases revealed that elevated levels of mRNA transcripts of SLC2A3 (Glut3), SLC2A14 (Glut14) and key Leloir pathway enzymes correlate with poor patient outcomes. GBM cultures proliferated when grown solely on Gal in Glc-free media and switching Glc-grown GBM cells into Gal-enriched/Glc-free media produced elevated levels of Glut3 and/or Glut14 enzymes. The ¹³C NMR-based metabolic flux analysis demonstrated a fully functional Leloir pathway and elevated pentose phosphate pathway activity for efficient Gal metabolism in GBM cells.

CONCLUSION

Expression of Glut3 and/or Glut14 together with the enzymes of the Leloir pathway allows GBM to transport and metabolize Gal at physiological glucose concentrations, providing GBM cells with an alternate energy source. The presence of this pathway in GBM and its selective targeting may provide new treatment strategies.

Amyloid-beta oligomers induce Parkin-mediated mitophagy by reducing Miro1

Alzheimer's disease (AD) is a neurodegenerative disease associated with the accumulation of amyloid-beta oligomers (AβO). Recent studies have demonstrated that mitochondria-specific autophagy (mitophagy) contributes to mitochondrial quality control by selectively eliminating the dysfunctional mitochondria. Mitochondria motility, which is regulated by Miro1, is also associated with neuronal cell functions. However, the role played by Miro1 in the mitophagy mechanism, especially relative to AβO and neurodegenerative disorders, remains unknown. In this study, AβO induced mitochondrial dysfunction, enhanced Parkin-mediated mitophagy, and reduced mitochondrial quantities in hippocampal neuronal cells (HT-22 cells). We demonstrated that AβO-induced mitochondrial fragmentation could be rescued to the elongated mitochondrial form and that mitophagy could be mitigated by the stable overexpression of Miro1 or by pretreatment with N-acetylcysteine (NAC)-a reactive oxygen species (ROS) scavenger-as assessed by immunocytochemistry. Moreover, using time-lapse imaging, under live cell-conditions, we verified that mitochondrial motility was rescued by the Miro1 overexpression. Finally, in hippocampus from amyloid precursor protein (APP)/presenilin 1 (PS1)/Tau triple-transgenic mice, we noted that the co-localization between mitochondria and LC3B puncta was increased. Taken together, these results indicated that up-regulated ROS, induced by AβO, increased the degree of mitophagy and decreased the Miro1 expression levels. In contrast, the Miro1 overexpression ameliorated AβO-mediated mitophagy and increased the mitochondrial motility. In AD model mice, AβO induced mitophagy in the hippocampus. Thus, our results would improve our understanding of the role of mitophagy in AD toward facilitating the development of novel therapeutic agents for the treatment of AβO-mediated diseases.

The regulatory roles of p53 in cardiovascular health and disease

Cardiovascular disease (CVD) remains the leading cause of mortality globally, so further investigation is required to identify its underlying mechanisms and potential targets for its prevention. The transcription factor p53 functions as a gatekeeper, regulating a myriad of genes to maintain normal cell functions. It has received a great deal of research attention as a tumor suppressor. In the past three decades, evidence has also shown a regulatory role for p53 in the heart. Basal p53 is essential for embryonic cardiac development; it is also necessary to maintain normal heart architecture and physiological function. In pathological cardiovascular circumstances, p53 expression is elevated in both patient samples and animal models. Elevated p53 plays a regulatory role via anti-angiogenesis, pro-programmed cell death, metabolism regulation, and cell cycle arrest regulation. This largely promotes the development of CVDs, particularly cardiac remodeling in the infarcted heart, hypertrophic cardiomyopathy, dilated cardiomyopathy, and diabetic cardiomyopathy. Roles for p53 have also been found in atherosclerosis and chemotherapy-induced cardiotoxicity. However, it has different roles in cardiomyocytes and non-myocytes, even in the same model. In this review, we describe the different effects of p53 in cardiovascular physiological and pathological conditions, in addition to potential CVD therapies targeting p53.

P53-independent partial restoration of the p53 pathway in tumors with mutated p53 through ATF4 transcriptional modulation by ERK1/2 and CDK9

A long-term goal in the cancer-field has been to develop strategies for treating p53-mutated tumors. A novel small-molecule, PG3-Oc, restores p53 pathway-signaling in tumor cells with mutant-p53, independently of p53/p73. PG3-Oc partially upregulates the p53-transcriptome (13.7% of public p53 target-gene dataset; 15.2% of in-house dataset) and p53-proteome (18%, HT29; 16%, HCT116-p53^−/−). Bioinformatic analysis indicates critical p53-effectors of growth-arrest (p21), apoptosis (PUMA, DR5, Noxa), autophagy (DRAM1), and metastasis-suppression (NDRG1) are induced by PG3-Oc. ERK1/2- and CDK9-kinases are required to upregulate ATF4 by PG3-Oc which restores p53 transcriptomic-targets in cells without functional-p53. PG3-Oc represses MYC (ATF4-independent), and upregulates PUMA (ATF4-dependent) in mediating cell death. With largely nonoverlapping transcriptomes, induced-ATF4 restores p53 transcriptomic targets in drug-treated cells including functionally important mediators such as PUMA and DR5. Our results demonstrate novel p53-independent drug-induced molecular reprogramming involving ERK1/2, CDK9, and ATF4 to restore upregulation of p53 effector genes required for cell death and tumor suppression.

Adaptation to Endoplasmic Reticulum Stress Enhances Resistance of Oral Cancer Cells to Cisplatin by Up-Regulating Polymerase η and Increasing DNA Repair Efficiency

Endoplasmic reticulum (ER) stress response is an adaptive program to cope with cellular stress that disturbs the function and homeostasis of ER, which commonly occurs during cancer progression to late stage. Late-stage cancers, mostly requiring chemotherapy, often develop treatment resistance. Chemoresistance has been linked to ER stress response; however, most of the evidence has come from studies that correlate the expression of stress markers with poor prognosis or demonstrate proapoptosis by the knockdown of stress-responsive genes. Since ER stress in cancers usually persists and is essentially not induced by genetic manipulations, we used low doses of ER stress inducers at levels that allowed cell adaptation to occur in order to investigate the effect of stress response on chemoresistance. We found that prolonged tolerable ER stress promotes mesenchymal-epithelial transition, slows cell-cycle progression, and delays the S-phase exit. Consequently, cisplatin-induced apoptosis was significantly decreased in stress-adapted cells, implying their acquisition of cisplatin resistance. Molecularly, we found that proliferating cell nuclear antigen (PCNA) ubiquitination and the expression of polymerase η, the main polymerase responsible for translesion synthesis across cisplatin-DNA damage, were up-regulated in ER stress-adaptive cells, and their enhanced cisplatin resistance was abrogated by the knockout of polymerase η. We also found that a fraction of p53 in stress-adapted cells was translocated to the nucleus, and that these cells exhibited a significant decline in the level of cisplatin-DNA damage. Consistently, we showed that the nuclear p53 coincided with strong positivity of glucose-related protein 78 (GRP78) on immunostaining of clinical biopsies, and the cisplatin-based chemotherapy was less effective for patients with high levels of ER stress. Taken together, this study uncovers that adaptation to ER stress enhances DNA repair and damage tolerance, with which stressed cells gain resistance to chemotherapeutics.

miR-708-5p enhances erlotinib/paclitaxel efficacy and overcomes chemoresistance in lung cancer cells

Lung cancer is a collection of aggressive tumors generally not diagnosed until late-stage, resulting in high mortality rates. The vast majority of non-small cell lung cancer (NSCLC) patients undergo combinatory chemotherapeutic treatment, which initially reduces tumor growth, but frequently becomes ineffective due to toxicity and resistance. Researchers have identified multiple signaling pathways involved in lung cancer chemoresistance, including cyclooxygenase-2 (COX-2)/microsomal prostaglandin E synthase-1 (mPGES-1) derived prostaglandin E2 (PGE₂). While COX-2 inhibitors have shown promise in the clinic, their use is limited due to severe side effects. One novel approach to effectively suppress COX-2 signaling is through microRNA (miRNA). MiRNAs are small-noncoding RNAs commonly misexpressed in cancer. One tumor suppressive miRNA, miR-708-5p, has been shown to repress pro-resistant signaling pathways, including COX-2 and mPGES-1. Here, we demonstrate that chemotherapies reduce COX-2 expression, possibly through induction of miR-708-5p. Moreover, combination treatment of erlotinib (ERL) or paclitaxel (PAC) with miR-708-5p enhances COX-2 and mPGES-1 protein suppression. We also show that combination chemotherapeutic and miR-708-5p treatment intensifies the anti-proliferative and pro-apoptotic effects of ERL and PAC. We also created ERL and PAC resistant lung cancer cell lines, which have increased COX-2 expression and diminished miR-708-5p levels compared to naïve lung cancer cells. While ERL and PAC treatments do not alter resistant cell phenotype alone, combination treatment with miR-708-5p partially restores the chemotherapies' anti-proliferative effects and fully restores their pro-apoptotic qualities. These data suggest miR-708-5p may have potential combinatory therapeutic value to more efficaciously treat lung tumors while overcoming chemoresistance.

P53 Activated by ER Stress Aggravates Caerulein-Induced Acute Pancreatitis Progression by Inducing Acinar Cell Apoptosis

BACKGROUND AND AIMS

Acute pancreatitis (AP) is a severe pancreatic disorder that remains associated with high mortality due to a lack of effective drugs and management strategies. This study aimed to investigate the molecular pathogenic mechanisms of AP involving p53 and endoplasmic reticulum (ER) stress pathways.

METHODS

Expression of PRSS1 and p53 in human AP tissues was detected by immunohistochemistry and Western blotting. AP was induced with caerulein in humanized PRSS1 transgenic mice, and its severity was verified by histological imaging, evaluation of edema, serum amylase, and trypsin activity assays. A transferase-mediated d-UTP nick end-labeling assay was performed to evaluate acinar cell apoptosis associated with AP. The expression of ER stress genes was assessed by quantitative RT-PCR (qRT-PCR) and Western blotting.

RESULTS

PRSS1 and p53 were highly expressed in human AP tissues. Expression of human PRSS1 in caerulein-treated mice induced significant acinar cell apoptosis and AP progression. P53 knockout significantly suppressed AP progression in humanized PRSS1 transgenic mice. The ER stress pathway was activated by PRSS1 and mediated the progression of AP in mouse pancreatic tissues. Application of a p53 inhibitor effectively ameliorated caerulein-induced AP in PRSS1 transgenic mice, while a p53 activator promoted the progression of AP.

CONCLUSION

P53, which was activated by the ER stress pathway, promoted the progression of AP in mice expressing PRSS1 by inducing acinar cell apoptosis.

Regulation of the p53 expression profile by hnRNP K under stress conditions

The p53 protein is one of the transcription factors responsible for cell cycle regulation and prevention of cancer development. Its expression is regulated at the transcriptional, translational and post-translational levels. Recent years of research have shown that the 5' terminus of p53 mRNA plays an important role in this regulation. This region seems to be a docking platform for proteins involved in p53 expression, particularly under stress conditions. Here, we applied RNA-centric affinity chromatography to search for proteins that bind to the 5' terminus of p53 mRNA and thus may be able to regulate the p53 expression profile. We found heterogeneous nuclear ribonucleoprotein K, hnRNP K, to be one of the top candidates. Binding of hnRNP K to the 5'-terminal region of p53 mRNA was confirmed in vitro. We demonstrated that changes in the hnRNP K level in the cell strongly affected the p53 expression profile under various stress conditions. Downregulation or overexpression of hnRNP K caused a decrease or an increase in the p53 mRNA amount, respectively, pointing to the transcriptional mode of expression regulation. However, when hnRNP K was overexpressed under endoplasmic reticulum stress and the p53 amount has elevated no changes in the p53 mRNA level were detected suggesting translational regulation of p53 expression. Our findings have shown that hnRNP K is not only a mutual partner of p53 in the transcriptional activation of target genes under stress conditions but it also acts as a regulator of p53 expression at the transcriptional and potentially translational levels.

Alternative Mechanisms of p53 Action During the Unfolded Protein Response

The tumor suppressor protein p53 orchestrates cellular responses to a vast number of stresses, with DNA damage and oncogenic activation being some of the best described. The capacity of p53 to control cellular events such as cell cycle progression, DNA repair, and apoptosis, to mention some, has been mostly linked to its role as a transcription factor. However, how p53 integrates different signaling cascades to promote a particular pathway remains an open question. One way to broaden its capacity to respond to different stimuli is by the expression of isoforms that can modulate the activities of the full-length protein. One of these isoforms is p47 (p53/47, Δ40p53, p53ΔN40), an alternative translation initiation variant whose expression is specifically induced by the PERK kinase during the Unfolded Protein Response (UPR) following Endoplasmic Reticulum stress. Despite the increasing knowledge on the p53 pathway, its activity when the translation machinery is globally suppressed during the UPR remains poorly understood. Here, we focus on the expression of p47 and we propose that the alternative initiation of p53 mRNA translation offers a unique condition-dependent mechanism to differentiate p53 activity to control cell homeostasis during the UPR. We also discuss how the manipulation of these processes may influence cancer cell physiology in light of therapeutic approaches.

Effect of ER stress on sphingolipid levels and apoptotic pathways in retinal pigment epithelial cells

Background

We aimed to determine sphingolipid levels and examine apoptotic pathways in human retinal pigment epithelial cells (ARPE-19) undergoing endoplasmic reticulum (ER) stress.

Methods

Cells were treated with tunicamycin (TM) to induce ER stress and tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, was administered to decrease cytotoxicity. Cell viability was measured by MTT assay. Levels of C16–C24 sphingomyelins (SM) and C16–C24 ceramides (CERs) were determined by LC-MS/MS. Glucose-regulated protein 78-kd (GRP78) and nuclear factor kappa-b subunit 1 (NFκB1) gene expressions were evaluated by quantitative PCR analysis, while GRP 78, NF-κB p65, cleaved caspase-3 and caspase-12 protein levels were assesed by immunofluorescence. Ceramide-1-phosphate (C1P) levels were determined by immunoassay, while caspase −3 and −12 activity in cell lysates were measured via a fluorometric method.

Results

Induction of ER stress in TM treated groups were confirmed by significantly increased mRNA and protein levels of GRP78. TM significantly decreased cell viability compared to controls. Treatment with TUDCA along with TM significantly increased cell viability compared to the TM group. A significant increase was observed in C22–C24 CERs, C1P, caspase-3, caspase-12, NFκB1 mRNA and NF-κB p65 protein levels in cells treated with TM compared to controls. Administration of TUDCA lead to a partial decrease in GRP78 expression, NFκB1 mRNA, NF-κB p65 protein, C22–C24 CERs and C1P levels along with a decrease in caspase-3 and -12 activity.

Conclusions

The results of this study reveal the presence of increased long chain CERs, C1P and apoptotic markers in retinal cells undergoing ER stress.

FOXD3, frequently methylated in colorectal cancer, acts as a tumor suppressor and induces tumor cell apoptosis under ER stress via p53

Forkhead box D3 (FOXD3), an important member of the forkhead box transcription factor family, has many biological functions. However, the role and signaling pathways of FOXD3 in colorectal cancer (CRC) are still unclear. We examined FOXD3 expression and methylation in normal colon mucosa, CRC cell lines and primary tumors by reverse transcription–polymerase chain reaction, methylation-specific PCR and bisulfite genomic sequencing. We also evaluated its tumor-suppressive function by examining its modulation of apoptosis under endoplasmic reticulum (ER) stress in CRC cells. The FOXD3 target signal pathway was identified by western blotting, immunofluorescence and chromatin immunoprecipitation. We found that FOXD3 was frequently methylated and silenced in CRC cell lines and was downregulated in CRC tissues compared with paired adjacent non-tumor tissues. Meanwhile, low FOXD3 protein expression was significantly correlated with poor histopathological grading, lymph node metastasis and poor prognosis of patients, indicating its potential as a tumor marker that may be of potential value as a therapeutic target for CRC. Moreover, restoration of FOXD3 expression inhibited the proliferation and migration of tumor cells. FOXD3 also increased mitochondrial apoptosis through the unfolded protein response under ER stress. Furthermore, we found that FOXD3 could bind directly to the promoter of p53 and enhance its expression. Knockdown of p53 impaired the effect of apoptosis induced by FOXD3. In conclusion, we showed for the first time that FOXD3, which is frequently methylated in CRC, acted as a tumor suppressor inducing tumor cell apoptosis under ER stress via p53.

RITA requires eIF2α-dependent modulation of mRNA translation for its anti-cancer activity

Tumor protein 53 (p53, encoded by the TP53 gene) is a key tumor suppressor regulating cell fates in response to internal and external stresses. As TP53 is mutated or silenced in a majority of tumors, reactivation of p53 by small molecules represents a promising strategy in cancer therapeutics. One such agent is RITA (reactivation of p53 and induction of tumor cell apoptosis), which restores p53 expression in cells with hyperactive HDM2 and induces apoptosis. Yet, mechanisms underlying the anticancer activity of RITA are incompletely understood. Here we show that RITA suppresses mRNA translation independently of p53 by inducing eIF2α phosphorylation. Surprisingly, reactivation of p53 following RITA treatment is critically dependent on eIF2α phosphorylation. Moreover, inhibition of eIF2α phosphorylation attenuates pro-apoptotic and anti-neoplastic effects of RITA, while inducing phosphorylation of eIF2α enhances the anticancer activity of RITA. Collectively, these findings demonstrate that the translational machinery plays a major role in determining the antineoplastic activity of RITA, and suggest that combining p53 activators and translation modulators may be beneficial.

Dynamics of Genomic, Epigenomic, and Transcriptomic Aberrations during Stepwise Hepatocarcinogenesis

Hepatocellular carcinoma (HCC) undergoes a stepwise progression from liver cirrhosis to low-grade dysplastic nodule (LGDN), high-grade dysplastic nodule (HGDN), early HCC (eHCC), and progressed HCC (pHCC). Here, we profiled multilayered genomic, epigenomic, and transcriptomic aberrations in the stepwise hepatocarcinogenesis. Initial DNA methylation was observed in eHCC (e.g., DKK3, SALL3, and SOX1) while more extensive methylation was observed in pHCC. In addition, eHCCs showed an initial loss of DNA copy numbers of tumor suppressor genes in the 4q and 13q regions, thereby conferring survival benefits to cancer cells. Transcriptome analysis revealed that HGDNs expressed endoplasmic reticulum (ER) stress-related genes, while eHCC started to express oncogenes. Furthermore, integrative analysis indicated that expression of the serine peptidase inhibitor, Kazal type 1 (SPINK1), played a pivotal role in eHCC development. Significant demethylation of SPINK1 was observed in eHCC compared to HGDN. The study also demonstrated that ER stress may induce SPINK1 demethylation and expression in liver cancer cells. In conclusion, these results reveal the dynamics of multiomic aberrations during malignant conversion of liver cancer, thus providing novel pathobiological insights into hepatocarcinogenesis. SIGNIFICANCE: Multiomics profiling and integrative analyses of stepwise hepatocarcinogenesis reveal novel mechanistic and clinical insights into hepatocarcinogenesis.

Unfolded protein response regulates P53 expression in the pulmonary endothelium

Lung endothelial barrier dysfunction leads to severe pathologies, including the lethal Acute Respiratory Distress Syndrome. P53 has been associated with anti-inflammatory activities. The current study employs a variety of unfolded protein response (UPR) activators and inhibitors to investigate the regulation of P53 by UPR in lung cells. The bovine cells that were exposed to the UPR inductors brefeldin A, dithiothreitol, and thapsigargin; demonstrated elevated expression levels of P53 compared to the vehicle-treated cells. On the contrary, the UPR inhibitors N-acetyl cysteine, kifunensine, and ATP-competitive IRE1α kinase-inhibiting RNase attenuator; produced the opposite effects. The outcomes of the present study reveal a positive regulation between UPR and P53. Since it has been shown that a mild induction of the unfolded protein response opposes inflammation, we suggest that P53 is involved in those protective activities in the lung.

Unfolded Protein Response supports endothelial barrier function

Ongoing efforts are oriented towards the development of novel therapeutic agents to repress lung hyperpermeability responses due to inflammation. The endothelial barrier dysfunction triggered by such events, may eventually lead to severe cardiovascular complications, such as the Acute Respiratory Distress Syndrome. Hsp90 inhibitors are anticancer compounds, associated with strong anti-inflammatory responses in the endothelium. Our latest observations in experimental models of Acute Lung Injury suggest that P53 orchestrates, at least in part, such activities. Remarkably, both Hsp90 inhibition and P53 induction are associated with the activation of the Unfolded Protein Response element. The purpose of the current manuscript, is to introduce the hypotheses that UPR induction protects the vasculature against inflammation.

The Unfolded Protein Response: A Key Player in Zika Virus-Associated Congenital Microcephaly

Zika virus (ZIKV) is a mosquito-borne virus that belongs to the Flaviviridae family, together with dengue, yellow fever, and West Nile viruses. In the wake of its emergence in the French Polynesia and in the Americas, ZIKV has been shown to cause congenital microcephaly. It is the first arbovirus which has been proven to be teratogenic and sexually transmissible. Confronted with this major public health challenge, the scientific and medical communities teamed up to precisely characterize the clinical features of congenital ZIKV syndrome and its underlying pathophysiological mechanisms. This review focuses on the critical impact of the unfolded protein response (UPR) on ZIKV-associated congenital microcephaly. ZIKV infection of cortical neuron progenitors leads to high endoplasmic reticulum (ER) stress. This results in both the stalling of indirect neurogenesis, and UPR-dependent neuronal apoptotic death, and leads to cortical microcephaly. In line with these results, the administration of molecules inhibiting UPR prevents ZIKV-induced cortical microcephaly. The discovery of the link between ZIKV infection and UPR activation has a broader relevance, since this pathway plays a crucial role in many distinct cellular processes and its induction by ZIKV may account for several reported ZIKV-associated defects.

Prolonged Bat Call Exposure Induces a Broad Transcriptional Response in the Male Fall Armyworm (Spodoptera frugiperda; Lepidoptera: Noctuidae) Brain

Predation risk induces broad behavioral and physiological responses that have traditionally been considered acute and transitory. However, prolonged or frequent exposure to predators and the sensory cues of their presence they broadcast to the environment impact long-term prey physiology and demographics. Though several studies have assessed acute and chronic stress responses in varied taxa, these attempts have often involved a priori expectations of the molecular pathways involved in physiological responses, such as glucocorticoid pathways and neurohormone production in vertebrates. While relatively little is known about physiological and molecular predator-induced stress in insects, many dramatic insect defensive behaviors have evolved to combat selection by predators. For instance, several moth families, such as Noctuidae, include members equipped with tympanic organs that allow the perception of ultrasonic bat calls and facilitate predation avoidance by eliciting evasive aerial flight maneuvers. In this study, we exposed adult male fall armyworm (Spodoptera frugiperda) moths to recorded ultrasonic bat foraging and attack calls for a prolonged period and constructed a de novo transcriptome based on brain tissue from predator cue-exposed relative to control moths kept in silence. Differential expression analysis revealed that 290 transcripts were highly up- or down-regulated among treatment tissues, with many annotating to noteworthy proteins, including a heat shock protein and an antioxidant enzyme involved in cellular stress. Though nearly 50% of differentially expressed transcripts were unannotated, those that were are implied in a broad range of cellular functions within the insect brain, including neurotransmitter metabolism, ionotropic receptor expression, mitochondrial metabolism, heat shock protein activity, antioxidant enzyme activity, actin cytoskeleton dynamics, chromatin binding, methylation, axonal guidance, cilia development, and several signaling pathways. The five most significantly overrepresented Gene Ontology terms included chromatin binding, macromolecular complex binding, glutamate synthase activity, glutamate metabolic process, and glutamate biosynthetic process. As a first assessment of transcriptional responses to ecologically relevant auditory predator cues in the brain of moth prey, this study lays the foundation for examining the influence of these differentially expressed transcripts on insect behavior, physiology, and life history within the framework of predation risk, as observed in ultrasound-sensitive Lepidoptera and other 'eared' insects.

A negative feedback loop between XBP1 and Fbw7 regulates cancer development

In cancer, activation of X-box binding protein (XBP1) has a critical role in tumorigenesis and cancer progression. Transcriptional regulatory mechanism of XBP1 in cancer development has been well known, however, regulation of ubiquitination and degradation of XBP1 has not been elucidated yet. Here we show that Fbw7, a substrate recognition component of the SKP1-Cullin-F-box-type E3 ligase, interacts with XBP1 in a phosphorylation-dependent manner, and facilitates XBP1 ubiquitination and protein degradation. Moreover, Fbw7 inhibits oncogenic pathways including NF-κB, AP1, and Myc induced by XBP1. Interestingly, XBP1 negatively regulates transcription of Fbw7 via a feedback mechanism through NF-κB/E2F-1 axis signaling pathway, suggesting that overexpression of XBP1s may contribute to low level of Fbw7 expression in human cancers. Therefore, a negative feedback loop between Fbw7 and XBP1 contributes to the regulation of tumor development and can be an attractive target for novel therapy in cancers.

p53-NF-κB Crosstalk in Febrile Temperature-Treated Human Umbilical Cord-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are successful for their therapeutic application in immune and inflammatory contexts due to their anti-inflammatory, trophic, and immunomodulatory roles. However, though MSCs have the potential to provide regenerative treatment toward a wide range of devastating diseases, massive cell death of transplanted MSCs remains an obstacle to overcome. The relation between MSCs and inflammation is multifactorial and challenging to comprehend. Fever is a critical component of the inflamed microenvironment. Also, the choice of MSC source could be critical in determining the fate of transplanted cells under stress conditions. Here we investigated the thermosensitivity of Wharton's jelly MSCs (WJ-MSCs) to elevated temperature in the physiological fever range. We explored the effect of febrile range temperature on morphology, viability, proliferation kinetics, and cell cycle status of WJ-MSCs. WJ-MSCs adopted a flattened morphology at 40°C, and our data from proliferation kinetics study using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and apoptosis assays showed that WJ-MSCs had reduced proliferation and viability at 40°C compared with control cultures. There was also a G0/G1 cell cycle arrest, which was further confirmed by messenger RNA (mRNA) levels of genes specific for different stages of cell cycle. On evaluating p53 status, we observed an increase in p53 protein expression and its nuclear localization in WJ-MSCs exposed to 40°C. Its downstream effector p21 too was upregulated. Moreover, this temperature-induced p53 induction was inhibited on exposure to 40°C in the presence of NF-κB pathway inhibitor, pyrrolidinedithiocarbamate (PDTC) or endonuclease-prepared small interfering RNA (esiRNA) targeting p65. Febrile temperature exposure did not affect the senescence status of WJ-MSCs. The MSC-specific surface antigen profile at 40°C was similar to control WJ-MSCs. Our findings suggest that under febrile temperature stress conditions, WJ-MSCs exhibit G0/G1 cell cycle arrest and reduction in viable cell count, while retaining their basic characteristics, with an underlying interplay of p53 and NF-κB pathway.

Sequential treatment with celecoxib and bortezomib enhances the ER stress-mediated autophagy-associated cell death of colon cancer cells

Treatment with celecoxib and bortezomib as single chemotherapeutic agents reduces the viability and proliferation of colorectal cancer cells. The use of these agents in combination with other chemotherapeutic agents is usually associated with adverse effects. In the present study, a combination of celecoxib and bortezomib was investigated for potential synergistic effects in colon cancer cells. The sequential exposure to celecoxib with bortezomib synergistically induced apoptotic death in human colon cancer cells compared with groups treated with a single drug or other drug combinations. c-Jun N-terminal kinase/p38-mitogen-activated protein kinase-induced endoplasmic reticulum (ER) stress through serial exposure to celecoxib and bortezomib may have induced the intracellular Ca²⁺ release, leading to the generation of autophagosomes in p53-expressing HCT-116 cells. Targeted inhibition of p53 activity or ER stress or treatment with the Ca²⁺-chelating agent BAPTA-AM suppressed the ER stress-mediated Ca²⁺ release and apoptosis. Although p53^-/- HCT-116 cells were less sensitive to sequential treatment with celecoxib and bortezomib, co-localization of autophagosomes was detected in the absence of CCAAT-enhancer-binding protein homologous protein expression. Treatment of p53^-/- HCT-116 cells with BAPTA-AM did not inhibit apoptosis following serial treatment with celecoxib and bortezomib. These results suggest that the order of drug administration is important in treating cancer and that the sequential treatment with celecoxib and bortezomib enhances the ER stress-mediated autophagy-associated cell death of colon cancer cells, regardless of p53 expression.

Z-FL-COCHO, a cathepsin S inhibitor, enhances oxaliplatin-mediated apoptosis through the induction of endoplasmic reticulum stress

Multiple cancer cells highly express cathepsin S, which has pro-tumoral effects. However, it was previously unknown whether knockdown or a pharmacological inhibitor (ZFL) of cathepsin S acts as an inducer of ER stress. Here, ZFL and knockdown of cathepsin S markedly induced ER stress through the up-regulation of calcium levels in the cytosol. Induction of calcium levels by inhibition of cathepsin S is markedly blocked by an inhibitor of the IP3 receptor and the ryanodine receptor Ca²⁺ channel in the ER, but an inhibitor of a mitochondrial Ca²⁺ uniporter had no effect on ZFL-induced calcium levels. Furthermore, production of mitochondrial ROS by ZFL was associated with an increase in cytosolic calcium levels. ZFL-mediated ER stress enhanced anti-cancer drug-induced apoptotic cell death, and pretreatment with chemical chaperones or down-regulation of ATF4 and CHOP by small interfering RNA markedly reduced ZFL plus oxaliplatin-induced apoptosis. Taken together, our findings reveal that inhibition of cathepsin S is an inducer of ER stress; these findings may contribute to the enhancement of therapeutic efficiency in cancer cells.

A drug that inhibits a key cancer enzyme could be used in combination with anti-cancer drugs to improve sensitivity to treatment. The intracellular endoplasmic reticulum (ER) is involved in several vital processes in cells, including folding and processing proteins. Taeg Kyu Kwon at Keimyung University, Daegu, South Korea, and co-workers have demonstrated how inhibition of cathepsin S, which is expressed in many cancer cells, induces ER stress. In trials on human kidney cancer cells grafted onto mice and in vitro, the team found that ZFL (cathepsin S inhibitor) triggered transient ER stress by increasing calcium levels inside cells. Subsequent treatment with the anti-cancer drug oxaliplatin resulted in increased cancer cell death.

Inhibition of granzyme B activity blocks inflammation induced by lipopolysaccharide through regulation of endoplasmic reticulum stress signaling in NK92 cells

Granzyme B (GrB) is a serine protease that is expressed in the lytic granules of natural killer (NK) cells and cytotoxic T lymphocytes (CTL), and which has been widely reported to serve a crucial role for target cell apoptosis. GrB may serve a non‑cytotoxic role in inflammation, but the evidence remains unclear. The present study aimed to establish an inflammatory cell model by using NK92 cells stimulated with lipopolysaccharide (LPS) to investigate whether GrB was involved in the development of inflammation. The extracellular levels of tumor necrosis factor‑α (TNF‑α), interleukin‑1β (IL‑1β) and GrB were examined by ELISA, and it was demonstrated that LPS treatment increased the extracellular levels of TNF‑α, IL‑1β and GrB, and these increased expression levels were inhibited by pretreatment with the GrB inhibitor serpin A3N (SA3N). The protein expression levels of glucose‑regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), nuclear factor‑κB (NF‑κB), inhibitor of NF‑κB (IκBα) and GrB were examined by western blot analysis. The results demonstrated that LPS stimulation increased the expression levels of GRP78, CHOP, NF‑κB and GrB, and decreased the expression of IκBα, and these changes were inhibited by SA3N, which indicated that inhibition of GrB activity may suppress endoplasmic reticulum (ER) stress signaling. Therefore, it was suggested that GrB may be a potential pro‑inflammatory factor, and inhibition of GrB activity may aid the prevention of the development of inflammation by suppressing ER stress signaling.

Mahanine drives pancreatic adenocarcinoma cells into endoplasmic reticular stress-mediated apoptosis through modulating sialylation process and Ca2+-signaling

Endoplasmic reticulum (ER) stress results from protein unfolding/misfolding during cellular maturation, which requires a coordinated action of several chaperones and enzymes and Ca²⁺ signalling. ER-stress possibly has a positive effect on survival of pancreatic cancer cell. Therefore, detailed insights into this complex signaling network are urgently needed. Here, we systematically analyzed the impact of ER stress-mediated unfolded protein response (UPR) and Ca²⁺-signaling cross-talk for the survival of pancreatic adenocarcinoma (PDAC) cells. We observed enhanced ER activity and initiation of UPR signaling induced by a carbazole alkaloid (mahanine). This event triggers a time-dependent increase of intracellular Ca²⁺ leakage from ER and subsequently Ca²⁺ signaling induced by enhanced reactive oxygen species (ROS) produced by this pro-oxidant agent. In addition, we observed an altered glycosylation, in particular with regard to reduced linkage-specific sialic acids possibly due to decreased sialyltransferase activity. Changes in sialylation entailed enhanced expression of the ganglioside GD3 in the treated cells. GD3, an inducer of apoptosis, inhibited pancreatic xenograft tumor. Taken together, our study describes a molecular scenario how PDAC cells are driven into apoptosis by mahanine by UPR-driven ER stress-associated and ROS-mediated calcium signaling and possibly defective sialylation.

MANF Is Essential for Neurite Extension and Neuronal Migration in the Developing Cortex

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) resident protein with neuroprotective effects. Previous studies have shown that MANF expression is altered in the developing rodent cortex in a spatiotemporal manner. However, the role of MANF in mammalian neurogenesis is not known. The aim of this study was to determine the role of MANF in neural stem cell (NSC) proliferation, differentiation, and cerebral cortex development. We found that MANF is highly expressed in neural lineage cells, including NSCs in the developing brain. We discovered that MANF-deficient NSCs in culture are viable and show no defect in proliferation. However, MANF-deficient cells have deficits in neurite extension upon neuronal differentiation. In vivo, MANF removal leads to slower neuronal migration and impaired neurite outgrowth. In vitro, mechanistic studies indicate that impaired neurite growth is preceded by reduced de novo protein synthesis and constitutively activated unfolded protein response (UPR) pathways. This study is the first to demonstrate that MANF is a novel and critical regulator of neurite growth and neuronal migration in mammalian cortical development.

Endocrine disruptors induce perturbations in endoplasmic reticulum and mitochondria of human pluripotent stem cell derivatives

Persistent exposure to man-made endocrine disrupting chemicals during fetal endocrine development may lead to disruption of metabolic homeostasis contributing to childhood obesity. Limited cellular platforms exist to test endocrine disrupting chemical-induced developmental abnormalities in human endocrine tissues. Here we use an human-induced pluripotent stem cell-based platform to demonstrate adverse impacts of obesogenic endocrine disrupting chemicals in the developing endocrine system. We delineate the effects upon physiological low-dose exposure to ubiquitous endocrine disrupting chemicals including, perfluoro-octanoic acid, tributyltin, and butylhydroxytoluene, in endocrine-active human-induced pluripotent stem cell-derived foregut epithelial cells and hypothalamic neurons. Endocrine disrupting chemicals induce endoplasmic reticulum stress, perturb NF-κB, and p53 signaling, and diminish mitochondrial respiratory gene expression, spare respiratory capacity, and ATP levels. As a result, normal production and secretion of appetite control hormones, PYY, α-MSH, and CART, are hampered. Blocking NF-κB rescues endocrine disrupting chemical-induced aberrant mitochondrial phenotypes and endocrine dysregulation, but not ER-stress and p53-phosphorylation changes.Harmful chemicals that disrupt the endocrine system and hormone regulation have been associated with obesity. Here the authors apply a human pluripotent stem cell-based platform to study the effects of such compounds on developing gut endocrine and neuroendocrine systems.

Comparative Proteomic Analysis of the Mitochondria-associated ER Membrane (MAM) in a Long-term Type 2 Diabetic Rodent Model

The mitochondria-associated ER membrane (MAM) plays a critical role in cellular energetics and calcium homeostasis; however, how MAM is affected under diabetic condition remains elusive. This study presented a comprehensive proteome profiling of isolated brain MAM from long-term type 2 diabetic mice vs. non-diabetic controls. MAM protein was extracted efficiently by a surfactant-aided precipitation/on-pellet digestion (SOD) method, and MAM proteome was quantified by an ion-current-based MS1 method combined with nanoLC-MS/MS. A total of 1,313 non-redundant proteins of MAM were identified, among which 144 proteins were found significantly altered by diabetes. In-depth IPA analysis identified multiple disease-relevant signaling pathways associated with the MAM proteome changes in diabetes, most significantly the unfolded protein response (UPR), p53, hypoxia-related transcription factors, and methyl CpG binding protein 2. Using immunofluorescence labeling we confirmed the activation of three UPR branches and increased ERp29 and calreticulin in diabetic retinas. Moreover, we found GRP75, a key MAM tethering protein, was drastically reduced by long-term diabetes. In vitro, acute high glucose treatment reduces ER-mitochondrial contact in retinal endothelial cells. This study provides first insight into the significant alterations in MAM proteome associated with activation of the UPR in diabetes, which may serve as novel benchmarks for the future studies of diabetic complications.

C/EBPβ LIP augments cell death by inducing osteoglycin

Many types of tumor cell are devoid of the extracellular matrix proteoglycan osteoglycin (Ogn), but its role in tumor biology is poorly studied. Here we show that RNAi of Ogn attenuates stress-triggered cell death, whereas its overexpression increases cell death. We found that the transcription factor C/EBPβ regulates the expression of Ogn. C/EBPβ is expressed as a full-length, active form (LAP) and as a truncated, dominant-negative form (LIP), and the LIP/LAP ratio is positively correlated with the extent of cell death under stress. For example, we reported that drug-resistant tumor cells lack LIP altogether, and its supplementation abolished their resistance to chemotherapy and to endoplasmic reticulum (ER) stress. Here we further show that elevated LIP/LAP ratio robustly increased Ogn expression and cell death under stress by modulating the mitogen-activated protein kinase/activator protein 1 pathway (MAPK/AP-1). Our findings suggest that LIP deficiency renders tumor cell resistant to ER stress by preventing the induction of Ogn.

Neutral sphingomyelinase inhibition alleviates apoptosis, but not ER stress, in liver ischemia-reperfusion injury

Previous studies have revealed the activation of neutral sphingomyelinase (N-SMase)/ceramide pathway in hepatic tissue following warm liver ischemia reperfusion (IR) injury. Excessive ceramide accumulation is known to potentiate apoptotic stimuli and a link between apoptosis and endoplasmic reticulum (ER) stress has been established in hepatic IR injury. Thus, this study determined the role of selective N-SMase inhibition on ER stress and apoptotic markers in a rat model of liver IR injury. Selective N-SMase inhibitor was administered via intraperitoneal injections. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Levels of sphingmyelin and ceramide in liver tissue were determined by an optimized multiple reactions monitoring (MRM) method using ultrafast-liquid chromatography (UFLC) coupled with tandem mass spectrometry (MS/MS). Spingomyelin levels were significantly increased in all IR groups compared with controls. Treatment with a specific N-SMase inhibitor significantly decreased all measured ceramides in IR injury. A significant increase was observed in ER stress markers C/EBP-homologous protein (CHOP) and 78 kDa glucose-regulated protein (GRP78) in IR injury, which was not significantly altered by N-SMase inhibition. Inhibition of N-SMase caused a significant reduction in phospho-NF-kB levels, hepatic TUNEL staining, cytosolic cytochrome c, and caspase-3, -8, and -9 activities which were significantly increased in IR injury. Data herein confirm the role of ceramide in increased apoptotic cell death and highlight the protective effect of N-SMase inhibition in down-regulation of apoptotic stimuli responses occurring in hepatic IR injury.

FAM172A controls endoplasmic reticulum (ER) stress related to NF-κB signaling pathway in hepatocellular carcinoma

FAM172A is an anti-oncogene and plays a vital role in controlling cell proliferation and cell cycle by inducing the arrest of G1/S.

Functional and clinical relevance of novel and known PCSK1 variants for childhood obesity and glucose metabolism

Objective

Variants in Proprotein Convertase Subtilisin/Kexin Type 1 (PCSK1) may be causative for obesity as suggested by monogenic cases and association studies. Here we assessed the functional relevance in experimental studies and the clinical relevance through detailed metabolic phenotyping of newly identified and known PCSK1 variants in children.

Results

In 52 obese children selected for elevated proinsulin levels and/or impaired glucose tolerance, we found eight known variants and two novel heterozygous variants (c.1095 + 1G > A and p.S24C) by sequencing the PCSK1 gene. Patients with the new variants presented with extreme obesity, impaired glucose tolerance, and PCOS. Functionally, c.1095 + 1G > A caused skipping of exon8 translation and a complete loss of enzymatic activity. The protein was retained within the endoplasmic reticulum (ER) causing ER stress. The p.S24C variant had no functional effect on protein size, cell trafficking, or enzymatic activity. The known variants rs6230, rs35753085, and rs725522 in the 5′ end did not affect PCSK1 promoter activity.

In clinical association studies in 1673 lean and obese children, we confirmed associations of rs6232 and rs6234 with BMI-SDS and of rs725522 with glucose stimulated insulin secretion and Matsuda index. We did not find the new variants in any other subjects.

Conclusions

We identified and functionally characterized two rare novel PCSK1 variants of which c.1095 + 1G > A caused complete loss of protein function. In addition to confirming rs6232 and rs6234 in PCSK1 as polygenic risk variants for childhood obesity, we describe an association of rs725522 with insulin metabolism. Our results support the contribution of PCSK1 variants to obesity predisposition in children.

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We identified two novel variants in PCSK1 in severely obese adolescents.

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The phenotype of these two heterozygous carriers is more severe than in “common childhood obesity”.

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The ΔEx8 variant leads to a truncated protein with a complete loss of function, which is retained within the ER.

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For common variant rs725522 detailed metabolic phenotyping revealed impaired glucose dynamics.

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Overall, variants in PCSK1 are not only associated with childhood obesity, but a more severe phenotype than in BMI-matched controls.

Silica nanoparticles induce endoplasmic reticulum stress response and activate mitogen activated kinase (MAPK) signalling

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Effects of silica nanoparticles (SiO₂-NPs) were investigated in Huh7 cells.

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SiO₂-NPs induced ER stress response and activated MAPK pathway.

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SiO₂-NPs induced inflammatory reaction by induction of TNF-α.

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Activation of MAPK may lead to activation of AP-1 complex.

Humans may be exposed to engineered silica nanoparticles (SiO₂-NPs) but potential adverse effects are poorly understood, in particular in relation to cellular effects and modes of action. Here we studied effects of SiO₂-NPs on cellular function in human hepatoma cells (Huh7). Exposure for 24 h to 10 and 50 μg/ml SiO₂-NPs led to induction of endoplasmic reticulum (ER) stress as demonstrated by transcriptional induction of DNAJB9, GADD34, CHOP, as well as CHOP target genes BIM, CHAC-1, NOXA and PUMA. In addition, CHOP protein was induced. In addition, SiO₂-NPs induced an inflammatory response as demonstrated by induction of TNF-α and IL-8. Activation of MAPK signalling was investigated employing a PCR array upon exposure of Huh7 cells to SiO₂-NPs. Five of 84 analysed genes, including P21, P19, CFOS, CJUN and KSR1 exhibited significant transcriptional up-regulation, and 18 genes a significant down-regulation. Strongest down-regulation occurred for the proto-oncogene BRAF, MAPK11, one of the four p38 MAPK genes, and for NFATC4. Strong induction of CFOS, CJUN, FRA1 and CMYC was found after exposure to 50 μg/ml SiO₂-NPs for 24 h. To analyse for effects derived from up-regulation of TNF-α, Huh7 cells were exposed to SiO₂-NPs in the presence of the TNF-α inhibitor sauchinone, which reduced the induction of the TNF-α transcript by about 50%. These data demonstrate that SiO₂-NPs induce ER stress, MAPK pathway and lead to inflammatory reaction in human hepatoma cells. Health implications of SiO₂-NPs exposure should further be investigated for a risk assessment of these frequently used nanoparticles.

TM7SF3, a novel p53-regulated homeostatic factor, attenuates cellular stress and the subsequent induction of the unfolded protein response

Earlier reported small interfering RNA (siRNA) high-throughput screens, identified seven-transmembrane superfamily member 3 (TM7SF3) as a novel inhibitor of pancreatic β-cell death. Here we show that TM7SF3 maintains protein homeostasis and promotes cell survival through attenuation of ER stress. Overexpression of TM7SF3 inhibits caspase 3/7 activation. In contrast, siRNA-mediated silencing of TM7SF3 accelerates ER stress and activation of the unfolded protein response (UPR). This involves inhibitory phosphorylation of eukaryotic translation initiation factor 2α activity and increased expression of activating transcription factor-3 (ATF3), ATF4 and C/EBP homologous protein, followed by induction of apoptosis. This process is observed both in human pancreatic islets and in a number of cell lines. Some of the effects of TM7SF3 silencing are evident both under basal conditions, in otherwise untreated cells, as well as under different stress conditions induced by thapsigargin, tunicamycin or a mixture of pro-inflammatory cytokines (tumor necrosis factor alpha, interleukin-1 beta and interferon gamma). Notably, TM7SF3 is a downstream target of p53: activation of p53 by Nutlin increases TM7SF3 expression in a time-dependent manner, although silencing of p53 abrogates this effect. Furthermore, p53 is found in physical association with the TM7SF3 promoter. Interestingly, silencing of TM7SF3 promotes p53 activity, suggesting the existence of a negative-feedback loop, whereby p53 promotes expression of TM7SF3 that acts to restrict p53 activity. Our findings implicate TM7SF3 as a novel p53-regulated pro-survival homeostatic factor that attenuates the development of cellular stress and the subsequent induction of the UPR.

Suppression of StarD7 promotes endoplasmic reticulum stress and induces ROS production

StarD7 is an intracellular lipid transport protein identified as up-regulated in the choriocarcinoma JEG-3 cell line. StarD7 facilitates the delivery of phosphatidylcholine (PC) to the mitochondria, and StarD7 knockdown causes a reduction in phospholipid synthesis. Since inhibition of PC synthesis may lead to endoplasmic reticulum (ER) stress we hypothesized that StarD7 may be involved in maintaining cell homeostasis. Here, we examined the effect of StarD7 silencing on ER stress response and on the levels of reactive oxygen species (ROS) in the human hepatoma cell line HepG2. StarD7 knockdown induced alterations in mitochondria and ER morphology. These changes were accompanied with an ER stress response as determined by increased expression of inositol-requiring enzyme 1α (IRE1α), calnexin, glucose regulated protein 78/immunoglobulin heavy chain-binding protein (Grp78/BiP), protein kinase-like ER kinase (PERK) as well as the phosphorylated eukaryotic translation initiation factor 2, subunit 1α (p-eIF2α). Additionally, a downregulation of the tumor suppressor p53 by a degradation mechanism was observed in StarD7 siRNA cells. Furthermore, StarD7 silencing induced ROS generation and reduced cell viability after H₂O₂ exposure. Decreased expression of StarD7 was associated to increased levels of the heme oxygenase-1 (HO-1) and catalase enzymes as well as in catalase enzymatic activity. Finally, no changes in levels of autophagy and apoptosis markers were observed in StarD7 siRNA treated cells respect to control cells. Taken together, these results indicate that StarD7 contributes to modulate cellular redox homeostasis.

Critical role of XBP1 in cancer signalling is regulated by PIN1

XBP1 (X-box-binding protein 1) is activated in cancer and has a pivotal role in tumorigenesis and progression of human cancer. In particular, the XBP1 transcriptional regulatory network is well known to drive cancer development, but little is known about whether the stability of XBP1 is regulated and, if so, what controls the stability of XBP1. In the present study we show that PIN1 prolyl isomerase interacts with the active form of XBP1 (XBP1s) in a phosphorylation-dependent manner and promotes XBP1s-induced cell proliferation and transformation through the regulation of XBP1 stability. By contrast, depletion of Pin1 in cancer cells reduced XBP1s expression, which subsequently inhibits cell proliferation and transformation. Interestingly, XBP1s activates multiple oncogenic pathways including NF-κB (nuclear factor κB), AP1 (activator protein 1) and Myc, and down-regulates PIN1 transcription via a negative-feedback mechanism through p53 induction. Ultimately, reciprocal regulation of Pin1 and XBP1s is associated with the activation of oncogenic pathways, and the relationship of PIN1 and XBP1 may be an attractive target for novel therapy in cancers.

Matrine inhibits diethylnitrosamine-induced HCC proliferation in rats through inducing apoptosis via p53, Bax-dependent caspase-3 activation pathway and down-regulating MLCK overexpression

The proliferation of hepatocellular carcinoma (HCC) cells is one of the leading causes of liver cancer mortality in humans. The inhibiting effects of matrine on HCC cell proliferation have been studied, but the mechanism of that inhibition has not been fully elucidated. Since, apoptosis plays an important role in HCC cell proliferation. We examined the apoptosis-inducing effect of matrine on tumor cells. Western blot analysis of p53, Bax, cleaved caspase-3 and myosin light chain kinase (MLCK) revealed that matrine induced tumor cell apoptosis by controlling anoikis. It activated p53, Bax-dependent caspase-3 and blocked the ECM-integrin mediated cell survival pathway through down-regulating MLCK over-expression in the liver of rats with diethyl nitrosamine (DENA)-induced HCC. Our results suggest that matrine can inhibit the proliferation of HCC cells through inducing tumor cell apoptosis via activation of the p53 pathway and inhibition of MLCK overexpression. Matrine may thus be used as a potentially promising reagent to inhibit HCC cell proliferation and MLCK may be a novel target for the treatment of HCC.

Endoplasmic Reticulum Stress in Heat- and Shake-Induced Injury in the Rat Small Intestine

We investigated the mechanisms underlying damage to rat small intestine in heat- and shake-induced stress. Eighteen Sprague-Dawley rats were randomly divided into a control group and a 3-day stressed group treated 2 h daily for 3 days on a rotary platform at 35°C and 60 r/min. Hematoxylin and eosin-stained paraffin sections of the jejunum following stress revealed shedding of the villus tip epithelial cells and lamina propria exposure. Apoptosis increased at the villus tip and extended to the basement membrane. Photomicrographs revealed that the microvilli were shorter and sparser; the nuclear envelope invaginated and gaps in the karyolemma increased; and the endoplasmic reticulum (ER) swelled significantly. Gene microarray analysis assessed 93 differentially expressed genes associated with apoptosis, ER stress, and autophagy. Relevant genes were compiled from the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Forty-one genes were involved in the regulation of apoptosis, fifteen were related to autophagy, and eleven responded to ER stress. According to KEGG, the apoptosis pathways, mitogen-activated protein kinase(MAPK) signaling pathway, the mammalian target of rapamycin (mTOR) signaling pathway, and regulation of autophagy were involved. Caspase3 (Casp3), caspase12 (Casp12), and microtubule-associate proteins 1 light chain 3(LC3) increased significantly at the villus tip while mTOR decreased; phosphorylated-AKT (P-AKT) decreased. ER stress was involved and induced autophagy and apoptosis in rat intestinal damage following heat and shake stress. Bioinformatic analysis will help determine the underlying mechanisms in stress-induced damage in the small intestine.