UPRER promotes lipophagy independent of chaperones to extend life span

Longevity is dictated by a combination of environmental and genetic factors. One of the key mechanisms to regulate life-span extension is the induction of protein chaperones for protein homeostasis. Ectopic activation of the unfolded protein response of the endoplasmic reticulum (UPR^ER) specifically in neurons is sufficient to enhance organismal stress resistance and extend life span. Here, we find that this activation not only promotes chaperones but also facilitates ER restructuring and ER function. This restructuring is concomitant with lipid depletion through lipophagy. Activation of lipophagy is distinct from chaperone induction and is required for the life-span extension found in this paradigm. Last, we find that overexpression of the lipophagy component, ehbp-1, is sufficient to deplete lipids, remodel ER, and promote life span. Therefore, UPR induction in neurons triggers two distinct programs in the periphery: the proteostasis arm through protein chaperones and metabolic changes through lipid depletion mediated by EH domain binding protein 1 (EHBP-1).

G604S-HERG mutation in LQT2 leads to autophagy via the UPR-related pathway

Congenital long QT syndrome (LQTS) is a heart channel disease associated with fatal ventricular arrhythmias or cardiac arrest. Human ether-a-go-go-related gene (HERG) mutation is one of the main causes in type 2 LQTS since it may lead to abundant immature HERG channel protein accumulate in the endoplasmic reticulum (ER). In our study, we have successfully constructed the G604S-HERG mutation in HEK293 cells and demonstrated that the immature HERG protein on ER via Western blot and immunofluorescence. Herein we found that unfolded protein reaction (UPR) process has been activated in order to counter this endoplasmic reticulum stress (ERS) since the main sensors got upregulated. Meanwhile, autophagy was also observed in this process and verified by Western blot and transmission electron microscopy. To explore the relationship underlying autophagy and UPR in the condition of ERS, we found that PERK-EIF2a-CHOP axis was activated. Our findings provides insight for G604S-HERG mutation in type 2 LQTS.

Pyroptosis is a critical inflammatory pathway in the placenta from early onset preeclampsia and in human trophoblasts exposed to hypoxia and endoplasmic reticulum stressors

Systemic manifestation of preeclampsia (PE) is associated with circulating factors, including inflammatory cytokines and damage-associated molecular patterns (DAMPs), or alarmins. However, it is unclear whether the placenta directly contributes to the increased levels of these inflammatory triggers. Here, we demonstrate that pyroptosis, a unique inflammatory cell death pathway, occurs in the placenta predominantly from early onset PE, as evidenced by elevated levels of active caspase-1 and its substrate or cleaved products, gasdermin D (GSDMD), IL-1β, and IL-18. Using cellular models mimicking pathophysiological conditions (e.g., autophagy deficiency, hypoxia, and endoplasmic reticulum (ER) stress), we observed that pyroptosis could be induced in autophagy-deficient human trophoblasts treated with sera from PE patients as well as in primary human trophoblasts exposed to hypoxia. Exposure to hypoxia elicits excessive unfolded protein response (UPR) and ER stress and activation of the NOD-like receptor pyrin-containing 3 (NLRP3) inflammasome in primary human trophoblasts. Thioredoxin-interacting protein (TXNIP), a marker for hyperactivated UPR and a crucial signaling molecule linked to NLRP3 inflammasome activation, is significantly increased in hypoxia-treated trophoblasts. No evidence was observed for necroptosis-associated events. Importantly, these molecular events in hypoxia-treated human trophoblasts are significantly observed in placental tissue from women with early onset PE. Taken together, we propose that placental pyroptosis is a key event that induces the release of factors into maternal circulation that possibly contribute to severe sterile inflammation and early onset PE pathology.

Lrrc55 is a novel prosurvival factor in pancreatic islets

Pancreatic islets adapt to the increase in insulin demand during pregnancy by upregulating β-cell number, insulin synthesis, and secretion. These changes require prolactin receptor (PrlR) signaling, as mice with PrlR deletion are glucose intolerant with a lower β-cell mass. Prolactin also prevents β-cell apoptosis. Many genes participate in these adaptive changes in the islet, and Lrrc55 is one of the most upregulated genes with unknown function in islets. Because Lrrc55 expression increases in parallel to the increase in β-cell number and insulin production during pregnancy, we hypothesize that Lrrc55 might regulate β-cell proliferation/apoptosis (thus β-cell number) and insulin synthesis. Here, we found that Lrrc55 expression was upregulated by >60-fold during pregnancy in a PrlR-dependent manner, and this increase was restricted only to the islets. Overexpression of Lrrc55 in β-cells had minimal effect on β-cell proliferation and glucose-stimulated insulin secretion but protected β-cells from glucolipotoxicity-induced reduction in insulin gene expression. Moreover, Lrrc55 protects β-cells from glucolipotoxicity-induced apoptosis, with upregulation of prosurvival signals and downregulation of proapoptotic signals of the endoplasmic reticulum (ER) stress pathway. Furthermore, Lrrc55 attenuated calcium depletion induced by glucolipotoxicity, which may contribute to its antiapoptotic effect. Hence our findings suggest that Lrrc55 is a novel prosurvival factor that is upregulated specifically in islets during pregnancy, and it prevents conversion of adaptive unfolded protein response to unresolved ER stress and apoptosis in β-cells. Lrrc55 could be a potential therapeutic target in diabetes by reducing ER stress and promoting β-cell survival.

EPO and TMBIM3/GRINA Promote the Activation of the Adaptive Arm and Counteract the Terminal Arm of the Unfolded Protein Response after Murine Transient Cerebral Ischemia

Ischemic stroke is known to cause the accumulation of misfolded proteins and loss of calcium homeostasis leading to impairment of endoplasmic reticulum (ER) function. The unfolded protein response (UPR) is an ER-located and cytoprotective pathway that aims to resolve ER stress. Transmembrane BAX inhibitor-1 motif-containing (TMBIM) protein family member TMBIM3/GRINA is highly expressed in the brain and mostly located at the ER membrane suppressing ER calcium release by inositol-1,4,5-trisphosphate receptors. GRINA confers neuroprotection and is regulated by erythropoietin (EPO) after murine cerebral ischemia. However, the role of GRINA and the impact of EPO treatment on the post-ischemic UPR have not been elucidated yet. We subjected GRINA-deficient (Grina^−/−) and wildtype mice to transient (30 min) middle cerebral artery occlusion (tMCAo) followed by 6 h or 72 h of reperfusion. We administered EPO or saline 0, 24 and 48 h after tMCAo/sham surgery. Oxygen–glucose deprivation (OGD) and pharmacological stimulation of the UPR using Tunicamycin and Thapsigargin were carried out in primary murine cortical mixed cell cultures. Treatment with the PERK-inhibitor GSK-2606414, IRE1a-RNase-inhibitor STF-083010 and EPO was performed 1 h prior to either 1 h, 2 h or 3 h of OGD. We found earlier and larger infarct demarcations in Grina^−/− mice compared to wildtype mice, which was accompanied by a worse neurological outcome and an abolishment of EPO-mediated neuroprotection after ischemic stroke. In addition, GRINA-deficiency increased apoptosis and the activation of the corresponding PERK arm of the UPR after stroke. EPO enhanced the post-ischemic activation of pro-survival IRE1a and counteracted the pro-apoptotic PERK branch of the UPR. Both EPO and the PERK-inhibitor GSK-2606414 reduced cell death and regulated Grina mRNA levels after OGD. In conclusion, GRINA plays a crucial role in post-ischemic UPR and the use of both GSK-2606414 and EPO might lead to neuroprotection.

Ribosomal mistranslation leads to silencing of the unfolded protein response and increased mitochondrial biogenesis

Translation fidelity is the limiting factor in the accuracy of gene expression. With an estimated frequency of 10-4, errors in mRNA decoding occur in a mostly stochastic manner. Little is known about the response of higher eukaryotes to chronic loss of ribosomal accuracy as per an increase in the random error rate of mRNA decoding. Here, we present a global and comprehensive picture of the cellular changes in response to translational accuracy in mammalian ribosomes impaired by genetic manipulation. In addition to affecting established protein quality control pathways, such as elevated transcript levels for cytosolic chaperones, activation of the ubiquitin-proteasome system, and translational slowdown, ribosomal mistranslation led to unexpected responses. In particular, we observed increased mitochondrial biogenesis associated with import of misfolded proteins into the mitochondria and silencing of the unfolded protein response in the endoplasmic reticulum.

Autophagy in Neurons

Autophagy is the major cellular pathway to degrade dysfunctional organelles and protein aggregates. Autophagy is particularly important in neurons, which are terminally differentiated cells that must last the lifetime of the organism. There are both constitutive and stress-induced pathways for autophagy in neurons, which catalyze the turnover of aged or damaged mitochondria, endoplasmic reticulum, other cellular organelles, and aggregated proteins. These pathways are required in neurodevelopment as well as in the maintenance of neuronal homeostasis. Here we review the core components of the pathway for autophagosome biogenesis, as well as the cell biology of bulk and selective autophagy in neurons. Finally, we discuss the role of autophagy in neuronal development, homeostasis, and aging and the links between deficits in autophagy and neurodegeneration.

Basic-leucine zipper 17 and Hmg-CoA reductase degradation 3A are involved in salt acclimation memory in Arabidopsis

Salt acclimation, which is induced by previous salt exposure, increases the resistance of plants to future exposure to salt stress. However, little is known about the underlying mechanism, particularly how plants store the "memory" of salt exposure. In this study, we established a system to study salt acclimation in Arabidopsis thaliana. Following treatment with a low concentration of salt, seedlings were allowed to recover to allow transitory salt responses to subside while maintaining the sustainable effects of salt acclimation. We performed transcriptome profiling analysis of these seedlings to identify genes related to salt acclimation memory. Notably, the expression of Basic-leucine zipper 17 (bZIP17) and Hmg-CoA reductase degradation 3A (HRD3A), which are important in the unfolded protein response (UPR) and endoplasmic reticulum-associated degradation (ERAD), respectively, increased following treatment with a low concentration of salt and remained at stably high levels after the stimulus was removed, a treatment which improved plant tolerance to future high-salinity challenge. Our findings suggest that the upregulated expression of important genes involved in the UPR and ERAD represents a "memory" of the history of salt exposure and enables more potent responses to future exposure to salt stress, providing new insights into the mechanisms underlying salt acclimation in plants.

Somatic mutations and cell identity linked by Genotyping of Transcriptomes

Defining the transcriptomic identity of malignant cells is challenging in the absence of surface markers that distinguish cancer clones from one another, or from admixed non-neoplastic cells. To address this challenge, here we developed Genotyping of Transcriptomes (GoT), a method to integrate genotyping with high-throughput droplet-based single-cell RNA sequencing. We apply GoT to profile 38,290 CD34+ cells from patients with CALR-mutated myeloproliferative neoplasms to study how somatic mutations corrupt the complex process of human haematopoiesis. High-resolution mapping of malignant versus normal haematopoietic progenitors revealed an increasing fitness advantage with myeloid differentiation of cells with mutated CALR. We identified the unfolded protein response as a predominant outcome of CALR mutations, with a considerable dependency on cell identity, as well as upregulation of the NF-κB pathway specifically in uncommitted stem cells. We further extended the GoT toolkit to genotype multiple targets and loci that are distant from transcript ends. Together, these findings reveal that the transcriptional output of somatic mutations in myeloproliferative neoplasms is dependent on the native cell identity.

The kinase PERK and the transcription factor ATF4 play distinct and essential roles in autophagy resulting from tunicamycin-induced ER stress

Endoplasmic reticulum (ER) stress is thought to activate autophagy via unfolded protein response (UPR)-mediated transcriptional up-regulation of autophagy machinery components and modulation of microtubule-associated protein 1 light chain 3 (LC3). The upstream UPR constituents pancreatic EIF2-α kinase (PERK) and inositol-requiring enzyme 1 (IRE1) have been reported to mediate these effects, suggesting that UPR may stimulate autophagy via PERK and IRE1. However, how the UPR and its components affect autophagic activity has not been thoroughly examined. By analyzing the flux of LC3 through the autophagic pathway, as well as the sequestration and degradation of autophagic cargo, we here conclusively show that the classical ER stressor tunicamycin (TM) enhances autophagic activity in mammalian cells. PERK and its downstream factor, activating transcription factor 4 (ATF4), were crucial for this induction, but surprisingly, IRE1 constitutively suppressed autophagic activity. TM-induced autophagy required autophagy-related 13 (ATG13), Unc-51-like autophagy-activating kinases 1/2 (ULK1/ULK2), and GABA type A receptor-associated proteins (GABARAPs), but interestingly, LC3 proteins appeared to be redundant. Strikingly, ATF4 was activated independently of PERK in both LNCaP and HeLa cells, and our further examination revealed that ATF4 and PERK regulated autophagy through separate mechanisms. Specifically, whereas ATF4 controlled transcription and was essential for autophagosome formation, PERK acted in a transcription-independent manner and was required at a post-sequestration step in the autophagic pathway. In conclusion, our results indicate that TM-induced UPR activates functional autophagy, and whereas IRE1 is a negative regulator, PERK and ATF4 are required at distinct steps in the autophagic pathway.

Metabolic and Innate Immune Cues Merge into a Specific Inflammatory Response via the UPR

Innate immune responses are intricately linked with intracellular metabolism of myeloid cells. Toll-like receptor (TLR) stimulation shifts intracellular metabolism toward glycolysis, while anti-inflammatory signals depend on enhanced mitochondrial respiration. How exogenous metabolic signals affect the immune response is unknown. We demonstrate that TLR-dependent responses of dendritic cells (DCs) are exacerbated by a high-fatty-acid (FA) metabolic environment. FAs suppress the TLR-induced hexokinase activity and perturb tricarboxylic acid cycle metabolism. These metabolic changes enhance mitochondrial reactive oxygen species (mtROS) production and, in turn, the unfolded protein response (UPR), leading to a distinct transcriptomic signature with IL-23 as hallmark. Interestingly, chemical or genetic suppression of glycolysis was sufficient to induce this specific immune response. Conversely, reducing mtROS production or DC-specific deficiency in XBP1 attenuated IL-23 expression and skin inflammation in an IL-23-dependent model of psoriasis. Thus, fine-tuning of innate immunity depends on optimization of metabolic demands and minimization of mtROS-induced UPR.

HSP-4/BiP expression in secretory cells is regulated by a developmental program and not by the unfolded protein response

Differentiation of secretory cells leads to sharp increases in protein synthesis, challenging endoplasmic reticulum (ER) proteostasis. Anticipatory activation of the unfolded protein response (UPR) prepares cells for the onset of secretory function by expanding the ER size and folding capacity. How cells ensure that the repertoire of induced chaperones matches their postdifferentiation folding needs is not well understood. We find that during differentiation of stem-like seam cells, a typical UPR target, the Caenorhabditis elegans immunoglobulin heavy chain-binding protein (BiP) homologue Heat-Shock Protein 4 (HSP-4), is selectively induced in alae-secreting daughter cells but is repressed in hypodermal daughter cells. Surprisingly, this lineage-dependent induction bypasses the requirement for UPR signaling. Instead, its induction in alae-secreting cells is controlled by a specific developmental program, while its repression in the hypodermal-fated cells requires a transcriptional regulator B-Lymphocyte–Induced Maturation Protein 1 (BLMP-1/BLIMP1), involved in differentiation of mammalian secretory cells. The HSP-4 induction is anticipatory and is required for the integrity of secreted alae. Thus, differentiation programs can directly control a broad-specificity chaperone that is normally stress dependent to ensure the integrity of secreted proteins.

A study in the nematode Caenorhabditis elegans shows that dedicated developmental programs can bypass the requirements for the unfolded protein response during the differentiation of secretory cells, anticipating their future high folding needs.

During differentiation, cells that specialize in secretion of proteins, such as antibody-secreting B cells, prepare for the onset of secretory function by expanding the size of the major secretory organelle, the endoplasmic reticulum (ER), and by increasing the expression of molecular chaperones and folding enzymes. This pre-emptive expansion of the ER depends on activation of the ER stress response pathways and is required for the secretory phenotype. In addition, cells may also need to up-regulate a selected subset of chaperones because different secreted proteins may require different chaperones for their folding and secretion. Except in specialized cases, how this selective up-regulation is achieved, and whether it depends on the ER stress pathways, is not well understood. Using Caenorhabditis elegans, we find that a chaperone BiP/HSP-4, which is usually induced in most cells by stress, is selectively induced during differentiation of stem cells into the alae-secreting cells while being repressed in their sister lineage, the hypodermal cells. We find that induction of this chaperone is independent of the known ER stress pathways, while its repression requires a known regulator of development in mammals, BLIMP1/BLMP-1. The pre-emptive induction of BiP/HSP-4 is important for the integrity of secreted alae and cuticle, suggesting that a general molecular chaperone that is a canonical target of ER stress pathways can be selectively regulated by development to ensure the quality of secreted proteome and functionality of the cells postdifferentiation.

Endoplasmic Reticulum Stress and Unfolded Protein Response in Breast Cancer: The Balance between Apoptosis and Autophagy and Its Role in Drug Resistance

The unfolded protein response (UPR) is a stress response activated by the accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum (ER) and its uncontrolled activation is mechanistically responsible for several human pathologies, including metabolic, neurodegenerative, and inflammatory diseases, and cancer. Indeed, ER stress and the downstream UPR activation lead to changes in the levels and activities of key regulators of cell survival and autophagy and this is physiologically finalized to restore metabolic homeostasis with the integration of pro-death or/and pro-survival signals. By contrast, the chronic activation of UPR in cancer cells is widely considered a mechanism of tumor progression. In this review, we focus on the relationship between ER stress, apoptosis, and autophagy in human breast cancer and the interplay between the activation of UPR and resistance to anticancer therapies with the aim to disclose novel therapeutic scenarios. The hypothesis that autophagy and UPR may provide novel molecular targets in human malignancies is discussed.

Alterations in tissue microRNA after heat stress in the conscious rat: potential biomarkers of organ-specific injury

BACKGROUND

Heat illness remains a significant cause of morbidity in susceptible populations. Recent research elucidating the cellular mechanism of heat stress leading to heat illness may provide information to develop better therapeutic interventions, risk assessment strategies, and early biomarkers of organ damage. microRNA (miRNA) are promising candidates for therapeutic targets and biomarkers for a variety of clinical conditions since there is the potential for high specificity for individual tissues and unique cellular functions. The objective of this study was to identify differentially expressed microRNAs and their putative mRNA targets in the heart, liver, kidney, and lung in rats at three time points: during heat stress (i.e., when core temperature reached 41.8 °C), or following a 24 or 48 h recovery period.

RESULTS

Rats did not show histological evidence of tissue pathology until 48 h after heat stress, with 3 out of 6 rats showing cardiac inflammation and renal proteinosis at 48 h. The three rats with cardiac and renal pathology had 86, 7, 159, and 37 differentially expressed miRNA in the heart, liver, kidney, or lung, respectively compared to non-heat stressed control animals. During heat stress one differentially expressed miRNA was found in the liver and five in the lung, with no other modulated miRNA after 24 h or 48 h in animals with no evidence of organ injury. Pathway enrichment analysis revealed enrichment in functional pathways associated with heat stress, with the greatest effects observed in animals with histological evidence of cardiac and renal damage at 48 h. Inhibiting miR-21 in cultured cardiomyocytes increased the percent apoptotic cells five hours after heat stress from 70.9 ± 0.8 to 84.8 ± 2.2%.

CONCLUSIONS

Global microRNA and transcriptomics analysis suggested that perturbed miRNA due to heat stress are involved in biological pathways related to organ injury, energy metabolism, the unfolded protein response, and cellular signaling. These miRNA may serve as biomarkers of organ injury and potential pharmacological targets for preventing heat illness or organ injury.

Experimental approach to study the effect of mutations on the protein folding pathway

Is it possible to compare the physicochemical properties of a wild-type protein and its mutant form under the same conditions? Provided the mutation has destabilized the protein, it may be more correct to compare the mutant protein under native conditions to the wild-type protein destabilized with a small amount of the denaturant. In general, is it appropriate to compare the properties of proteins destabilized by different treatments: mutations, pH, temperature, and denaturants like urea? These issues have compelled us to search for methods and ways of presentation of experimental results that would allow a comparison of mutant forms of proteins under different conditions and lead to conclusions on the effect of mutations on the protein folding/unfolding pathway. We have studied equilibrium unfolding of wild-type bovine carbonic anhydrase II (BCA II) and its six mutant forms using different urea concentrations. BCA II has been already studied in detail and is a good model object for validating new techniques. In this case, time-resolved fluorescence spectroscopy was chosen as the basic research method. The main features of this experimental method allowed us to compare different stages of unfolding of studied proteins and prove experimentally that a single substitution of the amino acid in three mutant forms of BCA II affected the native state of the protein but did not change its unfolding pathway. On the contrary, the inserted disulfide bridge in three other mutant forms of BCA II affected the protein unfolding pathway. An important result of this research is that we have validated the new approach allowing investigation of the effect of mutations on the folding of globular proteins, because in this way it is possible to compare proteins in the same structural states rather than under identical conditions.

Chloroplast protein homeostasis is coupled with retrograde signaling

Singlet oxygen (¹O₂) is a potent oxidizing agent, principally generated by photosystem II (PSII) as a byproduct of photosynthesis. Hence, ¹O₂ damages PSII, especially the PSII reaction center (RC) proteins, promoting a process called PSII repair cycle. The hetero-hexameric FtsH protease, located in the thylakoid membrane, is essential in degrading these damaged PSII RC proteins, which defines the first step of the PSII repair. The loss of the central subunit of the FtsH protease, FtsH2 (VAR2), weakens the PSII repair, thereby impairing PSII proteostasis. A recent study demonstrated that the impaired proteostasis (or accumulation of damaged proteins) in the chloroplasts of the var2 mutant induces an unfolded/misfolded protein response (UPR)-like response, more appropriately referred to as a damaged protein response (DPR), as evident in the accumulation of proteins related to the protein quality control (PQC). Comparison of data from chloroplast proteomics data with RNA sequencing in the context of the UPR-like response suggests a plausible activation of retrograde signaling in the var2 mutant. Either through the enhanced level of ¹O₂ or by impairing the substrate-unfolding activity of FtsH2, the reinforced defect appears to induce stress-related genes via the stress hormone salicylic acid (SA). This finding suggests that impaired chloroplast proteostasis (specifically for PSII proteins) may activate the chloroplast-established isochorismate pathway to produce SA. If this assumption is correct, then SA serves as a retrograde signaling molecule. In this review, we will discuss the impact of chloroplast proteostasis on chloroplasts-to-nucleus communication.

Obesity-related cellular stressors regulate gonadotropin releasing hormone gene expression via c-Fos/AP-1

Obesity is a risk factor for infertility, but mechanisms underlying this risk are unclear. Fertility is regulated by hypothalamic gonadotropin-releasing hormone, encoded by the Gnrh1 gene. Because obesity promotes endoplasmic reticulum (ER) stress, we sought to determine how tunicamycin-induced ER stress affected Gnrh1 gene expression in the mouse hypothalamic cell line GT1-7. Tunicamycin repressed expression of Gnrh1 in a PKC- and JNK-dependent manner, while upregulating expression of a known Gnrh1 repressor, Fos. Obesity is associated with increased circulating free fatty acids, and exposure to palmitate promoted ER stress and inflammation. Fos expression increased with palmitate dose, but Gnrh1 expression was upregulated with low-dose palmitate and repressed with high-dose palmitate. Using a small molecule inhibitor, we determined that AP-1 was required for Gnrh1 repression by high-dose palmitate or tunicamycin-induced ER stress. These findings suggest that hypogonadism driven by decreased hypothalamic GnRH may be a component of obesity-related infertility.

Linking Endoplasmic Reticular Stress and Alternative Splicing

RNA splicing patterns in antibody-secreting cells are shaped by endoplasmic reticulum stress, ELL2 (eleven-nineteen lysine-rich leukemia gene 2) induction, and changes in the levels of snRNAs. Endoplasmic reticulum stress induces the unfolded protein response comprising a highly conserved set of genes crucial for cell survival; among these is Ire1, whose auto-phosphorylation drives it to acquire a regulated mRNA decay activity. The mRNA-modifying function of phosphorylated Ire1 non-canonically splices Xbp1 mRNA and yet degrades other cellular mRNAs with related motifs. Naïve splenic B cells will activate Ire1 phosphorylation early on after lipopolysaccharide (LPS) stimulation, within 18 h; large-scale changes in mRNA content and splicing patterns result. Inhibition of the mRNA-degradation function of Ire1 is correlated with further differences in the splicing patterns and a reduction in the mRNA factors for snRNA transcription. Some of the >4000 splicing changes seen at 18 h after LPS stimulation persist into the late stages of antibody secretion, up to 72 h. Meanwhile some early splicing changes are supplanted by new splicing changes introduced by the up-regulation of ELL2, a transcription elongation factor. ELL2 is necessary for immunoglobulin secretion and does this by changing mRNA processing patterns of immunoglobulin heavy chain and >5000 other genes.

WRKY7, -11 and -17 transcription factors are modulators of the bZIP28 branch of the unfolded protein response during PAMP-triggered immunity in Arabidopsis thaliana

Plants must defend themselves against pathogens. The defense response requires greater protein synthesis, which generates endoplasmic reticulum (ER) stress, yet failure to attenuate this stress has detrimental effects. WRKY7/11/17 transcription factors (TFs) are negative regulators of immunity since mutants are more resistant to Pseudomonas syringae pv tomato (Pst) infection. Here, we reveal a connection between ER-stress and the molecular mechanisms underlying the wrky mutant phenotype. The bZIP28 TF upregulates ER-chaperone expression (BiP1/2, ERdj3B, and SDF2) upon exposure of Arabidopsis to a bacterial defense elicitor, flagellin 22 (Flg22). Also, the activation of ER-chaperones is more sustained in double and triple wrky mutants treated with Flg22, suggesting that WRKY7/11/17 TFs downregulate these genes. Moreover, wrky mutants accumulate more bZIP28 transcripts in response to Flg22, indicating that WRKY7/11/17 transcriptionally repress this TF. Using Arabidopsis protoplasts, we also demonstrate that WRKYs bind to the bZIP28 promoter via W-box elements. Additionally, triple wrky mutants are more resistant, whilst bzip28 mutants are more susceptible, to Pst infection. Finally, we postulate a model of PAMP-Triggered Immunity regulation, where Flg22 activates bZIP28-signaling inducing the expression of ER-stress genes, as well as WRKY7/11/17 expression, which in turn inhibits PTI by downregulating bZIP28, controlling physiological responses in the Arabidopsis-Pst interaction.

Integration of Stress Signaling in Caenorhabditis elegans Through Cell-Nonautonomous Contributions of the JNK Homolog KGB-1

Dealing with physiological stress is a necessity for all organisms, and the pathways charged with this task are highly conserved in Metazoa . Accumulating evidence highlights cell-nonautonomous activation as an important mode of integrating stress responses at the organism level. Work in Caenorhabditis elegans highlighted the importance of such regulation for the unfolded protein response (UPR) and for gene expression downstream of the longevity-associated transcription factor DAF-16 Here we describe a role for the JNK homolog KGB-1 in cell-nonautonomous regulation of these two response modules. KGB-1 protects developing larvae from heavy metals and from protein folding stress (which we found to be independent of canonical UPR pathways), but sensitizes adults to the same stress, further shortening life span under normal conditions. This switch is associated with age-dependent antagonistic regulation of DAF-16 Using transgenic tissue-specific KGB-1 expression or tissue-specific KGB-1 activation we examined the contributions of KGB-1 to gene regulation, stress resistance, and life span. While cell-autonomous contributions were observed, particularly in the epidermis, cell-nonautonomous contributions of neuronal KGB-1 (and also in muscle) were effective in driving intestinal gene induction, age-dependent regulation of intestinal DAF-16, and stress resistance, and did not require KGB-1 expression in the target tissue. Additional genetic analyses revealed requirement for UNC-13 in mediating neuronal contributions, indicating involvement of neurotransmission. Our results expand the role of KGB-1 in stress responses from providing local cellular protection to integrating stress responses at the level of the whole organism.

miRNA-mediated TUSC3 deficiency enhances UPR and ERAD to promote metastatic potential of NSCLC

Non-small cell lung carcinoma (NSCLC) is leading cause of cancer-related deaths in the world. The Tumor Suppressor Candidate 3 (TUSC3) at chromosome 8p22 known to be frequently deleted in cancer is often found to be deleted in advanced stage of solid tumors. However, the role of TUSC3 still remains controversial in lung cancer and context-dependent in several cancers. Here we propose that miR-224/-520c-dependent TUSC3 deficiency enhances the metastatic potential of NSCLC through the alteration of three unfolded protein response pathways and HRD1-dependent ERAD. ATF6α-dependent UPR is enhanced whereas the affinity of HRD1 to its substrates, PERK, IRE1α and p53 is weakened. Consequently, the alteration of UPRs and the suppressed p53-NM23H1/2 pathway by TUSC3 deficiency is ultimately responsible for enhancing metastatic potential of lung cancer. These findings provide mechanistic insight of unrecognized roles of TUSC3 in cancer progression and the oncogenic role of HRD1-dependent ERAD in cancer metastasis.

Tauopathy-associated PERK alleles are functional hypomorphs that increase neuronal vulnerability to ER stress

Tauopathies are neurodegenerative diseases characterized by tau protein pathology in the nervous system. EIF2AK3 (eukaryotic translation initiation factor 2 alpha kinase 3), also known as PERK (protein kinase R-like endoplasmic reticulum kinase), was identified by genome-wide association study as a genetic risk factor in several tauopathies. PERK is a key regulator of the Unfolded Protein Response (UPR), an intracellular signal transduction mechanism that protects cells from endoplasmic reticulum (ER) stress. PERK variants had previously been identified in Wolcott-Rallison Syndrome, a rare autosomal recessive metabolic disorder, and these variants completely abrogated the function of PERK's kinase domain or prevented PERK expression. In contrast, the PERK tauopathy risk variants were distinct from the Wolcott-Rallison variants and introduced missense alterations throughout the PERK protein. The function of PERK tauopathy variants and their effects on neurodegeneration are unknown. Here, we discovered that tauopathy-associated PERK alleles showed reduced signaling activity and increased PERK protein turnover compared to protective PERK alleles. We found that iPSC-derived neurons carrying PERK risk alleles were highly vulnerable to ER stress-induced injury with increased tau pathology. We found that chemical inhibition of PERK in human iPSC-derived neurons also increased neuronal cell death in response to ER stress. Our results indicate that tauopathy-associated PERK alleles are functional hypomorphs during the UPR. We propose that reduced PERK function leads to neurodegeneration by increasing neuronal vulnerability to ER stress-associated damage. In this view, therapies to enhance PERK signaling would benefit at-risk carriers of hypomorphic alleles.

Systemic signaling contributes to the unfolded protein response of the plant endoplasmic reticulum

The unfolded protein response (UPR) of the endoplasmic reticulum constitutes a conserved and essential cytoprotective pathway designed to survive biotic and abiotic stresses that alter the proteostasis of the endoplasmic reticulum. The UPR is typically considered cell-autonomous and it is yet unclear whether it can also act systemically through non-cell autonomous signaling. We have addressed this question using a genetic approach coupled with micro-grafting and a suite of molecular reporters in the model plant species Arabidopsis thaliana. We show that the UPR has a non-cell autonomous component, and we demonstrate that this is partially mediated by the intercellular movement of the UPR transcription factor bZIP60 facilitating systemic UPR signaling. Therefore, in multicellular eukaryotes such as plants, non-cell autonomous UPR signaling relies on the systemic movement of at least a UPR transcriptional modulator.

Identification of Therapeutic Targets in Rhabdomyosarcoma through Integrated Genomic, Epigenomic, and Proteomic Analyses

Personalized cancer therapy targeting somatic mutations in patient tumors is increasingly being incorporated into practice. Other therapeutic vulnerabilities resulting from changes in gene expression due to tumor specific epigenetic perturbations are progressively being recognized. These genomic and epigenomic changes are ultimately manifest in the tumor proteome and phosphoproteome. We integrated transcriptomic, epigenomic, and proteomic/phosphoproteomic data to elucidate the cellular origins and therapeutic vulnerabilities of rhabdomyosarcoma (RMS). We discovered that alveolar RMS occurs further along the developmental program than embryonal RMS. We also identified deregulation of the RAS/MEK/ERK/CDK4/6, G2/M, and unfolded protein response pathways through our integrated analysis. Comprehensive preclinical testing revealed that targeting the WEE1 kinase in the G2/M pathway is the most effective approach in vivo for high-risk RMS.

Amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) are characterised by differential activation of ER stress pathways: focus on UPR target genes

The endoplasmic reticulum (ER) plays an important role in maintenance of proteostasis through the unfolded protein response (UPR), which is strongly activated in most neurodegenerative disorders. UPR signalling pathways mediated by IRE1α and ATF6 play a crucial role in the maintenance of ER homeostasis through the transactivation of an array of transcription factors. When activated, these transcription factors induce the expression of genes involved in protein folding and degradation with pro-survival effects. However, the specific contribution of these transcription factors to different neurodegenerative diseases remains poorly defined. Here, we characterised 44 target genes strongly influenced by XBP1 and ATF6 and quantified the expression of a subset of genes in the human post-mortem spinal cord from amyotrophic lateral sclerosis (ALS) cases and in the frontal and temporal cortex from frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD) cases and controls. We found that IRE1α-XBP1 and ATF6 pathways were strongly activated both in ALS and AD. In ALS, XBP1 and ATF6 activation was confirmed by a substantial increase in the expression of both known and novel target genes involved particularly in co-chaperone activity and ER-associated degradation (ERAD) such as DNAJB9, SEL1L and OS9. In AD cases, a distinct pattern emerged, where targets involved in protein folding were more prominent, such as CANX, PDIA3 and PDIA6. These results reveal that both overlapping and disease-specific patterns of IRE1α-XBP1 and ATF6 target genes are activated in AD and ALS, which may be relevant to the development of new therapeutic strategies. Graphical abstract The endoplasmic reticulum (ER) plays an important role in maintenance of proteostasis through the unfolded protein response (UPR). Two major UPR signalling pathways are mediated by IRE1α and ATF6. Here, we demonstrate that these pathways activate differential gene sets in human post-mortem tissues derived from amyotrophic lateral sclerosis (ALS) compared to Alzheimer's disease (AD) cases. Our results identify IRE1α and ATF6 specific targets that can have major implications in the development of new therapeutic strategies and potential biomarkers.