Translational control is required for the unfolded protein response and in vivo glucose homeostasis

Crosstalk between ferroptosis and endoplasmic reticulum stress: A potential target for ovarian cancer therapy (Review)

Ferroptosis is a unique mode of cell death driven by iron‑dependent phospholipid peroxidation, and its mechanism primarily involves disturbances in iron metabolism, imbalances in the lipid antioxidant system and accumulation of lipid peroxides. Protein processing, modification and folding in the endoplasmic reticulum (ER) are closely related regulatory processes that determine cell function, fate and survival. The uncontrolled proliferative capacity of malignant cells generates an unfavorable microenvironment characterized by high metabolic demand, hypoxia, nutrient deprivation and acidosis, which promotes the accumulation of misfolded or unfolded proteins in the ER, leading to ER stress (ERS). Ferroptosis and ERS share common pathways in several diseases, and the two interact to affect cell survival and death. Additionally, cell death pathways are not linear signaling cascades, and different pathways of cell death may be interrelated at multiple levels. Ferroptosis and ERS in ovarian cancer (OC) have attracted increasing research interest; however, both are discussed separately regarding OC. The present review aims to summarize the associations and potential links between ferroptosis and ERS, aiming to provide research references for the development of therapeutic approaches for the management of OC.

De Novo Serine Synthesis Is a Metabolic Vulnerability That Can Be Exploited to Overcome Sunitinib Resistance in Advanced Renal Cell Carcinoma

Sunitinib is an oral tyrosine kinase inhibitor used in treating advanced renal cell carcinoma (RCC) that exhibits significant efficacy but faces resistance in 30% of patients. Identifying the molecular mechanisms underlying resistance could enable the development of strategies to enhance sunitinib sensitivity. In this study, we showed that sunitinib induces a metabolic shift leading to increased serine synthesis in RCC cells. Activation of the GCN2-ATF4 stress response pathway was identified as the mechanistic link between sunitinib treatment and elevated serine production. The increased serine biosynthesis supported nucleotide synthesis and sustained cell proliferation, migration, and invasion following sunitinib treatment. Inhibiting key enzymes in the serine synthesis pathway, such as phosphoglycerate dehydrogenase and phosphoserine aminotransferase 1, enhanced the sensitivity of resistant cells to sunitinib. Beyond RCC, similar activation of serine synthesis following sunitinib treatment occurred in a variety of other cancer types, suggesting a shared adaptive response to sunitinib therapy. Together, this study identifies the de novo serine synthesis pathway as a potential target to overcome sunitinib resistance, offering insights into therapeutic strategies applicable across diverse cancer contexts. Significance: Sunitinib treatment induces metabolic reprogramming to provide essential metabolite building blocks for tumor survival, resistance, and progression by upregulating serine biosynthesis, which represents a targetable dependency to enhance therapeutic efficacy.

Alzheimer's Is a Multiform Disease of Sustained Neuronal Integrated Stress Response Driven by the C99 Fragment Generated Independently of AβPP; Proteolytic Production of Aβ Is Suppressed in AD-Affected Neurons: Evolution of a Theory

The present Perspective analyzes the remarkable evolution of the Amyloid Cascade Hypothesis 2.0 (ACH2.0) theory of Alzheimer's disease (AD) since its inception a few years ago, as reflected in the diminishing role of amyloid-beta (Aβ) in the disease. In the initial iteration of the ACH2.0, Aβ-protein-precursor (AβPP)-derived intraneuronal Aβ (iAβ), accumulated to neuronal integrated stress response (ISR)-eliciting levels, triggers AD. The neuronal ISR, in turn, activates the AβPP-independent production of its C99 fragment that is processed into iAβ, which drives the disease. The second iteration of the ACH2.0 stemmed from the realization that AD is, in fact, a disease of the sustained neuronal ISR. It introduced two categories of AD-conventional and unconventional-differing mainly in the manner of their causation. The former is caused by the neuronal ISR triggered by AβPP-derived iAβ, whereas in the latter, the neuronal ISR is elicited by stressors distinct from AβPP-derived iAβ and arising from brain trauma, viral and bacterial infections, and various types of inflammation. Moreover, conventional AD always contains an unconventional component, and in both forms, the disease is driven by iAβ generated independently of AβPP. In its third, the current, iteration, the ACH2.0 posits that proteolytic production of Aβ is suppressed in AD-affected neurons and that the disease is driven by C99 generated independently of AβPP. Suppression of Aβ production in AD seems an oxymoron: Aβ is equated with AD, and the later is inconceivable without the former in an ingrained Amyloid Cascade Hypothesis (ACH)-based notion. But suppression of Aβ production in AD-affected neurons is where the logic leads, and to follow it we only need to overcome the inertia of the preexisting assumptions. Moreover, not only is the generation of Aβ suppressed, so is the production of all components of the AβPP proteolytic pathway. This assertion is not a quantum leap (unless overcoming the inertia counts as such): the global cellular protein synthesis is severely suppressed under the neuronal ISR conditions, and there is no reason for constituents of the AβPP proteolytic pathway to be exempted, and they, apparently, are not, as indicated by the empirical data. In contrast, tau protein translation persists in AD-affected neurons under ISR conditions because the human tau mRNA contains an internal ribosomal entry site in its 5'UTR. In current mouse models, iAβ derived from AβPP expressed exogenously from human transgenes elicits the neuronal ISR and thus suppresses its own production. Its levels cannot principally reach AD pathology-causing levels regardless of the number of transgenes or the types of FAD mutations that they (or additional transgenes) carry. Since the AβPP-independent C99 production pathway is inoperative in mice, the current transgenic models have no potential for developing the full spectrum of AD pathology. What they display are only effects of the AβPP-derived iAβ-elicited neuronal ISR. The paper describes strategies to construct adequate transgenic AD models. It also details the utilization of human neuronal cells as the only adequate model system currently available for conventional and unconventional AD. The final alteration of the ACH2.0, introduced in the present Perspective, is that AβPP, which supports neuronal functionality and viability, is, after all, potentially produced in AD-affected neurons, albeit not conventionally but in an ISR-driven and -compatible process. Thus, the present narrative begins with the "omnipotent" Aβ capable of both triggering and driving the disease and ends up with this peptide largely dislodged from its pedestal and retaining its central role in triggering the disease in only one, although prevalent (conventional), category of AD (and driving it in none). Among interesting inferences of the present Perspective is the determination that "sporadic AD" is not sporadic at all ("non-familial" would be a much better designation). The term has fatalistic connotations, implying that the disease can strike at random. This is patently not the case: The conventional disease affects a distinct subpopulation, and the basis for unconventional AD is well understood. Another conclusion is that, unless prevented, the occurrence of conventional AD is inevitable given a sufficiently long lifespan. This Perspective also defines therapeutic directions not to be taken as well as auspicious ways forward. The former category includes ACH-based drugs (those interfering with the proteolytic production of Aβ and/or depleting extracellular Aβ). They are legitimate (albeit inefficient) preventive agents for conventional AD. There is, however, a proverbial snowball's chance in hell of them being effective in symptomatic AD, lecanemab, donanemab, and any other "…mab" or "…stat" notwithstanding. They comprise Aβ-specific antibodies, inhibitors of beta- and gamma-secretase, and modulators of the latter. In the latter category, among ways to go are the following: (1) Depletion of iAβ, which, if sufficiently "deep", opens up a tantalizing possibility of once-in-a-lifetime preventive transient treatment for conventional AD and aging-associated cognitive decline, AACD. (2) Composite therapy comprising the degradation of C99/iAβ and concurrent inhibition of the neuronal ISR. A single transient treatment could be sufficient to arrest the progression of conventional AD and prevent its recurrence for life. Multiple recurrent treatments would achieve the same outcome in unconventional AD. Alternatively, the sustained reduction/removal of unconventional neuronal ISR-eliciting stressors through the elimination of their source would convert unconventional AD into conventional one, preventable/treatable by a single transient administration of the composite C99/iAβ depletion/ISR suppression therapy. Efficient and suitable ISR inhibitors are available, and it is explicitly clear where to look for C99/iAβ-specific targeted degradation agents-activators of BACE1 and, especially, BACE2. Directly acting C99/iAβ-specific degradation agents such as proteolysis-targeting chimeras (PROTACs) and molecular-glue degraders (MGDs) are also viable options. (3) A circumscribed shift (either upstream or downstream) of the position of transcription start site (TSS) of the human AβPP gene, or, alternatively, a gene editing-mediated excision or replacement of a small, defined segment of its portion encoding 5'-untranslated region of AβPP mRNA; targeting AβPP RNA with anti-antisense oligonucleotides is another possibility. If properly executed, these RNA-based strategies would not interfere with the protein-coding potential of AβPP mRNA, and each would be capable of both preventing and stopping the AβPP-independent generation of C99 and thus of either preventing AD or arresting the progression of the disease in its conventional and unconventional forms. The paper is interspersed with "validation" sections: every conceptually significant notion is either validated by the existing data or an experimental procedure validating it is proposed.

The unfolded protein response is a potential therapeutic target in pathogenic fungi

Pathogenic fungal infections cause significant morbidity and mortality, particularly in immunocompromised patients. The frequent emergence of multidrug-resistant strains challenges existing antifungal therapies, driving the need to investigate novel antifungal agents that target new molecular moieties. Pathogenic fungi are subjected to various environmental stressors, including pH, temperature, and pharmacological agents, both in natural habitats and the host body. These stressors elevate the risk of misfolded or unfolded protein production within the endoplasmic reticulum (ER) which, if not promptly mitigated, can lead to the accumulation of these proteins in the ER lumen. This accumulation triggers an ER stress response, potentially jeopardizing fungal survival. The unfolded protein response (UPR) is a critical cellular defense mechanism activated by ER stress to restore the homeostasis of protein folding. In recent years, the regulatory role of the UPR in pathogenic fungi has garnered significant attention, particularly for its involvement in fungal adaptation, regulation of virulence, and drug resistance. In this review, we comparatively analyze the UPRs of fungi and mammals and examine the potential utility of the UPR as a molecular antifungal target in pathogenic fungi. By clarifying the specificity and regulatory functions of the UPR in pathogenic fungi, we highlight new avenues for identifying potential therapeutic targets for antifungal treatments.

Maintenance of p-eIF2α levels by the eIF2B complex is vital for colorectal cancer

Protein synthesis is an essential process, deregulated in multiple tumor types showing differential dependence on translation factors compared to untransformed tissue. We show that colorectal cancer (CRC) with loss-of-function mutation in the APC tumor suppressor depends on an oncogenic translation program regulated by the ability to sense phosphorylated eIF2α (p-eIF2α). Despite increased protein synthesis rates following APC loss, eIF2α phosphorylation, typically associated with translation inhibition, is enhanced in CRC. Elevated p-eIF2α, and its proper sensing by the decameric eIF2B complex, are essential to balance translation. Knockdown or mutation of eIF2Bα and eIF2Bδ, two eIF2B subunits responsible for sensing p-eIF2α, impairs CRC viability, demonstrating that the eIF2B/p-eIF2α nexus is vital for CRC. Specifically, the decameric eIF2B linked by two eIF2Bα subunits is critical for translating growth-promoting mRNAs which are induced upon APC loss. Depletion of eIF2Bα in APC-deficient murine and patient-derived organoids establishes a therapeutic window, validating eIF2Bα as a target for clinical intervention. In conclusion, we demonstrate how the expression of the oncogenic signature in CRC is crucially controlled at the translational level.

Cannabinoids Activate Endoplasmic Reticulum Stress Response and Promote the Death of Avian Retinal Müller Cells in Culture

BACKGROUND/OBJECTIVES

Activation of cannabinoid CB1 or CB2 receptors induces the death of glial progenitors from the chick retina in culture. Here, by using an enriched retinal glial cell culture, we characterized some mechanisms underlying glial death promoted by cannabinoids.

METHODS AND RESULTS

Retinal cultures obtained from 8-day-old (E8) chick embryos and maintained for 12-15 days (C12-15) were used. MTT assays revealed that the CB1/CB2 agonist WIN 55,212-2 (WIN) decreased cell viability in the cultures in a time-dependent manner, with a concomitant increase in extracellular LDH activity, suggesting membrane integrity loss. Cell death was also dose-dependently induced by cannabidiol (CBD), Δ9-tetrahydrocannabinol (THC), and CP55940, another CB1/CB2 agonist. In contrast to WIN-induced cell death that was not blocked by either antagonist, the deleterious effect of CBD was blocked by the CB2 receptor antagonist SR144528, but not by PF514273, a CB1 receptor antagonist. WIN-treated cultures showed glial cells with large vacuoles in cytoplasm that were absent in cultures incubated with WIN plus 4-phenyl-butyrate (PBA), a chemical chaperone. Since cannabinoids induced the phosphorylation of eukaryotic initiation factor 2-alfa (eIF2α), these results suggest a process of endoplasmic reticulum (ER) swelling and stress. Incubation of the cultures with WIN for 4 h induced a ~five-fold increase in the number of cells labeled with the ROS indicator CM-H2DCFDA. WIN induced the phosphorylation of JNK but not of p38 in the cultures, and also induced an increase in the number of glial cells expressing cleaved-caspase 3 (c-CASP3). The decrease in cell viability and the expression of c-CASP3 was blocked by salubrinal, an inhibitor of eIF2α dephosphorylation.

CONCLUSIONS

These data suggest that cannabinoids induce the apoptosis of glial cells in culture by promoting ROS production, ER stress, JNK phosphorylation, and caspase-3 processing. The graphical abstract was created at Biorender.com.

Production of Amyloid-β in the Aβ-Protein-Precursor Proteolytic Pathway Is Discontinued or Severely Suppressed in Alzheimer's Disease-Affected Neurons: Contesting the 'Obvious'

A notion of the continuous production of amyloid-β (Aβ) via the proteolysis of Aβ-protein-precursor (AβPP) in Alzheimer's disease (AD)-affected neurons constitutes both a cornerstone and an article of faith in the Alzheimer's research field. The present Perspective challenges this assumption. It analyses the relevant empirical data and reaches an unexpected conclusion, namely that in AD-afflicted neurons, the production of AβPP-derived Aβ is either discontinued or severely suppressed, a concept that, if proven, would fundamentally change our understanding of the disease. This suppression, effectively self-suppression, occurs in the context of the global inhibition of the cellular cap-dependent protein synthesis as a consequence of the neuronal integrated stress response (ISR) elicited by AβPP-derived intraneuronal Aβ (iAβ; hence self-suppression) upon reaching certain levels. Concurrently with the suppression of the AβPP proteolytic pathway, the neuronal ISR activates in human neurons, but not in mouse neurons, the powerful AD-driving pathway generating the C99 fragment of AβPP independently of AβPP. The present study describes molecular mechanisms potentially involved in these phenomena, propounds novel approaches to generate transgenic animal models of AD, advocates for the utilization of human neuronal cells-based models of the disease, makes verifiable predictions, suggests experiments designed to validate the proposed concept, and considers its potential research and therapeutic implications. Remarkably, it opens up the possibility that the conventional production of AβPP, BACE enzymes, and γ-secretase components is also suppressed under the neuronal ISR conditions in AD-affected neurons, resulting in the dyshomeostasis of AβPP. It follows that whereas conventional AD is triggered by AβPP-derived iAβ accumulated to the ISR-eliciting levels, the disease, in its both conventional and unconventional (triggered by the neuronal ISR-eliciting stressors distinct from iAβ) forms, is driven not (or not only) by iAβ produced in the AβPP-independent pathway, as we proposed previously, but mainly, possibly exclusively, by the C99 fragment generated independently of AβPP and not cleaved at the γ-site due to the neuronal ISR-caused deficiency of γ-secretase (apparently, the AD-driving "substance X" predicted in our previous study), a paradigm consistent with a dictum by George Perry that Aβ is "central but not causative" in AD. The proposed therapeutic strategies would not only deplete the driver of the disease and abrogate the AβPP-independent production of C99 but also reverse the neuronal ISR and ameliorate the AβPP dyshomeostasis, a potentially significant contributor to AD pathology.

The mitochondrial integrated stress response: A novel approach to anti-aging and pro-longevity

The ISR is a cellular signaling pathway that responds to various physiological changes and types of stimulation. The mitochondrial integrated stress response (ISRmt) is a stress response specific to mitochondria which is initiated by eIF2α phosphorylation and is responsive to mitochondrial stressors. The ISRmt triggers diverse metabolic responses reliant on activating transcription factor 4 (ATF4). The preliminary phases of ISRmt can provoke an adaptive stress response that antagonizes age-related diseases and promotes longevity. In this review, we provide an overview of the molecular mechanisms of the ISRmt, with a particular focus on its potential as a therapeutic target for age-related disease and the promotion of longevity.

Roles of X-box binding protein 1 in liver pathogenesis

The prevalence of drug-induced liver injury (DILI) and viral liver infections presents significant challenges in modern healthcare and contributes to considerable morbidity and mortality worldwide. Concurrently, metabolic dysfunctionassociated steatotic liver disease (MASLD) has emerged as a major public health concern, reflecting the increasing rates of obesity and leading to more severe complications such as fibrosis and hepatocellular carcinoma. X-box binding protein 1 (XBP1) is a distinct transcription factor with a basic-region leucine zipper structure, whose activity is regulated by alternative splicing in response to disruptions in endoplasmic reticulum (ER) homeostasis and the unfolded protein response (UPR) activation. XBP1 interacts with a key signaling component of the highly conserved UPR and is critical in determining cell fate when responding to ER stress in liver diseases. This review aims to elucidate the emerging roles and molecular mechanisms of XBP1 in liver pathogenesis, focusing on its involvement in DILI, viral liver infections, MASLD, fibrosis/cirrhosis, and liver cancer. Understanding the multifaceted functions of XBP1 in these liver diseases offers insights into potential therapeutic strategies to restore ER homeostasis and mitigate liver damage.

Mapping the Genetic Architecture of the Adaptive Integrated Stress Response in S. cerevisiae

The integrated stress response (ISR) is a conserved eukaryotic signaling pathway that responds to diverse stress stimuli to restore proteostasis. The strength and speed of ISR activation must be tuned properly to allow protein synthesis while maintaining proteostasis. Here, we describe how genetic perturbations change the dynamics of the ISR in budding yeast. We treated ISR dynamics, comprising timecourses of ISR activity across different levels of stress, as a holistic phenotype. We profiled changes in ISR dynamics across thousands of genetic perturbations in parallel using CRISPR interference with barcoded expression reporter sequencing (CiBER-seq). We treated cells with sulfometuron methyl, a titratable inhibitor of branched-amino acid synthesis, and measured expression of an ISR reporter. Perturbations to translation such as depletion of aminoacyl-tRNA synthetases or tRNA biogenesis factors reduced cell growth and caused a strikingly proportionate activation of the ISR activation. In contrast, impaired ribosome biogenesis reduced basal ISR activity and weakened ISR dynamics. Reduced ribosome capacity may lower the demand for amino acids and thereby explain these changes. Our work illustrates how CiBER-seq enables high-throughput measurements of complex and dynamic phenotypes that shed light on adaptive and homeostatic mechanisms.

A stress paradox: the dual role of the unfolded protein response in the placenta

The placenta is a temporary organ that forms during pregnancy and is essential for fetal development and maternal health. As an endocrine organ, proper placental function requires continual production, folding, and transport of proteins and lipids. Central to these processes is the endoplasmic reticulum (ER), a dynamic organelle responsible for maintaining cellular protein and lipid synthesis and processing. ER stress occurs when there is an accumulation of unfolded or misfolded proteins, which triggers the activation of cellular pathways collectively called the unfolded protein response. Unfolded protein response pathways act to alleviate the misfolded protein burden and restore ER homeostasis, or if unresolved, initiate cell death. While prolonged ER stress has been linked to deficient placental function and adverse pregnancy outcomes, basal activation of unfolded protein response pathways is required for placental development and function. This review explores the importance of ER homeostasis in placental development and function, examining how disruptions in ER stress responses may contribute to adverse pregnancy outcomes.

Selective killing of castration-resistant prostate cancer cells by formycin A via the ATF4-CHOP axis

Prostate cancer is initially androgen-dependent but often relapses to an androgen-independent state called castration-resistant prostate cancer (CRPC). Currently approved therapies have limited efficacy against CRPC, highlighting the need for novel therapeutic strategies. To address this need, we conducted a drug screen in our previously established aggressive CRPC cell model. We found that formycin A induced cell death in CRPC model cells but not in parental prostate cancer cells. In addition, formycin A upregulated death receptor 5 through the induction of endoplasmic reticulum stress, activating the "extrinsic" apoptosis pathway in CRPC model cells. Moreover, formycin A showed in vivo antitumor efficacy against CRPC xenografts in castrated nude mice. Thus, our findings highlight the potential of formycin A as a CRPC therapeutic.

The Integrated Stress Response in Pancreatic Development, Tissue Homeostasis, and Cancer

Present in all eukaryotic cells, the integrated stress response (ISR) is a highly coordinated signaling network that controls cellular behavior, metabolism, and survival in response to diverse stresses. The ISR is initiated when any 1 of 4 stress-sensing kinases (protein kinase R-like endoplasmic reticulum kinase [PERK], general control non-derepressible 2 [GCN2], double-stranded RNA-dependent protein kinase [PKR], heme-regulated eukaryotic translation initiation factor 2α kinase [HRI]) becomes activated to phosphorylate the protein translation initiation factor eukaryotic translation initiation factor 2α (eIF2α), shifting gene expression toward a comprehensive rewiring of cellular machinery to promote adaptation. Although the ISR has been shown to play an important role in the homeostasis of multiple tissues, evidence suggests that it is particularly crucial for the development and ongoing health of the pancreas. Among the most synthetically dynamic tissues in the body, the exocrine and endocrine pancreas relies heavily on the ISR to rapidly adjust cell function to meet the metabolic demands of the organism. The hardwiring of the ISR into normal pancreatic functions and adaptation to stress may explain why it is a commonly used pro-oncogenic and therapy-resistance mechanism in pancreatic ductal adenocarcinoma and pancreatic neuroendocrine tumors. Here, we review what is known about the key roles that the ISR plays in the development, homeostasis, and neoplasia of the pancreas.

Protection of beta cells against cytokine-induced apoptosis by the gut microbial metabolite butyrate

Type 1 diabetes (T1D) is characterized by immune cell infiltration in the islets of Langerhans, leading to the destruction of insulin-producing beta cells. This destruction is driven by secreted cytokines and cytotoxic T cells inducing apoptosis in beta cells. Butyrate, a metabolite produced by the gut microbiota, has been shown to have various health benefits, including anti-inflammatory and anti-diabetic effects. In this study, we investigated the potential protective effects of butyrate on cytokine-induced apoptosis in beta cells and explored the underlying mechanisms. Insulin-secreting INS-1E cells and isolated mouse islets were treated with interleukin-1beta (IL-1β) or a combination of IL-1β and interferon-gamma (IFN-γ) in the presence or absence of butyrate. We analyzed apoptosis, nitric oxide (NO) levels, expression of stress-related genes, and immune cell migration. Our results demonstrated that butyrate significantly attenuated cytokine-induced apoptosis in both INS-1E cells and mouse islets, accompanied by a reduction in NO levels. Butyrate also decreased the expression of endoplasmic reticulum (ER) stress markers such as Chop, phosphorylated eIF2α and Atf4, as well as some pro-apoptotic genes including Dp5 and Puma. Butyrate reduced the cytokine-induced expression of the chemokine genes Cxcl1 and Cxcl10 in mouse islets, as well as the chemotactic activity of THP-1 monocytes toward conditioned media from IL-1β-exposed islets. In conclusion, these findings indicate that butyrate protects beta cells from cytokine-induced apoptosis and ER stress, suggesting its potential as a therapeutic agent to prevent beta cell destruction in T1D.

Sestrin2 serves as a scaffold protein to maintain cardiac energy and metabolic homeostasis during pathological stress

Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide. Metabolic imbalances and pathological stress often contribute to increased mortality. Sestrin2 (Sesn2) is a stress-inducible protein crucial in maintaining cardiac energy and metabolic homeostasis under pathological conditions. Sesn2 is upregulated in response to various stressors, including oxidative stress, hypoxia, and energy depletion, and mediates multiple cellular pathways to enhance antioxidant defenses, promote autophagy, and inhibit inflammation. This review explores the mechanisms through which Sesn2 regulates these pathways, focusing on the AMPK-mTORC1, Sesn2-Nrf2, and HIF1α-Sesn2 pathways, among others. We can identify the potential therapeutic targets for treating CVDs and related metabolic disorders by comprehending these complex mechanisms. Sesn2's unique ability to respond thoroughly to metabolic challenges, oxidative stress, and inflammation makes it a promising prospect for enhancing cardiac health and resilience against pathological stress.

Integrated stress response activator halofuginone protects mice from diabetes-like phenotypes

The integrated stress response (ISR) is a vital signaling pathway initiated by four kinases, PERK, GCN2, HRI and PKR, that ensure cellular resilience and protect cells from challenges. Here, we investigated whether increasing ISR signaling could rescue diabetes-like phenotypes in a mouse model of diet-induced obesity (DIO). We show that the orally available and clinically approved GCN2 activator halofuginone (HF) can activate the ISR in mouse tissues. We found that daily oral administration of HF increases glucose tolerance whilst reducing weight gain, insulin resistance, and serum insulin in DIO mice. Conversely, the ISR inhibitor GSK2656157, used at low doses to optimize its selectivity, aggravates glucose intolerance in DIO mice. Whilst loss of function mutations in mice and humans have revealed that PERK is the essential ISR kinase that protects from diabetes, our work demonstrates the therapeutic value of increasing ISR signaling by activating the related kinase GCN2 to reduce diabetes phenotypes in a DIO mouse model.

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.

Proteasome inhibition enhances the anti-leukemic efficacy of chimeric antigen receptor (CAR) expressing NK cells against acute myeloid leukemia

BACKGROUND

Relapsed and refractory acute myeloid leukemia (AML) carries a dismal prognosis. CAR T cells have shown limited efficacy in AML, partially due to dysfunctional autologous T cells and the extended time for generation of patient specific CAR T cells. Allogeneic NK cell therapy is a promising alternative, but strategies to enhance efficacy and persistence may be necessary. Proteasome inhibitors (PI) induce changes in the surface proteome which may render malignant cells more vulnerable to NK mediated cytotoxicity. Here, we investigated the potential benefit of combining PIs with CAR-expressing allogeneic NK cells against AML.

METHODS

We established the IC50 concentrations for Bortezomib and Carfilzomib against several AML cell lines. Surface expression of class-I HLA molecules and stress-associated proteins upon treatment with proteasome inhibitors was determined by multiparameter flow cytometry. Using functional in vitro assays, we explored the therapeutic synergy between pre-treatment with PIs and the anti-leukemic efficacy of NK cells with or without expression of AML-specific CAR constructs against AML cell lines and primary patient samples. Also, we investigated the tolerability and efficacy of a single PI application strategy followed by (CAR-) NK cell infusion in two different murine xenograft models of AML.

RESULTS

AML cell lines and primary AML patient samples were susceptible to Bortezomib and Carfilzomib mediated cytotoxicity. Conditioned resistance to Azacitidine/Venetoclax did not confer primary resistance to PIs. Treating AML cells with PIs reduced the surface expression of class-I HLA molecules on AML cells in a time-and-dose dependent manner. Stress-associated proteins were upregulated on the transcriptional level and on the cell surface. NK cell mediated killing of AML cells was enhanced in a synergistic manner. PI pre-treatment increased effector-target cell conjugate formation and Interferon-γ secretion, resulting in enhanced NK cell activity against AML cell lines and primary samples in vitro. Expression of CD33- and CD70-specific CARs further improved the antileukemic efficacy. In vivo, Bortezomib pre-treatment followed by CAR-NK cell infusion reduced AML growth, leading to prolonged overall survival.

CONCLUSIONS

PIs enhance the anti-leukemic efficacy of CAR-expressing allogeneic NK cells against AML in vitro and in vivo, warranting further exploration of this combinatorial treatment within early phase clinical trials.

Quintessential Synergy: Concurrent Transient Administration of Integrated Stress Response Inhibitors and BACE1 and/or BACE2 Activators as the Optimal Therapeutic Strategy for Alzheimer's Disease

The present study analyzes two potential therapeutic approaches for Alzheimer's disease (AD). One is the suppression of the neuronal integrated stress response (ISR). Another is the targeted degradation of intraneuronal amyloid-beta (iAβ) via the activation of BACE1 (Beta-site Aβ-protein-precursor Cleaving Enzyme) and/or BACE2. Both approaches are rational. Both are promising. Both have substantial intrinsic limitations. However, when combined in a carefully orchestrated manner into a composite therapy they display a prototypical synergy and constitute the apparently optimal, potentially most effective therapeutic strategy for AD.

PKR Mediates the Mitochondrial Unfolded Protein Response through Double-Stranded RNA Accumulation under Mitochondrial Stress

Mitochondrial stress, resulting from dysfunction and proteostasis disturbances, triggers the mitochondrial unfolded protein response (UPRMT), which activates gene encoding chaperones and proteases to restore mitochondrial function. Although ATFS-1 mediates mitochondrial stress UPRMT induction in C. elegans, the mechanisms relaying mitochondrial stress signals to the nucleus in mammals remain poorly defined. Here, we explored the role of protein kinase R (PKR), an eIF2α kinase activated by double-stranded RNAs (dsRNAs), in mitochondrial stress signaling. We found that UPRMT does not occur in cells lacking PKR, indicating its crucial role in this process. Mechanistically, we observed that dsRNAs accumulate within mitochondria under stress conditions, along with unprocessed mitochondrial transcripts. Furthermore, we demonstrated that accumulated mitochondrial dsRNAs in mouse embryonic fibroblasts (MEFs) deficient in the Bax/Bak channels are not released into the cytosol and do not induce the UPRMT upon mitochondrial stress, suggesting a potential role of the Bax/Bak channels in mediating the mitochondrial stress response. These discoveries enhance our understanding of how cells maintain mitochondrial integrity, respond to mitochondrial dysfunction, and communicate stress signals to the nucleus through retrograde signaling. This knowledge provides valuable insights into prospective therapeutic targets for diseases associated with mitochondrial stress.

Comparative Proteomic Analysis of Huh7 Cells Transfected with Sub-Saharan African Hepatitis B Virus (Sub)genotypes Reveals Potential Oncogenic Factors

In sub-Saharan Africa (SSA), the (sub)genotypes A1, D3, and E of the hepatitis B virus (HBV) prevail. Individuals infected with subgenotype A1 have a 4.5-fold increased risk of HCC compared to those infected with other (sub)genotypes. The effect of (sub)genotypes on protein expression and host signalling has not been studied. Mass spectrometry was used to analyse the proteome of Huh7 cells transfected with replication-competent clones. Proteomic analysis revealed significantly differentially expressed proteins between SSA (sub)genotypes. Different (sub)genotypes have the propensity to dysregulate specific host signalling pathways. Subgenotype A1 resulted in dysregulation within the Ras pathway. Ras-associated protein, RhoC, was significantly upregulated in cells transfected with subgenotype A1 compared to those transfected with other (sub)genotypes, on both a proteomic (>1.5-fold) and mRNA level (p < 0.05). Two of the main cellular signalling pathways involving RHOC, MAPK and PI3K/Akt/mTOR, regulate cell growth, motility, and survival. Downstream signalling products of these pathways have been shown to increase MMP2 and MMP9 expression. An extracellular MMP2 and MMP9 ELISA revealed a non-significant increase in MMP2 and MMP9 in the cells transfected with A1 compared to the other (sub)genotypes (p < 0.05). The upregulated Ras-associated proteins have been implicated as oncoproteins in various cancers and could contribute to the increased hepatocarcinogenic potential of A1.

Inhibition of the eukaryotic initiation factor-2α kinase PERK decreases risk of autoimmune diabetes in mice

Preventing the onset of autoimmune type 1 diabetes (T1D) is feasible through pharmacological interventions that target molecular stress-responsive mechanisms. Cellular stresses, such as nutrient deficiency, viral infection, or unfolded proteins, trigger the integrated stress response (ISR), which curtails protein synthesis by phosphorylating eukaryotic translation initiation factor-2α (eIF2α). In T1D, maladaptive unfolded protein response (UPR) in insulin-producing β cells renders these cells susceptible to autoimmunity. We found that inhibition of the eIF2α kinase PKR-like ER kinase (PERK), a common component of the UPR and ISR, reversed the mRNA translation block in stressed human islets and delayed the onset of diabetes, reduced islet inflammation, and preserved β cell mass in T1D-susceptible mice. Single-cell RNA-Seq of islets from PERK-inhibited mice showed reductions in the UPR and PERK signaling pathways and alterations in antigen-processing and presentation pathways in β cells. Spatial proteomics of islets from these mice showed an increase in the immune checkpoint protein programmed death-ligand 1 (PD-L1) in β cells. Golgi membrane protein 1, whose levels increased following PERK inhibition in human islets and EndoC-βH1 human β cells, interacted with and stabilized PD-L1. Collectively, our studies show that PERK activity enhances β cell immunogenicity and that inhibition of PERK may offer a strategy for preventing or delaying the development of T1D.

Redox regulation of UPR signalling and mitochondrial ER contact sites

Mitochondria and the endoplasmic reticulum (ER) have a synergistic relationship and are key regulatory hubs in maintaining cell homeostasis. Communication between these organelles is mediated by mitochondria ER contact sites (MERCS), allowing the exchange of material and information, modulating calcium homeostasis, redox signalling, lipid transfer and the regulation of mitochondrial dynamics. MERCS are dynamic structures that allow cells to respond to changes in the intracellular environment under normal homeostatic conditions, while their assembly/disassembly are affected by pathophysiological conditions such as ageing and disease. Disruption of protein folding in the ER lumen can activate the Unfolded Protein Response (UPR), promoting the remodelling of ER membranes and MERCS formation. The UPR stress receptor kinases PERK and IRE1, are located at or close to MERCS. UPR signalling can be adaptive or maladaptive, depending on whether the disruption in protein folding or ER stress is transient or sustained. Adaptive UPR signalling via MERCS can increase mitochondrial calcium import, metabolism and dynamics, while maladaptive UPR signalling can result in excessive calcium import and activation of apoptotic pathways. Targeting UPR signalling and the assembly of MERCS is an attractive therapeutic approach for a range of age-related conditions such as neurodegeneration and sarcopenia. This review highlights the emerging evidence related to the role of redox mediated UPR activation in orchestrating inter-organelle communication between the ER and mitochondria, and ultimately the determination of cell function and fate.

Inhibition of the Eukaryotic Initiation Factor-2-α Kinase PERK Decreases Risk of Autoimmune Diabetes in Mice

Preventing the onset of autoimmune type 1 diabetes (T1D) is feasible through pharmacological interventions that target molecular stress-responsive mechanisms. Cellular stresses, such as nutrient deficiency, viral infection, or unfolded proteins, trigger the integrated stress response (ISR), which curtails protein synthesis by phosphorylating eIF2α. In T1D, maladaptive unfolded protein response (UPR) in insulin-producing β cells renders these cells susceptible to autoimmunity. We show that inhibition of the eIF2α kinase PERK, a common component of the UPR and ISR, reverses the mRNA translation block in stressed human islets and delays the onset of diabetes, reduces islet inflammation, and preserves β cell mass in T1D-susceptible mice. Single-cell RNA sequencing of islets from PERK-inhibited mice shows reductions in the UPR and PERK signaling pathways and alterations in antigen processing and presentation pathways in β cells. Spatial proteomics of islets from these mice shows an increase in the immune checkpoint protein PD-L1 in β cells. Golgi membrane protein 1, whose levels increase following PERK inhibition in human islets and EndoC-βH1 human β cells, interacts with and stabilizes PD-L1. Collectively, our studies show that PERK activity enhances β cell immunogenicity, and inhibition of PERK may offer a strategy to prevent or delay the development of T1D.

Critical cis-parameters influence STructure assisted RNA translation (START) initiation on non-AUG codons in eukaryotes

In eukaryotes, translation initiation is a highly regulated process, which combines cis-regulatory sequences located on the messenger RNA along with trans-acting factors like eukaryotic initiation factors (eIF). One critical step of translation initiation is the start codon recognition by the scanning 43S particle, which leads to ribosome assembly and protein synthesis. In this study, we investigated the involvement of secondary structures downstream the initiation codon in the so-called START (STructure-Assisted RNA translation) mechanism on AUG and non-AUG translation initiation. The results demonstrate that downstream secondary structures can efficiently promote non-AUG translation initiation if they are sufficiently stable to stall a scanning 43S particle and if they are located at an optimal distance from non-AUG codons to stabilize the codon-anticodon base pairing in the P site. The required stability of the downstream structure for efficient translation initiation varies in distinct cell types. We extended this study to genome-wide analysis of functionally characterized alternative translation initiation sites in Homo sapiens. This analysis revealed that about 25% of these sites have an optimally located downstream secondary structure of adequate stability which could elicit START, regardless of the start codon. We validated the impact of these structures on translation initiation for several selected uORFs.

Correlation between TCF7L2 gene expression and certain biochemical parameters in type 2 diabetes mellitus

Objectives

The transcription factor 7-like 2 gene (TCF7L2) is associated with a predisposition to type 2 diabetes mellitus (T2DM) in different ethnic populations. This article investigated the relationship between TCF7L2 gene expression and several biochemical indexes among different age categories of T2DM in a sample of the Iraqi population.

Methods

One hundred and fifty blood samples were collected from three groups: young T2DM (10-35 years), old T2DM (40-80 years), and healthy control (10-65 years) groups. Both sexes were enrolled. qPCR was performed to explore the expression of the TCF7L2 gene. Biochemical tests were performed to assess hemoglobin A1C (HbA1c), triglyceride (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels. The body mass index (BMI) was calculated. The results were statistically analyzed.

Results

Patients with T2DM had higher BMI, TG, and LDL, and lower HDL than the control group. There was a strong positive correlation between hemoglobin A1C (HbA1c) and BMI, TG, and LDL and a negative correlation between HbA1c and HDL. Expression of the TCF7L2 gene showed a significant difference between old and young patients by 1.68 and 0.207 fold, respectively. These results showed that old patients had higher gene expression than young patients.

Conclusion

TCF7L2 gene expression was affected by age, with higher expression in old T2DM patients. This may influence beta cell functions and insulin secretion.

ACH2.0/E, the Consolidated Theory of Conventional and Unconventional Alzheimer's Disease: Origins, Progression, and Therapeutic Strategies

The centrality of amyloid-beta (Aβ) is an indisputable tenet of Alzheimer's disease (AD). It was initially indicated by the detection (1991) of a mutation within Aβ protein precursor (AβPP) segregating with the disease, which served as a basis for the long-standing Amyloid Cascade Hypothesis (ACH) theory of AD. In the intervening three decades, this notion was affirmed and substantiated by the discovery of numerous AD-causing and AD-protective mutations with all, without an exception, affecting the structure, production, and intraneuronal degradation of Aβ. The ACH postulated that the disease is caused and driven by extracellular Aβ. When it became clear that this is not the case, and the ACH was largely discredited, a new theory of AD, dubbed ACH2.0 to re-emphasize the centrality of Aβ, was formulated. In the ACH2.0, AD is caused by physiologically accumulated intraneuronal Aβ (iAβ) derived from AβPP. Upon reaching the critical threshold, it triggers activation of the autonomous AβPP-independent iAβ generation pathway; its output is retained intraneuronally and drives the AD pathology. The bridge between iAβ derived from AβPP and that generated independently of AβPP is the neuronal integrated stress response (ISR) elicited by the former. The ISR severely suppresses cellular protein synthesis; concurrently, it activates the production of a small subset of proteins, which apparently includes components necessary for operation of the AβPP-independent iAβ generation pathway that are absent under regular circumstances. The above sequence of events defines "conventional" AD, which is both caused and driven by differentially derived iAβ. Since the ISR can be elicited by a multitude of stressors, the logic of the ACH2.0 mandates that another class of AD, referred to as "unconventional", has to occur. Unconventional AD is defined as a disease where a stressor distinct from AβPP-derived iAβ elicits the neuronal ISR. Thus, the essence of both, conventional and unconventional, forms of AD is one and the same, namely autonomous, self-sustainable, AβPP-independent production of iAβ. What distinguishes them is the manner of activation of this pathway, i.e., the mode of causation of the disease. In unconventional AD, processes occurring at locations as distant from and seemingly as unrelated to the brain as, say, the knee can potentially trigger the disease. The present study asserts that these processes include traumatic brain injury (TBI), chronic traumatic encephalopathy, viral and bacterial infections, and a wide array of inflammatory conditions. It considers the pathways which are common to all these occurrences and culminate in the elicitation of the neuronal ISR, analyzes the dynamics of conventional versus unconventional AD, shows how the former can morph into the latter, explains how a single TBI can hasten the occurrence of AD and why it takes multiple TBIs to trigger the disease, and proposes the appropriate therapeutic strategies. It posits that yet another class of unconventional AD may occur where the autonomous AβPP-independent iAβ production pathway is initiated by an ISR-unrelated activator, and consolidates the above notions in a theory of AD, designated ACH2.0/E (for expanded ACH2.0), which incorporates the ACH2.0 as its special case and retains the centrality of iAβ produced independently of AβPP as the driving agent of the disease.

Endoplasmic reticulum stress in pancreatic β-cell dysfunction: The potential therapeutic role of dietary flavonoids

Diabetes mellitus (DM) is a global health burden that is characterized by the loss or dysfunction of pancreatic β-cells. In pancreatic β-cells, endoplasmic reticulum (ER) stress is a fact of life that contributes to β-cell loss or dysfunction. Despite recent advances in research, the existing treatment approaches such as lifestyle modification and use of conventional therapeutics could not prevent the loss or dysfunction of pancreatic β-cells to abrogate the disease progression. Therefore, targeting ER stress and the consequent unfolded protein response (UPR) in pancreatic β-cells may be a potential therapeutic strategy for diabetes treatment. Dietary phytochemicals have therapeutic applications in human health owing to their broad spectrum of biochemical and pharmacological activities. Flavonoids, which are commonly obtained from fruits and vegetables worldwide, have shown promising prospects in alleviating ER stress. Dietary flavonoids including quercetin, kaempferol, myricetin, isorhamnetin, fisetin, icariin, apigenin, apigetrin, vitexin, baicalein, baicalin, nobiletin hesperidin, naringenin, epigallocatechin 3-O-gallate hesperidin (EGCG), tectorigenin, liquiritigenin, and acacetin have shown inhibitory effects on ER stress in pancreatic β-cells. Dietary flavonoids modulate ER stress signaling components, chaperone proteins, transcription factors, oxidative stress, autophagy, apoptosis, and inflammatory responses to exert their pharmacological effects on pancreatic β-cells ER stress. This review focuses on the role of dietary flavonoids as potential therapeutic adjuvants in preserving pancreatic β-cells from ER stress. Highlights of the underlying mechanisms of action are also presented as well as possible strategies for clinical translation in the management of DM.

Endoplasmic Reticulum Dysfunction: An Emerging Mechanism of Vitiligo Pathogenesis

The endoplasmic reticulum (ER) is the main site of protein synthesis, transport, and modification. Its abnormal status has now emerged as an established cause of many pathological processes, such as tumors and autoimmune diseases. Recent studies also demonstrated that the defective functions of ER may lead to pigmentary diseases. Vitiligo is a depigmenting ailment skin disorder whose pathogenesis is now found to be associated with ER. However, the detailed mechanism is still unclear. In this review, we try to link the association between ER with its inter- and intra-organellar interactions in vitiligo pathogenesis and focus on the function, mechanism, and clinical potential of ER with vitiligo. Expand ER is found in melanocytes of vitiligo and ER stress (ERS) might be a bridge between oxidative stress and innate and adaptive immunity. Meanwhile, the tight association between ER and mitochondria or melanosomes in organelles levels, as well as genes and cytokines, is the new paradigm in the pathogenesis of vitiligo. This undoubtedly adds a new aspect to the understanding of vitiligo, facilitating the design of targeted therapies for vitiligo.

An upstream open reading frame (5'-uORF) links oxidative stress to translational control of ALCAT1 through phosphorylation of eIF2α

Acyl-CoA:lysocardiolipin acyltransferase 1 (ALCAT1) is an enzyme that promotes mitochondrial dysfunction by catalyzing pathological remodeling of cardiolipin. Upregulation of ALCAT1 protein expression by oxidative stress is implicated in the pathogenesis of age-related metabolic diseases, but the underlying molecular mechanisms remain elusive. In this study, we identified a highly conserved upstream open reading frame (uORF) at the 5'-untranslated region (5'-UTR) of ALCAT1 mRNA as a key regulator of ALCAT1 expression in response to oxidative stress. We show that the uORF serves as a decoy that prevents translation initiation of ALCAT1 under homeostatic condition. The inhibitory activity of the uORF on ALCAT1 mRNA translation is mitigated by oxidative stress but not ER stress, which requires the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α). Consequently, ablation of uORF or eIF2α phosphorylation at Ser51 renders ALCAT1 protein expression unresponsive to induction by oxidative stress. Taken together, our data show that the uORF links oxidative stress to translation control of ALCAT1 mRNAs through phosphorylation of eIF2α at Ser51.

To initiate or not to initiate: A critical assessment of eIF2A, eIF2D, and MCT-1·DENR to deliver initiator tRNA to ribosomes

Selection of the correct start codon is critical for high-fidelity protein synthesis. In eukaryotes, this is typically governed by a multitude of initiation factors (eIFs), including eIF2·GTP that directly delivers the initiator tRNA (Met-tRNAi Met ) to the P site of the ribosome. However, numerous reports, some dating back to the early 1970s, have described other initiation factors having high affinity for the initiator tRNA and the ability of delivering it to the ribosome, which has provided a foundation for further work demonstrating non-canonical initiation mechanisms using alternative initiation factors. Here we provide a critical analysis of current understanding of eIF2A, eIF2D, and the MCT-1·DENR dimer, the evidence surrounding their ability to initiate translation, their implications in human disease, and lay out important key questions for the field. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes Translation > Mechanisms Translation > Regulation.

Activation of goblet-cell stress sensor IRE1β is controlled by the mucin chaperone AGR2

Intestinal goblet cells are secretory cells specialized in the production of mucins, and as such are challenged by the need for efficient protein folding. Goblet cells express Inositol-Requiring Enzyme-1β (IRE1β), a unique sensor in the unfolded protein response (UPR), which is part of an adaptive mechanism that regulates the demands of mucin production and secretion. However, how IRE1β activity is tuned to mucus folding load remains unknown. We identified the disulfide isomerase and mucin chaperone AGR2 as a goblet cell-specific protein that crucially regulates IRE1β-, but not IRE1α-mediated signaling. AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. Depletion of endogenous AGR2 from goblet cells induces spontaneous IRE1β activation, suggesting that alterations in AGR2 availability in the endoplasmic reticulum set the threshold for IRE1β activation. We found that AGR2 mutants lacking their catalytic cysteine, or displaying the disease-associated mutation H117Y, were no longer able to dampen IRE1β activity. Collectively, these results demonstrate that AGR2 is a central chaperone regulating the goblet cell UPR by acting as a rheostat of IRE1β endonuclease activity.

Identification of the unfolded protein response pathway as target for radiosensitization in pancreatic cancer

BACKGROUND AND PURPOSE

Due to the high intrinsic radioresistance of pancreatic ductal adenocarcinoma (PDAC), radiotherapy (RT) is only beneficial in 30% of patients. Therefore, this study aimed to identify targets to improve the efficacy of RT in PDAC.

MATERIALS AND METHODS

Alamar Blue proliferation and colony formation assay (CFA) were used to determine the radioresponse of a cohort of 38 murine PDAC cell lines. A gene set enrichment analysis was performed to reveal differentially expressed pathways. CFA, cell cycle distribution, γH2AX FACS analysis, and Caspase 3/7 SYTOX assay were used to examine the effect of a combination treatment using KIRA8 as an IRE1α-inhibitor and Ceapin-A7 as an inhibitor against ATF6.

RESULTS

The unfolded protein response (UPR) was identified as a pathway highly expressed in radioresistant cell lines. Using the IRE1α-inhibitor KIRA8 or the ATF6-inhibitor Ceapin-A7 in combination with radiation, a radiosensitizing effect was observed in radioresistant cell lines, but no substantial alteration of the radioresponse in radiosensitive cell lines. Mechanistically, increased apoptosis by KIRA8 in combination with radiation and a cell cycle arrest in the G1 phase after ATF6 inhibition and radiation have been observed in radioresistant cell lines.

CONCLUSION

So, our data show evidence that the UPR is involved in radioresistance of PDAC. Increased apoptosis and a G1 cell cycle arrest seem to be responsible for the radiosensitizing effect of UPR inhibition. These findings are supportive for developing novel combination treatment concepts in PDAC to overcome radioresistance.

Esketamine induces apoptosis of nasopharyngeal carcinoma cells through the PERK/CHOP pathway

Nasopharyngeal carcinoma, a malignant tumor prevalent in southeast Asia and north Africa, still lacks effective treatment. Esketamine, an N-methyl-D-aspartatic acid (NMDA) receptor (NMDAR) antagonist, is widely used in clinical anesthesia. Emerging evidence suggests that esketamine plays an important role in inhibiting tumor cell activity. However, the underlying mechanisms of esketamine on nasopharyngeal carcinoma remain unknown. In this study, we found that esketamine inhibited the proliferation and migration of nasopharyngeal carcinoma cells. Mechanically, transcriptome sequencing and subsequent verification experiments revealed that esketamine promoted the apoptosis of nasopharyngeal carcinoma cells through endoplasmic reticulum stress PERK/ATF4/CHOP signaling pathway mediated by NMDAR. Additionally, when combined with esketamine, the inhibitory effect of cisplatin on the proliferation of nasopharyngeal carcinoma cells was significantly enhanced. These findings provide new insights into future anti-nasopharyngeal carcinoma clinical strategies via targeting the NMDAR/PERK/CHOP axis alone or in combination with cisplatin.

Impact of eIF2α phosphorylation on the translational landscape of mouse embryonic stem cells

The integrated stress response (ISR) is critical for cell survival under stress. In response to diverse environmental cues, eIF2α becomes phosphorylated, engendering a dramatic change in mRNA translation. The activation of ISR plays a pivotal role in the early embryogenesis, but the eIF2-dependent translational landscape in pluripotent embryonic stem cells (ESCs) is largely unexplored. We employ a multi-omics approach consisting of ribosome profiling, proteomics, and metabolomics in wild-type (eIF2α+/+) and phosphorylation-deficient mutant eIF2α (eIF2αA/A) mouse ESCs (mESCs) to investigate phosphorylated (p)-eIF2α-dependent translational control of naive pluripotency. We show a transient increase in p-eIF2α in the naive epiblast layer of E4.5 embryos. Absence of eIF2α phosphorylation engenders an exit from naive pluripotency following 2i (two chemical inhibitors of MEK1/2 and GSK3α/β) withdrawal. p-eIF2α controls translation of mRNAs encoding proteins that govern pluripotency, chromatin organization, and glutathione synthesis. Thus, p-eIF2α acts as a key regulator of the naive pluripotency gene regulatory network.

Congenital Hyperinsulinism in Humans and Insulin Secretory Dysfunction in Mice Caused by Biallelic DNAJC3 Variants

The BiP co-chaperone DNAJC3 protects cells during ER stress. In mice, the deficiency of DNAJC3 leads to beta-cell apoptosis and the gradual onset of hyperglycemia. In humans, biallelic DNAJC3 variants cause a multisystem disease, including early-onset diabetes mellitus. Recently, hyperinsulinemic hypoglycemia (HH) has been recognized as part of this syndrome. This report presents a case study of an individual with HH caused by DNAJC3 variants and provides an overview of the metabolic phenotype of individuals with HH and DNAJC3 variants. The study demonstrates that HH may be a primary symptom of DNAJC3 deficiency and can persist until adolescence. Additionally, glycemia and insulin release were analyzed in young DNACJ3 knockout (K.O.) mice, which are equivalent to human infants. In the youngest experimentally accessible age group of 4-week-old mice, the in vivo glycemic phenotype was already dominated by a reduced total insulin secretion capacity. However, on a cellular level, the degree of insulin release of DNAJC3 K.O. islets was higher during periods of increased synthetic activity (high-glucose stimulation). We propose that calcium leakage from the ER into the cytosol, due to disrupted DNAJC3-controlled gating of the Sec61 channel, is the most likely mechanism for HH. This is the first genetic mechanism explaining HH solely by the disruption of intracellular calcium homeostasis. Clinicians should screen for HH in DNAJC3 deficiency and consider DNAJC3 variants in the differential diagnosis of congenital hyperinsulinism.

Metal-based nanoparticles in cancer therapy: Exploring photodynamic therapy and its interplay with regulated cell death pathways

Photodynamic therapy (PDT) represents a non-invasive treatment strategy currently utilized in the clinical management of selected cancers and infections. This technique is predicated on the administration of a photosensitizer (PS) and subsequent irradiation with light of specific wavelengths, thereby generating reactive oxygen species (ROS) within targeted cells. The cellular effects of PDT are dependent on both the localization of the PS and the severity of ROS challenge, potentially leading to the stimulation of various cell death modalities. For many years, the concept of regulated cell death (RCD) triggered by photodynamic reactions predominantly encompassed apoptosis, necrosis, and autophagy. However, in recent decades, further explorations have unveiled additional cell death modalities, such as necroptosis, ferroptosis, cuproptosis, pyroptosis, parthanatos, and immunogenic cell death (ICD), which helps to achieve tumor cell elimination. Recently, nanoparticles (NPs) have demonstrated substantial advantages over traditional PSs and become important components of PDT, due to their improved physicochemical properties, such as enhanced solubility and superior specificity for targeted cells. This review aims to summarize recent advancements in the applications of different metal-based NPs as PSs or delivery systems for optimized PDT in cancer treatment. Furthermore, it mechanistically highlights the contribution of RCD pathways during PDT with metal NPs and how these forms of cell death can improve specific PDT regimens in cancer therapy.

Endoplasmic Reticulum Stress and Obesity

In recent years, the world has seen an alarming increase in obesity and is closely associated with insulin resistance, which is a state of low-grade inflammation, the latter characterized by elevated levels of proinflammatory cytokines in blood and tissues. A shift in energy balance alters systemic metabolic regulation and the important role that chronic inflammation, endoplasmic reticulum (ER) dysfunction, and activation of the unfolded protein response (UPR) plays in this process.Why obesity is so closely associated with insulin resistance and inflammation is not understood well. This suggests that there are probably many causes for obesity-related insulin resistance and inflammation. One of the faulty mechanisms is protein homeostasis, protein quality control system included protein folding, chaperone activity, and ER-associated degradation leading to endoplasmic reticulum (ER) stress.The ER is a vast membranous network responsible for the trafficking of a wide range of proteins and plays a central role in integrating multiple metabolic signals critical in cellular homeostasis. Conditions that may trigger unfolded protein response activation include increased protein synthesis, the presence of mutant or misfolded proteins, inhibition of protein glycosylation, imbalance of ER calcium levels, glucose and energy deprivation, hypoxia, pathogens, or pathogen-associated components and toxins. Thus, characterizing the mechanisms contributing to obesity and identifying potential targets for its prevention and treatment will have a great impact on the control of associated conditions, particularly T2D.

Cellular stress is triggered by tick-borne encephalitis virus and limits the virus replication in PMJ2-R mouse macrophage cell line

Viral infection may represent a stress condition to the host cell. Cells react to it by triggering the defence programme to restore homeostasis and these events may in turn impact the viral replication. The knowledge about tick-borne encephalitis virus (TBEV) infection-associated stress is limited. Here we investigated the interplay between TBEV infection and stress pathways in PMJ2-R mouse macrophage cell line, as macrophages are the target cells in early phases of TBEV infection. First, to determine how stress influences TBEV replication, the effect of stress inducers H2O2 and tunicamycin (TM) was tested. Viral multiplication was decreased in the presence of both stress inducers suggesting that the stress and cellular stress responses restrict the virus replication. Second, we investigated the induction of oxidative stress and endoplasmic reticulum (ER) stress upon TBEV infection. The level of oxidative stress was interrogated by measuring the reactive oxygen species (ROS). ROS were intermittently increased in infected cells at 12 hpi and at 72 hpi. As mitochondrial dysfunction may result in increased ROS level, we evaluated the mitochondrial homeostasis by measuring the mitochondrial membrane potential (MMP) and found that TBEV infection induced the hyperpolarization of MMP. Moreover, a transient increase of gene expression of stress-induced antioxidative enzymes, like p62, Gclm and Hmox1, was detected. Next, we evaluated the ER stress upon TBEV infection by analysing unfolded protein responses (UPR). We found that infection induced gene expression of two general sensors BiP and CHOP and activated the IRE1 pathway of UPR. Finally, since the natural transmission route of TBEV from its tick vector to the host is mediated via tick saliva, the impact of tick saliva from Ixodes ricinus on stress pathways in TBEV-infected cells was tested. We observed only marginal potentiation of UPR pathway. In conclusion, we found that TBEV infection of PMJ2-R cells elicits the changes in redox balance and triggers cellular stress defences, including antioxidant responses and the IRE1 pathway of UPR. Importantly, our results revealed the negative effect of stress-evoked events on TBEV replication and only marginal impact of tick saliva on stress cellular pathways.

Pharmacologic activation of a compensatory integrated stress response kinase promotes mitochondrial remodeling in PERK-deficient cells

The integrated stress response (ISR) comprises the eIF2α kinases PERK, GCN2, HRI, and PKR, which induce translational and transcriptional signaling in response to diverse insults. Deficiencies in PERK signaling lead to mitochondrial dysfunction and contribute to the pathogenesis of numerous diseases. We define the potential for pharmacologic activation of compensatory eIF2α kinases to rescue ISR signaling and promote mitochondrial adaptation in PERK-deficient cells. We show that the HRI activator BtdCPU and GCN2 activator halofuginone promote ISR signaling and rescue ER stress sensitivity in PERK-deficient cells. However, BtdCPU induces mitochondrial depolarization, leading to mitochondrial fragmentation and activation of the OMA1-DELE1-HRI signaling axis. In contrast, halofuginone promotes mitochondrial elongation and adaptive mitochondrial respiration, mimicking regulation induced by PERK. This shows halofuginone can compensate for deficiencies in PERK signaling and promote adaptive mitochondrial remodeling, highlighting the potential for pharmacologic ISR activation to mitigate mitochondrial dysfunction and motivating the pursuit of highly selective ISR activators.

Alphavirus-based replicons demonstrate different interactions with host cells and can be optimized to increase protein expression

IMPORTANCE

Alphavirus replicons are being developed as self-amplifying RNAs aimed at improving the efficacy of mRNA vaccines. These replicons are convenient for genetic manipulations and can express heterologous genetic information more efficiently and for a longer time than standard mRNAs. However, replicons mimic many aspects of viral replication in terms of induction of innate immune response, modification of cellular transcription and translation, and expression of nonstructural viral genes. Moreover, all replicons used in this study demonstrated expression of heterologous genes in cell- and replicon's origin-specific modes. Thus, many aspects of the interactions between replicons and the host remain insufficiently investigated, and further studies are needed to understand the biology of the replicons and their applicability for designing a new generation of mRNA vaccines. On the other hand, our data show that replicons are very flexible expression systems, and additional modifications may have strong positive impacts on protein expression.

Endoplasmic reticulum stress in pancreatic β cells induces incretin desensitization and β-cell dysfunction via ATF4-mediated PDE4D expression

Pancreatic β-cell dysfunction and eventual loss are key steps in the progression of type 2 diabetes (T2D). Endoplasmic reticulum (ER) stress responses, especially those mediated by the protein kinase RNA-like ER kinase and activating transcription factor 4 (PERK-ATF4) pathway, have been implicated in promoting these β-cell pathologies. However, the exact molecular events surrounding the role of the PERK-ATF4 pathway in β-cell dysfunction remain unknown. Here, we report our discovery that ATF4 promotes the expression of PDE4D, which disrupts β-cell function via a downregulation of cAMP signaling. We found that β-cell-specific transgenic expression of ATF4 led to early β-cell dysfunction and loss, a phenotype that resembles accelerated T2D. Expression of ATF4, rather than C/EBP homologous protein (CHOP), promoted PDE4D expression, reduced cAMP signaling, and attenuated responses to incretins and elevated glucose. Furthermore, we found that β-cells of leptin receptor-deficient diabetic (db/db) mice had elevated nuclear localization of ATF4 and PDE4D expression, accompanied by impaired β-cell function. Accordingly, pharmacological inhibition of the ATF4 pathway attenuated PDE4D expression in the islets and promoted incretin-simulated glucose tolerance and insulin secretion in db/db mice. Finally, we found that inhibiting PDE4 activity with selective pharmacological inhibitors improved β-cell function in both db/db mice and β-cell-specific ATF4 transgenic mice. In summary, our results indicate that ER stress causes β-cell failure via ATF4-mediated PDE4D production, suggesting the ATF4-PDE4D pathway could be a therapeutic target for protecting β-cell function during the progression of T2D.NEW & NOTEWORTHY Endoplasmic reticulum stress has been implied to cause multiple β-cell pathologies during the progression of type 2 diabetes (T2D). However, the precise molecular events underlying this remain unknown. Here, we discovered that elevated ATF4 activity, which was seen in T2D β cells, attenuated β-cell proliferation and impaired insulin secretion via PDE4D-mediated downregulation of cAMP signaling. Additionally, we demonstrated that pharmacological inhibition of the ATF4 pathway or PDE4D activity alleviated β-cell dysfunction, suggesting its therapeutic usefulness against T2D.

A Legionella toxin exhibits tRNA mimicry and glycosyl transferase activity to target the translation machinery and trigger a ribotoxic stress response

A widespread strategy employed by pathogens to establish infection is to inhibit host-cell protein synthesis. Legionella pneumophila, an intracellular bacterial pathogen and the causative organism of Legionnaires' disease, secretes a subset of protein effectors into host cells that inhibit translation elongation. Mechanistic insights into how the bacterium targets translation elongation remain poorly defined. We report here that the Legionella effector SidI functions in an unprecedented way as a transfer-RNA mimic that directly binds to and glycosylates the ribosome. The 3.1 Å cryo-electron microscopy structure of SidI reveals an N-terminal domain with an 'inverted L' shape and surface-charge distribution characteristic of tRNA mimicry, and a C-terminal domain that adopts a glycosyl transferase fold that licenses SidI to utilize GDP-mannose as a sugar precursor. This coupling of tRNA mimicry and enzymatic action endows SidI with the ability to block protein synthesis with a potency comparable to ricin, one of the most powerful toxins known. In Legionella-infected cells, the translational pausing activated by SidI elicits a stress response signature mimicking the ribotoxic stress response, which is activated by elongation inhibitors that induce ribosome collisions. SidI-mediated effects on the ribosome activate the stress kinases ZAKα and p38, which in turn drive an accumulation of the protein activating transcription factor 3 (ATF3). Intriguingly, ATF3 escapes the translation block imposed by SidI, translocates to the nucleus and orchestrates the transcription of stress-inducible genes that promote cell death, revealing a major role for ATF3 in the response to collided ribosome stress. Together, our findings elucidate a novel mechanism by which a pathogenic bacterium employs tRNA mimicry to hijack a ribosome-to-nuclear signalling pathway that regulates cell fate.

Increased levels of eIF2A inhibit translation by sequestering 40S ribosomal subunits

eIF2A was the first eukaryotic initiator tRNA carrier discovered but its exact function has remained enigmatic. Uncharacteristic of translation initiation factors, eIF2A is reported to be non-cytosolic in multiple human cancer cell lines. Attempts to study eIF2A mechanistically have been limited by the inability to achieve high yield of soluble recombinant protein. Here, we developed a purification paradigm that yields ∼360-fold and ∼6000-fold more recombinant human eIF2A from Escherichia coli and insect cells, respectively, than previous reports. Using a mammalian in vitro translation system, we found that increased levels of recombinant human eIF2A inhibit translation of multiple reporter mRNAs, including those that are translated by cognate and near-cognate start codons, and does so prior to start codon recognition. eIF2A also inhibited translation directed by all four types of cap-independent viral IRESs, including the CrPV IGR IRES that does not require initiation factors or initiator tRNA, suggesting excess eIF2A sequesters 40S subunits. Supplementation with additional 40S subunits prevented eIF2A-mediated inhibition and pull-down assays demonstrated direct binding between recombinant eIF2A and purified 40S subunits. These data support a model that eIF2A must be kept away from the translation machinery to avoid sequestering 40S ribosomal subunits.

Excitatory neuron-specific suppression of the integrated stress response contributes to autism-related phenotypes in fragile X syndrome

Dysregulation of protein synthesis is one of the key mechanisms underlying autism spectrum disorder (ASD). However, the role of a major pathway controlling protein synthesis, the integrated stress response (ISR), in ASD remains poorly understood. Here, we demonstrate that the main arm of the ISR, eIF2α phosphorylation (p-eIF2α), is suppressed in excitatory, but not inhibitory, neurons in a mouse model of fragile X syndrome (FXS; Fmr1-/y). We further show that the decrease in p-eIF2α is mediated via activation of mTORC1. Genetic reduction of p-eIF2α only in excitatory neurons is sufficient to increase general protein synthesis and cause autism-like behavior. In Fmr1-/y mice, restoration of p-eIF2α solely in excitatory neurons reverses elevated protein synthesis and rescues autism-related phenotypes. Thus, we reveal a previously unknown causal relationship between excitatory neuron-specific translational control via the ISR pathway, general protein synthesis, and core phenotypes reminiscent of autism in a mouse model of FXS.

Bridging Energy Need and Feeding Behavior: The Impact of eIF2α Phosphorylation in AgRP Neurons

Eukaryotic translation initiation factor 2α (eIF2α) is a key mediator of the endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR). In mammals, eIF2α is phosphorylated by overnutrition-induced ER stress and is related to the development of obesity. Here, we studied the function of phosphorylated eIF2α (p-eIF2α) in agouti-related peptide (AgRP) neurons using a mouse model (AgRPeIF2αA/A) with an AgRP neuron-specific substitution from Ser 51 to Ala in eIF2α, which impairs eIF2α phosphorylation in AgRP neurons. These AgRPeIF2αA/A mice had decreases in starvation-induced AgRP neuronal activity and food intake and an increased responsiveness to leptin. Intriguingly, impairment of eIF2α phosphorylation produced decreases in the starvation-induced expression of UPR and autophagy genes in AgRP neurons. Collectively, these findings suggest that eIF2α phosphorylation regulates AgRP neuronal activity by affecting intracellular responses such as the UPR and autophagy during starvation, thereby participating in the homeostatic control of whole-body energy metabolism.

ARTICLE HIGHLIGHTS

This study examines the impact of eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, triggered by an energy deficit, on hypothalamic AgRP neurons and its subsequent influence on whole-body energy homeostasis. Impaired eIF2α phosphorylation diminishes the unfolded protein response and autophagy, both of which are crucial for energy deficit-induced activation of AgRP neurons. This study highlights the significance of eIF2α phosphorylation as a cellular marker indicating the availability of energy in AgRP neurons and as a molecular switch that regulates homeostatic feeding behavior.

Lysosomal cystine governs ferroptosis sensitivity in cancer via cysteine stress response

The amino acid cysteine and its oxidized dimeric form cystine are commonly believed to be synonymous in metabolic functions. Cyst(e)ine depletion not only induces amino acid response but also triggers ferroptosis, a non-apoptotic cell death. Here, we report that unlike general amino acid starvation, cyst(e)ine deprivation triggers ATF4 induction at the transcriptional level. Unexpectedly, it is the shortage of lysosomal cystine, but not the cytosolic cysteine, that elicits the adaptative ATF4 response. The lysosome-nucleus signaling pathway involves the aryl hydrocarbon receptor (AhR) that senses lysosomal cystine via the kynurenine pathway. A blockade of lysosomal cystine efflux attenuates ATF4 induction and sensitizes ferroptosis. To potentiate ferroptosis in cancer, we develop a synthetic mRNA reagent, CysRx, that converts cytosolic cysteine to lysosomal cystine. CysRx maximizes cancer cell ferroptosis and effectively suppresses tumor growth in vivo. Thus, intracellular nutrient reprogramming has the potential to induce selective ferroptosis in cancer without systematic starvation.

Signal-noise metrics for RNA binding protein identification reveal broad spectrum protein-RNA interaction frequencies and dynamics

Recent efforts towards the comprehensive identification of RNA-bound proteomes have revealed a large, surprisingly diverse family of candidate RNA-binding proteins (RBPs). Quantitative metrics for characterization and validation of protein-RNA interactions and their dynamic interactions have, however, proven analytically challenging and prone to error. Here we report a method termed LEAP-RBP (Liquid-Emulsion-Assisted-Purification of RNA-Bound Protein) for the selective, quantitative recovery of UV-crosslinked RNA-protein complexes. By virtue of its high specificity and yield, LEAP-RBP distinguishes RNA-bound and RNA-free protein levels and reveals common sources of experimental noise in RNA-centric RBP enrichment methods. We introduce strategies for accurate RBP identification and signal-based metrics for quantifying protein-RNA complex enrichment, relative RNA occupancy, and method specificity. In this work, the utility of our approach is validated by comprehensive identification of RBPs whose association with mRNA is modulated in response to global mRNA translation state changes and through in-depth benchmark comparisons with current methodologies.

Cigarette smoke restricts the ability of mesenchymal cells to support lung epithelial organoid formation

Adequate lung epithelial repair relies on supportive interactions within the epithelial niche, including interactions with WNT-responsive fibroblasts. In fibroblasts from patients with chronic obstructive pulmonary disease (COPD) or upon in vitro cigarette smoke exposure, Wnt/β-catenin signalling is distorted, which may affect interactions between epithelial cells and fibroblasts resulting in inadequate lung repair. We hypothesized that cigarette smoke (CS), the main risk factor for COPD, interferes with Wnt/β-catenin signalling in fibroblasts through induction of cellular stress responses, including oxidative- and endoplasmic reticulum (ER) stress, and thereby alters epithelial repair support potential. Therefore, we assessed the effect of CS-exposure and the ER stress inducer Thapsigargin (Tg) on Wnt/β-catenin signalling activation in MRC-5 fibroblasts, and on their ability to support lung epithelial organoid formation. Exposure of MRC-5 cells for 15 min with 5 AU/mL CS extract (CSE), and subsequent 6 h incubation induced oxidative stress (HMOX1). Whereas stimulation with 100 nM Tg increased markers of both the integrated stress response (ISR - GADD34/PPP1R15A, CHOP) and the unfolded protein response (UPR - XBP1spl, GADD34/PPP1R15A, CHOP and HSPA5/BIP), CSE only induced GADD34/PPP1R15A expression. Strikingly, although treatment of MRC-5 cells with the Wnt activator CHIR99021 upregulated the Wnt/β-catenin target gene AXIN2, this response was diminished upon CSE or Tg pre-exposure, which was confirmed using a Wnt-reporter. Furthermore, pre-exposure of MRC-5 cells to CSE or Tg, restricted their ability to support organoid formation upon co-culture with murine pulmonary EpCam+ cells in Matrigel at day 14. This restriction was alleviated by pre-treatment with CHIR99021. We conclude that exposure of MRC-5 cells to CSE increases oxidative stress, GADD34/PPP1R15A expression and impairs their ability to support organoid formation. This inhibitory effect may be restored by activating the Wnt/β-catenin signalling pathway.

mir-98-5p regulates gluconeogenesis and lipogenesis by targeting PPP1R15B in hepatocytes

Several reports suggest that circulatory miRNAs are deregulated in diverse diseases and used as markers for disease diagnosis and prognosis. Here we show that miR-98-5p, that is down-regulated in the circulation during diabetes, regulates hepatic gluconeogenesis and lipogenesis by targeting PPP1R15B. miR-98-5p overexpression significantly decreased the transcript and protein levels of PPP1R15B in hepatic HepG2 cells and increased p-eIF2α expression and these were prevented in the presence of its inhibitor. Two major hepatic hallmarks during diabetes i.e. hepatic lipid accumulation and glucose output were explored towards physiological relevance. As compared to scramble, overexpression of miR-98-5p decreased the transcript levels of both gluconeogenic and lipogenic genes together with a significant reduction in hepatic glucose production and fat accumulation in HepG2 cells. Using PASTAA to detect common transcription factors regulating these altered genes, CREB emerged as the most significantly enriched transcription factor. While miR-98-5p overexpression did not change the transcript levels of CREB, there was a significant change in its protein levels. While similar effects on gluconeogenic and lipogenic gene expression were detected using the PPP1R15B siRNA, the opposite was observed in the presence of miR-98-5p inhibitor alone. All these suggest that by targeting PPP1R15B, miR-98-5p regulates hepatic steatosis and glucose output; deregulation of which are characteristic hepatic features during diabetes. Therapeutic intervention of the miR-98/PPP1R15B axis might offer a potential strategy to target aberrant hepatic metabolism during diabetes.