Edaravone counteracts redox and metabolic disruptions in an emerging zebrafish model of sporadic ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease in which the death of motor neurons leads to loss of muscle function. Additionally, cognitive and circadian disruptions are common in ALS patients, contributing to disease progression and burden. Most ALS cases are sporadic, and environmental exposures contribute to their aetiology. However, animal models of these sporadic ALS cases are scarce. The small vertebrate zebrafish is a leading organism to model neurodegenerative diseases; previous studies have proposed bisphenol A (BPA) or β-methylamino-l-alanine (BMAA) exposure to model sporadic ALS in zebrafish, damaging motor neurons and altering motor responses. Here we characterise the face and predictive validity of sporadic ALS models, showing their potential for the mechanistic study of ALS drugs. We phenotypically characterise the BPA and BMAA-induced models, going beyond motor activity and motor axon morphology, to include circadian, redox, proteostasis, and metabolomic phenotypes, and assessing their predictive validity for ALS modelling. BPA or BMAA exposure induced concentration-dependent activity impairments. Also, exposure to BPA but not BMAA induced motor axonopathy and circadian alterations in zebrafish larvae. Our further study of the BPA model revealed loss of habituation to repetitive startles, increased oxidative damage, endoplasmic reticulum (ER) stress, and metabolome abnormalities. The BPA-induced model shows predictive validity, since the approved ALS drug edaravone counteracted BPA-induced motor phenotypes, ER stress, and metabolic disruptions. Overall, BPA exposure is a promising model of ALS-related redox and ER imbalances, contributing to fulfil an unmet need for validated sporadic ALS models.

Licochalcone A induces endoplasmic reticulum stress-mediated apoptosis of endometrial cancer cells via upregulation of GRP78 expression

Licochalcone A (LicA), a natural compound extracted from licorice root, has been shown to exert a variety of anticancer activities. Whether LicA has such effects on endometrial cancer (EMC) is unclear. This study aims to investigate the antitumor effects of LicA on EMC. Our results show that LicA significantly reduced the viability and induced apoptosis of EMC cells and EMC-7 cells from EMC patients. LicA was also found to induce endoplasmic reticulum (ER) stress, leading to increased expression of ER-related proteins (GRP78/PERK/IRE1α/CHOP) in EMC cell lines. Suppression of GRP78 expression in human EMC cells treated with LicA significantly attenuated the effects of LicA, resulting in reduced ER-stress mediated cell apoptosis and decreased expression of ER- and apoptosis-related proteins. Our findings demonstrate that LicA induces apoptosis in EMC cells through the GRP78-mediated ER-stress pathway, emphasizing the potential of LicA as an anticancer therapy for EMC.

Identification of potential anti-mucor agents by targeting endothelial cell receptor glucose-regulated protein-78 using in silico approach

Mucormycosis is a fungal infection of the sinuses, brain and lungs that is the cause of approximately 50% mortality rate despite the available first-line therapy. Glucose-Regulated Protein 78 (GRP78) is already reported to be a novel host receptor that mediates invasion and damage of human endothelial cells by Rhizopus oryzae and Rhizopus delemar, the most common etiologic species of Mucorales. The expression of GRP78 is also regulated by the levels of iron and glucose in the blood. There are several antifungal drugs in the market but they pose a serious side effect to the vital organs of the body. Therefore, there is an immediate need to discover effective drug molecules having increased efficacy with no side effects. With the help of various computational tools, the current study was attempted to determine potential antimucor agents against GRP78. The receptor molecule GRP78 was screened against 8820 known drugs deposited in DrugBank library using high-throughput virtual screening method. Total top 10 compounds were selected based on the binding energies greater than the reference co-crystal molecule. Furthermore, molecular dynamic (MD) simulations using AMBER were performed to calculate the stability of the top-ranked compounds in the active site of GRP78. After extensive computational studies, we propose that two compounds (CID439153 and CID5289104) have inhibitory potency against mucormycosis and can serve as potential drugs that can form the basis of treating mucormycosis disease.Communicated by Ramaswamy H. Sarma.

Endoplasmic reticulum stress produced by Thapsigargin affects the occurrence of spike-wave discharge by modulating unfolded protein response pathways and activating immune responses in a dose-dependent manner

The Endoplasmic Reticulum (ER) is associated with many cellular functions, from post-transcriptional modifications to the proper folding of proteins, and disruption of these functions causes ER stress. Although the relationship between epileptic seizures and ER stress has been reported, the contribution of ER stress pathways to epileptogenesis is still unclear. This study aimed to investigate the possible effects of ER stress-related molecular pathways modulated by mild- and high-dose Thapsigargin (Tg) on absence epileptic activity, CACNA1H and immune responses in WAG/Rij rats. For this purpose, rats were divided into four groups; mild-dose (20ng) Tg, high-dose (200ng) Tg, saline, and DMSO and drugs administered intracerebroventriculary. EEG activity was recorded for one hour and 24 hour after drug administration following the baseline recording. In cortex and thalamus tissues, GRP78, ERp57, GAD153 protein changes (Western Blot), Eif2ak3, XBP-1, ATF6, CACNA1H mRNA expressions (RT-PCR), NF-κB and TNF-α levels (ELISA) were measured. Mild-dose-Tg administration resulted in increased spike-wave discharge (SWD) activity at the 24th hour compared to administration of saline, and high-dose-Tg and it also significantly increased the amount of GRP78 protein, the expression of Eif2ak3, XBP-1, and CACNA1H mRNA in the thalamus tissue. In contrast, high-dose-Tg administration suppressed SWD activity and significantly increased XBP-1 and ATF6 mRNA expression in the thalamus, and increased NF-κB and TNF-α levels. In conclusion, our findings indicate that Tg affects SWD occurrence by modulating the unfolded protein response pathway and activating inflammatory processes in a dose-dependent manner.

SARS-CoV-2 Spike Protein-Derived Cyclic Peptides as Modulators of Spike Interaction with GRP78

The human glucose-regulated protein GRP78 is a human chaperone that translocactes to the cell surface when cells are under stress. Theoretical studies suggested it could be involved in SARS-CoV-2 virus entry to cells. In this work, we used in vitro surface plasmon resonance-based assays to show that human GRP78 indeed binds to SARS-CoV-2 spike protein. We have designed and synthesised cyclic peptides based on the loop structure of amino acids 480-488 of the SARS-CoV-2 spike protein S1 domain from the Wuhan and Omicron variants and showed that both peptides bind to GRP78. Consistent with the greater infectiousness of the Omicron variant, the Omicron-derived peptide displays slower dissociation from the target protein. Both peptides significantly inhibit the binding of wild-type S1 protein to the human protein GRP78 suggesting that further development of these cyclic peptide motifs may provide a viable route to novel anti-SARS-CoV-2 agents.

A novel peptide-drug conjugate for glioma-targeted drug delivery

The existence of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) greatly limits the application of chemotherapy in glioma. To address this challenge, an optimal drug delivery system must efficiently cross the BBB/BBTB and specifically deliver therapeutic drugs into glioma cells while minimizing systemic toxicity. Here we demonstrated that glucose-regulated protein 78 (GRP78) and dopamine receptor D2 were highly expressed in patient-derived glioma tissues, and dopamine receptors were highly expressed on the BBB. Subsequently, we synthesized a novel "Y"-shaped peptide and compared the effects of different linkers on the receptor affinity and targeting ability of the peptide. A peptide-drug conjugate (pHA-AOHX-VAP-doxorubicin conjugate, pHA-AOHX-VAP-DOX) with a better affinity for glioma cells and higher solubility was derived for glioma treatment. pHA-AOHX-VAP-DOX could cross both BBB and BBTB via dopamine receptor and GRP78 receptor, and finally target glioma cells, significantly prolonging the survival time of nude mice bearing intracranial glioma. Furthermore, pHA-AOHX-VAP-DOX significantly reduced the toxicity of DOX and increased the maximum tolerated dose (MTD). Collectively, this work paves a new avenue for overcoming multiple barriers and effectively delivering chemotherapeutic agents to glioma cells while providing key evidence to identify potential receptors for glioma-targeted drug delivery.

Intranasal Administration of GRP78 Protein (HSPA5) Confers Neuroprotection in a Lactacystin-Induced Rat Model of Parkinson's Disease

The accumulation of misfolded and aggregated α-synuclein can trigger endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), leading to apoptotic cell death in patients with Parkinson's disease (PD). As the major ER chaperone, glucose-regulated protein 78 (GRP78/BiP/HSPA5) plays a key role in UPR regulation. GRP78 overexpression can modulate the UPR, block apoptosis, and promote the survival of nigral dopamine neurons in a rat model of α-synuclein pathology. Here, we explore the therapeutic potential of intranasal exogenous GRP78 for preventing or slowing PD-like neurodegeneration in a lactacystin-induced rat model. We show that intranasally-administered GRP78 rapidly enters the substantia nigra pars compacta (SNpc) and other afflicted brain regions. It is then internalized by neurons and microglia, preventing the development of the neurodegenerative process in the nigrostriatal system. Lactacystin-induced disturbances, such as the abnormal accumulation of phosphorylated pS129-α-synuclein and activation of the pro-apoptotic GRP78/PERK/eIF2α/CHOP/caspase-3,9 signaling pathway of the UPR, are substantially reversed upon GRP78 administration. Moreover, exogenous GRP78 inhibits both microglia activation and the production of proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), via the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway in model animals. The neuroprotective and anti-inflammatory potential of exogenous GRP78 may inform the development of effective therapeutic agents for PD and other synucleinopathies.

Intestinal heat shock proteins in metabolic syndrome: Novel mediators of obesity and its comorbidities resolution after metabolic surgery

Over the past 40 years, the prevalence of obesity has risen dramatically, reaching epidemic proportions. Metabolic surgery has proven to be highly effective in treating obesity, leading to significant improvements or complete resolution of obesity-related comorbidities. Research conducted in both animals and humans suggests that the metabolic benefits achieved through metabolic surgery cannot be solely attributed to weight loss. Indeed, there has been an increasing recognition of intestinal inflammation as a novel factor influencing obesity. The gastrointestinal tract is continuously exposed to dietary components, particularly diets rich in saturated fats, which are known to contribute to obesity. It is now widely accepted that heat shock proteins can be released from various cells including intestinal epithelial cells and act as proinflammatory signals. Several studies have shown that circulating levels of glucose-regulated protein 78 (GRP78) are increased in subjects with obesity and correlate with the severity of the disease. Moreover, mice with a partial knockout of GRP78 are protected from diet-induced obesity. In this review, we discuss the role of GRP78 in the development of obesity. Several evidence suggests that GRP78 can influence adipogenesis, lipid droplets stabilization, insulin resistance, and liver steatosis. We also provide an update on GRP78 regulation following metabolic surgery, focusing on the bypass of the small intestine as a key factor for GRP78 secretion. Finally, we discuss the potential role of monoclonal antibodies against GRP78 as a treatment for obesity.

Endoplasmic reticulum stress is upregulated in inflammatory bowel disease and contributed TLR2 pathway-mediated inflammatory response

OBJECTIVE

Endoplasmic reticulum stress (ERS) and Toll-like receptor 2 (TLR2) signaling play an important role in inflammatory bowel disease (IBD); however, the link between TLR2 and ERS in IBD is unclear. This study investigated whether Thapsigargin (TG) -induced ER protein expression levels contributed to TLR2-mediated inflammatory response.

METHODS

The THP-1 cells were treated with TLR2 agonist (Pam3CSK4), ERS inducer Thapsigargin (TG) or inhibitor (TUDCA). The mRNA expressions of TLR1-TLR10 were detected by qPCR. The production and secretion of inflammatory factors were detected by PCR and ELISA. Immunohistochemistry was used to detect the expressions of GRP78 and TLR2 in the intestinal mucosa of patients with Crohn's disease (CD). The IBD mouse model was established by TNBS in the modeling group. ERS inhibitor (TUDCA) was used in the treatment group.

RESULTS

The expression of TLRs was detected via polymerase chain reaction (PCR) in THP-1 cells treated by ERS agonist Thapsigargin (TG). According to the findings, TG could promote TLR2 and TLR5 expression. Subsequently, in TLR2 agonist Pam3CSK4 induced THP-1 cells, TG could lead to increased expression of the inflammatory factors such as TNF-α, IL-1β and IL-8, and ERS inhibitor (TUDCA) could block this effect. However, Pam3CSK4 did not significantly impact the GRP78 and CHOP expression. Based upon the immunohistochemical results, TLR2 and GRP78 expression were significantly increased in the intestinal mucosa of patients with Crohn's disease (CD). For in vivo experiments, TUDCA displayed the ability to inhibit intestinal mucosal inflammation and reduce GRP78 and TLR2 proteins.

CONCLUSIONS

ERS and TLR2 is upregulated in inflammatory bowel disease, ERS may promote TLR2 pathway-mediated inflammatory response. Moreover, ERS and TLR2 signaling could be novel therapeutic targets for IBD.

A2M possesses anti-bacterial functions by recruiting and enhancing phagocytosis through GRP78 in an echinoderm

Alpha-2-macroglobulin (A2M) is an extracellular macromolecule mainly known for its role as a broad-spectrum protease inhibitor in mammals. However, the immune recognition and regulation mechanisms of A2M in invertebrates are still not well investigated. In the current study, the role of sea cucumber Apostichopus japonicus A2M in the regulation of innate immune responses was explored. We found that AjA2M promotes phagocytosis of Vibrio splendidus in coelomocytes of sea cucumber. Then two major functional structural domains of AjA2M, the thioester domain (TED) and the receptor-binding structural domain (RBD) were cloned. It was found that the AjA2M-TED binds to pathogens while causing Vibrio splendidus aggregation; the AjA2M-RBD interacts with the Glucose Regulated Protein 78 (AjGRP78), subsequently AjGRP78 accelerates the degradation of Vibrio splendidus in lysosomes by facilitating polymerisation and rearrangement of the cytoskeleton. Collectively, the findings together suggest that A2M-GRP78 axis mediates immune signaling pathway of phagocytosis and AjA2M has been characterized to play an essential crucial role in antibacterial immune responses of invertebrates.

Recent insights into the effect of endoplasmic reticulum stress in the pathophysiology of intestinal ischaemia‒reperfusion injury

Intestinal ischaemia‒reperfusion (I/R) injury is a surgical emergency. This condition is associated with a high mortality rate. At present, there are limited number of efficient therapeutic measures for this injury, and the prognosis is poor. Therefore, the pathophysiological mechanisms of intestinal I/R injury must be elucidated to develop a rapid and specific diagnostic and treatment protocol. Numerous studies have indicated the involvement of endoplasmic reticulum (ER) stress in the development of intestinal I/R injury. Specifically, the levels of unfolded and misfolded proteins in the ER lumen are increased due to unfolded protein response. However, persistent ER stress promotes apoptosis of intestinal mucosal epithelial cells through three signalling pathways in the ER, impairing intestinal mucosal barrier function and leading to the dysfunction of intestinal tissues and distant organ compartments. This review summarises the mechanisms of ER stress in intestinal I/R injury, diagnostic indicators, and related treatment strategies with the objective of providing novel insights into future therapies for this condition.

GRP78 promotes bone metastasis of prostate cancer by regulating bone microenvironment through Sonic hedgehog signaling

Bone metastasis is the leading cause of tumor-related deaths in patients with prostate cancer (PCa). The interactions between PCa and the bone microenvironment form a vicious cycle. However, the complex molecular mechanism by which PCa regulates the bone microenvironment remains unclear. To determine the role of glucose-regulated protein (GRP78) in bone metastasis and growth, we established intracardiac injection and tibial injection models, and performed their histological staining. To assess the effect of GRP78 on the differentiation of osteoblasts and osteoclasts, we performed cell co-culture, enzyme-linked immunosorbent assay, alizarin red staining, and tartrate-resistant acid phosphatase staining. We found that GRP78 is upregulated in PCa tissues and that its upregulation is associated with PCa progression in patients. Functional experiments showed that GRP78 overexpression in PCa cells considerably promotes bone metastasis and induces bone microstructure changes. Silencing GRP78 substantially inhibits the migration and invasion of PCa cells in vitro and bone metastasis and tumor growth in vivo. Mechanistically, GRP78 promotes the migration and invasion of PCa cells via the Sonic hedgehog (Shh) signaling pathway. Cell co-culture showed that GRP78 promotes the differentiation of osteoblasts and osteoclasts through Shh signaling. Our findings suggest that tumor-bone matrix interactions owing to GRP78-activated paracrine Shh signaling by PCa cells regulate the differentiation of osteoblasts and osteoclasts. This process promotes bone metastasis and the proliferation of PCa cells in the bone microenvironment. Targeting the GRP78/Shh axis can serve as a therapeutic strategy to prevent bone metastasis and improve the quality of life of patients with PCa.

Prediction of the binding location between the nuclear inhibitor of DNA binding and differentiation 2 (ID2) and HSPA5

Glucose-regulated protein 78 (GRP78), also termed HSPA5, was widely studied in cancer. It was recently approved that GRP78 has nuclear localization potential that sheds light on its role in cancer development. The inhibitor of DNA binding and differentiation 2 (ID2) is the nuclear component that associates with GRP78. The interaction between these two proteins is not understood clearly. In the current study, the binding pattern of GRP78/ID2 is predicted using computational methods. Protein-protein docking is used along with molecular dynamics simulation. The substrate binding domain β of GRP78 can stably interact with the loop region (C42-S60) of ID2 as predicted in this study. This paves the way for a possible destabilizer for this association and cancer eradication.

Modulations of Homeostatic ACE2, CD147, GRP78 Pathways Correlate with Vascular and Endothelial Performance Markers during Pulmonary SARS-CoV-2 Infection

The pathologic consequences of Coronavirus Disease-2019 (COVID-19) include elevated inflammation and dysregulated vascular functions associated with thrombosis. In general, disruption of vascular homeostasis and ensuing prothrombotic events are driven by activated platelets, monocytes, and macrophages, which form aggregates (thrombi) attached to the endothelium lining of vessel walls. However, molecular pathways underpinning the pathological interactions between myeloid cells and endothelium during COVID-19 remain undefined. Here, we tested the hypothesis that modulations in the expression of cellular receptors angiotensin-converting enzyme 2 (ACE2), CD147, and glucose-regulated protein 78 (GRP78), which are involved in homeostasis and endothelial performance, are the hallmark responses induced by SARS-CoV-2 infection. Cultured macrophages and lungs of hamster model systems were used to test this hypothesis. The results indicate that while macrophages and endothelial cells are less likely to support SARS-CoV-2 proliferation, these cells may readily respond to inflammatory stimuli generated by the infected lung epithelium. SARS-CoV-2 induced modulations of tested cellular receptors correlated with corresponding changes in the mRNA expression of coagulation cascade regulators and endothelial integrity components in infected hamster lungs. Among these markers, tissue factor (TF) had the best correlation for prothrombotic events during SARS-CoV-2 infection. Furthermore, the single-molecule fluorescence in situ hybridization (smFISH) method alone was sufficient to determine the peak and resolution phases of SARS-CoV-2 infection and enabled screening for cellular markers co-expressed with the virus. These findings suggest possible molecular pathways for exploration of novel drugs capable of blocking the prothrombotic shift events that exacerbate COVID-19 pathophysiology and control the disease.

Regulator of Ribosome Synthesis 1 (RRS1) Stabilizes GRP78 and Promotes Breast Cancer Progression

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin-proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis.

Binding site prediction between lysozyme and glucose-regulated protein 78, a hope to fight amyloidosis

Amyloidosis is an extraordinarily vigorous and heterogeneous group of disorders that causes numerous organ failures due to the precipitation of misfolded proteins. Many of these damaged proteins are discarded before causing any fatal diseases due to the contribution of the protein quality control (PQC) system and its chaperons, including glucose-regulated protein (GRP78). One of the most important enzymatic proteins inside the body is lysozyme, which is reported to have many mutated variants that may cause amyloid fibrils. This study used structural bioinformatics and molecular dynamics simulations to test and suggest binding sites for the human lysozyme protein with GRP78. Multiple sequence alignment (MSA) shows that part of the lysozyme envelope protein (C65-C81 cyclic region) has high similarities (30.77% identity) with the cyclic Pep42. Additionally, the binding between the lysozyme cyclic region (C65-C81) and GRP78 substrate binding domain (SBD) is found favorable. The number and types of interactions vary between each of the mutant isoforms of lysozyme. The more significant the conformational changes in the mutation, the greater its probability of aggregation and the formation of amyloid fibrils. Each mutation leads to different interactions and binding patterns with GRP78. The present computational study suggests a lysozyme-GRP78 binding site, thus paving the way for drug designers to construct suitable carriers that can collect misfolded lysozyme proteins and eliminate them from the body, preventing their aggregation and amyloidogenesis.Communicated by Ramaswamy H. Sarma.

Peptide-scFv antigen recognition domains effectively confer CAR T cell multiantigen specificity

The emergence of immune escape is a significant roadblock to developing effective chimeric antigen receptor (CAR) T cell therapies against hematological malignancies, including acute myeloid leukemia (AML). Here, we demonstrate feasibility of targeting two antigens simultaneously by combining a GRP78-specific peptide antigen recognition domain with a CD123-specific scFv to generate a peptide-scFv bispecific antigen recognition domain (78.123). To achieve this, we test linkers with varying length and flexibility and perform immunophenotypic and functional characterization. We demonstrate that bispecific CAR T cells successfully recognize and kill tumor cells that express GRP78, CD123, or both antigens and have improved antitumor activity compared to their monospecific counterparts when both antigens are expressed. Protein structure prediction suggests that linker length and compactness influence the functionality of the generated bispecific CARs. Thus, we present a bispecific CAR design strategy to prevent immune escape in AML that can be extended to other peptide-scFv combinations.

Crosstalk between KDEL receptor and EGF receptor mediates cell proliferation and migration via STAT3 signaling

Hostile microenvironment of cancer cells provoke a stressful condition for endoplasmic reticulum (ER) and stimulate the expression and secretion of ER chaperones, leading to tumorigenic effects. However, the molecular mechanism underlying these effects is largely unknown. In this study, we reveal that the last four residues of ER chaperones, which are recognized by KDEL receptor (KDELR), is required for cell proliferation and migration induced by secreted chaperones. By combining proximity-based mass spectrometry analysis, split venus imaging and membrane yeast two hybrid assay, we present that EGF receptor (EGFR) may be a co-receptor for KDELR on the surface. Prior to ligand addition, KDELR spontaneously oligomerizes and constantly undergoes recycling near the plasma membrane. Upon KDEL ligand binding, the interactions of KDELR with itself and with EGFR increase rapidly, leading to augmented internalization of KDELR and tyrosine phosphorylation in the C-terminus of EGFR. STAT3, which binds the phosphorylated tyrosine motif on EGFR, is subsequently activated by EGFR and mediates cell growth and migration. Taken together, our results suggest that KDELR serves as a bona fide cell surface receptor for secreted ER chaperones and transactivates EGFR-STAT3 signaling pathway.

Endoplasmic reticulum stress caused by traumatic injury promotes cardiomyocyte apoptosis through acetylation modification of GRP78

Cardiomyocyte apoptosis is an important cause of trauma-induced secondary cardiac injury (TISCI), in which the endoplasmic reticulum stress (ERS)-mediated apoptosis signaling pathway is known to be first activated, but the mechanism remains unclear. In this study, rat models of traumatic injury are established by using the Noble-Collip trauma device. The expression of glucose-regulating protein 78 (GRP78, a molecular chaperone of the cardiomyocyte ER), acetylation modification of GRP78 and apoptosis of cardiomyocytes are determined. The results show that ERS-induced GRP78 elevation does not induce cardiomyocyte apoptosis in the early stage of trauma. However, with prolonged ERS, the GRP78 acetylation level is elevated, and the apoptosis of cardiomyocytes also increases significantly. In addition, in the early stage of trauma, the expression of histone acetyl-transferase (HAT) P300 is increased and that of histone deacetylase 6 (HDAC6) is decreased in cardiomyocytes. Inhibition of HDAC function could induce the apoptosis of traumatic cardiomyocytes by increasing the acetylation level of GRP78. Our present study demonstrates for the first time that post-traumatic protracted ERS can promote cardiomyocyte apoptosis by increasing the acetylation level of GRP78, which may provide an experimental basis for seeking early molecular events of TISCI.

GRP78 Downregulation in Keratinocytes Promotes Skin Inflammation through the Recruitment and Activation of CCR6+ IL-17A-Producing γδ T Cells

The migration of γδ T lymphocytes toward skin lesions and their concomitant pathogenic IL-17A production play a crucial role in the pathogenesis of psoriasis. However, the regulatory mechanisms of IL-17A production by γδ T cells and their migration remain to be fully explored. Intracellular GRP78 is a molecular chaperone that regulates endoplasmic reticulum stress, whereas secretory GRP78, as a member of the resolution-associated molecular patterns, exerts immunoregulatory effects. In this study, we reported that both the intracellular GRP78 in skin lesions and secretory GRP78 in the serum were significantly decreased in patients with psoriasis. A GRP78 knockdown exacerbated imiquimod-induced skin inflammation, whereas the application of recombinant GRP78 protein or BIP inducer X (a GRP78 inducer) attenuated the dermatitis. Mechanistically, the GRP78 knockdown in keratinocytes enhanced the production of chemokines, specifically CCL20, which regulates γδ T-cell migration. Moreover, recombinant GRP78 was found to directly bind to γδ T cells to suppress its migration ability and proinflammatory capacities by downregulating the CCR6 and IL-17A expression. Collectively, our results uncovered a pivotal role of GRP78 in the pathogenesis of psoriasis, which was mainly exerted by regulating the interaction between keratinocytes and γδ T cells, and might provide a promising target for psoriasis therapy.

GRP78 improves the therapeutic effect of mesenchymal stem cells on hemorrhagic shock-induced liver injury: Involvement of the NF-кB and HO-1/Nrf-2 pathways

Mesenchymal stem cells (MSCs) are a popular cell source for repairing the liver. Improving the survival rate and colonization time of MSCs may significantly improve the therapeutic outcomes of MSCs. Studies showed that 78-kDa glucose-regulated protein (GRP78) expression improves cell viability and migration. This study aims to examine whether GRP78 overexpression improves the efficacy of rat bone marrow-derived MSCs (rBMSCs) in HS-induced liver damage. Bone marrow was isolated from the femurs and tibias of rats. rBMSCs were transfected with a GFP-labeled GRP78 expression vector. Flow cytometry, transwell invasion assay, scratch assay immunoblotting, TUNEL assay, MTT assay, and ELISA were carried out. The results showed that GRP78 overexpression enhanced the migration and invasion of rBMSCs. Moreover, GRP78-overexpressing rBMSCs relieved liver damage, repressed liver oxidative stress, and inhibited apoptosis. We found that overexpression of GRP78 in rBMSCs inhibited activation of the NLRP3 inflammasome, significantly decreased the levels of inflammatory factors, and decreased the expression of CD68. Notably, GRP78 overexpression activated the Nrf-2/HO-1 pathway and inhibited the NF-κB pathway. High expression of GRP78 efficiently enhanced the effect of rBMSC therapy. GRP78 may be a potential target to improve the therapeutic efficacy of BMSCs.

In silico targeting of SARS-CoV-2 spike receptor-binding domain from different variants with chaga mushroom terpenoids

Terpenoids from the chaga mushroom have been identified as potential antiviral agents against SARS-CoV-2. This is because it can firmly bind to the viral spike receptor binding domain (RBD) and the auxiliary host cell receptor glucose-regulated protein 78 (GRP78). The current work examines the association of the chaga mushroom terpenoids with the RBD of various SARS-CoV-2 variants, including alpha, beta, gamma, delta, and omicron. This association was compared to the SARS-CoV-2 wild-type (WT) RBD using molecular docking analysis and molecular dynamics modeling. The outcomes demonstrated that the mutant RBDs, which had marginally greater average binding affinities (better binding) than the WT, were successfully inhibited by the chaga mushroom terpenoids. The results suggest that the chaga mushroom can be effective against various SARS-CoV-2 variants by targeting both the host-cell surface receptor GRP78 and the viral spike RBD.Communicated by Ramaswamy H. Sarma.

Experimental periodontitis induced hypoadiponectinemia by IRE1α-mediated endoplasmic reticulum stress in adipocytes

BACKGROUD

Hypoadiponectinemia is the important cause of insulin resistance. Recent studies have shown that periodontitis is associated with hypoadiponectinemia. The purpose of this study was to investigate the effect of periodontitis-induced endoplasmic reticulum stress (ERS) in visceral adipocytes on hypoadiponectinemia.

METHODS

Rat periodontitis models were established by local ligation with silk around the bilateral maxillary second molars. Porphyromonas gingivalis-lipopolysaccharid (P.g-LPS) was also used to stimulate the visceral adipocytes in vitro. The protein expression levels of glucose regulated protein 78 (GRP78), inositol-requiring protein 1α (IRE1α), protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6) and adiponectin were detected. IRE1α lentiviruses were transfected into visceral adipocytes in vitro, and an IRE1α inhibitor (KIRA6) was injected in epididymal adipose tissue of rats to detect and verify the effect of ERS on adiponectin expression in visceral adipocytes in vivo.

RESULTS

Hypoadiponectinemia was observed in periodontitis rat, and the expression levels of ERS key proteins GRP78 and the phosphorylation levels of IRE1α (p-IRE1α)/IRE1α in visceral adipocytes were increased, while the expression levels of adiponectin protein were decreased. After KIRA6 injection into epididymal adipose tissue of rats with periodontitis, adiponectin levels in visceral adipocytes increased, and serum adiponectin levels recovered to a certain extent. The protein expression levels of GRP78 and p-IRE1α/IRE1α were increased and adiponectin protein expression was decreased in P.g-LPS-induced visceral adipocytes. Overexpression of IRE1α further inhibited adiponectin expression in P.g-LPS-stimulated visceral adipocytes, and conversely, IRE1α inhibition restored adiponectin expression.

CONCLUSIONS

Our findings suggest that periodontitis induces ERS in visceral adipocytes leading to hypoadiponectinemia. IRE1α is a key protein regulating adiponectin expression in visceral adipocytes.

An RBM10 and NF-κB interacting host lncRNA promotes JEV replication and neuronal cell death

IMPORTANCE

Central nervous system infection by flaviviruses such as Japanese encephalitis virus, Dengue virus, and West Nile virus results in neuroinflammation and neuronal damage. However, little is known about the role of long non-coding RNAs (lncRNAs) in flavivirus-induced neuroinflammation and neuronal cell death. Here, we characterized the role of a flavivirus-induced lncRNA named JINR1 during the infection of neuronal cells. Depletion of JINR1 during virus infection reduces viral replication and cell death. An increase in GRP78 expression by JINR1 is responsible for promoting virus replication. Flavivirus infection induces the expression of a cellular protein RBM10, which interacts with JINR1. RBM10 and JINR1 promote the proinflammatory transcription factor NF-κB activity, which is detrimental to cell survival.

EIF3D promoted cervical carcinoma through Warburg effect by interacting with GRP78

The incidence of cervical cancer ranks third among all female tumours globally and second in developing countries. However, the role of eukaryotic translation initiation factor 3 subunit D (EIF3D) in cervical carcinoma is unknown. This study investigated the effects of EIF3D on cell progression of cervical carcinoma and its underlying mechanism in vivo and vitro models. There were increases of EIF3D expression mRNA and protein expression levels in patients with cervical carcinoma. Disease-free survival (DFS) and overall surviva (OS) of EIF3D lower expression in patients with cervical carcinoma was higher than those of EIF3D higher expression. EIF3D mRNA expression levels in cervical carcinoma cell lines (AV3, Hela229, CaSki and Hela cells) were up-regulated, compared with cervical normal cell line (UVECs). EIF3D promoted cell growth and Warburg effect in vitro model of cervical carcinoma. EIF3D interacting with GRP78 to reduce the activity of GRP78 in vitro model of cervical carcinoma. The inhibition of GRP78 reduced the effects of EIF3D on Warburg effect in vitro model of cervical carcinoma.Our work identifies EIF3D promoted cell growth and Warburg effect in vitro model of cervical carcinoma and the inhibition of EIF3D represents a potential therapeutic strategy for the treatment of cervical carcinoma.IMPACT STATEMENTWhat is already known on this subject? The incidence of cervical cancer ranks third among all female tumours globally and second in developing countries.What do the results of this study add? This study investigated the effects of EIF3D on cell progression of cervical carcinoma and its underlying mechanism in vivo and vitro models.What are the implications of these findings for clinical practice and/or further research? EIF3D promoted cell growth and Warburg effect in vitro model of cervical carcinoma and the inhibition of EIF3D represents a potential therapeutic strategy for the treatment of cervical carcinoma.

ACE2-independent SARS-CoV-2 virus entry through cell surface GRP78 on monocytes - evidence from a translational clinical and experimental approach

BACKGROUND

SARS-CoV-2 infects host cells via an ACE2/TMPRSS2 entry mechanism. Monocytes and macrophages, which play a key role during severe COVID-19 express only low or no ACE2, suggesting alternative entry mechanisms in these cells. In silico analyses predicted GRP78, which is constitutively expressed on monocytes and macrophages, to be a potential candidate receptor for SARS-CoV-2 virus entry.

METHODS

Hospitalized COVID-19 patients were characterized regarding their pro-inflammatory state and cell surface GRP78 (csGRP78) expression in comparison to healthy controls. RNA from CD14+ monocytes of patients and controls were subjected to transcriptome analysis that was specifically complemented by bioinformatic re-analyses of bronchoalveolar lavage fluid (BALF) datasets of COVID-19 patients with a focus on monocyte/macrophage subsets, SARS-CoV-2 infection state as well as GRP78 gene expression. Monocyte and macrophage immunohistocytochemistry on GRP78 was conducted in post-mortem lung tissues. SARS-CoV-2 spike and GRP78 protein interaction was analyzed by surface plasmon resonance, GST Pull-down and Co-Immunoprecipitation. SARS-CoV-2 pseudovirus or single spike protein uptake was quantified in csGRP78high THP-1 cells.

FINDINGS

Cytokine patterns, monocyte activation markers and transcriptomic changes indicated typical COVID-19 associated inflammation accompanied by upregulated csGRP78 expression on peripheral blood and lung monocytes/macrophages. Subsequent cell culture experiments confirmed an association between elevated pro-inflammatory cytokine levels and upregulation of csGRP78. Interaction of csGRP78 and SARS-CoV-2 spike protein with a dissociation constant of KD = 55.2 nM was validated in vitro. Infection rate analyses in ACE2low and GRP78high THP-1 cells showed increased uptake of pseudovirus expressing SARS-CoV-2 spike protein.

INTERPRETATION

Our results demonstrate that csGRP78 acts as a receptor for SARS-CoV-2 spike protein to mediate ACE2-independent virus entry into monocytes.

FUNDING

Funded by the Sino-German-Center for Science Promotion (C-0040) and the Germany Ministry BMWi/K [DLR-grant 50WB1931 and RP1920 to AC, DM, TW].

GRP78 acts as a cAMP/PKA signaling modulator through the MC4R pathway in porcine embryonic development

Glucose-regulated protein 78 (GRP78) binds to and stabilizes melanocortin 4 receptor (MC4R), which activates protein kinase A (PKA) by regulating G proteins. GRP78 is primarily used as a marker for endoplasmic reticulum stress; however, its other functions have not been well studied. Therefore, in this study, we aimed to investigate the function of GRP78 during porcine embryonic development. The developmental quality of porcine embryos, expression of cell cycle proteins, and function of mitochondria were evaluated by inhibiting the function of GRP78. Porcine oocytes were activated to undergo parthenogenesis, and blastocysts were obtained after 7 days of in vitro culture. GRP78 function was inhibited by adding 20 μM HA15 to the in vitro culture medium. The inhibition in GRP78 function led to a decrease in G proteins release, which subsequently downregulated the cyclic adenosine monophosphate (cAMP)/PKA pathway. Ultimately, inhibition of GRP78 function induced the inhibition of CDK1 and cyclin B expression and disruption of the cell cycle. In addition, inhibition of GRP78 function regulated DRP1 and SIRT1 expression, resulting in mitochondrial dysfunction. This study provides new insights into the role of GRP78 in porcine embryonic development, particularly its involvement in the regulation of the MC4R pathway and downstream cAMP/PKA signaling. The results suggest that the inhibition of GRP78 function in porcine embryos by HA15 treatment may have negative effects on embryo quality and development. This study also demonstrated that GRP78 plays a crucial role in the functioning of MC4R, which releases the G protein during porcine embryonic development.

The synthetic oleanane triterpenoid CDDO-2P-Im binds GRP78/BiP to induce unfolded protein response-mediated apoptosis in myeloma

Synthetic oleanane triterpenoids (SOTs) are small molecules with broad anticancer properties. A recently developed SOT, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-2-yl)-1H-imidazole (CDDO-2P-Im or '2P-Im'), exhibits enhanced activity and improved pharmacokinetics over CDDO-Im, a previous generation SOT. However, the mechanisms leading to these properties are not defined. Here, we show the synergy of 2P-Im and the proteasome inhibitor ixazomib in human multiple myeloma (MM) cells and 2P-Im activity in a murine model of plasmacytoma. RNA sequencing and quantitative reverse transcription PCR revealed the upregulation of the unfolded protein response (UPR) in MM cells upon 2P-lm treatment, implicating the activation of the UPR as a key step in 2P-Im-induced apoptosis. Supporting this hypothesis, the deletion of genes encoding either protein kinase R-like endoplasmic reticulum kinase (PERK) or DNA damage-inducible transcript 3 protein (DDIT3; also known as CHOP) impaired the MM response to 2P-Im, as did treatment with ISRIB, integrated stress response inhibitor, which inhibits UPR signaling downstream of PERK. Finally, both drug affinity responsive target stability and thermal shift assays demonstrated direct binding of 2P-Im to endoplasmic reticulum chaperone BiP (GRP78/BiP), a stress-inducible key signaling molecule of the UPR. These data reveal GRP78/BiP as a novel target of SOTs, and specifically of 2P-Im, and suggest the potential broader utility of this class of small molecules as modulators of the UPR.

GRP78-CAR T cell effector function against solid and brain tumors is controlled by GRP78 expression on T cells

Lack of targetable antigens is a key limitation for developing successful T cell-based immunotherapies. Members of the unfolded protein response (UPR) represent ideal immunotherapy targets because the UPR regulates the ability of cancer cells to resist cell death, sustain proliferation, and metastasize. Glucose-regulated protein 78 (GRP78) is a key UPR regulator that is overexpressed and translocated to the cell surface of a wide variety of cancers in response to elevated endoplasmic reticulum (ER) stress. We show that GRP78 is highly expressed on the cell surface of multiple solid and brain tumors, making cell surface GRP78 a promising chimeric antigen receptor (CAR) T cell target. We demonstrate that GRP78-CAR T cells can recognize and kill GRP78+ brain and solid tumors in vitro and in vivo. Additionally, our findings demonstrate that GRP78 is upregulated on CAR T cells upon T cell activation; however, this expression is tumor-cell-line specific and results in heterogeneous GRP78-CAR T cell therapeutic response.

Linagliptin and secoisolariciresinol diglucoside attenuate hyperlipidemia and cardiac hypertrophy induced by a high-methionine diet in rats via suppression of hyperhomocysteinemia-induced endoplasmic reticulum stress

Background: Cardiac hypertrophy (CH) is one of the contributing causes of morbidity and mortality. Hyperhomocysteinemia (HHcy) is one of the diseases which may predispose hyperlipidemia and CH. Linagliptin (Lina) and secoisolariciresinol diglucoside (SDG) are known to alleviate a variety of illnesses by reducing oxidative stress and inflammation. Aim: This study aimed to study the effect of HHcy on cardiac tissues, with a special focus on endoplasmic reticulum (ER) stress as a mainstay pathophysiological pathway. In addition, our study examined the protective effect of Lina, SDG, and their combination against HHcy-induced hyperlipidemia and CH in rats. Methods: Seventy-five male Sprague-Dawley rats were randomly divided into five groups, and for 60 days, the following regimen was administered: Group I: rats received distilled water; Group II: rats received methionine (MET) (2 g/kg/day, p.o.); groups III and IV: rats received Lina (3 mg/kg/day, p.o.) and SDG (20 mg/kg/day, p.o.), respectively, followed by MET (2 g/kg/day, p.o.); Group V: rats received Lina and SDG, followed by MET (2 g/kg/day, p.o.). Results: Pretreatment with Lina, SDG, and their combination showed a significant decrease in serum levels of HHcy and an improved lipid profile compared to the MET group. Moreover, both drugs improved cardiac injury, as evidenced by the substantial improvement in ECG parameters, morphological features of the cardiac muscle, and reduced serum levels of cardiac markers. Additionally, Lina and SDG significantly attenuated cardiac oxidative stress, inflammation, and apoptosis. Furthermore, Lina, SDG, and their combination remarkably downregulated the enhanced expression of endoplasmic reticulum (ER) stress markers, GRP78, PERK, ATF-4, CHOP, NF-κB, and SREBP1c compared to the MET-group. Conclusion: Lina and SDG showed cardioprotective effects against HHcy-induced heart hypertrophy and hyperlipidemia in rats.

Polyphyllin I attenuates the invasion and metastasis via downregulating GRP78 in drug-resistant hepatocellular carcinoma cells

Drug resistance to chemotherapy agents presents a major obstacle to the effective treatment of hepatocellular carcinoma (HCC), a common type of liver cancer. Increasing evidence indicates a link between drug resistance and the recurrence of HCC. Polyphyllin I (PPI), a promising pharmaceutical candidate, has shown potential therapeutic advantages in the treatment of sorafenib-resistant hepatocellular carcinoma (SR-HCC cells). In this study, we sought to investigate the mechanism underlying the inhibitory effect of PPI on the invasion and metastasis of SR-HCC cells. Our in vitro studies included scratch wound-healing migration assays and transwell assays to examine PPI's effect on HCC cell migration and invasion. Flow cytometry was employed to analyze the accumulation or efflux of chemotherapy drugs. The results of these experiments demonstrated that PPI increased the susceptibility of HCC to sorafenib while inhibiting SR-HCC cell growth, migration, and invasion. Molecular docking analysis revealed that PPI exhibited a higher binding affinity with GRP78. Western blot analysis and immunofluorescence experiments showed that PPI reduced the expression of GRP78, E-cadherin, N-cadherin, Vimentin, and ABCG2 in SR-HCC cells. Interference with and overproduction of GRP78 in vitro impacted the proliferation, migration, invasion, and metastasis of HCC cells. Further examination revealed that PPI hindered the expression of GRP78 protein, resulting in a suppressive effect on SR-HCC cell migration and invasion. Histological examination of tumor tissue substantiated that administering PPI via gavage to HepG2/S xenograft nude mice inhibited tumor growth and significantly reduced tumor size, as evidenced by xenograft experiments involving nude mice. Hematoxylin and eosin (HE) staining of tumor tissue specimens, along with immunohistochemistry (IHC), were conducted to evaluate the expression levels of Ki67, GRP78, N-cadherin, Vimentin, and ABCG2. The results indicated that PPI administration decreased the levels of proteins associated with metastasis and markers of drug resistance in tumor tissues, impeding tumor growth and spread. Overall, our findings demonstrated that PPI effectively suppressed the viability, proliferation, invasion, and metastasis of SR-HCC cells both in vitro and in vivo by modulating GRP78 activity. These findings provide new insights into the mechanism of PPI inhibition of SR-HCC cell invasion and metastasis, highlighting PPI as a potential treatment option for sorafenib-resistant HCC.

Isthmin-1 attenuates allergic Asthma by stimulating adiponectin expression and alveolar macrophage efferocytosis in mice

BACKGROUND

Allergic asthma is a common respiratory disease that significantly impacts human health. Through in silico analysis of human lung RNASeq, we found that asthmatic lungs display lower levels of Isthmin-1 (ISM1) expression than healthy lungs. ISM1 is an endogenous anti-inflammatory protein that is highly expressed in mouse lungs and bronchial epithelial cells, playing a crucial role in maintaining lung homeostasis. However, how ISM1 influences asthma remains unclear. This study aims to investigate the potential involvement of ISM1 in allergic airway inflammation and uncover the underlying mechanisms.

METHODS

We investigated the pivotal role of ISM1 in airway inflammation using an ISM1 knockout mouse line (ISM1-/-) and challenged them with house dust mite (HDM) extract to induce allergic-like airway/lung inflammation. To examine the impact of ISM1 deficiency, we analyzed the infiltration of immune cells into the lungs and cytokine levels in bronchoalveolar lavage fluid (BALF) using flow cytometry and multiplex ELISA, respectively. Furthermore, we examined the therapeutic potential of ISM1 by administering recombinant ISM1 (rISM1) via the intratracheal route to rescue the effects of ISM1 reduction in HDM-challenged mice. RNA-Seq, western blot, and fluorescence microscopy techniques were subsequently used to elucidate the underlying mechanisms.

RESULTS

ISM1-/- mice showed a pronounced worsening of allergic airway inflammation and hyperresponsiveness upon HDM challenge. The heightened inflammation in ISM1-/- mice correlated with enhanced lung cell necroptosis, as indicated by higher pMLKL expression. Intratracheal delivery of rISM1 significantly reduced the number of eosinophils in BALF and goblet cell hyperplasia. Mechanistically, ISM1 stimulates adiponectin secretion by type 2 alveolar epithelial cells partially through the GRP78 receptor and enhances adiponectin-facilitated apoptotic cell clearance via alveolar macrophage efferocytosis. Reduced adiponectin expression under ISM1 deficiency also contributed to intensified necroptosis, prolonged inflammation, and heightened severity of airway hyperresponsiveness.

CONCLUSIONS

This study revealed for the first time that ISM1 functions to restrain airway hyperresponsiveness to HDM-triggered allergic-like airway/lung inflammation in mice, consistent with its persistent downregulation in human asthma. Direct administration of rISM1 into the airway alleviates airway inflammation and promotes immune cell clearance, likely by stimulating airway adiponectin production. These findings suggest that ISM1 has therapeutic potential for allergic asthma.

Synovial-fluid-derived microparticles express vimentin and GRP78 in their surface and exhibit an in vitro stimulatory effect on fibroblast-like synoviocytes in rheumatoid arthritis

OBJECTIVES

To investigate the hypothesis that microparticles (MP) may be a source of autoantigens and drive disease progression in rheumatoid arthritis (RA) synovium.

METHODS

Synovial fluid (SF) was collected from the knee joints of 41 disease-modifying anti-rheumatic drug-naive RA patients and 30 osteoarthritis (OA) patients. Samples were stained with either anti-vimentin-AlexaFluor-488 or anti-glucose-regulated protein-78-Dylight-488 (GRP78) and Annexin-V-allophycocyanin for flow cytometry analysis. RA and OA fibroblast-like synoviocytes (FLS) were co-cultured with respective SF-derived MP in vitro for 24 h. Supernatant and cell-free SF was assayed for pro-inflammatory analytes by multiplex assays.

RESULTS

Elevated percentages of AnnexinV+  Vimentin+ MP (median 0.8, interquartile range [IQR] 1.30) and AnnexinV+  GRP78+ MP (median 0.3, IQR 0.28) were present in RA compared with OA patients. We observed that CXCL6 and CCL8 were secreted in excess by RA-FLS stimulated with RA-SF-MP but not by stimulation with MP-free RA-SF.

CONCLUSIONS

Microparticles express vimentin and GRP78 on their surface and stimulate synoviocytes to produce inflammatory molecules, thus sustaining local inflammation in the synovium in RA.

Valosin-containing protein (VCP/p97) is prognostically unfavorable in pediatric AML, and negatively correlates with unfolded protein response proteins IRE1 and GRP78: A report from the Children's Oncology Group

PURPOSE

The endoplasmic reticulum (ER) is the major site of protein synthesis and folding in the cell. ER-associated degradation (ERAD) and unfolded protein response (UPR) are the main mechanisms of ER-mediated cell stress adaptation. Targeting the cell stress response is a promising therapeutic approach in acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

Protein expression levels of valosin-containing protein (VCP), a chief element of ERAD, were measured in peripheral blood samples from in 483 pediatric AML patients using reverse phase protein array methodology. Patients participated in the Children's Oncology Group AAML1031 phase 3 clinical trial that randomized patients to standard chemotherapy (cytarabine (Ara-C), daunorubicin, and etoposide [ADE]) versus ADE plus bortezomib (ADE+BTZ).

RESULTS

Low-VCP expression was significantly associated with favorable 5-year overall survival (OS) rate compared to middle-high-VCP expression (81% versus 63%, p < 0.001), independent of additional bortezomib treatment. Multivariable Cox regression analysis identified VCP as independent predictor of clinical outcome. UPR proteins IRE1 and GRP78 had significant negative correlation with VCP. Five-year OS in patients characterized by low-VCP, moderately high-IRE1 and high-GRP78 improved after treatment with ADE+BTZ versus ADE (66% versus 88%, p = 0.026).

CONCLUSION AND CLINICAL RELEVANCE

Our findings suggest the potential of the protein VCP as biomarker in prognostication prediction in pediatric AML.

The chaperone protein GRP78 released from MPN cells increases the expression of lysyl oxidase in a human stromal cell line

Impaired function of the endoplasmic stress (ER) response causes numerous pathological conditions, including tissue fibrosis. In the present study, we aimed to determine the pathological role of ER stress response systems in myeloproliferative neoplasms (MPNs). We found increased expression of the chaperone protein glucose-regulated protein (GRP) 78, a central regulator of ER stress, in megakaryocytes from primary myelofibrosis or postessential thrombocythemia myelofibrosis patients. GRP78 was overexpressed in JAK2V617F-harboring cell lines; however, inhibitors of ER stress did not affect the expression levels of GRP78. In contrast, ruxolitinib, a well-known inhibitor of JAK2V617F, clearly blocked GRP78 expression in these cells through downregulation of transcription factor 4 (ATF4). Interestingly, GRP78 was secreted from HEL and SET-2 cells into culture media. Coculture of these cells with HS-5 cells, a human bone marrow stroma-derived cell line, induced enhanced expression of lysyl oxidase (LOX), which mediates cross-linking of collagen fibers and induces tissue fibrosis, in HS-5 cells. An anti-GRP78 neutralizing antibody abrogated LOX elevation; in contrast, recombinant GRP78 protein induced LOX protein expression in HS-5 cells. Our observations suggest that the oncogenic protein JAK2V617F induces overexpression and release of GRP78, which may induce a fibrotic phenotype in surrounding bone marrow stromal cells.

PLXNC1 interference alleviates the inflammatory injury, apoptosis and extracellular matrix degradation of IL-1β-exposed chondrocytes via suppressing GRP78 expression

BACKGROUND

Osteoarthritis (OA) is a frequently encountered debilitating joint disorder. Whether plexin C1 (PLXNC1) is implicated in OA is far from being investigated despite its well-documented pro-inflammatory property in human diseases. The goal of this study is to expound the specific role of PLXNC1 in OA and elaborate the probable action mechanism.

METHODS

Firstly, PLXNC1 expression in the cartilage tissues of patients with OA was examined with GEO database. In interleukin-1beta (IL-1β)-induced OA cell model, RT-qPCR and western blotting tested the expression of PLXNC1, glucose-regulating protein 78 (GRP78) and extracellular matrix (ECM) degradation-related factors. Cell viability and inflammation were respectively judged by CCK-8 assay and RT-qPCR. TUNEL and western blotting estimated cell apoptosis. The potential binding between PLXNC1 and GRP78 was corroborated by Co-IP assay. Western blotting also tested the expression of endoplasmic reticulum stress (ERS)-associated proteins.

RESULTS

As it turned out, PLXNC1 expression was elevated in the cartilage tissues of patients with OA and IL-1β-treated chondrocytes. When PLXNC1 was depleted, the viability injury, inflammation, apoptosis and ECM degradation of chondrocytes exposed to IL-1β were obstructed. Besides, GRP78 bond to PLXNC1 in IL-1β-treated chondrocytes. The ascending GRP78 expression in the chondrocytes exposed to IL-1β was depleted after PLXNC1 was silenced. Meanwhile, the impacts of PLXNC1 deficiency on the viability, inflammatory response, apoptosis, ECM degradation as well as ERS in IL-1β-exposed chondrocytes were abolished by GRP78 up-regulation.

CONCLUSION

In summary, PLXNC1 silencing might interact with and down-regulate GRP78 to mitigate the apoptosis, inflammation, and ECM degradation of IL-1β-insulted chondrocytes in OA.

Targeting of HPV E6 at the binding sites to the host-cell E6AP, p53, and the endoplasmic reticulum-resident chaperone, GRP78

Background: Human papillomavirus (HPV) represents an etiological factor for many cancer types, especially cervical cancer. Its oncoprotein E6 sheds drug designers who aim to stop its cellular protein associations, such as p53 and E6AP. Recently, it was discovered that the host-cell chaperone glucose-regulated protein 78 (GRP78) plays a crucial function in HPV infectivity by association with the viral E6 and E7 proteins. Therefore, we aimed to test small molecules inhibitor that could contradict the association between E6 and cellular factors E6AP, GRP78, and p53. Methods: In this study, molecular docking protocol was elaborated to test 115 small molecule compounds against the three binding sites of HPV E6 to the host-cell proteins; E6AP, p53, and GRP78. After that, molecular dynamics simulation and free energy calculations were performed on the best three complexes. Results: The results reveal the potency of 18 compounds against the HPV E6 at different binding sites, which give lower free energies than paclitaxel (positive control). The best two compounds, hypericin, and anabsinthin, could bind effectively and stably during the 100 ns MD simulation period to HPV E6. The calculated average free energies for hypericin and anabsinthin are -18.76 and -14.40 kcal/mol, respectively. They formed stable complexes with the three binding sites by forming hydrophobic contacts. The key residues that stabilize the two ligands in HPV E6 binding sites are V31, Y32, V62, and Y70 (E6AP), P13, C16, T22, I23 and A46 (p53), and M1, V31, L50, L67, and Q107 (GRP78). Conclusions: The best two compounds, hypericin, and anabsinthin, are potential candidates against HPV E6 at the host-cell factors binding sites, hence could block the oncoprotein activity of E6 in infected cells. Further experimental validation is yet to be performed and suggested as future work.Communicated by Ramaswamy H. Sarma.

COVID-19, Obesity, and GRP78: Unraveling the Pathological Link

The coronavirus disease 2019 (COVID-19) pandemic, driven by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to an unprecedented global surge in infections and fatalities. Notably, obesity has emerged as an important susceptibility factor for COVID-19; however, the pathological mechanisms for this remain poorly understood. Recent studies proposed a role for glucose-regulated protein 78 (GRP78), a protein implicated in both obesity and metabolic syndrome, which may function as a binding partner and/or co-receptor for SARS-CoV-2. Given its crucial involvement in diverse biological processes, GRP78 likely plays a major role in multiple facets of the viral life cycle and the pathology of COVID-19. This perspective review discusses the potential contributions of GRP78 to the dynamics of SARS-CoV-2 infection and pathology, particularly in the context of obesity. The primary objective is to facilitate a deeper understanding of the pathogenesis of COVID-19. Through this exploration, we aim to illuminate the complex interactions underpinning the nexus of COVID-19, obesity, and GRP78, ultimately paving the way for informed therapeutic strategies and preventive measures.

GRP78 inhibitor HA15 increases the effect of Bortezomib on eradicating multiple myeloma cells through triggering endoplasmic reticulum stress

Bortezomib (BTZ), a selective proteasome inhibitor, exhibits a significant efficacy in the therapy of multiple myeloma (MM) partly through triggering endoplasmic reticulum (ER) stress-dependent apoptosis. However, sensitivity to BTZ varies greatly among patients. ER stress functions as a double-edged sword in regulating cell survival depending on cell context and ER stress extent. The major aim of this study was to investigate whether GRP78 inhibitor, HA15, increased the therapeutic effect of BTZ on MM to through further increasing ER stress and shifting the balance towards cell apoptosis. The biological role of BTZ and HA15 was assessed using Cell counting kit- (CCK-) 8, colony formation, and Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labelling (TUNEL) assay. We found that BTZ combined with HA15 remarkably decreased MM cell viability more effective than BTZ monotherapy, though low dose of HA15 did not exhibit a significant cytotoxicity to MM cells. BTZ combined with HA15 also repressed colony formation ability of MM cell and accelerated MM cell apoptosis compared with BTZ monotherapy. Mechanistically, HA15 synergized with BTZ to trigger ER stress, as evidence by significantly increased expression of ER stress markers (GRP78, ATF4, CHOP, and XBP1). Importantly, unfolded protein response (UPR) inhibitor significantly damaged the effect of BTZ combined with HA15 on accelerating MM cell death. In vivo, combination treatment with BTZ and HA15 inhibited tumor growth more effective than BTZ alone, whereas these effects were blocked by UPR inhibitor. Taken together, these results demonstrate that ER stress is a critical pathway in regulating MM cell survival, and that combination treatment with BTZ and HA15 may be an effective strategy to treat MM patients that fail to respond to BTZ monotherapy.

Leishmania (L.) amazonensis LaLRR17 increases parasite entry in macrophage by a mechanism dependent on GRP78

Leishmaniases affect 12 million people worldwide. They are caused by Leishmania spp., protozoan parasites transmitted to mammals by female phlebotomine flies. During the life cycle, promastigote forms of the parasite live in the gut of infected sandflies and convert into amastigotes inside the vertebrate macrophages. The parasite evades macrophage's microbicidal responses due to virulence factors that affect parasite phagocytosis, survival and/or proliferation. The interaction between Leishmania and macrophage molecules is essential to phagocytosis and parasite survival. Proteins containing leucine-rich repeats (LRRs) are common in several organisms, and these motifs are usually involved in protein–protein interactions. We have identified the LRR17 gene, which encodes a protein with 6 LRR domains, in the genomes of several Leishmania species. We show here that promastigotes of Leishmania (L.) amazonensis overexpressing LaLRR17 are more infective in vitro. We produced recombinant LaLRR17 protein and identified macrophage 78 kDa glucose-regulated protein (GRP78) as a ligand for LaLRR17 employing affinity chromatography followed by mass spectrometry. We showed that GRP78 binds to LaLRR17 and that its blocking precludes the increase of infection conferred by LaLRR17. Our results are the first to report LRR17 gene and protein, and we hope they stimulate further studies on how this protein increases phagocytosis of Leishmania.

Anti-breast cancer drugs targeting cell-surface glucose-regulated protein 78: a drug repositioning in silico study

Breast cancer (BC) is prevalent worldwide and is a leading cause of death among women. However, cell-surface glucose-regulated protein 78 (cs-GRP78) is overexpressed in several types of cancer and during pathogen infections. This study examines two well-known BC drugs approved by the FDA as BC treatments to GRP78. The first type consists of inhibitors of cyclin-based kinases 4/6, including abemaciclib, palbociclib, ribociclib, and dinaciclib. In addition, tunicamycin, and doxorubicin, which are among the most effective anticancer drugs for early and late-stage BC, are tested against GRP78. As (-)-epiGallocatechin gallate inhibits GRP78, it is also being evaluated (used as positive control). Thus, using molecular dynamics simulation approaches, this study aims to examine the advantages of targeting GRP78, which represents a promising cancer therapy regime. In light of recent advances in computational drug response prediction models, this study aimed to examine the benefits of GRP78 targeting, which represents a promising cancer therapy regime, by utilizing combined molecular docking and molecular dynamics simulation approaches. The simulated protein (50 ns) was docked with the drugs, then a second round of dynamics simulation was performed for 100 ns. After that, the binding free energies were calculated from 30 to 100 ns for each complex during the simulation period. These findings demonstrate the efficacy of abemaciclib, ribociclib, and tunicamycin in binding to the nucleotide-binding domain of the GRP78, paving the way for elucidating the mode of interactions between these drugs and cancer (and other stressed) cells that overexpress GRP78.Communicated by Ramaswamy H. Sarma.

Unveiling the dark side of glucose-regulated protein 78 (GRP78) in cancers and other human pathology: a systematic review

Glucose-Regulated Protein 78 (GRP78) is a chaperone protein that is predominantly expressed in the lumen of the endoplasmic reticulum. GRP78 plays a crucial role in protein folding by assisting in the assembly of misfolded proteins. Under cellular stress conditions, GRP78 can translocate to the cell surface (csGRP78) were it interacts with different ligands to initiate various intracellular pathways. The expression of csGRP78 has been associated with tumor initiation and progression of multiple cancer types. This review provides a comprehensive analysis of the existing evidence on the roles of GRP78 in various types of cancer and other human pathology. Additionally, the review discusses the current understanding of the mechanisms underlying GRP78's involvement in tumorigenesis and cancer advancement. Furthermore, we highlight recent innovative approaches employed in downregulating GRP78 expression in cancers as a potential therapeutic target.

A computational peptide model induces cancer cells' apoptosis by docking Kringle 5 to GRP78

BACKGROUND

Cells can die through a process called apoptosis in both pathological and healthy conditions. Cancer development and progression may result from abnormal apoptosis. The 78-kDa glucose-regulated protein (GRP78) is increased on the surface of cancer cells. Kringle 5, a cell apoptosis agent, is bound to GRP78 to induce cancer cell apoptosis. Kringle 5 was docked to GRP78 using ClusPro 2.0. The interaction between Kringle 5 and GRP78 was investigated.

RESULTS

The interacting amino acids were found to be localized in three areas of Kringle 5. The proposed peptide is made up of secondary structure amino acids that contain Kringle 5 interaction residues. The 3D structure of the peptide model amino acids was created using the PEP-FOLD3 web tool.

CONCLUSIONS

The proposed peptide completely binds to the GRP78 binding site on the Kringle 5, signaling that it might be effective in the apoptosis of cancer cells.

ER chaperone GRP78/BiP translocates to the nucleus under stress and acts as a transcriptional regulator

Cancer cells are commonly subjected to endoplasmic reticulum (ER) stress. To gain survival advantage, cancer cells exploit the adaptive aspects of the unfolded protein response such as upregulation of the ER luminal chaperone GRP78. The finding that when overexpressed, GRP78 can escape to other cellular compartments to gain new functions regulating homeostasis and tumorigenesis represents a paradigm shift. Here, toward deciphering the mechanisms whereby GRP78 knockdown suppresses EGFR transcription, we find that nuclear GRP78 is prominent in cancer and stressed cells and uncover a nuclear localization signal critical for its translocation and nuclear activity. Furthermore, nuclear GRP78 can regulate expression of genes and pathways, notably those important for cell migration and invasion, by interacting with and inhibiting the activity of the transcriptional repressor ID2. Our study reveals a mechanism for cancer cells to respond to ER stress via transcriptional regulation mediated by nuclear GRP78 to adopt an invasive phenotype.

Tumor-secreted GRP78 induces M2 polarization of macrophages by promoting lipid catabolism

Macrophages in hypoxic regions of advanced colorectal tumors often exhibit M2-type features, but prefer oxygen-consuming lipid catabolism, which is contradictory in oxygen demand and supply. In this study, the results from bioinformatics analysis and intestinal lesions immunohistochemistry of 40 colorectal cancer patients illustrated that glucose-regulatory protein 78 (GRP78) was positively correlated with M2 macrophages. Furthermore, tumor-secreted GRP78 could enter macrophages and polarize them to M2-type. Mechanistically, entered GRP78 located in lipid droplets of macrophages, and elevated protein stabilization of adipose triglyceride lipase ATGL by interacting with it to inhibit its ubiquitination. Increased ATGL promoted the hydrolysis of triglycerides and the production of arachidonic acid (ARA) and docosahexaenoic acid (DHA). Excessive ARA and DHA interacted with PPARγ to encourage its activation, which mediated the M2 polarization of macrophages. In summary, our study showed that secreted GRP78 in the tumor hypoxic microenvironment mediated the domestication of tumor cells to macrophages and maintained tumor immunosuppressive microenvironment by promoting lipolysis, and the lipid catabolism not only provides energy for macrophages but also plays an important role in maintenance of immunosuppressive properties.

GRP78 Inhibitor YUM70 Suppresses SARS-CoV-2 Viral Entry, Spike Protein Production and Ameliorates Lung Damage

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the COVID-19 pandemic, has given rise to many new variants with increased transmissibility and the ability to evade vaccine protection. The 78-kDa glucose-regulated protein (GRP78) is a major endoplasmic reticulum (ER) chaperone that has been recently implicated as an essential host factor for SARS-CoV-2 entry and infection. In this study, we investigated the efficacy of YUM70, a small molecule inhibitor of GRP78, to block SARS-CoV-2 viral entry and infection in vitro and in vivo. Using human lung epithelial cells and pseudoviral particles carrying spike proteins from different SARS-CoV-2 variants, we found that YUM70 was equally effective at blocking viral entry mediated by original and variant spike proteins. Furthermore, YUM70 reduced SARS-CoV-2 infection without impacting cell viability in vitro and suppressed viral protein production following SARS-CoV-2 infection. Additionally, YUM70 rescued the cell viability of multi-cellular human lung and liver 3D organoids transfected with a SARS-CoV-2 replicon. Importantly, YUM70 treatment ameliorated lung damage in transgenic mice infected with SARS-CoV-2, which correlated with reduced weight loss and longer survival. Thus, GRP78 inhibition may be a promising approach to augment existing therapies to block SARS-CoV-2, its variants, and other viruses that utilize GRP78 for entry and infection.

Relevance of serum levels of the endoplasmic reticulum stress protein GRP78 (glucose-regulated protein 78 kDa) as biomarker in pulmonary diseases

Cellular stress and inflammation contribute to the initiation and progression of a variety of pulmonary diseases. Endoplasmic reticulum (ER) stress and its main regulator GRP78 (glucose-regulated protein 78 kDa) appear to be involved in the pathogenesis of pulmonary diseases, and GRP78 was found to be a biomarker in a wide range of inflammatory diseases. The aim of this study was to investigate the relevance of serum GRP78 in pulmonary disorders.In this prospective cohort study, 78 consecutive patients with chronic obstructive pulmonary disease (COPD, n = 28), asthma (n = 38) or interstitial lung disease (ILD, n = 12) underwent measurement of serum GRP78 levels by ELISA.The mean age of patients was 59.8 ± 12.4 years, 48.7% were female. Patients with elevated GRP78 levels (> median) offered a significantly better oxygenation status (capillary pO2: 75.3 ± 11.7 mmHg vs. 67.8 ± 15.9 mmHg, p = 0.02). Significant correlations were observed between GRP78, on the one hand, and haemoglobin, high-sensitivity C-reactive protein (hs-CRP) and eosinophil counts, on the other hand (haemoglobin: Pearson's r = -0.25, hs-CRP: r = 0.30, eosinophils: r = 0.63).Subsequently, we evaluated GRP78 measurements in function of severity stratifiers of the specific underlying pulmonary disease. ILD patients with a severe diffusion impairment (DLCO< 40% of predicted), exhibited a significant decrease in GRP78 levels (p = 0.01). In COPD and asthma, both characterized by obstructive ventilatory defects, a forced expiratory volume in one second (FEV1) <30% of predicted was accompanied by significantly lower GRP78 (p = 0.0075).In both obstructive and restrictive pulmonary disorders, GRP78 protein concentrations were reduced with increasing disease severity. These data suggest a prevalent role of GRP78 in the presently studied pulmonary disorders.

Endoplasmic reticulum chaperone GRP78 participates in fluoride-induced autophagy in LS8 cells by regulating the IRE1-TRAF2-JNK pathway

Fluoride induces endoplasmic reticulum (ER) stress in ameloblasts, which is responsible for enamel mineralization disorder. Fluoride induces autophagy in ameloblasts, but the molecular mechanisms through which ameloblasts respond to fluoride-induced cellular stress and autophagy remain unclear. This study investigated ER stress-induced autophagy and the regulatory role of the ER molecular chaperone GRP78 in fluoride-induced autophagy in ameloblast LS8 cells. To explore the relationship between fluoride-induced ER stress and autophagy, we assessed changes in fluoride-induced autophagy in LS8 cells following overexpression and/or silencing of the ER stress molecular chaperone GRP78. We found that autophagy induced by fluoride was further increased after GRP78 overexpression in LS8 cells. Fluoride-induced autophagy was reduced in GRP78-silenced LS8 cells. Furthermore, we found that ER stress can regulate autophagy in fluoride-treated ameloblasts (LS8 cells) and that the GRP78/IRE1/TRAF2/JNK pathway is involved in the underlying regulation. Our study suggests that ER stress plays a role in fluoride-induced damage by inducing ameloblast autophagy.

Melittin treatment prevents colorectal cancer from progressing in mice through ER stress-mediated apoptosis

OBJECTIVES

The primary goal of the current study was to investigate the effect of melittin on colorectal cancer (CRC).

METHODS

The viability of cancer cells was tested using the MTT assay, and the apoptosis of tumour cells was assayed using Annexin V/PI staining in vitro or TUNEL staining in vivo. The in vivo toxicity and efficacy of melittin were assessed in a xenograft mouse model.

RESULTS

Melittin inhibited the viability of CRC cell lines and induced apoptosis in SW480 cells by regulating apoptosis-related proteins. Melittin triggered endoplasmic reticulum (ER) stress and caused an imbalance in calcium homeostasis in SW480 cells. An absence of melittin triggered ER stress via the calcium chelating agent BAPTA/AM, and the IP3R inhibitor 2-aminoethoxydiphenyl borate (2-APB) impaired melittin-induced apoptosis in SW480 cells. Melittin treatment suppressed tumour growth but did not affect the body weight of SW480 tumour-bearing mice. Unlike cisplatin and 5-fluorouracil, melittin treatment did not change the biochemical and haematological parameters of the tumour-bearing mice. Finally, in these mice, melittin treatment induced ER stress, which was then blocked by BAPTA/AM, whilst 2-APB impaired the growth inhibitory effect of melittin.

CONCLUSION

Melittin treatment inhibits CRC progression by inducing ER stress and an imbalance in calcium homeostasis.

Effects of GRP78 on Endoplasmic Reticulum Stress and Inflammatory Response in Macrophages of Large Yellow Croaker (Larimichthys crocea)

Endoplasmic reticulum (ER) homeostasis plays a vital role in cell physiological functions. Various factors can destroy the homeostasis of the ER and cause ER stress. Moreover, ER stress is often related to inflammation. Glucose-regulated protein 78 (GRP78) is an ER chaperone, which plays a vital role in maintaining cellular homeostasis. Nevertheless, the potential effects of GRP78 on ER stress and inflammation is still not fully elucidated in fish. In the present study, ER stress and inflammation was induced by tunicamycin (TM) or palmitic acid (PA) in the macrophages of large yellow croakers. GRP78 was treated with an agonist/inhibitor before or after the TM/PA treatment. The results showed that the TM/PA treatment could significantly induce ER stress and an inflammatory response in the macrophages of large yellow croakers whereas the incubation of the GRP78 agonist could reduce TM/PA-induced ER stress and an inflammatory response. Moreover, the incubation of the GRP78 inhibitor could further induce TM/PA-induced ER stress and an inflammatory response. These results provide an innovative idea to explain the relationship between GRP78 and TM/PA-induced ER stress or inflammation in large yellow croakers.