Overexpression Of GRP78 Research Articles

4-Phenylbutyric acid suppresses psoralen-induced hepatotoxicity by inhibiting ERS and reestablishing mitochondrial fusion-fission balance in mice

Psoralen is a main active molecule of the traditional Chinese herb medicine Fructus Psoraleae. Our previous studies have shown that psoralen induced liver injury through the endoplasmic reticulum stress (ERS) signaling pathways. In this article, we studied whether the ERS inhibitor, 4-phenylbutyrate acid (4-PBA) could inhibit the liver toxicity caused by psoralen, and explored the underlying mechanisms. Mice were given the solvent, 20 mg/kg, 40 mg/kg, 80 mg/kg of psoralen, or 80 mg/kg of psoralen plus 4-PBA for 14 days. We found that 4-PBA significantly reduced the serum LDH and liver tissue MDA level, increased the activities of SOD and CAT, reduced liver weight and coefficient, repaired histopathological damage, and inhibited hepatocytes apoptosis induced by psoralen. RNA-seq transcriptomics found that except for the endoplasmic reticulum, the mitochondria was severely affected by psoralen. And genes involved in mitochondrial fusion, apoptosis, protein folding, and autophagy were found differently expressed in the psoralen group. Further studies found that 4-PBA inhibited the overexpression of GRP78 and CHOP, increased the Bcl-2/Bax ratio, and reduced the expression of Caspase-3. Moreover, 4-PBA reduced the overexpression of mitochondrial fission protein DRP1, increased the expression of fusion proteins Mfn-2 and OPA1, but has no inhibitory effects on autophagy proteins Atg5 or LC3A/B. In conclusion, 4-PBA inhibited ERS and reestablished mitochondrial fusion-fission balance, thereby blocking cell apoptosis, oxidative stress, and mitochondrial dysfunction, thus prevented against psoralen-induced hepatotoxicity.

DMDD, isolated from Averrhoa carambola L., ameliorates diabetic nephropathy by regulating endoplasmic reticulum stress-autophagy crosstalk

BackgroundStudies have shown that Averrhoa carambola L. possesses therapeutic potential for diabetes and related complications. However, the specific beneficial effects and molecular mechanisms of 2-dodecyl-6-meth-oxycyclohexa-2,5-diene-1,4-dione (DMDD) isolated from Averrhoa carambola L. on diabetic nephropathy (DN) require further investigation.Methods80 C57BL/6 J male mice were subjected to a 1-week adaptive feeding, followed by a high-fat diet and intraperitoneal injection of 100 mg/kg streptozotocin (STZ) to construct an in vivo DN model. Additionally, human renal proximal tubular epithelial cells (HK-2) induced by high glucose (HG) were used as an in vitro DN model. The expression levels of epithelial-mesenchymal transition (EMT), endoplasmic reticulum stress (ERS), and autophagy-related proteins in renal tubular cells were detected by Western Blot, flow cytometry, immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) staining. Transcriptome analysis revealed was conducted to elucidate the specific mechanism of by which DMDD mitigates DN by inhibiting ERS and autophagy. HK-2 cells were transfected with IRE1α overexpression lentivirus to reveal the role of IRE1α overexpression in HG-induced HK-2.ResultsThe experimental data showed that DMDD significantly reduced blood glucose levels and improved renal pathological alterations in DN mice. Additionally, DMDD inhibited the calcium (Ca2+) pathway, manifested by decreased autophagosome formation and downregulation of LC3II/I, Beclin-1, and ATG5 expression. Moreover, in HG-induced HK-2 cells, DMDD suppressed the overexpression of GRP78, CHOP, LC3II/I, Beclin1, and ATG5. Notably, IRE1α overexpression significantly increased autophagy incidence; however, DMDD treatment subsequently reduced the expression of LC3II/I, Beclin1, and ATG5.ConclusionDMDD effectively inhibits excessive ERS and autophagy, thereby reducing renal cell apoptosis through the IRE1α pathway and Ca 2+ pathway.

Targeting stress induction of GRP78 by cardiac glycoside oleandrin dually suppresses cancer and COVID-19

BackgroundDespite recent therapeutic advances, combating cancer resistance remains a formidable challenge. The 78-kilodalton glucose-regulated protein (GRP78), a key stress-inducible endoplasmic reticulum (ER) chaperone, plays a crucial role in both cancer cell survival and stress adaptation. GRP78 is also upregulated during SARS-CoV-2 infection and acts as a critical host factor. Recently, we discovered cardiac glycosides (CGs) as novel suppressors of GRP78 stress induction through a high-throughput screen of clinically relevant compound libraries. This study aims to test the possibility that agents capable of blocking stress induction of GRP78 could dually suppress cancer and COVID-19.ResultsHere we report that oleandrin (OLN), is the most potent among the CGs in inhibiting acute stress induction of total GRP78, which also results in reduced cell surface and nuclear forms of GRP78 in stressed cells. The inhibition of stress induction of GRP78 is at the post-transcriptional level, independent of protein degradation and autophagy and may involve translational control as OLN blocks stress-induced loading of ribosomes onto GRP78 mRNAs. Moreover, the human Na+/K+-ATPase α3 isoform is critical for OLN suppression of GRP78 stress induction. OLN, in nanomolar range, enhances apoptosis, sensitizes colorectal cancer cells to chemotherapeutic agents, and reduces the viability of patient-derived colon cancer organoids. Likewise, OLN, suppresses GRP78 expression and impedes tumor growth in an orthotopic breast cancer xenograft model. Furthermore, OLN blocks infection by SARS-CoV-2 and its variants and enhances existing anti-viral therapies. Notably, GRP78 overexpression mitigates OLN-mediated cancer cell apoptotic onset and suppression of virus release.ConclusionOur findings validate GRP78 as a target of OLN anti-cancer and anti-viral activities. These proof-of-principle studies support further investigation of OLN as a readily accessible compound to dually combat cancer and COVID-19.

Grp78 regulates NLRP3 inflammasome and participates in Sjogren’s syndrome

ObjectiveThe purpose of the present study was to potential effects of forsythiaside A (FA) on Sjogren’s syndrome (SS). MethodsEnzyme linked immunosorbent assay for detecting cytokines and Western blotting was used for detecting related protein expression. ResultsFA effectively reduced the secretion of inflammatory cytokines, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in SS. FA also effectively inhibited the high expression of Grp78 in SS. When Grp78 expression was silenced, it effectively reduced the secretion of inflammatory cytokines, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in the nucleus in SS. FA effectively inhibit the secretion of inflammatory cytokines induced by overexpression of Grp78, the expression of Caspase-1 and NLRP3 proteins and the expression of p65 in the nucleus in SS. ConclusionFA induces the degradation of Grp78 protein, regulates the NF-κB signaling pathway in SS and inhibited NLRP3 inflammasome activation and reduced the release of inflammatory cytokines to alleviate SS.

2-Deoxy-D-Glucose Downregulates Fatty Acid Synthase Gene Expression Via an Endoplasmic Reticulum Stress-Dependent Pathway in HeLa Cells.

Fatty acid synthase (FASN) catalyzes the rate-limiting step of cellular lipogenesis. FASN expression is upregulated in various types of cancer cells, implying that FASN is a potential target for cancer therapy. 2-Deoxy-D-glucose (2-DG) specifically targets cancer cells by inhibiting glycolysis and glucose metabolism, resulting in multiple anticancer effects. However, whether the effects of 2-DG involve lipogenic metabolism remains to be elucidated. We investigated the effect of 2-DG administration on FASN expression in HeLa human cervical cancer cells. 2-DG treatment for 24 h decreased FASN mRNA and protein levels and suppressed the activity of an exogenous rat Fasn promoter. The use of a chemical activator or inhibitors or of a mammalian expression plasmid showed that neither AMPK nor the Sp1 transcription factor is responsible for the inhibitory effect of 2-DG on FASN expression. Administration of thapsigargin, an endoplasmic reticulum (ER) stress inducer, or 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), a site 1 protease inhibitor, mimicked the inhibitory effect of 2-DG on FASN expression. 2-DG did not further decrease FASN expression in the presence of thapsigargin or AEBSF. Site 1 protease mediates activation of ATF6, an ER stress mediator, as well as sterol regulatory element-binding protein 1 (SREBP1), a robust transcription factor for FASN. Administration of 2-DG or thapsigargin for 24 h suppressed activation of ATF6 and SREBP1, as did AEBSF. We speculated that these effects of 2-DG or thapsigargin are due to feedback inhibition via increased GRP78 expression following ER stress. Supporting this, exogenous overexpression of GRP78 in HeLa cells suppressed SREBP1 activation and Fasn promoter activity. These results suggest that 2-DG suppresses FASN expression via an ER stress-dependent pathway, providing new insight into the molecular basis of FASN regulation in cancer.

Sestrin2 Protects Human Lens Epithelial Cells (HLECs) Against Apoptosis in Cataracts Formation: Interaction Between Endoplasmic Reticulum (ER) Stress and Oxidative Stress (OS) is Involved

Purpose To explore the correlation of endoplasmic reticulum stress (ERS) and oxidative stress (OS), and the protective effect of Sestrin2 (SESN2) on human lens epithelial cells (HLECs). Methods Tunicamycin (TM) was used to induce ERS in HLECs. 4-Phenylbutyric acid (4-PBA) was used to inhibit ERS. Eupatilin applied to HLECs as SESN2 agonist. SESN2 expression was knocked down via si-RNA in HLECs. The morphological changes of HLECs were observed by microscope. ER-tracker to evaluate ERS, ROS production assay to measure ROS, flow cytometry to calculate cell apoptosis rate. Immunofluorescence to observe Nrf2 translocation, and effects of TM or EUP on SESN2. Western blot and qPCR were used to evaluate the expression of GRP78, PERK, ATF4, CHOP, Nrf2, and SESN2 expression in HLECs with different treatment groups. Results ERS can elevate the expression of ROS and Nrf2 to induce OS. Upregulation of SESN2 was observed in ERS-mediate OS. Overexpression of SESN2 can reduce the overexpression of ERS-related protein GRP78, PERK, ATF4, proapoptotic protein CHOP, OS-related protein Nrf2, as well as ROS, and alleviate ERS injury at the same time. Whereas knockdown of SESN2 can upregulate the expression of GRP78, PERK, ATF4, CHOP, Nrf2, ROS, and deteriorate ERS damage. Conclusions ERS can induce OS, they form a vicious cycle to induce apoptosis in HLECs, which may contribute to cataract formation. SESN2 could protect HLECs against the apoptosis by regulating the vicious cycle between ERS and OS.

Endoplasmic reticulum stress in a circumventricular organ-hypothalamic neuronal circuit alters hepatic glucose and lipid metabolism during obesity

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic hepatic disorders and is associated with metabolic conditions such type 2 diabetes. Accumulating evidence points to endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) in the subfornical organ (SFO), a circumventricular nucleus situated outside of the blood-brain-barrier, as a major contributor to NAFLD development during obesity. We recently reported that ER stress in SFO neurons that project to the hypothalamic paraventricular nucleus (PVN, SFO→PVN neurons) drives liver triglyceride accumulation during obesity. However, the mechanism by which ER stress in this neural network mediates obesity-related hepatic steatosis remains unknown. Elevations in hepatic gluconeogenesis, lipogenesis, and free fatty acid uptake are all associated with the development of fatty liver. Based on this, we hypothesized that ER stress in SFO→PVN neurons may contribute to NAFLD through alterations in hepatic glucose/lipid metabolism during obesity. To investigate this, we used an intersectional viral strategy to selectively inhibit ER stress in SFO→PVN neurons in C57Bl/6J male mice that were fed a high-fat diet (HFD, 60% kCal fat) for 7 wks (n=4-5/group) and then underwent selective PVN targeting of a retrogradely transported Cre-recombinase virus (CAV2-Cre-GFP; CAV2-GFP served as a control). Concurrently, a Cre inducible vector to overexpress the ER chaperone glucose-regulated peptide 78 (GRP78; AAV-FLEX-GRP78-mStrawberry) was targeted to the SFO. This approach results in the overexpression of GRP78 specifically in SFO→PVN neurons, which has been established as an effective means of reducing ER stress. Four weeks following selective inhibition of SFO→PVN neuronal ER stress, body weight (46±2 vs 43±1 g, CAV2-GFP vs CAV2-Cre, P=0.26), food intake, and adipose mass were not different between groups. However, diminishing UPR activation in this circumventricular-hypothalamic circuit resulted in a reduction in hepatomegaly (1.8±0.1 vs 1.5±0.1 g, CAV2-GFP vs CAV2-Cre, P=0.08), hepatic triglyceride levels (4.3±0.6 vs 2.3±0.4 mM, CAV2-GFP vs CAV2-Cre, p<0.05), and plasma glucose (198±12 vs 168±8 mg/dL, CAV2-GFP vs CAV2-Cre, P=0.06). Interestingly, reducing ER stress in SFO→PVN neurons was also associated with a downregulation in hepatic mRNA levels of genes involved in hepatic gluconeogenesis (e.g. G6pase: 0.29±0.04; Pepck: 0.46±0.04 fold CAV2-GFP, both p<0.05), de novo lipogenesis (e.g. SREBP1: 0.65±0.1 fold CAV2-GFP, P=0.05) and free fatty acid synthesis and uptake (e.g. Fasn: 0.57±0.11 fold CAV2-GFP, P=0.09 and FATP5: 0.42±0.03, fold CAV2-GFP, p<0.05). Overactivation of the liver sympathetic nerves has recently been shown to contribute to obesity-related NAFLD, and inhibition of ER stress in SFO→PVN neurons resulted in a reduction in protein levels of hepatic tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis (0.58±0.03, fold CAV2-GFP, p<0.05). Notably, hepatic TH levels were significantly correlated with liver glucose/lipid metabolism-related gene expression and triglyceride content (e.g. Pepck: R2=0.57; Fasn: R2=0.80; FATP5: R2=0.77; triglycerides: R2=0.70, all p<0.05). Collectively, these results suggest that during obesity, ER stress in SFO→PVN neurons may drive liver sympathetic overactivity and subsequently disrupt hepatic glucose/lipid metabolism, thus contributing to NAFLD development. R01DK117007, R01HL141393, AHA932522. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

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.

Abstract 380: Co-downregulation of GRP78 and ATR enhances apoptosis in pancreatic ductal adenocarcinoma

Abstract Background: Targeting endoplasmic reticulum (ER) stress is a potential therapeutic strategy in preclinical models of pancreatic duct adenocarcinoma (PDAC). GRP78 is known as the master regulator of the unfolded protein response (UPR) pathway, regulating ER stress by activating the UPR pathway to avoid cell apoptosis and regulates the activation of UPR pathway signals by binding PERK. Overexpression of GRP78 in PDAC results in the retention of misfolded and unassembled proteins, as well as the accumulation of ROS, leading to the promotion of genomic instability. However, there has been limited research on targeting GRP78 as a therapeutic strategy in PDAC. In this study, we aimed to investigate the anticancer effects of BOLD-100, an inhibitor of GRP78, in PDAC. Methods: We used 9 PDAC cell lines (Capan-1, AsPC-1, HPAFII, MIA-PaCa2, Panc-1, Capan-2, SNU-213, SNU-324, SNU-2918). The mouse xenograft model of Capan-1 was established for in vivo study. BOLD-100 (GRP78 inhibitor), AZD6738 (ATR inhibitor), NAC (N-Acetylcysteine; ROS scavenger) and TUDCA (Tauroursodeoxycholic acid; ER stress inhibitor) were used. MTT assay, CFA assay, cell cycle analysis, RT-PCR, western blot, immunoprecipitation, DCF-DA staining and Annexin V assay were used to elucidate the action of BOLD-100. The combination of BOLD-100 with AZD6738 has been evaluated in both in vitro and in vivo model. Results: BOLD-100 suppressed the proliferation of PDAC cells and decreased the mRNA level of GRP78, which in turn disrupted the interaction between GRP78 and PERK. BOLD-100 increased ER stress and ROS, leading to activation of PERK, eIF2a, and CHOP. Activation of UPR pathway induced CHOP-dependent apoptosis and inhibited PDAC cell growth. Moreover, TUDCA reversed the ROS accumulation induced by BOLD-100, confirming that ER stress regulates ROS levels. The accumulation of ROS upregulated the active forms of ATR and CHK1, suggesting the activation of the DNA damage repair pathway. Notably, the treatment of NAC abrogated the activation of ATR-CHK1 axis by BOLD-100-induced ROS accumulation. AZD6738 synergized with BOLD-100 in in vitro and in vivo, by suppressing BOLD-100-induced ATR phosphorylation. Conclusion: GRP78 could serve as one of the potential therapeutic targets in PDAC. The combination of BOLD-100 and AZD6738 demonstrates a synergistic effect suggesting GRP78/ATR dual targeting as a promising therapeutic option for patients with PDAC. Citation Format: Su In Lee, Ah-Rong Nam, Kyoung-Seok Oh, Jae-Min Kim, Ju-Hee Bang, Yoojin Jeong, Sea Young Choo, Hyo Jung Kim, Jeesun Yoon, Tae-Yong Kim, Do-Youn Oh. Co-downregulation of GRP78 and ATR enhances apoptosis in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 380.

Abstract 4556: USP51-GRP78-ABCB1 axis promotes chemoresistance of triple negative breast cancer by decreasing the accumulation of doxorubicin in cells

Abstract Background: Resistance to chemotherapy remains an obstacle for triple-negative breast cancer (TNBC) patients. The core components of the ubiquitin-proteasome system have been demonstrated to regulate chemoresistance of TNBC. As a novel deubiquitinase (DUB), ubiquitin-specific peptidase 51 (USP51) plays a pivotal role in chemotherapeutic resistance in multiple malignancies. Herein, we sought to better understand how USP51 performs a cell-intrinsic role in mediating chemotherapeutic resistance in TNBC. Methods: Western blotting, RNA-sequencing and CCK8 assays were used to identify the DUBs for chemoresistance of breast cancer. Coimmunoprecipitation, GST-pulldown, protein deubiquitination and immunohistochemistry assays were then used to determine the biological phenotypes of ectopic USP51 in TNBC chemoresistance and associated signaling pathways in several different cell lines, mouse models and patient tissue samples. Ubiquitin-7-amido-4-methylcoumarin (Ub-AMC)-based deubiquitinase activity, cellular thermal shift and surface plasmon resonance (SPR) analyses were performed to investigate the activity of USP51 inhibitors. Results: To identify the critical DUBs involved in breast cancer chemoresistance, we established doxorubicin-resistant Cal51 and MDA-MB-231 TNBC cell lines by multiple dose exposure. We found ectopic USP51 in doxorubicin-resistant cells compared with their parental cells. Moreover, USP51-interfered chemoresistant tumor cells exhibited impaired cell viability as well as increased DNA damage and cell apoptosis upon treatment with doxorubicin. On the contrary, overexpression of USP51 performed the opposite effects to enhance cell viability but decrease DNA damage and apoptosis in response to doxorubicin; however, these outcomes were not shown for its catalytically inactive mutant USP51C372S. At the molecular level, GRP78 was identified as a bona fide substrate of USP51. Importantly, knockdown USP51 increased doxorubicin-induced DNA damage and apoptosis, which was rescued by overexpression of GRP78 in vitro and in vivo. In addition, the activity of ABCB1, the main efflux pump of doxorubicin, was enhanced by GRP78. Consistently, the expression of USP51, GRP78 and ABCB1 were correlated with chemoresistant phenotypes in TNBC patients. Of note, we also explored a small molecular inhibitor of USP51, WCY-4-1, which conferred chemosensitization in TNBC. Conclusion: These findings collectively indicated that ectopic USP51 enhances the activity of ABCB1 by deubiquitinating and stabilizing GRP78, which leads to decreased accumulation of doxorubicin as well as decreased DNA damage and cell apoptosis in TNBC. Our results also revealed that specific inhibition of USP51 significantly impairs doxorubicin-resistance in TNBC. Citation Format: Yang Ou, Kun Zhang, Qiuying Shuai, Chenyang Wang, Huayu Hu, Lixia Cao, Chunchun Qi, Min Guo, Zhaoxian Li, Jie Shi, Yuxin Liu, Siyu Zuo, Xiao Chen, Yanjing Wang, Mengdan Feng, Hang Wang, Yi Shi, Guang Yang, Shuang Yang. USP51-GRP78-ABCB1 axis promotes chemoresistance of triple negative breast cancer by decreasing the accumulation of doxorubicin in cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4556.

Δ(9)-tetrahydrocannabinol protects cardiac tissue against endoplasmic reticulum and oxidative stresses, apoptosis, and inflammation in rats with hyperinsulinemia.

In our study, we aimed to examine how δ(9)-tetrahydrocannabinol (THC) administration to hyperinsulinemia (HI) model rats would change endoplasmic reticulum stress (ERS), apoptosis, inflammation, and oxidative stress in cardiac tissue. Rats were divided into four groups (n = 32): Control (C), THC, HI, and Treatment (Tre). Fructose (10%) in the drinking water was given to HI and Tre rats for 12 weeks. 1.5 mg/kg/d THC was given intraperitoneally to THC and Tre rats in the last 4 weeks of the experiment. The mRNA expressions of ERS and apoptosis markers in the cardiac tissue were detected. TNF-α concentration and oxidative stress were also analyzed. THC treatment in rats with HI ameliorated the overexpression of GRP-78, IRE1α, ATF6, ATF4, CHOP, Cas-12, Cas-8, Cas-9, and Cas-3 mRNAs, markers of ERS and apoptosis (P < .0001 for all). In addition, THC has been shown to reduce inflammation in the Tre group by causing a decrease in increased cardiac TNF-α levels (P < .01). Moreover, THC prevented cardiac tissue damage by regulating the degraded oxidative stress marker levels and antioxidant enzyme activities in HI. Our findings suggest that THC treatment in rats with HI exhibited a significant effect in ameliorating cardiac tissue damage by improving the antioxidant defense system, inflammation, apoptosis, ERS, and oxidative stress.

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.

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.

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

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.

Chaperon Protein GRP78 Released from MPN Cells Increase Expression of Lysyl Oxidase in Human Stroma 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 an increased expression of the chaperone protein glucose-regulated protein (GRP)78, which is a central regulator of ER stress in megakaryocytes from primary myelofibrosis (PMF) (n=7) or post-essential thrombocythemia myelofibrosis(POST-ET-MF) patients (n=2) regardless of the type of driver mutation. In accord with these notions, we found that GRP78 was overexpressed in JAK2V617F-harboring cell lines (HEL and SET-2) and in UT-7/TPO cells overexpressing either type1 or type2 mutant form of calreticulin. To address the mechanism responsible for the induction of GRP78, we treated the HEL and SET-2 cells with 4-phenyl butyric acid and tauroursodeoxycholic acid both of which are well known inhibitors of ER stress, however, these inhibitors did not affect the expression levels of GRP78. These results indicated that overexpression of GRP78 shown in these cells were not a result of activation of ER stress. In contrast, ruxolitinib, an inhibitor of JAK2V617F, blocked GRP78 expression in these cells. We also found ruxolitinib blocked nuclear accumulation of the transcription factor 4 (ATF4), one of the main transcription factors which regulate GRP78. Furthermore, knockdown of ATF4 using siRNA also resulted in suppression of GRP78 levels in HEL and SET-2 cells. These results suggested that JAK2V617F induce GRP78 through activation of ATF4. We also confirmed that megakaryocytes from MF patients had statistically higher nuclear to cytoplasmic intensity of ATF4 compared to megakaryocytes found in control subjects. For the next step, we tried to find out the pathological action of GRP78 in MPN cells. Although the GRP78 usually works as chaperon protein in cytosol, some cancer cells secret GRP78 into tumor microenvironment and activates signal transduction molecules in surrounding cells. Therefore, we hypothesized that overexpressed GRP78 proteins in MPN cells may secret and modulate phenotype of bone marrow stroma cells. Initially, we confirmed the presence of GRP78 proteins in culture media from HEL and SET-2 cells. Next, we investigated whether GRP78 secreted by HEL and SET-2 cells affect phenotype of bone marrow stromal cells. For this purpose, we used human bone marrow stroma cell line, HS-5. HS-5 cells were co-cultured with HEL or SET-2 cells with trans-well system, and changes of several key molecules involved in development of fibrosis were analyzed. We found that co-culture with HEL or SET-2 cells clearly indued expression of lysyl oxidase (LOX) , which mediate cross-linking of collagen fiber and induce tissue fibrosis , in HS-5 cells. Anti-GRP78 neutralizing antibody abrogated LOX elevation, in contrast, recombinant form of GRP78 proteins induced LOX proteins in HS-5. According to the above results, we examined LOX expression in bone marrow specimens from MF patients. The areas of LOX expression cells were statistically higher in MF patients compared to control group. In addition, high power field observations detected not only in round cells but also in spindle like cells expressed LOX in MF patients, suggesting that bone marrow stromal cells in MF patients express LOX. In conclusion, we demonstrated that GRP78 was overexpressed both in MPN derived cell lines and also in primary megakaryocytes from MF patients. Our observations proposed that overexpressed GRP78 in MPN cells contribute development of myelofibrosis through secreted in microenvironment and induced expression of extracellular matrix modulating enzyme LOX in bone marrow stromal cells.

GRP78 is Overexpressed in Non-small Cell Lung Cancer Tissues and is Associated with High VEGF Expression in Squamous Cell Carcinoma: A Pilot Study.

Neovascularization is essential for the growth and progression of tumor tissues. GRP78 is frequently overexpressed in various cancers and has been suggested as a proangiogenic factor. This study aimed to investigate the expression levels of GRP78 and to test for significant relationships with the angiogenic markers, VEGF, and CD31. In this study, paraffin-embedded NSCLC tissue samples (71 adenocarcinomas and 23 squamous cell carcinoma) were retrospectively collected from 94 patients with NSCLC. The expressions of VEGF, CD31, and GRP78 were determined by immunohistochemistry. High expression levels of VEGF and GRP78 were observed in 65 and 74 cases, respectively. Thirty-six patients expressed high CD31 levels. Adenocarcinomas expressed higher levels of the three proteins than squamous cell carcinomas (p-value < 0.05). Moreover, a statistically significant association was found between the expression levels of VEGF and CD31 (p-value = 0.001) and VEGF and GRP78 (p-value=0.028). GRP78 overexpression was revealed in most of the investigated samples. The positive association between VEGF and GRP78 may indicate the proangiogenic role of GRP78 in lung cancer. Moreover, the positive association between VEGF and CD31 expression levels suggests that VEGF may cooperate with CD31 to promote angiogenesis in NSCLC.

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.

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.

Apelin-36 alleviates LPS-induced trophoblast cell injury by inhibiting GRP78/ASK1/JNK signaling

Pre-eclampsia (PE) is a type of hypertensive disorder of pregnancy that poses a serious threat to the health of both mother and fetus. Inhibition of the inflammatory environment on trophoblast cells is of great significance to improve PE. Apelin-36 is an endogenous active peptide with strong anti-inflammatory activity. Therefore, this study aims to investigate the effects of Apelin-36 on lipopolysaccharide (LPS)-induced trophoblast cells and its potential mechanism. The levels of inflammatory factors (TNF-α, IL-8, IL-6 and MCP-1) were detected by reverse transcription-quantitative PCR (RT-qPCR). The proliferation, apoptosis, migration and invasion capacities in trophoblast cells were detected by CCK-8, TUNEL staining, wound healing and Transwell assays, respectively. GRP78 was overexpressed by cell transfection. Western blot was applied for the identification of protein levels. Apelin concentration-dependently decreased the expression of inflammatory cytokines and p-p65 protein level in trophoblast cells induced by LPS. Apelin treatment reduced LPS-induced apoptosis and improved the proliferation, invasion and migration capacities of LPS-mediated trophoblast cells. Additionally, Apelin down-regulated GRP78, p-ASK1 and p-JNK protein levels. The inhibition on LPS-induced trophoblast cell apoptosis and the promotion on invasion and migration by Apelin-36 was counteracted by GRP78 overexpression. To sum up, Apelin-36 could alleviate LPS-induced cell inflammation and apoptosis and improve the invasion and migration of trophoblasts by inhibiting the GRP78/ASK1/JNK signaling.

Porcine Epidemic Diarrhea Virus and Its nsp14 Suppress ER Stress Induced GRP78.

Porcine epidemic diarrhea virus (PEDV), a member of the α-coronavirus genus, can cause vomiting, diarrhea, and dehydration in piglets. Neonatal piglets infected with PEDV have a mortality rate as high as 100%. PEDV has caused substantial economic losses to the pork industry. Endoplasmic reticulum (ER) stress, which can alleviate the accumulation of unfolded or misfolded proteins in ER, involves in coronavirus infection. Previous studies have indicated that ER stress could inhibit the replication of human coronaviruses, and some human coronaviruses in turn could suppress ER stress-related factors. In this study, we demonstrated that PEDV could interact with ER stress. We determined that ER stress could potently inhibit the replication of GⅠ, GⅡ-a, and GⅡ-b PEDV strains. Moreover, we found that these PEDV strains can dampen the expression of the 78 kDa glucose-regulated protein (GRP78), an ER stress marker, while GRP78 overexpression showed antiviral activity against PEDV. Among different PEDV proteins, PEDV non-structural protein 14 (nsp14) was revealed to play an essential role in the inhibition of GRP78 by PEDV, and its guanine-N7-methyltransferase domain is necessary for this role. Further studies show that both PEDV and its nsp14 negatively regulated host translation, which could account for their inhibitory effects against GRP78. In addition, we found that PEDV nsp14 could inhibit the activity of GRP78 promotor, helping suppress GRP78 transcription. Our results reveal that PEDV possesses the potential to antagonize ER stress, and suggest that ER stress and PEDV nsp14 could be the targets for developing anti-PEDV drugs.