78-kDa Glucose-regulated Protein Research Articles

Secreted GRP78 attenuates endothelial inflammation and predicts outcome in coronary artery disease

Abstract Background Endoplasmic-reticulum-stress (ER-Stress) chaperones like the main ER-Stress moderator GRP78 (glucose-regulated-protein, 78kDa) are involved in the pathogenesis of coronary artery disease (CAD). In addition to their established intracellular localization, chaperones are also secreted into the extracellular space. However, the significance of extracellular ER chaperones in CAD remains unclear. Here, we investigated the role of extracellular GRP78 in patients with suspected CAD and its impact on endothelial cell inflammation. Methods Serum concentration of GRP78 was measured by ELISA in 622 patients undergoing coronary angiography (70.0 ± 12.2 years, 33.6% female and 28.4% with acute coronary syndrome: ACS). The primary endpoint was defined as one-year mortality. Human coronary artery endothelial cells (HCAEC) were treated with ER-Stressors and the effects of ER-Stress conditioned medium (CM) on recipient cell viability, apoptosis, reactive oxygen species (ROS) formation and gene expression were examined. Results GRP78 levels were higher in blood samples of patients with CAD than in patients without CAD (2584 ng/ml vs. 2061 ng/ml, p = 0.047). In patients presenting with ACS, GRP78 levels were lower than in patients presenting with chronic coronary syndrome. Elevated GRP78 levels were independently associated with lower one-year mortality, even after adjustment for cardiovascular risk factors and demographic parameters (4.5% vs. 9.0%, log-rank p = 0.022; Fig.1A). Increased levels of GRP78 (> median of 1710 ng/ml) were associated with a higher BMI (29.0 kg/m2 ± 7.3 vs. 27.0 kg/m2 ± 6.2, p < 0.0001) while there was no difference regarding age, sex, or cardiovascular risk factors. Mass spectrometry analyses of the HCAEC secretome and ELISA revealed increased extracellular GRP78 secretion after ER-Stress activation. Co-incubation with Brefeldin A, an inhibitor of ER-Golgi-trafficking, confirmed active regulation of GRP78 secretion. GRP78-containing CM improved viability while reducing apoptosis, formation of ROS, ER-Stress-signaling, and inflammation in recipient HCAEC compared to CM lacking GRP78 due to BFA treatment or GRP78-knockdown. Likewise, recombinant GRP78 improved HCAEC viability while reducing expression of markers of inflammation and ER stress (Fig.1B). CRIPTO is a membrane-bound co-receptor for growth factors and was previously linked to GRP78-signalling. siRNA-Knockdown of CRIPTO reduces viability and leads to cell apoptosis, irrespective of GRP78-treatment (relative viability: Scr-siRNA+1µg/ml GRP78 vs. Criptodown+1µg/ml GRP78 1.22 ± 0.23 vs. 1.02 ± 0.13, p<0.01, Fig.1C). Thus, GRP78-mediated effects may be mediated by CRIPTO. Conclusion GRP78 is significantly increased in patients with CAD. Intriguingly, elevated levels are associated with reduced one-year mortality. ER-Stress-induced GRP78 secretion represents a feedback mechanism to ameliorate ER-Stress and inflammation in recipient endothelial cells (Fig.2).

Endoplasmic reticulum stress and expression of nitric oxide synthases in heart failure with preserved and with reduced ejection fraction - pilot study.

Unfolded Protein Response (UPR), endoplasmic reticulum (ER) stress, and inducible nitric oxide synthase (iNOS) overexpression have been found to influence heart failure with preserved ejection fraction (HFpEF) pathogenesis. Their importance in heart failure with reduced ejection fraction (HFrEF) is not entirely established; there is little data involving a detailed comparison between HFpEF and HFrEF from this perspective. This pilot study aimed to compare circulating levels of Glucose-regulated protein 78kDa (GRP78) (ER - stress marker) and all NOS isoforms between both HFpEF and HFrEF and to analyze the correlation between these markers and the clinical characteristics of the patients. Forty-two patients with HFpEF and thirty-eight with HFrEF were involved in this study. Clinical characteristics and echocardiographic data were obtained. Basic laboratory tests were performed and ELISA tests for iNOS, endothelial NOS (eNOS), neuronal NOS (nNOS), and GRP78. Patients with HFpEF had lower circulating levels of GRP78 and higher iNOS concentrations when compared to HFrEF patients (P = 0.023, P < 0.0001, accordingly). The subgroup of the HFpEF population with eGFR < 60 mL/min/1.73m2 had higher nNOS and eNOS levels than HFpEF patients with normal GFR (P = 0.049, P = 0.035, respectively). In the HFrEF subgroup, patients with coexistent diabetes mellitus had elevated concentrations of nNOS compared to the subpopulation without diabetes mellitus (P = 0.041). There was a positive correlation between eNOS and nNOS concentrations (ρ = 0.86, P < 0.0001). In HFpEF, there is a more intensified iNOS overexpression, while in HFrEF, ER stress is more prominent.

QRICH1 suppresses pediatric T-cell acute lymphoblastic leukemia by inhibiting GRP78

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that commonly affects children and adolescents with a poor prognosis. The terminal unfolded protein response (UPR) is an emerging anti-cancer approach, although its role in pediatric T-ALL remains unclear. In our pediatric T-ALL cohort from different centers, a lower QRICH1 expression was found associated with a worse prognosis of pediatric T-ALL. Overexpression of QRICH1 significantly inhibited cell proliferation and stimulated apoptosis of T-ALL both in vitro and in vivo. Upregulation of QRICH1 significantly downregulated 78 KDa glucose-regulated protein (GRP78) and upregulated CHOP, thus activating the terminal UPR. Co-overexpression of GRP78 in T-ALL cells overexpressing QRICH1 partially reverted the inhibited proliferation and stimulated apoptosis. QRICH1 bound to the residues Asp212 and Glu155 of the nucleotide-binding domain (NBD) of GRP78, thereby inhibiting its ATP hydrolysis activity. In addition, QRICH1 was associated with endoplasmic reticulum (ER) stress in T-ALL, and overexpression of QRICH1 reversed drug resistance. Overall, low QRICH1 expression is an independent risk factor for a poor prognosis of pediatric T-ALL. By inhibiting GRP78, QRICH1 suppresses pediatric T-ALL.

Small molecules targeting GRP78 mitigate anti-GRP78 autoantibody–mediated tissue factor procoagulant activity in cultured endothelial cells

BackgroundThe 78-kDa glucose-regulated protein (GRP78) expressed on the cell surface (csGRP78) has been reported to regulate tissue factor (TF) procoagulant activity (PCA) in lesion-resident endothelial cells (ECs), which is further enhanced by circulating anti-GRP78 autoantibodies that bind to the Leu98-Leu115 epitope in GRP78. ObjectivesDetermine the effects of the engagement of the anti-GRP78 autoantibody to csGRP78 on ECs and the underlying mechanisms that impact TF PCA. MethodsImmunofluorescent staining was used to determine the presence of csGRP78 in tumor necrosis factor α–treated ECs. An established TF PCA assay was used to evaluate human ECs following treatment with anti-GRP78 autoantibodies. The Fura 2-AM assay (Abcam) was used to quantify changes in intracellular Ca2+ levels. Small molecules predicted to bind GRP78 were identified using artificial intelligence. Enzyme-linked immunosorbent assays were used to assess the ability of these GRP78 binders to mitigate TF activity and interfere with the autoantibody/csGRP78 complex. ResultsIn tumor necrosis factor α–treated ECs, anti-GRP78 autoantibodies increased TF PCA. This observation was further enhanced by endoplasmic reticulum stress-induced elevation of csGRP78 levels. Anti-GRP78 autoantibody treatment increased intracellular Ca2+ levels. Sequestering the anti-GRP78 autoantibody with a conformational peptide or blocking with heparin attenuated anti-GRP78 autoantibody–induced TF PCA. We identified B07∗, as a GRP78 binder that diminished anti-GRP78 autoantibody–induced TF PCA on ECs. ConclusionThese findings show how anti-GRP78 autoantibodies enhance TF PCA that contributes to thrombosis and identify novel GRP78 binders that represent a potential novel therapeutic strategy for treating and managing atherothrombotic disease.

GRP78 recognizes EV-F 3D protein and activates NF-κB to repress virus replication by interacting with CHUK/IKBKB.

Enteroviruses are the causative agents associated with several human and animal diseases, posing a significant threat to human and animal health. As one of the host immune defense strategies, innate immunity plays a crucial role in defending against invading pathogens, where the host utilizes a variety of mechanisms to inhibit or eliminate the pathogen. Here, we report a new strategy for the host to repress enterovirus replication by the 78 kDa glucose-regulated protein (GRP78), also known as heat shock protein family A member 5 (HSPA5). The GRP78 recognizes the EV-encoded RNA-dependent RNA polymerases (RdRPs) 3D protein and interacts with the nuclear factor kappa B kinase complex (CHUK) and subunit beta gene (IKBKB) to facilitate the phosphorylation and nuclear translocation of NF-κB, which induces the production of inflammatory factors and leads to a broad inhibition of enterovirus replication. These findings demonstrate a new role of GRP78 in regulating host innate immunity in response to viral infection and provide new insights into the mechanism underlying enterovirus replication and NF-κB activation.IMPORTANCEGRP78 is known as a molecular chaperone for protein folding and plays a critical role in maintaining protein folding and participating in cell proliferation, cell survival, apoptosis, and metabolism. However, the functions of GRP78 to participate in enterovirus genome replication and innate immune responses are rarely documented. In this study, we explored the functions of the EV-3D-interacting protein GRP78 and found that GRP78 inhibits enterovirus replication by activating NF-κB through binding to EV-F 3D and interacting with the NF-κB signaling molecules CHUK/IKBKB. This is the first report that GRP78 interacts with CHUK/IKBKB to activate the NF-κB signaling pathway, which leads to the expression of the proinflammatory cytokines and inhibition of enterovirus replication. These results demonstrate a unique mechanism of virus replication regulation by GRP78 and provide insights into the prevention and treatment of viral infections.

Phelligridimer A enhances the expression of mitofusin 2 and protects against cerebral ischemia/reperfusion injury

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress play pivotal roles in the pathology of cerebral ischemia. In this study, we investigated whether phelligridimer A (PA), an active compound isolated from the medicinal and edible fungus Phellinus igniarius, ameliorates ischemic cerebral injury by restoring mitochondrial function and restricting ER stress. An in vitro cellular model of ischemic stroke-induced neuronal damage was established by exposing HT-22 neuronal cells to oxygen-glucose deprivation/reoxygenation (OGD/R). An in vivo animal model was established in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). The results showed that PA (1–10 μM) dose-dependently increased HT-22 cell viability, reduced OGD/R-induced lactate dehydrogenase release, and reversed OGD/R-induced apoptosis. PA reduced OGD/R-induced accumulation of reactive oxygen species, restored mitochondrial membrane potential, and increased ATP levels. Additionally, PA reduced the expression of the 78-kDa glucose-regulated protein (GRP78) and the phosphorylation of inositol-requiring enzyme-1α (p-IRE1α) and eukaryotic translation-initiation factor 2α (p-eIF2α). PA also inhibited the activation of the mitogen-activated protein kinase (MAPK) pathway in the OGD/R model. Moreover, treatment with PA restored the expression of mitofusin 2 (Mfn-2), a protein linking mitochondria and ER. The silencing of Mfn-2 abolished the protective effects of PA. The results from the animal study showed that PA (3–10 mg/kg) significantly reduced the volume of cerebral infarction and neurological deficits, which were accompanied by an increased level of Mfn-2, and decreased activation of the ER stress in the penumbra of the ipsilateral side after MCAO/R in rats. Taken together, these results indicate that PA counteracts cerebral ischemia-induced injury by restoring mitochondrial function and reducing ER stress. Therefore, PA might be a novel protective agent to prevent ischemia stroke-induced neuronal injury.

WITHDRAWN: Ip3r-Grp75-Vdac and Relevant Ca2+ Signaling Regulate Dietary Palmitic Acid-Induced De Novo Lipogenesis by Mitochondria-Associated ER Membrane (MAM) Recruiting Seipin in Yellow Catfish

BackgroundThe mitochondria-associated endoplasmic reticulum membrane (MAM) is the central hub for endoplasmic reticulum and mitochondria functional communication. It plays a crucial role in hepatic lipid homeostasis. However, even though MAM has been acknowledged to be rich in enzymes that contribute to lipid biosynthesis, no study has yet investigated the exact role of MAM on hepatic neutral lipid synthesis. ObjectivesTo address these gaps, this study investigated the systemic control mechanisms of MAM on neutral lipids synthesis by recruiting seipin, focusing on the role of the inositol trisphosphate receptor-1,4,5(Ip3r)-75 kDa glucose-regulated protein (Grp75)-voltage-dependent anion channel (Vdac) complex and their relevant Ca2+ signaling in this process. MethodsTo this end, a model animal for lipid metabolism, yellow catfish (Pelteobagrus fulvidraco), were fed 6 different diets containing a range of palmitic acid (PA) concentrations from 0–150 g/kg in vivo for 10 wk. In vitro, experiments were also conducted to intercept the MAM-mediated Ca2+ signaling in isolated hepatocytes by transfecting them with si-mitochondrial calcium uniporter (mcu). Because mcu was placed in the inner mitochondrial membrane (IMM), si-mcu cannot disrupt MAM’s structural integrity. Results1. Hepatocellular MAM subproteome analysis indicated excessive dietary PA intake enhanced hepatic MAM structure joined by activating Ip3r-Grp75-Vdac complexes. 2. Dietary PA intake induced hepatic neutral lipid accumulation through MAM recruiting Seipin, which activated lipid droplet biogenesis. Our findings also revealed a previously unidentified mechanism whereby MAM-recruited seipin and controlled hepatic lipid homeostasis, depending on Ip3r-Grp75-Vdac-controlled Ca2+ signaling and not only MAM’s structural integrity. ConclusionsThese results offer a novel insight into the MAM-recruited seipin in controlling hepatic lipid synthesis in a MAM structural integrity-dependent and Ca2+ signaling-dependent manner, highlighting the critical contribution of MAM in maintaining hepatic neutral lipid homeostasis.

GRP78 Contributes to the Beneficial Effects of SGLT2 Inhibitor on Proximal Tubular Cells in DKD.

Beneficial effects of SGLT2 inhibitors on kidney function are well-known; however, their molecular mechanisms are not fully understood. We focused on 78 kDa glucose-regulated protein (GRP78) and its interaction with SGLT2 and Integrin ß1 beyond the chaperone property of GRP78. In STZinduced diabetic mouse kidneys, GRP78, SGLT2, and Integrin ß1 increased in the plasma membrane fraction, while they were suppressed by canagliflozin. The altered subcellular localization of GRP78/Integrin ß1 in STZ mice promoted epithelial mesenchymal transition (EMT) and fibrosis, which were mitigated by canagliflozin. High glucose conditions reduced intracellular GRP78, increased its secretion, and caused EMT-like changes in cultured HK2 cells, which were again inhibited by canagliflozin. Urinary GRP78 increased in STZ mice, and in vitro experiments with recombinant GRP78 suggested that inflammation spread to surrounding tubular cells and canagliflozin reversed this effect. Under normal glucose culture, canagliflozin maintained SERCA activity, promoted endoplasmic reticulum (ER) robustness, reduced ER stress response impairment, and protected proximal tubular cells. In conclusion, canagliflozin restored subcellular localization of GRP78, SGLT2 and Integrin ß1 and inhibited EMT and fibrosis in DKD. In non-diabetic CKD, canagliflozin promoted ER robustness by maintaining SERCA activity and preventing ER stress response failure, and contribute to tubular protection.

Possible Involvement of X-Box Binding Protein-1 in the Onset of Pulpitis.

Endoplasmic reticulum (ER) stress plays important roles not only in stress avoidance, but also in cell differentiation and maturation, cell proliferation, and promotion of bone formation. This study aimed to investigate the involvement of ER stress in the onset of pulpitis. Immunohistochemical analysis was conducted on human teeth extracted for orthodontic reasons. The effects of tunicamycin (TM), an inducer of ER stress, lipopolysaccharide (LPS), and 4μ8c, an inhibitor of inositol-requiring enzyme 1 (IRE1) on cultured human dental pulp cells (hDPCs) were also examined. The expressions of two ER stress markers, X-box binding protein (XBP)-1 and binding immunoglobulin protein (BiP)/78 kDa glucose-regulated protein (GRP78), were found in the human pulp tissues of a decayed tooth that had not developed irreversible acute pulpitis, but not in an impacted tooth without inflammation in pulp tissue. Both TM and LPS increased the mRNA levels of XBP-1, interleukin (IL)-6, and IL-8, whereas TM, but not LPS, enhanced the mRNA expression of BiP/GRP78 in hDPCs. 4μ8c significantly suppressed the increased level of XBP-1 by LPS. This study is the first to demonstrate that XBP-1, in addition to inflammatory cytokines, may participate in the onset of pulpitis through IRE1. These findings provide a more comprehensive understanding of pulpitis pathogenesis through the cooperation of ER stress and inflammatory cytokines.

Gallic acid attenuates torsion/detorsion-induced testicular injury in rats through suppressing of HMGB1/NF-κB axis and endoplasmic reticulum stress.

It was aimed to evaluate whether gallic acid (GA) have a beneficial effect in the testicular ischemia/reperfusion injury (IRI) model in rats for the first time. Testicular malondialdehyde, 8-hydroxy-2'-deoxyguanosine, superoxide dismutase, catalase, high mobility group box 1 protein, nuclear factor kappa B, tumor necrosis factoralpha, interleukin-6, myeloperoxidase, 78-kDa glucose-regulated protein, activating transcription factor 6, CCAAT-enhancer-binding protein homologous protein and caspase-3 levels were determined using colorimetric methods. The oxidative stress, inflammation, endoplasmic reticulum stress and apoptosis levels increased statistically significantly in the IRI group compared with the sham operated group (p < 0.05). GA application improved these damage significantly (p < 0.05). Moreover, it was found that the results of histological examinations supported the biochemical results to a statistically significant extent. Our findings suggested that GA may be evaluated as a protective agent against testicular IRI.

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.

Salivary proteomic profile of young healthy subjects

Background: The incidence of noncommunicable diseases (NCDs) has been rapidly ramped up worldwide. Hence, there is an urgent need to non-invasively detect NCDs possibly by exploiting saliva as a ‘liquid biopsy’ to identify biomarkers of the health status. Since, the absence of standardized procedures of collection/analysis and the lack of normal ranges makes the use of saliva still tricky, our purpose was to outline a salivary proteomic profile which features healthy individuals.Methods: We collected saliva samples from 19 young blood donors as reference population and the proteomic profile was investigated through mass-spectrometry.Results: We identified 1,004 proteins of whose 243 proteins were shared by all subjects. By applying a data clustering approach, we found a set of six most representative proteins across all subjects including Coronin-1A, F-actin-capping protein subunit alpha, Immunoglobulin J chain, Prosaposin, 78 kDa glucose-regulated protein and Heat shock 70 kDa protein 1A and 1B.Conclusion: All of these proteins are involved in immune system activation, cellular stress responses, proliferation, and invasion thus suggesting their use as biomarkers in patients with NCDs.

Pan-Inhibition of Protein Disulfide Isomerase Caused Cell Death through Disrupting Cellular Proteostasis in Pancreatic Ductal Adenocarcinoma Cells.

The protein disulfide isomerase (PDI) family is a group of thioredoxin endoplasmic reticulum (ER)-resident enzymes and molecular chaperones that play crucial roles in the correct folding of proteins. PDIs are upregulated in multiple cancer types and are considered a novel target for cancer therapy. In this study, we found that a potent pan-PDI inhibitor, E64FC26, significantly decreased the proliferation of pancreatic ductal adenocarcinoma (PDAC) cells. As expected, E64FC26 treatment increased ER stress and the unfolded protein response (UPR), as evidenced by upregulation of glucose-regulated protein, 78-kDa (GRP78), phosphorylated (p)-PKR-like ER kinase (PERK), and p-eukaryotic initiation factor 2α (eIF2α). Persistent ER stress was found to lead to apoptosis, ferroptosis, and autophagy, all of which are dependent on lysosomal functions. First, there was little cleaved caspase-3 in E64FC26-treated cells according to Western blotting, but a higher dose of E64FC26 was needed to induce caspase activity. Then, E64FC26-induced cell death could be reversed by adding the iron chelator, deferoxamine, and the reactive oxygen species scavengers, ferrostatin-1 and N-acetylcysteine. Furthermore, the autophagosome-specific marker, light chain 3B (LC3B)-II, increased, but the autolysosome marker, sequestosome 1 (SQSTM1)/p62, was not degraded in E64FC26-treated cells. Using the FUW mCherry-LC3 plasmid and acridine orange staining, we also discovered a lower number of acidic vesicles, such as autolysosomes and mature lysosomes, in E64FC26-treated cells. Finally, E64FC26 treatment increased the cathepsin L precursor (pre-CTSL) but decreased mature CTSL expression according to Western blotting, indicating a defective lysosome. These results suggested that the PDI inhibitor, E64FC26, might initially impede proper folding of proteins, and then induce ER stress and disrupt proteostasis, subsequently leading to lysosomal defects. Due to defective lysosomes, the extents of apoptosis and ferroptosis were limited, and fusion with autophagosomes was blocked in E64FC26-treated cells. Blockade of autolysosomal formation further led to the autophagic cell death of PDAC cells.

Serum levels of the endoplasmic-reticulum-stress chaperone GRP78 are associated with inflammation, identify patients with coronary artery disease and predict mortality

Abstract Introduction Endoplasmic-reticulum-stress (ER Stress) and associated chaperones like the ER-Stress moderator GRP78 (glucose-regulated-protein, 78kDa) are involved in the pathogenesis of coronary artery disease (CAD). In addition to their intracellular effects, secretion and extracellular properties of chaperones, including GRP78, were recently described. In a recent study using proteomic data, we found coronary endothelial cells to secrete GRP78 into the extracellular space. Here, we investigated the significance of serum GRP78 in patients undergoing coronary angiography for suspected CAD. Methods Serum concentration of GRP78 was measured by ELISA in an all-comers cohort of 789 patients with clinical indication for coronary angiography. Samples were drawn from the arterial sheath. CAD was defined as &amp;gt;50% stenosis in any major epicardial coronary artery. Patients were stratified according to their clinical presentation (CCS: chronic coronary syndrome or ACS). Clinical endpoint was all-cause mortality after one year. Patients with malignant or active auto-immune diseases were excluded. Results Mean age was 70.8 ± 11.9 years and 65% of patients were male. 24% patients presented with acute coronary syndrome (ACS). CAD was found in 72.4% of patients. Mean GRP78 serum concentration was 2492 ng/ml. Increased levels of GRP78 (&amp;gt; median) were associated with diabetes (29.9% vs. 23.1%, p = 0.03), a higher BMI (28.9 kg/m2 ± 7.1 vs. 27.0 kg/m2 ± 6.0, p &amp;lt; 0.0001) and chronic kidney disease (CKD: 23.3 % vs. 17.1 %, p = 0.03). There was no difference regarding age or sex. We further compared GRP78 levels to other biomarkers including WBC, Hemoglobin, Troponin, Creatinine, and Interleukin-6 (IL-6). There was no association between GRP78 levels and the mentioned biomarkers, except for a positive correlation between GRP78 and levels of Interleukin-6 (Pearson r =0.14, p = 0.004). GRP78 levels were increased in patients with CAD when compared to patients without CAD (2640 ng/ml vs. 2178 ng/ml, p = 0.013). Interestingly, GRP78 levels were lower in patients with ACS than in patients with CCS (2284 ng/ml vs. 2822 ng/ml, p = 0.018). There was no difference between NSTEMI and STEMI patients. Finally, we assessed prognostic relevance of GRP78 in patients with CAD. Increased GRP78 levels were associated with lower occurrence of the clinical endpoint of one-year mortality (5.3% vs. 10.6 % vs. p = 0.016). Increased GRP78 levels were associated with reduced one-year mortality (HR: 0.48 [95% CI: 0.25 - 0.92]). After adjusting for IL-6, age, sex, BMI, diabetes, CKD, and ACS, GRP78 remained an independent predictor of one-year mortality in patients with CAD. Conclusion GRP78 serum levels are generally elevated in patients with CAD but are downregulated during ACS. Reduced levels are associated with increased one-year mortality. These results support previous findings that GRP78 secretion is a protective mechanism in cardiovascular diseases.

Protein misfolding: an additional player in the stroke-heart syndrome

Abstract Background Patients suffering from acute ischemic stroke experience an increased risk of major adverse cardiovascular events, introducing the term of stroke-heart syndrome (SHS). Beside common risk factors, the so-called brain-heart axis represents a relevant yet not fully understood biological matrix driving this multi-organ condition. Together with inflammatory and neurohormonal signals, protein misfolding appears as an additional component of this matrix. In fact, previous studies employing animal models of cerebral ischemia identified wrongly arranged toxic proteins (oligomers). In light of the spreading capabilities of such proteins, we questioned whether protein misfolding plays a role in the SHS. Purpose The purpose of this study is to investigate the occurrence of protein misfolding in the post-stroke cardiac dysfunction by assessing presence, origin, localization and routes of oligomers in the heart following an acute ischemic stroke. Its biological and physiological relevance are evaluated by in vivo and in vitro assessments of the myocardium. Methods Acute cerebral ischemic injury was induced in the mouse by left transient middle cerebral artery occlusion for 45 minutes followed by 48 hours of reperfusion in 3-4 month-old C57BL/6J wild type males. Sham operated littermate mice were used as controls. Forty-eight hours after acute cerebral ischemia, cardiac function was evaluated by electrocardiography and compared to pre-operative assessment. Organs were harvested after the abovementioned assessment for the localization and semi-quantification of oligomers in heart and lymph nodes. Furthermore, biological responses related to protein homeostasis in the myocardium were assessed on mRNA and protein levels. Results Our preliminary results show that acute ischemic stroke is associated with an increased presence of oligomers in the heart. In addition, higher levels of oligomers were detected in axillary lymph nodes isolated from stroke mice, suggesting a possible route of oligomers spreading (Fig 1A). Correlating with oligomers occurrence, molecular analyses showed significant upregulation of the inositol-requiring enzyme 1 (IRE1), and catalase at mRNA level (Fig 1B). On the other hand, the expression of the 78-kDa glucose-regulated protein (GRP78), and catalase significantly decreased at protein level, indicating impaired myocardial protein quality control and oxidative stress after acute ischemic stroke (Fig 1C). Stroke-induced cardiac dysfunction was presented by decreased heart weight to tibia length ratio as well as slower and irregular heart rhythm suggesting signs of arrhythmia (Fig 2). Conclusions Acute ischemic stroke is associated with an increased oligomers occurrence in the myocardium and ultimately correlates with altered cardiac resistance against proteotoxicity. Further experiments will be conducted in order to elucidate the role of oligomers as active players or bystanders in the stroke-heart syndrome.

Dengue virus NS1 secretion is regulated via importin-subunit β1 controlling expression of the chaperone GRp78 and targeted by the clinical drug ivermectin.

Dengue virus (DENV) is a major human pathogen that can cause hemorrhagic fever and shock syndrome. One important factor of DENV pathogenicity is non-structural protein 1 (NS1), a glycoprotein that is secreted from infected cells. Here we study the mode of action of the widely used drug ivermectin, used to treat parasitic infections and recently shown to lower NS1 blood levels in DENV-infected patients. We found that ivermectin blocks the nuclear transport of transcription factors required for the expression of chaperones that support the folding and secretion of glycoproteins, including NS1. Impairing nuclear transport of these transcription factors by ivermectin or depleting them from infected cells dampens NS1 folding and thus its secretion. These results reveal a novel mode of action of ivermectin that might apply to other flaviviruses as well.

MiR-199a-5p inhibits aortic valve calcification by targeting ATF6 and GRP78 in valve interstitial cells.

Calcific aortic valve disease (CAVD) is an important cause of disease burden among aging populations. Excessive active endoplasmic reticulum stress (ERS) was demonstrated to promote CAVD. The expression level of miR-199a-5p in patients with CAVD was reported to be downregulated. In this article, we aimed to investigate the function and mechanism of miR-199a-5p in CAVD. The expression level of miR-199a-5p and ERS markers was identified in calcific aortic valve samples and osteogenic induction by real-time quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry, and western blotting (WB). Alizarin red staining, RT-qPCR, and WB were used for the verification of the function of miR-199a-5p. The dual luciferase reporter assay and rescue experiment were conducted to illuminate the mechanism of miR-199a-5p. In our study, the expression level of miR-199a-5p was significantly decreased in calcified aortic valves and valve interstitial cells' (VICs) osteogenic induction model, accompanying with the upregulation of ERS markers. Overexpression of miR-199a-5p suppressed the osteogenic differentiation of VICs, while downregulation of miR-199a-5p promoted this function. 78 kDa glucose-regulated protein (GRP78) and activating transcription factor 6 (ATF6), both of which were pivotal modulators in ERS, were potential targets of miR-199a-5p. miR-199a-5p directly targeted GRP78 and ATF6 to modulate osteoblastic differentiation of VICs. miR-199a-5p inhibits osteogenic differentiation of VICs by regulating ERS via targeting GRP78 and ATF6.

Effects of Social Defeat Stress on Microtubule Regulating Proteins and Tubulin Polymerization.

: Microtubule (MT) stability in neurons is vital for brain development; instability is associated with neuropsychiatric disorders. The present study examined the effects of social defeat stress (SDS) on MT-regulating proteins and tubulin polymerization. : After 10 days of SDS, defeated mice were separated into susceptible (Sus) and unsusceptible (Uns) groups based on their performance in a social avoidance test. Using extracted brain tissues, we measured the expression levels of α-tubulin, acetylated α-tubulin, tyrosinated α-tubulin, MT-associated protein-2 (MAP2), stathmin (STMN1), phospho stathmin serine 16 (p-STMN1 [Ser16]), phospho stathmin serine 25 (p-STMN1 [Ser25]), phospho stathmin serine 38 (p-STMN1 [Ser38]), stathmin2 (STMN2), phospho stathmin 2 serine 73 (p-STMN2 [Ser73]), 78-kDa glucose-regulated protein (GRP-78), and CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using Western blot assay. The tubulin polymerization rate was also measured. : We observed increased and decreased expression of acetylated and tyrosinated α-tubulin, respectively, decreased expression of p-STMN1 (Ser16) and increased expression of p-STMN1 (Ser25), p-STMN2 (Ser73) and GRP-78 and CHOP in the prefrontal cortex and/or hippocampus of defeated mice. A reduced tubulin polymerization rate was observed in the Sus group compared to the Uns and Con groups. : Our findings suggest that SDS has detrimental effects on MT stability, and a lower tubulin polymerization rate could be a molecular marker for susceptibility to SDS.

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.

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

BackgroundCells 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.ResultsThe 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.ConclusionsThe 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.