GRP78 Protein Research Articles

P118 TARGETING ENDOPLASMIC RETICULUM STRESS FOR THE TREATMENT OF FIBROSIS IN CROHN’S DISEASE

Progressive tissue remodeling characterized by extensive collagen production and excess extracellular matrix deposition leads to intestinal fibrosis and stricture formation in patients with fibrostenotic Crohn’s disease. Currently medical therapies can delay but not prevent the development of critical fibrostenosis necessitating surgery. Endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) are associated with intestinal epithelial cells damage and apoptosis in Crohn’s disease. However, the role of ER stress and UPR signaling in subepithelial myofibroblasts (SEMF) during the development of intestinal fibrosis awaits further clarification. Previously, we reported that increase in ER stress and UPR signaling in SEMF isolated from strictured ileum contributes to activation of TGF-β1 and fibrosis. Increased interaction between GRP78 and latent TGF-β complex on the cell membrane leads to αVβ3 integrin-mediated activation of latent TGF-β. The ER stress response was augmented in SEMF by silencing of inhibitory miR-199a-5p by DNA methyltransferase-1 (DNMT1). In current study we investigated the effects of selective targeting of activated ER stress sensors on intestinal fibrosis in vitro. SEMF were prepared from cells isolated from affected ileum and from normal ileum in the same patient undergoing resection for Crohn’s disease. SEMF were transfected with siRNA to the ER stress proteins: Grp78, ATF6, XBP1 and IRE1α, and to DNMT1 to knockdown these proteins and compared to scramble sense siRNA treatment. Some cells were co-transfected with a Smad-binding element (SBE) luciferase reporter and TGFB1 transcriptional activity measured. The protein levels of GRP78, DNMT1 and collagen I were measured by immunoblot and normalized to β-actin. Active and total TGF-β1 was measured by ELISA. Our results showed that knockdown of DNMT1 decreased GRP78 protein production, diminished activation of TGF-β1, and blocked ER stress-induced TGF-β1-dependent collagen production. Knockdown of Grp78, Atf6α, Xbp1, and Ire1α in normal SEMF decreased ER stress-induced TGFB1 transcriptional activity by 30 ± 2%, 33 ± 1.5%, 35 ± 1.8%, and 23 ± 1.2%, respectively. In 3D culture of normal SEMF with Grp78 knocked down, tunicamycin failed to induce ER stress, increase activation of TGF-β1 or increase collagen production. Taken together, our results indicate that ER stress in part mediates development of intestinal fibrosis in Crohn’s disease by where DNMT1-induced silencing of miR-199a-5p allows a heighted ER Stress response that results in greater TGF-β1 activation and collagen production in the SEMF.

Profiling of apoptosis- and autophagy-associated molecules in human lung cancer A549 cells in response to cisplatin treatment using stable isotope labeling with amino acids in cell culture.

Cis‑diammine‑dichloro‑platinum II‑based adjuvant chemotherapy provides an alternative therapy to improve the survival of patients with lung tumors, especially those with non‑small cell lung cancer (NSCLC). However, drug resistance is a large clinical problem and its underlying mechanism remains unclear. In the present study, NSCLC A549 cells were treated with a low concentration of cisplatin in order to observe and determine the development of chemoresistance, via growth curves, colony forming assays and apoptosis assays. Then the induction of autophagy was examined in the cisplatin‑treated A549 cells with a fluorescence reporter. Profiled proteins in the cisplatin‑treated A549 cells were also assessed using the stable isotope labeling by amino acids in cell culture (SILAC) method, and then the differentially expressed molecules were verified. The results demonstrated that A549 cells became less sensitive to cisplatin [resistant A549 cells (A549R)] following 20passages in the medium containing a low concentration of cisplatin, with less apoptotic cells post‑cisplatin treatment. A549R cells grew more efficiently in the cisplatin medium, with more colony formation and more cells migrating across the baseline. In addition, NSCLC results demonstrated that more autophagy‑related proteins (ATGs) were expressed in the A549R cells. Furthermore, the western blotting results confirmed this upregulation of ATGs in A549R cells. In addition, two repeated SILAC screening experiments recognized 15proteins [glucose‑regulated protein, 78kDa (GRP78), heat shock protein71, pre‑mRNA processing factor19, polypyrimidine tract binding protein1, translationally controlled tumor protein, CathepsinD, Cytochromec, thioredoxin domain containing5, MutS homolog (MSH)6, AnnexinA2 (ANXA2), BRCA2 and Cyclin dependent kinase inhibitor1A interacting protein, MSH2, protein phosphatase2A 55kDa regulatory subunitBα, Rho glyceraldehyde‑3‑phosphate‑dissociation inhibitor1 and ANXA4] that were upregulated by >1.5‑fold in heavy(H)‑ and light(L)‑labeled A549R cells. In addition, 16 and 14proteins were downregulated by >1.5‑fold in the H‑ and L‑labeled A549R cells, respectively. The majority of the downregulated proteins were associated with apoptosis. In conclusion, the present study isolated a cisplatin‑resistant human lung cancer A549 cell clone, with reduced apoptosis and high levels of autophagy, in response to cisplatin treatment. In cisplatin‑resistant A549R cells, SILAC proteomics recognized the high expression of GRP78 and other proteins that are associated with anti‑apoptosis and/or autophagy promotion.

Plasticity in the Glucagon Interactome Reveals Novel Proteins That Regulate Glucagon Secretion in α-TC1-6 Cells.

Glucagon is stored within the secretory granules of pancreatic alpha cells until stimuli trigger its release. The alpha cell secretory responses to the stimuli vary widely, possibly due to differences in experimental models or microenvironmental conditions. We hypothesized that the response of the alpha cell to various stimuli could be due to plasticity in the network of proteins that interact with glucagon within alpha cell secretory granules. We used tagged glucagon with Fc to pull out glucagon from the enriched preparation of secretory granules in α-TC1-6 cells. Isolation of secretory granules was validated by immunoisolation with Fc-glucagon and immunoblotting for organelle-specific proteins. Isolated enriched secretory granules were then used for affinity purification with Fc-glucagon followed by liquid chromatography/tandem mass spectrometry to identify secretory granule proteins that interact with glucagon. Proteomic analyses revealed a network of proteins containing glucose regulated protein 78 KDa (GRP78) and histone H4. The interaction between glucagon and the ER stress protein GRP78 and histone H4 was confirmed through co-immunoprecipitation of secretory granule lysates, and colocalization immunofluorescence confocal microscopy. Composition of the protein networks was altered at different glucose levels (25 vs. 5.5 mM) and in response to the paracrine inhibitors of glucagon secretion, GABA and insulin. siRNA-mediated silencing of a subset of these proteins revealed their involvement in glucagon secretion in α-TC1-6 cells. Therefore, our results show a novel and dynamic glucagon interactome within α-TC1-6 cell secretory granules. We suggest that variations in the alpha cell secretory response to stimuli may be governed by plasticity in the glucagon “interactome.”

Liver parenchymal cells lacking Lipocalin 2 (LCN2) are prone to endoplasmic reticulum stress and unfolded protein response

Unfolded protein response (UPR) is an adaptive mechanism allowing the endoplasmic reticulum (ER) to react to an accumulation of unfolded proteins in its lumen, also known as ER stress. The UPR is interconnected with inflammation through several pathways such as reactive oxygen species (ROS) production resulting from the protein folding or alternatively, activation of nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) via IRE1, or induction of acute phase response (APR). Lipocalin 2 (LCN2) is one of the APR proteins induced under inflammatory conditions and up-regulated during ER stress. Upon incubation of Lcn2−/− and wild type (wt) primary hepatocytes with tunicamycin (TM) or thapsigargin (TG) we found the Lcn2−/− hepatocytes to react with strong UPR to the ER stress, as evidenced by significantly increased levels of Grp94, Bip and Chop mRNA and protein compared to the wt. TM and TG-treated hepatocytes activated p65 NF-κB and JNK, the pathways that respond to stress stimuli and playing a central role in inflammation and apoptosis, respectively. ER stress further activated and cleaved full-length CREBH/CREB3L3, the hepatocyte specific transcription factor to induce systemic inflammatory responses. Upregulation of the C/EBP homologous protein (CHOP) was very prominent in Lcn2−/− hepatocytes and sustained until 48 h, resulting in hepatocyte apoptosis as evidenced by increased cleaved caspase 3. We also explored the UPR of the Lcn2 null mouse livers in acute intoxication and inflammation stages with a single application of lipopolysaccharide (LPS) or carbon tetrachloride (CCl4). The Lcn2 null mice clearly developed stronger UPR in LPS- and CCl4-induced ER stress compared to the wt. Our findings indicate that the upregulation of LCN2 during ER stress-induced inflammatory responses protects hepatocytes from being overwhelmed by UPR upon liver injury.

The clinical and prognostic evaluation of GRP94 immunoexpression in Caucasian patients with colorectal adenocarcinoma.

IntroductionColorectal cancer (CRC) is traditionally regarded as the most commonly diagnosed gastrointestinal malignant disease. Nevertheless, despite advances in diagnosis and novel therapeutic options, the clinical outcomes of patients are still unsatisfactory.AimTo investigate the clinicopathological and prognostic roles of GRP94 expression, the immunohistochemical investigation was performed on samples of CRC tumour tissues, adjacent non-pathological mucosa, and metastatic foci in regional lymph nodes in Caucasian patients.Material and methodsParaffin-embedded adenocarcinoma samples were assessed immunohistochemically for GRP94 protein and scored according to the percentage of cells with positive reaction combined with staining intensity. Connections between GRP94 immunoexpression and clinicopathological factors including the overall survival (OS) were evaluated.ResultsThe level of the GRP94 immunohistochemical reactivity was correlated with the grade of the histological differentiation (H (2.92) = 25.906; p < 0.001), size of the primary tumour (Z = –4.010; p < 0.001), regional lymph node involvement (Z = –6.547; p < 0.001), and perineural invasion (Z = –6.235; p < 0.001). Kaplan-Meier survival analysis showed that the survival time for patients with a low expression of GRP94 was significantly longer than that for patients with a moderate or strong level of GRP94 immunoreactivity (p < 0.001).ConclusionsAn enhanced level of GRP94 immunoexpression was significantly associated with malignancy-related clinicopathological factors and reduced the 5-year overall survival in CRC patients. However, a multivariate analysis demonstrated that GRP94 was not revealed as an independent risk factor for CRC prognosis.

Long Interleukin-22 Binding Protein Isoform-1 Is an Intracellular Activator of the Unfolded Protein Response.

The human IL22RA2 gene co-produces three protein isoforms in dendritic cells [IL-22 binding protein isoform-1 (IL-22BPi1), IL-22BPi2, and IL-22BPi3]. Two of these, IL-22BPi2 and IL-22BPi3, are capable of neutralizing the biological activity of IL-22. The function of IL-22BPi1, which differs from IL-22BPi2 through an in-frame 32-amino acid insertion provided by an alternatively spliced exon, remains unknown. Using transfected human cell lines, we demonstrate that IL-22BPi1 is secreted detectably, but at much lower levels than IL-22BPi2, and unlike IL-22BPi2 and IL-22BPi3, is largely retained in the endoplasmic reticulum (ER). As opposed to IL-22BPi2 and IL-22BPi3, IL-22BPi1 is incapable of neutralizing or binding to IL-22 measured in bioassay or assembly-induced IL-22 co-folding assay. We performed interactome analysis to disclose the mechanism underlying the poor secretion of IL-22BPi1 and identified GRP78, GRP94, GRP170, and calnexin as main interactors. Structure-function analysis revealed that, like IL-22BPi2, IL-22BPi1 binds to the substrate-binding domain of GRP78 as well as to the middle domain of GRP94. Ectopic expression of wild-type GRP78 enhanced, and ATPase-defective GRP94 mutant decreased, secretion of both IL-22BPi1 and IL-22BPi2, while neither of both affected IL-22BPi3 secretion. Thus, IL-22BPi1 and IL-22BPi2 are bona fide clients of the ER chaperones GRP78 and GRP94. However, only IL-22BPi1 activates an unfolded protein response (UPR) resulting in increased protein levels of GRP78 and GRP94. Cloning of the IL22RA2 alternatively spliced exon into an unrelated cytokine, IL-2, bestowed similar characteristics on the resulting protein. We also found that CD14++/CD16+ intermediate monocytes produced a higher level of IL22RA2 mRNA than classical and non-classical monocytes, but this difference disappeared in immature dendritic cells (moDC) derived thereof. Upon silencing of IL22RA2 expression in moDC, GRP78 levels were significantly reduced, suggesting that native IL22RA2 expression naturally contributes to upregulating GRP78 levels in these cells. The IL22RA2 alternatively spliced exon was reported to be recruited through a single mutation in the proto-splice site of a Long Terminal Repeat retrotransposon sequence in the ape lineage. Our work suggests that positive selection of IL-22BPi1 was not driven by IL-22 antagonism as in the case of IL-22BPi2 and IL-22BPi3, but by capacity for induction of an UPR response.

Hypoxia-mediated alteration in cholesterol oxidation and raft dynamics regulates BDNF signalling and neurodegeneration in hippocampus.

Brain-derived neurotrophic factor (BDNF) which is primarily associated with neuronal survivability, differentiation and synaptic plasticity has been reported to mediate neurodegeneration in hypoxia through its p75 Neurotrophin receptors (p75NTR). The molecular events promoting BDNF-mediated pro-death signalling in hypoxia, however, still remain an enigma. This study attempts towards deciphering the signalling cascades involved in alteration of BDNF isoforms and its cognate receptor subtypes leading to neurodegeneration in hypoxia. Adult Sprague-Dawley rats were exposed to global hypobaric hypoxia simulating an altitude of 7620m at standard temperature and humidity. Chronic hypoxic exposure for 7days resulted in higher expression of pro-BDNF and alteration in N-linked glycosylation in hippocampus along with increased expression of endoplasmic reticulum stress markers viz., glucose-regulated protein (Grp78), calnexin and changes in the endoplasmic reticulum morphology. Our findings reveal enriched expression of p75NTR in lipid rafts and higher expression of tyrosine receptor kinase β (Trkβ) in non-raft regions following hypoxic exposure. Further investigations on membrane properties revealed decline in membrane fluidity along with increased cholesterol oxidation resulting in reduced translocation of Trkβ from non-raft to raft regions. Supplementation of vitamin E during hypoxic exposure on the other hand reduced cholesterol oxidation and increased translocation of Trkβ from non-raft to raft regions and promoted neuronal survival. Hence, our findings suggest a novel mechanism of cholesterol oxidation-induced alteration in raft dynamics which is promotes p75 receptor-mediated death signalling in hippocampal neurons during chronic hypoxia.

Effects of sera of rats fed with Huganqingzhi tablets on endoplasmic reticulum stress in a HepG2 cell model of nonalcoholic fatty liver disease

To investigate the effects of sera from rats fed with Huganqingzhi tablets (HGT) on endoplasmic reticulum (ER) stress in a steatotic hepatocyte model of free fatty acids (FFAs)-induced nonalcoholic fatty liver disease (NAFLD) and explore the possible mechanism. FFAs prepared by mixing oleic acid and palmitic acid at the ratio of 2:1. HepG2 cells were treated with the sera from rats fed with low-, moderate-or high-dose HGT (HGT sera) or sera of rats fed with fenofibrate (fenofibrate sera), followed by treatment with 1 mmol/L FFAs for 24 h to induce hepatic steatosis. Oil red O staining was used to observe the distribution of lipid droplets in the cells. The biochemical parameters including triglyceride (TG), lactated hydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured using a commercial kit. The morphological changes of the ER in the cells were observed using transmission electron microscopy. The protein/mRNA expressions of ER stress-related signal molecules including GRP78, PERK, p-PERK, ATF6, ATF4, CASPASE-12, CHOP, XBP-1, PKC, and p-PKC-δ were detected using Western blotting and/or quantitative real-time PCR (qRT-PCR). The changes in the protein expressions of GRP78, p-PERK, CASPASE-12 and CHOP were also detected in cells with transient transfection of PKC-δ siRNA for PKC-δ knockdown. Compared with the control cells, the cells treated with FFAs showed significantly increased levels of TG, AST, and ALT (P &lt; 0.05). Compared with FFAs-treated cells, the cells pretreated with HGT sera or fenofibrate sera all showed significantly decreased TG, AST and ALT levels (P &lt; 0.05), reduced accumulation of the lipid droplets (P &lt; 0.05), and lowered protein or mRNA expression levels of GRP78, p-PERK, ATF6, ATF4, CHOP, CASPASE-12, XBP-1 and p-PKC-δ (P &lt; 0.05). PKC-δ knockdown caused significantly reduced protein expressions of GRP78, p-PERK, CASPASE-12 and CHOP in the cells with FFA-induced hepatic steatosis (P &lt; 0.001); treatment with high-dose HGT serum more significantly reduced the expressions of GRP78 (P &lt; 0.001) and P-PERK (P &lt; 0.01) in FFAs-induced cells with PKC-δ knockdown. HGT serum can effectively prevent FFAs-induced steatosis in HepG2 cells by alleviating ER stress, in which PKC-δ may act as an important target.

Spatiotemporal Expression of GRP78 in the Blood Vessels of Rats Treated With 3-Nitropropionic Acid Correlates With Blood-Brain Barrier Disruption.

Glucose-regulated protein (GRP78) or BiP, a 78-kDa chaperone protein located in the endoplasmic reticulum (ER), has recently been reported to be involved in the neuroglial response to ischemia-induced ER stress. The present study was designed to study the expression patterns of this protein and the cell types involved in the induction of GRP78 expression in rats treated with the mitochondrial toxin 3-nitropropionic acid (3-NP). GRP78 immunoreactivity was almost exclusively localized to striatal neurons in saline-treated controls, but GRP78 expression was induced in activated glial cells, including reactive astrocytes and activated microglia/macrophages, in the striata of rats treated with 3-NP. In the lesion core, increased GRP78 immunoreactivity was observed in the vasculature; this was evident in the lesion periphery of the core at 3 days after lesion induction, and was evenly distributed throughout the lesion core by 7 days after lesion induction. Vascular GRP78 expression was correlated, both temporally and spatially, with infiltration of activated microglia into the lesion core. In addition, this was coincident with the time and pattern of blood–brain barrier (BBB) leakage, detected by the extravasation of fluorescein isothiocyanate-albumin, an established BBB permeability marker. Vascular GRP78-positive cells in the lesion core were identified as endothelial cells, smooth muscle cells, and adventitial fibroblast-like cells, in which GRP78 protein was specifically localized to the cisternae of the rough ER and perinuclear cisternae, but not to other organelles such as mitochondria or nuclei. Thus, our data provide novel insights into the phenotypic and functional heterogeneity of GRP78-positive cells within the lesion core, suggesting the involvement of GRP78 in the activation/recruitment of activated microglia/macrophages and its potential role in BBB impairment in response to a 3-NP-mediated neurotoxic insult.

Icariside II prevents hypertensive heart disease by alleviating endoplasmic reticulum stress via the PERK/ATF-4/CHOP signalling pathway in spontaneously hypertensive rats.

Reducing endoplasmic reticulum stress (ERS)-induced cardiomyocyte apoptosis is a key strategy for preventing hypertensive heart disease. In our previous study, Icariside II can improve left ventricular remodelling in spontaneously hypertensive rats (SHRs). This study aims to determine whether Icariside II can exert its effect by inhibiting ERS-induced cardiomyocyte apoptosis via the PERK/ATF-4/CHOP signalling pathway. Spontaneously hypertensive rats were randomly divided into model group and Icariside II groups. The rats in the Icariside II groups were intragastrically administrated with Icariside II 4, 8 and 16 mg/kg from 14 to 26 week-age, respectively. The left ventricular function was measured at the 18, 22 and 26 week-age by small animal ultrasound. At the end of the 26th week, cardiomyocyte apoptosis was analysed and the levels of GRP78, PERK, ATF-4 and CHOP gene and protein were detected. The function of left ventricular became declined with age in SHRs, but improved in Icariside II groups. Myocardial apoptosis was aggravated in SHRs, but alleviated in Icariside II groups. Icariside II could reduce the levels of GRP78, PERK, ATF-4, CHOP gene and protein that increased in SHRs. Icariside II prevents hypertensive heart disease by alleviating ERS-induced cardiomyocyte apoptosis, and its mechanism is related to the impediment of the PERK/ATF-4/CHOP signalling pathway.

Endoplasmic reticulum stress contributes to the pathogenesis of stress urinary incontinence in postmenopausal women.

ObjectiveTo investigate the relationship between endoplasmic reticulum stress (ERS) and the pathogenesis of stress urinary incontinence (SUI) in postmenopausal women.MethodsAnterior vaginal wall tissue was collected from postmenopausal women with SUI and control subjects. Western blotting was performed for glucose-regulated protein (GRP78), inositol-requiring enzyme 1(IRE1), protein kinase-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2). Additionally, mRNA expression levels of PERK, activating transcription factor 4 (ATF4), and CHOP were examined by real-time polymerase chain reaction.ResultsGRP78 protein and mRNA expression levels were significantly lower in women with SUI, compared with control subjects. PERK and p-PERK expression levels were higher in women with SUI than in control subjects. However, no differences in IRE1 or ATF6 expression levels were observed in either group. Notably, higher CHOP and lower Bcl-2 protein expression levels were detected in women with SUI, compared with control subjects. Furthermore, PERK, ATF4, and CHOP mRNA expression levels were significantly higher in women with SUI than in control subjects.ConclusionsAlterations of ERS markers in SUI suggest that ERS may be involved in the development of SUI in postmenopausal women.

Protective effect of Wuzi Yanzong recipe on testicular dysfunction through inhibition of germ cell apoptosis in ageing rats via endoplasmic reticulum stress.

It has been demonstrated that excessively activated endoplasmic reticulum stress (ERS) is closely associated with ageing-related diseases and male reproductive dysfunction. Wuzi Yanzong recipe (WZ) is a classical Traditional Chinese Medicine prescription for treatment of male reproductive system diseases. However, it remains unknown whether WZ improves testicular dysfunction with ageing via ERS. In this study, we investigated the protective effects and its mechanism of WZ on testicular dysfunction in ageing rats. The results showed that treatment with WZ for 4months significantly increased the testicular weight and index, sperm count and viability, and the levels of testosterone and decreased the levels of estradiol. In addition, WZ significantly activated the onset of ERS and prevented germ cell apoptosis by upregulating the expression levels of ERS-responsive proteins GRP78, phospho-PERK, phospho-eIF2α, ATF4, phospho-IRE-1α, XBP1 and ATF6α, and downregulating the expression levels of pro-apoptotic proteins p-JNK, Caspase12 and CHOP in testicular germ cell of ageing rats. Besides, WZ significantly decreased the numbers of TUNEL-positive cells. Taken together, WZ effectively improves ageing-related testicular dysfunction through inhibition of germ cell apoptosis via ERS.

Protective effects of Astragaloside IV on endoplasmic reticulum stress-induced renal tubular epithelial cells apoptosis in type 2 diabetic nephropathy rats

Diabetic nephropathy (DN) has become the leading cause of end-stage renal disease (ESRD) worldwide. Renal tubular injury plays an important role in the development and progression of DN. And apoptosis of renal tubular epithelial cells (RTEC) contribute to the loss of renal function, increased levels of serum creatinine (SCr), blood urea nitrogen (BUN), urine total protein to urine creatinine and microalbuminuria and reduction of creatinine clear rate (CCr). Moreover, recent findings suggested that endoplasmic reticulum (ER) stress may lead to apoptosis of renal cells. Astragalosides IV (AS-IV) has a variety of pharmacological effects such as anti-apoptosis. Thus, in this study we investigated the effects and mechanisms of AS-IV on apoptosis of RTEC in high-fat diets (HFD) and low-dose streptozotocin (STZ)-induced type 2 DN rats. The results showed that AS-IV (40, 80 mg/kg) could alleviate RTEC apoptosis in DN rats. Furthermore, body weight, the majority of biochemical and renal function parameters and histopathological changes in the diabetic kidney were also improved by AS-IV. And AS-IV could reduce the expression of apoptosis-related proteins cleaved caspase-3, Bax/Bcl-2 ratio. ER stress-related proteins GRP78, p-PERK, ATF4 and CHOP were also inhibited by AS-IV in kidney of DN rats. Taken together, our study suggests that the protective effects of AS-IV may be related to inhibit ER stress-induced apoptosis through down-regulating the expression of p-PERK, ATF4 and CHOP. And our study provides a new theoretical basis for the clinical treatment of patients with kidney diseases.

Heterozygosity of Chaperone Grp78 Reduces Intestinal Stem Cell Regeneration Potential and Protects against Adenoma Formation.

Deletion of endoplasmic reticulum resident chaperone Grp78 results in activation of the unfolded protein response and causes rapid depletion of the entire intestinal epithelium. Whether modest reduction of Grp78 may affect stem cell fate without compromising intestinal integrity remains unknown. Here, we employ a model of epithelial-specific, heterozygous Grp78 deletion by use of VillinCreERT2-Rosa26ZsGreen/LacZ-Grp78+/fl mice and organoids. We examine models of irradiation and tumorigenesis, both in vitro and in vivo Although we observed no phenotypic changes in Grp78 heterozygous mice, Grp78 heterozygous organoid growth was markedly reduced. Irradiation of Grp78 heterozygous mice resulted in less frequent regeneration of crypts compared with nonrecombined (wild-type) mice, exposing reduced capacity for self-renewal upon genotoxic insult. We crossed mice to Apc-mutant animals for adenoma studies and found that adenomagenesis in Apc heterozygous-Grp78 heterozygous mice was reduced compared with Apc heterozygous controls (1.43 vs. 3.33; P < 0.01). In conclusion, epithelium-specific Grp78 heterozygosity compromises epithelial fitness under conditions requiring expansive growth such as adenomagenesis or regeneration after γ-irradiation. These results suggest that Grp78 may be a therapeutic target in prevention of intestinal neoplasms without affecting normal tissue.Significance: Heterozygous disruption of chaperone protein Grp78 reduces tissue regeneration and expansive growth and protects from tumor formation without affecting intestinal homeostasis. Cancer Res; 78(21); 6098-106. ©2018 AACR.

HERP depletion inhibits zearalenone-induced apoptosis through autophagy activation in mouse ovarian granulosa cells

HERP is an endoplasmic reticulum (ER) membrane protein and is strongly induced by stress conditions. A recent study has indicated that HERP cooperates in apoptosis during zearalenone (ZEA) treatment. However, regulatory mechanisms and the role of HERP in ZEA-induced apoptosis remain elusive in ovarian granulosa cells. In this study, MTT and flow cytometry assays demonstrated that ZEA gradually decreased cell viability and increased apoptosis in granulosa cells in a dose-dependent manner. Western blot analysis showed that ZEA significantly activated autophagy by upregulating LC3-II. Chloroquine (CQ) significantly increased LC3-II and induced granulosa cell apoptosis. Moreover, Western blot analysis showed that ZEA inhibited the mTOR and ERK1/2 signaling pathways. Furthermore, we found that ZEA activated ER stress by upregulating the ER stress-related proteins GRP78, HERP and CHOP. 4-PBA significantly decreased GRP78, HERP, CHOP and LC3-II. In addition, knockdown of HERP (shHERP) significantly protected ovarian granulosa cells from apoptosis induced by ZEA. We found that HERP depletion activated autophagy and ERK1/2 signaling pathways, while it inhibited the mTOR and caspase-dependent mitochondrial signaling pathways. In summary, autophagy and ER stress cooperated in apoptosis induced by ZEA; HERP depletion inhibits ZEA-induced apoptosis of ovarian granulosa cells through autophagy activation and apoptotic pathway inhibition.

Effect of Duration of Exposure to Fluoride and Type of Diet on Lipid Parameters and De Novo Lipogenesis.

The effect of duration of chronic treatment with fluoride (F, 50mg/L as NaF) on the lipid profile, lipid droplets and triglycerides (TG) in liver was evaluated in mice with nonalcoholic fatty liver disease (NAFLD) previously induced by hyperlipidic diet and in animals fed normocaloric diet. In addition, the effect of F administered for a short period (20days) was evaluated on de novo lipogenesis, by nuclear magnetic resonance. GRP78, Apo-E, and sterol regulatory element-binding protein (SREBP) were quantified by Western blotting. Our data indicate that F interferes in lipid metabolism and lipid droplets, having a different action depending on the exposure time and type of diet administered. F improved lipid parameters and reduced steatosis only when administered for a short period of time (up to 20days) to animals fed normocaloric diet. However, when NAFLD was already installed, lipid parameters were only slightly improved at 20days of treatment, but no effect was observed on the degree of steatosis. In addition, lipid profile was in general impaired when the animals were treated with F for 30days, regardless of the diet. Moreover, F did not alter de novo lipogenesis in animals with installed NAFLD. Furthermore, hyperlipidic diet increased F accumulation in the body. GRP78 increased, while Apo-E and SREBP decreased in the F-treated groups. Our results provide new insights on how F affects lipid metabolism depending on the available energy source.

Protective effect of Wuzi Yanzong recipe on testicular germ cell apoptosis in natural ageing rats through endoplasmic reticulum stress

To study the protective effects of Wuzi Yanzong recipe on testis germ cell apoptosis in natural ageing rats through endoplasmic reticulum stress (ERS), 16-month-old male SPF grade SD rats were randomly divided into three groups: ageing model group, and low and high-dose Wuzi Yanzong recipe groups (WZ, 1 and 4 g·kg⁻¹), with 10 rats in each group. In addition, 2-month-old SD male rats were used as adult control group. The ageing model group and the adult control group were fed with normal diet for 4 months. WZ groups were given the medicated feed for 4 months. After fasting for 12 hours, the rats were put to death. Then, the testes were immediately collected. The change of testicular tissue morphology was observed by HE staining. The expression levels of ER stress-related proteins GRP78, p-PERK, p-eif2α, ATF4, p-IRE1, XBP1, ATF6 and apoptosis-related proteins CHOP, caspase12 and p-JNK in testes were detected by Western blot. Compared with the ageing model group, Wuzi Yanzong recipe alleviated the morphological changes of testicular tissue. Western blot results showed that Wuzi Yanzong recipe significantly increased the expression levels of endoplasmic reticulum stress-related proteins GRP78, p-PERK, p-eif2α, ATF4, p-IRE1, XBP1, ATF6 and significantly decreased the expression levels of endoplasmic reticulum-induced apoptosis-related proteins CHOP, caspase 12 and p-JNK. In conclusion, Wuzi Yanzong recipe can alleviate the ageing-related apoptosis of testicular germ cells in natural ageing rats by regulating endoplasmic reticulum stress.

Taurine exhibits an apoptosis-inducing effect on human nasopharyngeal carcinoma cells through PTEN/Akt pathways in vitro.

Nasopharyngeal carcinoma (NPC) is a distinctive type of head and neck malignancy with a high incidence in southern China. Previous studies have confirmed that taurine shows an anti-cancer effect on a variety of human tumors by inhibiting cell proliferation and inducing apoptosis. However, the underlying molecular mechanism of its anti-cancer effect on NPC is not well understood. To clarify these anti-cancer mechanisms, we performed cell viability and colony formation assays. Apoptotic cells were quantified by flow cytometry. The expression levels of apoptosis-related proteins were evaluated by Western blot. The results showed that taurine markedly inhibited cell proliferation in NPC cells, but only slightly in an immortalized normal nasopharyngeal cell line. Taurine suppressed colony formation and induced apoptosis of NPC cell lines in a dose-dependent manner. Furthermore, taurine increased the active form of caspase-9/3 in a dose-dependent manner. Taurine down-regulated the anti-apoptotic protein Bcl-xL and up-regulated the pro-apoptotic protein Bax and GRP78, a major endoplasmic reticulum (ER) chaperone. These results suggest the involvement of mitochondrial and ER stress signaling in apoptosis. In addition, taurine increased the levels of PTEN (phosphatase and tensin homolog deleted on chromosome 10) and p53, and reduced phosphorylated Akt (protein kinase B). In conclusion, taurine may inhibit cell proliferation and induce apoptosis in NPC through PTEN activation with concomitant Akt inactivation.

Understanding the role of glucose regulated protein 170 (GRP170) as a nucleotide exchange factor through molecular simulations

Glucose Regulated Protein 170 (GRP170), also called Oxygen Regulated Protein 150 (ORP150), is a major molecular chaperone resident in the endoplasmic reticulum (ER). It belongs to the heat shock protein (HSP70) super family and can be induced by conditions such as hypoxia, ischemia and interferences in calcium homeostasis. It was recently reported that GRP170 may act as a nucleotide exchange factor (NEF) for GRP78 or binding immunoglobulin protein (BiP), and the ER canonical HSP70. However, little is known about the mechanism underlying its NEF activity. In this study, two homology models of GRP170 were constructed based on the X-ray crystal structures of ADP and ATP bound HSP110, a cytosolic homolog of GRP170, in order to characterize the differences in the binding modes of both ligands. It was observed that the differences in the binding modes of ADP and ATP led to a conformation change in the substrate binding domain which could potentially influence the binding of its substrates such as BiP. Our findings help understand the effect of nucleotide binding on the function of this chaperone protein as a NEF as well as the structural differences between GRP170 and its family members.

Low-frequency ultrasound enhances chemotherapy sensitivity and induces autophagy in PTX-resistant PC-3 cells via the endoplasmic reticulum stress-mediated PI3K/Akt/mTOR signaling pathway.

BackgroundSonodynamic therapy (SDT) is an emerging tumor-inhibiting method that has gained attention in cancer therapy in the last several years. Although autophagy has been observed in SDT-treated cancer cells, its role and mechanism of action remain unclear. This study aimed to investigate the effects of low-frequency ultrasound on autophagy and drug-resistance of paclitaxel (PTX)-resistant PC-3 cells via the endoplasmic reticulum stress (ERs)-mediated PI3K/AT/mTOR signaling pathway.MethodsCCK-8 assay was conducted to select the appropriate exposure time for PTX-resistant PC-3 cells under low-frequency ultrasound. PTX-resistant PC-3 cells were divided into a control group, PTX group, ultrasound group, ultrasound + PTX group, ultrasound + PTX + autophagy-related gene 5 (Atg5) siRNA group, and ultrasound + 4-PBA (an ERs inhibitor) group. Autophagy was observed by transmission electron microscopy (TEM) and fluorescence microscopy. Cell proliferation was evaluated using CCK-8 assay; apoptosis was detected by flow cytometry. Expression of multiple drug-resistance genes was detected by qRT-PCR. Western blotting was used to detect the expression of ERS-related proteins, autophagy-related proteins, apoptosis-related proteins, and PI3K/AKT/mTOR pathway-related proteins.ResultsTen-second exposure was selected as optimal for all experiments. Compared to the PTX group, the level of autophagy, inhibition rate, apoptosis rate, and expression of ERS-related proteins (GRP78) increased, whereas the expression of multiple drug-resistance genes (MRP3, MRP7, and P-glycoprotein), PI3K/AKT/mTOR pathway-related proteins (PI3K, p-AKT, mTORC1), and apoptosis-related proteins (Bcl-2, NF-κB) decreased in PTX-resistant PC-3 cells after low-frequency ultrasound and PTX treatment for 24 h. These trends were more obvious after treatment with Atg5 siRNA, excluding the autophagy level. Post 4-PBA-treatment, the expression of GRP78 and LC3II proteins decreased, whereas that of PI3K, p-AKT, and mTORC1 increased.ConclusionResults indicated that ultrasound induces autophagy by ERs-mediated PI3K/AKT/mTOR signaling pathway in PTX-resistant PC-3 cells; this autophagy acts as a cytoprotector during low-frequency ultrasound-mediated reversal of drug resistance.