Exercise-induced modulation of miR-149-5p and MMP9 in LPS-triggered diabetic myoblast ER stress: licorice glycoside E as a potential therapeutic target

Background:This study explores the relationship between endoplasmic reticulum(ER)stress and diabetes,particularly focusing on the impact of physical exercise on ER stress mechanisms and identifying potential therapeutic drugs and targets for diabetes-related sepsis.The research also incorporates traditional physical therapy perspectives,emphasizing the genomic insights gained from exercise therapy in disease management and prevention.Methods:Gene analysis was conducted on the GSE168796 and GSE94717 datasets to identify ER stress-related genes.Gene interactions and immune cell correlations were mapped using GeneCard and STRING databases.A screening of 2,456 compounds from the TCMSP database was performed to identify potential therapeutic agents,with a focus on their docking potential.Techniques such as luciferase reporter gene assay and RNA interference were used to examine the interactions between microRNA-149-5p and MMP9.Results:The study identified 2,006 differentially expressed genes and 616 miRNAs.Key genes like MMP9,TNF-α,and IL1B were linked to an immunosuppressive state.Licorice glycoside E demonstrated high affinity for MMP9,suggesting its potential effectiveness in treating diabetes.The constructed miRNA network highlighted the regulatory roles of MMP9,IL1B,IFNG,and TNF-α.Experimental evidence confirmed the binding of microRNA-149-5p to MMP9,impacting apoptosis in diabetic cells.Conclusion:The findings highlight the regulatory role of microRNA-149-5p in managing MMP9,a crucial gene in diabetes pathophysiology.Licorice glycoside E emerges as a promising treatment option for diabetes,especially targeting MMP9 affected by ER stress.The study also underscores the significance of physical exercise in modulating ER stress pathways in diabetes management,bridging traditional physical therapy and modern scientific understanding.Our study has limitations.It focuses on the microRNA-149-5p-MMP9 network in sepsis,using cell-based methods without animal or clinical trials.Despite strong in vitro findings,in vivo studies are needed to confirm licorice glycoside E’s therapeutic potential and understand the microRNA-149-5p-MMP9 dynamics in real conditions.

当归补血汤通过调控Sirt1/ER Stress 通路改善糖尿病脑病的机制研究

目的 通过动物实验探讨当归补血汤改善糖尿病脑病的作用机制。方法 选取C57/BL6小鼠进行糖尿病脑病造模,并使用当归补血汤对其进行干预,观察其血糖、体重变化;Morris水迷宫法检测糖尿病小鼠的认知障碍程度;HE染色观察糖尿病脑病小鼠海马区神经元细胞病理状态;Western Blot法检测小鼠大脑海马组织中Sirt1/ER Stress通路相关蛋白的表达情况。结果 动物实验结果显示当归补血汤对糖尿病脑病小鼠的海马神经元细胞具有保护作用,能够改善糖尿病小鼠海马区神经元细胞形态及数量,降低糖尿病脑病小鼠血糖,缩短小鼠潜伏期,并使其穿越平台次数增加,平台停留时间延长,提高小鼠海马内Sirt1表达水平,降低PERK,IRE-1a的表达水平。结论 当归补血汤能够改善糖尿病脑病小鼠的学习记忆能力,并且对Sirt1/ER Stress相关蛋白有积极的调控作用。

Ginkgolide K protects the heart against ER stress injury by activating the IRE1α/XBP1 pathway

OBJECTIVE Here we investigated the effects and the underlying mechanism of Ginkgolide K(1,10-dihydroxy-3,14-didehydroginkgolide,GK)on cardiac ER stress.METHODS Cell death,apoptosis,and ER stressrelated signalling pathwayswere measuredin cultured neonatal rat cardiomyocytes(NRCMs),treated with the ER stress inducers tunicamycin,hydrogen peroxide,and thapsigargin.Acute myocardial infarction was established using left coronary artery occlusion in mice,and infarct size was measured by triphenyltetrazolium chloride(TTC)staining.Echocardiography was used to assess heart function and transmission electron microscopy for evaluating ER expansion.RESULTS GK significantly decreased ER stress-induced cell death in both in vitro and in vivomodels.In ischemic injured mice,GK treatment reduced infarct size,rescued heart dysfunction and ameliorated ER dilation.Mechanistic studies revealed that the beneficial effects of GK occur through enhancement of inositol-requiring enzyme 1α(IRE1α)/X box-binding protein-1(XBP1)activity,which in turn leads to increased ER-associated degradation(ERAD)-mediated clearance of misfolded proteins and autophagy.In addition,GK is also able to partially repress the pro-apoptotic action of regulated IRE1-dependent decay(RIDD)and JNK pathway.CONCLUSION GK acts through selective activation of the IRE1α/XBP1 pathway to limit ER stress injury.GK is revealed as a promising therapeutic agent to ameliorate ER stress for treating cardiovascular diseases.

Magnesium Demethylcantharidate induces apoptosis in hepatocellular carcinoma cells via ER stress

Cantharidin(CTD)is a bioactive ingredient isolated from Cantharis vesicatoria(blister beetles),which has potential therapeutic value as an anticancer agent.Magnesium Demethylcantharidate(MDC)is a recently developed derivative of Cantharidin(CTD),and previous studies have illustrated its excellent anticancer activity on HCC cells.However,the effect and mechanism of MDC remains unclear and need to be further studied.In particular,whether MDC can cause ER stress in HCC is still unknown.In this study,we demonstrated that endoplasmic reticulum stress(ERS)-related proteins were changed in SMMC-7721 and Bel-7402 cells after being exposed to MDC.Moreover,we found that MDC could significantly inhibit the growth of xenograft tumor in nude mice.In summary,we confirmed that MDC could induce ERS in HCC cells and thus induce apoptosis.

ER Stress-Mediated Cell Damage Contributes to the Release of EDA~＋ Fibronectin from Hepatocytes in Nonalcoholic Fatty Liver Disease

Fibronectin containing extra domain A（EDA~＋ FN）,a functional glycoprotein participating in several cellular processes,correlates with chronic liver disease.Herein,we aim to investigate the expression and secretion of EDA~＋ FN from hepatocytes in nonalcoholic fatty liver disease（NAFLD） and the underlying mechanisms.Circulating levels of EDA~＋ FN were determined by ELISA in clinical samples.Western blotting and flow cytometry were performed on L02 and Hep G2 cell lines to analyze whether the levels of EDA~＋ FN were associated with endoplasmic reticulum（ER） stress-related cell death.Circulating levels of EDA~＋ FN in NAFLD patients were significantly higher than those in control subjects,and positively related with severity of ultrasonographic steatosis score.In cultured hepatocytes,palmitate up-regulated the expression of EDA~＋ FN in a dose-dependent manner.Conversely,when the cells were pretreated with 4-phenylbutyrate,a specific inhibitor of ER stress,up-regulation of EDA~＋ FN could be abrogated.Moreover,silencing CHOP by sh RNA enhanced the release of EDA~＋ FN from hepatocytes following palmitate treatment,which was involved in ER stress-related cell damage.These findings suggest that the up-regulated level of EDA~＋ FN is associated with liver damage in NAFLD,and ER stress-mediated cell damage contributes to the release of EDA~＋ FN from hepatocytes.

ER stress及PUMA对5-FU诱导的肝脏细胞损伤与凋亡的影响

【目的】探讨内质网应激(ERS)及p53上调凋亡调控因子(PUMA)在5-氟尿嘧啶(5-FU)诱导的肝脏细胞的损伤与凋亡中发挥的作用。【方法】给予10只PUMA基因敲除小鼠(PUMA-KO)和20只野生型小鼠(PUMA-WT)腹腔注射等剂量的5-FU,建立小鼠肝脏损伤模型,其中10只WT小鼠同时给予腹腔注射ER stress抑制剂4-苯基丁酸(4-PBA),对照组10只KO小鼠及20只WT小鼠给予等量生理盐水,造模完成后收集小鼠的血清及肝脏组织,评估肝脏病理损伤程度,检测血清中ALT及AST表达水平以及肝脏组织中PUMA及GRP78表达水平,观察这些指标在不同处理组小鼠的变化。【结果】与WT对照组相比,5-FU组小鼠血清ALT及AST水平明显升高,H&E染色可见点状局灶性坏死,伴出血和炎症,TUNEL染色可见凋亡细胞明显增多(Z=3.78,P <0.001),PUMA及GRP78表达明显升高,提示PUMA及ER stress均参与了5-FU诱导肝脏细胞损伤和凋亡。同等剂量的5-FU刺激下,4-PBA组小鼠肝脏组织GRP78及PUMA表达均下调,同时TUNEL结果显示肝脏细胞凋亡减轻(χ~2=32.99,Z=3.78,P <0.001),进一步证实PUMA及ER stress均参与了肝脏细胞损伤和凋亡过程;随后发现在等剂量的5-FU诱导时,Cleaved caspase-3免疫组化染色显示PUMA基因敲除小鼠肝脏组织凋亡信号较WT小鼠明显减少(χ~2=33.99,Z=3.78,P <0.001),但两组小鼠GRP78的表达差异不具有统计学意义。以上结果说明,抑制ER stress会降低PUMA的表达并减轻肝脏细胞损伤与凋亡,敲除PUMA并不影响ER stress的激活,仅仅会减轻肝脏细胞损伤与凋亡。【结论】5-FU通过激活内质网应激上调PUMA的表达,进而促进了肝脏细胞的损伤以及凋亡。

Protein kinase CK2 in the ER stress response

The endoplasmic reticulum is the central organelle within a eukaryotic cell where newly synthesized proteins are processed and properly folded. An excess of unfolded or mis-folded proteins induces ER stress signalling pathways. Usually this means a pro-survival strategy for the cell, whereas under extended stress conditions the ER stress signalling pathways have a pro-apoptotic function. CK2 plays a key role in the regulation of the pro-survival as well as the proapoptotic ER stress signalling by directly modulating the activities of members of the ER stress signalling pathways by phosphorylation, regulating the expression of the key factors of the signalling pathways or binding to regulator proteins. The present review will summarize the state of the art in this new emerging field.

Protective effect of hyperoside on cardiac ischemia reperfusion injury through inhibition of ER stress and activation of Nrf2 signaling

Objective:To study the protective effect of hyperoside(Hyp) on cardiac ischemia reperfusion injury and its potential mechanism.Methods:Rats were divided into two groups for the evaluation,the Hyp(50 uM Hyp;n=8) and the control group(n=8).Rat hearts were isolated and perfused with Krebs-Henseleit buffer(KHB) for 30 min.After being inhibited with cardioplegic solution,they were stored for 4 h in B21 solution at 4℃.Afterwards,rat hearts were perfused with KHB again for 45 min.In this period.Hyp was added into solutions of cardioplegia for storage and KHB.Parameters of cardiac functions,including heart rate,the systolic pressure of the left ventricle,the end-diastolic pressure of the left ventricle,the developed pressure of the left ventricle,the left-ventricular systolic pressure and the peak rise rate of the pressure of the left ventricle were recorded.The levels of adenosine triphosphate(ATP),the content of malondialdehyde and apoptotic cells were determined to evaluate the protective effect of Hyp on hearts suffered from ischemia reperfusion injury.Moreover,cultured cardiac myocytes were subjected to the process simulating ischemia/reperfusion.What were analyzed included the endoplasmic reticulum(ER) stress hallmarks expressions,such as binding immunoglobulin protein and C/EBP homologous protein,using the western blot and real-time PCR.Besides,the NF-E2-related factor 2(Nrf2) expression was measured to explore the potential mechanism.Results:Compared with the control group,the Hyp group had better cardiac functional parameters and higher ATP levels;pretreatment of Hyp greatly relieved the apoptosis of myocyte,decreased oxidative stress as well as ER stress and activated the signaling pathway of anti-oxidative Nrf2 to a further extent.Conclusions:Hyp plays an important role in preserving cardiac function by improving ATP levels of tissue,easing oxidative injury of myocardium and reducing apoptosis following IRI dramatically,while the ER stress inhibition and the downstream Nrf2 signaling activation may contribute to the effects of protection.

Protopanaxadiol derivative DDPU improvesbehaviorand cognitive deficitin AD mice involving regulation of both ER stress and autophagy

OBJECTIVE To explore the potential effect and mechanisms of protopanaxadiol deriva.tive 1-(3,4-dimethoxyphenethyl)-3-(3-dehydroxyl-20(s)-protopa-naxadiol-3 b-yl)-urea(DDPU) in the treatment of Alzheimer disease.METHODS ELISA assay was performed in both HEK293-APPswe and CHO-APP cells to demonstrate the efficacy of DDPU in reducing Ab level.SH-SY5 Y,primary neurons and astrocyte cellswereused to study the regulation of DDPU against the signaling pathways involved in Aβ/ER-stress pathology.APP/PS1 transgenic mice wereusedto study the regulation of DDPU against ADL and cognitive deficits.APP/PS1 transgenic mice were randomly placed into three groups(n=10):The two 6-month transgenic groups were administrated with 30 mg·kg^(-1) DDPU or vehicle and the 6-month non-transgenic group was administrated with vehicle for 100 days by intraperitonealinjec.tion.After 100-day administration,nest construction assay and Morris water maze(MWM) assay were applied to evaluate the daily living activities and cognitive abilities of the mice with continuous DDPU treatment.Upon completion of behavior assays,mice were euthanized,and the brains were removed and bisected in mid-sagittal plane.The right hemispheres were frozen and stored at-80°C,and the left hemispheres were fixed in 4% paraformaldehyde.RESULTS DDPU effectively improved learning and memory impairments in APP/PS1 transgenic mice,and the underlying mechanisms have been inten.sively investigated.DDPU reduced Ab production by inhibiting the PERK/eIF2 a signaling-mediated BACE1 translation,while promoted Ab clearance as a PI3K inhibitor thus negatively regulating PI3K/AKT/mTOR signaling in promotion of autophagy.Moreover,DDPU also exhibited neuroprotective effect by attenuating ER stress.Therefore,all findings have clearly demonstrated the crosstalk between Ab and ER stress,and confirmed that targeting ER stress should be a potential target for innovative anti-AD drug development,while highlighted the potential of DDPU in the treatment of AD.

ER stress活化促进星形胶质细胞NLRP3表达和IL-1β合成分泌

目的:研究Aβ所诱星形胶质细胞NLRP3炎症小体和IL-1β合成分泌的可能调节作用及潜在的分子机制。方法:全营养正常培养新生鼠皮层星形胶质细胞,分别应用ELISA、免疫荧光、Western blot等试验方法检测Aβ对于星形胶质细胞ER stress相关GRP78表达的影响,并通过药理学方法研究ER stress激活对于星形胶质细胞NLRP3蛋白表达以及IL-1β合成分泌的影响。结果:相比对照组,Aβ明显促进ER stress相关蛋白GRP78表达。应用ER stress诱导剂TM处理发现,TM显著促进星形胶质细胞IL-1β、pro-IL-1β以及NLRP3合成表达。另外,应用ER stress阻断剂Sal干预后发现,Sal能明显阻断Aβ所致星形胶质细胞NLRP3炎症小体表达活化。结论:Aβ能够诱导星形胶质细胞ER stress活化,并能通过活化ER stress水平显著促进IL-1β、pro-IL-1β和NLRP3炎症小体表达活化。

Oroxyloside protects against dextran sulfate sodium-induced colitis by inhibiting ER stress via PPARγ activation

Ulcerative colitis (UC), a prevalent form of inflammatory bowel disease (IBD), may result from immune system dysfunction, leading to the sustained overproduction of reactive oxygen species (ROS) and subsequent cellular oxidative stress damage. Recent studies have identified both peroxisome proliferator-activated receptor-γ (PPARγ) and endoplasmic reticulum (ER) stress as critical targets for the treatment of IBD. Oroxyloside (C22H20O11), derived from the root of Scutellaria baicalensis Georgi, has traditionally been used in treating inflammatory diseases. In this study, we investigated the molecular mechanisms by which oroxyloside mitigates dextran sulfate sodium (DSS)-induced colitis. We examined the effects of oroxyloside on ROS-mediated ER stress in colitis, including the protein expressions of GRP78, p-PERK, p-eIF2α, ATF4, and CHOP, which are associated with ER stress. The beneficial impact of oroxyloside was reversed by the PPARγ antagonist GW9662 (1 mg·kg^(−1), i.v.) in vivo. Furthermore, oroxyloside decreased pro-inflammatory cytokines and ROS production in both bone marrow-derived macrophages (BMDM) and the mouse macrophage cell line RAW 264.7. However, PPARγ siRNA transfection blocked the anti-inflammatory effect of oroxyloside and even abolished ROS generation and ER stress activation inhibited by oroxyloside in vitro. In conclusion, our study demonstrates that oroxyloside ameliorates DSS-induced colitis by inhibiting ER stress via PPARγ activation, suggesting that oroxyloside might be a promising effective agent for IBD.

Restoring cellular calcium homeostasis to rescue ER stress by 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid acetoxymethyl ester-loaded lipid-mPLGA hybrid-nanoparticles for acute kidney injury therapy

Early pathogenesis of ischemia-reperfusion(I/R)-induced acute kidney injury(AKI)is dominated by intracellular calcium overload,which induces oxidative stress,intracellular energy metabolism disorder,inflammatory activation,and a series of pathologic cascaded reactions that are closely intertwined with self-amplifying and interactive feedback loops,ultimately resulting in cell damage and kidney failure.Currently,most nanomedicines originate from the perspective of antioxidant stress,which can only quench existing reactive oxide species(ROS)but cannot prevent the continuous production of ROS,resulting in insufficient efficacy.As a safe and promising drug,BAPTA-AM is hydrolyzed into BAPTA by intracellular esterase upon entering cells,which can rapidly chelate with overloaded Ca^(2+),restoring intracellular calcium homeostasis,thus inhibiting ROS regeneration at the source.Here,we designed a KTP-targeting peptide-modified yolk-shell structure of liposome–poly(ethylene glycol)methyl ether-block-poly(L-lactide-co-glycolic)(mPLGA)hybrid nanoparticles(<100 nm),with the characteristics of high encapsulation rate,high colloid stability,facile modification,and prolonged blood circulation time.Once the BA/mPLGA@Lipo-KTP was targeted to the site of kidney injury,the cholesteryl hemisuccinate(CHEMS)in the phospholipid bilayer,as an acidic cholesterol ester,was protonated in the simulated inflammatory slightly acidic environment(pH 6.5),causing the liposomes to rupture and release the BA/mPLGA nanoparticles,which were then depolymerized by intracellular esterase.The BAPTA-AM was diffused and hydrolyzed to produce BAPTA,which can rapidly cut off the malignant loop of calcium overload/ROS generation at its source,blocking the endoplasmic reticulum(ER)apoptosis pathway(ATF4–CHOP–Bax/Bcl-2,Casp-12–Casp-3)and the inflammatory pathway(TNF-α–NF-κB–IL-6 axes),thus alleviating pathological changes in kidney tissue,thereby inhibiting the expression of renal tubular marker kidney injury molecule 1(Kim-1)(reduced by 82.9%)and also exhibiting prominent anti-apoptotic capability(TUNEL-positive ratio decreased from 40.2%to 8.3%),significantly restoring renal function.Overall,this research holds huge potential in the treatment of I/R injury-related diseases.

Lactobacillus plantarum AR113 attenuates liver injury in D-galactose-induced aging mice via the inhibition of oxidative stress and endoplasmic reticulum stress

Probiotics could effectively eliminate excess reactive oxygen species(ROS)generated during aging or lipid metabolism disorders,but their mechanism is unclear.The major purpose of this study was to investigate the mechanism of Lactiplantibacillus plantarun AR113 alleviating oxidative stress injury in the D-galactose induced aging mice.The result showed that pretreatment with L.plantarun AR113 significantly relieving H_(2)O_(2)induced cytotoxicity in HepG2 cells by maintain cell membrane integrity and increasing antioxidant enzyme activities.In D-galactose induced aging mice,L.plantarun AR113 could significantly attenuate liver damage and inflammatory infiltration by promoting endogenous glutathione(GSH)synthesis and activating the Nrf2/Keap1 signaling pathway in mice,and increasing the expression of regulated phaseⅡdetoxification enzymes and antioxidant enzymes.Further analysis shown that gavage of L.plantarun AR113 could significantly reduce the expression of G protein-coupled receptor 78(GPR78)and C/EBP homologous protein(CHOP)proteins,and promote the restoration of endoplasmic reticulum(ER)homeostasis,thereby activating cell anti-apoptotic pathways.These results were also confirmed in H_(2)O_(2)-treated HepG2 experiments.It indicated that L.plantarun AR113 could inhibit D-galactose-induced liver injury through dual inhibition of ER stress and oxidative stress.L.plantarun AR113 have good application potential in anti-aging and alleviating metabolic disorders.

The VAMP-associated protein VAP27-1 plays a crucial role in plant resistance to ER stress by modulating ER–PM contact architecture in Arabidopsis

The endoplasmic reticulum(ER)and the plasma membrane(PM)form ER–PM contact sites(EPCSs)that allow the ER and PM to exchange materials and information.Stress-induced disruption of protein folding triggers ER stress,and the cell initiates the unfolded protein response(UPR)to resist the stress.However,whether EPCSs play a role in ER stress in plants remains unclear.VESICLE-ASSOCIATED MEMBRANE PROTEIN(VAMP)-ASSOCIATED PROTEIN 27-1(VAP27-1)functions in EPCS tethering and is encoded by a family of 10 genes(VAP27-1–10)in Arabidopsis thaliana.Here,we used CRISPR-Cas9-mediated genome editing to obtain a homozygous vap27-1 vap27-3 vap27-4(vap27-1/3/4)triple mutant lacking three of the key VAP27 family members in Arabidopsis.The vap27-1/3/4 mutant exhibits defects in ER–PM connectivity and EPCS architecture,as well as excessive UPR signaling.We further showed that relocation of VAP27-1 to the PM mediates specific VAP27-1-related EPCS remodeling and expansion under ER stress.Moreover,the spatiotemporal dynamics of VAP27-1 at the PM increase ER–PM connectivity and enhance Arabidopsis resistance to ER stress.In addition,we revealed an important role for intracellular calcium homeostasis in the regulation of UPR signaling.Taken together,these results broaden our understanding of the molecular and cellular mechanisms of ER stress and UPR signaling in plants,providing additional clues for improving plant broad-spectrum resistance to different stresses.

The Lumen-Facing Domain Is Important for the Biological Function and Organelle-to-Organelle Movement of bZIP28 during ER Stress in Arabidopsis

The membrane-associated transcription factor, bZlP28, is relocated from the endoplasmic reticulum （ER） to the Golgi and proteolytically released from the membrane mediated by two proteases, SlP and S2P, in response to ER stress in Arabidopsis. The activated N-terminal domain recruits nuclear factor Y （NF-Y） subunits in the nucleus to regulate ER stress downstream genes. Little is known about the functions of the bZIP28 C-terminal lumen-facing domain. Here, we provide novel insights into how the ER lumen-facing domain affects the biological function and organelle-to-organelle movement of bZIP28 in the ER stress response. First, we demonstrated the functional redundancy of bZlP28 and bZIP60 by generation and analysis of the bZIP28 and bZIP60 double mutant zip28zip60. Subsequent genetic complementation experiments in zip28zip60 background with deletions on bZlP28 lumen-facing domain highlighted the importance of lumen-facing domain for its in vivo function of bZIP28 in the ER stress response. The protein subcellular localization and Western blotting results further revealed that the bZIP28 lumen-facing domain contains ER retention signal which is important for the proteolytic activation of bZIP28. Thus, the bZIP28 lumen-facing C-terminus plays important roles in the ER-to-Golgi movement of bZlP28, which may contribute to the sensing of the ER stress.

Class A scavenger receptor activation inhibits endoplasmic reticulum stress-induced autophagy in macrophage

Macrophage death in advanced atherosclerosis promotes plaque necrosis and destabilization.Involvement of autophagy in bulk degradation of cellular components has been recognized recently as an important mechanism for cell survival under endoplasmic reticulum（ER） stress.We previously found that the engagement of class A scavenger receptor（SR-A） triggered JNK-dependent apoptosis in ER-stressed macrophages.However,pro-apoptotic mechanisms mediated by SR-A are not fully understood.Therefore,we sought to see if SR-A mediated apoptosis was associated with autophagy in macrophages.Here,we showed that fucoidan inhibited microtubule-associated protein light chain 3-phospholipid conjugates（LC3-Ⅱ） formation as well as the number of autophagosomes under ER stress.The inhibition of LC3-Ⅱ formation was paralleled by the activation of the mTOR pathway,and the inhibition of mTOR allowed LC3-Ⅱ induction in macrophages treated with thapsigargin plus fucoidan.Furthermore,apoptosis induced by fucoidan was prevented under ER stress by the mTOR inhibitor.We propose that fucoidan,a SR-A agonist,may contribute to macrophage apoptosis during ER stress by inhibiting autophagy.

Site-1 protease cleavage site is important for the ER stress-induced activation of membrane-associated transcription factor bZIP28 in Arabidopsis

Many sources of stress cause accumulation of unfolded or misfolded proteins in endoplasmic reticulum(ER), which elicits the unfolded protein response(UPR) to either promote cell survival or programmed cell death depending on different developmental context or stress severity. The Arabidopsis membrane-associated transcription factor, b ZIP28, is the functional equivalent of mammalian ATF6, which relocates from the ER to the Golgi where it is proteolytically processed and released from the membrane to the nucleus to mediate the UPR. Although the canonical site-1 protease(S1P) cleavage site on the ER lumen-facing domain is well conserved between b ZIP28 and ATF6, the importance of S1 P cleavage on b ZIP28 has not been experimentally demonstrated. Here we provide genetic evidence that the RRIL573 site, but not the RVLM373 site, on the lumen-facing domain of bZ IP28 is critical for the biological function of b ZIP28 under ER stress condition. Further biochemistry and cell biology studies demonstrated that the RRIL573 site, but not the RVLM373 site, is required for proteolytic processing and nuclear relocation of b ZIP28 in response to ER stress. Our results reveal that S1 P cleavage site plays a pivotal role in activation and function of b ZIP28 during UPR in plants.

Blocking of N-acetylglucosaminyltransferase V induces cellular endoplasmic reticulum stress in human hepatocarcinoma 7721 cells

N-acetylglucosaminyltransferase V （GnT-V） is an important tumorigenesis and metastasis-associated enzyme. To study its biofunction, the GnT-V stably suppressed cell line （GnT-V-AS/7721） was constructed from 7721 hepatocarcinoma cells in previous study. In this study, cDNA array gene expression profiles were compared between GnT-V-AS/7721 and parental 7721 cells. The data indicated that GnT-V-AS/7721 showed a characteristic expression pattern consistent with the ER stress. The molecular mechanism of the ER stress was explored in GnT-V-AS/7721 by the analysis on key molecules in both two unfolded protein response （UPR） pathways. For ATF6 and Irel/XBP-1 pathway, it was evidenced by the up-regulation of BIP at mRNA and protein level, and the appearance of the spliced form ofXBP-1. As for PERK/eIF2α pathway, the activation of ER eIF2α kinase PERK was observed. To confirm the results from GriT-V-AS/7721 cells, the key molecules in the UPR were examined again in 7721 cells interfered with the GnT-V by the specific RNAi treatment. The results were similar with those from GnT-V-AS/7721, indicating that blocking of GnT-V can specifically activate ER stress in 7721 cells. Rate of 3H-Man incorporation corrected with rate of 3H-Leu incorporation in GnT-V-AS/7721 was down-regulated greatly compared with the control, which demonstrated the deficient function of the enzyme synthesizing N-glycans after GnT-V blocking. Moreover, the faster migrating form of chaperone GRP94 associated with the underglycosylation, and the extensively changed N-glycans structures of intracellular glycoproteins were also detected in GnT-V-AS/7721. These results supported the mechanism that blocking of GnT-V expression impaired functions of chaperones and N-glycan-synthesizing enzymes, which caused UPR in vivo.

Hes1 Knockdown Exacerbates Ischemic Stroke Following tMCAO by Increasing ER Stress-Dependent Apoptosis via the PERK/ eIF2a/ATF4/CHOP Signaling Pathway

Apoptosis induced by endoplasmic reticulum(ER)stress plays a crucial role in mediating brain damage after ischemic stroke.Recently,Hes1(hairy and enhancer of split 1)has been implicated in the regulation of ER stress,but whether it plays a functional role after ischemic stroke and the underlying mechanism remain unclear.In this study,using a mouse model of ischemic stroke via transient middle cerebral artery occlusion(tMCAO),we found that Hes1 was induced following brain injury,and that siRNA-mediated knockdown of Hes1 increased the cerebral infarction and worsened the neurological outcome,suggesting that Hes1 knockdown exacerbates ischemic stroke.In addition,mechanistically,Hes1 knockdown promoted apoptosis and activated the PERK/eIF2a/ATF4/CHOP signaling pathway after tMCAO.These results suggest that Hes1 knockdown promotes ER stress-induced apoptosis.Furthermore,inhibition of PERK with the specific inhibitor GSK2606414 markedly attenuated the Hes1 knockdown-induced apoptosis and the increased cerebral infarction as well as the worsened neurological outcome following tMCAO,implying that the protection of Hes1 against ischemic stroke is associated with the amelioration of ER stress via modulating the PERK/eIF2a/ATF4/CHOP signaling pathway.Taken together,these results unveil the detrimental role of Hes1 knockdown after ischemic stroke and further relate it to the regulation of ER stress-induced apoptosis,thus highlighting the importance of targeting ER stress in the treatment of ischemic stroke.

Salidroside Protects Against 6-Hydroxydopamine-Induced Cytotoxicity by Attenuating ER Stress

Parkinson＇s disease （PD） is a neurodegenera- tive disease characterized by a persistent decline of dopaminergic （DA） neurons in the substantia nigra pars compacta. Despite its frequency, effective therapeutic strategies that halt the neurodegenerative processes are lacking, reinforcing the need to better understand the molecular drivers of this disease. Importantly, increasing evidence suggests that the endoplasmic reticulum （ER） stress-induced unfolded protein response is likely involved in DA neuronal death. Salidroside, a major compound isolated from Rhodiola rosea L., possesses potent anti- oxidative stress properties and protects against DA neu- ronal death. However, the underlying mechanisms are not well understood. In the present study, we demonstrate that salidroside prevents 6-hydroxydopamine （6-OHDA）- induced cytotoxicity by attenuating ER stress. Further- more, treatment of a DA neuronal cell line （SN4741） and primary cortical neurons with salidroside significantly reduced neurotoxin-induced increases in cytoplasmic reactive oxygen species and calcium, both of which cause ER stress, and cleaved caspase-12, which is responsible for ER stress-induced cell death. Together, these results sug- gest that salidroside protects SN4741 cells and primary cortical neurons from 6-OHDA-induced neurotoxicity by attenuating ER stress. This provides a rationale for the investigation of salidroside as a potential therapeutic agent in animal models of PD.