IRE1 Signaling Pathway Research Articles

Mechanism of acupuncture and moxibustion in ameliorating liver injury induced by cisplatin by regulating IRE-1 signaling pathway.

To investigate the mechanism of the effect of acupuncture and moxibustion on improving liver injury in cisplatin (DDP) induced liver injury model mice by observing the changes of inositol-requiring enzyme (IRE) -1 signaling pathway. Forty KM mice were randomly divided into control, model, acupuncture and moxibustion groups, with 10 mice in each group. The liver injury model was replicated by intraperitoneal injection of DDP (10 mg/kg). In the acupuncture group and the moxibustion group, acupuncture and moxibustion were performed at "Dazhui"(GV14), and bilateral "Ganshu"(BL18), "Shenshu" (BL23), and "Zusanli"(ST36), respectively for 6 min, once per day for 7 d. The apoptosis of hepatocytes was detected by TUNEL staining. The expression of phosphorylation(p)-IRE-1α, glucose-regulated protein (Grp) 78 and cysteine aspartic protease (Caspase) -12 in liver tissue were detected by immunohistochemistry and Western blot, respectively. The expression levels of Grp78 and Caspase-12 mRNA in liver tissue were detected by quantitative real-time PCR. Compared with the control group, the apoptosis rate of hepatocytes was increased (P<0.05), the positive expression and protein expression of p-IRE-1α, Grp78, and Caspase-12 were increased (P<0.05), the expression levels of Grp78 and Caspase-12 mRNA were increased (P<0.05) in the model group. Compared with the model group, all these indicators showed opposite trends (P<0.05) in the acupuncture and moxibustion groups. Acupuncture and moxibustion can reduce liver injury due to DDP chemotherapy by modulating IRE-1 signaling pathway, inhibiting the excessive activation of endoplasmic reticulum stress, and reducing liver cell apoptosis.

UPR-Activated IRE1 Signaling Pathway Promotes Malignant Growth of Breast Cancer

Initially, it was believed that the unfolded protein response (UPR) was a network signal that synchronized apoptotic and adaptive responses to the buildup of unfolded proteins in the endoplasmic reticulum (ER). The endoplasmic reticulum stress sensor IRE1 is a major player in the UPR, and overactivation of IRE1 can promote a variety of pathological phenomena, such as diabetes, neurodegenerative diseases, and cancer. Under endoplasmic reticulum stress, IRE1 is activated through autophosphorylation and oligomerization, leading to conformational changes in the RNase domain, thereby promoting two signaling pathways: 1) unconventional splicing of XBP1 and 2) regulated IRE1 dependence Decay (RIDD). Research has revealed that aggressive B-type breast cancer cells typically have an overexpressed and amplified IRE1 gene. Through the RIDD mechanism, IRE1 processes and regulates the breakdown of a fraction of tumor-suppressing micro-RNA, which in breast cancer cells results in the Ras oncogene GTPase. RAB3B is elevated. This article reveals the mechanism of action of the IRE1 signaling pathway and the RIE1-RIDD-miRNA pathway in promoting the malignant development of luminal breast cancer.

HIV-1 replication requires optimal activation of the unfolded protein response.

Several human diseases including viral infections activate the unfolded protein response (UPR) due to abnormal accumulation of unfolded/misfolded proteins. However, UPR modulation and its functional relevance in HIV-1 infection lack comprehensive elucidation. This study reveals that HIV-1 activates IRE1, PERK, and ATF6 signaling pathways of UPR. The knockdown of PERK and ATF6 reduces HIV-1 long terminal repeat (LTR)-driven gene expression, whereas the endoplasmic reticulum (ER) chaperone HSPA5 prevents proteasomal degradation of HIV-1 p24 through its chaperone activity. Interestingly, overstimulation of UPR by a chemical inducer leads to anti-HIV activity through an enhanced type-1 interferon response. Also, treatment with a chemical ER stress inhibitor reduces HIV-1 replication. These findings suggest that an optimal UPR activation is crucial for effective viral replication, as either overstimulating UPR or inhibiting ER stress leads to viral suppression.

Melatonin Ameliorates Hepatic Ferroptosis in NAFLD by Inhibiting ER Stress via the MT2/cAMP/PKA/IRE1 Signaling Pathway.

Ferroptosis, an iron-dependent cell death form, has recently been observed in the development of non-alcoholic fatty liver disease (NAFLD). Melatonin (Mel) shows potential benefits for preventing and treating liver diseases. Whether and how Mel ameliorates hepatic ferroptosis in NAFLD is not fully understood. Here we established a mouse model of NAFLD induced by long-term high-fat diet (HFD) feeding. We found that Mel treatment ameliorated global metabolic abnormalities and inhibited the progression of NAFLD in mice. Most importantly, Mel supplementation significantly improved HFD-induced iron homeostasis disorders in the liver, including iron overload and ferritin transport disorders. For another, Mel ameliorated HFD-induced hepatic lipid peroxidation. The recuperative role of exogenous Mel on hepatocyte ferroptosis was also observed in PA- or Erastin-treated HepG2 cells. Mechanistically, MT2, but not MT1, was involved in the effect of Mel. Furthermore, Mel treatment inhibited HFD or Erastin-activated ER stress and activated the PKA/IRE1 signaling pathway. Co-expression of p-PKA and p-IRE1 was enhanced by the MT2 antagonist. Inhibitions of PKA and IRE1 respectively improved hepatocyte ferroptosis, and activations of cAMP/PKA reversed Mel's effect on ferroptosis. Collectively, these findings suggest that exogenous Mel inhibits hepatic ferroptosis in NAFLD by ameliorating ER stress through the MT2/cAMP/PKA/IRE1 pathway, proving that Mel is a promising candidate drug for the treatment of hepatic ferroptosis in NAFLD.

Acute deltamethrin exposure induces oxidative stress, triggers endoplasmic reticulum stress, and impairs hypoxic resistance of crucian carp

Deltamethrin (Del) has been widely used for effectively controlling ectoparasites of crucian carp and was also strictly prohibited in a hypoxic environment. A previous study indicated that Del exposure causes gill injury in Carassius auratus, which is associated with oxidative stress and endoplasmic reticulum stress (ER stress), but the precise mechanism is not well understood. Here, crucian carp were exposed to Del (0.61, 1.22, 2.44, 4.88 μg/L) for 24 h and then subjected to acute hypoxia challenge (1.0 mg/L) for 24 h. The results revealed that acute exposure to Del notably increased MDA content but markedly decreased CAT activities. Moreover, the T-AOC and SOD activities first increased and then decreased in the 4.88 μg/L Del group. Likewise, the mRNA levels of Nrf2 signaling and its target genes (ho-1, mt, sod, cat, and gpx1) were significantly downregulated in the high concentration exposure groups, while the mRNA levels of keap1 showed the opposite change trend. Meanwhile, Del exposure evoked the PERK-ATF4-CHOP and IRE1 signaling pathways and triggered ER stress in a dose-dependent manner in crucian carp. Importantly, we found that Del exposure significantly decreased the survival rate of crucian carp after hypoxia challenge by reducing oxygen uptake, modifying energy metabolism, and promoting lactate accumulation. Additionally, Del exposure aggravated gill damage and apoptosis under hypoxic stress, which was confirmed by histological assays. Collectively, we inferred that acute exposure to deltamethrin induces oxidative stress and ER stress and impairs hypoxic resistance of crucian carp.

Fatty acid palmitate suppresses FoxO1 expression via PERK and IRE1 unfolded protein response in C2C12 myotubes

Forkhead Box O1 (FoxO1) is a transcription factor with a unique fork head domain that indirectly participates in a variety of physiological processes and plays an important role in type 2 diabetes. Palmitate as the most abundant free fatty acid, accounting for 28–32% of total free fatty acids in human plasma. There is a direct relationship between palmitate and insulin resistance-induced type 2 diabetes. In addition, palmitate can activate the unfolded protein response signaling pathway induced by endoplasmic reticulum (ER) stress. This study aimed to investigate the response of FoxO1 to palmitate and the relationship with ER stress in C2C12 myotubes. Treatment of palmitate or tunicamycin promoted ER stress-related genes expression but suppressed FoxO1 expression, while 4-phenylbutyrate presented the opposite activity in palmitate-pretreated C2C12 myotubes, indicating that ER stress might be closely associated with FoxO1 expression. Moreover, palmitate-suppressed FoxO1 expression was reversed in C2C12 cells when the PERK and IRE-1 signaling pathway was inhibited by treatment with GSK2656157 or 4μ8C. However, no differences were observed when the ATF6 signaling pathway was suppressed by knockout of the ATF6 gene. These findings suggest that palmitate suppressed FoxO1 expression via the PERK and IRE1 signaling pathways.

Iron deficiency promotes aortic media degeneration by activating endoplasmic reticulum stress-mediated IRE1 signaling pathway

BackgroundAortic dissection (AD) is a macrovascular disease which is pathologically characterized by aortic media degeneration (AMD). Our team's previous research found that iron deficiency (ID) promoted the formation of AMD through presentative research. In this study, we aimed to investigate the underlying mechanism of ID promoting AMD formation. MethodsThe human aortic tissues were harvested from AD patients and organ donors. ApoE-/- mice were simultaneously given AngII infusion and low-iron feed to investigate the relationship between ID and AD. The IRE1-XBP1-CHOP signal axis of endoplasmic reticulum (ER) stress was selectively inhibited with 4μ8C. Iron contents were detected by Perls staining. The expression of iron metabolism and ER stress-relative proteins were analyzed by IF and western blotting. Apoptosis rates of aortic tissue and ASMCs were detected by TUNEL staining and flow cytometry, and ROS content was also measured by the flow cytometry. ResultsID was accompanied by ER stress in patients with AD. Among the three signaling pathways of ER stress in ID-induced AMD, proteins of IRE1, PERK and ATF6 signaling pathways were up-regulated by 2.65 times, 1.14 times and 1.24 times, respectively. ID was positively related to ER stress, mitochondrial oxidative stress and aortic media apoptosis in vivo and in vitro assays, while 4μ8C reversed the severity of ER stress and AMD. ConclusionsID could activate ER stress by eliciting mitochondrial oxidative stress to activate the IRE1-XBP1-CHOP signaling pathway in the ER, which accelerated the apoptosis of ASMCs in aortic media, thus promoting the formation of AMD.

Effects of Sodium Selenite and Dithiothreitol on Expression of Endoplasmic Reticulum Selenoproteins and Apoptosis Markers in MSF7 Breast Adenocarcinoma Cells

The endoplasmic reticulum (ER) stress inducers dithiothreitol (DTT) and sodium selenite (SS) were tested for effect on expression of ER selenoproteins and apoptosis markers in MCF7 breast adenocarcinoma cells. DTT used at 1 or 5 mM did not affect the survival of MCF7 cells. Based on the real-time PCR data and the protein expression levels of ER stress markers, ER stress was assumed to evolve along an adaptation pathway in MCF7 cells treated with 1 or 5 mM DTT, involving mainly the transcription factors IRE1 and ATF6 and the selenoproteins SELS, SELK, SELT, SELM, and SELN. Cell treatment with 0.01 μM SS decreases the mRNA levels of all genes examined. When the SS concentration was increased to 0.1 μM, an increase in expression was observed for key ER stress genes and apoptosis markers, including CHOP, GADD34, PUMA, BIM, ATF4, sXBP, uXBP, AKT1, BAX, and BAK. Higher SS concentrations were assumed to trigger the unfolded protein response (UPR) via a proapoptic signaling pathway involving PERK and an alternative IRE1 signaling pathway. Used at 1 μM, SS increased the mRNA levels of apoptosis markers, upregulated expression of a spliced form of XBP1, and substantially decreased the cell survival. SS (1 μM) was assumed to trigger apoptosis in MCF7 cells. The results indicate that both adaptive and proapoptic UPR signaling pathways are activated in cells, depending on the nature and concentration of the ER stress inducer.

Heat stress-induced endoplasmic reticulum stress promotes liver apoptosis in largemouth bass (Micropterus salmoides)

Heat stress (HS), an important factor that affects the physiological state of fish, is known to induce apoptosis. To investigate relationships among HS, endoplasmic-reticulum stress (ERS) and apoptosis in fish liver, 72 largemouth bass were randomly exposed to three different water temperatures (33 °C, 35 °C and 37 °C) for 6 h. Then, histological sections and TUNEL assays were analyzed to evaluate the physiological status of the liver. Transcriptome analysis and RT-qPCR were also performed to discover the key pathways involved. HS caused liver tissue damage, enhanced the apoptotic index and up-regulated the expressions of caspase-3, caspase-8, caspase-9 and ER stress marker genes such as grp78 and grp94. The differentially expressed genes (DEGs) under HS were mainly enhanced in ‘protein processing in endoplasmic reticulum’ pathway. In particular, the PERK and ATF6 pathway genes including perk, eif2a, atf4, chop, bcl-2 and atf6 were significantly up-regulated at 33 °C and 35 °C, while the IRE1 pathway genes including ire1, traf2, ask1, jnk1 and jnk2 were significantly up-regulated with increasing temperature. These findings suggest that HS induced apoptosis and damage of largemouth bass liver were mainly mediated via ER-stress and the IRE1-signaling pathways. This study, which is the first to reveal that HS-induced ER stress triggers cellular apoptosis in largemouth bass liver, could provide a new approach to the study of HS in fish in the context of global warming.

IRE1 and PERK signaling regulates inflammatory responses in a murine model of contact hypersensitivity.

Contact sensitizers may interfere with correct protein folding. Generation of un-/misfolded proteins can activate the IRE-1 or PERK signaling pathways initiating the unfolded protein response (UPR) and thereby determine inflammatory immune responses. We have analyzed the effect of sensitizers with different potencies on the induction of UPR activation/inhibition and the subsequent generation of a pro-inflammatory micromilieu in vitro as well as the effect of UPR modulation on the inflammatory response in the murine contact hypersensitivity (CHS) in vivo. Semi-quantitative and quantitative PCR, fluorescence microscopy, ELISA, NF-κB activation and translocation assays, DC/keratinocyte co-culture assay, FACS, and in vivo CHS experiments were performed. Sensitizers and irritants activate IRE-1 and PERK in murine and human keratinocytes. Synergistic effects occur after combination of different weak sensitizers / addition of irritants. Moreover, tolerogenic dinitrothiocyanobenzene can be converted into a strong sensitizer by pre-activation of the UPR. Blocking UPR signaling results in decreased NF-κB activation and cytokine production in keratinocytes and in activation marker downregulation in a HaCaT/THP-1 co-culture. Interestingly, not only systemic but also topical application of UPR inhibitors abrogates CHS responses in vivo. These observations highlight an important role of the UPR in determination of the inflammatory response in vitro and in vivo further underlining the importance of tissue stress and damage responses in the development of ACD and provide mechanistically based concepts as a basis for the development of new therapeutic approaches to treat allergic contact dermatitis.

Genetic inhibition of FABP4 attenuated endoplasmic reticulum stress and mitochondrial dysfunction in rhabdomyolysis-induced acute kidney injury

AimsRhabdomyolysis-associated acute kidney injury (AKI) is life-threatening but effective treatments is lacking. Recently, fatty acid-binding protein 4 (FABP4) has been identified as a mediator of ischemic and toxic AKI through regulating endoplasmic reticulum (ER) stress in our previous studies. However, the role of FABP4 in rhabdomyolysis-induced AKI and extended organelle dysfunctions need to be explored and validated. Main methodsWe firstly performed mRNA-seq and bioinformatic analysis to investigate the role of FABP4. The mouse model was established via injecting glycerol to FABP4 wild type (WT) and knockout (KO) mice. Blood biochemical, inflammatory and apoptotic parameters were measured and compared across groups. Representative pathways of ER stress and mitochondrial dysfunction were also detected and quantified. Key findingsComparing FABP4 WT and FABP4 KO model groups, FABP4 deficiency significantly attenuated renal dysfunction, by reducing serum creatinine (165.90 ± 15.61 μmol/L vs 35.5 ± 8.33 μmol/L, p < 0.0001) and blood urea nitrogen (89.78 ± 6.82 mmol/L vs 19.75 ± 5.97 mmol/L, p < 0.0001), and alleviating tubular injury scores. Inflammatory and apoptotic responses were alleviated by FABP4 genetic inhibition. Mechanistically, glycerol injection triggered ER stress characterized by activated IRE1, PERK, and ATF6 signaling pathways, and induced mitochondrial dysfunction supported by ultrastructural damage, energy metabolic derangement, and excessive mitochondrial fission (upregulated DRP1/downregulated OPA1). These two organelle dysfunctions were effectively relieved by FABP4 deficiency. SignificanceTaken together, genetic inhibition of FABP4 protected against rhabdomyolysis-induced AKI via reducing ER stress as well as mitochondrial dysfunction. FABP4 might act as a novel therapeutic target in rhabdomyolysis-induced AKI.

The Role of Epigallocatechin-3-Gallate in Autophagy and Endoplasmic Reticulum Stress (ERS)-Induced Apoptosis of Human Diseases.

Tea containing abundant catechins is a popular non-alcoholic beverage worldwide. Epigallocatechin-3-gallate (EGCG) is the predominately active substance in catechins, exhibiting a wide range of functional properties including cancer suppression, neuroprotective, metabolic regulation, cardiovascular protection, stress adjustment, and antioxidant in various diseases. Autophagy, a basic cell function, participates in various physiological processes which include clearing away abnormally folded proteins and damaged organelles, and regulating growth. EGCG not only regulates autophagy via increasing Beclin-1 expression and reactive oxygen species generation, but also causing LC3 transition and decreasing p62 expression. EGCG-induced autophagy is involved in the occurrence and development of many human diseases, including cancer, neurological diseases, diabetes, cardiovascular diseases, and injury. Apoptosis is a common cell function in biology and is induced by endoplasmic reticulum stress (ERS) as a cellular stress response which is caused by various internal and external factors. ERS-induced apoptosis of EGCG influences cell survival and death in various diseases via regulating IRE1, ATF6, and PERK signaling pathways, and activating GRP78 and caspase proteins. The present manuscript reviews that the effect of EGCG in autophagy and ERS-induced apoptosis of human diseases.

Novel Role of HAX-1 in Neurons Protection After Spinal Cord Injury Involvement of IRE-1.

Spinal cord injury (SCI) is one of the diseases with high probability of causing disability in human beings, and there is no reliable treatment at present. Neuronal apoptosis is a vital component of secondary injury and plays a critical role in the development of neurological dysfunction after spinal cord injury. In this study, we found that the expression and distribution of HAX-1 in neurons increased 1day after SCI. PC12 cells overexpressing HAX-1 showed decreased apoptosis and PC12 cells are more likely to undergo apoptosis after down-regulating HAX-1, which was confirmed via TUNEL experiments. We found GRP94 showed the same trend as HAX-1 in expression and interacted with HAX-1 and IRE-1 in both spinal cord tissue and PC12 cells, and this interaction seems to be enhanced after SCI. When the expression of HAX-1 was up-regulated, GRP94 also increased, but IRE-1 did not change at all. Further studies showed that overexpression of HAX-1 decreased the expression of pIRE-1, rather than IRE-1, and downstream proteins of the IRE signaling pathway (Caspase12, pJNK and CHOP) were significantly reduced, and vice versa. In animals treated with HAX-1 expressing adenovirus there are more neuronal cells remaining in the damaged spinal cord tissue, and hindlimb motor function of rats was significantly improved. So, we speculate that HAX-1 might play a role in protecting neurons from apoptosis after SCI by regulating the IRE-1 signaling pathway via promoting the dissociation of GRP94 from IRE-1. This may provide a theoretical basis and a potential therapeutic target for clinical improvement of neural function recovery after SCI.

A single-cell transcriptomic atlas of primate pancreatic islet aging.

Aging-related degeneration of pancreatic islet cells contributes to impaired glucose tolerance and diabetes. Endocrine cells age heterogeneously, complicating the efforts to unravel the molecular drivers underlying endocrine aging. To overcome these obstacles, we undertook single-cell RNA sequencing of pancreatic islet cells obtained from young and aged non-diabetic cynomolgus monkeys. Despite sex differences and increased transcriptional variations, aged β-cells showed increased unfolded protein response (UPR) along with the accumulation of protein aggregates. We observed transcriptomic dysregulation of UPR components linked to canonical ATF6 and IRE1 signaling pathways, comprising adaptive UPR during pancreatic aging. Notably, we found aging-related β-cell-specific upregulation of HSP90B1, an endoplasmic reticulum-located chaperone, impeded high glucose-induced insulin secretion. Our work decodes aging-associated transcriptomic changes that underlie pancreatic islet functional decay at single-cell resolution and indicates that targeting UPR components may prevent loss of proteostasis, suggesting an avenue to delaying β-cell aging and preventing aging-related diabetes.

Effects of High-Fat Diet on Steatosis, Endoplasmic Reticulum Stress and Autophagy in Liver of Tilapia (Oreochromis niloticus)

Hepatic steatosis is the most common phenomenon of lipid metabolism disorder in farmed fish, but its molecular mechanism is poorly understood. Therefore, the present study was aimed to investigate steatosis induced by high-fat diet (HFD) and explore underlying mechanism in tilapia. The fish were fed on control diet or HFD for 90 days. The blood and liver tissues were collected to determine biochemical parameters, genes expression and proteins level after 30, 60 and 90 days and analyzed lipid accumulation, endoplasmic reticulum (ER) stress and autophagy. After 30 days of feeding, the plasma and hepatic lipid content (TG, TCH, LDL-C and HDL-C) and fatty acids (FAs) transportation (fabp1 and CD36) were enhanced significantly in HFD-fed tilapia. After 60 days, the lipid metabolism disorder, such as increase of TG synthesis and free CH formation, and decrease of FAs β-oxidation and biosynthesis, was observed in liver of HFD-fed tilapia. Further, with increasing lipid accumulation, ER stress was induced and worsen hepatic steatosis via activating IRE1 signaling pathway in liver of HFD group after 90 days. Meanwhile, the autophagy was suppressed via impairing AMPK and BFET pathways in HFD-fed tilapia liver after 90 days. Our results demonstrated that HFD feeding induced extensive lipid deposition, promoted ER stress, suppressed autophagy in tilapia liver. Interestingly, these pathological features were positively correlated with the duration of HFD feeding.

IRE1 signaling pathway mediates protective autophagic response against manganese-induced neuronal apoptosis in vivo and in vitro

Overexposure to manganese (Mn) can result in neurotoxicity and is associated with manganism, a Parkinson's-like neurological disorder. In addition, Mn can induce endoplasmic reticulum (ER) stress and autophagy. In this study, we used C57BL/6 mice to establish a model of manganism and found that Mn could induce cell injury. Our results also showed that Mn could initiate the unfolded protein response (UPR) signaling and autophagy, via initiation of the UPR signaling occurring earlier than autophagy. We further investigated the intrinsic relationship between the endoplasmic reticulum to nucleus 1(ERN1, also known as inositol requiring enzyme 1, IRE1) signaling pathway and autophagy induction in SH-SY5Y cells exposed to Mn. Our results revealed that autophagy activation was a protective response in Mn-induced toxicity. Additionally, we found that Jun N-terminal kinase (JNK) inhibition downregulated autophagy and interaction of c-Jun with the Beclin1 promoter. In addition, knockdown of IRE1 with the LV-IRE1 shRNA suppressed the expression of IRE1, TRAF2, p-ASK1, and p-JNK in Mn-treated SH-SY5Y cells. Furthermore, the expression of proteins associated with ASK1-TRAF2 complex formation and autophagy activation were reversed by the LV-IRE1 shRNA. These findings suggest that IRE1 was involved in the activation of JNK through the formation of the ASK1-TRAF2 complex, and JNK activation led to the induction of autophagy, which required Beclin1 transcription by c-Jun. In this study, we demonstrated that the IRE1 signaling pathway mediated the activation of JNK signaling via the formation of the ASK1-TRAF2 complex which could initiate autophagy and the protein c-Jun which regulates Beclin1 transcription in Mn-induced neurotoxicity.

Activation of Signal Pathways of Apoptosis under Conditions of Prolonged ER-Stress Caused by Exposure of Mouse Testicular Teratoma Cells to Selenium-Containing Compounds.

Aim to study the molecular mechanisms of apoptotic death of mouse testicular teratocarcinoma cells (line F-9) under exposure to the widely used selenium-containing compounds with antitumor activity, sodium selenite and methylseleninic acid. Methods fluorescence microscopy, MTT assay, Western blotting. Results It was shown that sodium selenite at a concentration of 10 μM and methylseleninic acid at concentrations of 1 and 10 μM cause apoptosis-dependent death of F-9 cells, excluding necrotic death. Western blotting showed an increase in the expression of XBP1s when treating F-9 cells with 1 μM methylseleninic acid. Conclusions 10 μM methylseleninic acid leads to cell apoptosis, most likely by activation of the IRE1 signaling pathway under prolonged stress of the endoplasmic reticulum.

PRKCSH contributes to tumorigenesis by selective boosting of IRE1 signaling pathway

Unfolded protein response (UPR) is an adaptive mechanism that aims at restoring ER homeostasis under severe environmental stress. Malignant cells are resistant to environmental stress, which is largely due to an activated UPR. However, the molecular mechanisms by which different UPR branches are selectively controlled in tumor cells are not clearly understood. Here, we provide evidence that PRKCSH, previously known as glucosidase II beta subunit, functions as a regulator for selective activation of the IRE1α branch of UPR. PRKCSH boosts ER stress–mediated autophosphorylation and oligomerization of IRE1α through mutual interaction. PRKCSH contributes to the induction of tumor-promoting factors and to tumor resistance to ER stress. Increased levels of PRKCSH in various tumor tissues are positively correlated with the expression of XBP1-target genes. Taken together, our data provide a molecular rationale for selective activation of the IRE1α branch in tumors and adaptation of tumor cells to severe environmental stress.

The IRE1 signaling pathway is involved in the protective effect of low-dose LPS on myocardial ischemia-reperfusion injury

AimThe IRE1 signaling pathway is implicated in I/R injury. However, little is known about the involvement of this pathway in low-dose LPS treatment of myocardial I/R injury. Thus, an attempt was made to determine the relationship between the IRE1 pathway and I/R injury using rats or in vitro H9C2 cell myocardial I/R injury models. Main methodsSprague-Dawley rats and cultured H9C2 cells were pretreated with low-dose LPS and subjected to myocardial I/R injury models. Key findingsLow-dose LPS did not affect normal rat or cellular function. Compared with the I/R group, treatment with LPS attenuated myocardial apoptosis, decreased plasma LDH and CK-MB activities, reduced myocardium infarct size, and downregulated caspase-3 expression. Moreover, the protein or mRNA expression levels of the IRE1 signaling pathway-related proteins Grp78, IRE1, p-ASK1, ASK1, p-JNK, and JNK were notably increased during I/R injury but significantly decreased by low-dose LPS treatment both in rats and in H9C2 cells. SignificanceLow-dose LPS exhibited therapeutic effects in myocardial I/R injury. Most importantly, the cardioprotective mechanism of low-dose LPS may be associated with the IRE1 signaling pathway.

Melatonin receptor depletion suppressed hCG-induced testosterone expression in mouse Leydig cells

Melatonin receptors MT1 and MT2 (genes officially named MTNR1A and MTNR1B, respectively) play crucial roles in melatonin-mediated regulation of circadian rhythms, the immune system, and control of reproduction in seasonally breeding animals. In this study, immunolocalization assay showed that MT1 and MT2 are highly expressed in Leydig cell membrane. To understand the biological function of melatonin receptors in hCG-induced testosterone synthesis, we generated melatonin receptor knockdown cells using specific siRNA and performed testosterone detection after hCG treatment. We found that knockdown of melatonin receptors, especially MTNR1A, led to an obvious decrease (> 60%) of testosterone level. Our further study revealed that knockdown of melatonin receptors repressed expression, at both the mRNA level and the protein level, of key steroidogenic genes, such as p450scc, p450c17 and StAR, which are essential for testosterone synthesis. hCG triggered endoplasmic reticulum (ER) stress to regulate steroidogenic genes’ expression and apoptosis. To further investigate the potential roles of melatonin receptors in hCG-induced regulation of ER stress and apoptosis, we examined expression of some crucial ER stress markers, including Grp78, Chop, ATF4, Xbp1, and IRE1. We found that inhibition of melatonin receptors increased hCG-induced expression of Grp78, Chop and ATF4, but not Xbp1 and IRE1, suggesting that hCG may modulate IRE1 signaling pathways in a melatonin receptor-dependent manner. In addition, our further data showed that knockdown of MTNR1A and MTNR1B promoted hCG-induced expression of apoptosis markers, including p53, caspase-3 and Bcl-2. These results suggested that the melatonin receptors MTNR1A and MTNR1B are essential to repress hCG-induced ER stress and cell apoptosis. Our studies demonstrated that the mammalian melatonin receptors MT1 and MT2 are involved in testosterone synthesis via mediating multiple cell pathways.