Role of Herp in the endoplasmic reticulum stress response

Application of differential display to cultured rat astrocytes allowed cloning of Herp cDNA. Although Herp was strongly induced by endoplasmic reticulum (ER) stress, it decayed rapidly consequent to proteasome-mediated degradation. To investigate the role of this molecule in terms of the stress response, Herp knockout cells were developed using F9 embryonic carcinoma cells. F9 Herp null cells were more vulnerable to ER stress compared with F9 wild-type cells. In the early period of ER stress (0-8 h after tunicamycin treatment), Herp null cells displayed enhanced ER stress signalling and stabilization of an endogenous ERAD substrate, compared with wild-type cells. In the intermediate period (8-20 h after tunicamycin treatment), Herp null cells displayed reduced ER stress signalling, whereas in the late period (20-40 h after tunicamycin treatment), Herp null cells manifested irreversible cellular changes that lead to apoptotic cell death. Transfection analysis revealed that the N-terminal region, including the ubiquitin-like domain of Herp, was required for the survival of F9 cells under ER stress. These results indicate that Herp is a short-lived Ub-like protein improving the balance of folding capacity and protein loads in the ER and plays crucial roles for the ER stress resistance in F9 cells.     

动脉粥样硬化中炎性反应与内质网应激的相互作用简

 炎性反应和内质网应激均是动脉粥样硬化发生和发展过程中的重要事件。炎性反应可通过多条途径诱发内质网应激,而内质网应激在疾病的不同阶段可抑制或者促进炎性反应。     

Biochemical and ultrastructural evidence of endoplasmic reticulum stress in LGMD2I

Limb girdle muscular dystrophy type 2I (LGMD2I) is due to mutations in the fukutin-related protein gene (FKRP), encoding a putative glycosyltransferase involved in alpha-dystroglycan processing. To further characterize the molecular pathogenesis of LGMD2I, we conducted a histological, immunohistochemical, ultrastructural and molecular analysis of ten muscle biopsies from patients with molecularly diagnosed LGMD2I. Hypoglycosylation of alpha-dystroglycan was observed in all FKRP-mutated patients. Muscle histopathology was consistent with either severe muscular dystrophy or myopathy with a mild inflammatory response consisting of up-regulation of class I major histocompatibility complex in skeletal muscle fibers and small foci of mononuclear cells. At the ultrastructural level, muscle fibers showed focal thinning of basal lamina and swollen endoplasmic reticulum cisternae with membrane re-arrangement. The pathways of the unfolded protein response (UPR; glucose-regulated protein 78 and CHOP) were significantly activated in LGMD2I muscle tissue. Our data suggest that the UPR response is activated in LGMD2I muscle biopsies, and the observed histopathological and ultrastructural alterations may be related to sarcoplasmic structures involved in FKRP and alpha-dystroglycan metabolism and malfunctioning.     

Mechanisms and models of endoplasmic reticulum stress in chondrodysplasia

Chondrodysplasias are a group of genetic disorders that affect the development and growth of cartilage. These disorders can result in extreme short stature, craniofacial defects, joint malformation, and early osteoarthritis; severely impacting quality of life for affected individuals. Many chondrodysplasias are caused by mutations in genes encoding cartilage extracellular matrix (ECM) proteins. These mutations typically result in synthesis of abnormal proteins that are improperly folded, and hence inappropriately retained within the endoplasmic reticulum (ER) of the cell, activating ER stress and the unfolded protein response (UPR), an adaptive cellular response to minimize production of the mutant protein and/or to enhance protein folding, degradation or export. If prolonged, activation of the UPR causes apoptotic cell death. Many human disorders have an underlying mechanism in UPR activation, and targeting ER stress pathways is showing promise for development of therapeutics for these conditions. Understanding and modeling the UPR in chondrodysplasia will be essential to advance such targeted approaches for the benefit of chondrodysplasia patients. The focus of this review is to compare the mechanistic sequelae of ECM protein mutations in chondrodysplasia that may cause chondrocyte ER stress and UPR activation, and to present current and future directions in chondrodysplasia disease modeling and therapeutic intervention. Developmental Dynamics 243:875–893, 2014. © 2014 Wiley Periodicals, Inc.     

内质网应激与巨噬细胞M1/M2极化的研究进展

内质网应激(endoplasmic reticulum stress,ERS)与巨噬细胞M1/M2极化密切相关,在肿瘤疾病中ERS引起的未折叠蛋白反应能调控巨噬细胞向M1型方向极化而诱导炎症反应,在肺纤维化和动脉粥样硬化发病过程中能促进巨噬细胞向M2型方向极化而抑制炎症反应。因此,通过对二者关系的深入研究,可以更好地理解这些疾病的发病机制,也有助于研发新的治疗药物并提供新的治疗策略。     

Role of endoplasmic reticulum stress in age-related susceptibility to lung fibrosis

The incidence of idiopathic pulmonary fibrosis (IPF) increases with age. The mechanisms that underlie the age-dependent risk for IPF are unknown. Based on studies that suggest an association of IPF and γherpesvirus infection, we infected young (2-3 mo) and old (≥18 mo) C57BL/6 mice with the murine γherpesvirus 68. Acute murine γherpesvirus 68 infection in aging mice resulted in severe pneumonitis and fibrosis compared with young animals. Progressive clinical deterioration and lung fibrosis in the late chronic phase of infection was observed exclusively in old mice with diminution of tidal volume. Infected aging mice showed higher expression of transforming growth factor-β during the acute phase of infection. In addition, aging, infected mice showed elevation of proinflammatory cytokines and the fibrocyte recruitment chemokine, CXCL12, in bronchoalveolar lavage. Analyses of lytic virus infection and virus reactivation indicate that old mice were able to control chronic infection and elicit antivirus immune responses. However, old, infected mice showed a significant increase in apoptotic responses determined by in situ terminal deoxynucleotidyl transferase dUTP nick end labeling assay, levels of caspase-3, and expression of the proapoptotitc molecule, Bcl-2 interacting mediator. Apoptosis of type II lung epithelial cells in aging lungs was accompanied by up-regulation of endoplasmic reticulum stress marker, binding immunoglobulin protein, and splicing of X-box-binding protein 1. These results indicate that the aging lung is more susceptible to injury and fibrosis associated with endoplasmic reticulum stress, apoptosis of type II lung epithelial cells, and activation of profibrotic pathways.     

Enhanced apoptotic and reduced protective response in chondrocytes following endoplasmic reticulum stress in osteoarthritic cartilage

Endoplasmic reticulum (ER) stress has been shown to participate in many disease pathologies. Although recent reports have demonstrated that ER stress in chondrocytes is present in human osteoarthritis (OA), its role in the pathology of cartilage degeneration, such as chondrocyte apoptosis, remains unclear. In the present study, we investigated the expression of phosphorylated PERK (pPERK), ubiquitin (Ub), GRP78, CHOP, phosphorylated JNK (pJNK) and cleaved caspase-3 (C-CASP3) and the mRNA splicing of XBP1 (XBP1 splicing) in human OA cartilage by immunohistochemistry and RT-PCR. Additionally, human chondrocytes were treated with several concentrations of tunicamycin, an ER stress inducer, to assess the impact of ER stress on the mRNA expression of CHOP, XBP1 splicing and apoptosis, as determined by real-time PCR, RT-PCR and ELISA analyses respectively. In human OA cartilage, the number of chondrocytes expressing pPERK, Ub, CHOP and pJNK positively correlated with cartilage degeneration and the number of C-CASP3-positive chondrocytes. XBP1 splicing and GRP78 expression in severe OA containing the greatest number of C-CASP3-positive chondrocytes were similar to the levels in mild OA, however, XBP1 splicing was higher in moderate OA than in mild and severe OA. Tunicamycin dose dependently increased CHOP expression and apoptosis of cultured chondrocytes. Although tunicamycin upregulated XBP1 splicing in cultured chondrocytes, its impact on XBP1 splicing was weakened at higher concentrations. In conclusion, the present results indicate that ER stress may contribute to chondrocyte apoptosis along with OA progression, which was closely associated with an enhanced apoptotic response and a reduced protective response by the cells.     

Developmental changes of eukaryotic initiation factor 2B subunits in rat hippocampus

Regulated protein synthesis is critical for neural development, such as the formation of synapses and neural circuits and the modulation of synaptic plasticity. Protein synthesis is controlled by translation factors, including initiation, elongation and release factors. Here we investigated the developmental changes of eukaryotic initiation factor 2B (eIF2B) subunits in rat hippocampus. The eIF2B beta, gamma, delta and epsilon subunit protein levels were maximal at embryonic day 18 and then decreased during development. Aged hippocampus contained only trace amounts of these subunits. The finding that eIF2B subunit levels are high in developing hippocampus suggests that regulated protein synthesis is active in young, highly plastic brain.     

内质网应激在丙肝病毒感染发病学中作用的研究进展

丙型肝炎病毒(HCV)常扰乱内质网稳态,其复制中间产物的积累可导致内质网应激(ERS),与多种疾病的发生密切相关.为了应对内质网应激所带来的有害影响,细胞激活未折叠蛋白反应(UPR)和凋亡通路.在病毒感染的初期,未折叠蛋白反应主要用于清除病毒产生的蛋白和其他中间产物;而当感染进一步深化,稳态不能维持时细胞则激活凋亡通路...     

内质网应激中活化转录因子6通路及相关调控因子对未折叠蛋白反应的调控

目的内质网应激在多种疾病的发病机制中起到关键作用,持续或强烈的内质网应激反应可诱导细胞凋亡。作为一种内质网跨膜蛋白,活化转录因子6(ATF6)可以感受内质网应激并传递信号诱导未折叠蛋白反应。我们主要对ATF6通路以及其调控凋亡的机制进行综述,重要概述了相关激活剂和抑制剂,希望能为一些神经退行性疾病的治疗提供参考。     

动脉粥样硬化中巨噬细胞凋亡与内质网应激机制

巨噬细胞是机体免疫系统的重要细胞成份,具有多种生理功能,在动脉粥样硬化等血管疾病的发生和发展中具有重要作用.巨噬细胞凋亡是造成动脉粥样硬化斑块不稳定的重要因素,在晚期动脉粥样硬化中,内质网应激与巨噬细胞凋亡密切相关.目前已知的巨噬细胞凋亡途径包括外源性的死亡受体途径、内源性的线粒体途径及内质网应激凋亡途径,其中内质网应...     

Expression of the eukaryotic translation initiation factors 4E and 2alpha in non-Hodgkin's lymphomas.

Transition of cells from quiescence to proliferation requires an increase in the rate of protein synthesis, which is regulated in part by two key translation initiation factors, 4E and 2alpha. The expression and activity of both factors are increased transiently when normal resting cells are stimulated to proliferate. They are constitutively elevated in oncogene transformed cultured cells, and overexpression of either initiation factor in rodent cells makes them tumorigenic. In this study we investigate an association between the expression of translation initiation factors and lymphomagenesis. We have analyzed the expression of the protein synthesis initiation factors 4E and 2alpha by immunohistochemistry in reactive lymph nodes and several types of non-Hodgkin's lymphoma representing a wide range of clinical behaviors based on the Revised European-American Lymphoma behavioral classification. The study included 7 benign lymph nodes with follicular hyperplasia, 26 indolent lymphomas (6 marginal zone lymphomas, 7 small lymphocytic lymphomas, and 13 follicular lymphomas, grades 1 and 2), 16 moderately aggressive lymphomas (8 mantle cell lymphomas and 8 follicular lymphomas, grade 3), 24 aggressive lymphomas (14 large-B-cell lymphomas and 10 anaplastic large-cell lymphomas), and 15 highly aggressive lymphomas (7 lymphoblastic lymphomas and 8 Burkitt's lymphomas). Strong expression of initiation factors 4E and 2alpha was demonstrated in the germinal centers of reactive follicles. Minimal or no expression was seen in the mantle zones and surrounding paracortices, indicating that high expression of initiation factors 4E and 2alpha is associated with the active proliferation of lymphocytes. Most cases of aggressive and highly aggressive lymphomas showed strong expression of initiation factors 4E and 2alpha, in contrast to the cases of indolent and moderately aggressive lymphoma, in which their expression was intermediate between the germinal centers and the mantles of reactive follicles. A positive correlation was found between the expression of both initiation factors 4E and 2alpha and the Revised European-American Lymphoma behavior classification (P < 0.05). Thus, constitutively increased expression of initiation factors 4E and 2alpha may play an important role in the development of lymphomas and is correlated with their biological aggressiveness.     

Atg8 and Ire1 in combination regulate the autophagy-related endoplasmic reticulum stress response in Candida albicans

The unfolded protein response (UPR) is an important pathway to prevent endoplasmic reticulum (ER) stress in eukaryotic cells. In Saccharomyces cerevisiae, Ire1 is a key regulatory factor required for HAC1 gene splicing for further production of functional Hac1 and activation of UPR gene expression. Autophagy is another mechanism involved in the attenuation of ER stress by ER-phagy, and Atg8 is a core protein in autophagy. Both autophagy and UPR are critical for ER stress response, but whether they act individually or in combination in Candida albicans is unknown. In this study, we explored the interaction between Ire1 and the autophagy protein Atg8 for the ER stress response by constructing the atg8Δ/Δire1Δ/Δ double mutant in the pathogenic fungus C. albicans. Compared to the single mutants atg8Δ/Δ or ire1Δ/Δ, atg8Δ/Δire1Δ/Δ exhibited much higher sensitivity to various ER stress-inducing agents and more severe attenuation of UPR gene expression under ER stress. Further investigations showed that the double mutant had a defect in ER-phagy, which was associated with attenuated vacuolar fusion under ER stress. This study revealed that Ire1 and Atg8 in combination function in the activation of the UPR and ER-phagy to maintain ER homeostasis under ER stress in C. albicans.     

Morphological response of endoplasmic reticulum in cerebellar Purkinje cells to calcium deprivation.

Mobilisable intracellular Ca2+ stores are highly enriched in the cerebellum, particularly in Purkinje cells. We have detected, by light and electron microscopy, striking morphological changes in the presumed Ca2+ stores of Purkinje cells when slices of eight-day-old rat cerebellum were incubated in Ca(2+)-deficient media. After 30 min under these conditions, the endoplasmic reticulum became thinned and elongated. By 2 h, it was transformed into multilamellar, whorl-like inclusions with electron-dense cores. These changes were reversed on reintroduction of Ca2+. Analogous changes in other neurons were not observed. The results suggest that Ca2+ storage sites within Purkinje cells are capable of dramatic morphological change depending on the availability of Ca2+. The transformations may reflect, initially, depletion of Ca2+ from the stores and then homeostatic alterations in their capacity.     

钙蛋白酶2及自噬相关蛋白5对内质网应激诱导的肝细胞凋亡的影响

目的:探讨二硫苏糖醇(DTT)诱导大鼠正常肝细胞BRL-3A发生内质网应激(ERS)过程中钙蛋白酶2(calpain-2)及自噬相关蛋白5(Atg5)对肝细胞凋亡的影响。方法:采用2.0 mmol/L DTT处理BRL-3A细胞0、6、12和24 h,诱导细胞发生ERS;实时无标记细胞分析仪(RTCA)检测DTT对BRL-3A细胞增殖的影响;流式细胞术检测细胞凋亡及细胞周期;real-time PCR检测calpain-2和Atg5的m RNA表达;Western blot检测calpain-2、Atg5、Atg7、Atg12和微管相关蛋白1轻链3(LC3)蛋白水平的变化;免疫共沉淀(Co-IP)方法研究calpain-2与Atg5之间的相互作用。结果:不同浓度的DTT处理细胞后,细胞增殖受到显著抑制;流式细胞术检测凋亡发现,DTT处理BRL-3A细胞6、12和24 h后,细胞凋亡较0 h组显著增多(P<0.05)。流式细胞术检测细胞周期发现,DTT处理细胞后,细胞被阻滞在G1期(P<0.05)。DTT处理细胞6、12和24 h后,细胞中calpain-2和Atg5的m R...