内质网应激与哺乳动物雄性生殖

内质网应激 (endoplasmic reticulum stress,ERS) 激活未折叠蛋白反应,维持哺乳动物细胞的胞内稳态,过度持续的ERS导致细胞凋亡。最新研究表明,ERS对哺乳动物雄性生殖有重要的调节作用,包括对精母细胞、睾丸结构及精子发生的影响。ERS是研究生殖细胞生存和凋亡的新通路。雄性不育可能是由过度ERS引起的。本文通过简述ERS的最新研究进展,分析雄性生殖与ERS的关系,并从ERS调控雄性生殖角度提出新的理解和展望。     

Targeted Induction of Endoplasmic Reticulum Stress Induces Cartilage Pathology

Pathologies caused by mutations in extracellular matrix proteins are generally considered to result from the synthesis of extracellular matrices that are defective. Mutations in type X collagen cause metaphyseal chondrodysplasia type Schmid (MCDS), a disorder characterised by dwarfism and an expanded growth plate hypertrophic zone. We generated a knock-in mouse model of an MCDS–causing mutation (COL10A1 p.Asn617Lys) to investigate pathogenic mechanisms linking genotype and phenotype. Mice expressing the collagen X mutation had shortened limbs and an expanded hypertrophic zone. Chondrocytes in the hypertrophic zone exhibited endoplasmic reticulum (ER) stress and a robust unfolded protein response (UPR) due to intracellular retention of mutant protein. Hypertrophic chondrocyte differentiation and osteoclast recruitment were significantly reduced indicating that the hypertrophic zone was expanded due to a decreased rate of VEGF–mediated vascular invasion of the growth plate. To test directly the role of ER stress and UPR in generating the MCDS phenotype, we produced transgenic mouse lines that used the collagen X promoter to drive expression of an ER stress–inducing protein (the cog mutant of thyroglobulin) in hypertrophic chondrocytes. The hypertrophic chondrocytes in this mouse exhibited ER stress with a characteristic UPR response. In addition, the hypertrophic zone was expanded, gene expression patterns were disrupted, osteoclast recruitment to the vascular invasion front was reduced, and long bone growth decreased. Our data demonstrate that triggering ER stress per se in hypertrophic chondrocytes is sufficient to induce the essential features of the cartilage pathology associated with MCDS and confirm that ER stress is a central pathogenic factor in the disease mechanism. These findings support the contention that ER stress may play a direct role in the pathogenesis of many connective tissue disorders associated with the expression of mutant extracellular matrix proteins.     

Degradation of the Endoplasmic Reticulum by Autophagy during Endoplasmic Reticulum Stress in Arabidopsis

In this article, we show that the endoplasmic reticulum (ER) in Arabidopsis thaliana undergoes morphological changes in structure during ER stress that can be attributed to autophagy. ER stress agents trigger autophagy as demonstrated by increased production of autophagosomes. In response to ER stress, a soluble ER marker localizes to autophagosomes and accumulates in the vacuole upon inhibition of vacuolar proteases. Membrane lamellae decorated with ribosomes were observed inside autophagic bodies, demonstrating that portions of the ER are delivered to the vacuole by autophagy during ER stress. In addition, an ER stress sensor, INOSITOL-REQUIRING ENZYME-1b (IRE1b), was found to be required for ER stress–induced autophagy. However, the IRE1b splicing target, bZIP60, did not seem to be involved, suggesting the existence of an undiscovered signaling pathway to regulate ER stress–induced autophagy in plants. Together, these results suggest that autophagy serves as a pathway for the turnover of ER membrane and its contents in response to ER stress in plants.     

Effects of Metformin on Burn-Induced Hepatic Endoplasmic Reticulum Stress in Male Rats

Severe burn injury causes hepatic dysfunction that results in major metabolic derangements including insulin resistance and hyperglycemia and is associated with hepatic endoplasmic reticulum (ER) stress. We have recently shown that insulin reduces ER stress and improves liver function and morphology; however, it is not clear whether these changes are directly insulin mediated or are due to glucose alterations. Metformin is an antidiabetic agent that decreases hyperglycemia by different pathways than insulin; therefore, we asked whether metformin affects postburn ER stress and hepatic metabolism. The aim of the present study is to determine the effects of metformin on postburn hepatic ER stress and metabolic markers. Male rats were randomized to sham, burn injury and burn injury plus metformin and were sacrificed at various time points. Outcomes measured were hepatic damage, function, metabolism and ER stress. Burn-induced decrease in albumin mRNA and increase in alanine transaminase (p < 0.01 versus sham) were not normalized by metformin treatment. In addition, ER stress markers were similarly increased in burn injury with or without metformin compared with sham (p < 0.05). We also found that gluconeogenesis and fatty acid metabolism gene expressions were upregulated with or without metformin compared with sham (p < 0.05). Our results indicate that, whereas thermal injury results in hepatic ER stress, metformin does not ameliorate postburn stress responses by correcting hepatic ER stress.     

内质网应激与疾病

内质网是蛋白质合成与折叠、维持Ca²⁺动态平衡及合成脂类和固醇的场所。遗传或环境损伤引起内质网功能紊乱导致内质网应激,激活未折叠蛋白反应。未折叠蛋白反应是一种细胞自我保护性措施,但是内质网应激过强或持续时间过久可引起细胞凋亡。因此,内质网应激与众多人类疾病的发生发展密切相关。最近研究证明,癌症、炎症性疾病、代谢性疾病、骨质疏松症及神经退行性疾病等有内质网应激信号传递参与。然而内质网应激作为一个有效靶点参与各种疾病发挥作用的功能和机制仍然有待进一步研究。在近年来发表的文献基础上对内质网应激与疾病的关系,以及其可能的作用机制进行综述。     

皮质酮诱导小鼠腹腔巨噬细胞发生内质网应激的作用

目的:观察内源性糖皮质激素皮质酮对小鼠腹腔巨噬细胞内质网应激相关蛋白GRP78、XBP1-S及ATF6蛋白表达水平的影响,并探讨皮质酮诱导小鼠腹腔巨噬细胞内质网应激的作用.方法:分离成年雄性C57/BL6小鼠腹腔巨噬细胞,随机分为四组,分别以终浓度为0、10、50及1000 ng/ml皮质酮处理小鼠腹腔巨噬细胞,时间为1h,提取细胞总蛋白,应用Western blotting方法检测内质网分子伴侣GRP78蛋白及未折叠蛋白反应信号转导通路转录因子XBP1-S和ATF6蛋白质表达变化.结果:低浓度皮质酮(10、50ng/ml)处理小鼠腹腔巨噬细胞1h后,均可显著地增加内质网分子伴侣GRP78蛋白表达,以50ng/ml皮质酮组增加最明显,而当皮质酮浓度达1000ng/ml时,GRP78蛋白增加不显著.并且,低浓度皮质酮(10、50ng/ml)可显著增强未折叠蛋白反应两个重要转录因子XBP1-S和p50 ATF6蛋白表达.结论:这些结果表明低浓度内源性糖皮质激素皮质酮可诱发小鼠腹腔巨噬细胞发生内质网应激,激活未折叠蛋白质反应信号转导通路,其可能与巨噬细胞免疫功能增强有关.     

骨关节炎软骨细胞发生内质网应激

目的：研究骨关节炎软骨细胞是否发生内质网应激现象。方法：对关节置换术后的人类骨关节炎软骨标本和正常关节软骨标本切片进行内质网应激标志分子免疫球蛋白重链结合蛋白（BiP）的免疫组织化学检测;对小鼠膝关节进行半月板切断术诱发实验性骨关节炎,在术后1、3和6周取材,对组织切片进行番红花“O”染色、Mankin评分及BiP的免疫组织化学检测。结果：所有人类骨关节炎标本中软骨细胞BiP的表达明显升高。番红花“O”染色结果表明,在小鼠骨关节炎模型中,全部手术侧关节表面发生磨损,且随着术后时间延长关节表面磨损范围逐步扩大,手术侧Mankn分值显著高于对照侧;此外,手术侧的软骨细胞内BiP呈阳性表达,且表达量随术后时间延长而增加。结论：在人类骨关节炎标本和实验性小鼠骨关节炎模型中,关节软骨细胞均发生明显的内质网应激现象。     

Overexpression of the Matrix Metalloproteinase Matrilysin Results in Premature Mammary Gland Differentiation and Male Infertility

To examine the role of matrilysin (MAT), an epithelial cell-specific matrix metalloproteinase, in the normal development and function of reproductive tissues, we generated transgenic animals that overexpress MAT in several reproductive organs. Three distinct forms of human MAT (wild-type, active, and inactive) were placed under the control of the murine mammary tumor virus promoter/enhancer. Although wild-type, active, and inactive forms of the human MAT protein could be produced in an in vitro culture system, mutations of the MAT cDNA significantly decreased the efficiency with which the MAT protein was produced in vivo. Therefore, animals carrying the wild-type MAT transgene that expressed high levels of human MAT in vivo were further examined. Mammary glands from female transgenic animals were morphologically normal throughout mammary development, but displayed an increased ability to produce β-casein protein in virgin animals. In addition, beginning at approximately 8 mo of age, the testes of male transgenic animals became disorganized with apparent disintegration of interstitial tissue that normally surrounds the seminiferous tubules. The disruption of testis morphology was concurrent with the onset of infertility. These results suggest that overexpression of the matrix-degrading enzyme MAT alters the integrity of the extracellular matrix and thereby induces cellular differentiation and cellular destruction in a tissue-specific manner.     

Mild Endoplasmic Reticulum Stress Promotes Retinal Neovascularization via Induction of BiP/GRP78

Endoplasmic reticulum (ER) stress occurs as a result of accumulation of unfolded or misfolded proteins in the ER and is involved in the mechanisms of various diseases, such as cancer and neurodegeneration. The goal of the present study was to clarify the relationship between ER stress and pathological neovascularization in the retina. Proliferation and migration of human retinal microvascular endothelial cells (HRMEC) were assessed in the presence of ER stress inducers, such as tunicamycin and thapsigargin. The expression of ER chaperone immunoglobulin heavy-chain binding protein (BiP), known as Grp78, was evaluated by real time RT-PCR, immunostaining, and Western blotting. Tunicamycin or thapsigargin was injected into the intravitreal body of oxygen-induced retinopathy (OIR) model mice at postnatal day 14 (P14) and retinal neovascularization was quantified at P17. The expression and localization of BiP in the retina was also evaluated in the OIR model. Exposure to tunicamycin and thapsigargin increased the proliferation and migration of HRMEC. Tunicamycin enhanced the expression of BiP in HRMEC at both the mRNA level and at the protein level on the cell surface, and increased the formation of a BiP/T-cadherin immunocomplex. In OIR model mice, retinal neovascularization was accelerated by treatments with ER stress inducers. BiP was particularly observed in the pathological vasculature and retinal microvascular endothelial cells, and the increase of BiP expression was correlated with retinal neovascularization. In conclusion, ER stress may contribute to the formation of abnormal vasculature in the retina via BiP complexation with T-cadherin, which then promotes endothelial cell proliferation and migration.     

Implication of Endoplasmic Reticulum Stress in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is categorized as a neurodevelopmental disorder according to the Diagnostic and Statistical Manual of Disorders, Fifth Edition and is defined as a congenital impairment of the central nervous system. ASD may be caused by a chromosomal abnormality or gene mutation. However, these etiologies are insufficient to account for the pathogenesis of ASD. Therefore, we propose that the etiology and pathogenesis of ASD are related to the stress of the endoplasmic reticulum (ER). ER stress, induced by valproic acid, increased in ASD mouse model, characterized by an unfolded protein response that is activated by this stress. The inhibition of neurite outgrowth and expression of synaptic factors are observed in ASD. Similarly, ER stress suppresses the neurite outgrowth and expression of synaptic factors. Additionally, hyperplasia of the brain is observed in patients with ASD. ER stress also enhances neuronal differentiation. Synaptic factors, such as cell adhesion molecule and shank, play important roles in the formation of neural circuits. Thus, ER stress is associated with the abnormalities of neuronal differentiation, neurite outgrowth, and synaptic protein expression. ER stress elevates the expression of the ubiquitin-protein ligase HRD1 for the degradation of unfolded proteins. HRD1 expression significantly increased in the middle frontal cortex in the postmortem of patients with ASD. Moreover, HRD1 silencing improved the abnormalities induced by ER stress. Because other ubiquitin ligases are related with neurite outgrowth, ER stress may be related to the pathogenesis of neuronal developmental diseases via abnormalities of neuronal differentiation or maturation.     

The Female Post-Mating Response Requires Genes Expressed in the Secondary Cells of the Male Accessory Gland in Drosophila melanogaster

Seminal proteins from the Drosophila male accessory gland induce post-mating responses (PMR) in females. The PMR comprise behavioral and physiological changes that include increased egg laying, decreased receptivity to courting males, and changes in the storage and use of sperm. Many of these changes are induced by a “sex peptide” (SP) and are maintained by SP’s binding to, and slow release from, sperm. The accessory gland contains two secretory cell types with distinct morphological and developmental characteristics. Products of these “main” and “secondary” cells work interdependently to induce and maintain the PMR. To identify individual genes needed for the morphology and function of secondary cells, we studied iab-6^cocu males, whose secondary cells have abnormal morphology and fail to provide products to maintain the PMR. By RNA-seq, we identified 77 genes that are downregulated by a factor of >5× in iab-6^cocu males. By functional assays and microscopy, we tested 20 candidate genes and found that at least 9 are required for normal storage and release of SP in mated females. Knockdown of each of these 9 genes consequently leads to a reduction in egg laying and an increase in receptivity over time, confirming a role for the secondary cells in maintaining the long-term PMR. Interestingly, only 1 of the 9 genes, CG3349, encodes a previously reported seminal fluid protein (Sfp), suggesting that secondary cells may perform essential functions beyond the production and modification of known Sfps. At least 3 of the 9 genes also regulate the size and/or abundance of secondary cell vacuoles, suggesting that the vacuoles’ contents may be important for the machinery used to maintain the PMR.     

大鼠严重烧伤后心肌细胞GRP94表达变化及其意义

目的观察严重烧伤大鼠心肌细胞内质网应激蛋白表达的改变及其意义,以探讨严重烧伤后心肌损伤与内质网应激的关系。方法建立大鼠30％Ⅲ度烫伤模型,酶联免疫法检测血浆中心肌肌钙蛋白T（cTnT）含量,放射免疫法检测血浆中TNFα的含量,RT-PCR和免疫组化分析GRP94的表达。结果烧伤组大鼠伤后3h血浆中cTnT含量即呈显著升高（P〈0．01）,心肌中GRP94 mRNA和蛋白表达于烧伤后3h显著性升高,12h达峰值,24h还呈显著升高;大鼠烧伤后3h心肌中Caspase-3活性开始升高,12h达高峰,48h后仍显著高于对照组。牛磺酸治疗组GRP94的表达和Caspase-3活性较烧伤组均有显著性降低（P〈0．05）。结论严重烧伤可引起心肌细胞内质网应激,牛磺酸对烧伤后早期心肌损害有保护作用。     

冠状病毒感染与内质网应激研究进展

内质网（Endoplasmic reticulum,ER）是真核细胞细胞器的重要组成部分,主要负责蛋白质合成和翻译后修饰等过程,还参与调控了钙离子储存和脂类合成,具有重要生理功能。冠状病毒感染细胞后,在复制其遗传信息的同时也在合成大量病毒蛋白,造成未折叠/错误折叠蛋白堆积,进而增加内质网工作负担,诱发内质网应激（Endoplasmic reticulum stress,ERS）,激活未折叠蛋白反应（Unfolded protein response,UPR）,引起一系列信号级联反应,如诱导细胞凋亡等,进而影响病毒复制。本文就冠状病毒感染与ERS及UPR信号通路的研究进展做一综述,为新型抗冠状病毒药物的研发提供新视角。     

昆虫雄性生殖腺分泌物的功能

昆虫两性成功交配后,雄性生殖腺分泌物使雌性昆虫的生理和行为都发生了巨大的改变。昆虫雄性生殖腺分泌物含有多种具有生物活性的分子,这些生物活性分子通过成功交配转移到雌虫生殖道后,对雌虫的生殖活动产生影响,使交配雌虫一段时间内不再交配,使已转移的精子易于在雌虫生殖道内储藏,使卵与精子完成受精过程,还可刺激雌虫产卵和卵的发育,调控排卵和产卵等生殖过程。在精子的转移过程中,雄性生殖腺分泌物中的抗菌媒介质能使雌虫的生殖导管提供友好的环境。此外,一些昆虫的雄性生殖腺分泌物还含有一些有毒的化学物质,保护已产下的卵不被天敌取食和病原体侵染。     

Endoplasmic Reticulum Stress Is Chronically Activated in Chronic Pancreatitis

The pathogenesis of chronic pancreatitis (CP) is poorly understood. Endoplasmic reticulum (ER) stress has now been recognized as a pathogenic event in many chronic diseases. However, ER stress has not been studied in CP, although pancreatic acinar cells seem to be especially vulnerable to ER dysfunction because of their dependence on high ER volume and functionality. Here, we aim to investigate ER stress in CP, study its pathogenesis in relation to trypsinogen activation (widely regarded as the key event of pancreatitis), and explore its mechanism, time course, and downstream consequences during pancreatic injury. CP was induced in mice by repeated episodes of acute pancreatitis (AP) based on caerulein hyperstimulation. ER stress leads to activation of unfolded protein response components that were measured in CP and AP. We show sustained up-regulation of unfolded protein response components ATF4, CHOP, GRP78, and XBP1 in CP. Overexpression of GRP78 and ATF4 in human CP confirmed the experimental findings. We used novel trypsinogen-7 knock-out mice (T^−/−), which lack intra-acinar trypsinogen activation, to clarify the relationship of ER stress to intra-acinar trypsinogen activation in pancreatic injury. Comparable activation of ER stress was seen in wild type and T^−/− mice. Induction of ER stress occurred through pathologic calcium signaling very early in the course of pancreatic injury. Our results establish that ER stress is chronically activated in CP and is induced early in pancreatic injury through pathologic calcium signaling independent of trypsinogen activation. ER stress may be an important pathogenic mechanism in pancreatitis that needs to be explored in future studies.     

Endoplasmic Reticulum Stress Interacts With Inflammation in Human Diseases

The endoplasmic reticulum (ER) is a critical organelle for normal cell function and homeostasis. Disturbance in the protein folding process in the ER, termed ER stress, leads to the activation of unfolded protein response (UPR) that encompasses a complex network of intracellular signaling pathways. The UPR can either restore ER homeostasis or activate pro‐apoptotic pathways depending on the type of insults, intensity and duration of the stress, and cell types. ER stress and the UPR have recently been linked to inflammation in a variety of human pathologies including autoimmune, infectious, neurodegenerative, and metabolic disorders. In the cell, ER stress and inflammatory signaling share extensive regulators and effectors in a broad spectrum of biological processes. In spite of different etiologies, the two signaling pathways have been shown to form a vicious cycle in exacerbating cellular dysfunction and causing apoptosis in many cells and tissues. However, the interaction between ER stress and inflammation in many of these diseases remains poorly understood. Further understanding of the biochemistry, cell biology, and physiology may enable the development of novel therapies that spontaneously target these pathogenic pathways. J. Cell. Physiol. 231: 288–294, 2016. © 2015 Wiley Periodicals, Inc.