内质网应激与缺血性脑损伤

内质网应激是内质网内未折叠或错误折叠蛋白积聚所致。作为对内质网应激的响应，细胞形成了一条称为未折叠蛋白反应（UPR）的自我保护信号转导通路。然而，如果脑缺血诱导的内质网应激严重且持续时间长，UPR最终会启动细胞凋亡通路，导致神经元死亡。文章对脑缺血再灌注绣导内质网应激和UPR的研究进展做了综述。     

内质网应激介导β细胞生存/死亡的研究进展

内质网应激（ERS）是细胞应激的重要组成部分,表现为内质网腔内错误折叠和未折叠蛋白聚集以及细胞内Ca^2＋平衡紊乱,与应激细胞的适应、损伤或凋亡直接相关。ERS诱发的主要信号通路有未折叠蛋白反应（UPR）、固醇调节级联反应以及凋亡信号通路。β细胞具有高度发达的内质网,对ERS极具易感性。β细胞可通过上述信号通路维持内质网稳态以求得细胞生存,但过长、过强的ERS可激活特有的凋亡通路导致β细胞的死亡。     

内质网应激与缺血性脑损伤

内质网(endoplasmic retieulum,ER)腔内错误折叠与未折叠蛋白聚集将引起内质网应激(endoplasmic reticuhum stress,ERS),可激活未折叠蛋白反应(unfolded protein response,UPR),从而对神经元的存活产生保护作用.然而,过强或持续时间过长的ERS最终会引起细胞凋亡.脑缺血会导致ER功能障碍,对ERS进行干预能减轻脑缺血再灌注损伤,从而为缺血性脑血管病的治疗找到新的途径.文章对脑缺血再灌注诱导ERS的研究进展进行了综述.     

内质网应激与神经退行性疾病的关系

<正>内质网(ER)是真核细胞内蛋白质折叠组装、Ca~(2+)动态平衡的重要场所。遗传或环境等因素导致的内质网内稳态失衡将引起内质网应激(ERS),激活一系列应激反应如未折叠蛋白反应(UPR)。未折叠蛋白反应和早期的ERS,是一种自身代偿过程,对细胞起着调节与保护作用,而持续、强烈的ERS可诱导细     

内质网应激介导β细胞凋亡的研究进展

内质网是真核细胞内蛋白质合成加工、Ca~(2+)稳态调节及脂类合成的重要场所。当环境、遗传因素影响内质网正常功能,使未折叠或错误折叠蛋白大量蓄积时,诱导内质网应激(ERS),进而激活未折叠蛋白反应(UPR)。UPR为细胞自身内质网稳态调节的一种自我保护机制,而持续过强的UPR最终导致细胞凋亡的发生。已有研究表明,T2DM中胰岛素分泌缺陷与β细胞凋亡致数量减少密切相关。本文回顾近年相关研究,对人胰岛淀粉样多肽(hIAPP)、糖脂细胞毒性、代谢性炎症、自噬障碍介导ERS反应,最终导致β细胞凋亡的相关机制进行综述。     

内质网应激与心血管疾病的研究进展

内质网(ER)是真核细胞最主要的膜性结构,是细胞内重要生理过程发生的关键细胞器。在多种内外因素的作用下,ER的稳态受到破坏,导致蛋白质加工运输受阻,未折叠蛋白或错误折叠蛋白在ER腔内聚集,形成内质网应激(ERS),并触发未折叠蛋白反应(UPR)。适度的ERS通过UPR信号通路减少蛋白质合成、促进蛋白质降解、增加协助蛋白质折叠的分子伴侣,最终缓解ER压力。但是,如果ERS过强或持续时间过长,超过细胞的自身调节能力时,UPR可启动细胞凋亡,亦可导致疾病。大量研究表明,ERS与多种心血管疾病(CVD)的发生发展密切相关。该综述主要阐述UPR在几种常见CVD中的研究进展和靶向UPR作为CVD的潜在治疗方法。     

内质网应激的信号通路及其与肝脏疾病的关系

内质网应激(ERS)表现为内质网腔内错误折叠与未折叠蛋白聚集以及钙离子平衡紊乱,可激活未折叠蛋白反应、内质网超负荷反应和固醇调节级联反应等信号通路,既能引发糖调节蛋白GRP78、GRP94等内质网分子伴侣表达而产生保护效应,亦能诱导细胞凋亡。目前,关于ERS参与肝脏疾病的发生发展尚无系统性认识。综述了ERS相关信号通路的新进展及与其相关的部分肝脏疾病新进展,并对ERS介导的细胞凋亡及其在肝脏疾病中的作用进行阐述。干预ERS信号通路有望为未来肝脏疾病研究及治疗提供参考。     

内质网应激在肝脏疾病中的研究进展

内质网应激（ERS）是指由于某种原因使内质网中未折叠或错误折叠的蛋白质聚集导致内质网结构、功能紊乱的病理过程。适度的ERS通过激活未折叠蛋白质反应（UPR）对细胞起保护作用,而强烈或持久的ERS则会诱导细胞凋亡。近年来诸多研究显示EBS是多种肝脏疾病发生、发展过程中的重要环节。本文就ERS在肝脏疾病中的研究进展作一综述。     

专家报告2:胰岛β细胞中内质网应激IRE1α信号通路的调控及其分子机制

细胞内质网应激反应(ER Stress)通过激活细胞内未折叠蛋白响应(UPR,Unfolded Protein Response)信号通路,在专职分泌的胰岛β细胞中对维持内质网稳态平衡和正常细胞功能至关重要.     

内质网应激与糖尿病相关性研究进展

内质网应激(ERS)是一种特殊类型的细胞内应激,是由内质网内错误折叠与未折叠蛋白聚集以及Ca+代谢紊乱所引起.研究表明,适度ERS通过激活未折叠蛋白反应起适应性的细胞保护作用,而过高和持久的ERS则通过诱导转录因子CHOP表达、激活caspase-12和c-Jun氨基末端激酶(JNK)等导致细胞凋亡.近年的研究显示,ERS通过促使胰岛β细胞凋亡及胰岛素抵抗参与糖尿病发病,而阻断ERS诱导的凋亡通路和胰岛素抵抗则可能为糖尿病治疗提供新的手段.     

Endoplasmic Reticulum Stress in Cardiometabolic Disorders

When endoplasmic reticulum (ER) homeostasis is disrupted, an adaptive signaling pathway, called the unfolded protein response (UPR) is activated to help ER cope with the stress. The UPR is an important signal transduction pathway, crucial for the survival and function of all cells. Recently, there has been a substantial progress made in understanding the molecular mechanisms of physiological UPR regulation and its role in the pathogenesis of many diseases including metabolic diseases. Studies using mouse models lacking or overexpressing the factors involved in ER stress signaling as well as work performed on humans have revealed the contribution of UPR to disease progression. This review focuses on the regulation of UPR signaling and its relevance in pathogenesis of metabolic diseases.     

Lipid-induced endoplasmic reticulum stress in liver cells results in two distinct outcomes: adaptation with enhanced insulin signaling or insulin resistance

Chronically elevated fatty acids contribute to insulin resistance through poorly defined mechanisms. Endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) have been implicated in lipid-induced insulin resistance. However, the UPR is also a fundamental mechanism required for cell adaptation and survival. We aimed to distinguish the adaptive and deleterious effects of lipid-induced ER stress on hepatic insulin action. Exposure of human hepatoma HepG2 cells or mouse primary hepatocytes to the saturated fatty acid palmitate enhanced ER stress in a dose-dependent manner. Strikingly, exposure of HepG2 cells to prolonged mild ER stress activation induced by low levels of thapsigargin, tunicamycin, or palmitate augmented insulin-stimulated Akt phosphorylation. This chronic mild ER stress subsequently attenuated the acute stress response to high-level palmitate challenge. In contrast, exposure of HepG2 cells or hepatocytes to severe ER stress induced by high levels of palmitate was associated with reduced insulin-stimulated Akt phosphorylation and glycogen synthesis, as well as increased expression of glucose-6-phosphatase. Attenuation of ER stress using chemical chaperones (trimethylamine N-oxide or tauroursodeoxycholic acid) partially protected against the lipid-induced changes in insulin signaling. These findings in liver cells suggest that mild ER stress associated with chronic low-level palmitate exposure induces an adaptive UPR that enhances insulin signaling and protects against the effects of high-level palmitate. However, in the absence of chronic adaptation, severe ER stress induced by high-level palmitate exposure induces deleterious UPR signaling that contributes to insulin resistance and metabolic dysregulation.     

PERK mediates cell-cycle exit during the mammalian unfolded protein response

The accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response (UPR)-signaling pathway. The UPR coordinates the induction of ER chaperones with decreased protein synthesis and growth arrest in the G(1) phase of the cell cycle. Three ER transmembrane protein kinases (Ire1alpha, Ire1beta, and PERK) have been implicated as proximal effectors of the mammalian UPR. We now demonstrate that activation of PERK signals the loss of cyclin D1 during the UPR, culminating in cell-cycle arrest. Overexpression of wild-type PERK inhibited cyclin D1 synthesis in the absence of ER stress, thereby inducing a G(1) phase arrest. PERK expression was associated with increased phosphorylation of the translation elongation initiation factor 2alpha (eIF2alpha), an event previously shown to block cyclin D1 translation. Conversely, a truncated form of PERK lacking its kinase domain acted as a dominant negative when overexpressed in cells, attenuating both cyclin D1 loss and cell-cycle arrest during the UPR without compromising induction of ER chaperones. These data demonstrate that PERK serves as a critical effector of UPR-induced growth arrest, linking stress in the ER to control of cell-cycle progression.     

Endoplasmic reticulum stress and inflammatory bowel disease

Endoplasmic reticulum (ER) stress arises from the accumulation of misfolded or unfolded proteins in the ER and elicits the unfolded protein response (UPR), an adaptive signalling pathway which aims at resolving ER stress. Genetic loci that confer risk for both forms of inflammatory bowel disease (IBD) include genes that are centrally involved in the UPR, including X-box binding protein-1 (XBP1), anterior gradient protein-2 (AGR2) and orosomucoid-1-like 3 (ORMDL3). The intestinal epithelium, in particular mucin-secreting goblet and antimicrobial peptide-secreting Paneth cells appear particularly sensitive towards disturbances of the UPR. Supportive of this view are mice with a genetic deletion of Xbp1 specifically in the intestinal epithelium, which develop spontaneous intestinal inflammation histologically remarkably similar to human IBD. Apart from such primary genetic factors that determine the threshold of tolerable ER stress within the epithelium, secondary factors emanating from the environment might intersect with the UPR as well. These secondary factors might include microbial products, inflammatory mediators per se, hypoxia and glucose deprivation, pharmacological agents, and many others. Interaction of such secondary factors in a genetically susceptible host might provide the basis for intestinal inflammation and might provide a framework to investigate gene-environment interactions in human IBD, whereby a normally homeostatic adaptive response (i.e. the UPR) transforms into a potent pathomechanism of intestinal inflammation in the context of unresolved (i.e. unresolvable) ER stress.     

Rationalizing translation attenuation in the network architecture of the unfolded protein response

Increased levels of unfolded proteins in the endoplasmic reticulum (ER) of all eukaryotes trigger the unfolded protein response (UPR). Lower eukaryotes solely use an ancient UPR mechanism, whereby they up-regulate ER-resident chaperones and other enzymatic activities to augment protein folding and enhance degradation of misfolded proteins. Metazoans have evolved an additional mechanism through which they attenuate translation of secretory pathway proteins by activating the ER protein kinase PERK. In mammalian professional secretory cells such as insulin-producing pancreatic β-cells, PERK is highly abundant and crucial for proper functioning of the secretory pathway. Through a modeling approach, we propose explanations for why a translation attenuation (TA) mechanism may be critical for β-cells, but is less important in nonsecretory cells and unnecessary in lower eukaryotes such as yeast. We compared the performance of a model UPR, both with and without a TA mechanism, by monitoring 2 variables: (i) the maximal increase in ER unfolded proteins during a response, and (ii) the accumulation of chaperones between 2 consecutive pulses of stress. We found that a TA mechanism is important for minimizing these 2 variables when the ER is repeatedly subjected to transient unfolded protein stresses and when it sustains a large flux of secretory pathway proteins which are both conditions encountered physiologically by pancreatic β-cells. Low expression of PERK in nonsecretory cells, and its absence in yeast, can be rationalized by lower trafficking of secretory proteins through their ERs.     

Melatonin reduces endoplasmic reticulum stress and preserves sirtuin 1 expression in neuronal cells of newborn rats after hypoxia–ischemia

Conditions that interfere with the endoplasmic reticulum (ER) functions cause accumulation of unfolded proteins in the ER lumen, referred to as ER stress, and activate a homeostatic signaling network known as unfolded protein response (UPR). We have previously shown that in neonatal rats subjected to hypoxia–ischemia (HI), melatonin administration significantly reduces brain damage. This study assessed whether attenuation of ER stress is involved in the neuroprotective effect of melatonin after neonatal HI. We found that the UPR was strongly activated after HI. Melatonin significantly reduced the neuron splicing of XBP‐1 mRNA, the increased phosphorylation of eIF2α, and elevated expression of chaperone proteins GRP78 and Hsp70 observed after HI in the brain. CHOP, which plays a convergent role in the UPR, was reduced as well. Melatonin also completely prevented the depletion of SIRT‐1 induced by HI, and this effect was observed in the same neurons that over‐express CHOP. These results demonstrate that melatonin reduces ER stress induced by neonatal HI and preserves SIRT‐1 expression, suggesting that SIRT‐1, due to its action in the modulation of a wide variety of signaling pathways involved in neuroprotection, may play a key role in the reduction of ER stress and neuroprotection observed after melatonin.     

The contribution of endoplasmic reticulum stress to liver diseases

The unfolded protein response (UPR) is an evolutionarily conserved cell signaling pathway that is activated to regulate protein synthesis and restore homeostatic equilibrium when the cell is stressed from increased client protein load or the accumulation of unfolded or malfolded proteins. Once activated, this signaling pathway can either result in the recovery of homeostasis or can activate a cascade of events that ultimately result in cell death. The UPR/endoplasmic reticulum (ER) stress response spectrum and its interplay with other cellular organelles play an important role in the pathogenesis of disease in secretory cells rich in ER, such as hepatocytes. Over the past 2 decades, the contribution of ER stress to various forms of liver diseases has been examined. Robust support for a contributing, as opposed to a secondary role, for ER stress response is seen in the nonalcoholic steatohepatitis, alcoholic liver disease, ischemia/reperfusion injury, and cholestatic models of liver disease. The exact direction of the cause and effect relationship between modes of cell injury and ER stress remains elusive. It is apparent that a complex interplay exists between ER stress response, conditions that promote it, and those that result from it. A vicious cycle in which ER stress promotes inflammation, cell injury, and steatosis and in which steatogenesis, inflammation, and cell injury aggravate ER stress seems to be at play. It is perhaps the nature of such a vicious cycle that is the key pathophysiologic concept. Therapeutic approaches aimed at interrupting the cycle may dampen the stress response and the ensuing injury.