The Unfolded Protein Response Protects from Tau Neurotoxicity In Vivo

The unfolded protein response is a critical system by which the cell handles excess misfolded protein in the secretory pathway. The role of the system in modulating the effects of aggregation prone cytosolic proteins has received less attention. We use genetic reporters to demonstrate activation of the unfolded protein response in a transgenic Drosophila model of Alzheimer's disease and related tauopathies. We then use loss of function genetic reagents to support a role for the unfolded protein response in protecting from tau neurotoxicity. Our findings suggest that the unfolded protein response can ameliorate the toxicity of tau in vivo

Unfolded protein response in rice (Oryza sativa L.) varieties with different level of salt stress tolerance

Plants activate the unfolded protein response as part of cellular adaptation, thereby maintaining the endoplasmic reticulum homeostasis during external stresses exposure. In this study, we examined the relationship between the degree of salt tolerance and unfolded protein response-related gene expression in India salt-tolerant Pokkali and INPARI 35 varieties compared to the Indica salt-sensitive counterpart IR64 and INPARI 4 varieties.  Our result showed that the salt tolerance of Pokkali and INPARI 35 had been confirmed by their higher survival rate, higher chlorophyll content, lower electrolyte leakage, and lower H2O2 and malondialdehyde content under salt stress conditions. Furthermore, the expression of unfolded protein response genes was highest in INPARI 35, whereas IR64 and INPARI 4 exhibited low gene induction during endoplasmic reticulum stress conditions. Among the four examined varieties the salt tolerant Pokkali surprisingly showed the lowest induction of all examined unfolded protein response-related genes. These results indicated the possibility that unfolded protein response supports the rice plant for adapting to the saline environment

IRE1β negatively regulates IRE1α signaling in response to endoplasmic reticulum stress

IRE1β is an ER stress sensor uniquely expressed in epithelial cells lining mucosal surfaces. Here, we show that intestinal epithelial cells expressing IRE1β have an attenuated unfolded protein response to ER stress. When modeled in HEK293 cells and with purified protein, IRE1β diminishes expression and inhibits signaling by the closely related stress sensor IRE1α. IRE1β can assemble with and inhibit IRE1α to suppress stress-induced XBP1 splicing, a key mediator of the unfolded protein response. In comparison to IRE1α, IRE1β has relatively weak XBP1 splicing activity, largely explained by a nonconserved amino acid in the kinase domain active site that impairs its phosphorylation and restricts oligomerization. This enables IRE1β to act as a dominant-negative suppressor of IRE1α and affect how barrier epithelial cells manage the response to stress at the host–environment interface

STING-mediated disruption of calcium homeostasis chronically activates ER stress and primes T cell death

STING gain-of-function mutations cause lung disease and T cell cytopenia through unknown mechanisms. Here, we found that these mutants induce chronic activation of ER stress and unfolded protein response (UPR), leading to T cell death by apoptosis in th

Fortilin Binds IRE1α and Prevents ER Stress from Signaling Apoptotic Cell Death

The endoplasmic reticulum, the cytoplasmic organelle that matures a massive amount of nascent secretory polypeptides, is particularly sensitive to stress. Endoplasmic reticulum stress causes unfolded proteins to populate the organelle, eliciting the unfolded protein response. During the unfolded protein response, GRP78—an endoplasmic reticulum master stress regulator—detaches from three endoplasmic reticulum stress sensors (IRE1α, PERK, and ATF6) and allows them to activate the apoptotic signaling pathway. Fortilin, a pro-survival molecule, is known to inhibit apoptosis by binding and inhibiting p53, but its role in endoplasmic reticulum stress-induced apoptosis remains unknown. Here, we report that fortilin directly interacts with the cytoplasmic domain of IRE1α, inhibits both kinase and endoribonuclease (RNase) activities of the stress sensor, and protects cells against apoptotic cell death at both cellular and whole animal levels. Our data support a role of fortilin in the unfolded protein response and its potential participation in human diseases caused by unfolded protein response

Yeast Bax Inhibitor, Bxi1p, Is an ER-Localized Protein that Links the Unfolded Protein Response and Programmed Cell Death in \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e

Bax inhibitor-1 (BI-1) is an anti-apoptotic gene whose expression is upregulated in a wide range of human cancers. Studies in both mammalian and plant cells suggest that the BI-1 protein resides in the endoplasmic reticulum and is involved in the unfolded protein response (UPR) that is triggered by ER stress. It is thought to act via a mechanism involving altered calcium dynamics. In this paper, we provide evidence that the Saccharomyces cerevisiae protein encoded by the open reading frame, YNL305C, is a bona fide homolog for BI-1. First, we confirm that yeast cells from two different strain backgrounds lacking YNL305C, which we have renamed BXI1, are more sensitive to heat-shock induced cell death than wildtype controls even though they have indistinguishable growth rates at 30°C. They are also more susceptible both to ethanol-induced and to glucose-induced programmed cell death. Significantly, we show that Bxi1p-GFP colocalizes with the ER localized protein Sec63p-RFP. We have also discovered that Δbxi1 cells are not only more sensitive to drugs that induce ER stress, but also have a decreased unfolded protein response as measured with a UPRE-lacZ reporter. Finally, we have discovered that deleting BXI1 diminishes the calcium signaling response in response to the accumulation of unfolded proteins in the ER as measured by a calcineurin-dependent CDRE-lacZ reporter. In toto, our data suggests that the Bxi1p, like its metazoan homologs, is an ER-localized protein that links the unfolded protein response and programmed cell death

Regulation of cell fate by the IRE1 α-TRAF2-JNK axis

Eukaryotic cells produce proteins continuously through translation, folding and quality control within the endoplasmic reticulum (ER). When unfolded proteins accumulate in the endoplasmic reticulum the unfolded protein response (UPR) attempts to restore cellular function by reducing the load of unfolded proteins. If cellular function is not restored the unfolded protein response causes cell death through apoptosis. The only known unfolded protein response protein in lower eukaryotes is inositol-requiring enzyme 1 α (IRE1 α). In this thesis we investigated whether the kinase domain of inositol-requiring enzyme 1 α alone regulates apoptosis or whether the RNase domain is required for apoptotic cell death through the unfolded. We found evidence to suggest that inositol-requiring enzyme 1 α kinase domain alone does not cause apoptosis. Juxtaposing these results, the kinase domain alone causes the presence of phosphorylated proteins that are precursors to apoptosis. Two theories are that mutations made to deactivate the RNase domain effected the folding of the kinase domain reducing its potency. The second theory is that inositol-requiring enzyme 1 α RNase domain plays an unknown role in apoptotic cell death in the unfolded protein response

Pancreatic adaptive responses in alcohol abuse: Role of the unfolded protein response.

The majority of those who drink excessive amounts of alcohol do not develop pancreatic disease. One overarching hypothesis is that alcohol abuse requires additional risk factors, either environmental or genetic, for disease to occur. However, another reason be a result of alcohol-induced activation of adaptive systems that protect the pancreas from the toxic effects of alcohol. We show that mechanisms within the unfolded protein response (UPR) of the endoplasmic reticulum (ER) that can lead to protection of the pancreas from pancreatic diseases with alcohol abuse. The remarkable ability of the pancreas to adapt its machinery to alcohol abuse using UPR systems and continue functioning is the likely reason that pancreatitis from alcohol abuse does not occur in the majority of heavy drinkers. These findings indicate that methods to enhance the protective responses of the UPR can provide opportunities for prevention and treatment of pancreatic diseases

Yap Regulates ATF6-Mediated Unfolded Protein Response

Hippo信号通路最早在果蝇里发现，是在进化上高度保守的一条激酶级联的通路，当Hippo通路的缺失会造其下游调控因子Yap或Taz的激活，促进细胞增殖，抑制细胞凋亡，从而导致器官增大和肿瘤产生。此外，大量文献阐述了内质网压力和肿瘤产生具有相关性。本实验室研究表明，Hippo通路的缺失或Yap蛋白的激活会引起内质网应激信号通路的激活和内质网的增大，并通过内质网应激反应导致肝脏器官增大和肿瘤生成。 当Hippo激酶，在高等动物的同源物为Mst1和Mst2激酶的缺失或Yap激活时，和内质网应激相关的三条信号通路中有两条是激活的，分别是PERK通路和ATF6通路。本研究是针对Mst1/2激酶的缺失或...Hippo pathway is an evolutionally conserved kinase cascade. Kinases Mst1 and Mst2 are the mammalin ortholog of Hippo. Absence of Mst1 and Mst2 leads to the activation of its downstream factors, the transcriptional coactivator Yes-associated protein (YAP) and its paralog, TAZ, which will increase cell proliferation, inhibit cell death and ultimately result in liver overgrowth and tumorigensis. More...学位：理学硕士院系专业：生命科学学院_细胞生物学学号：2162012115239

E-cigarette aerosols induce unfolded protein response in normal human oral keratinocytes.

Objective: Since the introduction in 2004, global usage of e-cigarettes (ECs) has risen exponentially. However, the risks of ECs on oral health are uncertain. The purpose of this study is to understand if EC aerosol exposure impacts the gene pathways of normal human oral keratinocytes (NHOKs), particularly the unfolded protein response (UPR) pathway. Materials and methods: EC aerosols were generated reproducibly with a home-made puffing device and impinged into the culture medium for NHOKs. DNA microarrays were used to profile the gene expression changes in NHOKs treated with EC aerosols, and the Ingenuity Pathway Analysis (IPA) was used to reveal signaling pathways altered by the EC aerosols. Quantitative PCR was used to validate the expression changes of significantly altered genes. Results: DNA microarray profiling followed by IPA revealed a number of signaling pathways, such as UPR, cell cycle regulation, TGF-β signaling, NRF2-mediated oxidative stress response, PI3K/AKT signaling, NF-κB signaling, and HGF signaling, activated by EC aerosols in NHOKs. The UPR pathway genes, C/EBP homologous protein (CHOP), activating transcription factor 4 (ATF4), X box binding protein 1 (XBP1), and inositol-requiring enzyme 1 alpha (IRE1α) were all significantly up-regulated in EC aerosol-treated NHOKs whereas immunoglobulin heavy-chain binding protein (BIP) and PRKR-like ER kinase (PERK) were slightly up-regulated. qPCR analysis results were found to be well correlated with those from the DNA microarray analysis. The most significantly changed genes in EC aerosol-treated NHOKs versus untreated NHOKs were CHOP, ATF4, XBP1, IRE1α and BIP. Meanwhile, Western blot analysis confirmed that CHOP, GRP78 (BIP), ATF4, IRE1α and XBP1s (spliced XBP1) were significantly up-regulated in NHOKs treated with EC aerosols. Conclusion: Our results indicate that EC aerosols up-regulate the UPR pathway genes in NHOKs, and the induction of UPR response is mediated by the PERK - EIF2α - ATF4 and IRE1α - XBP1 pathways