scholarly journals Loss of PIKfyve drives the spongiform degeneration in prion diseases

2021 ◽  
Author(s):  
Asvin KK Lakkaraju ◽  
Karl Frontzek ◽  
Emina Lemes ◽  
Uli Herrmann ◽  
Marco Losa ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Prion Diseases ◽  
Brain Slices ◽  
Prion Infection ◽  
Unfolded Protein ◽  
Phosphatidylinositol Kinase ◽  
Jakob Disease ◽  
Infected Cells ◽  
Spongiform Degeneration ◽  
Protein Response

Brain-matter vacuolation is a defining trait of all prion diseases, yet its cause is unknown. Here we report that prion infection and prion-mimetic antibodies deplete the phosphatidylinositol kinase PIKfyve in mouse brains, cultured cells, organotypic brain slices, and in brains of Creutzfeldt-Jakob Disease victims. We found that PIKfyve, an inositol kinase involved endolysosomal maturation, is acylated by zDHHC9 and zDHHC21, whose juxtavesicular topology is disturbed by prion infection, resulting in PIKfyve deacylation and destabilization. A protracted unfolded protein response (UPR), typical of prion diseases, also induced PIKfyve deacylation and degradation. Conversely, UPR antagonists restored PIKfyve levels in prion-infected cells. Overexpression of zDHHC9 and zDHHC21, administration of the antiprion polythiophene LIN5044, or supplementation with the PIKfyve reaction product PI(3,5)P2, suppressed prion-induced vacuolation. Thus, PIKfyve emerges as a central mediator of vacuolation and neurotoxicity in prion diseases.

scholarly journals Human Cytomegalovirus Induces the Endoplasmic Reticulum Chaperone BiP through Increased Transcription and Activation of Translation by Using the BiP Internal Ribosome Entry Site

2010 ◽  
Vol 84 (21) ◽  
pp. 11479-11486 ◽  
Author(s):  
Nicholas J. Buchkovich ◽  
Yongjun Yu ◽  
Francis J. Pierciey ◽  
James C. Alwine
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcriptional Activation ◽  
Internal Ribosome Entry Site ◽  
Hcmv Infection ◽  
Mrna Translation ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Unfolded Protein ◽  
Infected Cells ◽  
Protein Response

ABSTRACT The endoplasmic reticulum (ER) chaperone BiP (immunoglobulin binding protein) plays a major role in the control of the unfolded protein response. We have previously shown that BiP levels are dramatically increased during human cytomegalovirus (HCMV) infection, where BiP performs unique roles in viral assembly and egress. We show that BiP mRNA levels increase during infection due to activation of the BiP promoter by the major immediate-early (MIE) proteins. The BiP promoter, like other ER stress-activated promoters, contains endoplasmic reticulum stress elements (ERSEs), which are activated by unfolded protein response (UPR)-induced transcription factors. However, these elements are not needed for MIE protein-mediated transcriptional activation; thus, a virus-specific transcriptional activation mechanism is used. Transcriptional activation results in only a 3- to 4-fold increase in BiP mRNA, suggesting that additional mechanisms for BiP production are utilized. The BiP mRNA contains an internal ribosome entry site (IRES) which increases the level of BiP mRNA translation. We show that utilization of the BiP IRES is dramatically increased in HCMV-infected cells. Utilization of the BiP IRES can be activated by the La autoantigen, also called Sjögren's syndrome antigen B (SSB). We show that SSB/La levels are significantly increased during HCMV infection, and SSB/La depletion causes the loss of BiP IRES utilization and lowers endogenous BiP levels in infected cells. Our data show that BiP levels increase in HCMV-infected cells through the combination of increased BiP gene transcription mediated by the MIE proteins and increased BiP mRNA translation due to SSB/La-induced utilization of the BiP IRES.

scholarly journals West Nile Virus Infection Activates the Unfolded Protein Response, Leading to CHOP Induction and Apoptosis

2007 ◽  
Vol 81 (20) ◽  
pp. 10849-10860 ◽  
Author(s):  
Guruprasad R. Medigeshi ◽  
Alissa M. Lancaster ◽  
Alec J. Hirsch ◽  
Thomas Briese ◽  
W. Ian Lipkin ◽  
...  
Keyword(s):  
Transcription Factor ◽  
West Nile Virus ◽  
Unfolded Protein Response ◽  
Neuronal Damage ◽  
Initiation Factor ◽  
West Nile ◽  
Human Neuroblastoma ◽  
Unfolded Protein ◽  
Infected Cells ◽  
Protein Response

ABSTRACT West Nile virus (WNV)-mediated neuronal death is a hallmark of WNV meningitis and encephalitis. However, the mechanisms of WNV-induced neuronal damage are not well understood. We investigated WNV neuropathogenesis by using human neuroblastoma cells and primary rat hippocampal neurons. We observed that WNV activates multiple unfolded protein response (UPR) pathways, leading to transcriptional and translational induction of UPR target genes. We evaluated the role of the three major UPR pathways, namely, inositol-requiring enzyme 1-dependent splicing of X box binding protein 1 (XBP1) mRNA, activation of activating transcription factor 6 (ATF6), and protein kinase R-like endoplasmic reticulum (ER) kinase-dependent eukaryotic initiation factor 2α (eIF2α) phosphorylation, in WNV-infected cells. We show that XBP1 is nonessential or can be replaced by other UPR pathways in WNV replication. ATF6 was rapidly degraded by proteasomes, consistent with induction of ER stress by WNV. We further observed a transient phosphorylation of eIF2α and induction of the proapoptotic cyclic AMP response element-binding transcription factor homologous protein (CHOP). WNV-infected cells exhibited a number of apoptotic phenotypes, such as (i) induction of growth arrest and DNA damage-inducible gene 34, (ii) activation of caspase-3, and (iii) cleavage of poly(ADP-ribose) polymerase. The expression of WNV nonstructural proteins alone was sufficient to induce CHOP expression. Importantly, WNV grew to significantly higher viral titers in chop − / − mouse embryonic fibroblasts (MEFs) than in wild-type MEFs, suggesting that CHOP-dependent premature cell death represents a host defense mechanism to limit viral replication that might also be responsible for the widespread neuronal loss observed in WNV-infected neuronal tissue.

scholarly journals Brucella effector hijacks endoplasmic reticulum quality control machinery to prevent premature egress

2019 ◽  
Author(s):  
Jean-Baptiste Luizet ◽  
Julie Raymond ◽  
Thais Lourdes Santos Lacerda ◽  
Magali Bonici ◽  
Frédérique Lembo ◽  
...  
Keyword(s):  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Er Quality Control ◽  
Unfolded Protein ◽  
Type Iv ◽  
Endoplasmic Reticulum Quality Control ◽  
Fine Regulation ◽  
Infected Cells ◽  
The Unfolded Protein Response ◽  
Protein Response

AbstractPerturbation of endoplasmic reticulum (ER) functions can have critical consequences for cellular homeostasis. An elaborate surveillance system known as ER quality control (ERQC) ensures that only correctly assembled proteins reach their destination. Persistence of misfolded or improperly matured proteins upregulates the unfolded protein response (UPR) to cope with stress, activates ER associated degradation (ERAD) for delivery to proteasomes for degradation. We have identified a Brucella abortus type IV secretion system effector called BspL that targets Herp, a key component of ERQC and is able to augment ERAD. Modulation of ERQC by BspL results in tight control of the kinetics of autophagic Brucella-containing vacuole formation, preventing premature bacterial egress from infected cells. This study highlights how bacterial pathogens may hijack ERAD components for fine regulation of their intracellular trafficking.

scholarly journals Modulation of SARS-CoV-2 Spike-induced Unfolded Protein Response (UPR) in HEK293T cells by selected small chemical molecules

2021 ◽  
Author(s):  
Bijina Balakrishnan ◽  
Kent Lai
Keyword(s):  
Er Stress ◽  
Unfolded Protein Response ◽  
Viral Infections ◽  
Host Cells ◽  
Transfected Cells ◽  
Unfolded Protein ◽  
Infected Cells ◽  
Protein Response ◽  
Small Chemical ◽  
Stress Activation

Coronaviruses (CoV) exploits the endoplasmic reticulum (ER) of the host cells for replication and in doing so, increases ER stress. evokes Unfolded Protein Response (UPR) and possibly autophagy, which could all attribute to the pathophysiology of the viral infections. To date, little is known about the roles of ER stress, UPR, and autophagy in SARS-CoV-2 infection. Here we over-expressed the viral Spike (S) protein in cultured HEK293T cells, as it has been shown that such protein is largely responsible for UPR activation in other CoV-infected cells. We noticed, in the transfected cells, heightened ER stress, activation of the PERK-eIF2α arm of the UPR, induction of autophagy and cell death. When we treated the transfected cells with Tauroursodeoxycholic acid (TUDCA), 4-phenyl butyric acid (PBA), Salubrinal, Trazadone hydrochloride, and Dibenzoylmethane (DBM), we saw reduced the BiP/GRP78 levels, but only PBA and TUDCA could significantly diminish the levels of peIF2α and autophagy expression.

scholarly journals Soluble Aβ aggregates can inhibit prion propagation

Open Biology ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 170158 ◽  
Author(s):  
Claire J. Sarell ◽  
Emma Quarterman ◽  
Daniel C.-M. Yip ◽  
Cassandra Terry ◽  
Andrew J. Nicoll ◽  
...  
Keyword(s):  
Prion Diseases ◽  
Amyloid Β ◽  
Inhibitory Effect ◽  
Cellular Prion Protein ◽  
Amyloid Β Protein ◽  
Prion Infection ◽  
Cellular Models ◽  
Prion Propagation ◽  
Jakob Disease

Mammalian prions cause lethal neurodegenerative diseases such as Creutzfeldt–Jakob disease (CJD) and consist of multi-chain assemblies of misfolded cellular prion protein (PrP C ). Ligands that bind to PrP C can inhibit prion propagation and neurotoxicity. Extensive prior work established that certain soluble assemblies of the Alzheimer's disease (AD)-associated amyloid β-protein (Aβ) can tightly bind to PrP C , and that this interaction may be relevant to their toxicity in AD. Here, we investigated whether such soluble Aβ assemblies might, conversely, have an inhibitory effect on prion propagation. Using cellular models of prion infection and propagation and distinct Aβ preparations, we found that the form of Aβ assemblies which most avidly bound to PrP in vitro also inhibited prion infection and propagation. By contrast, forms of Aβ which exhibit little or no binding to PrP were unable to attenuate prion propagation. These data suggest that soluble aggregates of Aβ can compete with prions for binding to PrP C and emphasize the bidirectional nature of the interplay between Aβ and PrP C in Alzheimer's and prion diseases. Such inhibitory effects of Aβ on prion propagation may contribute to the apparent fall-off in the incidence of sporadic CJD at advanced age where cerebral Aβ deposition is common.

scholarly journals Stress responses in flavivirus-infected cells: activation of unfolded protein response and autophagy

2014 ◽  
Vol 5 ◽  
Author(s):  
Ana-Belén Blázquez ◽  
Estela Escribano-Romero ◽  
Teresa Merino-Ramos ◽  
Juan-Carlos Saiz ◽  
Miguel A. Martín-Acebes
Keyword(s):  
Unfolded Protein Response ◽  
Stress Responses ◽  
Unfolded Protein ◽  
Infected Cells ◽  
Protein Response

scholarly journals The inositol-requiring enzyme 1 (IRE1α) RNAse inhibitor, 4µ8C, is also a potent cellular antioxidant

2018 ◽  
Vol 475 (5) ◽  
pp. 923-929 ◽  
Author(s):  
Stanley M.H. Chan ◽  
Mark P. Lowe ◽  
Ashton Bernard ◽  
Alyson A. Miller ◽  
Terence P. Herbert
Keyword(s):  
Er Stress ◽  
Cultured Cells ◽  
Specific Inhibitor ◽  
Unfolded Protein ◽  
Ic50 Values ◽  
A Cell ◽  
Target Effect ◽  
The Unfolded Protein Response ◽  
Protein Response

Inositol-requiring enzyme 1 alpha (IRE1α) is an endoplasmic reticulum (ER)-transmembrane endonuclease that is activated in response to ER stress as part of the unfolded protein response (UPR). Chronic activation of the UPR has been implicated in the pathogenesis of many common diseases including diabetes, cancer, and neurological pathologies such as Huntington's and Alzheimer's disease. 7-Hydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde (4µ8C) is widely used as a specific inhibitor of IRE1α ribonuclease activity (IC50 of 6.89 µM in cultured cells). However, in this paper, we demonstrate that 4µ8C acts as a potent reactive oxygen species (ROS) scavenger, both in a cell-free assay and in cultured cells, at concentrations lower than that widely used to inhibit IRE1α activity. In vitro we show that, 4µ8C effectively decreases xanthine/xanthine oxidase catalysed superoxide production with an IC50 of 0.2 µM whereas in cultured endothelial and clonal pancreatic β-cells, 4µ8C inhibits angiotensin II-induced ROS production with IC50 values of 1.92 and 0.29 µM, respectively. In light of this discovery, conclusions reached using 4µ8C as an inhibitor of IRE1α should be carefully evaluated. However, this unexpected off-target effect of 4µ8C may prove therapeutically advantageous for the treatment of pathologies that are thought to be caused by, or exacerbated by, both oxidative and ER stress such as endothelial dysfunction and/or diabetes.

Molecular biology and genetics of prion diseases

1994 ◽  
Vol 343 (1306) ◽  
pp. 447-463 ◽  
Keyword(s):  
Nucleic Acid ◽  
De Novo ◽  
Prion Diseases ◽  
Spongiform Encephalopathy ◽  
Species Barrier ◽  
Prolonged Incubation ◽  
Brain Extracts ◽  
Jakob Disease ◽  
Spongiform Degeneration ◽  
The Difference

Scrapie was thought for m any years to be caused by a virus. Enriching fractions from Syrian hamster (SHa) brain for scrapie infectivity led to the discovery of the prion protein (PrP). To date, no scrapie-specific nucleic acid has been found. As well as scrapie, prion diseases include bovine spongiform encephalopathy (BSE) of cattle, as well as Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker syndrome (GSS) of humans. Transgenic (Tg) mice expressing both SHa and mouse (Mo) PrP genes were used to probe the molecular basis of the species barrier and the mechanism of scrapie prion replication. The prion inoculum was found to dictate which prions are synthesized de novo , even though the cells express both PrP genes. Discovery of mutations in the PrP genes of humans with GSS and familial CJD established that prion diseases are both genetic and infectious. Tg mice expressing MoPrP with the GSS point mutation spontaneously develop neurologic dysfunction, spongiform degeneration and astrocytic gliosis. Inoculation of brain extracts prepared from these Tg(MoPrP-P101L) mice produced neurodegeneration in many of the recipient animals after prolonged incubation times. These and other results suggest that prions are devoid of foreign nucleic acid and are thus different from viruses and viroids. Studies on the structure of PrP Sc and PrP c suggest that the difference is conformational. Whether one or more putative a-helices in PrP c are converted into (β-sheets during synthesis of PrP Sc is unknown. Distinct prion isolates or ‘strains’ exhibit different patterns of PrP Sc accumulation which are independent of incubation times. Whether variations in PrP Sc conformation are responsible for prion diversity remains to be established. Prion studies have given new insights into the etiologies of infectious, sporadic and inherited degenerative diseases.

scholarly journals Auxin confers protection against ER stress in Caenorhabditis elegans

2020 ◽  
Author(s):  
A. Bhoi ◽  
F. Palladino ◽  
P. Fabrizio
Keyword(s):  
Er Stress ◽  
Developmental Stages ◽  
Cultured Cells ◽  
Central Function ◽  
Extreme Caution ◽  
C Elegans ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Open Question

AbstractAuxins are plant growth regulators that influence most aspects of plant development through complex mechanisms. The development of an auxin-inducible degradation (AID) system has enabled rapid, conditional protein depletion in yeast and cultured cells. More recently, the system was successfully adapted to C. elegans to achieve auxin-dependent degradation of targets in all tissues and developmental stages. Whether auxin treatment alone has an impact on nematode physiology is an open question. Here we show that indole-3-acetic acid (IAA), the auxin most commonly used to trigger AID in worms, functions through the conserved IRE-1/XBP-1 branch of the Unfolded Protein Response (UPR) to promote resistance to Endoplasmic Reticulum (ER) stress. Because of the central function played by the UPR in protein folding, lipid biosynthesis and lifespan regulation, these results suggest that extreme caution should be exercised when using the AID system to study these and related processes.

scholarly journals Manipulation of the unfolded protein response: A pharmacological strategy against coronavirus infection

2021 ◽  
Vol 17 (6) ◽  
pp. e1009644
Author(s):  
Liliana Echavarría-Consuegra ◽  
Georgia M. Cook ◽  
Idoia Busnadiego ◽  
Charlotte Lefèvre ◽  
Sarah Keep ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Hepatitis Virus ◽  
Ribosome Profiling ◽  
Murine Hepatitis Virus ◽  
Unfolded Protein ◽  
Virion Release ◽  
Infected Cells ◽  
Coronavirus Infection ◽  
The Unfolded Protein Response ◽  
Protein Response

Coronavirus infection induces the unfolded protein response (UPR), a cellular signalling pathway composed of three branches, triggered by unfolded proteins in the endoplasmic reticulum (ER) due to high ER load. We have used RNA sequencing and ribosome profiling to investigate holistically the transcriptional and translational response to cellular infection by murine hepatitis virus (MHV), often used as a model for the Betacoronavirus genus to which the recently emerged SARS-CoV-2 also belongs. We found the UPR to be amongst the most significantly up-regulated pathways in response to MHV infection. To confirm and extend these observations, we show experimentally the induction of all three branches of the UPR in both MHV- and SARS-CoV-2-infected cells. Over-expression of the SARS-CoV-2 ORF8 or S proteins alone is itself sufficient to induce the UPR. Remarkably, pharmacological inhibition of the UPR greatly reduced the replication of both MHV and SARS-CoV-2, revealing the importance of this pathway for successful coronavirus replication. This was particularly striking when both IRE1α and ATF6 branches of the UPR were inhibited, reducing SARS-CoV-2 virion release (~1,000-fold). Together, these data highlight the UPR as a promising antiviral target to combat coronavirus infection.

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