scholarly journals Mevalonate pathway-mediated ER homeostasis is required for haploid stability in human somatic cells

2020 ◽  
Author(s):  
Kan Yaguchi ◽  
Kimino Sato ◽  
Koya Yoshizawa ◽  
Gabor Banhegyi ◽  
Eva Margittai ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Mevalonate Pathway ◽  
Somatic Cells ◽  
Cellular Processes ◽  
Lowering Drug ◽  
Cholesterol Supplementation ◽  
The Stability ◽  
Er Homeostasis ◽  
Cholesterol Inhibitor

AbstractThe somatic haploidy is unstable in diplontic animals, but cellular processes determining haploid stability remain elusive. Here, we found that inhibition of mevalonate pathway by pitavastatin, a widely used cholesterol-lowering drug, drastically destabilized the haploid state in HAP1 cells. Interestingly, cholesterol supplementation did not restore haploid stability in pitavastatin-treated cells, and cholesterol inhibitor U18666A did not phenocopy haploid destabilization. These results ruled out the involvement of cholesterol in haploid stability. Besides cholesterol perturbation, pitavastatin induced endoplasmic reticulum (ER) stress, the suppression of which by a chemical chaperon significantly restored haploid stability in pitavastatin-treated cells. Our data demonstrate the involvement of the mevalonate pathway in the stability of the haploid state in human somatic cells through managing ER stress, highlighting a novel link between ploidy and ER homeostatic control.

scholarly journals Endoplasmic reticulum stress induces a novel Ca2+ signalling system initiated by Ca2+ microdomains

2020 ◽  
Author(s):  
Constanza Feliziani ◽  
Gonzalo Quasollo ◽  
Deborah Holstein ◽  
Macarena Fernandez ◽  
James C Paton ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Cell Model ◽  
Signal Transduction Pathway ◽  
Unfolded Proteins ◽  
Potent Inducer ◽  
Human Astrocytes ◽  
Receptor Isoforms ◽  
A Cell ◽  
Er Homeostasis

AbstractThe accumulation of unfolded proteins within the Endoplasmic Reticulum (ER) activates a signal transduction pathway termed the unfolded protein response (UPR), which attempts to restore ER homeostasis. If homeostasis cannot be restored, UPR signalling ultimately induces apoptosis. Ca2+ depletion in the ER is a potent inducer of ER stress. Despite the ubiquity of Ca2+ as intracellular messenger, the precise mechanism (s) by which Ca2+ release affects the UPR remains unknown. Use of a genetically encoded Ca2+ indicator (GCamP6) that is tethered to the ER membrane, uncovered novel Ca2+ signalling events initiated by Ca2+ microdomains in human astrocytes under ER stress, as well as in a cell model deficient in all three IP3 Receptor isoforms. Pharmacological and molecular studies indicate that these local events are mediated by translocons. Together, these data reveal the existence of a previously unrecognized mechanism by which stressor-mediated Ca2+ release regulates ER stress.

scholarly journals The Impact of Endoplasmic Reticulum-Associated Protein Modifications, Folding and Degradation on Lung Structure and Function

2021 ◽  
Vol 12 ◽  
Author(s):  
Emily M. Nakada ◽  
Rui Sun ◽  
Utako Fujii ◽  
James G. Martin
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Unfolded Protein ◽  
Lung Structure ◽  
Selective Translation ◽  
The Unfolded Protein Response ◽  
And Function ◽  
Protein Response ◽  
Er Homeostasis ◽  
The Impact

The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and induces the unfolded protein response (UPR) and other mechanisms to restore ER homeostasis, including translational shutdown, increased targeting of mRNAs for degradation by the IRE1-dependent decay pathway, selective translation of proteins that contribute to the protein folding capacity of the ER, and activation of the ER-associated degradation machinery. When ER stress is excessive or prolonged and these mechanisms fail to restore proteostasis, the UPR triggers the cell to undergo apoptosis. This review also examines the overlooked role of post-translational modifications and their roles in protein processing and effects on ER stress and the UPR. Finally, these effects are examined in the context of lung structure, function, and disease.

scholarly journals Endoplasmic reticulum stress and the development of endothelial dysfunction

2017 ◽  
Vol 312 (3) ◽  
pp. H355-H367 ◽  
Author(s):  
M. L. Battson ◽  
D. M. Lee ◽  
C. L. Gentile
Keyword(s):  
Endoplasmic Reticulum ◽  
Endothelial Dysfunction ◽  
Er Stress ◽  
Critical Role ◽  
Unfolded Protein ◽  
Vasoactive Substances ◽  
Important Regulator ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Er Homeostasis

The vascular endothelium plays a critical role in cardiovascular homeostasis, and thus identifying the underlying causes of endothelial dysfunction has important clinical implications. In this regard, the endoplasmic reticulum (ER) has recently emerged as an important regulator of metabolic processes. Dysfunction within the ER, broadly termed ER stress, evokes the unfolded protein response (UPR), an adaptive pathway that aims to restore ER homeostasis. Although the UPR is the first line of defense against ER stress, chronic activation of the UPR leads to cell dysfunction and death and has recently been implicated in the pathogenesis of endothelial dysfunction. Numerous risk factors for endothelial dysfunction can induce ER stress, which may in turn disrupt endothelial function via direct effects on endothelium-derived vasoactive substances or by activating other pathogenic cellular networks such as inflammation and oxidative stress. This review summarizes the available data linking ER stress to endothelial dysfunction.

scholarly journals Arf1p Provides an Unexpected Link between COPI Vesicles and mRNA in Saccharomyces cerevisiae

2004 ◽  
Vol 15 (11) ◽  
pp. 5021-5037 ◽  
Author(s):  
Mark Trautwein ◽  
Jörn Dengjel ◽  
Markus Schirle ◽  
Anne Spang
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Short Range ◽  
Small Gtpase ◽  
Polya Tail ◽  
Cellular Processes ◽  
Golgi Membranes ◽  
The Stability ◽  
Ash1 Mrna

The small GTPase Arf1p is involved in different cellular processes that require its accumulation at specific cellular locations. The recruitment of Arf1p to distinct points of action might be achieved by association of Arf1p with different proteins. To identify new interactors of Arf1p, we performed an affinity chromatography with GTP- or GDP-bound Arf1p proteins. A new interactor of Arf1p-GTP was identified as Pab1p, which binds to the polyA-tail of mRNAs. Pab1p was found to associate with purified COPI-coated vesicles generated from Golgi membranes in vitro. The stability of the Pab1p–Arf1p complex depends on the presence of mRNA. Both symmetrically distributed mRNAs as well as the asymmetrically localized ASH1 mRNA are found in association with Arf1p. Remarkably, Arf1p and Pab1p are both required to restrict ASH1 mRNA to the bud tip. Arf1p and coatomer play an unexpected role in localizing mRNA independent and downstream of the SHE machinery. Hereby acts the SHE machinery in long-range mRNA transport, whereas COPI vesicles could act as short-range and localization vehicles. The endoplasmic reticulum (ER)–Golgi shuttle might be involved in concentrating mRNA at the ER.

Saturated fatty acids induce endoplasmic reticulum stress and apoptosis independently of ceramide in liver cells

2006 ◽  
Vol 291 (2) ◽  
pp. E275-E281 ◽  
Author(s):  
Yuren Wei ◽  
Dong Wang ◽  
Farran Topczewski ◽  
Michael J. Pagliassotti
Keyword(s):  
Fatty Acids ◽  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Unsaturated Fatty Acids ◽  
Saturated Fatty Acids ◽  
Liver Cells ◽  
Caspase Activity ◽  
Dna Laddering ◽  
Er Homeostasis

Accumulation of lipids in nonadipose tissues can lead to cell dysfunction and cell death, a phenomenon known as lipotoxicity. However, the signaling pathways and mechanisms linking lipid accumulation to cell death are poorly understood. The present study examined the hypothesis that saturated fatty acids disrupt endoplasmic reticulum (ER) homeostasis and promote apoptosis in liver cells via accumulation of ceramide. H4IIE liver cells were exposed to varying concentrations of saturated (palmitate or stearate) or unsaturated (oleate or linoleate) fatty acids. ER homeostasis was monitored using markers of the ER stress response pathway, including phosphorylation of IRE1α and eIF2α, splicing of XBP1 mRNA, and expression of molecular chaperone (e.g., GRP78) and proapoptotic (CCAAT/enhancer-binding protein homologous protein) genes. Apoptosis was monitored using caspase activity and DNA laddering. Palmitate and stearate induced ER stress, caspase activity, and DNA laddering. Inhibition of caspase activation prevented DNA laddering. Unsaturated fatty acids did not induce ER stress or apoptosis. Saturated fatty acids increased ceramide concentration; however, inhibition of de novo ceramide synthesis did not prevent saturated fatty acid-induced ER stress and apoptosis. Unsaturated fatty acids rescued palmitate-induced ER stress and apoptosis. These data demonstrate that saturated fatty acids disrupt ER homeostasis and induce apoptosis in liver cells via mechanisms that do not involve ceramide accumulation.

scholarly journals Coordination of stress, Ca2+, and immunogenic signaling pathways by PERK at the endoplasmic reticulum

2016 ◽  
Vol 397 (7) ◽  
pp. 649-656 ◽  
Author(s):  
Alexander R. van Vliet ◽  
Abhishek D. Garg ◽  
Patrizia Agostinis
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Signaling Pathways ◽  
Unfolded Protein ◽  
Independent Functions ◽  
Intracellular Ca ◽  
Stress Signals ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Er Homeostasis

AbstractThe endoplasmic reticulum (ER) is the main coordinator of intracellular Ca2+signaling, protein synthesis, and folding. The ER is also implicated in the formation of contact sites with other organelles and structures, including mitochondria, plasma membrane (PM), and endosomes, thereby orchestrating through interorganelle signaling pathways, a variety of cellular responses including Ca2+homeostasis, metabolism, and cell death signaling. Upon loss of its folding capacity, incited by a number of stress signals including those elicited by various anticancer therapies, the unfolded protein response (UPR) is launched to restore ER homeostasis. The ER stress sensor protein kinase RNA-like ER kinase (PERK) is a key mediator of the UPR and its role during ER stress has been largely recognized. However, growing evidence suggests that PERK may govern signaling pathways through UPR-independent functions. Here, we discuss emerging noncanonical roles of PERK with particular relevance for the induction of danger or immunogenic signaling and interorganelle communication.

scholarly journals The endocannabinoid 2-arachidonoylglycerol promotes endoplasmic reticulum stress in placental cells

Reproduction ◽  
2020 ◽  
Vol 160 (2) ◽  
pp. 171-180 ◽  
Author(s):  
Marta Almada ◽  
Lia Costa ◽  
Bruno Fonseca ◽  
Patrícia Alves ◽  
Jorge Braga ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Cannabinoid Receptor ◽  
Initiation Factor ◽  
Parp Cleavage ◽  
Ros Generation ◽  
Placental Development ◽  
Induced Apoptosis ◽  
The Unfolded Protein Response ◽  
Er Homeostasis

Proliferation, differentiation and apoptosis of trophoblast cells are required for normal placental development. Impairment of those processes may lead to pregnancy-related diseases. Disruption of endoplasmic reticulum (ER) homeostasis has been associated with several reproductive pathologies including recurrent pregnancy loss and preeclampsia. In the unfolded protein response (UPR), specific ER-stress signalling pathways are activated to restore ER homeostasis, but if the adaptive response fails, apoptosis is triggered. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and Activating transcription factor 6 (ATF6) are central players in UPR and in ER-stress-induced apoptosis, as well as downstream transcription factors, as C/EBP homologous protein (CHOP). Our previous studies have shown that the endocannabinoid 2-arachidonoylglycerol (2-AG) modulates trophoblast cell turnover. Nevertheless, the role of ER-stress on 2-AG induced apoptosis and cannabinoid signalling in trophoblast has never been addressed. In this work, we used BeWo cells and human primary cytotrophoblasts isolated from term-placenta. The expression of ER-stress markers was analysed by qRT-PCR and Western blotting. ROS generation was assessed by fluorometric methods, while apoptosis was detected by the evaluation of caspase -3/-7 activities and Poly (ADP-ribose) polymerase (PARP) cleavage. Our findings indicate that 2-AG is able to induce ER-stress and apoptosis. Moreover, the eukaryotic initiation factor 2 (eIF2α)/CHOP pathway involved in ER-stress-induced apoptosis is triggered through a mechanism dependent on cannabinoid receptor CB2 activation. The results bring novel insights on the importance of ER-stress and cannabinoid signalling on 2-AG mechanisms of action in placenta.

scholarly journals The Cross-Links of Endoplasmic Reticulum Stress, Autophagy, and Nurodegeneration in Parkinson’s Disease

2021 ◽  
Vol 13 ◽  
Author(s):  
Haigang Ren ◽  
Wanqing Zhai ◽  
Xiaojun Lu ◽  
Guanghui Wang
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Substantia Nigra Pars Compacta ◽  
Cellular Processes ◽  
Unfolded Protein ◽  
Cross Links ◽  
Main Component ◽  
Protein Response

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, and it is characterized by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc), as well as the presence of intracellular inclusions with α-synuclein as the main component in surviving DA neurons. Emerging evidence suggests that the imbalance of proteostasis is a key pathogenic factor for PD. Endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) and autophagy, two major pathways for maintaining proteostasis, play important roles in PD pathology and are considered as attractive therapeutic targets for PD treatment. However, although ER stress/UPR and autophagy appear to be independent cellular processes, they are closely related to each other. In this review, we focused on the roles and molecular cross-links between ER stress/UPR and autophagy in PD pathology. We systematically reviewed and summarized the most recent advances in regulation of ER stress/UPR and autophagy, and their cross-linking mechanisms. We also reviewed and discussed the mechanisms of the coexisting ER stress/UPR activation and dysregulated autophagy in the lesion regions of PD patients, and the underlying roles and molecular crosslinks between ER stress/UPR activation and the dysregulated autophagy in DA neurodegeneration induced by PD-associated genetic factors and PD-related neurotoxins. Finally, we indicate that the combined regulation of ER stress/UPR and autophagy would be a more effective treatment for PD rather than regulating one of these conditions alone.

scholarly journals Novel Insight into the Role of Endoplasmic Reticulum Stress in the Pathogenesis of Myocardial Ischemia-Reperfusion Injury

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Hang Zhu ◽  
Hao Zhou
Keyword(s):  
Endoplasmic Reticulum ◽  
Myocardial Ischemia ◽  
Er Stress ◽  
Stress Responses ◽  
Molecular Mechanisms ◽  
Defense Mechanism ◽  
Heart Function ◽  
Ischemia Reperfusion ◽  
Myocardial Ischemia Reperfusion ◽  
Er Homeostasis

Impaired function of the endoplasmic reticulum (ER) is followed by evolutionarily conserved cell stress responses, which are employed by cells, including cardiomyocytes, to maintain and/or restore ER homeostasis. ER stress activates the unfolded protein response (UPR) to degrade and remove abnormal proteins from the ER lumen. Although the UPR is an intracellular defense mechanism to sustain cardiomyocyte viability and heart function, excessive activation initiates ER-dependent cardiomyocyte apoptosis. Myocardial ischemia/reperfusion (I/R) injury is a pathological process occurring during or after revascularization of ischemic myocardium. Several molecular mechanisms contribute to the pathogenesis of cardiac I/R injury. Due to the dual protective/degradative effects of ER stress on cardiomyocyte viability and function, it is of interest to understand the basic concepts, regulatory signals, and molecular processes involved in ER stress following myocardial I/R injury. In this review, therefore, we present recent findings related to the novel components of ER stress activation. The complex effects of ER stress and whether they mitigate or exacerbate myocardial I/R injury are summarized to serve as the basis for research into potential therapies for cardioprotection through control of ER homeostasis.

scholarly journals Reticulon proteins modulate autophagy of the endoplasmic reticulum in maize endosperm

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Xiaoguo Zhang ◽  
Xinxin Ding ◽  
Richard Scott Marshall ◽  
Julio Paez-Valencia ◽  
Patrick Lacey ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Lipid Droplets ◽  
Autophagic Flux ◽  
Dependent Manner ◽  
Maize Endosperm ◽  
Transmembrane Segments ◽  
C Terminus ◽  
Er Homeostasis ◽  
Dose Dependent

Reticulon (Rtn) proteins shape tubular domains of the endoplasmic reticulum (ER), and in some cases are autophagy receptors for selective ER turnover. We have found that maize Rtn1 and Rtn2 control ER homeostasis and autophagic flux in endosperm aleurone cells, where the ER accumulates lipid droplets and synthesizes storage protein accretions metabolized during germination. Maize Rtn1 and Rtn2 are expressed in the endosperm, localize to the ER, and re-model ER architecture in a dose-dependent manner. Rtn1 and Rtn2 interact with Atg8a using four Atg8-interacting motifs (AIMs) located at the C-terminus, cytoplasmic loop, and within the transmembrane segments. Binding between Rtn2 and Atg8 is elevated upon ER stress. Maize rtn2 mutants display increased autophagy and up-regulation of an ER stress-responsive chaperone. We propose that maize Rtn1 and Rtn2 act as receptors for autophagy-mediated ER turnover, and thus are critical for ER homeostasis and suppression of ER stress.

Sign in / Sign up

Export Citation Format

Share Document