scholarly journals Age-related decline of the unfolded protein response in the heart promotes protein misfolding and cardiac pathology

2021 ◽  
Author(s):  
Christoph Hofmann ◽  
Erik A Blackwood ◽  
Tobias Jakobi ◽  
Clara Sandmann ◽  
Julia Groß ◽  
...  
Keyword(s):  
Heart Failure ◽  
Unfolded Protein Response ◽  
Cardiac Myocytes ◽  
Protein Misfolding ◽  
Cardiac Myocyte ◽  
Myocardial Dysfunction ◽  
Disease Process ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Cardiac myocyte death during heart failure is particularly detrimental, given that cardiac muscle exhibits limited regenerative potential. Protein aggregation was previously observed in end-stage heart failure, suggesting protein-misfolding in cardiac myocytes as a contributor to the disease process. However, the relationship between protein-misfolding, cardiac myocyte death, and myocardial dysfunction is yet to be clearly established. Here, we showed that protein synthesis and the unfolded protein response (UPR) declined as a function of mammalian postnatal development, especially in tissues with low mitotic activity, such as the heart. A deeper examination in animals models showed that compared to neonatal cardiac myocytes, adult cardiac myocytes expressed lower levels of the adaptive UPR transcription factor, ATF6, as well as lower levels of numerous ATF6-regulated genes, which was associated with susceptibility to ER stress-induced cell death. Further reduction of the ATF6-dependent gene program in ATF6 knock-out mice led to the accumulation of misfolded proteins in the myocardium and impaired myocardial function in response to cardiac stress, indicating that ATF6 plays a critical adaptive role in the setting of cardiac disease. Thus, strategies to increase ATF6 aimed at balancing proteostasis in cardiac myocytes might be a fruitful avenue for the development of novel therapies for heart disease and other age-associated diseases.

scholarly journals Protein Misfolding Induces Hypoxic Preconditioning via a Subset of the Unfolded Protein Response Machinery

2010 ◽  
Vol 30 (21) ◽  
pp. 5033-5042 ◽  
Author(s):  
Xianrong R. Mao ◽  
C. Michael Crowder
Keyword(s):  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Transcriptional Response ◽  
Hypoxic Preconditioning ◽  
Misfolded Proteins ◽  
Hypoxic Exposure ◽  
Hypoxic Injury ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

ABSTRACT Prolonged cellular hypoxia results in energy failure and ultimately cell death. However, less-severe hypoxia can induce a cytoprotective response termed hypoxic preconditioning (HP). The unfolded protein response pathway (UPR) has been known for some time to respond to hypoxia and regulate hypoxic sensitivity; however, the role of the UPR, if any, in HP essentially has been unexplored. We have shown previously that a sublethal hypoxic exposure of the nematode Caenorhabditis elegans induces a protein chaperone component of the UPR (L. L. Anderson, X. Mao, B. A. Scott, and C. M. Crowder, Science 323:630-633, 2009). Here, we show that HP induces the UPR and that the pharmacological induction of misfolded proteins is itself sufficient to stimulate a delayed protective response to hypoxic injury that requires the UPR pathway proteins IRE-1, XBP-1, and ATF-6. HP also required IRE-1 but not XBP-1 or ATF-6; instead, GCN-2, which is known to suppress translation and induce an adaptive transcriptional response under conditions of UPR activation or amino acid deprivation, was required for HP. The phosphorylation of the translation factor eIF2α, an established mechanism of GCN-2-mediated translational suppression, was not necessary for HP. These data suggest a model where hypoxia-induced misfolded proteins trigger the activation of IRE-1, which along with GCN-2 controls an adaptive response that is essential to HP.

ER stress and the unfolded protein response in intestinal inflammation

2010 ◽  
Vol 298 (6) ◽  
pp. G820-G832 ◽  
Author(s):  
Michael A. McGuckin ◽  
Rajaraman D. Eri ◽  
Indrajit Das ◽  
Rohan Lourie ◽  
Timothy H. Florin
Keyword(s):  
Er Stress ◽  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Intestinal Inflammation ◽  
Secretory Cells ◽  
Unfolded Protein ◽  
Bowel Diseases ◽  
Stressed Cells ◽  
The Unfolded Protein Response ◽  
Protein Response

Endoplasmic reticulum (ER) stress is a phenomenon that occurs when excessive protein misfolding occurs during biosynthesis. ER stress triggers a series of signaling and transcriptional events known as the unfolded protein response (UPR). The UPR attempts to restore homeostasis in the ER but if unsuccessful can trigger apoptosis in the stressed cells and local inflammation. Intestinal secretory cells are susceptible to ER stress because they produce large amounts of complex proteins for secretion, most of which are involved in mucosal defense. This review focuses on ER stress in intestinal secretory cells and describes how increased protein misfolding could occur in these cells, the process of degradation of misfolded proteins, the major molecular elements of the UPR pathway, and links between the UPR and inflammation. Evidence is reviewed from mouse models and human inflammatory bowel diseases that ties ER stress and activation of the UPR with intestinal inflammation, and possible therapeutic approaches to ameliorate ER stress are discussed.

scholarly journals The Unfolded Protein Response and Chemical Chaperones Reduce Protein Misfolding and Colitis in Mice

2013 ◽  
Vol 144 (5) ◽  
pp. 989-1000.e6 ◽  
Author(s):  
Stewart Siyan Cao ◽  
Ellen M. Zimmermann ◽  
Brandy–Mengchieh Chuang ◽  
Benbo Song ◽  
Anosike Nwokoye ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Chemical Chaperones ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Induction of the Unfolded Protein Response but Normal Basal Granulopoiesis in Mice Expressing G192X ELA2

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 314-314
Author(s):  
Mark Murakami ◽  
Jill Woloszynek ◽  
Jun Xia ◽  
Fulu Liu ◽  
Daniel Link
Keyword(s):  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Embryonic Stem ◽  
Clinical Samples ◽  
Developmental Defect ◽  
Granulocytic Differentiation ◽  
Transgenic Mouse Line ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Abstract Severe congenital neutropenia (SCN) is an inborn disorder of granulopoiesis characterized by chronic neutropenia, a block in granulocytic differentiation at the promyelocyte/myelocyte stage, and a marked propensity to develop acute myeloid leukemia. Most cases of SCN are associated with germline heterozygous mutations of ELA2, encoding neutrophil elastase (NE). To date, 59 different, mostly missense, mutations of ELA2 have been reported. A unifying mechanism by which all of the different ELA2 mutants disrupt granulopoiesis is lacking. We and others previously proposed a model in which the ELA2 mutations result in NE protein misfolding, induction of the unfolded protein response (UPR), and ultimately apoptosis of granulocytic precursors. Testing this (and other) models has been limited by the rarity of SCN and difficulty in obtaining clinical samples for testing. Herein, we report the preliminary description of a novel transgenic mouse line that expresses G192X Ela2, reproducing the G193X ELA2 mutation found in some patients with SCN. The G192X mutation was introduced into the murine Ela2 locus by homologous recombination in embryonic stem cells. Heterozygous or homozygous G192 Ela2 “knock-in” mice were healthy with no apparent developmental defect. While expression of Ela2 mRNA was normal, no mature NE protein was detected in the neutrophils of homozygous G192X Ela2 mice. However, in granulocytic precursors (mainly promyelocytes/myelocytes) a small amount of heavily glycosylated mutant NE protein was detected. Together, these observations suggest that G192X NE protein is retained in the endoplasmic reticulum (ER) and rapidly degraded. Consistent with ER stress and induction of the UPR, a significant increase in BiP/GRP78 and ATF6 mRNA expression in mutant granulocytic precursors were observed. Surprisingly, G192X Ela2 mice have normal basal granulopoiesis. The number of circulating neutrophils, granulocytic differentiation in the bone marrow, and number and cytokine responsiveness of myeloid progenitors were comparable to wild type mice. In summary, the G192X Ela2 mice appear to reproduce the NE protein misfolding and UPR activation observed in human SCN granulocytic precursors. However, expression of G192X Ela2 is not sufficient to disrupt basal granulopoiesis in mice. Studies of stress granulopoiesis are underway.

scholarly journals Modulating protein quality control

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Lars Plate ◽  
Ryan J Paxman ◽  
R Luke Wiseman ◽  
Jeffery W Kelly
Keyword(s):  
Quality Control ◽  
Small Molecules ◽  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Misfolding Diseases ◽  
Protein Response

Small molecules that modulate the unfolded protein response have the potential to treat a variety of human protein misfolding diseases.

scholarly journals Activation of the Unfolded Protein Response in Infarcted Mouse Heart and Hypoxic Cultured Cardiac Myocytes

2006 ◽  
Vol 99 (3) ◽  
pp. 275-282 ◽  
Author(s):  
Donna J. Thuerauf ◽  
Marie Marcinko ◽  
Natalie Gude ◽  
Marta Rubio ◽  
Mark A. Sussman ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Cardiac Myocytes ◽  
Mouse Heart ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

scholarly journals Translational and posttranslational regulation of XIAP by eIF2α and ATF4 promotes ER stress–induced cell death during the unfolded protein response

2014 ◽  
Vol 25 (9) ◽  
pp. 1411-1420 ◽  
Author(s):  
Nobuhiko Hiramatsu ◽  
Carissa Messah ◽  
Jaeseok Han ◽  
Matthew M. LaVail ◽  
Randal J. Kaufman ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Down Regulation ◽  
Unfolded Protein ◽  
Activity Loss ◽  
The Unfolded Protein Response ◽  
Protein Response

Endoplasmic reticulum (ER) protein misfolding activates the unfolded protein response (UPR) to help cells cope with ER stress. If ER homeostasis is not restored, UPR promotes cell death. The mechanisms of UPR-mediated cell death are poorly understood. The PKR-like endoplasmic reticulum kinase (PERK) arm of the UPR is implicated in ER stress–induced cell death, in part through up-regulation of proapoptotic CCAAT/enhancer binding protein homologous protein (CHOP). Chop−/− cells are partially resistant to ER stress–induced cell death, and CHOP overexpression alone does not induce cell death. These findings suggest that additional mechanisms regulate cell death downstream of PERK. Here we find dramatic suppression of antiapoptosis XIAP proteins in response to chronic ER stress. We find that PERK down-regulates XIAP synthesis through eIF2α and promotes XIAP degradation through ATF4. Of interest, PERK's down-regulation of XIAP occurs independently of CHOP activity. Loss of XIAP leads to increased cell death, whereas XIAP overexpression significantly enhances resistance to ER stress–induced cell death, even in the absence of CHOP. Our findings define a novel signaling circuit between PERK and XIAP that operates in parallel with PERK to CHOP induction to influence cell survival during ER stress. We propose a “two-hit” model of ER stress–induced cell death involving concomitant CHOP up-regulation and XIAP down-regulation both induced by PERK.

scholarly journals The proteasome biogenesis regulator Rpn4 cooperates with the unfolded protein response to promote resistance to endoplasmic reticulum stress

2018 ◽  
Author(s):  
Rolf M. Schmidt ◽  
Sebastian Schuck
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Misfolded Proteins ◽  
Secretory Proteins ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Multiple Signaling

ABSTRACTMisfolded proteins in the endoplasmic reticulum (ER) activate the unfolded protein response (UPR), which enhances protein folding to restore homeostasis. Additional pathways respond to ER stress, but how they help counteract protein misfolding is incompletely understood. Here, we develop a titratable system for the induction of ER stress in yeast to enable a genetic screen for factors that augment stress resistance independently of the UPR. We identify the proteasome biogenesis regulator Rpn4 and show that it cooperates with the UPR. Rpn4 abundance increases during ER stress, first by a post-transcriptional, then by a transcriptional mechanism. Induction of RPN4 transcription is triggered by cytosolic mislocalization of secretory proteins, is mediated by multiple signaling pathways and accelerates clearance of misfolded proteins from the cytosol. Thus, Rpn4 and the UPR are complementary elements of a modular cross-compartment response to ER stress.

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