scholarly journals BIK ubiquitination by the E3 ligase Cul5-ASB11 determines cell fate during cellular stress

2019 ◽  
Vol 218 (9) ◽  
pp. 3002-3018 ◽  
Author(s):  
Fei-Yun Chen ◽  
Min-Yu Huang ◽  
Yu-Min Lin ◽  
Chi-Huan Ho ◽  
Shu-Yu Lin ◽  
...  
Keyword(s):  
Er Stress ◽  
Cell Fate ◽  
E3 Ligase ◽  
Ubiquitin Proteasome System ◽  
Degradation Pathway ◽  
Unfolded Protein ◽  
Ubiquitin Proteasome ◽  
Cellular Stresses ◽  
The Unfolded Protein Response ◽  
Protein Response

The BH3-only pro-apoptotic protein BIK is regulated by the ubiquitin–proteasome system. However, the mechanism of this regulation and its physiological functions remain elusive. Here, we identify Cul5-ASB11 as the E3 ligase targeting BIK for ubiquitination and degradation. ER stress leads to the activation of ASB11 by XBP1s during the adaptive phase of the unfolded protein response, which stimulates BIK ubiquitination, interaction with p97/VCP, and proteolysis. This mechanism of BIK degradation contributes to ER stress adaptation by promoting cell survival. Conversely, genotoxic agents down-regulate this IRE1α–XBP1s–ASB11 axis and stabilize BIK, which contributes in part to the apoptotic response to DNA damage. We show that blockade of this BIK degradation pathway by an IRE1α inhibitor can stabilize a BIK active mutant and increase its anti-tumor activity. Our study reveals that different cellular stresses regulate BIK ubiquitination by ASB11 in opposing directions, which determines whether or not cells survive, and that blocking BIK degradation has the potential to be used as an anti-cancer strategy.

scholarly journals Opposing unfolded-protein-response signals converge on death receptor 5 to control apoptosis

Science ◽  
2014 ◽  
Vol 345 (6192) ◽  
pp. 98-101 ◽  
Author(s):  
Min Lu ◽  
David A. Lawrence ◽  
Scot Marsters ◽  
Diego Acosta-Alvear ◽  
Philipp Kimmig ◽  
...  
Keyword(s):  
Er Stress ◽  
Unfolded Protein Response ◽  
Cell Fate ◽  
Apoptotic Cell ◽  
Death Receptor ◽  
Caspase 8 ◽  
Death Receptor 5 ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Protein folding by the endoplasmic reticulum (ER) is physiologically critical; its disruption causes ER stress and augments disease. ER stress activates the unfolded protein response (UPR) to restore homeostasis. If stress persists, the UPR induces apoptotic cell death, but the mechanisms remain elusive. Here, we report that unmitigated ER stress promoted apoptosis through cell-autonomous, UPR-controlled activation of death receptor 5 (DR5). ER stressors induced DR5 transcription via the UPR mediator CHOP; however, the UPR sensor IRE1α transiently catalyzed DR5 mRNA decay, which allowed time for adaptation. Persistent ER stress built up intracellular DR5 protein, driving ligand-independent DR5 activation and apoptosis engagement via caspase-8. Thus, DR5 integrates opposing UPR signals to couple ER stress and apoptotic cell fate.

scholarly journals An HRD/DER-independent ER quality control mechanism involves Rsp5p-dependent ubiquitination and ER-Golgi transport

2002 ◽  
Vol 158 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Cole M. Haynes ◽  
Sabrina Caldwell ◽  
Antony A. Cooper
Keyword(s):  
Ubiquitin Ligase ◽  
Degradation Kinetics ◽  
Ubiquitin Proteasome System ◽  
Er Quality Control ◽  
Unfolded Protein ◽  
Ubiquitin Proteasome ◽  
Type Rate ◽  
Quality Control Mechanism ◽  
The Unfolded Protein Response ◽  
Protein Response

We have identified a new pathway of ER-associated degradation in Saccharomyces cerevisiae that functions separately from the HRD/DER pathway comprised of Hrd1p, Hrd3p, Der1p, and Ubc7p. This pathway, termed Hrd1p independent-proteolysis (HIP), is capable of recognizing and degrading both lumenal (CPY* and PrA*), and integral membrane proteins (Sec61–2p) that misfold in the ER. CPY* overexpression likely saturates the HRD/DER pathway and activates the HIP pathway, so the slowed degradation kinetics of CPY* in a hrd1Δ strain is restored to a wild-type rate when CPY* is overexpressed. Substrates of HIP require vesicular trafficking between the ER and Golgi apparatus before degradation by the ubiquitin-proteasome system. Ubiquitination of HIP substrates does not involve the HRD/DER pathway ubiquitin ligase Hrd1p, but instead uses another ubiquitin ligase, Rsp5p. HIP is regulated by the unfolded protein response as Ire1p is necessary for the degradation of CPY* when overexpressed, but not when CPY* is expressed at normal levels. Both the HIP and HRD/DER pathways contribute to the degradation of CPY*, and only by eliminating both is CPY* degradation completely blocked.

scholarly journals The Structure, Activation and Signaling of IRE1 and Its Role in Determining Cell Fate

Biomedicines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 156
Author(s):  
Natalia Siwecka ◽  
Wioletta Rozpędek-Kamińska ◽  
Adam Wawrzynkiewicz ◽  
Dariusz Pytel ◽  
J. Alan Diehl ◽  
...  
Keyword(s):  
Er Stress ◽  
Cell Fate ◽  
Stress Conditions ◽  
Molecular Characteristics ◽  
Detailed Knowledge ◽  
Drug Candidates ◽  
Unfolded Protein ◽  
Novel Therapeutic Strategies ◽  
The Unfolded Protein Response ◽  
Protein Response

Inositol-requiring enzyme type 1 (IRE1) is a serine/threonine kinase acting as one of three branches of the Unfolded Protein Response (UPR) signaling pathway, which is activated upon endoplasmic reticulum (ER) stress conditions. It is known to be capable of inducing both pro-survival and pro-apoptotic cellular responses, which are strictly related to numerous human pathologies. Among others, IRE1 activity has been confirmed to be increased in cancer, neurodegeneration, inflammatory and metabolic disorders, which are associated with an accumulation of misfolded proteins within ER lumen and the resulting ER stress conditions. Emerging evidence suggests that genetic or pharmacological modulation of IRE1 may have a significant impact on cell viability, and thus may be a promising step forward towards development of novel therapeutic strategies. In this review, we extensively describe the structural analysis of IRE1 molecule, the molecular dynamics associated with IRE1 activation, and interconnection between it and the other branches of the UPR with regard to its potential use as a therapeutic target. Detailed knowledge of the molecular characteristics of the IRE1 protein and its activation may allow the design of specific kinase or RNase modulators that may act as drug candidates.

scholarly journals The Sec61 translocon limits IRE1α signaling during the unfolded protein response

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Arunkumar Sundaram ◽  
Rachel Plumb ◽  
Suhila Appathurai ◽  
Malaiyalam Mariappan
Keyword(s):  
Er Stress ◽  
Cell Fate ◽  
Stress Conditions ◽  
Native Page ◽  
Cell Fate Decisions ◽  
Unfolded Protein ◽  
Blue Native Page ◽  
Oligomeric Complex ◽  
The Unfolded Protein Response ◽  
Protein Response

IRE1α is an endoplasmic reticulum (ER) localized endonuclease activated by misfolded proteins in the ER. Previously, we demonstrated that IRE1α forms a complex with the Sec61 translocon, to which its substrate XBP1u mRNA is recruited for cleavage during ER stress (<xref ref-type="bibr" rid="bib39">Plumb et al., 2015</xref>). Here, we probe IRE1α complexes in cells with blue native PAGE immunoblotting. We find that IRE1α forms a hetero-oligomeric complex with the Sec61 translocon that is activated upon ER stress with little change in the complex. In addition, IRE1α oligomerization, activation, and inactivation during ER stress are regulated by Sec61. Loss of the IRE1α-Sec61 translocon interaction as well as severe ER stress conditions causes IRE1α to form higher-order oligomers that exhibit continuous activation and extended cleavage of XBP1u mRNA. Thus, we propose that the Sec61-IRE1α complex defines the extent of IRE1α activity and may determine cell fate decisions during ER stress conditions.

scholarly journals Cytosolic Ca2+ modulates Golgi structure through PKC-mediated GRASP55 phosphorylation

2019 ◽  
Author(s):  
Stephen C. Ireland ◽  
Saiprasad Ramnarayanan ◽  
Mingzhou Fu ◽  
Xiaoyan Zhang ◽  
Dabel Emebo ◽  
...  
Keyword(s):  
Er Stress ◽  
Unfolded Protein ◽  
Protein Kinase Cα ◽  
Intracellular Ca ◽  
Golgi Fragmentation ◽  
Golgi Structure ◽  
Cellular Stresses ◽  
The Unfolded Protein Response ◽  
And Function ◽  
Protein Response

ABSTRACTIt has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tu) and Dithiothreitol (DTT), and found that only TG treatment caused Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, demonstrating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevated intracellular Ca2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including Phorbol 12-myristate 13-acetate (PMA) and histamine, modulates the Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca2+ modulates Golgi structure and function.

scholarly journals Ubiquilin and p97/VCP bind erasin, forming a complex involved in ERAD

2009 ◽  
Vol 187 (2) ◽  
pp. 201-217 ◽  
Author(s):  
Precious J. Lim ◽  
Rebecca Danner ◽  
Jing Liang ◽  
Howard Doong ◽  
Christine Harman ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Degradation Pathway ◽  
Human Cells ◽  
Unfolded Protein ◽  
Er Stress Response ◽  
Stress Response Genes ◽  
Trimeric Complex ◽  
The Unfolded Protein Response ◽  
Protein Response

Unwanted proteins in the endoplasmic reticulum (ER) are exported into the cytoplasm and degraded by the proteasome through the ER-associated protein degradation pathway (ERAD). Disturbances in ERAD are linked to ER stress, which has been implicated in the pathogenesis of several human diseases. However, the composition and organization of ERAD complexes in human cells is still poorly understood. In this paper, we describe a trimeric complex that we propose functions in ERAD. Knockdown of erasin, a platform for p97/VCP and ubiquilin binding, or knockdown of ubiquilin in human cells slowed degradation of two classical ERAD substrates. In Caenorhabditis elegans, ubiquilin and erasin are ER stress-response genes that are regulated by the ire-1 branch of the unfolded protein response pathway. Loss of ubiquilin or erasin resulted in activation of ER stress, increased accumulation of polyubiquitinated proteins, and shortened lifespan in worms. Our results strongly support a role for this complex in ERAD and in the regulation of ER stress.

scholarly journals Small molecule strategies to harness the unfolded protein response: where do we go from here?

2020 ◽  
Vol 295 (46) ◽  
pp. 15692-15711 ◽  
Author(s):  
Julia M. D. Grandjean ◽  
R. Luke Wiseman
Keyword(s):  
Er Stress ◽  
Unfolded Protein Response ◽  
Cell Fate ◽  
Human Disease ◽  
Lessons Learned ◽  
Cellular Physiology ◽  
Unfolded Protein ◽  
Advantages And Disadvantages ◽  
The Unfolded Protein Response ◽  
Protein Response

The unfolded protein response (UPR) plays a central role in regulating endoplasmic reticulum (ER) and global cellular physiology in response to pathologic ER stress. The UPR is comprised of three signaling pathways activated downstream of the ER membrane proteins IRE1, ATF6, and PERK. Once activated, these proteins initiate transcriptional and translational signaling that functions to alleviate ER stress, adapt cellular physiology, and dictate cell fate. Imbalances in UPR signaling are implicated in the pathogenesis of numerous, etiologically-diverse diseases, including many neurodegenerative diseases, protein misfolding diseases, diabetes, ischemic disorders, and cancer. This has led to significant interest in establishing pharmacologic strategies to selectively modulate IRE1, ATF6, or PERK signaling to both ameliorate pathologic imbalances in UPR signaling implicated in these different diseases and define the importance of the UPR in diverse cellular and organismal contexts. Recently, there has been significant progress in the identification and characterization of UPR modulating compounds, providing new opportunities to probe the pathologic and potentially therapeutic implications of UPR signaling in human disease. Here, we describe currently available UPR modulating compounds, specifically highlighting the strategies used for their discovery and specific advantages and disadvantages in their application for probing UPR function. Furthermore, we discuss lessons learned from the application of these compounds in cellular and in vivo models to identify favorable compound properties that can help drive the further translational development of selective UPR modulators for human disease.

scholarly journals The UPRosome – decoding novel biological outputs of IRE1α function

2020 ◽  
Vol 133 (15) ◽  
pp. jcs218107 ◽  
Author(s):  
Hery Urra ◽  
Philippe Pihán ◽  
Claudio Hetz
Keyword(s):  
Er Stress ◽  
Cell Fate ◽  
Biological Significance ◽  
Functional Enrichment ◽  
Data Sets ◽  
Unfolded Protein ◽  
Binding Partners ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Cytoskeleton Dynamics

ABSTRACTDifferent perturbations alter the function of the endoplasmic reticulum (ER), resulting in the accumulation of misfolded proteins in its lumen, a condition termed ER stress. To restore ER proteostasis, a highly conserved pathway is engaged, known as the unfolded protein response (UPR), triggering adaptive programs or apoptosis of terminally damaged cells. IRE1α (also known as ERN1), the most conserved UPR sensor, mediates the activation of responses to determine cell fate under ER stress. The complexity of IRE1α regulation and its signaling outputs is mediated in part by the assembly of a dynamic multi-protein complex, named the UPRosome, that regulates IRE1α activity and the crosstalk with other pathways. We discuss several studies identifying components of the UPRosome that have illuminated novel functions in cell death, autophagy, DNA damage, energy metabolism and cytoskeleton dynamics. Here, we provide a theoretical analysis to assess the biological significance of the UPRosome and present the results of a systematic bioinformatics analysis of the available IRE1α interactome data sets followed by functional enrichment clustering. This in silico approach decoded that IRE1α also interacts with proteins involved in the cell cycle, transport, differentiation, response to viral infection and immune response. Thus, defining the spectrum of IRE1α-binding partners will reveal novel signaling outputs and the relevance of the pathway to human diseases.

scholarly journals Ubiquitination of Inositol-requiring Enzyme 1 (IRE1) by the E3 Ligase CHIP Mediates the IRE1/TRAF2/JNK Pathway

2014 ◽  
Vol 289 (44) ◽  
pp. 30567-30577 ◽  
Author(s):  
Xu Zhu ◽  
Ju Zhang ◽  
Huiying Sun ◽  
Cuicui Jiang ◽  
Yusheng Dong ◽  
...  
Keyword(s):  
Er Stress ◽  
E3 Ligase ◽  
Hek293 Cells ◽  
Jnk Pathway ◽  
Dynamic Regulation ◽  
Interacting Protein ◽  
Jnk Signaling ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Deciphering the inositol-requiring enzyme 1 (IRE1) signaling pathway is fundamentally important for understanding the unfolded protein response (UPR). The ubiquitination of proteins residing on the endoplasmic reticulum (ER) membrane has been reported to be involved in the UPR, although the mechanism has yet to be fully elucidated. Using immunoprecipitation and mass spectrometry, IRE1 was identified as a substrate of the E3 ligase CHIP (carboxyl terminus of HSC70-interacting protein) in HEK293 cells under geldanamycin-induced ER stress. Two residues of IRE1, Lys545 and Lys828, were targeted for Lys63-linked ubiquitination. Moreover, in CHIP knockdown cells, IRE1 phosphorylation and the IRE1-TRAF2 interaction were nearly abolished under ER stress, which may be due to lacking ubiquitination of IRE1 on Lys545 and Lys828, respectively. The cellular responses were evaluated, and the data indicated that CHIP-regulated IRE1/TRAF2/JNK signaling antagonized the senescence process. Therefore, our findings suggest that CHIP-mediated ubiquitination of IRE1 contributes to the dynamic regulation of the UPR.

Sign in / Sign up

Export Citation Format

Share Document