Comprehensive Characterization of Genes Required for Protein Folding in the Endoplasmic Reticulum

Jonikas, Martin C.; Collins, Sean R.; Denic, Vladimir; Oh, Eun Hae; Quan, Erin M.; Schmid, Volker; Weibezahn, Jimena; Schwappach, Blanche; Walter, Peter; Weissman, Jonathan S.; Schuldiner, Maya

doi:10.1126/science.1167983

Cited by 676 publications

(986 citation statements)

References 37 publications

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“…Supporting this, Jonikas et al (2009), the original discoverers of the EMC, show by co-immunoprecipitation analyses that Sop4 and YDR056C are interacting partners of FLAG-tagged Emc3. This experiment not only confirms my bioinformatic classification but also puts into perspective a previous study on Sop4’s role in membrane protein quality control ( Luo et al , 2002).…”

Section: Resultsmentioning

confidence: 74%

“…In Homo sapiens , the EMC comprises ten subunits, Emc1-10, whereas in Saccharomyces cerevisiae the complex comprises only Emc1-6 ( Jonikas et al , 2009). The EMC has been implicated in several cellular processes.…”

Section: Introductionmentioning

confidence: 99%

“…The EMC has been implicated in several cellular processes. It has been implicated in ERAD (ER-associated degradation) ( Christianson et al , 2012; Jonikas et al , 2009; Richard et al , 2013) but the molecular mechanism for how EMC triggers ERAD has remained elusive. Emc6 contains a Rab5 interacting domain and has been shown to interact with Rab5A in humans during autophagosome formation ( Li et al , 2013).…”

Section: Introductionmentioning

confidence: 99%

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The ubiquitous and ancient ER membrane protein complex (EMC): tether or not?

Wideman

2015

F1000Res

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The recently discovered endoplasmic reticulum (ER) membrane protein complex (EMC) has been implicated in ER-associated degradation (ERAD), lipid transport and tethering between the ER and mitochondrial outer membranes, and assembly of multipass ER-membrane proteins. The EMC has been studied in both animals and fungi but its presence outside the Opisthokont clade (animals + fungi + related protists) has not been demonstrated. Here, using homology-searching algorithms, I show that the EMC is truly an ancient and conserved protein complex, present in every major eukaryotic lineage. Very few organisms have completely lost the EMC, and most, even over 2 billion years of eukaryote evolution, have retained a majority of the complex members. I identify Sop4 and YDR056C in Saccharomyces cerevisiae as Emc7 and Emc10, respectively, subunits previously thought to be specific to animals. This study demonstrates that the EMC was present in the last eukaryote common ancestor (LECA) and is an extremely important component of eukaryotic cells even though its primary function remains elusive.

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Section: Resultsmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The ubiquitous and ancient ER membrane protein complex (EMC): tether or not?

Wideman

2015

F1000Res

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“…Activation of the endonuclease activity of IRE1 leads to unconventional splicing of Xbp1 mRNA, resulting in the translation of the active transcription factor XBP1s. 1 The functions of genes upregulated by XBP1s are aimed at clearing the ER of unfolded proteins, 2,3 thus splicing of XBP1 is generally thought to enhance pro-survival functions. However, IRE1 endonuclease activity has been shown to splice additional mRNAs and microRNAs, which has been interpreted both as a pro-survival mechanism when occurring early during ER stress and as contributing to apoptosis when occurring late during ER stress.…”

mentioning

confidence: 99%

Imaging of single cell responses to ER stress indicates that the relative dynamics of IRE1/XBP1 and PERK/ATF4 signalling rather than a switch between signalling branches determine cell survival

et al. 2015

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An accumulation of misfolded proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response (UPR) mediated via the activation of three transmembrane proteins IRE1, PERK and ATF6. Signalling through these proteins is aimed at enhancing the ER folding capacity and reducing the folding load. If these processes fail to re-establish protein homeostasis within the ER, then cell death prevails via apoptosis. How the shift from pro-survival to pro-apoptotic signalling is regulated remains unclear with both IRE1 and PERK signalling associated with pro-survival as well as pro-apoptotic signalling. To investigate the temporal activation of IRE1 and PERK in live cells and their relationship to cellular fate, we devised single cell reporters for both ER stress signalling branches. SH-SY5Y neural cells stably expressing these fluorescent protein reporter constructs to monitor IRE1-splicing activity and PERK-mediated ATF4-translation were imaged using single cell and high content time lapse live cell microscopy. We could correlate an early onset and attenuation of XBP1 splicing in the IRE1-reporter cells as cytoprotective. Indeed, silencing of IRE1 expression using shRNA inhibited splicing of XBP1 resulting in an early onset of cell death. In contrast, in the PERK-reporter cells, we observed that a slow rate of ATF4-translation and late re-initiation of general translation coincided with cells which were resistant to ER stress-induced cell death. Interestingly, whereas silencing of PERK did not affect overall levels of cell death in response to ER stress, it did increase sensitivity to ER stressors at early time points following treatment. Our results suggest that apoptosis activation in response to ER stress is not caused by a preferential activation of a single UPR branch, or by a switch from one branch to the other. Rather, our data indicated that the relative timing of IRE1 and PERK signalling determines the shift from cell survival to apoptosis.

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“…A weak, but physiologically significant, signal may become detectable as FPs accumulate. For example, deletion of the gene SCS3 does not cause detectable splicing of HAC1 mRNA [54], but analysis of scs3 Δ with a GFP driven by the UPR element reveals a low, but above background, level of fluorescence consistent with low level constitutive activation [55]. …”

Section: Approaches For Imaging Er Stress and Upr Activity In Livinmentioning

confidence: 99%

Approaches to imaging unfolded secretory protein stress in living cells

Lajoie

Fazio

Snapp

2014

Endoplasmic Reticulum Stress in Diseases

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The endoplasmic reticulum (ER) is the point of entry of proteins into the secretory pathway. Nascent peptides interact with the ER quality control machinery that ensures correct folding of the nascent proteins. Failure to properly fold proteins can lead to loss of protein function and cytotoxic aggregation of misfolded proteins that can lead to cell death. To cope with increases in the ER unfolded secretory protein burden, cells have evolved the Unfolded Protein Response (UPR). The UPR is the primary signaling pathway that monitors the state of the ER folding environment. When the unfolded protein burden overwhelms the capacity of the ER quality control machinery, a state termed ER stress, sensor proteins detect accumulation of misfolded peptides and trigger the UPR transcriptional response. The UPR, which is conserved from yeast to mammals, consists of an ensemble of complex signaling pathways that aims at adapting the ER to the new misfolded protein load. To determine how different factors impact the ER folding environment, various tools and assays have been developed. In this review, we discuss recent advances in live cell imaging reporters and model systems that enable researchers to monitor changes in the unfolded secretory protein burden and activation of the UPR and its associated signaling pathways.

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Comprehensive Characterization of Genes Required for Protein Folding in the Endoplasmic Reticulum

Cited by 676 publications

References 37 publications

The ubiquitous and ancient ER membrane protein complex (EMC): tether or not?

The ubiquitous and ancient ER membrane protein complex (EMC): tether or not?

Imaging of single cell responses to ER stress indicates that the relative dynamics of IRE1/XBP1 and PERK/ATF4 signalling rather than a switch between signalling branches determine cell survival

Approaches to imaging unfolded secretory protein stress in living cells

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