Optogenetic control of the integrated stress response reveals proportional encoding and the stress memory landscape
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE210019 | GEO | 2022/07/31
REPOSITORIES: GEO
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Project description:The integrated stress response (ISR) is a key cellular signaling pathway activated by environmental alterations that represses protein synthesis to restore homeostasis. To prevent sustained damage, the ISR is counteracted by the upregulation of Growth Arrest and DNA Damage inducible 34 (GADD34), a stress-induced regulatory subunit of protein phosphatase 1 that mediates translation reactivation and stress recovery. Here, we uncover a novel ISR regulatory mechanism that post-transcriptionally controls the stability of PPP1R15A mRNA encoding GADD34. We established that the 3' untranslated region of PPP1R15A mRNA contains an active AU-rich element recognized by proteins of the ZFP36 family, promoting its rapid decay under normal conditions and stabilization for efficient expression of GADD34 in response to stress. We identify the tight temporal control of PPP1R15A mRNA turnover as a key step in establishing the ISR molecular memory, which sets the threshold for cellular responsiveness and mediates adaptation to repeated stress conditions.
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Project description:In response to different cellular stressors, the ISR kinases, PERK, PKR, HRI and GCN2, activate downstream transcriptional programs. While the core ISR transcription program is well characterized, markers that are specific to each individual ISR kinase activation pathway are not known. To identify markers that are induced by PERK or GCN2, but not the other ISR kinases, we subjected WT, GCN2-/-, and PERK-/- MEFs to amino acid starvation (RPMI 1640 SILAC -Lys -Arg) or Thapsigargin (200nM) treatment for 6 hours to activate the GCN2 and PERK pathways, respectively and performed RNA sequencing.
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Project description:Gene functional study and the emerging mRNA therapy technology heavily rely on in vitro transcribed (IVT) mRNA, but the double-stranded RNA (dsRNA) by-product generated during IVT is often recognized by cells as a marker of virus replication, leading to the integrated stress response (ISR).The biological effects of dsRNA in undifferentiated cells differ significantly from those of differentiated counterparts.Here, we found that dsRNA triggered an unprecedented ISR in zebrafish early embryos, leading to developmental delay, severe cell necrosis, and lethal malformations.Mechanistically, dsRNA stimulation caused a PKR-eIF2α independent global translation inhibition and a burst of p53 signaling. In turn, p53 activated Interferon Stimulated Genes (ISGs) and other defense-related genes in the absence of the IFN system. Unexpectedly, p53 does not promote cell death; instead, it plays a protective role in weakening the damage of translation repression by compromising protein turnover via enhanced ISGylation.This study thus unveils a distinct ISR upon dsRNA stimulation, which may help perform faithful gene overexpression in early embryos and shed light on the strategies of undifferentiated cells against RNA virus infection.
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Project description:Gene functional study and the emerging mRNA therapy technology heavily rely on in vitro transcribed (IVT) mRNA, but the double-stranded RNA (dsRNA) by-product generated during IVT is often recognized by cells as a marker of virus replication, leading to the integrated stress response (ISR).The biological effects of dsRNA in undifferentiated cells differ significantly from those of differentiated counterparts.Here, we found that dsRNA triggered an unprecedented ISR in zebrafish early embryos, leading to developmental delay, severe cell necrosis, and lethal malformations.Mechanistically, dsRNA stimulation caused a PKR-eIF2α independent global translation inhibition and a burst of p53 signaling. In turn, p53 activated Interferon Stimulated Genes (ISGs) and other defense-related genes in the absence of the IFN system. Unexpectedly, p53 does not promote cell death; instead, it plays a protective role in weakening the damage of translation repression by compromising protein turnover via enhanced ISGylation.This study thus unveils a distinct ISR upon dsRNA stimulation, which may help perform faithful gene overexpression in early embryos and shed light on the strategies of undifferentiated cells against RNA virus infection.
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Project description:Down syndrome (DS) is the most common genetic cause of intellectual disability and a major biomedical concern. Despite a general consensus that protein homeostasis is essential for normal brain function, little is known about its role in DS. Here, we show that the integrated stress response (ISR)—a conserved signaling network that maintains proteostasis by controlling protein synthesis—is activated in the brains of DS mice and individuals with DS, leading to reduced translation. Genetic and pharmacological suppression of the ISR, either by inhibiting the ISR-initiating double-stranded RNA-activated protein kinase (PKR) or boosting the function of the eIF2•eIF2B complex, which becomes limiting upon ISR activation, de-repressed translation, reversed enhanced inhibitory synaptic transmission, and rescued the deficits in synaptic plasticity and memory in DS mice. Our findings unveil a crucial role for the ISR in DS pathophysiology and suggest tuning of the ISR as a promising therapeutic intervention for DS.
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Project description:Dysregulated inflammation is a key driver of disease following infection with the globally important human pathogens, Zika virus (ZIKV) and dengue virus. However, specific mechanisms of inflammation are not well defined. Here, we demonstrate that ZIKV antagonizes mitophagy, or the process of selective degradation of damaged mitochondria. The mechanism of antagonism was through interactions between NS5 and the host protein Ajuba to prevent Ajuba translocation to depolarized mitochondria. We further identify a role of Ajuba in mitophagy through augmenting PINK1 kinase activity. Mitophagy suppression in infected Ajuba-/- cells amplified the cellular integrated stress response (ISR) to promote ZIKV replication, and increased pro-inflammatory cytokine expression dependent on the ISR kinase, PKR. Thus, ZIKV suppresses mitophagy to favor replication and this failure of mitochondrial quality control is translated to inflammation by PKR, suggesting new therapeutic targets to treat flavivirus disease.
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Project description:We elucidate the transcriptome effects of optogenetics on developing neural stem cells population. The application of optogenetics in neural stem cell (NSC), allow photo-modulation of NSC in an activity-dependent manner. This provided spatio-temporal tool for studying activity dependent neurogenesis, including the potential of regulating the differentiation and maturation process of transplanted NSC. Currently, this is mainly driven by virally transfected of Channelrhodopsin-2 (ChR2) gene, which also requires high irradiance and complex in vitro stimulation systems. Additionally, despite the extensive application of optogenetics in neuroscience, the question of what transcriptome changes does optogenetic stimulation induced in developing NSCs have not been elucidated yet. To address these questions, we established a NSC line, expressing high light-sensitivity step-function opsin (SFO) variant of the chimeric channelrhodopsin, ChRFR(C167A) (~40x higher than ChR2), via the non-viral piggyBac transposon system. We set up a simple low-irradiance optogenetics stimulation-incubation system, which sufficiently induced depolarization in differentiating NSCs. We significantly enhance neurogenesis with low power optogenetic stimulation by 3 folds. Through microarray analysis, we have identified the genes and signaling pathways in axonal remodeling, synaptic plasticity and microenvironment modulation from optogenetic stimulation. Our results elucidate the transcriptome effects of optogenetics and the ability to drive neurogenesis with low irradiance optogenetics.
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