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Peter Walter - One of the best experts on this subject based on the ideXlab platform.
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viral evasion of the Integrated Stress Response through antagonistic eif2 p mimicry
bioRxiv, 2021Co-Authors: Michael Schoof, Adam Frost, Morgane Boone, Rosalie Lawrence, Lynn Wang, J Z Cogan, J D Wuerth, Peter WalterAbstract:Abstract Viral infection triggers activation of the Integrated Stress Response (ISR). In Response to viral double-stranded RNA (dsRNA), RNA-activated protein kinase (PKR) phosphorylates the translation initiation factor eIF2, converting it from a translation initiator into a potent translation inhibitor and this restricts the synthesis of viral proteins. Phosphorylated eIF2 (eIF2-P) inhibits translation by binding to eIF2’s dedicated, heterodecameric nucleotide exchange factor eIF2B and conformationally inactivating it. We show that the NSs protein of Sandfly Fever Sicilian virus (SFSV) allows the virus to evade the ISR. Mechanistically, NSs tightly binds to eIF2B (KD = 43 nM), blocks eIF2-P binding, and rescues eIF2B GEF activity. Cryo-EM structures demonstrate that SFSV NSs and eIF2-P directly compete, with the primary NSs contacts to eIF2Bα mediated by five ‘aromatic fingers’. NSs binding preserves eIF2B activity by maintaining eIF2B’s conformation in its active A-State.
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eif2b conformation and assembly state regulate the Integrated Stress Response
bioRxiv, 2020Co-Authors: Michael Schoof, Adam Frost, Morgane Boone, Lan Wang, Rosalie Lawrence, Peter WalterAbstract:The Integrated Stress Response (ISR) is activated by phosphorylation of the translation initiation factor eIF2 in Response to various Stress conditions. Phosphorylated eIF2 (eIF2-P) inhibits eIF29s nucleotide exchange factor eIF2B, a two-fold symmetric heterodecamer assembled from subcomplexes. Here, we monitor and manipulate eIF2B assembly in vitro and in vivo. In the absence of eIF2B9s α-subunit, the ISR is induced because unassembled eIF2B tetramer subcomplexes accumulate in cells. Upon addition of the small-molecule ISR inhibitor ISRIB, eIF2B tetramers assemble into active octamers. Surprisingly, ISRIB inhibits the ISR even in the context of fully assembled eIF2B decamers, revealing an allosteric communication between the physically distant eIF2, eIF2-P, and ISRIB binding sites. Cryo-EM structures suggest a rocking motion in eIF2B that couples these binding sites. eIF2-P binding converts eIF2B decamers into 9conjoined tetramers9 with greatly diminished activity. Thus, ISRIB9s effects in disease models could arise from eIF2B decamer stabilization, allosteric modulation, or both.
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The Integrated Stress Response: From mechanism to disease
Science, 2020Co-Authors: Mauro Costa-mattioli, Peter WalterAbstract:Protein quality control is essential for the proper function of cells and the organisms that they make up. The resulting loss of proteostasis, the processes by which the health of the cell's proteins is monitored and maintained at homeostasis, is associated with a wide range of age-related human diseases. Here, we highlight how the Integrated Stress Response (ISR), a central signaling network that responds to proteostasis defects by tuning protein synthesis rates, impedes the formation of long-term memory. In addition, we address how dysregulated ISR signaling contributes to the pathogenesis of complex diseases, including cognitive disorders, neurodegeneration, cancer, diabetes, and metabolic disorders. The development of tools through which the ISR can be modulated promises to uncover new avenues to diminish pathologies resulting from it for clinical benefit.
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Integrated Stress Response inhibitor reverses sex dependent behavioral and cell specific deficits after mild repetitive head trauma
Journal of Neurotrauma, 2020Co-Authors: Karen Krukowski, Elma S. Frias, Amber Nolan, Katherine Grue, Mckenna Becker, Gonzalo Ureta, Luz Delgado, Sebastian Bernales, Vikaas S Sohal, Peter WalterAbstract:Mild repetitive traumatic brain injury (rTBI) induces chronic behavioral and cognitive alterations and increases the risk for dementia. Currently, there are no therapeutic strategies to prevent or mitigate chronic deficits associated with rTBI. Previously we developed an animal model of rTBI that recapitulates the cognitive and behavioral deficits observed in humans. We now report that rTBI results in an increase in risk-taking behavior in male but not female mice. This behavioral phenotype is associated with chronic activation of the Integrated Stress Response and cell-specific synaptic alterations in the type A subtype of layer V pyramidal neurons in the medial prefrontal cortex. Strikingly, by briefly treating animals weeks after injury with ISRIB, a selective inhibitor of the Integrated Stress Response (ISR), we (1) relieve ISR activation, (2) reverse the increased risk-taking behavioral phenotype and maintain this reversal, and (3) restore cell-specific synaptic function in the affected mice. Our results indicate that targeting the ISR even at late time points after injury can permanently reverse behavioral changes. As such, pharmacological inhibition of the ISR emerges as a promising avenue to combat rTBI-induced behavioral dysfunction.
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structural insights into isrib a memory enhancing inhibitor of the Integrated Stress Response
FEBS Journal, 2020Co-Authors: Peter Walter, Aditya A. AnandAbstract:The Integrated Stress Response (ISR) regulates protein synthesis under conditions of Stress. Phosphorylation of translation initiation factor eIF2 by Stress-sensing kinases converts eIF2 from substrate to competitive inhibitor of its dedicated nucleotide exchange factor, eIF2B, arresting translation. A drug-like molecule called Integrated Stress Response inhibitor (ISRIB) reverses the effects of eIF2 phosphorylation and restores translation by targeting eIF2B. When administered to mice, ISRIB enhances cognition and limits cognitive decline due to brain injury. To determine ISRIB's mechanism of action, we solved an atomic structure of ISRIB bound to the human eIF2B decamer. We found that ISRIB acts as a molecular staple, pinning together tetrameric subcomplexes of eIF2B along the assembly path to a fully active, decameric enzyme. In this Structural Snapshot, we discuss ISRIB's mechanism, its ability to rescue disease mutations in eIF2B and conservation of the enzyme and ISRIB-binding pocket.
Stefan J. Marciniak - One of the best experts on this subject based on the ideXlab platform.
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The Integrated Stress Response in pulmonary disease.
European Respiratory Review, 2020Co-Authors: Giulia Emanuelli, Nikou Nassehzadeh-tabriz, Nicholas W. Morrell, Stefan J. MarciniakAbstract:The respiratory tract and its resident immune cells face daily exposure to Stress, both from without and from within. Inhaled pathogens, including severe acute respiratory syndrome coronavirus 2, and toxins from pollution trigger a cellular defence system that reduces protein synthesis to minimise viral replication or the accumulation of misfolded proteins. Simultaneously, a gene expression programme enhances antioxidant and protein folding machineries in the lung. Four kinases (PERK, PKR, GCN2 and HRI) sense a diverse range of Stresses to trigger this "Integrated Stress Response". Here we review recent advances identifying the Integrated Stress Response as a critical pathway in the pathogenesis of pulmonary diseases, including pneumonias, thoracic malignancy, pulmonary fibrosis and pulmonary hypertension. Understanding the Integrated Stress Response provides novel targets for the development of therapies.
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The Integrated Stress Response regulates BMP signalling through effects on translation.
BMC Biology, 2018Co-Authors: Elke Malzer, Caia S. Dominicus, Joseph E. Chambers, Jennifer A. Dickens, Souradip Mookerjee, Stefan J. MarciniakAbstract:Developmental pathways must be responsive to the environment. Phosphorylation of eIF2α enables a family of Stress-sensing kinases to trigger the Integrated Stress Response (ISR), which has pro-survival and developmental consequences. Bone morphogenetic proteins (BMPs) regulate multiple developmental processes in organisms from insects to mammals. Here we show in Drosophila that GCN2 antagonises BMP signalling through direct effects on translation and indirectly via the transcription factor crc (dATF4). Expression of a constitutively active GCN2 or loss of the eIF2α phosphatase dPPP1R15 impairs developmental BMP signalling in flies. In cells, inhibition of translation by GCN2 blocks downstream BMP signalling. Moreover, loss of d4E-BP, a target of crc, augments BMP signalling in vitro and rescues tissue development in vivo. These results identify a novel mechanism by which the ISR modulates BMP signalling during development.
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The Integrated Stress Response regulates BMP signaling through effects on translation
2018Co-Authors: Elke Malzer, Caia S. Dominicus, Joseph E. Chambers, Souradip Mookerjee, Stefan J. MarciniakAbstract:Developmental pathways must be responsive to the environment. Phosphorylation of eIF2α enables a family of Stress sensing kinases to trigger the Integrated Stress Response (ISR), which has pro-survival and developmental consequences. Mutations of the ISR kinase GCN2 have been implicated in the development of pulmonary arterial hypertension, a disorder known to be associated with defects of BMP signaling, but how the ISR and BMP signaling might interact is unknown. Here we show in Drosophila that GCN2 antagonises BMP signaling through direct effects on translation and indirectly via the transcription factor crc (dATF4). Expression of a constitutively active GCN2 or loss of the eIF2α phosphatase dPPP1R15 impair developmental BMP signaling in flies. In cells, inhibition of translation by GCN2 blocks downstream BMP signaling. Moreover, loss of d4E-BP, a target of crc, augments BMP signaling in vitro and rescues tissue development in vivo. These results identify a novel mechanism by which the ISR modulates BMP signaling during development. Since abnormalities of both GCN2 and BMP signaling lead to pulmonary hypertension, these findings may have wider relevance for the development of therapies for this disease.
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Bioactive small molecules reveal antagonism between the Integrated Stress Response and sterol-regulated gene expression.
Cell Metabolism, 2005Co-Authors: Heather P. Harding, Stefan J. Marciniak, Randal J Kaufman, Yuhong Zhang, Sonya M. Khersonsky, Donalyn Scheuner, Norman B. Javitt, Young-tae Chang, David RonAbstract:Summary Phosphorylation of translation initiation factor 2α (eIF2α) coordinates a translational and transcriptional program known as the Integrated Stress Response (ISR), which adapts cells to endoplasmic reticulum (ER) Stress. A screen for small molecule activators of the ISR identified two related compounds that also activated sterol-regulated genes by blocking cholesterol biosynthesis at the level of CYP51. Ketoconazole, a known CYP51 inhibitor, had similar effects, establishing that perturbed flux of precursors to cholesterol activates the ISR. Surprisingly, compound-mediated activation of sterol-regulated genes was enhanced in cells with an ISR-blocking mutation in the regulatory phosphorylation site of eIF2α. Furthermore, induction of the ISR by an artificial drug-activated eIF2α kinase reduced the level of active sterol regulatory element binding protein (SREBP) and sterol-regulated mRNAs. These findings suggest a mechanism by which interactions between sterol metabolism, the ISR, and the SREBP pathway affect lipid metabolism during ER Stress.
Heather P. Harding - One of the best experts on this subject based on the ideXlab platform.
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higher order phosphatase substrate contacts terminate the Integrated Stress Response
bioRxiv, 2021Co-Authors: Yahui Yan, Heather P. Harding, David RonAbstract:Many regulatory PPP1R subunits join few catalytic PP1c subunits to mediate phosphoserine and phosphothreonine dephosphorylation in metazoans. Regulatory subunits are known to engage PP1c9s surface, locally affecting flexible phosphopeptides access to the active site. However, catalytic efficiency of holophosphatases towards their natively-folded phosphoprotein substrates is largely unexplained. Here we present a Cryo-EM structure of the tripartite PP1c/PPP1R15A/G-actin holophosphatase that terminates signalling in the Integrated Stress Response (ISR) in pre-dephosphorylation complex with its substrate, translation initiation factor 2α (eIF2α). G-actin9s role in eIF2α dephosphorylation is supported crystallographically by the structure of the binary PPP1R15A-G-actin complex, and by biochemical and genetic confirmation of the essential role of PPP1R15A-G-actin contacts to eIF2αP dephosphorylation. In the pre-dephosphorylation CryoEM complex, G-actin aligns the catalytic and regulatory subunits, creating a composite surface that engages eIF2α9s N-terminal domain to position the distant phosphoserine-51 at the active site. eIF2α residues specifying affinity for the holophosphatase are confirmed here to make critical contacts with the eIF2α kinase PERK. Thus, a convergent process of higher-order substrate recognition specifies functionally-antagonistic phosphorylation and dephosphorylation in the ISR.
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higher order phosphatase substrate contacts terminate the Integrated Stress Response
Nature Structural & Molecular Biology, 2021Co-Authors: Yahui Yan, Heather P. Harding, David RonAbstract:Many regulatory PPP1R subunits join few catalytic PP1c subunits to mediate phosphoserine and phosphothreonine dephosphorylation in metazoans. Regulatory subunits engage the surface of PP1c, locally affecting flexible access of the phosphopeptide to the active site. However, catalytic efficiency of holophosphatases towards their phosphoprotein substrates remains unexplained. Here we present a cryo-EM structure of the tripartite PP1c–PPP1R15A–G-actin holophosphatase that terminates signaling in the mammalian Integrated Stress Response (ISR) in the pre-dephosphorylation complex with its substrate, translation initiation factor 2α (eIF2α). G-actin, whose essential role in eIF2α dephosphorylation is supported crystallographically, biochemically and genetically, aligns the catalytic and regulatory subunits, creating a composite surface that engages the N-terminal domain of eIF2α to position the distant phosphoserine-51 at the active site. Substrate residues that mediate affinity for the holophosphatase also make critical contacts with eIF2α kinases. Thus, a convergent process of higher-order substrate recognition specifies functionally antagonistic phosphorylation and dephosphorylation in the ISR. Structures of the dephosphorylation complex for phosphorylated eIF2α reveal how contacts with the regulatory PPP1R15A subunit mediate substrate selectivity, providing a paradigm for dephosphorylation reactions by diverse combinatorially assembled holophosphatases.
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isrib blunts the Integrated Stress Response by allosterically antagonising the inhibitory effect of phosphorylated eif2 on eif2b
Molecular Cell, 2021Co-Authors: Alisa Zyryanova, Kazuhiro Kashiwagi, Madoka Nishimoto, Ayako Sakamoto, Mayumi Yonemochi, Heather P. Harding, Claudia Rato, Ana Crespillocasado, Luke A Perera, Mikako ShirouzuAbstract:Summary The small molecule ISRIB antagonizes the activation of the Integrated Stress Response (ISR) by phosphorylated translation initiation factor 2, eIF2(αP). ISRIB and eIF2(αP) bind distinct sites in their common target, eIF2B, a guanine nucleotide exchange factor for eIF2. We have found that ISRIB-mediated acceleration of eIF2B's nucleotide exchange activity in vitro is observed preferentially in the presence of eIF2(αP) and is attenuated by mutations that desensitize eIF2B to the inhibitory effect of eIF2(αP). ISRIB's efficacy as an ISR inhibitor in cells also depends on presence of eIF2(αP). Cryoelectron microscopy (cryo-EM) showed that engagement of both eIF2B regulatory sites by two eIF2(αP) molecules remodels both the ISRIB-binding pocket and the pockets that would engage eIF2α during active nucleotide exchange, thereby discouraging both binding events. In vitro, eIF2(αP) and ISRIB reciprocally opposed each other's binding to eIF2B. These findings point to antagonistic allostery in ISRIB action on eIF2B, culminating in inhibition of the ISR.
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Dual role of the Integrated Stress Response in medulloblastoma tumorigenesis.
Oncotarget, 2016Co-Authors: Sarrabeth Stone, David Ron, Heather P. Harding, Stephanie Jamison, Wensheng LinAbstract:// Sarrabeth Stone 1, 2, 3, * , Yeung Ho 1, 2, 3, * , Xiting Li 1, 2, 3, 4 , Stephanie Jamison 1, 2, 3 , Heather P. Harding 5 , David Ron 5 , Wensheng Lin 1, 2, 3 1 Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 2 Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 3 Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, United States 4 Department of Periodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China 5 Cambridge Institute of Medical Research, University of Cambridge, Cambridge, United Kingdom * These authors contributed equally to this work Correspondence to: Wensheng Lin, email: linw@umn.edu Keywords: medulloblastoma, Integrated Stress Response, ER Stress, GADD34, tumorigenesis Received: May 27, 2016 Accepted: September 01, 2016 Published: September 06, 2016 ABSTRACT In Response to endoplasmic reticulum (ER) Stress, activation of pancreatic ER kinase (PERK) coordinates an adaptive program known as the Integrated Stress Response (ISR) by phosphorylating translation initiation factor 2α (eIF2α). Phosphorylated eIF2α is quickly dephosphorylated by the protein phosphatase 1 and growth arrest and DNA damage 34 (GADD34) complex. Data indicate that the ISR can either promote or suppress tumor development. Our previous studies showed that the ISR is activated in medulloblastoma in both human patients and animal models, and that the decreased ISR via PERK heterozygous deficiency attenuates medulloblastoma formation in Patched1 heterozygous deficient ( Ptch1 +/−) mice by enhancing apoptosis of pre-malignant granule cell precursors (GCPs) during cell transformation. We showed here that GADD34 heterozygous mutation moderately enhanced the ISR and noticeably increased the incidence of medulloblastoma in adult Ptch1 +/− mice. Surprisingly, GADD34 homozygous mutation strongly enhanced the ISR, but significantly decreased the incidence of medulloblastoma in adult Ptch1 +/− mice. Intriguingly, GADD34 homozygous mutation significantly enhanced pre-malignant GCP apoptosis in cerebellar hyperplastic lesions and reduced the lesion numbers in young Ptch1 +/− mice. Nevertheless, neither GADD34 heterozygous mutation nor GADD34 homozygous mutation had a significant effect on medulloblastoma cells in adult Ptch1 +/− mice. Collectively, these data imply the dual role of the ISR, promoting and inhibiting, in medulloblastoma tumorigenesis by regulating apoptosis of pre-malignant GCPs during the course of malignant transformation.
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Enhanced Integrated Stress Response Promotes Myelinating Oligodendrocyte Survival in Response to Interferon-γ
The American Journal of Pathology, 2008Co-Authors: Wensheng Lin, Phillip E. Kunkler, Heather P. Harding, David Ron, Richard P. Kraig, Brian PopkoAbstract:The T-cell-derived, pleiotropic cytokine interferon (IFN)-γ is believed to play a key regulatory role in immune-mediated demyelinating disorders of the central nervous system, including multiple sclerosis and experimental autoimmune encephalomyelitis. Our previous work has demonstrated that the endoplasmic reticulum (ER) Stress Response modulates the Response of oligodendrocytes to this cytokine. The ER Stress Response activates the pancreatic ER kinase, which coordinates an adaptive program known as the Integrated Stress Response by phosphorylating translation initiation factor 2α (eIF2α). In this study, we found that growth arrest and DNA damage 34 (GADD34), a Stress-inducible regulatory subunit of a phosphatase complex that dephosphorylates eIF2α, was selectively up-regulated in myelinating oligodendrocytes in mice that ectopically expressed IFN-γ in the central nervous system. We also found that a GADD34 mutant strain of mice displayed increased levels of phosphorylated eIF2α (p-eIF2α) in myelinating oligodendrocytes when exposure to IFN-γ, as well as diminished oligodendrocyte loss and hypomyelination. Furthermore, treatment with salubrinal, a small chemical compound that specifically inhibits protein phosphatase 1(PP1)-GADD34 phosphatase activity, increased the levels of p-eIF2α and ameliorated hypomyelination and oligodendrocyte loss in cultured hippocampal slices exposed to IFN-γ. Thus, our data provide evidence that an enhanced Integrated Stress Response could promote oligodendrocyte survival in immune-mediated demyelination diseases.
Guido Kroemer - One of the best experts on this subject based on the ideXlab platform.
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Lysosomotropic agents including azithromycin, chloroquine and hydroxychloroquine activate the Integrated Stress Response
Cell Death and Disease, 2021Co-Authors: Ai-ling Tian, Peng Liu, Liwei Zhao, Isabelle Martins, Oliver Kepp, Marion Leduc, Guido KroemerAbstract:The Integrated Stress Response manifests with the phosphorylation of eukaryotic initiation factor 2α (eIF2α) on serine residue 51 and plays a major role in the adaptation of cells to endoplasmic reticulum Stress in the initiation of autophagy and in the ignition of immune Responses. Here, we report that lysosomotropic agents, including azithromycin, chloroquine, and hydroxychloroquine, can trigger eIF2α phosphorylation in vitro (in cultured human cells) and, as validated for hydroxychloroquine, in vivo (in mice). Cells bearing a non-phosphorylatable eIF2α mutant (S51A) failed to accumulate autophagic puncta in Response to azithromycin, chloroquine, and hydroxychloroquine. Conversely, two inhibitors of eIF2α dephosphorylation, nelfinavir and salubrinal, enhanced the induction of such autophagic puncta. Altogether, these results point to the unexpected capacity of azithromycin, chloroquine, and hydroxychloroquine to elicit the Integrated Stress Response.
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Autophagy and the Integrated Stress Response
Molecular Cell, 2010Co-Authors: Guido Kroemer, Guillermo Mariño, Beth LevineAbstract:Autophagy is a tightly regulated pathway involving the lysosomal degradation of cytoplasmic organelles or cytosolic components. This pathway can be stimulated by multiple forms of cellular Stress, including nutrient or growth factor deprivation, hypoxia, reactive oxygen species, DNA damage, protein aggregates, damaged organelles, or intracellular pathogens. Both specific, stimulus-dependent and more general, stimulus-independent signaling pathways are activated to coordinate different phases of autophagy. Autophagy can be Integrated with other cellular Stress Responses through parallel stimulation of autophagy and other Stress Responses by specific Stress stimuli, through dual regulation of autophagy and other Stress Responses by multifunctional Stress signaling molecules, and/or through mutual control of autophagy and other Stress Responses. Thus, autophagy is a cell biological process that is a central component of the Integrated Stress Response.
David Ron - One of the best experts on this subject based on the ideXlab platform.
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higher order phosphatase substrate contacts terminate the Integrated Stress Response
Nature Structural & Molecular Biology, 2021Co-Authors: Yahui Yan, Heather P. Harding, David RonAbstract:Many regulatory PPP1R subunits join few catalytic PP1c subunits to mediate phosphoserine and phosphothreonine dephosphorylation in metazoans. Regulatory subunits engage the surface of PP1c, locally affecting flexible access of the phosphopeptide to the active site. However, catalytic efficiency of holophosphatases towards their phosphoprotein substrates remains unexplained. Here we present a cryo-EM structure of the tripartite PP1c–PPP1R15A–G-actin holophosphatase that terminates signaling in the mammalian Integrated Stress Response (ISR) in the pre-dephosphorylation complex with its substrate, translation initiation factor 2α (eIF2α). G-actin, whose essential role in eIF2α dephosphorylation is supported crystallographically, biochemically and genetically, aligns the catalytic and regulatory subunits, creating a composite surface that engages the N-terminal domain of eIF2α to position the distant phosphoserine-51 at the active site. Substrate residues that mediate affinity for the holophosphatase also make critical contacts with eIF2α kinases. Thus, a convergent process of higher-order substrate recognition specifies functionally antagonistic phosphorylation and dephosphorylation in the ISR. Structures of the dephosphorylation complex for phosphorylated eIF2α reveal how contacts with the regulatory PPP1R15A subunit mediate substrate selectivity, providing a paradigm for dephosphorylation reactions by diverse combinatorially assembled holophosphatases.
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higher order phosphatase substrate contacts terminate the Integrated Stress Response
bioRxiv, 2021Co-Authors: Yahui Yan, Heather P. Harding, David RonAbstract:Many regulatory PPP1R subunits join few catalytic PP1c subunits to mediate phosphoserine and phosphothreonine dephosphorylation in metazoans. Regulatory subunits are known to engage PP1c9s surface, locally affecting flexible phosphopeptides access to the active site. However, catalytic efficiency of holophosphatases towards their natively-folded phosphoprotein substrates is largely unexplained. Here we present a Cryo-EM structure of the tripartite PP1c/PPP1R15A/G-actin holophosphatase that terminates signalling in the Integrated Stress Response (ISR) in pre-dephosphorylation complex with its substrate, translation initiation factor 2α (eIF2α). G-actin9s role in eIF2α dephosphorylation is supported crystallographically by the structure of the binary PPP1R15A-G-actin complex, and by biochemical and genetic confirmation of the essential role of PPP1R15A-G-actin contacts to eIF2αP dephosphorylation. In the pre-dephosphorylation CryoEM complex, G-actin aligns the catalytic and regulatory subunits, creating a composite surface that engages eIF2α9s N-terminal domain to position the distant phosphoserine-51 at the active site. eIF2α residues specifying affinity for the holophosphatase are confirmed here to make critical contacts with the eIF2α kinase PERK. Thus, a convergent process of higher-order substrate recognition specifies functionally-antagonistic phosphorylation and dephosphorylation in the ISR.
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Dual role of the Integrated Stress Response in medulloblastoma tumorigenesis.
Oncotarget, 2016Co-Authors: Sarrabeth Stone, David Ron, Heather P. Harding, Stephanie Jamison, Wensheng LinAbstract:// Sarrabeth Stone 1, 2, 3, * , Yeung Ho 1, 2, 3, * , Xiting Li 1, 2, 3, 4 , Stephanie Jamison 1, 2, 3 , Heather P. Harding 5 , David Ron 5 , Wensheng Lin 1, 2, 3 1 Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 2 Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 3 Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota, United States 4 Department of Periodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China 5 Cambridge Institute of Medical Research, University of Cambridge, Cambridge, United Kingdom * These authors contributed equally to this work Correspondence to: Wensheng Lin, email: linw@umn.edu Keywords: medulloblastoma, Integrated Stress Response, ER Stress, GADD34, tumorigenesis Received: May 27, 2016 Accepted: September 01, 2016 Published: September 06, 2016 ABSTRACT In Response to endoplasmic reticulum (ER) Stress, activation of pancreatic ER kinase (PERK) coordinates an adaptive program known as the Integrated Stress Response (ISR) by phosphorylating translation initiation factor 2α (eIF2α). Phosphorylated eIF2α is quickly dephosphorylated by the protein phosphatase 1 and growth arrest and DNA damage 34 (GADD34) complex. Data indicate that the ISR can either promote or suppress tumor development. Our previous studies showed that the ISR is activated in medulloblastoma in both human patients and animal models, and that the decreased ISR via PERK heterozygous deficiency attenuates medulloblastoma formation in Patched1 heterozygous deficient ( Ptch1 +/−) mice by enhancing apoptosis of pre-malignant granule cell precursors (GCPs) during cell transformation. We showed here that GADD34 heterozygous mutation moderately enhanced the ISR and noticeably increased the incidence of medulloblastoma in adult Ptch1 +/− mice. Surprisingly, GADD34 homozygous mutation strongly enhanced the ISR, but significantly decreased the incidence of medulloblastoma in adult Ptch1 +/− mice. Intriguingly, GADD34 homozygous mutation significantly enhanced pre-malignant GCP apoptosis in cerebellar hyperplastic lesions and reduced the lesion numbers in young Ptch1 +/− mice. Nevertheless, neither GADD34 heterozygous mutation nor GADD34 homozygous mutation had a significant effect on medulloblastoma cells in adult Ptch1 +/− mice. Collectively, these data imply the dual role of the ISR, promoting and inhibiting, in medulloblastoma tumorigenesis by regulating apoptosis of pre-malignant GCPs during the course of malignant transformation.
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Enhanced Integrated Stress Response Promotes Myelinating Oligodendrocyte Survival in Response to Interferon-γ
The American Journal of Pathology, 2008Co-Authors: Wensheng Lin, Phillip E. Kunkler, Heather P. Harding, David Ron, Richard P. Kraig, Brian PopkoAbstract:The T-cell-derived, pleiotropic cytokine interferon (IFN)-γ is believed to play a key regulatory role in immune-mediated demyelinating disorders of the central nervous system, including multiple sclerosis and experimental autoimmune encephalomyelitis. Our previous work has demonstrated that the endoplasmic reticulum (ER) Stress Response modulates the Response of oligodendrocytes to this cytokine. The ER Stress Response activates the pancreatic ER kinase, which coordinates an adaptive program known as the Integrated Stress Response by phosphorylating translation initiation factor 2α (eIF2α). In this study, we found that growth arrest and DNA damage 34 (GADD34), a Stress-inducible regulatory subunit of a phosphatase complex that dephosphorylates eIF2α, was selectively up-regulated in myelinating oligodendrocytes in mice that ectopically expressed IFN-γ in the central nervous system. We also found that a GADD34 mutant strain of mice displayed increased levels of phosphorylated eIF2α (p-eIF2α) in myelinating oligodendrocytes when exposure to IFN-γ, as well as diminished oligodendrocyte loss and hypomyelination. Furthermore, treatment with salubrinal, a small chemical compound that specifically inhibits protein phosphatase 1(PP1)-GADD34 phosphatase activity, increased the levels of p-eIF2α and ameliorated hypomyelination and oligodendrocyte loss in cultured hippocampal slices exposed to IFN-γ. Thus, our data provide evidence that an enhanced Integrated Stress Response could promote oligodendrocyte survival in immune-mediated demyelination diseases.
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The Integrated Stress Response prevents demyelination by protecting oligodendrocytes against immune-mediated damage
Journal of Clinical Investigation, 2007Co-Authors: Wensheng Lin, Stephen D. Miller, Heather P. Harding, David Ron, Samantha L. Bailey, Brian PopkoAbstract:In Response to ER Stress, the pancreatic endoplasmic reticulum kinase (PERK) coordinates an adaptive program known as the Integrated Stress Response (ISR) by phosphorylating the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha). IFN-gamma, which activates the ER Stress Response in oligodendrocytes, is believed to play a critical role in the immune-mediated CNS disorder multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis (EAE). Here we report that CNS delivery of IFN-gamma before EAE onset ameliorated the disease course and prevented demyelination, axonal damage, and oligodendrocyte loss. The beneficial effects of IFN-gamma were accompanied by PERK activation in oligodendrocytes and were abrogated in PERK-deficient animals. Our results indicate that IFN-gamma activation of PERK in mature oligodendrocytes attenuates EAE severity and suggest that therapeutic approaches to activate the ISR could prove beneficial in MS.