Abstract
The general translation initiation factor eIF2 is a major translational control point. Multiple signaling pathways in the integrated stress response phosphorylate eIF2 serine-51, inhibiting nucleotide exchange by eIF2B. ISRIB, a potent drug-like small molecule, renders cells insensitive to eIF2α phosphorylation and enhances cognitive function in rodents by blocking long-term depression. ISRIB was identified in a phenotypic cell-based screen, and its mechanism of action remained unknown. We now report that ISRIB is an activator of eIF2B. Our reporter-based shRNA screen revealed an eIF2B requirement for ISRIB activity. Our results define ISRIB as a symmetric molecule, show ISRIB-mediated stabilization of activated eIF2B dimers, and suggest that eIF2B4 (δ-subunit) contributes to the ISRIB binding site. We also developed new ISRIB analogs, improving its EC50 to 600 pM in cell culture. By modulating eIF2B function, ISRIB promises to be an invaluable tool in proof-of-principle studies aiming to ameliorate cognitive defects resulting from neurodegenerative diseases.
Keywords:
ISRIB; biochemistry; cell biology; eIF2; eIF2B; human; integrated stress response; protein synthesis; unfolded protein response.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetamides / chemical synthesis
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Acetamides / chemistry*
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Acetamides / pharmacology
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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Cyclohexylamines / chemical synthesis
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Cyclohexylamines / chemistry*
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Cyclohexylamines / pharmacology
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Endoplasmic Reticulum Stress / drug effects
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Eukaryotic Initiation Factor-2B / antagonists & inhibitors
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Eukaryotic Initiation Factor-2B / genetics*
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Eukaryotic Initiation Factor-2B / metabolism
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Gene Expression
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Genes, Reporter
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HEK293 Cells
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HeLa Cells
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High-Throughput Screening Assays
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Humans
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K562 Cells
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Neuroprotective Agents / chemical synthesis
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Neuroprotective Agents / chemistry*
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Neuroprotective Agents / pharmacology
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Nootropic Agents / chemical synthesis
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Nootropic Agents / chemistry*
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Nootropic Agents / pharmacology
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Phosphorylation
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Protein Binding
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Protein Multimerization / drug effects
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Protein Subunits / antagonists & inhibitors
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Protein Subunits / genetics*
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Protein Subunits / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Structure-Activity Relationship
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Thapsigargin / antagonists & inhibitors
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Thapsigargin / pharmacology
Substances
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2-(4-chlorophenoxy)-N-(4-(2-(4-chlorophenoxy)acetamido)cyclohexyl)acetamide
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Acetamides
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Bacterial Proteins
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Cyclohexylamines
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Eukaryotic Initiation Factor-2B
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Luminescent Proteins
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Neuroprotective Agents
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Nootropic Agents
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Protein Subunits
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RNA, Small Interfering
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yellow fluorescent protein, Bacteria
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Thapsigargin