The Small Molecule ISRIB Reverses the Effects of eIF2a Phosphorylation on Translation and Stress Granule Assembly

We recently identified ISRIB as a potent inhibitor of the integrated stress response (ISR). ISRIB renders cells resistant to the effects of eIF2a phosphorylation and enhances long-term memory in rodents (10.7554/eLife.00498). Here we show by genome-wide in vivo ribosome profiling that translation of a restricted subset of mRNAs is induced upon ISR activation. ISRIB substantially reversed the translational effects elicited by phosphorylation of eIF2a and induced no major changes in translation or mRNA levels in unstressed cells. eIF2a phosphorylation-induced stress granule (SG) formation was blocked by ISRIB. Strikingly, ISRIB addition to stressed cells with pre-formed SGs induced their rapid disassembly, liberating mRNAs into the actively translating pool. Restoration of mRNA translation and modulation of SG dynamics may be an effective treatment of neurodegenerative diseases characterized by eIF2a phosphorylation, SG formation and cognitive loss. Overall design: Ribosome profiling with paired RNA-seq