IMPACT is a GCN2 inhibitor that limits lifespan in Caenorhabditis elegans

Rafael C. Ferraz, Henrique Camara, Evandro A. De-Souza, Silas Pinto, Ana Paula F. Pinca, Richard C. Silva, Vitor N. Sato, Beatriz A. Castilho, Marcelo A. Mori

The General Control Nonderepressible 2 (GCN2) kinase is a conserved member of the integrated stress response (ISR) pathway that represses protein translation and helps cells to adapt to conditions of nutrient shortage. As such, GCN2 is required for longevity and stress resistance induced by dietary restriction (DR). IMPACT is an ancient protein that inhibits GCN2. Here, we tested whether IMPACT down-regulation mimics the effects of DR in C. elegans. Knockdown of the C. elegans IMPACT homolog impt-1 activated the ISR pathway and increased lifespan and stress resistance of worms in a gcn-2-dependent manner. Impt-1 knockdown exacerbated DR-induced longevity and required several DR-activated transcription factors to extend lifespan, among them SKN-1 and DAF-16, which were induced during larval development and adulthood, respectively, in response to impt-1 RNAi. IMPACT inhibits the ISR pathway, thus limiting the activation of stress response factors that are beneficial during aging and required under DR.