Mild impairment of mitochondrial function increases longevity and pathogen resistance through ATFS-1-driven activation of p38-regulated innate immunity

Abstract

While mitochondrial function is essential for life in all multicellular organisms, a mild impairment of mitochondrial function can extend longevity. By understanding the molecular mechanisms involved, these pathways might be targeted to promote healthy aging. In studying two long-lived mitochondrial mutants in C. elegans, we found that disrupting subunits of the mitochondrial electron transport chain resulted in upregulation of genes involved in innate immunity, which we found to be dependent on not only the canonical p38-mediated innate immune signaling pathway but also on the mitochondrial unfolded protein response. Both of these pathways are absolutely required for the increased resistance to bacterial pathogens and extended longevity of the long-lived mitochondrial mutants, as is the FOXO transcription factor DAF-16. This work demonstrates that both the p38-mediated innate immune signaling pathway and the mitochondrial unfolded protein response can act on the same innate immunity genes to promote resistance to bacterial pathogens, and that input from the mitochondria can extend longevity by signaling through these two pathways. Combined, this indicates that multiple evolutionarily conserved genetic pathways controlling innate immunity also function to modulate lifespan. Significance StatementIn this work, we explore the relationship between mitochondrial function, aging and innate immunity. We find that mild impairment of mitochondrial function results in upregulation of genes involved in innate immunity, increased resistance to bacterial pathogens and lifespan extension, all of which are dependent on two evolutionarily conserved signaling pathways. This work demonstrates how changes in functional status of the mitochondria can trigger activation of innate immunity, and that the underlying mechanisms are important for the longevity of the organism. This work advances our understanding of connections between metabolism and immunity. As the pathways studied here are conserved up to mammals, these insights may help us to understand the role of mitochondrial health, innate immunity and lifespan in humans.