title: Absence of autophagy results in reactive oxygen species-dependent amplification of RLR signaling.
abstract: Autophagy is a highly conserved process that maintains homeostasis by clearing damaged organelles and long-lived proteins. The consequences of deficiency in autophagy manifest in a variety of pathological states including neurodegenerative diseases, inflammatory disorders, and cancer. Here, we studied the role of autophagy in the homeostatic regulation of innate antiviral defense. Single-stranded RNA viruses are recognized by the members of the RIG-I-like receptors (RLRs) in the cytosol. RLRs signal through IPS-1, resulting in the production of the key antiviral cytokines, type I IFNs. Autophagy-defective Atg5(-/-) cells exhibited enhanced RLR signaling, increased IFN secretion, and resistance to infection by vesicular stomatitis virus. In the absence of autophagy, cells accumulated dysfunctional mitochondria, as well as mitochondria-associated IPS-1. Reactive oxygen species (ROS) associated with the dysfunctional mitochondria were largely responsible for the enhanced RLR signaling in Atg5(-/-) cells, as antioxidant treatment blocked the excess RLR signaling. In addition, autophagy-independent increase in mitochondrial ROS by treatment of cells with rotenone was sufficient to amplify RLR signaling in WT cells. These data indicate that autophagy contributes to homeostatic regulation of innate antiviral defense through the clearance of dysfunctional mitochondria, and revealed that ROS associated with mitochondria play a key role in potentiating RLR signaling.
authors.affiliation: Department of Immunobiology, Pathology, and Genetics, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Michal Caspi
authors.initials: MC
authors.lastname: Tal
authors.forename: Miwa
authors.initials: M
authors.lastname: Sasai
authors.forename: Heung Kyu
authors.initials: HK
authors.lastname: Lee
authors.forename: Brian
authors.initials: B
authors.lastname: Yordy
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Shadel
authors.forename: Akiko
authors.initials: A
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D002478:Cells, Cultured; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D004272:DNA, Mitochondrial / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007370:Interferon Type I / Q000096:biosynthesis; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D004272:DNA, Mitochondrial; D007370:Interferon Type I; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; C503356:Ddx58 protein, mouse; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases