Autophagic control of RLR signaling - PubMed (original) (raw)

Autophagic control of RLR signaling

Michal Caspi Tal et al. Autophagy. 2009 Jul.

Abstract

Innate immunity to viral infection is initiated within the infected cells through the recognition of unique viral signatures by pattern recognition receptors (PRRs) that mediate the induction of potent antiviral factor, type I interferons (IFNs). Infection with RNA viruses is recognized by the members of the retinoic acid inducible gene I (RIG-I)-like receptor (RLR) family in the cytosol. Our recent study demonstrates that IFN production in response to RNA viral ligands is increased in the absence of autophagy. The process of autophagy functions as an internal cleanup crew within the cell, shuttling damaged cellular organelles and long-lived proteins to the lysosomes for degradation. Our data show that the absence of autophagy leads to the amplification of RLR signaling in two ways. First, in the absence of autophagy, mitochondria accumulate within the cell leading to the buildup of mitochondrial associated protein, IPS-1, a key signaling protein for RLRs. Second, damaged mitochondria that are not degraded in the absence of autophagy provide a source of reactive oxygen species (ROS), which amplify RLR signaling in Atg5 knockout cells. Our study provides the first link between ROS and cytosolic signaling mediated by the RLRs, and suggests the importance of autophagy in the regulation of signaling emanating from mitochondria.

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Figures

Figure 1

Figure 1. The mitochondria as a point of intersect between autophagy and RLR signaling

Top: a schematic representation of RLR signaling and mitochondrial clearance by autophagy. Bottom: two possibilities are illustrated for how the absence of autophagy and the resultant mitochondrial accumulation results in increased IFN and inflammatory cytokine signaling in response to RLR stimulation. First, mitochondrial accumulation results in increased levels of the mitochondrial protein IPS-1, which results in subsequent amplification of IFN and inflammatory cytokine signaling by RLRs. Second, levels of mitochondria-associated ROS rise as damaged and potentially leaky mitochondria fail to be cleared, potentiating RLR signaling.

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