Cytosolic sensing of immuno-stimulatory DNA, the enemy within

Publication date: February 2018
Source:Current Opinion in Immunology, Volume 50
Author(s): Rekha Dhanwani, Mariko Takahashi, Sonia Sharma
In the cytoplasm, DNA is sensed as a universal danger signal by the innate immune system. Cyclic GMP–AMP synthase (cGAS) is a cytosolic DNA sensor/enzyme that catalyzes formation of 2′–5′-cGAMP, an atypical cyclic di-nucleotide second messenger that binds and activates the Stimulator of Interferon Genes (STING), resulting in recruitment of Tank Binding Kinase 1 (TBK1), activation of the transcription factor Interferon Regulatory Factor 3 (IRF3), and trans-activation of innate immune response genes, including type I Interferon cytokines (IFN-I). Activation of the pro-inflammatory cGAS–STING–IRF3 response is triggered by direct recognition of the DNA genomes of bacteria and viruses, but also during RNA virus infection, neoplastic transformation, tumor immunotherapy and systemic auto-inflammatory diseases. In these circumstances, the source of immuno-stimulatory DNA has often represented a fundamental yet poorly understood aspect of the response. This review focuses on recent findings related to cGAS activation by an array of self-derived DNA substrates, including endogenous retroviral elements, mitochondrial DNA (mtDNA) and micronuclei generated as a result of genotoxic stress and DNA damage. These findings emphasize the role of the cGAS axis as a cell-intrinsic innate immune response to a wide variety of genomic insults.



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