Identification of cGAS as an innate immune sensor of extracellular bacterium .

Cyclic GMP-AMP synthase (cGAS) is reported essential for detecting intracellular bacteria. However, it remains to be determined whether and how cGAS is involved in extracellular bacterial infection. Here, we report that cGAS is essential for mediating type I interferon (IFN) production in infection by multiple extracellular pathogens, including , , and In addition, the canonical cGAS-stimulator of interferon gene (STING)-IFN axis is required for protecting mice from induced mouse acute pulmonary infection, confirmed in cGAS pathway-specific gene deficiency mouse models. and mice exhibited reduced type I IFNs production, excessive inflammatory response accompanied with decreased resistance to challenge. Unfolded protein response was also modulated by cGAS through IRF3 and type I IFNs under infection. Collectively, these findings uncover the importance of cGAS in initiating immune responses against extracellular bacterial infection.