Abstract
The innate immune system recognizes cytosolic DNA associated with microbial infections and cellular stress via the cGAS/STING pathway, leading to activation of phospho-IRF3 and downstream IFN-I and senescence responses. To prevent hyperactivation, cGAS/STING is presumed to be nonresponsive to chromosomal self-DNA during open mitosis, although specific regulatory mechanisms are lacking. Given a role for the Golgi in STING activation, we investigated the state of the cGAS/STING pathway in interphase cells with artificially vesiculated Golgi and in cells arrested in mitosis. We find that whereas cGAS activity is impaired through interaction with mitotic chromosomes, Golgi integrity has little effect on the enzyme's production of cGAMP. In contrast, STING activation in response to either foreign DNA (cGAS-dependent) or exogenous cGAMP is impaired by a vesiculated Golgi. Overall, our data suggest a secondary means for cells to limit potentially harmful cGAS/STING responses during open mitosis via natural Golgi vesiculation.
Highlights
Cells possess intrinsic sensory pathways as part of the innate immune system to detect microbial infection or other physiological insults [1]
Prior work has shown that HaCaT cells express an intact cGAS/STING pathway [60, 67, 68, 69, 70, 71], we sought to ensure the cGAS/STING pathway was functional and responsive in our HaCaT line and that this pathway was the primary mode of IRF3 phosphorylation in response to foreign DNA
HaCaTs were transfected with siRNAs targeting the cGAS/STING pathway and subsequently transfected with endotoxin-free dsDNA plasmid pGL3 (Fig 1)
Summary
Cells possess intrinsic sensory pathways as part of the innate immune system to detect microbial infection or other physiological insults [1]. We find that chemical dispersal of the Golgi abrogates cGAS/STING-dependent phospho-IRF3 responses to transfected DNA. We show that cGAS/STING activity in response to transfected DNA is diminished during open mitosis, correlating with the vesiculated state of the mitotic Golgi.
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