A Hybrid Virology-Proteomics Approach Defines the Mechanisms of Cellular Immune Response to Viral DNA

摘要

In mammalian cells, detection of an intracellular virus initiates immunological cellular programs required for ultimately clearing systemic infection. To this end, the cell utilizes specialized proteins called "DNA sensors" for detecting and responding to the presence of viral DNA within the cellular milieu. Several DNA sensors have already been demonstrated to bind directly to viral nucleic acids and induce antiviral cytokines and innate immunity. We have previously characterized the human PYHIN protein IFI16 as the first DNA sensor to function as a sensor of two nuclear-replicating herpesviruses, herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV) within the nucleus; however, the mechanisms by which IFI16 elicits immune signaling remains poorly characterized. To define these uncharacterized signaling pathways, we generated IFI16 protein interaction networks during HSV-1 infection. To begin, we infected human fibroblasts with HSV-1 and tracked IFI16 levels throughout infection. Interestingly, IFI16 was observed to be rapidly degraded, beginning immediately upon infection and being completely degraded by 4 hours post-infection (Figure 1). This degradation was not due to changes at the RNA level, as demonstrated by qPCR. IFI16 destabilization was dependent upon activity of the proteasome as treatment with proteasome inhibitor MG132 rescued IFI16 loss during HSV-1 infection.