TBK1 and IKKe protect target cells from IFNgamma-mediated inflammatory apoptosis

T cells produce interferon gamma (IFN?), but it is unclear whether they can use IFN? to directly kill target cells. Here, we report that tumor targets lacking TBK1 and IKKe are killed by IFN?, which induces expression of TNFR1 and the Z-nucleic acid sensor, ZBP1 to trigger RIPK1-dependent apoptosis. Concurrent with apoptosis, IFN? unexpectedly also induces hyperactivation of NF?B in TBK1 and IKKe double-deficient cells. The two kinases normally function to inhibit IKKa/b activity and in their absence, IFN? induces elevated expression of inflammatory genes. Thus, IFN? can induce an inflammatory form of apoptosis that is normally suppressed by TBK1 and IKKe. These kinases regulate three responses: (1) induction of type I IFN; (2) inhibition of RIPK1-dependent death; and (3) inhibition of NF?B-dependent inflammation. We propose that these kinases evolved these intertwined functions so that cells infected by pathogens encoding TBK1/IKKe antagonists to block type I IFN expression will be killed by IFN?-secreting T cells to generate an alternate NF?B-dependent inflammatory response. Overall design: To determine if target cells deficient in TBK1 and IKKe are sensitive to IFN?-mediated cell death, we established B16-F1 melanoma cells with both kinases knocked-out by Crispr-Cas (DKO). B16 cells were also transduced with a non-targeting sgRNA as a control (NTNT). NTNT and DKO B16-F1 cells were treated with either media or IFN? for 16 and 24 hours. We performed gene expression profiling and gene set enrichment analysis with the data obtained from RNA-seq comparing the 4 sample groups.