IFNγ potentiates TNFα/TNFR1 signaling to induce FAT10 expression in macrophages

Introduction: The tight regulation of the cytokine network during macrophage activation is of prime importance to enable a fast and potent innate immune response against exogenous pathogens. The inflammation mediating ubiquitin-like protein HLA-F adjacent transcript number 10 (FAT10) was shown to be transcriptionally regulated by and also regulate the nuclear factor-kappa (NF kappa B) signaling pathway. However, very little is known about the regulation of FAT10 gene expression during macrophage activation. Results: RNA sequencing of interferon (IFN)gamma-stimulated mouse peritoneal macrophages analyzed by ingenuity pathway analysis revealed significant involvement of tumor necrosis factor receptor 1 (TNFR1) signaling in addition to IFN gamma signaling. Subsequently, IFN gamma robustly upregulated FAT10 expression compared to a milder induction seen with TNF alpha or lipopolysaccharide (LPS) stimulation. While low dose IFN gamma with TNF alpha synergistically elevated FAT10 expression, preincubation of macrophages with IFN gamma strongly augmented TNF alpha-induced FAT10 expression. Moreover, a short preincubation with IFN gamma, which did not elevate FAT10, was sufficient to potentiate the induction of FAT10 by TNF alpha. A double augmentation mechanism of TNF alpha signaling was demonstrated, where IFN gamma rapidly induced the expression of TNF alpha and TNFR1, which further augmented the induction of TNF alpha and TNFR1 expression by TNF alpha. Importantly, the induction of FAT10 by IFN gamma in macrophages from TNF alpha-deficient or TNFR1-deficient mice was completely inhibited compared to macrophages from wild type (WT) mice. Finally, we show that TNF alpha-induced FAT10 expression is dependent on NF kappa B signaling. Conclusion: IFN gamma potentiates the TNF alpha/TNFR1 signaling pathway to induce FAT10 expression in mouse macrophages, mediated through NF kappa B network.