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-κB (NFκB) signaling pathway. However, very little is known about the regulation of FAT10 gene expression during macrophage activation. Results: RNA sequencing of interferon (IFN)γ-stimulated mouse peritoneal macrophages analyzed by ingenuity pathway analysis revealed significant involvement of tumor necrosis factor receptor 1 (TNFR1) signaling in addition to IFNγ signaling. Subsequently, IFNγ robustly upregulated FAT10 expression compared to a milder induction seen with TNFα or lipopolysaccharide (LPS) stimulation. While low dose IFNγ with TNFα synergistically elevated FAT10 expression, preincubation of macrophages with IFNγ strongly augmented TNFα-induced FAT10 expression. Moreover, a short preincubation with IFNγ, which did not elevate FAT10, was sufficient to potentiate the induction of FAT10 by TNFα. A double augmentation mechanism of TNFα signaling was demonstrated, where IFNγ rapidly induced the expression of TNFα and TNFR1, which further augmented the induction of TNFα and TNFR1 expression by TNFα. Importantly, the induction of FAT10 by IFNγ in macrophages from TNFα-deficient or TNFR1-deficient mice was completely inhibited compared to macrophages from wild type (WT) mice. Finally, we show that TNFα-induced FAT10 expression is dependent on NFκB signaling. Conclusion: IFNγ potentiates the TNFα/TNFR1 signaling pathway to induce FAT10 expression in mouse macrophages, mediated through NFκB network.