Cyclic-di-GMP and cyclic-di-AMP are second messengers produced by bacteria and influence bacterial cell survival, differentiation, colonization, biofilm formation, virulence, and bacteria-host interactions. Here, we show that in both RAW264.7 macrophage cells and primary bone-marrow–derived macrophages (BMM) the production of IFNβ and IL-6, but not TNF, in response to cyclic-di-AMP and cyclic-di-GMP requires MPYS (also known as STING, MITA, and TMEM173). Furthermore, expression of MPYS was required for interferon response factor (IRF)-3 but not nuclear factor κB (NFκB) activation in response to these bacterial metabolites. We also confirm that MPYS is required for type I IFN production by cultured macrophages infected with the intracellular pathogens Listeria monocytogenes and Francisella tularensis. However, during systemic infection with either pathogen, MPYS deficiency did not impact bacterial burdens in infected spleens. Serum IFNβ and IL-6 concentrations in the infected control and MPYS−/− mice were also similar at 24 hpi, suggesting that these pathogens stimulate MPYS-independent cytokine production during in vivo infection. Our findings indicate that bifurcating MPYS-dependent and -independent pathways mediate sensing of cytosolic bacterial infections.

Steroid hormone receptors are multi-domain proteins composed of conserved well-structured regions, such as ligand (LBD) and DNA binding domains (DBD), plus other naturally unstructured regions including the amino-terminal domain (NTD) and the hinge region between the LBD and DBD. The hinge is more than just a flexible region between the DBD and LBD and is capable of binding co-regulatory proteins and the minor groove of DNA flanking hormone response elements. Because the hinge can directly participate in DNA binding it has also been termed the carboxyl terminal extension (CTE) of the DNA binding domain. The CTE and NTD are dynamic regions of the receptor that can adopt multiple conformations depending on the environment of interacting proteins and DNA. Both regions have important regulatory roles for multiple receptor functions that are related to the ability of the CTE and NTD to form multiple active conformations. This review focuses on studies of the CTE and NTD of progesterone receptor (PR), as well as related work with other steroid/nuclear receptors.

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The ability of type I interferons (IFNs) to increase susceptibility to certain bacterial infections correlates with down regulation of myeloid cell surface IFNGR, the receptor for the type II IFN (IFNγ), and reduced myeloid cell responsiveness to IFNγ. Here, we show that the rapid reductions in mouse and human myeloid cell surface IFNGR1 expression that occur in response to type I IFN treatment reflect a rapid silencing of new ifngr1 transcription by repressive transcriptional regulators. Treatment of macrophages with IFNβ reduced cellular abundance of ifngr1 transcripts as rapidly and effectively as actinomycin D treatment. IFNβ treatment also significantly reduced the amounts of activated RNA polymerase II (pol II) and acetylated histones H3 and H4 at the ifngr1 promoter, and the activity of an ifngr1-luc reporter construct in macrophages. The suppression of ifngr1-luc activity required an intact early growth response factor (Egr)-binding site in the proximal ifngr1 promoter. Three Egr proteins and two Egr/NGFI-A binding (Nab) proteins were found to be expressed in bone macrophages, but only Egr3 and Nab1 were recruited to the ifngr1 promoter upon IFNβ stimulation. Knockdown of Nab1 in a macrophage cell line prevented down regulation of IFNGR1 and prevented the loss of acetylated histones from the ifngr1 promoter. These data suggest that type I IFN stimulation induces a rapid recruitment of a repressive Egr3/Nab1 complex that silences transcription from the ifngr1 promoter. This mechanism of gene silencing may contribute to the anti-inflammatory effects of type I IFNs.