NLRs (NOD-like receptors) are intracellular sensors, serving divergent functions in the regulation of innate immunity. While the best-studied NLRs exhibit positive function during immunity, we and others documented several NLRs that are anti-inflammatory in nature and these cause reduced inflammatory and immune activation during infection and inflammation. As examples, NLRX1 and NLRC3 serve as brakes of inflammatory response during viral and/or bacterial infection. One of the functions mediated by NLRX1 is that it reduces the RNA sensing pathway. By contrast, another inhibitory NLR, NLRC3, reduces the DNA sensing pathway mediated by STING and attenuates the proliferative pathway mediated by PI3K. Interestingly, two groups have shown that the LRR domain of NLRX1 can bind RNA, although the functional consequence of this finding is less clear. Recently, we have obtained multiple evidence that NLRC3 is an intracellular receptor for nucleic acids as well. Evidence for the direct binding of NLRs to their ligands is of paramount importance because an over-riding issue in the NLR field is whether NLRs are authentic ligand-binding receptors. The association of these NLRs with their putative nucleic acid agonists provides transformative evidence that some NLRs are indeed receptors of nucleic acids. An investigation of the interaction of NLRX1 and NLRC3 with nucleic acids, and how this interaction impacts cellular responses during microbial and non-microbial associated perturbation should be of great significance. In addition, at least two members within the NLR family are authentic transcriptional regulators, namely, CIITA which is a master regulator of class II MHC, and NLRC5 which is a transcriptional regulator of class I MHC in immune cells. We will explore if other NLRs might also represent transcriptional activators.
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