Revised with Changes 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, we also find that another NLR, NLRP12, might intersect with the RNA sensing pathway. We will investigate if this is achieved through direct RNA binding or through indirect interactions with other RNA binding receptors. Finally, we find that a DNA receptor, AIM2, is highly expressed in immune cells other than macrophages. We will explore its functions in other immune cells, and propose experiments to assess if it has functions other than inflammasome activation.
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