A mouse model to distinguish NLRP6-mediated inflammasome-dependent and -independent functions

Significance

NLRP6 is an IEC-specific NLR that senses microbial dsRNA and LTA, which mediates inflammasome and type I IFN activation and may regulate NF-κB and MAPK pathways. Previous studies used complete knock-out of NLRP6 in mice to study its in vivo function, which cannot distinguish the multiple pathways mediated by NLRP6. Here, we generated a mutant mouse model by knocking in the R39E and W50E mutations to specifically block NLRP6-mediated inflammasome activation, which could distinguish inflammasome-dependent and -independent functions of NLRP6 in vivo.

Abstract

The NOD-like receptor (NLR) family pyrin domain containing 6 (NLRP6) serves as a sensor for microbial dsRNA or lipoteichoic acid (LTA) in intestinal epithelial cells (IECs), and initiating multiple pathways including inflammasome pathway and type I interferon (IFN) pathway, or regulating nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. NLRP6 can exert its function in both inflammasome-dependent and inflammasome-independent manners. However, there is no tool to distinguish the contribution of individual NLRP6-mediated pathway to the physiology and pathology in vivo. Here, we validated that Arg39 and Trp50 residues in the pyrin domain (PYD) of murine NLRP6 are required for ASC recruitment and inflammasome activation, but are not important for the RNA binding and PYD-independent NLRP6 oligomerization. We further generated the Nlrp6 ^R39E&W50E mutant mice, which showed reduced inflammasome activation in either steady state intestine or during viral infection. However, the type I IFN production in cells or intestine tissue from Nlrp6 ^R39E&W50E mutant mice remain normal. Interestingly, NLRP6-mediated inflammasome activation or the IFN-I production seems to play distinct roles in the defense responses against different types of RNA viruses. Our work generated a useful tool to study the inflammasome-dependent role of NLRP6 in vivo, which might help to understand the complexity of multiple pathways mediated by NLRP6 in response to the complicated and dynamic environmental cues in the intestine.