Investigation of NLRP13's cleavage and its role in macrophage polarization

Abstract

The NOD-like receptors (NLRs) are mainly known for their roles in inflamma tory responses and host defense against microbial pathogens, but they are also asso ciated with metabolic disorders, autophagy regulation, transcription regulation, early embryogenesis, reproduction, and yet unknown functions. Several NLRs have been demonstrated to assemble inflammasomes which are cytosolic multiprotein complexes that can induce pyroptosis. NLRP13 is a PYRIN containing NLR protein that is found in non-rodents. There is little to no information about NLRP13 in the literature. It is determined that NLRP13 is involved in inflammasome formation and cleaved forms of this protein can be found in the cell, by the former students of our lab. In my thesis project, NLRP13’s cleavage and its possible involvement in macrophage polarization were investigated. We showed that the C-terminal of NLRP13 protein colocalizes with mitochondria after being cleaved by Caspase-8 in an overexpression model utilizing immunofluorescence and visualization by confocal microscopy. It was indicated that NLRP13 does not participate in intracellular endosomal trafficking. Additionally, it was suspected that NLRP13 might be involved in macrophage polarization. For this, THP-1 monocytes were differentiated into M1 and M2 macrophages to be analyzed by RT-qPCR and flow cytometry. No difference was observed for wild-type, plasmid control, and NLRP13 overexpressing THP-1 macrophages. Overall, the localization of cleaved forms of NLRP13 in vitro was determined and it was shown that NLRP13 has no role in macrophage polarization in THP1.