NLRP3 inflammasome activation and subsequent inflammation is an essential line of defence to protect against infectious organisms or other potential threats to the host. However, NLRP3 inflammasome activation can contribute to the chronic inflammation observed in disease. The NLRP3 inflammasome indirectly regulates the activation of the pro-inflammatory cytokine IL-1a, which is a key player in driving harmful inflammation. Therefore, the activation of the NLRP3 inflammasome and IL-1a must be tightly regulated to avoid disease. IL-1a is produced in a precursor form (pro-IL-1a), with a highly conserved pro-domain and nuclear localisation sequence (NLS). Therefore, pro-IL-1a is thought to have an intracellular function, in addition to its secreted pro-inflammatory role. The aim of this thesis was to investigate the subcellular regulation of the NLRP3 inflammasome and pro-IL-1a. Firstly, this thesis reports that NLRP3-activating stimuli cause a disruption in endocytic traffic. It characterises the subcellular localisation of NLRP3 with respect to organelles involved in endocytic traffic and suggests that localisation of NLRP3 to endolysosomal compartments containing the phosphatidylinositol, PI4P, may be an important common step in activation of the NLRP3 inflammasome. Additionally, this research reveals a protein interactome for NLRP3, highlighting novel interactors of NLRP3 that are involved in endocytic trafficking. This study suggests that the trafficking protein TPD54, interacts with NLRP3 following nigericin stimulation, and genetic deletion of TPD54 in a THP-1 monocyte cell line potentiates NLRP3 inflammasome activation. These data suggest that a disruption in endocytic traffic may be a common cellular event in the activation of the NLRP3 inflammasome. This thesis also characterises the pro-IL-1a interactome, and through bioinformatic analysis suggests a novel role of pro-IL-1a inside the cell. The interaction of pro-IL-1a with histone acetyltransferase proteins may point to the intracellular function of pro-IL-1a. These findings build on our current understanding of the subcellular regulation of the NLRP3 inflammasome and IL-1a. Developing this work further will allow greater insight into the fundamental biology of inflammation and may prove beneficial in identifying new targets for the treatment of inflammatory disease.
Understanding the subcellular regulation of the NLRP3 inflammasome and IL-1a
Wellens, R. (Author). 1 Aug 2024
Student thesis: Phd