INFLAFRAN · Cell biology of inflammasome activation in macrophages infected with Francisella

The inflammasome is an innate immune signalling pathway that is key to fight infections. Inflammasome activation leads to caspase-1 activation, secretion of pro-inflammatory cytokines and host cell death. Inflammation and cell death can be deleterious for the host and the inflammasome has been involved in numerous inflammatory syndromes. Despite its key importance in the immune responses to infections and in diseases, the cell biology of inflammasome activation remains unclear. Particularly, the spatiotemporal localization of the different players (the receptor, the adaptor ASC and the effector caspase-1) remains to be studied. Furthermore, the interaction of the inflammasome pathway with other innate immune pathways such as the autophagy pathway or with bacterial virulence factors is still unclear. Francisella tularensis is a highly infectious bacterium that causes tularemia. Its pathogenicity is linked to its ability to replicate within the cytosol of macrophages. The outcome of the infection depends on the balance between bacterial virulence factors and host immune responses, which include the inflammasome and the autophagy pathways. Francisella infection is detected by the macrophages through the Aim2 inflammasome. In this project, we propose to set up an inflammasome reporter system to monitor in real time and in single cells, the dynamic of Aim2, ASC and caspase-1. This will allow us to dissect the cell biology of inflammasome activation during Francisella infection and particularly to address the following points:• What are the spatiotemporal dynamics of the different players?• What is the connection between the inflammasome and the autophagy pathways?• What are the molecular mechanisms of Francisella virulence factors that modulate inflammasome activation?We believe development of inflammasome fluorescent reporter systems will increase our fine knowledge on the inflammasome activation and will lead to new insights into its biology and its regulation.