The cellular stress response has a vital role in regulating homeostasis by modulating cell survival and death. Stress granules are cytoplasmic compartments that enable cells to survive various stressors. Defects in the assembly and disassembly of stress granules are linked to neurodegenerative diseases, aberrant antiviral responses and cancer 1-5. Inflammasomes are multiprotein heteromeric complexes that sense molecular patterns that are associated with damage or intracellular pathogens, and assemble into cytosolic compartments known as ASC specks to

Programmed cell death plays crucial roles in organismal development and host defense. Recent studies have highlighted mechanistic overlaps and extensive, multifaceted crosstalk between pyroptosis, apoptosis, and necroptosis, three programmed cell death pathways traditionally considered autonomous. The growing body of evidence, in conjunction with the identification of molecules controlling the concomitant activation of all three pathways by pathological triggers, has led to the development of the concept of PANoptosis. During PANoptosis, inflammatory cell death occurs through the collective activation of pyroptosis, apoptosis, and necroptosis, which can circumvent pathogen-mediated inhibition of individual death pathways. Many of the molecular details of this emerging pathway are unclear. Here, we describe the activation of PANoptosis by bacterial and viral triggers and report protein interactions that reveal the formation of a PANoptosome complex. Infection of macrophages with influenza A virus, vesicular stomatitis virus, Listeria monocytogenes, or Salmonella enterica serovar Typhimurium resulted in robust cell death and the hallmarks of PANoptosis activation. Combined deletion of the PANoptotic components caspase-1 (CASP1), CASP11, receptor-interacting serine/threonine-protein kinase 3 (RIPK3), and CASP8 largely protected macrophages from cell death induced by these pathogens, while deletion of individual components provided reduced or no protection. Further, molecules from the pyroptotic, apoptotic, and necroptotic cell death pathways interacted to form a single molecular complex that we have termed the PANoptosome. Overall, our study identifies pathogens capable of activating PANoptosis and the formation of a PANoptosome complex.

The opportunistic fungal pathogen Aspergillus fumigatus is increasingly found as a coinfecting agent along with Pseudomonas aeruginosa in cystic fibrosis patients. Amongst the numerous molecules secreted by P. aeruginosa during its growth, phenazines constitute a major class. P. aeruginosa usually secreted four phenazines, pyocyanin (PYO), phenazine-1-carboxamide (PCN), 1-hydroxyphenazine (1-HP) and phenazine-1-carboxylic acid (PCA). These phenazines inhibited the growth of A. fumigatus but the underlying mechanisms and the impact of these four phenazines on A. fumigatus biology were not known. In the present study, we analyzed the functions of the four phenazines and their mode of action on A. fumigatus. All four phenazines showed A. fumigatus growth inhibitory effects by inducing production of reactive oxygen species (ROS), specifically O2·−, and reactive nitrogen species (RNS), ONOO−. A. fumigatus Sod2p was the major factor involved in resistance against the ROS and RNS induced by phenazines. Sub-inhibitory concentrations of PYO, PCA and PCN promote A. fumigatus growth by an independent iron-uptake acquisition. Of the four phenazines 1-HP had a redox-independent function; being able to chelate metal ions 1-HP induced A. fumigatus iron starvation. Our data show the fine-interactions existing between A. fumigatus and P. aeruginosa, which can lead to stimulatory or antagonistic effects.