Phagolysosomal proteomics identifies different macrophage activation profiles in response to Aspergillus fumigatus conidia

An Aspergillus fumigatus infection is initialized by the inhalation and germination of airborne asexual spores (conidia). Alveolar macrophages are the first immune cells to counteract an infection by phagocytosis of conidia and intracellular degradation of the pathogen. However, A. fumigatus circumvents its intracellular killing by the manipulation of the phagolysosomal maturation. With a comparative proteomic study of the phagolysosomal proteome of a virulent wild type A. fumigatus strain and an avirulent mutant strain we aimed at the identification of proteins and processes that are hijacked by the virulent strain. We found that wild type conidia strongly modulate the protein composition of the phagolysosome. Assembly and activity of vATPase, formation of lipid rafts, signal transduction pathways as well as the generation of energy and metabolites were significantly regulated in the wild type conidia containing phagolysosomes. In different experimental setups we confirmed a disassembly of the vATPase complex, reduced formation of lipid rafts and altered abundances of mTOR, MAPK signaling molecules, Rab5 and Vamp8 mediators of endosomal trafficking as well as LAMP1 and cathepsin Z lysosomal markers. Our interactome analysis indicates that A. fumigatus proteins target small GTPases of the endosomal trafficking system and signal transducers of the host, which might lead to a reduced fungicidal activity of the phagolysosome.