AfuInf - Proteome and polysaccharidome of Aspergillus fumigatus at early stage of infection
Final Report Abstract
Despite its obvious medical relevance, timely diagnosis and efficient antifungal treatment of A. fumigatus infection remain major challenges. Proteins on the surface of conidia and mycelium directly mediate host-pathogen interactions and also may serve as targets for diagnosis and immunotherapy. However, the similarity of protein sequences between A. fumigatus and other organisms, sometimes even including the human host, makes selection of targets for immunological-based studies difficult. Using surface protein biotinylation coupled with LC-MS/MS analysis, we identified hundreds of A. fumigatus surface proteins, including several well-known proteins such as RodA, CcpA, DppV, some known allergens, and heat shock proteins, with exposed regions. These surface-exposed regions are candidates for direct interaction with host cells and may represent antigenic epitopes that either induce protective immune responses or mediate immune evasion. Thus, our data sets provided and compiled here represent reasonable immunotherapy and diagnostic targets for future investigations. Fungal, bacterial and viral pathogens have developed various strategies to escape phagolysosomal killing and proliferate within host cells. In the case of A. fumigatus, 1,8-dihydroxynaphthalene (DHN)- melanin plays a key role in prevention of phagolysosome maturation. However, also other surface molecules including polysaccharides, and surface exposed proteins mediate the first contact with host cells and could play an important role in fungal infection. In this study, we discovered a novel important fungal protein binding to epithelial cells and thus acting as virulence factor. This is the surface-exposed chaperone protein HscA. It is a 70-kDa heat shock protein of A. fumigatus that contributes to invasion of host cells by binding to the host protein p11 (also named S100A10, annexin A2 light chain, calpactin I light chain). p11 is a multifunctional protein that forms a heterotetrameric complex with annexin A2 (AnxA2), particularly at cell membranes. The p112/AnxA22 heterotetramer or p11 itself interacts with multiple receptors and channels and regulates their cellular localization and function. AnxA2 and p112/AnxA22 heterotetramer have also been implicated in a wide range of intracellular processes including membrane domain organization, membrane fusion, vesicle trafficking, cytoskeletal-membrane dynamics, exocytosis, endocytosis, phagocytosis, and transcriptional regulation. A. fumigatus infection induces the expression of p11 and also the surface translocation of the p112/AnxA22 heterotetramer on host cells (lung epithelial cells), which contributes the association and internalization of conidia by host cells. By binding to p112/AnxA22, the cell surface-exposed HscA stabilizes p112/AnxA22 on the membrane of phagosomes and thus affects phagosome maturation. First data indicate that deletion of HscA or p11 leads to recruitment of Rab7 to the phagosomes containing A. fumigatus conidia. Rab7 is a key regulator of phagolysosome maturation. Rab7-labelled phagosomes fuse with lysosomes in the perinuclear region. By contrast, the presence of p112/AnxA22 on phagosomes excludes the recruitment of Rab7, and rather leads to recruitment of Rab11, which is a marker of recycling endosomes, and the Rab11 effector Sec15. As a consequence, A. fumigatus conidia either germinate in the less hostile environment of a phagosome or such phagosomes are transported to the surface of host cells. In summary, HscA mediates a new mechanism of A. fumigatus pathogenesis to escape delivery to phagolyososomes and helped to identify p11 as a major factor controlling the fate of phagosomes. Noteworthy, our data until now indicate a specific SNP in the non-coding region of the p11 gene in humans that is associated with higher susceptibility for invasive aspergillosis. This finding could help to identify genetic predisposition for development of invasive aspergillosis and thus help exclude distints donors for hematopoietic stem cell transplantation. On the other hand, the surface-exposed region of HscA may represent a promising target for the development of monoclonal antibodies to be used for immunotherapy.
Publications
- (2020) Biotinylated surfome profiling identifies potential biomarkers for diagnosis and therapy of Aspergillus fumigatus infection. mSphere 5(4):e00535-20
Jia LJ, Krüger T, Blango MG, von Eggeling F, Kniemeyer O, Brakhage AA
(See online at https://doi.org/10.1128/msphere.00535-20) - (2020) Dynamic surface proteomes of allergenic fungal conidia. J Proteome Res. 19:2092-2104
Blango MG, Pschibul A, Rivieccio F, Krüger T, Rafiq M, Jia LJ, Zheng T, Goldmann M, Voltersen V, Li J, Panagiotou G, Kniemeyer O, Brakhage AA
(See online at https://doi.org/10.1021/acs.jproteome.0c00013) - (2020) The role of RodA-conserved cysteine residues in the Aspergillus fumigatus conidial surface organization. J Fungi 6(3):151
Valsecchi I, Stephen-Victor E, Wong SSW, Karnam A, Sunde M, Guijarro JI, Rodríguez de Francisco B, Krüger T, Kniemeyer O, Brown GD, Willment JA, Latgé JP, Brakhage AA, Bayry J, Aimanianda V
(See online at https://doi.org/10.3390/jof6030151)
