Abstract
Aspergillus fumigatus, a filamentous fungus that is ubiquitous in the environment, causes several human pulmonary disorders, including chronic and acute invasive infections and allergic diseases. Lysin motif (LysM) is a small protein domain that binds chitin, a major component of fungal cell wall polysaccharides. Several secreted LysM-domain proteins without catalytic function (LysM effectors) have been identified. They act as virulence factors in plant pathogenic fungi by preventing the immune response induced by chitin; however, LysM proteins in mammalian pathogenic fungi remain largely unexplored. We describe two novel LysM-domain proteins, LdpA and LdpB, in A. fumigatus. Functional analyses of single and double knockouts revealed no significant effects on cell wall chitin content, cell wall integrity, fungal morphology and fungal growth. Fluorescent signals from LdpA-green fluorescent protein (GFP) and LdpB-GFP were observed in cell wall and extracellular matrix. In a mouse model of invasive pulmonary aspergillosis, survival did not differ between ΔldpA/B and wild-type infection; however, further studies are required to reveal their functions in fungal−host interactions.
Highlights
Lysin motif (LysM) was first described as a protein domain within the C-terminus of the lysozyme of bacteriophage[7]
To evaluate the gene expression pattern, total RNA was extracted from dormant conidia, swollen conidia and hyphae and analysed by quantitative real-time polymerase chain reaction (PCR) (Fig. 1B). ldpA was primarily expressed in hyphae, whereas ldpB was primarily expressed in dormant conidia (Fig. 1B)
We describe the characteristics of two novel LysM-domain proteins, namely, LysM-domain protein A (LdpA) and LdpB, from the human pathogenic fungus A. fumigatus
Summary
Lysin motif (LysM) was first described as a protein domain within the C-terminus of the lysozyme of bacteriophage[7]. Several LysM effectors have already been identified as virulence factors in plant pathogenic fungi[11]. Some reports have indicated that the cell wall chitin of A. fumigatus recruits lung eosinophils[20,21,22,23]. These studies suggest that mammalian pathogenic fungi produce LysM effector proteins to circumvent chitin-triggered host immunity, similar to plant pathogens. We identified novel LysM-domain protein A (LdpA) and B (LdpB) in A. fumigatus. We investigated their protein functions by using single-gene deletion mutants ΔldpA and ΔldpB and double-gene www.nature.com/scientificreports/. We investigated the involvement of LdpA and LdpB in A. fumigatus pathogenicity by using a mouse model of IPA
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