Secretion of Proteases by an Opportunistic Fungal Pathogen Scedosporium aurantiacum

Abstract

Scedosporium aurantiacum is an opportunistic filamentous fungus increasingly isolated from the sputum of cystic fibrosis patients, and is especially prevalent in Australia. At the moment, very little is known about the infection mechanism of this fungus. Secreted proteases have been shown to contribute to fungal virulence in several studies with other fungi. Here we have compared the profiles of proteases secreted by a clinical isolate Scedosporium aurantiacum (WM 06.482) and an environmental strain (WM 10.136) grown on a synthetic cystic fibrosis sputum medium supplemented with casein or mucin. Protease activity was assessed using class-specific substrates and inhibitors. Subtilisin-like and trypsin-like serine protease activity was detected in all cultures. The greatest difference in the secretion of proteases between the two strains occurred in mucin-supplemented medium, where the activities of the elastase-like, trypsin-like and aspartic proteases were, overall, 2.5–75 fold higher in the clinical strain compared to the environmental strain. Proteases secreted by the two strains in the mucin-supplemented medium were further analyzed by mass spectrometry. Six homologs of fungal proteases were identified from the clinical strain and five from the environmental strain. Of these, three were common for both strains including a subtilisin peptidase, a putative leucine aminopeptidase and a PA-SaNapH-like protease. Trypsin-like protease was identified by mass spectrometry only in the clinical isolate even though trypsin-like activity was present in all cultures. In contrast, high elastase-like activity was measured in the culture supernatant of the clinical strain but could not be identified by mass spectrometry searching against other fungi in the NCBI database. Future availability of an annotated genome will help finalise identification of the S. aurantiacum proteases.

Respiratory mycobiome and suggestion of inter-kingdom network during acute pulmonary exacerbation in cystic fibrosis

“…jsf) revealed a number of genes encoding putative ankyrin motif-containing proteins, methyltransferases and oxidoreductases larger than the one of A. fumigatus genome 65 . Whether this larger magnitude of activities allows the mold to use a wider range of nutritive substrates or to be able to synthesize specialized metabolites including ammonia fermentation remains to be elucidated [64][65][66] , but it may participate in its successful establishment within the respiratory tract of CF patients. Over time, the interchange of these states will lead to the emergence of new Climax communities that are more and more adapted to the airway remodeling, leading to a less diverse community, composed of microorganisms highly resistant to antibiotic or antifungal agents such as Pseudomonas or Scedosporium.…”

Chymotrypsin- and trypsin-like activities secreted by the multidrug-resistant yeasts forming the Candida haemulonii complex

“…In the same way, secreted elastase-like serine peptidases from Aspergillus fumigatus assist this pathogen in lung infection during invasive arpergillosis (Kolattukudy et al 1993). In turn, the secretion of trypsin-like peptidases has already been described in opportunistic pathogens such as Scedosporium aurantiacum (Han et al 2017). Herein, the secretion of serine peptidases from the S1 family, including chymotrypsin-, trypsin-and elastase-like activities, was reported in C. haemulonii species complex.…”

“…albicans, C. guilliermondii, C. parapsilosis, C. tropicalis, C. dubliniensis and C. lipolytica (Santos and Soares 2005, Santos et al 2006, Melo et al 2007, Vermelho et al 2010, Portela et al 2010. Secreted serine-type peptidases belonging to the S1 family (e.g., trypsin-, chymotrypsin-and elastaselike peptidases) (Dubovenko et al 2010) have gained prominence due to their multiple roles in the pathogenicity of opportunistic fungi (Muszewska et al 2017), such as Scedosporium, Sporothrix and Aspergillus (Muhsin et al 1997, Barata et al 2002, Han et al 2017. these serine peptidases have great similarities in their sequences and tridimensional structures; however, they present different substrate specificities (Haën et al 1975, Ma et al 2005, in which trypsin-like peptidases have affinity for basic amino acid residues (e.g., lysine and arginine), chymotrypsin-like peptidases have affinity for aromatic amino acid residues (e.g., phenylalanine, tyrosine and tryptophan) (Vajda and Szabó 1976), while elastase-like peptidases have preference for aliphatic amino acid residues, particularly alanine (Zimmerman and Ashe 1977).…”

Recent Advances in the Treatment of Scedosporiosis and Fusariosis

“…Individuals suffering from near-drowning events in water are also at risk of disease, which may be associated with central nervous system (CNS) involvement [ 19 ]. Species of Scedosporium , including S. boydii , S. apiospermum , and S. aurantiacum are among the most commonly recovered molds from respiratory secretions of patients with chronic pulmonary diseases such as cystic fibrosis (CF) and may lead to invasive disease [ 4 , 7 , 20 , 21 ].…”

“…Scedosporium species are typically resistant to polyenes, as well as to fluconazole and demonstrate reduced susceptibility to echinocandins [ 29 , 30 ]. The high degrees of intrinsic antifungal resistance among species of Scedosporium make these infections difficult to manage and susceptibility testing of isolates from patients with scedosporiosis is highly recommended [ 21 , 31 ]. Reversal of immunosuppression is often crucial for successful management of infection [ 19 ].…”