The Human Pathogen Paracoccidioides brasiliensis Has a Unique 1-Cys Peroxiredoxin That Localizes Both Intracellularly and at the Cell Surface

Abstract

Paracoccidioides brasiliensis is a temperature-dependent dimorphic fungus that causes systemic paracoccidioidomycosis, a granulomatous disease. The massive production of reactive oxygen species (ROS) by the host's cellular immune response is an essential strategy to restrain the fungal growth. Among the ROS, the hydroperoxides are very toxic antimicrobial compounds and fungal peroxidases are part of the pathogen neutralizing antioxidant arsenal against the host's defense. Among them, the peroxiredoxins are highlighted, since some estimates suggest that they are capable of decomposing most of the hydroperoxides generated in the host's mitochondria and cytosol. We presently characterized a unique P. brasiliensis 1-Cys peroxiredoxin (PbPrx1). Our results reveal that it can decompose hydrogen peroxide and organic hydroperoxides very efficiently. We showed that dithiolic, but not monothiolic compounds or heterologous thioredoxin reductant systems, were able to retain the enzyme activity. Structural analysis revealed that PbPrx1 has an α/β structure that is similar to the 1-Cys secondary structures described to date and that the quaternary conformation is represented by a dimer, independently of the redox state. We investigated the PbPrx1 localization using confocal microscopy, fluorescence-activated cell sorter, and immunoblot, and the results suggested that it localizes both in the cytoplasm and at the cell wall of the yeast and mycelial forms of P. brasiliensis , as well as in the yeast mitochondria. Our present results point to a possible role of this unique P. brasiliensis 1-Cys Prx1 in the fungal antioxidant defense mechanisms.

Immunoproteomic Analysis Reveals Novel Candidate Antigens for the Diagnosis of Paracoccidioidomycosis Due to Paracoccidioides lutzii

“…The 25 specific immunogenic proteins of P. brasiliensis can be divided into three main groups. Group 1 comprises 13 proteins that have already been described in Paracoccidioides under experimental physiological condition, namely, triosephosphate isomerase, spermidine synthase, glyceraldehyde-3-phosphate dehydrogenase, 4-hydroxyphenylpyruvate dioxygenase, thioredoxin reductase, ATP synthase subunit beta, hexokinase, HSP75-like protein, HSP60-like protein, HSP7-like protein, aconitate hydratase, mitochondrial, 1-Cys peroxiredoxin, and an uncharacterized protein (XP_010758132) [ 54 , 70 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 ], all of them enriched in our STRING network. Proteins in group 2 correspond to antigens that have already been described in human PCM [ 70 ] or immunogens that have already been described to elicit a humoral immune response in BALB/c mice, such as HSP7-like protein and HSP 60-like protein [ 71 ].…”

“…The presence of these moonlighting proteins in vesicles produced by other fungi has already been demonstrated for Histoplasma capsulatum [ 119 ], Cryptococcus neoformans [ 118 ], and Saccharomyces cerevisiae [ 120 ]. These moonlighting proteins are usually present in increased levels in the fungus cell wall during interaction with host cells, suggesting they may be involved in host–parasite interactions and virulence [ 95 , 116 , 121 , 122 , 123 ]. Some of these proteins have already been demonstrated to be crucial vaccine candidates in pathogenic fungi (e.g., glyceraldehyde-3-phosphate dehydrogenase, enolase, 14-3-3 protein, and fructose-1,6-bisphosphate aldolase), since they are highly expressed and have low identity with homolog proteins in the human host [ 124 , 125 ].…”

“…A unique P. brasiliensis 1-Cys peroxiredoxin (PbPrx1; XP_010758730) was only recently reported to localize in the cytoplasm and at the cell wall of the yeast and mycelial forms of P. brasiliensis , as well as in the yeast mitochondria [ 95 ]. Longo et al suggest a possible role of PbPrx1 in the fungal antioxidant defense mechanisms [ 95 ], and here, we report PbPrx1 as an antigen in human PCM due to P. brasiliensis s. str .…”

“…A unique P. brasiliensis 1-Cys peroxiredoxin (PbPrx1; XP_010758730) was only recently reported to localize in the cytoplasm and at the cell wall of the yeast and mycelial forms of P. brasiliensis , as well as in the yeast mitochondria [ 95 ]. Longo et al suggest a possible role of PbPrx1 in the fungal antioxidant defense mechanisms [ 95 ], and here, we report PbPrx1 as an antigen in human PCM due to P. brasiliensis s. str . Interestingly, in plants, 1-Cys peroxiredoxin has been shown to not only relieve oxidative stresses but also play a central role as molecular chaperones under severe conditions during seed germination, and that overoxidation controls the switch in function of 1-Cys-peroxiredoxins from peroxidases to molecular chaperones [ 164 ].…”

“…The immunogenic proteins were grouped according to the subcellular localization predicted by the WoLF PSORT [ 69 ]. Pieces of information about the report of these proteins as antigens in human [ 70 ] or murine PCM [ 71 ], the presence in the cell wall [ 95 , 116 , 126 ] and extracellular vesicles [ 90 ], during interaction with macrophages [ 122 ] or associated with virulence processes in Paracoccidioides [ 54 , 57 , 106 ] were noted. The illustration was partially based on Servier Medical Art elements and licensed under a Creative Commons Attribution 3.0 Unported License.…”