The ZrfC alkaline zinc transporter is required forAspergillus fumigatusvirulence and its growth in the presence of the Zn/Mn-chelating protein calprotectin

Abstract

Summary Aspergillus fumigatus can invade the lungs of immunocompromised individuals causing a lifethreatening disease called invasive pulmonary aspergillosis (IPA). To grow in the lungs,A. fumigatus obtains from the host all nutrients, including zinc. In living tissues, however, most zinc is tightly bound to zinc-binding proteins. Moreover, during infection the bioavailability of zinc can be further decreased by calprotectin, an antimicrobial Zn/Mn-chelating protein that is released by neutrophils in abscesses. Nevertheless, A. fumigatus manages to uptake zinc from and grow within the lungs of susceptible individuals. Thus, in this study we investigated the role of the zrfA, zrfB and zrfC genes, encoding plasma membrane zinc transporters, in A. fumigatus virulence. We showed that zrfC is essential for virulence in the absence of zrfA and zrfB, which contribute to fungal pathogenesis to a lesser extent than zrfC and are dispensable for virulence in the presence of zrfC. The special ability of ZrfC to scavenge and uptake zinc efficiently from lung tissue depended on its N-terminus, which is absent in the ZrfA and ZrfB transporters. In addition, under Zn-and/or Mn-limiting conditions zrfC enables A. fumigatus to grow in the presence of calprotectin, which is detected in fungal abscesses of non-leucopenic animals. This study extends our knowledge about the pathobiology of A. fumigatus and suggests that fungal zinc uptake could be a promising target for new antifungals.

Role of Calprotectin in Withholding Zinc and Copper from Candida albicans

“…With this response to CP, C. albicans maintains constant intracellular Zn over numerous cell divisions despite virtually undetectable bioavailable Zn outside the cell. Similar findings with Zn transporters and CP have been reported for the fungal pathogen A. fumigatus (17,18), and upregulation of transition metal import genes is also an effective strategy against CP in bacterial pathogens including Acinetobacter baumannii, S. aureus, and Salmonella (14,16,20,65,66). Aside from Zn, we demonstrate for the first time that CP can withhold Cu from a microbial organism by virtue of its picomolar affinity for Cu(II).…”

“…CP has been well studied for its Zn-withholding properties from various pathogenic organisms, including Gram-positive and Gramnegative bacteria as well as the fungus Aspergillus fumigatus, where a mutant deficient in Zn sensing shows greater susceptibility toward CP in vivo (6,(13)(14)(15)(16)(17)(18). In addition to Zn, CP can withhold Mn from bacterial pathogens in vitro and in vivo (13,14,16,19,20) and can deplete Fe and Ni from specific microbial cultures in vitro (21,22).…”

An alternative host model of a mixed fungal infection by azole susceptible and resistantAspergillusspp strains

“…23 In this model the PCR assay was able to detect 100% of samples from mice with proven infection infected with A. fumigatus (10/10) or A. lentulus (10/10).…”

“…22,23 Murine infections were performed in compliance with Real Decreto 223/ 1988 for the protection of experimental animals and the Project License CBA PA_02_2013. The experiments were carried out with 8 mice per group.…”

Exploration of Sulfur Assimilation of Aspergillus fumigatus Reveals Biosynthesis of Sulfur-Containing Amino Acids as a Virulence Determinant

“…For instance, biosynthesis of lysine (14,15), aromatic amino acids (16), and folate (17); siderophore-dependent acquisition of iron (18); and transporter-mediated uptake of zinc (19) or calcium (20) are essential for the fungus to grow within the lungs and, therefore, determine its pathogenic effects. On the other hand, any sources of nitrogen in pulmonary tissue have not yet been clearly identified, despite many studies addressing N me-tabolism (21)(22)(23)(24)(25)(26), and there are indications that A. fumigatus endures nitrogen starvation during intrapulmonary growth (27).…”