Hemoglobin uptake by Paracoccidioides spp. is receptor-mediated

PLoS Negl Trop Dis. 2014 May 15;8(5):e2856. doi: 10.1371/journal.pntd.0002856. eCollection 2014 May.

Abstract

Iron is essential for the proliferation of fungal pathogens during infection. The availability of iron is limited due to its association with host proteins. Fungal pathogens have evolved different mechanisms to acquire iron from host; however, little is known regarding how Paracoccidioides species incorporate and metabolize this ion. In this work, host iron sources that are used by Paracoccidioides spp. were investigated. Robust fungal growth in the presence of the iron-containing molecules hemin and hemoglobin was observed. Paracoccidioides spp. present hemolytic activity and have the ability to internalize a protoporphyrin ring. Using real-time PCR and nanoUPLC-MSE proteomic approaches, fungal growth in the presence of hemoglobin was shown to result in the positive regulation of transcripts that encode putative hemoglobin receptors, in addition to the induction of proteins that are required for amino acid metabolism and vacuolar protein degradation. In fact, one hemoglobin receptor ortholog, Rbt5, was identified as a surface GPI-anchored protein that recognized hemin, protoporphyrin and hemoglobin in vitro. Antisense RNA technology and Agrobacterium tumefaciens-mediated transformation were used to generate mitotically stable Pbrbt5 mutants. The knockdown strain had a lower survival inside macrophages and in mouse spleen when compared with the parental strain, which suggested that Rbt5 could act as a virulence factor. In summary, our data indicate that Paracoccidioides spp. can use hemoglobin as an iron source most likely through receptor-mediated pathways that might be relevant for pathogenic mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Erythrocytes
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Heme / metabolism
  • Hemoglobins / metabolism*
  • Hemolysis
  • Iron / metabolism
  • Iron-Binding Proteins / metabolism
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Paracoccidioides / growth & development
  • Paracoccidioides / metabolism*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Sheep

Substances

  • Fungal Proteins
  • Hemoglobins
  • Iron-Binding Proteins
  • Receptors, Cell Surface
  • Heme
  • Iron

Grants and funding

This work at Universidade Federal de Goiás was supported by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq: http://www.cnpq.br), Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG: http://www.fapeg.go.gov.br/sitefapeg) and Financiadora de Estudos e Projetos (FINEP: http://www.finep.gov.br). EFLCB, LLP and MGSB were supported by a fellowship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES: http://www.capes.gov.br). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.