Hemoglobin uptake by Paracoccidioides spp. is receptor-mediated

Area of Science:

• Mycology
• Infectious Diseases
• Molecular Biology

Background:

• Iron is vital for fungal pathogen proliferation, but its host availability is limited.
• Fungal pathogens have diverse iron acquisition strategies, yet Paracoccidioides species' mechanisms remain poorly understood.

Purpose of the Study:

• To investigate host iron sources utilized by Paracoccidioides species.
• To elucidate the molecular mechanisms of iron incorporation and metabolism in Paracoccidioides.

Main Methods:

• Assessing fungal growth with hemin and hemoglobin.
• Analyzing gene and protein expression changes using real-time PCR and nanoUPLC-MSE.
• Generating and characterizing Pbrbt5 mutants via antisense RNA and Agrobacterium tumefaciens transformation.
• Evaluating fungal survival in macrophages and mouse spleen models.

Main Results:

• Paracoccidioides species exhibit robust growth with hemin and hemoglobin, demonstrating hemolytic activity and protoporphyrin internalization.
• Hemoglobin exposure upregulates transcripts for putative hemoglobin receptors and proteins involved in amino acid metabolism and vacuolar degradation.
• The Rbt5 protein, a surface GPI-anchored molecule, binds hemin, protoporphyrin, and hemoglobin in vitro.
• Pbrbt5 knockdown mutants show reduced survival in host environments, indicating Rbt5's role as a virulence factor.

Conclusions:

• Paracoccidioides species effectively utilize host hemoglobin as an iron source.
• Receptor-mediated pathways, involving Rbt5, are likely critical for hemoglobin iron acquisition in Paracoccidioides.
• These findings highlight potential targets for therapeutic intervention against Paracoccidioides infections.