Proteomic Analysis of Sporothrix schenckii Exposed to Oxidative Stress Induced by Hydrogen Peroxide.

Sporothrix schenckii modulates the expression of its cell wall proteins (CWPs) in response to reactive oxygen species (ROS) generated by the phagocytic cells of the human host, which allows it to evade and escape the immune system. In this study, we performed a comparative proteomic analysis of the CW of S. schenckii after exposure and nonexposure to H2O2. Several CWPs involved in CW remodeling and fungal pathogenesis that modulated their expression in response to this oxidizing agent were identified, as were a number of antioxidant enzymes and atypical CWPs, called moonlighting proteins, such as the Hsp70-5, lipase 1 (Lip1), enolase (Eno), and pyruvate kinase (Pk). Moreover, RT-qPCR assays demonstrated that the transcription of genes HSP70-5, LIP1, ENO, and PK is regulated in response to the oxidant. The results indicated that S. schenckii differentially expressed CWPs to confer protection against ROS upon this fungus. Furthermore, among these proteins, antioxidant enzymes and interestingly, moonlighting-like CWPs play a role in protecting the fungus from oxidative stress (OS), allowing it to infect human host cells.

Differential toxicity of antifungal protein AFP against mutants of Fusarium oxysporum.

Antifungal protein (AFP) from Aspergillus giganteus was assayed for toxicity against the Fusarium oxysporum wild-type strain and mutants in genes involved in cell signaling (DeltapacC, pacCc Deltafmk1) or cell-wall biogenesis (DeltachsV, Deltachs7, Deltagas1). The mutants were classified into two groups according to their sensitivity to AFP: DeltapacC, Deltagas1 and Deltachs7, which were significantly more resistant to AFP than the wild-type, and pacCC, Deltafmk1 and DeltachsV, which were more sensitive. Western blot analysis revealed increased binding of AFP to the three resistant mutants, DeltapacC, Deltagas1 and Deltachs7, but also to DeltachsV, indicating that differential binding may not be a key determinant for sensitivity. Addition of Ca2+ or K+ dramatically reduced antifungal activity and binding of AFP, suggesting that these cations compete for the same targets as AFP at the surface of the fungal cell.