High osmolarity glycerol response PtcB phosphatase is important for Aspergillus fumigatus virulence

Area of Science:

• Medical Mycology
• Molecular Biology
• Signal Transduction

Background:

• Aspergillus fumigatus is an opportunistic fungal pathogen causing significant human disease.
• Understanding fungal signal transduction pathways is vital for developing effective antifungal strategies.
• Protein phosphatases play key roles in regulating cellular processes, including stress responses and virulence.

Purpose of the Study:

• To identify and characterize protein phosphatases involved in Aspergillus fumigatus virulence.
• To investigate the role of the high osmolarity glycerol (HOG) response pathway in A. fumigatus pathogenesis.
• To elucidate the function of the PtcB phosphatase in regulating fungal adaptation and host defense evasion.

Main Methods:

• Genome-wide identification of phosphatase catalytic subunit encoding genes in A. fumigatus.
• Construction and phenotypic analysis of a ΔptcB deletion mutant.
• Assessment of p38 MAPK (SakA) phosphorylation and osmo-dependent gene expression.
• Evaluation of fungal cell wall integrity, biofilm formation, and virulence in a murine invasive pulmonary aspergillosis model.

Main Results:

• 32 phosphatase catalytic subunit encoding genes were identified in A. fumigatus.
• PtcB was identified as a regulator within the HOG pathway.
• The ΔptcB mutant exhibited increased SakA phosphorylation and osmo-dependent gene expression.
• ΔptcB strains showed increased sensitivity to cell wall damaging agents, elevated chitin and β-1,3-glucan content, and impaired biofilm formation.
• The ΔptcB mutant was avirulent in a murine invasive pulmonary aspergillosis model.

Conclusions:

• The PtcB phosphatase is essential for Aspergillus fumigatus virulence.
• The HOG pathway, regulated by PtcB, plays a critical role in fungal pathogenicity.
• Targeting PtcB or the HOG pathway could represent a novel strategy for controlling invasive aspergillosis.