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Updated: May 24, 2025
High-resolution Respirometry to Assess Mitochondrial Function in Permeabilized and Intact Cells
Published on: February 8, 2017
Propionate consumption activates mitochondrial activity, methylcitrate cycle and promotes changes in the cell wall of
Luiz Paulo Araújo Santos1, Dayane Moraes1, Leandro do Prado Assunção1
1Laboratório de Biologia Molecular (LBM), Instituto de Ciências Biológicas (ICB), Universidade Federal de Goiás (UFG), Brazil.
Abstract:
Histoplasma capsulatum is the fungal causative agent of the systemic mycosis Histoplasmosis, a disease with high incidence in the Americas and with worldwide occurrence. During infection, H. capsulatum yeast cells may metabolize nutrients such as odd fatty acids and amino acids, which render propionyl-CoA, a three-carbon molecule that may be toxic in high concentrations. In fungi, propionyl-CoA metabolism occurs mainly via the methylcitrate cycle (MCC). Therefore, this work aimed to analyze the adaptation of H. capsulatum to propionate. In silico analysis indicated potential genes coding for MCC specific enzymes, such as methylcitrate synthase (MCS), methylcitrate dehydratase (MCD) and methylisocitrate lyase (MCL). Propionate-grown cells induced the expression of MCS and MCL. Additionally, MCS enzymatic activity increased in propionate, regardless of the presence of the preferred carbon source glucose. Although propionate alone does not promote strong growth of H. capsulatum, propionate was consumed from the medium. Proteomic analyses identified 348 propionate-regulated proteins, 133 down-regulated and 215 up-regulated. Propionate metabolization increased ROS accumulation, cell wall remodeling, and fatty acid and amino acid oxidations. Altogether, these findings suggest that propionate metabolization activates the MCC, promotes changes in the cell wall, increases oxidative stress and activates alternative carbon source utilization.
Insights
Histoplasma capsulatum metabolizes propionate via the methylcitrate cycle (MCC), activating specific enzymes and altering cellular processes. This adaptation involves increased oxidative stress and cell wall remodeling.
Area of Science:
- Mycology
- Medical Mycology
- Fungal Pathogenesis
Background:
- Histoplasma capsulatum causes Histoplasmosis, a significant systemic mycosis.
- During infection, H. capsulatum utilizes nutrients yielding propionyl-CoA, a potentially toxic molecule.
- The methylcitrate cycle (MCC) is crucial for propionyl-CoA metabolism in fungi.
Purpose of the Study:
- To investigate the adaptation of H. capsulatum to propionate metabolism.
- To identify genes and proteins involved in propionate utilization.
- To understand the physiological and cellular responses to propionate.
Main Methods:
- In silico analysis of MCC-specific genes.
- Gene expression analysis (MCS, MCL) in propionate-grown cells.
- Enzymatic activity assays for MCS.
- Proteomic analysis to identify regulated proteins.
- Measurement of reactive oxygen species (ROS) and cell wall changes.
Main Results:
- In silico analysis identified potential MCC enzyme genes (MCS, MCD, MCL).
- Propionate induced MCS and MCL gene expression and increased MCS enzymatic activity.
- Proteomics revealed 348 propionate-regulated proteins, with 215 upregulated.
- Propionate metabolism led to increased ROS, cell wall remodeling, and altered fatty acid/amino acid oxidation.
Conclusions:
- Propionate metabolism in H. capsulatum activates the MCC pathway.
- The fungus undergoes significant cellular adaptations, including cell wall changes and increased oxidative stress.
- These findings shed light on H. capsulatum's metabolic flexibility and response to nutrient availability during infection.
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