Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Scott, Jennifer, Sueiro-Olivares, Monica, Thornton, Benjamin P, Owens, Rebecca A, Muhamadali, Howbeer, Fortune-Grant, Rachael, Thomson, Darren, Thomas, Riba, Hollywood, Katherine, Doyle, Sean
et al (show 4 more authors) (2020) Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence. MBIO, 11 (5). e01985-e01920.

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There is an urgent need to develop novel antifungals to tackle the threat fungal pathogens pose to human health. Here, we have performed a comprehensive characterization and validation of the promising target methionine synthase (MetH). We show that in <i>Aspergillus fumigatus</i> the absence of this enzymatic activity triggers a metabolic imbalance that causes a reduction in intracellular ATP, which prevents fungal growth even in the presence of methionine. Interestingly, growth can be recovered in the presence of certain metabolites, which shows that <i>metH</i> is a conditionally essential gene and consequently should be targeted in established infections for a more comprehensive validation. Accordingly, we have validated the use of the tetOFF genetic model in fungal research and improved its performance <i>in vivo</i> to achieve initial validation of targets in models of established infection. We show that repression of <i>metH</i> in growing hyphae halts growth <i>in vitro</i>, which translates into a beneficial effect when targeting established infections using this model <i>in vivo</i> Finally, a structure-based virtual screening of methionine synthases reveals key differences between the human and fungal structures and unravels features in the fungal enzyme that can guide the design of novel specific inhibitors. Therefore, methionine synthase is a valuable target for the development of new antifungals.<b>IMPORTANCE</b> Fungal pathogens are responsible for millions of life-threatening infections on an annual basis worldwide. The current repertoire of antifungal drugs is very limited and, worryingly, resistance has emerged and already become a serious threat to our capacity to treat fungal diseases. The first step to develop new drugs is often to identify molecular targets in the pathogen whose inhibition during infection can prevent its growth. However, the current models are not suitable to validate targets in established infections. Here, we have characterized the promising antifungal target methionine synthase in great detail, using the prominent fungal pathogen <i>Aspergillus fumigatus</i> as a model. We have uncovered the underlying reason for its essentiality and confirmed its druggability. Furthermore, we have optimized the use of a genetic system to show a beneficial effect of targeting methionine synthase in established infections. Therefore, we believe that antifungal drugs to target methionine synthase should be pursued and additionally, we provide a model that permits gaining information about the validity of antifungal targets in established infections.

Item Type: Article
Uncontrolled Keywords: antifungal target, Aspergillus fumigatus, doxycycline, established infection, fungal virulence, methionine synthase, primary metabolism, target validation, TetOFF
Depositing User: Symplectic Admin
Date Deposited: 28 Oct 2020 14:39
Last Modified: 18 Jan 2023 23:25
DOI: 10.1128/mBio.01985-20
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