Targeting a critical step in fungal hexosamine biosynthesis

Abstract

<jats:p><jats:italic>Aspergillus fumigatus</jats:italic> is a human opportunistic fungal pathogen whose cell wall protects it from the extracellular environment including host defenses. Chitin, an essential component of the fungal cell wall, is synthesized from UDP-GlcNAc produced in the hexosamine biosynthetic pathway. As this pathway is critical for fungal cell wall integrity, the hexosamine biosynthesis enzymes represent potential targets of antifungal drugs. Here, we provide genetic and chemical evidence that glucosamine 6-phosphate <jats:italic>N</jats:italic>-acetyltransferase (Gna1), a key enzyme in this pathway, is an exploitable antifungal drug target. <jats:italic>GNA1</jats:italic> deletion resulted in loss of fungal viability and disruption of the cell wall, phenotypes that could be rescued by exogenous GlcNAc, the product of the Gna1 enzyme. In a murine model of aspergillosis, the Δ<jats:italic>gna1</jats:italic> mutant strain exhibited attenuated virulence. Using a fragment-based approach, we discovered a small heterocyclic scaffold that binds proximal to the Gna1 active site and can be optimized to a selective submicromolar binder. Taken together, we have provided genetic, structural, and chemical evidence that Gna1 is an antifungal target in <jats:italic>A. fumigatus</jats:italic>.</jats:p>

Fragment-to-Lead Medicinal Chemistry Publications in 2020

“… 22 While a string of other 2020 publications describe antimicrobial FBLD hit-finding and exploration studies, they do not meet all the criteria for F2L table inclusion. Examples include studies focused on bacterial targets such as metallo-β-lactamase(MBL)NDM-1, 54 dihydrofolate reductase from M. tuberculosis (MtDHFR), 55 M. tuberculosis MabA (FabG1) 56 and tRNA-modifying enzyme TGT, where a hit fragment opens a transient subpocket that can be exploited by a new series of ligands; 57 tRNA modification enzyme TrmD, 58 fungal targets such as glucosamine 6-phosphate N -acetyltransferase (Gna1), which is a key enzyme in the biosynthesis of an essential fungal cell-wall component; 59 parasite targets such as the cysteine protease enzyme cruzain; 60 allosteric binders for farnesyl pyrophosphate synthase of Trypanosoma brucei ; 61 bromodomain-containing factor 3 of Trypanosoma cruzi ; 62 membrane-bound pyrophosphatases (mPPases); virus targets (e.g., viral DNA-binding proteins Epstein–Barr nuclear antigen 1 (EBNA1) and latency-associated nuclear antigen (LANA); 63 and, as indicated above, several efforts to probe and target SARS-CoV-2 proteins. Another interesting study developed PqsR-targeting quorum-sensing inhibitors (a study that uses biophysical screening and enthalpic efficiency evaluations, and introduces relatively flexible linkers).…”

GFAT2 and AMDHD2 act in tandem to control the hexosamine biosynthetic pathway

“…Since breakdown of GlcNAc can be used as an energy source by bacteria and fungi, NagA plays a crucial role in their energy metabolism 28–31 . For this reason, HBP enzymes are attractive selective targets for antifungal and antibiotic drugs 32–35 . While catabolism of aminosugars connects GlcNAc with glycolysis, AMDHD2 had not been implicated in a regulatory role of the HBP and cellular UDP-GlcNAc homeostasis.…”

Plasmodium falciparum Apicomplexan-Specific Glucosamine-6-Phosphate N -Acetyltransferase Is Key for Amino Sugar Metabolism and Asexual Blood Stage Development

“…The amino sugar pathway has been explored in different organisms as a possible source of novel therapeutic targets, and inhibitors of the Aspergillus fumigatus GNA1 enzyme have been recently identified ( 32 , 33 , 41 ). The independent evolution and sequence divergence of apicomplexan GNA1, together with its essentiality in P. falciparum , highlight the potential of the enzyme as a selective therapeutic target against the malaria parasite ( 10 ).…”