Targeting a critical step in fungal hexosamine biosynthesis

Abstract

<jats:title>Summary</jats:title><jats:p><jats:italic>Aspergillus fumigatus</jats:italic> is a human opportunistic fungal pathogen with a cell wall that protects it from the extracellular environment. Chitin, an essential cell wall component, is synthesised from UDP-GlcNAc that is produced by the hexosamine biosynthetic pathway. 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. Deletion of <jats:italic>GNA1</jats:italic> results in loss of viability and disruption of the cell wall, phenotypes that can be rescued by the product of the enzyme. In a murine model of aspergillosis, the <jats:italic>Δgna1</jats:italic> mutant strain attenuates virulence. Using a fragment-based approach, we discovered a small heterocyclic scaffold that binds proximal to the active site and can be optimised to a selective sub-micromolar binder. Taken together, we have provided genetic, structural and chemical evidence for Gna1 as an antifungal target in <jats:italic>Aspergillus fumigatus</jats:italic>.</jats:p>

Genetic and structural validation of phosphomannomutase as a cell wall target in Aspergillus fumigatus

“…With the advent of fragment‐based drug discovery (Scott et al., 2012) and PROTAC (Proteolysis targeting chimera) technology (Zou et al., 2019), it is possible to exploit and identify molecules with selectivity based on subtle differences in protein structure and even for undruggable targets. For instance, inhibitors have been developed against other enzymes involved in sugar nucleotide biosynthesis, such as N‐acetylphosphoglucosamine mutase Af Agm1 (Fang et al., 2013a), glucosamine 6‐phosphate N‐acetyltransferase Af Gna1 (Lockhart et al., 2020), and N‐acetylglucosamine pyrophosphorylase Uap1 in A. fumigatus and Trypanosoma brucei (Fang et al., 2013b; Urbaniak et al., 2013). Similarly, although N‐myristoyltransferase (Nmt) from Plasmodium falciparum only displays a single residue difference at the active site from human Nmt, selective inhibitors have been successfully identified and further optimized (Bell et al., 2012; Rackham et al., 2014).…”