Molecular mechanisms of fungal cell wall assembly

Pathogenic fungi, such as A. fumigatus and C. albicans, are widespread and most of us carry spores of these organisms. Normally our immune system is perfectly capable of suppressing the growth of these organisms. However, under conditions where the immune system is weakened, for instance during chemotheraphy, organ transplants or HIV infection, these microbes are able to establish lethal infections that are not uniformly/well treatable with currently available drugs - there is a significant unmet medical need. This proposal aims to give us an understanding of enzymes that are important for building the cell wall - a structure that protects these microbes from their environment. This work will ultimately lead to the identification of opportunities for the discovery of novel anti-fungal drugs by the pharmaceutical industry.

The fungal cell wall is a dynamic and multi-layered structure, containing a core of crosslinked chitin and glucan. Despite decades of work, there are huge gaps in our knowledge of the enzymes responsible for cell wall synthesis, modification and crosslinking. This is particularly pressing given the significant rise in fatal fungal infections of immunocompromised patients, and thus the need for novel, properly genetically/chemically validated, drug targets.

This proposal uses a multidisciplinary approach (covering genetics, biochemistry, structural biology, high throughout screening, synthetic chemistry and cell biology) to significantly advance our understanding of the function, biochemistry, inhibition and genetic/chemical validation of A. fumigatus/C. albicans enzymes involved in fungal cell wall biogenesis. The proposal covers four areas:

Cell wall synthesis - with the aims of generating overexpression systems for the membrane enzymes chitin/glucan synthase, determining their crystal structures and probing their mechanisms using novel assays/inhibitors and mutagenesis.

UDP-GlcNAc biosynthesis - with the aims of genetically validating this pathway in A. fumigatus, determining the crystal structures for these enzymes to assess exploitable differences with their human orthologues, and discover novel inhibitors through screening approaches.

Chitin modification - with the aims of genetically and chemically validating A. fumigatus chitinases and chitin deacetylases as potential drug targets and synthesis/discovery of novel inhibitors.

Crosslinking/transglycosylation - with the aims of determining the crystal structures, mechanism and substrate binding of the Gel/Gas and Crh transglycosylases, discover the first ever inhibitors for these enzymes and use these for chemical validation.

The output will be:
1) a significant increase in our molecular understanding of fungal cell wall biogenesis enzymes,
2) a collection of novel chemical tools for use by the fungal scientific community, and
3) a springboard for novel antifungal drug discovery by follow-up translational research and/or the pharmaceutical industry.