Structure based drug design of novel anti-fungal agents imported into cells by the integral membrane transporter, UapA

Aspergillosis, a collection of conditions caused by the Aspergillus fungus, is a major cause of lung disease and death in individuals with prior lung conditions (e.g. tuberculosis, asthma, cystic fibrosis and chronic obstructive pulmonary disease), and in those who are immunocompromised, as a result of organ transplantation or chemotherapy. Even following aggressive treatment with existing antifungals, fatality rates exceed 50% for invasive Aspergillosis. Consequentially, the development of novel antifungals capable of eliminating these infections is imperative.

This research is focusing on developing novel drugs that are taken up into fungal cells via integral membrane transporters. Here the focus is on UapA, a high-affinity uric acid/xanthine proton symporter from the filamentous fungus Aspergillus nidulans, and shares high sequence homology with the high-affinity, high-capacity purine symporter AfUapC from the related pathogenic fungus, Aspergillus fumigatus.

Allopurinol is an existing xanthine oxidase inhibitor and approved treatment for hyperuricemia. More recently, allopurinol has been shown to be effective against Leishmania infections, however it has not yet been explored as a template for novel antifungals. It is known that allopurinol is a non-native substrate of UapA, but little is understood about its translocation mechanism and effect on fungal growth. The structure of UapA + allopurinol has proved challenging to obtain however we have a structure of UapA in complex with the native substrate xanthine. Thus, initial efforts have focused on structure-based drug design using both allopurinol and xanthine as templates.

The objectives of the studentship are to:
Design derivatives of allopurinol and xanthine
Develop synthesis protocols for the production of these novel compounds
Establish methods for the screening of these novel compounds in terms of a) engagement with UapA, b) inhibitory effects on fungal growth in vitro
Characterise the transport kinetics of these compounds through UapA.