To design, synthesize and optimize small molecules to probe the function of BCPs in Leishmania.

Leishmaniases are a complex of diseases originating from more than 20 different species of the protozoan parasite Leishmania. There are three main forms in which the disease manifests; visceral (VL, also known as kala-azar and the most serious form of the disease), cutaneous (CL, the most common) and mucocutaneous leishmaniasis (MCL). Epidemics are a severe public health problem in some of the poorest communities in Africa, Asia and Latin America, where malnutrition, weak immune systems, poor housing and sanitation, and lack of financial resources increase the risk of the disease. The World Health Organisation (WHO) estimate that there are annually between 700 000 and 1 million new cases of the disease, and 26 000 to 65 000 leishmaniasis related deaths. Treatments for the disease do exist, however many of the commonly used drugs exhibit severe side effects, and an increasingly pressing issue with current chemotherapeutics is emerging resistance in Leishmania. Moreover, most antileishmanial drugs (antimonials, miltefosine, paromomycin, and pentamidine) have no target proteins identified. Leishmania adapt to different habitats in their life cycle and exist in two different forms: the promastigote in the phlebotomine sandfly vector, and the amastigote in the mammalian host. We predict that epigenetic processes mediate the phenotypic changes that occur when the parasite adapts to its environment. Bromodomains exist as part of bromodomain-containing proteins (BCPs) and play a key role in regulating transcription in humans. Bromodomains mediate protein-protein interactions by binding to acetylated lysine residues (KAc) found in histone proteins, which condense and structure DNA stored in chromatin. Acetyl lysine mimic based small molecule ligands binding to human bromodomains have been identified and the proteins have been postulated as potential targets for several diseases including cancer, inflammation, and diabetes. Given the fundamental role played by bromodomains in regulating transcription in humans, we hypothesise that BCPs play an equally important role in other organisms. We will investigate whether these proteins are novel therapeutic targets to impede the life cycle of Leishmania dononavi and provide new avenues for the treatment of Leishmaniasis. In this project we will collaborate with Dr Nathaniel Jones, Prof. Jeremy Mottram, Prof. Anthony Wilkinson and Catherine Russell (University of York) who have cloned the Leishmania bromodomain coding sequences for LdBD2, LdBD3 and LdBD5.1 and LdBD5.2 in Leishmania donovani. Co-crystal structures of known human bromodomain ligands, Bromosporine, SCG-CBP30 and BI-2536, demonstrate complexing with some of these BCPs, although Kd values for the ligands have not yet been evaluated. To provide the basis for an antiparasitic drug, we require a ligand with high affinity for the parasite protein and low affinity for the human protein. We will adopt a fragment-based screening approach with acetylated lysine mimics and evaluate the small molecule binding to Leishmania bromodomains in biophysical assays. Once we establish the criteria for protein binding, we will apply this knowledge to design novel ligands for Leishmania bromodomains. The aim of the project is to design, synthesize and optimize small molecules to probe the function of BCPs in Leishmania. In collaboration with GSK, our ligands will be used in phenotypic screening to provide information for future drug discovery efforts for targeting bromodomains in Leishmania. This project will also contribute to our wider understanding of parasite epigenetics and help us to determine whether epigenetic functions more generally are effective targets for antiparasitic drugs. This project falls within the EPSRC Chemical Biology Research Area and is well aligned with the Healthcare Technologies Theme.