The AEGIS Targets
For the AEGIS project we have selected distinct types of drug targets that are representative of features posing particular challenges for drug discovery but that are of highest biomedical relevance for emerging threats to human health: Protein-protein interactions (PPI), oligomerisation control, flexible binding interfaces and allosteric inhibition of enzymes are in the focus of our research proposal.
The AEGIS project will focus on developing novel inhibitors for four targets that are involved in Trypanosomiasis, Tuberculosis, Malaria and Leishmanias.
- Pex14 is an essential membrane-bound protein required for the biogenesis of glycosomes in Trypanosoma parasites (responsible for African Trypanosomiasis, Chagas disease Leishmaniasis and animal trypanosomiases). The N-terminal domain of Pex14 is required for binding the glycosomal targeting receptor Pex5. HMGU has determined high-resolution structures of the Pex14-Pex5 complex for both the human and trypanosomal proteins and has established that specific inhibition of this interaction is a promising route to target Trypanosomal metabolism. HMGU has designed proof-of-concept inhibitors with micromolar binding affinity in vitro. Cellular assays performed show that these inhibitors are able to kill Trypanosomes with no toxic effects on human cells. In the course of AEGIS we will develop new, druggable inhibitors for trypanosomiases treatment.
- The protein UMPK from M. tuberculosis (UMPKmt) is a particularly interesting target as no counterpart exists in eukaryotes. The allosteric regulation of this enzyme was shown to be typical for Gram-positive bacterial UMPKs: UMPKmt exhibits cooperativity toward ATP binding and an allosteric regulation by GTP (positive effector) and UTP (negative effector). The crystal structure of UMPKmt identified the positive effector binding site, and key residues involved in the “cross-talk” between the active site and the effector binding pocket have been confirmed by site-directed mutagenesis and biochemical studies. With an in-house screening campaign an allosteric inhibitor was identified that binds to the negative effector binding site. AEGIS will pursue development of druggable allosteric inhibitors of UMPK.
- The malarial enzyme malate dehydrogenase (MDH) is responsible for the reversible conversion of malate into oxaloacetate, an essential metabolite in the mitochondrial tri-carboxylic acid (TCA) cycle, thus suggesting MDH as an anti-malarial target. Preliminary data indicate that disruption of the oligomeric interfaces in MDH has a highly inhibitory effect on the enzymatic activity. Specific inhibition of malate recycling or increase of the oxaloacetate to malate activity of MDH will also limit the parasite’s ability to produce oxaloacetate, a necessary metabolite in the biosynthesis of aspartate, pyrimidine and purines. Cellular and biochemical assays show that MDH interference negatively impacts parasite survivability in blood-stage cultures. While general MDH inhibitors are available, no compounds that distinguish between the host and parasitic MDH have yet been discovered, which is the primary objective of the current proposal.
- Parasite farnesyl pyrophosphate synthase (FPPS) is a validated target to treat protozoan parasite diseases such as Chagas disease (American trypanosomiasis) or Leishmaniases. Bisphosphonates are known FPPS inhibitors and potent inhibitors of parasitic replication. However, they cannot be used as anti-parasitic drugs because of their poor pharmacokinetic properties. Human FPPS has an allosteric pocket that enables the enzyme to be inhibited by non-bisphosphonate chemotypes, and the presence of such an allosteric site is also expected for parasitic FPPS, which
then may be used in the design of novel anti-parasitic agents.