Exploring the Trypanosoma brucei Hsp83 Potential as a Target for Structure Guided Drug Design

Abstract

Human African trypanosomiasis is a neglected parasitic disease that is fatal if untreated. The current drugs available to eliminate the causative agent Trypanosoma brucei have multiple liabilities, including toxicity, increasing problems due to treatment failure and limited efficacy. There are two approaches to discover novel antimicrobial drugs - whole-cell screening and target-based discovery. In the latter case, there is a need to identify and validate novel drug targets in Trypanosoma parasites. The heat shock proteins (Hsp), while best known as cancer targets with a number of drug candidates in clinical development, are a family of emerging targets for infectious diseases. In this paper, we report the exploration of T. brucei Hsp83 – a homolog of human Hsp90 – as a drug target using multiple biophysical and biochemical techniques. Our approach included the characterization of the chemical sensitivity of the parasitic chaperone against a library of known Hsp90 inhibitors by means of differential scanning fluorimetry (DSF). Several compounds identified by this screening procedure were further studied using isothermal titration calorimetry (ITC) and X-ray crystallography, as well as tested in parasite growth inhibitions assays. These experiments led us to the identification of a benzamide derivative compound capable of interacting with TbHsp83 more strongly than with its human homologs and structural rationalization of this selectivity. The results highlight the opportunities created by subtle structural differences to develop new series of compounds to selectively target the Trypanosoma brucei chaperone and effectively kill the sleeping sickness parasite.

Unveiling the Trypanosoma cruzi Nuclear Proteome

“…Heat shock proteins (HSP) are involved in homeostasis in the course of stress treatment [ 29 ] and have been identified before in most Trypanosome proteome and subproteome analyses [ 7 – 9 , 29 , 30 ], including nuclei [ 31 ]. HSP have also been considered as potential targets to design new drugs against African trypanosomiasis [ 32 ]. RHS proteins, on the other hand, were described as one of the largest gene family in T .…”

Model System Identifies Kinetic Driver of Hsp90 Inhibitor Activity against African Trypanosomes and Plasmodium falciparum

“…S1 in the supplemental material) (15,16). T. brucei and P. falciparum each have a homologue 60% identical to human Hsp90, and both have a conserved N-terminal ATP-binding Bergerat fold (17,18). However, the clients and cochaperones in these primitive eukaryotes are almost certainly divergent from those in mammalian cells (19,20).…”

Hsp90 Inhibitors in Parasitic Nematodes: Prospects and Challenges

“…Using yeast strains transfected with either parasite or human hsp90, the differential susceptibility of P. falciparum Hsp90 to the 7-azaindole compounds was confirmed. Drug repurposing is a popular concept for tropical diseases and screening of existing libraries of Hsp90 inhibitors identified compounds with preferential effects on T. brucei Hsp83 (the T. brucei orthologue of hsp90) compared to human Hsp90 [18].…”

“…Recent work on T. brucei Hsp83 [18] and on Hsp90 from the malaria parasite, P. falciparum, [17] provides good examples of this approach. However, as discussed previously, at least for some parasitic nematodes, differences in the function of Hsp90 between parasite and host may provide a chink in the armor suitable for exploitation.…”