A chemical proteomic strategy to identify novel drug targets in Plasmodium falciparum and corresponding lead compounds for the development of new antimalarials
Zusammenfassung der Projektergebnisse
This project aimed to identify new inhibitor classes that target essential proteins in pathogenic P. falciparum. We synthesized a suite of electrophilic thiirane, oxirane, aziridine, and gammalactone compounds that are equipped with an alkyne handle for target identification via click chemistry to functionalized azides. The synthesis of all desired compounds were achieved and profiling of parasites with these molecules was subsequently performed in India. The treated proteomes were clicked and analysed in Germany. Labelling of promising and distinct protein bands on analytical scale were obtained, however, all our efforts failed to enrich these proteins on a quantitative scale for target identification. One challenge in this endeavour was the upscale of parasite cultures that probably did not reveal sufficient amounts for detection. In addition we cannot exclude that sterilization methods and transport, required to ship samples to Germany, did harm the treated proteomes. While we were optimizing these labeling procedures we started with the validation of compounds in bacterial pathogens to obtain a general overview on their target selectivity and bioactivity. The probes were screened against S. aureus and multiresistant isolates (MRSA) and several crucial proteins important for bacterial viability and virulence were identified. Accordingly, the molecules either killed bacteria or significantly reduced their toxin production, respectively. These results are intriguing and show the suitable reactivity of the designed probes for essential cellular pathways. Several of the identified target proteins were further investigated by recombinant overexpression, inhibition studies and functional knockouts. Moreover, we refined our initial anti-parasite beta-lactone hit molecule U1 by structure activity relationship studies to optimize it for P. falciparum ClpP inhibition. PfClpP is an important drug target since it is essential for parasite viability. Synthesis of all four stereoisomers revealed a strong preference of PfClpP solely for the SS configured compound which represents an important result for future drug optimization efforts. Additional betalactone derivatives were tested and one of the best inhibitors also revealed a promising bioactivity in parasite killing assays performed in India. These results provide a basis for future drug design together with our on-going efforts to enable quantitative proteome profiling in parasites.
Projektbezogene Publikationen (Auswahl)
- "Target analysis of α-alkylidene-γ-butyrolactones in uropathogenic E. coli", Mol. BioSyst. 2012, 8, 3061-3067
Kunzmann, M., Sieber, S.A.
- “Antibiotic activity and target discovery of threemembered natural product-derived heterocycles in pathogenic bacteria”, Chem. Sci., 2012, 3, 2035-2041
Pitscheider, M., Mäusbacher, N., Sieber, S.A.
- "α-Methylene-γ-butyrolactones attenuate Staphylococcus aureus virulence by inhibition of transcriptional regulation", Chem. Sci., 2014, 5, 1158-1167
Kunzmann, M. H., Bach, N. C., Bauer, B., Sieber, S. A.
(Siehe online unter https://doi.org/10.1039/c3sc52228h)
