Clinically relevant benzoxaboroles inhibit mRNA processing in Trypanosoma brucei

Abstract

Objective The cleavage and polyadenylation endonuclease CPSF73 is thought to be the target of the anti-trypanosomal benzoxaboroles AN7973, acoziborole and AN11736. We previously showed that AN7973 inhibits mRNA processing. We here investigated whether the drug candidates acoziborole (for human sleeping sickness) and AN11736 (for nagana in cattle) have the same effect. We also affinity purified tagged CPSF73 from parasites without, or after, AN7973 treatment, and analysed differentially co-purified proteins by mass spectrometry. Results AN11736 and acoziborole both inhibited mRNA processing, as demonstrated by decreased levels of spliced mRNAs and accumulation of di- and tri-cistronic mRNAs from the alpha-beta tubulin locus. Treating the cells with AN7973 for 30 min. did not significantly affect the proteins that copurified with CPSF73.

Targeted protein degradation of the CPSF complex by benzoxaboroles through sumoylation

“…This evidence suggests a conserved mechanism underpinning BoB toxicity (Sonoiki et al, 2017, Palencia et al, 2017, Wall et al, 2018, Mowbray et al, 2021). Evidence is also consistent with the direct inhibition of CPSF3 function, based on in silico modeling, mutagenesis and phenotypic data that indicates compromised trans -splicing in trypanosomes, and also confirming that CPSF3 acts within mRNA maturation in trypanosomes (Begolo et al, 2018, Waithaka and Clayton 2022). However, a more complex interaction between BoBs and trypanosomes may be relevant and specifically the modest level of resistance obtained by overexpression of CPSF3, an approximate threefold change to EC 50 , compared with more than a hundredfold for a block to a prodrug processing pathway suggests a possible additional factor is important (Zhang et al, 2018, Wall et al, 2018).…”

“…CPSF3 is the sole catalytic component of the CPSF complex and the target of several distinct BoBs in multiple unicellular protozoan parasites, including Plasmodium falciparum, Toxoplasma gondii, Trypanosoma brucei and T. cruzi (reviewed in Swale and Hakimi 2023, Has et al, 2023). Evidence that CPSF3 represents the trypanosome target is supported by demonstrations that trans -splicing is inhibited by multiple BoBs (Begolo et al, 2018, Waithaka and Clayton 2022) and from overexpression screens and drug resistance-associated mutation at the drug-binding site (Wall et al, 2018). Significantly, CPSF3 is not the target for BoB action in bacteria or fungi, albeit that this most likely depends on additional determinants in the BoB structure as well as biochemical factors (Ganapathay et al, 2023).…”

Tackling Sleeping Sickness: Current and Promising Therapeutics and Treatment Strategies

“…In addition to fexinidazole, which has been approved for clinical use, several drugs with the potential to yield the effective treatment of HAT have recently progressed to clinical trials [136]. A class of compounds, referred to as benzoxaboroles, has emerged as promising novel drugs for the treatment of HAT [137]. The compounds are derivatives of an oxaborole heterocycle (boron heterocyclic) that is coupled to a phenyl group [138,139].…”