Abstract
BackgroundProtein ubiquitylation is an important post-translational regulation, which has been shown to be necessary for life cycle progression and survival of Plasmodium falciparum. Ubiquitin is a highly conserved 76 amino acid polypeptide, which attaches covalently to target proteins through combined action of three classes of enzymes namely, the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2) and ubiquitin-protein ligase (E3). Ubiquitin E1 and E2 are highly conserved within eukaryotes. However, the P. falciparum E3 ligase is substantially variable and divergent compared to the homologs from other eukaryotes, which make the E3 ligase a parasite-specific target.MethodsA set of selected E3 ubiquitin ligase inhibitors was tested in vitro against a chloroquine-sensitive P. falciparum D6 strain (PfD6) and a chloroquine-resistant P. falciparum W2 strain (PfW2). The inhibitors were also tested against Vero and transformed THP1 cells for cytotoxicity. The lead antimalarial E3 ubiquitin ligase inhibitors were further evaluated for the stage-specific antimalarial action and effects on cellular development of P. falciparum in vitro. Statistics analysis was done by two-way ANOVA followed by Tukey and Sidak multiple comparison test using GraphPad Prism 6.ResultsE3 ligase inhibitors namely, JNJ 26854165, HLI 373 and Nutlin 3 showed prominent antimalarial activity against PfD6 and PfW2. These inhibitors were considerably less cytotoxic to mammalian Vero cells. JNJ 26854165, HLI 373 and Nutlin 3 blocked the development of P. falciparum parasite at the trophozoite and schizont stages, resulting in accumulation of distorted trophozoites and immature schizonts.ConclusionsInterruption of trophozoites and schizont maturation by the antimalarial E3 ligase inhibitors suggest the role of ubiquitin/proteasome functions in the intraerythrocytic development of malaria parasite. The ubiquitin/proteasome functions may be critical for schizont maturation. Further investigations on the lead E3 ligase inhibitors shall provide better understanding regarding the importance of E3 ligase functions in the malaria parasite as a potential new antimalarial drug target and a new class of antimalarial drug leads.
Highlights
Protein ubiquitylation is an important post-translational regulation, which has been shown to be necessary for life cycle progression and survival of Plasmodium falciparum
The proteomic analysis of P. falciparum ubiquitome has shown that the level of ubiquitin was more in rings and trophozoites than in schizonts [4], which suggested that ubiquitylation of proteins occurred more prominently in schizonts’ and might be necessary for schizonts’ maturation and their further differentiation into invasive merozoites [4]
The antimalarial activity of HLI 373 was considerably different against P. falciparum D6 strain (PfD6) as compared to P. falciparum W2 strain (PfW2) at 48, 72, 96 and 120 h
Summary
Protein ubiquitylation is an important post-translational regulation, which has been shown to be necessary for life cycle progression and survival of Plasmodium falciparum. Drug resistance of P. falciparum is the greatest challenge in the fight against malaria, as the parasite has developed resistance to most of the drugs presently used for the treatment of malaria. These factors have led to the earnest need to discover new molecular targets and identify new drug leads against those targets [2]. Post-translational modifications are necessary for the progression of P. falciparum life cycle [3, 4] Among these modifications, protein ubiquitylation plays an important role. Proteasome-dependent ubiquitylation pathway involves various biological processes comprising specific components, which make this pathway a potential therapeutic target to develop new anti-malarial
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
