The proteasome inhibitor MLN-273 blocks exoerythrocytic and erythrocytic development of Plasmodium parasites

Abstract

Protein degradation is regulated during the cell cycle of all eukaryotic cells and is mediated by the ubiquitin-proteasome pathway. Potent and specific peptide-derived inhibitors of the 20S proteasome have been developed recently as anti-cancer agents, based on their ability to induce apoptosis in rapidly dividing cells. Here, we tested a novel small molecule dipeptidyl boronic acid proteasome inhibitor, named MLN-273 on blood and liver stages of Plasmodium species, both of which undergo active replication, probably requiring extensive proteasome activity. The inhibitor blocked Plasmodium falciparum erythrocytic development at an early ring stage as well as P. berghei exoerythrocytic progression to schizonts. Importantly, neither uninfected erythrocytes nor hepatocytes were affected by the drug. MLN-273 caused an overall reduction in protein degradation in P. falciparum, as demonstrated by immunoblots using anti-ubiquitin antibodies to label ubiquitin-tagged protein conjugates. This led us to conclude that the target of the drug was the parasite proteasome. The fact that proteasome inhibitors are presently used as anti-cancer drugs in humans forms a solid basis for further development and makes them potentially attractive drugs also for malaria chemotherapy.

Characterization and Structural Studies of the Plasmodium falciparum Ubiquitin and Nedd8 Hydrolase UCHL3

“…Crystallization and Adduct Formation-Crystals of free PfUCHL3 grew from sitting drops at 4°C in conditions containing 100 mM Bicine, 25% polyethylene glycol 2000, 15% glycerol, 300 mM MgCl 2 , pH 9.0, as thin plates with maximal dimensions of 0.3 ϫ 0.2 ϫ 0.03 mm 3 . For cryoprotection, crystals were incubated in reservoir solution supplemented with glycerol in increments of 5% from 5 to 20% (v/v) prior to flash cryo-cooling crystals in liquid N 2 .…”

“…Fractions containing PfUCHL3-UbVME were concentrated to 10 mg/ml and used in crystallization trials. Crystals of the complex grew at 20°C from a condition containing 100 mM Bis-Tris, pH 5.5, 200 mM NaCl, 25% polyethylene glycol 3350 to maximal dimensions of 0.05 ϫ 0.05 ϫ 0.1 mm 3 . Crystals were soaked in crystallization solution supplemented with 20% glycerol (v/v) prior to flash cryo-cooling in liquid N 2 .…”

“…Although there is little direct evidence that the livelihood of eukaryotic parasites is dependent on UBLs, it is axiomatic that they use Ub and other Ub-like modifiers to regulate their physiology. Studies have reported a lethal effect on malaria parasites following treatment with proteasome inhibitors (2,3). Therefore, parasitic UBL-regulating enzymes present interesting candidates for biological manipulation.…”

Critical role for phosphoinositide 3-kinase gamma in parasite invasion and disease progression of cutaneous leishmaniasis

“…Therefore, treating infectious diseases by targeting host pathways that are critical for pathogen invasion and survival has recently been considered as a viable option for developing new therapeutic agents against infectious diseases (31). Some studies have reported that targeting host molecules inhibits intracellular growth of bacteria and parasites such as Plasmodium in the host cell in vitro (32). However, the therapeutic efficacy of this approach in vivo has not been tested in the treatment of bacterial or parasitic diseases in vivo.…”

Triclosan inhibit the growth of the late liver‐stage of Plasmodium

“…Chloroquine, mefloquine, quinine, and artemisinin-based compounds have little or no efficacy against the hepatic parasite. Experimental compounds belonging to other chemical classes, for example, antibiotics, antihistaminics, or anticancer drugs (26)(27)(28) have been reported to have activity against the Plasmodium liverstage parasites.…”