ABSTRACT
Antimalarial drugs have thus far been chiefly derived from two sources-natural products and synthetic drug-like compounds. Here we investigate whether antimalarial agents with novel mechanisms of action could be discovered using a diverse collection of synthetic compounds that have three-dimensional features reminiscent of natural products and are underrepresented in typical screening collections. We report the identification of such compounds with both previously reported and undescribed mechanisms of action, including a series of bicyclic azetidines that inhibit a new antimalarial target, phenylalanyl-tRNA synthetase. These molecules are curative in mice at a single, low dose and show activity against all parasite life stages in multiple in vivo efficacy models. Our findings identify bicyclic azetidines with the potential to both cure and prevent transmission of the disease as well as protect at-risk populations with a single oral dose, highlighting the strength of diversity-oriented synthesis in revealing promising therapeutic targets.
Subject(s)
Antimalarials/chemical synthesis , Antimalarials/pharmacology , Azetidines/therapeutic use , Drug Discovery , Life Cycle Stages/drug effects , Malaria, Falciparum/drug therapy , Plasmodium falciparum/drug effects , Plasmodium falciparum/growth & development , Animals , Antimalarials/administration & dosage , Antimalarials/therapeutic use , Azabicyclo Compounds/administration & dosage , Azabicyclo Compounds/chemical synthesis , Azabicyclo Compounds/pharmacology , Azabicyclo Compounds/therapeutic use , Azetidines/administration & dosage , Azetidines/adverse effects , Azetidines/pharmacology , Cytosol/enzymology , Disease Models, Animal , Female , Liver/drug effects , Liver/parasitology , Macaca mulatta/parasitology , Malaria, Falciparum/prevention & control , Malaria, Falciparum/transmission , Male , Mice , Phenylalanine-tRNA Ligase/antagonists & inhibitors , Phenylurea Compounds/administration & dosage , Phenylurea Compounds/chemical synthesis , Phenylurea Compounds/pharmacology , Phenylurea Compounds/therapeutic use , Plasmodium falciparum/cytology , Plasmodium falciparum/enzymology , SafetyABSTRACT
The 7-methyl guanosine cap structure of RNA is essential for key aspects of RNA processing, including pre-mRNA splicing, 3' end formation, U snRNA transport, nonsense-mediated decay and translation. Two cap-binding proteins mediate these effects: cytosolic eIF-4E and nuclear cap-binding protein complex (CBC). The latter consists of a CBP20 subunit, which binds the cap, and a CBP80 subunit, which ensures high-affinity cap binding. Here we report the 2.1 A resolution structure of human CBC with the cap analog m7GpppG, as well as the structure of unliganded CBC. Comparisons between these structures indicate that the cap induces substantial conformational changes within the N-terminal loop of CBP20, enabling Tyr 20 to join Tyr 43 in pi-pi stacking interactions with the methylated guanosine base. CBP80 stabilizes the movement of the N-terminal loop of CBP20 and locks the CBC into a high affinity cap-binding state. The structure for the CBC bound to m7GpppG highlights interesting similarities and differences between CBC and eIF-4E, and provides insights into the regulatory mechanisms used by growth factors and other extracellular stimuli to influence the cap-binding state of the CBC.
Subject(s)
Dinucleoside Phosphates/chemistry , Models, Molecular , Nuclear Cap-Binding Protein Complex/chemistry , RNA Caps/chemistry , Binding Sites , Crystallography, X-Ray , Dinucleoside Phosphates/metabolism , Eukaryotic Initiation Factor-4E/chemistry , Humans , Nuclear Cap-Binding Protein Complex/metabolism , Protein Binding , Protein Conformation , Protein Subunits , RNA Caps/metabolismABSTRACT
[structure: see text] The absolute stereochemistry of the heptaprenoids didemnaketals B (2) and C (3), isolated from a Palauan ascidian, was determined using a combination of degradation and derivatization experiments, chiral shift methods, and comparison of fragments to known compounds.
