mupirocin and borrelidin

Inhibition of tRNA aminoacylation has proven to be an effective antimicrobial strategy, impeding an essential step of protein synthesis. Mupirocin, the well-known selective inhibitor of bacterial isoleucyl-tRNA synthetase, is one of three aminoacylation inhibitors now approved for human or animal use. However, design of novel aminoacylation inhibitors is complicated by the steadfast requirement to avoid off-target inhibition of protein synthesis in human cells. Here we review available data regarding known aminoacylation inhibitors as well as key amino-acid residues in aminoacyl-tRNA synthetases (aaRSs) and nucleotides in tRNA that determine the specificity and strength of the aaRS-tRNA interaction. Unlike most ligand-protein interactions, the aaRS-tRNA recognition interaction represents coevolution of both the tRNA and aaRS structures to conserve the specificity of aminoacylation. This property means that many determinants of tRNA recognition in pathogens have diverged from those of humans-a phenomenon that provides a valuable source of data for antimicrobial drug development.

Topics: Anti-Bacterial Agents; Escherichia coli; Fatty Alcohols; Humans; Isoleucine-tRNA Ligase; Mupirocin; Piperidines; Protein Synthesis Inhibitors; Quinazolinones; RNA, Transfer, Leu; Species Specificity; Structure-Activity Relationship; Thermus thermophilus; Transfer RNA Aminoacylation

Blood-stage Plasmodium parasites cause morbidity and mortality from malaria. Parasite resistance to drugs makes development of new chemotherapies an urgency. Aminoacyl-tRNA synthetases have been validated as antimalarial drug targets. We explored long-term effects of borrelidin and mupirocin in lethal P. yoelii murine malaria.. Long-term (up to 340 days) immunological responses to borrelidin or mupirocin were measured after an initial 4 day suppressive test. Prophylaxis and cure were evaluated and the inhibitory effect on the parasites analysed.. Borrelidin protected against lethal malaria at 0.25 mg·kg⁻¹·day⁻¹. Antimalarial activity of borrelidin correlated with accumulation of trophozoites in peripheral blood. All infected mice treated with borrelidin survived and subsequently developed immunity protecting them from re-infection on further challenges, 75 and 340 days after the initial infection. This long-term immunity in borrelidin-treated mice resulted in negligible parasitaemia after re-infections and marked increases in total serum levels of antiparasite IgGs with augmented avidity. Long-term memory IgGs mainly reacted against high and low molecular weight parasite antigens. Immunofluorescence microscopy showed that circulating IgGs bound predominantly to late intracellular stage parasites, mainly schizonts.. Low borrelidin doses protected mice from lethal malaria infections and induced protective immune responses after treatment. Development of combination therapies with borrelidin and selective modifications of the borrelidin molecule to specifically inhibit plasmodial threonyl tRNA synthetase should improve therapeutic strategies for malaria.

Topics: Animals; Antibodies, Protozoan; Antibody Affinity; Antimalarials; Drug Evaluation, Preclinical; Enzyme Inhibitors; Fatty Alcohols; Female; Immunity, Humoral; Malaria; Mice; Mice, Inbred Strains; Mupirocin; Parasitemia; Plasmodium yoelii; Protozoan Proteins; Random Allocation; Schizonts; Secondary Prevention; Specific Pathogen-Free Organisms; Survival Analysis; Threonine-tRNA Ligase

The causative agent of malaria, Plasmodium, possesses three translationally active compartments: the cytosol, the mitochondrion and a relic plastid called the apicoplast. Aminoacyl-tRNA synthetases to charge tRNA are thus required for all three compartments. However, the Plasmodiumfalciparum genome encodes too few tRNA synthetases to supply a unique enzyme for each amino acid in all three compartments. We have investigated the subcellular localisation of three tRNA synthetases (AlaRS, GlyRS and ThrRS), which occur only once in the nuclear genome, and we show that each of these enzymes is dually localised to the P. falciparum cytosol and the apicoplast. No mitochondrial fraction is apparent for these three enzymes, which suggests that the Plasmodium mitochondrion lacks at least these three tRNA synthetases. The unique Plasmodium ThrRS is the presumed target of the antimalarial compound borrelidin. Borrelidin kills P. falciparum parasites quickly without the delayed death effect typical of apicoplast translation inhibitors and without an observable effect on apicoplast morphology. By contrast, mupirocin, an inhibitor of the apicoplast IleRS, kills with a delayed death effect that inhibits apicoplast growth and division. Because inhibition of dual targeted tRNA synthetases should arrest translation in all compartments of the parasite, these enzymes deserve further investigation as potential targets for antimalarial drug development.

Topics: Amino Acyl-tRNA Synthetases; Antimalarials; Cytosol; Fatty Alcohols; Mupirocin; Plasmodium falciparum; Plastids; Protein Transport

We further examined the usefulness of previously reported Bacillus subtilis biosensors for antibacterial mode-of-action studies. The biosensors could not detect the tRNA synthetase inhibitors mupirocin, indolmycin, and borrelidin, some inhibitors of peptidoglycan synthesis, and most membrane-damaging agents. However, the biosensors confirmed the modes of action of several RNA polymerase inhibitors and DNA intercalators and provided new insights into the possible modes of action of ciprofloxacin, anhydrotetracycline, corralopyronin, 8-hydroxyquinoline, and juglone.

Topics: Amino Acyl-tRNA Synthetases; Anti-Bacterial Agents; Bacillus subtilis; Biosensing Techniques; Ciprofloxacin; Enzyme Inhibitors; Fatty Alcohols; Indoles; Mupirocin; Naphthoquinones; Oxyquinoline; Tetracyclines