Dataset Information

Functional expression of parasite drug targets and their human orthologs in yeast.

ABSTRACT:

Background

The exacting nutritional requirements and complicated life cycles of parasites mean that they are not always amenable to high-throughput drug screening using automated procedures. Therefore, we have engineered the yeast Saccharomyces cerevisiae to act as a surrogate for expressing anti-parasitic targets from a range of biomedically important pathogens, to facilitate the rapid identification of new therapeutic agents.

Methodology/principal findings

Using pyrimethamine/dihydrofolate reductase (DHFR) as a model parasite drug/drug target system, we explore the potential of engineered yeast strains (expressing DHFR enzymes from Plasmodium falciparum, P. vivax, Homo sapiens, Schistosoma mansoni, Leishmania major, Trypanosoma brucei and T. cruzi) to exhibit appropriate differential sensitivity to pyrimethamine. Here, we demonstrate that yeast strains (lacking the major drug efflux pump, Pdr5p) expressing yeast ((Sc)DFR1), human ((Hs)DHFR), Schistosoma ((Sm)DHFR), and Trypanosoma ((Tb)DHFR and (Tc)DHFR) DHFRs are insensitive to pyrimethamine treatment, whereas yeast strains producing Plasmodium ((Pf)DHFR and (Pv)DHFR) DHFRs are hypersensitive. Reassuringly, yeast strains expressing field-verified, drug-resistant mutants of P. falciparum DHFR ((Pf)dhfr(51I,59R,108N)) are completely insensitive to pyrimethamine, further validating our approach to drug screening. We further show the versatility of the approach by replacing yeast essential genes with other potential drug targets, namely phosphoglycerate kinases (PGKs) and N-myristoyl transferases (NMTs).

Conclusions/significance

We have generated a number of yeast strains that can be successfully harnessed for the rapid and selective identification of urgently needed anti-parasitic agents.

SUBMITTER: Bilsland E

PROVIDER: S-EPMC3186757 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Publications

Functional expression of parasite drug targets and their human orthologs in yeast.

Bilsland Elizabeth E Pir Pınar P Gutteridge Alex A Johns Alexander A King Ross D RD Oliver Stephen G SG

PLoS neglected tropical diseases 20111004 10

<h4>Background</h4>The exacting nutritional requirements and complicated life cycles of parasites mean that they are not always amenable to high-throughput drug screening using automated procedures. Therefore, we have engineered the yeast Saccharomyces cerevisiae to act as a surrogate for expressing anti-parasitic targets from a range of biomedically important pathogens, to facilitate the rapid identification of new therapeutic agents.<h4>Methodology/principal findings</h4>Using pyrimethamine/di ...[more]

PMID: 21991399

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Project description:Despite over a billion years of evolutionary divergence, several thousand human genes possess clearly identifiable orthologs in yeast, and many have undergone lineage-specific duplications in one or both lineages. These duplicated genes may have been free to diverge in function since their expansion, and it is unclear how or at what rate ancestral functions are retained or partitioned among co-orthologs between species and within gene families. Thus, in order to investigate how ancestral functions are retained or lost post-duplication, we systematically replaced hundreds of essential yeast genes with their human orthologs from gene families that have undergone lineage-specific duplications, including those with single duplications (1 yeast gene to 2 human genes, 1:2) or higher-order expansions (1:>2) in the human lineage. We observe a variable pattern of replaceability across different ortholog classes, with an obvious trend toward differential replaceability inside gene families, and rarely observe replaceability by all members of a family. We quantify the ability of various properties of the orthologs to predict replaceability, showing that in the case of 1:2 orthologs, replaceability is predicted largely by the divergence and tissue-specific expression of the human co-orthologs, i.e., the human proteins that are less diverged from their yeast counterpart and more ubiquitously expressed across human tissues more often replace their single yeast ortholog. These trends were consistent with in silico simulations demonstrating that when only one ortholog can replace its corresponding yeast equivalent, it tends to be the least diverged of the pair. Replaceability of yeast genes having more than 2 human co-orthologs was marked by retention of orthologous interactions in functional or protein networks as well as by more ancestral subcellular localization. Overall, we performed >400 human gene replaceability assays, revealing 50 new human-yeast complementation pairs, thus opening up avenues to further functionally characterize these human genes in a simplified organismal context.

Project description:BackgroundCalcium (Ca²?) signalling is fundamental for host cell invasion, motility, in vivo synchronicity and sexual differentiation of the malaria parasite. Consequently, cytoplasmic free Ca²? is tightly regulated through the co-ordinated action of primary and secondary Ca²? transporters. Identifying selective inhibitors of Ca²? transporters is key towards understanding their physiological role as well as having therapeutic potential, therefore screening systems to facilitate the search for potential inhibitors are a priority. Here, the methodology for the expression of a Calcium membrane transporter that can be scaled to high throughputs in yeast is presented.MethodsThe Plasmodium falciparum Ca²?/H? antiporter (PfCHA) was expressed in the yeast Saccharomyces cerevisiae and its activity monitored by the bioluminescence from apoaequorin triggered by divalent cations, such as calcium, magnesium and manganese.ResultsBioluminescence assays demonstrated that PfCHA effectively suppressed induced cytoplasmic peaks of Ca²?, Mg²? and Mn²? in yeast mutants lacking the homologue yeast antiporter Vcx1p. In the scalable format of 96-well culture plates pharmacological assays with a cation antiporter inhibitor allowed the measurement of inhibition of the Ca²? transport activity of PfCHA conveniently translated to the familiar concept of fractional inhibitory concentrations. Furthermore, the cytolocalization of this antiporter in the yeast cells showed that whilst PfCHA seems to locate to the mitochondrion of P. falciparum, in yeast PfCHA is sorted to the vacuole. This facilitates the real-time Ca²?-loading assays for further functional and pharmacological studies.DiscussionThe functional expression of PfCHA in S. cerevisiae and luminescence-based detection of cytoplasmic cations as presented here offer a tractable system that facilitates functional and pharmacological studies in a high-throughput format. PfCHA is shown to behave as a divalent cation/H? antiporter susceptible to the effects of cation/H? inhibitors such as KB-R7943. This type of gene expression systems should advance the efforts for the screening of potential inhibitors of this type of divalent cation transporters as part of the malaria drug discovery initiatives and for functional studies in general.ConclusionThe expression and activity of the PfCHA detected in yeast by a bioluminescence assay that follows the levels of cytoplasmic Ca²? as well as Mg²? and Mn²? lend itself to high-throughput and quantitative settings for pharmacological screening and functional studies.

Dataset Information

Functional expression of parasite drug targets and their human orthologs in yeast.

Background

Methodology/principal findings

Conclusions/significance

Publications

Functional expression of parasite drug targets and their human orthologs in yeast.

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