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Chemical genetics of Plasmodium falciparum.

Guiguemde WA, Shelat AA, Bouck D, Duffy S, Crowther GJ, Davis PH, Smithson DC, Connelly M, Clark J, Zhu F, Jiménez-Díaz MB, Martinez MS, Wilson EB, Tripathi AK, Gut J, Sharlow ER, Bathurst I, El Mazouni F, Fowble JW, Forquer I, McGinley PL, Castro S, Angulo-Barturen I, Ferrer S, Rosenthal PJ, Derisi JL, Sullivan DJ, Lazo JS, Roos DS, Riscoe MK, Phillips MA, Rathod PK, Van Voorhis WC, Avery VM, Guy RK - Nature (2010)

Bottom Line: A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins.Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans.One exemplar compound displayed efficacy in a murine model.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

ABSTRACT
Malaria caused by Plasmodium falciparum is a disease that is responsible for 880,000 deaths per year worldwide. Vaccine development has proved difficult and resistance has emerged for most antimalarial drugs. To discover new antimalarial chemotypes, we have used a phenotypic forward chemical genetic approach to assay 309,474 chemicals. Here we disclose structures and biological activity of the entire library-many of which showed potent in vitro activity against drug-resistant P. falciparum strains-and detailed profiling of 172 representative candidates. A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins. Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans. One exemplar compound displayed efficacy in a murine model. Our findings provide the scientific community with new starting points for malaria drug discovery.

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Related in: MedlinePlus

Reduced representation of the network map showing the interaction of the cross-validated hits with potential biological targetsThe network map on the left displays compounds targeting well validated protein targets as measured in inhibition assays (EC50 ≤ 15 μM). The map on the right shows compounds that bind to purified malarial proteins according to thermal-melt shift experiments. The size of nodes representing active or binding compounds is increased for clarity. Note that few of the compounds discovered in this study are potent inhibitors of known targets or bind potently to putative targets. Data in supplementary file (‘Guiguemde_Excel_SI ’, ‘Sensitivity’ tab).
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Figure 3: Reduced representation of the network map showing the interaction of the cross-validated hits with potential biological targetsThe network map on the left displays compounds targeting well validated protein targets as measured in inhibition assays (EC50 ≤ 15 μM). The map on the right shows compounds that bind to purified malarial proteins according to thermal-melt shift experiments. The size of nodes representing active or binding compounds is increased for clarity. Note that few of the compounds discovered in this study are potent inhibitors of known targets or bind potently to putative targets. Data in supplementary file (‘Guiguemde_Excel_SI ’, ‘Sensitivity’ tab).

Mentions: Three high-priority, well characterized biological targets were evaluated in activity assays (Fig. 3, left): P. falciparum dihydroorotate dehydrogenase (PfDHOD), hemozoin formation, and falcipain-2 (PfFP-2). PfDHOD, catalyzes the oxidation of dihydroorotate to orotate in de novo pyrimidine biosynthesis, which is essential for parasite viability.14 ,15 Three compounds inhibited this enzyme: two triazolopyrimidines, structurally related to known PfDHOD inhibitors with comparable potencies,14 and a dihydropyridine, structurally related to the calcium blocker felodipine. The potency of these compounds against PfDHOD strongly correlated with their antimalarial activities (Supplementary Table 5). Furthermore, these compounds were inactive against transgenic parasites expressing Saccharomyces cerevisiae dihydroorotate dehydrogenase (Supplementary Table 6). Next, hemozoin formation inhibition was investigated. The parasite digests host hemoglobin to provide amino acids, detoxifying the resulting heme molecules by conversion to a crystallized form known as hemozoin. Heme detoxification is believed to be the target of many antimalarial drugs.16 Twelve compounds exhibited appreciable efficacy in an in vitro hemozoin formation assay,17 including analogs of quinazoline, benzofuran, benzimidazole, and carbazole as well as amodiaquine, a known hemozoin formation inhibitor present in our library. The correlation between enzyme inhibitory potency and antimalarial potency was similar to that displayed by the positive controls quinine and amodiaquine (Supplementary Table 5). The third enzyme assayed was PfFP-2, which plays a critical role in hemoglobin degradation.18 Falcipains are redundant in P. falciparum, with four known homologs including two (falcipain-2 and falcipain-3) that appear to play key roles in erythrocytic stage parasites.19 Three weakly FP-2 inhibitors were identified. Thus 19 compounds (11%) were inhibitors of validated antimalarial targets.


Chemical genetics of Plasmodium falciparum.

Guiguemde WA, Shelat AA, Bouck D, Duffy S, Crowther GJ, Davis PH, Smithson DC, Connelly M, Clark J, Zhu F, Jiménez-Díaz MB, Martinez MS, Wilson EB, Tripathi AK, Gut J, Sharlow ER, Bathurst I, El Mazouni F, Fowble JW, Forquer I, McGinley PL, Castro S, Angulo-Barturen I, Ferrer S, Rosenthal PJ, Derisi JL, Sullivan DJ, Lazo JS, Roos DS, Riscoe MK, Phillips MA, Rathod PK, Van Voorhis WC, Avery VM, Guy RK - Nature (2010)

Reduced representation of the network map showing the interaction of the cross-validated hits with potential biological targetsThe network map on the left displays compounds targeting well validated protein targets as measured in inhibition assays (EC50 ≤ 15 μM). The map on the right shows compounds that bind to purified malarial proteins according to thermal-melt shift experiments. The size of nodes representing active or binding compounds is increased for clarity. Note that few of the compounds discovered in this study are potent inhibitors of known targets or bind potently to putative targets. Data in supplementary file (‘Guiguemde_Excel_SI ’, ‘Sensitivity’ tab).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2874979&req=5

Figure 3: Reduced representation of the network map showing the interaction of the cross-validated hits with potential biological targetsThe network map on the left displays compounds targeting well validated protein targets as measured in inhibition assays (EC50 ≤ 15 μM). The map on the right shows compounds that bind to purified malarial proteins according to thermal-melt shift experiments. The size of nodes representing active or binding compounds is increased for clarity. Note that few of the compounds discovered in this study are potent inhibitors of known targets or bind potently to putative targets. Data in supplementary file (‘Guiguemde_Excel_SI ’, ‘Sensitivity’ tab).
Mentions: Three high-priority, well characterized biological targets were evaluated in activity assays (Fig. 3, left): P. falciparum dihydroorotate dehydrogenase (PfDHOD), hemozoin formation, and falcipain-2 (PfFP-2). PfDHOD, catalyzes the oxidation of dihydroorotate to orotate in de novo pyrimidine biosynthesis, which is essential for parasite viability.14 ,15 Three compounds inhibited this enzyme: two triazolopyrimidines, structurally related to known PfDHOD inhibitors with comparable potencies,14 and a dihydropyridine, structurally related to the calcium blocker felodipine. The potency of these compounds against PfDHOD strongly correlated with their antimalarial activities (Supplementary Table 5). Furthermore, these compounds were inactive against transgenic parasites expressing Saccharomyces cerevisiae dihydroorotate dehydrogenase (Supplementary Table 6). Next, hemozoin formation inhibition was investigated. The parasite digests host hemoglobin to provide amino acids, detoxifying the resulting heme molecules by conversion to a crystallized form known as hemozoin. Heme detoxification is believed to be the target of many antimalarial drugs.16 Twelve compounds exhibited appreciable efficacy in an in vitro hemozoin formation assay,17 including analogs of quinazoline, benzofuran, benzimidazole, and carbazole as well as amodiaquine, a known hemozoin formation inhibitor present in our library. The correlation between enzyme inhibitory potency and antimalarial potency was similar to that displayed by the positive controls quinine and amodiaquine (Supplementary Table 5). The third enzyme assayed was PfFP-2, which plays a critical role in hemoglobin degradation.18 Falcipains are redundant in P. falciparum, with four known homologs including two (falcipain-2 and falcipain-3) that appear to play key roles in erythrocytic stage parasites.19 Three weakly FP-2 inhibitors were identified. Thus 19 compounds (11%) were inhibitors of validated antimalarial targets.

Bottom Line: A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins.Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans.One exemplar compound displayed efficacy in a murine model.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.

ABSTRACT
Malaria caused by Plasmodium falciparum is a disease that is responsible for 880,000 deaths per year worldwide. Vaccine development has proved difficult and resistance has emerged for most antimalarial drugs. To discover new antimalarial chemotypes, we have used a phenotypic forward chemical genetic approach to assay 309,474 chemicals. Here we disclose structures and biological activity of the entire library-many of which showed potent in vitro activity against drug-resistant P. falciparum strains-and detailed profiling of 172 representative candidates. A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins. Phylochemogenetic profiling in several organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans. One exemplar compound displayed efficacy in a murine model. Our findings provide the scientific community with new starting points for malaria drug discovery.

Show MeSH
Related in: MedlinePlus