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The glutathione biosynthetic pathway of Plasmodium is essential for mosquito transmission.

Vega-Rodríguez J, Franke-Fayard B, Dinglasan RR, Janse CJ, Pastrana-Mena R, Waters AP, Coppens I, Rodríguez-Orengo JF, Srinivasan P, Jacobs-Lorena M, Serrano AE - PLoS Pathog. (2009)

Bottom Line: Despite a significant reduction in GSH levels, blood stage forms of pbggcs(-) parasites showed only a defect in growth as compared to wild type.In contrast, a dramatic effect on development of the parasites in the mosquito was observed.These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico.

ABSTRACT
Infection of red blood cells (RBC) subjects the malaria parasite to oxidative stress. Therefore, efficient antioxidant and redox systems are required to prevent damage by reactive oxygen species. Plasmodium spp. have thioredoxin and glutathione (GSH) systems that are thought to play a major role as antioxidants during blood stage infection. In this report, we analyzed a critical component of the GSH biosynthesis pathway using reverse genetics. Plasmodium berghei parasites lacking expression of gamma-glutamylcysteine synthetase (gamma-GCS), the rate limiting enzyme in de novo synthesis of GSH, were generated through targeted gene disruption thus demonstrating, quite unexpectedly, that gamma-GCS is not essential for blood stage development. Despite a significant reduction in GSH levels, blood stage forms of pbggcs(-) parasites showed only a defect in growth as compared to wild type. In contrast, a dramatic effect on development of the parasites in the mosquito was observed. Infection of mosquitoes with pbggcs(-) parasites resulted in reduced numbers of stunted oocysts that did not produce sporozoites. These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito.

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Proliferation of wild type and pbgccs− parasites in mice.The course of parasitemia was determined in groups of 5 mice infected with either 2×102 (A) or 2×103 (B) parasites and followed for 10 days. Each point represents the mean parasitemia. Bars represent standard errors of the mean.
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ppat-1000302-g003: Proliferation of wild type and pbgccs− parasites in mice.The course of parasitemia was determined in groups of 5 mice infected with either 2×102 (A) or 2×103 (B) parasites and followed for 10 days. Each point represents the mean parasitemia. Bars represent standard errors of the mean.

Mentions: When the mutant parasite lines were cloned by limiting dilution, we observed a minor decrease in the growth rate of the mutant parasites as compared to wild type. After injecting mice with a single wild type parasite, parasitemias reached 0.5–2% at 8 days post infection (d.p.i.) (mean = 8.0; st.dev. = 0; n = 6). The same level of parasitemia was reached by parasites of the mutant lines one day later (mean = 8.7; st.dev.  = 0.5; n = 6). These results suggest a delay in growth of pbggcs− parasites as compared to wild type. To further examine the potential effect of the absence of γ-GCS on growth rate, the course of parasitemia in groups of mice infected with 2×102 or 2×103 mutant or wild type parasites was followed in a second set of experiments (Fig. 3). The rate and extent of parasite multiplication was reduced in the mutant parasites. Therefore, although γ-GCS is not essential for growth and multiplication of blood stage Plasmodium in vivo, the absence of γ-GCS expression affects parasite growth.


The glutathione biosynthetic pathway of Plasmodium is essential for mosquito transmission.

Vega-Rodríguez J, Franke-Fayard B, Dinglasan RR, Janse CJ, Pastrana-Mena R, Waters AP, Coppens I, Rodríguez-Orengo JF, Srinivasan P, Jacobs-Lorena M, Serrano AE - PLoS Pathog. (2009)

Proliferation of wild type and pbgccs− parasites in mice.The course of parasitemia was determined in groups of 5 mice infected with either 2×102 (A) or 2×103 (B) parasites and followed for 10 days. Each point represents the mean parasitemia. Bars represent standard errors of the mean.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2636896&req=5

ppat-1000302-g003: Proliferation of wild type and pbgccs− parasites in mice.The course of parasitemia was determined in groups of 5 mice infected with either 2×102 (A) or 2×103 (B) parasites and followed for 10 days. Each point represents the mean parasitemia. Bars represent standard errors of the mean.
Mentions: When the mutant parasite lines were cloned by limiting dilution, we observed a minor decrease in the growth rate of the mutant parasites as compared to wild type. After injecting mice with a single wild type parasite, parasitemias reached 0.5–2% at 8 days post infection (d.p.i.) (mean = 8.0; st.dev. = 0; n = 6). The same level of parasitemia was reached by parasites of the mutant lines one day later (mean = 8.7; st.dev.  = 0.5; n = 6). These results suggest a delay in growth of pbggcs− parasites as compared to wild type. To further examine the potential effect of the absence of γ-GCS on growth rate, the course of parasitemia in groups of mice infected with 2×102 or 2×103 mutant or wild type parasites was followed in a second set of experiments (Fig. 3). The rate and extent of parasite multiplication was reduced in the mutant parasites. Therefore, although γ-GCS is not essential for growth and multiplication of blood stage Plasmodium in vivo, the absence of γ-GCS expression affects parasite growth.

Bottom Line: Despite a significant reduction in GSH levels, blood stage forms of pbggcs(-) parasites showed only a defect in growth as compared to wild type.In contrast, a dramatic effect on development of the parasites in the mosquito was observed.These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico.

ABSTRACT
Infection of red blood cells (RBC) subjects the malaria parasite to oxidative stress. Therefore, efficient antioxidant and redox systems are required to prevent damage by reactive oxygen species. Plasmodium spp. have thioredoxin and glutathione (GSH) systems that are thought to play a major role as antioxidants during blood stage infection. In this report, we analyzed a critical component of the GSH biosynthesis pathway using reverse genetics. Plasmodium berghei parasites lacking expression of gamma-glutamylcysteine synthetase (gamma-GCS), the rate limiting enzyme in de novo synthesis of GSH, were generated through targeted gene disruption thus demonstrating, quite unexpectedly, that gamma-GCS is not essential for blood stage development. Despite a significant reduction in GSH levels, blood stage forms of pbggcs(-) parasites showed only a defect in growth as compared to wild type. In contrast, a dramatic effect on development of the parasites in the mosquito was observed. Infection of mosquitoes with pbggcs(-) parasites resulted in reduced numbers of stunted oocysts that did not produce sporozoites. These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito.

Show MeSH
Related in: MedlinePlus