The glutathione biosynthetic pathway of Plasmodium is essential for mosquito transmission.
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.
Vega-Rodríguez
Joel
J
Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico.
Franke-Fayard
Blandine
B
Dinglasan
Rhoel R
RR
Janse
Chris J
CJ
Pastrana-Mena
Rebecca
R
Waters
Andrew P
AP
Coppens
Isabelle
I
Rodríguez-Orengo
José F
JF
Srinivasan
Prakash
P
Jacobs-Lorena
Marcelo
M
Serrano
Adelfa E
AE
D000704:Analysis of Variance; D000818:Animals; D000852:Anopheles / Q000469:parasitology; D049109:Cell Proliferation; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D015870:Gene Expression; D018390:Gene Targeting; D005721:Glutamate-Cysteine Ligase / Q000235:genetics* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D008288:Malaria / Q000469:parasitology / Q000635:transmission*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008928:Mitochondria; D033661:Oocysts / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D010962:Plasmodium berghei / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D034101:Sporozoites / Q000378:metabolism; D018709:Statistics, Nonparametric
D005721:Glutamate-Cysteine Ligase; D005978:Glutathione