Genome-Scale Identification of Essential Metabolic Processes for Targeting the Plasmodium Liver Stage

Abstract

SummaryPlasmodium gene functions in mosquito and liver stages remain poorly characterized due to limitations in the throughput of phenotyping at these stages. To fill this gap, we followed more than 1,300 barcoded P. berghei mutants through the life cycle. We discover 461 genes required for efficient parasite transmission to mosquitoes through the liver stage and back into the bloodstream of mice. We analyze the screen in the context of genomic, transcriptomic, and metabolomic data by building a thermodynamic model of P. berghei liver-stage metabolism, which shows a major reprogramming of parasite metabolism to achieve rapid growth in the liver. We identify seven metabolic subsystems that become essential at the liver stages compared with asexual blood stages: type II fatty acid synthesis and elongation (FAE), tricarboxylic acid, amino sugar, heme, lipoate, and shikimate metabolism. Selected predictions from the model are individually validated in single mutants to provide future targets for drug development.

Vitamin and cofactor acquisition in apicomplexans: Synthesis versus salvage

“…iTgo contains 556 metabolic genes and integrates all available data sets to serve as a valuable platform for model-guided investigations. To harmonize the model with the genome-wide fitness scores for metabolic genes, additional constraints on substrate availabilities from the host as well as reaction utilization based on transcriptomics data were applied (16,30). The workflow led to a model, 80% consistent with experimentally observed phenotypes, 3 allowing for reliable hypothesis generation for experimental validation.…”

“…The two previous metabolic reconstructions (13,15) identified several essential metabolic functions and differences within the clonal strains of T. gondii that display distinct virulence profiles. Within the apicomplexans, the most studied and comprehensive metabolic reconstructions were generated for P. falciparum and the rodent malaria parasite, Plasmodium berghei (14,16,31). Constant modeling efforts with the incorporation of physiological parameters, such as metabolomics and fluxomics, continue to expand our knowledge of the metabolic versatility of the apicomplexans.…”

A screen forPlasmodium falciparumsporozoite surface protein binding to human hepatocyte surface receptors identifies novel host-pathogen interactions

“…Pf34 has orthologs in rodent parasites but there are, to our knowledge, no studies to show the role of this protein in sporozoite invasion of hepatocytes. Its P. berghei ortholog (PBANKA_0721800) was not covered in recent large-scale ‘PlasmoGEM’ screens of gene essentiality in the P. berghei blood, mosquito, and pre-erythrocytic stages [20, 21].…”

MRE11 is crucial for malaria transmission and its absence affects expression of interconnected networks of key genes essential for life

“…The DSBR pathway is a target of intense investigation for the development of cancer therapies (16). However, despite the initial studies in Apicomplexa, the function of MRE11 throughout the Plasmodium lifecycle is still unclear and genome-wide studies have not investigated its role at the different stages (17,18). Here we use the rodent malaria parasite Plasmodium berghei (Pb) to provide a functional, ultrastructural and transcriptomic analysis of Pbmre11.…”

“…Thus the increase in OGG1 expression coupled with reduction in RAD10, RAD14 and MMS19-like protein gene expression (all playing key roles in the NER pathway) could all contribute to accumulation of deleterious DNA damage that is usually regulated by MRE11.Finally, several studies have highlighted a number of genes that are essential for Plasmodium ookinete adhesion and invasion, and oocyst development(50), a number of which may be affected due to MRE11's absence. A previous genome-wide screening study did not analyze MRE11, but it did suggest that RAD50, the MRN complex partner of MRE11, is essential for parasite transmission(18). This suggests that MRE11 and RAD50 may form a complex that is essential for successful oocyst development.…”