Dual metabolomic profiling uncovers Toxoplasma manipulation of the host metabolome and the discovery of a novel parasite metabolic capability

Abstract

<jats:title>Abstract</jats:title><jats:p>The obligate intracellular parasite <jats:italic>Toxoplasma gondii</jats:italic> is auxotrophic for several key metabolites and must scavenge these from the host. It is unclear how <jats:italic>Toxoplasma</jats:italic> manipulates host metabolism for its overall growth rate and non-essential metabolites. To address this question, we measured changes in the joint host-parasite metabolome over a time course of infection. Host and parasite transcriptomes were simultaneously generated to determine potential changes in metabolic enzyme levels. <jats:italic>Toxoplasma</jats:italic> infection increased activity in multiple metabolic pathways, including the tricarboxylic acid cycle, the pentose phosphate pathway, glycolysis, amino acid synthesis, and nucleotide metabolism. Our analysis indicated that changes in some pathways, such as the tricarboxylic acid cycle, derive from the parasite, while changes in others, like the pentose phosphate pathway, were host and parasite driven. Further experiments led to the discovery of a <jats:italic>Toxoplasma</jats:italic> enzyme, sedoheptulose bisphosphatase, which funnels carbon from glycolysis into ribose synthesis through a energetically driven dephosphorylation reaction. This second route for ribose synthesis resolves a conflict between the <jats:italic>Toxoplasma</jats:italic> tricarboxylic acid cycle and pentose phosphate pathway, which are both NADP+ dependent. During periods of high energetic and ribose need, the competition for NADP+ could result in lethal redox imbalances. Sedoheptulose bisphosphatase represents a novel step in <jats:italic>Toxoplasma</jats:italic> central carbon metabolism that allows <jats:italic>Toxoplasma</jats:italic> to satisfy its ribose demand without using NADP+. Sedoheptulose bisphosphatase is not present in humans, highlighting its potential as a drug target.</jats:p><jats:sec><jats:title>Author Summary</jats:title><jats:p>The obligate intracellular parasite <jats:italic>Toxoplasma</jats:italic> is commonly found among human populations worldwide and poses severe health risks to fetuses and individuals with AIDS. While some treatments are available they are limited in scope. A possible target for new therapies is <jats:italic>Toxoplasma</jats:italic>’s limited metabolism, which makes it heavily reliant in its host. In this study, we generated a joint host/parasite metabolome to better understand host manipulation by the parasite and to discover unique aspects of <jats:italic>Toxoplasma</jats:italic> metabolism that could serve as the next generation of drug targets. Metabolomic analysis of <jats:italic>Toxoplasma</jats:italic> during an infection time course found broad activation of host metabolism by the parasite in both energetic and biosynthetic pathways. We discovered a new <jats:italic>Toxoplasma</jats:italic> enzyme, sedoheptulose bisphosphatase, which redirects carbon from glycolysis into ribose synthesis. Humans lack sedoheptulose bisphosphatase, making it a potential drug target. The wholesale remodeling of host metabolism for optimal parasite growth is also of interest, although the mechanisms behind this host manipulation must be further studied before therapeutic targets can be identified.</jats:p></jats:sec>

In vitromaturation ofToxoplasma gondiibradyzoites in human myotubes and their metabolomic characterization

“…They have been shown to independently affect lethality of antibiotics against bacterial microbes, with metabolism being the dominant factor (Lopatkin et al, 2019). While multiple metabolomic investigations on the tachyzoite stage of T. gondii revealed unexpected features of key metabolic pathways such as the GABA-shunt of the tricarboxylic acid (TCA) cycle, a constitutively active gluconeogenic fructose 1,6-bisphosphatase and the presence of a non-oxidative pentose phosphate pathway (Blume et al, 2015; MacRae et al, 2012; Olson et al, 2020), the metabolism of bradyzoites has only been characterized indirectly (Blume and Seeber, 2018), largely due to experimental constraints. In contrast to tachyzoites, bradyzoites depend on the turnover of the storage polysaccharide amylopectin by glycogen phosphorylase (Murata et al, 2017), the hexose kinase (Shukla et al, 2018) and on a dedicated isoform of lactate dehydrogenase (Abdelbaset et al, 2017).…”

Novel Approaches for Systems Biology of Metabolism-Oriented Pathogen-Human Interactions: A Mini-Review

“…The results enlightened the substrates directly used by the pathogen as biomass precursors and the ones further metabolized for energy or building blocks. On the other hand, pathogen/host joint metabolomics and dual transcriptomics data were investigated together to shed light on the metabolic changes during Toxoplasma gondii infection of human (Olson et al, 2018). Paired analysis of joint metabolome and dual transcriptome data uncovered the manipulation of the host metabolome by Toxoplasma and identified sedoheptulose biphosphatase driven ribose synthesis from glucose as a novel metabolic capability of the parasite.…”

Minireview: Applications of NMR‐based metabolomics for the detection and characterisation of toxoplasmosis in felids

“…It has been discovered elsewhere that the parasite has its own unique enzyme called sedoheptulose bisphosphatase, which is not present in mammalian host cells 10 . It has been concluded that the sedoheptulose bisphosphatase enzyme could drive carbon into the non‐oxidative pentose phosphate pathway, where it might be converted into ribose 10 . This leads to an additional pathway for ribose synthesis.…”

“…Moreover, the nucleotide metabolism of a host was transcriptionally activated during the infection. Also, denosine kinase and hypoxanthine phosphoribosyltransferase enzymes have been found highly expressed in host cells 10 …”