Olson, W. J. | Search bioRxiv

bioRxiv2022

Kiss and spit metabolomics highlights the role of the host cN-II enzyme on purine metabolism during pathogen infection

Intracellular pathogens are auxotrophic for many metabolites and must rely on the host. While this reliance is well established, how pathogens manipulate host metabolism to their benefit is not understood. For intracellular pathogens, distinguishing the origin of the metabolite as host- or pathogen-derived is challenging. The obligate intracellular parasite Toxoplasma gondii alters the host cell by a pre-invasion process known as "kiss and spit", where the contents of the parasite rhoptry organelles are secreted into the host cytoplasm before invasion occurs. This separation of microbe from the host offers a rare opportunity to demonstrate pathogen manipulation of the host. Using mass spectrometry-based metabolomics, we determined that kiss and spit changed host metabolites in nucleotide synthesis, the pentose phosphate pathway, glycolysis, and amino acid synthesis. An increase in 2,3-bisphosphoglycerate (2,3-BPG) abundance led us to hypothesize that high levels of host 2,3-BPG contribute to the activation of host cytosolic nucleosidase II (cN-II) to alter purine availability. Treatment with the cN-II inhibitor fludarabine and a cell line with a cN-II genetic knockout reduced T. gondii growth. Our results demonstrate that T. gondii rhoptry contents discharged during kiss and spit remodel host metabolism. They also suggest that T. gondii manipulates the host cN-II enzyme to acquire its necessary purine metabolites.

microbiology↗

bioRxiv2018

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

The obligate intracellular parasite Toxoplasma gondii is auxotrophic for several key metabolites and must scavenge these from the host. It is unclear how Toxoplasma 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. Toxoplasma 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 Toxoplasma 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 Toxoplasma 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 Toxoplasma central carbon metabolism that allows Toxoplasma to satisfy its ribose demand without using NADP+. Sedoheptulose bisphosphatase is not present in humans, highlighting its potential as a drug target.\n\nAuthor SummaryThe obligate intracellular parasite Toxoplasma 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 Toxoplasmas 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 Toxoplasma metabolism that could serve as the next generation of drug targets. Metabolomic analysis of Toxoplasma during an infection time course found broad activation of host metabolism by the parasite in both energetic and biosynthetic pathways. We discovered a new Toxoplasma 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.

microbiology↗