Toxoplasma growth in vitro is dependent on exogenous tyrosine and is independent of AAH2 even in tyrosine-limiting conditions

Marino, Nicole D.; Boothroyd, John C.

doi:10.1016/j.exppara.2017.02.018

Cited by 23 publications

(35 citation statements)

References 18 publications

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“…WT and Δ apiAT5-3 parasites were grown in DMEM containing 0 – 2.5 mM L-Tyr. Growth of WT parasites in the absence of L-Tyr was severely impaired (Fig S8A), consistent with a previous study that indicated T. gondii parasites are auxotrophic for this amino acid (20). WT parasites grew normally in [L-Tyr] as low as 10 μM (Fig 8A).…”

Section: Resultssupporting

confidence: 92%

“…The evolution of apicomplexan ancestors from a free-living to an obligate parasitic life-style was associated with the loss of numerous biosynthetic pathways, including those for amino acid synthesis (23, 24). In particular, T. gondii is auxotrophic for many amino acids, including the aromatic amino acids L-Tyr, L-Phe and L-Trp ((5, 20, 21, 25–27); this study). Parasites must scavenge essential amino acids from their environment, although, in the case of apicomplexan parasites, how they do so is poorly understood.…”

Section: Discussionmentioning

confidence: 90%

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Characterization of the apicomplexan amino acid transporter (ApiAT) family inToxoplasma gondii

Parker

Fairweather

Rajendran

et al. 2018

Preprint

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Apicomplexan parasites are auxotrophic for a range of amino acids which must be salvaged from their host cells, either through direct uptake or degradation of host proteins. Here, we describe a family of plasma membrane-localized amino acid transporters, termed the Apicomplexan Amino acid Transporters (ApiATs), that are ubiquitous in apicomplexan parasites. Functional characterization of the ApiATs of Toxoplasma gondii indicate that several of these transporters are important for intracellular growth of the tachyzoite stage of the parasite, which is responsible for acute infections. We demonstrate that the ApiAT protein TgApiAT5-3 is an exchanger for aromatic and large neutral amino acids, with particular importance for L-tyrosine scavenging and amino acid homeostasis, and that TgApiAT5-3 is critical for parasite virulence. Our data indicate that T. gondii expresses additional proteins involved in the uptake of aromatic amino acids, and we present a model for the uptake and homeostasis of these amino acids. Our findings identify a family of amino acid transporters in apicomplexans, and highlight the importance of amino acid scavenging for the biology of this important phylum of intracellular parasites.Author SummaryThe Apicomplexa comprise a large number of parasitic protozoa that have obligate intracellular lifestyles and cause significant human and animal diseases, including malaria, cryptosporidiosis, toxoplasmosis, coccidiosis in poultry, and various cattle fevers. Apicomplexans must scavenge essential nutrients from their hosts in order to proliferate and cause disease, including a range of amino acids. The direct uptake of these nutrients is presumed to be mediated by transporter proteins located in the plasma membrane of intracellular stages, although the identities of these proteins are poorly defined. Using a combination of bioinformatic, genetic, cell biological, and physiological approaches, we have characterized a family of plasma membrane-localized transporter proteins that we have called the Apicomplexan Amino acid Transporters (ApiATs). The family is found in apicomplexans and their closest free-living relatives. We show that TgApiAT5-3, a member of the family in the apicomplexan Toxoplasma gondii, is an exchanger for aromatic and large neutral amino acids. In particular, it is critical for uptake of tyrosine, and for parasite virulence in a mouse infection model. We conclude that ApiATs are a family of plasma membrane transporters that play crucial roles in amino acid scavenging by apicomplexan parasites.

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Section: Resultssupporting

confidence: 92%

Section: Discussionmentioning

confidence: 90%

Characterization of the apicomplexan amino acid transporter (ApiAT) family inToxoplasma gondii

Parker

Fairweather

Rajendran

et al. 2018

Preprint

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“…In infected cells, the important purine synthetic enzyme tetrahydrofolate synthase (MTHFD1) was upregulated compared to uninfected cells from 6 to 48 HPI (Table 1). PRPP Synthase (PRS1), which is Triplicate infected and uninfected dishes of HFFs were metabolically quenched and metabolites were extracted at 8 times points (1.5,3,6,9,12,24,36,and 48 HPI). Metabolomes were quantified using HPLC-MS and metabolites were identified with known standards.…”

Section: Nucleotide Synthesis Increasesmentioning

confidence: 99%

“…These central pathways are generally fueled by glucose or glutamine scavenged from the host cell. Other areas of metabolism, including amino acid, nucleotide, and lipid synthesis, are partially present but rely on host metabolism to provide certain metabolites, including arginine [10], tryptophan [11], tyrosine [12], purines [13] and cholesterol [14].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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The obligate intracellular parasite Toxoplasma gondii is auxotrophic for several key metabolites and must scavenge these from the host. It is unclear how T. gondii manipulates host metabolism to support its overall growth rate and non-essential metabolites. To investigate 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 expression of metabolic enzymes. T. gondii infection changed metabolite abundance 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, were mirrored by changes in parasite transcription, while changes in others, like the pentose phosphate pathway, were paired with changes in both the host and parasite transcriptomes. Further experiments led to the discovery of a T. gondii enzyme, sedoheptulose bisphosphatase, which funnels carbon from glycolysis into the pentose phosphate pathway through an energetically driven dephosphorylation reaction. This additional route for ribose synthesis appears to resolve the conflict between the T. gondii tricarboxylic acid cycle and pentose phosphate pathway, which are both NADP+ dependent. Sedoheptulose bisphosphatase represents a novel step in T. gondii central carbon metabolism that allows T. gondii to energetically-drive ribose synthesis without using NADP+.

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“…As a eukaryote T. gondii possesses a complex metabolism with most of the major metabolic pathways complete, including the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway (PPP), gluconeogenesis and glycolysis [6-13]. Other areas of metabolism, including amino acid and nucleotide synthesis, are partially present but rely on host metabolism to provide certain precursors and products [2-4,12,14]. T. gondii metabolism also contains unusual pathways for a eukaryote, including a fungal-like shikimate pathway for aromatic amino acid synthesis and an algal-like fatty acid synthesis II pathway [15-17].…”

Section: Introductionmentioning

confidence: 99%

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

Olson

Stevenson

Amador‐Noguez

et al. 2018

Preprint

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AbstractThe 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.Author 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 Toxoplasma’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 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.

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Toxoplasma growth in vitro is dependent on exogenous tyrosine and is independent of AAH2 even in tyrosine-limiting conditions

Cited by 23 publications

References 18 publications

Characterization of the apicomplexan amino acid transporter (ApiAT) family inToxoplasma gondii

Characterization of the apicomplexan amino acid transporter (ApiAT) family inToxoplasma gondii

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

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

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