bims-toxgon 2026-02-08 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2026–02–08
twelve papers selected by
Lakesh Kumar, BITS Pilani

ZFT is the major iron and zinc transporter in Toxoplasma gondii.
Microtubule inner proteins in apicomplexan parasites.
Toxoplasma gondii as a drug for anti-tumor immunotherapy: mechanisms, challenges, and perspectives.
Discovery and Evaluation of SA-18 as an Anti-Toxoplasma Agent.
IFN-γ protects the human blood-brain barrier from Toxoplasma gondii-mediated dysfunction via CCL2 suppression.
Transferrin Receptor 1 is Required for CD4+ T Cell Iron-Dependent Response During Acute Toxoplasma gondii Infection.
PfApiAT2 is a proline transporter essential for the transmission of Plasmodium falciparum by the mosquito vector.
Enzyme Assays for Phosphoinositide Kinases and Phosphatases and Inhibitor Screens.
SIRT4 regulates antiviral and autoimmune responses by promoting cGAS-mediated signaling pathways.
Illuminating spatial dynamics of glutamine metabolism with a sensitive genetically encoded biosensor.
Metabolite control of enzyme activity links stress to biosynthetic regulation.
Exploring Protein Interactomes Using TurboID-Directed Proximity Labeling and Mass Spectrometry.

Elife. 2026 Feb 05. pii: RP108666. [Epub ahead of print]14

ZFT is the major iron and zinc transporter in Toxoplasma gondii.

Dana Aghabi, Cecilia Gallego Rubio, Miguel Cortijo Martinez, Augustin Pouzache, Erin J Gibson, Lucas Pagura, Stephen J Fairweather, Giel G van Dooren, Clare R Harding.

  Transition metals, such as iron and zinc, are indispensable trace elements for eukaryotic life, acting as co-factors in essential processes ranging from metabolism to DNA replication. These metals can be transported into cells by an evolutionary-conserved family of metal transporters; however, how the ubiquitous mammalian parasite Toxoplasma gondii acquires essential metals has been unknown. Here, we have identified and characterised the first iron and zinc importer in T. gondii. This transporter, named ZFT, localised to the parasite plasma membrane and is essential for the parasite's life cycle. We find ZFT is regulated by iron availability and overexpression sensitises cells to excess iron and zinc. Using a conditional knockdown system, we find that knockdown of ZFT leads to reduction in mitochondrial respiration and a switch to a more quiescent lifecycle stage. To confirm transport activity, we find that knockdown of ZFT leads to a reduction in parasite-associated zinc and iron, and ZFT expression complements loss of zinc transporter activity in a yeast model. Further, expression of ZFT in Xenopus oocytes demonstrates direct uptake of iron, which is outcompeted in the presence of zinc. Overall, we have identified the first metal uptake transporter in T. gondii and demonstrated the importance of iron and zinc to the parasite. This finding advances our understanding of how this obligate intracellular parasite acquires nutrients from its host.

Keywords:  Toxoplasma gondii; infectious disease; iron; metabolism; microbiology; transporter; zinc

DOI:  https://doi.org/10.7554/eLife.108666
Biochem Soc Trans. 2026 Feb 02. pii: BST20253092. [Epub ahead of print]54(2):

Microtubule inner proteins in apicomplexan parasites.

Annika M Binder, Friedrich Frischknecht, Franziska Hentzschel.

  Microtubule inner proteins (MIPs) are integral components within the microtubule lumen of various organisms, contributing to microtubule structural integrity and functionality. Apicomplexan parasites, including Plasmodium spp. and Toxoplasma gondii, exhibit a range of specialized tubulin structures, such as axonemal microtubules, subpellicular microtubules (SPMTs), and conoid fibers, playing critical roles in cellular morphology and motility. Yet, in contrast with model organisms, only a few MIPs have been characterized in apicomplexans so far. Recent advances in cryo-electron tomography and structural proteomics have facilitated the study of MIPs, shedding light on unique adaptations that distinguish apicomplexan microtubules from those in model eukaryotes. Key findings include the identification of an interrupted luminal helix in SPMTs, which is critical for stabilizing microtubules under stress. The relatively small repertoire of axonemal MIPs contrasts markedly with the numerous MIPs observed in other systems, possibly reflecting adaptations for rapid microtubule assembly without intraflagellar transport. Furthermore, emerging evidence points to multiple MIPs within the conoid and SPMTs, suggesting further roles for MIPs in these parasites. This review highlights the currently known contributions of MIPs to the survival and proliferation of these parasites, while emphasizing the need for continued research to fully characterize their diverse roles and molecular mechanisms.

Keywords:   Plasmodium ; Toxoplasma ; Apicomplexa; Microtubules; microtubule inner proteins

DOI:  https://doi.org/10.1042/BST20253110
Parasite. 2026 ;33 4

Toxoplasma gondii as a drug for anti-tumor immunotherapy: mechanisms, challenges, and perspectives.

Jing Li, Eman E El Shanawany, Soad E Hassan, Peng-Yao Li, Jia-Hui Sun, Hong-Mei Li, Shao-Hong Lu, Xiao-Nong Zhou, Bin Zheng.

  Toxoplasma gondii is an intracellular protozoan parasite known to infect a wide range of hosts, including humans, and is a significant cause of health issues, particularly in pregnant women and immunocompromised individuals. However, it has garnered attention for its potential in cancer treatment due to its diverse anti-cancer mechanisms. Toxoplasma gondii induces key cytokines such as IL-12 and IFN-γ, triggering robust Th1 immune responses that effectively target tumor cells. Furthermore, it modulates the immunosuppressive tumor microenvironment (TME), reduces inhibitory immune cells, promotes activated immune cells, induces apoptosis in tumor cells, inhibits proliferation, and disrupts tumor angiogenesis through regulatory signaling pathways. Despite these promising antitumor attributes, significant limitations hinder its translation into clinical practice. These include strain-dependent differences in virulence and therapeutic efficacy, ethical and biosafety concerns associated with wild-type strains, limited applicability of animal data to human therapy, and the possibility that the parasite may promote tumorigenesis under certain conditions. Innovative approaches such as engineered strains for precise tumor targeting, exploitation of its bioactive agents, use as a drug carrier for brain tumors, and combination therapies with other anti-cancer modalities show promise. These advances, coupled with comprehensive cost-effectiveness assessments, present new opportunities and hope for integrating T. gondii into cancer therapy.

Keywords:  Anti-tumor; Immunity; Toxoplasma gondii

DOI:  https://doi.org/10.1051/parasite/2026006
FASEB J. 2026 Feb 28. 40(4): e71476

Discovery and Evaluation of SA-18 as an Anti-Toxoplasma Agent.

Huiyu Du, Wanxin Luo, Hongxi Zhang, Lihua Xiao, Yaoyu Feng, Lan He, Hao Shao, Ningbo Xia.

  Toxoplasma gondii, a globally prevalent apicomplexan parasite, causes severe morbidity and mortality in immunocompromised individuals and livestock. Current therapies exhibit limited efficacy against chronic bradyzoite stages and face drug resistance. Here, we screened imidocarb and its derivatives for anti-Toxoplasma activity. Among 20 synthesized compounds, squaramide derivative 18 (SA-18) emerged as a promising candidate with nanomolar EC50 against tachyzoites, potent inhibition of bradyzoite differentiation, and > 100-fold selectivity index. Transcriptomic analysis revealed transcriptional dysregulation in parasite metabolic pathways and downregulation of bradyzoite marker BAG1. In vivo studies exhibited significant parasite load reduction in murine models, albeit with suboptimal survival rates. These findings highlight SA-18 as a novel candidate for toxoplasmosis therapy, warranting further optimization for clinical translation.

Keywords:  apicomplexa; compounds; drug efficacy; imidocarb; toxoplasmosis

DOI:  https://doi.org/10.1096/fj.202502937R
Res Sq. 2026 Jan 14. pii: rs.3.rs-8524866. [Epub ahead of print]

IFN-γ protects the human blood-brain barrier from Toxoplasma gondii-mediated dysfunction via CCL2 suppression.

Mia C Somenzi, Kameron T Bell, Abigail M Bitters, Collin S Stratton, Samantha R Springston, Kamryn E Zadeii, Rylee J Anderson, Daisy Woellner-Santos, Scott G Canfield, Américo H López-Yglesias.

The obligate intracellular parasite Toxoplasma gondii infects nearly one-third of the global population, yet its impact on human blood-brain barrier (BBB) function remains poorly defined. In this study, we use human induced pluripotent stem cell-derived (iPSC) brain-like microvascular endothelial cells (BMECs), a physiologically relevant BBB model, to investigate if T. gondii infection directly compromises barrier integrity. We show that infection induces robust monocyte chemotactic protein-1 (also known as CCL2) secretion from BMECs, and that CCL2 itself serves as a previously unrecognized driver of BBB dysfunction. Notably, interferon-gamma (IFN-γ) limits BMEC-derived CCL2 release and protects against parasite-mediated barrier damage. These findings identify an IFN-γ-dependent, BMEC-intrinsic defense mechanism that helps preserve central nervous system (CNS) integrity during infection. Collectively, this work establishes a mechanistic foundation for understanding how T. gondii disrupts the human BBB and reveals a novel protective role for IFN-γ in mitigating CNS barrier dysfunction.

DOI: https://doi.org/10.21203/rs.3.rs-8524866/v1
bioRxiv. 2024 Oct 02. pii: 2023.06.28.546960. [Epub ahead of print]

Transferrin Receptor 1 is Required for CD4+ T Cell Iron-Dependent Response During Acute Toxoplasma gondii Infection.

Stephen L Denton, Tathagato Roy, Hunter K Keplinger, Sai K Ng, Jason P Gigley.

Elemental iron is an essential nutrient involved in many biological processes including infection and immunity. How iron impacts Toxoplasma gondii ( T. gondii ) in vivo and development of immunity during infection is unclear. We found that although iron is required for parasite proliferation in vitro, paradoxically, iron restriction in vivo increased parasite burdens during acute and persistent infection stages and decreased survival of mice. Iron restriction lowered IL-12 and IFN γ in spleen and serum, but ratios of myeloid cells and the number and function of Natural Killer cells were unchanged. Iron restriction significantly impaired the development of CD4+ and CD8+ T cell responses to T. gondii during replicating type II and attenuated vaccine strain cps1-1 infection. Low iron conditions reduced the percent and absolute numbers of antigen experienced CD11a+CD49d+, functional IFN γ +, and CD62L-KLRG1+ effector T cells. Iron restriction also decreased vaccine efficacy of cps1-1 strain against secondary lethal challenge. Antigen experienced CD4+ and CD8+ T cells both upregulated their iron transporter Transferrin receptor 1 (CD71) during infection regardless of iron restriction. Mice whose CD4+ T cells were deficient in CD71 had reduced CD4+ T cell antigen experience and polyfunctionality, yet CD8+ T cell responses remained intact, and their long term survival was not affected compared to wild type litter mate controls. This study highlights that iron acquisition by T cells is required for activation and vaccine induced long-term protection against T. gondii . Understanding how iron affects multiple immune compartments will be essential to define iron regulation of immunity to T. gondii .

DOI: https://doi.org/10.1101/2023.06.28.546960
bioRxiv. 2026 Jan 20. pii: 2026.01.20.700404. [Epub ahead of print]

PfApiAT2 is a proline transporter essential for the transmission of Plasmodium falciparum by the mosquito vector.

Malhar Khushu, R Charles Kissel, Jamie Kauffman, Claudia Taccheri, Naresh Singh, Robert L Summers, Leigh D Plant, Dyann F Wirth, Flaminia Catteruccia, Selina Bopp.

Plasmodium falciparum oocysts undergo an explosive biomass increase during development in Anopheles mosquitoes, a dramatic growth process likely promoted by as-yet unknown nutrients scavenged from the mosquito. We previously observed in blood-stage parasites, that the amino acid transporter PfApiAT2, although dispensable, regulates proline homeostasis and mediates resistance to halofuginone, a potent proline-tRNA synthetase inhibitor. Here, we demonstrate that PfApiAT2 is a proline-specific transporter essential for early oocyst development in Anopheles gambiae . Halofuginone-resistant pfapiat2 -mutant parasites form stunted oocysts severely defective in sporozoite production. This phenotype is recapitulated in PfApiAT2-knockout parasites that undergo a complete block in sporogony, forming oocysts that stall and degenerate. Remarkably, this growth defect can be rescued by nutrient supplementation to the mosquito vector. By identifying an amino acid transporter essential for oocyst growth, our data unveil a vulnerability in P. falciparum transmission, revealing a critical nutritional dependency of the parasite on its mosquito vector.

DOI: https://doi.org/10.64898/2026.01.20.700404
Methods Mol Biol. 2026 ;3014 291-299

Enzyme Assays for Phosphoinositide Kinases and Phosphatases and Inhibitor Screens.

Mengjin Gao, Manoj Koirala, Natalie B Warren, Jacqueline C Bede, Igor Cestari.

  In vitro enzyme assays provide sensitive and quantitative approaches to studying activity, identifying substrates or performing inhibitor analysis. These approaches can help to study enzymes that regulate different cellular processes in an organism. In addition, enzyme assays can be used to screen protein inhibitors to identify novel drug candidates. In eukaryotes, phosphatidylinositol kinase and phosphatase are enzymes that regulate the level of phosphorylated phosphatidylinositol, which controls several cellular processes. They also regulate several processes in many pathogens, such as kinetoplastid and apicomplexan parasites, and are validated drug targets. Here, we describe protocols to determine the activity of purified phosphoinositide kinases and phosphatases and screens to identify potential inhibitors. The assays are luminescence- and absorbance-based to measure the activity of phosphatidylinositol kinase and phosphatase enzymes, respectively. These assays can be adapted to other protein kinases and phosphatases.

Keywords:  Enzyme assay; Enzyme inhibitor; Inositol phosphates; Michaelis-Menten kinetics; Phosphatidylinositol

DOI:  https://doi.org/10.1007/978-1-0716-5146-9_19
EMBO Rep. 2026 Feb 03.

SIRT4 regulates antiviral and autoimmune responses by promoting cGAS-mediated signaling pathways.

Bo Yang, Yanjie Zhang, Saiyu Wang, Yufei Wu, Zilu Diao, Qunmei Zhang, Chen Lu, Mengyang Shen, Xuewei Zhang, Shujun Ma, Chunsheng Yang, Jinyong Pei, Hongxia Xing, Yinming Liang, Jie Wang.

  Cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS) is a critical cytosolic DNA sensor, whose activity can be regulated by acetylation. Here, we show that nicotinamide adenine dinucleotide (NAD+)-dependent lysine deacetylase SIRT4 interacts with cGAS and positively regulates innate immune responses triggered by DNA viruses or cytoplasmic DNA. Overexpression of SIRT4 inhibits HSV-1 infection, whereas knockdown of SIRT4 has the opposite effect. Deficiency of SIRT4, or treatment with a SIRT4 inhibitor, impairs antiviral innate immune signaling in response to DNA viruses or cytoplasmic DNA, both in vitro and in vivo. Moreover, SIRT4 inhibitor treatment attenuates type I interferon signaling in Trex1-deficient cells and in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE). Mechanistically, SIRT4 deacetylates cGAS and enhances its association with double‑stranded DNA. Collectively, our study identifies SIRT4 as a positive regulator of cGAS-mediated innate immune signaling pathways, which advances the understanding of the regulation of cGAS activity.

Keywords:  Acetylation; Antiviral Innate Immune Responses; Autoimmune Responses; DNA Virus; Signal Transduction

DOI:  https://doi.org/10.1038/s44319-026-00708-5
bioRxiv. 2026 Jan 16. pii: 2026.01.15.699810. [Epub ahead of print]

Illuminating spatial dynamics of glutamine metabolism with a sensitive genetically encoded biosensor.

Jack M Scully, Michael J Sun, Siddharth Das, Nataly J Arias, Edmund D Kapelczak, Tiffany D Robinson, Katie G Vineall, Teagan S Dean, Tara TeSlaa, Ajit S Divakaruni, Danielle L Schmitt.

Glutamine is the most abundant amino acid in serum, used as a key nutrient by cells for protein synthesis, energy production, carbon and nitrogen metabolism, and cellular redox balance. The use of glutamine in the cell is highly compartmentalized, but the dynamics of glutamine metabolism across organelles and individual cells are not fully understood. To illuminate subcellular glutamine dynamics, we developed an intracellular glutamine optical reporter, iGlo. We find iGlo is sensitive and specific for glutamine and can be used to measure glutamine uptake, production, and consumption with high spatiotemporal resolution in multiple cell types. Furthermore, multiplexed imaging of iGlo with a lactate biosensor in single cells reveals temporal crosstalk between glucose and glutamine metabolism to maintain energy homeostasis. Thus, iGlo enables the sensitive and precise study of compartmentalized glutamine dynamics and represents a new and enhanced tool for studying the spatiotemporal dynamics and regulation of metabolism.

DOI: https://doi.org/10.64898/2026.01.15.699810
Proc Natl Acad Sci U S A. 2026 Feb 10. 123(6): e2529243123

Metabolite control of enzyme activity links stress to biosynthetic regulation.

Wilhelmina van de Ven, Manhoi Hur, María Fernanda Gómez-Méndez, Jingzhe Guo, Haiyan Ke, Raisul Awal Mahmood, Sunghwan Kim, Thomas D Sharkey, Katayoon Dehesh.

  Cells must continuously adjust metabolic output to maintain homeostasis under changing environmental conditions, yet the mechanisms that enable rapid and reversible control of pathway activity remain largely unknown. The methylerythritol phosphate (MEP) pathway, of bacterial origin and conserved in plastid-bearing eukaryotes, including plants and apicomplexan parasites, produces isoprenoid precursors essential for growth and stress adaptation. Here, we identify methylerythritol cyclodiphosphate (MEcPP) as a dual-function metabolite that serves both as a biosynthetic intermediate and a direct modulator of enzyme activity. Genetic perturbations and high light stress revealed step-specific MEcPP accumulation independent of transcriptional regulation. Biochemical and protease-protection assays showed that MEcPP destabilizes and inhibits methylerythritol cytidylyltransferase (MCT) while modestly stabilizing hydroxymethylbutenyl diphosphate synthase (HDS). Molecular docking analyses indicate that MEcPP interacts directly with the MCT catalytic site, displacing the natural substrate and thereby attenuating enzyme activity, suggesting a competitive, feedback-like mechanism of metabolic control. These results define MEcPP as a metabolic feedback signal that translates stress-induced changes into targeted enzymatic control. This mechanism illustrates how pathway intermediates dynamically coordinate biosynthetic activity with environmental cues, representing a broadly conserved strategy for metabolite-driven control of cellular metabolism.

Keywords:  MEP pathway; MEcPP; isoprenoid biosynthesis; metabolic feedback regulation; plastidial stress response

DOI:  https://doi.org/10.1073/pnas.2529243123
Methods Mol Biol. 2026 ;3013 315-342

Exploring Protein Interactomes Using TurboID-Directed Proximity Labeling and Mass Spectrometry.

Elvio Rodríguez Araya, Gonzalo Martínez Peralta, Lucila Attala, Victoria Boselli, Azul de Hernández, Julia Pinheiro Chagas da Cunha, Esteban Serra.

  Proximity labeling (PL) with TurboID provides a powerful alternative to traditional protein interaction mapping methods, allowing the capture of both stable and transient interactions in living cells. Here, we describe a standardized and optimized protocol for generating high-confidence proximity proteomes in Trypanosoma cruzi using a novel vector system, pTcTurboID. This vector allows the stable and regulatable expression of TurboID fusion proteins, ensuring minimal bait expression to preserve physiological function while maintaining sufficient biotinylation activity for protein detection. The protocol comprises eight steps, including the generation of spatial control and bait lineages, optimization of biotinylation conditions, and refinement of the purification process with magnetic streptavidin beads. Key features include the use of compartment-specific spatial controls to minimize nonspecific background and statistical analysis to identify true interactors. Our methodology has been validated with nuclear and cytoplasmic baits, yielding reproducible proximity interactomes. This protocol provides an efficient, reproducible, and robust framework for proximity proteomics in T. cruzi.

Keywords:  Biotinylation; Interactomics; Mass spectrometry; Protein–protein interactions; Proteomics; Proximity labeling; Trypanosoma cruzi; TurboID

DOI:  https://doi.org/10.1007/978-1-0716-5142-1_17