bims-toxgon 2025-02-09 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2025–02–09
twelve papers selected by
Lakesh Kumar, BITS Pilani

The TgAMPK-TgPFKII axis essentially regulates protein lactylation in the zoonotic parasite Toxoplasma gondii.
Phospho-relay feedback loops control egress vs. intracellular development in Toxoplasma gondii.
The HCF101 protein is an important component of the cytosolic iron-sulfur synthesis pathway in Toxoplasma gondii.
mSphere of Influence: Lighting up organellar communication in protozoan parasites.
Iron-mediated post-transcriptional regulation in Toxoplasma gondii.
PfFBXO1 is essential for inner membrane complex formation in Plasmodium falciparum during both asexual and transmission stages.
Evaluation of Toxoplasma gondii Perforin-like Proteins (PLPs) to Find the Potential Epitopes for Immunization through in silico Approach.
Sirtuins in kidney homeostasis and disease: where are we now?
Protective immune response induced by cationic liposomes bearing soluble antigens improves the survival of BALB/c mice against Toxoplasma gondii RH strain.
Characteristics of Plasmodium vivax apicomplexan amino acid transporter 8 (PvApiAT8) in the cationic amino acid transport.
Biochemical characterization and discovery of inhibitors for PfSir2A: new tricks for an old enzyme.
Structural basis of SIRT7 nucleosome engagement and substrate specificity.

Microbiol Spectr. 2025 Feb 07. e0204424

The TgAMPK-TgPFKII axis essentially regulates protein lactylation in the zoonotic parasite Toxoplasma gondii.

Chenghuan Li, Yang Zhao, Qilong Li, Ran Chen, Ying Feng, Xiaoyu Sang, Xiangrui Li, Bang Shen, Ning Jiang, Qijun Chen.

  Toxoplasma gondii infects nucleated cells of warm-blooded animals and cause zoonotic toxoplasmosis. Lysine lactylation, as a novel post-translational modification, is essential for epigenetic regulation and cellular processes, and proteomic analyses have shown that lactylated proteins are involved in a wide range of biological processes including energy metabolism, gene regulation, and protein biosynthesis. Additionally, protein lactylation is prevalent in T. gondii, while its regulatory mechanisms have not been fully understood. In this study, we investigated the role of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in the invasion, replication, and lactylation regulation of T. gondii. We localized TgPFKII in the cytoplasm of T. gondii tachyzoites and demonstrated its necessity for parasite growth and protein lactylation through auxin-induced degradation. Our results showed that inhibition of the AMPK pathway led to decreased TgPFKII expression and reduced protein lactylation levels. Furthermore, AMPK-specific inhibitors significantly impaired parasite invasion and proliferation. These findings highlight TgPFKII as a crucial regulator of lactylation and underscore the importance of the AMPK pathway in T. gondii's pathogenic mechanisms, offering potential targets for therapeutic intervention.IMPORTANCEUnderstanding the intricate mechanisms by which Toxoplasma gondii invades and proliferates within host cells is essential for developing novel therapeutic strategies against toxoplasmosis. This study focuses on the pivotal roles of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in regulating protein lactylation in association with parasite invasion and growth. By elucidating the cellular localization and functional importance of TgPFKII, as well as its regulation through AMPK-specific inhibitors, we provide comprehensive insights into the metabolic and signaling networks that underpin T. gondii pathogenicity. Our findings reveal that TgPFKII is a critical regulator of lactylation and that the AMPK pathway significantly influences T. gondii's ability to invade and replicate within host cells. These insights pave the way for targeted interventions aimed at disrupting key metabolic and signaling pathways in T. gondii, potentially leading to more effective treatments for toxoplasmosis.

Keywords:  AMPK inhibitor; AMPK signaling pathway; TgPFKII; Toxoplasma gondii; lactylation

DOI:  https://doi.org/10.1128/spectrum.02044-24
Cell Rep. 2025 Feb 03. pii: S2211-1247(25)00031-2. [Epub ahead of print]44(2): 115260

Phospho-relay feedback loops control egress vs. intracellular development in Toxoplasma gondii.

Ja E Claywell, Yong Fu, L David Sibley.

  The intracellular parasite Toxoplasma gondii alternates between a motile invasive and a quiescent intracellular replicative form, yet how these transitions are regulated is unknown. A positive feedback loop involving protein kinase G (PKG) and calcium-dependent PKs (CDPKs) controls motility, invasion, and egress by Toxoplasma gondii, while PKA isoform c1 (PKAc1) counteracts this pathway. Shortly after invasion, PKAc1 is activated by cyclic AMP (cAMP) produced by adenylate cyclases, leading to the suppression of the PKG/CDPK pathway. PKAc1 further activates phosphodiesterase 2, which selectively consumes cAMP, thus forming a negative feedback loop, causing transient activation of PKAc1. Perturbation of cyclic GMP (cGMP) vs. calcium demonstrates that PKAc1 acts on targets between guanylate cyclase and calcium release. The combined activation of PKG/CDPKs and inhibition by PKAc1, controlled by a transient negative feedback loop, ensures that the parasite is responsive to environmental signals needed to activate motility while also ensuring periods of long-term stable intracellular growth.

Keywords:  CP: Microbiology; CP: Molecular biology; calcium; homeostasis; phosphodiesterase; phosphorylation; protein kinase A; signaling

DOI:  https://doi.org/10.1016/j.celrep.2025.115260
PLoS Biol. 2025 Feb 06. 23(2): e3003028

The HCF101 protein is an important component of the cytosolic iron-sulfur synthesis pathway in Toxoplasma gondii.

Eléa A Renaud, Ambre J M Maupin, Laurence Berry, Julie Bals, Yann Bordat, Vincent Demolombe, Valérie Rofidal, Florence Vignols, Sébastien Besteiro.

Several key cellular functions depend on proteins harboring an iron-sulfur (Fe-S) cofactor. As these Fe-S proteins localize to several subcellular compartments, they require a dedicated machinery for cofactor assembly. For instance, in plants and algae there are Fe-S cluster synthesis pathways localizing to the cytosol, but also present in the mitochondrion and in the chloroplast, 2 organelles of endosymbiotic origin. Toxoplasma gondii is a plastid-bearing parasitic protist responsible for a pathology affecting humans and other warm-blooded vertebrates. We have characterized the Toxoplasma homolog of HCF101, originally identified in plants as a protein transferring Fe-S clusters to photosystem I subunits in the chloroplast. Contrarily to plants, we have shown that HCF101 does not localize to the plastid in parasites, but instead is an important component of the cytosolic Fe-S assembly (CIA) pathway which is vital for Toxoplasma. While the CIA pathway is widely conserved in eukaryotes, it is the first time the involvement of HCF101 in this pan-eukaryotic machinery is established. Moreover, as this protein is essential for parasite viability and absent from its mammalian hosts, it constitutes a novel and promising potential drug target.

DOI: https://doi.org/10.1371/journal.pbio.3003028
mSphere. 2025 Feb 06. e0057424

mSphere of Influence: Lighting up organellar communication in protozoan parasites.

Diego Huet.

  Diego Huet works in molecular parasitology, focusing on the organellar biology of Toxoplasma gondii. In this mSphere of Influence article, he reflects on how the article "Efficient proximity labeling in living cells and organisms with turboID" (Branon et al., 2018) impacted his research and the strategies used to dissect inter-organellar interactions in T. gondii.

Keywords:  Toxoplasma; organelles; proximity biotinylation

DOI:  https://doi.org/10.1128/msphere.00574-24
PLoS Pathog. 2025 Feb;21(2): e1012857

Iron-mediated post-transcriptional regulation in Toxoplasma gondii.

Megan A Sloan, Adam Scott, Dana Aghabi, Lucia Mrvova, Clare R Harding.

Iron is required to support almost all life; however, levels must be carefully regulated to maintain homeostasis. Although the obligate parasite Toxoplasma gondii requires iron, how it responds upon iron limitation has not been investigated. Here, we show that iron depletion triggers significant transcriptional changes in the parasite, including in iron-dependent pathways. We find that a subset of T. gondii transcripts contain stem-loop structures, which have been associated with post-transcriptional iron-mediated regulation in other cellular systems. We validate one of these (found in the 3' UTR of TGME49_261720) using a reporter cell line. We show that the presence of the stem-loop-containing UTR is sufficient to confer accumulation at the transcript and protein levels under low iron. This response is dose and time-dependent and is specific for iron. The accumulation of transcript is likely driven by an increased reporter mRNA stability under low iron. Interestingly, we find iron-mediated changes in mRNA stability in around 400 genes. To examine the potential mechanism of this stability, we tested aconitase interaction with mRNA in low iron and found 43 enriched transcripts, but no specific interaction with our reporter UTR. However, the endogenous UTR led to maintenance of protein levels and increased survival of the parasite under low iron. Our data demonstrate the existence of iron-mediated post-transcriptional regulation in Toxoplasma for the first time; and suggests iron-mediated regulation may be important to the parasite in low iron environments.

DOI: https://doi.org/10.1371/journal.ppat.1012857
Commun Biol. 2025 Feb 07. 8(1): 190

PfFBXO1 is essential for inner membrane complex formation in Plasmodium falciparum during both asexual and transmission stages.

Sreelakshmi K Sreenivasamurthy, Carlos Gustavo Baptista, Christopher M West, Ira J Blader, Jeffrey D Dvorin.

Plasmodium species replicate via schizogony, which involves asynchronous nuclear divisions followed by semi-synchronous segmentation and cytokinesis. Successful segmentation requires a double-membranous structure known as the inner membrane complex (IMC). Here we demonstrate that PfFBXO1 (PF3D7_0619700) is critical for both asexual segmentation and gametocyte maturation. In Toxoplasma gondii, the FBXO1 homolog, TgFBXO1, is essential for the development of the daughter cell scaffold and a component of the daughter cell IMC. We demonstrate PfFBXO1 forming a similar IMC initiation scaffold near the apical region of developing merozoites and unilaterally positioned in gametocytes of P. falciparum. While PfFBXO1 initially localizes to the apical region of dividing parasites, it displays an IMC-like localization as segmentation progresses. Similarly, PfFBXO1 localizes to the IMC region in gametocytes. Following inducible knockout of PfFBXO1, parasites undergo abnormal segmentation and karyokinesis, generating inviable daughters. PfFBXO1-deficient gametocytes are abnormally shaped and fail to fully mature. Proteomic analysis identified PfSKP1 as one of PfBXO1's stable interacting partners, while other major proteins included multiple IMC pellicle and membrane proteins. We hypothesize that PfFBXO1 is necessary for IMC biogenesis, chromosomal maintenance, vesicular transport, and ubiquitin-mediated translational regulation of proteins in both sexual and asexual stages of P. falciparum.

DOI: https://doi.org/10.1038/s42003-025-07619-6
Recent Adv Inflamm Allergy Drug Discov. 2025 Jan 31.

Evaluation of Toxoplasma gondii Perforin-like Proteins (PLPs) to Find the Potential Epitopes for Immunization through in silico Approach.

Seyyed Amir Hosseini, Mohamad Hosein Safari, Davood Siamian, Hamidreza Majidiani, Gholam Basati, Ali Asghari.

   BACKGROUND: Toxoplasma gondii (T. gondii) is a widespread apicomplexan parasite that affects approximately one-third of the global population, posing particular risks to pregnant women and individuals with weakened immune systems. Despite its significant impact, there is currently no vaccine available for humans.
OBJECTIVE: This study employs computational methods (in silico) to investigate the physicochemical, antigenic, and structural properties of Perforin-like proteins (PLPs) from T. gondii, as well as to identify immunogenic epitopes within these antigens.
METHODS: For this aim, amino acid sequences of TgPLP1 and TgPLP2 were retrieved and submitted to the ProtParam (physicochemical), VaxiJen v2.0 (antigenicity), NetSurfP-6.0 (2D structure), Robetta (3D structure) web servers, along with the IEDB server to decipher the immunogenic epitopes. Subcellular characteristics such as signal peptide, transmembrane domain, post-translational modifications (PTMs), and cellular localization were also predicted.
RESULTS: Both proteins had a high MW of 125.50 and 92.21, respectively, with an alkaline pI, a 30 hours half-life in mammalian reticulocytes, good thermotolerance (high aliphatic index), and hydrophilicity properties (negative GRAVY). They also showed good antigenicity (0.7021 [PLP1] vs 0.5701 [PLP2]), while they were non-allergenic. Both proteins were extracellular with numerous post-translational modification sites (phosphorylation, glycosylation, and acetylation), and a transmembrane domain was only present in TgPLP1, with no signal peptide in both. Furthermore, numerous immunogenic B- and T-cell epitopes were identified within the TgPLPs sequences, suggesting their potential for inclusion in multi-epitope vaccine designs.
CONCLUSION: Further studies are needed to confirm these findings and assess the efficacy of the proposed vaccine constructs.

Keywords:  In silico; PLPs; Zoonosis; immunoinformatics; toxoplasmosis; vaccine design

DOI:  https://doi.org/10.2174/0127722708342006250116162454
Front Endocrinol (Lausanne). 2024 ;15 1524674

Sirtuins in kidney homeostasis and disease: where are we now?

Zhongyu Fan, Xuejiao Wei, Xiaoyu Zhu, Yujun Du.

  Sirtuins, identified as (NAD+)- dependent class III histone deacetylases, engage in a spectrum of biological functions, encompassing DNA damage repair, oxidative stress, immune modulation, mitochondrial homeostasis, apoptosis and autophagy. Sirtuins play an apoptosis role in regulating cellular operations and overall organism health. Mounting data indicate that dysregulated sirtuin expression is linked to the onset of renal diseases. Effective modulation of sirtuins expression and activity has been shown to improve renal function and attenuate the advancement of kidney diseases. In this review, we present a comprehensive overview of the biological impacts of sirtuins and their molecular targets in regulating renal diseases. Additionally, we detail advancements in elucidating sirtuin roles in the pathophysiology of both chronic and acute renal disorders. We review compounds that modulate sirtuin activity through activation or inhibition, potentially improving outcomes in renal disease. In summary, strategic manipulation of sirtuin activity represents a prospective therapeutic approach for renal diseases.

Keywords:  acute kidney injury; chronic kidney disease; inflammation; mitochondria; oxidative stress; sirtuins

DOI:  https://doi.org/10.3389/fendo.2024.1524674
Iran J Basic Med Sci. 2025 ;28(3): 347-354

Protective immune response induced by cationic liposomes bearing soluble antigens improves the survival of BALB/c mice against Toxoplasma gondii RH strain.

Hadi Mirahmadi, Ahmad Mehravaran, Mahdi Kavand, Ali Reza Salimi Khorashad, Nasrin Rezaee.

   Objectives: An ideal strategy to control acute or chronic toxoplasmosis can be the development and production of an effective vaccine. Liposomes as immunoadjuvants may be utilized to boost immune reactions for various antigens.
Materials and Methods: In this study, we encapsulated soluble Toxoplasma antigen (SA) in 1, 2-Dioleoyl-3-trimethylammonium propane (DOTAP) liposomes to assess the elicited immunological response. BALB/C mice received three intramuscular injections of various formulations separated by two weeks. The kind of immune reaction that was created, the degree of protection, the percentage of BALB/c mice that survived the Toxoplasma gondii challenge, the immune reaction assessment with cytokine synthesis (IFN-γ, IL-4), and the titration of IgG isotypes were all evaluated.
Results: Compared to other groups, the liposome DOTAP + imiquimod + SA-immunized mice showed a significantly lower death rate (P<0.01). Liposome DOTAP + Imiquimod + SA had higher IgG2a and IFN-γ secretion levels than the control group (P<0.001 and P<0.0001, respectively).
Conclusion: According to the study's findings, the liposome DOTAP + imiquimod + SA formulation generates a cellular immunological response, making it resistant to the T. gondii challenge.

Keywords:  Adjuvant; Cationic liposome; Immune response; Survival rate; Toxoplasma gondii

DOI:  https://doi.org/10.22038/ijbms.2024.82123.17770
Sci Rep. 2025 Feb 04. 15(1): 4234

Characteristics of Plasmodium vivax apicomplexan amino acid transporter 8 (PvApiAT8) in the cationic amino acid transport.

Wang-Jong Lee, Ernest Mazigo, Jin-Hee Han, Seok Ho Cha.

  Plasmodium vivax is the most widespread malaria parasite affecting humans, and its eradication is challenging due to the spread of drug-resistant parasites and their ability to remain in liver as a dormant stage. These parasites invade and multiply extensively within hepatocytes and erythrocytes in the host, relying on nutrient acquisition for their growth and replication. A promising new treatment aimed at targeting P. vivax involves blocking cationic amino acid uptake, which is a biological source of nutrients for the parasite. Novel Putative Transporter 1 (NPT1), identified as a cationic amino acid transporter in Apicomplexan, has a homologue in Plasmodium species known as apicomplexan amino acid transporter 8 (ApiAT8). This study focuses on P. vivax ApiAT8 to understand its precise role. PvApiAT8 was expressed in Xenopus laevis oocytes and shown to selectively uptake cationic amino acids. The uptake activity of [3H] L-arginine was shown to depend on PvApiAT8 expression time and substrate incubation time. PvApiAT8 was sodium-independent and functioned at pH levels between 6.5 and 8.5, with no efflux activity observed. Kinetic analysis showed saturable uptake for L-arginine consistent with Michaelis-Menten kinetics, with a Km of 1.5 ± 0.3 µM and a Vmax of 25.0 ± 4.8 pmol/oocyte/hr. Inhibition assays further confirmed its selectivity for cationic amino acids such as L-arginine, L-lysine, L-histidine, and L-ornithine. Sequence and structural analyses revealed a conserved binding pocket for cationic amino acids in Plasmodium species, distinct from that in Toxoplasma gondii NPT1. These findings highlight the potential of targeting PvApiAT8 in developing new treatments for P. vivax malaria.

Keywords:   Plasmodium vivax ; Xenopus laevis oocyte; Apicomplexan amino acid; Arginine; Cationic amino acid transporter; Histidine; Lysine; Malaria; PvApiAT8; Uptake

DOI:  https://doi.org/10.1038/s41598-025-88746-2
RSC Chem Biol. 2025 Jan 23.

Biochemical characterization and discovery of inhibitors for PfSir2A: new tricks for an old enzyme.

Dickson Donu, Emily Boyle, Alyson Curry, Yana Cen.

The Sir2 enzyme from Plasmodium falciparum (PfSir2A) is essential for the antigenic variation of this parasite, and its inhibition is expected to have therapeutic effects for malaria. Selective PfSir2A inhibitors are not available yet, partially due to the fact that this enzyme demonstrates extremely weak in vitro deacetylase activity, making the characterization of its inhibitors rather challenging. In the current study, we report the biochemical characterization and inhibitor discovery for this enzyme. PfSir2A exhibits greater enzymatic activity in the presence of DNA for both the peptide and histone protein substrates, suggesting that nucleosomes may be the real substrates of this enzyme. Indeed, it demonstrates robust deacetylase activity against nucleosome substrates, stemming primarily from the tight binding interactions with the nucleosome. In addition to DNA/nucleosome, free fatty acids (FFAs) are also identified as endogenous PfSir2A regulators. Myristic acid, a biologically relevant FFA, shows differential regulation of the two distinct activities of PfSir2A: activates deacetylation, but inhibits defatty-acylation. The structural basis of this differential regulation was further explored. Moreover, synthetic small molecule inhibitors of PfSir2A were discovered through the screening of a library of human sirtuin regulators. The mechanism of inhibition of the lead compounds were investigated. Collectively, the mechanistic insights and inhibitors described in this study will facilitate the future development of small molecule PfSir2A inhibitors as antimalarial agents.

DOI: https://doi.org/10.1039/d4cb00206g
Nat Commun. 2025 Feb 04. 16(1): 1328

Structural basis of SIRT7 nucleosome engagement and substrate specificity.

Carlos Moreno-Yruela, Babatunde E Ekundayo, Polina N Foteva, Dongchun Ni, Esther Calvino-Sanles, Henning Stahlberg, Beat Fierz.

Chromatin-modifying enzymes target distinct residues within histones to finetune gene expression profiles. SIRT7 is an NAD+-dependent deacylase often deregulated in cancer, which deacetylates either H3 lysine 36 (H3K36) or H3K18 with high specificity within nucleosomes. Here, we report structures of nucleosome-bound SIRT7, and uncover the structural basis of its specificity towards H3K36 and K18 deacylation, combining a mechanism-based cross-linking strategy, cryo-EM, and enzymatic and cellular assays. We show that the SIRT7 N-terminus represents a unique, extended nucleosome-binding domain, reaching across the nucleosomal surface to the acidic patch. The catalytic domain binds at the H3-tail exit site, engaging both DNA gyres of the nucleosome. Contacting H3K36 versus H3K18 requires a change in binding pose, and results in structural changes in both SIRT7 and the nucleosome. These structures reveal the basis of lysine specificity, allowing us to engineer SIRT7 towards enhanced H3K18ac selectivity, and provides a basis for small molecule modulator development.

DOI: https://doi.org/10.1038/s41467-025-56529-y