bims-toxgon 2025-09-21 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2025–09–21
eight papers selected by
Lakesh Kumar, BITS Pilani

Considerations on Structural Vaccinology and Epitope Screening of Calcium-Dependent Protein Kinases 8 as a Potential Vaccine Target Against Toxoplasma gondii.
Perforation of the host cell plasma membrane during Toxoplasma invasion requires rhoptry exocytosis.
The invasion pore induced by Toxoplasma gondii.
Reconstituted ferredoxin-MEP pathway of Apicomplexa in E. coli as an in situ screening platform for inhibitors and essential enzyme mutations.
Structural basis of SIRT2 pre-catalysis NAD+ binding dynamics and mechanism.
Genetic crosses reveal genomic loci responsible for virulence in Cryptosporidium parvum infection.
SETD2 suppresses tumorigenesis in a KRASG12C-driven lung cancer model, and its catalytic activity is regulated by histone acetylation.
Nitrogen enrichment reduces parasitism in an annual hemiparasite.

Interdiscip Perspect Infect Dis. 2025 ;2025 4426082

Considerations on Structural Vaccinology and Epitope Screening of Calcium-Dependent Protein Kinases 8 as a Potential Vaccine Target Against Toxoplasma gondii.

Amirhossein Abedi, Ali Dalir Ghaffari.

  Introduction:Toxoplasma gondii (T. gondii) is a widely prevalent parasite from the phylum apicomplexan and is the causative agent of toxoplasmosis, which affects almost all warm-blooded animals, including humans. Presently, conventional treatments for toxoplasmosis have limited effectiveness against the cystic forms of the parasite. Thus, developing an efficient and safe vaccine for control and prevention of toxoplasmosis is crucial. Calcium-dependent protein kinases (CDPKs) are essential in governing crucial biological processes like anchoring to host cell, cellular infiltration, dynamic locomotion, and escape mechanisms. Because there are no reports on immunization with CDPK8 to date, this study evaluated the fundamental biochemical traits and immunogenic epitopes of the CDPK8 protein through diverse bioinformatics tools. Materials and Methods: We examined the physicochemical attributes, antigenicity, potential B- and T-cell epitopes, tertiary and secondary structures, transmembrane domains, subcellular localization, allergenicity, and other characteristics of the CDPK8 protein. Results: CDPK8 exhibited notable surface accessibility, flexibility, antigenicity, and hydrophilicity indices. Epitope prediction results from diverse bioinformatics databases revealed multiple premiums T-cell and B-cell within the CDPK8 protein shows its viability as an essential component in a T. gondii vaccine formulation. Our findings suggest that to minimize the risk of errors and failures in the laboratory, utilizing in silico software for predicting the functional and structural properties of the CDPK8 protein could be a crucial and essential step in preventing cost wastage. Conclusion: To confirm the immunogenicity of the anticipated sequences, validation in an appropriate mouse model using various bioinformatics tools is recommended. Therefore, it is highly recommended that this protein be evaluated in silico and biological platforms settings to characterize its structural and immunological roles for potential prophylactic agent.

Keywords:  CDPK8; Toxoplasma gondii; bioinformatics; in silico

DOI:  https://doi.org/10.1155/ipid/4426082
EMBO Rep. 2025 Sep 19.

Perforation of the host cell plasma membrane during Toxoplasma invasion requires rhoptry exocytosis.

Frances Male, Yuto Kegawa, Paul S Blank, Irene Jiménez-Munguía, Saima M Sidik, Dylan Valleau, Sebastian Lourido, Maryse Lebrun, Joshua Zimmerberg, Gary E Ward.

  Toxoplasma gondii is an obligate intracellular parasite. Proteins released during host cell invasion from apical secretory organelles known as rhoptries are delivered into the host cell cytosol to perform functions critical for parasite survival and virulence. How these effector proteins move across the host cell plasma membrane is unknown but may involve a previously noted temporary loss of host cell plasma membrane barrier integrity. Here, we use high-speed, multi-wavelength fluorescence imaging to spatially monitor the barrier integrity of the host cell plasma membrane, in real time, during invasion. The data reveal that early in invasion the parasite creates a transient perforation in the host cell membrane. The perforation occurs at the point on the host membrane in contact with the parasite's apical end. Parasites depleted of any of five proteins known to be required for rhoptry exocytosis are unable to perforate the host cell membrane. These data suggest a model in which perforating agents stored within rhoptries are released onto the host cell at the initiation of invasion to create a conduit for the delivery of rhoptry effector proteins.

Keywords:   Toxoplasma ; Apicomplexa; Invasion; Parasite; Rhoptry

DOI:  https://doi.org/10.1038/s44319-025-00564-9
EMBO Rep. 2025 Sep 19.

The invasion pore induced by Toxoplasma gondii.

Yuto Kegawa, Frances Male, Irene Jiménez-Munguía, Paul S Blank, Elena Mekhedov, Gary E Ward, Joshua Zimmerberg.

  The parasite Toxoplasma gondii invades its host cell only after secreting proteins such as invasion-requisite RON2 that inserts into the host cell membrane to establish the moving junction. Electrophysiological recordings at sub-200 µs resolution show a transient increase in host cell membrane conductance following parasite exposure. Transients always precede invasion, but parasites depleted of RON2 generate transients without invading. Thus RON2 is not essential for transient generation. Time-series analysis developed here and applied to the 910,000 data point transient dataset reveal multiple quantal conductance changes in the parasite-induced transient, consistent with rapid insertion, then slower removal, blocking, or inactivation of potential pore components. Quantal steps for wild-type RH strain parasites have a principal mode with Gaussian mean of 0.26 nS, similar in step size to the pore forming protein EXP2, part of the PTEX translocon of malaria parasites. Without RON2 the quantal mean (0.19 nS) is significantly different. Because we observe no parasite invasion without poration, the term "invasion pore" is proposed to describe this transient breach in host cell membrane barrier integrity during invasion.

Keywords:  Cell Membrane; Membrane Poration; Parasite; Rhoptry Secretion; Whole-Cell Patch-Clamp

DOI:  https://doi.org/10.1038/s44319-025-00565-8
J Biol Chem. 2025 Sep 16. pii: S0021-9258(25)02578-5. [Epub ahead of print] 110726

Reconstituted ferredoxin-MEP pathway of Apicomplexa in E. coli as an in situ screening platform for inhibitors and essential enzyme mutations.

Ojo-Ajogu Akuh, Deborah Maus, Martin Blume, Kevin J Saliba, Frank Seeber.

  The apicoplast, an essential plastid-like organelle of apicomplexan parasites, including Plasmodium spp. and Toxoplasma gondii, harbors unique metabolic pathways absent in the host. Within the apicoplast, the ferredoxin redox system consists of plant-type ferredoxin-NADP+ reductase (ptFNR) and its redox partner, plant-type ferredoxin (ptFd). It donates electrons to the last two enzymes in the essential methylerythritol phosphate (MEP) pathway of isoprenoid biosynthesis. To establish an easy-to-handle platform for screening for enzyme inhibitors or functional mutations of the P. falciparum MEP pathway in situ, we established an E. coli model where bacterial growth depended on the last enzyme IspH and its redox system ptFd and ptFNR. For this, we supplemented a flavodoxin and ispH E. coli double mutant with expression constructs for ptFd, ptFNR, and IspH from P. falciparum. These proteins could functionally replace the two essential endogenous E. coli enzymes, reconstituting the last step in the isoprenoid biosynthesis pathway of the apicoplast. To validate this strain as a screening platform we used point mutations in ptFd as a surrogate for chemical pathway inhibitors. Several single mutants were evaluated by growth assays to identify amino acids that are essential for proliferation. We verified the mutants' consequences on the depletion of MEP metabolites by LC-MS analysis. Finally, some mutants were used to complement a conditional T. gondii Fd knockout strain. The results mirrored those of the respective E. coli mutant, highlighting the model's utility in identifying functional mutations or ptFd/MEP pathway inhibitors before conducting more labor-intensive and time-consuming assays in parasites.

Keywords:  MEP pathway; Plasmodium; Toxoplasma gondii; apicoplast; ferredoxin; flavodoxin; iron‐sulfur protein; isoprenoid; parasite metabolism; redox regulation

DOI:  https://doi.org/10.1016/j.jbc.2025.110726
RSC Chem Biol. 2025 Sep 01.

Structural basis of SIRT2 pre-catalysis NAD+ binding dynamics and mechanism.

Nan Zhang, Kah Chee Pow, Lanfang Chen, Quan Hao.

Sirtuins are an evolutionarily conserved family of NAD+-dependent deacylases whose catalytic mechanism remains under active investigation. While previous studies have captured sirtuin reaction intermediates using thioacetyl-lysine analogs, here we report six crystal structures of human SIRT2 in complex with native myristoylated peptides and NAD+, revealing the sequence of changes from initial NAD+ binding to the formation of intermediate I. Our structures provide direct structural evidence for: (1) zinc-binding domain shift during NAD+ entry, (2) water-mediated hydrogen-bond formation that disrupts nicotinamide aromaticity preceding cleavage, and (3) the formation of intermediate I. Additionally, we determined the structures of two functionally critical mutants (SIRT2F96A and SIRT2H187A), demonstrating their roles in stabilizing NAD+ in a productive conformation. These findings complete the comprehensive structural framework for the sirtuin deacylation mechanism and highlight key residues governing catalytic efficiency.

DOI: https://doi.org/10.1039/d5cb00169b
Cell Rep. 2025 Sep 18. pii: S2211-1247(25)01086-1. [Epub ahead of print]44(10): 116315

Genetic crosses reveal genomic loci responsible for virulence in Cryptosporidium parvum infection.

Sebastian Shaw, Xue Li, Gracyn Y Buenconsejo, Tiffany H Zhou, Allison Cohen, Daniel Yasur-Landau, Rui Xiao, Daniel P Beiting, Timothy J C Anderson, Boris Striepen.

  The relationship between parasite genotype and pathogenesis is largely unknown for Cryptosporidium, a leading cause of diarrheal disease in children. An array of parasites with similar genomes produces varied disease outcomes in different hosts. Here, we isolate and characterize Cryptosporidium parvum strains that show marked differences in virulence and persistence in mice. Taking advantage of the sexual life cycle of this eukaryotic pathogen, we use genetic crosses to discover the underlying chromosomal loci. Whole-genome sequencing and bulk segregant analysis of infection-selected progeny mapped three loci on chromosomes 2, 6, and 7 associated with the ability to colonize and persist in mice and the positions of drug resistance genes. The chromosome 6 locus encodes the hyper-polymorphic surface glycoprotein GP60. Reverse genetic studies in both parental strains demonstrate that GP60 controls parasite burden and virulence, but not persistence, and reveal the dominance of the less virulent allele, suggesting it restricts virulence.

Keywords:  CP: Microbiology; Cryptosporidium parvum; GP60 glycoprotein; allelic replacement; bulk segregant analysis; dense granule proteins; genetic crosses; persistence; virulence

DOI:  https://doi.org/10.1016/j.celrep.2025.116315
Elife. 2025 Sep 15. pii: RP107451. [Epub ahead of print]14

SETD2 suppresses tumorigenesis in a KRASG12C-driven lung cancer model, and its catalytic activity is regulated by histone acetylation.

Ricardo J Mack, Natasha M Flores, Geoffrey C Fox, Hanyang Dong, Metehan Cebeci, Simone Hausmann, Tourkian Chasan, Jill M Dowen, Brian D Strahl, Pawel K Mazur, Or Gozani.

  Histone H3 trimethylation at lysine 36 (H3K36me3) is a key chromatin modification that regulates fundamental physiological and pathological processes. In humans, SETD2 is the only known enzyme that catalyzes H3K36me3 in somatic cells and is implicated in tumor suppression across multiple cancer types. While there is considerable crosstalk between the SETD2-H3K36me3 axis and other epigenetic modifications, much remains to be understood. Here, we show that Setd2 functions as a potent tumor suppressor in a KRASG12C-driven lung adenocarcinoma (LUAD) mouse model, and that acetylation enhances SETD2 in vitro methylation of H3K36 on nucleosome substrates. In vivo, Setd2 ablation accelerates lethality in an autochthonous KRASG12C-driven LUAD mouse tumor model. Biochemical analyses reveal that polyacetylation of histone tails in a nucleosome context promotes H3K36 methylation by SETD2. In addition, monoacetylation exerts position-specific effects to stimulate SETD2 methylation activity. In contrast, mono-ubiquitination at various histone sites, including at H2AK119 and H2BK120, does not affect SETD2 methylation of nucleosomes. Together, these findings provide insight into how SETD2 integrates histone modification signals to regulate H3K36 methylation and highlights the potential role of SETD2-associated epigenetic crosstalk in cancer pathogenesis.

Keywords:  KRAS; NSD2; SETD2; cancer biology; epigenetic; histone methylation; human; lung cancer

DOI:  https://doi.org/10.7554/eLife.107451
Am J Bot. 2025 Sep 18. e70101

Nitrogen enrichment reduces parasitism in an annual hemiparasite.

Jasmine Taite, Paul D Nabity.

   PREMISE: Anthropogenic activities such as fossil fuel combustion and synthetic fertilizer synthesis have resulted in nitrogen (N) deposition and elevated N availability in ecosystems. Many parasitic plants are adapted to low N environments and have evolved mechanisms to sequester water, N, and other limiting nutrients from hosts. Anthropogenic N deposition may perturb these host-parasite interactions, thereby altering nutrient cycling and ultimately reducing biodiversity.
METHODS: To test how N enrichment affects the incidence and degree of plant parasitism, we assayed host-parasite performance and in vitro root growth under supplemental N levels representative of urban areas experiencing N deposition. We focused on the annual hemiparasite Castilleja exserta and two co-occurring host species, Nasella lepida and N. pulchra.
RESULTS: Elevated N decreased haustoria formation and host-seeking behavior by roots but did not affect growth, suggesting N enrichment may reduce parasitism without associated loss of parasite biomass. We confirmed that parasitism decreased host performance and that the degree of parasitism was positively related to host biomass and earlier flowering. We also found N. lepida may be preferred over N. pulchra as a host.
CONCLUSIONS: These results indicate that N pollution altered parasitism in C. exserta and highlight the far-reaching ecological effects of N pollution on host-parasite interactions within plant communities.

Keywords:  Castilleja exserta; Nasella lepida; Nasella pulchra; Orobanchaceae; Poaceae; climate change; haustoria; plant parasite; pollution; root behavior

DOI:  https://doi.org/10.1002/ajb2.70101