bims-toxgon 2025-03-23 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2025–03–23
nine papers selected by
Lakesh Kumar, BITS Pilani

AP2XII-9 is essential for parasite growth and suppresses bradyzoite differentiation in Toxoplasma gondii.
Toxoplasmosis accelerates the progression of hereditary spastic paraplegia.
Inheritance of the genome-less apicoplast in the "apicoplast-minus" Plasmodium falciparum.
Interaction between the liver transcriptome and gut microbiota in mice during Toxoplasma gondii infection as identified by integrated transcriptomic and microbiome analysis.
tRNA lysidinylation is essential for the minimal translation system in the Plasmodium falciparum apicoplast.
Regulation of acetyl-CoA biosynthesis via an intertwined acetyl-CoA synthetase/acetyltransferase complex.
A limitation lifted: A conditional knockdown system reveals essential roles for Polo-like kinase and Aurora kinase 1 in Trypanosoma cruzi cell division.
Synthesis and biological evaluation of the Fluoro analog of Romidepsin with improved selectivity for class I histone deacetylases (HDACs).
Sirtuins as therapeutic targets in diabetes.

FASEB J. 2025 Mar 31. 39(6): e70476

AP2XII-9 is essential for parasite growth and suppresses bradyzoite differentiation in Toxoplasma gondii.

Xiao-Jing Wu, Meng Wang, Nian-Zhang Zhang, Ting-Ting Li, Jin Gao, Li-Xiu Sun, Xing-Quan Zhu, Jin-Lei Wang.

  Cyst formation, resulting from the differentiation of rapidly replicating tachyzoites into slowly growing bradyzoites, is the primary cause of chronic toxoplasmosis. Although the mechanisms governing bradyzoite differentiation have been partially elucidated, they remain incompletely understood. In this study, we show that the transcription factor AP2XII-9 is localized in the nucleus and exhibits periodic expression during the tachyzoite stage, with peak expression observed during the synthesis and mitosis phases. Conditional knockdown of AP2XII-9 in both the type I RH strain and type II cyst-forming Pru strain revealed that AP2XII-9 plays a critical role in the lytic cycle by regulating the formation of the inner membrane complex, proper apicoplast inheritance, and normal cell division, underscoring its essential role in T. gondii growth. Furthermore, depletion of AP2XII-9 induced bradyzoite differentiation even in the absence of alkaline stress. Transcriptomic analysis revealed that the deletion of AP2XII-9 resulted in the downregulation of tachyzoite growth-related genes and upregulation of a series of bradyzoite-specific genes. Taken together, these findings indicate that AP2XII-9 is essential for maintaining the rapid and normal replication of tachyzoites while actively repressing bradyzoite differentiation, reflecting the complexity of the mechanisms underlying bradyzoite differentiation.

Keywords:   Toxoplasma gondii ; AP2XII‐9; apicoplast inheritance; asynchronous division; bradyzoite differentiation; growth; membrane defect

DOI:  https://doi.org/10.1096/fj.202402593RR
mSphere. 2025 Mar 18. e0082624

Toxoplasmosis accelerates the progression of hereditary spastic paraplegia.

James R Alvin, Carlos J Ramírez-Flores, Caitlin A Mendina, Anjon Audhya, Laura J Knoll, Molly M Lettman.

  The parasitic protozoa Toxoplasma gondii chronically infects the central nervous system of an estimated one-third of the human population. Infection is generally subclinical, but immunocompromised individuals can experience a variety of neurological symptoms. Meta-analyses of T. gondii seropositivity have suggested a correlation between T. gondii infection and neurologic disease. Although mechanistic studies on the relationship between T. gondii infection and neurologic disease have been attempted in mice, they are particularly susceptible to T. gondii, making them an effective model for investigating mechanisms of infection, but not ideal for examining the relationship between long-term chronic T. gondii infection and neurologic disease. Rats more closely mimic human T. gondii cyst levels after acute infection, but a lack of rat models for neurologic disease has limited studies on the interplay between T. gondii infection and neurologic disease progression. We have employed a previously characterized rat model of a complex form of hereditary spastic paraplegia (HSP), a class of neurodegenerative disorders that cause axonal degeneration and lower limb spasticity, in order to assess the effect of chronic T. gondii infection on neurodegenerative disease. We find that infected rats with hereditary spastic paraplegia exhibit significantly exacerbated behavioral and neuromorphological HSP symptoms compared with uninfected HSP mutant rats, with little correlative effect in infected versus uninfected control animals. We further find that all infected rats, regardless of genotype, exhibit a robust immune response to T. gondii infection, presenting with parasite levels below the limit of detection of multiple assays of parasitemia and exhibiting no detectable increase in neuroinflammation 7 weeks post-infection. These results suggest that chronic undetected T. gondii infection may exacerbate neurodegenerative disease even in immunocompetent individuals and may contribute to neurodegenerative disease heterogeneity.IMPORTANCEThe long-term consequences of previous acute infections are poorly understood but are becoming increasingly appreciated, particularly in the era of long COVID. Altered progression of other diseases later in life may be among the long-term consequences of previous infections. Here, we investigate the relationship between previous infections with the parasite Toxoplasma gondii, which infects ~30% of the global population, and neurodegenerative disease using a rat model of hereditary spastic paraplegia (HSP). We find that previous infections with T. gondii accelerate motor dysfunction in HSP rats, despite robust clearance of the parasite by infected rats. Our results suggest that previously cleared infections may alter the progression of other diseases later in life and contribute to neurodegenerative disease heterogeneity.

Keywords:  Toxoplasma; chronic infection; hereditary spastic paraplegia; neurodegeneration

DOI:  https://doi.org/10.1128/msphere.00826-24
bioRxiv. 2025 Mar 05. pii: 2025.03.05.641705. [Epub ahead of print]

Inheritance of the genome-less apicoplast in the "apicoplast-minus" Plasmodium falciparum.

Wei Xu, Ikechukwu Nwankwo, Sean T Prigge, Hangjun Ke.

Most apicomplexan parasites contain a plastid-derived organelle called the apicoplast, which originated through secondary endosymbiosis. As a result of this evolutionary trajectory, the non-photosynthetic apicoplast is surrounded by four membranes and contains many bacterial-like, druggable targets. It is widely accepted that asexual malaria parasites ( Plasmodium falciparum ) can thrive under antibiotic treatment if supplemented with high concentrations of isopentenyl pyrophosphate (IPP, 200 µM) and these IPP-rescued parasites are thought to lack the apicoplast and its 35 kb genome but possess many vesicles. However, our findings challenge this apicoplast-minus concept. In late-stage schizonts, we observed that the apicoplast-derived vesicles nearly colocalize with mitochondria and are properly distributed into merozoites during schizogony, suggesting that they are inherited rather than newly synthesized in each asexual cycle. Further, immuno-electron microscopy (immuno-EM) revealed that the "apicoplast-minus" parasites possess structures surrounded by four membranes, in addition to single-membrane-surrounded entities. The presence of four-membrane-bound structures suggests that the apicoplast has not truly disappeared in the "apicoplast-minus" P. falciparum but remains in a distinct, diminished form. We termed this genome-less apicoplast derivative the apicosome, drawing an analogy to the genome-less mitochondrial derivative known as the mitosome. We propose that apicosomes retain essential biochemical and/or structural functions, which act as barriers to the complete loss of apicoplast when the parasites face antibiotic stress and IPP rescue.

DOI: https://doi.org/10.1101/2025.03.05.641705
BMC Microbiol. 2025 Mar 14. 25(1): 137

Interaction between the liver transcriptome and gut microbiota in mice during Toxoplasma gondii infection as identified by integrated transcriptomic and microbiome analysis.

Yang Zou, He Ma, Xing Yang, Xin-Yu Wei, Chao Chen, Jing Jiang, Tao Jiang.

   BACKGROUND: Toxoplasma gondii is a single-cell parasite capable of infecting both humans and a variety of animal species. Although T. gondii infection is known to adversely affect the liver and gut microbiota, the precise interplay between the gut microbiome and the liver transcriptome in infected mice remains largely unknown. In this study, we artificially induced acute and chronic stages of T. gondii infection in BALB/c mice via the oral of low doses (n = 10) of PRU (Type II) bradyzoites. Then, we performed fecal 16S rRNA gene amplicon sequencing and RNA transcriptome sequencing to investigate the composition of the gut microbiota and the expression profiles of long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) in the livers of mice infected with T. gondii at different stages of infection.
RESULTS: Analysis revealed dynamic alterations in the gut microbiota of mice following infection with T. gondii over the course of the infection cycle. Notably, we observed a significant increase in the abundance of Enterobacteriaceae during the acute stage of infection, while the abundance of Lactobacteriaceae was elevated during the chronic stage. Liver transcriptome analysis identified numerous differentially expressed (DE) non-coding RNAs and mRNAs potentially potentially involved in mediating liver immune responses and inflammation induced by T. gondii. During the acute stage of infection, several pro-inflammatory genes, including Lpin1, Usp2, Pim3, and Il6ra were significantly up-regulated in the liver. Among these, Lpin1 may be closely associated with the development of Enterobacteriaceae overgrowth. Conversely, some anti-inflammatory genes, such as Dmbt1, and Ddit4, were exclusively up-regulated during the chronic stage of infection. Gene ontology (GO) enrichment analysis further revealed the stage-specific features of liver functionality. Specifically, during the acute stage of infection, pathways associated with inflammation were significantly enriched. Interestingly, during the chronic stage of infection, pathways related to microbiota regulation, such as 'defense response to Gram-negative bacterium', 'antimicrobial humoral immune response mediated by antimicrobial peptide', and 'antimicrobial humoral response' were enriched. Additionally, competing endogenous RNAs (CeRNAs) networks revealed that numerous DElncRNAs and DEcircRNAs competitively regulated DEmiRNA mmu-miR-690, which targets the Nr1d1 gene. These findings provide insights into the complex interplay between the liver and gut microbiota during different stages of T. gondii infection.
CONCLUSIONS: In summary, our results highlight the intricate interaction between the liver and gut microbiota in mice during T. gondii infection, with dynamic alterations observed in both the gut microbiota composition and the expression profiles of key genes in the liver over the course of the infection cycle.

Keywords:   Toxoplasma gondii ; CeRNA networks; Gut microbiota; Interaction; Liver; Non-coding RNAs; RNA sequencing

DOI:  https://doi.org/10.1186/s12866-025-03852-5
EMBO Rep. 2025 Mar 20.

tRNA lysidinylation is essential for the minimal translation system in the Plasmodium falciparum apicoplast.

Rubayet Elahi, Sean T Prigge.

  For decades, researchers have sought to define minimal translation systems to uncover fundamental principles of life and advance biotechnology. tRNAs, essential components of this machinery, decode mRNA codons into amino acids. The apicoplast of malaria parasites contains 25 tRNA isotypes in its organellar genome-the lowest number found in known translation systems. Efficient translation in such minimal systems depends heavily on post-transcriptional tRNA modifications. One such modification, lysidine at the wobble position (C34) of tRNACAU, distinguishes between methionine (AUG) and isoleucine (AUA) codons. tRNA isoleucine lysidine synthetase (TilS) produces lysidine, which is nearly ubiquitous in bacteria and essential for cellular viability. Here, we report a TilS ortholog (PfTilS) targeted to the apicoplast of Plasmodium falciparum. We demonstrate that PfTilS activity is essential for parasite survival and apicoplast function, likely due to its role in protein translation. This study is the first to characterize TilS in an endosymbiotic organelle, contributing to research on eukaryotic organelles and minimal translational systems. Moreover, the absence of lysidine in humans highlights a potential target for antimalarial strategies.

Keywords:  Apicoplast; Lysidine; Plasmodium; Protein Translation; tRNA Modification

DOI:  https://doi.org/10.1038/s44319-025-00420-w
Nat Commun. 2025 Mar 15. 16(1): 2557

Regulation of acetyl-CoA biosynthesis via an intertwined acetyl-CoA synthetase/acetyltransferase complex.

Liujuan Zheng, Yifei Du, Wieland Steinchen, Mathias Girbig, Frank Abendroth, Ekaterina Jalomo-Khayrova, Patricia Bedrunka, Isabelle Bekeredjian-Ding, Christopher-Nils Mais, Georg K A Hochberg, Johannes Freitag, Gert Bange.

Acetyl-CoA synthetase (Acs) generates acetyl-coenzyme A (Ac-CoA) but its excessive activity can deplete ATP and lead to a growth arrest. To prevent this, Acs is regulated through Ac-CoA-dependent feedback inhibition executed by Ac-CoA-dependent acetyltransferases such as AcuA in Bacillus subtilis. AcuA acetylates the catalytic lysine of AcsA turning the synthetase inactive. Here, we report that AcuA and AcsA form a tightly intertwined complex - the C-terminal domain binds to acetyltransferase domain of AcuA, while the C-terminus of AcuA occupies the CoA-binding site in the N-terminal domain of AcsA. Formation of the complex reduces AcsA activity in addition to the well-established acetylation of the catalytic lysine 549 in AcsA which we show can disrupt the complex. Thus, different modes of regulation accomplished through AcuA adjust AcsA activity to the concentrations of the different substrates of the reaction. In summary, our study provides detailed mechanistic insights into the regulatory framework underlying acetyl-CoA biosynthesis from acetate.

DOI: https://doi.org/10.1038/s41467-025-57842-2
Proc Natl Acad Sci U S A. 2025 Feb 25. 122(8): e2416009122

A limitation lifted: A conditional knockdown system reveals essential roles for Polo-like kinase and Aurora kinase 1 in Trypanosoma cruzi cell division.

Justin Wiedeman, Ruby Harrison, Ronald Drew Etheridge.

  While advances in genome editing technologies have simplified gene disruption in many organisms, the study of essential genes requires development of conditional disruption or knockdown systems that are not available in most organisms. Such is the case for Trypanosoma cruzi, a parasite that causes Chagas disease, a severely neglected tropical disease endemic to Latin America that is often fatal. Our knowledge of the identity of essential genes and their functions in T. cruzi has been severely constrained by historical challenges in very basic genetic manipulation and the absence of RNA interference machinery. Here, we describe the development and use of self-cleaving RNA sequences to conditionally regulate essential gene expression in T. cruzi. Using these tools, we identified essential roles for Polo-like and Aurora kinases in T. cruzi cell division, mirroring their functions in Trypanosoma brucei. Importantly, we demonstrate conditional knockdown of essential genes in intracellular amastigotes, the disease-causing stage of the parasite in its human host. This conditional knockdown system enables the efficient and scalable functional characterization of essential genes in T. cruzi and provides a framework for the development of conditional gene knockdown systems for other nonmodel organisms.

Keywords:  Trypanosoma cruzi; aptazyme; conditional knockdown; parasite; protozoan

DOI:  https://doi.org/10.1073/pnas.2416009122
Bioorg Chem. 2025 Mar 13. pii: S0045-2068(25)00228-7. [Epub ahead of print]159 108348

Synthesis and biological evaluation of the Fluoro analog of Romidepsin with improved selectivity for class I histone deacetylases (HDACs).

Xinluo Song, Hanqi Wang, Ya Gao, Wei Zhang, Xinsheng Lei.

  Selective inhibition of Class I HDACs has emerged as a promising approach for cancer therapy. Building on our previous work with Largazole (a member of the natural depsipeptide family), we have applied a similar fluorination modification to Romidepsin and synthesized its fluoro analog (12) in 12 steps. This analog exhibits potent inhibitory activity against Class I HDACs but shows no inhibitory effect on HDAC6, confirming its selectivity as a Class I HDAC inhibitor (IC50 HDAC1 0.95 nM, HDAC2 0.86, HDAC 3 1.1 nM, HDAC8 4.2 nM, HDAC6 > 103 nM). Compared with Romidepsin, compound 12 demonstrates significant growth inhibition in two cancer cell lines (NCI-H1975 and HT29) while exhibiting markedly less growth inhibition in two normal cell lines (WRL-68 and HEK293). Further studies reveal that 12 is capable of blocking the cell cycle and inducing apoptosis, thereby exerting anticancer activity. Moreover, 12 possesses metabolic stability comparable to Romidepsin. In a mouse model, 12 demonstrates strong in vivo antitumor efficacy similar to that of Romidepsin, yet with significantly reduced toxicity. These findings support the potential of this fluoro analog as a highly selective Class I HDAC inhibitor and highlight its promise as a superior alternative to Romidepsin for further development.

Keywords:  Class I HDACs; Fluorination; Inhibitors; Romidepsin; Selectivity

DOI:  https://doi.org/10.1016/j.bioorg.2025.108348
Expert Opin Ther Targets. 2025 Mar 21.

Sirtuins as therapeutic targets in diabetes.

Kajetan Kielbowski, Aleksandra Wiktoria Bratborska, Estera Bakinowska, Andrzej Pawlik.

   INTRODUCTION: Sirtuins (SIRTs) are NAD+-dependent deacetylases that mediate post-translational modifications of proteins. Seven members of the SIRT family have been identified in mammals. Importantly, SIRTs interact with numerous metabolic and inflammatory pathways. Thus, researchers have investigated their role in metabolic and inflammatory disorders.
AREAS COVERED: In this review, we comprehensively discuss the involvement of SIRTs in the processes of pancreatic β-cell dysfunction, glucose tolerance, insulin secretion, lipid metabolism, and adipocyte functions. In addition, we describe the current evidence regarding modulation of the expression and activity of SIRTs in diabetes, diabetic complications, and obesity.
EXPERT OPINION: The development of specific SIRT activators and inhibitors that exhibit high selectivity toward specific SIRT isoforms remains a major challenge. This involves the need to elucidate the physiological pathways involving SIRTs, as well as their important role in the development of metabolic disorders. Molecular modeling techniques will be helpful to develop new compounds that modulate the activity of SIRTs, which may contribute to the preparation of new drugs that selectively target specific SIRTs. SIRTs hold promise as potential targets in metabolic disease, but there is much to learn about specific modulators and the final answers will await clinical trials.

Keywords:  Adipocyte; Diabetes; Obesity; Resveratrol; Sirtuins; insulin resistance; insulin secretion; pancreatic β-cell

DOI:  https://doi.org/10.1080/14728222.2025.2482563