bims-toxgon Biomed News
on Toxoplasma gondii metabolism
Issue of 2025–02–16
thirteen papers selected by
Lakesh Kumar, BITS Pilani
  1. Motility-dependent processes in Toxoplasma gondii tachyzoites and bradyzoites: same same but different.
  2. High-Throughput Repurposing Screen Reveals Compounds with Activity against Toxoplasma gondii Bradyzoites.
  3. In Silico Analysis and Characterization of the Immunogenicity of Toxoplasma gondii Rhoptry Protein 18.
  4. Transcriptional profiles analysis of effects of Toxoplasma gondii rhoptry protein 16 on THP-1 macrophages.
  5. Functional consequences of lysine acetylation of phosphofructokinase isozymes.
  6. Emerging roles of mitochondrial sirtuin SIRT5 in succinylation modification and cancer development.
  7. Lysine acetylation in cyanobacteria: emerging mechanisms and functions.
  8. Histone deacetylases in the regulation of cell death and survival mechanisms in resistant BRAF-mutant cancers.
  9. Selisistat, a SIRT1 inhibitor, enhances paclitaxel activity in luminal and triple-negative breast cancer: in silico, in vitro, and in vivo studies.
  10. Regulation of HDAC6 Catalytic Activity in Cancer: The Role of Post-Translational Modifications and Protein-Protein Interactions.
  11. Discovery of novel vaccine candidates based on the immunogenic epitopes derived from Toxoplasma membrane proteins.
  12. Role of protein post-translational modifications in unexplained recurrent pregnancy loss.
  13. Subcellular dynamics in unicellular parasites.
  1. mSphere. 2025 Feb 12. e0085524
    Motility-dependent processes in Toxoplasma gondii tachyzoites and bradyzoites: same same but different.
    Robyn S Kent, Gary E Ward.
      During infection, Toxoplasma gondii tachyzoites must be able to move in order to migrate through tissues, cross biological barriers, and penetrate into and egress from cells they infect. Bradyzoite-stage parasites, which establish infection in naïve hosts, also require motility to escape from cysts after they are ingested and to subsequently migrate to the gut wall, where they either invade cells of the intestinal epithelium or squeeze between these cells to infect the underlying tissue. Little is known about the motility of bradyzoites, which we analyze in detail here and compare to the well-characterized motility and motility-dependent processes of tachyzoites. Unexpectedly, bradyzoites were found to be as motile as tachyzoites in a three-dimensional model extracellular matrix, and they showed increased invasion into and transmigration across monolayers of certain cell types, consistent with their need to establish infection in the gut. The motility of the two stages was inhibited to the same extent by cytochalasin D and KNX-002, compounds known to target the parasite's actomyosin-based motor. Other compounds that impact tachyzoite motility (tachyplegin and enhancer 5) have a reduced effect on bradyzoites. Furthermore, rapid bradyzoite egress from infected cells is not triggered by treatment with calcium ionophores, as it is with tachyzoites. The similarities and differences between these two life cycle stages highlight the need to characterize both tachyzoites and bradyzoites for a more complete understanding of the role of motility in the parasite life cycle and the effect that motility-targeting therapeutics will have on disease establishment and progression.
    IMPORTANCE: Toxoplasma gondii is a parasite that chronically infects around one-third of the world's population. Toxoplasma uses motility for multiple purposes during infection, including extracellular migration, invasion into host cells, and host cell egress. These motility-dependent processes have been extensively studied in the life cycle stage responsible for acute infection, the tachyzoite. In contrast, motility and motility-dependent processes are poorly understood in bradyzoite-stage parasites, which are responsible for both establishing infection after consumption of infected meat and initiating potentially life-threatening reactivated infections in the brains of immunocompromised individuals. We show here that the motility and motility-dependent processes of bradyzoites are similar in many respects to those of tachyzoites but markedly different in others. The results of this study highlight the need to consider both life cycle stages in attempts to develop drugs targeting parasite motility and the signaling processes that regulate motility-dependent processes during infection by these important human pathogens.
    Keywords:  Toxoplasma gondii; apicomplexan parasites; bradyzoite; chronic infection; motility; tachyzoite
    DOI:  https://doi.org/10.1128/msphere.00855-24
  2. ACS Infect Dis. 2025 Feb 11.
    High-Throughput Repurposing Screen Reveals Compounds with Activity against Toxoplasma gondii Bradyzoites.
    Taher Uddin, Jing Xia, Yong Fu, Case W McNamara, Arnab K Chatterjee, L David Sibley.
      Toxoplasma gondii causes widespread chronic infections that are not cured by current treatments due to the inability to affect semidormant bradyzoite stages within tissue cysts. To identify compounds to eliminate chronic infection, we developed an HTS using a recently characterized strain of T. gondii that undergoes efficient conversion to bradyzoites in vitro. Stage-specific expression of luciferase was used to selectively monitor the growth inhibition of bradyzoites by the Library of Pharmacological Active Compounds, consisting of 1280 drug-like compounds. We identified 44 compounds with >50% inhibitory effects against bradyzoites, including new highly potent compounds, several of which have precedent for antimicrobial activity. Subsequent characterization of the compound sanguinarine sulfate revealed potent and rapid killing against in vitro-produced bradyzoites and bradyzoites harvested from chronically infected mice, including potent activity against intact cysts. These findings provide a platform for expanded screening and identify promising compounds for further preclinical development against T. gondii bradyzoites that are responsible for chronic infection.
    Keywords:  chronic infection; high throughput screening; toxoplasmosis
    DOI:  https://doi.org/10.1021/acsinfecdis.4c00689
  3. Bioinform Biol Insights. 2025 ;19 11779322251315924
    In Silico Analysis and Characterization of the Immunogenicity of Toxoplasma gondii Rhoptry Protein 18.
    Masoud Foroutan, Amir Karimipour-Saryazdi, Ali Dalir Ghaffari, Hamidreza Majidiani, Arezo Arzani Birgani, Elaheh Karimzadeh-Soureshjani, Shahrzad Soltani, Hany M Elsheikha.
      Rhoptry protein 18 (ROP18) is a key virulence factor secreted into host cells during the invasion of Toxoplasma gondii (T. gondii) and plays an important role in the pathogenesis of infection. Due to its potential as a vaccine candidate, this study aimed to characterize several properties of the T. gondii ROP18 (TgROP18) protein to support its inclusion in vaccine formulations. Using a range of bioinformatics tools, we investigated its T-cell and B-cell epitopes, physicochemical properties, subcellular localization, transmembrane domains, and tertiary and secondary structures. Our analysis revealed 48 post-translational modification sites in TgROP18. The secondary structure was composed of 4.87% beta-turns, 38.45% random coils, 42.42% alpha helices, and 14.26% extended strands. Several potential T- and B-cell epitopes were identified on ROP18. The Ramachandran plot of both crude and refined models showed that 85.8% and 95.3% of the amino acid residues, respectively, fell within favored regions, indicating energetically stable conformations. Allergenicity and antigenicity assessments indicated that TgROP18 is a nonallergenic, immunogenic protein. Predictions using the C-ImmSim server suggest that TgROP18 can stimulate humoral and cell-mediated immune responses, based on antibody titers and cytokine profiles following antigen administration. These findings provide baseline data for future investigations focused on the potential of TgROP18 in developing therapeutic strategies against toxoplasmosis.
    Keywords:  ROP18; Toxoplasma gondii; immunogenicity; immunoinformatics; in silico; vaccine
    DOI:  https://doi.org/10.1177/11779322251315924
  4. Front Cell Infect Microbiol. 2024 ;14 1436712
    Transcriptional profiles analysis of effects of Toxoplasma gondii rhoptry protein 16 on THP-1 macrophages.
    Ningai Yang, Mingyang Li, Hong Yang, Jiaming Li, Tiantian Dang, Guangqi Li, Zhijun Zhao.
       Introduction: Toxoplasma gondii, an intracellular parasitic protozoan, is globally recognized for its ability to cause parasitic diseases and has developed diverse strategies to evade immune-mediated elimination. The protein ROP16 of T.gondii plays a crucial role in this evasion process by specifically targeting macrophages and mononuclear phagocytes in vivo. However, the precise mechanisms underlying the involvement of type II ROP16 proteins in infection, inflammation, and other processes remain unknown.
    Methods: To investigate the mechanism of action of gonococcal ROP16 proteins in human macrophages, we constructed a lentivirus overexpressing ROP16 and established stably transfected cell lines. We then analyzed the gene transcriptional profiles of ROP16 II in THP-1 macrophages using transcriptome sequencing. Interaction networks were constructed by screening differentially expressed genes and performing gene function enrichment analysis.
    Results: As a result, five differentially expressed genes were identified: AAMDC, GPR158, RAD9A, STOML1, and STRA13. Immuno-featured differential analysis showed that type 17 T helper cells were more strongly correlated with GPR158 and STRA13, while CD8 T-cell was most strongly correlated with STOML1.
    Discussion: Therefore, we conclude that the ROP16 protein plays a pivotal role in THP-1 macrophage infection and these five differentially expressed genes may serve as promising molecular targets for the prevention or control of toxoplasmosis. These findings have significant implications for the diagnosis and treatment of toxoplasmosis.
    Keywords:  RNA-seq; ROP16; THP-1; Toxoplasma gondii; macrophage
    DOI:  https://doi.org/10.3389/fcimb.2024.1436712
  5. FEBS J. 2025 Feb 12.
    Functional consequences of lysine acetylation of phosphofructokinase isozymes.
    Xinyu Li, Nour Fatema, Qinglei Gan, Chenguang Fan.
      Phosphofructokinase (Pfk) catalyzes the phosphorylation of fructose 6-phosphate and is a key regulatory point in the glycolysis pathway. Multiple lysine residues in both Pfk isozymes, PfkA and PfkB, have been identified to be acetylated in Escherichia coli by proteomic studies, but no studies have been implemented to further characterize these acetylation events. To investigate the role of Pfk acetylation, the genetic code expansion strategy was used to generate homogeneously acetylated Pfk variants at target lysine sites that have been reported to be acetylated in nature. We found that acetylation of K309 of PfkA and K27 of PfkB decreased PfK enzyme activities significantly. We further investigated the deacetylation and acetylation processes of Pfk isozymes biochemically and genetically. Acetyl phosphate-mediated non-enzymatic acetylation could be the major mechanism of Pfk isozyme acetylation in E. coli, whereas NAD-dependent protein deacylase CobB can remove most of the acetylated lysine residues but not K309 of PfkA and K27 of PfkB, which affect enzyme activities. Because of the important role of Pfk in cellular metabolism, the results of the present study are expected to facilitate studies in the fields of metabolic engineering and research.
    Keywords:  deacetylase; genetic code expansion; glycolysis; lysine acetylation; phosphofructokinase
    DOI:  https://doi.org/10.1111/febs.70014
  6. Front Immunol. 2025 ;16 1531246
    Emerging roles of mitochondrial sirtuin SIRT5 in succinylation modification and cancer development.
    Zhangmin Ke, Kaikai Shen, Li Wang, Hao Xu, Xia Pan, Zhenjue Qian, Yuting Wen, Tangfeng Lv, Xiuwei Zhang, Yong Song.
      Succinylation represents an emerging class of post-translational modifications (PTMs), characterized by the enzymatic or non-enzymatic transfer of a negatively charged four-carbon succinyl group to the ϵ-amino group of lysine residues, mediated by succinyl-coenzyme A. Recent studies have highlighted the involvement of succinylation in various diseases, particularly cancer progression. Sirtuin 5 (SIRT5), a member of the sirtuin family, has been extensively studied for its robust desuccinylase activity, alongside its deacetylase function. To date, only a limited number of SIRT5 substrates have been identified. These substrates mediate diverse physiological processes such as glucose oxidation, fatty acid oxidation, ammonia detoxification, reactive oxygen species scavenging, anti-apoptosis, and inflammatory responses. The regulation of these activities can occur through either the same enzymatic activity acting on different substrates or distinct enzymatic activities targeting the same substrate. Aberrant expression of SIRT5 has been closely linked to tumorigenesis and disease progression; however, its role remains controversial. SIRT5 exhibits dual functionalities: it can promote tumor proliferation, metastasis, drug resistance, and metabolic reprogramming, thereby acting as an oncogene; conversely, it can also inhibit tumor cell growth and induce apoptosis, functioning as a tumor suppressor gene. This review aims to provide a comprehensive overview of the current research status of SIRT5. We discuss its structural characteristics and regulatory mechanisms, compare its functions with other sirtuin family members, and elucidate the mechanisms regulating SIRT5 activity. Specifically, we focus on the role of succinylation modification mediated by SIRT5 in tumor progression, highlighting how desuccinylation by SIRT5 modulates tumor development and delineating the underlying mechanisms involved.
    Keywords:  SIRT5; cancer; desuccinylase; sirtuin; succinylation
    DOI:  https://doi.org/10.3389/fimmu.2025.1531246
  7. Biochem Soc Trans. 2025 Feb 12. pii: BST20241037. [Epub ahead of print]53(1):
    Lysine acetylation in cyanobacteria: emerging mechanisms and functions.
    Xin Liu, Mingkun Yang, Feng Ge, Jindong Zhao.
      Cyanobacteria are ancient and abundant photosynthetic prokaryotes that play crucial roles in global carbon and nitrogen cycles. They exist in a variety of environments and have been used extensively as model organisms for studies of photosynthesis and environmental adaptation. Lysine acetylation (Kac), a widespread and evolutionarily conserved protein posttranslational modification, is reversibly catalyzed by lysine acetyltransferases (KAT) and lysine deacetylases (KDACs). Over the past decade, a growing number of acetylated proteins have been identified in cyanobacteria, and Kac is increasingly recognized as having essential roles in many cellular processes, such as photosynthesis, energy metabolism, and stress responses. Recently, cGNAT2 and CddA were identified as KAT and KDAC in the model cyanobacterium Synechococcus sp. PCC 7002, respectively. The identified Kac regulatory enzymes provide novel insight into the mechanisms that globally regulate photosynthesis in cyanobacteria and potentially other photosynthetic organisms. This review summarizes recent progress in our understanding of the functions and mechanisms of lysine acetylation in Cyanobacteria. The challenges and future perspectives in this field are also discussed.
    Keywords:  cyanobacteria; lysine acetylation; lysine acetyltransferase (KAT); lysine deacetylase (KDAC); metabolic pathways; photosynthesis; stress responses
    DOI:  https://doi.org/10.1042/BST20241037
  8. Cancer Drug Resist. 2025 ;8 6
    Histone deacetylases in the regulation of cell death and survival mechanisms in resistant BRAF-mutant cancers.
    Bernhard Biersack, Bianca Nitzsche, Michael Höpfner.
      Small-molecule BRAF inhibitors (e.g., vemurafenib and dabrafenib) and MEK (MAPK/ERK) kinases inhibitors (e.g., trametinib) have distinctly improved the survival of patients suffering from BRAF-mutant cancers such as melanomas. However, the emergence of resistance to BRAF and MEK inhibitor-based melanoma therapy, as well as the reduced sensitivity of other BRAF-mutant cancers such as CRC, poses a considerable clinical problem. For instance, the reactivation of MAPK/ERK signaling hampering cell death induction mechanisms was responsible for BRAF inhibitor resistance, which can be correlated with distinct post-translational and epigenetic processes. Histone deacetylases (HDACs) are prominent epigenetic drug targets and some HDAC inhibitors have already been clinically approved for the therapy of various blood cancers. In addition, several HDACs were identified, which also play a crucial role in the drug resistance of BRAF-mutant cancers. Consequently, inhibition of HDACs was described as a promising approach to overcome resistance. This review summarizes the influence of HDACs (Zn2+-dependent HDACs and NAD+-dependent sirtuins) on BRAF-mutant cancers and BRAF inhibitor resistance based on upregulated survival mechanisms and the prevention of tumor cell death. Moreover, it outlines reasonable HDAC-based strategies to circumvent BRAF-associated resistance mechanisms based on downregulated cell death mechanisms.
    Keywords:  Apoptosis; BRAF-mutant cancer; autophagy; drug resistance; histone deacetylase; melanoma; senescence; sirtuin
    DOI:  https://doi.org/10.20517/cdr.2024.125
  9. J Enzyme Inhib Med Chem. 2025 Dec;40(1): 2458554
    Selisistat, a SIRT1 inhibitor, enhances paclitaxel activity in luminal and triple-negative breast cancer: in silico, in vitro, and in vivo studies.
    Anna Wawruszak, Jarogniew Luszczki, Damian Bartuzi, Joanna Kalafut, Estera Okon, Arkadiusz Czerwonka, Andrzej Stepulak.
      Sirtuins (SIRTs) are NAD+-dependent histone deacetylases, which play a key role in cancer progression; however, their prognostic values in breast cancer (BC) remain a subject of debate and controversy. Accumulative evidence suggests that each sirtuin possesses individual character, implicating its role in the regulation of multifaceted biological functions leading to BC initiation, progression and metastasis. Selisistat (EX527) is a potent, cell permeable, highly selective SIRT1 inhibitor. In the study, the tumour-suppressive effects of the SIRT1 inhibitor EX527 (selisistat) alone and in combination with paclitaxel (PAX) in different breast cancer cell lines and zebrafish xenograft models were investigated. The type of pharmacological drug-drug interaction between EX527 and PAX was determined using the isobolographic method. EX527 and PAX used individually inhibited proliferation, induced apoptosis and caused cell cycle arrest in G1 and subG1/G2 phases. Interestingly, the combination of these compounds used in the 1:1 dose-ratio augmented all these effects (IC50add 29.52 ± 3.29 - 38.45 ± 5.26). The co-treatment of EX527 with PAX generated desirable additive drug-drug interaction. The simultaneous application of EX527 and PAX induced a stronger inhibition of tumour growth compared to individual treatments in zebrafish xenografts. In silico analysis revealed a protein-protein interaction pathway (SIRT1-AKT-S1PR1-GNAI1/GNAO1-Tubulin) connecting molecular targets of both ligands. To summarise, the combination of EX527 and PAX more effectively impairs breast cancer cell growth compared to individual treatments. However, further investigations are required to clarify the specific targets and molecular mechanisms underlying the activity of EX527:PAX in other preclinical models.
    Keywords:  Breast cancer; histone deacetylase inhibitor; paclitaxel; selisistat; sirtuin inhibitor
    DOI:  https://doi.org/10.1080/14756366.2025.2458554
  10. Int J Mol Sci. 2025 Feb 01. pii: 1274. [Epub ahead of print]26(3):
    Regulation of HDAC6 Catalytic Activity in Cancer: The Role of Post-Translational Modifications and Protein-Protein Interactions.
    Leen Asaad, Benjamin Pepperrell, Emma McErlean, Fiona Furlong.
      Histone deacetylase 6 (HDAC6) is a large multidomain protein that deacetylates lysine residues on cytoplasmic proteins, influencing numerous cellular processes. Both the catalytic and noncatalytic functions of HDAC6 have been implicated in cancer development and progression. Over a decade of research on catalytic domain inhibitors has shown that these drugs are well tolerated, exhibit anticancer activity, and can alleviate chemotherapy-induced peripheral neuropathies. However, their effectiveness in treating solid tumours remains uncertain. HDAC6 activity is regulated by protein-protein interactions and post-translational modifications, which may allosterically influence its catalytic domains. As a result, effective inhibition of HDAC6 in cancer using small molecule inhibitors requires a more sophisticated understanding of its role within tumour cells, including whether its expression correlates with deacetylase activity. A comprehensive understanding of cancer-specific HDAC6 expression, functional activity, and activation states will be critical for refining the use of HDAC6 inhibitors in cancer therapy.
    Keywords:  HDAC6; cancer; post-translational modification
    DOI:  https://doi.org/10.3390/ijms26031274
  11. Clin Exp Vaccine Res. 2025 Jan;14(1): 86-100
    Discovery of novel vaccine candidates based on the immunogenic epitopes derived from Toxoplasma membrane proteins.
    Seyyed Amir Hosseini, Saman Hashemi, Davood Siamian, Ali Asghari, Mohammad Fathollahzadeh, Hamidreza Majidiani, Iman Shahraki, Mohamad Hosein Safari.
       Purpose: Due to the widespread distribution and importance of Toxoplasma gondii infection as a parasitic zoonosis, multi-epitope vaccine design was implemented using a set of immunodominant epitopes screened out of a wide scope of membrane proteins.
    Materials and Methods: On this basis, 5 vaccine candidates were created using linkers ([GGGGS]2, KK, AAY, GPGPG, GDGDG, EAAAK) and adjuvants (RS-09 peptide, Mycobacterium tuberculosis resuscitation-promoting factor E [RpfE] and 50S ribosomal protein, human interferon [IFN]-γ).
    Results: Polytopes with RS-09 alone (Toxo-App) and with IFN-γ (Toxo-Apfn), and one with 50S ribosomal protein (Toxo-Ribos) showed the highest immunogenicity during in silico prediction, and their 3-dimensional structure was refined. Protein-protein docking and molecular dynamics simulation analysis was done between the Toxo-App and human toll-like receptor (TLR)-4, rendering a stable connection. Codon optimization and in silico cloning was done ultimately for the selected vaccine candidate.
    Conclusion: In conclusion, potent multi-epitope vaccine candidates were designed against toxoplasmosis using a diverse set of in silico techniques, while further wet experiments are recommended.
    Keywords:  Immunoinformatics; Toxoplasma gondii; Vaccination; Vaccine design
    DOI:  https://doi.org/10.7774/cevr.2025.14.e4
  12. Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2024 Sept 28;49(9):pii: 1672-7347(2024)09-1495-08. [Epub ahead of print]49(9): 1495-1502
    Role of protein post-translational modifications in unexplained recurrent pregnancy loss.
    Qianqian Gao, Jiajie Ren, Dingren Niu, Luqin Guo, Xiaoling Feng.
      Unexplained recurrent pregnancy loss (URPL) is a complex pathological condition that poses significant challenges for women of childbearing age. As a critical component of epigenetics, post-translational modifications (PTMs) not only regulate protein expression and enhance its diversity but also modulate interactions between proteins and other molecules. PTMs play an essential role in the onset and progression of URPL. For example, methylation modifications can hinder decidualization and regulate trophoblast migration and invasion. Phosphorylation modifications can balance regulatory T cells (Treg)/T helper 17 cells (Th17), polarize macrophages, alter dendritic cell populations, and promote trophoblast apoptosis. Acetylation modifications can induce trophoblasts autophagy and suppress M2 macrophage polarization. Ubiquitination modifications can modulate trophoblast migration and invasion and disrupt the immune microenvironment. Glycosylation modifications can inhibit trophoblast migration and invasion, while lactylation modifications maintain endometrial receptivity. The role of PTMs in URPL highlights their potential as a research entry point and therapeutic target for this condition.
    Keywords:  acetylation; methylation; phosphorylation; protein post-translational modification; ubiquitination; unexplained recurrent pregnancy loss
    DOI:  https://doi.org/10.11817/j.issn.1672-7347.2024.240365
  13. Trends Parasitol. 2025 Feb 10. pii: S1471-4922(25)00007-8. [Epub ahead of print]
    Subcellular dynamics in unicellular parasites.
    Thomas Müller, Timothy Krüger, Markus Engstler.
      Bioimaging has made tremendous advances in this century. Innovations in high- and super-resolution microscopy are well established, and live-cell imaging is extensively used to gain an overview of dynamic processes. But the combination of high spatial and temporal resolution necessary to capture intracellular dynamics is rarely achieved. Further, efficient software pipelines - that can handle the recorded data and allow comprehensive analyses - are being developed but lag behind other technical innovations in applicability for broad groups of researchers. Especially in parasites, which offer great potential for studying subcellular dynamics, the possibilities have only begun to be probed. In all cases, the complete description of dynamic molecular movement in 3D space remains a challenging necessity.
    Keywords:  3D; dynamics; imaging; parasites; single-particle tracking
    DOI:  https://doi.org/10.1016/j.pt.2025.01.007
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