bims-toxgon Biomed News
on Toxoplasma gondii metabolism
Issue of 2024–08–18
twelve papers selected by
Lakesh Kumar, BITS Pilani
  1. The Toxoplasma gondii homolog of ATPase inhibitory factor 1 is critical for mitochondrial cristae maintenance and stress response.
  2. Toxoplasma gondii rhoptry discharge factor 3 is essential for invasion and microtubule-associated vesicle biogenesis.
  3. Constitutive upregulation of transcription factors underlies permissive bradyzoite differentiation in a natural isolate of Toxoplasma gondii.
  4. SPARK regulates AGC kinases central to the Toxoplasma gondii asexual cycle.
  5. Development of an indirect ELISA for detecting Toxoplasma gondii IgG antibodies based on a recombinant TgIMP1 protein.
  6. ACLY and ACSS2 link nutrient-dependent chromatin accessibility to CD8 T cell effector responses.
  7. PruΔcdpk2 Protects Pigs against Acute Toxoplasmosis Depending on T-Lymphocyte Subsets and Natural Killer Cell Responses.
  8. Functions and mechanisms of non-histone protein acetylation in plants.
  9. SIRT2 regulates high mobility group protein B1 nucleoplasmic shuttle and degradation via deacetylation in microglia.
  10. Genetic Deletion of Skeletal Muscle Inositol Polyphosphate Multikinase Disrupts Glucose Homeostasis and Impairs Exercise Tolerance.
  11. SIRT1 improves lactate homeostasis in the brain to alleviate parkinsonism via deacetylation and inhibition of PKM2.
  12. Legume-type glutamate dehydrogenase: Structure, activity, and inhibition studies.
  1. bioRxiv. 2024 Aug 10. pii: 2024.08.09.607411. [Epub ahead of print]
    The Toxoplasma gondii homolog of ATPase inhibitory factor 1 is critical for mitochondrial cristae maintenance and stress response.
    Madelaine M Usey, Anthony A Ruberto, Diego Huet.
      The production of energy in the form of ATP by the mitochondrial ATP synthase must be tightly controlled. One well-conserved form of regulation is mediated via ATPase inhibitory factor 1 (IF1), which governs ATP synthase activity and gene expression patterns through a cytoprotective process known as mitohormesis. In apicomplexans, the processes regulating ATP synthase activity are not fully elucidated. Using the model apicomplexan Toxoplasma gondii , we found that knockout and overexpression of TgIF1, the structural homolog of IF1, significantly affected gene expression. Additionally, TgIF1 overexpression resulted in the formation of a stable TgIF1 oligomer that increased the presence of higher order ATP synthase oligomers. We also show that parasites lacking TgIF1 exhibit reduced mitochondrial cristae density, and that while TgIF1 levels do not affect growth in conventional culture conditions, they are crucial for parasite survival under hypoxia. Interestingly, TgIF1 overexpression enhances recovery from oxidative stress, suggesting a mitohormetic function. In summary, while TgIF1 does not appear to play a role in metabolic regulation under conventional growth conditions, our work highlights its importance for adapting to stressors faced by T. gondii and other apicomplexans throughout their intricate life cycles.
    SIGNIFICANCE STATEMENT: Toxoplasma gondii is a member of the Apicomplexa, a phylum consisting of parasites responsible for significant global morbidity and mortality. An intact mitochondrial ATP synthase is critical T. gondii survival, but how this enzyme is regulated is not completely understood. Our work demonstrates that the T. gondii homolog of ATPase inhibitory factor 1 (TgIF1) does not impact metabolism under standard culture conditions, but plays a role in mitochondrial cristae density and stress responses. This study reveals the role of TgIF1 in regulating ATP synthase activity under stressful conditions and increases our understanding of this divergent enzyme in T. gondii .
    DOI:  https://doi.org/10.1101/2024.08.09.607411
  2. PLoS Biol. 2024 Aug 13. 22(8): e3002745
    Toxoplasma gondii rhoptry discharge factor 3 is essential for invasion and microtubule-associated vesicle biogenesis.
    Rouaa Ben Chaabene, Matthew Martinez, Alessandro Bonavoglia, Bohumil Maco, Yi-Wei Chang, Gaëlle Lentini, Dominique Soldati-Favre.
      Rhoptries are specialized secretory organelles conserved across the Apicomplexa phylum, essential for host cell invasion and critical for subverting of host cellular and immune functions. They contain proteins and membranous materials injected directly into the host cells, participating in parasitophorous vacuole formation. Toxoplasma gondii tachyzoites harbor 8 to 12 rhoptries, 2 of which are docked to an apical vesicle (AV), a central element associated with a rhoptry secretory apparatus prior to injection into the host cell. This parasite is also equipped with 5 to 6 microtubule-associated vesicles, presumably serving as AV replenishment for iterative rhoptry discharge. Here, we characterized a rhoptry protein, rhoptry discharge factor 3 (RDF3), crucial for rhoptry discharge and invasion. RDF3 enters the secretory pathway, localizing near the AV and associated with the rhoptry bulb. Upon invasion, RDF3 dynamically delocalizes, suggesting a critical role at the time of rhoptry discharge. Cryo-electron tomography analysis of RDF3-depleted parasites reveals irregularity in microtubule-associated vesicles morphology, presumably impacting on their preparedness to function as an AV. Our findings suggest that RDF3 is priming the microtubule-associated vesicles for rhoptry discharge by a mechanism distinct from the rhoptry secretory apparatus contribution.
    DOI:  https://doi.org/10.1371/journal.pbio.3002745
  3. mBio. 2024 Aug 16. e0064124
    Constitutive upregulation of transcription factors underlies permissive bradyzoite differentiation in a natural isolate of Toxoplasma gondii.
    Jing Xia, Yong Fu, Wanyi Huang, Taher Uddin, L David Sibley.
      Toxoplasma gondii bradyzoites play a critical role in pathology due to their long-term persistence in intermediate hosts and their potential to reactivate, resulting in severe diseases in immunocompromised individuals. Currently, there is no effective treatment for eliminating bradyzoites. Hence, better in vitro models of T. gondii bradyzoite development would facilitate identification of therapeutic targets for bradyzoites. Herein, we characterized a natural isolate of T. gondii, called Tg68, which showed slower in vitro replication of tachyzoites, and permissive bradyzoite development under stress conditions in vitro. Transcriptional analysis revealed constitutive expression in Tg68 tachyzoites of the key regulators of bradyzoite development including BFD1, BFD2, and several AP2 factors. Consistent with this finding, Tg68 tachyzoites expressed high levels of bradyzoite-specific genes including BAG1, ENO1, and LDH2. Moreover, after stress-induced differentiation, Tg68 bradyzoites exhibited gene expression profiles of mature bradyzoites, even at early time points. These data suggest that Tg68 tachyzoites exist in a pre-bradyzoite stage primed to readily develop into mature bradyzoites under stress conditions in vitro. Tg68 presents a novel model for differentiation in vitro that will serve as a useful tool for the investigation of bradyzoite biology and the development of therapeutics.
    IMPORTANCE: Toxoplasma gondii is a widespread protozoan that chronically infects ~30% of the world's population. T. gondii can differentiate between the fast-growing life stage that causes acute infection and the slow-growing stage that persists in the host for extended periods of time. The slow-growing stage cannot be eliminated by the host immune response or currently known antiparasitic drugs. Studies on the slow-growing stage have been limited due to the limitations of in vivo experiments and the challenges of in vitro manipulation. Here, we characterize a natural isolate of T. gondii, which constitutively expresses factors that drive development and that is permissive to convert to the slow-growing stage under stress conditions in vitro. The strain presents a novel in vitro model for studying the chronic phase of toxoplasmosis and identifying new therapeutic treatments for chronic infections.
    Keywords:  Apetala 2 transcription factor; Chronic infection; stress-induced differentiation; tissue cyst
    DOI:  https://doi.org/10.1128/mbio.00641-24
  4. Elife. 2024 Aug 13. pii: RP93877. [Epub ahead of print]13
    SPARK regulates AGC kinases central to the Toxoplasma gondii asexual cycle.
    Alice L Herneisen, Michelle L Peters, Tyler A Smith, Emily Shortt, Sebastian Lourido.
      Apicomplexan parasites balance proliferation, persistence, and spread in their metazoan hosts. AGC kinases, such as PKG, PKA, and the PDK1 ortholog SPARK, integrate environmental signals to toggle parasites between replicative and motile life stages. Recent studies have cataloged pathways downstream of apicomplexan PKG and PKA; however, less is known about the global integration of AGC kinase signaling cascades. Here, conditional genetics coupled to unbiased proteomics demonstrates that SPARK complexes with an elongin-like protein to regulate the stability of PKA and PKG in the model apicomplexan Toxoplasma gondii. Defects attributed to SPARK depletion develop after PKG and PKA are down-regulated. Parasites lacking SPARK differentiate into the chronic form of infection, which may arise from reduced activity of a coccidian-specific PKA ortholog. This work delineates the signaling topology of AGC kinases that together control transitions within the asexual cycle of this important family of parasites.
    Keywords:  AGC kinases; Toxoplasma gondii; infectious disease; microbiology; signaling
    DOI:  https://doi.org/10.7554/eLife.93877
  5. PLoS Negl Trop Dis. 2024 Aug 14. 18(8): e0012421
    Development of an indirect ELISA for detecting Toxoplasma gondii IgG antibodies based on a recombinant TgIMP1 protein.
    Hongjie Dong, Junmei Zhang, Qi Wang, Yanmei Shen, Beibei Zhou, Lisha Dai, Wenju Zhu, Hang Sun, Xiaoman Xie, Huanhuan Xie, Chao Xu, Guihua Zhao, Kun Yin.
      Toxoplasma gondii (T. gondii) is widely spread around the world, which can cause serious harm to immunosuppressed patients. Currently, the commercial test kits are poor at assessing T. gondii infection and vaccine effectiveness, making an urgent need to exploit effective enzyme-linked immunosorbent assay with great performance to compensate for this deficiency. Here, the TgIMP1 recombinant protein was expressed in E. coli BL(21) cells. The TgIMP1 was purified with affinity chromatography and the reactivity was retained with anti-TgIMP1 antibodies. The TgIMP1 was then used to develop an indirect ELISA (IMP1-iELISA) and the reaction conditions of IMP1-iELISA were optimized. As a result, the cut-off value was determined to be 0.2833 by analyzing the OD450nm values of forty T. gondii-negative sera. The coefficient of variation of 6 T. gondii-positive sera within and between runs were both less than 10%. The IMP1-iELISA was non-cross-reactive with the sera of cytomegalovirus, herpes virus, rubella virus, Cryptosporidium spp., Theileria spp., Neospora spp. and Plasmodium spp.. Furthermore, the sensitivity and specificity of IMP1-iELISA were 98.9% and 96.7%, respectively, based on testing 150 serum samples. The results suggest that this IMP1-iELISA is specific, sensitive, repeatable and can be applied to the detection of T. gondii infections in the medical and health industries.
    DOI:  https://doi.org/10.1371/journal.pntd.0012421
  6. J Exp Med. 2024 Sep 02. pii: e20231820. [Epub ahead of print]221(9):
    ACLY and ACSS2 link nutrient-dependent chromatin accessibility to CD8 T cell effector responses.
    Irem Kaymak, McLane J Watson, Brandon M Oswald, Shixin Ma, Benjamin K Johnson, Lisa M DeCamp, Batsirai M Mabvakure, Katarzyna M Luda, Eric H Ma, Kin Lau, Zhen Fu, Brejnev Muhire, Susan M Kitchen-Goosen, Alexandra Vander Ark, Michael S Dahabieh, Bozena Samborska, Matthew Vos, Hui Shen, Zi Peng Fan, Thomas P Roddy, Gillian A Kingsbury, Cristovão M Sousa, Connie M Krawczyk, Kelsey S Williams, Ryan D Sheldon, Susan M Kaech, Dominic G Roy, Russell G Jones.
      Coordination of cellular metabolism is essential for optimal T cell responses. Here, we identify cytosolic acetyl-CoA production as an essential metabolic node for CD8 T cell function in vivo. We show that CD8 T cell responses to infection depend on acetyl-CoA derived from citrate via the enzyme ATP citrate lyase (ACLY). However, ablation of ACLY triggers an alternative, acetate-dependent pathway for acetyl-CoA production mediated by acyl-CoA synthetase short-chain family member 2 (ACSS2). Mechanistically, acetate fuels both the TCA cycle and cytosolic acetyl-CoA production, impacting T cell effector responses, acetate-dependent histone acetylation, and chromatin accessibility at effector gene loci. When ACLY is functional, ACSS2 is not required, suggesting acetate is not an obligate metabolic substrate for CD8 T cell function. However, loss of ACLY renders CD8 T cells dependent on acetate (via ACSS2) to maintain acetyl-CoA production and effector function. Together, ACLY and ACSS2 coordinate cytosolic acetyl-CoA production in CD8 T cells to maintain chromatin accessibility and T cell effector function.
    DOI:  https://doi.org/10.1084/jem.20231820
  7. Foodborne Pathog Dis. 2024 Aug 12.
    PruΔcdpk2 Protects Pigs against Acute Toxoplasmosis Depending on T-Lymphocyte Subsets and Natural Killer Cell Responses.
    Yi-Min Fan, Wen-Qian Shi, Qi-Wang Jin, Ming Pan, Zhao-Feng Hou, Lizhi Fu, Jian-Ping Tao, Si-Yang Huang.
      Toxoplasma gondii is a widespread protozoan parasite approximately infecting one-third of the world population and can cause serious public health problems. In this study, we investigated the protective effect of the attenuated vaccine Pru:Δcdpk2 against acute toxoplasmosis and explored the underlying immune mechanisms of the protection in pigs. The systemic T-cell and natural killer (NK) cell responses were analyzed, including kinetics, phenotype, and multifunctionality (interferon [IFN]-γ, tumor necrosis factor [TNF]-α), and the IFN-γ levels were analyzed in PBMCs. Our results showed that T. gondii-specific antibodies were induced by Pru:Δcdpk2. After challenging with RH, the antibodies were able to respond quickly in the immunized group, and the expression level was significantly higher than that in the unimmunized group. The expression level of IFN-γ significantly increased after vaccination, and the CD3+ γδ-, NK, and CD3+ γδ+ cell subsets also significantly increased. At the same time, functional analysis indicated that these cells were polarized toward a Th1 phenotype, showing the ability to secrete IFN-γ and TNF-α. The CD4+CD8α-T cell population exhibited a higher frequency of IFN-γ+ producing cells compared with the CD4-CD8α+ and CD4+CD8α+ cell populations during the early days of vaccination. Our results indicated that the attenuated vaccine could induce the expression of NK, γδ, and CD3αβ cells in pigs, and IFN-γ and TNF-α secreted by these cells are important for resistance to T. gondii infection.
    Keywords:  T cell response; Toxoplasma gondii; cytokine; pig
    DOI:  https://doi.org/10.1089/fpd.2024.0060
  8. J Integr Plant Biol. 2024 Aug 13.
    Functions and mechanisms of non-histone protein acetylation in plants.
    Xia Jin, Xiaoshuang Li, Jaime A Teixeira da Silva, Xuncheng Liu.
      Lysine acetylation, an evolutionarily conserved post-translational protein modification, is reversibly catalyzed by lysine acetyltransferases and lysine deacetylases. Lysine acetylation, which was first discovered on histones, mainly functions to configure the structure of chromatin and regulate gene transcriptional activity. Over the past decade, with advances in high-resolution mass spectrometry, a vast and growing number of non-histone proteins modified by acetylation in various plant species have been identified. Lysine acetylation of non-histone proteins is widely involved in regulating biological processes in plants such as photosynthesis, energy metabolism, hormone signal transduction and stress responses. Moreover, in plants, lysine acetylation plays crucial roles in regulating enzyme activity, protein stability, protein interaction and subcellular localization. This review summarizes recent progress in our understanding of the biological functions and mechanisms of non-histone protein acetylation in plants. Research prospects in this field are also noted.
    Keywords:  acetylomics; lysine acetylation; lysine deacetylation; non‐histone acetylation; post‐translational modification
    DOI:  https://doi.org/10.1111/jipb.13756
  9. J Cell Physiol. 2024 Aug 11. e31364
    SIRT2 regulates high mobility group protein B1 nucleoplasmic shuttle and degradation via deacetylation in microglia.
    Wan-Qun Xing, Xian-Ji Piao, Qi Han, Hui-Ying Shi, Wen-Cong Wu, Fan Si, Jing-Jing Lu, Tie-Zhong Zhou, Jing-Ru Guo, Shi-Ze Li, Bin Xu.
      High mobility group protein B1 (HMGB1) acts as a pathogenic inflammatory response to mediate ranges of conditions such as epilepsy, septic shock, ischemia, traumatic brain injury, Parkinson's disease, Alzheimer's disease and mass spectrometry. HMGB1 promotes inflammation during sterile and infectious damage and plays a crucial role in disease development. Mobilization from the nucleus to the cytoplasm is the first important step in the release of HMGB1 from activated immune cells. Here, we demonstrated that Sirtuin 2 (SIRT2) physically interacts with and deacetylates HMGB1 at 43 lysine residue at nuclear localization signal locations, strengthening its interaction with HMGB1 and causing HMGB1 to be localized in the cytoplasm. These discoveries are the first to shed light on the SIRT2 nucleoplasmic shuttle, which influences HMGB1 and its degradation, hence revealing novel therapeutic targets and avenues for neuroinflammation treatment.
    Keywords:  SIRT2; deacetylation; high mobility group protein B1; neuroinflammation; nucleoplasmic shuttle
    DOI:  https://doi.org/10.1002/jcp.31364
  10. bioRxiv. 2024 Aug 05. pii: 2024.07.28.605526. [Epub ahead of print]
    Genetic Deletion of Skeletal Muscle Inositol Polyphosphate Multikinase Disrupts Glucose Homeostasis and Impairs Exercise Tolerance.
    Ji-Hyun Lee, Ik-Rak Jung, Becky Tu-Sekine, Sunghee Jin, Frederick Anokye-Danso, Rexford S Ahima, Sangwon F Kim.
      Inositol phosphates are critical signaling messengers involved in a wide range of biological pathways in which inositol polyphosphate multikinase (IPMK) functions as a rate-limiting enzyme for inositol polyphosphate metabolism. IPMK has been implicated in cellular metabolism, but its function at the systemic level is still poorly understood. Since skeletal muscle is a major contributor to energy homeostasis, we have developed a mouse model in which skeletal muscle IPMK is specifically deleted and examined how a loss of IPMK affects whole-body metabolism. Here, we report that mice in which IPMK knockout is deleted, specifically in the skeletal muscle, displayed an increased body weight, disrupted glucose tolerance, and reduced exercise tolerance under the normal diet. Moreover, these changes were associated with an increased accumulation of triglyceride in skeletal muscle. Furthermore, we have confirmed that a loss of IPMK led to reduced beta-oxidation, increased triglyceride accumulation, and impaired insulin response in IPMK-deficient muscle cells. Thus, our results suggest that IPMK mediates the whole-body metabolism via regulating muscle metabolism and may be potentially targeted for the treatment of metabolic syndromes.
    Keywords:  IPMK; Inositol polyphosphate; exercise; insulin; skeletal muscle
    DOI:  https://doi.org/10.1101/2024.07.28.605526
  11. Cell Rep Med. 2024 Aug 06. pii: S2666-3791(24)00405-1. [Epub ahead of print] 101684
    SIRT1 improves lactate homeostasis in the brain to alleviate parkinsonism via deacetylation and inhibition of PKM2.
    Bolin Lian, Jing Zhang, Xiang Yin, Jiayan Wang, Li Li, Qianqian Ju, Yuejun Wang, Yuhui Jiang, Xiaoyu Liu, Yu Chen, Xin Tang, Cheng Sun.
      Sirtuin 1 (SIRT1) is a histone deacetylase and plays diverse functions in various physiological events, from development to lifespan regulation. Here, in Parkinson's disease (PD) model mice, we demonstrated that SIRT1 ameliorates parkinsonism, while SIRT1 knockdown further aggravates PD phenotypes. Mechanistically, SIRT1 interacts with and deacetylates pyruvate kinase M2 (PKM2) at K135 and K206, thus leading to reduced PKM2 enzyme activity and lactate production, which eventually results in decreased glial activation in the brain. Administration of lactate in the brain recapitulates PD-like phenotypes. Furthermore, increased expression of PKM2 worsens PD symptoms, and, on the contrary, inhibition of PKM2 by shikonin or PKM2-IN-1 alleviates parkinsonism in mice. Collectively, our data indicate that excessive lactate in the brain might be involved in the progression of PD. By improving lactate homeostasis, SIRT1, together with PKM2, are likely drug targets for developing agents for the treatment of neurodegeneration in PD.
    DOI:  https://doi.org/10.1016/j.xcrm.2024.101684
  12. Int J Biol Macromol. 2024 Aug 12. pii: S0141-8130(24)05453-9. [Epub ahead of print]278(Pt 2): 134648
    Legume-type glutamate dehydrogenase: Structure, activity, and inhibition studies.
    Marta Grzechowiak, Joanna Sliwiak, Andreas Link, Milosz Ruszkowski.
      Glutamate dehydrogenases (GDHs) are key enzymes at the crossroads of N and C metabolism in plants. Legumes, whose N metabolism is particularly intricate, possess a unique type of GDH. This study presents an analysis of a legume-type GDH (isoform 2) from Medicago truncatula (MtGDH2). We measured MtGDH2 activity in both the Glu → 2-oxoglutarate (2OG) and 2OG → Glu reaction directions and obtained kinetic parameters for Glu, 2OG, NAD+, and NADH. Inhibition assays revealed that compounds possessing di- or tricarboxylates act as inhibitors of plant GDHs. Interestingly, 2,6-pyridinedicarboxylate (PYR) weakly inhibits MtGDH2 compared to Arabidopsis thaliana homologs. Furthermore, we explored tetrazole derivatives to discover 3-(1H-tetrazol-5-yl)benzoic acid (TBA) as an MtGDH2 inhibitor. The kinetic experiments are supported by six crystal structures, solved as: (i) unliganded enzyme, (ii) trapping the reaction intermediate 2-amino-2-hydroxyglutarate and NAD+, and also complexed with NAD+ and inhibitors such as (iii) citrate, (iv) PYR, (v) isophthalate, and (vi) TBA. The complex with TBA revealed a new mode of action that, in contrast to other inhibitors, prevents domain closure. This discovery points to TBA as a starting point for the development of novel GDH inhibitors to study the functions of GDH in plants and potentially boost biomass production.
    Keywords:  Carbon metabolism; Glutamate dehydrogenase; Inhibitors; NAD(+); Nitrogen metabolism
    DOI:  https://doi.org/10.1016/j.ijbiomac.2024.134648
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