bims-toxgon Biomed News
on Toxoplasma gondii metabolism
Issue of 2024‒11‒10
seven papers selected by
Lakesh Kumar, BITS Pilani
  1. Toxoplasma gondii Sustains Survival by Regulating Cholesterol Biosynthesis and Uptake via SREBP2 Activation.
  2. Submicrometre spatiotemporal characterization of the Toxoplasma adhesion strategy for gliding motility.
  3. An optimized ROP6 mRNA construct successfully expressed immunogenic Toxoplasma gondii ROP6 protein in cell culture.
  4. Apicomplexan Espionage: Orchestrated Miscommunication at the Host-Parasite Interface.
  5. Mycobacterium tuberculosis exploits SIRT2 to trap iron for its intracellular survival.
  6. Unlocking the Epigenetic Symphony: Histone Acetylation Orchestration in Bone Remodeling and Diseases.
  7. O-GlcNAcylation of RPA2 at S4/S8 antagonizes phosphorylation and regulates checkpoint activation during replication stress.
  1. J Lipid Res. 2024 Oct 25. pii: S0022-2275(24)00189-5. [Epub ahead of print] 100684
    Toxoplasma gondii Sustains Survival by Regulating Cholesterol Biosynthesis and Uptake via SREBP2 Activation.
    Yi-Min Fan, Qing-Qi Zhang, Ming Pan, Zhao-Feng Hou, Lizhi Fu, Xiulong Xu, Si-Yang Huang.
      Toxoplasma gondii (T. gondii) is an obligate intracellular parasite that cannot biosynthesize cholesterol via the mevalonate pathway, it sources this lipid from its host. We discovered that T. gondii infection upregulated the expression of host cholesterol synthesis related genes HMG-CoA reductase(HMGCR), squalene epoxidase (SQLE) and dehydrocholesterol reductase-7 (DHCR7), and increased the uptake pathway gene low-density lipoprotein receptor (LDLR). We found a protein, sterol regulatory element binding protein 2 (SREBP2), which is the key protein regulating the host cholesterol synthesis and uptake during T. gondii infection. T. gondii induced a dose-dependent nuclear translocation of SREBP2. Knockdown SREBP2 reduced T. gondii-induced cholesterol biosynthesis and uptake. Consequently, the parasite's ability to acquire cholesterol was significantly diminished, impairing its invasion, replication, and bradyzoites development. Interfering cholesterol metabolism using AY9944 effectively inhibited T. gondii replication. In summary, SREBP2 played an important role in T. gondii infection in vitro, serving as a potential target for regulating T. gondii-induced cholesterol metabolism, offering insights into the prevention and treatment of toxoplasmosis.
    Keywords:  HMGCR; LDLR; SQLE; SREBP2; Toxoplasma gondii; cholesterol
    DOI:  https://doi.org/10.1016/j.jlr.2024.100684
  2. Nat Microbiol. 2024 Nov 04.
    Submicrometre spatiotemporal characterization of the Toxoplasma adhesion strategy for gliding motility.
    Luis Vigetti, Bastien Touquet, Delphine Debarre, Thierry Rose, Lionel Bureau, Dima Abdallah, Galina V Dubacheva, Isabelle Tardieux.
      Toxoplasma gondii is a protozoan apicomplexan parasite that uses an adhesion-dependent mode of motility termed gliding to access host cells and disseminate into tissues. Previous studies on Apicomplexa motile morphotypes, including the T. gondii tachyzoite, have identified a cortical actin-myosin motor system that drives the rearward translocation of transmembrane adhesins, thus powering forward movement. However, this model is currently questioned. Here, combining micropatterning and tunable surface chemistry (to edit parasite surface ligands) with flow force and live or super-resolution imaging, we show that tachyzoites build only one apical anchoring contact with the substrate, over which it slides. Furthermore, we show that glycosaminoglycan-parasite interactions are sufficient to promote such force-productive contact and find that the apicobasal flow is set up independent of adhesin release and surface interactions. These findings should enable further characterization of the molecular functions at the T. gondii-substrate mechanosensitive interface and their comparison across apicomplexans.
    DOI:  https://doi.org/10.1038/s41564-024-01818-3
  3. Gene. 2024 Nov 01. pii: S0378-1119(24)00954-5. [Epub ahead of print]935 149073
    An optimized ROP6 mRNA construct successfully expressed immunogenic Toxoplasma gondii ROP6 protein in cell culture.
    Sedef Erkunt Alak, Ceren Gül, Mervenur Güvendi, Aytül Gül, Muhammet Karakavuk, Aysu Değirmenci Döşkaya, Seren Kaplan, Cemal Ün, Adnan Yüksel Gürüz, Mert Döşkaya, Hüseyin Can.
      Toxoplasma gondii is an apicomplexan parasite infecting all mammals including humans and causes toxoplasmosis. There is no vaccine available for humans and thus vaccine development efforts continue using novel antigens and/or vaccine platforms. Since our previous microarray screening study showed that ROP6 is a suitable antigen to be used in vaccine studies, in this study, we aimed to design an optimized mRNA construct encoding the ROP6 protein and then demonstrate its efficiency and immunogenicity using in vitro methods. For this, we constructed a pT7CFE1-Chis/ROP6 vector encoding optimized ROP6 mRNA containing EMCV 5'UTR with IRES and a 20 nucleotides fragment from alpha globin 3' UTR. Then, we generated the optimized ROP6 mRNAs with anti-reverse cap analogue (ARCA) and approximately 150 nucleotide long poly-A tail. Next, HEK293T cells were transfected with the optimized ROP6 mRNAs to show recombinant ROP6 protein expression capability. Moreover, we expressed in vitro recombinant ROP6 protein in HeLa cell lysate using the pT7CFE1-Chis/ROP6 vector to reveal the immunogenicity of recombinant ROP6 protein using sera samples collected from mice infected with PRU strain of T. gondii. The IFA and Western blot results showed that the optimized ROP6 mRNAs successfully expressed the recombinant ROP6 protein in HEK293T cells. Moreover the recombinant ROP6 protein expressed in HeLa cell lysate strongly reacted with sera samples collected from mice. The absorbance difference detected among positive and negative mice serum samples analyzed was statistically significant, indicating that the recombinant ROP6 protein was immunogenic (P = 0.0003). In conclusion, this study demonstrated that the optimized ROP6 mRNAs can be used in the development of mRNA vaccines against toxoplasmosis.
    Keywords:  ROP6 protein; Toxoplasma gondii; Toxoplasmosis; mRNA design
    DOI:  https://doi.org/10.1016/j.gene.2024.149073
  4. ACS Infect Dis. 2024 Nov 05.
    Apicomplexan Espionage: Orchestrated Miscommunication at the Host-Parasite Interface.
    Vaisak Mohan, Sandeep Reddy Vinjamuri, Parnika Sahoo, Abhinav Hatwar, Sandra S N, Usha Krishna, Vyshnav P V, Kamalakannan Vijayan.
      Intracellular parasites, including Toxoplasma and Plasmodium, are entirely reliant on the active scavenging of host-derived nutrients to fuel their replicative cycle, as they are confined within a specialized membrane-bound compartment, the parasitophorous vacuole (PV). Initial observations, based on the proximity of host vesicles to the parasitophorous vacuole membrane (PVM), suggested that parasites utilize host vesicles to obtain essential nutrients. However, mounting evidence has now unequivocally demonstrated that intracellular pathogens establish membrane contacts with host organelles, establishing control over host cellular machinery. These intimate interactions enable the parasites to gain unimpeded access to cytosolic resources critical for development while evading host immune responses. This review consolidates the latest advancements in understanding the molecular machinery driving these transkingdom contacts and their functional roles. Further investigation into these processes promises to revolutionize our understanding of organelle communication, with profound implications for identifying new therapeutic targets and strategies.
    Keywords:  Chlamydia; Membrane contact site; Plasmodium; Toxoplasma; host−pathogen interaction; nutrient scavenging
    DOI:  https://doi.org/10.1021/acsinfecdis.4c00526
  5. Free Radic Biol Med. 2024 Oct 28. pii: S0891-5849(24)01008-6. [Epub ahead of print]225 794-804
    Mycobacterium tuberculosis exploits SIRT2 to trap iron for its intracellular survival.
    Sharmila Talukdar, Radheshyam Modanwal, Gaurav Kumar Chaubey, Asmita Dhiman, Rahul Dilawari, Chaaya Iyengar Raje, Manoj Raje.
      Iron is a critical nutrient for all organisms ranging from bacteria to humans. Ensuring control of this strategic vital resource significantly influences the dynamics of the struggle between host and invading pathogen. Mycobacterium tuberculosis (Mtb), the causative agent of the pulmonary disease tuberculosis (TB), has been plaguing humans for millennia and has evolved to successfully persist and multiply within host cells evading the mammalian immune defences. Invading Mtb appropriates host iron for its survival while the host innate immune response attempts to prevent its stores of this strategic mineral from being appropriated. SIRT2 is a member of the Sirtuin family. These are evolutionary conserved NAD+-dependent deacetylases involved in various cellular processes including regulation of cellular iron homeostasis. Upon Mtb infection of macrophages, SIRT2 expression is enhanced and it translocates from cytosol to nucleus. This is accompanied with a breakdown of the host's iron restriction strategy that compromises host defence mechanisms. However, the underlying mechanism as to how invading Mtb exploits SIRT2 for commandeering host iron remains unknown. In the current study, we report that the decreased bacillary load in cells wherein SIRT2 had been chemically inhibited or knocked down is due to diminished availability of iron. Inhibition or knockdown of SIRT2 in infected cells displays differential modulation of iron import and export proteins suggesting an ongoing struggle by host to limit the bioavailability of iron to pathogen. Flow cytometry analysis of infected macrophages revealed that these cells utilize a non-canonical pathway for evacuation of intracellular iron. This involves the recruitment of a specific pleioform of the moonlighting protein glyceraldehyde-3 phosphate dehydrogenase (GAPDH) to cell surface for capture of iron transporter protein apo-transferrin. Collectively, our findings reveal the process of SIRT2-mediated iron regulation in Mtb pathogenesis and could provide leads for design of novel host-targeted therapeutics.
    Keywords:  ApoTf; Flow cytometry; GAPDH; Iron; Mtb; Pathogenesis; Sirtuin 2
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.10.300
  6. Stem Cell Rev Rep. 2024 Nov 04.
    Unlocking the Epigenetic Symphony: Histone Acetylation Orchestration in Bone Remodeling and Diseases.
    Jingyi Cai, Yudi Deng, Ziyang Min, Chaoyuan Li, Zhihe Zhao, Jianru Yi, Dian Jing.
      Histone acetylation orchestrates a complex symphony of gene expression that controls cellular fate and activities, including the intricate processes of bone remodeling. Despite its proven significance, a systematic illustration of this process has been lacking due to its complexity, impeding clinical application. In this review, we delve into the central regulators of histone acetylation, unveiling their multifaceted roles in modulating bone physiology. We explore both contradictory and overlapping roles among these regulators and assess their potential as therapeutic targets for various bone disorders. Furthermore, we highlight current applications and discuss looming questions for a more effective use of epigenetic therapy in bone diseases, aiming to address gaps in knowledge and clinical practice. By providing a panoramic view of histone acetylation's impact on bone health and disease, this review unveils promising avenues for therapeutic intervention and enhances our understanding of skeletal physiology, crucial for improving therapeutical outcomes and quality of patients' life.
    Keywords:  Bone Disorders; Bone Remodeling; Epigenetics; Histone Acetylation
    DOI:  https://doi.org/10.1007/s12015-024-10807-2
  7. J Biol Chem. 2024 Nov 02. pii: S0021-9258(24)02458-X. [Epub ahead of print] 107956
    O-GlcNAcylation of RPA2 at S4/S8 antagonizes phosphorylation and regulates checkpoint activation during replication stress.
    Jianxin Zhao, Guangcan Shao, Xiaoxuan Lu, Zhuan Lv, Meng-Qiu Dong, Xiaoqian Liu, Jing Li.
      O-linked N-acetylglucosamine (O-GlcNAc) is the most abundant mono-saccharide modification occurring in the cytoplasm, nucleus and mitochondria. Recent advent of the mass spectrometry technology has enabled identification of abundant O-GlcNAc transferase (OGT) substrates in diverse biological processes, such as cell cycle progression, replication and DNA damage response. Herein we report the O-GlcNAcylation of Replication Protein A2 (RPA2), a component of the heterotrimeric RPA complex pivotal for DNA metabolism. We found that RPA2 interacts with OGT, and a topoisomerase II inhibitor, etoposide, diminishes the association. Using higher-energy collisional dissociation mass spectrometry, we mapped RPA2 O-GlcNAc sites to be Ser-4/Ser-8, which are well-known PIKK-dependent RPA2 phosphorylation sites involved in checkpoint activation upon replication stress. We further demonstrated that Ser-4/Ser-8 O-GlcNAcylation antagonizes phosphorylation and impairs downstream Chk1 activation. Moreover, RPA2 O-GlcNAcylation sustains H2AX phosphorylation upon etoposide treatment, and promotes inappropriate cell cycle progression, indicative of checkpoint defects. Our work not only unveils a new OGT substrate, but also underscores the distinct roles of OGT in replication versus replication stress.
    Keywords:  O-GlcNAc; RPA2; checkpoint; phosphorylation; replication stress
    DOI:  https://doi.org/10.1016/j.jbc.2024.107956
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