bims-toxgon 2025-01-26 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2025–01–26
fourteen papers selected by
Lakesh Kumar, BITS Pilani

mGBP2 engages Galectin-9 for immunity against Toxoplasma gondii.
A novel cross-priming amplification technique combined with lateral flow strips for rapid and visual detection of zoonotic Toxoplasma gondii.
Cellular Senescence Contributes to Colonic Barrier Integrity Impairment Induced by Toxoplasma gondii Infection.
Ultrastructure expansion microscopy: Enlarging our perspective on apicomplexan cell division.
Numerous rRNA molecules form the apicomplexan mitoribosome via repurposed protein and RNA elements.
Vesicular mechanisms of drug resistance in apicomplexan parasites.
Toxoplasma gondii Infection in the Male Reproductive System: A Systematic Review.
Acetylation-enhanced Sp1 transcriptional activity suppresses Mlph expression.
Revealing the Complex Interaction of Noncoding RNAs, Sirtuin Family, and Mitochondrial Function.
KAT6A acetylation drives metabolic adaptation to mediate cellular growth and mitochondrial metabolism through AMPK interaction.
Mitochondrial fatty acid oxidation regulates monocytic type I interferon signaling via histone acetylation.
Sirtuin 2 exacerbates renal tubule injury and inflammation in diabetic mice via deacetylation of c-Jun/c-Fos.
Constitutive expression of Cas9 and rapamycin-inducible Cre recombinase facilitates conditional genome editing in Plasmodium berghei.
Glutamine Synthetase: Diverse Regulation and Functions of an Ancient Enzyme.

PLoS One. 2025 ;20(1): e0316209

mGBP2 engages Galectin-9 for immunity against Toxoplasma gondii.

Elisabeth Kravets, Gereon Poschmann, Sebastian Hänsch, Veronica Raba, Stefanie Weidtkamp-Peters, Daniel Degrandi, Kai Stühler, Klaus Pfeffer.

Guanylate binding proteins (GBPs) are large interferon-inducible GTPases, executing essential host defense activities against Toxoplasma gondii, an invasive intracellular apicomplexan protozoan parasite of global importance. T. gondii establishes a parasitophorous vacuole (PV) which shields the parasite from the host's intracellular defense mechanisms. Murine GBPs (mGBPs) recognize T. gondii PVs and assemble into supramolecular mGBP homo- and heterocomplexes that are required for the disruption of the membrane of PVs eventually resulting in the cell-autonomous immune control of vacuole-resident pathogens. We have previously shown that mGBP2 plays an important role in T. gondii immune control. Here, to unravel mGBP2 functions, we report Galectin-9 (Gal9) as a critical mGBP2 interaction partner engaged for immunity to T. gondii. Interestingly, Gal9 also accumulates and colocalizes with mGBP2 at the T. gondii PV. Furthermore, we could prove the requirement of Gal9 for growth control of T. gondii by CRISPR/Cas9 mediated gene editing. These discoveries clearly indicate that Gal9 is a crucial factor for the mGBP2-coordinated cell-autonomous host defense mechanism against T. gondii.

DOI: https://doi.org/10.1371/journal.pone.0316209
Vet Parasitol. 2025 Jan 20. pii: S0304-4017(25)00013-5. [Epub ahead of print]334 110402

A novel cross-priming amplification technique combined with lateral flow strips for rapid and visual detection of zoonotic Toxoplasma gondii.

Yao Liang, Yuan-Hui He, Shu-Feng Yang, Shi-Chen Xie, Yi-Han Lv, Wei Cong, Hany M Elsheikha, Xing-Quan Zhu.

  Toxoplasma gondii, an obligate intracellular protozoan, infects almost all warm-blooded animals and humans, with felines serving as its sole definitive hosts. Cats release T. gondii oocysts into the environment through feces, contributing to environmental contamination that can lead to toxoplasmosis in humans upon exposure through ingestion of contaminated food, water, or soil. Effective detection of T. gondii in environmental samples is essential for protecting public health and preventing disease transmission. In the present study, we developed a cross-priming amplification (CPA) assay coupled with lateral flow immunoassay strips for the rapid and visual detection of T. gondii in environmental samples. CPA offers simplicity and eliminates the need for complex laboratory equipment. The assay demonstrated high specificity, accurately identifying nine genotypes of T. gondii without cross-reacting with 11 related parasites. Sensitivity testing revealed a detection limit of 1 × 10² copies/μL at the molecular level (plasmid) and 10 oocysts in real-world environmental samples. Furthermore, CPA effectively detected T. gondii in diverse environmental samples, including soil, water, and cat feces, with results consistent with known infection rates. These findings underscore CPA's potential as a reliable, rapid, and accessible tool for detecting T. gondii in environmental settings, contributing to improved public health surveillance and disease prevention.

Keywords:  Cross-priming amplification; Detection techniques; Environmental samples; Lateral flow immunoassay strips; Toxoplasma gondii

DOI:  https://doi.org/10.1016/j.vetpar.2025.110402
Inflammation. 2025 Jan 18.

Cellular Senescence Contributes to Colonic Barrier Integrity Impairment Induced by Toxoplasma gondii Infection.

Yingting Huang, Yumeng Zhou, Zhicheng He, Jiayi Yang, Jianqi Gu, Bingqian Cui, Siyu Li, Heng Deng, Wendi Zhao, Xiaoying Yang, Fenfen Sun, Cheng He, Wei Pan.

  Toxoplasma gondii (T. gondii) induces gut barrier integrity impairment, which is crucial to the establishment of long-term infection in hosts. Cellular senescence is an imperative event that drives disease progression. Several studies have indicated that T. gondii induces oxidative stress and cell cycle blockade in the tissues of hosts, suggesting cellular senescence induced by the parasite. Here, we explored whether cell senescence is involved in T. gondii-mediated colonic barrier integrity damage in mice. C57BL/6J mice were infected with 10 cysts of T. gondii. Senolytic therapy (dasatinib and quercetin, DQ, a combination therapy for reducing senescent cells) was given by oral gavage 4 weeks post-infection. Alcian blue staining, immunofluorescence, western blot, quantitative PCR (qPCR), and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate the thickness of the colonic mucus layer, the expression profiles of genes and proteins related to tight junction function and cellular senescence in the colonic tissues, and the levels of serum lipopolysaccharides (LPS), respectively. T. gondii-infected mice exhibited deteriorated secreted mucus, shortened length, decreased expression of zonula occludens-1 (ZO-1) and occludin in the colon, accompanied by elevated levels of serum LPS. Moreover, the infection upregulated cell senescence-related markers (p16INK4A, p21CIP1) while inhibiting Lamin B1 expression. In addition, the expression levels of senescence-associated secretory phenotypes (SASPs), including IL-1β, TNF-α, IL-6, MMP9 and CXCL10, were upregulated post-infection. Notably, reducing cell senescence with DQ administration, significantly ameliorated the colonic pathological alterations induced by T. gondii infection. This study uncovers for the first time that cellular senescence contributes to the colonic barrier integrity damage induced by chronic T. gondii infection. Importantly, we provide evidence that senolytic therapy exerts a therapeutic effect on the intestinal pathological lesions.

Keywords:   Toxoplasma gondii ; Barrier integrity damage; Cellular senescence; Dasatinib; Quercetin; Senolytic therapy

DOI:  https://doi.org/10.1007/s10753-024-02213-0
J Microsc. 2025 Jan 24.

Ultrastructure expansion microscopy: Enlarging our perspective on apicomplexan cell division.

Sofía Horjales, Florencia Sena, María E Francia.

  Apicomplexans, a large phylum of protozoan intracellular parasites, well known for their ability to invade and proliferate within host cells, cause diseases with major health and economic impacts worldwide. These parasites are responsible for conditions such as malaria, cryptosporidiosis, and toxoplasmosis, which affect humans and other animals. Apicomplexans exhibit complex life cycles, marked by diverse modes of cell division, which are closely associated with their pathogenesis. All the unique structural and evolutionary characteristics of apicomplexan parasites, the biology underlying life stage transitions, and the singular mechanisms of cell division alongside their associated biomedical relevance have captured the attention of parasitologists of all times. Traditional light and electron microscopy have set the fundamental foundations of our understanding of these parasites, including the distinction among their modes of cell division. This has been more recently complemented by microscopy advances through the implementation of superresolution fluorescence microscopy, and variants of electron microscopy, such as cryo-EM and tomography, revealing intricate details of organelles and cell division. Ultrastructure Expansion Microscopy has emerged as a transformative, accessible approach that enhances resolution by physically expanding samples isometrically, allowing nanoscale visualisation on standard light microscopes. In this work, we review the most recent contributions of U-ExM and its recent improvements and innovations, in providing unprecedented insights into apicomplexan ultrastructure and its associated mechanisms, focusing particularly on cell division. We highlight the power of U-ExM in combination with protein-specific labelling, in aiding the visualisation of long oversighted organelles and detailed insights into the assembly of parasite-specific structures, such as the conoid in Plasmodia, and the apical-basal axis in Toxoplasma, respectively, during new parasite assembly. Altogether, the contributions of U-ExM reveal conserved and unique structural features across species while nearing super resolution. The development of these methodologies and their combination with different technologies are crucial for advancing our mechanistic understanding of apicomplexan biology, offering new perspectives that may facilitate novel therapeutic strategies against apicomplexan-caused diseases.

Keywords:  apicomplexan cell division; endodyogeny; endopolygeny; schizogony; ultrastructure expansion microscopy

DOI:  https://doi.org/10.1111/jmi.13387
Nat Commun. 2025 Jan 18. 16(1): 817

Numerous rRNA molecules form the apicomplexan mitoribosome via repurposed protein and RNA elements.

Shikha Shikha, Victor Tobiasson, Mariana Ferreira Silva, Jana Ovciarikova, Dario Beraldi, Alexander Mühleip, Lilach Sheiner.

Mitochondrial ribosomes (mitoribosomes) are essential, and their function of synthesising mitochondrial proteins is universal. The core of almost all mitoribosomes is formed from a small number of long and self-folding rRNA molecules. In contrast, the mitoribosome of the apicomplexan parasite Toxoplasma gondii assembles from over 50 extremely short rRNA molecules. Here, we use cryo-EM to discover the features that enable this unusual mitoribosome to perform its function. We reveal that poly-A tails added to rRNA molecules are integrated into the ribosome, and we demonstrate their essentiality for mitoribosome formation and for parasite survival. This is a distinct function for poly-A tails, which are otherwise known primarily as stabilisers of messenger RNAs. Furthermore, while ribosomes typically consist of unique rRNA sequences, here nine sequences are used twice, each copy integrated in a different mitoribosome domain, revealing one of the mechanisms enabling the extreme mitochondrial genome reduction characteristic to Apicomplexa and to a large group of related microbial eukaryotes. Finally, several transcription factor-like proteins are repurposed to compensate for reduced or lost critical ribosomal domains, including members of the ApiAP2 family thus far considered to be DNA-binding transcription factors.

DOI: https://doi.org/10.1038/s41467-025-56057-9
Microbiol Mol Biol Rev. 2025 Jan 24. e0001024

Vesicular mechanisms of drug resistance in apicomplexan parasites.

Kasturi Haldar, Souvik Bhattacharjee.

  SUMMARYVesicular mechanisms of drug resistance are known to exist across prokaryotes and eukaryotes. Vesicles are sacs that form when a lipid bilayer 'bends' to engulf and isolate contents from the cytoplasm or extracellular environment. They have a wide range of functions, including vehicles of communication within and across cells, trafficking of protein intermediates to their rightful organellar destinations, and carriers of substrates destined for autophagy. This review will provide an in-depth understanding of vesicular mechanisms of apicomplexan parasites, Plasmodium and Toxoplasma (that respectively cause malaria and toxoplasmosis). It will integrate mechanistic and evolutionarily insights gained from these and other pathogenic eukaryotes to develop a new model for plasmodial resistance to artemisinins, a class of drugs that have been the backbone of modern campaigns to eliminate malaria worldwide. We also discuss extracellular vesicles that present major vesicular mechanisms of drug resistance in parasite protozoa (that apicomplexans are part of). Finally, we provide a broader context of clinical drug resistance mechanisms of Plasmodium, Toxoplasma, as well as Cryptosporidium and Babesia, that are prominent members of the phyla, causative agents of cryptosporidiosis and babesiosis and significant for human and animal health.

Keywords:  apicomplexan parasites; artemisinin; drug resistance mechanisms; vesicular trafficking

DOI:  https://doi.org/10.1128/mmbr.00010-24
Acta Parasitol. 2025 Jan 24. 70(1): 29

Toxoplasma gondii Infection in the Male Reproductive System: A Systematic Review.

Pablo Tabares Tejada, Walter D Cardona Maya.

   PURPOSE: Toxoplasmosis is a worldwide widespread parasitic infection; it affects about 30% of the global population, either through acute toxoplasmosis or its sequels. Even though the male reproductive system is not the primary target for Toxoplasma gondii (T. gondii), studies have inquired into the possibility of presenting repercussions in this system directly or indirectly due to toxoplasmosis. Therefore, this systematic literature review aims to summarize the available evidence on the effects of infection caused by T. gondii on the male reproductive tract.
METHODS: We searched PubMed, Scopus, LILACS and Google Scholar until June 2024 to identify studies of T. gondii and the human male reproductive system. Finally, we analyzed 24 papers published between 1986 and 2024. The Joanna Briggs Institute (JBI) Critical Appraisal Checklist was used to assess the potential risk of bias and the quality of the results.
RESULTS: Infertility is a multicausal issue, including various stages in which the infection caused by T. gondii could interfere, but the mechanisms are not fully understood yet. Studies in animals, particularly rats, have shown the harmful effects of the parasite on sperm performance and endocrine function. In the same way, sexual transmission of T. gondii has been extensively studied in animals, with the parasite detected in the semen of various species. In humans, this transmission route remains theoretical due to study limitations. However, discrepancies in findings call for further research to understand the mechanisms and make the T. gondii's infection impact on the male reproductive system a topic of growing interest.
CONCLUSION: Acute and chronic infection by T. gondii in the male reproductive system is a topic of growing interest due to its possible implications for reproductive health.

Keywords:  Fertility; Male reproductive system; Semen; Toxoplasma gondii; Toxoplasmosis

DOI:  https://doi.org/10.1007/s11686-024-00978-w
Sci Rep. 2025 Jan 17. 15(1): 2338

Acetylation-enhanced Sp1 transcriptional activity suppresses Mlph expression.

Chan Song Jo, Hairu Zhao, Jae Sung Hwang.

  Melanosome transport is regulated by major proteins, including Rab27a, Melanophilin (Mlph), and Myosin Va (Myo-Va), that form a tripartite complex. Mutation of these proteins causes melanosome aggregation around the nucleus. Among these proteins, Mlph is a linker between Rab27a and Myo-Va. There are some studies about the regulation of Mlph transcriptional expression. However, its regulation by post-translational modifications remains unclear. In this study, inhibition of HDACs by SAHA and TSA disrupted melanosome transport, causing melanosome aggregation. Specifically, we identified a novel mechanism in which HDAC5 regulates Mlph expression via Sp1. Knockdown of HDAC5 increased the acetylation of Sp1 and the binding to the Mlph promoter, thereby modulating its expression. This study highlights the crucial role of HDAC5 in melanosome transport through its interaction with Sp1. These findings suggest that HDAC5-mediated deacetylation is pivotal in the post-translational modification of melanosome transport, providing insights into the molecular mechanisms underlying this process.

Keywords:  Acetylation; HDAC5; Melanophilin; Melanosome transport; Post-translational modifications; Sp1

DOI:  https://doi.org/10.1038/s41598-025-86282-7
J Gene Med. 2025 Jan;27(1): e70007

Revealing the Complex Interaction of Noncoding RNAs, Sirtuin Family, and Mitochondrial Function.

Ludong Yuan, Leijing Yin, Xiaofang Lin, Jing Li, Pengfei Liang, Bimei Jiang.

  Mitochondria are key organelles that perform and coordinate various metabolic processes in the cell, and their homeostasis is essential for the maintenance of eukaryotic life. To maintain mitochondrial homeostasis and cellular health, close communication between noncoding RNAs (ncRNAs) and proteins is required. For example, there are numerous crosstalk between ncRNAs and the sirtuin (SIRT1-7) family, which is a group of nicotinamide adenine dinucleotides (NAD(+))-dependent Type III deacetylases. NcRNAs are involved in the regulation of gene expression of sirtuin family members, and deacetylation of sirtuin family members can also influence the generation of ncRNAs. This review focuses on the relationship between the two mentioned above and summarizes the impact of their interactions on mitochondrial metabolism, oxidative stress, mitochondrial apoptotic pathways, mitochondrial biogenesis, mitochondrial dynamics, and other mitochondria-related pathophysiological processes. Finally, the review also describes targeted and appropriate treatment strategies. In conclusion, we provide an overview of the ncRNA-sirtuins/mitochondria relationship that could provide a reference for related research in the mitochondrial field and help the future development of new biomedical applications in this area.

Keywords:  apoptosis; metabolism; mitochondria; noncoding RNAs; oxidative stress; sirtuins

DOI:  https://doi.org/10.1002/jgm.70007
bioRxiv. 2025 Jan 14. pii: 2025.01.14.633047. [Epub ahead of print]

KAT6A acetylation drives metabolic adaptation to mediate cellular growth and mitochondrial metabolism through AMPK interaction.

Mariko Aoyagi Keller, Andreas Ivessa, Tong Liu, Hong Li, Peter J Romanienko, Michinari Nakamura.

Diets influence metabolism and disease susceptibility, with lysine acetyltransferases (KATs) serving as key regulators through acetyl-CoA. We have previously demonstrated that a ketogenic diet alleviates cardiac pathology, though the underlying mechanisms remain largely unknown. Here we show that KAT6A acetylation is crucial for mitochondrial function and cell growth. Proteomic analysis revealed that KAT6A is acetylated at lysine (K)816 in the hearts of mice fed a ketogenic diet under hypertension, which enhances its interaction with AMPK regulatory subunits. RNA-sequencing analysis demonstrated that the KAT6A acetylation-mimetic mutant stimulates AMPK signaling in cardiomyocytes. Moreover, the acetylation-mimetic mutant mitigated phenylephrine-induced mitochondrial dysfunction and cardiomyocyte hypertrophy via AMPK activation. However, KAT6A-K816R acetylation-resistant knock-in mice unexpectedly exhibited smaller hearts with enhanced AMPK activity, conferring protection against neurohumoral stress-induced cardiac hypertrophy and remodeling. These findings indicate that KAT6A regulates metabolism and cellular growth by interacting with and modulating AMPK activity through K816-acetylation in a cell type-specific manner.

DOI: https://doi.org/10.1101/2025.01.14.633047
Sci Adv. 2025 Jan 24. 11(4): eadq9301

Mitochondrial fatty acid oxidation regulates monocytic type I interferon signaling via histone acetylation.

Jing Wu, Komudi Singh, Vivian Shing, Anand Gupta, Brett C Arenberg, Rebecca D Huffstutler, Duck-Yeon Lee, Michael N Sack.

Although lipid-derived acetyl-coenzyme A (CoA) is a major carbon source for histone acetylation, the contribution of fatty acid β-oxidation (FAO) to this process remains poorly characterized. To investigate this, we generated mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1, distal FAO enzyme) knockout macrophages. 13C-carbon tracing confirmed reduced FA-derived carbon incorporation into histone H3, and RNA sequencing identified diminished interferon-stimulated gene expression in the absence of ACAT1. Chromatin accessibility at the Stat1 locus was diminished in ACAT1-/- cells. Chromatin immunoprecipitation analysis demonstrated reduced acetyl-H3 binding to Stat1 promoter/enhancer regions, and increasing histone acetylation rescued Stat1 expression. Interferon-β release was blunted in ACAT1-/- and recovered by ACAT1 reconstitution. Furthermore, ACAT1-dependent histone acetylation required an intact acetylcarnitine shuttle. Last, obese subjects' monocytes exhibited increased ACAT1 and histone acetylation levels. Thus, our study identifies an intriguing link between FAO-mediated epigenetic control of type I interferon signaling and uncovers a potential mechanistic nexus between obesity and type I interferon signaling.

DOI: https://doi.org/10.1126/sciadv.adq9301
Cell Mol Life Sci. 2025 Jan 21. 82(1): 45

Sirtuin 2 exacerbates renal tubule injury and inflammation in diabetic mice via deacetylation of c-Jun/c-Fos.

Li Chen, Dan Li, Zishun Zhan, Jingjing Quan, Juan Peng, Zhijun Huang, Bin Yi.

  Diabetic nephropathy (DN) is a serious complication of diabetes, and inflammation plays a crucial role. Sirtuin 2 (SIRT2), a NAD+-dependent deacetylase, which is involved in the regulation of cell metabolism, proliferation and longevity through deacetylation. Our previous research showed a positive correlation between urinary SIRT2 levels and renal injury markers in DN patients. Therefore, this study explored the specific role of SIRT2 in DN and its regulatory relationship with inflammatory response. Increased expression of SIRT2 was observed in kidney tissues of DN mice and in HK2 cells induced by HG/PA. SIRT2 knockout mice alleviated microalbuminuria, inflammatory responses, and kidney damage induced by HFD/STZ. In HK2 cells, reducing SIRT2 expression or inhibiting its acetylase activity alleviated the inflammatory response induced by HG/PA, whereas overexpression of SIRT2 exacerbated this response. Further investigation revealed that SIRT2 directly interacts with c-Jun/c-Fos, promoting their deacetylation. And inhibitors of c-Jun/c-Fos partially reversed the upregulation of inflammatory factors caused by SIRT2 overexpression. Meanwhile, disrupting SIRT2 reduced the binding activity between AP-1 and the MCP-1 promoter, while overexpressing SIRT2 further increased their binding activity in HK2 cells. Interestingly, SIRT2 increased its phosphorylation while deacetylating c-Jun, leading to nuclear accumulation of p-c-Jun. In conclusion, SIRT2 knockout can alleviate kidney injury and inflammatory response in HFD/STZ mice. The mechanism is related to the increased acetylation of c-Jun/c-Fos in renal tubular epithelial cells, accompanied by crosstalk between c-Jun phosphorylation and acetylation. Blocking SIRT2 could therefore be a potential therapeutic target for DN.

Keywords:  Acetylation/deacetylation; Crosstalk; Diabetic nephropathy; HK2 cell; MCP-1

DOI:  https://doi.org/10.1007/s00018-024-05567-8
Sci Rep. 2025 Jan 23. 15(1): 2949

Constitutive expression of Cas9 and rapamycin-inducible Cre recombinase facilitates conditional genome editing in Plasmodium berghei.

Samhita Das, Tanaya Unhale, Carine Marinach, Belsy Del Carmen Valeriano Alegria, Camille Roux, Hélène Madry, Badreddine Mohand Oumoussa, Rogerio Amino, Shiroh Iwanaga, Sylvie Briquet, Olivier Silvie.

  Malaria is caused by protozoan parasites of the genus Plasmodium and remains a global health concern. The parasite has a highly adaptable life cycle comprising successive rounds of asexual replication in a vertebrate host and sexual maturation in the mosquito vector Anopheles. Genetic manipulation of the parasite has been instrumental for deciphering the function of Plasmodium genes. Conventional reverse genetic tools cannot be used to study essential genes of the asexual blood stages, thereby necessitating the development of conditional strategies. Among various such strategies, the rapamycin-inducible dimerisable Cre (DiCre) recombinase system emerged as a powerful approach for conditional editing of essential genes in human-infecting P. falciparum and in the rodent malaria model parasite P. berghei. We previously generated a DiCre-expressing P. berghei line and validated it by conditionally deleting several essential asexual stage genes, revealing their important role also in sporozoites. Another potent tool is the CRISPR/Cas9 technology, which has enabled targeted genome editing with higher accuracy and specificity and greatly advanced genome engineering in Plasmodium spp. Here, we developed new P. berghei parasite lines by integrating the DiCre cassette and a fluorescent marker in parasites constitutively expressing Cas9. Owing to the dual integration of CRISPR/Cas9 and DiCre, these new lines allow unparalleled levels of gene modification and conditional regulation simultaneously. To illustrate the versatility of this new tool, we conditionally knocked out the essential gene encoding the claudin-like apicomplexan micronemal protein (CLAMP) in P. berghei and confirmed the role of CLAMP during invasion of erythrocytes.

Keywords:   Plasmodium ; CRISPR; Conditional mutagenesis; Malaria

DOI:  https://doi.org/10.1038/s41598-025-87114-4
Biochemistry. 2025 Jan 22.

Glutamine Synthetase: Diverse Regulation and Functions of an Ancient Enzyme.

Markus C B Tecson, Cyrina Geluz, Yuly Cruz, Eric R Greene.

Glutamine synthetase (GS) is a ubiquitous enzyme central to nitrogen metabolism, catalyzing the ATP-dependent formation of glutamine from glutamate and ammonia. Positioned at the intersection of nitrogen metabolism with carbon metabolism, the activity of GS is subject to sophisticated regulation. While the intricate regulatory pathways that govern Escherichia coli GS were established long ago, recent work has demonstrated that homologues are controlled by multiple distinct regulatory patterns, such as the metabolite induced oligomeric state formation in archaeal GS by 2-oxoglutarate. Such work was enabled in large part by advances in cryo-electron microscopy (cryoEM) that allowed greater structural access to this large enzyme complex, such as assessment of the large heterogeneous oligomeric states of GS and protein-interactor-GS complexes. This perspective highlights recent advances in understanding GS regulation, focusing on the dynamic interplay between its oligomeric state, metabolite binding, and protein interactors. These interactions modulate GS activity, influencing cellular processes such as nitrogen assimilation, carbon metabolism, and stress responses. Furthermore, we explore the emerging concept of GS "moonlighting" functions, revealing its roles in palmitoylation, cell cycle regulation, and ion channel modulation. These diverse functions highlight a newfound versatility of GS beyond its primary catalytic role and suggest complex roles in health and disease that warrant further study.

DOI: https://doi.org/10.1021/acs.biochem.4c00763