bims-toxgon 2023-10-15 papers

bims-toxgon

Biomed News

on Toxoplasma gondii metabolism

Issue of 2023–10–15
seventeen papers selected by
Lakesh Kumar, BITS Pilani

A newly characterized dense granule protein (GRA76) is important for the growth and virulence of Toxoplasma gondii.
The SUN-like protein TgSLP1 is essential for nuclear division in the apicomplexan parasite Toxoplasma gondii.
TgLaforin, a glucan phosphatase, reveals the dynamic role of storage polysaccharides in Toxoplasma gondii tachyzoites and bradyzoites.
High-throughput identification of Toxoplasma gondii effector proteins that target host cell transcription.
Phosphoproteomic Analysis Reveals the Predominating Cellular Processes and the Involved Key Phosphoproteins Essential for the Proliferation of Toxoplasma gondii.
Proteomic profile of Toxoplasma gondii stress granules by high resolution mass spectrometry.
Plasmodium falciparum OPA3-like protein (PfOPA3) is essential for maintenance of mitochondrial homeostasis and parasite proliferation.
Rapid and visual detection of Toxoplasma gondii oocyst in cat feces using loop-mediated isothermal amplification (LAMP) assay.
Multiomics and bioinformatics identify differentially expressed effectors in the brain of Toxoplasma gondii infected masked palm civet.
Deacetylation by sirtuins is important for Aspergillus fumigatus pathogenesis and virulence.
SIRT1 is a regulator of autophagy: implications for the progression and treatment of myocardial ischemia-reperfusion.
Mitochondrion of the Trypanosoma brucei long slender bloodstream form is capable of ATP production by substrate-level phosphorylation.
AMPK Regulates Phagophore-to-Autophagosome Maturation.
Exonuclease Xrn1 regulates TORC1 signaling in response to SAM availability.
Microrchidia 2/Histone Deacetylase 1 Complex Regulates E-cadherin Gene Expression and Function.
Research Progress on Histone Deacetylases Regulating Programmed Cell Death in Atherosclerosis.
Interaction of Klotho and sirtuins.

Int J Parasitol. 2023 Oct 11. pii: S0020-7519(23)00191-1. [Epub ahead of print]

A newly characterized dense granule protein (GRA76) is important for the growth and virulence of Toxoplasma gondii.

Xiao-Nan Zheng, Li-Xiu Sun, Hany M Elsheikha, Ting-Ting Li, Jin Gao, Xiao-Jing Wu, Zhi-Wei Zhang, Meng Wang, Bao-Quan Fu, Xing-Quan Zhu, Jin-Lei Wang.

  Pathogenicity of the zoonotic pathogen Toxoplasma gondii largely depends on the secretion of effector proteins into the extracellular milieu and host cell cytosol, including the dense granule proteins (GRAs). The protein-encoding gene TGME49_299780 was previously identified as a contributor to parasite fitness. However, its involvement in parasite growth, virulence and infectivity in vitro and in vivo remains unknown. Here, we comprehensively examined the role of this new protein, termed GRA76, in parasite pathogenicity. Subcellular localization revealed high expression of GRA76 in tachyzoites inside the parasitophorous vacuole (PV). However, its expression was significantly decreased in bradyzoites. A CRISPR-Cas9 approach was used to knock out the gra76 gene in the T. gondii type I RH strain and type II Pru strain. The in vitro plaque assays and intracellular replication showed the involvement of GRA76 in replication of RH and Pru strains. Deletion of the gra76 gene significantly decreased parasite virulence, and reduced the brain cyst burden in mice. Using RNA sequencing, we detected a significant increase in the expression of bradyzoite-associated genes such as BAG1 and LDH2 in the PruΔgra76 strain compared with the wild-type Pru strain. Using an in vitro bradyzoite differentiation assay, we showed that loss of GRA76 significantly increased the propensity for parasites to form bradyzoites. Immunization with PruΔgra76 conferred partial protection against acute and chronic infection in mice. These findings show the important role of GRA76 in the pathogenesis of T. gondii and highlight the potential of PruΔgra76 as a candidate for a live-attenuated vaccine.

Keywords:  Bradyzoite differentiation; Dense granule proteins; GRA76; Replication; Toxoplasma gondii; Vaccine; Virulence

DOI:  https://doi.org/10.1016/j.ijpara.2023.09.001
J Cell Sci. 2023 Oct 10. pii: jcs.260337. [Epub ahead of print]

The SUN-like protein TgSLP1 is essential for nuclear division in the apicomplexan parasite Toxoplasma gondii.

Mirjam Wagner, Yuan Song, Elena Jiménez-Ruiz, Sonja Härtle, Markus Meissner.

  Connections between the nucleus and the cytoskeleton are important for positioning and division of the nucleus. In most eukaryotes, the LINC complex (Linker of Nucleoskeleton and Cytoskeleton) spans the outer and inner nuclear membranes and connects the nucleus to the cytoskeleton. In opisthokonts, it is composed of Klarsicht, ANC-1 and Syne Homology (KASH) domain proteins and Sad1 and UNC-84 (SUN) domain proteins. Given that the nucleus is positioned at the posterior pole of Toxoplasma gondii, we speculated that apicomplexan parasites must have a similar mechanism that integrates the nucleus and the cytoskeleton. Here, we identified three UNC family proteins in the genome of the apicomplexan parasite T. gondii. While the UNC-50 protein TgUNC1 localised to the Golgi and appeared to be not essential for the parasite, the SUN domain protein TgSLP2 showed a diffuse pattern throughout the parasite. The second SUN domain protein, TgSLP1, was expressed in a cell cycle-dependent manner and was localised close to the mitotic spindle and, more detailed, at the kinetochore. We demonstrate that conditional knockout of TgSLP1 leads to failure of nuclear division and loss of centrocone integrity.

Keywords:   Toxoplasma ; LINC; Parasite; Replication; SUN protein

DOI:  https://doi.org/10.1242/jcs.260337
bioRxiv. 2023 Sep 29. pii: 2023.09.29.560185. [Epub ahead of print]

TgLaforin, a glucan phosphatase, reveals the dynamic role of storage polysaccharides in Toxoplasma gondii tachyzoites and bradyzoites.

Robert D Murphy, Cortni A Troublefield, Joy S Miracle, Lyndsay E A Young, Corey O Brizzee, Animesh Dhara, Ramon C Sun, Craig W Vander Kooi, Matthew S Gentry, Anthony P Sinai.

The asexual stages of Toxoplasma gondii are defined by the rapidly growing tachyzoite during the acute infection and by the slow growing bradyzoite housed within tissue cysts during the chronic infection. These stages represent unique physiological states, each with distinct glucans reflecting differing metabolic needs. A defining feature of T. gondii bradyzoites is the presence of insoluble storage glucans known as amylopectin granules (AGs) that are believed to play a role in reactivation, but their functions during the chronic infection remain largely unexplored. More recently, the presence of storage glucans has been recognized in tachyzoites where their precise function and architecture have yet to be fully defined. Importantly, the T. gondii genome encodes activities needed for glucan turnover: a glucan phosphatase (TgLaforin; TGME49_205290) and a glucan kinase (TgGWD; TGME49_214260) that catalyze a cycle of reversible glucan phosphorylation required for glucan degradation by amylases. The expression of these enzymes in tachyzoites supports the existence of a storage glucan, evidence that is corroborated by specific labeling with the anti-glycogen antibody IV58B6. Disruption of reversible glucan phosphorylation via a CRISPR/Cas9 knockout (KO) of TgLaforin revealed no growth defects under nutrient-replete conditions in tachyzoites. However, the growth of TgLaforin-KO tachyzoites was severely stunted when starved of glutamine, even under glucose replete conditions. The loss of TgLaforin also resulted in the attenuation of acute virulence in mice accompanied by a lower cyst burden. Defective cyst formation due to profound changes in AG morphology was also observed in TgLaforin-KO parasites, both in vitro and in vivo . Together, these data demonstrate the importance of glucan turnover across the T. gondii asexual cycle. These findings, alongside our previously identified class of small molecules that inhibit TgLaforin, implicate reversible glucan phosphorylation as a legitimate target for the development of new drugs against chronic T. gondii infections.

DOI: https://doi.org/10.1101/2023.09.29.560185
Cell Host Microbe. 2023 Oct 11. pii: S1931-3128(23)00370-0. [Epub ahead of print]31(10): 1748-1762.e8

High-throughput identification of Toxoplasma gondii effector proteins that target host cell transcription.

Simon Butterworth, Kristina Kordova, Sambamurthy Chandrasekaran, Kaitlin K Thomas, Francesca Torelli, Eloise J Lockyer, Amelia Edwards, Robert Goldstone, Anita A Koshy, Moritz Treeck.

  Intracellular pathogens and other endosymbionts reprogram host cell transcription to suppress immune responses and recalibrate biosynthetic pathways. This reprogramming is critical in determining the outcome of infection or colonization. We combine pooled CRISPR knockout screening with dual host-microbe single-cell RNA sequencing, a method we term dual perturb-seq, to identify the molecular mediators of these transcriptional interactions. Applying dual perturb-seq to the intracellular pathogen Toxoplasma gondii, we are able to identify previously uncharacterized effector proteins and directly infer their function from the transcriptomic data. We show that TgGRA59 contributes to the export of other effector proteins from the parasite into the host cell and identify an effector, TgSOS1, that is necessary for sustained host STAT6 signaling and thereby contributes to parasite immune evasion and persistence. Together, this work demonstrates a tool that can be broadly adapted to interrogate host-microbe transcriptional interactions and reveal mechanisms of infection and immune evasion.

Keywords:  CRISPR screening; STAT6; Toxoplasma gondii; effector proteins; host-microbe interactions; host-pathogen interactions; immune evasion; perturb-seq; single-cell RNA sequencing

DOI:  https://doi.org/10.1016/j.chom.2023.09.003
Acta Parasitol. 2023 Oct 11.

Phosphoproteomic Analysis Reveals the Predominating Cellular Processes and the Involved Key Phosphoproteins Essential for the Proliferation of Toxoplasma gondii.

Xin-Zhu Chen, Rui-Xue Bai, Fei-Yu Qin, Hong-Juan Peng, Jin-Feng Ren, Lang Hu, Yu-di Li, Cheng He.

   PURPOSE: To explore the essential roles of phosphorylation in mediating the proliferation of T. gondii in its cell lytic life.
METHODS: We profiled the phosphoproteome data of T. gondii residing in HFF cells for 2 h and 6 h, representing the early- and late-stages of proliferation (ESP and LSP) within its first generation of division.
RESULTS: We identified 70 phosphoproteins, among which 8 phosphoproteins were quantified with the phosphorylation level significantly regulated. While only two of the eight phosphoproteins, GRA7 and TGGT1_242070, were significantly down-regulated at the transcriptional level in the group of LSP vs. ESP. Moreover, GO terms correlated with host membrane component were significantly enriched in the category of cellular component, suggesting phosphoprotein played important roles in acquiring essential substance from host cell via manipulating host membrane. Further GO analysis in the categories of molecular function and biological process and pathway analysis revealed that the cellular processes of glucose and lipid metabolism were regulated by T. gondii phosphoproteins such as PMCAA1, LIPIN, Pyk1 and ALD. Additionally, several phosphoproteins were enriched at the central nodes in the protein-protein interaction network, which may have essential roles in T. gondii proliferation including GAP45, MLC1, fructose-1,6-bisphosphate aldolase, GRAs and so on.
CONCLUSION: This study revealed the main cellular processes and key phosphoproteins crucial for the intracellular proliferation of T. gondii, which would provide clues to explore the roles of phosphorylation in regulating the development of tachyzoites and new insight into the mechanism of T. gondii development in vitro.

Keywords:  Cellular process; Phosphoproteins; Phosphoproteome analysis; Proliferation; Toxoplasma gondii

DOI:  https://doi.org/10.1007/s11686-023-00720-y
Can J Microbiol. 2023 Oct 12.

Proteomic profile of Toxoplasma gondii stress granules by high resolution mass spectrometry.

Scott Roscoe, Yue Gou, Otis Vacratsis, Sirinart Ananvoranich.

Ribonucleoprotein granules are bio-condensates which form a diverse group of dynamic membrane-less organelles implicated in several cellular functions including stress response and cellular survival. In Toxoplasma gondii, a type of bio-condensates referred to as stress granules (SGs) are formed prior to the parasites' egress from the host cell and are implicated in the survival and invasion competency of extracellular tachyzoites. We used paraformaldehyde to fix and cross-link SG proteins to allow purification by centrifugation and analysis by mass spectrometry. We profiled protein components of SGs at 10 min and 30 min post-egress when parasite's invasion ability is significantly diminished. Thirty-three proteins were identified from 10-min SGs, and additional 43 proteins were identified from 30-min SGs. Notably, common SG components such as proteins with intrinsically disordered domains were not identified. Gene ontology analysis of both 10-min and 30-min SGs shows that overall molecular functions of SGs' proteins are ATP-binding, GTP-binding and GTPase activity. Discernable differences between 10-min and 30-min SGs are in the proportions of translation and microtubule related proteins. 10-min SGs have a higher proportion of microtubule-related proteins and a lower proportion of ribosome related proteins, while a reverse correlation was identified for those of 30-min. It remains to be investigated whether this reverse correlation contributes to the ability of extracellular tachyzoites to reinvade host cells.

DOI: https://doi.org/10.1139/cjm-2023-0091
FASEB J. 2023 Nov;37(11): e23235

Plasmodium falciparum OPA3-like protein (PfOPA3) is essential for maintenance of mitochondrial homeostasis and parasite proliferation.

Monika Narwal, Shilpi Jain, Sumit Rathore, Asif Mohmmed.

  Metabolic pathways and proteins responsible for maintaining mitochondrial dynamics and homeostasis in the Plasmodium parasite, the causative agent of malaria, remain to be elucidated. Here, we identified and functionally characterized a novel OPA3-like domain-containing protein in P. falciparum (PfOPA3). We show that PfOPA3 is expressed in the intraerythrocytic stages of the parasite and localizes to the mitochondria. Inducible knock-down of PfOPA3 using GlmS ribozyme hindered the normal intraerythrocytic cycle of the parasites; specifically, PfOPA3-iKD disrupted parasite development as well as parasite division and segregation at schizont stages, which resulted in a drastic reduction in the number of merozoites progenies. Parasites lacking PfOPA3 show severe defects in the development of functional mitochondria; the mitochondria showed reduced activity of mtETC but not ATP synthesis, as evidenced by reduced activity of complex III of the mtETC, and increased sensitivity for drugs targeting DHODH as well as complex III, but not to the drugs targeting complex V. Further, PfOPA3 downregulation leads to reduction in the level of mitochondrial proton transport uncoupling protein (PfUCP) to compensate reduced activity of complex III and maintain proton efflux across the inner membrane. The reduced activity of DHODH, which is responsible for pyrimidine biosynthesis required for nuclear DNA synthesis, resulted in a significant reduction in parasite nuclear division and generation of progeny. In conclusion, we show that PfOPA3 is essential for the functioning of mtETC and homeostasis required for the development of functional mitochondria as well as for parasite segregation, and thus PfOPA3 is crucial for parasite survival during blood stages.

Keywords:   Plasmodium ; OPA3; malaria; mitochondrial homeostasis; mtETC; schizogony

DOI:  https://doi.org/10.1096/fj.202201386RR
Sci Rep. 2023 Oct 12. 13(1): 17269

Rapid and visual detection of Toxoplasma gondii oocyst in cat feces using loop-mediated isothermal amplification (LAMP) assay.

Lingwei Sheng, Qiqi Xue, Sijia Xu, Fang Can, Ning Yao, Minghui Zou, Qiao Teng, Yuanyuan Li, Saeed El-Ashram, Yongsheng Ji, Jinhong Zhao.

Toxoplasma gondii is an obligate parasitic protozoon that transmits to animals and humans via ingested food. Cats that act as T. gondii's final hosts play a critical role in T. gondii transmission by shedding millions of oocysts. Timely diagnosis of infected cats is essential for preventing toxoplasmosis because oocysts are a putative T. gondii source in epidemiology. We developed a new visual LAMP assay targeting the B1 gene to analyze single oocysts in cat feces in this study. The amplification result could be visually estimated based on the color change. LAMP assay analytical sensitivity was 101 copies/µL for the B1 gene plasmid, which was tenfold better than the PCR reaction. There were no cross-reactions with other parasites. The LAMP assay can detect a single T. gondii oocyst in 200 mg of cat feces. The LAMP assay detected a single oocyst in 200 mg cat feces at a higher rate than the PCR assay (83.3% vs. 50.0%).

DOI: https://doi.org/10.1038/s41598-023-44658-7
Front Cell Infect Microbiol. 2023 ;13 1267629

Multiomics and bioinformatics identify differentially expressed effectors in the brain of Toxoplasma gondii infected masked palm civet.

Hao Yuan, Tiantian Jiang, Wei-Dong Zhang, Zipeng Yang, Shengjun Luo, Xiaohu Wang, Xiaojing Zhu, Shuting Qi, Yasser S Mahmmod, Xiu-Xiang Zhang, Zi-Guo Yuan.

   Introduction: The masked palm civet (Paguma larvata) serves as a reservoir in transmitting pathogens, such as Toxoplasma gondii, to humans. However, the pathogenesis of T. gondii infection in masked palm civets has not been explored. We studied the molecular changes in the brain tissue of masked palm civets chronically infected with T. gondii ME49.
Methods: The differentially expressed proteins in the brain tissue were investigated using iTRAQ and bioinformatics.
Results: A total of 268 differential proteins were identified, of which 111 were upregulated and 157 were downregulated. KEGG analysis identified pathways including PI3K-Akt signaling pathway, proteoglycans in cancer, carbon metabolism, T-cell receptor signaling pathway. Combing transcriptomic and proteomics data, we identified 24 genes that were differentially expressed on both mRNA and protein levels. The top four upregulated proteins were REEP3, REEP4, TEP1, and EEPD1, which was confirmed by western blot and immunohistochemistry. KEGG analysis of these 24 genes identified signaling cascades that were associated with small cell lung cancer, breast cancer, Toll-like receptor signaling pathway, Wnt signaling pathways among others. To understand the mechanism of the observed alteration, we conducted immune infiltration analysis using TIMER databases which identified immune cells that are associated with the upregulation of these proteins. Protein network analysis identified 44 proteins that were in close relation to all four proteins. These proteins were significantly enriched in immunoregulation and cancer pathways including PI3K-Akt signaling pathway, Notch signaling pathway, chemokine signaling pathway, cell cycle, breast cancer, and prostate cancer. Bioinformatics utilizing two cancer databases (TCGA and GEPIA) revealed that the four genes were upregulated in many cancer types including glioblastoma (GBM). In addition, higher expression of REEP3 and EEPD1 was associated with better prognosis, while higher expression of REEP4 and TEP1 was associated with poor prognosis in GBM patients.
Discussion: We identified the differentially expressed genes in the brain of T. gondii infected masked palm civets. These genes were associated with various cellular signaling pathways including those that are immune- and cancer-related.

Keywords:  Toxoplasma gondii; glioblastoma; masked palm civet; proteomics; transcriptome

DOI:  https://doi.org/10.3389/fcimb.2023.1267629
bioRxiv. 2023 Sep 25. pii: 2023.09.25.558961. [Epub ahead of print]

Deacetylation by sirtuins is important for Aspergillus fumigatus pathogenesis and virulence.

Natália Sayuri Wassano, Gabriela Bassi da Silva, Artur Honorato Reis, Jaqueline A Gerhardt, Everton P Antoniel, Daniel Akiyama, Caroline Patini Rezende, Leandro Xavier Neves, Elton Vasconcelos, Fernanda L Figueiredo, Fausto Almeida, Patrícia Alves de Castro, Camila Figueiredo Pinzan, Gustavo H Goldman, Adriana F P Leme, Taicia P Fill, Nilmar S Moretti, André Damasio.

Protein acetylation is a crucial post-translational modification that controls gene expression and a variety of biological processes. Sirtuins, a prominent class of NAD + -dependent lysine deacetylases, serve as key regulators of protein acetylation and gene expression in eukaryotes. In this study, six single knockout strains of fungal pathogen Aspergillus fumigatus were constructed, in addition to a strain lacking all predicted sirtuins (SIRTKO). Phenotypic assays suggest that sirtuins are involved in cell wall integrity, secondary metabolite production, thermotolerance, and virulence. AfsirE deletion resulted in attenuation of virulence, as demonstrated in murine and Galleria infection models. The absence of AfSirE leads to altered acetylation status of proteins, including histones and non-histones, resulting in significant changes in the expression of genes associated with secondary metabolism, cell wall biosynthesis, and virulence factors. These findings encourage testing sirtuin inhibitors as potential therapeutic strategies to combat A. fumigatus infections or in combination therapy with available antifungals.

DOI: https://doi.org/10.1101/2023.09.25.558961
Pharmacol Res. 2023 Oct 09. pii: S1043-6618(23)00313-4. [Epub ahead of print] 106957

SIRT1 is a regulator of autophagy: implications for the progression and treatment of myocardial ischemia-reperfusion.

Xiaoqing Ding, Chenyu Zhu, Wenhong Wang, Mengying Li, Chunwei Ma, Binghong Gao.

  SIRT1 is a highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase. It is involved in the regulation of various pathophysiological processes, including cell proliferation, survival, differentiation, autophagy, and oxidative stress. Therapeutic activation of SIRT1 protects the heart and cardiomyocytes from pathology-related stress, particularly myocardial ischemia/reperfusion (I/R). Autophagy is an important metabolic pathway for cell survival during energy or nutrient deficiency, hypoxia, or oxidative stress. Autophagy is a double-edged sword in myocardial I/R injury. The activation of autophagy during the ischemic phase removes excess metabolic waste and helps ensure cardiomyocyte survival, whereas excessive autophagy during reperfusion depletes the cellular components and leads to autophagic cell death. Increasing research on I/R injury has indicated that SIRT1 is involved in the process of autophagy and regulates myocardial I/R. SIRT1 regulates autophagy through various pathways, such as the deacetylation of FOXOs, ATGs, and LC3. Recent studies have confirmed that SIRT1-mediated autophagy plays different roles at different stages of myocardial I/R injury. By targeting the mechanism of SIRT1-mediated autophagy at different stages of I/R injury, new small-molecule drugs, miRNA activators, or blockers can be developed. For example, resveratrol, sevoflurane, quercetin, and melatonin in the ischemic stage, coptisine, curcumin, berberine, and some miRNAs during reperfusion, were involved in regulating the SIRT1-autophagy axis, exerting a cardioprotective effect. Here, we summarize the possible mechanisms of autophagy regulation by SIRT1 in myocardial I/R injury and the related molecular drug applications to identify strategies for treating myocardial I/R injury.

Keywords:  SIRT1; autophagy; ischemia–reperfusion; molecular drugs; myocardial; myocardial I/R injury

DOI:  https://doi.org/10.1016/j.phrs.2023.106957
PLoS Pathog. 2023 Oct 11. 19(10): e1011699

Mitochondrion of the Trypanosoma brucei long slender bloodstream form is capable of ATP production by substrate-level phosphorylation.

Gergana Taleva, Michaela Husová, Brian Panicucci, Carolina Hierro-Yap, Erika Pineda, Marc Biran, Martin Moos, Petr Šimek, Falk Butter, Frédéric Bringaud, Alena Zíková.

The long slender bloodstream form Trypanosoma brucei maintains its essential mitochondrial membrane potential (ΔΨm) through the proton-pumping activity of the FoF1-ATP synthase operating in the reverse mode. The ATP that drives this hydrolytic reaction has long been thought to be generated by glycolysis and imported from the cytosol via an ATP/ADP carrier (AAC). Indeed, we demonstrate that AAC is the only carrier that can import ATP into the mitochondrial matrix to power the hydrolytic activity of the FoF1-ATP synthase. However, contrary to expectations, the deletion of AAC has no effect on parasite growth, virulence or levels of ΔΨm. This suggests that ATP is produced by substrate-level phosphorylation pathways in the mitochondrion. Therefore, we knocked out the succinyl-CoA synthetase (SCS) gene, a key mitochondrial enzyme that produces ATP through substrate-level phosphorylation in this parasite. Its absence resulted in changes to the metabolic landscape of the parasite, lowered virulence, and reduced mitochondrial ATP content. Strikingly, these SCS mutant parasites become more dependent on AAC as demonstrated by a 25-fold increase in their sensitivity to the AAC inhibitor, carboxyatractyloside. Since the parasites were able to adapt to the loss of SCS in culture, we also analyzed the more immediate phenotypes that manifest when SCS expression is rapidly suppressed by RNAi. Importantly, when performed under nutrient-limited conditions mimicking various host environments, SCS depletion strongly affected parasite growth and levels of ΔΨm. In totality, the data establish that the long slender bloodstream form mitochondrion is capable of generating ATP via substrate-level phosphorylation pathways.

DOI: https://doi.org/10.1371/journal.ppat.1011699
bioRxiv. 2023 Sep 30. pii: 2023.09.28.559981. [Epub ahead of print]

AMPK Regulates Phagophore-to-Autophagosome Maturation.

Carlo Barnaba, David G Broadbent, Gloria I Perez, Jens C Schmidt.

Autophagy is an important metabolic pathway that can non-selectively recycle cellular material or lead to targeted degradation of protein aggregates or damaged organelles. Autophagosome formation starts with autophagy factors accumulating on lipid vesicles containing ATG9. These phagophores attach to donor membranes, expand via ATG2-mediated lipid transfer, capture cargo, and mature into autophagosomes, ultimately fusing with lysosomes for their degradation. Autophagy can be activated by nutrient stress, for example by a reduction in the cellular levels of amino acids. In contrast, how autophagy is regulated by low cellular ATP levels via the AMP-activated protein kinase (AMPK), an important therapeutic target, is less clear. Using live-cell imaging and an automated image analysis pipeline, we systematically dissect how nutrient starvation regulates autophagosome biogenesis. We demonstrate that glucose starvation downregulates autophagosome maturation by AMPK mediated inhibition of phagophores tethering to donor membranes. Our results clarify AMPK's regulatory role in autophagy and highlight its potential as a therapeutic target to reduce autophagy.

DOI: https://doi.org/10.1101/2023.09.28.559981
bioRxiv. 2023 Sep 28. pii: 2023.09.28.559955. [Epub ahead of print]

Exonuclease Xrn1 regulates TORC1 signaling in response to SAM availability.

Madeline M McGinnis, Benjamin M Sutter, Samira Jahangiri, Benjamin P Tu.

Autophagy is a conserved process of cellular self-digestion that promotes survival during nutrient stress. In yeast, methionine starvation is sufficient to induce autophagy. One pathway of autophagy induction is governed by the SEACIT complex, which regulates TORC1 activity in response to amino acids through the Rag GTPases Gtr1 and Gtr2. However, the precise mechanism by which SEACIT senses amino acids and regulates TORC1 signaling remains incompletely understood. Here, we identify the conserved 5'-3' RNA exonuclease Xrn1 as a surprising and novel regulator of TORC1 activity in response to methionine starvation. This role of Xrn1 is dependent on its catalytic activity, but not on degradation of any specific class of mRNAs. Instead, Xrn1 modulates the nucleotide-binding state of the Gtr1/2 complex, which is critical for its interaction with and activation of TORC1. This work identifies a critical role for Xrn1 in nutrient sensing and growth control that extends beyond its canonical housekeeping function in RNA degradation and indicates an avenue for RNA metabolism to function in amino acid signaling into TORC1.

DOI: https://doi.org/10.1101/2023.09.28.559955
Biochem J. 2023 Oct 10. pii: BCJ20230304. [Epub ahead of print]

Microrchidia 2/Histone Deacetylase 1 Complex Regulates E-cadherin Gene Expression and Function.

Liz Thomas, Namita Chutani, Krishna R, Asha S Nair, Nanda Kumar Yellapu, Karyala Prashanthi, Suresh Babu Pakala.

  Although Microrchidia 2 (MORC2) is widely overexpressed in human malignancies and linked to cancer cell proliferation, metabolism, and metastasis, the mechanism of action of MORC2 in cancer cell migration and invasion is yet undeciphered. Here, we identified for the first time that MORC2, a chromatin remodeler, regulates E-cadherin expression and, subsequently regulates breast cancer cell migration and invasion. We observed a negative correlation between the expression levels of MORC2 and E-cadherin in breast cancer. Further, the overexpression of MORC2 resulted in decreased expression levels of E-cadherin. In addition, coimmunoprecipitation and chromatin immunoprecipitation assays revealed that MORC2 interacts with HDAC1 and gets recruited onto the E-cadherin promoter to inhibit its transcription, thereby suppress its expression. Consequently, knockdown of HDAC1 in MORC2-overexpressing cells led to reduced cancer cell migration and invasion. Interestingly, we noticed that MORC2 regulated glucose metabolism via c-Myc, and LDHA, also modulates the expression of E-cadherin. Collectively, these results demonstrate for the first time a mechanistic role for MORC2 as an upstream regulator of E-cadherin expression and its associated functions in breast cancer.

Keywords:  Breast Cancer; E-cadherin; Glucose metabolism; HDAC1; MORC2

DOI:  https://doi.org/10.1042/BCJ20230304
J Cardiovasc Transl Res. 2023 Oct 11.

Research Progress on Histone Deacetylases Regulating Programmed Cell Death in Atherosclerosis.

Gang Zhou, Yanfang Liu, Hui Wu, Dong Zhang, Qingzhuo Yang, Yi Li.

  Histone deacetylases (HDACs) are epigenetic modifying enzyme that is closely related to chromatin structure and gene transcription, and numerous studies have found that HDACs play an important regulatory role in atherosclerosis disease. Apoptosis, autophagy and programmed necrosis as the three typical programmed cell death modalities that can lead to cell loss and are closely related to the developmental process of atherosclerosis. In recent years, accumulating evidence has shown that the programmed cell death mediated by HDACs is increasingly important in the pathophysiology of atherosclerosis. This paper first gives a brief overview of HDACs, the mechanism of programmed cell death, and their role in atherosclerosis, and then further elaborates on the role and mechanism of HDACs in regulating apoptosis, autophagy, and programmed necrosis in atherosclerosis, respectively, to provide new effective measures and theoretical basis for the prevention and treatment of atherosclerosis.

Keywords:  Apoptosis; Atherosclerosis; Autophagy; Ferroptosis; Histone deacetylases; Programmed cell death; Pyroptosis

DOI:  https://doi.org/10.1007/s12265-023-10444-z
Exp Gerontol. 2023 Oct 06. pii: S0531-5565(23)00227-9. [Epub ahead of print]182 112306

Interaction of Klotho and sirtuins.

Farzaneh Rostamzadeh, Yasamin Moosavi-Saeed, Mahboobeh Yeganeh-Hajahmadi.

   OBJECTIVE: In this article, we review the articles that have reported the interaction between Klotho and sirtuins.
RECENT FINDINGS: Sirtuins are a family of histone deacetylase enzymes that are considered to be the main regulators of biological processes. This family is one of the essential factors for postponing aging and increasing the life span of organisms. Sirtuins play a role in regulating the function of various cellular processes such as cellular metabolism, oxidative stress, apoptosis, and inflammation. It has also been shown that various diseases are related to these enzymes. Klotho is an anti-aging protein that exists as a membrane protein as well as a soluble circulating form. The membrane type of this protein acts as a co-receptor of the FGF endocrine family. It has been shown that the Klotho gene is related to age-related diseases, including osteoporosis, coronary artery, brain diseases, diabetes, etc. At the same time, it is difficult to separate the actions of Klotho and endocrine FGFs. Several studies have shown that Klotho and sirtuins interact with each other at different regulatory levels. However, it is necessary to carry out more in-vivo investigations to create new windows towards the treatment or prevention of various diseases.

Keywords:  Aging; Cell signaling; Interaction; Klotho; Sirtuins

DOI:  https://doi.org/10.1016/j.exger.2023.112306