bims-mepmim 2024-01-21 papers

bims-mepmim

Biomed News

on Metabolites in pathological microenvironments and immunometabolism

Issue of 2024–01–21
twenty-two papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

Gpcpd1-GPC metabolic pathway is dysfunctional in aging and its deficiency severely perturbs glucose metabolism.
Increased iron uptake by splenic hematopoietic stem cells promotes TET2-dependent erythroid regeneration.
Residual Complex I activity and amphidirectional Complex II operation support glutamate catabolism through mtSLP in anoxia.
Glucose-derived glutamate drives neuronal terminal differentiation in vitro.
Acetyl-CoA production by Mediator-bound 2-ketoacid dehydrogenases boosts de novo histone acetylation and is regulated by nitric oxide.
Thiol starvation triggers melanoma state switching in an ATF4 and NRF2-dependent manner.
A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors.
MITOL deficiency triggers hematopoietic stem cell apoptosis via ER stress response.
Amyloid beta 42 alters cardiac metabolism and impairs cardiac function in male mice with obesity.
Bone marrow monocytes sustain NK cell-poiesis during non-alcoholic steatohepatitis.
The orphan G protein-coupled receptor 141 expressed in myeloid cells functions as an inflammation suppressor.
Depletion of SAM leading to loss of heterochromatin drives muscle stem cell ageing.
The CUL5 E3 ligase complex negatively regulates central signaling pathways in CD8+ T cells.
Catalytic mechanism of trans-2-enoyl-CoA reductases in the fatty acid elongation cycle and its cooperative action with fatty acid elongases.
In situ architecture of Opa1-dependent mitochondrial cristae remodeling.
O6-methylguanine DNA methyltransferase regulates β-glucan-induced trained immunity of macrophages via farnesoid X receptor and AMPK.
AMPKα2 regulates fasting-induced hyperketonemia by suppressing SCOT ubiquitination and degradation.
Tumor-educated Gr1+CD11b+ cells drive breast cancer metastasis via OSM/IL6-JAK-induced cancer cell plasticity.
Nutrient sensing in macrophages linked to reorganized tumor vasculature.
ATF4 expression in thermogenic adipocytes is required for cold-induced thermogenesis in mice via FGF21-independent mechanisms.
Mitochondrial stress activates YAP/TAZ through RhoA oxidation to promote liver injury.
Inhibition of xanthine oxidase by allopurinol suppresses HMGB1 secretion and ameliorates experimental asthma.

Nat Aging. 2024 Jan;4(1): 80-94

Gpcpd1-GPC metabolic pathway is dysfunctional in aging and its deficiency severely perturbs glucose metabolism.

Domagoj Cikes, Michael Leutner, Shane J F Cronin, Maria Novatchkova, Lorenz Pfleger, Radka Klepochová, Benjamin Lair, Marlène Lac, Camille Bergoglio, Nathalie Viguerie, Gerhard Dürnberger, Elisabeth Roitinger, Mihaela Grivej, Eric Rullman, Thomas Gustafsson, Astrid Hagelkruys, Geneviève Tavernier, Virginie Bourlier, Claude Knauf, Michael Krebs, Alexandra Kautzky-Willer, Cedric Moro, Martin Krssak, Michael Orthofer, Josef M Penninger.

Skeletal muscle plays a central role in the regulation of systemic metabolism during lifespan. With aging, this function is perturbed, initiating multiple chronic diseases. Our knowledge of mechanisms responsible for this decline is limited. Glycerophosphocholine phosphodiesterase 1 (Gpcpd1) is a highly abundant muscle enzyme that hydrolyzes glycerophosphocholine (GPC). The physiological functions of Gpcpd1 remain largely unknown. Here we show, in mice, that the Gpcpd1-GPC metabolic pathway is perturbed in aged muscles. Further, muscle-specific, but not liver- or fat-specific, inactivation of Gpcpd1 resulted in severely impaired glucose metabolism. Western-type diets markedly worsened this condition. Mechanistically, Gpcpd1 muscle deficiency resulted in accumulation of GPC, causing an 'aged-like' transcriptomic signature and impaired insulin signaling in young Gpcpd1-deficient muscles. Finally, we report that the muscle GPC levels are markedly altered in both aged humans and patients with type 2 diabetes, displaying a high positive correlation between GPC levels and chronological age. Our findings reveal that the muscle GPCPD1-GPC metabolic pathway has an important role in the regulation of glucose homeostasis and that it is impaired during aging, which may contribute to glucose intolerance in aging.

DOI: https://doi.org/10.1038/s43587-023-00551-6
Nat Commun. 2024 Jan 15. 15(1): 538

Increased iron uptake by splenic hematopoietic stem cells promotes TET2-dependent erythroid regeneration.

Yu-Jung Tseng, Yuki Kageyama, Rebecca L Murdaugh, Ayumi Kitano, Jong Hwan Kim, Kevin A Hoegenauer, Jonathan Tiessen, Mackenzie H Smith, Hidetaka Uryu, Koichi Takahashi, James F Martin, Md Abul Hassan Samee, Daisuke Nakada.

Hematopoietic stem cells (HSCs) are capable of regenerating the blood system, but the instructive cues that direct HSCs to regenerate particular lineages lost to the injury remain elusive. Here, we show that iron is increasingly taken up by HSCs during anemia and induces erythroid gene expression and regeneration in a Tet2-dependent manner. Lineage tracing of HSCs reveals that HSCs respond to hemolytic anemia by increasing erythroid output. The number of HSCs in the spleen, but not bone marrow, increases upon anemia and these HSCs exhibit enhanced proliferation, erythroid differentiation, iron uptake, and TET2 protein expression. Increased iron in HSCs promotes DNA demethylation and expression of erythroid genes. Suppressing iron uptake or TET2 expression impairs erythroid genes expression and erythroid differentiation of HSCs; iron supplementation, however, augments these processes. These results establish that the physiological level of iron taken up by HSCs has an instructive role in promoting erythroid-biased differentiation of HSCs.

DOI: https://doi.org/10.1038/s41467-024-44718-0
Sci Rep. 2024 Jan 19. 14(1): 1729

Residual Complex I activity and amphidirectional Complex II operation support glutamate catabolism through mtSLP in anoxia.

Dora Ravasz, David Bui, Sara Nazarian, Gergely Pallag, Noemi Karnok, Jennie Roberts, Bryan P Marzullo, Daniel A Tennant, Bennett Greenwood, Alex Kitayev, Collin Hill, Timea Komlódi, Carolina Doerrier, Kristyna Cunatova, Erika Fernandez-Vizarra, Erich Gnaiger, Michael A Kiebish, Alexandra Raska, Krasimir Kolev, Bence Czumbel, Niven R Narain, Thomas N Seyfried, Christos Chinopoulos.

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in the mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in isolated mitochondria in real-time, we demonstrate that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. 13C metabolic tracing or untargeted analysis of metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system showed that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase Complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Complex II operated amphidirectionally during the anoxic event, providing quinones to Complex I and reducing fumarate to succinate. Our results highlight the importance of quinone provision to Complex I oxidizing NADH maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.

DOI: https://doi.org/10.1038/s41598-024-51365-4
EMBO Rep. 2024 Jan 19.

Glucose-derived glutamate drives neuronal terminal differentiation in vitro.

Laura D'Andrea, Matteo Audano, Silvia Pedretti, Silvia Pelucchi, Ramona Stringhi, Gabriele Imperato, Giulia De Cesare, Clara Cambria, Marine H Laporte, Nicola Zamboni, Flavia Antonucci, Monica Di Luca, Nico Mitro, Elena Marcello.

  Neuronal maturation is the phase during which neurons acquire their final characteristics in terms of morphology, electrical activity, and metabolism. However, little is known about the metabolic pathways governing neuronal maturation. Here, we investigate the contribution of the main metabolic pathways, namely glucose, glutamine, and fatty acid oxidation, during the maturation of primary rat hippocampal neurons. Blunting glucose oxidation through the genetic and chemical inhibition of the mitochondrial pyruvate transporter reveals that this protein is critical for the production of glutamate, which is required for neuronal arborization, proper dendritic elongation, and spine formation. Glutamate supplementation in the early phase of differentiation restores morphological defects and synaptic function in mitochondrial pyruvate transporter-inhibited cells. Furthermore, the selective activation of metabotropic glutamate receptors restores the impairment of neuronal differentiation due to the reduced generation of glucose-derived glutamate and rescues synaptic local translation. Fatty acid oxidation does not impact neuronal maturation. Whereas glutamine metabolism is important for mitochondria, it is not for endogenous glutamate production. Our results provide insights into the role of glucose-derived glutamate as a key player in neuronal terminal differentiation.

Keywords:  Glutamate; Local Protein Translation in Neurons; Metabolism; Mitochondrial Pyruvate Carrier

DOI:  https://doi.org/10.1038/s44319-023-00048-8
Mol Cell. 2024 Jan 10. pii: S1097-2765(23)01079-1. [Epub ahead of print]

Acetyl-CoA production by Mediator-bound 2-ketoacid dehydrogenases boosts de novo histone acetylation and is regulated by nitric oxide.

Marta Russo, Francesco Gualdrini, Veronica Vallelonga, Elena Prosperini, Roberta Noberini, Silvia Pedretti, Carolina Borriero, Pierluigi Di Chiaro, Sara Polletti, Gabriele Imperato, Mattia Marenda, Chiara Ghirardi, Fabio Bedin, Alessandro Cuomo, Simona Rodighiero, Tiziana Bonaldi, Nico Mitro, Serena Ghisletti, Gioacchino Natoli.

  Histone-modifying enzymes depend on the availability of cofactors, with acetyl-coenzyme A (CoA) being required for histone acetyltransferase (HAT) activity. The discovery that mitochondrial acyl-CoA-producing enzymes translocate to the nucleus suggests that high concentrations of locally synthesized metabolites may impact acylation of histones and other nuclear substrates, thereby controlling gene expression. Here, we show that 2-ketoacid dehydrogenases are stably associated with the Mediator complex, thus providing a local supply of acetyl-CoA and increasing the generation of hyper-acetylated histone tails. Nitric oxide (NO), which is produced in large amounts in lipopolysaccharide-stimulated macrophages, inhibited the activity of Mediator-associated 2-ketoacid dehydrogenases. Elevation of NO levels and the disruption of Mediator complex integrity both affected de novo histone acetylation within a shared set of genomic regions. Our findings indicate that the local supply of acetyl-CoA generated by 2-ketoacid dehydrogenases bound to Mediator is required to maximize acetylation of histone tails at sites of elevated HAT activity.

Keywords:  2-ketoacid dehydrogenases; LPS; LPS tolerance; Mediator; acetylation; chromatin; lipopolysaccharide; macrophages; nitric oxide; pyruvate dehydrogenase

DOI:  https://doi.org/10.1016/j.molcel.2023.12.033
Redox Biol. 2023 Dec 27. pii: S2213-2317(23)00412-3. [Epub ahead of print]70 103011

Thiol starvation triggers melanoma state switching in an ATF4 and NRF2-dependent manner.

Madlen Meinert, Christina Jessen, Anita Hufnagel, Julia Katharina Charlotte Kreß, Mychal Burnworth, Theo Däubler, Till Gallasch, Thamara Nishida Xavier da Silva, Ancély Ferreira Dos Santos, Carsten Patrick Ade, Werner Schmitz, Susanne Kneitz, José Pedro Friedmann Angeli, Svenja Meierjohann.

The cystine/glutamate antiporter xCT is an important source of cysteine for cancer cells. Once taken up, cystine is reduced to cysteine and serves as a building block for the synthesis of glutathione, which efficiently protects cells from oxidative damage and prevents ferroptosis. As melanomas are particularly exposed to several sources of oxidative stress, we investigated the biological role of cysteine and glutathione supply by xCT in melanoma. xCT activity was abolished by genetic depletion in the Tyr::CreER; BrafCA; Ptenlox/+ melanoma model and by acute cystine withdrawal in melanoma cell lines. Both interventions profoundly impacted melanoma glutathione levels, but they were surprisingly well tolerated by murine melanomas in vivo and by most human melanoma cell lines in vitro. RNA sequencing of human melanoma cells revealed a strong adaptive upregulation of NRF2 and ATF4 pathways, which orchestrated the compensatory upregulation of genes involved in antioxidant defence and de novo cysteine biosynthesis. In addition, the joint activation of ATF4 and NRF2 triggered a phenotypic switch characterized by a reduction of differentiation genes and induction of pro-invasive features, which was also observed after erastin treatment or the inhibition of glutathione synthesis. NRF2 alone was capable of inducing the phenotypic switch in a transient manner. Together, our data show that cystine or glutathione levels regulate the phenotypic plasticity of melanoma cells by elevating ATF4 and NRF2.

DOI: https://doi.org/10.1016/j.redox.2023.103011
J Biol Chem. 2024 Jan 16. pii: S0021-9258(24)00025-5. [Epub ahead of print] 105649

A cholesterol switch controls phospholipid scrambling by G protein-coupled receptors.

Indu Menon, Taras Sych, Yeeun Son, Takefumi Morizumi, Joon Lee, Oliver P Ernst, George Khelashvili, Erdinc Sezgin, Joshua Levitz, Anant K Menon.

  Class A G protein-coupled receptors (GPCRs), a superfamily of cell membrane signaling receptors, moonlight as constitutively active phospholipid scramblases. The plasma membrane of metazoan cells is replete with GPCRs, yet has a strong resting trans-bilayer phospholipid asymmetry, with the signaling lipid phosphatidylserine confined to the cytoplasmic leaflet. To account for the persistence of this lipid asymmetry in the presence of GPCR scramblases, we hypothesized that GPCR-mediated lipid scrambling is regulated by cholesterol, a major constituent of the plasma membrane. We now present a technique whereby synthetic vesicles reconstituted with GPCRs can be supplemented with cholesterol to a level similar to that of the plasma membrane and show that the scramblase activity of two prototypical GPCRs, opsin and the β1-adrenergic receptor, is impaired upon cholesterol loading. Our data suggest that cholesterol acts as a switch, inhibiting scrambling above a receptor-specific threshold concentration to disable GPCR scramblases at the plasma membrane.

Keywords:  G protein‐coupled receptor (GPCR); cholesterol; fluorescence; liposome; membrane transporter reconstitution; phospholipid; plasma membrane; rhodopsin; scramblase; single particle profiling

DOI:  https://doi.org/10.1016/j.jbc.2024.105649
EMBO J. 2024 Jan 18.

MITOL deficiency triggers hematopoietic stem cell apoptosis via ER stress response.

Wenjuan Ma, Shah Adil Ishtiyaq Ahmad, Michihiro Hashimoto, Ahad Khalilnezhad, Miho Kataoka, Yuichiro Arima, Yosuke Tanaka, Shigeru Yanagi, Terumasa Umemoto, Toshio Suda.

  Hematopoietic stem cell (HSC) divisional fate and function are determined by cellular metabolism, yet the contribution of specific cellular organelles and metabolic pathways to blood maintenance and stress-induced responses in the bone marrow remains poorly understood. The outer mitochondrial membrane-localized E3 ubiquitin ligase MITOL/MARCHF5 (encoded by the Mitol gene) is known to regulate mitochondrial and endoplasmic reticulum (ER) interaction and to promote cell survival. Here, we investigated the functional involvement of MITOL in HSC maintenance by generating MX1-cre inducible Mitol knockout mice. MITOL deletion in the bone marrow resulted in HSC exhaustion and impairment of bone marrow reconstitution capability in vivo. Interestingly, MITOL loss did not induce major mitochondrial dysfunction in hematopoietic stem and progenitor cells. In contrast, MITOL deletion induced prolonged ER stress in HSCs, which triggered cellular apoptosis regulated by IRE1α. In line, dampening of ER stress signaling by IRE1α inihibitor KIRA6 partially rescued apoptosis of long-term-reconstituting HSC. In summary, our observations indicate that MITOL is a principal regulator of hematopoietic homeostasis and protects blood stem cells from cell death through its function in ER stress signaling.

Keywords:  Apoptosis; Cell Cycle; ER Stress Response; IRE1; MITOL

DOI:  https://doi.org/10.1038/s44318-024-00029-0
Nat Commun. 2024 Jan 15. 15(1): 258

Amyloid beta 42 alters cardiac metabolism and impairs cardiac function in male mice with obesity.

Liam G Hall, Juliane K Czeczor, Timothy Connor, Javier Botella, Kirstie A De Jong, Mark C Renton, Amanda J Genders, Kylie Venardos, Sheree D Martin, Simon T Bond, Kathryn Aston-Mourney, Kirsten F Howlett, James A Campbell, Greg R Collier, Ken R Walder, Matthew McKenzie, Mark Ziemann, Sean L McGee.

There are epidemiological associations between obesity and type 2 diabetes, cardiovascular disease and Alzheimer's disease. The role of amyloid beta 42 (Aβ42) in these diverse chronic diseases is obscure. Here we show that adipose tissue releases Aβ42, which is increased from adipose tissue of male mice with obesity and is associated with higher plasma Aβ42. Increasing circulating Aβ42 levels in male mice without obesity has no effect on systemic glucose homeostasis but has obesity-like effects on the heart, including reduced cardiac glucose clearance and impaired cardiac function. The closely related Aβ40 isoform does not have these same effects on the heart. Administration of an Aβ-neutralising antibody prevents obesity-induced cardiac dysfunction and hypertrophy. Furthermore, Aβ-neutralising antibody administration in established obesity prevents further deterioration of cardiac function. Multi-contrast transcriptomic analyses reveal that Aβ42 impacts pathways of mitochondrial metabolism and exposure of cardiomyocytes to Aβ42 inhibits mitochondrial complex I. These data reveal a role for systemic Aβ42 in the development of cardiac disease in obesity and suggest that therapeutics designed for Alzheimer's disease could be effective in combating obesity-induced heart failure.

DOI: https://doi.org/10.1038/s41467-023-44520-4
Cell Rep. 2024 Jan 11. pii: S2211-1247(24)00004-4. [Epub ahead of print]43(1): 113676

Bone marrow monocytes sustain NK cell-poiesis during non-alcoholic steatohepatitis.

Elsa Bourayou, Thibaut Perchet, Sylvain Meunier, Hugo Bouvier, Marie-Pierre Mailhe, Evie Melanitou, Ana Cumano, Rachel Golub.

  Natural killer (NK) cells are the predominant lymphocyte population in the liver. At the onset of non-alcoholic steatohepatitis (NASH), an accumulation of activated NK cells is observed in the liver in parallel with inflammatory monocyte recruitment and an increased systemic inflammation. Using in vivo and in vitro experiments, we unveil a specific stimulation of NK cell-poiesis during NASH by medullary monocytes that trans-present interleukin-15 (IL-15) and secrete osteopontin, a biomarker for patients with NASH. This cellular dialogue leads to increased survival and maturation of NK precursors that are recruited to the liver, where they dampen the inflammatory monocyte infiltration. The increase in the production of both osteopontin and the IL-15/IL-15Rα complex by bone marrow monocytes is induced by endotoxemia. We propose a tripartite gut-liver-bone marrow axis regulating the immune population dynamics and effector functions during liver inflammation.

Keywords:  CP: Immunology; IL-15; NASH; NK cells; NK survival; bone marrow; gut-liver axis; liver; monocytes; non-alcoholic steatohepatitis; osteopontin

DOI:  https://doi.org/10.1016/j.celrep.2024.113676
J Leukoc Biol. 2024 Jan 16. pii: qiae009. [Epub ahead of print]

The orphan G protein-coupled receptor 141 expressed in myeloid cells functions as an inflammation suppressor.

Atsuya Sawabe, Shogo Okazaki, Akira Nakamura, Ryo Goitsuka, Tomonori Kaifu.

  G protein-coupled receptors (GPCRs) regulate many cellular processes in response to various stimuli, including light, hormones, neurotransmitters, and odorants, some of which play critical roles in innate and adaptive immune responses. However, the physiological functions of many GPCRs and the involvement of them in autoimmune diseases of the central nervous system remain unclear. Here, we demonstrate that GPR141, an orphan GPCR belonging to the class A receptor family, suppresses immune responses. High GPR141 mRNA levels were expressed in myeloid-lineage cells, including neutrophils (CD11b + Gr1+), monocytes (CD11b + Gr1-Ly6C+ and CD11b + Gr1-Ly6C-), macrophages (F4/80+), and dendritic cells (DCs) (CD11c+). Gpr141-/- mice, that we independently generated, displayed almost no abnormalities in myeloid cell differentiation and compartmentalization in the spleen and bone marrow under steady-state conditions. However, Gpr141 deficiency exacerbated disease conditions of experimental autoimmune encephalomyelitis (EAE), an autoimmune disease model for multiple sclerosis, with increased inflammation in the spinal cord. Gpr141-/- mice showed increased CD11b + Gr1+ neutrophils, CD11b + Gr1- monocytes, CD11c+ DC, and CD4+ T cell infiltration into the EAE-induced spinal cord compared to littermate control mice. Lymphocytes enriched from Gpr141-/- mice immunized with myelin oligodendrocyte glycoprotein (MOG)35-55 produced high amounts of interferon-γ, interleukin (IL)-17A, and IL-6 compared to those from WT mice. Moreover, CD11c+ DCs purified from Gpr141-/- mice increased cytokine production of MOG35-55 specific T cells. These findings suggest that GPR141 functions as a negative regulator of immune responses by controlling the functions of monocytes and DCs and that targeting GPR141 may be a possible therapeutic intervention for modulating chronic inflammatory diseases.

Keywords:  G protein-coupled receptor 141; autoimmune disease; dendritic cells; experimental autoimmune encephalomyelitis; monocytes; myeloid cells

DOI:  https://doi.org/10.1093/jleuko/qiae009
Nat Metab. 2024 Jan 19.

Depletion of SAM leading to loss of heterochromatin drives muscle stem cell ageing.

Jengmin Kang, Daniel I Benjamin, Soochi Kim, Jayesh S Salvi, Gurkamal Dhaliwal, Richard Lam, Armon Goshayeshi, Jamie O Brett, Ling Liu, Thomas A Rando.

The global loss of heterochromatin during ageing has been observed in eukaryotes from yeast to humans, and this has been proposed as one of the causes of ageing. However, the cause of this age-associated loss of heterochromatin has remained enigmatic. Here we show that heterochromatin markers, including histone H3K9 di/tri-methylation and HP1, decrease with age in muscle stem cells (MuSCs) as a consequence of the depletion of the methyl donor S-adenosylmethionine (SAM). We find that restoration of intracellular SAM in aged MuSCs restores heterochromatin content to youthful levels and rejuvenates age-associated features, including DNA damage accumulation, increased cell death, and defective muscle regeneration. SAM is not only a methyl group donor for transmethylation, but it is also an aminopropyl donor for polyamine synthesis. Excessive consumption of SAM in polyamine synthesis may reduce its availability for transmethylation. Consistent with this premise, we observe that perturbation of increased polyamine synthesis by inhibiting spermidine synthase restores intracellular SAM content and heterochromatin formation, leading to improvements in aged MuSC function and regenerative capacity in male and female mice. Together, our studies demonstrate a direct causal link between polyamine metabolism and epigenetic dysregulation during murine MuSC ageing.

DOI: https://doi.org/10.1038/s42255-023-00955-z
Nat Commun. 2024 Jan 19. 15(1): 603

The CUL5 E3 ligase complex negatively regulates central signaling pathways in CD8+ T cells.

Xiaofeng Liao, Wenxue Li, Hongyue Zhou, Barani Kumar Rajendran, Ao Li, Jingjing Ren, Yi Luan, David A Calderwood, Benjamin Turk, Wenwen Tang, Yansheng Liu, Dianqing Wu.

CD8+ T cells play an important role in anti-tumor immunity. Better understanding of their regulation could advance cancer immunotherapies. Here we identify, via stepwise CRISPR-based screening, that CUL5 is a negative regulator of the core signaling pathways of CD8+ T cells. Knocking out CUL5 in mouse CD8+ T cells significantly improves their tumor growth inhibiting ability, with significant proteomic alterations that broadly enhance TCR and cytokine signaling and their effector functions. Chemical inhibition of neddylation required by CUL5 activation, also enhances CD8 effector activities with CUL5 validated as a major target. Mechanistically, CUL5, which is upregulated by TCR stimulation, interacts with the SOCS-box-containing protein PCMTD2 and inhibits TCR and IL2 signaling. Additionally, CTLA4 is markedly upregulated by CUL5 knockout, and its inactivation further enhances the anti-tumor effect of CUL5 KO. These results together reveal a negative regulatory mechanism for CD8+ T cells and have strong translational implications in cancer immunotherapy.

DOI: https://doi.org/10.1038/s41467-024-44885-0
J Biol Chem. 2024 Jan 13. pii: S0021-9258(24)00032-2. [Epub ahead of print] 105656

Catalytic mechanism of trans-2-enoyl-CoA reductases in the fatty acid elongation cycle and its cooperative action with fatty acid elongases.

Ryoya Kato, Yuka Takenaka, Yusuke Ohno, Akio Kihara.

  The fatty acid (FA) elongation cycle produces very-long-chain FAs with ≥C21, which have unique physiological functions. Trans-2-enoyl-CoA reductases (yeast, Tsc13; mammals, TECR) catalyze the reduction reactions in the fourth step of the FA elongation cycle and in the sphingosine degradation pathway. However, their catalytic residues and coordinated action in the FA elongation cycle complex are unknown. To reveal these, we generated and analyzed Ala-substituted mutants of 15 residues of Tsc13. An in vitro FA elongation assay showed that nine of these mutants were less active than WT protein, with E91A and Y256A being the least active. Growth complementation analysis, measurement of ceramide levels, and deuterium-sphingosine labeling revealed that the function of the E91A mutant was substantially impaired in vivo. In addition, we found that the activity of FA elongases, which catalyze the first step of the FA elongation cycle, were reduced in the absence of Tsc13. Similar results were observed in Tsc13 E91A-expressing cells, which is attributable to reduced interaction between the Tsc13 E91A mutant and the FA elongases Elo2/Elo3. Finally, we found that E94A and Y248A mutants of human TECR, which correspond to E91A and Y256A mutants of Tsc13, showed reduced and almost no activity, respectively. Based on these results and the predicted three-dimensional structure of Tsc13, we speculate that Tyr256/Tyr248 of Tsc13/TECR is the catalytic residue that supplies a proton to trans-2-enoyl-CoAs. Our findings provide a clue concerning the catalytic mechanism of Tsc13/TECR and the coordinated action in the FA elongation cycle complex.

Keywords:  ceramide; enzyme catalysis; fatty acid; fatty acid elongation cycle; fatty acid metabolism; lipid; sphingolipid; trans-2-enoyl-CoA reductase; very-long-chain fatty acid; yeast

DOI:  https://doi.org/10.1016/j.jbc.2024.105656
EMBO J. 2024 Jan 15.

In situ architecture of Opa1-dependent mitochondrial cristae remodeling.

Michelle Y Fry, Paula P Navarro, Pusparanee Hakim, Virly Y Ananda, Xingping Qin, Juan C Landoni, Sneha Rath, Zintis Inde, Camila Makhlouta Lugo, Bridget E Luce, Yifan Ge, Julie L McDonald, Ilzat Ali, Leillani L Ha, Benjamin P Kleinstiver, David C Chan, Kristopher A Sarosiek, Luke H Chao.

  Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria, while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and show a compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling.

Keywords:  Cristae Remodeling; Cryo-Electron Tomography; Cryo-Focused Ion Beam Milling; Mitochondrial Biology

DOI:  https://doi.org/10.1038/s44318-024-00027-2
iScience. 2024 Jan 19. 27(1): 108733

O6-methylguanine DNA methyltransferase regulates β-glucan-induced trained immunity of macrophages via farnesoid X receptor and AMPK.

Salisa Benjaskulluecha, Atsadang Boonmee, MdFazlul Haque, Benjawan Wongprom, Thitiporn Pattarakankul, Chitsuda Pongma, Kittitach Sri-Ngern-Ngam, Pornlapat Keawvilai, Thadaphong Sukdee, Benjawan Saechue, Patipark Kueanjinda, Tanapat Palaga.

  Trained immunity is the heightened state of innate immune memory that enhances immune response resulting in nonspecific protection. Epigenetic changes and metabolic reprogramming are critical steps that regulate trained immunity. In this study, we reported the involvement of O6-methylguanine DNA methyltransferase (MGMT), a DNA repair enzyme of lesion induced by alkylating agents, in regulation the trained immunity induced by β-glucan (BG). Pharmacological inhibition or silencing of MGMT expression altered LPS stimulated pro-inflammatory cytokine productions in BG-trained bone marrow derived macrophages (BMMs). Targeted deletion of Mgmt in BMMs resulted in reduction of the trained responses both in vitro and in vivo models. The transcriptomic analysis revealed that the dampening trained immunity in MGMT KO BMMs is partially mediated by ATM/FXR/AMPK axis affecting the MAPK/mTOR/HIF1α pathways and the reduction in glycolysis function. Taken together, a failure to resolve a DNA damage may have consequences for innate immune memory.

Keywords:  Cell biology; Immunology; Molecular biology; Transcriptomics

DOI:  https://doi.org/10.1016/j.isci.2023.108733
Sci Rep. 2024 Jan 19. 14(1): 1713

AMPKα2 regulates fasting-induced hyperketonemia by suppressing SCOT ubiquitination and degradation.

Lingxue Zhang, Yanqiao Lu, Junqing An, Yin Wu, Zhixue Liu, Ming-Hui Zou.

Ketone bodies serve as an energy source, especially in the absence of carbohydrates or in the extended exercise. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a crucial energy sensor that regulates lipid and glucose metabolism. However, whether AMPK regulates ketone metabolism in whole body is unclear even though AMPK regulates ketogenesis in liver. Prolonged resulted in a significant increase in blood and urine levels of ketone bodies in wild-type (WT) mice. Interestingly, fasting AMPKα2-/- and AMPKα1-/- mice exhibited significantly higher levels of ketone bodies in both blood and urine compared to fasting WT mice. BHB tolerance assays revealed that both AMPKα2-/- and AMPKα1-/- mice exhibited slower ketone consumption compared to WT mice, as indicated by higher blood BHB or urine BHB levels in the AMPKα2-/- and AMPKα1-/- mice even after the peak. Interestingly, fasting AMPKα2-/- and AMPKα1-/- mice exhibited significantly higher levels of ketone bodies in both blood and urine compared to fasting WT mice. . Specifically, AMPKα2ΔMusc mice showed approximately a twofold increase in blood BHB levels, and AMPKα2ΔMyo mice exhibited a 1.5-fold increase compared to their WT littermates after a 48-h fasting. However, blood BHB levels in AMPKα1ΔMusc and AMPKα1ΔMyo mice were as same as in WT mice. Notably, AMPKα2ΔMusc mice demonstrated a slower rate of BHB consumption in the BHB tolerance assay, whereas AMPKα1ΔMusc mice did not show such an effect. Declining rates of body weights and blood glucoses were similar among all the mice. Protein levels of SCOT, the rate-limiting enzyme of ketolysis, decreased in skeletal muscle of AMPKα2-/- mice. Moreover, SCOT protein ubiquitination increased in C2C12 cells either transfected with kinase-dead AMPKα2 or subjected to AMPKα2 inhibition. AMPKα2 physiologically binds and stabilizes SCOT, which is dependent on AMPKα2 activity.

DOI: https://doi.org/10.1038/s41598-023-49991-5
J Clin Invest. 2024 Jan 18. pii: e166847. [Epub ahead of print]

Tumor-educated Gr1+CD11b+ cells drive breast cancer metastasis via OSM/IL6-JAK-induced cancer cell plasticity.

Sanam Peyvandi, Manon Bulliard, Alev Yilmaz, Annamaria Kauzlaric, Rachel Marcone, Lisa Haerri, Oriana Coquoz, Yu-Ting Huang, Nathalie Duffey, Laetitia Gafner, Girieca Lorusso, Nadine Fournier, Qiang Lan, Curzio Rüegg.

  Cancer cell plasticity contributes to therapy resistance and metastasis, which represent the main causes of cancer-related death, including in breast cancer. The tumor microenvironment drives cancer cell plasticity and metastasis, and unravelling the underlying cues may provide novel strategies to manage metastatic disease. Using breast cancer experimental models and transcriptomic analyses, we showed that stem cell antigen-1 positive (SCA1+) murine breast cancer cells enriched during tumor progression and metastasis had higher in vitro cancer stem cell-like properties, enhanced in vivo metastatic ability, and generated tumors rich in Gr1high Ly6G+CD11b+ cells. In turn, tumor-educated Gr1+CD11b+(Tu-Gr1+CD11b+) cells rapidly and transiently converted low metastatic SCA1- cells into highly metastatic SCA1+ cells via secreted OSM and IL6. JAK inhibition prevented OSM/IL6-induced SCA1+ population enrichment while OSM/IL6 depletion suppressed Tu-Gr1+CD11b+-induced SCA1+ population enrichment in vitro and metastasis in vivo. Moreover, chemotherapy-selected highly metastatic 4T1 cells maintained high SCA1+ positivity through autocrine IL6 production and in vitro JAK inhibition blunted SCA1 positivity and metastatic capacity. Importantly, Tu-Gr1+CD11b+ cells invoked a gene signature in tumor cells predicting shorter OS, RFS and lung metastasis in breast cancer patients. Collectively, our data identified OSM/IL6-JAK as a clinically relevant paracrine/autocrine axis instigating breast cancer cell plasticity and triggering metastasis.

Keywords:  Breast cancer; Oncology

DOI:  https://doi.org/10.1172/JCI166847
Cancer Res. 2024 Jan 19.

Nutrient sensing in macrophages linked to reorganized tumor vasculature.

Hilda L Chan, Xiang H-F Zhang.

Macrophages are plastic immune cells that have varying functions dependent on stimulation from their environment. In a recent issue of Immunity, Do and colleagues demonstrated that activating mechanistic target of rapamycin complex 1 signaling in tumor macrophages alters their metabolism, localization, and function. Specifically, these tumor macrophages promote vascular remodeling that develops a hypoxic environment toxic to cancer cells. This culminates in a tangible reduction in tumor burden in a murine model of breast cancer. Their findings reveal a unique strategy to promote vascular remodeling through macrophage polarization and thereby highlight the intimate connections between macrophage metabolism and function. Additionally, their model highlights parallels between tumor progression and wound healing contexts while emphasizing the amplified effect of small perturbations to a tumor ecosystem.

DOI: https://doi.org/10.1158/0008-5472.CAN-24-0201
Sci Rep. 2024 01 18. 14(1): 1563

ATF4 expression in thermogenic adipocytes is required for cold-induced thermogenesis in mice via FGF21-independent mechanisms.

Sarah H Bjorkman, Alex Marti, Jayashree Jena, Luis Miguel García-Peña, Eric T Weatherford, Kevin Kato, Jivan Koneru, Jason Chen, Ayushi Sood, Matthew J Potthoff, Christopher M Adams, E Dale Abel, Renata O Pereira.

In brown adipose tissue (BAT), short-term cold exposure induces the activating transcription factor 4 (ATF4), and its downstream target fibroblast growth factor 21 (FGF21). Induction of ATF4 in BAT in response to mitochondrial stress is required for thermoregulation, partially by increasing FGF21 expression. In the present study, we tested the hypothesis that Atf4 and Fgf21 induction in BAT are both required for BAT thermogenesis under physiological stress by generating mice selectively lacking either Atf4 (ATF4 BKO) or Fgf21 (FGF21 BKO) in UCP1-expressing adipocytes. After 3 days of cold exposure, core body temperature was significantly reduced in ad-libitum-fed ATF4 BKO mice, which correlated with Fgf21 downregulation in brown and beige adipocytes, and impaired browning of white adipose tissue. Conversely, despite having reduced browning, FGF21 BKO mice had preserved core body temperature after cold exposure. Mechanistically, ATF4, but not FGF21, regulates amino acid import and metabolism in response to cold, likely contributing to BAT thermogenic capacity under ad libitum-fed conditions. Importantly, under fasting conditions, both ATF4 and FGF21 were required for thermogenesis in cold-exposed mice. Thus, ATF4 regulates BAT thermogenesis under fed conditions likely in a FGF21-independent manner, in part via increased amino acid uptake and metabolism.

DOI: https://doi.org/10.1038/s41598-024-52004-8
Cell Death Dis. 2024 Jan 15. 15(1): 51

Mitochondrial stress activates YAP/TAZ through RhoA oxidation to promote liver injury.

Ari Kwon, Na Young Lee, Jae-Hyun Yu, Myeung Gi Choi, Jeongwoo Park, Ja Hyun Koo.

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1; also known as TAZ) are the main effectors of the Hippo pathway and their dysregulation contributes to diseases in tissues including the liver. Although mitochondria are capable of transmitting signals to change transcriptomic landscape of diseased hepatocytes, such retrograde signaling and the related nuclear machinery are largely unknown. Here, we show that increased YAP activity is associated with mitochondrial stress during liver injury; and this is required for secondary inflammation, promoting hepatocyte death. Mitochondrial stress inducers robustly promoted YAP/TAZ dephosphorylation, nuclear accumulation, and target gene transcription. RNA sequencing revealed that the majority of mitochondrial stress transcripts required YAP/TAZ. Mechanistically, direct oxidation of RhoA by mitochondrial superoxide was responsible for PP2A-mediated YAP/TAZ dephosphorylation providing a novel physiological input for the Hippo pathway. Hepatocyte-specific Yap/Taz ablation suppressed acetaminophen-induced liver injury and blunted transcriptomic changes associated with the pathology. Our observations uncover unappreciated pathway of mitochondrial stress signaling and reveal YAP/TAZ activation as the mechanistic basis for liver injury progression.

DOI: https://doi.org/10.1038/s41419-024-06448-5
Redox Biol. 2024 Jan 05. pii: S2213-2317(23)00422-6. [Epub ahead of print]70 103021

Inhibition of xanthine oxidase by allopurinol suppresses HMGB1 secretion and ameliorates experimental asthma.

Yanhong Wang, Yanqing Le, Jie Wu, Wenqu Zhao, Qian Zhang, Guiling Xu, Zhaoqian Gong, Maosheng Xu, Yanyan Ma, Changhui Yu, Shaoxi Cai, Haijin Zhao.

   BACKGROUND: Extracellular high mobility group box 1 (HMGB1) is a key mediator in driving allergic airway inflammation and contributes to asthma. Yet, mechanism of HMGB1 secretion in asthma is poorly defined. Pulmonary metabolic dysfunction is recently recognized as a driver of respiratory pathology. However, the altered metabolic signatures and the roles of metabolic to allergic airway inflammation remain unclear.
METHODS: Male C57BL/6 J mice were sensitized and challenged with toluene diisocyanate (TDI) to generate a chemically induced asthma model. Pulmonary untargeted metabolomics was employed. According to results, mice were orally administered allopurinol, a xanthine oxidase (XO) inhibitor. Human bronchial epithelial cells (16HBE) were stimulated by TDI-human serum albumin (HSA).
RESULTS: We identified the purine metabolism was the most enriched pathway in TDI-exposed lungs, corresponding to the increase of xanthine and uric acid, products of purine degradation mediated by XO. Inhibition of XO by allopurinol ameliorates TDI-induced oxidative stress and DNA damage, mixed granulocytic airway inflammation and Th1, Th2 and Th17 immunology as well as HMGB1 acetylation and secretion. Mechanistically, HMGB1 acetylation was caused by decreased activation of the NAD+-sirtuin 1 (SIRT1) axis triggered by hyperactivation of the DNA damage sensor poly (ADP-ribose)-polymerase 1 (PARP-1). This was rescued by allopurinol, PARP-1 inhibitor or supplementation with NAD+ precursor in a SIRT1-dependent manner. Meanwhile, allopurinol attenuated Nrf2 defect due to SIRT1 inactivation to help ROS scavenge.
CONCLUSIONS: We demonstrated a novel regulation of HMGB1 acetylation and secretion by purine metabolism that is critical for asthma onset. Allopurinol may have therapeutic potential in patients with asthma.

Keywords:  Allopurinol; Asthma; HMGB1; Purine metabolism; SIRT1

DOI:  https://doi.org/10.1016/j.redox.2023.103021