bims-mepmim Biomed News
on Metabolites in pathological microenvironments and immunometabolism
Issue of 2024–06–02
seventeen papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism
  1. PNPO-PLP axis senses prolonged hypoxia in macrophages by regulating lysosomal activity.
  2. Rab30 facilitates lipid homeostasis during fasting.
  3. G-protein-coupled receptor 84 regulates acute inflammation in normal and diabetic skin wounds.
  4. Reciprocal Regulation of Cardiac β-Oxidation and Pyruvate Dehydrogenase by Insulin.
  5. 13C metabolite tracing reveals glutamine and acetate as critical in vivo fuels for CD8 T cells.
  6. Inflammation causes insulin resistance in mice via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels.
  7. Spatially resolved lipidomics shows conditional transfer of lipids produced by Bacteroidesthetaiotaomicron into the mouse gut.
  8. Multifaceted mitochondria in innate immunity.
  9. A mitochondrial-targeted activity-based sensing probe for ratiometric imaging of formaldehyde reveals key regulators of the mitochondrial one-carbon pool.
  10. Circadian control of tumor immunosuppression affects efficacy of immune checkpoint blockade.
  11. STAT3 drives the expression of ACSL4 in acute kidney injury.
  12. Drug screening in human physiologic medium identifies uric acid as an inhibitor of rigosertib efficacy.
  13. Nitric oxide-dependent cell death in glioblastoma and squamous cell carcinoma via prodeath mitochondrial clustering.
  14. mitoBKCa is functionally expressed in murine and human breast cancer cells and potentially contributes to metabolic reprogramming.
  15. Redistribution of defective mitochondria-mediated dihydroorotate dehydrogenase imparts 5-fluorouracil resistance in colorectal cancer.
  16. Cystine/glutamate antiporter xCT controls skeletal muscle glutathione redox, bioenergetics and differentiation.
  17. The temporal progression of lung immune remodeling during breast cancer metastasis.
  1. Nat Metab. 2024 May 31.
    PNPO-PLP axis senses prolonged hypoxia in macrophages by regulating lysosomal activity.
    Hiroki Sekine, Haruna Takeda, Norihiko Takeda, Akihiro Kishino, Hayato Anzawa, Takayuki Isagawa, Nao Ohta, Shohei Murakami, Hideya Iwaki, Nobufumi Kato, Shu Kimura, Zun Liu, Koichiro Kato, Fumiki Katsuoka, Masayuki Yamamoto, Fumihito Miura, Takashi Ito, Masatomo Takahashi, Yoshihiro Izumi, Hiroyuki Fujita, Hitoshi Yamagata, Takeshi Bamba, Takaaki Akaike, Norio Suzuki, Kengo Kinoshita, Hozumi Motohashi.
      Oxygen is critical for all metazoan organisms on the earth and impacts various biological processes in physiological and pathological conditions. While oxygen-sensing systems inducing acute hypoxic responses, including the hypoxia-inducible factor pathway, have been identified, those operating in prolonged hypoxia remain to be elucidated. Here we show that pyridoxine 5'-phosphate oxidase (PNPO), which catalyses bioactivation of vitamin B6, serves as an oxygen sensor and regulates lysosomal activity in macrophages. Decreased PNPO activity under prolonged hypoxia reduced an active form of vitamin B6, pyridoxal 5'-phosphate (PLP), and inhibited lysosomal acidification, which in macrophages led to iron dysregulation, TET2 protein loss and delayed resolution of the inflammatory response. Among PLP-dependent metabolism, supersulfide synthesis was suppressed in prolonged hypoxia, resulting in the lysosomal inhibition and consequent proinflammatory phenotypes of macrophages. The PNPO-PLP axis creates a distinct layer of oxygen sensing that gradually shuts down PLP-dependent metabolism in response to prolonged oxygen deprivation.
    DOI:  https://doi.org/10.1038/s42255-024-01053-4
  2. Nat Commun. 2024 May 25. 15(1): 4469
    Rab30 facilitates lipid homeostasis during fasting.
    Danielle M Smith, Brian Y Liu, Michael J Wolfgang.
      To facilitate inter-tissue communication and the exchange of proteins, lipoproteins, and metabolites with the circulation, hepatocytes have an intricate and efficient intracellular trafficking system regulated by small Rab GTPases. Here, we show that Rab30 is induced in the mouse liver by fasting, which is amplified in liver-specific carnitine palmitoyltransferase 2 knockout mice (Cpt2L-/-) lacking the ability to oxidize fatty acids, in a Pparα-dependent manner. Live-cell super-resolution imaging and in vivo proximity labeling demonstrates that Rab30-marked vesicles are highly dynamic and interact with proteins throughout the secretory pathway. Rab30 whole-body, liver-specific, and Rab30; Cpt2 liver-specific double knockout (DKO) mice are viable with intact Golgi ultrastructure, although Rab30 deficiency in DKO mice suppresses the serum dyslipidemia observed in Cpt2L-/- mice. Corresponding with decreased serum triglyceride and cholesterol levels, DKO mice exhibit decreased circulating but not hepatic ApoA4 protein, indicative of a trafficking defect. Together, these data suggest a role for Rab30 in the selective sorting of lipoproteins to influence hepatocyte and circulating triglyceride levels, particularly during times of excessive lipid burden.
    DOI:  https://doi.org/10.1038/s41467-024-48959-x
  3. Cell Rep. 2024 May 29. pii: S2211-1247(24)00616-8. [Epub ahead of print]43(6): 114288
    G-protein-coupled receptor 84 regulates acute inflammation in normal and diabetic skin wounds.
    Paula O Cooper, Sarah S Kleb, Satish K Noonepalle, Veronica M Amuso, Rohan Varshney, Michael C Rudolph, Tanvir K Dhaliwal, Darlene V Nguyen, Miguel F Mazumder, Najuma S Babirye, Ruchi Gupta, Bao-Ngoc Nguyen, Brett A Shook.
      Lipids have emerged as potent regulators of immune cell function. In the skin, adipocyte lipolysis increases the local pool of free fatty acids and is essential for coordinating early macrophage inflammation following injury. Here, we investigate G-protein-coupled receptor 84 (GPR84), a medium-chain fatty acid (MCFA) receptor, for its potential to propagate pro-inflammatory signaling after skin injury. GPR84 signaling was identified as a key component of regulating myeloid cell numbers and subsequent tissue repair through in vivo administration of a pharmacological antagonist and the MCFA decanoic acid. We found that impaired injury-induced dermal adipocyte lipolysis is a hallmark of diabetes, and lipidomic analysis demonstrated that MCFAs are significantly reduced in diabetic murine wounds. Furthermore, local administration of decanoic acid rescued myeloid cell numbers and tissue repair during diabetic wound healing. Thus, GPR84 is a readily targetable lipid signaling pathway for manipulating injury-induced tissue inflammation with beneficial effects on acute diabetic healing.
    Keywords:  CP: Metabolism; GPR84; diabetes; inflammation; macrophage; medium-chain fatty acid; wound healing
    DOI:  https://doi.org/10.1016/j.celrep.2024.114288
  4. J Biol Chem. 2024 May 23. pii: S0021-9258(24)01913-6. [Epub ahead of print] 107412
    Reciprocal Regulation of Cardiac β-Oxidation and Pyruvate Dehydrogenase by Insulin.
    Abdallah Elnwasany, Heba A Ewida, Ivan Menendez-Montes, Monika Mizerska, Xiaorong Fu, Chai-Wan Kim, Jay D Horton, Shawn C Burgess, Beverly A Rothermel, Pamela A Szweda, Luke I Szweda.
      The heart alters the rate and relative oxidation of fatty acids and glucose based on availability and energetic demand. Insulin plays a crucial role in this process diminishing fatty acid and increasing glucose oxidation when glucose availability increases. Loss of insulin sensitivity and metabolic flexibility can result in cardiovascular disease. It is therefore important to identify mechanisms by which insulin regulates substrate utilization in the heart. Mitochondrial pyruvate dehydrogenase (PDH) is the key regulatory site for the oxidation of glucose for ATP production. Nevertheless, the impact of insulin on PDH activity has not been fully delineated, particularly in the heart. We sought in vivo evidence that insulin stimulates cardiac PDH and that this process is driven by inhibition of fatty acid oxidation. Mice injected with insulin exhibited dephosphorylation and activation of cardiac PDH. This was accompanied by an increase in the content of malonyl-CoA, an inhibitor of carnitine palmitoyltransferase 1 (CPT1) and, thus, mitochondrial import of fatty acids. Administration of the CPT1 inhibitor oxfenicine was sufficient to activate PDH. Malonyl-CoA is produced by acetyl-CoA carboxylase (ACC). Pharmacologic inhibition or knockout of cardiac ACC diminished insulin-dependent production of malonyl-CoA and activation of PDH. Finally, circulating insulin and cardiac glucose utilization exhibit daily rhythms reflective of nutritional status. We demonstrate that time of day-dependent changes in PDH activity are mediated, in part, by ACC-dependent production of malonyl-CoA. Thus, by inhibiting fatty acid oxidation, insulin reciprocally activates PDH. These studies identify potential molecular targets to promote cardiac glucose oxidation and treat heart disease.
    Keywords:  Acetyl-CoA Carboxylase; Heart; Insulin; Malonyl-CoA; Mitochondria; Pyruvate Dehydrogenase; β-Oxidation
    DOI:  https://doi.org/10.1016/j.jbc.2024.107412
  5. Sci Adv. 2024 May 31. 10(22): eadj1431
    13C metabolite tracing reveals glutamine and acetate as critical in vivo fuels for CD8 T cells.
    Eric H Ma, Michael S Dahabieh, Lisa M DeCamp, Irem Kaymak, Susan M Kitchen-Goosen, Brandon M Oswald, Joseph Longo, Dominic G Roy, Mark J Verway, Radia M Johnson, Bozena Samborska, Lauren R Duimstra, Catherine A Scullion, Mya Steadman, Matthew Vos, Thomas P Roddy, Connie M Krawczyk, Kelsey S Williams, Ryan D Sheldon, Russell G Jones.
      Infusion of 13C-labeled metabolites provides a gold standard for understanding the metabolic processes used by T cells during immune responses in vivo. Through infusion of 13C-labeled metabolites (glucose, glutamine, and acetate) in Listeria monocytogenes-infected mice, we demonstrate that CD8 T effector (Teff) cells use metabolites for specific pathways during specific phases of activation. Highly proliferative early Teff cells in vivo shunt glucose primarily toward nucleotide synthesis and leverage glutamine anaplerosis in the tricarboxylic acid (TCA) cycle to support adenosine triphosphate and de novo pyrimidine synthesis. In addition, early Teff cells rely on glutamic-oxaloacetic transaminase 1 (Got1)-which regulates de novo aspartate synthesis-for effector cell expansion in vivo. CD8 Teff cells change fuel preference over the course of infection, switching from glutamine- to acetate-dependent TCA cycle metabolism late in infection. This study provides insights into the dynamics of Teff metabolism, illuminating distinct pathways of fuel consumption associated with CD8 Teff cell function in vivo.
    DOI:  https://doi.org/10.1126/sciadv.adj1431
  6. Nat Commun. 2024 May 30. 15(1): 4605
    Inflammation causes insulin resistance in mice via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels.
    Shuai Yan, Anna Santoro, Micah J Niphakis, Antonio M Pinto, Christopher L Jacobs, Rasheed Ahmad, Radu M Suciu, Bryan R Fonslow, Rachel A Herbst-Graham, Nhi Ngo, Cassandra L Henry, Dylan M Herbst, Alan Saghatelian, Barbara B Kahn, Evan D Rosen.
      Obesity-induced inflammation causes metabolic dysfunction, but the mechanisms remain elusive. Here we show that the innate immune transcription factor interferon regulatory factor (IRF3) adversely affects glucose homeostasis through induction of the endogenous FAHFA hydrolase androgen induced gene 1 (AIG1) in adipocytes. Adipocyte-specific knockout of IRF3 protects male mice against high-fat diet-induced insulin resistance, whereas overexpression of IRF3 or AIG1 in adipocytes promotes insulin resistance on a high-fat diet. Furthermore, pharmacological inhibition of AIG1 reversed obesity-induced insulin resistance and restored glucose homeostasis in the setting of adipocyte IRF3 overexpression. We, therefore, identify the adipocyte IRF3/AIG1 axis as a crucial link between obesity-induced inflammation and insulin resistance and suggest an approach for limiting the metabolic dysfunction accompanying obesity.
    DOI:  https://doi.org/10.1038/s41467-024-48220-5
  7. Cell Host Microbe. 2024 May 17. pii: S1931-3128(24)00141-0. [Epub ahead of print]
    Spatially resolved lipidomics shows conditional transfer of lipids produced by Bacteroidesthetaiotaomicron into the mouse gut.
    Claudia Mirretta Barone, Stacey L Heaver, Lars Gruber, Fabian Zundel, Dai Long Vu, Ruth E Ley.
      The extent to which bacterial lipids produced by the gut microbiota penetrate host tissues is unclear. Here, we combined mass spectrometry approaches to identify lipids produced by the human gut symbiont Bacteroides thetaiotaomicron (B. theta) and spatially track these bacterial lipids in the mouse colon. We characterize 130 B. theta lipids by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using wild-type and mutant B. theta strains to confidently identify lipid structures and their interconnected pathways in vitro. Of these, 103 B. theta lipids can be detected and spatially mapped in a single MALDI mass spectrometry imaging run. We map unlabeled bacterial lipids across colon sections of germ-free and specific-pathogen-free (SPF) mice and mice mono-colonized with wild-type or sphingolipid-deficient (BTMUT) B. theta. We observe co-localization of bacterially derived phosphatidic acid with host tissues in BTMUT mice, consistent with lipid penetration into host tissues. These results indicate limited and selective transfer of bacterial lipids to the host.
    Keywords:  B. theta; Bacteroides; MALDI mass spectrometry; host-microbial interactions; lipids; lipodomics; sphingolipids
    DOI:  https://doi.org/10.1016/j.chom.2024.04.021
  8. NPJ Metab Health Dis. 2024 ;2(1): 6
    Multifaceted mitochondria in innate immunity.
    Eloïse Marques, Robbin Kramer, Dylan G Ryan.
      The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.
    Keywords:  Energy metabolism; Mitochondria
    DOI:  https://doi.org/10.1038/s44324-024-00008-3
  9. Chem Sci. 2024 May 29. 15(21): 8080-8088
    A mitochondrial-targeted activity-based sensing probe for ratiometric imaging of formaldehyde reveals key regulators of the mitochondrial one-carbon pool.
    Logan Tenney, Vanha N Pham, Thomas F Brewer, Christopher J Chang.
      Formaldehyde (FA) is both a highly reactive environmental genotoxin and an endogenously produced metabolite that functions as a signaling molecule and one-carbon (1C) store to regulate 1C metabolism and epigenetics in the cell. Owing to its signal-stress duality, cells have evolved multiple clearance mechanisms to maintain FA homeostasis, acting to avoid the established genotoxicity of FA while also redirecting FA-derived carbon units into the biosynthesis of essential nucleobases and amino acids. The highly compartmentalized nature of FA exposure, production, and regulation motivates the development of chemical tools that enable monitoring of transient FA fluxes with subcellular resolution. Here we report a mitochondrial-targeted, activity-based sensing probe for ratiometric FA detection, MitoRFAP-2, and apply this reagent to monitor endogenous mitochondrial sources and sinks of this 1C unit. We establish the utility of subcellular localization by showing that MitoRFAP-2 is sensitive enough to detect changes in mitochondrial FA pools with genetic and pharmacological modulation of enzymes involved in 1C and amino acid metabolism, including the pervasive, less active genetic mutant aldehyde dehydrogenase 2*2 (ALDH2*2), where previous, non-targeted versions of FA sensors are not. Finally, we used MitoRFAP-2 to comparatively profile basal levels of FA across a panel of breast cancer cell lines, finding that FA-dependent fluorescence correlates with expression levels of enzymes involved in 1C metabolism. By showcasing the ability of MitoRFAP-2 to identify new information on mitochondrial FA homeostasis, this work provides a starting point for the design of a broader range of chemical probes for detecting physiologically important aldehydes with subcellular resolution and a useful reagent for further studies of 1C biology.
    DOI:  https://doi.org/10.1039/d4sc01183j
  10. Nat Immunol. 2024 May 28.
    Circadian control of tumor immunosuppression affects efficacy of immune checkpoint blockade.
    Bridget M Fortin, Shannon M Pfeiffer, Jacob Insua-Rodríguez, Hamad Alshetaiwi, Alexander Moshensky, Wei A Song, Alisa L Mahieu, Sung Kook Chun, Amber N Lewis, Alex Hsu, Isam Adam, Oliver S Eng, Nicholas R Pannunzio, Marcus M Seldin, Ivan Marazzi, Francesco Marangoni, Devon A Lawson, Kai Kessenbrock, Selma Masri.
      The circadian clock is a critical regulator of immunity, and this circadian control of immune modulation has an essential function in host defense and tumor immunosurveillance. Here we use a single-cell RNA sequencing approach and a genetic model of colorectal cancer to identify clock-dependent changes to the immune landscape that control the abundance of immunosuppressive cells and consequent suppression of cytotoxic CD8+ T cells. Of these immunosuppressive cell types, PD-L1-expressing myeloid-derived suppressor cells (MDSCs) peak in abundance in a rhythmic manner. Disruption of the epithelial cell clock regulates the secretion of cytokines that promote heightened inflammation, recruitment of neutrophils and the subsequent development of MDSCs. We also show that time-of-day anti-PD-L1 delivery is most effective when synchronized with the abundance of immunosuppressive MDSCs. Collectively, these data indicate that circadian gating of tumor immunosuppression informs the timing and efficacy of immune checkpoint inhibitors.
    DOI:  https://doi.org/10.1038/s41590-024-01859-0
  11. iScience. 2024 Jun 21. 27(6): 109737
    STAT3 drives the expression of ACSL4 in acute kidney injury.
    Virginie Poindessous, Helene Lazareth, Gilles Crambert, Lydie Cheval, Julio L Sampaio, Nicolas Pallet.
      Long-chain acyl-CoA synthetase family 4 (ACSL4) metabolizes long-chain polyunsaturated fatty acids (PUFAs), enriching cell membranes with phospholipids susceptible to peroxidation and drive ferroptosis. The role of ACSL4 and ferroptosis upon endoplasmic-reticulum (ER)-stress-induced acute kidney injury (AKI) is unknown. We used lipidomic, molecular, and cellular biology approaches along with a mouse model of AKI induced by ER stress to investigate the role of ACSL4 regulation in membrane lipidome remodeling in the injured tubular epithelium. Tubular epithelial cells (TECs) activate ACSL4 in response to STAT3 signaling. In this context, TEC membrane lipidome is remodeled toward PUFA-enriched triglycerides instead of PUFA-bearing phospholipids. TECs expressing ACSL4 in this setting are not vulnerable to ferroptosis. Thus, ACSL4 activity in TECs is driven by STAT3 signaling, but ACSL4 alone is not enough to sensitize ferroptosis, highlighting the significance of the biological context associated with the study model.
    Keywords:  Integrative aspects of cell biology; omics; pathophysiology
    DOI:  https://doi.org/10.1016/j.isci.2024.109737
  12. JCI Insight. 2024 May 30. pii: e174329. [Epub ahead of print]
    Drug screening in human physiologic medium identifies uric acid as an inhibitor of rigosertib efficacy.
    Vipin Rawat, Patrick DeLear, Prarthana Prashanth, Mete Emir Ozgurses, Anteneh Tebeje, Philippa A Burns, Kelly O Conger, Christopher Solís, Yasir Hasnain, Anna Novikova, Jennifer E Endress, Paloma González-Sánchez, Wentao Dong, Greg Stephanopoulos, Gina M DeNicola, Isaac Harris, David Sept, Frank M Mason, Jonathan L Coloff.
      The non-physiological nutrient levels found in traditional culture media have been shown to affect numerous aspects of cancer cell physiology, including how cells respond to certain therapeutic agents. Here, we comprehensively evaluated how physiological nutrient levels impact therapeutic response by performing drug screening in human plasma-like medium (HPLM). We observed dramatic nutrient-dependent changes in sensitivity to a variety of FDA-approved and clinically trialed compounds including rigosertib, an experimental cancer therapeutic that has recently failed in phase 3 clinical trials. Mechanistically, we found that the ability of rigosertib to destabilize microtubules is strongly inhibited by the purine metabolism end product uric acid, which is uniquely abundant in humans relative to traditional in vitro and in vivo cancer models. These results demonstrate the broad and dramatic effects nutrient levels can have on drug response, and how incorporation of human-specific physiological nutrient media might help to identify compounds whose efficacy could be impacted in humans.
    Keywords:  Cancer; Cell biology; Cytoskeleton; Drug screens; Oncology
    DOI:  https://doi.org/10.1172/jci.insight.174329
  13. Eur J Cell Biol. 2024 May 18. pii: S0171-9335(24)00039-6. [Epub ahead of print]103(2): 151422
    Nitric oxide-dependent cell death in glioblastoma and squamous cell carcinoma via prodeath mitochondrial clustering.
    Yushi Ochiai, Manami Suzuki-Karasaki, Takashi Ando, Miki Suzuki-Karasaki, Hideki Nakayama, Yoshihiro Suzuki-Karasaki.
      Besides the fission-fusion dynamics, the cellular distribution of mitochondria has recently emerged as a critical biological parameter in regulating mitochondrial function and cell survival. We previously found that mitochondrial clustering on the nuclear periphery, or monopolar perinuclear mitochondrial clustering (MPMC), accompanies the anticancer activity of air plasma-activated medium (APAM) against glioblastoma and human squamous cell carcinoma, which is closely associated with oxidant-dependent tubulin remodeling and mitochondrial fragmentation. Accordingly, this study investigated the regulatory roles of nitric oxide (NO) in the anticancer activity of APAM. Time-lapse analysis revealed a time-dependent increase in NO accompanied by MPMC. In contrast, APAM caused minimal increases in MPMC and NO levels in nontransformed cells. NO, hydroxyl radicals, and lipid peroxide levels increased near the damaged nuclear periphery, possibly within mitochondria. NO scavenging prevented tubulin remodeling, MPMC, perinuclear oxidant production, nuclear damage, and cell death. Conversely, synthetic NO donors augmented all the prodeath events and acted synergistically with APAM. Salinomycin, an emerging drug against multidrug-resistant cancers, had similar NO-dependent effects. These results suggest that APAM and salinomycin induce NO-dependent cell death, where MPMC and oxidative mitochondria play critical roles. Our findings encourage further investigations on MPMC as a potential target for NO-driven anticancer agents against drug-resistant cancers.
    Keywords:  cancer; mitochondria; nitric oxide; perinuclear mitochondrial clustering; plasma-treated solution; salinomycin
    DOI:  https://doi.org/10.1016/j.ejcb.2024.151422
  14. Elife. 2024 May 29. pii: RP92511. [Epub ahead of print]12
    mitoBKCa is functionally expressed in murine and human breast cancer cells and potentially contributes to metabolic reprogramming.
    Helmut Bischof, Selina Maier, Piotr Koprowski, Bogusz Kulawiak, Sandra Burgstaller, Joanna Jasińska, Kristian Serafimov, Monika Zochowska, Dominic Gross, Werner Schroth, Lucas Matt, David Arturo Juarez Lopez, Ying Zhang, Irina Bonzheim, Florian A Büttner, Falko Fend, Matthias Schwab, Andreas L Birkenfeld, Roland Malli, Michael Lämmerhofer, Piotr Bednarczyk, Adam Szewczyk, Robert Lukowski.
      Alterations in the function of K+ channels such as the voltage- and Ca2+-activated K+ channel of large conductance (BKCa) reportedly promote breast cancer (BC) development and progression. Underlying molecular mechanisms remain, however, elusive. Here, we provide electrophysiological evidence for a BKCa splice variant localized to the inner mitochondrial membrane of murine and human BC cells (mitoBKCa). Through a combination of genetic knockdown and knockout along with a cell permeable BKCa channel blocker, we show that mitoBKCa modulates overall cellular and mitochondrial energy production, and mediates the metabolic rewiring referred to as the 'Warburg effect', thereby promoting BC cell proliferation in the presence and absence of oxygen. Additionally, we detect mitoBKCa and BKCa transcripts in low or high abundance, respectively, in clinical BC specimens. Together, our results emphasize, that targeting mitoBKCa could represent a treatment strategy for selected BC patients in future.
    Keywords:  K+ channels; Kcnma1; Slo1; Warburg effect; biosensors; breast cancer; cancer biology; cell biology; human; metabolic reprogramming; mitoBKCa; mouse
    DOI:  https://doi.org/10.7554/eLife.92511
  15. Redox Biol. 2024 May 23. pii: S2213-2317(24)00185-X. [Epub ahead of print]73 103207
    Redistribution of defective mitochondria-mediated dihydroorotate dehydrogenase imparts 5-fluorouracil resistance in colorectal cancer.
    Shuohui Dong, Mingguang Zhang, Zhiqiang Cheng, Xiang Zhang, Weili Liang, Songhan Li, Linchuan Li, Qian Xu, Siyi Song, Zitian Liu, Guangwei Yang, Xiang Zhao, Ze Tao, Shuo Liang, Kexin Wang, Guangyong Zhang, Sanyuan Hu.
      Although 5-fluorouracil (5-FU) is the primary chemotherapy treatment for colorectal cancer (CRC), its efficacy is limited by drug resistance. Ferroptosis activation is a promising treatment for 5-FU-resistant cancer cells; however, potential therapeutic targets remain elusive. This study investigated ferroptosis vulnerability and dihydroorotate dehydrogenase (DHODH) activity using stable, 5-FU-resistant CRC cell lines and xenograft models. Ferroptosis was characterized by measuring malondialdehyde levels, assessing lipid metabolism and peroxidation, and using mitochondrial imaging and assays. DHODH function is investigated through gene knockdown experiments, tumor behavior assays, mitochondrial import reactions, intramitochondrial localization, enzymatic activity analyses, and metabolomics assessments. Intracellular lipid accumulation and mitochondrial DHODH deficiency led to lipid peroxidation overload, weakening the defense system of 5-FU-resistant CRC cells against ferroptosis. DHODH, primarily located within the inner mitochondrial membrane, played a crucial role in driving intracellular pyrimidine biosynthesis and was redistributed to the cytosol in 5-FU-resistant CRC cells. Cytosolic DHODH, like its mitochondrial counterpart, exhibited dihydroorotate catalytic activity and participated in pyrimidine biosynthesis. This amplified intracellular pyrimidine pools, thereby impeding the efficacy of 5-FU treatment through molecular competition. These findings contribute to the understanding of 5-FU resistance mechanisms and suggest that ferroptosis and DHODH are promising therapeutic targets for patients with CRC exhibiting resistance to 5-FU.
    Keywords:  Chemoresistance; Colorectal cancer; Dihydroorotate dehydrogenase; Ferroptosis; Lipid metabolic reprogramming
    DOI:  https://doi.org/10.1016/j.redox.2024.103207
  16. Redox Biol. 2024 May 25. pii: S2213-2317(24)00191-5. [Epub ahead of print]73 103213
    Cystine/glutamate antiporter xCT controls skeletal muscle glutathione redox, bioenergetics and differentiation.
    Michel N Kanaan, Chantal A Pileggi, Charbel Y Karam, Luke S Kennedy, Claire Fong-McMaster, Miroslava Cuperlovic-Culf, Mary-Ellen Harper.
      Cysteine, the rate-controlling amino acid in cellular glutathione synthesis is imported as cystine, by the cystine/glutamate antiporter, xCT, and subsequently reduced to cysteine. As glutathione redox is important in muscle regeneration in aging, we hypothesized that xCT exerts upstream control over skeletal muscle glutathione redox, metabolism and regeneration. Bioinformatic analyses of publicly available datasets revealed that expression levels of xCT and GSH-related genes are inversely correlated with myogenic differentiation genes. Muscle satellite cells (MuSCs) isolated from Slc7a11sut/sut mice, which harbour a mutation in the Slc7a11 gene encoding xCT, required media supplementation with 2-mercaptoethanol to support cell proliferation but not myotube differentiation, despite persistently lower GSH. Slc7a11sut/sut primary myotubes were larger compared to WT myotubes, and also exhibited higher glucose uptake and cellular oxidative capacities. Immunostaining of myogenic markers (Pax7, MyoD, and myogenin) in cardiotoxin-damaged tibialis anterior muscle fibres revealed greater MuSC activation and commitment to differentiation in Slc7a11sut/sut muscle compared to WT mice, culminating in larger myofiber cross-sectional areas at 21 days post-injury. Slc7a11sut/sut mice subjected to a 5-week exercise training protocol demonstrated enhanced insulin tolerance compared to WT mice, but blunted muscle mitochondrial biogenesis and respiration in response to exercise training. Our results demonstrate that the absence of xCT inhibits cell proliferation but promotes myotube differentiation by regulating cellular metabolism and glutathione redox. Altogether, these results support the notion that myogenesis is a redox-regulated process and may help inform novel therapeutic approaches for muscle wasting and dysfunction in aging and disease.
    Keywords:  Glutathione; Glycolysis; Mitochondria; Myogenesis; Oxidative phosphorylation; Redox
    DOI:  https://doi.org/10.1016/j.redox.2024.103213
  17. Cancer Cell. 2024 May 24. pii: S1535-6108(24)00167-3. [Epub ahead of print]
    The temporal progression of lung immune remodeling during breast cancer metastasis.
    Christopher S McGinnis, Zhuang Miao, Daphne Superville, Winnie Yao, Andrei Goga, Nathan E Reticker-Flynn, Juliane Winkler, Ansuman T Satpathy.
      Tumor metastasis requires systemic remodeling of distant organ microenvironments that impacts immune cell phenotypes, population structure, and intercellular communication. However, our understanding of immune phenotypic dynamics in the metastatic niche remains incomplete. Here, we longitudinally assayed lung immune transcriptional profiles in the polyomavirus middle T antigen (PyMT) and 4T1 metastatic breast cancer models from primary tumorigenesis, through pre-metastatic niche formation, to the final stages of metastatic outgrowth at single-cell resolution. Computational analyses of these data revealed a TLR-NFκB inflammatory program enacted by both peripherally derived and tissue-resident myeloid cells that correlated with pre-metastatic niche formation and mirrored CD14+ "activated" myeloid cells in the primary tumor. Moreover, we observed that primary tumor and metastatic niche natural killer (NK) cells are differentially regulated in mice and human patient samples, with the metastatic niche featuring elevated cytotoxic NK cell proportions. Finally, we identified cell-type-specific dynamic regulation of IGF1 and CCL6 signaling during metastatic progression that represents anti-metastatic immunotherapy candidate pathways.
    Keywords:  NF-κB; TLR; cancer immunology; immunosuppression; inflammation; metastasis; myeloid; natural killer cells; single-cell genomics
    DOI:  https://doi.org/10.1016/j.ccell.2024.05.004
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