bims-glucam Biomed News
on Glutamine cancer metabolism
Issue of 2024–05–19
fiveteen papers selected by
Sreeparna Banerjee, Middle East Technical University
  1. HIF2α-dependent inhibition of mitochondrial clustering of glutaminase suppresses clear cell renal cell carcinoma.
  2. Targeting the glutamine metabolism to suppress cell proliferation in mesenchymal docetaxel-resistant prostate cancer.
  3. Overcoming Nutrient Stress: Integrin αvβ3-Driven Metabolic Adaptation Supports Tumor Initiation.
  4. IGF2BP3 promotes glutamine metabolism of endometriosis by interacting with UCA1 to enhances the mRNA stability of GLS1.
  5. Metabolic Rewiring in Cancer: Small Molecule Inhibitors in Colorectal Cancer Therapy.
  6. NADPH composite index analysis quantifies the relationship between compartmentalized NADPH dynamics and growth rates in cancer cells.
  7. Enhancing breast cancer outcomes with machine learning-driven glutamine metabolic reprogramming signature.
  8. L-2-hydroxyglutarate remodeling of the epigenome and epitranscriptome creates a metabolic vulnerability in kidney cancer models.
  9. Glutamine promotes human CD8+ T cells and counteracts imiquimod-induced T cell hyporesponsiveness.
  10. Enteral glutamine for trauma patients in intensive care unit - Comment on: ESPEN practical and partially revised guideline: Clinical nutrition in the intensive care unit.
  11. Spatial hepatocyte plasticity of gluconeogenesis during the metabolic transitions between fed, fasted and starvation states.
  12. The emerging roles of glutamine amidotransferases in metabolism and immune defense.
  13. Emerging Trends in Gastrointestinal Cancer Targeted Therapies: Harnessing Tumor Microenvironment, Immune Factors, and Metabolomics Insights.
  14. Retinal metabolism displays evidence for uncoupling of glycolysis and oxidative phosphorylation via Cori-, Cahill-, and mini-Krebs-cycle.
  15. IRE1α determines ferroptosis sensitivity through regulation of glutathione synthesis.
  1. bioRxiv. 2024 May 05. pii: 2024.05.04.592520. [Epub ahead of print]
    HIF2α-dependent inhibition of mitochondrial clustering of glutaminase suppresses clear cell renal cell carcinoma.
    Boa Kim, Wencao Zhao, Nathan J Coffey, Caitlyn E Bowman, Michael Noji, Cholsoon Jang, M Celeste Simon, Zoltan Arany.
      Clear cell renal cell carcinomas (ccRCC) are largely driven by HIF2α and are avid consumers of glutamine. However, inhibitors of glutaminase1 (GLS1), the first step in glutaminolysis, have not shown benefit in phase III trials, and HIF2α inhibition, recently FDA-approved for treatment of ccRCC, shows great but incomplete benefits, underscoring the need to better understand the roles of glutamine and HIF2α in ccRCC. Here, we report that glutamine deprivation rapidly redistributes GLS1 into isolated clusters within mitochondria across diverse cell types, excluding ccRCC. GLS1 clustering is rapid (1-3 hours) and reversible, is specifically driven by the level of intracellular glutamate, and is mediated by mitochondrial fission. Clustered GLS1 has markedly enhanced glutaminase activity and promotes cell death under glutamine-deprived conditions. We further show that HIF2α prevents GLS1 clustering, independently of its transcriptional activity, thereby protecting ccRCC cells from cell death induced by glutamine deprivation. Reversing this protection, by genetic expression of GLS1 mutants that constitutively cluster, enhances ccRCC cell death in culture and suppresses ccRCC growth in vivo . These finding provide multiple insights into cellular glutamine handling, including a novel metabolic pathway by which HIF2α promotes ccRCC, and reveals a potential therapeutic avenue to synergize with HIF2α inhibition in the treatment of ccRCC.
    DOI:  https://doi.org/10.1101/2024.05.04.592520
  2. Oncogene. 2024 May 15.
    Targeting the glutamine metabolism to suppress cell proliferation in mesenchymal docetaxel-resistant prostate cancer.
    Alicia-Marie K Beier, Celina Ebersbach, Tiziana Siciliano, Jana Scholze, Jörg Hofmann, Pia Hönscheid, Gustavo B Baretton, Kevin Woods, Borhane Guezguez, Anna Dubrovska, Sascha D Markowitsch, Christian Thomas, Martin Puhr, Holger H H Erb.
      Docetaxel (DX) serves as a palliative treatment option for metastatic prostate cancer (PCa). Despite initial remission, acquired DX resistance is inevitable. The mechanisms behind DX resistance have not yet been deciphered, but a mesenchymal phenotype is associated with DX resistance. Mesenchymal phenotypes have been linked to metabolic rewiring, obtaining most ATP production by oxidative phosphorylation (OXPHOS) powered substantially by glutamine (Gln). Likewise, Gln is known to play an essential role in modulating bioenergetic, redox homeostasis and autophagy. Herein, investigations of Gln deprivation on DX-sensitive and -resistant (DR) PCa cells revealed that the DR cell sub-lines were susceptible to Gln deprivation. Mechanistically, Gln deprivation reduced OXPHOS and ATP levels, causing a disturbance in cell cycle progression. Genetic and chemical inhibition of the Gln-metabolism key protein GLS1 could validate the Gln deprivation results, thereby representing a valid therapeutic target. Moreover, immunohistological investigation of GLS1 revealed a high-expressing GLS1 subgroup post-docetaxel failure, exhibiting low overall survival. This subgroup presents an intriguing opportunity for targeted therapy focusing on glutamine metabolism. Thus, these findings highlight a possible clinical rationale for the chemical inhibition of GLS1 as a therapeutic strategy to target mesenchymal DR PCa cells, thereby delaying accelerated tumour progression.
    DOI:  https://doi.org/10.1038/s41388-024-03059-4
  3. Cancer Res. 2024 May 15. 84(10): 1543-1545
    Overcoming Nutrient Stress: Integrin αvβ3-Driven Metabolic Adaptation Supports Tumor Initiation.
    Elena Rainero.
      Nutrient stress accompanies several stages of tumor progression, including metastasis formation. Metabolic reprogramming is a hallmark of cancer, and it has been associated with stress tolerance and anchorage-independent cell survival. Adaptive responses are required to support cancer cell survival under these conditions. In this issue of Cancer Research, Nam and colleagues showed that the extracellular matrix (ECM) receptor integrin β3 was upregulated in lung cancer cells in response to nutrient starvation, resulting in increased cell survival that was independent from ECM binding. Delving into the molecular mechanisms responsible for this, the authors found that integrin β3 promoted glutamine metabolism and oxidative phosphorylation (OXPHOS) by activating a Src/AMPK/PGC1α signaling pathway. Importantly, in vivo experiments confirmed that OXPHOS inhibition suppressed tumor initiation in an orthotopic model of lung cancer, while β3 knockout completely abrogated tumor initiation. These observations indicate that targeting signaling pathways downstream of αvβ3 could represent a promising therapeutic avenue to prevent lung cancer progression and metastasis. See related article by Nam et al., p. 1630.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-24-0453
  4. Mol Med. 2024 May 17. 30(1): 64
    IGF2BP3 promotes glutamine metabolism of endometriosis by interacting with UCA1 to enhances the mRNA stability of GLS1.
    Honglin Wang, Yingying Cao, Yanling Gou, Hao Wang, Zongwen Liang, Qiong Wu, Jiahuan Tan, Jinming Liu, Zhi Li, Jing Cui, Huiyan Zhang, Zongfeng Zhang.
       BACKGROUND: Insulin like growth factor II mRNA binding protein 3 (IGF2BP3) has been implicated in numerous inflammatory and cancerous conditions. However, its precise molecular mechanisms in endometriosis (EMs) remains unclear. The aim of this study is to examine the influence of IGF2BP3 on the occurrence and progression of EMs and to elucidate its underlying molecular mechanism.
    METHODS: Efects of IGF2BP3 on endometriosis were confrmed in vitro and in vivo. Based on bioinformatics analysis, RNA immunoprecipitation (RIP), RNA pull-down assays and Fluorescent in situ hybridization (FISH) were used to show the association between IGF2BP3 and UCA1. Single-cell spatial transcriptomics analysis shows the expression distribution of glutaminase 1 (GLS1) mRNA in EMs. Study the effect on glutamine metabolism after ectopic endometriotic stromal cells (eESCs) were transfected with Sh-IGF2BP3 and Sh-UCA1 lentivirus.
    RESULTS: Immunohistochemical staining have revealed that IGF2BP3 was upregulated in ectopic endometriotic lesions (EC) compared to normal endometrial tissues (EN). The proliferation and migration ability of eESCs were greatly reduced by downregulating IGF2BP3. Additionally, IGF2BP3 has been observed to interact with urothelial carcinoma associated 1 (UCA1), leading to increased stability of GLS1 mRNA and subsequently enhancing glutamine metabolism. Results also demonstrated that IGF2BP3 directly interacts with the 3' UTR region of GLS1 mRNA, influencing its expression and stability. Furthermore, UCA1 was able to bind with c-MYC protein, stabilizing c-MYC mRNA and consequently enhancing GLS1 expression through transcriptional promotion.
    CONCLUSION: These discoveries underscored the critical involvement of IGF2BP3 in the elevation and stability of GLS1 mRNA in the context of glutamine metabolism by interacting with UCA1 in EMs. The implications of our study extended to the identification of possible therapeutic targets for individuals with EMs.
    Keywords:  Endometriosis; GLS1; Glutamine metabolism; IGF2BP3; UCA1; c-MYC
    DOI:  https://doi.org/10.1186/s10020-024-00834-7
  5. Molecules. 2024 May 02. pii: 2110. [Epub ahead of print]29(9):
    Metabolic Rewiring in Cancer: Small Molecule Inhibitors in Colorectal Cancer Therapy.
    Domiziana Masci, Michela Puxeddu, Romano Silvestri, Giuseppe La Regina.
      Alterations in cellular metabolism, such as dysregulation in glycolysis, lipid metabolism, and glutaminolysis in response to hypoxic and low-nutrient conditions within the tumor microenvironment, are well-recognized hallmarks of cancer. Therefore, understanding the interplay between aerobic glycolysis, lipid metabolism, and glutaminolysis is crucial for developing effective metabolism-based therapies for cancer, particularly in the context of colorectal cancer (CRC). In this regard, the present review explores the complex field of metabolic reprogramming in tumorigenesis and progression, providing insights into the current landscape of small molecule inhibitors targeting tumorigenic metabolic pathways and their implications for CRC treatment.
    Keywords:  Warburg effect; cancer; colorectal cancer; glutaminolysis; lactate dehydrogenase; lipid metabolism; metabolism
    DOI:  https://doi.org/10.3390/molecules29092110
  6. bioRxiv. 2024 Apr 29. pii: 2024.04.27.591477. [Epub ahead of print]
    NADPH composite index analysis quantifies the relationship between compartmentalized NADPH dynamics and growth rates in cancer cells.
    Sun Jin Moon, Anush Chiappino-Pepe, Wentao Dong, Joanne K Kelleher, Matthew Vander Heiden, Gregory Stephanopoulos, Hadley D Sikes.
      NADPH, a highly compartmentalized electron donor in mammalian cells, plays essential roles in cell metabolism. However, little is known about how cytosolic and mitochondrial NADPH dynamics relate to cancer cell growth rates in response to varying nutrient conditions. To address this issue, we present NADPH composite index analysis, which quantifies the relationship between compartmentalized NADPH dynamics and growth rates using genetically encoded NADPH sensors, automated image analysis pipeline, and correlation analysis. Through this analysis, we demonstrated that compartmentalized NADPH dynamics patterns were cancer cell-type dependent. Specifically, cytosolic and mitochondrial NADPH dynamics of MDA-MB-231 decreased in response to serine deprivation, while those of HCT-116 increased in response to serine or glutamine deprivation. Furthermore, by introducing a fractional contribution parameter, we correlated cytosolic and mitochondrial NADPH dynamics to growth rates. Using this parameter, we identified cancer cell lines whose growth rates were selectively inhibited by targeting cytosolic or mitochondrial NADPH metabolism. Mechanistically, we identified citrate transporter as a key mitochondrial transporter that maintains compartmentalized NADPH dynamics and growth rates. Altogether, our results present a significant advance in quantifying the relationship between compartmentalized NADPH dynamics and cancer cell growth rates, highlighting a potential of targeting compartmentalized NADPH metabolism for selective cancer cell growth inhibitions.
    DOI:  https://doi.org/10.1101/2024.04.27.591477
  7. Front Immunol. 2024 ;15 1369289
    Enhancing breast cancer outcomes with machine learning-driven glutamine metabolic reprogramming signature.
    Xukui Li, Xue Li, Bin Yang, Songyang Sun, Shu Wang, Fuxun Yu, Tao Wang.
       Background: This study aims to identify precise biomarkers for breast cancer to improve patient outcomes, addressing the limitations of traditional staging in predicting treatment responses.
    Methods: Our analysis encompassed data from over 7,000 breast cancer patients across 14 datasets, which included in-house clinical data and single-cell data from 8 patients (totaling 43,766 cells). We utilized an integrative approach, applying 10 machine learning algorithms in 54 unique combinations to analyze 100 existing breast cancer signatures. Immunohistochemistry assays were performed for empirical validation. The study also investigated potential immunotherapies and chemotherapies.
    Results: Our research identified five consistent glutamine metabolic reprogramming (GMR)-related genes from multi-center cohorts, forming the foundation of a novel GMR-model. This model demonstrated superior accuracy in predicting recurrence and mortality risks compared to existing clinical and molecular features. Patients classified as high-risk by the model exhibited poorer outcomes. IHC validation in 30 patients reinforced these findings, suggesting the model's broad applicability. Intriguingly, the model indicates a differential therapeutic response: low-risk patients may benefit more from immunotherapy, whereas high-risk patients showed sensitivity to specific chemotherapies like BI-2536 and ispinesib.
    Conclusions: The GMR-model marks a significant leap forward in breast cancer prognosis and the personalization of treatment strategies, offering vital insights for the effective management of diverse breast cancer patient populations.
    Keywords:  BI-2536; breast cancer; glutamine metabolism programming; immunotherapy; prognosis
    DOI:  https://doi.org/10.3389/fimmu.2024.1369289
  8. J Clin Invest. 2024 May 14. pii: e171294. [Epub ahead of print]
    L-2-hydroxyglutarate remodeling of the epigenome and epitranscriptome creates a metabolic vulnerability in kidney cancer models.
    Anirban Kundu, Garrett J Brinkley, Hyeyoung Nam, Suman Karki, Richard Kirkman, Madhuparna Pandit, EunHee Shim, Hayley Widden, Juan Liu, Yasaman Heidarian, Nader H Mahmoudzadeh, Alexander J Fitt, Devin Absher, Han-Fei Ding, David K Crossman, William J Placzek, Jason W Locasale, Dinesh Rakheja, Jonathan E McConathy, Rekha Ramachandran, Sejong Bae, Jason M Tennessen, Sunil Sudarshan.
      Tumor cells are known to undergo considerable metabolic reprogramming to meet their unique demands and drive tumor growth. At the same time, this reprogramming may come at a cost with resultant metabolic vulnerabilities. The small molecule L-2-hdroxyglutarate (L-2HG) is elevated in the most common histology of renal cancer. Similar to other oncometabolites, L-2HG has the potential to profoundly impact gene expression. Here, we demonstrate that L-2HG remodels amino acid metabolism in renal cancer cells through the combined effects on histone methylation and RNA N6-methyladenosine (m6A). The combined effects of L-2HG result in a metabolic liability that renders tumors cells reliant on exogenous serine to support proliferation, redox homeostasis, and tumor growth. In concert with these data, high L-2HG kidney cancers demonstrates reduced expression of multiple serine biosynthetic enzymes. Collectively, our data indicate that high L-2HG renal tumors could be specifically targeted by strategies that limit serine availability to tumors.
    Keywords:  Metabolism; Oncology; Urology
    DOI:  https://doi.org/10.1172/JCI171294
  9. iScience. 2024 May 17. 27(5): 109767
    Glutamine promotes human CD8+ T cells and counteracts imiquimod-induced T cell hyporesponsiveness.
    Luisa Bopp, Maria Lopéz Martinez, Clara Schumacher, Robert Seitz, Manuel Huerta Arana, Henning Klapproth, Dominika Lukas, Ju Hee Oh, Daniela Neumayer, Jan W Lackmann, Stefan Mueller, Esther von Stebut, Bent Brachvogel, Susanne Brodesser, Ramon I Klein Geltink, Mario Fabri.
      T cells protect tissues from cancer. Although investigations in mice showed that amino acids (AA) critically regulate T cell immunity, this remains poorly understood in humans. Here, we describe the AA composition of interstitial fluids in keratinocyte-derived skin cancers (KDSCs) and study the effect of AA on T cells using models of primary human cells and tissues. Gln contributed to ∼15% of interstitial AAs and promoted interferon gamma (IFN-γ), but not granzyme B (GzB) expression, in CD8+ T cells. Furthermore, the Toll-like receptor 7 agonist imiquimod (IMQ), a common treatment for KDSCs, down-regulated the metabolic gatekeepers c-MYC and mTORC1, as well as the AA transporter ASCT2 and intracellular Gln, Asn, Ala, and Asp in T cells. Reduced proliferation and IFN-γ expression, yet increased GzB, paralleled IMQ effects on AA. Finally, Gln was sufficient to promote IFN-γ-production in IMQ-treated T cells. Our findings indicate that Gln metabolism can be harnessed for treating KDSCs.
    Keywords:  Dermatology; Immunology
    DOI:  https://doi.org/10.1016/j.isci.2024.109767
  10. Clin Nutr. 2024 Apr 30. pii: S0261-5614(24)00143-2. [Epub ahead of print]43(6): 1522-1523
    Enteral glutamine for trauma patients in intensive care unit - Comment on: ESPEN practical and partially revised guideline: Clinical nutrition in the intensive care unit.
    Artur Barbosa Gomes, David de Sousa Cortez Barros, Ana Beatriz Gonçalves Portela Alves de Sousa, Lara Rafaela Alves Dos Santos.
      
    Keywords:  Enteral nutrition; Glutamine; Intensive care unit
    DOI:  https://doi.org/10.1016/j.clnu.2024.04.036
  11. bioRxiv. 2024 Apr 29. pii: 2024.04.29.591168. [Epub ahead of print]
    Spatial hepatocyte plasticity of gluconeogenesis during the metabolic transitions between fed, fasted and starvation states.
    Junichi Okada, Austin Landgraf, Alus M Xiaoli, Li Liu, Maxwell Horton, Victor L Schuster, Fajun Yang, Simone Sidoli, Yunping Qiu, Irwin J Kurland, Carolina Eliscovich, Kosaku Shinoda, Jeffrey E Pessin.
      The liver acts as a master regulator of metabolic homeostasis in part by performing gluconeogenesis. This process is dysregulated in type 2 diabetes, leading to elevated hepatic glucose output. The parenchymal cells of the liver (hepatocytes) are heterogeneous, existing on an axis between the portal triad and the central vein, and perform distinct functions depending on location in the lobule. Here, using single cell analysis of hepatocytes across the liver lobule, we demonstrate that gluconeogenic gene expression ( Pck1 and G6pc ) is relatively low in the fed state and gradually increases first in the periportal hepatocytes during the initial fasting period. As the time of fasting progresses, pericentral hepatocyte gluconeogenic gene expression increases, and following entry into the starvation state, the pericentral hepatocytes show similar gluconeogenic gene expression to the periportal hepatocytes. Similarly, pyruvate-dependent gluconeogenic activity is approximately 10-fold higher in the periportal hepatocytes during the initial fasting state but only 1.5-fold higher in the starvation state. In parallel, starvation suppresses canonical beta-catenin signaling and modulates expression of pericentral and periportal glutamine synthetase and glutaminase, resulting in an enhanced pericentral glutamine-dependent gluconeogenesis. These findings demonstrate that hepatocyte gluconeogenic gene expression and gluconeogenic activity are highly spatially and temporally plastic across the liver lobule, underscoring the critical importance of using well-defined feeding and fasting conditions to define the basis of hepatic insulin resistance and glucose production.
    DOI:  https://doi.org/10.1101/2024.04.29.591168
  12. Nucleosides Nucleotides Nucleic Acids. 2024 May 14. 1-15
    The emerging roles of glutamine amidotransferases in metabolism and immune defense.
    Taolin Xie, Chao Qin, Ali Can Savas, Wayne Wei Yeh, Pinghui Feng.
      Glutamine amidotransferases (GATs) catalyze the synthesis of nucleotides, amino acids, glycoproteins and an enzyme cofactor, thus serving as key metabolic enzymes for cell proliferation. Carbamoyl-phosphate synthetase, Aspartate transcarbamoylase, and Dihydroorotase (CAD) is a multifunctional enzyme of the GAT family and catalyzes the first three steps of the de novo pyrimidine synthesis. Following our findings that cellular GATs are involved in immune evasion during herpesvirus infection, we discovered that CAD reprograms cellular metabolism to fuel aerobic glycolysis and nucleotide synthesis via deamidating RelA. Deamidated RelA activates the expression of key glycolytic enzymes, rather than that of the inflammatory NF-κB-responsive genes. As such, cancer cells prime RelA for deamidation via up-regulating CAD activity or accumulating RelA mutations. Interestingly, the recently emerged SARS-CoV-2 also activates CAD to couple evasion of inflammatory response to activated nucleotide synthesis. A small molecule inhibitor of CAD depletes nucleotide supply and boosts antiviral inflammatory response, thus greatly reducing SARS-CoV-2 replication. Additionally, we also found that CTP synthase 1 (CTPS1) deamidates interferon (IFN) regulatory factor 3 (IRF3) to mute IFN induction. Our previous studies have implicated phosphoribosyl formylglycinamidine synthase (PFAS) and phosphoribosyl pyrophosphate amidotransferase (PPAT) in deamidating retinoic acid-inducible gene I (RIG-I) and evading dsRNA-induced innate immune defense in herpesvirus infection. Overall, these studies have uncovered an unconventional enzymatic activity of cellular GATs in metabolism and immune defense, offering a molecular link intimately coupling these fundamental biological processes.
    Keywords:  Glutamine amidotransferase; innate immunity; nucleotide synthesis; protein deamidation; tumor metabolism; viral infection
    DOI:  https://doi.org/10.1080/15257770.2024.2351135
  13. Gastroenterology. 2024 May 15. pii: S0016-5085(24)04917-5. [Epub ahead of print]
    Emerging Trends in Gastrointestinal Cancer Targeted Therapies: Harnessing Tumor Microenvironment, Immune Factors, and Metabolomics Insights.
    Sanchita Rauth, Mokenge Malafa, Moorthy P Ponnusamy, Surinder K Batra.
      Gastrointestinal (GI) cancers are the leading cause of new cancer cases and cancer-related deaths worldwide. The treatment strategies for patients with GI tumors have focused on oncogenic molecular profiles associated with tumor cells. Recent evidence demonstrated that tumor cell functions are modulated by its microenvironment, compromising fibroblasts, ECMs, microbiome, immune cells, and the enteric nervous system. Along with the TME components, alterations in key metabolic pathways have emerged as a hallmark of tumor cells. From these perspectives, this review will highlight the functions of different cellular components of the GI tumor microenvironment (TME) and their implications for treatment. Furthermore, we discuss the major metabolic reprogramming in GI tumor cells and how understanding metabolic rewiring could lead to new therapeutic strategies. Finally, we briefly summarize the targeted agents currently being studied in GI cancers. Understanding the complex interplay between tumor cell-intrinsic and cell-extrinsic during tumor progression is critical for developing new therapeutic strategies.
    Keywords:  Gastrointestinal cancers; Immune landscapes; Metabolic reprogramming; Targeted therapies; Tumor microenvironment
    DOI:  https://doi.org/10.1053/j.gastro.2024.05.005
  14. Elife. 2024 May 13. pii: RP91141. [Epub ahead of print]12
    Retinal metabolism displays evidence for uncoupling of glycolysis and oxidative phosphorylation via Cori-, Cahill-, and mini-Krebs-cycle.
    Yiyi Chen, Laimdota Zizmare, Victor Calbiague, Lan Wang, Shirley Yu, Fritz W Herberg, Oliver Schmachtenberg, Francois Paquet-Durand, Christoph Trautwein.
      The retina consumes massive amounts of energy, yet its metabolism and substrate exploitation remain poorly understood. Here, we used a murine explant model to manipulate retinal energy metabolism under entirely controlled conditions and utilised 1H-NMR spectroscopy-based metabolomics, in situ enzyme detection, and cell viability readouts to uncover the pathways of retinal energy production. Our experimental manipulations resulted in varying degrees of photoreceptor degeneration, while the inner retina and retinal pigment epithelium were essentially unaffected. This selective vulnerability of photoreceptors suggested very specific adaptations in their energy metabolism. Rod photoreceptors were found to rely strongly on oxidative phosphorylation, but only mildly on glycolysis. Conversely, cone photoreceptors were dependent on glycolysis but insensitive to electron transport chain decoupling. Importantly, photoreceptors appeared to uncouple glycolytic and Krebs-cycle metabolism via three different pathways: (1) the mini-Krebs-cycle, fuelled by glutamine and branched chain amino acids, generating N-acetylaspartate; (2) the alanine-generating Cahill-cycle; (3) the lactate-releasing Cori-cycle. Moreover, the metabolomics data indicated a shuttling of taurine and hypotaurine between the retinal pigment epithelium and photoreceptors, likely resulting in an additional net transfer of reducing power to photoreceptors. These findings expand our understanding of retinal physiology and pathology and shed new light on neuronal energy homeostasis and the pathogenesis of neurodegenerative diseases.
    Keywords:  aerobic glycolysis; glucose transport; glucose-alanine cycle; mouse; neuroscience; photoreceptor metabolism; retinal metabolism; retinitis pigmentosa
    DOI:  https://doi.org/10.7554/eLife.91141
  15. Nat Commun. 2024 May 15. 15(1): 4114
    IRE1α determines ferroptosis sensitivity through regulation of glutathione synthesis.
    Dadi Jiang, Youming Guo, Tianyu Wang, Liang Wang, Yuelong Yan, Ling Xia, Rakesh Bam, Zhifen Yang, Hyemin Lee, Takao Iwawaki, Boyi Gan, Albert C Koong.
      Cellular sensitivity to ferroptosis is primarily regulated by mechanisms mediating lipid hydroperoxide detoxification. We show that inositol-requiring enzyme 1 (IRE1α), an endoplasmic reticulum (ER) resident protein critical for the unfolded protein response (UPR), also determines cellular sensitivity to ferroptosis. Cancer and normal cells depleted of IRE1α gain resistance to ferroptosis, while enhanced IRE1α expression promotes sensitivity to ferroptosis. Mechanistically, IRE1α's endoribonuclease activity cleaves and down-regulates the mRNA of key glutathione biosynthesis regulators glutamate-cysteine ligase catalytic subunit (GCLC) and solute carrier family 7 member 11 (SLC7A11). This activity of IRE1α is independent of its role in regulating the UPR and is evolutionarily conserved. Genetic deficiency and pharmacological inhibition of IRE1α have similar effects in inhibiting ferroptosis and reducing renal ischemia-reperfusion injury in mice. Our findings reveal a previously unidentified role of IRE1α to regulate ferroptosis and suggests inhibition of IRE1α as a promising therapeutic strategy to mitigate ferroptosis-associated pathological conditions.
    DOI:  https://doi.org/10.1038/s41467-024-48330-0
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