bims-mibica 2024-03-10 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2024‒03‒10
24 papers selected by
Kelsey Fisher-Wellman, East Carolina University

CLU (clusterin) and PPARGC1A/PGC1α coordinately control mitophagy and mitochondrial biogenesis for oral cancer cell survival.
Inhibition of mitochondrial folate metabolism drives differentiation through mTORC1 mediated purine sensing.
Acquired Multidrug Resistance in AML Is Caused by Low Apoptotic Priming in Relapsed Myeloblasts.
Mitochondrial ATP generation is more proteome efficient than glycolysis.
Autophagy sustains mitochondrial respiration and determines resistance to BRAFV600E inhibition in thyroid carcinoma cells.
Regulation of metastatic potential by drug repurposing and mitochondrial targeting in colorectal cancer cells.
A mitochondrial NADPH-cholesterol axis regulates extracellular vesicle biogenesis to support hematopoietic stem cell fate.
Identification of a novel MT-ND3 variant and restoring mitochondrial function by allotopic expression of MT-ND3 gene.
Everolimus decreases [U-13C]glucose utilization by pyruvate carboxylase in breast cancer cells in vitro and in vivo.
Fatty acid oxidation fuels natural killer cell responses against infection and cancer.
Mitochondrial fission enhances IL-6-induced metastatic potential in ovarian cancer via ERK1/2 activation.
Regulation of urea cycle by reversible high-stoichiometry lysine succinylation.
Hepatic malonyl-CoA synthesis restrains gluconeogenesis by suppressing fat oxidation, pyruvate carboxylation, and amino acid availability.
Mechanism of proton-powered c-ring rotation in a mitochondrial ATP synthase.
Two ancient membrane pores mediate mitochondrial-nucleus membrane contact sites.
Mechanisms of resistance to venetoclax in hematologic malignancies.
How and When to Measure Mitochondrial Inner Membrane Potentials.
Hepatocellular carcinoma cells downregulate NADH:Ubiquinone Oxidoreductase Subunit B3 to maintain reactive oxygen species homeostasis.
Absence of both MGME1 and POLG EXO abolishes mtDNA whereas absence of either creates unique mtDNA duplications.
The MYC-NFATC2 axis maintains the cell cycle and mitochondrial function in acute myeloid leukaemia cells.
ISGylation of DRP1 closely balances other post-translational modifications to mediate mitochondrial fission.
Metabolic collaboration between cells in the tumor microenvironment has a negligible effect on tumor growth.
Impact of NDUFAF6 on breast cancer prognosis: linking mitochondrial regulation to immune response and PD-L1 expression.
Targeting carnitine palmitoyl transferase 1A (CPT1A) induces ferroptosis and synergizes with immunotherapy in lung cancer.

Autophagy. 2024 Mar 06. 1-25

CLU (clusterin) and PPARGC1A/PGC1α coordinately control mitophagy and mitochondrial biogenesis for oral cancer cell survival.

Prakash P Praharaj, Srimanta Patra, Amruta Singh, Debasna P Panigrahi, Hwa Y Lee, Mohammad F Kabir, Muhammad K Hossain, Samir K Patra, Birija S Patro, Shankargouda Patil, Daniel J Klionsky, Han J Chae, Sujit K Bhutia.

  Mitophagy involves the selective elimination of defective mitochondria during chemotherapeutic stress to maintain mitochondrial homeostasis and sustain cancer growth. Here, we showed that CLU (clusterin) is localized to mitochondria to induce mitophagy controlling mitochondrial damage in oral cancer cells. Moreover, overexpression and knockdown of CLU establish its mitophagy-specific role, where CLU acts as an adaptor protein that coordinately interacts with BAX and LC3 recruiting autophagic machinery around damaged mitochondria in response to cisplatin treatment. Interestingly, CLU triggers class III phosphatidylinositol 3-kinase (PtdIns3K) activity around damaged mitochondria, and inhibition of mitophagic flux causes the accumulation of excessive mitophagosomes resulting in reactive oxygen species (ROS)-dependent apoptosis during cisplatin treatment in oral cancer cells. In parallel, we determined that PPARGC1A/PGC1α (PPARG coactivator 1 alpha) activates mitochondrial biogenesis during CLU-induced mitophagy to maintain the mitochondrial pool. Intriguingly, PPARGC1A inhibition through small interfering RNA (siPPARGC1A) and pharmacological inhibitor (SR-18292) treatment counteracts CLU-dependent cytoprotection leading to mitophagy-associated cell death. Furthermore, co-treatment of SR-18292 with cisplatin synergistically suppresses tumor growth in oral cancer xenograft models. In conclusion, CLU and PPARGC1A are essential for sustained cancer cell growth by activating mitophagy and mitochondrial biogenesis, respectively, and their inhibition could provide better therapeutic benefits against oral cancer.

Keywords:  Clusterin; PPARGC1A/PGC1α; mitochondrial biogenesis; mitophagy; mitophagy-associated cell death

DOI:  https://doi.org/10.1080/15548627.2024.2309904
Nat Commun. 2024 Mar 02. 15(1): 1931

Inhibition of mitochondrial folate metabolism drives differentiation through mTORC1 mediated purine sensing.

Martha M Zarou, Kevin M Rattigan, Daniele Sarnello, Engy Shokry, Amy Dawson, Angela Ianniciello, Karen Dunn, Mhairi Copland, David Sumpton, Alexei Vazquez, G Vignir Helgason.

Supporting cell proliferation through nucleotide biosynthesis is an essential requirement for cancer cells. Hence, inhibition of folate-mediated one carbon (1C) metabolism, which is required for nucleotide synthesis, has been successfully exploited in anti-cancer therapy. Here, we reveal that mitochondrial folate metabolism is upregulated in patient-derived leukaemic stem cells (LSCs). We demonstrate that inhibition of mitochondrial 1C metabolism through impairment of de novo purine synthesis has a cytostatic effect on chronic myeloid leukaemia (CML) cells. Consequently, changes in purine nucleotide levels lead to activation of AMPK signalling and suppression of mTORC1 activity. Notably, suppression of mitochondrial 1C metabolism increases expression of erythroid differentiation markers. Moreover, we find that increased differentiation occurs independently of AMPK signalling and can be reversed through reconstitution of purine levels and reactivation of mTORC1. Of clinical relevance, we identify that combination of 1C metabolism inhibition with imatinib, a frontline treatment for CML patients, decreases the number of therapy-resistant CML LSCs in a patient-derived xenograft model. Our results highlight a role for folate metabolism and purine sensing in stem cell fate decisions and leukaemogenesis.

DOI: https://doi.org/10.1038/s41467-024-46114-0
Blood Cancer Discov. 2024 Mar 04. OF1-OF22

Acquired Multidrug Resistance in AML Is Caused by Low Apoptotic Priming in Relapsed Myeloblasts.

Elyse A Olesinski, Karanpreet Singh Bhatia, Chuqi Wang, Marissa S Pioso, Xiao Xian Lin, Ahmed M Mamdouh, Shu Xuan Ng, Vedant Sandhu, Shaista Shabbir Jasdanwala, Binyam Yilma, Stephan Bohl, Jeremy A Ryan, Disha Malani, Marlise R Luskin, Olli Kallioniemi, Kimmo Porkka, Sophia Adamia, Wee Joo Chng, Motomi Osato, David M Weinstock, Jacqueline S Garcia, Anthony Letai, Shruti Bhatt.

In many cancers, mortality is associated with the emergence of relapse with multidrug resistance (MDR). Thus far, the investigation of cancer relapse mechanisms has largely focused on acquired genetic mutations. Using acute myeloid leukemia (AML) patient-derived xenografts (PDX), we systematically elucidated a basis of MDR and identified drug sensitivity in relapsed AML. We derived pharmacologic sensitivity for 22 AML PDX models using dynamic BH3 profiling (DBP), together with genomics and transcriptomics. Using in vivo acquired resistant PDXs, we found that resistance to unrelated, narrowly targeted agents in distinct PDXs was accompanied by broad resistance to drugs with disparate mechanisms. Moreover, baseline mitochondrial apoptotic priming was consistently reduced regardless of the class of drug-inducing selection. By applying DBP, we identified drugs showing effective in vivo activity in resistant models. This study implies evasion of apoptosis drives drug resistance and demonstrates the feasibility of the DBP approach to identify active drugs for patients with relapsed AML.SIGNIFICANCE: Acquired resistance to targeted therapy remains challenging in AML. We found that reduction in mitochondrial priming and common transcriptomic signatures was a conserved mechanism of acquired resistance across different drug classes in vivo. Drugs active in vivo can be identified even in the multidrug resistant state by DBP.

DOI: https://doi.org/10.1158/2643-3230.BCD-24-0001
Nat Chem Biol. 2024 Mar 06.

Mitochondrial ATP generation is more proteome efficient than glycolysis.

Yihui Shen, Hoang V Dinh, Edward R Cruz, Zihong Chen, Caroline R Bartman, Tianxia Xiao, Catherine M Call, Rolf-Peter Ryseck, Jimmy Pratas, Daniel Weilandt, Heide Baron, Arjuna Subramanian, Zia Fatma, Zong-Yen Wu, Sudharsan Dwaraknath, John I Hendry, Vinh G Tran, Lifeng Yang, Yasuo Yoshikuni, Huimin Zhao, Costas D Maranas, Martin Wühr, Joshua D Rabinowitz.

Metabolic efficiency profoundly influences organismal fitness. Nonphotosynthetic organisms, from yeast to mammals, derive usable energy primarily through glycolysis and respiration. Although respiration is more energy efficient, some cells favor glycolysis even when oxygen is available (aerobic glycolysis, Warburg effect). A leading explanation is that glycolysis is more efficient in terms of ATP production per unit mass of protein (that is, faster). Through quantitative flux analysis and proteomics, we find, however, that mitochondrial respiration is actually more proteome efficient than aerobic glycolysis. This is shown across yeast strains, T cells, cancer cells, and tissues and tumors in vivo. Instead of aerobic glycolysis being valuable for fast ATP production, it correlates with high glycolytic protein expression, which promotes hypoxic growth. Aerobic glycolytic yeasts do not excel at aerobic growth but outgrow respiratory cells during oxygen limitation. We accordingly propose that aerobic glycolysis emerges from cells maintaining a proteome conducive to both aerobic and hypoxic growth.

DOI: https://doi.org/10.1038/s41589-024-01571-y
Autophagy. 2024 Mar 04. 1-15

Autophagy sustains mitochondrial respiration and determines resistance to BRAFV600E inhibition in thyroid carcinoma cells.

Sergio Díaz-Gago, Javier Vicente-Gutiérrez, Jose Manuel Ruiz-Rodríguez, Josep Calafell, Alicia Álvarez-Álvarez, Marina Lasa, Antonio Chiloeches, Pablo Baquero.

  BRAFV600E is the most prevalent mutation in thyroid cancer and correlates with poor prognosis and therapy resistance. Although selective inhibitors of BRAFV600E have been developed, more advanced tumors such as anaplastic thyroid carcinomas show a poor response in clinical trials. Therefore, the study of alternative survival mechanisms is needed. Since metabolic changes have been related to malignant progression, in this work we explore metabolic dependencies of thyroid tumor cells to exploit them therapeutically. Our results show that respiration of thyroid carcinoma cells is highly dependent on fatty acid oxidation and, in turn, fatty acid mitochondrial availability is regulated through macroautophagy/autophagy. Furthermore, we show that both lysosomal inhibition and the knockout of the essential autophagy gene, ATG7, lead to enhanced lipolysis; although this effect is not essential for survival of thyroid carcinoma cells. We also demonstrate that following inhibition of either autophagy or fatty acid oxidation, thyroid tumor cells compensate oxidative phosphorylation deficiency with an increase in glycolysis. In contrast to lipolysis induction, upon autophagy inhibition, glycolytic boost in autophagy-deficient cells is essential for survival and, importantly, correlates with a higher sensitivity to the BRAFV600E selective inhibitor, vemurafenib. In agreement, downregulation of the glycolytic pathway results in enhanced mitochondrial respiration and vemurafenib resistance. Our work provides new insights into the role of autophagy in thyroid cancer metabolism and supports mitochondrial targeting in combination with vemurafenib to eliminate BRAFV600E-positive thyroid carcinoma cells.Abbreviations: AMP: adenosine monophosphate; ATC: anaplastic thyroid carcinoma; ATG: autophagy related; ATP: adenosine triphosphate; BRAF: B-Raf proto-oncogene, serine/threonine kinase; Cas9: CRISPR-associated protein; CREB: cAMP responsive element binding protein; CRISPR: clustered regularly interspaced short palindromic repeats; 2DG: 2-deoxyglucose; FA: fatty acid; FAO: fatty acid oxidation; FASN: fatty acid synthase; FCCP: trifluoromethoxy carbonyl cyanide phenylhydrazone; LAMP1: lysosomal associated membrane protein 1; LIPE/HSL: lipase E, hormone sensitive type; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; OCR: oxygen consumption rate; OXPHOS: oxidative phosphorylation; PRKA/PKA: protein kinase cAMP-activated; PTC: papillary thyroid carcinoma; SREBF1/SREBP1: sterol regulatory element binding transcription factor 1.

Keywords:  Cancer metabolism; fatty acid oxidation; glycolysis; oxidative phosphorylation; thyroid cancer; vemurafenib resistance

DOI:  https://doi.org/10.1080/15548627.2024.2312790
BMC Cancer. 2024 Mar 08. 24(1): 323

Regulation of metastatic potential by drug repurposing and mitochondrial targeting in colorectal cancer cells.

Shashank Mathur, Pransu Srivastava, Anubhav Srivastava, Neeraj Kumar Rai, Sabiya Abbas, Ashok Kumar, Meenakshi Tiwari, Lokendra Kumar Sharma.

  BACKGROUND: Increased mitochondrial activities contributing to cancer cell proliferation, invasion, and metastasis have been reported in different cancers; however, studies on the therapeutic targeting of mitochondria in regulating cell proliferation and invasiveness are limited. Because mitochondria are believed to have evolved through bacterial invasion in mammalian cells, antibiotics could provide an alternative approach to target mitochondria, especially in cancers with increased mitochondrial activities. In this study, we investigated the therapeutic potential of bacteriostatic antibiotics in regulating the growth potential of colorectal cancer (CRC) cells, which differ in their metastatic potential and mitochondrial functions.METHODS: A combination of viability, cell migration, and spheroid formation assays was used to measure the effect on metastatic potential. The effect on mitochondrial mechanisms was investigated by measuring mitochondrial DNA copy number by qPCR, biogenesis (by qPCR and immunoblotting), and functions by measuring reactive oxygen species, membrane potential, and ATP using standard methods. In addition, the effect on assembly and activities of respiratory chain (RC) complexes was determined using blue native gel electrophoresis and in-gel assays, respectively). Changes in metastatic and cell death signaling were measured by immunoblotting with specific marker proteins and compared between CRC cells.
RESULTS: Both tigecycline and tetracycline effectively reduced the viability, migration, and spheroid-forming capacity of highly metastatic CRC cells. This increased sensitivity was attributed to reduced mtDNA content, mitochondrial biogenesis, ATP content, membrane potential, and increased oxidative stress. Specifically, complex I assembly and activity were significantly inhibited by these antibiotics in high-metastatic cells. Significant down-regulation in the expression of mitochondrial-mediated survival pathways, such as phospho-AKT, cMYC, phospho-SRC, and phospho-FAK, and upregulation in cell death (apoptosis and autophagy) were observed, which contributed to the enhanced sensitivity of highly metastatic CRC cells toward these antibiotics. In addition, the combined treatment of the CRC chemotherapeutic agent oxaliplatin with tigecycline/tetracycline at physiological concentrations effectively sensitized these cells at early time points.
CONCLUSION: Altogether, our study reports that bacterial antibiotics, such as tigecycline and tetracycline, target mitochondrial functions specifically mitochondrial complex I architecture and activity and would be useful in combination with cancer chemotherapeutics for high metastatic conditions.

Keywords:  Metastasis; Mitochondria; Mitochondrial antibiotics; Mitochondrial complex I; Oxidative stress

DOI:  https://doi.org/10.1186/s12885-024-12064-5
Cell Stem Cell. 2024 Mar 07. pii: S1934-5909(24)00047-X. [Epub ahead of print]31(3): 359-377.e10

A mitochondrial NADPH-cholesterol axis regulates extracellular vesicle biogenesis to support hematopoietic stem cell fate.

Massimo Bonora, Claudia Morganti, Nick van Gastel, Kyoko Ito, Enrica Calura, Ilaria Zanolla, Letizia Ferroni, Yang Zhang, Yookyung Jung, Gabriele Sales, Paolo Martini, Takahisa Nakamura, Francesco Massimo Lasorsa, Toren Finkel, Charles P Lin, Barbara Zavan, Paolo Pinton, Irene Georgakoudi, Chiara Romualdi, David T Scadden, Keisuke Ito.

  Mitochondrial fatty acid oxidation (FAO) is essential for hematopoietic stem cell (HSC) self-renewal; however, the mechanism by which mitochondrial metabolism controls HSC fate remains unknown. Here, we show that within the hematopoietic lineage, HSCs have the largest mitochondrial NADPH pools, which are required for proper HSC cell fate and homeostasis. Bioinformatic analysis of the HSC transcriptome, biochemical assays, and genetic inactivation of FAO all indicate that FAO-generated NADPH fuels cholesterol synthesis in HSCs. Interference with FAO disturbs the segregation of mitochondrial NADPH toward corresponding daughter cells upon single HSC division. Importantly, we have found that the FAO-NADPH-cholesterol axis drives extracellular vesicle (EV) biogenesis and release in HSCs, while inhibition of EV signaling impairs HSC self-renewal. These data reveal the existence of a mitochondrial NADPH-cholesterol axis for EV biogenesis that is required for hematopoietic homeostasis and highlight the non-stochastic nature of HSC fate determination.

Keywords:  HSC self-renewal; NADPH; cholesterol; exosomes; extracellular vesicles; fate determination; fatty acid oxidation; hematopoietic stem cell; metabolism; mitochondria

DOI:  https://doi.org/10.1016/j.stem.2024.02.004
Mitochondrion. 2024 Mar 02. pii: S1567-7249(24)00016-3. [Epub ahead of print] 101858

Identification of a novel MT-ND3 variant and restoring mitochondrial function by allotopic expression of MT-ND3 gene.

Nurun Nahar Borna, Yoshihito Kishita, Masaru Shimura, Kei Murayama, Akira Ohtake, Yasushi Okazaki.

  Mitochondrial diseases are caused by nuclear, or mitochondrial DNA (mtDNA) variants and related co-factors. Here, we report a novel m.10197G > C variant in MT-ND3 in a patient, and two other patients with m.10191 T > C. MT-ND3 variants are known to cause Leigh syndrome or mitochondrial complex I deficiency. We performed the functional analyses of the novel m.10197G > C variant that significantly lowered MT-ND3 protein levels, causing complex I assembly and activity deficiency, and reduction of ATP synthesis. We adapted a previously described re-engineering technique of delivering mitochondrial genes into mitochondria through codon optimization for nuclear expression and translation by cytoplasmic ribosomes to rescue defects arising from the MT-ND3 variants. We constructed mitochondrial targeting sequences along with the codon-optimized MT-ND3 and imported them into the mitochondria. To achieve the goal, we imported codon-optimized MT-ND3 into mitochondria in three patients with m.10197G > C and m.10191 T > C missense variants in the MT-ND3. Nuclear expression of the MT-ND3 gene partially restored protein levels, complex I deficiency, and significant improvement of ATP production indicating a functional rescue of the mutant phenotype. The codon-optimized nuclear expression of mitochondrial protein and import inside the mitochondria can supplement the requirements for ATP in energy-deficient mitochondrial disease patients.

Keywords:  Allotopic expression; Codon-optimization; Leigh Syndrome; MT-ND3; Mitochondrial DNA

DOI:  https://doi.org/10.1016/j.mito.2024.101858
Biomed Pharmacother. 2024 Mar 02. pii: S0753-3322(24)00246-4. [Epub ahead of print]173 116362

Everolimus decreases [U-13C]glucose utilization by pyruvate carboxylase in breast cancer cells in vitro and in vivo.

Gerke Ariaans, Jiske F Tiersma, Bernardus Evers, Albert Gerding, Stijn J H Waaijer, Remco A Koster, Daan J Touw, Barbara M Bakker, Dirk-Jan Reijngoud, Steven de Jong, Mathilde Jalving.

  Reprogrammed metabolism is a hallmark of cancer, but notoriously difficult to target due to metabolic plasticity, especially in response to single metabolic interventions. Combining mTOR inhibitor everolimus and mitochondrial complex 1 inhibitor metformin results in metabolic synergy in in vitro models of triple-negative breast cancer. Here, we investigated whether the effect of this drug combination on tumor size is reflected in changes in tumor metabolism using [U-13C]glucose labeling in an MDA-MB-231 triple negative breast cancer xenograft model. The in vitro effects of everolimus and metformin treatment on oxidative phosphorylation and glycolysis reflected changes in 13C-labeling of metabolites in MDA-MB-231 cells. Treatment of MDA-MB-231 xenografts in SCID/Beige mice with everolimus resulted in slower tumor growth and reduced tumor size and tumor viability by 35%. Metformin treatment moderately inhibited tumor growth but did not enhance everolimus-induced effects. High serum levels of everolimus were reached, whereas levels of metformin were relatively low. Everolimus decreased TCA cycle metabolite labeling and inhibited pyruvate carboxylase activity. Metformin only caused a mild reduction in glycolytic metabolite labeling and did not affect pyruvate carboxylase activity or TCA cycle metabolite labeling. In conclusion, treatment with everolimus, but not metformin, decreased tumor size and viability. Furthermore, the efficacy of everolimus was reflected in reduced 13C-labeling of TCA cycle intermediates and reduced pyruvate carboxylase activity. By using in-depth analysis of drug-induced changes in glucose metabolism in combination with measurement of drug levels in tumor and plasma, effects of metabolically targeted drugs can be explained, and novel targets can be identified.

Keywords:  Breast cancer; Cancer metabolism; Everolimus; Metformin; [U-(13)C]glucose

DOI:  https://doi.org/10.1016/j.biopha.2024.116362
Proc Natl Acad Sci U S A. 2024 Mar 12. 121(11): e2319254121

Fatty acid oxidation fuels natural killer cell responses against infection and cancer.

Sam Sheppard, Katja Srpan, Wendy Lin, Mariah Lee, Rebecca B Delconte, Mark Owyong, Peter Carmeliet, Daniel M Davis, Joao B Xavier, Katharine C Hsu, Joseph C Sun.

  Natural killer (NK) cells are a vital part of the innate immune system capable of rapidly clearing mutated or infected cells from the body and promoting an immune response. Here, we find that NK cells activated by viral infection or tumor challenge increase uptake of fatty acids and their expression of carnitine palmitoyltransferase I (CPT1A), a critical enzyme for long-chain fatty acid oxidation. Using a mouse model with an NK cell-specific deletion of CPT1A, combined with stable 13C isotope tracing, we observe reduced mitochondrial function and fatty acid-derived aspartate production in CPT1A-deficient NK cells. Furthermore, CPT1A-deficient NK cells show reduced proliferation after viral infection and diminished protection against cancer due to impaired actin cytoskeleton rearrangement. Together, our findings highlight that fatty acid oxidation promotes NK cell metabolic resilience, processes that can be optimized in NK cell-based immunotherapies.

Keywords:  NK cells; T cells; cancer; metabolism; virus infection

DOI:  https://doi.org/10.1073/pnas.2319254121
Cancer Sci. 2024 Mar 03.

Mitochondrial fission enhances IL-6-induced metastatic potential in ovarian cancer via ERK1/2 activation.

Juwon Lee, Youngjin Han, Soochi Kim, HyunA Jo, Wenyu Wang, Untack Cho, Se Ik Kim, Boyun Kim, Yong Sang Song.

  Ovarian cancer is a lethal gynecologic cancer mostly diagnosed in an advanced stage with an accumulation of ascites. Interleukin-6 (IL-6), a pro-inflammatory cytokine is highly elevated in malignant ascites and plays a pleiotropic role in cancer progression. Mitochondria are dynamic organelles that undergo fission and fusion in response to external stimuli and dysregulation in their dynamics has been implicated in cancer progression and metastasis. Here, we investigate the effect of IL-6 on mitochondrial dynamics in ovarian cancer cells (OVCs) and its impact on metastatic potential. Treatment with IL-6 on ovarian cancer cell lines (SKOV3 and PA-1) led to an elevation in the metastatic potential of OVCs. Interestingly, a positive association was observed between dynamin-related protein 1 (Drp1), a regulator of mitochondrial fission, and IL-6R in metastatic ovarian cancer tissues. Additionally, IL-6 treatment on OVCs was linked to the activation of Drp1, with a notable increase in the ratio of the inhibitory form p-Drp1(S637) to the active form p-Drp1(S616), indicating enhanced mitochondrial fission. Moreover, IL-6 treatment triggered the activation of ERK1/2, and inhibiting ERK1/2 mitigated IL-6-induced mitochondrial fission. Suppressing mitochondrial fission through siRNA transfection and a pharmacological inhibitor reduced the IL-6-induced migration and invasion of OVCs. This was further supported by 3D invasion assays using patient-derived spheroids. Altogether, our study suggests the role of mitochondrial fission in the metastatic potential of OVCs induced by IL-6. The inhibition of mitochondrial fission could be a potential therapeutic approach to suppress the metastasis of ovarian cancer.

Keywords:  Drp13; IL-62; metastasis5; mitochondria1; ovarian cancer4

DOI:  https://doi.org/10.1111/cas.16064
Nat Metab. 2024 Mar 06.

Regulation of urea cycle by reversible high-stoichiometry lysine succinylation.

Ran Zhang, Jingqi Fang, Xueshu Xie, Chris Carrico, Jesse G Meyer, Lei Wei, Joanna Bons, Jacob Rose, Rebeccah Riley, Ryan Kwok, Prasanna Vadhana Ashok Kumaar, Yini Zhang, Wenjuan He, Yuya Nishida, Xiaojing Liu, Jason W Locasale, Birgit Schilling, Eric Verdin.

The post-translational modification lysine succinylation is implicated in the regulation of various metabolic pathways. However, its biological relevance remains uncertain due to methodological difficulties in determining high-impact succinylation sites. Here, using stable isotope labelling and data-independent acquisition mass spectrometry, we quantified lysine succinylation stoichiometries in mouse livers. Despite the low overall stoichiometry of lysine succinylation, several high-stoichiometry sites were identified, especially upon deletion of the desuccinylase SIRT5. In particular, multiple high-stoichiometry lysine sites identified in argininosuccinate synthase (ASS1), a key enzyme in the urea cycle, are regulated by SIRT5. Mutation of the high-stoichiometry lysine in ASS1 to succinyl-mimetic glutamic acid significantly decreased its enzymatic activity. Metabolomics profiling confirms that SIRT5 deficiency decreases urea cycle activity in liver. Importantly, SIRT5 deficiency compromises ammonia tolerance, which can be reversed by the overexpression of wild-type, but not succinyl-mimetic, ASS1. Therefore, lysine succinylation is functionally important in ammonia metabolism.

DOI: https://doi.org/10.1038/s42255-024-01005-y
Cell Metab. 2024 Mar 01. pii: S1550-4131(24)00050-0. [Epub ahead of print]

Hepatic malonyl-CoA synthesis restrains gluconeogenesis by suppressing fat oxidation, pyruvate carboxylation, and amino acid availability.

Stanislaw Deja, Justin A Fletcher, Chai-Wan Kim, Blanka Kucejova, Xiaorong Fu, Monika Mizerska, Morgan Villegas, Natalia Pudelko-Malik, Nicholas Browder, Melissa Inigo-Vollmer, Cameron J Menezes, Prashant Mishra, Eric D Berglund, Jeffrey D Browning, John P Thyfault, Jamey D Young, Jay D Horton, Shawn C Burgess.

  Acetyl-CoA carboxylase (ACC) promotes prandial liver metabolism by producing malonyl-CoA, a substrate for de novo lipogenesis and an inhibitor of CPT-1-mediated fat oxidation. We report that inhibition of ACC also produces unexpected secondary effects on metabolism. Liver-specific double ACC1/2 knockout (LDKO) or pharmacologic inhibition of ACC increased anaplerosis, tricarboxylic acid (TCA) cycle intermediates, and gluconeogenesis by activating hepatic CPT-1 and pyruvate carboxylase flux in the fed state. Fasting should have marginalized the role of ACC, but LDKO mice maintained elevated TCA cycle intermediates and preserved glycemia during fasting. These effects were accompanied by a compensatory induction of proteolysis and increased amino acid supply for gluconeogenesis, which was offset by increased protein synthesis during feeding. Such adaptations may be related to Nrf2 activity, which was induced by ACC inhibition and correlated with fasting amino acids. The findings reveal unexpected roles for malonyl-CoA synthesis in liver and provide insight into the broader effects of pharmacologic ACC inhibition.

Keywords:  Nrf2; TCA cycle; acetyl-CoA carboxylase; anaplerosis; autophagy; gluconeogenesis; lipogenesis; malonyl-CoA; protein synthesis; proteolysis

DOI:  https://doi.org/10.1016/j.cmet.2024.02.004
Proc Natl Acad Sci U S A. 2024 Mar 12. 121(11): e2314199121

Mechanism of proton-powered c-ring rotation in a mitochondrial ATP synthase.

Florian E C Blanc, Gerhard Hummer.

  Proton-powered c-ring rotation in mitochondrial ATP synthase is crucial to convert the transmembrane protonmotive force into torque to drive the synthesis of adenosine triphosphate (ATP). Capitalizing on recent cryo-EM structures, we aim at a structural and energetic understanding of how functional directional rotation is achieved. We performed multi-microsecond atomistic simulations to determine the free energy profiles along the c-ring rotation angle before and after the arrival of a new proton. Our results reveal that rotation proceeds by dynamic sliding of the ring over the a-subunit surface, during which interactions with conserved polar residues stabilize distinct intermediates. Ordered water chains line up for a Grotthuss-type proton transfer in one of these intermediates. After proton transfer, a high barrier prevents backward rotation and an overall drop in free energy favors forward rotation, ensuring the directionality of c-ring rotation required for the thermodynamically disfavored ATP synthesis. The essential arginine of the a-subunit stabilizes the rotated configuration through a salt bridge with the c-ring. Overall, we describe a complete mechanism for the rotation step of the ATP synthase rotor, thereby illuminating a process critical to all life at atomic resolution.

Keywords:  ATP synthase; bioenergetics; c-ring; molecular dynamics simulations; rotary motor

DOI:  https://doi.org/10.1073/pnas.2314199121
J Cell Biol. 2024 Apr 01. pii: e202304075. [Epub ahead of print]223(4):

Two ancient membrane pores mediate mitochondrial-nucleus membrane contact sites.

Jana Ovciarikova, Shikha Shikha, Alice Lacombe, Flavie Courjol, Rosalind McCrone, Wasim Hussain, Andrew Maclean, Leandro Lemgruber, Erica S Martins-Duarte, Mathieu Gissot, Lilach Sheiner.

Coordination between nucleus and mitochondria is essential for cell survival, and thus numerous communication routes have been established between these two organelles over eukaryotic cell evolution. One route for organelle communication is via membrane contact sites, functional appositions formed by molecular tethers. We describe a novel nuclear-mitochondrial membrane contact site in the protozoan Toxoplasma gondii. We have identified specific contacts occurring at the nuclear pore and demonstrated an interaction between components of the nuclear pore and the mitochondrial protein translocon, highlighting them as molecular tethers. Genetic disruption of the nuclear pore or the TOM translocon components, TgNup503 or TgTom40, respectively, result in contact site reduction, supporting their potential involvement in this tether. TgNup503 depletion further leads to specific mitochondrial morphology and functional defects, supporting a role for nuclear-mitochondrial contacts in mediating their communication. The discovery of a contact formed through interaction between two ancient mitochondrial and nuclear complexes sets the ground for better understanding of mitochondrial-nuclear crosstalk in eukaryotes.

DOI: https://doi.org/10.1083/jcb.202304075
Adv Clin Exp Med. 2024 Mar 01.

Mechanisms of resistance to venetoclax in hematologic malignancies.

Klaudia Zielonka, Krzysztof Jamroziak.

  Venetoclax, a BH3 mimetic, is a novel targeted anti-cancer drug with a unique mechanism of action leading to the execution of apoptosis through inhibition of the Bcl-2 protein. The development of venetoclax has revolutionized the treatment paradigm of several hematologic malignancies, including treatment-naïve and relapsed or refractory chronic lymphocytic leukemia (CLL) as well as acute myeloid leukemia (AML) in unfit patients. However, despite the high effectiveness of venetoclax in these diseases, some patients, as in the case with other targeted therapies, develop primary or secondary resistance to the drug. Various mechanisms contributing to the resistance to venetoclax have been elucidated, including selection of mutations in the BCL-2 binding groove which decrease affinity to venetoclax, or compensatory overexpression of anti-apoptotic proteins such as MCL-1. Moreover, alterations in cell metabolism and signaling pathways like MAPK or ERK activation have also been reported, suggesting the resistance to venetoclax is highly complex and involves multiple pathways. This review aimed to describe the mechanisms of resistance to venetoclax in AML, CLL, multiple myeloma, and other hematologic malignancies, as well as to propose a perspective to circumvent it.

Keywords:  acute myeloid leukemia; apoptosis; chronic lymphocytic leukemia; resistance; venetoclax

DOI:  https://doi.org/10.17219/acem/181145
Biophys J. 2024 Mar 06. pii: S0006-3495(24)00176-0. [Epub ahead of print]

How and When to Measure Mitochondrial Inner Membrane Potentials.

Alicia J Kowaltowski, Fernando Abdulkader.

The scientific literature on mitochondria has increased significantly over the years, due to findings that these organelles have widespread roles in the onset and progression of pathological conditions such as metabolic disorders, neurodegenerative and cardiovascular diseases, inflammation, and cancer. Researchers have extensively explored how mitochondrial properties and functions are modified in different models, often using fluorescent inner mitochondrial membrane potential (ΔΨm) probes to assess functional mitochondrial aspects such as protonmotive force and oxidative phosphorylation. This review provides an overview of existing techniques to measure ΔpH and ΔΨm, highlighting their advantages, limitations, and applications. It discusses drawbacks of ΔΨm probes, especially when used without calibration, and conditions where alternative methods should replace ΔΨm measurements for the benefit of the specific scientific objectives entailed. Studies investigating mitochondria and their vast biological roles would be significantly advanced by the understanding of the correct applications as well as limitations of protonmotive force measurements and use of fluorescent ΔΨm probes, adopting more precise, artifact-free, sensitive, and quantitative measurements of mitochondrial functionality.

DOI: https://doi.org/10.1016/j.bpj.2024.03.011
Hepatol Commun. 2024 Mar 01. pii: e0395. [Epub ahead of print]8(3):

Hepatocellular carcinoma cells downregulate NADH:Ubiquinone Oxidoreductase Subunit B3 to maintain reactive oxygen species homeostasis.

Zhendong Zhang, Qianwei Zhao, Zexuan Wang, Fang Xu, Yixian Liu, Yaoyu Guo, Chenglong Li, Ting Liu, Ying Zhao, Xiaolei Tang, Jintao Zhang.

BACKGROUND: HCC is a leading cause of cancer-related death. The role of reactive oxygen species (ROS) in HCC remains elusive. Since a primary ROS source is the mitochondrial electron transport chain complex Ι and the NADH:ubiquinone Oxidoreductase Subunit B3 (NDUFB3), a complex I subunit, is critical for complex I assembly and regulates the associated ROS production, we hypothesize that some HCCs progress by hijacking NDUFB3 to maintain ROS homeostasis.METHODS: NDUFB3 in human HCC lines was either knocked down or overexpressed. The cells were then analyzed in vitro for proliferation, migration, invasiveness, colony formation, complex I activity, ROS production, oxygen consumption, apoptosis, and cell cycle. In addition, the in vivo growth of the cells was evaluated in nude mice. Moreover, the role of ROS in the NDUFB3-mediated changes in the HCC lines was determined using cellular and mitochondrion-targeted ROS scavengers.
RESULTS: HCC tissues showed reduced NDUFB3 protein expression compared to adjacent healthy tissues. In addition, NDUFB3 knockdown promoted, while its overexpression suppressed, HCC cells' growth, migration, and invasiveness. Moreover, NDUFB3 knockdown significantly decreased, whereas its overexpression increased complex I activity. Further studies revealed that NDUFB3 overexpression elevated mitochondrial ROS production, causing cell apoptosis, as manifested by the enhanced expressions of proapoptotic molecules and the suppressed expression of the antiapoptotic molecule B cell lymphoma 2. Finally, our data demonstrated that the apoptosis was due to the activation of the c-Jun N-terminal kinase (JNK) signaling pathway and cell cycle arrest at G0/G1 phase.
CONCLUSIONS: Because ROS plays essential roles in many biological processes, such as aging and cancers, our findings suggest that NDFUB3 can be targeted for treating HCC and other human diseases.

DOI: https://doi.org/10.1097/HC9.0000000000000395
J Biol Chem. 2024 Mar 01. pii: S0021-9258(24)01623-5. [Epub ahead of print] 107128

Absence of both MGME1 and POLG EXO abolishes mtDNA whereas absence of either creates unique mtDNA duplications.

Christian D Gonzalez, Nadee Nissanka, Derek Van Booven, Anthony J Griswold, Carlos T Moraes.

Both POLG and MGME1 are needed for mitochondrial DNA (mtDNA) maintenance in animal cells. POLG, the primary replicative polymerase of the mitochondria, has an exonuclease activity (3'→5') that corrects for the misincorporation of bases. MGME1 serves as an exonuclease (5'→3'), producing ligatable DNA ends. Although both have a critical role in mtDNA replication and elimination of linear fragments, these mechanisms are still not fully understood. Using digital PCR to evaluate and compare mtDNA integrity, we show that Mgme1 knock out (Mgme1 KK) tissue mtDNA is more fragmented than POLG exonuclease deficient "Mutator" (Polg MM) or WT tissue. In addition, next generation sequencing of mutant hearts showed abundant duplications in/nearby the D-loop region and unique 100bp duplications evenly spaced throughout the genome only in Mgme1 KK hearts. However, despite these unique mtDNA features at steady-state, we observed a similar delay in the degradation of mtDNA after an induced double strand DNA break in both Mgme1 KK and Polg MM models. Lastly, we characterized double mutant (Polg MM/Mgme1 KK) cells and show that mtDNA cannot be maintained without at least one of these enzymatic activities. We propose a model for the generation of these genomic abnormalities which suggests a role for MGME1 outside of nascent mtDNA end ligation. Our results highlight the role of MGME1 in and outside of the D-loop region during replication, support the involvement of MGME1 in dsDNA degradation and demonstrate that POLG EXO and MGME1 can partially compensate for each other in maintaining mtDNA.

DOI: https://doi.org/10.1016/j.jbc.2024.107128
Mol Oncol. 2024 Mar 08.

The MYC-NFATC2 axis maintains the cell cycle and mitochondrial function in acute myeloid leukaemia cells.

Shaun D Patterson, Matthew E Massett, Xu Huang, Heather G Jørgensen, Alison M Michie.

  Acute myeloid leukaemia (AML) is a clonal haematological malignancy affecting the myeloid lineage, with generally poor patient outcomes owing to the lack of targeted therapies. The histone lysine demethylase 4A (KDM4A) has been established as a novel therapeutic target in AML, due to its selective oncogenic role within leukaemic cells. We identify that the transcription factor nuclear factor of activated T cells 2 (NFATC2) is a novel binding and transcriptional target of KDM4A in the human AML THP-1 cell line. Furthermore, cytogenetically diverse AML cell lines, including THP-1, were dependent on NFATC2 for colony formation in vitro, highlighting a putative novel mechanism of AML oncogenesis. Our study demonstrates that NFATC2 maintenance of cell cycle progression in human AML cells was driven primarily by CCND1. Through RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq), NFATc2 was shown to bind to the promoter region of genes involved in oxidative phosphorylation and subsequently regulate their gene expression in THP-1 cells. Furthermore, our data show that NFATC2 shares transcriptional targets with the transcription factor c-MYC, with MYC knockdown phenocopying NFATC2 knockdown. These data suggest a newly identified co-ordinated role for NFATC2 and MYC in the maintenance of THP-1 cell function, indicative of a potential means of therapeutic targeting in human AML.

Keywords:  AML; CCND1; NFATC2; metabolic function

DOI:  https://doi.org/10.1002/1878-0261.13630
Cell Death Dis. 2024 Mar 02. 15(3): 184

ISGylation of DRP1 closely balances other post-translational modifications to mediate mitochondrial fission.

Palamou Das, Oishee Chakrabarti.

Dynamin related protein 1 (DRP1), a pivotal mitochondrial fission protein, is post-translationally modified by multiple mechanisms. Here we identify a new post-translational modification of DRP1 by the ubiquitin-like protein, interferon-stimulated gene 15 (ISG15). DRP1 ISGylation is mediated by ISG15 E3 ligase, HERC5; this promotes mitochondrial fission. DeISGylation of DRP1 however leads to hyperfusion. Heterologous expression of SARS-CoV2 PLpro, a deISGylating enzyme, results in similar mitochondrial filamentation, significant decrease in total DRP1 protein levels and efflux of mtDNA. We report that deISGylated DRP1 gets ubiquitylated and degraded by TRIM25, instead of PARKIN and MITOL. While the cytosolic pool of DRP1 is primarily ISGylated, both mitochondrial and cytosolic fractions may be ubiquitylated. It is known that phosphorylation of DRP1 at S616 residue regulates its mitochondrial localisation; we show that ISGylation of phospho-DRP1 (S616) renders fission competence at mitochondria. This is significant because DRP1 ISGylation affects its functionality and mitochondrial dynamics in Alzheimer's disease pathophysiology.

DOI: https://doi.org/10.1038/s41419-024-06543-7
Innovation (Camb). 2024 Mar 04. 5(2): 100583

Metabolic collaboration between cells in the tumor microenvironment has a negligible effect on tumor growth.

Johan Gustafsson, Fariba Roshanzamir, Anders Hagnestål, Sagar M Patel, Oseeyi I Daudu, Donald F Becker, Jonathan L Robinson, Jens Nielsen.

The tumor microenvironment is composed of a complex mixture of different cell types interacting under conditions of nutrient deprivation, but the metabolism therein is not fully understood due to difficulties in measuring metabolic fluxes and exchange of metabolites between different cell types in vivo. Genome-scale metabolic modeling enables estimation of such exchange fluxes as well as an opportunity to gain insight into the metabolic behavior of individual cell types. Here, we estimated the availability of nutrients and oxygen within the tumor microenvironment using concentration measurements from blood together with a metabolite diffusion model. In addition, we developed an approach to efficiently apply enzyme usage constraints in a comprehensive metabolic model of human cells. The combined modeling reproduced severe hypoxic conditions and the Warburg effect, and we found that limitations in enzymatic capacity contribute to cancer cells' preferential use of glutamine as a substrate to the citric acid cycle. Furthermore, we investigated the common hypothesis that some stromal cells are exploited by cancer cells to produce metabolites useful for the cancer cells. We identified over 200 potential metabolites that could support collaboration between cancer cells and cancer-associated fibroblasts, but when limiting to metabolites previously identified to participate in such collaboration, no growth advantage was observed. Our work highlights the importance of enzymatic capacity limitations for cell behaviors and exemplifies the utility of enzyme-constrained models for accurate prediction of metabolism in cells and tumor microenvironments.

DOI: https://doi.org/10.1016/j.xinn.2024.100583
Cancer Cell Int. 2024 Mar 08. 24(1): 99

Impact of NDUFAF6 on breast cancer prognosis: linking mitochondrial regulation to immune response and PD-L1 expression.

Baohong Jiang, Sixuan Wu, Lijun Zeng, Yuanbin Tang, Lunqi Luo, Lianjie Ouyang, Wenjie Feng, Yeru Tan, Yuehua Li.

  BACKGROUND: Breast cancer is a major global health concern, and there is a continuous search for novel biomarkers to predict its prognosis. The mitochondrial protein NDUFAF6, previously studied in liver cancer, is now being investigated for its role in breast cancer. This study aims to explore the expression and functional significance of NDUFAF6 in breast cancer using various databases and experimental models.METHODS: We analyzed breast cancer samples from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Human Protein Atlas (HPA) databases, supplemented with immunohistochemistry (IHC) staining to assess NDUFAF6 expression. A breast cancer cell xenograft mouse model was used to evaluate tumor growth, apoptosis, and NDUFAF6 expression. Survival probabilities were estimated through Kaplan-Meier plots and Cox regression analysis. A Protein-Protein Interaction (PPI) network was constructed, and differentially expressed genes related to NDUFAF6 were analyzed using GO, KEGG, and GSEA. The relationship between NDUFAF6 expression, immune checkpoints, and immune infiltration was also evaluated.
RESULTS: NDUFAF6 was found to be overexpressed in breast cancer patients and in the xenograft mouse model. Its expression correlated with worse clinical features and prognosis. NDUFAF6 expression was an independent predictor of breast cancer outcomes in both univariate and multivariate analyses. Functionally, NDUFAF6 is implicated in several immune-related pathways. Crucially, NDUFAF6 expression correlated with various immune infiltrating cells and checkpoints, particularly promoting PD-L1 expression by inhibiting the NRF2 signaling pathway.
CONCLUSION: The study establishes NDUFAF6 as a potential prognostic biomarker in breast cancer. Its mechanism of action, involving the inhibition of NRF2 to upregulate PD-L1, highlights its significance in the disease's progression and potential as a target for immunotherapy.

Keywords:  Breast cancer; Immune infiltration; NDUFAF6; NRF2; PD-L1; Prognosis

DOI:  https://doi.org/10.1186/s12935-024-03244-1
Signal Transduct Target Ther. 2024 Mar 07. 9(1): 64

Targeting carnitine palmitoyl transferase 1A (CPT1A) induces ferroptosis and synergizes with immunotherapy in lung cancer.

Lei Ma, Chong Chen, Chunxing Zhao, Tong Li, Lingyu Ma, Jiayu Jiang, Zhaojun Duan, Qin Si, Tsung-Hsien Chuang, Rong Xiang, Yunping Luo.

Despite the successful application of immune checkpoint therapy, no response or recurrence is typical in lung cancer. Cancer stem cells (CSCs) have been identified as a crucial player in immunotherapy-related resistance. Ferroptosis, a form of cell death driven by iron-dependent lipid peroxidation, is highly regulated by cellular metabolism remolding and has been shown to have synergistic effects when combined with immunotherapy. Metabolic adaption of CSCs drives tumor resistance, yet the mechanisms of their ferroptosis defense in tumor immune evasion remain elusive. Here, through metabolomics, transcriptomics, a lung epithelial-specific Cpt1a-knockout mouse model, and clinical analysis, we demonstrate that CPT1A, a key rate-limiting enzyme of fatty acid oxidation, acts with L-carnitine, derived from tumor-associated macrophages to drive ferroptosis-resistance and CD8+ T cells inactivation in lung cancer. Mechanistically, CPT1A restrains ubiquitination and degradation of c-Myc, while c-Myc transcriptionally activates CPT1A expression. The CPT1A/c-Myc positive feedback loop further enhances the cellular antioxidant capacity by activating the NRF2/GPX4 system and reduces the amount of phospholipid polyunsaturated fatty acids through ACSL4 downregulating, thereby suppressing ferroptosis in CSCs. Significantly, targeting CPT1A enhances immune checkpoint blockade-induced anti-tumor immunity and tumoral ferroptosis in tumor-bearing mice. The results illustrate the potential of a mechanism-guided therapeutic strategy by targeting a metabolic vulnerability in the ferroptosis of CSCs to improve the efficacy of lung cancer immunotherapy.

DOI: https://doi.org/10.1038/s41392-024-01772-w