bims-mibica 2023-04-30 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2023–04–30
24 papers selected by
Kelsey Fisher-Wellman, East Carolina University

The Warburg effect: a signature of mitochondrial overload.
Dysregulated cellular redox status during hyperammonemia causes mitochondrial dysfunction and senescence by inhibiting sirtuin-mediated deacetylation.
Mitochondrial complex III deficiency drives c-MYC overexpression and illicit cell cycle entry leading to senescence and segmental progeria.
Mitophagy promotes resistance to BH3 mimetics in acute myeloid leukemia.
Chromatin remodeling due to degradation of citrate carrier impairs osteogenesis of aged mesenchymal stem cells.
Mitoribosome sensitivity to HSP70 inhibition uncovers metabolic liabilities of castration-resistant prostate cancer.
Methodologies in Mitochondrial Testing: Diagnosing a Primary Mitochondrial Respiratory Chain Disorder.
Therapy-Resistant Acute Myeloid Leukemia Stem Cells Are Resensitized to Venetoclax + Azacitidine by Targeting Fatty Acid Desaturases 1 and 2.
HAMLET effect on cell death and mitochondrial respiration in colorectal cancer cell lines with KRAS/BRAF mutations.
Autophagy Inhibition as a Potential Therapeutic Strategy for Breast Cancer with Mitochondrial Translation Defect Caused by CBFB-Deficiency.
Mitochondrial carriers set the epigenetic age.
MTSviewer: A database to visualize mitochondrial targeting sequences, cleavage sites, and mutations on protein structures.
Multifaceted mitochondria: moving mitochondrial science beyond function and dysfunction.
Branched-chain amino acid catabolism in muscle affects systemic BCAA levels but not insulin resistance.
BCR-ABL triggers a glucose-dependent survival program during leukemogenesis through the suppression of TXNIP.
FBXL4 ubiquitin ligase deficiency promotes mitophagy by elevating NIX levels.
Improved Tumor Control Following Radiosensitization with Ultrasound-Sensitive Oxygen Microbubbles and Tumor Mitochondrial Respiration Inhibitors in a Preclinical Model of Head and Neck Cancer.
MICU1 regulates mitochondrial cristae structure and function independently of the mitochondrial Ca2+ uniporter channel.
Discovery of decreased ferroptosis in male colorectal cancer patients with KRAS mutations.
Shikonin Induces ROS-Dependent Apoptosis Via Mitochondria Depolarization and ER Stress in Adult T Cell Leukemia/Lymphoma.
Mitochondrial Function and Signaling to Regulate Cellular Life.
Combined inhibition of BCL-2 and MCL-1 overcomes BAX deficiency-mediated resistance of TP53-mutant acute myeloid leukemia to individual BH3 mimetics.
Clonally resolved single-cell multi-omics identifies routes of cellular differentiation in acute myeloid leukemia.
Structure of the human respiratory complex II.

Trends Cell Biol. 2023 Apr 26. pii: S0962-8924(23)00070-3. [Epub ahead of print]

The Warburg effect: a signature of mitochondrial overload.

Yahui Wang, Gary J Patti.

  A long-standing question in cancer biology has been why oxygenated tumors ferment the majority of glucose they consume to lactate rather than oxidizing it in their mitochondria, a phenomenon known as the 'Warburg effect.' An abundance of evidence shows not only that most cancer cells have fully functional mitochondria but also that mitochondrial activity is important to proliferation. It is therefore difficult to rationalize the metabolic benefit of cancer cells switching from respiration to fermentation. An emerging perspective is that rather than mitochondrial metabolism being suppressed in tumors, as is often suggested, mitochondrial activity increases to the level of saturation. As such, the Warburg effect becomes a signature of excess glucose being released as lactate due to mitochondrial overload.

Keywords:  Warburg effect; aerobic fermentation; aerobic glycolysis; cancer metabolism; mitochondrial metabolism

DOI:  https://doi.org/10.1016/j.tcb.2023.03.013
Aging Cell. 2023 Apr 26. e13852

Dysregulated cellular redox status during hyperammonemia causes mitochondrial dysfunction and senescence by inhibiting sirtuin-mediated deacetylation.

Saurabh Mishra, Nicole Welch, Manikandan Karthikeyan, Annette Bellar, Ryan Musich, Shashi Shekhar Singh, Dongmei Zhang, Jinendiran Sekar, Amy H Attaway, Aruna Chelluboyina, Shuhui Wang Lorkowski, Sanjoy Roychowdhary, Ling Li, Belinda Willard, Jonathan D Smith, Charles L Hoppel, Vidula Vachharajani, Avinash Kumar, Srinivasan Dasarathy.

  Perturbed metabolism of ammonia, an endogenous cytotoxin, causes mitochondrial dysfunction, reduced NAD+ /NADH (redox) ratio, and postmitotic senescence. Sirtuins are NAD+ -dependent deacetylases that delay senescence. In multiomics analyses, NAD metabolism and sirtuin pathways are enriched during hyperammonemia. Consistently, NAD+ -dependent Sirtuin3 (Sirt3) expression and deacetylase activity were decreased, and protein acetylation was increased in human and murine skeletal muscle/myotubes. Global acetylomics and subcellular fractions from myotubes showed hyperammonemia-induced hyperacetylation of cellular signaling and mitochondrial proteins. We dissected the mechanisms and consequences of hyperammonemia-induced NAD metabolism by complementary genetic and chemical approaches. Hyperammonemia inhibited electron transport chain components, specifically complex I that oxidizes NADH to NAD+ , that resulted in lower redox ratio. Ammonia also caused mitochondrial oxidative dysfunction, lower mitochondrial NAD+ -sensor Sirt3, protein hyperacetylation, and postmitotic senescence. Mitochondrial-targeted Lactobacillus brevis NADH oxidase (MitoLbNOX), but not NAD+ precursor nicotinamide riboside, reversed ammonia-induced oxidative dysfunction, electron transport chain supercomplex disassembly, lower ATP and NAD+ content, protein hyperacetylation, Sirt3 dysfunction and postmitotic senescence in myotubes. Even though Sirt3 overexpression reversed ammonia-induced hyperacetylation, lower redox status or mitochondrial oxidative dysfunction were not reversed. These data show that acetylation is a consequence of, but is not the mechanism of, lower redox status or oxidative dysfunction during hyperammonemia. Targeting NADH oxidation is a potential approach to reverse and potentially prevent ammonia-induced postmitotic senescence in skeletal muscle. Since dysregulated ammonia metabolism occurs with aging, and NAD+ biosynthesis is reduced in sarcopenia, our studies provide a biochemical basis for cellular senescence and have relevance in multiple tissues.

Keywords:  acetylation; human inducible pluripotent stem cells; mitochondria; multiomics; redox; sirtuin; skeletal muscle; systems biology

DOI:  https://doi.org/10.1111/acel.13852
Nat Commun. 2023 Apr 24. 14(1): 2356

Mitochondrial complex III deficiency drives c-MYC overexpression and illicit cell cycle entry leading to senescence and segmental progeria.

Janne Purhonen, Rishi Banerjee, Vilma Wanne, Nina Sipari, Matthias Mörgelin, Vineta Fellman, Jukka Kallijärvi.

Accumulating evidence suggests mitochondria as key modulators of normal and premature aging, yet whether primary oxidative phosphorylation (OXPHOS) deficiency can cause progeroid disease remains unclear. Here, we show that mice with severe isolated respiratory complex III (CIII) deficiency display nuclear DNA damage, cell cycle arrest, aberrant mitoses, and cellular senescence in the affected organs such as liver and kidney, and a systemic phenotype resembling juvenile-onset progeroid syndromes. Mechanistically, CIII deficiency triggers presymptomatic cancer-like c-MYC upregulation followed by excessive anabolic metabolism and illicit cell proliferation against lack of energy and biosynthetic precursors. Transgenic alternative oxidase dampens mitochondrial integrated stress response and the c-MYC induction, suppresses the illicit proliferation, and prevents juvenile lethality despite that canonical OXPHOS-linked functions remain uncorrected. Inhibition of c-MYC with the dominant-negative Omomyc protein relieves the DNA damage in CIII-deficient hepatocytes in vivo. Our results connect primary OXPHOS deficiency to genomic instability and progeroid pathogenesis and suggest that targeting c-MYC and aberrant cell proliferation may be therapeutic in mitochondrial diseases.

DOI: https://doi.org/10.1038/s41467-023-38027-1
Cancer Discov. 2023 Apr 24. pii: CD-22-0601. [Epub ahead of print]

Mitophagy promotes resistance to BH3 mimetics in acute myeloid leukemia.

Christina Glytsou, Xufeng Chen, Emmanouil Zacharioudakis, Wafa Al-Santli, Hua Zhou, Bettina Nadorp, Soobeom Lee, Audrey Lasry, Zhengxi Sun, Dimitrios Papaioannou, Michael Cammer, Kun Wang, Tomasz Zal, Malgorzata Anna Zal, Bing Z Carter, Jo Ishizawa, Raoul Tibes, Aristotelis Tsirigos, Michael Andreeff, Evripidis Gavathiotis, Iannis Aifantis.

BH3-mimetics are used as an efficient strategy to induce cell death in several blood malignancies, including acute myeloid leukemia (AML). Venetoclax, a potent BCL-2 antagonist, is used clinically in combination with hypomethylating agents for the treatment of AML. Moreover, MCL-1 or dual BCL-2/BCL-xL antagonists are under investigation. Yet, resistance to single or combinatorial BH3-mimetics therapies eventually ensues. Integration of multiple genome-wide CRISPR/Cas9 screens revealed that loss of mitophagy modulators sensitizes AML cells to various BH3-mimetics targeting different BCL-2 family members. One such regulator is MFN2, whose protein levels positively correlate with drug resistance in patients with AML. MFN2 overexpression is sufficient to drive resistance to BH3-mimetics in AML. Insensitivity to BH3-mimetics is accompanied by enhanced mitochondria-endoplasmic reticulum interactions and augmented mitophagy flux which acts as a pro-survival mechanism to eliminate mitochondrial damage. Genetic or pharmacologic MFN2 targeting synergizes with BH3-mimetics by impairing mitochondrial clearance and enhancing apoptosis in AML.

DOI: https://doi.org/10.1158/2159-8290.CD-22-0601
Nat Aging. 2021 Sep;1(9): 810-825

Chromatin remodeling due to degradation of citrate carrier impairs osteogenesis of aged mesenchymal stem cells.

Andromachi Pouikli, Swati Parekh, Monika Maleszewska, Chrysa Nikopoulou, Maarouf Baghdadi, Ignacio Tripodi, Kat Folz-Donahue, Yvonne Hinze, Andrea Mesaros, David Hoey, Patrick Giavalisco, Robin Dowell, Linda Partridge, Peter Tessarz.

Aging is accompanied by a general decline in the function of many cellular pathways. However, whether these are causally or functionally interconnected remains elusive. Here, we study the effect of mitochondrial-nuclear communication on stem cell aging. We show that aged mesenchymal stem cells exhibit reduced chromatin accessibility and lower histone acetylation, particularly on promoters and enhancers of osteogenic genes. The reduced histone acetylation is due to impaired export of mitochondrial acetyl-CoA, owing to the lower levels of citrate carrier (CiC). We demonstrate that aged cells showed enhanced lysosomal degradation of CiC, which is mediated via mitochondrial-derived vesicles. Strikingly, restoring cytosolic acetyl-CoA levels either by exogenous CiC expression or via acetate supplementation, remodels the chromatin landscape and rescues the osteogenesis defects of aged mesenchymal stem cells. Collectively, our results establish a tight, age-dependent connection between mitochondrial quality control, chromatin and stem cell fate, which are linked together by CiC.

DOI: https://doi.org/10.1038/s43587-021-00105-8
PNAS Nexus. 2023 Apr;2(4): pgad115

Mitoribosome sensitivity to HSP70 inhibition uncovers metabolic liabilities of castration-resistant prostate cancer.

Frank J Echtenkamp, Ryo Ishida, Genesis M Rivera-Marquez, Marisa Maisiak, Oleta T Johnson, Jonathan H Shrimp, Arnav Sinha, Stephen John Ralph, Ian Nisbet, Murali Krishna Cherukuri, Jason E Gestwicki, Leonard M Neckers.

The androgen receptor is a key regulator of prostate cancer and the principal target of current prostate cancer therapies collectively termed androgen deprivation therapies. Insensitivity to these drugs is a hallmark of progression to a terminal disease state termed castration-resistant prostate cancer. Therefore, novel therapeutic options that slow progression of castration-resistant prostate cancer and combine effectively with existing agents are in urgent need. We show that JG-98, an allosteric inhibitor of HSP70, re-sensitizes castration-resistant prostate cancer to androgen deprivation drugs by targeting mitochondrial HSP70 (HSPA9) to suppress aerobic respiration. Rather than impacting androgen receptor stability as previously described, JG-98's primary effect is inhibition of mitochondrial translation, leading to disruption of electron transport chain activity. Although functionally distinct from HSPA9 inhibition, direct inhibition of the electron transport chain with a complex I or II inhibitor creates a similar physiological state capable of re-sensitizing castration-resistant prostate cancer to androgen deprivation therapies. These data identify a significant role for HspA9 in mitochondrial ribosome function and highlight an actionable metabolic vulnerability of castration-resistant prostate cancer.

DOI: https://doi.org/10.1093/pnasnexus/pgad115
Clin Chem. 2023 Apr 26. pii: hvad037. [Epub ahead of print]

Methodologies in Mitochondrial Testing: Diagnosing a Primary Mitochondrial Respiratory Chain Disorder.

Emily L Gill, Jing Wang, Angela N Viaene, Stephen R Master, Rebecca D Ganetzky.

BACKGROUND: Mitochondria are cytosolic organelles within most eukaryotic cells. Mitochondria generate the majority of cellular energy in the form of adenosine triphosphate (ATP) through oxidative phosphorylation (OxPhos). Pathogenic variants in mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) lead to defects in OxPhos and physiological malfunctions (Nat Rev Dis Primer 2016;2:16080.). Patients with primary mitochondrial disorders (PMD) experience heterogeneous symptoms, typically in multiple organ systems, depending on the tissues affected by mitochondrial dysfunction. Because of this heterogeneity, clinical diagnosis is challenging (Annu Rev Genomics Hum Genet 2017;18:257-75.). Laboratory diagnosis of mitochondrial disease depends on a multipronged analysis that can include biochemical, histopathologic, and genetic testing. Each of these modalities has complementary strengths and limitations in diagnostic utility.
CONTENT: The primary focus of this review is on diagnosis and testing strategies for primary mitochondrial diseases. We review tissue samples utilized for testing, metabolic signatures, histologic findings, and molecular testing approaches. We conclude with future perspectives on mitochondrial testing.
SUMMARY: This review offers an overview of the current biochemical, histologic, and genetic approaches available for mitochondrial testing. For each we review their diagnostic utility including complementary strengths and weaknesses. We identify gaps in current testing and possible future avenues for test development.

DOI: https://doi.org/10.1093/clinchem/hvad037
Metabolites. 2023 Mar 24. pii: 467. [Epub ahead of print]13(4):

Therapy-Resistant Acute Myeloid Leukemia Stem Cells Are Resensitized to Venetoclax + Azacitidine by Targeting Fatty Acid Desaturases 1 and 2.

Rachel Culp-Hill, Brett M Stevens, Courtney L Jones, Shanshan Pei, Monika Dzieciatkowska, Mohammad Minhajuddin, Craig T Jordan, Angelo D'Alessandro.

  Recent advances in targeting leukemic stem cells (LSCs) using venetoclax with azacitidine (ven + aza) has significantly improved outcomes for de novo acute myeloid leukemia (AML) patients. However, patients who relapse after traditional chemotherapy are often venetoclax-resistant and exhibit poor clinical outcomes. We previously described that fatty acid metabolism drives oxidative phosphorylation (OXPHOS) and acts as a mechanism of LSC survival in relapsed/refractory AML. Here, we report that chemotherapy-relapsed primary AML displays aberrant fatty acid and lipid metabolism, as well as increased fatty acid desaturation through the activity of fatty acid desaturases 1 and 2, and that fatty acid desaturases function as a mechanism of recycling NAD+ to drive relapsed LSC survival. When combined with ven + aza, the genetic and pharmacologic inhibition of fatty acid desaturation results in decreased primary AML viability in relapsed AML. This study includes the largest lipidomic profile of LSC-enriched primary AML patient cells to date and indicates that inhibition of fatty acid desaturation is a promising therapeutic target for relapsed AML.

Keywords:  acute myeloid leukemia; fatty acid metabolism; leukemic stem cells; lipidomics

DOI:  https://doi.org/10.3390/metabo13040467
J Cancer Res Clin Oncol. 2023 Apr 26.

HAMLET effect on cell death and mitochondrial respiration in colorectal cancer cell lines with KRAS/BRAF mutations.

Justas Žilinskas, Darius Stukas, Aldona Jasukaitienė, Jurgita Šapauskienė, Rasa Banienė, Sonata Trumbeckaitė, Saulius Švagždys, Marco Cicciu, Žilvinas Dambrauskas, Antanas Gulbinas, Algimantas Tamelis.

   PURPOSE: Treatment of advanced colorectal cancer (CRC) depends on the correct selection of personalized strategies. HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) is a natural proteolipid milk compound that might serve as a novel cancer prevention and therapy candidate. Our purpose was to investigate HAMLET effect on viability, death pathway and mitochondrial bioenergetics of CRC cells with different KRAS/BRAF mutational status in vitro.
METHODS: We treated three cell lines (Caco-2, LoVo, WiDr) with HAMLET to evaluate cell metabolic activity and viability, flow cytometry of apoptotic and necrotic cells, pro- and anti-apoptotic genes, and protein expressions. Mitochondrial respiration (oxygen consumption) rate was recorded by high-resolution respirometry system Oxygraph-2 k.
RESULTS: The HAMLET complex was cytotoxic to all investigated CRC cell lines and this effect is irreversible. Flow cytometry revealed that HAMLET induces necrotic cell death with a slight increase in an apoptotic cell population. WiDr cell metabolism, clonogenicity, necrosis/apoptosis level, and mitochondrial respiration were affected significantly less than other cells.
CONCLUSION: HAMLET exhibits irreversible cytotoxicity on human CRC cells in a dose-dependent manner, leading to necrotic cell death and inhibiting the extrinsic apoptosis pathway. BRAF-mutant cell line is more resistant than other type lines. HAMLET decreased mitochondrial respiration and ATP synthesis in CaCo-2 and LoVo cell lines but did not affect WiDr cells' respiration. Pretreatment of cancer cells with HAMLET has no impact on mitochondrial outer and inner membrane permeability.

Keywords:  Bioactive milk components; Colorectal cancer; EGFR; KRAS and BRAF mutation; Mitochondrial respiration

DOI:  https://doi.org/10.1007/s00432-023-04777-0
Autophagy. 2023 Apr 28.

Autophagy Inhibition as a Potential Therapeutic Strategy for Breast Cancer with Mitochondrial Translation Defect Caused by CBFB-Deficiency.

Navdeep Malik, Hualong Yan, Young-Im Kim, Gamze Ayaz, Shasha Wang, Payel Mondal, Ji Luo, Jing Huang.

  Autophagy plays a crucial role in tumor initiation and progression. However, targeting autophagy in cancer has proven challenging due to genetic or epigenetic factors that may affect the efficacy of autophagy inhibition. Therefore, identifying biomarkers is crucial for selecting patients who are likely to benefit from this treatment modality. We show that dysregulation of mitochondrial translation caused by CBFB (core-binding factor subunit beta) deficiency can sensitize the tumors to autophagy inhibition. CBFB and its binding partner HNRNPK (heterogeneous nuclear ribonucleoprotein K) interact with mRNAs encoded by the mitochondrial genome (mt-mRNAs) and maintain their translation. Specifically, CBFB enhances the binding of TUFM (Tu translation elongation factor, mitochondrial), an elongation factor for mitochondrial translation, to mt-mRNAs. CBFB deficiency, which often occurs in estrogen receptor-positive breast tumors, results in elevated autophagy and mitophagy that promote cancer cell survival. Consequently, these cells are hypersensitive to autophagy inhibition, creating a targetable vulnerability. Studies using in vivo models have shown that inhibiting autophagy selectively eliminates breast tumor cells with mitochondrial translation defects resulting from CBFB deficiency. Our results suggest that autophagy inhibition may be an effective treatment option for breast tumors carrying CBFB alterations.

Keywords:  Autophagy; CBFB; PIK3CA; autophagy in cancer; autophagy targeting; breast cancer; mitochondria; mitochondrial translation; mitophagy

DOI:  https://doi.org/10.1080/15548627.2023.2208481
Nat Aging. 2021 Sep;1(9): 755-756

Mitochondrial carriers set the epigenetic age.

Carina Groh, Johannes M Herrmann.

DOI: https://doi.org/10.1038/s43587-021-00111-w
PLoS One. 2023 ;18(4): e0284541

MTSviewer: A database to visualize mitochondrial targeting sequences, cleavage sites, and mutations on protein structures.

Andrew N Bayne, Jing Dong, Saeid Amiri, Sali M K Farhan, Jean-François Trempe.

Mitochondrial dysfunction is implicated in a wide array of human diseases ranging from neurodegenerative disorders to cardiovascular defects. The coordinated localization and import of proteins into mitochondria are essential processes that ensure mitochondrial homeostasis. The localization and import of most mitochondrial proteins are driven by N-terminal mitochondrial targeting sequences (MTS's), which interact with import machinery and are removed by the mitochondrial processing peptidase (MPP). The recent discovery of internal MTS's-those which are distributed throughout a protein and act as import regulators or secondary MPP cleavage sites-has expanded the role of both MTS's and MPP beyond conventional N-terminal regulatory pathways. Still, the global mutational landscape of MTS's remains poorly characterized, both from genetic and structural perspectives. To this end, we have integrated a variety of tools into one harmonized R/Shiny database called MTSviewer (https://neurobioinfo.github.io/MTSvieweR/), which combines MTS predictions, cleavage sites, genetic variants, pathogenicity predictions, and N-terminomics data with structural visualization using AlphaFold models of human and yeast mitochondrial proteomes. Using MTSviewer, we profiled all MTS-containing proteins across human and yeast mitochondrial proteomes and provide multiple case studies to highlight the utility of this database.

DOI: https://doi.org/10.1371/journal.pone.0284541
Nat Metab. 2023 Apr;5(4): 546-562

Multifaceted mitochondria: moving mitochondrial science beyond function and dysfunction.

Anna S Monzel, José Antonio Enríquez, Martin Picard.

Mitochondria have cell-type specific phenotypes, perform dozens of interconnected functions and undergo dynamic and often reversible physiological recalibrations. Given their multifunctional and malleable nature, the frequently used terms 'mitochondrial function' and 'mitochondrial dysfunction' are misleading misnomers that fail to capture the complexity of mitochondrial biology. To increase the conceptual and experimental specificity in mitochondrial science, we propose a terminology system that distinguishes between (1) cell-dependent properties, (2) molecular features, (3) activities, (4) functions and (5) behaviours. A hierarchical terminology system that accurately captures the multifaceted nature of mitochondria will achieve three important outcomes. It will convey a more holistic picture of mitochondria as we teach the next generations of mitochondrial biologists, maximize progress in the rapidly expanding field of mitochondrial science, and also facilitate synergy with other disciplines. Improving specificity in the language around mitochondrial science is a step towards refining our understanding of the mechanisms by which this unique family of organelles contributes to cellular and organismal health.

DOI: https://doi.org/10.1038/s42255-023-00783-1
Nat Metab. 2023 Apr;5(4): 589-606

Branched-chain amino acid catabolism in muscle affects systemic BCAA levels but not insulin resistance.

Megan C Blair, Michael D Neinast, Cholsoon Jang, Qingwei Chu, Jae Woo Jung, Jessie Axsom, Marc R Bornstein, Chelsea Thorsheim, Kristina Li, Atsushi Hoshino, Steven Yang, Rachel J Roth Flach, Bei B Zhang, Joshua D Rabinowitz, Zoltan Arany.

Elevated levels of plasma branched-chain amino acids (BCAAs) have been associated with insulin resistance and type 2 diabetes since the 1960s. Pharmacological activation of branched-chain α-ketoacid dehydrogenase (BCKDH), the rate-limiting enzyme of BCAA oxidation, lowers plasma BCAAs and improves insulin sensitivity. Here we show that modulation of BCKDH in skeletal muscle, but not liver, affects fasting plasma BCAAs in male mice. However, despite lowering BCAAs, increased BCAA oxidation in skeletal muscle does not improve insulin sensitivity. Our data indicate that skeletal muscle controls plasma BCAAs, that lowering fasting plasma BCAAs is insufficient to improve insulin sensitivity and that neither skeletal muscle nor liver account for the improved insulin sensitivity seen with pharmacological activation of BCKDH. These findings suggest potential concerted contributions of multiple tissues in the modulation of BCAA metabolism to alter insulin sensitivity.

DOI: https://doi.org/10.1038/s42255-023-00794-y
Cell Death Dis. 2023 Apr 24. 14(4): 287

BCR-ABL triggers a glucose-dependent survival program during leukemogenesis through the suppression of TXNIP.

Lin Feng, Ruxin Ding, Xuan Qu, Yuanchun Li, Tong Shen, Lei Wang, Ruikai Li, Juan Zhang, Yi Ru, Xin Bu, Yang Wang, Min Li, Wenqi Song, Liangliang Shen, Pengxia Zhang.

Imatinib is highly effective in the treatment of chronic myelogenous leukemia (CML), but the primary and acquired imatinib resistance remains the big hurdle. Molecular mechanisms for CML resistance to tyrosine kinase inhibitors, beyond point mutations in BCR-ABL kinase domain, still need to be addressed. Here, we demonstrated that thioredoxin-interacting protein (TXNIP) is a novel BCR-ABL target gene. Suppression of TXNIP was responsible for BCR-ABL triggered glucose metabolic reprogramming and mitochondrial homeostasis. Mechanistically, Miz-1/P300 complex transactivates TXNIP through the recognition of TXNIP core promoter region, responding to the c-Myc suppression by either imatinib or BCR-ABL knockdown. TXNIP restoration sensitizes CML cells to imatinib treatment and compromises imatinib resistant CML cell survival, predominantly through the blockage of both glycolysis and glucose oxidation which results in the mitochondrial dysfunction and ATP production. In particular, TXNIP suppresses expressions of the key glycolytic enzyme, hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), potentially through Fbw7-dependent c-Myc degradation. In accordance, BCR-ABL suppression of TXNIP provided a novel survival pathway for the transformation of mouse bone marrow cells. Knockout of TXNIP accelerated BCR-ABL transformation, whereas TXNIP overexpression suppressed this transformation. Combination of drug inducing TXNIP expression with imatinib synergistically kills CML cells from patients and further extends the survival of CML mice. Thus, the activation of TXNIP represents an effective strategy for CML treatment to overcome resistance.

DOI: https://doi.org/10.1038/s41419-023-05811-2
EMBO J. 2023 Apr 27. e112799

FBXL4 ubiquitin ligase deficiency promotes mitophagy by elevating NIX levels.

Hannah Elcocks, Ailbhe J Brazel, Katy R McCarron, Manuel Kaulich, Koraljka Husnjak, Heather Mortiboys, Michael J Clague, Sylvie Urbé.

  Selective autophagy of mitochondria, mitophagy, is linked to mitochondrial quality control and as such is critical to a healthy organism. We have used a CRISPR/Cas9 approach to screen human E3 ubiquitin ligases for influence on mitophagy under both basal cell culture conditions and upon acute mitochondrial depolarization. We identify two cullin-RING ligase substrate receptors, VHL and FBXL4, as the most profound negative regulators of basal mitophagy. We show that these converge, albeit via different mechanisms, on control of the mitophagy adaptors BNIP3 and BNIP3L/NIX. FBXL4 restricts NIX and BNIP3 levels via direct interaction and protein destabilization, while VHL acts through suppression of HIF1α-mediated transcription of BNIP3 and NIX. Depletion of NIX but not BNIP3 is sufficient to restore mitophagy levels. Our study contributes to an understanding of the aetiology of early-onset mitochondrial encephalomyopathy that is supported by analysis of a disease-associated mutation. We further show that the compound MLN4924, which globally interferes with cullin-RING ligase activity, is a strong inducer of mitophagy, thus providing a research tool in this context and a candidate therapeutic agent for conditions linked to mitochondrial dysfunction.

Keywords:  BNIP3; FBXL4; NIX; VHL; mitophagy

DOI:  https://doi.org/10.15252/embj.2022112799
Pharmaceutics. 2023 Apr 21. pii: 1302. [Epub ahead of print]15(4):

Improved Tumor Control Following Radiosensitization with Ultrasound-Sensitive Oxygen Microbubbles and Tumor Mitochondrial Respiration Inhibitors in a Preclinical Model of Head and Neck Cancer.

Quezia Lacerda, Hebah Falatah, Ji-Bin Liu, Corinne E Wessner, Brian Oeffinger, Ankit Rochani, Dennis B Leeper, Flemming Forsberg, Joseph M Curry, Gagan Kaushal, Scott W Keith, Patrick O'Kane, Margaret A Wheatley, John R Eisenbrey.

  Tumor hypoxia (oxygen deficiency) is a major contributor to radiotherapy resistance. Ultrasound-sensitive microbubbles containing oxygen have been explored as a mechanism for overcoming tumor hypoxia locally prior to radiotherapy. Previously, our group demonstrated the ability to encapsulate and deliver a pharmacological inhibitor of tumor mitochondrial respiration (lonidamine (LND)), which resulted in ultrasound-sensitive microbubbles loaded with O2 and LND providing prolonged oxygenation relative to oxygenated microbubbles alone. This follow-up study aimed to evaluate the therapeutic response to radiation following the administration of oxygen microbubbles combined with tumor mitochondrial respiration inhibitors in a head and neck squamous cell carcinoma (HNSCC) tumor model. The influences of different radiation dose rates and treatment combinations were also explored. The results demonstrated that the co-delivery of O2 and LND successfully sensitized HNSCC tumors to radiation, and this was also enhanced with oral metformin, significantly slowing tumor growth relative to unsensitized controls (p < 0.01). Microbubble sensitization was also shown to improve overall animal survival. Importantly, effects were found to be radiation dose-rate-dependent, reflecting the transient nature of tumor oxygenation.

Keywords:  contrast-enhanced ultrasound; drug delivery; head and neck cancer; lonidamine; metformin; oxygen-loaded microbubbles; radiotherapy; tumor hypoxia

DOI:  https://doi.org/10.3390/pharmaceutics15041302
Sci Signal. 2023 04 25. 16(782): eabi8948

MICU1 regulates mitochondrial cristae structure and function independently of the mitochondrial Ca2+ uniporter channel.

Dhanendra Tomar, Manfred Thomas, Joanne F Garbincius, Devin W Kolmetzky, Oniel Salik, Pooja Jadiya, Suresh K Joseph, April C Carpenter, György Hajnóczky, John W Elrod.

MICU1 is a calcium (Ca2+)-binding protein that regulates the mitochondrial Ca2+ uniporter channel complex (mtCU) and mitochondrial Ca2+ uptake. MICU1 knockout mice display disorganized mitochondrial architecture, a phenotype that is distinct from that of mice with deficiencies in other mtCU subunits and, thus, is likely not explained by changes in mitochondrial matrix Ca2+ content. Using proteomic and cellular imaging techniques, we found that MICU1 localized to the mitochondrial contact site and cristae organizing system (MICOS) and directly interacted with the MICOS components MIC60 and CHCHD2 independently of the mtCU. We demonstrated that MICU1 was essential for MICOS complex formation and that MICU1 ablation resulted in altered cristae organization, mitochondrial ultrastructure, mitochondrial membrane dynamics, and cell death signaling. Together, our results suggest that MICU1 is an intermembrane space Ca2+ sensor that modulates mitochondrial membrane dynamics independently of matrix Ca2+ uptake. This system enables distinct Ca2+ signaling in the mitochondrial matrix and at the intermembrane space to modulate cellular energetics and cell death in a concerted manner.

DOI: https://doi.org/10.1126/scisignal.abi8948
Redox Biol. 2023 Apr 14. pii: S2213-2317(23)00100-3. [Epub ahead of print]62 102699

Discovery of decreased ferroptosis in male colorectal cancer patients with KRAS mutations.

Hong Yan, Ronan Talty, Abhishek Jain, Yuping Cai, Jie Zheng, Xinyi Shen, Engjel Muca, Philip B Paty, Marcus W Bosenberg, Sajid A Khan, Caroline H Johnson.

  Aberrant tumor metabolism is a hallmark of cancer in which metabolic rewiring can support tumor growth under nutrient deficient conditions. KRAS mutations occur in 35-45% of all colorectal cancer (CRC) cases and are difficult to treat. The relationship between mutant KRAS and aberrant metabolism in CRCs has not been fully explored and could be a target for intervention. We previously acquired non-targeted metabolomics data from 161 tumor tissues and 39 normal colon tissues from stage I-III chemotherapy naïve CRC patients. In this study, we revealed that only in male patients, tumors with KRAS mutations had several altered pathways that suppress ferroptosis, including glutathione biosynthesis, transsulfuration activity, and methionine metabolism. To validate this phenotype, MC38 CRC cells (KRASG13R) were treated with a ferroptosis inducer; RAS-selected lethal (RSL3). RSL3 altered metabolic pathways in the opposite direction to that seen in KRAS mutant tumors from male patients confirming a suppressed ferroptosis metabolic phenotype in these patients. We further validated gene expression data from an additional CRC patient cohort (Gene Expression Omnibus (GEO)), and similarly observed differences in ferroptosis-related genes by sex and KRAS status. Further examination of the relationship between these genes and overall survival (OS) in the GEO cohort showed that KRAS mutant tumors are associated with poorer 5-year OS compared to KRAS wild type tumors, and only in male patients. Additionally, high compared to low expression of GPX4, FTH1, FTL, which suppress ferroptosis, were associated with poorer 5-year OS only in KRAS mutant tumors from male CRC patients. Additionally, low compared to high expression of ACSL4 was associated with poorer OS for this group. Our results show that KRAS mutant tumors from male CRC patients have suppressed ferroptosis, and gene expression changes that suppress ferroptosis associate with adverse outcomes for these patients, revealing a novel potential avenue for therapeutic approaches.

Keywords:  Colorectal cancer; Ferroptosis; KRAS; Metabolomics; Sex differences

DOI:  https://doi.org/10.1016/j.redox.2023.102699
Antioxidants (Basel). 2023 Apr 02. pii: 864. [Epub ahead of print]12(4):

Shikonin Induces ROS-Dependent Apoptosis Via Mitochondria Depolarization and ER Stress in Adult T Cell Leukemia/Lymphoma.

Piyanard Boonnate, Ryusho Kariya, Seiji Okada.

  Adult T cell leukemia/lymphoma (ATLL) is an aggressive T-cell malignancy that develops in some elderly human T-cell leukemia virus (HTVL-1) carriers. ATLL has a poor prognosis despite conventional and targeted therapies, and a new safe and efficient therapy is required. Here, we examined the anti-ATLL effect of Shikonin (SHK), a naphthoquinone derivative that has shown several anti-cancer activities. SHK induced apoptosis of ATLL cells accompanied by generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential, and induction of endoplasmic reticulum (ER) stress. Treatment with a ROS scavenger, N-acetylcysteine (NAC), blocked both loss of mitochondrial membrane potential and ER stress, and prevented apoptosis of ATLL cells, indicating that ROS is an upstream trigger of SHK-induced apoptosis of ATLL cells through disruption of the mitochondrial membrane potential and ER stress. In an ATLL xenografted mouse model, SHK treatment suppressed tumor growth without significant adverse effects. These results suggest that SHK could be a potent anti-reagent against ATLL.

Keywords:  Reactive Oxygen Species (ROS); Shikonin (SHK); adult T cell leukemia/lymphoma (ATLL); apoptosis; endoplasmic reticulum (ER) stress; mitochondria depolarization

DOI:  https://doi.org/10.3390/antiox12040864
Life (Basel). 2023 Apr 09. pii: 975. [Epub ahead of print]13(4):

Mitochondrial Function and Signaling to Regulate Cellular Life.

Rafael A Casuso.

Mitochondria are essential organelles found in nearly all eukaryotic cells, responsible for producing the energy that drives cellular processes [...].

DOI: https://doi.org/10.3390/life13040975
Blood Cancer J. 2023 04 24. 13(1): 57

Combined inhibition of BCL-2 and MCL-1 overcomes BAX deficiency-mediated resistance of TP53-mutant acute myeloid leukemia to individual BH3 mimetics.

Bing Z Carter, Po Yee Mak, Wenjing Tao, Edward Ayoub, Lauren B Ostermann, Xuelin Huang, Sanam Loghavi, Steffen Boettcher, Yuki Nishida, Vivian Ruvolo, Paul E Hughes, Phuong K Morrow, Torsten Haferlach, Steven Kornblau, Muharrem Muftuoglu, Michael Andreeff.

TP53-mutant acute myeloid leukemia (AML) respond poorly to currently available treatments, including venetoclax-based drug combinations and pose a major therapeutic challenge. Analyses of RNA sequencing and reverse phase protein array datasets revealed significantly lower BAX RNA and protein levels in TP53-mutant compared to TP53-wild-type (WT) AML, a finding confirmed in isogenic CRISPR-generated TP53-knockout and -mutant AML. The response to either BCL-2 (venetoclax) or MCL-1 (AMG176) inhibition was BAX-dependent and much reduced in TP53-mutant compared to TP53-WT cells, while the combination of two BH3 mimetics effectively activated BAX, circumventing survival mechanisms in cells treated with either BH3 mimetic, and synergistically induced cell death in TP53-mutant AML and stem/progenitor cells. The BH3 mimetic-driven stress response and cell death patterns after dual inhibition were largely independent of TP53 status and affected by apoptosis induction. Co-targeting, but not individual targeting of BCL-2 and MCL-1 in mice xenografted with TP53-WT and TP53-R248W Molm13 cells suppressed both TP53-WT and TP53-mutant cell growth and significantly prolonged survival. Our results demonstrate that co-targeting BCL-2 and MCL-1 overcomes BAX deficiency-mediated resistance to individual BH3 mimetics in TP53-mutant cells, thus shifting cell fate from survival to death in TP53-deficient and -mutant AML. This concept warrants clinical evaluation.

DOI: https://doi.org/10.1038/s41408-023-00830-w
Cell Stem Cell. 2023 Apr 19. pii: S1934-5909(23)00119-4. [Epub ahead of print]

Clonally resolved single-cell multi-omics identifies routes of cellular differentiation in acute myeloid leukemia.

Sergi Beneyto-Calabuig, Anne Kathrin Merbach, Jonas-Alexander Kniffka, Magdalena Antes, Chelsea Szu-Tu, Christian Rohde, Alexander Waclawiczek, Patrick Stelmach, Sarah Gräßle, Philip Pervan, Maike Janssen, Jonathan J M Landry, Vladimir Benes, Anna Jauch, Michaela Brough, Marcus Bauer, Birgit Besenbeck, Julia Felden, Sebastian Bäumer, Michael Hundemer, Tim Sauer, Caroline Pabst, Claudia Wickenhauser, Linus Angenendt, Christoph Schliemann, Andreas Trumpp, Simon Haas, Michael Scherer, Simon Raffel, Carsten Müller-Tidow, Lars Velten.

  Inter-patient variability and the similarity of healthy and leukemic stem cells (LSCs) have impeded the characterization of LSCs in acute myeloid leukemia (AML) and their differentiation landscape. Here, we introduce CloneTracer, a novel method that adds clonal resolution to single-cell RNA-seq datasets. Applied to samples from 19 AML patients, CloneTracer revealed routes of leukemic differentiation. Although residual healthy and preleukemic cells dominated the dormant stem cell compartment, active LSCs resembled their healthy counterpart and retained erythroid capacity. By contrast, downstream myeloid progenitors constituted a highly aberrant, disease-defining compartment: their gene expression and differentiation state affected both the chemotherapy response and leukemia's ability to differentiate into transcriptomically normal monocytes. Finally, we demonstrated the potential of CloneTracer to identify surface markers misregulated specifically in leukemic cells. Taken together, CloneTracer reveals a differentiation landscape that mimics its healthy counterpart and may determine biology and therapy response in AML.

Keywords:  AML; CSC; HSC; LSC; acute myeloid leukemia; cancer stem cells; cellular differentiation; computational biology; computational method; hematopoietic stem cells; leukemic stem cells; single-cell RNA-seq; single-cell genomics; single-cell transcriptomics

DOI:  https://doi.org/10.1016/j.stem.2023.04.001
Proc Natl Acad Sci U S A. 2023 May 02. 120(18): e2216713120

Structure of the human respiratory complex II.

Zhanqiang Du, Xiaoting Zhou, Yuezheng Lai, Jinxu Xu, Yuying Zhang, Shan Zhou, Ziyan Feng, Long Yu, Yanting Tang, Weiwei Wang, Lu Yu, Changlin Tian, Ting Ran, Hongming Chen, Luke W Guddat, Fengjiang Liu, Yan Gao, Zihe Rao, Hongri Gong.

  Human complex II is a key protein complex that links two essential energy-producing processes: the tricarboxylic acid cycle and oxidative phosphorylation. Deficiencies due to mutagenesis have been shown to cause mitochondrial disease and some types of cancers. However, the structure of this complex is yet to be resolved, hindering a comprehensive understanding of the functional aspects of this molecular machine. Here, we have determined the structure of human complex II in the presence of ubiquinone at 2.86 Å resolution by cryoelectron microscopy, showing it comprises two water-soluble subunits, SDHA and SDHB, and two membrane-spanning subunits, SDHC and SDHD. This structure allows us to propose a route for electron transfer. In addition, clinically relevant mutations are mapped onto the structure. This mapping provides a molecular understanding to explain why these variants have the potential to produce disease.

Keywords:  cryoelectron microscopy; electron transport chain; human complex II

DOI:  https://doi.org/10.1073/pnas.2216713120