bims-mibica 2021-12-26 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2021‒12‒26
37 papers selected by
Kelsey Fisher-Wellman, East Carolina University

Hyaluronic acid fuels pancreatic cancer cell growth.
Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.
Reuterin in the healthy gut microbiome suppresses colorectal cancer growth through altering redox balance.
Mitochondrial DNA mutations are involved in the acquisition of cisplatin resistance in human lung cancer A549 cells.
Clinically Relevant Oxygraphic Assay to Assess Mitochondrial Energy Metabolism in Acute Myeloid Leukemia Patients.
Mitochondrial DNA damage as driver of cellular outcomes.
Post-translational modifications on mitochondrial metabolic enzymes in cancer.
Metabolic reprogramming during hyperammonemia targets mitochondrial function and postmitotic senescence.
The FoxQ1 transcription factor is a novel regulator of electron transport chain complex I subunits in human breast cancer cells.
Analysis of Mitochondrial Calcium Retention Capacity in Cultured Cells: Permeabilized Cells Versus Isolated Mitochondria.
Microbial metabolite delta-valerobetaine is a diet-dependent obesogen.
Overexpression of CERKL Protects Retinal Pigment Epithelium Mitochondria from Oxidative Stress Effects.
Skeletal muscle mitochondrial dysfunction and muscle and whole-body functional deficits in cancer patients with weight loss.
ATAD3A has a scaffolding role regulating mitochondria inner membrane structure and protein assembly.
Mutations in the Yeast Cox12 Subunit Severely Compromise the Activity of the Mitochondrial Complex IV.
Microtubule Integrity Is Associated with the Functional Activity of Mitochondria in HEK293.
Multi-Omic Metabolic Enrichment Network Analysis reveals metabolite-protein physical interaction subnetworks altered in cancer.
Mitochondrial Bioenergetic and Proteomic Phenotyping Reveals Organ-Specific Consequences of Chronic Kidney Disease in Mice.
Coupling/Uncoupling Reversibility in Isolated Mitochondria from Saccharomyces cerevisiae.
Mito-TIPTP Increases Mitochondrial Function by Repressing the Rubicon-p22phox Interaction in Colitis-Induced Mice.
Antiproliferative, Antiangiogenic, and Antimetastatic Therapy Response by Mangiferin in a Syngeneic Immunocompetent Colorectal Cancer Mouse Model Involves Changes in Mitochondrial Energy Metabolism.
The effects of Acyclovir administration to NCI-H1975 non-small cell lung cancer cells.
Mitochondrial glutamine metabolism regulates sensitivity of cancer cells after chemotherapy via amphiregulin.
Bone marrow microenvironment drives AML cell OXPHOS addiction and AMPK inhibition to resist chemotherapy.
Valine tRNA levels and availability regulate complex I assembly in leukaemia.
Extracellular citrate and metabolic adaptations of cancer cells.
VJ21.089The subcompartmented oxphosomic model of the phosphorylating system organization in mitochondria.
Mitochondrial complex I inhibitors suppress tumor growth through concomitant acidification of the intra- and extracellular environment.
Catalase Overexpression Drives an Aggressive Phenotype in Glioblastoma.
Enforced DYRK2 expression by adenovirus-mediated gene transfer inhibits tumor growth and metastasis of colorectal cancer.
FDFT1 predicts poor prognosis in stage I-III colon adenocarcinoma and synergizes SQLE to promote tumor progression.
Dinner is served, sir: Fighting cancer with the right diet.
The kinase complex mTORC2 promotes the longevity of virus-specific memory CD4+ T cells by preventing ferroptosis.
Mitochondrial Respiration of Platelets: Comparison of Isolation Methods.
On the Design Principles of Metabolic Flux Sensing.
SIRT5 functions as a tumor suppressor in renal cell carcinoma by reversing the Warburg effect.
Late-life exercise mitigates skeletal muscle epigenetic aging.

Elife. 2021 Dec 24. pii: e62645. [Epub ahead of print]10

Hyaluronic acid fuels pancreatic cancer cell growth.

Peter K Kim, Christopher J Halbrook, Samuel A Kerk, Megan Radyk, Stephanie Wisner, Daniel M Kremer, Peter Sajjakulnukit, Anthony Andren, Sean W Hou, Ayush Trivedi, Galloway Thurston, Abhinav Anand, Liang Yan, Lucia Salamanca-Cardona, Samuel D Welling, Li Zhang, Matthew R Pratt, Kayvan R Keshari, Haoqiang Ying, Costas Lyssiotis.

  Rewired metabolism is a hallmark of pancreatic ductal adenocarcinomas (PDA). Previously, we demonstrated that PDA cells enhance glycosylation precursor biogenesis through the hexosamine biosynthetic pathway (HBP) via activation of the rate limiting enzyme, glutamine-fructose 6-phosphate amidotransferase 1 (GFAT1). Here, we genetically ablated GFAT1 in human PDA cell lines, which completely blocked proliferation in vitro and led to cell death. In contrast, GFAT1 knockout did not preclude the growth of human tumor xenografts in mice, suggesting that cancer cells can maintain fidelity of glycosylation precursor pools by scavenging nutrients from the tumor microenvironment. We found that hyaluronic acid (HA), an abundant carbohydrate polymer in pancreatic tumors composed of repeating N-acetyl-glucosamine (GlcNAc) and glucuronic acid sugars, can bypass GFAT1 to refuel the HBP via the GlcNAc salvage pathway. Together, these data show HA can serve as a nutrient fueling PDA metabolism beyond its previously appreciated structural and signaling roles.

Keywords:  cancer biology; human; mouse

DOI:  https://doi.org/10.7554/eLife.62645
Elife. 2021 Dec 23. pii: e72593. [Epub ahead of print]10

Disruption of the TCA cycle reveals an ATF4-dependent integration of redox and amino acid metabolism.

Dylan Gerard Ryan, Ming Yang, Hiran A Prag, Giovanny Rodriguez Blanco, Efterpi Nikitopoulou, Marc Segarra-Mondejar, Christopher A Powell, Tim Young, Nils Burger, Jan Lj Miljkovic, Michal Minczuk, Michael P Murphy, Alex von Kriegsheim, Christian Frezza.

  The Tricarboxylic Acid Cycle (TCA) cycle is arguably the most critical metabolic cycle in physiology and exists as an essential interface coordinating cellular metabolism, bioenergetics, and redox homeostasis. Despite decades of research, a comprehensive investigation into the consequences of TCA cycle dysfunction remains elusive. Here, we targeted two TCA cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDH), and combined metabolomics, transcriptomics, and proteomics analyses to fully appraise the consequences of TCA cycle inhibition (TCAi) in murine kidney epithelial cells. Our comparative approach shows that TCAi elicits a convergent rewiring of redox and amino acid metabolism dependent on the activation of ATF4 and the integrated stress response (ISR). Furthermore, we also uncover a divergent metabolic response, whereby acute FHi, but not SDHi, can maintain asparagine levels via reductive carboxylation and maintenance of cytosolic aspartate synthesis. Our work highlights an important interplay between the TCA cycle, redox biology and amino acid homeostasis.

Keywords:  biochemistry; cell biology; chemical biology; mouse

DOI:  https://doi.org/10.7554/eLife.72593
Cancer Cell. 2021 Dec 14. pii: S1535-6108(21)00613-9. [Epub ahead of print]

Reuterin in the healthy gut microbiome suppresses colorectal cancer growth through altering redox balance.

Hannah N Bell, Ryan J Rebernick, Joshua Goyert, Rashi Singhal, Miljan Kuljanin, Samuel A Kerk, Wesley Huang, Nupur K Das, Anthony Andren, Sumeet Solanki, Shannon L Miller, Peter K Todd, Eric R Fearon, Costas A Lyssiotis, Steven P Gygi, Joseph D Mancias, Yatrik M Shah.

  Microbial dysbiosis is a colorectal cancer (CRC) hallmark and contributes to inflammation, tumor growth, and therapy response. Gut microbes signal via metabolites, but how the metabolites impact CRC is largely unknown. We interrogated fecal metabolites associated with mouse models of colon tumorigenesis with varying mutational load. We find that microbial metabolites from healthy mice or humans are growth-repressive, and this response is attenuated in mice and patients with CRC. Microbial profiling reveals that Lactobacillus reuteri and its metabolite, reuterin, are downregulated in mouse and human CRC. Reuterin alters redox balance, and reduces proliferation and survival in colon cancer cells. Reuterin induces selective protein oxidation and inhibits ribosomal biogenesis and protein translation. Exogenous Lactobacillus reuteri restricts colon tumor growth, increases tumor reactive oxygen species, and decreases protein translation in vivo. Our findings indicate that a healthy microbiome and specifically, Lactobacillus reuteri, is protective against CRC through microbial metabolite exchange.

Keywords:  Lactobacillus reuteri; Microbiome; Reuterin; colorectal cancer; metabolites; protein oxidation

DOI:  https://doi.org/10.1016/j.ccell.2021.12.001
Oncol Rep. 2022 Feb;pii: 32. [Epub ahead of print]47(2):

Mitochondrial DNA mutations are involved in the acquisition of cisplatin resistance in human lung cancer A549 cells.

Sayo Horibe, Kaori Ishikawa, Kazuto Nakada, Masaki Wake, Norihiko Takeda, Toru Tanaka, Shoji Kawauchi, Naoto Sasaki, Yoshiyuki Rikitake.

  The efficacy of cisplatin (CDDP) has been demonstrated in the treatment of various cancers as monotherapy and combination therapy with immunotherapy. However, acquired CDDP resistance is a major obstacle to successful treatment. In the present study, the mechanisms underlying acquired CDDP resistance were examined using ACR20 cells, which are CDDP‑resistant cells derived from A549 lung cancer cells. CDDP induces cytotoxicity by binding nuclear DNA and generating reactive oxygen species (ROS). Contrary to our expectation, ROS levels were elevated in ACR20 cells not treated with CDDP. Pretreatment with an ROS inhibitor enhanced the sensitivity of ACR20 cells to CDDP and prevented the activation of nuclear factor (NF)‑кB signaling and upregulation of inhibitor of apoptosis proteins (IAPs). Notably, evaluation of the mitochondrial oxygen consumption rate and mitochondrial superoxide levels revealed a deterioration of mitochondrial function in ACR20 cells. Mitochondrial DNA PCR‑RFLP analysis revealed four mutations with varying percentage levels in ACR20 cells. In addition, in cytoplasmic hybrids with mitochondria from ACR20 cells, intrinsic ROS levels were elevated, expression of IAPs was increased, and complex I activity and sensitivity to CDDP were decreased. Analysis of three‑dimensional structure data indicated that a mutation (ND2 F40L) may impact the proton translocation pathway, thereby affecting mitochondrial complex I activity. Together, these findings suggest that intrinsic ROS levels were elevated by mitochondrial DNA mutations, which decreased the sensitivity to CDDP via activation of NF‑κB signaling and induction of IAP expression in ACR20 cells. These findings indicate that newly identified mutations in mitochondrial DNA may lead to acquired cisplatin resistance in cancer.

Keywords:  acquired resistance; cisplatin; complex I; mitochondria; reactive oxygen species

DOI:  https://doi.org/10.3892/or.2021.8243
Cancers (Basel). 2021 Dec 17. pii: 6353. [Epub ahead of print]13(24):

Clinically Relevant Oxygraphic Assay to Assess Mitochondrial Energy Metabolism in Acute Myeloid Leukemia Patients.

Quentin Fovez, William Laine, Laure Goursaud, Celine Berthon, Nicolas Germain, Claire Degand, Jean-Emmanuel Sarry, Bruno Quesnel, Philippe Marchetti, Jerome Kluza.

  Resistant acute myeloid leukemia (AML) exhibits mitochondrial energy metabolism changes compared to newly diagnosed AML. This phenotype is often observed by evaluating the mitochondrial oxygen consumption of blasts, but most of the oximetry protocols were established from leukemia cell lines without validation on primary leukemia cells. Moreover, the cultures and storage conditions of blasts freshly extracted from patient blood or bone marrow cause stress, which must be evaluated before determining oxidative phosphorylation (OXPHOS). Herein, we evaluated different conditions to measure the oxygen consumption of blasts using extracellular flow analyzers. We first determined the minimum number of blasts required to measure OXPHOS. Next, we compared the OXPHOS of blasts cultured for 3 h and 18 h after collection and found that to maintain metabolic organization for 18 h, cytokine supplementation is necessary. Cytokines are also needed when measuring OXPHOS in cryopreserved, thawed and recultured blasts. Next, the concentrations of respiratory chain inhibitors and uncoupler FCCP were established. We found that the FCCP concentration required to reach the maximal respiration of blasts varied depending on the patient sample analyzed. These protocols provided can be used in future clinical studies to evaluate OXPHOS as a biomarker and assess the efficacy of treatments targeting mitochondria.

Keywords:  OCR; XFe24 Seahorse; XFe96 Seahorse; energy metabolism; functional biomarker; leukemia; resistance; uncoupling respiration

DOI:  https://doi.org/10.3390/cancers13246353
Am J Physiol Cell Physiol. 2021 Dec 22.

Mitochondrial DNA damage as driver of cellular outcomes.

Cristina A Nadalutti, Sylvette Ayala-Peña, Janine H Santos.

  Mitochondria are primarily involved in energy production through the process of oxidative phosphorylation (OXPHOS). Increasing evidence has shown that mitochondrial function impacts a plethora of different cellular activities, including metabolism, epigenetics and innate immunity. Like the nucleus, mitochondria own their genetic material, which is maternally inherited. The mitochondrial DNA (mtDNA) encodes 37 genes that are solely involved in OXPHOS. Maintenance of mtDNA, through replication and repair, requires the import of nuclear DNA encoded proteins. Thus, mitochondria completely rely on the nucleus to prevent mitochondrial genetic alterations. As every cell contains hundreds to thousands of mitochondria, it follows that the shear number of organelles allow for the buffering of dysfunction - at least to some extent - before tissue homeostasis becomes impaired. Only red blood cells lack mitochondria entirely. Impaired mitochondrial function is a hallmark of aging and is involved in a number of different disorders, including neurodegenerative diseases, diabetes, cancer, and autoimmunity. While alterations in mitochondrial processes unrelated to OXPHOS, such as fusion and fission, contribute to aging and disease, maintenance of mtDNA integrity is critical for proper organellar function. Here, we focus on how mtDNA damage contributes to cellular dysfunction and health outcomes.

Keywords:  DNA repair; cellular outcomes; mitochondrial dysfunction; mtDNA damage

DOI:  https://doi.org/10.1152/ajpcell.00389.2021
Free Radic Biol Med. 2021 Dec 17. pii: S0891-5849(21)01116-3. [Epub ahead of print]179 11-23

Post-translational modifications on mitochondrial metabolic enzymes in cancer.

Yunhua Peng, Huadong Liu, Jiankang Liu, Jiangang Long.

  Mitochondrion is the powerhouse of the cell. The research of nearly a century has expanded our understanding of mitochondrion, far beyond the view that mitochondrion is an important energy generator of cells. During the initiation, growth and survival of tumor cells, significant mitochondrial metabolic changes have taken place in the important enzymes of respiratory chain and tricarboxylic acid cycle, mitochondrial biogenesis and dynamics, oxidative stress regulation and molecular signaling. Therefore, mitochondrial metabolic proteins are the key mediators of tumorigenesis. Post-translational modification is the molecular switch that regulates protein function. Understanding how these mitochondria-related post-translational modification function during tumorigenesis will bring new ideas for the next generation of cancer treatment.

Keywords:  Metabolism; Mitochondrial biogenesis; Mitophagy; OXPHOS; Post-translational modification; TCA cycle

DOI:  https://doi.org/10.1016/j.freeradbiomed.2021.12.264
JCI Insight. 2021 Dec 22. pii: e154089. [Epub ahead of print]6(24):

Metabolic reprogramming during hyperammonemia targets mitochondrial function and postmitotic senescence.

Avinash Kumar, Nicole Welch, Saurabh Mishra, Annette Bellar, Rafaella Nasciemento Silva, Ling Li, Shashi Shekhar Singh, Mary Sharkoff, Alexis Kerr, Aruna Kumar Chelluboyina, Jinendiran Sekar, Amy H Attaway, Charles Hoppel, Belinda Willard, Gangarao Davuluri, Srinivasan Dasarathy.

  Ammonia is a cytotoxic metabolite with pleiotropic molecular and metabolic effects, including senescence induction. During dysregulated ammonia metabolism, which occurs in chronic diseases, skeletal muscle becomes a major organ for nonhepatocyte ammonia uptake. Muscle ammonia disposal occurs in mitochondria via cataplerosis of critical intermediary metabolite α-ketoglutarate, a senescence-ameliorating molecule. Untargeted and mitochondrially targeted data were analyzed by multiomics approaches. These analyses were validated experimentally to dissect the specific mitochondrial oxidative defects and functional consequences, including senescence. Responses to ammonia lowering in myotubes and in hyperammonemic portacaval anastomosis rat muscle were studied. Whole-cell transcriptomics integrated with whole-cell, mitochondrial, and tissue proteomics showed distinct temporal clusters of responses with enrichment of oxidative dysfunction and senescence-related pathways/proteins during hyperammonemia and after ammonia withdrawal. Functional and metabolic studies showed defects in electron transport chain complexes I, III, and IV; loss of supercomplex assembly; decreased ATP synthesis; increased free radical generation with oxidative modification of proteins/lipids; and senescence-associated molecular phenotype-increased β-galactosidase activity and expression of p16INK, p21, and p53. These perturbations were partially reversed by ammonia lowering. Dysregulated ammonia metabolism caused reversible mitochondrial dysfunction by transcriptional and translational perturbations in multiple pathways with a distinct skeletal muscle senescence-associated molecular phenotype.

Keywords:  Cell Biology; Cellular senescence; Hepatology; Mitochondria; Skeletal muscle

DOI:  https://doi.org/10.1172/jci.insight.154089
Mol Carcinog. 2021 Dec 22.

The FoxQ1 transcription factor is a novel regulator of electron transport chain complex I subunits in human breast cancer cells.

Su-Hyeong Kim, Shivendra V Singh.

  The FoxQ1 is an oncogenic transcription factor that is overexpressed in basal-like and luminal-type human breast cancers when compared to the normal mammary tissue. The FoxQ1 is implicated in mammary tumor progression. However, the mechanism by which FoxQ1 promotes mammary tumorigenesis is not fully understood. In this study, we present experimental evidence for a novel function of FoxQ1 in the regulation of complex I activity of the electron transport chain. The RNA-seq data from FoxQ1 overexpressing basal-like SUM159 cells revealed a statistically significant increase in the expression of complex I subunits NDUFS1 and NDUFS2 when compared to the empty vector (EV) transfected control cells. Consistent with these results, the basal and ATP-linked oxygen consumption rates were significantly increased by FoxQ1 overexpression in SUM159 and luminal-type MCF-7 cells. The FoxQ1 overexpression in both cell lines resulted in increased intracellular levels of pyruvate, lactate, and ATP that was associated with overexpression of pyruvate dehydrogenase and pyruvate carboxylase proteins. Activity and assembly of complex I were significantly enhanced by FoxQ1 overexpression in SUM159 and MCF-7 cells that correlated with increased mRNA and/or protein levels of complex I subunits NDUFS1, NDUFS2, NDUFV1, and NDUFV2. The chromatin immunoprecipitation assay revealed the recruitment of FoxQ1 at the promoters of both NDUFS1 and NDUFV1. The cell proliferation of SUM159 and MCF-7 cells was increased significantly by overexpression of NDUFS1 as well as NDUFV1 proteins. In conclusion, we propose that increased complex I-linked oxidative phosphorylation is partly responsible for oncogenic role of FoxQ1 at least in human breast cancer cells.

Keywords:  FoxQ1; NDUFS1; NDUFV1; breast cancer; complex I

DOI:  https://doi.org/10.1002/mc.23381
Front Physiol. 2021 ;12 773839

Analysis of Mitochondrial Calcium Retention Capacity in Cultured Cells: Permeabilized Cells Versus Isolated Mitochondria.

Sehwan Jang, Xavier R Chapa-Dubocq, Silvia Fossati, Sabzali Javadov.

  In response to various pathological stimuli, such as oxidative and energy stress accompanied by high Ca2+, mitochondria undergo permeability transition (PT) leading to the opening of the non-selective PT pores (PTP) in the inner mitochondrial membrane. Opening of the pores at high conductance allows the passage of ions and solutes <1.5 kD across the membrane, that increases colloid osmotic pressure in the matrix leading to excessive mitochondrial swelling. Calcium retention capacity (CRC) reflects maximum Ca2+ overload of mitochondria that occurs just before PTP opening. Quantification of CRC is important for elucidating the effects of different pathological stimuli and the efficacy of pharmacological agents on the mitochondria. Here, we performed a comparative analysis of CRC in mitochondria isolated from H9c2 cardioblasts, and in permeabilized H9c2 cells in situ to highlight the strengths and weaknesses of the CRC technique in isolated cell mitochondria vs. permeabilized cells. The cells were permeabilized by digitonin or saponin, and the Ca2+-sensitive fluorescence probe Calcium Green-5N was used in both preparations. Results demonstrated the interference of dye-associated fluorescence signals with saponin and the adverse effects of digitonin on mitochondria at high concentrations. Analysis of the CRC in permeabilized cells revealed a higher CRC in the saponin-permeabilized cells in comparison with the digitonin-permeabilized cells. In addition, the mitochondrial CRC in saponin-permeabilized cells was higher than in isolated mitochondria. Altogether, these data demonstrate that the quantification of the mitochondrial CRC in cultured cells permeabilized by saponin has more advantages compared to the isolated mitochondria.

Keywords:  calcium retention capacity; mitochondria; mitochondrial swelling; permeability transition pore; permeabilized cells

DOI:  https://doi.org/10.3389/fphys.2021.773839
Nat Metab. 2021 Dec;3(12): 1694-1705

Microbial metabolite delta-valerobetaine is a diet-dependent obesogen.

Ken H Liu, Joshua A Owens, Bejan Saeedi, Catherine E Cohen, Moriah P Bellissimo, Crystal Naudin, Trevor Darby, Samuel Druzak, Kristal Maner-Smith, Michael Orr, Xin Hu, Jolyn Fernandes, Mary Catherine Camacho, Sarah Hunter-Chang, David VanInsberghe, Chunyu Ma, Thota Ganesh, Samantha M Yeligar, Karan Uppal, Young-Mi Go, Jessica A Alvarez, Miriam B Vos, Thomas R Ziegler, Michael H Woodworth, Colleen S Kraft, Rheinallt M Jones, Eric Ortlund, Andrew S Neish, Dean P Jones.

Obesity and obesity-related metabolic disorders are linked to the intestinal microbiome. However, the causality of changes in the microbiome-host interaction affecting energy metabolism remains controversial. Here, we show the microbiome-derived metabolite δ-valerobetaine (VB) is a diet-dependent obesogen that is increased with phenotypic obesity and is correlated with visceral adipose tissue mass in humans. VB is absent in germ-free mice and their mitochondria but present in ex-germ-free conventionalized mice and their mitochondria. Mechanistic studies in vivo and in vitro show VB is produced by diverse bacterial species and inhibits mitochondrial fatty acid oxidation through decreasing cellular carnitine and mitochondrial long-chain acyl-coenzyme As. VB administration to germ-free and conventional mice increases visceral fat mass and exacerbates hepatic steatosis with a western diet but not control diet. Thus, VB provides a molecular target to understand and potentially manage microbiome-host symbiosis or dysbiosis in diet-dependent obesity.

DOI: https://doi.org/10.1038/s42255-021-00502-8
Antioxidants (Basel). 2021 Dec 19. pii: 2018. [Epub ahead of print]10(12):

Overexpression of CERKL Protects Retinal Pigment Epithelium Mitochondria from Oxidative Stress Effects.

Rocío García-Arroyo, Aleix Gavaldà-Navarro, Francesc Villarroya, Gemma Marfany, Serena Mirra.

  The precise function of CERKL, a Retinitis Pigmentosa (RP) causative gene, is not yet fully understood. There is evidence that CERKL is involved in the regulation of autophagy, stress granules, and mitochondrial metabolism, and it is considered a gene that is resilient against oxidative stress in the retina. Mutations in most RP genes affect photoreceptors, but retinal pigment epithelium (RPE) cells may be also altered. Here, we aimed to analyze the effect of CERKL overexpression and depletion in vivo and in vitro, focusing on the state of the mitochondrial network under oxidative stress conditions. Our work indicates that the depletion of CERKL increases the vulnerability of RPE mitochondria, which show a shorter size and altered shape, particularly upon sodium arsenite treatment. CERKL-depleted cells have dysfunctional mitochondrial respiration particularly upon oxidative stress conditions. The overexpression of two human CERKL isoforms (558 aa and 419 aa), which display different protein domains, shows that a pool of CERKL localizes at mitochondria in RPE cells and that CERKL protects the mitochondrial network-both in size and shape-against oxidative stress. Our results support CERKL being a resilient gene that regulates the mitochondrial network in RPE as in retinal neurons and suggest that RPE cell alteration contributes to particular phenotypic traits in patients carrying CERKL mutations.

Keywords:  CERKL; mitochondrial network; oxidative stress; retinal pigment epithelium; retinitis pigmentosa

DOI:  https://doi.org/10.3390/antiox10122018
J Appl Physiol (1985). 2021 Dec 23.

Skeletal muscle mitochondrial dysfunction and muscle and whole-body functional deficits in cancer patients with weight loss.

Hawley E Kunz, John D Port, Kenton R Kaufman, Aminah Jatoi, Corey R Hart, Kevin J Gries, Ian R Lanza, Rajiv Kumar.

  Reductions in skeletal muscle mass and function are often reported in patients with cancer-associated weight loss and are associated with reduced quality of life, impaired treatment tolerance, and increased mortality. Although cellular changes, including altered mitochondrial function, have been reported in animals, such changes have been incompletely characterized in humans with cancer. Whole body and skeletal muscle physical function, skeletal muscle mitochondrial function and whole-body protein turnover were assessed in 8 patients with cancer-associated weight loss (10.1±4.2% body weight over 6-12 months) and 19 age-, sex-, and BMI-matched healthy controls to characterize skeletal muscle changes at the whole body, muscle, and cellular level. Potential pathways involved in cancer-induced alterations in metabolism and mitochondrial function were explored by interrogating skeletal muscle and plasma metabolomes. Despite similar lean mass compared to control participants, patients with cancer exhibited reduced habitual physical activity (57% fewer daily steps), cardiorespiratory fitness (22% lower VO2peak [mL/kg/min]) and leg strength (35% lower isokinetic knee extensor strength) and greater leg neuromuscular fatigue (36% greater decline in knee extensor torque). Concomitant with these functional declines, patients with cancer had lower mitochondrial oxidative capacity (25% lower State 3 O2 flux [pmol/s/mg tissue]) and ATP production (23% lower State 3 ATP production [pmol/s/mg tissue]) and alterations in phospholipid metabolite profiles indicative of mitochondrial abnormalities. Whole body protein turnover was unchanged. These findings demonstrate mitochondrial abnormalities concomitant with whole-body and skeletal muscle functional derangements associated with human cancer, supporting future work studying the role of mitochondria in the muscle deficits associated with cancer.

Keywords:  cancer-associated weight loss; mitochondria; muscle strength; physical activity; skeletal muscle

DOI:  https://doi.org/10.1152/japplphysiol.00746.2021
Cell Rep. 2021 Dec 21. pii: S2211-1247(21)01635-1. [Epub ahead of print]37(12): 110139

ATAD3A has a scaffolding role regulating mitochondria inner membrane structure and protein assembly.

Tania Arguello, Susana Peralta, Hana Antonicka, Gabriel Gaidosh, Francisca Diaz, Ya-Ting Tu, Sofia Garcia, Ramin Shiekhattar, Antonio Barrientos, Carlos T Moraes.

  The ATPase Family AAA Domain Containing 3A (ATAD3A), is a mitochondrial inner membrane protein conserved in metazoans. ATAD3A has been associated with several mitochondrial functions, including nucleoid organization, cholesterol metabolism, and mitochondrial translation. To address its primary role, we generated a neuronal-specific conditional knockout (Atad3 nKO) mouse model, which developed a severe encephalopathy by 5 months of age. Pre-symptomatic mice showed aberrant mitochondrial cristae morphogenesis in the cortex as early as 2 months. Using a multi-omics approach in the CNS of 2-to-3-month-old mice, we found early alterations in the organelle membrane structure. We also show that human ATAD3A associates with different components of the inner membrane, including OXPHOS complex I, Letm1, and prohibitin complexes. Stochastic Optical Reconstruction Microscopy (STORM) shows that ATAD3A is regularly distributed along the inner mitochondrial membrane, suggesting a critical structural role in inner mitochondrial membrane and its organization, most likely in an ATPase-dependent manner.

Keywords:  ATAD3; cardiolipin; cristae; inner membrane; mitochondria

DOI:  https://doi.org/10.1016/j.celrep.2021.110139
Biochemistry (Mosc). 2021 Dec;86(12): 1607-1623

Mutations in the Yeast Cox12 Subunit Severely Compromise the Activity of the Mitochondrial Complex IV.

Shubhojit Das, Soumyajit Mukherjee, Minakshi Bedi, Alok Ghosh.

  Cytochrome c oxidase 6B1 (COX6B1) is one of the less characterized subunits of the mitochondrial electron transport chain complex IV (CIV). Here, we studied the pathobiochemical and respiratory functions of Cox12 (yeast ortholog of COX6B1) using Saccharomyces cerevisiae BY4741 (cox12Δ) cells deficient by the Cox12 protein. The cells exhibited severe growth deficiency in the respiratory glycerol-ethanol medium, which could be reverted by complementation with the yeast COX12 or human COX6B1 genes. Cox12 with arginine 17 residue substituted by histidine (R17H) or cysteine (R17C) (mutations analogous to those observed in human patients) failed to complement the loss of Cox12 function. When cox12Δ cells were grown in rich respiratory/fermentative galactose medium, no changes in the expression of individual respiratory chain subunits were observed. Blue native PAGE/Western blotting analysis using antibodies against Rip1 and Cox1, which are specific components of complexes III (CIII) and IV (CIV), respectively, revealed no noticeable decrease in the native CIII2CIV2 and CIII2CIV1 supercomplexes (SCs). However, the association of the respiratory SC factor 2 (Rcf2) and Cox2 subunit within the SCs of cox12Δ cells was reduced, while the specific activity of CIV was downregulated by 90%. Both basal respiration and succinate-ADP stimulated state 3 respiration, as well as the mitochondrial membrane potential, were decreased in cox12Δ cells. Furthermore, cox12Δ cells and cells synthesizing Cox12 mutants R17H and R17C showed higher sensitivity to the H2O2-induced oxidative stress compared to the wild-type (WT) cells. In silico structural modeling of the WT yeast SCs revealed that Cox12 forms a network of interactions with Rcf2 and Cox2. Together, our results establish that Cox12 is essential for the CIV activity.

Keywords:  Cox12; complex IV; cytochrome c oxidase 6B1; supercomplexes

DOI:  https://doi.org/10.1134/S0006297921120105
Cells. 2021 Dec 20. pii: 3600. [Epub ahead of print]10(12):

Microtubule Integrity Is Associated with the Functional Activity of Mitochondria in HEK293.

Min Jeong Cho, Yu Jin Kim, Won Dong Yu, You Shin Kim, Jae Ho Lee.

  Mitochondria move along the microtubule network and produce bioenergy in the cell. However, there is no report of a relationship between bioenergetic activity of mitochondria and microtubule stability in mammalian cells. This study aimed to investigate this relationship. We treated HEK293 cells with microtubule stabilizers (Taxol and Epothilone D) or a microtubule disturber (vinorelbine), and performed live-cell imaging to determine whether mitochondrial morphology and bioenergetic activity depend on the microtubule status. Treatment with microtubule stabilizers enhanced the staining intensity of microtubules, significantly increased ATP production and the spare respiratory capacity, dramatically increased mitochondrial fusion, and promoted dynamic movement of mitochondria. By contrast, bioenergetic activity of mitochondria was significantly decreased in cells treated with the microtubule disturber. Our data suggest that microtubule stability promotes mitochondrial functional activity. In conclusion, a microtubule stabilizer can possibly recover mitochondrial functional activity in cells with unstable microtubules.

Keywords:  bioenergetic activity; disturber; microtubule; mitochondria; stability

DOI:  https://doi.org/10.3390/cells10123600
Mol Cell Proteomics. 2021 Dec 18. pii: S1535-9476(21)00161-4. [Epub ahead of print] 100189

Multi-Omic Metabolic Enrichment Network Analysis reveals metabolite-protein physical interaction subnetworks altered in cancer.

Benjamin C Blum, Weiwei Lin, Matthew L Lawton, Qian Liu, Julian Kwan, Isabella Turcinovic, Ryan Hekman, Pingzhao Hu, Andrew Emili.

  Metabolism is recognized as an important driver of cancer progression and other complex diseases, but global metabolite profiling remains a challenge. Protein expression profiling is often a poor proxy since existing pathway enrichment models provide an incomplete mapping between the proteome and metabolism. To overcome these gaps, we introduce MOMENTA, an integrative multi-omic data analysis framework for more accurately deducing metabolic pathway changes from proteomics data alone in a gene set analysis context by leveraging protein interaction networks to extend annotated metabolic models. We apply MOMENTA to proteomic data from diverse cancer cell lines and human tumors to demonstrate its utility at revealing variation in metabolic pathway activity across cancer types, which we verify using independent metabolomics measurements. The novel metabolic networks we uncover in breast cancer and other tumors are linked to clinical outcomes, underscoring the pathophysiological relevance of the findings.

Keywords:  Cancer; Multi-omic; Networks; Proteomics; Systems Biology

DOI:  https://doi.org/10.1016/j.mcpro.2021.100189
Cells. 2021 Nov 24. pii: 3282. [Epub ahead of print]10(12):

Mitochondrial Bioenergetic and Proteomic Phenotyping Reveals Organ-Specific Consequences of Chronic Kidney Disease in Mice.

Trace Thome, Madeline D Coleman, Terence E Ryan.

  Chronic kidney disease (CKD) results in reduced kidney function, uremia, and accumulation of uremic metabolites. Mitochondrial alterations have been suggested to play a role in the disease pathology within various tissues. The purpose of this study was to perform a comprehensive bioenergetic and proteomic phenotyping of mitochondria from skeletal muscle (SkM), cardiac muscle (CM), and renal tissue from mice with CKD. The 5-month-old C57BL/6J male mice were fed a casein control or adenine-supplemented diet for 6 months. CKD was confirmed by blood urea nitrogen. A mitochondrial diagnostic workflow was employed to examine respiratory function, membrane and redox potential, reactive oxygen species production, and maximal activities of matrix dehydrogenases and electron transport system (ETS) protein complexes. Additionally, tandem-mass-tag-assisted proteomic analyses were performed to uncover possible differences in mitochondrial protein abundance. CKD negatively impacted mitochondrial energy transduction (all p < 0.05) in SkM, CM, and renal mitochondria, when assessed at physiologically relevant cellular energy demands (ΔGATP) and revealed the tissue-specific impact of CKD on mitochondrial health. Proteomic analyses indicated significant abundance changes in CM and renal mitochondria (115 and 164 proteins, p < 0.05), but no differences in SkM. Taken together, these findings reveal the tissue-specific impact of chronic renal insufficiency on mitochondrial health.

Keywords:  CKD; bioenergetics; cardiac; kidney; mitochondria; muscle; proteomics

DOI:  https://doi.org/10.3390/cells10123282
Life (Basel). 2021 Nov 27. pii: 1307. [Epub ahead of print]11(12):

Coupling/Uncoupling Reversibility in Isolated Mitochondria from Saccharomyces cerevisiae.

Lilia Morales-García, Carolina Ricardez-García, Paulina Castañeda-Tamez, Natalia Chiquete-Félix, Salvador Uribe-Carvajal.

  The yeast Saccharomyces cerevisiae uses fermentation as the preferred pathway to obtain ATP and requires the respiratory chain to re-oxidize the NADH needed for activity of Glyceraldehyde-3-phosphate. This process is favored by uncoupling of oxidative phosphorylation (OxPhos), which is at least partially controlled by the mitochondrial unspecific pore (ScMUC). When mitochondrial ATP synthesis is needed as in the diauxic phase or during mating, a large rise in Ca2+ concentration ([Ca2+]) closes ScMUC, coupling OxPhos. In addition, ScMUC opening/closing is mediated by the ATP/ADP ratio, which indicates cellular energy needs. Here, opening and closing of ScMUC was evaluated in isolated mitochondria from S. cerevisiae at different incubation times and in the presence of different ATP/ADP ratios or varying [Ca2+]. Measurements of the rate of O2 consumption, mitochondrial swelling, transmembrane potential and ROS generation were conducted. It was observed that ScMUC opening was reversible, a high ATP/ADP ratio promoted opening and [Ca2+] closed ScMUC even after several minutes of incubation in the open state. In the absence of ATP synthesis, closure of ScMUC resulted in an increase in ROS.

Keywords:  Ca2+; ScMUC; mitochondrial permeability transition reversibility; physiological uncoupling; yeast mitochondria

DOI:  https://doi.org/10.3390/life11121307
Antioxidants (Basel). 2021 Dec 06. pii: 1954. [Epub ahead of print]10(12):

Mito-TIPTP Increases Mitochondrial Function by Repressing the Rubicon-p22phox Interaction in Colitis-Induced Mice.

Jae-Sung Kim, Ye-Ram Kim, Sein Jang, Sang Geon Wang, Euni Cho, Seok-Jun Mun, Hye-In Jeon, Hyo-Keun Kim, Sun-Joon Min, Chul-Su Yang.

  The run/cysteine-rich-domain-containing Beclin1-interacting autophagy protein (Rubicon) is essential for the regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by interacting with p22phox to trigger the production of reactive oxygen species (ROS) in immune cells. In a previous study, we demonstrated that the interaction of Rubicon with p22phox increases cellular ROS levels. The correlation between Rubicon and mitochondrial ROS (mtROS) is poorly understood. Here, we report that Rubicon interacts with p22phox in the outer mitochondrial membrane in macrophages and patients with human ulcerative colitis. Upon lipopolysaccharide (LPS) activation, the binding of Rubicon to p22phox was elevated, and increased not only cellular ROS levels but also mtROS, with an impairment of mitochondrial complex III and mitochondrial biogenesis in macrophages. Furthermore, increased Rubicon decreases mitochondrial metabolic flux in macrophages. Mito-TIPTP, which is a p22phox inhibitor containing a mitochondrial translocation signal, enhances mitochondrial function by inhibiting the association between Rubicon and p22phox in LPS-primed bone-marrow-derived macrophages (BMDMs) treated with adenosine triphosphate (ATP) or dextran sulfate sodium (DSS). Remarkably, Mito-TIPTP exhibited a therapeutic effect by decreasing mtROS in DSS-induced acute or chronic colitis mouse models. Thus, our findings suggest that Mito-TIPTP is a potential therapeutic agent for colitis by inhibiting the interaction between Rubicon and p22phox to recover mitochondrial function.

Keywords:  Rubicon; colitis; mitochondria; p22phox; reactive oxygen species

DOI:  https://doi.org/10.3390/antiox10121954
Front Pharmacol. 2021 ;12 670167

Antiproliferative, Antiangiogenic, and Antimetastatic Therapy Response by Mangiferin in a Syngeneic Immunocompetent Colorectal Cancer Mouse Model Involves Changes in Mitochondrial Energy Metabolism.

Julio César Rodriguez-Gonzalez, Ivones Hernández-Balmaseda, Ken Declerck, Claudina Pérez-Novo, Emilie Logie, Claudia Theys, Patrycja Jakubek, Olga Luisa Quiñones-Maza, Geovanni Dantas-Cassali, Diego Carlos Dos Reis, Guy Van Camp, Miriam Teresa Lopes Paz, Idania Rodeiro-Guerra, René Delgado-Hernández, Wim Vanden Berghe.

  In spite of the current advances and achievements in cancer treatments, colorectal cancer (CRC) persists as one of the most prevalent and deadly tumor types in both men and women worldwide. Drug resistance, adverse side effects and high rate of angiogenesis, metastasis and tumor relapse remain one of the greatest challenges in long-term management of CRC and urges need for new leads of anticancer drugs. We demonstrate that CRC treatment with the phytopharmaceutical mangiferin (MGF), a glucosylxanthone present in Mango tree stem bark and leaves (Mangifera Indica L.), induces dose-dependent tumor regression and decreases lung metastasis in a syngeneic immunocompetent allograft mouse model of murine CT26 colon carcinoma, which increases overall survival of mice. Antimetastatic and antiangiogenic MGF effects could be further validated in a wound healing in vitro model in human HT29 cells and in a matrigel plug implant mouse model. Interestingly, transcriptome pathway enrichment analysis demonstrates that MGF inhibits tumor growth, metastasis and angiogenesis by multi-targeting of mitochondrial oxidoreductase and fatty acid β-oxidation metabolism, PPAR, SIRT, NFκB, Stat3, HIF, Wnt and GP6 signaling pathways. MGF effects on fatty acid β-oxidation metabolism and carnitine palmitoyltransferase 1 (CPT1) protein expression could be further confirmed in vitro in human HT29 colon cells. In conclusion, antitumor, antiangiogenic and antimetastatic effects of MGF treatment hold promise to reduce adverse toxicity and to mitigate therapeutic outcome of colorectal cancer treatment by targeting mitochondrial energy metabolism in the tumor microenvironment.

Keywords:  Mangiferin (PubChem CID: 5081647); antiangiogenesis; antimetastasic; antitumor; colon carcinoma; mitochondrial metabolism

DOI:  https://doi.org/10.3389/fphar.2021.670167
Toxicol In Vitro. 2021 Dec 16. pii: S0887-2333(21)00226-5. [Epub ahead of print] 105301

The effects of Acyclovir administration to NCI-H1975 non-small cell lung cancer cells.

Serena Benedetti, Simona Catalani, Barbara Canonico, Maria Gemma Nasoni, Francesca Luchetti, Stefano Papa, Lucia Potenza, Francesco Palma.

  The biochemical mechanisms by which the antiviral drug Acyclovir (ACV) may induce anticancer effects even without detecting human herpesviruses (HHVs) are still poorly understood. Herein, we investigated for the first time how NCI-H1975 non-small cell lung cancer cells responded in vitro to ACV administration by exploring mitochondrial damage and apoptosis induction. We confirmed ACV ability to cause the inhibition of cancer cell growth even without detecting intracellular HHVs; the drug also significantly inhibited the colony formation capacity of NCI-H1975 cells. Cell cycle analysis revealed an increase of the sub-G1 hypodiploid peak after ACV treatment; the activation of caspase-3 and the presence of DNA laddering sustained the capacity of the drug to induce apoptotic cell death. Regarding mitochondrial toxicity, a reduction of mitochondrial membrane potential, altered mitochondrial size and shape, and mtDNA damage were found after ACV administration. Furthermore, an increment of intracellular reactive oxygen species levels as well as the upregulation of NudT3 involved in DNA repair mechanisms were observed. Altogether, these findings suggest that mitochondria may be possible initial targets and/or sites of ACV cytotoxicity within cancer cells in the absence of intracellular HHVs.

Keywords:  Acyclovir; Apoptosis induction; Mitochondrial toxicity; Non-small cell lung cancer cells

DOI:  https://doi.org/10.1016/j.tiv.2021.105301
Cell Death Discov. 2021 Dec 20. 7(1): 395

Mitochondrial glutamine metabolism regulates sensitivity of cancer cells after chemotherapy via amphiregulin.

Sunsook Hwang, Seungyeon Yang, Minjoong Kim, Youlim Hong, Byungjoo Kim, Eun Kyung Lee, Seung Min Jeong.

The DNA damage response is essential for sustaining genomic stability and preventing tumorigenesis. However, the fundamental question about the cellular metabolic response to DNA damage remains largely unknown, impeding the development of metabolic interventions that might prevent or treat cancer. Recently, it has been reported that there is a link between cell metabolism and DNA damage response, by repression of glutamine (Gln) entry into mitochondria to support cell cycle arrest and DNA repair. Here, we show that mitochondrial Gln metabolism is a crucial regulator of DNA damage-induced cell death. Mechanistically, inhibition of glutaminase (GLS), the first enzyme for Gln anaplerosis, sensitizes cancer cells to DNA damage by inducing amphiregulin (AREG) that promotes apoptotic cell death. GLS inhibition increases reactive oxygen species production, leading to transcriptional activation of AREG through Max-like protein X (MLX) transcription factor. Moreover, suppression of mitochondrial Gln metabolism results in markedly increased cell death after chemotherapy in vitro and in vivo. The essentiality of this molecular pathway in DNA damage-induced cell death may provide novel metabolic interventions for cancer therapy.

DOI: https://doi.org/10.1038/s41420-021-00792-7
J Leukoc Biol. 2021 Dec 20.

Bone marrow microenvironment drives AML cell OXPHOS addiction and AMPK inhibition to resist chemotherapy.

Ruolan You, Diyu Hou, Bin Wang, Jingru Liu, Xiaoting Wang, Qirong Xiao, Zhipeng Pan, Dongliang Li, Xiaoming Feng, Lixia Kang, Ping Chen, Huifang Huang.

  The stromal niche plays a pivotal role in AML chemoresistance and energy metabolism reprogramming is a hallmark of a tumor. 5'-Adenosine monophosphate-activated protein kinase (AMPK) is an important energy sensor suppressing mammalian target of rapamycin complex 1 (mTORC1) activity. However, the role of AMPK-mTORC1 pathway on connecting AML cell energy metabolism reprogramming and chemoresistance induced by the bone marrow microenvironment (BMM) is not defined. Here, with a co-culture system that simulates the interaction between BMM and AML cells, it is shown that stromal contact led to a decreased sensitivity to chemotherapy accompanied by an increase of oxidative phosphorylation (OXPHOS) activity and mitochondrial ATP synthesis in AML cells. The increased OXPHOS activity and excessive ATP production promoted chemoresistance of AML cells through inhibiting AMPK activity and in turn activating mTORC1 activity. In an in vivo AML mouse model, depletion of AMPK activity with genetic targeting promoted AML progression and reduced their sensitivity to chemotherapeutic drugs. Collectively, AML cells' acquired increased OXPHOS activity as well as AMPK inhibition could be therapeutically exploited in an effort to overcome BMM-mediated chemoresistance.

Keywords:  AMPK-mTORC1 pathway; ATP; OXPHOS; acute myeloid leukemia; chemotherapy resistance

DOI:  https://doi.org/10.1002/JLB.6A0821-409RR
Nature. 2021 Dec 22.

Valine tRNA levels and availability regulate complex I assembly in leukaemia.

Palaniraja Thandapani, Andreas Kloetgen, Matthew T Witkowski, Christina Glytsou, Anna K Lee, Eric Wang, Jingjing Wang, Sarah E LeBoeuf, Kleopatra Avrampou, Thales Papagiannakopoulos, Aristotelis Tsirigos, Iannis Aifantis.

Although deregulation of transfer RNA (tRNA) biogenesis promotes the translation of pro-tumorigenic mRNAs in cancers1,2, the mechanisms and consequences of tRNA deregulation in tumorigenesis are poorly understood. Here we use a CRISPR-Cas9 screen to focus on genes that have been implicated in tRNA biogenesis, and identify a mechanism by which altered valine tRNA biogenesis enhances mitochondrial bioenergetics in T cell acute lymphoblastic leukaemia (T-ALL). Expression of valine aminoacyl tRNA synthetase is transcriptionally upregulated by NOTCH1, a key oncogene in T-ALL, underlining a role for oncogenic transcriptional programs in coordinating tRNA supply and demand. Limiting valine bioavailability through restriction of dietary valine intake disrupted this balance in mice, resulting in decreased leukaemic burden and increased survival in vivo. Mechanistically, valine restriction reduced translation rates of mRNAs that encode subunits of mitochondrial complex I, leading to defective assembly of complex I and impaired oxidative phosphorylation. Finally, a genome-wide CRISPR-Cas9 loss-of-function screen in differential valine conditions identified several genes, including SLC7A5 and BCL2, whose genetic ablation or pharmacological inhibition synergized with valine restriction to reduce T-ALL growth. Our findings identify tRNA deregulation as a critical adaptation in the pathogenesis of T-ALL and provide a molecular basis for the use of dietary approaches to target tRNA biogenesis in blood malignancies.

DOI: https://doi.org/10.1038/s41586-021-04244-1
Cancer Metastasis Rev. 2021 Dec 21.

Extracellular citrate and metabolic adaptations of cancer cells.

E Kenneth Parkinson, Jerzy Adamski, Grit Zahn, Andreas Gaumann, Fabian Flores-Borja, Christine Ziegler, Maria E Mycielska.

  It is well established that cancer cells acquire energy via the Warburg effect and oxidative phosphorylation. Citrate is considered to play a crucial role in cancer metabolism by virtue of its production in the reverse Krebs cycle from glutamine. Here, we review the evidence that extracellular citrate is one of the key metabolites of the metabolic pathways present in cancer cells. We review the different mechanisms by which pathways involved in keeping redox balance respond to the need of intracellular citrate synthesis under different extracellular metabolic conditions. In this context, we further discuss the hypothesis that extracellular citrate plays a role in switching between oxidative phosphorylation and the Warburg effect while citrate uptake enhances metastatic activities and therapy resistance. We also present the possibility that organs rich in citrate such as the liver, brain and bones might form a perfect niche for the secondary tumour growth and improve survival of colonising cancer cells. Consistently, metabolic support provided by cancer-associated and senescent cells is also discussed. Finally, we highlight evidence on the role of citrate on immune cells and its potential to modulate the biological functions of pro- and anti-tumour immune cells in the tumour microenvironment. Collectively, we review intriguing evidence supporting the potential role of extracellular citrate in the regulation of the overall cancer metabolism and metastatic activity.

Keywords:  Cancer-associated cells; Citrate; OXPHOS; Redox; Senescence; Warburg effect

DOI:  https://doi.org/10.1007/s10555-021-10007-1
Vavilovskii Zhurnal Genet Selektsii. 2021 Nov;25(7): 778-786

VJ21.089The subcompartmented oxphosomic model of the phosphorylating system organization in mitochondria.

I V Ukolova.

  The oxidative phosphorylation (OXPHOS) system of mitochondria supports all the vitally important energy-consuming processes in eukaryotic cells, providing them with energy in the form of ATP. OXPHOS enzymes (complexes I-V) are located in the inner mitochondrial membrane, mainly in the cristae subcompartment. At present, there is a large body of data evidencing that the respiratory complexes I, III2 and IV under in vivo conditions can physically interact with each other in diverse stoichiometry, thereby forming supercomplexes. Despite active accumulation of knowledge about the structure of the main supercomplexes of the OXPHOS system, its physical and functional organization in vivo remains unclear. Contemporary models of the OXPHOS system's organization in the inner membrane of mitochondria are contradictory and presume the existence of either highly organized respiratory strings, or, by contrast, a set of randomly dispersed respiratory supercomplexes and complexes. Furthermore, it is assumed that ATP-synthase (complex V) does not form associations with respiratory enzymes and operates autonomously. Our latest data obtained on mitochondria of etiolated shoots of pea evidence the possibility of physical association between the respiratory supercomplexes and dimeric ATP-synthase. These data have allowed us to reconsider the contemporary concept of the phosphorylation system organization and propose a new subcompartmented oxphosomic model. According to this model, a substantial number of the OXPHOS complexes form oxphosomes, which in a def inite stoichiometry include complexes I-V and are located predominantly in the cristae subcompartment of mitochondria in the form of highly organized strings or patches. These suprastructures represent "mini-factories" for ATP production. It is assumed that such an organization (1) contributes to increasing the eff iciency of the OXPHOS system operation, (2) involves new levels of activity regulation, and (3) may determine the inner membrane morphology to some extent. The review discusses the proposed model in detail. For a better understanding of the matter, the history of development of concepts concerning the OXPHOS organization with the emphasis on recent contemporary models is brief ly considered. The principal experimental data accumulated over the past 40 years, which conf irm the validity of the oxphosomic hypothesis, are also provided.

Keywords:  mitochondria; models of the OXPHOS organization; oxphosome; supercomplexes; system of oxidative phosphorylation

DOI:  https://doi.org/10.18699/VJ21.089
iScience. 2021 Dec 17. 24(12): 103497

Mitochondrial complex I inhibitors suppress tumor growth through concomitant acidification of the intra- and extracellular environment.

Junjiro Yoshida, Tomokazu Ohishi, Hikaru Abe, Shun-Ichi Ohba, Hiroyuki Inoue, Ihomi Usami, Masahide Amemiya, Raphael Oriez, Chiharu Sakashita, Shingo Dan, Minoru Sugawara, Tokuichi Kawaguchi, Junko Ueno, Yuko Asano, Ami Ikeda, Manabu Takamatsu, Gulanbar Amori, Yasumitsu Kondoh, Kaori Honda, Hiroyuki Osada, Tetsuo Noda, Takumi Watanabe, Takao Shimizu, Masakatsu Shibasaki, Manabu Kawada.

  The disruption of the tumor microenvironment (TME) is a promising anti-cancer strategy, but its effective targeting for solid tumors remains unknown. Here, we investigated the anti-cancer activity of the mitochondrial complex I inhibitor intervenolin (ITV), which modulates the TME independent of energy depletion. By modulating lactate metabolism, ITV induced the concomitant acidification of the intra- and extracellular environment, which synergistically suppressed S6K1 activity in cancer cells through protein phosphatase-2A-mediated dephosphorylation via G-protein-coupled receptor(s). Other complex I inhibitors including metformin and rotenone were also found to exert the same effect through an energy depletion-independent manner as ITV. In mouse and patient-derived xenograft models, ITV was found to suppress tumor growth and its mode of action was further confirmed. The TME is usually acidic owing to glycolytic cancer cell metabolism, and this condition is more susceptible to complex I inhibitors. Thus, we have demonstrated a potential treatment strategy for solid tumors.

Keywords:  Cancer; Cell biology; Microenvironment

DOI:  https://doi.org/10.1016/j.isci.2021.103497
Antioxidants (Basel). 2021 Dec 14. pii: 1988. [Epub ahead of print]10(12):

Catalase Overexpression Drives an Aggressive Phenotype in Glioblastoma.

Susanne Flor, Claudia R Oliva, Md Yousuf Ali, Kristen L Coleman, Jeremy D Greenlee, Karra A Jones, Varun Monga, Corinne E Griguer.

  Glioblastoma remains the deadliest form of brain cancer, largely because these tumors become resistant to standard of care treatment with radiation and chemotherapy. Intracellular production of reactive oxygen species (ROS) is necessary for chemo- and radiotherapy-induced cytotoxicity. Here, we assessed whether antioxidant catalase (CAT) affects glioma cell sensitivity to temozolomide and radiation. Using The Cancer Genome Atlas database, we found that CAT mRNA expression is upregulated in glioma tumor tissue compared with non-tumor tissue, and the level of expression negatively correlates with the overall survival of patients with high-grade glioma. In U251 glioma cells, CAT overexpression substantially decreased the basal level of hydrogen peroxide, enhanced anchorage-independent cell growth, and facilitated resistance to the chemotherapeutic drug temozolomide and ionizing radiation. Importantly, pharmacological inhibition of CAT activity reduced the proliferation of glioma cells isolated from patient biopsy samples. Moreover, U251 cells overexpressing CAT formed neurospheres in neurobasal medium, whereas control cells did not, suggesting that the radio- and chemoresistance conferred by CAT may be due in part to the enrichment of glioma stem cell populations. Finally, CAT overexpression significantly decreased survival in an orthotopic mouse model of glioma. These results demonstrate that CAT regulates chemo- and radioresistance in human glioma.

Keywords:  catalase; glioblastoma multiforme; hydrogen peroxide; radiation; reactive oxygen species (ROS); temozolomide

DOI:  https://doi.org/10.3390/antiox10121988
Cancer Sci. 2021 Dec 21.

Enforced DYRK2 expression by adenovirus-mediated gene transfer inhibits tumor growth and metastasis of colorectal cancer.

Yuta Imaizumi, Saishu Yoshida, Yumi Kanegae, Ken Eto, Kiyotsugu Yoshida.

  Colorectal cancer is one of the most common gastrointestinal tumors with good outcomes, but when it has distant metastasis, the outcomes turn to be poor. Novel treatment methods are eager to develop. Our in vitro studies demonstrate that dual-specificity tyrosine-regulated kinase 2 (DYRK2) functions as a tumor suppressor in colorectal cancer by regulating cell survival, proliferation, and apoptosis induction. In addition, DYRK2 expression is decreased in tumor tissues compared to non-tumor tissues in colorectal cancer, indicating a correlation with clinical prognosis. In this context, we devise a novel therapeutic strategy to overexpress DYRK2 in tumors by the adenovirus-mediated gene transfer. The present study shows that overexpression of DYRK2 in colon cancer cell lines by adenovirus inhibits cell proliferation and induces apoptosis in vitro. Furthermore, in mouse subcutaneous xenograft and liver metastasis models, enforced expression of DYRK2 by direct injection or intravenous administration of adenovirus to the tumor significantly inhibits tumor growth. Taken together, these findings demonstrate that adenovirus-based overexpression of DYRK2 may be a novel gene therapy for liver metastasis of colorectal cancer.

Keywords:  DYRK2; adenovirus; colorectal cancer; gene therapy; liver metastasis

DOI:  https://doi.org/10.1111/cas.15247
Cancer Sci. 2021 Dec 22.

FDFT1 predicts poor prognosis in stage I-III colon adenocarcinoma and synergizes SQLE to promote tumor progression.

Huihong Jiang, Erjiang Tang, Ying Chen, Hailong Liu, Yun Zhao, Moubin Lin, Luwei He.

  Colon adenocarcinoma (COAD) is one of the most prevalent malignancies, with poor prognosis and lack of effective treatment targets. Squalene synthase (FDFT1) is an upstream enzyme of squalene epoxidase (SQLE) in cholesterol biosynthesis. In previous study, we have revealed SQLE promotes colon cancer cell proliferation in vitro and in vivo. Here, we investigate the prognostic value of FDFT1 in stage I-III COAD and explore the potential underlying mechanisms. FDFT1 was significantly upregulated in stage I-III COAD and positively correlated with poor differentiation and advanced tumor stage. High expression of FDFT1 was an independent predictor of overall and relapse-free survival, and the nomograms based on FDFT1 could effectively identify patients at high risk of poor outcome. FDFT1 accelerated colon cancer cell proliferation and promoted tumor growth. Lack of FDFT1 resulted in accumulating NAT8 and D-Pantethine to lower ROS level and inhibit colon cancer cell proliferation. Moreover, the combinational inhibition of FDFT1 and SQLE induced the greater suppressive effect on cell proliferation and tumor growth than single inhibition. Taken together, these results indicate that FDFT1 predicts poor prognosis in stage I-III COAD and has the tumor promoting effect on COAD through regulating NAT8 and D-Pantethine. Targeting both FDFT1 and SQLE is a more promising therapy than their single inhibition for stage I-III COAD.

Keywords:  Squalene synthase; colon adenocarcinoma; prognostic marker; squalene epoxidase; tumor progression

DOI:  https://doi.org/10.1111/cas.15248
Cell. 2021 Dec 22. pii: S0092-8674(21)01386-6. [Epub ahead of print]184(26): 6226-6228

Dinner is served, sir: Fighting cancer with the right diet.

Andrés Méndez-Lucas, Mariia Yuneva.

Altered metabolism of tumors offers an opportunity to use metabolic interventions as a therapeutic strategy. Lien et al. demonstrate that understanding how specific diets with different carbohydrate and fat composition affect tumor metabolism is essential in order to use this opportunity efficiently.

DOI: https://doi.org/10.1016/j.cell.2021.11.036
Nat Immunol. 2021 Dec 23.

The kinase complex mTORC2 promotes the longevity of virus-specific memory CD4+ T cells by preventing ferroptosis.

Yifei Wang, Qin Tian, Yaxing Hao, Wei Yao, Jinjin Lu, Cheng Chen, Xiangyu Chen, Yao Lin, Qizhao Huang, Lifan Xu, Jianjun Hu, Shun Lei, Zhengping Wei, Yuan Luo, Zhirong Li, Li Hu, Jianfang Tang, Qing Wu, Xinyuan Zhou, Yuzhang Wu, Zhinan Yin, Jianqing Xu, Lilin Ye.

Antigen-specific memory CD4+ T cells can persist and confer rapid and efficient protection from microbial reinfection. However, the mechanisms underlying the long-term maintenance of the memory CD4+ T cell pool remain largely unknown. Here, using a mouse model of acute infection with lymphocytic choriomeningitis virus (LCMV), we found that the serine/threonine kinase complex mammalian target of rapamycin complex 2 (mTORC2) is critical for the long-term persistence of virus-specific memory CD4+ T cells. The perturbation of mTORC2 signaling at memory phase led to an enormous loss of virus-specific memory CD4+ T cells by a unique form of regulated cell death (RCD), ferroptosis. Mechanistically, mTORC2 inactivation resulted in the impaired phosphorylation of downstream AKT and GSK3β kinases, which induced aberrant mitochondrial reactive oxygen species (ROS) accumulation and ensuing ferroptosis-causative lipid peroxidation in virus-specific memory CD4+ T cells; furthermore, the disruption of this signaling cascade also inhibited glutathione peroxidase 4 (GPX4), a major scavenger of lipid peroxidation. Thus, the mTORC2-AKT-GSK3β axis functions as a key signaling hub to promote the longevity of virus-specific memory CD4+ T cells by preventing ferroptosis.

DOI: https://doi.org/10.1038/s41590-021-01090-1
Biomedicines. 2021 Dec 08. pii: 1859. [Epub ahead of print]9(12):

Mitochondrial Respiration of Platelets: Comparison of Isolation Methods.

Andrea Vernerova, Luiz Felipe Garcia-Souza, Ondrej Soucek, Milan Kostal, Vit Rehacek, Lenka Kujovska Krcmova, Erich Gnaiger, Ondrej Sobotka.

  Multiple non-aggregatory functions of human platelets (PLT) are widely acknowledged, yet their functional examination is limited mainly due to a lack of standardized isolation and analytic methods. Platelet apheresis (PA) is an established clinical method for PLT isolation aiming at the treatment of bleeding diathesis in severe thrombocytopenia. On the other hand, density gradient centrifugation (DC) is an isolation method applied in research for the analysis of the mitochondrial metabolic profile of oxidative phosphorylation (OXPHOS) in PLT obtained from small samples of human blood. We studied PLT obtained from 29 healthy donors by high-resolution respirometry for comparison of PA and DC isolates. ROUTINE respiration and electron transfer capacity of living PLT isolated by PA were significantly higher than in the DC group, whereas plasma membrane permeabilization resulted in a 57% decrease of succinate oxidation in PA compared to DC. These differences were eliminated after washing the PA platelets with phosphate buffer containing 10 mmol·L-1 ethylene glycol-bis (2-aminoethyl ether)-N,N,N',N'-tetra-acetic acid, suggesting that several components, particularly Ca2+ and fuel substrates, were carried over into the respiratory assay from the serum in PA. A simple washing step was sufficient to enable functional mitochondrial analysis in subsamples obtained from PA. The combination of the standard clinical PA isolation procedure with PLT quality control and routine mitochondrial OXPHOS diagnostics meets an acute clinical demand in biomedical research of patients suffering from thrombocytopenia and metabolic diseases.

Keywords:  density gradient centrifugation; flow cytometry; high-resolution respirometry; human platelets; mitochondria; oxidative phosphorylation; platelet apheresis; thrombocytes

DOI:  https://doi.org/10.3390/biomedicines9121859
Biophys J. 2021 Dec 21. pii: S0006-3495(21)03946-1. [Epub ahead of print]

On the Design Principles of Metabolic Flux Sensing.

Christian Euler, Radhakrishnan Mahadevan.

  Metabolism is precisely coordinated, with the goal of balancing fluxes to maintain robust growth. However, coordinating fluxes requires information about rates, which can only be inferred through concentrations. While flux sensitive metabolites have been reported, the design principles underlying such sensing have not been clearly elucidated. Here we use kinetic modelling to show that substrate concentrations of thermodynamically constrained reactions reflect upstream flux and therefore carry information about rates. Then we use untargeted multi-omic data from E. coli and S. cerevisiae to show that the concentrations of some metabolites in central carbon metabolism reflect fluxes as a result of thermodynamic constraints. We then establish, using 37 real concentration-flux relationships across both organisms, that in vivo ΔG∘≥-4 kJ/mol is the threshold above which substrates are likely to be sensitive to upstream flux(es).

Keywords:  design principles; metabolic regulation; metabolism; multi-omics; thermodynamics

DOI:  https://doi.org/10.1016/j.bpj.2021.12.022
J Transl Med. 2021 Dec 20. 19(1): 521

SIRT5 functions as a tumor suppressor in renal cell carcinoma by reversing the Warburg effect.

Liu Yihan, Wang Xiaojing, Liu Ao, Zhang Chuanjie, Wang Haofei, Shen Yan, He Hongchao.

  BACKGROUND: The aim of this study was to investigate the biological functions and underlying mechanisms of SIRT5 in clear cell renal cell carcinoma (ccRCC).METHODS: SIRT5 expression data in The Cancer Genome Atlas Kidney Clear Cell Carcinoma (TCGA-KIRC) were selected, and the correlations between SIRT5 expression and various clinicopathological parameters were analysed. SIRT5 expression in ccRCC tissues was examined using immunohistochemistry. Stable cell lines with SIRT5 knockdown were established. In vitro and in vivo experiments were conducted to investigate the functional roles of SIRT5 in the cellular biology of ccRCC, including cell viability assays, wound healing assays, soft agar colony formation assays, Transwell invasion assays, qRT-PCR, and Western blotting. In addition, microarrays, rescue experiments and Western blotting were used to investigate the molecular mechanisms underlying SIRT5 functions.
RESULTS: SIRT5 expression was downregulated in ccRCC compared with normal tissues, which correlated with a poor prognosis of ccRCC. SIRT5 knockdown significantly increased cell proliferation, migration and invasion in vitro. In vivo experiments revealed that SIRT5 knockdown promoted ccRCC tumorigenesis and metastasis. Mechanistically, SIRT5 deglycosylated PDHA1 at K351 and increased PDC activity, thereby altering the metabolic crosstalk with the TCA cycle and inhibiting the Warburg effect. SIRT5 overexpression was related to low succinylation of PDHA1.
CONCLUSIONS: Downregulated SIRT5 expression in ccRCC accelerated the Warburg effect through PDHA1 hypersuccinylation and induced tumorigenesis and progression, indicating that SIRT5 may become a potential target for ccRCC therapy.

Keywords:  Desuccinylation; PDHA1; Renal cell carcinoma; SIRT5; Warburg effect

DOI:  https://doi.org/10.1186/s12967-021-03178-6
Aging Cell. 2021 Dec 21. e13527

Late-life exercise mitigates skeletal muscle epigenetic aging.

Kevin A Murach, Andrea L Dimet-Wiley, Yuan Wen, Camille R Brightwell, Christine M Latham, Cory M Dungan, Christopher S Fry, Stanley J Watowich.

  There are functional benefits to exercise in muscle, even when performed late in life, but the contributions of epigenetic factors to late-life exercise adaptation are poorly defined. Using reduced representation bisulfite sequencing (RRBS), ribosomal DNA (rDNA) and mitochondrial-specific examination of methylation, targeted high-resolution methylation analysis, and DNAge™ epigenetic aging clock analysis with a translatable model of voluntary murine endurance/resistance exercise training (progressive weighted wheel running, PoWeR), we provide evidence that exercise may mitigate epigenetic aging in skeletal muscle. Late-life PoWeR from 22-24 months of age modestly but significantly attenuates an age-associated shift toward promoter hypermethylation. The epigenetic age of muscle from old mice that PoWeR-trained for eight weeks was approximately eight weeks younger than 24-month-old sedentary counterparts, which represents ~8% of the expected murine lifespan. These data provide a molecular basis for exercise as a therapy to attenuate skeletal muscle aging.

Keywords:   Rbm10 ; Timm8a1 ; Horvath clock; PoWeR; rDNA

DOI:  https://doi.org/10.1111/acel.13527