bims-mibica 2022-12-25 papers

bims-mibica

Biomed News

on Mitochondrial bioenergetics in cancer

Issue of 2022–12–25
23 papers selected by
Kelsey Fisher-Wellman, East Carolina University

The structure of the human LACTB filament reveals the mechanisms of assembly and membrane binding.
Moms' mitochondria may refresh cells in sick kids.
Mitochondrial-targeted nanoparticles: delivery and therapeutic agents in cancer.
Contribution of the Collective Excitations to the Coupled Proton and Energy Transport along Mitochondrial Cristae Membrane in Oxidative Phosphorylation System.
Pharmacological targeting of the mitochondrial calcium-dependent potassium channel KCa3.1 triggers cell death and reduces tumor growth and metastasis in vivo.
Dynamic partitioning of branched-chain amino acids-derived nitrogen supports renal cancer progression.
Revisiting the Warburg Effect with Focus on Lactate.
Ubiquitination Occurs in the Mitochondrial Matrix by Eclipsed Targeted Components of the Ubiquitination Machinery.
Microenvironmental ammonia enhances T cell exhaustion in colorectal cancer.
Metabolic Rewiring toward Oxidative Phosphorylation Disrupts Intrinsic Resistance to Ferroptosis of the Colon Adenocarcinoma Cells.
Usnic Acid-Mediated Exchange of Protons for Divalent Metal Cations across Lipid Membranes: Relevance to Mitochondrial Uncoupling.
Metabolomic and Mitochondrial Fingerprinting of the Epithelial-to-Mesenchymal Transition (EMT) in Non-Tumorigenic and Tumorigenic Human Breast Cells.
mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.
Metabolic enzyme LDHA activates Rac1 GTPase as a noncanonical mechanism to promote cancer.
Mitochondrial Non-Coding RNAs Are Potential Mediators of Mitochondrial Homeostasis.
Evaluation of the gene encoding carnitine transporter (OCTN2/SLC22A5) expression in human breast cancer and its association with clinicopathological characteristics.
Multi-color live-cell STED nanoscopy of mitochondria with a gentle inner membrane stain.
Preferred Migration of Mitochondria toward Cells and Tissues with Mitochondrial Damage.
Membrane Lipid Reshaping Underlies Oxidative Stress Sensing by the Mitochondrial Proteins UCP1 and ANT1.
Deciphering a mitochondria-related signature to supervise prognosis and immunotherapy in hepatocellular carcinoma.
Multi-SUMOylation of NAC1 is essential for the growth of prostate cancer cells.
Uncoupling protein 2 deficiency of non-cancerous tissues inhibits the progression of pancreatic cancer in mice.
BCL-xL inhibition potentiates cancer therapies by redirecting the outcome of p53 activation from senescence to apoptosis.

PLoS Biol. 2022 Dec 19. 20(12): e3001899

The structure of the human LACTB filament reveals the mechanisms of assembly and membrane binding.

Jeremy A Bennett, Lottie R Steward, Johannes Rudolph, Adam P Voss, Halil Aydin.

Mitochondria are complex organelles that play a central role in metabolism. Dynamic membrane-associated processes regulate mitochondrial morphology and bioenergetics in response to cellular demand. In tumor cells, metabolic reprogramming requires active mitochondrial metabolism for providing key metabolites and building blocks for tumor growth and rapid proliferation. To counter this, the mitochondrial serine beta-lactamase-like protein (LACTB) alters mitochondrial lipid metabolism and potently inhibits the proliferation of a variety of tumor cells. Mammalian LACTB is localized in the mitochondrial intermembrane space (IMS), where it assembles into filaments to regulate the efficiency of essential metabolic processes. However, the structural basis of LACTB polymerization and regulation remains incompletely understood. Here, we describe how human LACTB self-assembles into micron-scale filaments that increase their catalytic activity. The electron cryo-microscopy (cryoEM) structure defines the mechanism of assembly and reveals how highly ordered filament bundles stabilize the active state of the enzyme. We identify and characterize residues that are located at the filament-forming interface and further show that mutations that disrupt filamentation reduce enzyme activity. Furthermore, our results provide evidence that LACTB filaments can bind lipid membranes. These data reveal the detailed molecular organization and polymerization-based regulation of human LACTB and provide new insights into the mechanism of mitochondrial membrane organization that modulates lipid metabolism.

DOI: https://doi.org/10.1371/journal.pbio.3001899
Science. 2022 Dec 23. 378(6626): 1267

Moms' mitochondria may refresh cells in sick kids.

Mitch Leslie.

Technique is designed to treat mitochondrial disease.

DOI: https://doi.org/10.1126/science.adg3936
Drug Discov Today. 2022 Dec 15. pii: S1359-6446(22)00462-7. [Epub ahead of print] 103469

Mitochondrial-targeted nanoparticles: delivery and therapeutic agents in cancer.

Chaithaithanya Ganji, Veda Muppala, Musaab Khan, Ganji Purnachandra Nagaraju, Batoul Farran.

  Mitochondria are the powerhouses of cells and modulate the essential metabolic functions required for cellular survival. Various mitochondrial pathways, such as oxidative phosphorylation or production of reactive oxygen species (ROS) are dysregulated during cancer growth and development, rendering them attractive targets against cancer. Thus, the delivery of antitumor agents to mitochondria has emerged as a potential approach for treating cancer. Recent advances in nanotechnology have provided innovative solutions for overcoming the physical barriers posed by the structure of mitochondrial organelles, and have enabled the development of efficient mitochondrial nanoplatforms. In this review, we examine the importance of mitochondria during neoplastic development, explore the most recent smart designs of nano-based systems aimed at targeting mitochondria, and highlight key mitochondrial pathways in cancer cells. Teaser: Dysregulation of mitochondria is a hallmark of cancer development. Nanotechnology has allowed the development of mitochondria-targeted agents that enhance cancer cell death through the generation of reactive oxygen species and reduced mitochondrial membrane potential.

Keywords:  cancer; drug; mitochondria; nanoparticles; therapy

DOI:  https://doi.org/10.1016/j.drudis.2022.103469
Entropy (Basel). 2022 Dec 13. pii: 1813. [Epub ahead of print]24(12):

Contribution of the Collective Excitations to the Coupled Proton and Energy Transport along Mitochondrial Cristae Membrane in Oxidative Phosphorylation System.

Semen V Nesterov, Lev S Yaguzhinsky, Raif G Vasilov, Vasiliy N Kadantsev, Alexey N Goltsov.

  The results of many experimental and theoretical works indicate that after transport of protons across the mitochondrial inner membrane (MIM) in the oxidative phosphorylation (OXPHOS) system, they are retained on the membrane-water interface in nonequilibrium state with free energy excess due to low proton surface-to-bulk release. This well-established phenomenon suggests that proton trapping on the membrane interface ensures vectorial lateral transport of protons from proton pumps to ATP synthases (proton acceptors). Despite the key role of the proton transport in bioenergetics, the molecular mechanism of proton transfer in the OXPHOS system is not yet completely established. Here, we developed a dynamics model of long-range transport of energized protons along the MIM accompanied by collective excitation of localized waves propagating on the membrane surface. Our model is based on the new data on the macromolecular organization of the OXPHOS system showing the well-ordered structure of respirasomes and ATP synthases on the cristae membrane folds. We developed a two-component dynamics model of the proton transport considering two coupled subsystems: the ordered hydrogen bond (HB) chain of water molecules and lipid headgroups of MIM. We analytically obtained a two-component soliton solution in this model, which describes the motion of the proton kink, corresponding to successive proton hops in the HB chain, and coherent motion of a compression soliton in the chain of lipid headgroups. The local deformation in a soliton range facilitates proton jumps due to water molecules approaching each other in the HB chain. We suggested that the proton-conducting structures formed along the cristae membrane surface promote direct lateral proton transfer in the OXPHOS system. Collective excitations at the water-membrane interface in a form of two-component soliton ensure the coupled non-dissipative transport of charge carriers and elastic energy of MIM deformation to ATP synthases that may be utilized in ATP synthesis providing maximal efficiency in mitochondrial bioenergetics.

Keywords:  collective excitations; mitochondrial cristae membrane; oxidative phosphorylation system; proton conducting networks; proton transport; soliton dynamics

DOI:  https://doi.org/10.3390/e24121813
Cell Death Dis. 2022 Dec 20. 13(12): 1055

Pharmacological targeting of the mitochondrial calcium-dependent potassium channel KCa3.1 triggers cell death and reduces tumor growth and metastasis in vivo.

Magdalena Bachmann, Andrea Rossa, Tatiana Varanita, Bernard Fioretti, Lucia Biasutto, Stefan Milenkovic, Vanessa Checchetto, Roberta Peruzzo, Syed A Ahmad, Sameer H Patel, Robert Lukowski, Michael J Edwards, Matteo Ceccarelli, Erich Gulbins, Mario Zoratti, Andrea Mattarei, Ildiko Szabo.

Ion channels are non-conventional, druggable oncological targets. The intermediate-conductance calcium-dependent potassium channel (KCa3.1) is highly expressed in the plasma membrane and in the inner mitochondrial membrane (mitoKCa3.1) of various cancer cell lines. The role mitoKCa3.1 plays in cancer cells is still undefined. Here we report the synthesis and characterization of two mitochondria-targeted novel derivatives of a high-affinity KCa3.1 antagonist, TRAM-34, which retain the ability to block channel activity. The effects of these drugs were tested in melanoma, pancreatic ductal adenocarcinoma and breast cancer lines, as well as in vivo in two orthotopic models. We show that the mitochondria-targeted TRAM-34 derivatives induce release of mitochondrial reactive oxygen species, rapid depolarization of the mitochondrial membrane, fragmentation of the mitochondrial network. They trigger cancer cell death with an EC50 in the µM range, depending on channel expression. In contrast, inhibition of the plasma membrane KCa3.1 by membrane-impermeant Maurotoxin is without effect, indicating a specific role of mitoKCa3.1 in determining cell fate. At sub-lethal concentrations, pharmacological targeting of mitoKCa3.1 significantly reduced cancer cell migration by enhancing production of mitochondrial reactive oxygen species and nuclear factor-κB (NF-κB) activation, and by downregulating expression of Bcl-2 Nineteen kD-Interacting Protein (BNIP-3) and of Rho GTPase CDC-42. This signaling cascade finally leads to cytoskeletal reorganization and impaired migration. Overexpression of BNIP-3 or pharmacological modulation of NF-κB and CDC-42 prevented the migration-reducing effect of mitoTRAM-34. In orthotopic models of melanoma and pancreatic ductal adenocarcinoma, the tumors at sacrifice were 60% smaller in treated versus untreated animals. Metastasis of melanoma cells to lymph nodes was also drastically reduced. No signs of toxicity were observed. In summary, our results identify mitochondrial KCa3.1 as an unexpected player in cancer cell migration and show that its pharmacological targeting is efficient against both tumor growth and metastatic spread in vivo.

DOI: https://doi.org/10.1038/s41419-022-05463-8
Nat Commun. 2022 Dec 20. 13(1): 7830

Dynamic partitioning of branched-chain amino acids-derived nitrogen supports renal cancer progression.

Marco Sciacovelli, Aurelien Dugourd, Lorea Valcarcel Jimenez, Ming Yang, Efterpi Nikitopoulou, Ana S H Costa, Laura Tronci, Veronica Caraffini, Paulo Rodrigues, Christina Schmidt, Dylan Gerard Ryan, Timothy Young, Vincent R Zecchini, Sabrina H Rossi, Charlie Massie, Caroline Lohoff, Maria Masid, Vassily Hatzimanikatis, Christoph Kuppe, Alex Von Kriegsheim, Rafael Kramann, Vincent Gnanapragasam, Anne Y Warren, Grant D Stewart, Ayelet Erez, Sakari Vanharanta, Julio Saez-Rodriguez, Christian Frezza.

Metabolic reprogramming is critical for tumor initiation and progression. However, the exact impact of specific metabolic changes on cancer progression is poorly understood. Here, we integrate multimodal analyses of primary and metastatic clonally-related clear cell renal cancer cells (ccRCC) grown in physiological media to identify key stage-specific metabolic vulnerabilities. We show that a VHL loss-dependent reprogramming of branched-chain amino acid catabolism sustains the de novo biosynthesis of aspartate and arginine enabling tumor cells with the flexibility of partitioning the nitrogen of the amino acids depending on their needs. Importantly, we identify the epigenetic reactivation of argininosuccinate synthase (ASS1), a urea cycle enzyme suppressed in primary ccRCC, as a crucial event for metastatic renal cancer cells to acquire the capability to generate arginine, invade in vitro and metastasize in vivo. Overall, our study uncovers a mechanism of metabolic flexibility occurring during ccRCC progression, paving the way for the development of novel stage-specific therapies.

DOI: https://doi.org/10.1038/s41467-022-35036-4
Cancers (Basel). 2022 Dec 07. pii: 6028. [Epub ahead of print]14(24):

Revisiting the Warburg Effect with Focus on Lactate.

Eva Kocianova, Viktoria Piatrikova, Tereza Golias.

  Rewired metabolism is acknowledged as one of the drivers of tumor growth. As a result, aerobic glycolysis, or the Warburg effect, is a feature of many cancers. Increased glucose uptake and glycolysis provide intermediates for anabolic reactions necessary for cancer cell proliferation while contributing sufficient energy. However, the accompanying increased lactate production, seemingly wasting glucose carbon, was originally explained only by the need to regenerate NAD+ for successive rounds of glycolysis by the lactate dehydrogenase (LDH) reaction in the cytosol. After the discovery of a mitochondrial LDH isoform, lactate oxidation entered the picture, and lactate was recognized as an important oxidative fuel. It has also been revealed that lactate serves a variety of signaling functions and helps cells adapt to the new environment. Here, we discuss recent findings on lactate metabolism and signaling in cancer while attempting to explain why the Warburg effect is adopted by cancer cells.

Keywords:  Warburg effect; glucose metabolism; lactate; lactate dehydrogenase; lactate oxidation; lactate shuttle; lactate signaling; lactylation

DOI:  https://doi.org/10.3390/cancers14246028
Cells. 2022 Dec 17. pii: 4109. [Epub ahead of print]11(24):

Ubiquitination Occurs in the Mitochondrial Matrix by Eclipsed Targeted Components of the Ubiquitination Machinery.

Yu Zhang, Ofri Karmon, Koyeli Das, Reuven Wiener, Norbert Lehming, Ophry Pines.

  Ubiquitination is a critical type of post-translational modification in eukaryotic cells. It is involved in regulating nearly all cellular processes in the cytosol and nucleus. Mitochondria, known as the metabolism heart of the cell, are organelles that evolved from bacteria. Using the subcellular compartment-dependent α-complementation, we detect multiple components of ubiquitination machinery as being eclipsed distributed to yeast mitochondria. Ubiquitin conjugates and mono-ubiquitin can be detected in lysates of isolated mitochondria from cells expressing HA-Ub and treated with trypsin. By expressing MTS (mitochondrial targeting sequence) targeted HA-tagged ubiquitin, we demonstrate that certain ubiquitination events specifically occur in yeast mitochondria and are independent of proteasome activity. Importantly, we show that the E2 Rad6 affects the pattern of protein ubiquitination in mitochondria and provides an in vivo assay for its activity in the matrix of the organelle. This study shows that ubiquitination occurs in the mitochondrial matrix by eclipsed targeted components of the ubiquitin machinery, providing a new perspective on mitochondrial and ubiquitination research.

Keywords:  E2; Rad6; dual targeting; eclipsed distribution; mitochondrial matrix; ubiquitination

DOI:  https://doi.org/10.3390/cells11244109
Cell Metab. 2022 Dec 12. pii: S1550-4131(22)00504-6. [Epub ahead of print]

Microenvironmental ammonia enhances T cell exhaustion in colorectal cancer.

Hannah N Bell, Amanda K Huber, Rashi Singhal, Navyateja Korimerla, Ryan J Rebernick, Roshan Kumar, Marwa O El-Derany, Peter Sajjakulnukit, Nupur K Das, Samuel A Kerk, Sumeet Solanki, Jadyn G James, Donghwan Kim, Li Zhang, Brandon Chen, Rohit Mehra, Timothy L Frankel, Balázs Győrffy, Eric R Fearon, Marina Pasca di Magliano, Frank J Gonzalez, Ruma Banerjee, Daniel R Wahl, Costas A Lyssiotis, Michael Green, Yatrik M Shah.

  Effective therapies are lacking for patients with advanced colorectal cancer (CRC). The CRC tumor microenvironment has elevated metabolic waste products due to altered metabolism and proximity to the microbiota. The role of metabolite waste in tumor development, progression, and treatment resistance is unclear. We generated an autochthonous metastatic mouse model of CRC and used unbiased multi-omic analyses to reveal a robust accumulation of tumoral ammonia. The high ammonia levels induce T cell metabolic reprogramming, increase exhaustion, and decrease proliferation. CRC patients have increased serum ammonia, and the ammonia-related gene signature correlates with altered T cell response, adverse patient outcomes, and lack of response to immune checkpoint blockade. We demonstrate that enhancing ammonia clearance reactivates T cells, decreases tumor growth, and extends survival. Moreover, decreasing tumor-associated ammonia enhances anti-PD-L1 efficacy. These findings indicate that enhancing ammonia detoxification can reactivate T cells, highlighting a new approach to enhance the efficacy of immunotherapies.

Keywords:  ammonia; cancer metabolism; immunotherapy; tumor microenvironment

DOI:  https://doi.org/10.1016/j.cmet.2022.11.013
Antioxidants (Basel). 2022 Dec 06. pii: 2412. [Epub ahead of print]11(12):

Metabolic Rewiring toward Oxidative Phosphorylation Disrupts Intrinsic Resistance to Ferroptosis of the Colon Adenocarcinoma Cells.

Célia Gotorbe, Jérôme Durivault, Willian Meira, Shamir Cassim, Maša Ždralević, Jacques Pouysségur, Milica Vučetić.

  Glutathione peroxidase 4 (GPX4) has been reported as one of the major targets for ferroptosis induction, due to its pivotal role in lipid hydroperoxide removal. However, recent studies pointed toward alternative antioxidant systems in this context, such as the Coenzyme Q-FSP1 pathway. To investigate how effective these alternative pathways are in different cellular contexts, we used human colon adenocarcinoma (CRC) cells, highly resistant to GPX4 inhibition. Data obtained in the study showed that simultaneous pharmacological inhibition of GPX4 and FSP1 strongly compromised the survival of the CRC cells, which was prevented by the ferroptosis inhibitor, ferrostatin-1. Nonetheless, this could not be phenocopied by genetic deletion of FSP1, suggesting the development of resistance to ferroptosis in FSP1-KO CRC cells. Considering that CRC cells are highly glycolytic, we used CRC Warburg-incompetent cells, to investigate the role metabolism plays in this phenomenon. Indeed, the sensitivity to inhibition of both anti-ferroptotic axes (GPx4 and FSP1) was fully revealed in these cells, showing typical features of ferroptosis. Collectively, data indicate that two independent anti-ferroptotic pathways (GPX4-GSH and CoQ10-FSP1) operate within the overall physiological context of cancer cells and in some instances, their inhibition should be coupled with other metabolic modulators, such as inhibitors of glycolysis/Warburg effect.

Keywords:  OXPHOS; Warburg effect; colorectal adenocarcinoma; ferroptosis; ferroptosis suppressor protein 1; glutathione peroxidase 4

DOI:  https://doi.org/10.3390/antiox11122412
Int J Mol Sci. 2022 Dec 19. pii: 16203. [Epub ahead of print]23(24):

Usnic Acid-Mediated Exchange of Protons for Divalent Metal Cations across Lipid Membranes: Relevance to Mitochondrial Uncoupling.

Tatyana I Rokitskaya, Alexander M Arutyunyan, Ljudmila S Khailova, Alisa D Kataeva, Alexander M Firsov, Elena A Kotova, Yuri N Antonenko.

  Usnic acid (UA), a unique lichen metabolite, is a protonophoric uncoupler of oxidative phosphorylation, widely known as a weight-loss dietary supplement. In contrast to conventional proton-shuttling mitochondrial uncouplers, UA was found to carry protons across lipid membranes via the induction of an electrogenic proton exchange for calcium or magnesium cations. Here, we evaluated the ability of various divalent metal cations to stimulate a proton transport through both planar and vesicular bilayer lipid membranes by measuring the transmembrane electrical current and fluorescence-detected pH gradient dissipation in pyranine-loaded liposomes, respectively. Thus, we obtained the following selectivity series of calcium, magnesium, zinc, manganese and copper cations: Zn2+ > Mn2+ > Mg2+ > Ca2+ >> Cu2+. Remarkably, Cu2+ appeared to suppress the UA-mediated proton transport in both lipid membrane systems. The data on the divalent metal cation/proton exchange were supported by circular dichroism spectroscopy of UA in the presence of the corresponding cations.

Keywords:  bilayer lipid membrane; circular dichroism; divalent metal cation/proton exchange; mitochondrial uncoupler; protonophore; usnic acid

DOI:  https://doi.org/10.3390/ijms232416203
Cancers (Basel). 2022 Dec 16. pii: 6214. [Epub ahead of print]14(24):

Metabolomic and Mitochondrial Fingerprinting of the Epithelial-to-Mesenchymal Transition (EMT) in Non-Tumorigenic and Tumorigenic Human Breast Cells.

Elisabet Cuyàs, Salvador Fernández-Arroyo, Sara Verdura, Ruth Lupu, Jorge Joven, Javier A Menendez.

  Epithelial-to-mesenchymal transition (EMT) is key to tumor aggressiveness, therapy resistance, and immune escape in breast cancer. Because metabolic traits might be involved along the EMT continuum, we investigated whether human breast epithelial cells engineered to stably acquire a mesenchymal phenotype in non-tumorigenic and H-RasV12-driven tumorigenic backgrounds possess unique metabolic fingerprints. We profiled mitochondrial-cytosolic bioenergetic and one-carbon (1C) metabolites by metabolomic analysis, and then questioned the utilization of different mitochondrial substrates by EMT mitochondria and their sensitivity to mitochondria-centered inhibitors. "Upper" and "lower" glycolysis were the preferred glucose fluxes activated by EMT in non-tumorigenic and tumorigenic backgrounds, respectively. EMT in non-tumorigenic and tumorigenic backgrounds could be distinguished by the differential contribution of the homocysteine-methionine 1C cycle to the transsulfuration pathway. Both non-tumorigenic and tumorigenic EMT-activated cells showed elevated mitochondrial utilization of glycolysis end-products such as lactic acid, β-oxidation substrates including palmitoyl-carnitine, and tricarboxylic acid pathway substrates such as succinic acid. Notably, mitochondria in tumorigenic EMT cells distinctively exhibited a significant alteration in the electron flow intensity from succinate to mitochondrial complex III as they were highly refractory to the inhibitory effects of antimycin A and myxothiazol. Our results show that the bioenergetic/1C metabolic signature, the utilization rates of preferred mitochondrial substrates, and sensitivity to mitochondrial drugs significantly differs upon execution of EMT in non-tumorigenic and tumorigenic backgrounds, which could help to resolve the relationship between EMT, malignancy, and therapeutic resistance in breast cancer.

Keywords:  breast cancer; complex III; metabolism; mitochondria; phenotypic screening; therapy resistance

DOI:  https://doi.org/10.3390/cancers14246214
Nat Metab. 2022 Dec;4(12): 1792-1811

mTORC1 regulates a lysosome-dependent adaptive shift in intracellular lipid species.

Aaron M Hosios, Meghan E Wilkinson, Molly C McNamara, Krystle C Kalafut, Margaret E Torrence, John M Asara, Brendan D Manning.

The mechanistic target of rapamycin complex 1 (mTORC1) senses and relays environmental signals from growth factors and nutrients to metabolic networks and adaptive cellular systems to control the synthesis and breakdown of macromolecules; however, beyond inducing de novo lipid synthesis, the role of mTORC1 in controlling cellular lipid content remains poorly understood. Here we show that inhibition of mTORC1 via small molecule inhibitors or nutrient deprivation leads to the accumulation of intracellular triglycerides in both cultured cells and a mouse tumor model. The elevated triglyceride pool following mTORC1 inhibition stems from the lysosome-dependent, but autophagy-independent, hydrolysis of phospholipid fatty acids. The liberated fatty acids are available for either triglyceride synthesis or β-oxidation. Distinct from the established role of mTORC1 activation in promoting de novo lipid synthesis, our data indicate that mTORC1 inhibition triggers membrane phospholipid trafficking to the lysosome for catabolism and an adaptive shift in the use of constituent fatty acids for storage or energy production.

DOI: https://doi.org/10.1038/s42255-022-00706-6
Nat Metab. 2022 Dec;4(12): 1830-1846

Metabolic enzyme LDHA activates Rac1 GTPase as a noncanonical mechanism to promote cancer.

Juan Liu, Cen Zhang, Tianliang Zhang, Chun-Yuan Chang, Jianming Wang, Ludvinna Bazile, Lanjing Zhang, Bruce G Haffty, Wenwei Hu, Zhaohui Feng.

The glycolytic enzyme lactate dehydrogenase A (LDHA) is frequently overexpressed in cancer, which promotes glycolysis and cancer. The oncogenic effect of LDHA has been attributed to its glycolytic enzyme activity. Here we report an unexpected noncanonical oncogenic mechanism of LDHA; LDHA activates small GTPase Rac1 to promote cancer independently of its glycolytic enzyme activity. Mechanistically, LDHA interacts with the active form of Rac1, Rac1-GTP, to inhibit Rac1-GTP interaction with its negative regulator, GTPase-activating proteins, leading to Rac1 activation in cancer cells and mouse tissues. In clinical breast cancer specimens, LDHA overexpression is associated with higher Rac1 activity. Rac1 inhibition suppresses the oncogenic effect of LDHA. Combination inhibition of LDHA enzyme activity and Rac1 activity by small-molecule inhibitors displays a synergistic inhibitory effect on breast cancers with LDHA overexpression. These results reveal a critical oncogenic mechanism of LDHA and suggest a promising therapeutic strategy for breast cancers with LDHA overexpression.

DOI: https://doi.org/10.1038/s42255-022-00708-4
Biomolecules. 2022 Dec 13. pii: 1863. [Epub ahead of print]12(12):

Mitochondrial Non-Coding RNAs Are Potential Mediators of Mitochondrial Homeostasis.

Weihan Sun, Yijian Lu, Heng Zhang, Jun Zhang, Xinyu Fang, Jianxun Wang, Mengyang Li.

  Mitochondria are the energy production center in cells, which regulate aerobic metabolism, calcium balance, gene expression and cell death. Their homeostasis is crucial for cell viability. Although mitochondria own a nucleus-independent and self-replicating genome, most of the proteins, which fulfill mitochondrial functions and mitochondrial quality control, are encoded by the nuclear genome and are imported into mitochondria. Hence, the regulation of mitochondrial protein expression and translocation is considered essential for mitochondrial homeostasis. By means of high-throughput RNA sequencing and bioinformatic analysis, non-coding RNAs localized in mitochondria have been generally identified. They are either generated from the mitochondrial genome or the nuclear genome. The mitochondrial non-coding RNAs can directly interact with mitochondrial DNAs or transcripts to affect gene expression. They can also bind nuclear genome-encoded mitochondrial proteins to regulate their mitochondrial import, protein level and combination. Generally, mitochondrial non-coding RNAs act as regulators for mitochondrial processes including oxidative phosphorylation and metabolism. In this review, we would like to introduce the latest research progressions regarding mitochondrial non-coding RNAs and summarize their identification, biogenesis, translocation, molecular mechanism and function.

Keywords:  epigenetics; homeostasis; mitochondria; non-coding RNAs

DOI:  https://doi.org/10.3390/biom12121863
Mol Biol Rep. 2022 Dec 21.

Evaluation of the gene encoding carnitine transporter (OCTN2/SLC22A5) expression in human breast cancer and its association with clinicopathological characteristics.

Negar Dinarvand, Farzaneh Karimi, Reza Azizi, Sedighe Rastaghi, Abdolkarim Sheikhi, Morteza Pourfarzam.

   BACKGROUND: Fatty acid oxidation (FAO) is a major energy-generating process in the mitochondria and supports proliferation, growth, and survival of cancer cells. L-Carnitine is an essential co-factor for carrying long-chain fatty acids into the mitochondria. The entry of l-carnitine across cell membrane is regulated by OCTN2 (SLC22A5). Thus, it can plays a significant role in the mitochondrial fatty acid oxidation. This study aimed to evaluate the OCTN2 expression and its association with clinicopathological characteristics in breast cancer.
METHODS: In this work, OCTN2 was examined in 54 pairs of fresh samples of breast cancer (BC) and adjacent noncancerous tissue using quantitative real-time polymerase chain reaction and immunohistochemistry (IHC). The IHC approach was also used to investigate the expression of additional clinicopathological features.
RESULTS: The present research findings revealed that the relative expression of OCTN2 in BC tissues was substantially higher than the adjacent normal tissues. This up-regulation was correlated positively with tumor size and Ki-67 and negatively with the progesterone receptor (PR) status, providing evidence of the opposite effects of OCTN2 and PR on tumor development.
CONCLUSION: The study shows that the OCTN2 expression in BC patients may be used as a prognostic biomarker and a tumor oncogene. As a result, it could be considered a possible therapeutic target. Nevertheless, the significance of the findings needs to be confirmed by further studies.

Keywords:  Breast cancer; Fatty acid oxidation; OCTN2

DOI:  https://doi.org/10.1007/s11033-022-08152-z
Proc Natl Acad Sci U S A. 2022 Dec 27. 119(52): e2215799119

Multi-color live-cell STED nanoscopy of mitochondria with a gentle inner membrane stain.

Tianyan Liu, Till Stephan, Peng Chen, Jan Keller-Findeisen, Jingting Chen, Dietmar Riedel, Zhongtian Yang, Stefan Jakobs, Zhixing Chen.

  Capturing mitochondria's intricate and dynamic structure poses a daunting challenge for optical nanoscopy. Different labeling strategies have been demonstrated for live-cell stimulated emission depletion (STED) microscopy of mitochondria, but orthogonal strategies are yet to be established, and image acquisition has suffered either from photodamage to the organelles or from rapid photobleaching. Therefore, live-cell nanoscopy of mitochondria has been largely restricted to two-dimensional (2D) single-color recordings of cancer cells. Here, by conjugation of cyclooctatetraene (COT) to a benzo-fused cyanine dye, we report a mitochondrial inner membrane (IM) fluorescent marker, PK Mito Orange (PKMO), featuring efficient STED at 775 nm, strong photostability, and markedly reduced phototoxicity. PKMO enables super-resolution (SR) recordings of IM dynamics for extended periods in immortalized mammalian cell lines, primary cells, and organoids. Photostability and reduced phototoxicity of PKMO open the door to live-cell three-dimensional (3D) STED nanoscopy of mitochondria for 3D analysis of the convoluted IM. PKMO is optically orthogonal with green and far-red markers, allowing multiplexed recordings of mitochondria using commercial STED microscopes. Using multi-color STED microscopy, we demonstrate that imaging with PKMO can capture interactions of mitochondria with different cellular components such as the endoplasmic reticulum (ER) or the cytoskeleton, Bcl-2-associated X protein (BAX)-induced apoptotic process, or crista phenotypes in genetically modified cells, all at sub-100 nm resolution. Thereby, this work offers a versatile tool for studying mitochondrial IM architecture and dynamics in a multiplexed manner.

Keywords:  STED nanoscopy; cristae; mitochondria

DOI:  https://doi.org/10.1073/pnas.2215799119
Int J Mol Sci. 2022 Dec 12. pii: 15734. [Epub ahead of print]23(24):

Preferred Migration of Mitochondria toward Cells and Tissues with Mitochondrial Damage.

Seo-Eun Lee, Young Cheol Kang, Yujin Kim, Soomin Kim, Shin-Hye Yu, Jong Hyeok Park, In-Hyeon Kim, Hyeon-Young Kim, Kyuboem Han, Hong Kyu Lee, Sung-Hwan Kim, Chun-Hyung Kim.

  Mitochondria are organelles that play a vital role in cellular survival by supplying ATP and metabolic substrates via oxidative phosphorylation and the Krebs cycle. Hence, mitochondrial dysfunction contributes to many human diseases, including metabolic syndromes, neurodegenerative diseases, cancer, and aging. Mitochondrial transfer between cells has been shown to occur naturally, and mitochondrial transplantation is beneficial for treating mitochondrial dysfunction. In this study, the migration of mitochondria was tracked in vitro and in vivo using mitochondria conjugated with green fluorescent protein (MTGFP). When MTGFP were used in a coculture model, they were selectively internalized into lung fibroblasts, and this selectivity depended on the mitochondrial functional states of the receiving fibroblasts. Compared with MTGFP injected intravenously into normal mice, MTGFP injected into bleomycin-induced idiopathic pulmonary fibrosis model mice localized more abundantly in the lung tissue, indicating that mitochondrial homing to injured tissue occurred. This study shows for the first time that exogenous mitochondria are preferentially trafficked to cells and tissues in which mitochondria are damaged, which has implications for the delivery of therapeutic agents to injured or diseased sites.

Keywords:  mitochondria; mitochondrial dysfunction; trafficking; transplantation

DOI:  https://doi.org/10.3390/ijms232415734
Antioxidants (Basel). 2022 Nov 23. pii: 2314. [Epub ahead of print]11(12):

Membrane Lipid Reshaping Underlies Oxidative Stress Sensing by the Mitochondrial Proteins UCP1 and ANT1.

Olga Jovanović, Ksenia Chekashkina, Sanja Škulj, Kristina Žuna, Mario Vazdar, Pavel V Bashkirov, Elena E Pohl.

  Oxidative stress and ROS are important players in the pathogenesis of numerous diseases. In addition to directly altering proteins, ROS also affects lipids with negative intrinsic curvature such as phosphatidylethanolamine (PE), producing PE adducts and lysolipids. The formation of PE adducts potentiates the protonophoric activity of mitochondrial uncoupling proteins, but the molecular mechanism remains unclear. Here, we linked the ROS-mediated change in lipid shape to the mechanical properties of the membrane and the function of uncoupling protein 1 (UCP1) and adenine nucleotide translocase 1 (ANT1). We show that the increase in the protonophoric activity of both proteins occurs due to the decrease in bending modulus in lipid bilayers in the presence of lysophosphatidylcholines (OPC and MPC) and PE adducts. Moreover, MD simulations showed that modified PEs and lysolipids change the lateral pressure profile of the membrane in the same direction and by the similar amplitude, indicating that modified PEs act as lipids with positive intrinsic curvature. Both results indicate that oxidative stress decreases stored curvature elastic stress (SCES) in the lipid bilayer membrane. We demonstrated that UCP1 and ANT1 sense SCES and proposed a novel regulatory mechanism for the function of these proteins. The new findings should draw the attention of the scientific community to this important and unexplored area of redox biochemistry.

Keywords:  bending moduli; lateral pressure profile; lipid shape; lipid–protein interaction; mitochondrial membrane protein; protonophoric function; reactive aldehydes; stored curvature elastic stress

DOI:  https://doi.org/10.3390/antiox11122314
Front Immunol. 2022 ;13 1070593

Deciphering a mitochondria-related signature to supervise prognosis and immunotherapy in hepatocellular carcinoma.

Yanlong Shi, Guo Huang, Fei Jiang, Jun Zhu, Qiyang Xu, Hanlu Fang, Sheng Lan, Ziyuan Pan, Haokun Jian, Li Li, Yewei Zhang.

   Background: Hepatocellular carcinoma (HCC) is a major public health problem in humans. The imbalance of mitochondrial function has been discovered to be closely related to the development of cancer recently. However, the role of mitochondrial-related genes in HCC remains unclear.
Methods: The RNA-sequencing profiles and patient information of 365 samples were derived from the Cancer Genome Atlas (TCGA) dataset. The mitochondria-related prognostic model was established by univariate Cox regression analysis and LASSO Cox regression analysis. We further determined the differences in immunity and drug sensitivity between low- and high-risk groups. Validation data were obtained from the International Cancer Genome Consortium (ICGC) dataset of patients with HCC. The protein and mRNA expression of six mitochondria-related genes in tissues and cell lines was verified by immunohistochemistry and qRT-PCR.
Results: The six mitochondria-related gene signature was constructed for better prognosis forecasting and immunity, based on which patients were divided into high-risk and low-risk groups. The ROC curve, nomogram, and calibration curve exhibited admirable clinical predictive performance of the model. The risk score was associated with clinicopathological characteristics and proved to be an independent prognostic factor in patients with HCC. The above results were verified in the ICGC validation cohort. Compared with normal tissues and cell lines, the protein and mRNA expression of six mitochondria-related genes was upregulated in HCC tissues and cell lines.
Conclusion: The signature could be an independent factor that supervises the immunotherapy response of HCC patients and possess vital guidance value for clinical diagnosis and treatment.

Keywords:  consensus clustering; drug sensitivity; hepatocellular carcinoma; immunotherapy; mitochondria; tumor microenvironment

DOI:  https://doi.org/10.3389/fimmu.2022.1070593
Biochem Biophys Res Commun. 2022 Dec 10. pii: S0006-291X(22)01676-X. [Epub ahead of print]641 148-154

Multi-SUMOylation of NAC1 is essential for the growth of prostate cancer cells.

Donghua Wen, Min Hu, Wenzheng Guo, Jingjing Wu, Yingli Wu.

  Nucleus accumbens-associated 1 (NAC1) is a member of pox virus and zinc finger/bric-a-brac tramtrack broad complex (BTB/POZ) gene family. Overexpression of NAC1 is implicated in cancer development, recurrence and chemotherapy resistance. In our previous study, we found NAC1 was a potential small ubiquitin-like modifier (SUMO) substrate in prostate cancer cells. However, there was still lack of evidences to further support and validate the result. In this work, we found that NAC1 is a multi-SUMO-sites acceptor. The SUMO acceptor lysines were K167, K318, K368, K483 and K498. SUMOylation didn't alter the localization of NAC1, but facilitated the formation of NAC1 nuclear bodies. Compared with NAC1 wild type (NAC1 WT), the SUMO-sites mutant of NAC1 (NAC1 SM) suppressed cell proliferation and tumor growth in cellular and animal levels. This work uncovered the function of SUMOylation of NAC1 in prostate cancer cells.

Keywords:  Nuclear body; Nucleus accumbens associated 1; Prostate cancer; SUMOylation; Tumor proliferation

DOI:  https://doi.org/10.1016/j.bbrc.2022.12.015
Hepatobiliary Pancreat Dis Int. 2022 Dec 14. pii: S1499-3872(22)00281-8. [Epub ahead of print]

Uncoupling protein 2 deficiency of non-cancerous tissues inhibits the progression of pancreatic cancer in mice.

Denis Revskij, Jakob Runst, Camilla Umstätter, Luise Ehlers, Sarah Rohde, Dietmar Zechner, Manuela Bastian, Brigitte Müller-Hilke, Georg Fuellen, Larissa Henze, Hugo Murua Escobar, Christian Junghanss, Axel Kowald, Uwe Walter, Rüdiger Köhling, Olaf Wolkenhauer, Robert Jaster.

   BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a disease of the elderly mostly because its development from preneoplastic lesions depends on the accumulation of gene mutations and epigenetic alterations over time. How aging of non-cancerous tissues of the host affects tumor progression, however, remains largely unknown.
METHODS: We took advantage of a model of accelerated aging, uncoupling protein 2-deficient (Ucp2 knockout, Ucp2 KO) mice, to investigate the growth of orthotopically transplanted Ucp2 wild-type (WT) PDAC cells (cell lines Panc02 and 6606PDA) in vivo and to study strain-dependent differences of the PDAC microenvironment.
RESULTS: Measurements of tumor weights and quantification of proliferating cells indicated a significant growth advantage of Panc02 and 6606PDA cells in WT mice compared to Ucp2 KO mice. In tumors in the knockout strain, higher levels of interferon-γ mRNA despite similar numbers of tumor-infiltrating T cells were observed. 6606PDA cells triggered a stronger stromal reaction in Ucp2 KO mice than in WT animals. Accordingly, pancreatic stellate cells from Ucp2 KO mice proliferated at a higher rate than cells of the WT strain when they were incubated with conditioned media from PDAC cells.
CONCLUSIONS: Ucp2 modulates PDAC microenvironment in a way that favors tumor progression and implicates an altered stromal response as one of the underlying mechanisms.

Keywords:  Fibrosis; Orthotopic model; Pancreatic cancer; Uncoupling protein 2

DOI:  https://doi.org/10.1016/j.hbpd.2022.12.003
Cell Rep. 2022 Dec 20. pii: S2211-1247(22)01718-1. [Epub ahead of print]41(12): 111826

BCL-xL inhibition potentiates cancer therapies by redirecting the outcome of p53 activation from senescence to apoptosis.

Vijaya Bharti, Reese Watkins, Amrendra Kumar, Rebecca L Shattuck-Brandt, Alexis Mossing, Arjun Mittra, Chengli Shen, Allan Tsung, Alexander E Davies, Walter Hanel, John C Reneau, Catherine Chung, Gina M Sizemore, Ann Richmond, Vivian L Weiss, Anna E Vilgelm.

  Cancer therapies trigger diverse cellular responses, ranging from apoptotic death to acquisition of persistent therapy-refractory states such as senescence. Tipping the balance toward apoptosis could improve treatment outcomes regardless of therapeutic agent or malignancy. We find that inhibition of the mitochondrial protein BCL-xL increases the propensity of cancer cells to die after treatment with a broad array of oncology drugs, including mitotic inhibitors and chemotherapy. Functional precision oncology and omics analyses suggest that BCL-xL inhibition redirects the outcome of p53 transcriptional response from senescence to apoptosis, which likely occurs via caspase-dependent down-modulation of p21 and downstream cytostatic proteins. Consequently, addition of a BCL-2/xL inhibitor strongly improves melanoma response to the senescence-inducing drug targeting mitotic kinase Aurora kinase A (AURKA) in mice and patient-derived organoids. This study shows a crosstalk between the mitochondrial apoptotic pathway and cell cycle regulation that can be targeted to augment therapeutic efficacy in cancers with wild-type p53.

Keywords:  Aurora kinase; BAX; BCL-2; BCL-xL; CP: Cancer; p21; p53; patient-derived organoids; senescence; senogenic; senolytic

DOI:  https://doi.org/10.1016/j.celrep.2022.111826