bims-camemi 2023-01-01 papers

bims-camemi

Biomed News

on Mitochondrial metabolism in cancer

Issue of 2023–01–01
23 papers selected by
Christian Frezza, Universität zu Köln

Regulation and function of the mammalian tricarboxylic acid cycle.
Multi-substrate metabolic tracing reveals marked heterogeneity and dependency on fatty acid metabolism in human prostate cancer.
Mitochondrial genome recovery by ATFS-1 is essential for development after starvation.
UCP2-dependent redox sensing in POMC neurons regulates feeding.
Metabolic adaptation supports enhanced macrophage efferocytosis in limited-oxygen environments.
How does density of the inner mitochondrial membrane influence mitochondrial performance?
Hindering NAT8L expression in hepatocellular carcinoma increases cytosolic aspartate delivery that fosters pentose phosphate pathway and purine biosynthesis promoting cell proliferation.
Brain capillary pericytes are metabolic sentinels that control blood flow through a KATP channel-dependent energy switch.
DNA damage repair kinase DNA-PK and cGAS synergize to induce cancer-related inflammation in glioblastoma.
Wdr59 promotes or inhibits TORC1 activity depending on cellular context.
Infiltration of tumors is regulated by T cell-intrinsic nitric oxide synthesis.
Mitochondria directly sense osmotic stress to trigger rapid metabolic remodeling via regulation of pyruvate dehydrogenase (PDH) phosphorylation.
Decoding the coupled decision-making of the epithelial-mesenchymal transition and metabolic reprogramming in cancer.
Mitochondria-localized lncRNA HITT inhibits fusion by attenuating formation of mitofusin-2 homo- or heterotypic complexes.
Mitochondria and peroxisomes: partners in autophagy.
Kidney tubular epithelial cell ferroptosis links glomerular injury to tubulointerstitial pathology in lupus nephritis.
The ectonucleotidase CD39 identifies tumor-reactive CD8+ T cells predictive of immune checkpoint blockade efficacy in human lung cancer.
NADP(H)-dependent biocatalysis without adding NADP(H).
ERK and c-Myc signaling in host-derived tumor endothelial cells is essential for solid tumor growth.
The lipid flippase SLC47A1 blocks metabolic vulnerability to ferroptosis.
Characterization of Protein (2SC) Succination as a Biomarker for Fumarate Hydratase-deficient Renal Cell Carcinoma.
A circadian clock translational control mechanism targets specific mRNAs to cytoplasmic messenger ribonucleoprotein granules.
Tissue fluidification promotes a cGAS-STING cytosolic DNA response in invasive breast cancer.

J Biol Chem. 2022 Dec 26. pii: S0021-9258(22)01281-9. [Epub ahead of print] 102838

Regulation and function of the mammalian tricarboxylic acid cycle.

Paige K Arnold, Lydia W S Finley.

The tricarboxylic acid (TCA) cycle, otherwise known as the Krebs cycle, is a central metabolic pathway that performs the essential function of oxidizing nutrients to support cellular bioenergetics. More recently, it has become evident that TCA cycle behavior is dynamic and products of the TCA cycle can be co-opted in cancer and other pathologic states. In this review, we revisit the TCA cycle, including its potential origins and the history of its discovery. We provide a detailed accounting of the requirements for sustained TCA cycle function and the critical regulatory nodes that can stimulate or constrain TCA cycle activity. We also discuss recent advances in our understanding of the flexibility of TCA cycle wiring and the increasingly appreciated heterogeneity in TCA cycle activity exhibited by mammalian cells. Deeper insight into how the TCA cycle can be differentially regulated and, consequently, configured in different contexts will shed light on how this pathway is primed to meet the requirements of distinct mammalian cell states.

DOI: https://doi.org/10.1016/j.jbc.2022.102838
Mol Cancer Res. 2022 Dec 27. pii: MCR-22-0796. [Epub ahead of print]

Multi-substrate metabolic tracing reveals marked heterogeneity and dependency on fatty acid metabolism in human prostate cancer.

Gio Fidelito, David P De Souza, Birunthi Niranjan, William de Nardo, Shivakumar Keerthikumar, Kristin Brown, Renea A Taylor, Matthew J Watt.

Cancer cells undergo metabolic reprogramming to meet increased bioenergetic demands. Studies in cells and mice have highlighted the importance of oxidative metabolism and lipogenesis in prostate cancer, however, the metabolic landscape of human prostate cancer remains unclear. To address this knowledge gap, we performed radiometric (14C) and stable (13C) isotope tracing assays in precision-cut slices of patient-derived xenografts (PDXs). Glucose, glutamine, and fatty acid oxidation was variably upregulated in malignant PDXs compared to benign PDXs. De novo lipogenesis (DNL) and storage of free fatty acids into phospholipids and triacylglycerols were increased in malignant PDXs. There was no difference in substrate utilization between localized and metastatic PDXs and hierarchical clustering revealed marked metabolic heterogeneity across all PDXs. Mechanistically, glucose utilization was mediated by acetyl-CoA production rather than carboxylation of pyruvate, while glutamine entered the TCA cycle through transaminase reactions before being utilized via oxidative or reductive pathways. Blocking fatty acid uptake or fatty acid oxidation with pharmacological inhibitors was sufficient to reduce cell viability in PDX-derived organoids (PDXOs), whereas blockade of DNL, or glucose or glutamine oxidation induced variable and limited therapeutic efficacy. These findings demonstrate that human prostate cancer, irrespective of disease stage, can effectively utilize all metabolic substrates, albeit with marked heterogeneity across tumors. We also confirm that fatty acid uptake and oxidation are targetable metabolic dependencies in human prostate cancer. Implications: Prostate cancer utilizes multiple substrates to fuel energy requirements, yet pharmacological targeting of fatty acid uptake and oxidation reveals metabolic dependencies in localised and metastatic tumors.

DOI: https://doi.org/10.1158/1541-7786.MCR-22-0796
Cell Rep. 2022 Dec 27. pii: S2211-1247(22)01771-5. [Epub ahead of print]41(13): 111875

Mitochondrial genome recovery by ATFS-1 is essential for development after starvation.

Nandhitha Uma Naresh, Sookyung Kim, Tomer Shpilka, Qiyuan Yang, Yunguang Du, Cole M Haynes.

  Nutrient availability regulates the C. elegans life cycle as well as mitochondrial physiology. Food deprivation significantly reduces mitochondrial genome (mtDNA) numbers and leads to aging-related phenotypes. Here we show that the bZIP (basic leucine zipper) protein ATFS-1, a mediator of the mitochondrial unfolded protein response (UPRmt), is required to promote growth and establish a functional germline after prolonged starvation. We find that recovery of mtDNA copy numbers and development after starvation requires mitochondrion-localized ATFS-1 but not its nuclear transcription activity. We also find that the insulin-like receptor DAF-2 functions upstream of ATFS-1 to modulate mtDNA content. We show that reducing DAF-2 activity represses ATFS-1 nuclear function while causing an increase in mtDNA content, partly mediated by mitochondrion-localized ATFS-1. Our data indicate the importance of the UPRmt in recovering mitochondrial mass and suggest that atfs-1-dependent mtDNA replication precedes mitochondrial network expansion after starvation.

Keywords:  ATFS-1; C. elegans; CP: Metabolism; CP: Molecular biology; DAF-2; UPR; UPRmt; insulin receptor; mitochondria; mtDNA; starvation; stress response

DOI:  https://doi.org/10.1016/j.celrep.2022.111875
Cell Rep. 2022 Dec 27. pii: S2211-1247(22)01793-4. [Epub ahead of print]41(13): 111894

UCP2-dependent redox sensing in POMC neurons regulates feeding.

Nal Ae Yoon, Sungho Jin, Jung Dae Kim, Zhong Wu Liu, Qiushi Sun, Rebecca Cardone, Richard Kibbey, Sabrina Diano.

  Paradoxically, glucose, the primary driver of satiety, activates a small population of anorexigenic pro-opiomelanocortin (POMC) neurons. Here, we show that lactate levels in the circulation and in the cerebrospinal fluid are elevated in the fed state and the addition of lactate to glucose activates the majority of POMC neurons while increasing cytosolic NADH generation, mitochondrial respiration, and extracellular pyruvate levels. Inhibition of lactate dehydrogenases diminishes mitochondrial respiration, NADH production, and POMC neuronal activity. However, inhibition of the mitochondrial pyruvate carrier has no effect. POMC-specific downregulation of Ucp2 (Ucp2PomcKO), a molecule regulated by fatty acid metabolism and shown to play a role as transporter in the malate-aspartate shuttle, abolishes lactate- and glucose-sensing of POMC neurons. Ucp2PomcKO mice have impaired glucose metabolism and are prone to obesity on a high-fat diet. Altogether, our data show that lactate through redox signaling and blocking mitochondrial glucose utilization activates POMC neurons to regulate feeding and glucose metabolism.

Keywords:  CP: Metabolism; CP: Neuroscience; NADH; UCP2; feeding behavior; glucose; hypothalamus; lactate; lipid utilization; mitochondria; pro-opiomelanocortin neurons; redox signaling

DOI:  https://doi.org/10.1016/j.celrep.2022.111894
Cell Metab. 2022 Dec 21. pii: S1550-4131(22)00542-3. [Epub ahead of print]

Metabolic adaptation supports enhanced macrophage efferocytosis in limited-oxygen environments.

Ya-Ting Wang, Alissa J Trzeciak, Waleska Saitz Rojas, Pedro Saavedra, Yan-Ting Chen, Rachel Chirayil, Jon Iker Etchegaray, Christopher D Lucas, Daniel J Puleston, Kayvan R Keshari, Justin S A Perry.

  Apoptotic cell (AC) clearance (efferocytosis) is performed by phagocytes, such as macrophages, that inhabit harsh physiological environments. Here, we find that macrophages display enhanced efferocytosis under prolonged (chronic) physiological hypoxia, characterized by increased internalization and accelerated degradation of ACs. Transcriptional and translational analyses revealed that chronic physiological hypoxia induces two distinct but complimentary states. The first, "primed" state, consists of concomitant transcription and translation of metabolic programs in AC-naive macrophages that persist during efferocytosis. The second, "poised" state, consists of transcription, but not translation, of phagocyte function programs in AC-naive macrophages that are translated during efferocytosis. Mechanistically, macrophages efficiently flux glucose into a noncanonical pentose phosphate pathway (PPP) loop to enhance NADPH production. PPP-derived NADPH directly supports enhanced efferocytosis under physiological hypoxia by ensuring phagolysosomal maturation and redox homeostasis. Thus, macrophages residing under physiological hypoxia adopt states that support cell fitness and ensure performance of essential homeostatic functions rapidly and safely.

Keywords:  apoptotic cell clearance; cellular adaptation; efferocytosis; homeostasis; metabolism; oxygen; pentose phosphate pathway; physiological hypoxia

DOI:  https://doi.org/10.1016/j.cmet.2022.12.005
Am J Physiol Regul Integr Comp Physiol. 2022 Dec 26.

How does density of the inner mitochondrial membrane influence mitochondrial performance?

Kyle B Heine, Hailey A Parry, Wendy R Hood.

  Our current understanding of variation in mitochondrial performance is incomplete. The production of ATP via oxidative phosphorylation is dependent, in part, upon the structure of the inner mitochondrial membrane. Morphology of the inner membrane is crucial for the formation of the proton gradient across the inner membrane and, therefore, ATP synthesis. The inner mitochondrial membrane is dynamic, changing shape and surface area. These changes alter density (amount per volume) of the inner mitochondrial membrane within the confined space of the mitochondrion. Because the number of electron transport system proteins within the inner mitochondrial membrane changes with inner mitochondrial membrane area, a change in the amount of inner membrane alters the capacity for ATP production within the organelle. This review outlines the evidence that the association between ATP synthases, inner mitochondrial membrane density, and mitochondrial density (number of mitochondria per cell), impact ATP production by mitochondria. Further, we consider possible constraints on the capacity of mitochondria to produce ATP by increasing inner mitochondrial membrane density.

Keywords:  ATP synthase; cristae; inter-membrane space; matrix; oxidative phosphorylation

DOI:  https://doi.org/10.1152/ajpregu.00254.2022
Redox Biol. 2022 Dec 24. pii: S2213-2317(22)00357-3. [Epub ahead of print]59 102585

Hindering NAT8L expression in hepatocellular carcinoma increases cytosolic aspartate delivery that fosters pentose phosphate pathway and purine biosynthesis promoting cell proliferation.

Pamela De Falco, Giacomo Lazzarino, Federica Felice, Enrico Desideri, Serena Castelli, Illari Salvatori, Fabio Ciccarone, Maria Rosa Ciriolo.

  N-acetylaspartate (NAA) is synthesized by the mitochondrial enzyme NAT8L, which uses acetyl-CoA and aspartate as substrates. These metabolites are fundamental for bioenergetics and anabolic requirements of highly proliferating cells, thus, NAT8L modulation may impinge on the metabolic reprogramming of cancer cells. Specifically, aspartate represents a limiting amino acid for nucleotide synthesis in cancer. Here, the expression of the NAT8L enzyme was modulated to verify how it impacts the metabolic adaptations and proliferative capacity of hepatocellular carcinoma. We demonstrated that NAT8L downregulation is associated with increased proliferation of hepatocellular carcinoma cells and immortalized hepatocytes. The overexpression of NAT8L instead decreased cell growth. The pro-tumoral effect of NAT8L silencing depended on glutamine oxidation and the rewiring of glucose metabolism. Mechanistically, NAT8L downregulation triggers aspartate outflow from mitochondria via the exporter SLC25A13 to promote glucose flux into the pentose phosphate pathway, boosting purine biosynthesis. These results were corroborated by the analyses of human and mouse hepatocellular carcinoma samples revealing a decrease in NAT8L expression compared to adjacent non-tumoral tissues. Overall, this work demonstrates that NAT8L expression in liver cells limits the cytosolic availability of aspartate necessary for enhancing the pentose phosphate pathway and purine biosynthesis, counteracting cell proliferation.

Keywords:  Aspartate; Mitochondria; NAA; Nucleotides; Pentose phosphate pathway

DOI:  https://doi.org/10.1016/j.redox.2022.102585
Cell Rep. 2022 Dec 27. pii: S2211-1247(22)01768-5. [Epub ahead of print]41(13): 111872

Brain capillary pericytes are metabolic sentinels that control blood flow through a KATP channel-dependent energy switch.

Ashwini Hariharan, Colin D Robertson, Daniela C G Garcia, Thomas A Longden.

  Despite the abundance of capillary thin-strand pericytes and their proximity to neurons and glia, little is known of the contributions of these cells to the control of brain hemodynamics. We demonstrate that the pharmacological activation of thin-strand pericyte KATP channels profoundly hyperpolarizes these cells, dilates upstream penetrating arterioles and arteriole-proximate capillaries, and increases capillary blood flow. Focal stimulation of pericytes with a KATP channel agonist is sufficient to evoke this response, mediated via KIR2.1 channel-dependent retrograde propagation of hyperpolarizing signals, whereas genetic inactivation of pericyte KATP channels eliminates these effects. Critically, we show that decreasing extracellular glucose to less than 1 mM or inhibiting glucose uptake by blocking GLUT1 transporters in vivo flips a mechanistic energy switch driving rapid KATP-mediated pericyte hyperpolarization to increase local blood flow. Together, our findings recast capillary pericytes as metabolic sentinels that respond to local energy deficits by increasing blood flow to neurons to prevent energetic shortfalls.

Keywords:  CP: Neuroscience; K(IR) channels; KATP channels; capillaries; cerebral blood flow; endothelial cells; energy; functional hyperemia; glucose; metabolism; neurovascular coupling; pericytes

DOI:  https://doi.org/10.1016/j.celrep.2022.111872
EMBO J. 2022 Dec 27. e111961

DNA damage repair kinase DNA-PK and cGAS synergize to induce cancer-related inflammation in glioblastoma.

Clara Taffoni, Johanna Marines, Hanane Chamma, Soumyabrata Guha, Mathilde Saccas, Amel Bouzid, Ana-Luiza Chaves Valadao, Clément Maghe, Jane Jardine, Mi Kyung Park, Katarzyna Polak, Mara De Martino, Claire Vanpouille-Box, Maguy Del Rio, Celine Gongora, Julie Gavard, Nicolas Bidère, Min Sup Song, Donovan Pineau, Jean-Philippe Hugnot, Karima Kissa, Laura Fontenille, Fabien P Blanchet, Isabelle K Vila, Nadine Laguette.

  Cytosolic DNA promotes inflammatory responses upon detection by the cyclic GMP-AMP (cGAMP) synthase (cGAS). It has been suggested that cGAS downregulation is an immune escape strategy harnessed by tumor cells. Here, we used glioblastoma cells that show undetectable cGAS levels to address if alternative DNA detection pathways can promote pro-inflammatory signaling. We show that the DNA-PK DNA repair complex (i) drives cGAS-independent IRF3-mediated type I Interferon responses and (ii) that its catalytic activity is required for cGAS-dependent cGAMP production and optimal downstream signaling. We further show that the cooperation between DNA-PK and cGAS favors the expression of chemokines that promote macrophage recruitment in the tumor microenvironment in a glioblastoma model, a process that impairs early tumorigenesis but correlates with poor outcome in glioblastoma patients. Thus, our study supports that cGAS-dependent signaling is acquired during tumorigenesis and that cGAS and DNA-PK activities should be analyzed concertedly to predict the impact of strategies aiming to boost tumor immunogenicity.

Keywords:  DNA-PK; cGAS; inflammation; tumor immunogenicity

DOI:  https://doi.org/10.15252/embj.2022111961
Proc Natl Acad Sci U S A. 2023 Jan 03. 120(1): e2212330120

Wdr59 promotes or inhibits TORC1 activity depending on cellular context.

Yingbiao Zhang, Chun-Yuan Ting, Shu Yang, John Reich, Karenne Fru, Mary A Lilly.

  Target of Rapamycin Complex I (TORC1) is a central regulator of metabolism in eukaryotes that responds to a wide array of negative and positive inputs. The GTPase-activating protein toward Rags (GATOR) signaling pathway acts upstream of TORC1 and is comprised of two subcomplexes. The trimeric GATOR1 complex inhibits TORC1 activity in response to amino acid limitation by serving as a GTPase-activating protein (GAP) for the TORC1 activator RagA/B, a component of the lysosomally located Rag GTPase. The multi-protein GATOR2 complex inhibits the activity of GATOR1 and thus promotes TORC1 activation. Here we report that Wdr59, originally assigned to the GATOR2 complex based on studies performed in tissue culture cells, unexpectedly has a dual function in TORC1 regulation in Drosophila. We find that in the ovary and the eye imaginal disc brain complex, Wdr59 inhibits TORC1 activity by opposing the GATOR2-dependent inhibition of GATOR1. Conversely, in the Drosophila fat body, Wdr59 promotes the accumulation of the GATOR2 component Mio and is required for TORC1 activation. Similarly, in mammalian HeLa cells, Wdr59 prevents the proteolytic destruction of GATOR2 proteins Mio and Wdr24. Consistent with the reduced levels of the TORC1-activating GATOR2 complex, Wdr59KOs HeLa cells have reduced TORC1 activity which is restored along with GATOR2 protein levels upon proteasome inhibition. Taken together, our data support the model that the Wdr59 component of the GATOR2 complex functions to promote or inhibit TORC1 activity depending on cellular context.

Keywords:  Drosophila; GATOR1; GATOR2; TORC1; Wdr59

DOI:  https://doi.org/10.1073/pnas.2212330120
Cancer Immunol Res. 2022 Dec 27. pii: CIR-22-0387. [Epub ahead of print]

Infiltration of tumors is regulated by T cell-intrinsic nitric oxide synthesis.

Pedro P Cunha, David Bargiela, Eleanor Minogue, Lena C M Krause, Laura Barbieri, Carolin Brombach, Milos Gojkovic, Emilia Marklund, Sandra Pietsch, Iosifina Foskolou, Cristina M Branco, Pedro Veliça, Randall S Johnson.

Nitric oxide (NO) is a signaling molecule produced by NO synthases (NOS1-3) to control processes such as neurotransmission, vascular permeability, and immune function. Although myeloid cell-derived NO has been shown to suppress T-cell responses, the role of NO synthesis in T cells themselves is not well understood. Here, we showed that significant amounts of NO were synthesized in human and murine CD8+ T cells following activation. Tumor growth was significantly accelerated in a T cell-specific, Nos2-null mouse model. Genetic deletion of Nos2 expression in murine T cells altered effector differentiation, reduced tumor infiltration, and inhibited recall responses and adoptive cell transfer function. These data show that endogenous NO production plays a critical role in T cell-mediated tumor immunity.

DOI: https://doi.org/10.1158/2326-6066.CIR-22-0387
J Biol Chem. 2022 Dec 26. pii: S0021-9258(22)01280-7. [Epub ahead of print] 102837

Mitochondria directly sense osmotic stress to trigger rapid metabolic remodeling via regulation of pyruvate dehydrogenase (PDH) phosphorylation.

Takeshi Ikizawa, Kazutaka Ikeda, Makoto Arita, Shojiro Kitajima, Tomoyoshi Soga, Hidenori Ichijo, Isao Naguro.

  A high-salt diet significantly impacts various diseases, including cancer and immune diseases. Recent studies suggest that the high-salt/hyperosmotic environment in the body may alter the chronic properties of cancer and immune cells in the disease context. However, little is known about the acute metabolic changes in hyperosmotic stress. Here, we found that hyperosmotic stress for a few minutes induces Warburg-like metabolic remodeling in HeLa and Raw264.7 cells and suppresses fatty acid oxidation. Regarding Warburg-like remodeling, we determined that the pyruvate dehydrogenase (PDH) phosphorylation status was altered bidirectionally (high in hyperosmolarity and low in hypoosmolarity) to osmotic stress in isolated mitochondria, suggesting that mitochondria themselves have an acute osmo-sensing mechanism. Additionally, we demonstrate that Warburg-like remodeling is required for HeLa cells to maintain ATP levels and survive under hyperosmotic conditions. Collectively, our findings suggest that cells exhibit acute metabolic remodeling under osmotic stress via the regulation of PDH phosphorylation by direct osmosensing within mitochondria.

Keywords:  Acyl-carnitine; Metabolic remodeling; Mitochondria; Osmotic stress; Pyruvate dehydrogenase

DOI:  https://doi.org/10.1016/j.jbc.2022.102837
iScience. 2023 Jan 20. 26(1): 105719

Decoding the coupled decision-making of the epithelial-mesenchymal transition and metabolic reprogramming in cancer.

Madeline Galbraith, Herbert Levine, José N Onuchic, Dongya Jia.

  Cancer metastasis relies on an orchestration of traits driven by different interacting functional modules, including metabolism and epithelial-mesenchymal transition (EMT). During metastasis, cancer cells can acquire a hybrid metabolic phenotype (W/O) by increasing oxidative phosphorylation without compromising glycolysis and they can acquire a hybrid epithelial/mesenchymal (E/M) phenotype by engaging EMT. Both the W/O and E/M states are associated with high metastatic potentials, and many regulatory links coupling metabolism and EMT have been identified. Here, we investigate the coupled decision-making networks of metabolism and EMT. Their crosstalk can exhibit synergistic or antagonistic effects on the acquisition and stability of different coupled metabolism-EMT states. Strikingly, the aggressive E/M-W/O state can be enabled and stabilized by the crosstalk irrespective of these hybrid states' availability in individual metabolism or EMT modules. Our work emphasizes the mutual activation between metabolism and EMT, providing an important step toward understanding the multifaceted nature of cancer metastasis.

Keywords:  Cancer systems biology; Metabolic flux analysis

DOI:  https://doi.org/10.1016/j.isci.2022.105719
J Biol Chem. 2022 Dec 22. pii: S0021-9258(22)01268-6. [Epub ahead of print] 102825

Mitochondria-localized lncRNA HITT inhibits fusion by attenuating formation of mitofusin-2 homo- or heterotypic complexes.

Xingwen Wang, Yi Zhang, Qingyu Lin, Kunming Zhao, Dantong Zhu, Ying Hu.

  Long non-coding RNAs (lncRNAs) are emerging as essential players in multiple biological processes. Mitochondrial dynamics, comprising the continuous cycle of fission and fusion, are required for healthy mitochondria that function properly. Despite long-term recognition of its significance in cell-fate control, the mechanism underlying mitochondrial fusion is not completely understood, particularly regarding the involvement of lncRNAs. Here, we show that the lncRNA HITT (HIF-1α inhibitor at translation level), can specifically localize in mitochondria. Cells expressing higher levels of HITT contain fragmented mitochondria. Conversely, we show that HITT knockdown cells have more tubular mitochondria than is present in control cells. Mechanistically, we demonstrate HITT directly binds mitofusin-2 (MFN2), a core component that mediates mitochondrial outer membrane fusion, by the in vitro RNA pull-down and UV-cross-linking RNA-IP (CLIP) assays. In doing so, we found HITT disturbs MFN2 homo- or heterotypic complex formation, attenuating mitochondrial fusion. Under stress conditions, such as ultraviolet radiation, we in addition show HITT stability increases as a consequence of MiR-205 downregulation, inhibiting MFN2-mediated fusion and leading to apoptosis. Overall, our data provide significant insights into the roles of organelle (mitochondria)-specific resident lncRNAs in regulating mitochondrial fusion, and also reveal how such a mechanism controls cellular sensitivity to UV radiation-induced apoptosis.

Keywords:  LINC00637; MFN2; apoptosis; mitochondrial dynamics; mitochondrial fusion

DOI:  https://doi.org/10.1016/j.jbc.2022.102825
Autophagy. 2022 Dec 26. 1-2

Mitochondria and peroxisomes: partners in autophagy.

Léa P Wilhelm, Ian G Ganley.

  Mitochondria, often called "the powerhouse" of the cell due to their role as the main energy supplier, regulate numerous complex processes including intracellular calcium homeostasis, reactive oxygen species (ROS) production, regulation of immune responses, and apoptosis. So, mitochondria are a fundamental metabolic hub that also control cell survival and cell death. However, they are not unique in all these functions. Indeed, peroxisomes are small cytoplasmic organelles that also ensure metabolic functions such as fatty acid oxidation and ROS production. This common relationship also extends beyond function as peroxisomes themselves can form from mitochondrial-derived precursors. Given this interconnection between mitochondria and peroxisomes involving biogenesis and function, in our recent work we determined if their turnover was also linked.

Keywords:  Autophagy; BNIP3L; NIX; mitophagy; pexophagy

DOI:  https://doi.org/10.1080/15548627.2022.2155368
Clin Immunol. 2022 Dec 22. pii: S1521-6616(22)00294-7. [Epub ahead of print] 109213

Kidney tubular epithelial cell ferroptosis links glomerular injury to tubulointerstitial pathology in lupus nephritis.

Abdel A Alli, Dhruv Desai, Ahmed Elshika, Marcus Conrad, Bettina Proneth, William Clapp, Carl Atkinson, Mark Segal, Louis A Searcy, Nancy D Denslow, Subhashini Bolisetty, Borna Mehrad, Laurence Morel, Yogesh Scindia.

  Ferroptosis is a druggable, iron-dependent form of cell death that is characterized by lipid peroxidation but has received little attention in lupus nephritis. Kidneys of lupus nephritis patients and mice showed increased lipid peroxidation mainly in the tubular segments and an increase in Acyl-CoA synthetase long-chain family member 4, a pro-ferroptosis enzyme. Nephritic mice had an attenuated expression of SLC7A11, a cystine importer, an impaired glutathione synthesis pathway, and low expression of glutathione peroxidase 4, a ferroptosis inhibitor. Lipidomics of nephritic kidneys confirmed ferroptosis. Using nephrotoxic serum, we induced immune complex glomerulonephritis in congenic mice and demonstrate that impaired iron sequestration within the proximal tubules exacerbates ferroptosis. Lupus nephritis patient serum rendered human proximal tubular cells susceptibility to ferroptosis which was inhibited by Liproxstatin-2, a novel ferroptosis inhibitor. Collectively, our findings identify intra-renal ferroptosis as a pathological feature and contributor to tubular injury in human and murine lupus nephritis.

Keywords:  ACSL4; Ferroptosis; GPX4; Iron; Liproxstatin; Lupus nephritis; SLE

DOI:  https://doi.org/10.1016/j.clim.2022.109213
Immunity. 2022 Dec 19. pii: S1074-7613(22)00605-7. [Epub ahead of print]

The ectonucleotidase CD39 identifies tumor-reactive CD8+ T cells predictive of immune checkpoint blockade efficacy in human lung cancer.

Andrew Chow, Fathema Z Uddin, Michael Liu, Anton Dobrin, Barzin Y Nabet, Levi Mangarin, Yonit Lavin, Hira Rizvi, Sam E Tischfield, Alvaro Quintanal-Villalonga, Joseph M Chan, Nisargbhai Shah, Viola Allaj, Parvathy Manoj, Marissa Mattar, Maximiliano Meneses, Rebecca Landau, Mariana Ward, Amanda Kulick, Charlene Kwong, Matthew Wierzbicki, Jessica Yavner, Jacklynn Egger, Shweta S Chavan, Abigail Farillas, Aliya Holland, Harsha Sridhar, Metamia Ciampricotti, Daniel Hirschhorn, Xiangnan Guan, Allison L Richards, Glenn Heller, Jorge Mansilla-Soto, Michel Sadelain, Christopher A Klebanoff, Matthew D Hellmann, Triparna Sen, Elisa de Stanchina, Jedd D Wolchok, Taha Merghoub, Charles M Rudin.

  Improved identification of anti-tumor T cells is needed to advance cancer immunotherapies. CD39 expression is a promising surrogate of tumor-reactive CD8+ T cells. Here, we comprehensively profiled CD39 expression in human lung cancer. CD39 expression enriched for CD8+ T cells with features of exhaustion, tumor reactivity, and clonal expansion. Flow cytometry of 440 lung cancer biospecimens revealed weak association between CD39+ CD8+ T cells and tumoral features, such as programmed death-ligand 1 (PD-L1), tumor mutation burden, and driver mutations. Immune checkpoint blockade (ICB), but not cytotoxic chemotherapy, increased intratumoral CD39+ CD8+ T cells. Higher baseline frequency of CD39+ CD8+ T cells conferred improved clinical outcomes from ICB therapy. Furthermore, a gene signature of CD39+ CD8+ T cells predicted benefit from ICB, but not chemotherapy, in a phase III clinical trial of non-small cell lung cancer. These findings highlight CD39 as a proxy of tumor-reactive CD8+ T cells in human lung cancer.

Keywords:  CD8(+) T cells; T cell receptors; immune checkpoint blockade; non-small cell lung cancer; tumor mutation burden

DOI:  https://doi.org/10.1016/j.immuni.2022.12.001
Proc Natl Acad Sci U S A. 2023 Jan 03. 120(1): e2214123120

NADP(H)-dependent biocatalysis without adding NADP(H).

Ryan A Herold, Raphael Reinbold, Christopher J Schofield, Fraser A Armstrong.

  Isocitrate dehydrogenase 1 (IDH1) naturally copurifies and crystallizes in a resting state with a molecule of its exchangeable cofactor, NADP+/NADPH, bound in each monomer of the homodimer. We report electrochemical studies with IDH1 that exploit this property to reveal the massive advantage of nanoconfinement to increase the efficiency of multistep enzyme-catalyzed cascade reactions. When coloaded with ferredoxin NADP+ reductase in a nanoporous conducting indium tin oxide film, IDH1 carries out the complete electrochemical oxidation of 6 mM isocitrate (in 4mL) to 2-oxoglutarate (2OG), using only the NADP(H) that copurified with IDH1 and was carried into the electrode pores as cargo-the system remains active for days. The entrapped cofactor, now quantifiable by cyclic voltammetry, undergoes ~160,000 turnovers during the process. The results from a variety of electrocatalysis experiments imply that the local concentrations of the two nanoconfined enzymes lie around the millimolar range. The combination of crowding and entrapment results in a 102 to 103-fold increase in the efficiency of NADP(H) redox cycling. The ability of the method to drive cascade catalysis in either direction (oxidation or reduction) and remove and replace substrates was exploited to study redox-state dependent differences in cofactor binding between wild-type IDH1 and the cancer-linked R132H variant that catalyzes the "gain of function" reduction of 2OG to 2-hydroxyglutarate instead of isocitrate oxidation. The combined results demonstrate the power of nanoconfinement for facilitating multistep enzyme catalysis (in this case energized and verified electrochemically) and reveal insights into the dynamic role of nicotinamide cofactors as redox (hydride) carriers.

Keywords:  NADPH; biocatalysis; electrocatalysis; isocitrate dehydrogenase; nanoconfinement

DOI:  https://doi.org/10.1073/pnas.2214123120
Proc Natl Acad Sci U S A. 2023 Jan 03. 120(1): e2211927120

ERK and c-Myc signaling in host-derived tumor endothelial cells is essential for solid tumor growth.

Zehua Zuo, Jie Liu, Zhihao Sun, Yu-Wei Cheng, Michael Ewing, Thomas H Bugge, Toren Finkel, Stephen H Leppla, Shihui Liu.

  The limited efficacy of the current antitumor microenvironment strategies is due in part to the poor understanding of the roles and relative contributions of the various tumor stromal cells to tumor development. Here, we describe a versatile in vivo anthrax toxin protein delivery system allowing for the unambiguous genetic evaluation of individual tumor stromal elements in cancer. Our reengineered tumor-selective anthrax toxin exhibits potent antiproliferative activity by disrupting ERK signaling in sensitive cells. Since this activity requires the surface expression of the capillary morphogenesis protein-2 (CMG2) toxin receptor, genetic manipulation of CMG2 expression using our cell-type-specific CMG2 transgenic mice allows us to specifically define the role of individual tumor stromal cell types in tumor development. Here, we established mice with CMG2 only expressed in tumor endothelial cells (ECs) and determined the specific contribution of tumor stromal ECs to the toxin's antitumor activity. Our results demonstrate that disruption of ERK signaling only within tumor ECs is sufficient to halt tumor growth. We discovered that c-Myc is a downstream effector of ERK signaling and that the MEK-ERK-c-Myc central metabolic axis in tumor ECs is essential for tumor progression. As such, disruption of ERK-c-Myc signaling in host-derived tumor ECs by our tumor-selective anthrax toxins explains their high efficacy in solid tumor therapy.

Keywords:  ERK signaling; anthrax lethal toxin; c-Myc; endothelial cells; tumor microenvironment

DOI:  https://doi.org/10.1073/pnas.2211927120
Nat Commun. 2022 Dec 27. 13(1): 7965

The lipid flippase SLC47A1 blocks metabolic vulnerability to ferroptosis.

Zhi Lin, Jiao Liu, Fei Long, Rui Kang, Guido Kroemer, Daolin Tang, Minghua Yang.

Ferroptosis is a type of regulated necrosis caused by unrestricted lipid peroxidation and subsequent plasma membrane rupture. However, the lipid remodeling mechanism that determines sensitivity to ferroptosis remains poorly understood. Here, we report a previously unrecognized role for the lipid flippase solute carrier family 47 member 1 (SLC47A1) as a regulator of lipid remodeling and survival during ferroptosis. Among 49 phospholipid scramblases, flippases, and floppases we analyzed, only SLC47A1 had mRNA that was selectively upregulated in multiple cancer cells exposed to ferroptotic inducers. Large-scale lipidomics and functional analyses revealed that the silencing of SLC47A1 increased RSL3- or erastin-induced ferroptosis by favoring ACSL4-SOAT1-mediated production of polyunsaturated fatty acid cholesterol esters. We identified peroxisome proliferator activated receptor alpha (PPARA) as a transcription factor that transactivates SLC47A1. The depletion of PPARA and SLC47A1 similarly sensitized cells to ferroptosis induction, whereas transfection-enforced re-expression of SLC47A1 restored resistance to ferroptosis in PPARA-deficient cells. Pharmacological or genetic blockade of the PPARA-SLC47A1 pathway increased the anticancer activity of a ferroptosis inducer in mice. These findings establish a direct molecular link between ferroptosis and lipid transporters, which may provide metabolic targets for overcoming drug resistance.

DOI: https://doi.org/10.1038/s41467-022-35707-2
Hum Pathol. 2022 Dec 26. pii: S0046-8177(22)00291-X. [Epub ahead of print]

Characterization of Protein (2SC) Succination as a Biomarker for Fumarate Hydratase-deficient Renal Cell Carcinoma.

Rahul Mannan, Xiaoming Wang, Pushpinder S Bawa, Seema Chugh, Anya K Chinnaiyan, Roshni Rangaswamy, Yuping Zhang, Xuhong Cao, Steven C Smith, Kiril Trpkov, Sean Williamson, Ankur R Sangoi, Sambit Mohanty, Jesse K McKenney, Sounak Gupta, Cristina Magi-Galluzzi, Pedram Argani, Adeboye O Osunkoya, Arul M Chinnaiyan, Saravana M Dhanasekaran, Rohit Mehra.

  Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is an aggressive, rare genetic disease affecting the kidney and other organ systems. We constructed a specialized multi-institutional cohort of 20 primary FH-deficient RCC cases with aims of characterizing a new commercially available antibody, S-(2-succino)-cysteine (2SC). Herein, we present our findings on the biomarker characterization and performance of 2SC expression by immunohistochemistry (IHC) in FH-deficient RCC, and other common and rare RCC subtypes. Morphological assessment revealed characteristic cytomorphologic features and a majority (55%) of FH-deficient RCC had mixed architectural growth patterns. We observed predominantly diffuse and strong cytoplasmic staining with limited nuclear positivity for 2SC staining on IHC. Receiver operating characteristic curves (ROC) for 2SC identified the threshold IHC score (cut-off) as 90; with the sensitivity and specificity being 100% and 91% respectively. The findings of the present study along with the prior evidence in literature encourages utilization of 2SC as a positive marker along with the loss of fumarate hydratase (FH) expression by anti-FH IHC staining as a negative marker, in clinical and/or pathologic scenarios when considering FH-deficient RCC in the differential diagnosis. FH-/2SC+ may serve as a comprehensive IHC panel in identifying such cases and excluding morphologically similar entities.

Keywords:  2SC; FH; HLRCC; biomarker; renal cell carcinoma; succination

DOI:  https://doi.org/10.1016/j.humpath.2022.12.013
Cell Rep. 2022 Dec 27. pii: S2211-1247(22)01775-2. [Epub ahead of print]41(13): 111879

A circadian clock translational control mechanism targets specific mRNAs to cytoplasmic messenger ribonucleoprotein granules.

Kathrina D Castillo, Cheng Wu, Zhaolan Ding, Osiris K Lopez-Garcia, Emma Rowlinson, Matthew S Sachs, Deborah Bell-Pedersen.

  Phosphorylation of Neurospora crassa eukaryotic initiation factor 2 α (eIF2α), a conserved translation initiation factor, is clock controlled. To determine the impact of rhythmic eIF2α phosphorylation on translation, we performed temporal ribosome profiling and RNA sequencing (RNA-seq) in wild-type (WT), clock mutant Δfrq, eIF2α kinase mutant Δcpc-3, and constitutively active cpc-3c cells. About 14% of mRNAs are rhythmically translated in WT cells, and translation rhythms for ∼30% of these mRNAs, which we named circadian translation-initiation-controlled genes (cTICs), are dependent on the clock and CPC-3. Most cTICs are expressed from arrhythmic mRNAs and contain a P-body (PB) localization motif in their 5' leader sequence. Deletion of SNR-1, a component of cytoplasmic messenger ribonucleoprotein granules (cmRNPgs) that include PBs and stress granules (SGs), and the PB motif on one of the cTIC mRNAs, zip-1, significantly alters zip-1 rhythmic translation. These results reveal that the clock regulates rhythmic translation of specific mRNAs through rhythmic eIF2α activity and cmRNPg metabolism.

Keywords:  CP: Molecular biology; CPC-3; GCN2; Neurospora crassa; P-body; circadian clock; cytoplasmic messenger ribonucleoprotein granules; eIF2α; ribosome profiling; translation control

DOI:  https://doi.org/10.1016/j.celrep.2022.111879
Nat Mater. 2022 Dec 29.

Tissue fluidification promotes a cGAS-STING cytosolic DNA response in invasive breast cancer.

Emanuela Frittoli, Andrea Palamidessi, Fabio Iannelli, Federica Zanardi, Stefano Villa, Leonardo Barzaghi, Hind Abdo, Valeria Cancila, Galina V Beznoussenko, Giulia Della Chiara, Massimiliano Pagani, Chiara Malinverno, Dipanjan Bhattacharya, Federica Pisati, Weimiao Yu, Viviana Galimberti, Giuseppina Bonizzi, Emanuele Martini, Alexander A Mironov, Ubaldo Gioia, Floriana Ascione, Qingsen Li, Kristina Havas, Serena Magni, Zeno Lavagnino, Fabrizio Andrea Pennacchio, Paolo Maiuri, Silvia Caponi, Maurizio Mattarelli, Sabata Martino, Fabrizio d'Adda di Fagagna, Chiara Rossi, Marco Lucioni, Richard Tancredi, Paolo Pedrazzoli, Andrea Vecchione, Cristiano Petrini, Francesco Ferrari, Chiara Lanzuolo, Giovanni Bertalot, Guilherme Nader, Marco Foiani, Matthieu Piel, Roberto Cerbino, Fabio Giavazzi, Claudio Tripodo, Giorgio Scita.

The process in which locally confined epithelial malignancies progressively evolve into invasive cancers is often promoted by unjamming, a phase transition from a solid-like to a liquid-like state, which occurs in various tissues. Whether this tissue-level mechanical transition impacts phenotypes during carcinoma progression remains unclear. Here we report that the large fluctuations in cell density that accompany unjamming result in repeated mechanical deformations of cells and nuclei. This triggers a cellular mechano-protective mechanism involving an increase in nuclear size and rigidity, heterochromatin redistribution and remodelling of the perinuclear actin architecture into actin rings. The chronic strains and stresses associated with unjamming together with the reduction of Lamin B1 levels eventually result in DNA damage and nuclear envelope ruptures, with the release of cytosolic DNA that activates a cGAS-STING (cyclic GMP-AMP synthase-signalling adaptor stimulator of interferon genes)-dependent cytosolic DNA response gene program. This mechanically driven transcriptional rewiring ultimately alters the cell state, with the emergence of malignant traits, including epithelial-to-mesenchymal plasticity phenotypes and chemoresistance in invasive breast carcinoma.

DOI: https://doi.org/10.1038/s41563-022-01431-x